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ACTA TECHNICA CORVINIENS IS – BULLETIN of ENGINEERING

Indexes & Databases ACTA TECHNICA CORVINIENSIS – BULLETIN of ENGINEERING is accredited and ranked in the “B+” CATEGORY Journal by CNCSIS – The National University Research Council’s Classification of Romanian Journals, positionno. 940 (http://cncsis.gov.ro/). The Journal is a part of theSCIPIO - The Romanian Editorial Platform (http://www.scipio.ro/). ACTA TECHNICA CORVINIENSIS – BULLETIN of ENGINEERING is indexed, abstracted and covered in the world-known bibliographical databases and directories including: INDEX COPERNICUS – JOURNAL MASTER LIST http://journals.indexcopernicus.com/ GENAMICSJOURNALSEEK Database http://journalseek.net/ DOAJ – Directory of Open Access Journals http://www.doaj.org/ EVISA Database http://www.speciation.net/ CHEMICAL ABSTRACTS SERVICE (CAS) http://www.cas.org/ EBSCO Publishing http://www.ebscohost.com/ GOOGLE SCHOLAR http://scholar.google.com SCIRUS - Elsevier http://www.scirus.com/ ULRICHSweb – Global serials directory http://ulrichsweb.serialssolutions.com getCITED http://www.getcited.org BASE - Bielefeld Academic Search Engine http://www.base-search.net Electronic Journals Library http://rzblx1.uni-regensburg.de Open J-Gate http://www.openj-gate.com ProQUEST Research Library http://www.proquest.com Directory of Research Journals Indexing http://www.drji.org/ Directory Indexing of International Research Journals http://www.citefactor.org/

ACTA TECHNICA CORVINIENSIS – BULLETIN of ENGINEERING is also indexed in the digital libraries of the following world's universities and research centers: WorldCat – the world's largest library catalog https://www.worldcat.org/ National Lybrary of Australia http://trove.nla.gov.au/ University Library of Regensburg – GIGA German Institute of Global and Area Studies http://opac.giga-hamburg.de/ezb/ Simon Fraser University – Electronic Journals Library http://cufts2.lib.sfu.ca/ University of Wisconsin-Madison Libraries http://library.wisc.edu/ University of Toronto Libraries http://search.library.utoronto.ca/ The University of Queensland https://www.library.uq.edu.au/ The New York Public Library http://nypl.bibliocommons.com/ State Library of New South Wales http://library.sl.nsw.gov.au/ University of Alberta Libraries - University of Alberta http://www.library.ualberta.ca/ The University of Hong Kong Libraries http://sunzi.lib.hku.hk/ The University Library - The University of California http://harvest.lib.ucdavis.edu/ We are very pleased to inform that our international scientific journal ACTA TECHNICA CORVINIENSIS - Bulletin of Engineering completed its seven years of publication successfully [2008 – 2014, Tome I – VII]. In a very short period the ACTA TECHNICA CORVINIENSIS - Bulletin of Engineering has acquired global presence and scholars from all over the world have taken it with great enthusiasm. We are extremely grateful and heartily acknowledge the kind of support and encouragement from all contributors and all collaborators!

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809

AIMS, MISSION & SCOPE General Aims

ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering is an international and interdisciplinary journal which reports on scientific and technical contributions. Every year, in four online issues (fascicules 1 - 4), ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering [e-ISSN: 2067-3809] publishes a series of reviews covering the most exciting and developing areas of engineering. Each issue contains papers reviewed by international researchers who are experts in their fields. The result is a journal that gives the scientists and engineers the opportunity to keep informed of all the current developments in their own, and related, areas of research, ensuring the new ideas across an increasingly the interdisciplinary field. Topical reviews in materials science and engineering, each including:  surveys of work accomplished to date  current trends in research and applications  future prospects. As an open-access journal ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering will serve the whole engineering research community, offering a stimulating combination of the following:  Research Papers - concise, high impact original research articles,  Scientific Papers - concise, high impact original theoretical articles,  Perspectives - commissioned commentaries highlighting the impact and wider implications of research appearing in the journal. ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering encourages the submission of comments on papers published particularly in our journal. The journal publishes articles focused on topics of current interest within the scope of the journal and coordinated by invited guest editors. Interested authors are invited to contact one of the Editors for further details.

Mission

ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering is an international and interdisciplinary journal which reports on scientific and technical contributions. The ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering advances the understanding of both the fundamentals of engineering science and its application to the solution of challenges and problems in engineering and management, dedicated to the publication of high quality papers on all aspects of the engineering sciences and the management. You are invited to contribute review or research papers as well as opinion in the fields of science and technology including engineering. We accept contributions (full papers) in the fields of applied sciences and technology including all branches of engineering and management. Submission of a paper implies that the work described has not been published previously (except in the form of an abstract or as part of a published lecture or academic thesis) that it is not under consideration for publication elsewhere. It is not accepted to submit materials which in any way violate copyrights of third persons or law rights. An author is fully responsible ethically and legally for breaking given conditions or misleading the Editor or the Publisher. The Editor reserves the right to return papers that do not conform to the instructions for paper preparation and template as well as papers that do not fit the scope of the journal, prior to refereeing. The Editor reserves the right not to accept the paper for print in the case of a negative review made by reviewers and also in the case of not paying the required fees if such will be fixed and in the case time of waiting for the publication of the paper would extend the period fixed by the Editor as a result of too big number of papers waiting for print. The decision of the Editor in that matter is irrevocable and their aim is care about the high content-related level of that journal. The mission of the ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering is to disseminate academic knowledge across the scientific realms and to provide applied research knowledge to the appropriate stakeholders. We are keen to receive original contributions from researchers representing any Science related field. We strongly believe that the open access model will spur research across the world especially as researchers gain unrestricted access to high quality research articles. Being an Open Access Publisher, Academic Journals does not receive payment for subscription as the journals are freely accessible over the internet.

History

ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering has been published since 2008, as an online supplement of the ANNALS OF FACULTY ENGINEERING HUNEDOARA – International Journal Of Engineering. Now, the ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering is a free-access, online, international and multidisciplinary publication of the Faculty of Engineering Hunedoara. ACTA TECHNICA CORVINIENSIS – BULLETIN OF ENGINEERING exchange similar publications with similar institutions of our country and from abroad. © copyright Faculty of Engineering - Hunedoara, University POLITEHNICA Timisoara

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Fascicule 1 [January – March] Tome VIII [2015]

ENGINEERING  Mechanical Engineering  Metallurgical Engineering  Agricultural Engineering  Control Engineering  Electrical Engineering  Civil Engineering  Biomedical Engineering  Transport Engineering  Nanoengineering CHEMISTRY  General Chemistry  Analytical Chemistry  Inorganic Chemistry  Materials Science & Metallography  Polymer Chemistry  Spectroscopy  Thermo-chemistry

EARTH SCIENCES  Geodesy  Geology  Hydrology  Seismology  Soil science ENVIRONMENTAL  Environmental Chemistry  Environmental Science & Ecology  Environmental Soil Science  Environmental Health BIOTECHNOLOGY  Biomechanics  Biotechnology  Biomaterials MATHEMATICS  Applied mathematics  Modeling & Optimization  Foundations & methods

General Topics

Invitation

ECONOMICS  Agricultural Economics  Development Economics  Environmental Economics  Industrial Organization  Mathematical Economics  Monetary Economics  Resource Economics  Transport Economics  General Management  Managerial Economics  Logistics AGRICULTURE  Agricultural & Biological Engineering  Food Science & Engineering  Horticulture COMPUTER & INFORMATION SCIENCES  Computer Science  Information Science

We are looking forward to a fruitful collaboration and we welcome you to publish in our ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering. You are invited to contribute review or research papers as well as opinion in the fields of science and technology including engineering. We accept contributions (full papers) in the fields of applied sciences and technology including all branches of engineering and management. ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering publishes invited review papers covering the full spectrum of engineering and management. The reviews, both experimental and theoretical, provide general background information as well as a critical assessment on topics in a state of flux. We are primarily interested in those contributions which bring new insights, and papers will be selected on the basis of the importance of the new knowledge they provide. Submission of a paper implies that the work described has not been published previously (except in the form of an abstract or as part of a published lecture or academic thesis) that it is not under consideration for publication elsewhere. It is not accepted to submit materials which in any way violate copyrights of third persons or law rights. An author is fully responsible ethically and legally for breaking given conditions or misleading the Editor or the Publisher.

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809

ASSOCIATE EDITORS & REGIONAL COLLABORATORS Manager & Chairman

Romania Imre KISS , University Politehnica TIMISOARA, Faculty of Engineering HUNEDOARA, Department of Engineering & Management, General Association of Romanian Engineers (AGIR) – branch HUNEDOARA

Editors from:

Romania Vasile ALEXA, University Politehnica TIMIŞOARA, Faculty of Engineering – HUNEDOARA Sorin Aurel RAŢIU, University Politehnica TIMIŞOARA, Faculty of Engineering – HUNEDOARA Vasile George CIOATĂ, University Politehnica TIMIŞOARA, Faculty of Engineering – HUNEDOARA Simona DZIŢAC, University of ORADEA, Faculty of Energy Engineering – ORADEA Valentin VLĂDUŢ, National Institute of Research – Development for Machines and Installations – BUCUREŞTI Valentina POMAZAN, University “Ovidius” Constanţa, Mechanical Engineering Faculty – CONSTANŢA Dan Ludovic LEMLE, University Politehnica TIMIŞOARA, Faculty of Engineering – HUNEDOARA

Regional Editors from:

Hungary Tamás HARTVÁNYI, Széchenyi István University in GYŐR, Department of Logistics & Forwarding – GYŐR Arpád FERENCZ, College of KECSKEMÉT, Faculty of Horticulture, Department of Economics – KECSKEMÉT József SÁROSI, University of SZEGED, Faculty of Engineering – SZEGED Attila BARCZI, Szent István University, Department Nature Conservation & Landscape Ecology – GÖDÖLLÓ György KOVÁCS, University of MISKOLC, Faculty of Mechanical Engineering and Information Science – MISKOLC Zsolt Csaba JOHANYÁK, College of KECSKEMÉT, Faculty of Mechanical Engineering and Automation – KECSKEMÉT Gergely DEZSŐ, College of NYÍREGYHÁZA, Engineering and Agriculture Faculty – NYÍREGYHÁZA Krisztián LAMÁR, Óbuda University BUDAPEST, Kálmán Kandó Faculty of Electrical Engineering – BUDAPEST Márta NÓTÁRI, College of KECSKEMÉT, Faculty of Horticulture, Department of Economics – KECSKEMÉT Valeria NAGY, University of SZEGED, Faculty of Engineering – SZEGED Sándor BESZÉDES, University of SZEGED, Faculty of Engineering – SZEGED Loránt KOVÁCS, College of KECSKEMÉT, Faculty of Mechanical Engineering and Automation – KECSKEMÉT Slovakia Juraj ŠPALEK, University of ŽILINA, Faculty of Electrical Engineering – ŽILINA Peter KOŠTÁL, Slovak University of Technology – BRATISLAVA, Faculty Materials Science & Technology – TRNAVA Otakav BOKŮVKA, University of ŽILINA, Faculty of Mechanical Engineering – ŽILINA Tibor KRENICKÝ, Technical University of KOŠICE, Faculty of Manufacturing Technologies – PREŠOV Beata HRICOVÁ, Technical University of KOŠICE, Faculty of Mechanical Engineering – KOŠICE Peter KRIŽAN, Slovak University of Technology in BRATISLAVA, Faculty of Mechanical Engineering – BRATISLAVA Croatia Gordana BARIC, University of ZAGREB, Faculty of Mechanical Engineering and Naval Architecture – ZAGREB Goran DUKIC, University of ZAGREB, Faculty of Mechanical Engineering and Naval Architecture – ZAGREB Serbia Zoran ANIŠIC, University of NOVI SAD, Faculty of Technical Sciences – NOVI SAD Milan RACKOV, University of NOVI SAD, Faculty of Technical Sciences – NOVI SAD Igor FÜRSTNER, SUBOTICA Tech, College of Applied Sciences – SUBOTICA Imre NEMEDI, SUBOTICA Tech, College of Applied Sciences – SUBOTICA Ana LANGOVIC MILICEVIC, Graduate School of Business Studies, Megatrend University – BELGRAD Eleonora DESNICA, University of Novi Sad, Technical Faculty “M. Pupin” – ZRENJANIN Milan BANIC, University of NIŠ, Mechanical Engineering Faculty – NIŠ Aleksander MILTENOVIC, University of NIŠ, Faculty of Mechanical Engineering – NIŠ Slobodan STEFANOVIĆ, Graduate School of Applied Professional Studies – VRANJE Maja TURK-SEKULIĆ, University of NOVI SAD, Faculty of Technical Sciences – NOVI SAD Masa BUKUROV, University of NOVI SAD, Faculty of Technical Sciences – NOVI SAD Sinisa BIKIĆ, University of NOVI SAD, Faculty of Technical Sciences – NOVI SAD © copyright Faculty of Engineering - Hunedoara, University POLITEHNICA Timisoara

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Fascicule 1 [January – March] Tome VIII [2015]

Bosnia & Tihomir LATINOVIC, University in BANJA LUKA, Faculty of Mechanical Engineering – BANJA LUKA Herzegovina Sabahudin JASAREVIC, University of ZENICA, Faculty of Mechanical Engineering – ZENICA Šefket GOLETIĆ, University of Zenica, Faculty of Mechanical Engineering – ZENICA Bulgaria Krasimir Ivanov TUJAROV, “Angel Kanchev” University of ROUSSE, Faculty of Agricultural Mechanization – ROUSSE Ognyan ALIPIEV, University of ROUSSE, Department Theory of Mechanisms and Machines – ROUSSE Ivanka ZHELEVA, Anghel Kanchev University of ROUSSE, Department of Termotechnics & Manufacturing – ROUSSE Poland Bożena GAJDZIK, The Silesian University of Technology, Faculty of Materials, Science and Metallurgy – KATOWICE

The Editor and editorial board members do not receive any remuneration. These positions are voluntary. The members of the Editorial Board may serve as scientific reviewers. We are very pleased to inform that our journal ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering is going to complete its seven years of publication successfully. In a very short period it has acquired global presence and scholars from all over the world have taken it with great enthusiasm. We are extremely grateful and heartily acknowledge the kind of support and encouragement from you. ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering seeking qualified researchers as members of the editorial team. Like our other journals, ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering will serve as a great resource for researchers and students across the globe. We ask you to support this initiative by joining our editorial team. If you are interested in serving as a member of the editorial team, kindly send us your resume to [emailprotected].

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809

INTERNATIONAL SCIENTIFIC COMMITTEE & SCIENTIFIC REVIEWERS Manager & Chairman

Romania Imre KISS , University Politehnica TIMISOARA, Faculty of Engineering HUNEDOARA, Department of Engineering & Management, General Association of Romanian Engineers (AGIR) – branch HUNEDOARA

International Scientific Committee Members & Scientific Reviewers from:

Hungary Imre DEKÁNY, University of SZEGED, Department of Colloid Chemistry – SZEGED Béla ILLÉS, University of MISKOLC, Faculty of Mechanical Engineering and Information Science – MISKOLC Imre J. RUDAS, Óbuda University of BUDAPEST, Department of Structural Engineering – BUDAPEST Tamás KISS, University of SZEGED, Department of Inorganic and Analytical Chemistry – SZEGED Cecilia HODÚR, University of SZEGED, College Faculty of Food Engineering – SZEGED Arpád FERENCZ, College of KECSKEMÉT, Faculty of Horticulture, Department of Economics – KECSKEMÉT Imre TIMÁR, University of Pannonia, Department of Silicate and Materials Engineering – VESZPRÉM Károly JÁRMAI, University of MISKOLC, Faculty of Mechanical Engineering – MISKOLC Gyula MESTER, University of SZEGED, Department of Informatics – SZEGED Ádám DÖBRÖCZÖNI, University of MISKOLC, Faculty of Mechanical Engineering and Information Science – MISKOLC György SZEIDL, University of MISKOLC, Faculty of Mechanical Engineering and Information Science – MISKOLC István PÁCZELT, University of Miskolc, Department Of Mechanics – MISKOLC Lajos BORBÁS, University of Technology & Economics, Department of Vehicle Parts & Drives – BUDAPEST István J. JÓRI, BUDAPEST University of Technology & Economics, Machine & Product Design – BUDAPEST Miklós TISZA, University of MISKOLC, Department of Mechanical Engineering – MISKOLC Attila BARCZI, Szent István University, Department Nature Conservation & Landscape Ecology – GÖDÖLLÓ István BIRÓ, University of SZEGED, Faculty of Engineering – SZEGED Gyula VARGA, University of MISKOLC, Faculty of Mechanical Engineering & Information Science – MISKOLC József GÁL, University of SZEGED, Faculty of Engineering – SZEGED Ferenc FARKAS, University of SZEGED, Faculty of Engineering – SZEGED Slovakia Štefan NIZNIK, Technical University of KOŠICE, Faculty of Metallurgy, Department of Materials Science – KOŠICE Karol VELIŠEK, Slovak University of Technology BRATISLAVA, Faculty Materials Science & Technology – TRNAVA Jozef NOVAK-MARČINCIN,Technical University of KOSICE, Faculty of Manufacturing Technologies – PRESOV Ľubomir ŠOOŠ, Slovak University of Technology in BRATISLAVA, Faculty of Mechanical Engineering – BRATISLAVA Miroslav BADIDA, Technical University of KOŠICE, Faculty of Mechanical Engineering – KOŠICE Ervin LUMNITZER, Technical University of KOŠICE, Faculty of Mechanical Engineering – KOŠICE Ladislav GULAN, Slovak University of Technology, Institute of Transport Technology & Designing – BRATISLAVA Milan DADO, University of ŽILINA, Faculty of Electrical Engineering – ŽILINA Miroslav VEREŠ, Slovak University of Technology in BRATISLAVA, Faculty of Mechanical Engineering – BRATISLAVA Milan SAGA, University of ŽILINA, Faculty of Mechanical Engineering – ŽILINA Imrich KISS, Institute of Economic & Environmental Security, University of Security Management – KOŠICE Michal CEHLÁR, Technical University KOSICE, Faculty of Mining, Ecology & Geotechnologies – KOSICE Pavel NEČAS, Armed Forces Academy of General Milan Rastislav Stefanik – LIPTOVSKÝ MIKULÁŠ Vladimir MODRAK, Technical University of KOSICE, Faculty of Manufacturing Technologies – PRESOV Michal HAVRILA, Technical University of KOSICE, Faculty of Manufacturing Technologies – PRESOV Croatia Drazan KOZAK, Josip Juraj Strossmayer University of OSIJEK, Mechanical Engineering Faculty – SLAVONKI BROD Predrag COSIC, University of ZAGREB, Faculty of Mechanical Engineering and Naval Architecture – ZAGREB Miroslav CAR, University of ZAGREB, Faculty of Mechanical Engineering and Naval Architecture – ZAGREB Antun STOIĆ, Josip Juraj Strossmayer University of OSIJEK, Mechanical Engineering Faculty – SLAVONKI BROD Ivo ALFIREVIĆ, University of ZAGREB, Faculty of Mechanical Engineering and Naval Architecture – ZAGREB © copyright Faculty of Engineering - Hunedoara, University POLITEHNICA Timisoara

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Fascicule 1 [January – March] Tome VIII [2015]

Romania Teodor HEPUŢ, University Politehnica TIMIŞOARA, Faculty of Engineering – HUNEDOARA Caius PĂNOIU, University Politehnica TIMIŞOARA, Faculty of Engineering – HUNEDOARA Carmen ALIC, University Politehnica TIMIŞOARA, Faculty of Engineering – HUNEDOARA Iulian RIPOŞAN, University Politehnica BUCUREŞTI, Faculty of Materials Science and Engineering – BUCUREŞTI Ioan MĂRGINEAN, University Politehnica BUCUREŞTI, Faculty of Materials Science and Engineering – BUCUREŞTI Victor BUDĂU, University Politehnica TIMIŞOARA, Faculty of Mechanical Engineering – TIMIŞOARA Liviu MIHON, University Politehnica TIMIŞOARA, Faculty of Mechanical Engineering – TIMIŞOARA Mircea BEJAN, Tehnical University of CLUJ-NAPOCA, Faculty of Mechanical Engineering – CLUJ-NAPOCA Ioan VIDA-SIMITI, Technical University of CLUJ-NAPOCA, Faculty of Materials Science & Engineering – CLUJ-NAPOCA Csaba GYENGE, Technical University of CLUJ-NAPOCA, Machine Building Faculty – CLUJ-NAPOCA Laurenţiu POPPER, University of ORADEA, Faculty of Energy Engineering – ORADEA Sava IANICI, “Eftimie Murgu” University of REŞIŢA, Faculty of Engineering – REŞIŢA Serbia Sinisa KUZMANOVIC, University of NOVI SAD, Faculty of Technical Sciences – NOVI SAD Mirjana VOJINOVIĆ MILORADOV, University of NOVI SAD, Faculty of Technical Sciences – NOVI SAD Miroslav PLANČAK, University of NOVI SAD, Faculty of Technical Sciences – NOVI SAD Milosav GEORGIJEVIC, University of NOVI SAD, Faculty of Engineering – NOVI SAD Vojislav MILTENOVIC, University of NIŠ, Mechanical Engineering Faculty – NIŠ Aleksandar RODIĆ, Robotics Laboratory, “Mihajlo Pupin” Institute – BELGRADE Milan PAVLOVIC, University of NOVI SAD, Technical Faculty “Mihajlo Pupin” – ZRENJANIN Zoran ANIŠIC, University of NOVI SAD, Faculty of Technical Sciences – NOVI SAD Radomir SLAVKOVIĆ, Department of Mehatronics, University of KRAGUJEVAC, Technical Faculty – CACAK Zvonimir JUGOVIĆ, Department of Mehatronics, University of KRAGUJEVAC, Technical Faculty – CACAK Branimir JUGOVIĆ, Institute of Technical Science, Serbian Academy of Science and Arts – BELGRAD Miomir JOVANOVIC, University of NIŠ, Faculty of Mechanical Engineering – NIŠ Vidosav MAJSTOROVIC, University of BELGRADE, Mechanical Engineering Faculty – BELGRAD Predrag DAŠIĆ, Production Engineering and Computer Science, High Technical Mechanical School – TRSTENIK Lidija MANČIĆ, Institute of Technical Sciences of Serbian Academy of Sciences and Arts (SASA) – BELGRAD Bulgaria Kliment Blagoev HADJOV, University of Chemical Technology and Metallurgy, Department of Applied Mechanics – SOFIA Nikolay MIHAILOV, Anghel Kanchev University of ROUSSE, Faculty of Electrical and Electronic Engineering – ROUSSE Krassimir GEORGIEV, Institute of Mechanics, Bulgarian Academy of Sciences – SOFIA Portugal João Paulo DAVIM, University of AVEIRO, Department of Mechanical Engineering – AVEIRO José MENDES MACHADO, University of MINHO, Mechanical Engineering Department, School of Engineering – GUIMARÃES

Bosnia & Tihomir LATINOVIC, University in BANJA LUKA, Faculty of Mechanical Engineering – BANJA LUKA Herzegovina Safet BRDAREVIĆ, University of ZENICA, Faculty of Mechanical Engineering – ZENICA Ranko ANTUNOVIC, University of EAST SARAJEVO, Faculty of Mechanical Engineering – East SARAJEVO Isak KARABEGOVIĆ, University of BIHAĆ, Technical Faculty – BIHAĆ Italy Alessandro GASPARETTO, University of UDINE, Faculty of Engineering – UDINE Alessandro RUGGIERO, University of SALERNO, Department of Mechanical Engineering – SALERNO Adolfo SENATORE, University of SALERNO, Department of Mechanical Engineering – SALERNO Poland Leszek A. DOBRZANSKI, Institute of Engineering Materials and Biomaterials, Silesian University of Technology – GLIWICE Stanisław LEGUTKO, Institute of Mechanical Technology, Polytechnic University – POZNAN Andrzej WYCISLIK, Silesian University of Technology – KATOWICE, Faculty of Materials Science & Metallurgy– KATOWICE Antoni ŚWIĆ, LUBLIN University of Technology, Institute of Technological Systems of Information – LUBLIN Marian Marek JANCZAREK, LUBLIN University of Technology, Institute of Technological Systems of Information – LUBLIN Michał WIECZOROWSKI, POZNAN University of Technology, Institute of Mechanical Technology – POZNAN Jarosław ZUBRZYCKI, LUBLIN University of Technology, Institute of Technological Systems of Information – LUBLIN Aleksander SŁADKOWSKI, Silesian University of Technology – KATOWICE, Faculty of Transport – KATOWICE Argentina Gregorio PERICHINSKY, University of BUENOS AIRES, Faculty of Engineering – BUENOS AIRES Atilio GALLITELLI, Institute of Technology, Centro de desarrollo en Gestión Tecnológica Y Operación – BUENOS AIRES Carlos F. MOSQUERA, University of BUENOS AIRES, School of Engineering, Laser Laboratory – BUENOS AIRES Elizabeth Myriam Jimenez REY, University of BUENOS AIRES, Faculty of Engineering, Dept. of Computer Science – BUENOS AIRES Arturo Carlos SERVETTO, University of BUENOS AIRES, Faculty of Engineering, Dept. of Computer Science – BUENOS AIRES Slovenia Janez GRUM, University of LJUBLJANA, Faculty of Mechanical Engineering – LJUBLJANA Štefan BOJNEC, University of Primorska, Faculty of Management – KOPER |8|

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Fascicule 1 [January – March] Tome VIII [2015]

Macedonia Valentina GECEVSKA, University "St. Cyril and Methodius" SKOPJE, Faculty of Mechanical Engineering – SKOPJE Zoran PANDILOV, University "St. Cyril and Methodius" SKOPJE, Faculty of Mechanical Engineering – SKOPJE Robert MINOVSKI, University "St. Cyril and Methodius" SKOPJE, Faculty of Mechanical Engineering – SKOPJE France Bernard GRUZZA, Universite Blaise Pascal, Institut des Sciences de L'Ingenieur (CUST) – CLERMONT-FERRAND Abdelhamid BOUCHAIR, Universite Blaise Pascal, Institut des Sciences de L'Ingenieur (CUST) – CLERMONT-FERRAND Khalil EL KHAMLICHI DRISSI, Universite Blaise Pascal, Institut des Sciences de L'Ingenieur (CUST) – CLERMONT-FERRAND Mohamed GUEDDA, Université de Picardie Jules Verne, Unité de Formation et de Recherche des Sciences – AMIENS Ahmed RACHID, Université de Picardie Jules Verne, Unité de Formation et de Recherche des Sciences – AMIENS Yves DELMAS, University of REIMS, Technological Institute of CHALONS-CHARLEVILLE – REIMS Jean GRENIER GODARD, L’ecole Superieure des Technologies et des Affaires (ESTA) – BELFORT India Sugata SANYAL, Tata Consultancy Services – MUMBAI Siby ABRAHAM, University of MUMBAI, Guru Nanak Khalsa College – MUMBAI Anjan KUMAR KUNDU, University of CALCUTTA, Institute of Radiophysics & Electronics – KOLKATA Spain Patricio FRANCO, Universidad Politecnica of CARTAGENA, Ingenieria de Materiales y Fabricacion – CARTAGENA Luis Norberto LOPEZ De LACALLE, University of Basque Country, Faculty of Engineering – BILBAO Aitzol Lamikiz MENTXAKA, University of Basque Country, Faculty of Engineering – BILBAO Carolina Senabre BLANES, Universidad Miguel Hernández, Department of Mechanic Engineering – ELCHE Morocco Saad BAKKALI, Abdelmalek Essaâdi University, Faculty of Sciences and Techniques – TANGIER Mahacine AMRANI, Abdelmalek Essaâdi University, Faculty of Sciences and Techniques – TANGIER

Cuba Norge I. COELLO MACHADO, Universidad Central “Marta Abreu” LAS VILLAS, Faculty of Mechanical Engineering – SANTA CLARA José Roberto Marty DELGADO, Universidad Central “Marta Abreu” LAS VILLAS, Faculty of Mechanical Engineering – SANTA CLARA Israel Abraham TAL, University TEL-AVIV, Space and Remote Sensing Division ICTAF – TEL-AVIV Amnon EINAV, University TEL-AVIV, Space and Remote Sensing Division ICTAF – TEL-AVIV Finland Antti Samuli KORHONEN, HELSINKI University of Technology, Department of Materials Science & Engineering – HELSINKI Pentti KARJALAINEN, University of OULU, Centre for Advanced Steels Research – OULU Norway Trygve THOMESSEN, The Norwegian University of Science and Technology – TRONDHEIM Gábor SZIEBIG, Narvik University College,Department of Industrial Engineering – NARVIK Greece Nicolaos VAXEVANIDIS, University of THESSALY, Department of Mechanical & Industrial Engineering – VOLOS Austria Branko KATALINIC, VIENNA University of Technology, Institute of Production Engineering – VIENNA USA David HUI, University of NEW ORLEANS, Department of Mechanical Engineering – NEW ORLEANS Turkey Ali Naci CELIK, Abant Izzet Baysal University, Faculty of Engineering and Architecture – BOLU OR

The Scientific Committee members and Reviewers do not receive any remuneration. These positions are voluntary. We are extremely grateful and heartily acknowledge the kind of support and encouragement from all contributors and all collaborators!

REVIEW PROCESS & EDITORIAL POLICY ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering is dedicated to publishing material of the highest engineering interest, and to this end we have assembled a distinguished Editorial Board and Scientific Committee of academics, professors and researchers. ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering publishes invited review papers covering the full spectrum of engineering. The reviews, both experimental and theoretical, provide general background information as well as a critical assessment on topics in a state of flux. We are primarily interested in those contributions which bring new insights, and papers will be selected on the basis of the importance of the new knowledge they provide.

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Fascicule 1 [January – March] Tome VIII [2015]

ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering encourages the submission of comments on papers published particularly in our journal. The journal publishes articles focused on topics of current interest within the scope of the journal and coordinated by invited guest editors. Interested authors are invited to contact one of the Editors for further details. ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering accept for publication unpublished manuscripts on the understanding that the same manuscript is not under simultaneous consideration of other journals. Publication of a part of the data as the abstract of conference proceedings is exempted. Manuscripts submitted (original articles, technical notes, brief communications and case studies) will be subject to peer review by the members of the Editorial Board or by qualified outside reviewers. Only papers of high scientific quality will be accepted for publication. Manuscripts are accepted for review only when they report unpublished work that is not being considered for publication elsewhere. The evaluated paper may be recommended for:  Acceptance without any changes – in that case the authors will be asked to send the paper electronically in the required .doc format according to authors’ instructions;  Acceptance with minor changes – if the authors follow the conditions imposed by referees the paper will be sent in the required .doc format;  Acceptance with major changes – if the authors follow completely the conditions imposed by referees the paper will be sent in the required .doc format;  Rejection – in that case the reasons for rejection will be transmitted to authors along with some suggestions for future improvements (if that will be considered necessary). The manuscript accepted for publication will be published in the next issue of ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering after the acceptance date. All rights are reserved by ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering. The publication, reproduction or dissemination of the published paper is permitted only be written consent of one of the Managing Editors. All the authors and the corresponding author in particular take the responsibility to ensure that the text of the article does not contain portions copied from any other published material which amounts to plagiarism. We also request the authors to familiarize themselves with the good publication ethics principles before finalizing their manuscripts.

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809

TABLE of CONTENTS Tome VIII [2015] Fascicule 1 [January – March] 1. Sugata SANYAL, Niva DAS, Tanmoy SARKAR – INDIA

17 Abstract: With invent of new technologies and devices, Intrusion has become an area of concern because of security issues, in the ever growing area of cyber-attack. An intrusion detection system (IDS) is defined as a device or software application which monitors system or network activities for malicious activities or policy violations. It produces reports to a management station. In this paper we are mainly focused on different IDS concepts based on Host and Network systems. 2. Vladimir BLANUŠA, Milan ZELJKOVIĆ, Aleksandar ŽIVKOVIĆ – SERBIA

SURVEY ON HOST AND NETWORK BASED INTRUSION DETECTION SYSTEM

PREDICTION THERMAL ELASTIC BEHAVIOR OF THE CYLINDRICAL ROLLER BEARING FOR RAILWAY VEHICLES AND CALCULATINGBEARING LIFE

21 Abstract: This paper presents a calculation model the thermal elastic behavior ofthe cylindrical roller bearing for bearings towed vehicle in railways. The present mathematical model allows to definethe value ofthe moment friction due to lubrication, the friction moment due to the radial and axial loads. Heat generated in the bearing calculated based on the value of previously defined moments. Also, it shows the method of calculating the coefficients of conduction and convection of heat in bearing. Using programming system general purpose analyzed ther mal elastic behavior of the cylindrical roller bearing for bearings axle to wed vehicle in railways. Finite element method determined by temperature values in the characteristic points of the bearing depending on the speed wheel for different time periods. Also, it determined of displacement in characteristic points of bearing due to the heat load in the steady temperature state, maximal stress and bearing life. 3. Richard JANURA, Jozef JURČÍK, Miroslav GUTTEN, Daniel KORENČIAK – SLOVAKIA 27 TRANSFORMER INSULATION ANALYSIS BY TIME DOMAIN METHOD Abstract: The article discusses the state of transformer insulation. For a more accurate determination of the transformer insulation state are used three methods. The measurement of insulation resistance is the basic method and is set in the standard, value demonstrates the state of total insulation of transformer. Because the determination of moisture content of the paper insulation of transformer is very difficult process and it is necessary take a sample of paper, in this case is used method of return voltage. Return voltage measurement is more complex method and in many cases is determine a clear result very difficult. For evaluation of results have mainly impact moisture content and degree of aging of paper insulation and of course, content of conductive impurities in oil. Because the moisture content in oil is much lower than in the paper, return voltage measurement is used to determine the moisture content in paper insulation only. To confirm the results of return voltage measurement is used frequency domain spectroscopy, which clearly, according computational model, calculates the moisture content in the paper insulation. 4. Daniel R. WEISZ, Felix A. HIMMELSTOSS – AUSTRIA 31 LED CONVERTER WITH LIMITED DUTYCYCLE Abstract: Light emitting diodes (LEDs) can be used for many lightning applications in offices, in homes, and in streets. A special converter with limited duty cycle for driving LEDs is treated. The basic analysis is done resulting in dimensioning equations of the converter. The basic analyses have to be done with idealized components (that means no parasitic resistors, no switching losses) and for the continuous mode in steady (stationary) state. A mathematical model based on state-space description is derived. Some experimental results are shown. The converter is useful for street, home, and automotive lightning applications. 5. Vladimir CHUDACIK, Ladislav JANOUSEK, Milan SMETANA – SLOVAKIA

EVALUATION OF SPATIAL COMPONENTS ON EDDY CURRENT TESTING RESPONSE SIGNALS OF SELECTED DEFECT PARAMETERS

35 Abstract: In this article, the presence of inhom*ogeneities in solid electrically conducting plate is inspected by non-destructive way with use of eddy current testing method where the perturbed electromagnetic field caused by the defect is detected. We perform three-dimensional finite element simulations of this structure with pre-defined material inhom*ogeneities and they are evaluated by an induction coil. This study is motivated by the novel eddy current testing technique which is based on sensing of all the three components of the perturbed field. Basically we performed parametric study to quantify the impact of various parameters – depth and electrical conductivity of the inhom*ogeneity. The analyses provide reference results to understand the effectiveness, feasibility and capability of this approach. © copyright Faculty of Engineering - Hunedoara, University POLITEHNICA Timisoara

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Fascicule 1 [January – March] Tome VIII [2015]

6. Maciej BIELECKI,Andrzej SZYMONIK – POLAND

39 Abstract: One of the most important purposes of each logistics system functioning is to define the desired security state. It should be noted that the various elements that refer to the security of the logistics system are related to a number of both external and internal conditions of the company. There is also a number of security areas dependent and independent from the company. On this basis, one can make a statement that the product itself, having specified characteristics and properties can affect the security of the logistics system. The article is an attempt to identify and describe the impact of logistics security conditions on vulnerability of product design, and consequently on the logistical efficiency of the product. 7. Ján ĎURECH, Marián HRUBOŠ, Mária FRANEKOVÁ, Aleš JANOTA – SLOVAKIA 45 IMPLEMENTATION OF DATA FROM THE MOBILE MEASUREMENT PLATFORM TO VANET APPLICATION Abstract: The paper deals with an idea of informing the car drivers on problem of road degradation via sending of warning messages from road side units. The initial part of the paper summarized the up–to–now realized concept of the mobile measurement platform (MMS) and its mathematical principles showing how detailed data on road surface may be obtained. The main part of the paper is aimed at design of integration of data from MMS into the VANET application. Practical realisation is based on the warning message generation with GPS coordinates which is assuring by digital signature ECDSA cryptography algorithm via OpenSSL tool. 8. Horst TREIBLMAIER – AUSTRIA 49 ACLASSIFICATION FRAMEWORK FOR SUPPLY CHAIN FORECASTING LITERATURE Abstract: Forecasting in Supply Chain Management (SCM) is an important yet underestimated research topic. Over the past years numerous methods and concepts have been developed, tested and deployed. In this paper we present a classification framework for the SC Forecasting literature using eight criteria, namely focus, approach, method triangulation, data generation, range, timeline, theoretical background, and target group. Additionally, we present examples for the respective criteria and summarize the major findings. This state-of-the-art review paper is targeted toward both researchers and industry experts who want to get an overview of the goals of contemporary SC Forecasting research. 9. Abdelnaser OMRAN – MALAYSIA

THE IMPACT OF LOGISTICS SECURITY CONDITIONS ON THE LOGISTICAL EFFICIENCY OF THE PRODUCT

Abdulsalam ABDULRAHIM – LYBIA BARRIERS TO PRIORITIZING LEAN CONSTRUCTION IN THE LIBYAN CONSTRUCTION INDUSTRY

53 Abstract: Engaging in Lean construction efforts could prove to be highly rewarding for building firms in Libya. However, lean construction is risky and can be disastrous if not properly managed. Lean production efforts in some other countries have not been successful due to the many barriers to its successful implementation. This study sets out intends to explore identify the barriers that affecting the prioritizing of lean construction with the objective of determining the barriers that affects the use of lean construction in construction industry in Libya. Forty six (46) questionnaires were distributed to various construction firms in Libya. This study presents nine (9) barriers and investigates their influence (strength) on the success of lean construction initiatives. This study indicates that extra efforts still needed to be done on the awareness and use of lean construction in the Libyan construction industry. 10. Norge Isaías COELLO MACHADO – CUBA Elke GLISTAU – GERMANY Béla ILLES – HUNGARY PROCEDURE TO SET VALUES FOR THE STATISTICAL PARAMETERS IN THE PROCESSES WITH SPECIFICATION LIMITS – 57 APPLICATIONIN LOGISTICS Abstract: Processes with specification limits (tolerance) are typical in industrial practice, for example in the control of the manufacturing process. Often these tools are be used in all engineering processes, here is shown an application in the control of the logistics process. To ensure theeffectiveness of the process and to meet customer expectations it is necessary to ensurestrict compliance with the tolerances. Classic control methods base on variables that require monitoring related to the limits set by the natural process tolerance. In this work considerations expressed for estimating values of the dispersion and the permissible central tendency of the variables from the specification limits, the purpose is to obtain acceptable process capability for the specific case. Considerations are be done in the reverse order, dispersion values and the central tendency is not executed after he process determines in this case the maximum permissible values of dispersion andcentral tendency referred to tolerance specification are estimated to guarantee the required quality before you start the process, so this method can be considered as a preventive tool quality. 11. Mohamed ZELLAGUI, Abdelaziz CHAGHI – ALGERIA 61 APPLICATION KHA FOR OPTIMAL COORDINATION OF DIRECTIONAL OVERCURRENT RELAYS IN THE PRESENCE MULTI GCSC Abstract: Optimal coordination of direction overcurrent relays in the power systems in the presence of GTO Controlled Series Capacitor (GCSC) installed on meshed power system is studied in this paper. The coordination problem is formulated as a non-linear constrained mono-objective optimization problem. The objective function of this optimization problem is the minimization of the operation time of the associated relays in the systems, and the decision variables are: the time dial setting and the pickup current setting of each overcurrent relay. To solve this complex non linear optimization problem, a variant of evolutionary optimization algorithms named Krill Herd Algorithm (KHA) is used. The proposed algorithm is validated on IEEE 14bus transmission network test system considering various scenarios. The obtained results show a high efficiency of the proposed method to solve such complex optimization problem, in such a way the relays coordination is guaranteed for all simulation scenarios with minimum operating time for each relays. The results of objective function are compared to other optimization algorithms. | 12 |

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Fascicule 1 [January – March] Tome VIII [2015]

12. Peter PAVLASEK, Stanislav ĎURIŠ, Rudolf PALENČAR , Lukáš ĎURIŠ, Martin KOVAL – SLOVAKIA

69 Abstract: Measurements of temperature have a great importance in wide range of industrial applications. As temperature affects the quality, safety and effectives of many of these applications, a great effort has been made to enhance the precision and reliability of temperature measuring sensors. One of the main types of temperature sensors that are used in industry are thermoelectric sensors, more commonly known as thermocouples. These sensors play a irreplaceable role in high temperature industrial measurements. Their robust construction, the ability to withstand high temperatures and harsh conditions had made them popular among many users. As thermocouples are active sensors, they work on the principle of the Seebeck effect. This effect is dependant from wire material purity and composition thus any change in these properties will result in change of their voltage output thus temperature. These changes of Seebeck coefficient can be caused by many factors, like chemical impurities, changes in metal lattice of the wire material, reaction between the materials of which the thermocouple consist of etc. This work deals with the analysis of various factors that can effect the Seebeck coefficient of the thermocouple wire material. Influences that affect the long term stability of the thermocouple voltage output have been analysed and a measuring procedure to determine the level of contribution to the Seebeck coefficient is presented. Furthermore the paper deals with the time stability of base metal Type N thermocouples in the MIMS (Mineral Insulated Metal Sheathed) configuration. The presented results determine the level of Seebeck coefficient change during a long time exposure to temperatures from 1200°C to 1250°C. 13. Marek PAVLICA, Jana PETRŮ, Robert ČEP – CZECH REPUBLIC 73 SELECTION OF THE OPTIMAL PARAMETERS FOR LASER CUTTING Abstract: The current high requirements for quality, accuracy and durability of produced parts lead to a permanent improvement of the production process. For reasons of efficiency and competitiveness have become increasingly to the forefront of non-conventional machining methods. Nonconventional technology is characterized by the use, physical, chemical or a combination of these processes. Currently, the most commonly used for industrial cutting continuous CO2 laser with an average power. Because of the high requirements for the quality of the cutting edge is necessary to choose the optimal method of cutting either melting laser cutting or oxidizing laser cutting. The main parameters that we can significantly affect the quality of the cutting edges are: laser power, length of focal optics, cutting speed, gas pressure, gap between the nozzle and plate, shaped nozzles etc. If the cutting edge after laser cutting does not reach the required quality, it may negatively affect the price of the product, due to add additional operations, as may be chamfering, grinding, etc. For this reason, high demands are made to the professional knowledge on operator of laser equipment. 14. G. ADEDOKUN, J.A. OLADOSU – NIGERIA 77 DEVELOPMENT OF A GSM-BASED REMOTE CONTROL SYSTEM FOR HOME ELECTRICAL APPLIANCES Abstract: Electrical power is often used as a source of power to operate electrical appliances. However, inconsistent of electricity supply leads to obliviousness of the users to switch off their home appliances; thereby, resulting in energy wastage or eventual damage to appliances when power is restored. Meanwhile, developments in information technology could be used to eliminate this problem. Consequently, a GSM based remote control system has been developed to control and monitor electrical devices that required constant attention using mobile phone. This system is very handy when users forget to turn ON/OFF the electrical appliances at their home or office after they have set out. They can now control or monitor such appliances remotely by sending a text message from their mobile phone. This development ultimately saves a lot of time and effort. Likewise, daily electrical energy savings is made more efficient and effective. In constructing this system, basic components like mobile phones, SIM card, Liquid Crystal Display, relays and microcontroller were used to develop a cost-effective and adaptable system. 15. Tarik El OUAFY, Abdelilah CHTAINI, Hassan OULFAJRITE, Rachida NAJIH – MOROCCO

TIME INSTABILITY OF BASE METAL THERMOCOUPLES

CARBON PASTE ELECTRODE MODIFIED WITH CLAY FOR ELECTROCHEMICAL DETECTION OF COPPER (II) USING CYCLIC VOLTAMMETRY

81 Abstract: This paper reports on the use of carbon paste electrode modified with clay (Clay-CPE) and cyclic voltammetry (CV) for analytical detection of trace copper (II) in Na2SO4 0.1M. The electroanalytical procedure for determination of the Cu(II) comprises two steps: the chemical accumulation of the analyze under open-circuit conditions followed by the electrochemical detection of the preconcentrated species using cyclic voltammetry. The electrochemical responses obtained by CV at Clay-CPE were found to be analytically suitable to develop a method for the determination of copper at low concentration levels. 16. Jana POLÁČKOVÁ, Petr SAJDL, Jana PETRŮ , Daniela MARUŠÁKOVÁ – CZECH REPUBLIC 85 EFFECT OF CHEMICAL REGIMES ON OXIDE LAYERS OF MATERIALS IN POWER ENGINEERING Abstract: Nowadays most commonly used materials in power engineering are stainless steels. Temperatures and pressures in systems are currently increased to achieve higher efficiency. In some plants are applied even supercritical values. This paper is focused on improvement of corrosion protection possibilities. Except new materials (titanium, nickel superalloys), different types of surface treatments or layers are used to reduce problems caused by corrosion. If passive film is formed on treated surface, e.g. nitrided, there can appear differences in its properties. The oxidic layers are common, however in operation of water-steam cycles in power plants arise problems like exfoliation, bigger porosity or disparity of passive layer. Consequence is larger corrosion rate, which leads up to degradation of the material and failure of equipment. In experimental section were created oxidic layers in laboratory conditions and was monitored the behavior of materials used in power industry. Thereafter were evaluated their properties and composition, which permits to analyze what terms are for given materials most suitable. Samples were exposed in autoclave in terms of different cycle chemistry and then analyzed by method of ESCA, X-ray diffraction and metallography. | 13 |

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Fascicule 1 [January – March] Tome VIII [2015]

17. Michal SVÁTEK, Peter KRIŽAN – SLOVAKIA

MUTUAL INTERACTION OF SELECTED PARAMETERS OF OAK SAWDUST DENSIFICATION PROCESS BY THE DENSITY RESPONSE SURFACE

89 Abstract: The aim of this contribution is to present research results - the impact and mutual interaction of selected parameters of the oak sawdust densification process by the response surface. The briquette density represents a measurable indicator of briquette quality. In most cases (analysis) is final density considered with numerical values which are under review by the individual criteria. The response surface creates a separate section and a possibility of its appraisal. A three-dimensional graph creates the response surface of the final briquettes density, whose points are the individual density values in a particular setting of selected parameters of densification process. By an intersection of the individual response surfaces with the selected parameters it´s possible to optimized these parameters with the aim to improve the quality of briquette. Showing the possibility to apply this optimizing method of the technological parameters and to analyse their mutual interaction represents our intention through this article. 18. Eva ŠEBELOVÁ, Josef CHLADIL – CZECH REPUBLIC 93 STUDY OF THE TOOL WEAR PROCESS IN THE MACHINING OF NON-METALLIC MATERIALS Abstract: The issue of tool wear in the machining of non-metallic materials is a very under-researched area. The theory is based on the findings known in metals and is extended by interaction of the tool with wood-based materials. These materials have completely different properties, most of them are characterized by poor thermal conductivity and a different behaviour in different directions of load (axial, radial and tangential). The course is based on a tool wear in the wear curves. Criterion wear defines the maximum wear – a period corresponding to the working state of edge. Studying the process of wear is monitored mainly due to determine dependencies between the durability of the cutting tool and the cutting speed. Addiction is characterized by Taylor's relationship. Determination of tool life vs. cutting speed is the starting basis for determining machinability. It is a material property that characterizes its suitability for machining. Measurement of tool wear in metal materials was carried out mainly on the back or top rake. However, for non-metallic materials, this wear is negligible and difficult to measure. This article is focusing on the issue of defining &measuring the radial edge wear. 19. A. S. ADEKUNLE, K. A. ADEBIYI, M. O. DUROWOJU – NIGERIA 97 PERFORMANCE EVALUATION OF GROUNDNUT OIL AND MELON OIL AS CUTTING FLUIDS IN MACHINING OPERATION Abstract: Coolants are used during machining for variety of reasons such as improving tool life, reducing work-piece thermal deformation and surface finish. Traditionally, coolants in machining are based on conventional oil as the base fluid, but because of its non-biodegradability which results in environmental pollution and danger to human health, there is a growing demand for biodegradable material thus opening an avenue for vegetable oils for use as coolants. In this work, groundnut and melon oils were used as coolants during the turning operation of mild steel using carbide cutting tool at different spindle speeds and depths of cut. The cooling ability, surface finish and chip shapes were studied during the machining process. The results showed that the cooling ability of melon oil was better than that of groundnut oil and the surface finish produced by the vegetable oils was better than that of soluble oil with melon giving the best surface finish. Soluble oil extracted heat the most. The chips formed using vegetable oil coolants are more ductile and continuous than those obtained using soluble oil coolant. Vegetable oil coolants were seen to enhance tool life better than the conventional oil and as such can be used as alternative to soluble oil coolants. 20. Csaba Attila GHEORGHIU – ROMANIA 101 STUDY ON THE INFLUENCE OF CONTINUOUS CASTING PARAMETERS ON QUALITY OF SEMI-FINISHED PRODUCTS Abstract: In today's siderurgical industry, more than 99% of the global steel production is made using two types of metallurgical facilities, i.e. oxygen converter and electric arc furnace. Worldwide, for both types of processes, there are several versions of construction and key technology, but the basic principle is maintained in each case, i.e. intensive use of the oxygen in oxygen converters and of electricity in the electric arc furnaces. Regardless of the steelmaking method/facility, more than 99% of the entire steel production is cast using the continuous casting method, and not more than 1% as ingot (destination: steel forging, tool steels, etc.). This paper deals with the influence of continuous casting parameters on the quality of semi-finished products, i.e. chemical composition, steel casting temperature, casting speed, drawing and solidification, and the billet cooling parameters influence on the defects generated during casting, solidification and cooling. 21. Libor HARGAŠ, Dušan KONIAR, Miroslav HRIANKA, Anna SIMONOVÁ, Zuzana LONCOVÁ – SLOVAKIA 105 DIAGNOSTICS OF RESPIRATORY DISEASES BASED ON VIRTUAL INSTRUMENTATION Abstract: Since the stethoscope was found, acoustic analysis was used for diagnostics of patients with pulmonary diseases. This method is characteristic with high level of subjectivity and results of auscultation vary between specialists. Last 10 years we can see significant development of signal digitization and its processing, what is the main engine of auscultation objectivity. Modern medical methods are characterized by influence of electronics to conventional and subjective diagnostics. In this article we propose integration of virtual instrumentation based on LabVIEW to respirology. Designed LabVIEW instruments can be applied each phase of implementation: sound acquisition, signal filtering and processing, representation and results visualization. Flexible LabVIEW instruments can replace many specialized and expensive tools and detectors. 22. Neven LOVRIN, Željko VRCAN – CROATIA 109 THE INFLUENCE OF ENGINEERING ETHICS ON ECOLOGY AND SUSTAINABLE DEVELOPMENT Abstract: Engineering is an important and learned profession, which has a direct and vital impact on the quality of life for all people. Engineers have to be aware of the fact that by using available engineering technologies it is possible to provide abundance for all human beings, but also to destroy all life on Earth. Accordingly, engineers should be committed to improving the environment to enhance the quality of life and to sustain the balance in nature. They shall hold the safety, health and welfare of the public as paramount, and strive to comply with the principles of sustainable development. | 14 |

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

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Tomaz KOSTANJEVEC, Matej VOGRINČIČ – SLOVENIA IMPROVED PRODUCT DEVELOPMENT APPROACH WITH MULTI-CRITERIA ANALYSIS

115 Abstract: The early stages of the new product development process are most often defined as idea generation, idea screening, concept development, and concept testing. These stages represent the development of an idea prior to its taking any physical form. In most industries it is from this point onwards that costs will rise significantly. It is clearly far easier to change a concept than a physical product. The innovative approach has become an important aspect in the design and implementation of the organizational strategy. The multi-criteria (MC) model allows for the systematic planning of successful investments. 24. Michal WIECZOROWSKI – POLAND

Thomas MATHIA, Serge CARRAS – FRANCE Damian SMIERZCHALSKI – POLAND SURFACE TOPOGRAPHY INSPECTION IN MULTISENSOR APPROACH

119

I. M. SEBASTINE – UNITED KINGDOM REDUCING AND CONTROLLING THE HYDROCARBON EMISSIONS FROM RICH AMINE REGENERATOR UNITS IN THE NATURAL GAS SWEETENING PROCESS: A CASE STUDY AND SIMULATION

129

Abstract: In contemporary solutions for surface asperities measurements some concepts appear where different sensors, basing on different physical principles are used. It is an idea from one side to measure various surfaces impossible to inspect with a standard tactile inductive probe, and from another to measure the same surface with several sensors. Thus it is possible to get more information and draw more complex and versatile conclusions. In the paper a concept of such a multisensor device was shown with a construction and some applications. Here, confocal probes as well as interferometric one and tactile sensors were used. 25. Juraj ŽDÁNSKY, Karol RÁSTOČNÝ – SLOVAKIA 123 INFLUENCE OF REDUNDANCY ON SAFETY INTEGRITY OF SRCS WITH SAFETY PLC Abstract: PLCs produced at present have incomparably wider range of application options than PLCs produced in the past. One of the options where the using of PLC has not yet been common is the safety-critical processes control. PLCs used for this purpose form a special category of PLCs and are known as safety PLCs. Safety PLCs (Programmable Logic Controller) are one of the appropriate tools for implementation of safety-related control system (SRCS). Their modular construction allows implementation not only control systems of defined safety integrity level (SIL), but even redundant control systems with defined availability. The contribution considers influence of redundant architectures on safety integrity of SRCS with safety PLC. 26. R. K. ABDULRAHMAN , R. A. SURAMAIRY – IRAQ

Abstract: Natural gas has been the most popular fossil fuel in recent years, and the demand for it has been dramatic. In fact, natural gas possesses several useful features: it has a high heating value, it can be utilised as a raw material in several petrochemical industries and it is a cheap fuel source. However, raw natural gas usually contains a variety of non-hydrocarbon components, e.g., acid gases, helium, nitrogen and mercury. Raw natural gas sources with large amounts of acid gases are known as sour gas. Sour gases should be treated and sweetened to meet natural gas pipeline specifications and sale contracts. The amine gas sweetening process is widely utilised in the gas industry, eitherto reduce or to remove acid gases from sour natural gas streams. Indeed, amine gas sweetening has several advantages over other sweetening processes; it is more economical than other processes, and it operates continuously. Indeed, the global hydrocarbon emissions from the oil and gas industries have been dramatic. Moreover, methane, ethane and propane may be the most obvious gases that are emitted by the natural gas industry. In many cases, these emissions occur from gas processing units, e.g., gas sweetening and gas dehydration processes. In fact, these hydrocarbon gas emissions contribute to global warming and environmental pollution. Moreover, hydrocarbon emissions lead to huge losses of precious hydrocarbons every hour. Therefore, this study aims to study the effects of the solvent circulation rate on the hydrocarbon carryover from the amine gas sweetening using Aspen HYSYS software. The study also used a Murban gas stream in the simulation process because it is loaded with a high concentration of acid gases. The study determined that the amine circulation rate may have significant effects on the hydrocarbon losses during the sweetening process. Moreover, the study also recommended several methods to reduce this effect and the emission, e.g., balancing the amine circulation rate with both the sweetening efficiency and the hydrocarbon emissions. 27. Lateef Owolabi MUDASHIRU – NIGERIA

RESPONSE SURFACE METHODOLOGY FOR STUDYING THE EFFECT OF OPERATING VARIABLES ON QUENCHING IN OIL MEDIUM

133 Abstract: Quenching is being described as one of the most common heat treatment processes used to impart the desire mechanical properties such as high strength, hardness and near resistance to metal parts using quenchants such as air, water and polymer solution. The quenching process parameters such as time, radial distance and immersion speed played a major role in deciding the heat treatment quality of the steel sample. In this research, response surface methodology was used to study the effect of process parameters on temperature distribution during the quenching process of AISI1020 steel sample. A total of seventeen experimental runs were designed using the three variables adopting Box-Behnken design with full replication technique and mathematical model was developed. Sensitivity analysis was carried out to identify critical parameters. Time was found to be the most influencing parameter on the temperature distribution, followed by immersion speed and the least effect was given by radial distance. The quadratic model developed was evaluated at p-value greater than 95% confidence level, having correlation coefficient R-squared of 0.9997, adjusted R-squared of 0.9993 and predicted R-squared of 0.9953. | 15 |

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

28. Arshad ALI, Muhammad Ashfaq MAITLA, Shahid IQBAL – PAKISTAN

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Makbol Ahmed MURSHID – THAILAND ENERGY CRISES IN PAKISTAN VIS-À-VIS DISASTERS

139 Abstract: Pakistan by the grace of Almighty Allah is having huge energy positional but this capability has not been explored fully but with exception of some large hydel works. An endeavor has been put-in by the Govt now to incorporate renewable energy in the development strategy. The strategy will be implemented in three phases. Exploring different energy resources and their use can help Pakistan to come out from this quagmire. Hosts of allied problems like extra costs and dangers of fuel stocking, carriage, and alternative arrangements will be minimized. Global warming, green house gasses, environmental degradation and other related problems will be reduced using alternative energy resources. This will also reduce the energy related hazards. 29. Y. YASREBINIA, M. DAEI, S. Esgandarzadeh FARD, M. Sameie PAGHALEH – IRAN

APPLICATION OF AMPLITUDE-FREQUENCY FORMULATION TO A NONLINEAR OSCILLATOR ARISING IN THE MICROELECTRO-MECHANICAL SYSTEM (MEMS)

143 Abstract: Study the application of microelectromechanical system (MEMS) devices especially the electrically actuated MEMS devices which require few mechanical components and small voltage levels for actuation is continuously growing. The MEMS devices are widely used as capacitive accelerometer, capacitive sensor, switches and so on. In this paper, the energy balance method has been successfully used to study a nonlinear oscillator arising in the microbeam-based microelectromechanical system (MEMS). The nonlinear ODE equation is solved by a powerful mathematical tool, the amplitudefrequency formulation. The good agreement of results got from amplitude-frequency formulation with results from fourth-order RungeeKutta method indicates that the obtained period is of high accuracy. 30. Mohamed A. A. El-SHAER , Ghada M. El-MAHDY – EGYPT 147 STRUCTURAL ANALYSIS OF MONO-SYMMETRIC PLATE GIRDERS IN COMPOSITE BRIDGES Abstract: Mono-symmetric plate girders are often used in simply supported composite bridges to eliminate local plate buckling in the compression flange during construction. This causes the neutral axis of the plate girder to shift downwards subjecting more of the web to compressive stresses due to bending. In slender webs this increases the possibility of local buckling in the compression part of the web during construction. However, depending on the slenderness (width-to-thickness ratio) of the web, the post-buckling reserve capacity may accommodate this local buckling within the elastic limit of the web for during construction loads. Hence, this would allow for the use of more slender webs in composite plate girder construction without the need for longitudinal web stiffeners or the reduction of the overall composite section due to local plate buckling in the web. Recommended values of stress level are given for mono-symmetric plate girders in the non-composite stage based on the results of a non-linear finite element analysis. *** Technical Book Rewiew

József FARKAS, Károly JÁRMAI: OPTIMUM DESIGN OF STEEL STRUCTURES,

Springer-Verlag Berlin Heidelberg, New York, Dordrecht, London, ISBN 978-3-642-36867-7 *** MANUSCRIPT PREPARATION – GENERAL GUIDELINES

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The ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering, Tome VIII/2015, Fascicule 1 [January–March/2015] includes scientific papers presented in the sections of: th » The 10 International Conference – ELEKTRO 2014, organized by the Faculty of Electrical Engineering, University of Žilina, in Rajecke Teplice, SLOVAKIA (May 19th–20th, 2014). The current identification numbers of the papers are # 3–5, 7, 21 and 25, according to the present contents list. th » The 8 International Conference for Young Researchers and PhD Students – ERIN 2014, organized by the Brno University of Technology, in Blansko - Češkovice, CZECH REPUBLIC (April 23rd–25th, 2014). The current identification numbers of the selected papers are # 12–13 and # 16–18, according to the present contents list. » The International Conference on Industrial Logistics – ICIL 2014, hosted by the Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb and International Centre for Innovation and Industrial Logistics (ICIIL), in Bol on island Brač, CROATIA (June 11th–13rd, 2014). The current identification numbers of the papers are # 6 and # 8, according to the present contents list. th » The 6 International Scientific Conference on Management of Technology Step to Sustainable Production – MOTSP 2014, placed in Bol, Brač, CROATIA as a joint project organized by the Faculty of Mechanical Engineering and Naval Architecture and Faculty of Graphical Arts both from the University of Zagreb, CROATIA, Faculty of Management, University of Primorska, Koper and Faculty of Mechanical Engineering, University of Maribor, SLOVENIA, Faculty of Mechanical Engineering, Ss. Cyril and Methodius University, Skopje, MACEDONIA, and Politecnico di Torino, ITALY (June 11th–13rd, 2014). The current identification numbers of the papers are # 22–24, according to the present contents list. Also, the ACTA TECHNICA CORVINIENSIS – Bulletin of Engineering, Tome VIII/2015, Fascicule 1 [January–March/2015], includes original papers submitted to the Editorial Board, directly by authors or by the regional collaborators of the Journal. copyright © University “POLITEHNICA” Timisoara, Faculty of Engineering Hunedoara, 5, Revolutiei, 331128, Hunedoara, ROMANIA http://acta.fih.upt.ro | 16 |

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Sugata SANYAL, 2. Niva DAS, 3. Tanmoy SARKAR

SURVEY ON HOST AND NETWORK BASED INTRUSION DETECTION SYSTEM 1.

Corporate Technology Office, Tata Consultancy Services, Mumbai, INDIA 2. University of Calcutta, Kolkata, INDIA 3. Neudesic India Pvt. Limited, Hyderabad, INDIA

Abstract: With invent of new technologies and devices, Intrusion has become an area of concern because of security issues, in the ever growing area of cyber-attack. An intrusion detection system (IDS) is defined as a device or software application which monitors system or network activities for malicious activities or policy violations. It produces reports to a management station. In this paper we are mainly focused on different IDS concepts based on Host and Network systems. Keywords: Intrusion, Intrusion Detection System (IDS), Host based Intrusion Detection System (HIDS); Network based Intrusion Detection System (NIDS)

INTRODUCTION With the recent advances in technology, people are sharing more and more information among each other. Some organizations like medicine, military etc. are sharing data which is highly sensitive and important. For secure communication, people are using cryptography, using secret key, so that only authenticated receiver can decrypt the message and authenticity of message remains intact. But intruders are not interested to decrypt message. They can use sophisticated tools to attack the host on the network and get access to the sensitive data. Here, IDS comes as a savior. IDS provide three important security functions of monitoring, detecting and responding to unauthorized activities [2]. It usually provides three services: Observing and analyzing the host and the network activities, audit system configurations and evaluating of integrity of critical information by estimating abnormal activities. IDS are generally classified as follows: 1. Host-Based (HIDS): Host based intrusion detection systems run on individual hosts / devices on the network. It monitors the incoming and outgoing packets from the device and alerts the administrator on detection of suspicious activity. 2. Network-Based (NIDS): Network based intrusion detection systems monitor traffic between all devices on the network. On performing an analysis for a passing traffic on the entire subnet (in a promiscuous mode), it subsequently matches the traffic on the subnets to the collection of known attacks. On finding a match, alert is sent to the administrator. Today, IDS becomes necessary for every organization to secure their sensitive data from intruders. In the next sections, we will discuss about various tools and techniques used in Host based and Network based Intrusion detection systems.

HOST BASED IDS Host based IDS is aimed at collection and analysis of information on a particular host or system [3]. This Host agent monitors and prevents intruders to compromise system security policy. HIDS plays different role from Anti-virus. Anti-virus is supposed to monitor all the activities inside the system but not concerned with buffer overflow attacks on system memory nor malicious behavior of operating system process but HIDS checks and collect system data including File System, Network Events, System Calls to verify whether any inconsistency has occurred or not. HIDS system relies heavily on audit trail and system logs to detect unusual activities inside the system. Host-based systems can monitor access to user specific information which is a major advantage [3], [4]. HIDS can identify an improper user of company resources. On detection of similar pattern (similar to past attacks or suggestive of an attack); activity with that workstation can be stopped, thus blocking the attack. This is greatly useful in systems where system resources are accessed remotely in a routine manner. Some major disadvantages as follows: (1) they cannot see the network traffic [3]; (2) HIDS rely heavily on audit trails which can exhaust a lot of resource and space in server, and (3) lack of cross-platform interoperability. Inspection of system configuration files to check for failure-prone setting and of other system objects for security policy violations are the basic job of a HIDS host-based mechanism [3]. If intruders succeed in modifying the HIDS itself then there is no way to detect intrusion – unless security administrators take appropriate precautions. ELM Enterprise Manager [6], an enterprise class event log management solution, collects event logs from different devices in

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

real-time. On detection of critical events, immediate email alerts are helpful in activating more stringent security policies. [8] has proposed an Intrusion Detection System where they compare the performance of their fuzzy rule based classifiers for IDS with similar performance obtained from the decision tree, support vector mechanisms and linear genetic programming. Toosi et al. [9] presented a method to classify the normal and abnormal behavior in network, proposing Adaptive Neuro Fuzzy Inference system to categorize normal and suspicious behavior and detect intrusion. Abraham et al. [10] have proposed an Intrusion Detection System which uses Distributed IDS to detect intrusion in a network. The approach makes use of three fuzzy rule based classifiers in a distributed environment to detect intrusion detection. David et al [28] introduce concept of mimicry attack which allows an advanced intruder to hide their identification to avoid IDS detection. The authors then propose theoretical concept to detect and prevent mimicry attacks. Yeung et al [29] adopt an anomaly detection approach. They detect possible intrusions, based on program or user profiles, built from normal usage data. Here the dynamic modeling approach, based on Hidden Markov Models (HMM) and the static modeling approach, based on event occurrence frequency distribution have been extensively used. STATL is a state/transition based attack description language, which is extensible. This is developed by Eckmann et al [30]. It is intended to describe intrusion detection type activity. A STATL helps describe both domain-independent attacks and for providing constructs to help extending the language. This is for taking care of attacks to particular domain and environments. NETWORK BASED IDS Network Based Intrusion Detection Systems (NIDS) are active systems. These are deployed on networks to primarily monitor the network traffic. NIDS are operated under promiscuous mode without exposing itself to the potential attackers. NIDS systems generally work by identifying attacking signature within the networks. NIDS are OS independent and also compromising one NIDS will not affect the system if multiple NIDS are deployed to monitor the traffic flow. Sometimes network people raise a question like what can NIDS do that Firewall can’t? The firewall is the equivalent of a security fence around a property and the guard post at the front gate. But Firewall is not able to detect what is happing inside [3]. Firewalls are subject to many attacks, tunneling attacks and application-based attacks are most prominent. On the other hand a NIDS system works like a body guard which is monitoring both inside and outside of a property. It monitors packets, matches pattern; find attacking signature from already existing attacks done in the past and sometime statistical analysis of the information to detect abnormal behavior. However NIDS system cannot scan the content if network traffic is encrypted, it cannot efficiently handle high speed networks.

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Snort [5], an open source network intrusion prevention system, is capable of performing real-time traffic analysis and packet logging on IP networks. It can handle various intrusion detection techniques like buffer overflow, protocol analysis, CGI attack and many more. Trivedi et al. [7] proposed an Intrusion Detection System which defines a term called “Reputation” that is assigned to every node in the network. Every node monitors the behavior of its next-hop neighbor through promiscuous mode. A reputation manager keeps track of all the “Reputation” values from all the nodes, for updating the reputation value. A node is declared as malicious whenever it crosses a predefined threshold. A warning message is sent only to the immediate neighbors. Each node also contains an Avoid list. It contains a list of malicious nodes and no further communication is done through these already identified malicious nodes. Toosi et al. [11] presented a method to classify the normal and the intrusive behavior in a network. They used a combination of neurofuzzy networks, fuzzy interference and genetic algorithm to classify the network. Parallel neuro-fuzzy classifiers did the initial classification and its output was the basis of the fuzzy inference system. Finally, the genetic algorithm approach was used to optimize the decision. Faysel and Haque [12] surveyed various methods of cyber-attack detection and classification technique. These are based on neural networks and data mining. They have also discussed IDS evaluation criteria and dataset for IDS validation. Trivedi et al. [13] suggested a Semi Distributed Reputation-based IDS method for Mobile Ad Hoc Networks (MANETs) proposing a unique concept of redemption and fading with path manager and monitor system, making the system invulnerable to many MANET attacks. An Ant Colony based IDS was proposed by Banerjee et al. [14] which keeps track of the intruder trails and works in conjunction with the machine learning system to make sensor networks less vulnerable to intrusion attacks. Saravanakumar et al. [15] tackle the issue of complexity and throughput, prime important points in the current Intrusion Detection Systems (IDS). They compare various IDS systems that use different algorithms to detect the intrusions. They proposed a scheme that uses a combination of Artificial Neural Network algorithms to design IDS. This enables faster convergence and delivers better performance. Shun and Malki [16] have a scheme which uses feed forward neural networks with back propagation training to predict and detect the attacks on network. With appropriate training the proposed IDS system greatly enhances the performance of the IDS system and detects the known and unknown attacks with higher probability. Intrusion Detection System (IDS), developed by Chavan et al. [17], uses Fuzzy Inference System and Artificial Neural Networks and it is trained by creating a signature pattern database, using Protocol Analysis and Neuro-fuzzy learning method. Dal et al. [18] proposed an Intrusion Detection System method which applies Genetic Algorithm with Artificial Immune System (AIS). They have evolved a Primary Response following the concept of memory cells which is dominant in Natural Immune System, enabling faster

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detection of already encountered attacks. These cells are random in nature, dependent on the evolution of the detectors, thus granting greater immunity from anomalies and attacks. Dasgupta et al. [19] focuses on the recent improvements in Artificial Immune System [AIS]. Yang et al. [20] use a related method in AIS to enhance the performance of IDS, using antibody concentration to evaluate the damaging power of the intrusion in the network. Hosseinpour et al. [21] suggested a method to improve the detection performance and accuracy of IDS system, proposing a distributed multilayered framework to improve the detection and efficiency of IDS. The genetic algorithm proposed by them enhances the secondary immune response of the system. Jie et al. [22] devised a method for signal detection using Artificial Immune System [AIS] for anomalistic signal detection in an electromagnetic environment. Saboori et al. [23] proposed an Apriori Algorithm to detect an anomaly in the system. It predicts a novel attack and generates a set of real-time rules for the firewall, and functions by extracting the correlation relationships among large data sets. Nikolova and Jecheva [24] suggested an anomaly based Intrusion Detection System (IDS) using data mining techniques like classification trees to describe the normal activity of the system. Similarity coefficients are used to detect the intrusion in the system, which compare the similarity between the normal behavior and the observed behavior. Depending on the measured degree of similarity, a decision is reached about the system being under attack or not. Karim [25] described application of Computer Intelligence in the Network Intrusion Detection, explaining the usage of clustering, feature selection, and anomaly detection. Jianhua et al. [26] describes detection and exclusion of misbehaving nodes by dropping packets forwarded through them. A reputationbased scheme for efficiently solving the problem has been suggested where nodes with bad comprehensive reputation will be excluded from the network. Thakur et al [27] described a multi-dimensional approach towards intrusion detection. Network and system usage parameters like source and destination IP addresses, ports; incoming and outgoing network traffic data rate and number of CPU cycles per request are divided into multiple dimensions. Authors established a conditional function during the training phase for each dimension. CONCLUSION Network-based and host-based IDS prevent both insider as well as outsider attacks. There are ever evolving methods of intrusion detection but most systems utilize signatures to search for patterns of misuse and either automatically respond to the misuse or intimates system administrator to take appropriate action. Some intrusion detection systems even sense misappropriation by using behavioral data forensics. Due to inherent risk of some automated responses, there is still need for human intervention that can supervise and ensure the state of the system.

REFERENCES

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[1.] http://en.wikipedia.org/wiki/Intrusion_detection_system [2.] Defeng Wang, Yeung, D.S., and Tsang, E.C., “Weighted Mahalanobis Distance Kernels for Support Vector Machines”, IEEE Transactions on Neural Networks, Vol. 18, No. 5, Pp. 1453-1462, 2007 [3.] Bace, Rebecca: An Introduction to Intrusion Detection & Assessment. Infidel Inc., prepared for ICSA Inc. Copyright 1998. [4.] Brackney, R: Cyber-Intrusion Response. Proceedings of Seventeenth IEEE Symposium on Reliable Distributed Systems, West Lafayette, IN, 20-23 Oct, 1998, pp. 413-415. [5.] Matthew Richard, “Intrusion Detection FAQ: Are there limitations of Intrusion Signatures?” http://www.sans.org/securityresources/idfaq/limitations.php, April 5, 2001. [6.] “Comprehensive Windows Event Log Monitoring - Servers, Desktops & Devices”, http://www.tntsoftware.com/, June 12, 2014. [7.] Animesh Trivedi, Rishi Kapoor, Rajan Arora, Sudip Sanyal, Sugata Sanyal, “RISM - Reputation Based Intrusion Detection System for Mobile Ad hoc Networks”, Third International Conference on Computers and Devices for Communication (CODEC-06), Institute of Radio Physics and Electronics, University of Calcutta, December 18-20, 2006, pp. 234-237. [8.] Ajith Abraham, Ravi Jain, Sugata Sanyal, Sang Yong Han, “SCIDS: A Soft Computing Intrusion Detection System”, 6th International Workshop on Distributed Computing (IWDC-2004), Springer Verlag, Germany, Lecture Notes in Computer Science, Vol. 3326. 2004, pp. 252-257 [9.] A. N. Toosi, M. Kahani, R. Monsefi, "Network Intrusion Detection based on Neuro-fuzzy classification," International Conference on Computing & Informatics, (ICOCI '06), Kuala Lumpur, Malaysia, June 6-8, 2006, pp. 1-5. [10.] Ajith Abraham, Ravi Jain, Johnson Thomas, and Sang Yong Han. "DSCIDS: Distributed soft computing intrusion detection system." Journal of Network and Computer Applications 30, no. 1 (2007): 81-98. [11.] A. N. Toosi, M. Kahani. "A new approach to intrusion detection based on an evolutionary soft computing model using neuro-fuzzy classifiers." Computer Communications 30, no. 10 (2007): 22012212. [12.] Mohammad A. Faysel, Syed S. Haque, “Towards Cyber Defense: Research in Intrusion Detection and Intrusion Prevention Systems”, IJCSNS International Journal of Computer Science and Network Security, Vol.10 No.7, July 2010, pp. 316-325. [13.] Animesh K Trivedi, Rajan Arora, Rishi Kapoor, Sudip Sanyal, Sugata Sanyal, “A Semi-distributed Reputation-based Intrusion Detection System for Mobile Ad hoc Networks”, Journal of Information Assurance and Security (JIAS), Volume 1, Issue 4, Dec. 2006, pp. 265274. [14.] S. Banerjee, C. Grosan, A. Abraham, P. K. Mahanti, "Intrusion detection in sensor networks using emotional ants," Proceedings of 5th International Conference on Intelligent Systems Design and Applications, (ISDA '05), Wroclaw, Poland, Sept. 8-10, 2005, pp. 344349. [15.] S. Saravana Kumar, Umamaheswari, D. Jayalakshmi, R. Sugumar, “Development and implementation of artificial neural networks for intrusion detection in computer network”, IJCSNS: Int. Journal of

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[18.]

[19.] [20.]

[21.]

[22.]

[23.]

[24.]

[25.]

[26.]

[27.]

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Computer Science and Network Security. 2010. vol. 10, No. 7, pp. 271- [28.] David Wagner, Paolo Soto “Mimicry Attacks on Host-Based Intrusion 275. Detection Systems” CCS’02, November 18–22, 2002, Washington, DC, Jimmy Shun and Heidar A. Malki, “Network Intrusion Detection USA. Copyright 2002 ACM 1-58113-612-9/02/0011. System Using Neural Networks”, Fourth International Conference on [29.] Dit-Yan Yeung, Yuxin Ding “Host based Intrusion detection using dynamic and static behavioral models”, Pattern Recognition, Volume Natural Computation,(ICNC '08),vol.5, Oct. 18-20, 2008, pp.242-246. 36, Issue 1, January 2003, Pages 229-243 Sampada Chavan, Khusbu Shah, Neha Dave, Sanghamitra Mukherjee, Ajith Abraham, Sugata Sanyal, “Adaptive Neuro-Fuzzy Intrusion [30.] Steven T. Eckmann, Giovanni Vigna, Richard A. Kemmerer, "STATL: An attack language for state-based intrusion detection”. Computer Detection Systems”, IEEE International Conference on Information Science and Networking and Security, Volume 10, Number 1-2 / 2002, Technology: Coding andComputing,2004 (ITCC ’04), Proceedings of Pages 71-103. ITCC 2004, Vol. 1, 2004, Las Vegas, Nevada, pp. 70-74. Divyata Dal, Siby Abraham, Ajith Abraham, Sugata Sanyal, Mukund Sanglikar, “Evolution Induced Secondary Immunity: An Artificial Immune System based Intrusion Detection System”, 7th International Conference on Computer Information Systems and Industrial Management Applications, (CISIM '08), June 26-28, 2008, pp.65-70 D. Dasgupta, S. Yu, F. Nino, “Recent Advances in Artificial Immune Systems: Models and Applications”, Applied Soft Computing, Elsevier, Vol. 11, March, 2011, pp.1574-1587. Jin Yang, Yi Liu, Jian Jun Wang, Jian Dong Zhang, Bin Li, "Dynamical Immunological Surveillance for Network Danger Evaluation Model," 5th International Conference on Wireless Communications, Networking and Mobile Computing (WiCom '09), Beijing, China, Sept. 24-26, 2009, pp.1-4. F. Hosseinpour, K. Abu Bakar, A. Hatami Hardoroudi, A. Farhang Dareshur, "Design of a new distributed model for Intrusion Detection System based on Artificial Immune System," 2010 6th International Conference on Advanced Information Management and Service (IMS), Seoul, Korea, Nov. 30-Dec. 2, 2010, pp.378-383. MA Jie, SHI Ying-chun, ZHONG Zi-fa, LIU Xiang, "An Anomalistic Electromagnetism Signal Detection Model Based on Artificial Immune System," 2010 International Conference on Communications and Intelligence Information Security (ICCIIS), NanNing, China, Oct. 13-14, 2010,pp.256-260. E. Saboori, S. Parsazad, Y. Sanatkhani, "Automatic firewall rules generator for anomaly detection systems with Apriori algorithm," 2010 3rd International Conference on Advanced Computer Theory and Engineering (ICACTE), Chengdu, China,Vol.6, 2010, pp.V6-57-V6-60. Evgeniya Nikolova, Veselina Jecheva, “Some similarity coefficients and application of data mining techniques to the anomaly-based IDS”, Telecommunication Systems, December, 2010, Springer Netherlands, pp. 1-9. Asim Karim, “Computational Intelligence for Network Intrusion Detection: Recent Contributions and Security”, Computational Intelligence and Security, International Conference, CIS 2005, Xi an, China, December 15-19, 2005, Proceedings, Part I. Volume 3801 of Lecture Notes in Computer Science, pp. 170-175. Song Jianhua, Ma ChuanXiang “A reputation-based scheme against malicious packet dropping for mobile ad hoc networks”, IEEE International Conference on Intelligent Computing and Intelligent Systems, 2009. ICIS 2009, volume 3, 20-22 Nov. 2009, Pages 113 – copyright © 117, E-ISBN 978-1-4244-4738-1. Manoj Rameshchandra Thakur, Sugata Sanyal, “A Multi-Dimensional University POLITEHNICA Timisoara, Faculty of Engineering Hunedoara, 5, Revolutiei, 331128, Hunedoara, ROMANIA approach towards Intrusion Detection System” in arXiv preprint arXiv: http://acta.fih.upt.ro 1205.2340, 2012.

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Vladimir BLANUŠA, 2. Milan ZELJKOVIĆ, 3. Aleksandar ŽIVKOVIĆ

PREDICTION THERMAL ELASTIC BEHAVIOR OF THE CYLINDRICAL ROLLER BEARING FOR RAILWAY VEHICLES AND CALCULATING BEARING LIFE 1-3

Faculty of Technical Sciences, University of Novi Sad, SERBIA

Abstract: This paper presents a calculation model the thermal elastic behavior of the cylindrical roller bearing for bearings towed vehicle in railways. The present mathematical model allows to define the value of the moment friction due to lubrication, the friction moment due to the radial and axial loads. Heat generated in the bearing calculated based on the value of previously defined moments. Also, it shows the method of calculating the coefficients of conduction and convection of heat in bearing. Using programming system general purpose analyzed thermal elastic behavior of the cylindrical roller bearing for bearings axle towed vehicle in railways. Finite element method determined by temperature values in the characteristic points of the bearing depending on the speed wheel for different time periods. Also, it determined of displacement in characteristic points of bearing due to the heat load in the steady temperature state, maximal stress and bearing life. Keywords: Thermal elastic behaviour, cylindrical roller bearing for railway vehicles, finite element method

INTRODUCTION The advent of railway in the mid-nineteenth century certainly represents a significant technological innovation as it is no doubt possible to play a revolutionary role and enormous contribution to the industrial development and economic progress of society. The rapid development of the construction and exploitation railways has made a significant impact on the development of strength science and theory construction, [16], because it appeared a series of new problems (particularly in relationship with the design and construction of railways, bridges, locomotives, vagon and etc..) that should be solved. Although in comparison with other types of transport railway has a number of advantages in terms of economic viability (lower power energy and especially environmental sustainability), inefficiencies created by the railway regulations have placed restrictions on the industry that have prevented effective competition. Stoppages in innovation railway technology and inadequate answer to significant increase in the quantity goods of small packaging, reducing the goods suitable for carriage by rail (such as ore and coal), have primary explanation because of for example the share railways in freight traffic SAD that is after the Second World War was nearly 70% of intercity ton miles, up in 1975. years dropped to 37% [17]. The European Union treated rail as a transporter of the future and seeks to reaffirm rail transport, with requirement of a competitive, secure and high-quality transport all kinds of goods. Achieving these goals among other things requires the construction of modern wagons customized market challenges, specific technological

requirements and systems which to quickly perform the loading / unloading operations [2]. Cylindrical roller bearings for railway are key components of wheel towed vehicles and their cancellation can have disastrous consequences. Bearing temperature is one of the most important parameters bearing whose by monitoring the can be determined state of bearing in exploitation. For this reason were performed tests using different lubricants (grease) and based on the test results it can be concluded that the lubricant has a significant influence on the bearing temperature in exploitation. Roller bearings for railways usually lubricated with grease that are accommodated in a closed housing with bearings so as to ensure proper lubrication. During the rotation of grease comes into contact with rollers and the rings and after the certain period of time leads to the mechanical the degradation of grease. For this reason is very important replace the grease before it has loses her mechanical properties. In paper [11] were performed tests in winter and summer period (in winter temperature was -15 °C and in the summer 20 °C) and led to the values of temperature in the steady state temperature in depending on the type of grease which is used for lubrication. The temperature in winter period was between 15 ÷ 51 °C and in the summer of 33 ÷ 59 °C. The heat generated due to the rolling wheel on the rails transferred to the entire assembly wheel for railway vehicles. One part of this heat transferred to the bearings. Cole and others [3] examined this influence of experimental and computer modeling. For value generated amount of heat due to the movement of the wheel on rail (Q = 1834 W) in steady temperature state were determined by the

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

temperature in characteristic points wheel and rings bearing. In this paper is not considered the fact that due to the rotation of bearing in him generates heat which has great influence on his temperature. In addition to the heat generated due to the motion of the wheel on rail on heating assembly wheel significantly affected have the heat that is generated due to the braking locomotives and railway freight wagons (at the contact between the brake block and wheel) [4]. The value of the heat generated between the brake block and wheels, as well as the value of the mechanisms heat transfer on wheel calculated mathematically, and using the finite element method were determined by the temperature on wheel. The value of heat generated due to the contact of brake block and wheel was Q = 446 W. Verification of mathematical calculations and finite element methods performed on a laboratory plant on one side brake block of the shaft. Mohan [12] by applying the finite element method performed prediction of thermal and static behavior wheel locomotive and railway freight wagons. The value of the temperature on the flange wheel was 70 °C. Static analysis determined the value of Von Mises's stress depending on the deformations caused by the static load. The maximum displacement was on wheel and amounted to 0.2196 mm, and the maximum stress on wheel 46,34 N/mm2. Integrated thermal and static behavior in one model were determined by values of displacements and stresses on wheel. The maximum displacement on the flange wheel amounted to 1.084 mm and maximum stress on wheel amounted to 148.98 N/mm2. Preventive maintenance and remont bearing in the exact prescribed intervals is essential on bearing life. In case when remont bearing don’t make in prescribed time intervals may lead to disastrous consequences such as damage axle wheels, damaged parts rail and popping train for rails. Because of this reason it is very important change the inner ring bearing before it reaches his damage due to material fatigue that have disastrous consequences [6]. In this paper analyzes the influencing parameters that lead to damage railway line. Bearing was completely damaged due to the material fatigue that led to the cracking of the inner ring. Slipping of the inner ring on the axle has led to the generation of large of heat generated which led to the change in structure of the material in the bearing and on surface axle. MECHANISM OF HEAT GENERATION Introdiction Bearings assembly wheel railway freight wagons can make different types of bearings (cylindrical roller bearing, spherical roller and taper roller). In this paper discusses the bearing assembly wheel with cylindrical roller bearings (mark of the bearing 324 NJ EC.M1C4 VA301). On Figure 1 shows assembly wheel as well as details bearings mounted on the axle. This paper considers only the heat generated in the bearing (without heat generated by the movement of wheel on railway line). The heat generated determined on the basis of the friction torque due to lubrication and friction torque due to the load (axial and radial) [1].

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Figure 1. Assembly wheel with details bearings Determination of the friction torque 𝑀𝑀 = 𝑀𝑀0 + 𝑀𝑀1 + 𝑀𝑀2 Nmm M0- friction torque due to lubrication, M1- friction torque due to the radial load, M2- friction torque due to axial load.

(1)

3 𝑀𝑀0 = 10−7 ∙ 𝑓𝑓0 (𝜈𝜈 ∙ 𝑛𝑛)3 ∙ 𝑑𝑑𝑚𝑚 Nmm

( 2) f0 – coefficient depended of the bearing type and lubrication type (for cylindrical roller bearing it value is 3), 𝜈𝜈- kinematic viscosity of the lubrication 𝜈𝜈=18, n- bearing speed [rev/min], dm - middle bearing diameter (dm=190 mm). 𝑀𝑀1 = 𝑓𝑓1 ∙ 𝐹𝐹𝑟𝑟 ∙ 𝑑𝑑𝑚𝑚 Nmm (3) 𝐺𝐺1 𝐹𝐹𝑟𝑟 = (4) 4 𝐺𝐺1 =

𝐺𝐺

𝑛𝑛𝑡𝑡

(5)

f1 - coefficient which depends of the bearing type (for cylindrical roller bearing it value is between 0,0003-0,0004), 𝐹𝐹𝑟𝑟 - radial static load acting on one bearing (Fr= 55181 N), G1- radial static load acting on one wheel set (G1=220725 N), G- weight of the vehicle, nt- number of wheel sets. 𝑀𝑀2 = 𝑓𝑓2 ∙ 𝐹𝐹𝑎𝑎 ∙ 𝑑𝑑𝑚𝑚 Nmm (6) f2- based n dm 𝜈𝜈 i 𝐹𝐹𝑎𝑎 /𝐴𝐴, 2,1 A=𝑘𝑘𝐵𝐵 ∙ 10−3 ∙ 𝑑𝑑𝑚𝑚 (7) A-surface, 𝐹𝐹𝑎𝑎 -axial load bearing. The axial load bearing occurs when the train move a curve. For a radius curvature R = 500 m and height superelevation on one side stripes h = 110 mm can be defined by the maximum permitted speed move of the train in a curve, and it is v = 68 km/h. The value of axial load calculated for the speed of move the train in a curve of v = 50 km/h. Permissible speed of movement of the train in a curve calculated from the following equation:

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11,8∙𝑣𝑣 2

the continuity equation: (8) where V-volume air flow obtained from 𝑢𝑢 1

𝑅𝑅

for 50 km/h axial load is Fa=16479 N, and coefficient f2=0,008. Table 1 shows the values of the friction torque due to lubrication, radial and axial load, and the total value of the friction torque M for the different speed movement of the train. Table 1. The values of the friction torque n M0 M1 M2 M rev /min Nmm Nmm Nmm Nmm 300 629 4193 25080 29902 450 991 4193 25080 30264 700 1107 4193 25080 30380 Determination of the heat generated heat in the bearing Heat generated in the bearing determined by the equation (9): 2

2 𝑄𝑄𝑢𝑢𝑢𝑢𝑢𝑢 = 1,05 ∙ 10−4 ∙ 𝑑𝑑𝑚𝑚 ∙ 𝑛𝑛 �𝑓𝑓0 (𝜈𝜈 ∙ 𝑛𝑛)3 ∙ 𝑑𝑑𝑚𝑚 ∙ 10−7 +

𝑓𝑓1 ∙ 𝐹𝐹𝑅𝑅 + 𝑓𝑓2 ∙ 𝐹𝐹𝑎𝑎 ∙ 0,1� W

(9) In table 2 shows the values of heat generated during movement of the train at speed of 50, 80 and 120 km / h (operational speed bearing ). Accepted that the vagon has such a path in exploitation to move 90% straight and 10% in the curve (5 % left and 5 % right curves and the speed of movement in curve v = 50 km/h, this values have been adopted on the basis of recommendations for calculation bearing wheel car). Table 2. Value of the generated heat n Quku rev /min W 300 231 450 364 700 573 THE HEAT TRANSFER MECHANISMS IN THE BEARING Heat transfer mechanism at bearing (embedded as shown in Figure 1) are convection due to the rotation, conduction between the inner ring and the axle and the outer ring and housing [1]. Convection due to rotation the bearing Heat transfer through the bearing is realized only between bearings and surroundings air. Absorbed heat from the grease, in this paper is not discussed. Because of the small difference in temperature radiation could be neglected, coefficient of the heat transfer is calculated according to condition of the flow air through bearing which belong to the turbulent motion. At this transfer, total air flow velocity, caused by the bearing rotation, is calculated from the axial and tangential component. Surfaces for the axial flow air between the inner and outer track rolling: 𝜋𝜋 𝐴𝐴𝑎𝑎𝑎𝑎 = ∙ (𝐷𝐷2 − 𝑑𝑑2 ) 𝑚𝑚 (10) 4 Axial flow velocity could be calculated as a velocity between two cylinders, from the relation: 𝑉𝑉 4∙𝑉𝑉 𝑢𝑢𝑎𝑎𝑎𝑎 = = m2/s (11) 𝐴𝐴 𝜋𝜋∙(𝐷𝐷+𝑑𝑑)

𝑉𝑉 = 𝑢𝑢𝑠𝑠𝑠𝑠 ∙ 𝐴𝐴𝑆𝑆 = ∙ 𝐵𝐵 ∙ 𝑠𝑠 = ∙ 𝑑𝑑𝑚𝑚 ∙ 𝜔𝜔 ∙ 𝑠𝑠 ∙ 2

𝑚𝑚3

(12) In previous equation is considered medium velocity air through the cross-sectional area 𝐴𝐴𝑠𝑠 = 𝐵𝐵 ∙ 𝑠𝑠. Tangential velocity component, on the midlle diameter, could be calculated from relation for air flow between movable and immobile cylinder: 𝜔𝜔∙𝑑𝑑 𝜋𝜋∙𝑓𝑓∙(𝐷𝐷+𝑑𝑑) 2 𝑢𝑢𝑎𝑎𝑎𝑎 = 𝑚𝑚 = m /s (13) 4 2 where are: f-frequency bearing Hz, D- diameter outer ring m, d- diameter inner ring m. The resulting air velocity during rotation bearing is obtained from axial and tangential components according to [1]. 2 2 + 𝑢𝑢 2 𝑈𝑈 = �𝑢𝑢𝑎𝑎𝑎𝑎 (14) 𝑎𝑎𝑎𝑎 m /s Coefficient convection is calculate according to [1]: 𝑊𝑊 𝛼𝛼 = (𝑐𝑐0 + 𝑐𝑐1 ∙ 𝑈𝑈 2 ) (15) 𝑚𝑚2 𝐾𝐾 c0 i c1 are constants obtained experimentally (c0=10 a c1=5). In table 3 shows the values of the coefficient of convection during rotation bearing, depending on the speed. Table 3 . Values of the coefficient of convection Coefficient convection 𝑊𝑊 Speed bearing rev /min 𝐵𝐵

𝑠𝑠

𝑚𝑚2 ∙ 𝐾𝐾

250 450 700

10,5 35,3 71,2

Heat convection between ring and housing and ring and axle The coefficient of thermal conductivity depends on the gap between the outer ring and the housing and the inner ring and axle. Thermal conductivity between the two elements can be determined on the basis of equation [8]: 𝜆𝜆𝑖𝑖𝑖𝑖 =

𝑟𝑟𝑗𝑗 𝑟𝑟𝑖𝑖

𝑙𝑙𝑙𝑙� �

𝑟𝑟𝑗𝑗 𝑟𝑟 𝑙𝑙𝑙𝑙� 1 � 𝑟𝑟𝑖𝑖 𝑟𝑟1 � 𝑅𝑅𝑤𝑤 + 𝑟𝑟 + 𝜆𝜆𝑗𝑗 𝜆𝜆𝑖𝑖 1

𝑙𝑙𝑙𝑙�

(16)

where are λi i λj thermal conductivity of ring and housing. Other marks are shown in Figure 2.

𝑎𝑎𝑎𝑎

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Figure 2: Schematic representation the contact between the outer ring and housing [16]

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

In the previous equation Rw represents the thermal contact resistance on place of contact of the ring with housing, and according to [8] can be calculated as follows: 𝑟𝑟 𝑟𝑟 +∆ 𝑅𝑅𝑤𝑤 = 1 𝑙𝑙𝑙𝑙 � 1 � (17) 𝑟𝑟 𝜆𝜆 𝑖𝑖𝑖𝑖

Fascicule 1 [January – March] Tome VIII [2015]

After the calculation and after post processing obtained is graph showing the temperature distribution on elements bearing for speed n = 450 rev/min, respectively with speed moving a train of 80 km/h (Figure 5). The maximum temperature is marked with red color and equals to 54 °C and minimal with blue and equals to 53 °C in the steady temperature state bearing.

Temperature [°C]

where is Δ - clearance between outer ring and housing. On similar method are determine conduction at contact between the inner ring and axle. In Table 4 shows the values coefficient thermal conductivity of certain based on the previous equation. Table 4 .The values of coefficient thermal conductivity between the ring and the housing and ring and axle Coefficient conduction Place contact λ W/m2K Inner ring/axle 60,5 Outer ring/ housing 90,9 Figure 5. Graphical representation temperature on elements bearing Based on results of modeling in Figure 5 show temperature changes MODELING THERMAL ELASTIC BEHAVIOR on rings bearing in depending from time for three different speeds Figure 3 shows a model of a cylindrical roller bearing modeled using movement of the train (v=50, v=80 i v=120 km/h). On diagram the program system PTC Creo Parametric. This bearing used for the maximum temperature represents temperature of the inner ring and bearing assembly wheel in railways. the minimum temperature is the temperature of the outer ring. Setting the coordinate system, the choice of contact pairs (CONTA 174, Observation diagrams shows in Figure 6 can see that the steady 53 contact pairs), defining of heat generated in the bearing, the temperature state bearing with highest speed motion (n = 700 choice of the type of finite element (SOLID 87, mesh than 8021 rev/min, v = 120 km/h]) reached in shortest period of time. elements and 31720 nodes) and defining the elements between 50 km/h which there is conduction and convection heat transfer has been done 45 in the framework of preprocessing. As a result of the previous on Minimum 40 temperature Figure 4 shown discretized model considered bearing. 35 30 25 20

Maximum temperature

5000 10000 15000 20000

Time [s] Temperature [°C]

80 km/h

Temperature [°C]

Figure 3. Appearance a cylindrical roller bearing for the bearing assembly wheel for railway

50 40

Minimum temperature

Maximum temperature

20 0

5000 10000 15000 20000

Time [s] 120 km/h

70 60 50 40 30 20

Minimum temperature Maximum temperature

5000 10000 15000 20000

Time [s]

Figure 4. Appearance discretized model bearing

Figure 6. Change of the temperature on rings bearing depending on the time and speed of movement | 24 |

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Fascicule 1 [January – March] Tome VIII [2015]

Based on the previously defined thermal model (temperature fields) can be determined by displacement in nodes bearing. The thermal load is defined on basis of the results of thermal analysis, and it represents the temperature of in nodes of the bearing. On elastic model is necessary to define limits displacement and it is shown in Figure 7.

Figure 9. Distribution of stress on the bearing Bearing life for towed vehicles on railways determined following equation:

Figure 7. Constraints displacement In Figures 8 a. (displacement in the direction of x-axis), 8 b. (displacement in the direction of y-axis) and 8 c. (displacement in the direction of z-axis) shows the computer models of cylindrical rolling bearing for railway after heat load for speed n = 700 rev/min in the direction x, y and z axes. In figures shown characteristic points in which discussed displacement.

a. b. c. Figure 8. The results of computer modeling of elastic behavior of the bearing after effects of heat load The obtained results can be seen that maximum displacement in the axial direction (direction x-axis ) was 51 [μm], and in the radial direction displacement was 55 [μm]. Displacement values in characteristic points S1, S2, S3 and S4 are shown in Table 5. Table 5. Values displacement in characteristic points Values displacement characteristic points μm Axis S1 S2 S3 S4 x 51 51 51 51 y -55 0 55 0 z 0 55 0 -55 Stress (Von Misses's) appearing in bearing have a maximum value at the place of contact rollers and outer ring bearing and the amount 58 N/mm2. In Figure 9 shows the distribution of stress on the bearing.

𝐿𝐿10 =

𝐶𝐶 3 � 𝑟𝑟� 𝑃𝑃𝑟𝑟

∙ 𝜋𝜋 ∙ 𝐷𝐷𝑘𝑘 ∙ 10−3

where are: Cr-basic radial dynamic load rating (Cr=465 KN) Pr-radial equivalent dynamic load acting on one bearing

(18)

𝑃𝑃𝑟𝑟 = 𝐹𝐹𝑟𝑟 ∙ 𝑓𝑓𝑑𝑑 (19) fd-factors of additional forces (fd=1,2÷1,4) Dk-diameter of the vehicle wheel (Dk=0,92 m) On basis equation (18) and previously shown calculations obtained bearing life, which is 1 million kilometers. CONCLUSION In this paper were analyzed thermal elastic behavior cylindrical roller bearings for railway. Mathematical modeling of cylindrical roller bearing defined by the finite element method. Based on the results of thermal behavior can be seen that the maximum temperature bearing was 68 °C which is considerably less than the maximum permissible temperature of 120 °C. Maximum stress in bearing is 58 N/mm2 which is much lower than the permissible stress in bearing. The calculated bearing life corresponds to the required recommendations EN C (2006) 3345. ACKNOWLEDGEMENT In this paper presents the results of the research on project "Modern approaches in the development of special solutions bearings in mechanical engineering and medical prosthetics" TR 35025, financed by Ministry of Education, Science and Technological Development of Republic of Serbia. REFERENCES [1] Bossmanns, B., Jay, F.: A thermal model for high speed motorized spindles, International Journal of Machine Tools and Manufacture, ISSN: 0890-6955, Vol. 39, Pages 1345-1366, 1999. [2] Brkljač, N.: Proračunski modeli nosećih konstrukcija sa primenom na rešenja železničkih vagona za prevoz tereta, Doktorska disertacija, Fakultet tehničkih nauka, Novi Sad, 2013 [3] Cole, D., K., Tarawneh, M., C., Fuentes, A., A., Wilson, M., B., Navaro, L.: Thermal models of railroad wheels and bearings,

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Fascicule 1 [January – March] Tome VIII [2015]

International Journal of Heat and mass transfer, ISSN:0017-9310, Fatique, ISSN: 0142-1123, Volume 50, Page: 40-46, 2013. Volume 53, Issue 9-10, Page: 1636-1645, 2010. [19] Živković, A.: Računarska i eksperimentalna analiza ponašanja [4] Fekete, G., Varadi, K.: Thermal FE analysis of a one side brake kugličnih ležaja za specijalne namene, Doktorska disertacija, block test equipment (Part 1), Periodica polytechnic, Mechanical Fakultet tehničkih nauka, Novi Sad, 2012. Engineering, doi: 10.3311/PPme.7014, Page: 27-33, 2013. [5] FKL, Tehnička dokumentacija za ležaj NJ 324 EC.M C4 VA301, Br. 9560, Temerin, 2009. [6] Gerdun, V., Sedmak, T., Šinkovec, V., Kovše, I., Cene, B.: Failures of bearings and axles in railway freight wagons, Engineering Failure Analysis, ISSN: 1350-6307, Volume 14, Issue 5, Page: 884894, 2007. [7] Horvath, T.: A vasúti kocsik forgóvázai, Műszaki Könyvkiadó, ISBN: 963 10 6399 2, Budapest, 1987. [8] Jedrzejewski, J.: Effect of the thermal contact resistance on thermal behavior of the spindle radial bearings, International Journal of Machine Tools and Manufacture, ISSN: 08909-6955, Vol.28, No.4, Pages 409-416, 1988. [9] Lindahl, M.: Track geometry for high-speed railways, A literature survey and simulation of dynamic vehicle response, Railway Technology, Department of Vehicle Engineering, Rayal Institute of Technology, ISSN: 1103-470X, Stockholm, 2001. [10] Lukaszewicz, P.: Energy consumption and running time for trains, Modelling of running resistance and driver behavior based on full scale testing, Doctoral Thesis, Railway Technology, Department of Vehicle Engineering, Rayal Institute of Technology, ISSN: 1103470X, Stockholm, 2001. [11] Lundberg, J., Parida, A., Soderholm, P.: Running temperature and mechanical stability of grease as maintenance parameters of railway bearings, ISSN: 1751-8520, Volume 7, Issue 2, Page: 160166, 2010. [12] Mohan, M., P.: Analysis of railway wheel to study thermal and structural behaviour, International Journal of Scientific & Engineering Research, ISSN: 2229-5518, Volume 3, Issue 11, Page: 1-4, 2012. [13] Sostarics, G., Balog, V.: Vasúti járművek, Tankönyvkiadó, ISBN: 963 18 3113 2, Budapest, 1991. [14] Tepić, J., Kostelac, M., Herold, Z.: Methodology for determining of train curving resistances with respect to vehicle mass and speed, Strojarstvo, ISSN: 0562-1887, Volume 51, No. 6, Page: 641-647, 2009. [15] Tepić, J.: Istraživanje uticaja mase i brzine šinskih vozila na vrednost otpora od krivine, Doktorska disertacija, Fakultet tehničkih nauka, Novi Sad, 2006. [16] Timošenko, S. P.: Istorija otp*rnosti materijala, Građevinska knjiga, Beograd, 1965. [17] Winston, C.: The United States: Private and deregulated, str. 135copyright © 153 / Competition in the railway industry: An international University POLITEHNICA Timisoara, Faculty of Engineering Hunedoara, comparative analysis, Massachusetts, SAD, 2006. 5, Revolutiei, 331128, Hunedoara, ROMANIA [18] Yasniu, O., Lapusta, Y., Pyndus, Y., Sorochak, A., Yasniy, V.: http://acta.fih.upt.ro Assessment of lifetime of railway axle, International Journal of | 26 |

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Richard JANURA, 2.Jozef JURČÍK, 3.Miroslav GUTTEN, 4.Daniel KORENČIAK

TRANSFORMER INSULATION ANALYSIS BY TIME DOMAIN METHOD 1-4.

Department of Measurement & Applied Electrical Engineering, Faculty of Electrical Engineering, University of Žilina, Žilina, SLOVAKIA

Abstract: The article discusses the state of transformer insulation. For a more accurate determination of the transformer insulation state

are used three methods. The measurement of insulation resistance is the basic method and is set in the standard, value demonstrates the state of total insulation of transformer. Because the determination of moisture content of the paper insulation of transformer is very difficult process and it is necessary take a sample of paper, in this case is used method of return voltage. Return voltage measurement is more complex method and in many cases is determine a clear result very difficult. For evaluation of results have mainly impact moisture content and degree of aging of paper insulation and of course, content of conductive impurities in oil. Because the moisture content in oil is much lower than in the paper, return voltage measurement is used to determine the moisture content in paper insulation only. To confirm the results of return voltage measurement is used frequency domain spectroscopy, which clearly, according computational model, calculates the moisture content in the paper insulation. Keywords: transformer; return voltage; insulation resistance; polarization index; time domain; paper; oil INTRODUCTION

Operating conditions has a major impact on aging of individual parts of transformer and also affect the change of the major electrical and mechanical properties. To the check of the condition greatly contributes electro-technical diagnosis, whose main task is to find a clear relation between the change in functional characteristics of the machine and some measurable values. The assessment of these measured values must be visible not only the level of change, but also whether it is a permanent or reversible state. The aim of diagnostics of transformers is to verify that the machine complies with the determined conditions in accordance with standards [1]. Economically reliable and effective power delivery always is the primary concern to utilities all over the world. Insulation diagnostics is one of the requirements for safe operation of transformers. Conventional methods to assessment of insulation condition are its loss factor, insulation resistance and partial discharge measurement, etc. These methods, however, provide only partial picture about the polarization processes in insulating material. Deregulation of power market has increased the competition and also emphasized on the search for the new, efficient and effective methods for diagnosing the insulating system. The use of the return voltage method is significant way to detect ageing of the insulation of operating power transformer in a non-destructive manner [2]. MEASUREMENT THEORY A. Insulation resistance of winding Insulation resistance usually responds to the weakest point of the transformer insulation system and its decline is often coupled with the

influence of conductive impurities and moisture. In measuring of the insulation resistance are read two values of the absorption current in 15 and 60 seconds after the applied of voltage. Absolute size of the insulation resistance is value measured in 60 seconds after the applied of voltage. Both values of the absorption current are necessary for the determination of polarization index pi from the equation: i (1) p i = 15 , i 60 where i15 is the absorption current to 15 seconds and i60 is the absorption current in 60 seconds after the applied of voltage to the transformer [1]. Additional variable characterizing the transformer insulation system is the time constant τ, whose absolute value is independent of the geometric dimensions of the winding. Time constant is calculated from measured values of insulation resistance and capacitance of the transformer. τ = R 60 C 50 (2) where R60 is insulating resistance in 60 seconds after the applied of voltage and C50 is capacitance of insulation measured at 50 Hz. The value of the polarization index for new and transformers after revision should be at least 1.7 [1]. B. Return voltage When a direct voltage is applied to a dielectric for a long period of time, and is then short circuited for a short period, after opening the short circuit, the charge bounded by the polarization will turn into free charges i.e., a voltage will build up between the electrodes on the dielectric. This phenomenon is called the return voltage. Now, the

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

process of polarization and the equations to describe this process will be described in [3], [4]. When a dielectric material is charged with an electric field the material become polarized. The total current density is the summation of the displacement current density and the conduction current density, which is given by dD j (t ) = σE (t ) + , (3) dt where σ is the direct conductivity, and is the electric displacement given by (4). D (t ) = εE (t ) + ∆P (t ) = ε 0ε r E (t ) + ∆P (t ) (4) where ε0 is the vacuum permittivity, and εr is the relative permittivity at power frequency. The ΔP(t) term is related to the response function f (t) by the convolution integral shown in (5). t

∆P (t ) = ε 0 ∫ f (t −τ )E (τ )dτ . 0

(5)

If we expose the insulation to a step voltage at time t = 0 the charging current density is given by (6) j p = E (σ + ε 0f (t )) . If we consider the case where an insulation system with geometrical capacitance C0 is exposed to a step voltage, Ua, the polarization current can be given by σ  (7) i p = C 0U a  + f (t ) .  ε0  If the step voltage is now disconnected from the insulation i d = −C 0U a [f (t ) − f (t + t ch )] (8) gives the depolarization current. The charging time normally should be at least ten times larger than the time for which the response function is calculated then the second term in (8) can be neglected. Therefore, the response function becomes proportional to the depolarization current. Hence, the response function and conductivity can be calculated simultaneously by using polarization and depolarization currents. Very often, the response function needs to be expressed in a parameterized form. The response function can be written in the general form: A . (9) f (t ) = n m t  t    +   t0  t0  The response function describes the fundamental memory property of any dielectric system and can provide significant information about the insulation material. After opening the short circuit, the charge bounded by the polarization will turn into free charges i.e., a voltage will build up between the electrodes on the dielectric. This phenomenon is the return voltage. The return voltage arises from the relaxation processes inside the dielectric material. The current density during the return voltage measurement is zero and d d t j (t ) = σE (t ) + ε 0ε r E (t ) + ε 0  ∫0f (t −τ )E (τ )dτ  (10)  dt dt 

Fascicule 1 [January – March] Tome VIII [2015]

gives the expression of current density, where E(t) is the electric field resulting from the return voltage build up across the open circuited dielectric. Equation (10) shows that the return voltage depends on the conductivity σ, relative permittivity εr and dielectric response function f(t). These parameters are all affected by aging and moisture in the insulation. The response function can be obtained from the polarization and depolarization currents. These currents depend on the geometric capacitance and on the applied step excitation. The response function and conductivity can be calculated from equations (7) and (8) if the geometric capacitance of the transformer composite insulation is known. If the proper geometry of the transformer oilpaper insulation is known then by solving (10), return voltage for a transformer can be estimated. The return voltage also depends on the applied electric field and if the dielectric material is assumed to be linear this problem is resolved easily for the interpretation of results [5]. A modeling tool can be very useful to investigate the impact of geometry on return voltage results [6]. TRANSFORMER MEASUREMENT A. Insulation resistance and polarization index The measurement was performer in the laboratory of the Department of measurement and applied electrical engineering on the transformer, which parameters are given in table 1. Table 1. Tested transformer parameters Connection Yz1 Power 30 kVA Voltage transfer 22 / 0.4 kV Current ratio 0.787 / 43.3 A Year of production 1958 Manufacturer BEZ

The transformer wasn’t before this measurement in operation for over two years and the oil state was deliberately under the operation level. Firstly the insulation resistance and polarization index was measured by MEGGER series 1-5000. The low and high voltage terminals were connected to test voltage 2500 V in measuring the insulation resistance of the windings. Results of the measurement are shown in table 2. Table 2. Insulation resistance measured values Test voltage 2500 V After 1 min 3.85 GΩ Insulation resistance After 5 min 5.8 GΩ After 10 min 6.33 GΩ Polarization index 1.64

According to (1), the absolute size of the insulation resistance is equal to 3.85 GΩ. As was expected, the value of polarization index is below 1.7, but the measured value 1.64 is above the assumptions and says that the insulation is in very good condition. The value of the polarization index in such transformers is approximately 1.4. B. Measurement and evaluation of return voltage To measure of return voltage can be used, for example, device RVM 5462. Because we used two separated devices – DC source and switch panel, which consists of electromechanical switching relays, the disadvantage is theimpossibility to perform measurements at

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Fascicule 1 [January – March] Tome VIII [2015]

charging times below 1 second. Return voltage measurement consists of four steps (figure1 and figure 2): 1. Charging (during the time tc the voltage is connected to LV and HV terminals), 2. Discharging (during the time t d = tc / 2 LV and HV are shortcircuited), 3. Measurement Umax and tmax (measured voltage between LV and HV terminals), 4. Recovery before the next cycle (during the time t = tcLV and HV terminals are short-circuited).

Figure 1. Return voltage measurement connection

Umax

2 tctdtmax

400

6s 12s

300

24s

200

48s

100

96s

0 0

t(ms)

500

next cycle

400 300

recovery

200

Figure 2. The test voltage shape

Table 3 shows the measured and calculated values from return 100 voltage measurement. The time constant is equal to the time, 0 0 at which the value of voltage 0.63Uss is reached: t (Uτ ) ≅ t (0.63U ss ) . The voltage Uss is steady-state value at different times of charging. tc (s) 2 4 6 12 24 48 96

Umax(mV) 600

dUr/ dt 1

500

Figure 3. Dependence of voltage in time at different times of charging Figure 4 shows the dependence of the maximum voltage response by charging time, from which is apparent that at lower charging times tc< 2 s, the curve took the opposite, thus decreasing tendency. This phenomenon shows that the transformer insulation is on the border of operable condition and before the full load of transformer is necessary to carry out oil filtration andthen slowly increase the transformer load by reason of residual moisture content in paper insulation.

Ground

U(mV) 600

Table 3. Measured and calculated values of return voltage Umax tmax Uss Uτ τ (mV) (ms) (mV) (mV) (ms) 587.50 12.5 542.41 341.72 2.3034 493.75 14.5 481.69 303.46 2.4547 443.75 16.7 386.16 243.28 2.5621 437.50 16.9 390.35 239.62 2.6224 362.50 19.1 312.05 196.59 2.3956 212.50 13.1 208.48 131.34 2.3016 162.50 10.9 147.77 93.09 2.2839

tc(s) 100

Figure 4. Maximum voltage response

at different times of charging

tmax (ms) 25 20 15 10 5

From the measured values were compiled curves (fig. 3-fig. 6). Figure 3 shows the measured voltage values at time for different times of charging. From this curves it is obvious that the maximum voltage response was reached at the time of charging tc = 2 s.According to [7] and [8] could be stated that the maximum size of voltage response was reached at the point 2 s, which implies that the moisture content is approximately 3.5%. Figure 5 shows time in which the maximum voltageis reached for different charging times. As the curve shows, the longest time to achieve the maximum voltage response was for charging time tc = 24 s.

0 0

tc (s) 100

Figure 5. Time in which the voltage peak was achieved

at different times of charging From the measured values,the time constant at different charging times was calculated.The curve is depicted on fig. 6. It shows that the values at different charging times are not much uneven, so could be declared that the dependence of the time constant of the equivalent circuit of the insulation system is independent on time of operation of DC voltage in the range of measured times. The average value was τA = 2.417 ms.

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2

Fascicule 1 [January – March] Tome VIII [2015]

τ (ms)

80 tc (s) 100

Figure 6. Time constant at different times of charging CONCLUSION Return voltage measurement was designed for cable insulation state investigation. The most of measuring devices for cable investigations don’t allow measurement at different times of charging or discharging. Whereas the cable insulation like transformer windings insulation could this measuring method use also for transformers. It doesn't matter whether the insulation is dry or oleic. Due to the large use of oil transformers was this measurement aimed right at them. We could obtain moisture level content in oil transformers with using the RVM method too. An attempt has been made in order to use the initial slope of the decay voltage and the initial slope of the return voltage (single cycle) to separately investigate the moisture and ageing in the oil impregnated paper insulation. From the results, it could be seen that in some situations the initial slope of the decay voltage could provide a good indication of the moisture level. The initial slope of the single cycle RVM reflects the combined effect of ageing and moisture. As in many other methods also in RVM is difficult to evaluate the results but in combination with PDC method a more accurate evaluation of the measurement results could be achieved. Moisture content in paper and oil insulation of transformer could be more reliably determined using FDS method. The final moisture contents of the paper insulation by RVM and FDS methods are almost identical. Moisture content determined by RVM is approximately 3.5 % and by the FDS method is 3.3%. The advantage of using both methods is their similarity and accurate determination of moisture content in paper insulation of transformer is therefore simpler.

Acknowledgment This work was supported by the Grant Agency VEGA from the Ministry of Education of Slovak Republic under contract 1/0624/13. References [1.] MENTLÍK, V. et al., Diagnostics of electrical equipment. Prague: BEN, 2008. 439 p. ISBN 978-80-7300-232-9. [2.] MONATANARI G. C., Polarization and space charge behavior of unaged and electrically aged crosslinked polyethylene, IEEE Trans. Dielectr. Electr. Insul., vol. 7, pp 474-479, 2000. [3.] GAFVERT, U. et al., Modeling of dielectric measurements on power transformers, in Proc. CIGRE Session, Paris, France, Aug. 30-Sept. 5, 1998, Paper 15-103. [4.] JONSCHER, A. K., Dielectric relaxation in solids. New York: Chelsea Dielectric, 1984.

[5.] Electrical and chemical diagnostics of transformer insulation, Part A: Aged transformers samples, IEEE Trans. Power Delivery, vol. 12, pp. 1547-1554, Oct. 1997. [6.] SAHA, T. K., YAO, T. Z. Experience with return voltage measurements for assessing insulation conditions in service-aged transformers, IEEE Trans. Power Delivery, vol. 18, pp. 128-135, Jan. 2003. [7.] JURČÍK, J.: Analysis of insulating state on transformer model using PDC method, Elektro 9th International Conference, Rajecké Teplice, SR, pp. 423-426, May 2012. [8.] FILIPOVIĆ-GRČIĆ, B., FILIPOVIĆ-GRČIĆ, D., UGLEŠIĆ, I.: Modeling of polarization in oil-paper insulation using recovery voltage measurements. In: International review of electrical engineering. Vol. 6, 2011, ISSN 1827-6660, No. 1, p. 430-437. [9.] JURČÍK, J., GUTTEN, M., KORENČIAK, D.: Analysis of transient actions influence in power transformer, In: Advances in Electrical and Electronic Engineering, Vol. 9, 2011, ISSN 1804-3119, No. 2, p. 65-69. [10.] BRANDT, M., FAKTOROVÁ, D., SEEWALD, R.: Identification of the breakdown and analysis of transformer 22/0,4 kV, In: Materials Engineering, Vol.20, No.4, 2013, ISSN 1338-6174. [11.] PROSR, P., BRANDT, M., MENTLÍK, V., MICHALÍK, J.: Condition asssessment of oil-paper transformer insulating system. In: Journal of energy and power engineering. Vol. 5, 2011, ISSN 1934-8975, No. 2, p. 173-178.

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Daniel R. WEISZ, 2. Felix A. HIMMELSTOSS

LED CONVERTER WITH LIMITED DUTYCYCLE Department of Energy and Industrial Electronics, University of Applied Science Technikum Wien, Vienna, AUSTRIA 1-2.

Abstract: Light emitting diodes (LEDs) can be used for many lightning applications in offices, in homes, and in streets. A special converter

with limited duty cycle for driving LEDs is treated. The basic analysis is done resulting in dimensioning equations of the converter. The basic analyses have to be done with idealized components (that means no parasitic resistors, no switching losses) and for the continuous mode in steady (stationary) state. A mathematical model based on state-space description is derived. Some experimental results are shown. The converter is useful for street, home, and automotive lightning applications. Keywords: LED converter; limited duty cycle; peak-current-control; high-power LED INTRODUCTION Light emitting diodes (LEDs) can be used for many lightning applications in offices, in homes, and in streets. There exists a rich literature about converter topologies and control. The [1] shows a classical boost converter used to drive a series connection of LEDs. In [2] a good overview about possible converter topologies is given. Buck, boost, buck-boost, flyback and a resonant converter are treated. Peak current control is used. The control concepts of peak and hysteresis control are discussed in [3]. The voltage controlled non-inverting buckboost and the Sepic converter are explained in [4] and [5], respectively. A system analysis and a control description for a boost converter are given in [6]. A combined power factor corrector and LED driver based on a flyback converter is explained in [7]. An interesting concept based on a kind of three-level converter is shown in [8]. Deep insight views on power electronics are given in [9, 10].

of the converter is that a duty cycle greater than 0.5 is necessary as will be shown in the following section. BASIC ANALYSIS The basic analyses have to be done with idealized components (that means no parasitic resistors, no switching losses) and for the continuous mode in steady (stationary) state. A good way to start is to consider the voltage across the inductors. The duty cycle d is the ratio of the on-time of the active switch related to the switching period. Since for the stationary case the absolute values of the voltage-timeareas of the inductors have to be equal (the voltage across the inductor has to be zero in the average), we can easily draw the shapes according to Figures 2 and 3. (Here the capacitor is assumed to be so large that the voltage can be regarded constant during a pulse period). The shapes are drawn with a duty cycle of 70%. The forward voltage of an LED is symbolized by VD.

Figure 1 .Converter schematic

The here described converter was first published in the patent literature [12] and is shown in Figure 1. The converter consists of an active switch (S), two inductors (L1, L2), one capacitor (C), and two strings of LEDs. The upper one has m diodes (D1b till Dmb) and can be replaced by only one diode, working as a freewheel path. The other string has n diodes connected in series (D1a till Dna) which is in series to the second inductor and is the main light source. The current through this series connection can be easily controlled by a bang-bang controller. The special feature © copyright Faculty of Engineering - Hunedoara, University POLITEHNICA Timisoara

Figure 2. Voltage across inductor L1

Figure 3. Voltage across inductor L2

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The equal voltage-time-areas of inductor L1 are U 1 ⋅d ⋅T = (U C + mVD )⋅(1− d )⋅T and therefore the capacitor mean voltage in steady-state is

The current through the first inductor depends on the load (LED) current (1) and the duty cycle. The mean value of iL1i s always larger than the current through the load. DIMENSIONING OF THE COMPONENTS U ⋅d − mVD ⋅(1− d ) (2) UC = 1 Capacitor (1− d ) The change of the capacitor voltage during one period can be described The equal voltage-time-areas of inductor L2 are (3) by ( −nVD + U C )⋅d ⋅T = (nVD + U 1 + mVD )⋅(1− d )⋅T dT 1 (8) ∆u C1 = ⋅ ∫ i C1dt and therefore the mean voltage across the series connection D1a till C 0 Dna(output voltage of the converter U2) in steady-state is U 1 − 2d the duty cycle can be calculated to With M = 2 = U 1 ⋅(1− 2d ) − mVD ⋅(1− d ) U 1 (d − 1) (4) U2 = U +U (d − 1) d= 2 1 (9) U When only one free-wheeling diode is used instead of the series 2 + 2U 1 connection D1b till Dmb, the idealized voltage transformation rate of the The capacitor can now be dimensioned by 1 U 1 +U 2 1 converter is C= ⋅I LED ⋅ ⋅ (10) f ∆u C 2U 1 + U 2 U 2 1− 2d (5) M= = U 1 (d − 1) The higher the switching frequency f the lower is the capacitor value. The duty cycle must be greater equal than 0.5 and smaller than one. If Inductors the duty cycle is smaller than a half, the output voltage would change With the chosen current ripple ∆I L1 and ∆I L 2 of the inductors, the its sign. That is impossible due to the used semiconductors. The inductor values can be calculated out of the basic equation of the converter is a step-up-down converter, useful for step-up rates of up to inductor to about four. Figure 4 shows the voltage transformation rate of the U U +U 1 (11) L1 = 1 ⋅ 1 2 ⋅ converter. ∆I L1 2U 1 + U 2 f U U +U 1 L2 = 1 ⋅ 1 2 ⋅ ∆I L1 2U 1 + U 2 f

Figure 4 . Voltage transformation rate in dependence of the dutycycle

In steady-state the mean-value of the current through a capacitor must be zero. Therefore, the positive and the negative current-time-areas must be equal. With the mean values of the inductor currents, one can write (6) d ⋅I L 2 = (1− d )⋅I L1 The mean value of the current through inductor L2 is equal to the mean value of the current through the LED string (D1a till Dna) (7) I LED = I L 2 The current through the inductors has a pronounced current ripple (shown in Figure 5) depending on the voltage and the inductor value.

Voltage stress of the semiconductors The highest voltage stress of the active switch is during the freewheeling stage and is (13) U S = UC + U 1 + mVD which can be converted to (14) U S = 2U 1 + U 2 + mVD Using a free-wheeling diode and ideal devices one gets (15) U S = 2U 1 + U 2 The maximum stress across the free-wheeling diode or the LED string D1b till Dmb occurs during the on-time of the active switch and its absolute value is the same as in (15). Current stress of the semiconductors When the active switch is on, the sum of the inductor currents is flowing through it. Using the mean values one can calculate the mean value of the current through the active switch according to (16) I S = (I 1 + I 2 )⋅d The maximum value of the current through the active switch is ∆I + ∆I L 2 (17) I max, S = I 1 + I 2 + L1 2

Figure 5 .Current through the capacitor

(12)

Using the mean values (assuming that the inductor current ripple is low) one can approximately calculate the rms value to (18) I rms ,S = (I 1 + I 2 ) ⋅ d When the active switch is off, the sum of the inductor currents is flowing to the freewheeling diode or the LED string D1b till Dmb. Using | 32 |

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the mean values one can calculate the mean value of the current through the passive switch or the diode string acting as the freewheeling path according to (19) I S = (I 1 + I 2 )⋅(1− d ) The maximum value of the current through the passive switch is equal to the active switch and can be again calculated by (17). Using the mean values (assuming that the inductor current ripple is low) one can approximately calculate the rms value to Figure 7. Equivalent circuit for state 2 (20) I rms ,S = (I 1 + I 2 )⋅ (1− d ) The describing equations are STATE SPACE MODEL d iL1 − i L1 ⋅(RL1 + RD 2 + RC 1 ) − i L 2 ⋅RD 2 − mV D−uC 1 (25) = The state variables are the inductor currents iL1, iL2, and the capacitor dt L1 voltage uC. The input variables are the input voltage u1 and the fixed d iL 2 − i L1 ⋅RD 2 − i L 2 ⋅(RL 2 + RD 1 + RD 2 ) − mVD − nVD − u1 (26) forward voltage of the LED strings mVD and nVD. The LEDs are modeled = dt L2 as a fixed forward voltage VD and an additional voltage drop depending duc i L1 on the differential resistor of the LED diodes RD). The other parasitic (27) = dt C 1 resistances are the on-resistance of the active switch RS, the series resistance of the converter coils RL1, RL2, and the series resistor of the leading to the state-space matrix description according to 1 R capacitor RC.  − (RL1 + RD 2 + RC 1 ) − D2 −   L1 L1 L1   i  In continuous inductor current mode there are two states. In state one  iL1    L1  RD 2 (RL 2 + RD 1 + RD 2 ) d   0  ⋅ iL 2  + − − the active switch is turned on and the passive switch or the LED string  iL 2  =  L2 L2 dt      D1b till Dmb is turned off. Figure 6 shows switching state one.  uC     uC  (28) 1 

0  1 + −  L2  0

Figure 6 . Equivalent circuit for state 1

(21) (22) (23)

leading to the state-space matrix description according to  − (RL1 + R S )

  iL1  d     iL 2  =  dt     uC  



1 L 1 + 0  0 

L1 RS − L2

R − S

(R + R + R + R ) − L2 D1 S C 1

0  0    1  ⋅ (U 1 ) + −  L2    0 

−

0   i  L1  1     ⋅ iL 2  + L2      uC  0  

0     ⋅ (U 1 ) + − 1  L2     0



 1 − L    1   ⋅(nVD ) + − 1  ⋅(mVD ).  L    2  0      

Under the condition that the system time constants are large compared to the switching period, we can combine these two sets of equations (24, 28) to the state-space model

The state space equations are now

d iL1 − i L1 ⋅(RL1 + R S ) − i L 2 ⋅R S + u1 = dt L1 d iL 2 − i L1 ⋅R S − i L 2 ⋅(R L 2 + R D 1 + R S + R C 1 ) − nVD + u C = L2 dt duc − i L 2 = dt C

      

(24)

 0    ⋅(nVD ) + 0  ⋅(mVD ).     0  

 i L1  d  i  = dt  L 2     uC  [d ⋅ R + (1 − d ) ⋅ (R D 2 + RC 1 ) + R L1 )] [d ⋅ R + (1 − d ) ⋅ R D 2 ] (d − 1) − S − S L1 L1 L1 [d ⋅ R S + (1 − d ) ⋅ R D 2 ] [d ⋅ (R S + RC 1 ) + (1 − d ) ⋅ R D 2 + R L 2 + R D 1 )] d − − L2 L2 L2 (1 − d ) d 0 − C C  d  (d − 1)   L  L    0 1   1     (d − 1)   (d − 1)  1   + ⋅ (nVD ) +   ⋅ (U 1 ) + −  ⋅ (mVD ). L   L2   L2   2   0 0  0          

  i    L1   ⋅  iL2  +      uC  

(29)

By this equation the dynamic behavior of the converter is described correctly in the average. The superimposed ripple (which appears very pronounced in the coils) is of no importance for qualifying the dynamic In state two the active switch is turned off and the passive switch or the behavior. This model is also appropriate as large-signal model, LED string D1b till Dmb is turned on. Figure 7 shows this switching state because no limitations with respect to the signal values have been two. made. | 33 |

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[2] H. Van der Broeck, Power driver topologies and control schemes for EXPERIMENTAL MODEL OF THE CONVERTER LEDs, Applied Power Electronics Conference, APEC 2007 - Twenty In Figure 8 a picture of the experimental converter is shown. The values Second Annual IEEE, Feb. 25 2007-March 1, 2007, pp. 1319-1325. of the devices are included. Five LUXEON Altilon LED were used. The [3] In-Hwan Oh, An Analysis of Current Accuracies in Peak and Hysteretic Current Controlled Power LED Drivers, Applied Power Electronics typical of the forward voltage of one chip is about 6.4 V. [4]

[5]

[6]

Figure 8 . Experimental Converter

In Figure 9 the voltage across the capacitor, the current through the load, and the drain voltage of the active switch are shown. Due to an [7] RCD snubber the spikes at switch-off are minimized. [8] [9] [10] [11] Figure 9 . Voltage across the capacitor (turquois), the current through the load (green), and the drain voltage of the active switch (blue)

Figure 10 shows the converter with a series connection of five LED in [12] action.

Conference and Exposition, APEC 2008, Twenty-Third Annual IEEE, Feb. 2008, pp. 572-577. Wing Yan Leung, Man, T.Y. and Chan, M., A high-power-LED driver with power-efficient LED-current sensing circuit, Solid-State Circuits Conference, ESSCIRC 2008, 34th European, 15-19 Sept.2008, pp.354357 Zhongming Ye, Greenfeld, F. and Zhixiang Liang, Offline SEPIC converter to drive the high brightness white LED for lighting applications, Industrial Electronics, IECON 2008, 34th Annual Conference of IEEE, 1013Nov. 2008, pp. 1994-2000 Ray-Lee Lin and Yi-Fan Chen, System Analysis of CCM Dual-Loop Controlled Light-Emitting-Diode Boost Driver, IEEE Industry Applications Society Annual Meeting, IAS 2009, 4-8 Oct. 2009, pp.1-6 Ying-Chun Chuang, Yu-Lung Ke, Hung-Shiang Chuang and Chia-Chieh Hu, Single-Stage Power-Factor-Correction Circuit with Flyback Converter to Drive LEDs for Lighting Applications, IEEE Industry Applications Society Annual Meeting (IAS), 3-7 Oct. 2010, pp. 1-9 Cong Zheng, Wensong Yu, Jih-Sheng Lai and Hongbo Ma, Single-switch three-level boost converter for PWM dimming LED lighting, Energy Conversion Congress and Exposition (ECCE), 2011 IEEE, pp. 2589-2596 N. Mohan, T. Undeland and W. Robbins: Power Electronics, Converters, Applications and Design, 3nd ed. New York: W. P. John Wiley & Sons, 2003. Zach, F.: Power Electronics, in German: Leistungselektronik, Wien: Springer, 4th ed., 2010. Masahiro Nishikawat, Yoichi Ishizukat, Hirofumi Matsuot and Koichi Shigematsut, An LED Drive Circuit with Constant-Output-Current Control and Constant-Luminance Control, Telecommunications Energy Conference, INTELEC '06, 28th Annual International, Sept. 2006, pp. 16. F. A. Himmelstoss, Stellglied mit eingeschränktem Tastverhältnis zur Ansteuerung von lichtemittierenden Dioden, Patent A512118 B1, 201309-15 (filed 2011-10-18).

Figure 10 . Converter in action

CONCLUSION A novel LED converter with limited duty cycle was analyzed. The advantage of this converter is its continuous output current and a duty cycle which is always greater than 0.5. If loss-less snubbers are used, more than the half switching period is available to discharge the snubber capacitor. The input and the output have the same reference point (ground) so avoiding common mode disturbance. The current can be controlled with a standard current control IC. The freewheeling path can also be used to drive further LED in series. The converter is easily dimmable. References [1] Ray-Lee Lin and Yi-Fan Chen, System Analysis of CCM Dual-Loop Controlled Light-Emitting-Diode Boost Driver, IEEE Industry Applications Society Annual Meeting, 4-8 Oct. 2009, pp. 1-6.

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Vladimir CHUDACIK, 2. Ladislav JANOUSEK, 3. Milan SMETANA

EVALUATION OF SPATIAL COMPONENTS ON EDDY CURRENT TESTING RESPONSE SIGNALS OF SELECTED DEFECT PARAMETERS Department of Electromagnetic and Biomedical Engineering, Faculty of Electrical Engineering, University of Zilina, SLOVAKIA

1-3.

Abstract: In this article, the presence of inhom*ogeneities in solid electrically conducting plate is inspected by non-destructive way with use of eddy current testing method where the perturbed electromagnetic field caused by the defect is detected. We perform three-dimensional finite element simulations of this structure with pre-defined material inhom*ogeneities and they are evaluated by an induction coil. This study is motivated by the novel eddy current testing technique which is based on sensing of all the three components of the perturbed field. Basically we performed parametric study to quantify the impact of various parameters - depth and electrical conductivity of the inhom*ogeneity. The analyses provide reference results to understand the effectiveness, feasibility and capability of this approach. Keywords: spatial components, three-axes sensing, eddy current testing coil, material inhom*ogeneities

INTRODUCTION The importance of non-destructive testing (NDT) and evaluation (NDE) of the materials increase along with industrial development and the need of optimal and cost-efficient material consumption. The continuous assessment of material characteristics during the production process is used to increase the quality of the end product but also to avoid additional production costs. Controlling during the operation is valuable information. It can help to increase the overall reliability and maintain the required safety of the product. These requirements are followed by a strong demand on development of new NDT techniques which can overcome some of the limitations of already available techniques, [1]. Development of new testing techniques, which allow preventing functional losses, is still continuing and their number went up to over a hundred. Especially the electromagnetic methods are widely spread due to their simplicity and flexibility of application. Among these methods the eddy current testing (ECT) is predominant for examination of non (fero-) magnetic materials. It can be applied for detection of close-to-surface defect anomalies which lead to a change in electrical conductivity. The principle of this method lies in electromagnetic induction phenomena. When an alternating current is used to excite a coil, an alternating magnetic field is produced and magnetic lines of flux are concentrated at the center of the coil. Then, as the coil is brought near an electrically conductive material, the alternating magnetic field penetrates the material and generates continuous, circular eddy currents as shown Figure1. As the penetration of the induced field increases, the eddy currents become weaker, therefore larger eddy currents are produced near the test surface.

Figure 1. Distribution of the current field in a conductive material sample with non-conducting defect

The induced eddy currents produce an opposing (secondary) magnetic field, Figure1. This opposing magnetic field, coming from the material, has a weakening effect on the primary magnetic field and the test coil can sense this change. In effect, the impedance of the test coil is reduced proportionally as eddy currents are increased in the test piece. Changes in the coil impedance (self inductance sensor) or in the induced voltage (mutual inductance sensor) due to a presence of discontinuity are sensed during mechanical movement of a sensor over an inspected region of a material. The main purpose is the detection and reliable characterization of defects or inhom*ogeneities. Eddy current probe is the main link between an eddy current instrument and a component under the test. Success of eddy current testing for a specific inspection application depends on sensor, instrument and on selection of test parameters. The probe plays two important roles: it induces the eddy currents and it senses the distortion of their flow caused by the defects.

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inspected in this study, shown Figure 4. The material has the conductivity of σ = 1.35 MS/m and the relative permeability of μr = 1.

Figure 2. Basic principle of the ECT method

The design and development of eddy current probes is very important as it is the probe that dictates the probability of detection, sensitivity, resolution and the reliability of characterization. Traditional eddy current testing methods based on excitation-detection coils is fundamentally limited by the lower sensitivity of the detection coils at low frequencies. Nowadays, different types of magnetic detection elements such as Hall sensors, SQUID, GMR, Fluxgate, AMR and others have been employed in order to increase the detection probability and the sensitivity. The main focus in these research areas nowadays is to increase the information value of the detected response signal to get more information about the dimensions of the material defect. For this purpose was used new approach where all the three (X, Y, Z) axes of electromagnetic field are sensed. These components are evaluated and analyzed by numerical simulations and their influence to different inhom*ogeneities parameters (depth, electrical conductivity) of all electromagnetic components is presented. NUMERICAL MODELING Definition of the problem The model of the simulated problem was investigated by numerical way. Commercially available software for numerical analyses of electromagnetic fields OPERA 3D, based on the finite element method, is employed for the above-mentioned purposes. The eddy currents are driven by a circular coil standard self-inductance probe, shown Figure3. The probe is positioned normally in a view of the plate surface with lift-off 1 mm. The coil is driven by the harmonic current with a frequency of f = 10 kHz and current density J = 2 A/mm2.

Figure 4. Dimensions of the inspected material

The non-conductive defects with rectangular shape are modeled and positioned in the middle of the plate. The defects have a width of wc = 0.2 mm, a length of lc = 10 mm and their depth dc and electrical conductivity are varied according to Table1. The electrical conductivity is changing from σd= 0% to 10% of the base material conductivity. These interpretations are used for modeling of the stress corrosion cracks. Only one parameter is varied in numerical simulations for one case, while other parameters are kept constant.

Figure 5. Dimensions of the simulated imhom*ogeneity Table 1. Change in parameters of the Defects Depth (dc) [mm] 0 1 2 3 4 5 6 7 Conductivity [%] 0 1 2 5

The inspection of the material is realized as a 2D scan. In order to assure a thorough inspection of the sample, the coil moves over the material surface in both X and Y axes as shown Figure 4. The three spatial components of the magnetic flux density vector Bx, By, Bz with respect to coordinate system are considered as response signals. NUMERICAL SIMULATIONS RESULTS Eddy current method does not provide a direct measure of the size or severity of the defects. The response signal is usually found by subtracting the reference signal from the one gained over a defect. A reference signal is collected over a defect-free region. Any flaws, defects, or conductivity and dimensional changes produce the changes in the response signal. Figure 3. Dimensions of the coil Conductive plate specimen with a thickness of h = 10 mm and having The peak value of gained differential response signals for all three the electromagnetic parameters of the stainless steel SUS316L is spatial components of the magnetic flux density vector has been identified as an important characteristic of the response signals. | 36 |

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Figures 6-8 show the surface distribution of the maximum values of the differential response signals for all the three spatial components of magnetic flux density vector B. The surface distribution is different for different defect dimension and properties and it also influence the maximum value of each spatial component. The position of the maximum value depends on the analyzed defect parameter.

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Impact of defect parameters on response signals The impact of defect parameters on responses is analyzed in this section. Real defects are mostly represented by fatigue cracks or stress corrosion ones. The area of fatigue crack is narrow and nonconductive, while the stress corrosion crack has more complicated structure, which is wider and particularly conductive. Hence, in numerical simulation the defect depth and electrical conductivity has been changed according to Table1.

Figure 6. Surface distribution of the differential signal Bx; defect 0.2x10x3mm, probe position x,y=[0,0]mm above a middle of defect Figure 9. The dependence of amplitude changes on depth of defect for each B component

Figure 7. Surface distribution of the differential signal By; defect 0.2x10x3mm, probe position x,y=[0,0]mm above a middle of defect Figure 10. The dependence of amplitude changes on conductivity changes for each B component

Figure 8. Surface distribution of the differential signal Bz; defect 0.2x10x3mm, probe position x,y=[0,0]mm above a middle of defect

Figure 9 and 10 demonstrate the parameters influence of real defects on each spatial component of the vector B. It can be clearly seen that these waveform varies for each component differently. With increasing depth of the defect the value of each component increasing, shown Figure 9. On the other hand with increasing the crack's partial conductivity the values for each component are decreasing and slowly settle down, Figure10. Presented results clearly showed that each change in the defect parameters affect the distribution of eddy current density near defect, resulting in different values and different spatial components of the vector B. Spatial components of the vector B are not linearly dependent on each other and they reflect the specific parameter of the defect in slightly different way. These results confirm the expectation that in the investigation and identification of real defects | 37 |

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it would be beneficial to consider all three spatial components of the magnetic flux density vector. CONCLUSION In the article the eddy current method of non-destructive evaluation was discussed. The exciting coil was used to perform simulated 2D scan above the inspected structure and surface distribution of all three spatial components of B vector was sensed and analyzed. The impact of various crack parameters on response signals was investigated by numerical way. From the presented results it is clearly obvious that all the three spatial components of the magnetic flux density vector significantly modify their distribution depending on the dimensions and electromagnetic properties of the crack and on the position of the excitation coil towards to defect. The obtained knowledge are of great asset to this work and it confirm the expected conclusion that for the investigation and identification of the real defects, it is necessary to take into account the spatial distribution of the sensed values of the field, because this significantly increases the information value of detected signals. Further work of the authors will be concentrated on realization of the simulation where the other parameters as width, length will change too. The unique response signal database from parametric analysis could be used in the future as a source of information for inverse problems solutions, where the geometry of the defect will be reconstructed. ACKNOWLEDGEMENT This work was supported by the Slovak Research and Development Agency under the contracts No. APVV-0349-10. REFERENCES

[1.] Zec, M., Uhlig R.P.,Ziolkowski M., Brauer H.: Three-dimensional Numerical Investigation of Lorentz Force Eddy Current Testing, Electromagnetic Nondestructive Evaluation (XVI), Studies in Applied Electromagnetics and Mechanics, Vol. 38, IOS Press 2014, ISSN 1879-8322, pp. 83-93. [2.] N.Yusa, Miya K., Discussion on the equivalent conductivity and resistance of stress corrosion cracks in eddy current simulations, NDT&E International 42 (2009), 9-15 [3.] Uhlig R.P., Zec M, Brauer H.: Lorentz Force Eddy Current Testingmodel experiments and Numerical Calculations for Deep Lying Defects, Electromagnetic Nondestructive Evaluation (XVI), Studies in Applied Electromagnetics and Mechanics, Vol. 38, IOS Press 2014, ISSN 1879-8322, pp. 66-73. [4.] Chady, T., Kowalczyk, J., Psuj, G.: Stress corrosion cracks evaluation in 316 austenitic stainless steel plate, Studies in Applied Electromagnetics and Mechanics, Volume 35, 2011, Pages 282-287, (Conference Paper), ISSN: 13837281.

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Maciej BIELECKI, 2. Andrzej SZYMONIK

THE IMPACT OF LOGISTICS SECURITY CONDITIONS ON THE LOGISTICAL EFFICIENCY OF THE PRODUCT Lodz University of Technology, Faculty of Organization and Management, Department of Production Management and Logistics, Wolczanska 215, 90-924 Lodz, POLAND 1-2.

Abstract: One of the most important purposes of each logistics system functioning is to define the desired security state. It should be noted that the various elements that refer to the security of the logistics system are related to a number of both external and internal conditions of the company. There is also a number of security areas dependent and independent from the company. On this basis, one can make a statement that the product itself, having specified characteristics and properties can affect the security of the logistics system. The article is an attempt to identify and describe the impact of logistics security conditions on vulnerability of product design, and consequently on the logistical efficiency of the product. Keywords: security, vulnerability, efficiency, product, logistics

INTRODUCTION The challenges faced by manufacturing companies of the 21st century increasingly more often concentrate around the problems related to the flow of goods and information which in a natural way associates itself with logistics, defined as the process of efficient and costeffective flow of goods and information from the point of their origin to the place of consumption. This forces enterprises to re-think their functional and global strategies, into such that would account for the primacy of logistics problems. This leads to the necessity of introducing new concepts and ideas, which include the concept of Total Logistics Management (TLM) formulated by the authors. The concept of TLM should become a strategic declaration of the enterprise, with its foundation considering the complexity of problems and organizational challenges of the 21st century. One of the key elements of the TLM concept is the need to compose some part of the logistical conditioning into the product itself, which is dependent on multiple factors and elements. Another challenge of TLM is the problem of logistic security. The below article is an attempt to interconnect both fields and define the conditions of logistic security that are possible to be composed into an item within the concept of the logistical efficiency of the product. THE CONCEPT OF LOGISTICAL EFFICIENCY OF THE PRODUCT IN THE CONTEXT OF TOTAL LOGISTIC MANAGEMENT For many companies the vision of managing through logistics – TLM, is strongly dependent on the product itself and the information connected to it. Both the product and the information should be subject to successful and efficient flow. The concept of TLM itself is connected with a certain group of concepts that are usually placed before logistics, such as:  the comprehensive implementation of the “7R” rule (right product, right quantity, right condition, right place, right time, right customer, right price) [9],

 cost rationalization in management of entire supply chain [13],  comprehensive managing of the product in the context of

logistics – the concept of a logistically efficient product.  Provision of logistics security,  ensuring logistic security,  accounting for goods identification and IT support for the flow of goods and information. One of the elements mentioned above is connected with the idea of comprehensive product management in logistic context. Thus, the idea of a logistically efficient product arises. The concept of logistical efficiency of the product is based on the notion that the features and characteristics of the product itself have a fundamental influence on logistic management in the enterprise. We may therefore attempt a general statement that the correct product assessment in terms of logistical efficiency should be the starting point for any actions related to shaping the functional or global strategy of the company based on logistics (whether conceptual or adjustive [2]). However, in order to be able to implement this rule in the economic life reality on should first define the basic criteria of the discussed concept, including any conditioning that might be crucial here from the logistic perspective Analysing every product of the market exchange, one may state that it has some features and characteristics. Features are defined as elements distinguishing or characterizing the objects in some way, as an ingredient that does not function autonomously and may be differentiated only by means of thought analysis. Characteristics are defined as whatever is typical of the given item (the dominant features) [3]. Both features and characteristics of the product can either be natural of acquired. From the logistics perspective, this notion is extremely important as it allows to use a particular chosen logistic strategy and thus, directly or indirectly, influence the product itself.

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

The analysis and assessment in terms of natural and added features that foster logistic processes, is bound with the concept of logistical design vulnerability. Every product may be viewed as a set of natural features and characteristics, some of which can be modified and other that cannot undergo any transformation process. All those features and characteristics which are purposely designed create the set of acquired properties. The logistical design vulnerability of the product [4], [12] (composed of the transport, storage and organizational aspects) diagnoses the scope of possible changes that can positively influence logistic management. The key question here would be whether the analysis of the logistic security issues would make it easier to extract a group of factors that can be considered in the logistically efficient product design. SELECTED NOTIONS OF LOGISTIC SECURITY The rapid technological development and increasing range of economic globalization, along with the disappearance of traditional boundaries, are some of the many factors causing an increase in security threats within logistics systems. The number of factors generating risk is constantly growing along with the development of civilization. Among these we might include: rising energy and transport costs, the unexpected bankruptcy of strategic logistics providers, difficulty in maintaining regular cash flow, the need to adapt to the new requirements (including eco-logistics) of the local and international law, shortage of skilled employees among the shippers performing the loading of the goods or those providing transport services and logistics, rising insurance, road and credit fees. The optimistic thing is that when new types of threats appear people are able to combat them by creating new methods, or by improving the older ways to organize prevention. The logistic systems, which are vulnerable to all changes and threats, both close and remote ones, due to the global length and width of the supply chain, must adapt to new technological, technical and legal conditions both in on the national and international scale. The safety status of every system unstable and thus it cannot be seen as an item that is granted to the economic system once and for all. In the real world there are constant threats, caused both by the forces of nature as well as unintentional and intentional effects of human activities. Therefore every logistic system must put effort to assure itself a stable security status and, as a link in the supply chain, should include the possibility to react quickly to all changes, both internal and external, including the possibility of cooperation with other entities within the scope of the security system. This statement is nothing new as in the middle of the previous century, the father of contemporary management Drucker while proposing the criteria of choosing and designing an organization stated that every enterprise should have an end stability to survive in the time of confusion and the ability to adjust to new conditions [10]. The adopted strategy of logistic functioning should not be targeted only on implementing logistic processes and lowering costs but also should take into account the issues of contemporary threats along the whole supply chain.

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Every action in logistics both in the planning and real phase is burdened with uncertainty that may be caused by the arising threat (threats) or disruption(s). By threats to logistic security we mean all actions (events, incidents) that disrupt the realization of logistic processes, the flow of goods and information (along with the logistics processes associated with them, such as the processes of transport, warehousing, packaging, order handling and inventory management). One also needs to note that logistic security is hugely influenced by the logistics management areas that are indirectly or directly connected with the above-mentioned processes: the infrastructure of logistics stream and logistic costs. These kinds of events may occur individually or jointly, creating a situation that is hazardous from the business perspective for the economic system and all participants of the supply chains. These threats may be directed inwards or outwards, and the measures taken to reduce them should go in the same direction. Threats can be destructive to the logistic system disrupting the flow of the goods and information. These disruptions can be divided based on [6]:  the place where the threat occurs;  subsystem (according to the phase or functional approach to logistics [8]);  duration;  physical properties;  range. The short description of disruptions according to the duration or range criteria may not be included here as it is difficult to distinguish particular categories within these issues that can be used in the concept of logistical efficiency of the product. The remaining threats should be presented so that they might be referred to in the following chapter. The disruptions depicted within the place criterion will mainly apply to: routes of all transport modes (i.e. road, rail, air, inland-waterway and marine); the modal points of the logistic network often called transport points [11] (e.g. a warehouse, independent container points, airports, marine ports, logistics centers; auxiliary devices facilitating service on roads and at transport points, management (i.e. lack of full identification of threat effects, overestimation of capabilities, inaccurate interpretation of results, lack of tools for optimization and simulation of activities, growing prices of energy and transport, sudden bankruptcy of logistic service providers). The disruptions depicted under the criterion of the functional subsystem refer to: transport (e.g. a fire, an explosion, an accident of the transport means, washing off the deck, lack of possibility to move due to weather conditions, defective transport means, unadjusted internal transportation, change in regulations of the transport management, thefts, catastrophes), related to inventory storage and shaping (e.g. thefts, losses due to oversized inventories, fires, floods, construction disasters, grid and IT network downtime, damage of the automatic identification system), packaging services (e.g. environment contamination, damage of the goods while

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transportation resulting from bad weather conditions), handling customer’s orders (e.g. shortage of inventories, incorrect order or invoice, late delivery, damaged goods delivered to the customer, lack of response to complaints and delays, fire, theft, destruction of goods). Information-related (e.g. loss of confidentiality, integrity and possibility to dispose, natural threats such as fire, climate disruptions, electrostatic disruptions, passive and active attacks, random errors); The disruptions depicted within the subsystem that accounts for the phase division of logistics are related to supply (e.g. lack of timeliness, bad quality, price or quantity, bad assortment, bribery, corruption, lack of possibility to obtain components for manufacturing, information system corruption, lack of buffer stock), production (e.g. inefficient manufacturing system, damage, losses, thefts of resources, availability of professional staff, production interruptions, technical failures, floods, fires, disasters), distribution (e.g. new products, new producers, thefts, economic crisis, neglecting customer relationship management, neglecting flow of goods management within the supply chain). The disruptions classification that considers the materiality criterion is divided into: material ones (e.g. transport-related) information-based ones (e.g. damage of information system, damage of automated identification system), energy-related ones (e.g. concerning gas or fuel), assets-related (e.g. financial crisis); Disruptions and threats have a direct influence on logistic security. However to be able to describe this notion, one needs to predefine what characterizes the safety of actions in logistic networks and channels. By definition, it can be said that it is a state that gives the feeling of certainty and a guarantee for:  the flow of material goods and services;  the flow of information for planning and management of logistics processes;  protection and survival during dangerous situations (threats);  adaption to new conditions (flexibility in unplanned situations). The security level of logistics processes is dependent on the condition of the hazards of cooperating participants in the channels and networks at local and global levels. The security of a logistics system is associated with:  preparation and resistance level of the system to combat emergency situations (the majority of the attention is concentrated on recognition, monitoring, analysing data and correct decision-making within the scope of logistic operation along the entire supply chain);  the quality of the created and functioning security system understood as a set of forces and means of ensuring a security status acceptable by the participants of the international logistics network. A certain degree of safety of international logistics can be achieved in various ways - not only by providing a predetermined efficiency of direct countermeasures towards occurred events. The people managing the company have the opportunity to shape the security

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level of international logistics services through thier management, which can be defined as a set of coordinated actions taken at the time of the emergence of threats (interference), aimed at the logistical resources of all members of the supply chain, with a view to achieve the objective, which may be the security of supply, reduce risks, to realize the conditions set by the owner of the cargo and the protection of market position and brand. Controllable values in this case are the parameters characterizing the factors affecting the level of security of the system, which is associated with1:  prevention of possible threats to the security processes implemented within the framework of international logistics.  preparation of the logistics systems for the event of activation of these risks;  resources countering these threats;  removal of the consequences of the event. Referring the presented notions to the logistic efficiency of the product it can be noticed that in fact the biggest influence on the product itself should be the prevention of possible threats to the security of the international logistics which includes:  formulation of security policies by all members of supply chain;  risk assessment [7][8] during the implementation of processes in the supply chain;  developing a plan for managing and reducing the identified threats;  detection, identification, recording and control the possible risks;  foreseeing the possibility of crisis (e.g. with the use of data warehouses or computerized systems);  examination of the acceptance level of risks in the supply chain among its members;  determination of the type and scope of activities to prevent risks in the area such as road transport, warehousing, distribution, logistics costs – increased fuel costs;  providing training to the people involved in logistics on both micro-level (individual economic system) and macro-level, with particular attention to: » the institutionalization of logistic relations » standardization of logistics processes, » standardization of processes (e.g. according to GS1) » increasing the requirements of the economic system transparency in business and logistics contacts, » tightening the criteria for risk-taking and the professionalization of activities within the supply chain » need to broaden international cooperation of science and industry in the field of improvement of logistics processes, » reconstruction of destroyed ecosystems and wider use of renewable energy sources, » trust management, risk and security in logistics operations See. E. Kołodziński, Istota inżynierii systemów zarządzania bezpieczeństwem, http://www.uwm.edu.pl, 10.04.2012. 1

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The tools that help to manage the security of logistic systems at the micro and macro scale are the solutions that arise from the norms provided by national and international organizations as well as from various technical and technological aspects. As for the normalization, it should be noted that in most cases it relates to the establishment of standards that systemically solve issues such as risk management in a supply chain (ISO 28000 2007), or ensure the continuity of the action (BS 25999:2007). The group of technical and technological solutions includes among others: traceability (comprehensive traceability or origin identification of the batch of the product, raw materials used for its manufacture, followed by individual identification of each product comprising the batch during production and/or distribution to the direct consumer), GS1 standard (bar codes and electronic product codes), Business Intelligence - BI (business intelligence) or the monitoring network. THE IMPACT OF LOGISTIC SECURITY ON THE LOGISTIC EFFICIENCY OF THE PRODUCT The above-presented logistics and security issues should be the basis of the considerations related to the design of the product itself as seen in the light of hereby discussed issues. The logistical efficiency of the product should allow for incorporation of certain solutions in the product itself to make it possible to provide more efficient and effective management across the entire supply chain. The presented overview of selected topics on logistics management clearly shows that there is a group of logistic security issues, which cannot be included in the logistical efficiency of the product. However, to attempt a discussion as to which safety features can be included in the product, one needs first to look closer at the issues that might possibly generate threats to logistics and analyse their impact on the product itself. The division of disruptions presented in the article allows us to notice, that the factors categorized within the groups associated with the place, subsystem and physical attributes should have an impact on the concept of logistical efficiency of the product. The question of where disturbances occur, i.e. all modes of transport routes, modal points, auxiliary equipment to facilitate road maintenance and transport points, is in fact related to the concepts of transport, storage and organization vulnerability. The combination of the three together creates the logistic vulnerability of the product, which in turn is a key element of the logistics efficiency of the product. The same applies to the interference generated by the subsystems in terms of the functional and phase approach. The same might be said, to an even greater degree, of disruptions associated with physical properties, where the division to material and information-related interference, allows to decide which of the basic vulnerability analyses might include particular disturbances from this group. In the context of logistics system security, the level of preparedness and resilience of the system to the prevention of emergency situations, as well as the quality of the functioning security solutions, is inextricably linked to

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the organizational vulnerability of the product. Another, separate matter would be to investigate which of the elements associated with the preparation, resistance and quality of such a system can be integrated into the widely understood product, or, more precisely, into the its organizational vulnerability aspect. In case of both preventive measures and tools that assist safety management, one may see that, as regards the latter, that the impact of particular standards widely associated with logistics security, usually applies to the organizational sphere of company activity, forgetting the product itself. In most cases, no one analyses the possible changes in the product just adapt it to some specific standard unless this standard is enforced by law. The situation is different with technical and technological solutions. The implementation of identification systems based on the GS1standard barcode or RFID or comprehensive Tracing, often forces the producers to incorporate specific sets of characters either directly into the product or its packaging, thus allowing to identify individual elements in each dimension. The described preventive actions range shows that the available range of processes affects product modification only indirectly. That so happens because they are mostly related only to the way the system is organized or managed, i.e. to its organizational vulnerability. SUMMARY The concept of logistic efficiency of the product implies the possibility of incorporating the optimum number of features and characteristics that would facilitate the flow of this product along with related information. To be able to discuss the issue further, one need to distinguish the design vulnerability of the product, which consists of transportability, storage and organization and describe the circ*mstances that may impact all of these vulnerabilities. The sphere of logistics security is one of the groups of conditions described here, which similarly to the customer service subsystem is mainly related to organization and management of logistic system. Organizational vulnerability clearly provides framework to the debated issue, at the same time affecting the logistical efficiency of the product. The further scientific research intended by the authors will involve the identification of these factors of organizational susceptibility (including logistics security), which may already be intentionally designed at the stage of product design, thus increasing the subsequent efficiency of the entire logistic chain. Moreover, the above presentation of logistic security issues and logistical efficiency of the product allows the reader to notice that specific analytical tools allowing to diagnose the scale of threats and uncertainties of logistic operations in terms of security and the product itself, are yet missing; this matter will also become a focus of the further conducted research. REFERENCES [1.] Bielecki M., The influence of a logistically efficient product one the Logistics of a Manufacturing Enterprises, ICIL 2012 Conference Proceedings, Faculty of Mechanical Engineering and

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Naval Architecture Zagreb, International Centre for Innovation and Industrial Logistics, Zagreb, Croatia 2012 [2.] Bielecki M., The logistical Efficiency of the product in Logistics Strategies of Manufacturing Enterprises, Carphatian Logistic Congress, Congress proceedings, Jesenik, Czech Republic 2012, [3.] Bogdanowicz, S. Podatność. Teoria i zastosowanie w transporcie, Oficyna Wydawnicza Politechniki Warszawskiej, Warsaw, 2012, 14-15. [4.] Bielecki M., Madej M., Skoczylas A., Design vulnerability as the key element of the logistics efficiency of the product, Logistics and Transport, Vol 21 No 1, Wroclaw, 2014 [5.] Wittenbrink, P., Risken im Transport und Logistikbereich, Internationales Verkehrswesen, 2//2013, p. 20-23 [6.] Szymonik A., Eurologistyka Teoria i Praktyka, Difin, Warsaw 2014, p. 251. [7.] Szymonik, A., Logistyka jako system racjonalnego pozyskiwania wyrobów obronnych, AON, Warsaw 2007., p. 130 [8.] Komorowski, J., Cele przedsiębiorstwa a rozwój gospodarczy Ujęcie behawioralne, SGH, Warsaw 2012, p. 191. [9.] Coyle J. J., Bardi E. J., Langrey Jr. J. C., Management of Business Logistics, West Publishing Co U.S., 1980, [10.] [10] Drucker P., Innovation and Entrepreneurship, HarperCollins Publishers, New York, U.S., 1985 [11.] [11] Gołembska E., Kompendium wiedzy o logistyce, PWN, Poznan-Warszawa 1999, p. 276 [12.] [12] Kröger W., Zio E., Vulnerable Systems, Springer-Verlag, London, 2011 [13.] [13] Harrison A., van Hoek R., Logistic Management and Strategy. Competing through a supply chain – 3rd edition, Pearson Education Limited – Prentice Hall, England, 2008

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Ján ĎURECH, 2.Marián HRUBOŠ, 3.Mária FRANEKOVÁ, 4.Aleš JANOTA

IMPLEMENTATION OF DATA FROM THE MOBILE MEASUREMENT PLATFORM TO VANET APPLICATION 1–4.

Department of Control and Information Systems, University of Žilina, 010 26 Žilina, SLOVAKIA

Abstract: The paper deals with an idea of informing the car drivers on problem of road degradation via sending of warning messages from road side units. The initial part of the paper summarized the up–to–now realized concept of the mobile measurement platform (MMS) and its mathematical principles showing how detailed data on road surface may be obtained. The main part of the paper is aimed at design of integration of data from MMS into the VANET application. Practical realisation is based on the warning message generation with GPS coordinates which is assuring by digital signature ECDSA cryptography algorithm via OpenSSL tool. Keywords: point cloud; 3D model; data fusion; VANET; C2C; C2I, vehicular communications; cryptography; OpenSSL

INTRODUCTION In the field of road transport currently many countries are facing the problem of degradation especially of older roads. Constantly raising intensity of road traffic has negative effect on quality of road communications. Various sorts of defects of road surfaces such as cracks, potholes, longitudinal and transverse bumps, ripples of surface, local falls or beaten tracks have negative effects on driving comfort and cause greater wear of some parts of motor cars. For measurement of deformations which can occur on the road surface several measurement methods and devices have been created. Generally, manual methods for measurement of surface attributes are being replaced with methods based on electronic measuring devices. One big group of measuring devices used for measurement of road deformations is based on utilization of the laser measurement systems. They measure flight of time of laser impulses to find out what is a distance between the laser scanner and road surface. For detection of road texture there have been many methods developed so far, resulting in a number of various coefficients and attributes proposed to define surface roughness in an optimal way. In the Slovak Republic devices of VIDEOCAR and Profilograph GE are currently being used for measurement of surface roughness. The Progilografh GE (see Figure 1) measures the texture and gives data on an average depth of texture. At the same time it is also used as a volumetric method for determining of an average texture depth. VIDEOCAR is a device which is used for fast visual inspection of the road surface. Data are collected using the VW Caravelle vehicle type. Basic task of fast visual survey is to collect data about state of road surface and determine defects attributes for the following purposes:  Data collection and filling databases of the Road databank for consecutive rating of individual sections of selected roads further utilized in the Road management system.

 Search engine, which serves for processing of detailed visual

inspection if needed.

 Solutions of the research projects and projects of scientific–

technological development.

Figure 1. Mobile measurement platform (MMP) Basic conditions required for data collection are good optical conditions and dry unpolluted surface of the road. However, these methods do not provide all necessary information about the measured road and its surrounding area. In the context of ITS (Intelligent Transport Systems) development integration of other offered services into one complex service package seems to be one of actual tasks. Some of those services may require communication connections based on C2C and/or C2I communication using wireless communication standards, through VANET (Vehicular Ad Hoc Networks) [1], which additionally requires authentication of services provided. For measuring of attributes of road surface and surrounding areas the authors proposed the solution shown in Figure2 consisting of the MMP (Mobile Measuring Platform), It should be capable of storing scanned data about potholes positions into server connected to the

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 (α 0n + i * ∆α n + α rn + 90 )* π   β *π  * cos  rn   + x 0n 180  180   

RSU (Road Side Unit) and thought VANET networks transmitting warning messages to all vehicles finding themselves in a communication range. To ensure authenticity and integrity of such messages a cryptography method is used to generate digital signature on the base of elliptic curve mechanism.

x in′ = d in * sin

 (α 0n + i * ∆α n + α rn + 90 )* π   + y 0n 180  

y in′ = d in * cos 

 (α 0n + i * ∆α n + α rn + 90 )* π   β rn * π   * sin 180  180    

z in′ = d in * sin

′ x in = x in

Figure 2. Interconnection of MMP with VANET application MATHEMATICAL PRINCIPLE USED IN THE MOBILE MEASUREMENT PLATFORM The MMP is primary dedicated for measuring of geometric changes of road surface. The secondary assignment of this platform is measuring surrounding areas around the road itself. The conception of the MMP is based on gathering of data characterizing a measured road and its surrounding areas and on its fast processing and graphical interpretation appropriate for next analysis. Processing of data obtained from the laser scanner is principally performed by off–line methods. It means that all measured data are first saved to the hard disk and after surveying the whole intended road section the computing algorithm is being initiated to calculate and get coordinates of all measured points [2]. The MMP illustrated in Fig1 can be used in generally for creation of the 3D model of real objects within road infrastructure such as roads, buildings, bridges or tunnels. By fusion of data coming from multiple sensors integrated in the MMP we are able to generate the 3D model of the real environment with its texture. Thus we are able to merge for example data from the laser scanner and a GPS receiver and generate the 3D model consisting of cloud of points. Subsequently the algorithm for creation of surfaces in the points cloud may be applied to obtained data as a precondition of the following step – application of texture itself. Textures data are obtained from a set of cameras integrated in the MMP and monitoring the whole space around. To calculate cloud of points the equations (1) may be used, designed on the base of analysis of data gathered from the following data sources: laser scanner, GPS receiver and INS (Inertial Navigation System) [3]. Thanks to data from the laser scanner we can obtain the following quantities [4]:  Starting angle α0n,  Sequence number of a current point i,  Angle increment Δαn,  Measured distance between an object and the laser scanner din. After re–calculations of GPS receiver data we get position of the MMP in the form of coordinates x0n, y0n and z0n. The INS helps us to get data on rotation of the MMP in each axis αrn, βrn and γrn.

rin′ = y in′ 2 + z in′ 2  y ′ * 180  γ in′ = arccos  in   rin′ * π 

′ )* π   (γ + γ in y in = rin′ * cos  rn  180   ′ )* π   (γ rn + γ in z in = rin′ * sin  + z 0n 180  

(1)

The problem of calculations and needed data conversions is discussed in more details in [5]. Trajectory of the MMP can be also calculated by tracking the center line as the main road surface marking. Such an idea can also be found implemented in e.g. the LDWS (Lane Departure Warning System) where different methods of image processing based on computer vision are used to detect the line– for more details see e.g. [6]. For searching of defects on the road surface one must know the height of the laser scanner head situated at the MMP. In our case the laser scanner is located in the height of 108 cm above the road surface. Defects are searched in a programmable way by systematic searching of points whose distances from the laser scanner are greater than 108 cm. The algorithm provides an output in the form of output file which contains data on GPS position of identified defect, its length and depth. The 3D model may be used to create a visualized model of road surface that can make the process of subsequent road maintenance easier. DESIGN OF INTEGRATION OF DATA FROM THE MMP INTO THE VANET APPLICATION The authors have extended the concept of the MMP and the idea of recording defects in road surface in this paper for application of the warning system RHCN (Road Hazard Control Notification), In case of detection of potentially dangerous situations (pothole, ice, ...) this system can send through the VANET all nearby vehicle warning message, informing drivers about dangerous situation or dangerous spot on road communication / infrastructure. The principal scheme of this idea is shown in Figure3.

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Figure 3. Warning system in VANET network

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Figure 4. Example of signed message with using ECDSA algorithm realised via OpenSSL

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As explained in the previous chapter, the MMP after computing all sensed data evaluates which data represent defects in road surface and record data about their positions to the server connected to the roadside unit RSU. The RSU through short range communication DSRC (Dedicated Short Range Communication) sends warning message to vehicles available in range of the relevant RSU. The proposed concept can be used also for warning drivers about blind spots and other dangerous situations. This is a modified method of C2C communication, respectively C2I where in the case of the proposed application the road infrastructure (relevant RSU) communicates with vehicles. Considerations of wireless communication bring higher possibility for abuse and potential existence of attacks to the communication system. If a vehicle (respectively RSU unit) doesn’t have security features implemented in the control unit, other vehicles may not consider and mark received warning messages as secured, it means there is no warranty about authentication of sent messages. Security solutions of C2C and C2I communication are actually solved by the C2C–CC organization [7]. The use of IPv6 (Internet Protocol v6) protocol is being advocated actually there. IPv6 according to the set configuration solves the following security requirements for the communication in the VANET:  Authentication of message and its integrity – protection of message prior to its modification, the ability to identify the sender.  Non–repudiation of messages – the sender cannot deny that he sent the message.  The timeliness of reports – the recipient can be sure that the message is fresh and was generated within the specified interval.  Access control – a decision which nodes in the network can perform their assigned actions.  Confidentiality of message – preservation of content messages secret from unauthorized parties. In the practical part of the paper, the authors deal only with issues of authentication of message and its integrity. Currently in modern cryptography cryptographic authentication protocols are based on scheme of digital signature mostly based on asymmetric cryptography. In commercial applications there are currently expanded several types of digital signature schemes:  RSA (Rivest, Shamir, Adleman) digital signature scheme,  DSA (Digital Signature Algorithm),  ECDSA (Elliptic Curve Digital Signature Algorithm).

The most important parameters of digital signatures in the transport system are: the size of the signature, public key size, generation time of signature and time of signature verification. Matter of choosing an efficient digital signature schemes for authentication purposes in VANET networks is devoted to a number of projects. Project SeVeCom [8] supports the use of a modified version of a digital signature scheme based on ECDSA. PRACTICAL REALISATION The authors have chosen the ECDSA digital signature scheme to ensure the credibility of message transmission from MMP which is also supported by the results of testing three schemes of digital signatures: RSA–1024, DSA–1024 and ESDSA–160 from the perspective of time sessions for generating and verifying signatures (see Table 1) which was implemented in the OpenSSL tool. All three schemes were applied to the message of the same length on one type of PC with Intel Dual Core processor with frequency of 2.3 GHz. Given the large number of tests performed in several projects with different results always the best and the worst case of available data is given in the table. Additional crucial parameter for choosing an algorithm is the size of the key. As shown in Table 1 in the case ECDSA scheme compared with other schemes the process of signature generating and certificating is very fast, which predetermines the algorithm used in applications with a focus on performance, which can also include sensor networks. Table 1. Time demands of algorithms RSA, DSA, ECDSA Size of Size of public Generating of Verification of signature signature signature key [Byte] [Byte] RSA – 1024 15 – 154.5 1 128 128 DSA – 1024 8.7 – 80 9.9 – 97.72 40 128 ECDSA 160 0.9 – 6.94 1.382 – 14.01 40 20

Before sending safety–relevant messages (in our application – "RHCN") a digital signature (Figure5) is generated in the RSU using its private key SK1 which is function of message M and message header H. The header may contain, for example, information about location of roughness on the road.

Figure 5. Authorized transfer of messages between RSU and vehicle via VANET network

Thus created cryptographic number is attached to the message simultaneously with a certificate Cert, which is tied to the i–th anonymous public key of the sender VKi1, which certifies the corresponding CA (Certification Authority). On the side of the vehicle V the received certificate is validated first (if it was not done before) and the received digital signature is verified using the i–th public key

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of the vehicle VKiV1, that is downloaded by the vehicle V (resp. other vehicles) in regular intervals. At the same time information of geostamp type (about position of place where emergency condition happened) is verified from the header H and after completing these procedures the safety–related message is either accepted or rejected. The process of generating a digital signature in RSU can be mathematically expressed: (2) RSU → : M, H, SignSKi [(M, H) | T ], Cert RSU . where: M represents sent safety–relevant message, H represents the message header, SKi is a short–term private key RSU in the i–th moment, VKi is a short–term public key RSU, in the i–th moment, T is the time stamp, Cert is a short–term certificate of the RSU (for the anonymous public key pre VKi1), represents the number of receivers (in the case, that message was sent to multiple vehicles in mode „broadcast“). Current certificate of the RSU valid in the i–th point of time for the anonymous public key RSU V1 (VKi1) includes: (3) Cert i V 1 [VK i 1 ]= VK i | Sign SK -CA [VK i | ID CA ]. where: SignSK–CA represents signature of certificate signed by relevant certification authority based on its private key SK–CA, IDCArepresents the unique identification number of the certification authority. When the MMP finds a pothole on the road, respectively other roughness, it generates a message that consists of GPS coordinates and by using the selected cryptographic algorithm (in our case ECDC scheme) sign and send the message to the nearest RSU unit. The experiment has been realized using MMP in the University of Žilina Campus. We walked through the campus with MMP and after recording the potholes, message containing its GPS coordinates has been generated. Subsequently the message was signed. The process of signing the message has been simulated using the OpenSSL in which elliptic curve over a 384 bit prime field has been chosen. We have chosen prime field curve because of more effective implementation in the software implementation. Digital signature is shown in Figure4. Next step would be adding signature and send message with public key to the vehicle. Subsequently vehicle can verify message using public key, and if the vehicle verify the message, warning can be shown. CONCLUSION The aim of this paper was to describe integration of the RHCN system into the C2I communication. An initial part of the paper shows the concept of data fusion that helps us reach a 3D model covered with surfaces where surface textures may be applied. One of the tasks potentially covered by the presented concept of the MMP is detection of road surface deformations. Data on these findings may be further used to calculate and send warning messages to passing vehicles, signed by digital signature within the VANETs. Described methods and algorithms of data fusion have been implemented in MATLAB

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programming environment. Example of the digital signature scheme ECDSA has been realized with the help of the OpenSLL library. Furthermore, the realized software applications of detecting potholes can be amendment to detection of transverse and longitudinal tracks. Choosing a digital signature scheme with focus on elliptic curve algorithm ECDSA has been chosen on the basis of comparison of the effectiveness signing scheme e.g. referred to [9] due to the described applications where except security performance of the used digital signature scheme is also an important parameter.

Acknowledgment The paper has been written with the partial support of the project ITMS– 26220220089 “New methods of measurement of physical dynamic parameters and interactions of motor vehicles, traffic flow and road” [50%] and partial support of the Educational grant agency KEGA within the project Nr: 024ŽU–4/2012 “Modernization of educational technologies and methods with focus on cryptography for safety relevant applications“ [50%].

References

[1.] Hartenstein, H., Laberteaux, K., P.: VANET: Applications and Inter– Networking Technologies. WILEY. ISBN 978–0–470–74056–9 [2.] Halgaš, J., Hruboš, M., Pirník, R., Janota, A.: Determination of Formulas for Processing of Measured Points Representing Road Surface Deformations. Archives of Transport System Telematics, vol. 5, No. 1, 2012, ISSN 1899–8208, pp. 7–10. [3.] Hruboš, M.: A Tool to Detect Status of Road Degradation over Time.In: Slovak. MSc. thesis, No. 28260220122010, University of Zilina, 2012 [4.] https://www.mysick.com/saqqara/im0031422.pdf [5.] Šimák, V., Nemec, D., Hrbček, J.: Calculation of robot position utilizing accelerometers in non–inertial frame of reference. In: Proc. of the 9th International Conference ELEKTRO 2012, May 21 – 22, 2012, IEEE Catalog Number: CFP1248S–ART, ISBN 978–1–4673–1179–3 [6.] Bubeníková, E., Muzikářová, Ľ., Halgaš, J.: Application of Image Processing in Intelligent Transport Systems, In: 11 th IFAC/IEEE International conference on programmable Devices and Embedded Systems, Brno, May 23th–25th 2012, ISBN: 978–3–902823–21–2, ISSN 14746670 [7.] Car2Car Communication Consortium. In: http://www.car–2–car.org/M. [8.] SeVeCom: Security Vehicle Communication. In: http://www.sevecom.org/

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Horst TREIBLMAIER

A CLASSIFICATION FRAMEWORK FOR SUPPLY CHAIN FORECASTING LITERATURE 1.

University of Applied Sciences Upper Austria, Logistikum Wehrgrabengasse 1-3, Steyr, AUSTRIA

Abstract: Forecasting in Supply Chain Management (SCM) is an important yet underestimated research topic. Over the past years numerous methods and concepts have been developed, tested and deployed. In this paper we present a classification framework for the SC Forecasting literature using eight criteria, namely focus, approach, method triangulation, data generation, range, timeline, theoretical background, and target group. Additionally, we present examples for the respective criteria and summarize the major findings. This state-of-the-art review paper is targeted toward both researchers and industry experts who want to get an overview of the goals of contemporary SC Forecasting research. Keywords: Forecasting, Forecasting Models, Supply Chain Forecasting, Supply Chain Management

INTRODUCTION Forecasting is an important and well-established research topic in economics as well as in business. Not only exists a plethora of literature which deals with various aspects of forecasting and prediction, but even highly specialized journals (e.g. Long Range Planning, Journal of Forecasting, Journal of Business Forecasting, International Journal of Forecasting, Foresight: The International Journal of Applied Forecasting) and conferences (e.g. Supply Chain Forecasting and Planning Conference, Sales & Operations Planning (S&OP) Conference, Workshop on Industry & Practices for Forecasting) exclusively focus on that area. Notwithstanding the long tradition of this research stream, Datta et al. [1] state that “Forecasting is an underestimated field of research in Supply Chain Management” (SCM) (p.187). At first sight, this seems surprising, given the high importance of forecasting for an effective and efficient supply chain. For instance, one of the most important phenomena in business, the so-called Bullwhip (Forrester) effect, was discovered more than 50 years ago [2]. Today scholarly papers still deal with this highly complex subject [3] [4]. We found four major reasons for the enduring importance of SC Forecasting on which we will elaborate in the following subsections. Increasing Market Volatility The financial crisis of 2007/08, which was followed by a global recession that affected the entire world economy, has caused many companies to rethink their overall business strategies. Following the economic downturn, a general awareness now exists that increasingly complex international business networks lead to dependencies on business partners and a greater-than-ever vulnerability to market fluctuations triggered by political crises, natural disasters and economic cycles [5]. Current research and political indicators point towards an ongoing market volatility in the future [6], which tend to make corporate forecasting and planning crucial yet increasingly difficult.

Methodological Developments New and innovative methods take time to diffuse from formal to applied science and finally to the industry. Frequently, established methods are modified in order to fit a prevalent problem. Datta et al. [7], for example, illustrate how to adapt an advanced forecasting technique, GARCH (i.e. Generalized Autoregressive Conditional Heteroskedasticity) with the goal of improving it into a flexible decision support tool. Those models are based on ARCH models, which were originally developed by Nobel prize laureate Robert Engle [8] decades ago. Datta et al. [7] further refine them by adding vector auto regression (VAR) methodology and model volatility for a vector rather than a single series. They suggest to call the proposed model VAR-MGARCH and conclude that “in one isolated experiment [...] the model provided a forecast that was appreciably closer to the observed or realized value” (p. 1469). However, they also stress the need for further methodological refinement: “This observation is immature. [...] Several more experiments with rigorous controls must be performed before this result may be even considered to offer ‘preliminary’ evidence that the GARCH type model proposed in this paper may represent an advanced tool” (p. 1469). This is but one of many examples in which existing methods are altered in order to fit the demand of modern SCM. Big Data In a current issue of the Journal of Business Logistics (JBL), Waller and Fawcett [9] describe data science, predictive analysis and big data as “a revolution that will transform supply chain design and management” (p. 77). They show that, in spite of being often named a buzzword, big data holds a lot of potential for those companies which understand how to capitalize on it. The opportunities for organizations to gain valuable information from big datasets are simply too attractive to ignore them. Furthermore, as is the case with most hypes, numerous companies are afraid of losing market share to competitors who capitalize on the “first mover advantage”. Modern

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

technology has made it possible to easily gather data in hitherto unimaginable quantities. Quite naturally, in many cases these data contain valuable information which can be used for extracting meaningful forecasting information that helps to generate agile supply chains [10]. Supply Chain Focus Although a significant amount of papers exists which exclusively deals with forecasting in the supply chain, the majority of published research either focuses on methodological issues or has a different kind of operational focus. Hence, a huge untapped potential of forecasting knowledge exists, which allows SC researchers to simply transfer existing know-how in order to tackle problems specifically pertaining to supply chains. This is of crucial importance, since the overall importance of SC Forecasting is constantly growing [11]. The remainder of this paper is organized as follows: In section 2 we will briefly elaborate on the methodology we used for this research, followed by the presentation and discussion of our classification framework in section 3. Finally, we summarize our findings, highlight implications and options for further research and also mention several limitations. METHODOLOGY In this conceptual research-in-progress paper we followed the procedure suggested by Tranfield et al. [12] for conducting a systematic literature review. We first identified relevant keywords related to SC Forecasting and used the scholarly databases “ProQuest” and “EBSCO” as a starting point. The literature review was carried out from September 2013 until March 2014 and was constantly refined by including articles being cited in the analyzed papers or which we found via Internet search (e.g. by using Google Scholar). We finally ended up with a total of 92 papers which had both a focus on supply chains as well as forecasting and which we deemed relevant for the study at hand. In the first phase we classified each paper according to its main research goal. Next, we created various categories suitable to further categorize the papers. If a paper did not fit into one of our categories, we revised and extended our framework. In line with the qualitative and explorative nature of this research, we did not strive to categorize all papers exhaustively and did not provide any descriptive data pertaining to the absolute number of papers within a specific category, but rather used the publications in order to create a sufficient number of categories in our framework. In the following section we will not only introduce the framework itself, but also briefly discuss various examples of papers in order to illustrate the meaning of the respective categories. SCM FORECASTING IN THE LITERATURE: A CLASSIFICATION FRAMEWORK During the classification process a total of 8 different categories emerged. It has to be noticed that this framework is neither fully exhaustive nor mutually exclusive, but its main purpose is rather to highlight the various existing goals of contemporary SC Forecasting

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research. We will provide one or more examples in each category for illustration purposes. Focus A lot of published research in academic literature focuses on developing and refining methods. Apart from the previously mentioned paper from Datta et al. [7], another example stems from Ferbar et al. [13], who utilize the theory of wavelets in order to create a wavelet denoising model which they find to be superior to the commonly used exponential smoothing method. A second stream of research focuses on the classification of existing methods. Armstrong [14], for example, presents a selection tree for various forecasting methods, whose choice depends on criteria such as available data, expected changes, available expertise, similar cases and domain knowledge. This tree may be used to select the best suited method for a given problem with various characteristics. Finally, scholarly papers exist which compare methods and give recommendations on how to choose the most appropriate one. Acar and Gardner [15], for example, select the most appropriate method based on operational performance in a real supply chain. They compare various exponential smoothing methods and base their final choice on tradeoff curves between total costs and customer service. Approach In academic literature, quantitative approaches are prevalent, as is shown by the meta-study from Fildes et al. [16] who analyzed a total of 558 publications in forecasting research. 27.2% of the papers used univariate methods, 21.5% causal and multivariate methods and 13.4% computer-intensive methods such as non-linear statistical methods and neural nets. Only in 8.2% of the cases judgment, i.e. a qualitative approach, was used. The authors also categorized 879 articles from operational research journals and found a similar dominance of quantitative methods with only 8.5% of the papers under investigation using judgment. This coincides with our findings that the vast majority of the scholarly papers relies on quantitative data. However, we also found examples for papers which combine qualitative and quantitative approaches [17] [18], or which solely rely on a qualitative approach. An example of the latter category comes from McCarty and Golicic [19], who use depth interviews with executives in three firms in order to come up with seven guidelines for implementing interfirm collaborative forecasting. As far as quantitative research is concerned, the majority of publications deals with the development, testing and refinement of forecasting techniques. However, we also found evidence for survey-based research. Nakano [20], for example, administered a survey among 65 Japanese manufacturers and used confirmatory factor analysis in order to examine the perceived impact of internal and external collaborative forecasting and planning on logistics and production performance. Method Triangulation The aforementioned study from Fildes et al. [16] also lists the usage of method triangulation, i.e. the combination of various methods in

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order to study a situation or phenomenon. 3.8% of the forecasting and 6.1% of the operational research publications actually applied method triangulation, indicating that the vast majority of publications relies on using a single method only. Notable exemptions include Caniato et al. [17] who integrate quantitative and qualitative approaches to improve demand forecasting in the cement industry and who report improved forecasting accuracy as well as increased knowledge within the organization. The second example stems from Forge [18], who uses a qualitative forecast derived from a scenario for a quantitative projection. Although not exclusively focused on SCM, his approach may be used for all studies which need to simultaneously take into account socio-economic, technological and market developments. Third, Goodwin and Fildes [21] report that in the industry statistical forecasts are frequently adjusted using management judgment. They differentiate between large adjustments, which tend to improve accuracy, and small ones, which often turned out to be a waste of time. Data Generation Another distinctive feature which we observed in the literature is the type of data generation. Researchers have a choice between collecting real world data from companies [22] and using some kind of Monte Carlo experiment in order to obtain the required distribution of an unknown probabilistic entity [23]. We observed the latter procedure mainly in the context of testing new methods. In some cases the authors split an existing real world data set in order to create a model and use the remaining data for testing purposes [24]. Range Collaborative planning, forecasting and replenishment (CPFR), i.e. the joint planning of key supply chain activities, has gained significant attention in recent years. Previous research has shown that CPFR yields numerous positive results, such as the need to innovate and strong relationships between business partners [25]. Several authors therefore consider the potential impact of decisions that go beyond company boundaries. Aviv [26], for example, presents a time-series framework for supply chain inventory management which takes into account the benefits of various types of information-sharing agreements between supply chain members. He presents a methodology which allows for the investigation of the benefits of various types of information-sharing options, such as sharing subsets of demand-related information or sharing information in one direction of the channel. Acar and Gardner [15] discuss the case of a global manufacturer which owns plants in America, Europe and Asia. Their paper is about forecasting method selection in a real supply chain and they conclude that “forecasting must be evaluated at the aggregate level […] for the entire supply chain” (p. 847). Timeline We found a large number of publications investigating changes over time, which is common in forecasting research. Although it is possible that these papers are purely conceptual and do not use data, as is the case with Giloni et al. [27] who investigate the problem of demand

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propagation in multi-stage supply chain and demonstrate the benefits of information sharing, many of the papers we found rely on actual time series data [30]. Theoretical Background The importance of theory varies between scholarly disciplines, as does its purpose and usage [28]. We found that most research on SC Forecasting focuses on solving specific operational problems and does not refer to a specific underlying theoretical background. Notable exceptions include Stapleton et al. [29] who discuss in their conceptual paper the applicability of chaos theory principles to selected supply chain functions and who conclude that chaos theory bears some potential to help explain unpredictability within nonlinear systems. Ferbar et al. [13] use a mathematical approach when they apply the theory of wavelets in order to denoise signals. Target Group We found that the publication outlet mainly determines the respective target group (researchers vs. practitioners), which is usually the case in all kinds of academic and non-academic communities. We were therefore especially interested in publications which might serve as a bridge between these groups, i.e. which might be well-suited to transfer cutting-edge knowledge into the industry. We found several examples, e.g. in the Journal of Business Forecasting Methods & Systems, such as the papers from Peterson [31], who reports on the supply chain integration efforts of the Bayer HealthCare Division and how they improved forecasting by reducing bias, and Picksley and Brentnall [32] who describe how Bayesian modeling might help to enhance supply chain forecasting and planning. A similar outlet is the Journal of Business Forecasting, in which Khadar [33], for example, describes how a vendor inventory management program helped to create visibility in the supply chain and let to improved forecasting. Occasionally, relevant papers were published in high-impact journals such as Harvard Business Review (HBR), as is evidenced by the publication from Fisher et al. [34] who illustrate how companies manage to cope with uncertain demand. Table 1 – SCM Forecasting Literature Framework Category Focus Methodology vs. Application Approach Quantitative vs. Qualitative Method Triangulation Yes vs. No Data Generation Real World Data vs. Simulation Range Single Location vs. Chain Timeline Cross Sectional vs. Time Series Theoretical Background Yes vs. No Target Group Researchers vs. Industry Table 1 summarizes the eight major categories of our framework. Most papers can be classified according to all of the criteria, some of which overlap. CONCLUSIONS AND LIMITATIONS Supply Chain Forecasting is a topic which is of utmost importance to both practitioners and academics. Numerous papers in this area have been published over the past decades, and new methods and concepts are constantly being developed, tested and refined. In this review paper we present a framework which may be used for

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classifying existing research according to its main goal. We differentiate between eight categories (focus, approach, method triangulation, data generation, range, timeline, theoretical background, target group) and provide several examples in order to illustrate the respective categories. We show that numerous papers exist which shed light on the intricate subject of SC Forecasting from different angles. Authors use a wide variety of methodological approaches, data generation methods and research designs in order to make useful contributions for their respective target groups. This paper is research in progress and part of an extensive SC Forecasting project. Therefore, several limitations exist. First, our framework needs to be refined with further categories and a more detailed distinction between them. Rather than having only two options in each category, more choices might be appropriate. Second, we suggest to find categories which are mutually exclusive and collectively exhaustive, and, third, a comprehensive quantitative study is needed which shows the distribution of papers in each category. Finally, we also want to highlight opportunities for further research. Our preliminary results already suggest potential research gaps, such as the significant time lag of knowledge diffusion into the industry. We found a huge number of cutting-edge research papers, but there is strong indication that the actual application of novel research findings in the industry frequently has a significant delay. Future studies might enhance our framework and use the results in order to systematically identify research gaps in the area of SC Forecasting.

REFERENCES [1.] Datta, S. et al.: Forecasting and Risk Analysis in Supply Chain Management: GARCH Proof of Concept, in: Managing Supply Chain Risk and Vulnerability: Tools and Methods for Suppy Chain Decision Makers, Eds: Teresa Wu et al., Springer, Dordrecht et al., 2009, 187203. [2.] Forrester, J. W.: Industrial Dynamics. MIT Press, Cambridge, MA, 1961. [3.] Barlas, Y. and Gunduz, B.: Demand Forecasting and Sharing Strategies to Reduce Fluctuations and the Bullwhip Effect in Supply Chains, Journal of the Operational Research Society, 2011, 62(3), 458–473. [4.] Cho, D. W. and Lee Y. H.: Bullwhip Effect Mesure in a Seasonal Supply Chain, Journal of Intelligent Manufacturing, 2012, 23(6), 2295–2305. [5.] McKinsey: McKinsey on Supply Chain: Select Publications, McKinsey&Company, 2011, 1–31. [6.] Lawrie E. Market Volatility on Fears US Must Revisit Debt Debate, Investment Adviser, October 21, 2013. [7.] Datta, S. et al.: Management of Supply Chain: An Alternative Modelling Technique for Forecasting, Journal of the Operational Research Society, 2007, 58(11), 1459–1469. [8.] Engle, R. F.: Autoregressive Conditional Heteroskedasticity with Estimates of the Variance of United Kingdom Inflation, Econometrica, 1982, 50(4), 987–1007. [9.] Waller, M. A. and Fawcett, S. E.: Data Science, Predictive Analytics, and Big Data: A Revolution That Will Transform Supply Chain Design and Management, Journal of Business Logistics, 2013, 34(2), 77–84. [10.] Byrne, R. F.: Driving Profitable Growth with Big Data and Better Forecasts, Supply Chain Europe, 2012, 21(1), 40–41. [11.] Oliva, R. and Watson, N.: Managing Functional Biases in Organizational Forecasts: A Case Study of Consensus Forecasting in Supply Chain Planning, Production and Operations Management, 2009, 18(2), 138–151. [12.] Tranfield, D. et al.: Towards a Methodology for Developing EvidenceInformed Management Knowledge by Means of Systematic Review, British Journal of Management, 2003,14(3), 207–222.

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[13.] Ferbar, L. et al.: Demand Forecasting Methods in a Supply Chain: Smoothing and Denoising, International Journal of Production Economics, 2009, 118(1), 49–54. [14.] Armstrong, S. J.: Selecting Forecasting Methods, in: In Principles of Forecasting: A Handbook for Researchers and Practitioners, Ed: J. Scott Armstrong, Kluver, 2001, 365-386. [15.] Acar, Y. and Gardner, E. S.: Forecasting Method Selection in a Global Supply Chain, International Journal of Forecasting, 2012, 28(4), 842– 848. [16.] Fildes, R. et al.: Forecasting and Operational Research: A Review, Journal of the Operational Research Society, 2008, 59(9), 1150–1172. [17.] Caniato, F. et al.: Integrating Quantitative and Qualitative Forecasting Approaches: Organizational Learning in an Action Research Case, Journal of the Operational Research Society, 2011, 62(3), 413–424. [18.] Forge, S.: Forecasting Quantitatively Using Micro/Meso/MacroEconomics with Scenarios for Qualitative Balance, foresight, 2009, 11(1), 43–60. [19.] McCarthy, T. M. and Golicic S. L.: Implementing Collaborative Forecasting to Improve Supply Chain Performance, International Journal of Physical Distribution & Logistics Management, 2002, 32(6), 431–454. [20.] Nakano, M.: Collaborative Forecasting and Planning in Supply Chains: The Impact on Performance in Japanese Manufacturers, International Journal of Physical Distribution & Logistics Management 2009, 39(2), 84–105. [21.] Goodwin, P. and Fildes, R.: Forecasting in Supply Chain Companies: Should You Trust Your Judgment?, OR Insight, 2011, 24(3), 159–167. [22.] Rahman, M. A. et al.: Peak Demand Forecasting for a Seasonal Product Using Bayesian Approach, The Journal of the Operational Research Society, 2011, 62(6), 1019–1028. [23.] Sari, K.: Inventory Inaccuracy and Performance of Collaborative Supply Chain Practices, Industrial Management + Data Systems, 2008, 108(4), 495–509. [24.] Azadeh, A. et al.: Forecasting and Optimization of Service Level in Vague and Complex SCM by a Flexible Neural Network - Fuzzy Mathematical Programming Approach, International Journal of Advanced Manufacturing Technology, 2013, 68(5-8), 1453–1470. [25.] Attaran, M.: Collaborative Supply Chain Management, Business Process Management, 2007, 13(3), 390–404. [26.] Aviv, Y.: A Time-Series Framework for Supply-Chain Inventory Management, Operations Research, 2003, 51(2), 210–227. [27.] Giloni, A. et al.: Forecasting and Information Sharing in Supply Chains Under ARMA Demand, IIE Transactions, 2014, 46(1), 35–54. [28.] regor, S.: The Nature of Theory in Information Systems, MIS Quarterly, 2006, 30(3), 611–642. [29.] Stapleton, D. et al.: Enhancing Supply Chain Solutions with the Application of Chaos Theory, Supply Chain Management 2006, 11(2), 108–114. [30.] Syntetos, A. A. et al.: The Effects of Integrating Management Judgement into Intermittent Demand Forecasts, International Journal of Production Economics, 2009,118(1), 72-81. [31.] Petersen, H.: Integrating the Forecasting Process with the Supply Chain: Bayer Healtcare's Journey, Journal of Business Forecasting Methods & Systems, 2004, 22(4), 11–16. [32.] Picksley, J. D. and Brentnall, G. J.: Bayesian Modeling Enhances Supply Chain Forecasting and Planning, Journal of Business Forecasting Methods & Systems 1999, 18(3), 19-23. [33.] Khadar, S. A.: VMI Program Improves Forecasting & Supply Chain Arasco's Case Study, Journal of Business Forecasting, 2007, 26(3), 29– 32. [34.] Fisher, M.L. et al.: Making Supply Meed Demand in an Uncertain World, Harvard Business Review, 1994, 72(3), 83–93.

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Abdelnaser OMRAN, 2. Abdulsalam ABDULRAHIM

BARRIERS TO PRIORITIZING LEAN CONSTRUCTION IN THE LIBYAN CONSTRUCTION INDUSTRY 1.

School of Economics, Finance and Banking, College of Business, Universiti Utara Malaysia, 06010, Sintok, Kedah, MALAYSIA 2. Engineering Department, Construction Company, Sebha city, LIBYA

Abstract: Engaging in Lean construction efforts could prove to be highly rewarding for building firms in Libya. However, lean construction is risky and can be disastrous if not properly managed. Lean production efforts in some other countries have not been successful due to the many barriers to its successful implementation. This study sets out intends to explore identify the barriers that affecting the prioritizing of lean construction with the objective of determining the barriers that affects the use of lean construction in construction industry in Libya. Forty six (46) questionnaires were distributed to various construction firms in Libya. This study presents nine (9) barriers and investigates their influence (strength) on the success of lean construction initiatives. The strongest barrier is the provision of inputs exactly when required. Additionally, the barriers were ranked according to the ease of overcoming each. The easiest barrier to overcome is keeping the required items in the right place. This study indicates that extra efforts still needed to be done on the awareness and use of lean construction in the Libyan construction industry. Additionally, a graphical aid is provided to enable decision makers to concentrate their efforts on the influential (strong), yet easy to overcome barriers. A lack of buildable designs and a participative management style for the workforce are the most important barriers to successful waste reduction in terms of strength and ease of overcome. On the other hand, a lack of an organizational culture that supports teamwork, a lack of prefabrication and a lack of knowledgeable and skilled workers are regarded as low in strength, and at the same time difficult to overcome. This therefore shows that efforts still need to be done on the awareness and use of lean construction in the Libyan construction industry. Keywords: Lean construction, Barriers, Construction industry, Efforts, Libya

INTRODUCTION The construction industry in Libya faces serious challenges and difficulties due to fast developments and dependence on foreign experts. The current capacity of the Libyan construction industry is unable to meet national housing supply needs. New homes, airports, ports, railway, and roads need to be built and upgraded. Hotels, office building and resorts are required to meet the needs of an expanding tourism industry. The building industry is often described as an industry with many troubles and a lack of efficiency. The solution to all of these evils is said to be in using the concept of lean construction. The word lean was distinct by (Howell, 2001). The lean construction knowledge developed by Toyota is, for many people, regarded as the only path for the building industry. Lean production or manufacturing concept comprises a variety of production systems that share certain principles, including waste minimization, responsiveness to change, effective relationships within the value stream, continuous improvement, and quality from the beginning by (Murman et al., 2002). Lean construction concepts have recently received attention as a modern way to improve construction performance and labor productivity (Abdel-Razek et al., 2007).Lean production is currently a buzzword in many manufacturing industries (Fellows et al., 2002), and some in the construction sector have tried to adapt it. The proponents of lean construction argue that it has the potential of

tapping into new and presented production theories committed to minimizing wasteful activities and values adding. Waste includes overproduction, wait time, transportation, assessment, inventories, movement and production of defective parts and products. To improve on craft and mass production, lean production combines the advantages of both (Sowards, 2006; Koskela, 1992). Koskela (1992) stated that construction is exceptional in the sense that it is one-of kind nature of projects, site production and provisional multi organization. However, breakdown of establishing a good management system in the construction project will lead to many problems that would cause cost of project increases, a late conclusion of project and low quality, which finally reduce the profit of the contractor. In order to overcome this problems, lean thinking or lean construction is been introduced in the construction sector. According to Howell, (1999), lean construction is one of the new philosophies that is been implemented by Toyota in their developed process, which now applied to the construction industry in order to smoothen the construction project and increase the contractor’s profit by eliminating waste. This is supported by Ballard and Howell, (1998) who also stated the same facts that lean thinking in construction concerned in waste reduction. Lean concepts have been brought to the construction industries of USA, Australia, Brazil, Denmark, Ecuador, Finland and Singapore (Ballard and Howell, 1998). Lean

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

construction project is very different compared to traditional construction project management where a lean approach aims to maximize performance for the customer at the project level, set well defined objective clearly for deliverance process, design concurrent product and process and applies production control throughout the life of the project (Howell, 1999). This study therefore intends to determine the barriers that are affecting lean construction in the construction industry in Libya. This work will also contribute to knowledge in that there are no case studies or actual documentation of lean construction being implemented in the local construction industry as this will provide a better and concrete result. To the building firms operating in Libya, this study will present the force and ease of overcoming lean production barriers. This study can be useful to the practitioners in diverse ways. RESEARCH METHOD The use of structured questionnaire was employed for data collection and was distributed using a non-probability sampling which is based on the personal judgment of the researchers. The structure of the questionnaire consists of two sections; section “A” is made up of five (5) items which consist of information about the respondent background, while section “B” consist of forty (40) items based on the potential barriers in implementing lean construction, these barriers were listed into nine (9). The aim was to investigate the barriers for prioritizing lean construction in the Libyan construction industry. Data were collected from respondent. The data collection commenced on 1st October 2011 and finished by 15th January 2012. Of the questionnaires that were sent out, only forty six (46) were returned fully filled and therefore used in the analysis. RESULTS ANALYSIS AND DISCUSSION On teamwork, inadequate knowledge and skills have the highest mean score of 3.80 (SD= 0.868), while the least problem is the lack of group culture, shared vision and consensus with a mean score of 3.33(SD =1.0). This result agrees with Alinaitwe (2009) where it was identified that inadequate knowledge and skill is a major barrier that strongly influenced worker’s productivity. Annie et al. (2003) had also identified ability to measure performance of the team as one of the elements to achieve a more effective approach to managing the resources function within large construction firms which therefore means that inability of measuring performance will affect the firm, this is achieved here with a means score of 3.58 (SD= 0.866), which shows that it is a strong barrier. The total average mean average means score of 3.53 shows that teamwork is a barrier to the prioritizing of lean construction in the Libyan construction industry. The next item that was measured is based on Total Quality Management (TQM) in Table (2), the most important items for barriers to TQM in Libya are identified as lack of management leadership first ranked with a mean score of 3.60 (SD= 1.136) and it was documented by Venkatraman (2007) that a common barrier to both industry and education in implementing TQM is lack of proper leadership. Another important item that was identified is Poor

Fascicule 1 [January – March] Tome VIII [2015]

communication with a mean score of 3.58 (SD of 0.891), This is backed up by Sebastianelli and Tamimi (2003), who pointed out that poor communication between departments, was a real barrier to implementation of TQM. Table 1. Teamwork Barriers to prioritizing of lean construction in the Libyan Construction Industry Standard Items Score deviation Inadequate knowledge and skills 3.80 0.868 Lack of organizational culture supporting 3.60 0.863 team work Inability to measure performance of the team 3.58 0.866 and to gauge the team progress Individual needs and personal differences of 3.53 0.726 team members Defined focus 3.47 0.968 Lack of capability of team to maintain 3.42 0.965 alignment with other team Lack of group culture, shared vision and 3.33 1.00 consensus Total 3.53 0.894 Table 2. Barriers for Implementing of Total quality Management i n the Libyan Construction Industry Standard Total Quality Management Mean Score Deviation Lack of Management Leadership 3.60 1.136 Inadequate Teamwork 3.60 0.836 Poor Communication 3.58 0.891 Lack of understanding customers’ 3.47 0.842 needs Lack of continuous improvement 3.40 0.654

Table (3) summarized of all the barriers and their mean scores. Amongst nine barriers provided in the below Table, it was found that “Business Process Review” have the highest mean score of 3.65 (SD= 0.854), this shows that a lack of a defined process at which the construction activities will be reviewed is a strong barrier to the implementation of the concept of lean construction in the Libyan construction industry. This is quite in tandem with Mamish, (2011) where it was identified that under the business review process, inadequate project team skills is one of the factors leading to organizations failing to implement changes. Abdul-Hadi, (2005) also identified organisational culture of the construction firms as being an impediment in Business Process Review. Pull scheduling comes next with a mean score of 3.59 (SD= 0.897), this include inadequate resources and planning. As detailed by Ahlstrom (1998) that organizations need to devote effort and resources to a set of principles in parallel in order to achieve pull scheduling for implementation of lean production, which implies that if the resources are inadequate, it may not be possible to realize lean production. Matthew et al. (2000) on their part in regards to inadequate planning stated that programming and planning on

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

construction projects are critical to the overall success of the project. Simplification which comprise of incomplete designs and complicated designs have a mean score of 3.58 (SD= 0.775) as it is difficult to use lean construction when the design cannot be understood by the construction workers and in most situations, the design is incomplete leaving room for many variations to come into the design. Alinaitwe (2009) stated that incomplete or complicated designs are barriers to the use of lean construction in the industry. Concurrent engineering consist of four items which are lack of knowledge on how to implement; Lack of management support; Reward system based on individual goals and Lack of client and suppliers involvement in the scheme of events. This have a mean score of 3.55 (SD= 0.852) as where the stakeholders are not carried along and entrenched in the scheme of events, the construction firm may not be able to meet the stakeholders demand, also where the management is not in support of innovation, the project manager cannot achieve much on site, these therefore are barriers that impedes on the implementation of lean construction. Prasad (2000) confirms that lack of management support is a major organizational roadblock in concurrent engineering while Anumba et al. (2000) posited that lack of client and supplier involvement is a barrier to lean construction. Teamwork has a mean score of 3.53 (SD = 0.894) has been previously explained in Table (1). It is made up of seven items. Total Quality Management has a mean score of 3.53 (SD of 0.872) and was explained in Table (2) which included five items. Just in Time have a mean score of 3.48 (SD=0.796), it consists of seven items which are; uncertainty in the supply chain, uncertainty in the production process, high inflation rates, price cuts in case of early purchasing, poor transportation and communication, unavailability of materials in the local markets; and discounts of prices of large amounts of materials. Pheng and Chuan (2001) showed that transportation and communication are an important factor in construction site, and if it not properly managed can become a barrier to JIT, also price cut in case of early purchasing according to Low and Wu (1997) suggested that it was feasible to apply the JIT purchasing system to procure the raw materials, which can significantly reduce the amount of buffer stock on site. Benchmarking consist of five items which are: fragmented nature of the business, cyclic nature of the business, diversity in organizational sizes and structures, ambiguous nature of inputs and outputs; and lack of agreed methodology. These have a mean score of 3.45 (SD=0.796) which portray the issue of benchmarking as a problem in lean construction implementation. Diversity in organizational sizes and structures according to Bergin (2000) is a barrier as small companies will find it difficult to benchmark. While large businesses have taken to benchmarking to gain and maintain the competitive advantage. However, small businesses are slower to adopt benchmarking in their own operations. Lack of agreed methodology as specified by Lee et al. (2005) is to provide the industry with a common set of metric definitions; therefore, if there is no common agreed methodology, then the objectives of the benchmarking will

Fascicule 1 [January – March] Tome VIII [2015]

not be realized. The last barrier that was considered is flow reliability which consisted of four items: use of non-standard components, lack of accurate pre-planning, lack of prefabrication and lack of best practices in the procurement process. These have a mean score of 3.37 (SD= 0.941) reflecting that where best practice is not used for procurement, it will be difficult to use lean construction and also since there are no uniform standard of prefabrication of the materials to be used, it will pose a problem of getting the needed materials as at when needed. Alinaitwe (2009) had also identified the use of nonstandard components as a barrier while Haas et al. (2000) also identified the lack of prefabrication. Prefabrication can be approached differently, and these may result in change of the flow of the project. In productivity of construction project, onsite reassembly is ranked first followed by on site prefabrication and construction projects using offsite prefabrication are ranked last. Table 3. List of the Barriers to Prioritizing Lean Construction in Libyan Construction Industry Standard Barriers Mean Score Deviation Business Process 3.65 0.854 Accepted Review Pull scheduling 3.59 0.897 Accepted Simplification 3.58 0.775 Accepted Concurrent 3.55 0.852 Accepted engineering Teamwork 3.53 0.894 Accepted TQM 3.53 0.872 Accepted Just in Time 3.48 0.796 Accepted Benchmarking 3.45 0.796 Accepted Flow reliability 3.37 0.941 Accepted

CONCLUSION In conclusion, this study has been able to identify nine barriers to the prioritization of lean construction in Libya which are; Business process review, pull scheduling, concurrent engineering, team work, total quality management, Just in Time, Benchmarking and Flow Reliability. These are in order of importance to the construction industry in Libya. The findings are in agreement with previous authors who have identified the under listed as barriers to successful implementation of lean construction in the construction industry. The study therefore provides an understanding of the Libyan construction industry such that these problems can be resolved in other to move the industry forward. It is however recommended that training programs about lean construction be provided to industry professionals as these programs will help to upgrade their knowledge, skills, techniques and processes in order to improve on the barriers for prioritizing lean construction in construction industry.

REFERENCES [1.] Abdel-Razek, R., Elshakour, H.A., & Abdel-Hamid, M. Labour Productivity: Benchmarking and variability in Egyptian, International Journal of Project Management Projects,25(2): 189–197, 2007. [2.] Abdul Hadi, N., Corresponding, A.A.S., &Alqahtani, S. Prioritizing barriers to successful business process reengineering (BPR) efforts in

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering [3.] [4.] [5.] [6.] [7.]

[8.] [9.] [10.] [11.] [12.] [13.] [14.] [15.]

[16.] [17.] [18.] [19.]

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Saudi Arabian construction industry. Construction Management and Economics, 23(3): 305-315, 2005. Åhlström, P. Sequences in the implementation of lean production. European Management Journal, 16(3): 327-334, 1998. Alinaitwe, H.M. Prioritisinglean construction barriers in Uganda's construction industry. Journal of Construction in Developing Countries, 14(1):15-30, 2009. Anumba, C.J., Baugh, C., &Khalfan, M.M.A. Organisational structures to support concurrent engineering in construction. Industrial Management & Data Systems, 102(5): 260-270, 2002. Ballard, G., & Howell, G. Shielding production: Essential Journal of Construction Engineering step I production control. Journal of Construction Engineering and Management,124(1): 11–17, 1998. Bergin, S. Benchmarking small business performance: barriers and benefits. International Council for Small Business World Conference Entrepreneurial SMEs - Engines for Growth in the Millennium.Brisbane, Queensland, 2000. Fellows, R., Langford, D., Newcombe, R., &Urry, S. Construction Management in Practice Oxford: Blackwell Science, 2002. Haas, C.T., O’Connor, J.T., Tucker, R., Eickmann, J., &fa*gerlund, W.R. Prefabrication and preassembly trends and effects on the construction workforce: Center for Construction Industry Studies, 2000. Howell, G.A. What is lean construction. Proceedings of the 7th International Group for Lean Construction, University of California, Berkeley, CA, USA, 1999. Koskela, L. Application of the New Production Philosophy to Construction. Technical Report 72, CIFE, Stanford University. Stanford, CA, 1992. Lee, S. H., Thomas, S. R., & Tucker, R. L. Web-based benchmarking system for the construction industry. Journal of Construction Engineering and Management, 131, 790, 2005. Low, S.P., & Chan, Y.M. Managing Productivity in Construction JIT Operations and Measurements. Brookfield Vt: Ashgate Publishing Co., 1997. Mamish, M. HR Best Practices: Change Management Best Practices, 2011. [Matthews, J., Pellew, L., Phua, F., &Rowlinson, S. Quality relationships: partnering in the construction supply chain. International Journal of Quality &Reliability Management, 17(4/5): 493-510, 2000. Pheng, L.S., & Shang, G. The Application of the Just-in-Time Philosophy in the Chinese Construction Industry. Journal of Construction in Developing Countries, 16(1): 91-111, 2011. Sebastianelli, R., &Tamimi, N. Understanding the obstacles to TQM success. Quality Management Journal, 10(3): 45-56, 2003. Sowards, D. Waste is everywhere but isn't inevitable, Contractor, 53(1): 48, 2006. Venkatraman, S. A framework for implementing TQM in higher education programs.Quality Assurance in Education, 15(1): 92-112, 2007.

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Norge Isaías COELLO MACHADO, 2. Elke GLISTAU, 3. Béla ILLES

PROCEDURE TO SET VALUES FOR THE STATISTICAL PARAMETERS IN THE PROCESSES WITH SPECIFICATION LIMITS – APPLICATION IN LOGISTICS 1.

Universidad Central “Marta Abreu” de Las Villas. Faculty of Mechanical Engineering, Santa Clara, CUBA 2. Otto-von-Guericke-University Magdeburg. Faculty of Mechanical Engineering, ILM, GERMANY 3. Universityof Miskolc.Chair Materials Transportation and Logistics, HUNGARY

Abstract: Processes with specification limits (tolerance) are typical in industrial practice, for example in the control of the manufacturing process. Often these tools are be used in all engineering processes, here is shown an application in the control of the logistics process. To ensure the effectiveness of the process and to meet customer expectations it is necessary to ensure strict compliance with the tolerances [1]. Classic control methods base on variables that require monitoring related to the limits set by the natural process tolerance. In this work considerations expressed for estimating values of the dispersion and the permissible central tendency of the variables from the specification limits, the purpose is to obtain acceptable process capability for the specific case [2], [3]. Considerations are be done in the reverse order, dispersion values and the central tendency is not execute dafter he process determines in this case the maximum permissible valuesof dispersion and central tendency referred to tolerance specification are estimated to guarantee the required quality before you start the process, so this method can be considered as a preventive tool quality. Keywords: Quality Management, Logistics

INTRODUCTION The current industry companies have a commercial and technological competence, this competence involves harmonizing measurement systems, and update technologies to obtain satisfactory results with modern control systems quality. Besides the benefits that provide safe and reliable measurements and allows for comparisons with other companies. Current trends in quality control are the key element for continuous improvement; it uses a wide range of engineering tools and techniques, ranging fundamental tools to important development in current manufacturing technologies. It is necessary to find and use new sources of quality improvement, which leads to the use of statistical process control and the use of preventive techniques, i.e., focusing on the control of key input variables of the process, which contributes to creating the output of the desired product in an established quality. Statistical control bases on the application of statistical methods for the analysis, monitoring and control of processes. Logistics and Quality Management In logistics appear frequently qualitative parameters, which are measured and whose magnitudes are in turn defined by a maximum and a minimum tolerance limit that is set for that variable. We must have the tolerance as wide as possible and as close as necessary. This is being manifested in various processes and products, which is being treated extensively in the literature mainly with regard to

manufacturing processes. An application is being shown in this case to control logistical process. The logistics product is actually a service. These services are essentially sending, collecting or receiving from the client covered by a contract:  The correct object= What?  The correct amount=How much?  In the right place=Where?  At the right time=When, how often?  With appropriate costs=How many expenses?  With the right quality=No damage, incur additional services  Environmentally=with less environmental involvement These aspects lead to a nomenclature to describe a product logistics. Here it refers to "What"(object) to the entire physical world from a needle to a heavy equipment opencast mining, as shown in Figure 1[1]. Each of these terms simplest in turns one or more variables to be controlled, which in turn describe the corresponding quality parameter. Each of these specifications can be expressed by a variable for which the corresponding limits are set and the goal of that variable is within specification limits pursued. A common way to control the behavior of these variables is the control charts, as shown in Figure 2 [1].

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Fascicule 1 [January – March] Tome VIII [2015] The coefficients km and km' are calculated as: (5) kmx = u (1−α/2 ) / n for α = 0,27 % km = 3 / n

Goods Material level

People

Animals

Solids

Liquids

Units Level of unitization Packed level

Type level

Loading units

- pallets - container - packaging

Bulk

km'

Not unitized units

Unitized units

Charging aids

Gases

Packaging units Means cargo security - naylon - bands - tapes

Packing means

Packaging aids

- cans - casks - cartridges

- coils - staples - quilter

Other units Loading units (wrapper) - bottles - ball - bags

Control Chart - Inventory

Stock (pieces)

550

Loading units adapted - stackable - abuttably

Upper control limit

400

300 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

mean

Time (days)

Figure 2: Chart control limits applied to a logistic process

Control charts for regulation of central tendency. Control charts for the mean ( X -Control Charts). For the statistical control of the central tendency of processes primarily control charts for the mean ( X - CC) are used in practice. The main objective of the application of control charts for the mean is to immediately and safety determine the existence of systematic distortions in the process expressed in the form of trend. Practical experiences in the industry, as well as the mathematics of probability, recognize these control charts as the most efficient means to recognizing systematic process changes and interruptions. Conventional data collection and manual mathematical processing require a relatively long time, which minimizes the applicability of these control charts. Now an automated collection and processing of data significantly increases the benefits of this graph, so that the fundamental criterion for the selection of the type of control chart is its effectiveness. The calculation of the control limits (CL) and warning limits (WL) for a X -GC obtains for the case that the standard deviation (σ) is sufficiently known and it is referred to the central tendency (µ) of the process: (1) UCLM = μ + km .σ = μ − .σ (2) LCLM km = + µ . σ (3) UWLM km' = µ − . σ (4) LWLM km' x

1−α / 2 )

Lower control limit

250

LS kT

LCLT

= LI + kT x .σ

(7) (8)

- Percentile of the distribution of the mean values.

For the case in which p = 0,27 % and α = 0,27 % obtained:

Lower limit warning

350

1− p / 2

Average

450

UCLT

The factor kT x is calculated as: kT x = u(1− p/ 2 ) − u(1−α / 2 ) / n with u( ) - Percentile of the distribution of the individual values.

Upper warning limit

500

= 1,96 / n for α = 5 %

In case there are predetermined limits or tolerances specification (ULupper limit, LL-lower limit) calculation of control limits for a process capability indexes Cp≥ 1 are performed according: (6) = − .σ

Figure 1: Goods classification

(

= 3 1−1/ n

)

Control charts for monitoring the standard deviation (s- Control Charts). The control charts to monitor the dispersion of samples or process (sGC), are previously seldom used. That is why the mathematical complexity of the calculations is necessary for preparation, this limitation has almost no effect today with the introduction of new computing techniques in manufacturing processes and processes in general, however provides a great advantage from the point of view of its effectiveness to detect changes in the dispersion process. This effectiveness bases on the high information content of the standard deviation and its effectiveness to interpret outliers [1]. The calculation of the control limits (CL) for the control charts for the standard deviation (s-Control Charts) bases on the standard deviation of the process σin the form: (9) OCLs = kso .σ (10) LCLs = ksu .σ Tobe accepted for an error probabilityα = 0,27 % obtained: 2 (11) ks = c + 3 1 − c o

ks = c u

− 3 1 − c2 n 2

(12)

The general procedure for the preparation and implementation of Control Charts for the control variables should be divided in to the following steps:  Determination of the statistical parameters describing the process under control by the process mean (µ) and dispersion process (σ). This determination is made by statistical analysis, in some cases a statistical look ahead is performed or refers to historical data from similar productions.  For different types of Control Charts for the corresponding statistical parameters (individual values or mean value and

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dispersion for defined volume of the sample) are determined and a proof distribution model is made. There are some exceptions such as non-normal distributions among others; logarithmic distributions and other transformations.  For the process under statistical control are determined µo, σo and on that basis the boundaries or limits (L) are calculated, into which you can move the corresponding statistical parameters of the sample without the need to intervene in the process. Solution for the in determinacy of the sample statically moments Performing a practical analysis of this problema contradiction occurs in the majority of practical applications. If you have no initial data for the mean and dispersion characterizing the process (µo, σo) or any estimate there of would be affected by errors, other times the volume of the process does not allow for an initial sample and this forces to establish control of 100% with the known consequences. A possible solution in this case is proposed to proceed as follows: The fundamental objective is to ensure the quality parameter that expresses the given variable for tolerance (T). (13) T = OL − LL The centre of the tolerance is expressed by: OL + LL 2

(14)

T OL − LL = 6σ 6σ

(15)

EC =

The potential of a process is known to: cp =

and:

c pk = c p −

EC − μ 3σ

(16)

Given this relationship it can be inferred that the limit values μo, σo for parameters (central tendency and dispersion) can be set to fulfill the conditions described by the tolerance specification. It is to assume that the process have to be sufficiently focused, following the techniques of Taguchi, such that the distance from the central tendency to the upper limit is equal to the distance from the central tendency to the lower limit. Mathematically this condition describes the maximum value of cpk (cpk=cp) which reaches to the condition expressed in equation 17. μ = EC =

OL − LL 2

Fascicule 1 [January – March] Tome VIII [2015]

1.0, it is neither possible to expound the measurement uncertainty nor the possible displacement of the position, as shown in figure 3. For this general form a minimal value of cp= 1.33 is required. _

Dmed = Cp = 1,0 Cpk = 1,0

Individual values

Measurement uncertainty

T = 6σ

Dmin

Dmax

Figure 3: Graphical representation of the behavior of the uncertainty in the threshold limit values and considering cp=1.

Based on the practical consideration of the characteristic of dispersion and the centering the minimal recommended value of cp has to be stipulated to 1.33, because this value permits a position displacement. Due to this value there is an equal distance of σ in both directions without increasing the possibility of the variable to exceed the limits of specification. For the stipulating of adequate values different considerations should exist for every case concerning the economic and technological characteristics. According to these considerations the measurement uncertainty has to be estimated by using the corresponding, statistical parameters [4]. These displacements exist in every case, even if they can be small. This value can be big for special cases, including the case that the philosophy of 6σ leads to a cp value of 2.0, as shown in figure 4. 1,5 σ

EC Cp = 2 Cpk = 1,5

T = 12 σ

(17)

The limits for the parameters μo, σo may be defined so that that the requirements of the tolerance can be fulfilled. σ=

T 6c p

Figure 4: Dispersion of process conditions for six sigma (6σ)

(18) To establish appropriate values for each case other considerations of By this expression the magnitude of the dispersion refers to the economic and technological nature [1] should be taken. Alongside process required potential and its relationship with the tolerance these considerations must be assessed the need for the present measurement uncertainty using the corresponding statistical specification. Using this expression the value of dispersion can be derived from the parameters [4]. Also in all cases, even the displacement of the central process capability (necessary process potential) and the correlation to tendency for these movements to be small is always present. This the tolerance of specification. In the case of a process capability of cp= value may be higher for special cases, even where a philosophy that is valued 6σ, would have a value of c p= 2.0. This is an example of | 59 |

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employment and improvement of quality tools to prevent potential quality defects and errors, which leads to a conscious action on the rational use of all resources. In general the proposed procedures areas follows figure 5, independence of the values of the average and the dispersion, besides taking into account the capacity of the manufacturing process. Process design (T) 1 µ;σ known

no Set up Cp , Cpk

yes calculate Cp ; Cpk no

calculate µ , σ

Cp > 1,3 Cpk > 1 yes

process control (CC) hyper regulation

yes

review the process

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ACKNOWLEDGEMENTS The authors would like to thank all colleagues of the three universities Magdeburg (Germany), Santa Clara (Cuba) und Miskolc (Hungary) for their support, valuable comments and assistance with this project. REFERENCES [1.] Illés, B., E. Glistau, and N.-I. Coello-Machado, Logística y Gestión de la Calidad. 1 ed. Vol. 1. 2013, Miskolc: Universidad de Miskolc. 194. [2.] Machado-Osés, C. and A. Alfonso-Martínez, Prozessoptimierung in Produktion und Lieferkette durch Prozessfähigkeitsanalyse Ein neuer Fähigkeitsindex.MSL, 2008. Heft 24 (Logisch GmbH): p. 9-16. [3.] Coello-Machado, N.-I., E. Glistau, and B. Illés. Estimación de los valores de dispersión y centrado para procesos logísticos con límites de especificación. in COMEC 2008. 2008. Santa Clara, Cuba: Editorial Feijoó. [4.] Grote, K.-H. and E. Antonsson, Handbook of Mechanical Engineering. 1 ed. 2009, Berlin-Heidelberg-New York: Springer Verlag. 1580.

calculateu

no review the process control

µ ≤[ µ]

yes executing the process

Figure 5: Proposed procedures for allocating the actual tolerance

In consequence of the widespread application of these tools and the awareness of those who must carry it out, it is known that in reference to quality often environmental and sustainability issues are expressed in a close relationship with all aspects relating to quality product. In the development of joint projects in the field of quality management, quality engineering, logistics and the environmental aspect has been sensitizing stake holders on these issues. CONCLUSIONS Tools and methods of simple and well-developed assessment can help efficient use of resources for sustainable ecological, economic and social development. The conscious use of preventive quality tools is a potential to be considered in this regard. The possibility of making a prediction oft he values of central tendency and dispersion in the case of control variables allows for a preventive control in the process. Any deviation of the dispersion values and the central tendency established for the process leads to the generation of a signal and thus a required analysis of the causes. That can be supported by using tools of the quality management from a histogram to an experimental design. The solution extends the scope of control charts to those processes in which the valuesof central tendency and dispersion (μo, σo) are unknown and where it is difficult to carry out a preliminary statistical analysis due to the small volume of production.

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Mohamed ZELLAGUI, 2.Abdelaziz CHAGHI

APPLICATION KHA FOR OPTIMAL COORDINATION OF DIRECTIONAL OVERCURRENT RELAYS IN THE PRESENCE MULTI GCSC 1-2.

LSPIE Laboratory, Faculty of Technology, Department of Electrical Engineering, University of Batna, ALGERIA

Abstract: Optimal coordination of direction overcurrent relays in the power systems in the presence of GTO Controlled Series Capacitor (GCSC) installed on meshed power system is studied in this paper. The coordination problem is formulated as a non-linear constrained mono-objective optimization problem. The objective function of this optimization problem is the minimization of the operation time of the associated relays in the systems, and the decision variables are: the time dial setting and the pickup current setting of each overcurrent relay. To solve this complex non linear optimization problem, a variant of evolutionary optimization algorithms named Krill Herd Algorithm (KHA) is used. The proposed algorithm is validated on IEEE 14bus transmission network test system considering various scenarios. The obtained results show a high efficiency of the proposed method to solve such complex optimization problem, in such a way the relays coordination is guaranteed for all simulation scenarios with minimum operating time for each relays. The results of objective function are compared to other optimization algorithms. Keywords:Meshed Power System, GTO Controlled Series Capacitor, Overcurrent Relay, Coordination Time, Krill Herd Algorithm

INTRODUCTION System protection is an important part in the power network systems. The most important part in designing the protection needs to consider such as the type of relays, the size of circuit breaker and fuse, the type and size of current transformer, the coordination of relays, and them component to maintain the stability of the system. Then to maintain the stability each relay in the power network must setting in proper technique in term of current and time operation. During the operation of modern interconnected power systems, abnormal conditions can frequently occur. Such conditions cause interruption of the supply, and may damage the equipments connected to the system, arising the importance of designing a reliable protective system. In order to achieve such reliability, a back-up protective scheme is provided to act as a second line of defense in case of any failure in the primary protection. In other words, it should operate after a certain time delay known as Coordination Tine Interval (CTI), giving the chance for the primary protection to operate. The fore mentioned situation leads to the formulation of the wellknown protective relay setting coordination, that consists of the selection of a suitable setting of each relay such that their fundamental protective function is met under the desirable qualities of protective relaying, namely sensitivity, selectivity, reliability, and speed [1]. Overcurrent relaying, which is simple and economic, is commonly used for providing primary protection and as backup protection on power systems [2]. To reduce the power outages, maloperation of the backup relays should be avoided, and therefore, Overcurrent relay coordination in power transmission and distribution

networks is a major concern of protection engineer. A relay must get sufficient chance to protect the zone under its primary protection. Only if the primary protection does not clear the fault, the back-up protection should initiate tripping. Each protection relay in the power system needs to be coordinated with the relays protecting the adjacent equipment [3], the overall protection coordination is thus very complicated. Overcurrent relay have two types of settings: pickup current and dial time settings. Recently, it is noticeable that the power demand has been increasing substantially worldwide. On the other hand, the expansion of power generation and transmission facilities and equipment has been severely limited due to limited resources and environmental restrictions. As a consequence, some transmission lines are heavily loaded and the system stability becomes a power transfer-limiting factor. Flexible AC Transmission Current (FACTS) controllers offer many benefits to the network and have been mainly used for solving various power system steady state control problems [4, 5]. In recent years, many research efforts have been made to achieve optimum protection coordination (optimum solution for relay settings) without GCSC on power system using different optimization techniques, including Random Search (RS) technique is reported in [6], Evolutionary Algorithms (EA) is presented in [7] while Differential Evolution Algorithm (DEA) in [8], Modified Differential Evolution Algorithm (MDEA) in [9], and Self-Adaptive Differential Evolutionary (SADE) algorithm in [10], application Particle Swarm Optimization (PSO) in [11], and Modified Particle Swarm Optimizer in [12, 13], and Evolutionary Particle Swarm Optimization (EPSO)

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Algorithm in [14], Box-Muller Harmony Search (BMHS) in [15], Zeroone Integer Programming (ZOIP) Approach in [16], Seeker Algorithm (SA) is presented in [17], and Teaching Learning-Based Optimization (TLBO) in [18]. This paper presents the solution of the coordination problem of IDMT directional overcurrent relays on meshed power system using KHA approach. The problem is formulated as a non linear constrained mono-objective optimization problem. Our goal behind this optimization is to find an optimal setting of Time Dial Setting (TDS) and Pickup current (IP) of each relay that minimizes the operating time (T) of overall relays. The new idea presented in this paper, is taking into account the variation of the effective impedance of the line caused by the action of GCSC devices of the transmissions line. Two simulation scenarios with and without multi GCSCs are considered in this paper. APPARENT RECTANCE INJECTED BY GCSC The GCSC presented in thefigure1.a is the first that appearsin the family of seriescompensators. It consists ofacapacitance (C)connected in serieswith the transmission line andcontrolled by avalve-type GTOthyristorsmounted in anti-paralleland controlled byafiring angle (γ) variedbetween 0° and180° [19-22].

Fascicule 1 [January – March] Tome VIII [2015]  π −β  1  X GCSC ( β ) = X C .Max 1 −   − sin (π (π − β ) )  (4)   π  π 

The relation of injected voltage is calculated by flowing equation:

 π −β  1  VGCSC ( β ) = VMax 1 −   − sin (π (π − β ) )  (5)   π  π 

Where, VMaxis maximum voltage injected and controlled by GCSC. The total transmission line (ZAB-GCSC) impedance with GCSC inserted on midline is given by: (6) Z AB −GCSC = RAB + j [ X AB − X GCSC ( β ) ] In the presence three phase fault, the fault current (IF) is defined by [22]: IF =

Figure 1. Transmission line in the presence of GCSC device. a). Control principle, b). Apparent reactance.

(7)

Where, ZAB.1and XGCSC.1is positive component of line impedance compensated and GCSC respectively. From equation (7), the fault current is only related to parameters of transmission line and parameters of GCSC installed (VGCSC and XGCSC). PROBLEM FORMULATION AND CONSTRAINTS The coordination of directional overcurrent relays in a multi-loop system is formulated as an optimization problem. The coordination problem, including objective function and constraints, should satisfy three requirements. Objective Function The aim of this function (f) is to minimize the total operating time of all overcurrent protection relays in the system with respect to the coordination time constraint between the backup and primary relays. N  f = Min ∑ Ti   i =1 

(a)

(b)

3. (VA + VGCSC ) Z AB.1 + X GCSC .1

(8)

Where, Ti represents the operating time of the ith relay, N represents the number of relays in the power system. For each protective relay the operating time T is defined by [9-11]: α (9) = Ti TDS × β  IM

 +γ

 I  Thiscompensator is installed in the transmission line AB between busP  bars A (source) and B (load) and modeled as a variablecapacitive Where, T is relay operating time (sec), TDS is time dial setting (sec), IM reactance(XGCSC). From figure1.b, this capacitive reactance is definedby is the fault current measured by relay (A), IP is pickup current (A). The the equation [21, 22]: constant α, β, and γ depend on the characteristic curve for IDMT 1  2  (1) directional overcurrent relay. The current IM is defined by: X GCSC (= γ ) X C .Max 1 − γ − sin(2π )  I π π   (10) IM = F where, K CT (2) where, IF is the fault current, and KCT is ratio of the current X C .Max = 1 CGCSC .ω The conduction angle (β) which varies between 0 to 90°, is defined by transformer. Constraints next relation: The coordination problem has two types of constraints, including the π  β =π − 2γ =2  − γ  (3) constraints of the relay characteristic and coordination constraints. 2  Relay constraints include limits of relay operating time and settings. From equation (3), the equation (2) becomes: Coordination constraints are related to the coordination of primary and backup relays. | 62 |

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

The operating time of a relay is a function of the pickup current setting and the fault current seen by the relay. Based on the type of relay, the operating time is determined via standard characteristic curves or analytic formula. The bounds on operating time are expressed by: (11) Ti min ≤ Ti ≤ Ti max min max Where, Ti and Ti are the minimum and maximum operating times of the ithovercurrent relay. During the optimization procedure, the coordination between the primary and the backup relays must be verified. In this paper, the chronometric coordination between the primary and the backup relays is used as follows equation: (12) Tbackup − Tprimary ≥ CTI Where, Tbackup and Tprimary are the operating time of the backup relay and the primary relay respectively, CTI is the coordination time interval. The time dial setting (TDS) adjusts the time delay before the relay operates when the fault current reaches a value equal to, or greater than, the pickup current (IP) setting [6-12]. (13) TDSimin ≤ TDSi ≤ TDSimax (14) I Pimin ≤ I Pi ≤ I Pimax min max where, TDSi and TDSi are the minimum and the maximum limits of TDS for the ithrelay. I Pimin and I Pimax are the minimum and the maximum limits of IP for the ithrelay. KRILL HERD ALGORITHM (KHA) KHA is a recently developed heuristic algorithm based on the herding behavior of krill individuals. It has been first proposed by Gandomi and Alavi in 2012 [22-24]. It is a population based method consisting of a large number of krill in which each krill moves through a multidimensional search space to look for food. In this algorithm, the positions of krill individuals are considered as different design variables and the distance of the food from the krill individual is analogous to the fitness value of the objective function. In KHA, the individual krill alters its position and moves to the better positions. Induction In this process, the velocity of each krill is influenced by the movement of other krill individuals of the multi-dimensional search space and its velocity is dynamically adjusted by the local, target and repulsive vector. The velocity of the ith krill at the mth movements may be formulated as follows [22]: (15) Vi m α iVi max + ωnVi m −1 = and, f −f   Z −Z i  αi = ∑j =1  f i − fj × Z − Z i+ randj (0,1) +2 rand (0,1) + i  fibest X ibest max  i j  w b   NS

Fascicule 1 [January – March] Tome VIII [2015]

population; fi, fjare the fitness value of the ithand jthindividuals respectively. NS is the number of krill individuals surrounding the particular krill; i, imax are the current iteration and the maximum iteration number. A sensing distance (SDi) parameter is used to identify the neighboring members of each krill individual. The sensing distance may be represented by [23]: n 1 (17) SDi = ∑ Zi − Z k p

5n p

   i  V fmi =0.02  2 1 − f   imax  i  

  k + fi best X ibest  + ωxV fmi −1  1  fj 

∑f k =1 NS

∑ k =1

(18)

where, ωxis the inertia weight of the foraging motion, Vfim-1, Vfim, are the foraging motion of the ithkrill at the (m - 1)th and m movement. Random Diffusion The diffusion speed of krill individuals may be expressed as follows [22]: (19) VDm = µVDmax where, VDmax is the maximum diffusion speed; µ is a directional vector uniformly. Position Update In KHA, the krill individuals fly around in the multi-dimensional space and each krill adjusts its position based on induction motion, foraging motion and diffusion motion. The updated position of the ithkrill may be expressed as [24]: N (20) Z im +1 = Z im + (Vi m + V fim + VDim ) Pt ∑ ( u j − l j ) i

j =1

where, Nd is the number of control variables uj, ljare the maximum and minimum limits of the jthcontrol variable; Pt is the position constant factor. Crossover Depending upon the crossover probability, each krill individual interacts with others to update its position. The jth components of the ithkrill may be updated by [22-24]:  Z k , j if , rand ≤ CRi = Zi, j  = where, k 1, 2, ... n p ; k ≠ 1  Z i , j if , rand > CRi

(21)

where, CRiis the crossover probability and is given by [22]:

(16)

where, Vimax is the maximum induced motion: Vim, Vim-1 are the induced motion of the ithkrill at the mthand (m-1)thmovement; ωn is the inertia weight of the motion induced: fw and fb are the worst and the best position respectively, among all krill individuals, of the

k =1

where, np is the population size, Zi and Zk are the position of the ith and kth krill respectively. Foraging Action The foraging velocity of the ith krill at the mth movement may be expressed by [22]:

CR i = 0.2 fi best

(22)

Mutation In this process [24], a scalar number FR scales the difference of tworandomly selected vectors Zm,j and Zn,jand the scaled difference is added to the best vector Zbest,jwhence the mutant vectors Zi,jm is obtained.

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Fascicule 1 [January – March] Tome VIII [2015]

Zi, j = Z best , j + FR ( Z m , j − Z n , j )

(23) of 42 directional overcurrent relays. The power system study is Using mutation probability (MR) the modified value, Zi,jmod is selected compensated with five GCSCs located at middle of the transmission lines (1-5, 3-4, 4-5, 9-14, and 13-14), where conduction angle (β) from Zi,jm and Zi,jand it may mathematically expressed as [22, 24]: varied between 5°, 45°, and 90° for all installed GCSCs on power m  Z i , j if rand ≤ M R mod (24) system. Zi, j =  Z rand > M if Impact of GCSC on CTI  i , j R Table 1 presents, the CTI values of the overcurrent relays without and The proposed optimization algorithm includes steps below: Step no. 1: Structure definition of data, the limit of scope and with multi GCSC on three compensation degree. Table 1. Impact of multi GCSC on CTI value parameters, With GCSC Primary Backup Without Step no. 2: Definition of initial population, relay relay GCSC β = 5° β = 45° β = 90° Step no. 3: Calculation of the propriety of each Krill according to its 5 6 0.3400 -0.1124 -1.2366 -0.2507 location in the search environment, 11 12 0.3600 -0.1462 -1.6086 -0.7261 Step no. 4: Calculation of the movement of each Krill, 15 16 0.3200 -0.1123 -1.2352 -0.2504 Step no. 5: Induced movement of other Krill, 33 34 0.3893 -0.0778 -0.8553 -0.4734 Step no. 6: Movement towards food, 35 36 0.3321 -0.1061 -1.1666 -0.2365 Step no. 7: Physical diffusion based on chaotic portrait, From this table, it is clear that all relays are coordinated in the case Step no. 8: Implementation of genetic operators, Step no. 9: The update process of each krill in the search environment, without multi GCSC (superior reference value 0.3 sec), but among of Step no. 10: Repetition of step no. 3 to 6 up to the desired accuracy, them are not coordinated in the presence multi GCSC for all angle β (CTI value written in bold). Thus, we can conclude that GCSC causes a Step no. 11: End. loss of coordination between the relays protection line. In this CASE STUDY AND RESULTS The impact of GCSC on directional relays coordination is performed on situation, we must compute the new settings of the relays to ensure the following two scenarios: without and with multi GCSC installed at the coordination. IEEE 14 bus transmission power systems. As we mentioned above, the relays coordination problem is formulated as constrained monoobjective problem and solved using the KHA optimization algorithm considering 82 decision variables (42 variables represent the IP and 42 variables represent the TDS).

(a)

Figure 2. IEEE 14-bus power system with multi GCSC

Figure 2, represents the case study of a network fed by 02 generators and with 14 buses, 20 transmission lines. The power system consists | 64 |

Figure 3: Convergence characteristics of KHA for all cases. a). Without GCSC, b). With GCSC.

(b)

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Optimal Settings and Coordination The optimization constraints for case all study in absence or presence multi GCSCs are:  CTI = 0.3 sec,  50 ≤ IPi ≤ 1700 (A),  0.02 ≤ TDSi ≤ 0.30 (sec),  0.05 ≤ Ti ≤ 1.50 (sec),  Type of curve: very inverse. The KHA parameters are:  Vimax = 0.01,  VDmax = 0.15,  Pt= 0.20,  ωn = 0.90,  ωx = 0.90,  Gmax= 180. The convergence characteristics of the KHA without and with multi GCSCs are depicted in Figures 3.a and 3.b respectively. From Figure 4.a, we can see that the optimization algorithm proposed is convergence within 120 iterations, and the value of objective function is 14.5384 sec. From Figure 4.b, the value of objective function in the presence multi GCSC is 16.4321 sec, 17.0347, and 19.3246 with conduction angle β equal 90°, 45° and 5 ° respectively. The optimal settings relay (IP and TDS) for all cases are represented in Tables 2 and 3. Relay No. 1 2 3 4 5 6 7 8 9 10 11 12 13 13 15 16 17 18 19 20 21

Table 2: Optimal relays settings without GCSC IP Relay IP TDS (sec) TDS (sec) (A) No. (A) 876 0.031 22 526 0.180 368 0.042 23 175 0.196 368 0.046 24 701 0.226 876 0.031 25 421 0.127 548 0.072 26 1314 0.143 245 0.035 27 245 0.021 245 0.053 28 350 0.152 329 0.121 29 175 0.044 350 0.113 30 788 0.086 140 0.099 31 131 0.170 350 0.072 32 70 0.046 105 0.227 33 701 0.129 245 0.064 34 175 0.226 548 0.081 35 280 0.131 438 0.129 36 526 0.168 245 0.168 37 131 0.158 394 0.128 38 280 0.136 210 0.022 39 105 0.060 701 0.193 40 767 0.121 280 0.175 41 876 0.162 350 0.201 42 280 0.105

Relay No. 1 2 3 4 5 6 7 8 9 10 11 12 13 13 15 16 17 18 19 20 21 Relay No. 1 2 3 4 5 6 7 8 9 10 11 12 13 13 15 16 17 18 19 20 21

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Table 3: Optimal relays settings with multi GCSC a). β = 5°, b). β = 45°, c). β = 90°. (a) IP Relay IP TDS (sec) (A) No. (A) 1011 0.036 22 607 425 0.048 23 202 425 0.048 24 809 1011 0.036 25 485 632 0.083 26 1517 283 0.041 27 283 283 0.061 28 404 379 0.140 29 202 404 0.131 30 910 162 0.114 31 152 404 0.083 32 81 121 0.262 33 809 283 0.074 34 202 632 0.094 35 324 506 0.149 36 607 283 0.194 37 152 455 0.148 38 324 243 0.025 39 121 809 0.223 40 885 324 0.202 41 1011 404 0.232 42 324 (b) IP Relay IP TDS (sec) (A) No. (A) 974 0.034 22 584 409 0.047 23 195 409 0.049 24 779 974 0.034 25 468 609 0.080 26 1461 273 0.039 27 273 273 0.058 28 390 365 0.135 29 195 390 0.126 30 877 156 0.110 31 146 390 0.080 32 78 117 0.253 33 779 273 0.071 34 195 609 0.090 35 312 487 0.143 36 584 273 0.186 37 146 438 0.142 38 312 234 0.024 39 117 779 0.215 40 852 312 0.194 41 974 390 0.223 42 312

TDS (sec) 0.208 0.227 0.260 0.147 0.165 0.022 0.175 0.051 0.100 0.196 0.053 0.148 0.261 0.151 0.193 0.182 0.157 0.069 0.140 0.187 0.121 TDS (sec) 0.201 0.218 0.251 0.141 0.159 0.021 0.169 0.049 0.096 0.189 0.051 0.143 0.252 0.145 0.186 0.176 0.152 0.066 0.135 0.181 0.116

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Relay No. 1 2 3 4 5 6 7 8 9 10 11 12 13 13 15 16 17 18 19 20 21

IP (A) 859 361 361 859 537 240 240 322 343 137 343 103 240 537 429 240 386 206 687 275 343

(c)

TDS (sec) 0.030 0.041 0.044 0.030 0.071 0.035 0.052 0.119 0.111 0.097 0.070 0.223 0.063 0.080 0.126 0.164 0.125 0.023 0.189 0.171 0.197

Relay No. 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

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IP (A) 515 172 687 412 1288 240 343 172 773 129 69 687 172 275 515 129 275 103 751 859 275

TDS (sec) 0.177 0.192 0.221 0.125 0.140 0.020 0.149 0.043 0.085 0.166 0.045 0.126 0.222 0.128 0.164 0.155 0.134 0.058 0.119 0.159 0.103

The new optimal value for coordination between primary and backup relays in the presence multi GCSC is presented in Table 4. After this table that all directional overcurrent relays are well coordinated (superior reference value equal 0.3 sec) after optimization using KHA optimization algorithm. Table 4. CTI value in the presence multi GCSC after optimization Primary relay

5 11 15 33 35

Backup relay

6 12 16 34 36

Without GCSC

0.3212 0.3354 0.3137 0.3523 0.3455

With GCSC β = 5° β = 45°

0.3171 0.4211 0.3156 0.3044 0.3577

0.3321 0.3034 0.3166 0.4371 0.3105

β = 90°

0.3324 0.3097 0.3135 0.4278 0.3044

Comparison with Published Results For comparison purpose Table 5, presents a comparison of the best obtained value of the objective function (OF) for scenario without multi GCSC with other published results.

OF (sec)

Table 5: Comparison of published results MPSO LP NLP NM [25] [26] [26] [26] 61.7200 30.8451 18.0099 16.5948

KHA 14.5384

From the results of Table 3, it can be also seen that the proposed optimization algorithm KHA has given better performance and provides the best solution compared with other results.

CONCLUSIONS In this paper we present an optimal relays coordination in the presence of multi GCSCs in the transmission power system for different conduction angle. We propose the formulation of the relays coordination problem as three scenarios. The obtained results show that the multi GCSC has a great impact on the setting and the coordination of the numerical directional overcurrent protections. Furthermore, the proposed optimization algorithm KHA show a high efficiency to solve such complex optimization problem, in such a way the coordination of the relays is guaranteed for all simulation scenarios. The results showed that the proposed algorithms are able to find superior IP and TDS and thus minimum operating time of the directional overcurrent relays and minimum CTI.The effectiveness of KHA can be observed from the results in terms of objective function values, which are better in comparison to other optimization algorithms used in the literature. The continuity of this work will be the coordination of the overcurrent relays in the presence of FACTS devices and renewable energy considering several conflicting objective functions and various power system topologies (transmission and distribution) using new optimization algorithms, and hybrid optimization algorithms. REFERENCES [1] P.M. Anderson, “Power System Protection”, published by McGraw-Hill, New York, USA, 1999. [2] A.Y. Abdelaziz, H.E.A. Talaat, A.I. Nosseir, and A.A. Hajjar, “An Adaptive Protection Scheme for Optimal Coordination of Overcurrent Relays”, Electrical Power System Research, Vol. 61, No.1, pp. 1-9, 2002. [3] H. Zeienldin, E.F. El-Saadany, and M.A. Salama, “A Novel Problem Formulation for Directional Overcurrent Relay Coordination”, IEEE Large Engineering Systems Conference on Power Engineering (LESCOPE), Halifax, Nova Scotia, Canada, 2830 July, 2004. [4] K.K. Sen, and M.L. Sen, “Introduction to FACTS Controllers: Theory, Modeling and Applications”, John Wiley Sons, and IEEE Press, USA, 2009. [5] X.P. Zhang, C. Rehtanz, and B. Pal, “Flexible AC Transmission Systems: Modelling and Control”, Springer Publishers, Heidelberg - Germany, 2006. [6] D. Birla, R. Prakash, H. Om, K. Deep, and M. Thakur, “Application of Random Search Technique in Directional Overcurrent Relay Coordination”, International Journal of Emerging Electrical Power Systems, Vol. 7, No. 1, pp. 1-14, 2006. [7] J.A. Sueiro, E. Diaz-Dorado, E. Míguez, and J. Cidrás, “Coordination of Directional Overcurrent Relay using Evolutionary Algorithm and Linear Programming”, International Journal of Electrical Power and Energy Systems, Vol. 42, pp. 299305, 2012.

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Series FACTS Devices on Distance Relay Setting in 400 kV Transmission Line”, Journal of Electrical and Electronics Engineering (JEEE), Vol. 5, No. 2, pp. 111-116, 2012. M. Zellagui, R. Benabid, A. Chaghi, and M. Boudour, “Impact of GCSC on IDMT Directional Overcurrent Relay in the Presence Phase to Earth Fault”, Serbian Journal of Electrical Engineering (SJEE), Vol.10, No. 3, pp. 381-398, 2013. A.H. Gandomi, and A.H. Alavi, “Krill Herd: New Bio-Inspired Optimization Algorithm”, Commune in Nonlinear Science Numerical Simulation, Vol. 17, No.12, pp. 4831-4845, 2012. G.G. Wang, A.H. Gandomi, and A.H. Alavi, “Stud Krill Herd Algorithm”, Neurocomputing, Vol. 128, No. 27, pp. 363-370, 2014. B. Mandal, P.K. Roy, and S. Mandal, “Economic Load Dispatch using Krill Herd Algorithm”,International Journal of Electrical Power and Energy Systems, Vol. 57, pp. 1-10, 2014. H.H. Zeineldin, E.F. El-Saadany, and M.M.A. Salama, “Optimal Coordination of Overcurrent Relays using a Modified Particle Swarm Optimization”, Electric Power Systems Research, Vol. 76, pp. 988-995, 2006. M. Ezzeddine, R. Kaczmarek, and M.U. Iftikhar, “Coordination of Directional Overcurrent Relays using a Novel Method to Select their Settings”, IET Generation, Transmission & Distribution, Vol. 5, No. 7, pp. 743-750, 2011.

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1,2.

Peter PAVLASEK , 1. Stanislav ĎURIŠ , 1. Rudolf PALENČAR , 1. Lukáš ĎURIŠ , 1,2. Martin KOVAL

TIME INSTABILITY OF BASE METAL THERMOCOUPLES 1.

Slovak University of Technology, Faculty of Mechanical engineering, Nám. Slobody 17, Bratislava 812 31, SLOVAKIA 2. Temperature Department, Slovak Institute of Metrology, Karloveská 63, Bratislava 842 55, SLOVAKIA

Abstract: Measurements of temperature have a great importance in wide range of industrial applications. As temperature affects the quality, safety and effectives of many of these applications, a great effort has been made to enhance the precision and reliability of temperature measuring sensors. One of the main types of temperature sensors that are used in industry are thermoelectric sensors, more commonly known as thermocouples. These sensors play a irreplaceable role in high temperature industrial measurements. Their robust construction, the ability to withstand high temperatures and harsh conditions had made them popular among many users. As thermocouples are active sensors, they work on the principle of the Seebeck effect. This effect is dependant from wire material purity and composition thus any change in these properties will result in change of their voltage output thus temperature. These changes of Seebeck coefficient can be caused by many factors, like chemical impurities, changes in metal lattice of the wire material, reaction between the materials of which the thermocouple consist of etc. This work deals with the analysis of various factors that can effect the Seebeck coefficient of the thermocouple wire material. Influences that affect the long term stability of the thermocouple voltage output have been analysed and a measuring procedure to determine the level of contribution to the Seebeck coefficient is presented. Furthermore the paper deals with the time stability of base metal Type N thermocouples in the MIMS (Mineral Insulated Metal Sheathed) configuration. The presented results determine the level of Seebeck coefficient change during a long time exposure to temperatures from 1200°C to 1250°C. This work was realized thanks to the support of National Physical Laboratories, Slovak Institute of Metrology, the Slovak University of Technology, grant agency VEGA - grant number 1/0120/12, APVV – grant number 0090-10 and program KEGA grant number 005STU-4/2012. Keywords:thermocouples, time stability, base metal

INTRODUCTION Metrological procedures and measuring techniques of temperature affect a wide variety of application that include engineering ,metallurgy, chemical, food, aerospace industry and medical applications. In the field of contact measurement of temperature thermocouples are one of the most used sensors today. This is thanks to their robust construction, reliability and temperature range. As every sensor their precision and reliability directly affect the quality, safety, effectiveness of the manufacturing processes and applications. Due to their wide use and their irreplaceable role in contact high temperature measurements it is of great interest to investigate the behaviour of these sensors in boundary conditions. One of these boundary situations is when a thermocouple in introduced to high temperatures over a long periods of time. This paper is focused on the effect that a long term high temperature exposure has on the thermocouple output. It furthermore deals with the possible relationship between the thermocouple thermoelements (of which the thermocouple consists of) diameter and the drift rate of the voltage output. The thermocouples tested in this study are of type N in a MIMS (Mineral Insulated Metal sheathed) configuration. This work also presents the proposed experimental setup that will be used for the future measurements.

STABILITY PROBLEMATIC IN THERMOCOUPLES The stability of voltage output of thermocouples is one of the significant issues that occur in each type of thermocouples. This process is caused by many different factors that alter the Seebeck coefficient value. This material constant is unique for each individual material and for its combinations. By changing its value the voltage output of the thermocouple changes as well. These changes are caused by altering the physical and chemical properties of the thermocouple wire material. These changes can be of a temporary or of a permanent nature. There are three cases in which the tested MIMS thermocouples Seebeck coefficient is affected. The first case that occurs is the annealing effect by which the thermocouple is exposed to temperatures above 600°C (changes in the inner material structure occurs). Hysteresis is the second effect that occurs in thermocouples and it can be experienced at temperatures up to 1000°C. In the third case the EMF (Electro Motive Force – the generate voltage by the thermocouple) is altered by chemical contamination. This last mentioned case occurs at temperatures above 1000°C. This study is going to deal with the chemical induced changes thus the permanent change in Seebeck coefficient. These permanent changes arise in nickel based thermocouples (type N and K) at temperatures above 600°C. An increasing voltage output can be seen when thermocouples without a protective sheathing are exposed to these temperatures. This positive drift can be seen in

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a calibrated noble metal type R thermocouple was made. After establishing the temperature profile the ideal depth for the thermocouples was determined and was set for 550mm (position of the tip of sensor from the opening of the furnace). Temperature time stability was also determined with the same type R thermocouple. The resulting stability over a 5 hour test was not more than 0.11°C which was considered as sufficient for our study. Furthermore to be confident about the furnaces temperature stability a calibrated type R thermocouple was used to monitor the temperature inside the furnace. All the initial tests were done at work temperature of 1200°C which was the later used testing temperature as well. The temperature stability of the reference point is also of great importance because it determines the voltage output of the thermocouple and its temperature instability would result in the voltage output instability of the thermocouple which would make the drift detection difficult. This reference point temperature stability was ensured by a dry block cell with a high long term stability of ± 0.005°C. To be able to determine the level of drift from the thermoelements diameter the thermocouples had to be exposed to an identical temperature conditions. This was ensured by putting all the tested sensors to a narrow ceramic tube which ensured that the temperature conditions would be sufficient for our measurement. After setting up the measuring equipment and the initial testing phase the first batch of thermocouples was exposed to a temperature of 1200°C for a time period of more than 80 hours. The results of this continuous testing are presented in the following part of the paper. RESULTS The data presented was recorded using an automatic recording system which consisted of a switch system, multimeter device and PC with recording software. The recording interval of all the sensors voltage output was set for one minute. By this quick and automatic recording we ensured the comparability of the data from each sensor due to virtually identical data record time. The recorded data has a certain level of noise which was compensated using mathematical filtration methods. After this initial filtration an average value vas calculated for each five hour sections to make the interpretation of the drift level clearer. The results of the measurements that were obtained at temperature of 1200°C are presented in Figure1. The figure shows the voltage output difference of type N thermocouples of different diameters from the initial state of the voltage. As we can see from the Figure 1 a decrees of the voltage output is Table 1: Outer and lead diameters of tested type N thermocouples Outer diameter of Type N Thermo element wire diameter visible. The highest level of voltage decrees was noticeable on the smaller thermoelement diameters. This highest level of decrees can thermocouples (mm) (mm) 0.5 0.085 be seen on the thermocouple with the smallest outer diameter of 1.0 0.140 0.5mm. The level of decrees was 5°C from the initial state after 84 1.5 0.280 hour. Other diameters of thermocouples show a different maximum 2.0 0.340 level of decrees and their values are presented in Table 2. The results One of the main issues that needed to be deal with was ensuring the have confirmed that the exposure of nickel based thermocouples to temperature stability and hom*ogeneity of the testing furnace. To high temperatures causes a drop of voltage with time. These results determine these crucial factors initial furnace hom*ogeneity scans with

nickel based thermocouples with metal sheathing and mineral insulation (MIMS) but only at temperatures between 600°C to 900°C. By higher temperatures a significant and constant voltage drop occurs. This behaviour was described in various publication [1, 2, 3] with the same results for type N and type K thermocouples. The mentioned publications describe the process of drift by the migration of particles between the thermocouple thermoelements and the mineral isolation material and the metal sheath. The main source of contamination according to publications [1, 2] is considered manganese (Mn) as the main element that causes drift. This elements can be found in the sheathing material of the thermocouple and at temperatures over 1100°C it contaminates the thermocouple thermoelements affecting the Seebeck coefficient. The publications [1, 2] also points out that the concentration of manganese in the sheathing material also determine the level of the drift. For instance when a Inconel 600 which has a 1% concentration of manganese was used as sheathing material the voltage output drop wasn't so high as when a AISI 310 material with 2% manganese concentration was used. Publications [4, 5] show a decrees of indicated temperature of type N and K MIMS thermocouples with a 3mm outer diameter. At temperature of 1100°C the measured temperature difference form the initial state was 10°C and at temperature of 1200°C the drop was 24°C. These results were obtained after a 1000 hour testing cycle. Several publications deals with the thermocouple drift and time stability in which they point out that a considerable degree of long term stability of nickel based thermocouples is an issue that needs further investigation. In this presented paper we are going to deal with this drift problematic but in a relation to the diameter of the thermocouple thermoelements wires. EXPERIMENTS PROCEDINGS The drift of the voltage output and diameter relationship was measured on type N thermocouples in MIMS configuration. The sheath material for the tested thermocouples was made of Inconel 600 and with mineral insulation inside the sheath. Eight thermocouples of the highest precision class for the mentioned type were tested. The outer diameters together with the corresponding wire diameter are presented in Tab. 1. One pair of the same thermocouple diameter and type from the same manufacturer was tested to avoid possible error caused by the manufacturing process. Furthermore two runs of the drift testing were planned to proof the repeatable behaviour of drift for individual diameter of sensors.

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Fascicule 1 [January – March] Tome VIII [2015]

have also proven that the levels of voltage output decrease and be seen in Fig. 1 and 2. These figures show the different trends of thermocouple thermoelements diameter size are related. voltage decrease and average °C/hour drop for different thermoelements diameters. This behaviour of nickel based thermocouples in NIMS configuration agrees with the publications [1, 2, 3]. The publications describe the cause of the drift as a chemical contamination of the thermoelement material by manganese (Mn) which can be found in the sheath material of the thermocouple. According to the publications the contamination process starts to occur at temperatures above 1000°C. By analysing the previously made studies in this field we have come to the conclusion that the levels of drift for different thermoelement diameters rely from the amount of material that is contaminated. Smaller diameters are therefore naturally doped faster by the Mn than the larger diameter Figure 1: Voltage output difference form initial state for type N thermoelements. thermocouples of different diameters Table 2: Maximum temperature difference from the initial state for various thermoelement diameters at 1200°C. Thermo element wire Temperature difference from the diameter (mm) initial state after 84 hours (°C) 0.085 -5 0.140 -3 0.280 -2 0.340 -4

Values of temperature decrees and the corresponding wire diameters have been used to establish a drift function for the type N thermocouples in MIMS configuration. This function that can be seen in Fig. 2 shows the dependence of average temperature decrees by one hour and the thermoelement diameter when thermocouples are exposed to a temperature of 1200°C. As can be seen from the Figure 2 the smaller thermoelement diameters show a higher level of average °C/hour decrease than the higher diameters. This is not the case for the 0.340mm thermoelement where an anomaly occurs that need to be further examined and analysed.

ACKNOWLEDGMENT The authors would like to thank NPL (National Physical Laboratories) and the Slovak University of Technology for their support. Furthermore the authors would like to thank the grant agency VEGA – grant number 1/0120/12, APVV – grant number 0090-10 and program KEGA grant number 005STU-4/2012. REFERENCE [1] Robin E. Bentley: Theory and practice of Thermoelectric Thermometri, Springer, Csiro, Volume 3, ISBN 981 – 4021 – 11 – 3, 1998 [2] University of Cambridge - Department of Materials Science and Metallurgy: Thermoelectric Materials for Thermocouples – Type K Thermocouples: MIMS Configuration, 2009 [3] University of Cambridge - Department of Materials Science and Metallurgy: Thermoelectric Materials for Thermocouples – Type K Thermocouples: Bare wire Configuration, 2009 [4] Robin E. Bentley and T. L. Morgan: Ni-Based thermocouples in the mineral insulated metal-sheathed format: thermoelectric instabilities to 1100°C, J. Phys. E., 19:262-68, 1986 [5] R.L. Anderson, J.D.Lyons, T.G. Kollie, W.H. Christie, R.Eby, "Decalibration of sheathed thermocouples". Temperature: its measurement and control in science and industry.,Volume5,1982

Figure 2: Function of type N thermocouple thermoelements diameter and an average temperature decrees in temperature from the initial state after one hour (measured at 1200°C).

CONCLUSIONS The measured data show a clear relationship between the level of voltage output decrease and the thermocouple thermoelements diameter. This drift behaviour was observed at temperatures above 1200°C. The sources form which this conclusion was determined can | 71 |

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Marek PAVLICA , 2. Jana PETRŮ, 3. Robert ČEP

SELECTION OF THE OPTIMAL PARAMETERS FOR LASER CUTTING 1 -3.

Department of Machining and Assembly, 17. listopadu 15/2172, Ostrava 708 33, CZECH REPUBLIC

Abstract: The current high requirements for quality, accuracy and durability of produced parts lead to a permanent improvement of the production process. For reasons of efficiency and competitiveness have become increasingly to the forefront of non-conventional machining methods. Nonconventional technology is characterized by the use, physical, chemical or a combination of these processes. Currently, the most commonly used for industrial cutting continuous CO2 laser with an average power. Because of the high requirements for the quality of the cutting edge is necessary to choose the optimal method of cutting either melting laser cutting or oxidizing laser cutting. The main parameters that we can significantly affect the quality of the cutting edges are: laser power, length of focal optics, cutting speed, gas pressure, gap between the nozzle and plate, shaped nozzles etc. If the cutting edge after laser cutting does not reach the required quality, it may negatively affect the price of the product, due to add additional operations, as may be chamfering, grinding, etc. For this reason, high demands are made to the professional knowledge on operator of laser equipment. Keywords: CO2 Laser, optimal parameters, quality of cutting edge

INTRODUCTION Separation of materials is still a very important matter of public manufacturing operations. It is used to draw a number of methods, each of which has developed its area of optimum use. In engineering is nowadays the most advanced laser technology between modes of action on human material in the production process. With their help it is possible significantly improve the quality, technology and productivity. Thermal cutting of materials can be used in within the engineering operations include the preparation of the material. Under this term we mean cutting technology, working on the principle of local melting, combustion, or evaporation, or a combination of these phenomena, the energy required to initiate the process and its process is supplied by various heat sources. Thermal cutting of materials can be used in within the engineering operations include the preparation of the material. Generally, thermal cutting of materials applied to a wide range of engineering materials: unalloyed and low-alloy steels, high alloy steels and nickel based alloys, non-ferrous metals and their alloys (aluminium, copper) highly reactive materials and their alloys are sensitive to oxygen (magnesium, titanium) non-metallic materials (plastics, composites, wood, paper, glass) PRINCIPLE OF LASER Every laser system is comprised of three substantial parts. These parts include active environment (active substance), the excitation (pump) source and a resonant system. A suitable excitation of the active substance is achieved by the phenomenon that is called population inversion. If there are more atoms at higher energy levels than the lower, it is a state of imbalance. Population inversion is inside the

active environment necessary condition for that there was a light amplification.

Figure 1: The resonator Active medium is meant a substance, whether gaseous, solid or liquid, which is saturated with more atoms at higher energy levels. These atoms can also emit twice the light energy. The active medium is the most important part of the laser device because in it there is stimulated emission. The resonator is an optical cavity into which is inserted the active substance. In most cases, a resonator formed by two mirrors, one mirror is reflecting and second semi-permeable and from outside is equipped with a condenser. Due to the large number of photons and their accidental movement, some of them start to move in a direction perpendicular to both mirrors and begin to amplify larger and larger waves. This is enabled due to the metastable levels of electrons that will last for the surface until it hits them in some of the emitted photons. Other photons that are flying in a direction perpendicular to the mirror fly out a space between them, or are pulled down to just photons flying in the perpendicular

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

direction. When photon will increase to a certain level, a half mirror released out and it results required beam. This is coherent and monochromatic. PRINCIPLE OF CO2 LASER With gas laser beam is formed in a gaseous environment, which is most commonly argon, helium or neon. The light emission occurs after applying a sufficiently high voltage to electrodes located inside the gas tube. Gas lasers for industrial use can achieve very high performance the disadvantage is the need for a complex cooling the relative expensiveness. It is the most common gas laser, whose active medium consists of a molecule of dioxide excited by an electric the smoldering discharge. The radiation generated by this type of laser in the far infrared region. CO2 lasers are characterized by a relatively high efficiency of 8-10%. Currently, only CO2 laser reaches the desired range of output power of 1kW to 30 kW and therefore belongs among the most widely used lasers. Except for high performance and high efficiency excels CO2 laser still decent quality the laser beam. Other properties are not desirable. The wavelength is 10.6 µm, despite the fact that it does not pass through optical fibers and laser irradiation is necessary to destination transport system of mirrors, is not well suited for precision machining. Due to the small volumetric power density of the CO2 laser is based on high-performance laser systems and a lot of great material and equipment is not practical mobile. It is also dependent the coolant inlet and the supply of the working gas mixture which, except carbon dioxide also contains nitrogen and expensive helium. Given the complexity and operational performance of such devices requires uninterrupted inspection and maintenance. Despite these shortcomings has achieved maximum performance due to CO2 laser on competition and holds its place particularly in areas such as welding and cutting metal sheets of large thicknesses. The worldfamous producer of CO2 lasers is mainly German company Trumpf.

Figure 2: CO2 laser METHODS FOR LASER CUTTING Fusion cutting

Nitrogen or argon is used as the cutting gas here. The gas is blown through the kerf at pressures ranging from 2 to 20 bar. Argon and nitrogen are inert gases. This means that they do not react with the molten metal in the kerf. They simply blow it out toward the bottom. Simultaneously, they shield the cut edge from the air.

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The advantage of fusion cutting is the cut edges are oxide-free and do not require additional treatment. The laser beam supplies the energy needed for cutting. This is why cutting speeds as fast as those in flame cutting can only be achieved in thin sheets when fusion cutting. Piercing is also more difficult. Some cutting systems allow you to use oxygen to pierce the material and then switch over to nitrogen for cutting.

Flame cutting

In flame cutting, oxygen is used as the cutting gas. The oxygen is blown into the kerf at pressures of up to 6 bar. There, the heated metal reacts with the oxygen and it begins to burn and oxidize. The chemical reaction releases large amounts of energy – up to five times the laser energy – and assists the laser beam. Flame cutting makes it possible to cut at high speeds and handle jobs involving thick plates such as mild steel. Sublimation cutting

In this process, the idea is to use the laser to vaporize the material with as little melting as possible. In the kerf, the material vapor creates high pressure that expels the molten material from the top and bottom of the kerf. The process gas – nitrogen, argon, or helium – serves solely to shield the cut surfaces from the environment. It ensures that the edges remain oxide free. For this reason, a gas pressure of 1 to 3 bar is sufficient. More energy is needed to vaporize metal than to melt it. Therefore, sublimation cutting requires high laser power and is slower than other cutting processes. However, it produces high-quality cuts. This process is rarely used in sheet metal fabrication. Its use, however, becomes attractive in applications involving particularly delicate cutting work.

Figure 3: Principle of sublimation cutting PARAMETERS INFLUENCING THE QUALITY OF CUTTING The experimental part was carried out at NC Line s.r.o., which deals with the processing of sheet metal components using laser technology for 20 years. Today, the company is a leading supplier of sheet metal parts to companies such as Linde, Still, Pro-Logic, Liebherr and many others. The essence of the experiment is to evaluate the surface roughness depending on the performance parameters of the laser. In the production of test samples in NC Line s.r.o. Company was used material Raex 250 C Laser. Evaluation of the samples was carried out in laboratories VSB-TU Ostrava.

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The test material Raex 250 C Laser is a high-strength and wear-resistant steel with favourable hardness and impact toughness. The plate thicknesses now range from 2 mm up to 80 mm providing a solution to all wear needs. With Raex wear plate you can extend the lifespan of machinery, decrease wear in structural components and save costs. Raex steel grades also enable innovative design and lightweight products improving energy efficiency and lowering fuel costs. Raex is utilised in various applications of mechanical engineering by, for example, the automotive, heavy lifting and transportation, and mining industries. Thickness of the test material was 10 mm. Applications       

Buckets and containers Cutting edges for earth moving machina Wear parts for mining machina Wear parts for concrete mixing plants and wood processing machina Platform structures Feeders, funnels Tipper bodies

Device for measuring of roughness For measuring of surface roughness was used Mitutoyo SJ-400. This is a portable device for measuring the roughness of the surface without sliding blocks with touch control panel and an integrated printer. Large 5.7 "color LCD display for easy navigation through the measurement conditions, results and graphs analysis. Possibility of sensor measurements without slip feet for the measurement of unfiltered profile (P), the roughness profile (R), filtered waviness profile (W), and others. This device complies with many standards, industrial DIN EN ISO, VDA, ANSI and JIS. Internal memory can store up to 10 different measurement conditions and up to 500 programs on an optional SD memory card.

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experiment, there was a change in focal length, power, feed rate, nozzle distance from the material and the gas pressure. Sample No. 1 was cutted by experience of the staff, which was used parameters viz. table. During the gradual modification of parameters failed to achieve better surface roughness parameters. During the experiment, the different parameters at which the laser ceased to perform its function and scrapes material. Table 1: Machine parameters sample sample sample sample sample sample 1 2 3 4 5 6

Length of focal optics [mm] 3,5 Performance [W] 4800 Speed [m·min-1] 2,4 Distance of the nozzle [mm] 1,2 Gas pressure [MPa] 0,8

3.5

4800 2,4

4000 2,4

4800 2.2

4800 2.4

1.2

0.8

1.2

0.8

0.9

When evaluating the samples in laboratories VSB-TU Ostrava focused on the arithmetic mean deviation of the profile Ra and Rz roughness of the profile. The best value of the sample was No. 1 and the worst value of the sample was No. 4 This showed that the set of parameters that can affect the quality of the cut staff is able to tune themselves according to their experience. Unable to clearly determine the parameters chosen for different materials such as aluminium, copper, stainless steel, because the cut quality is influenced by many other factors. Generally not say that the reduction or increase of gas pressure there was a worsening of quality of cut as well as in increasing or decreasing the focal length.

Figure 4: Portable surface roughness tester Mitutoyo SJ-400 Selection of optimal parameters The procedure for selecting the optimal parameters was that the best sample cutted by operator experience and consequently there to modify parameters and evaluation of the sample. During the | 75 |

Figure 5: Measurement of sample Table 2: Values of roughness

sample sample sample sample sample sample 1 2 3 4 5 6 Ra [µm] 2,65 4,12 7,09 25,10 8,83 7,09 Rz [µm] 14,50 22,30 37,40 95,10 43,20 37,40

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[4.] BENKO B., FODEREK P., KOSECEK M., BIELAK R.l: Laserovétechnológie,1.vyd., Bratislava, Vydavatelstvo STU, 2000, edice 4859, ISBN 80-227-1425-9 [5.] Drsnost povrchu. Cutting [online]. Dostupné z: http://www.atryx.cz/prakticka-prirucka/drsnost-povrchu/ [6.] infrared.cz. Lasery [online].Dostupné z:

Figure 6: The worst sample

Figure 7: The best samp

CONCLUSION In this article, the possibility was investigated how the operator can affect the laser cutting quality. As the test material was used Raex 250 C Laser thickness of 10 mm. The experiment was conducted on CO2 laser manufacturer Trumpf in cooperation with NC Line s.r.o. In the actual experiment, the focus was on the main parameters affecting the quality of the cutting area, namely: power of the laser beam focus position to the material being cut, cutting speed and cutting gas pressure and nozzle position on the material from depending on these variables was carved twelve samples which were subjected to measurement of the quality of cut surfaces and the results of these measurements are further processed and evaluated. For best quality results achieved sample cut with the following parameters (the sample number 1) :  Laser power 4800W  Focal length 3.5 mm  Cutting speed 2.4 m • min-1  Gas pressure 0.8 bar  Distance of the nozzle 1,2 mm ACKNOWLEDGMENT This paper was supported by the Students Grant Competition of the Ministry of Education, Youth and Sports and Faculty of Mechanical Engineering VŠB-TUO. REFERENCES [1.] Laserart.wbs.cz [online]. 2009-03-26. Historie laseru. Dostupné z, WWW: [2.] Laser processing : Technical information [online]. Ditzingen : TRUMPF Werkzeugmaschinen GmbH + Co. KG, 2007-02. Dostupné z, WWW: . [3.] Nekonvenční metody obrábění [online]. Dostupné z:

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G. ADEDOKUN, 2. J.A. OLADOSU

DEVELOPMENT OF A GSM-BASED REMOTE CONTROL SYSTEM FOR HOME ELECTRICAL APPLIANCES 1, 2.

Department of Electrical/Electronic Engineering, Osun State College of Technology, Esa-Oke, NIGERIA

Abstract: Electrical power is often used as a source of power to operate electrical appliances. However, inconsistent of electricity supply leads to obliviousness of the users to switch off their home appliances; thereby, resulting in energy wastage or eventual damage to appliances when power is restored. Meanwhile, developments in information technology could be used to eliminate this problem. Consequently, a GSM based remote control system has been developed to control and monitor electrical devices that required constant attention using mobile phone. This system is very handy when users forget to turn ON/OFF the electrical appliances at their home or office after they have set out. They can now control or monitor such appliances remotely by sending a text message from their mobile phone. This development ultimately saves a lot of time and effort. Likewise, daily electrical energy savings is made more efficient and effective. In constructing this system, basic components like mobile phones, SIM card, Liquid Crystal Display, relays and microcontroller were used to develop a cost-effective and adaptable system. Keywords: GSM, Microcontroller, Electrical, appliance, hardware, software, relay and Switch

INTRODUCTION Nowadays, most people have access to mobile phone so that at any given moment, a specific person can be contacted by making voice call or sending a text message. Instant text messaging allows quick transmission of Short Message Services (SMS), and this allows individual to share relevant info. Nonetheless, the applications of mobile phone cannot be restricted to sending text message or making conversations. New innovation can still be derived which can further expand its scope of applications. Currently, electrical power is regularly used as one of the key source of energy to power electrical appliances. However, erratic power supply leads to forgetfulness of electricity’s users to switch off their home appliances when they were set out for their respective work and this always cause a lot of hazard to environ and energy wastage on power restoration. Therefore, there arises a need to develop and implement a system that will allow user to be able to control and monitor their home appliances ubiquitously and also provide security on detection of intrusion via SMS using GSM technology. Remote management of several household electrical appliances using Global System for Mobile communications (GSM) technology is a subject of growing interest which has found its application in different areas. Tan, Lee, and Mok, 2007 developed an automatic power meter reading system using GSM network. It utilizes the network to send power usage reading to an authorized office to generate the billing cost and send back the cost to the respective consumer through SMS. This concept has been used to develop a GSM-based remote control system which acts as a platform to receive SMS sent from a user mobile phone to control and monitor electrical appliances. The system allows control from a remote area to the desired location so that the need to be physically present in order to

control household electrical appliances or office equipment is eliminated. The approach used in designing this system is implementation of a microcontroller-based control module that will receive command from a user’s mobile phone over GSM network and then carry out the issued command and communicate the status of a given device back to the user’s handset. SYSTEM DESCRIPTION System block diagram of the developed GSM-Based Remote Control System is shown in Figure 1, which is a simple illustration of how the system and the various parts involved had been implemented. The system has two main parts, namely: hardware and software. AC-DC CONVERSION (BATTERY CHARGER)

Nokia (3310)

Schmitt

GATES

Mobile Set TX

MAINS SUPPLY

VOLTAGE REGULATORS

12V BATTERY

MICROCONTR OLLER

RELAY DRIVERS

(PIC18F4550)

ZERO CROSSING DETECTOR

12V DC RELAYS

ELECTRICAL SOCKETS AND LAMP HOLDERS

20 x 4 Lines Liquid Crystal Display

USER GSM HANDSET

Figure 1. System Block Diagram The hardware architecture consists of a stand-alone embedded system that is based on 8-bit microcontroller (PIC18F4550), GSM

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

handsets, driver circuit and DC relays. The GSM handsets provide the communication medium between user and system by means of SMS which consist of command to be executed. The SMS message is sent to the receiver GSM handset via the GSM cellular networks as a text message with a specific predefined format. The principle in which the system is based is fairly simple; user GSM handset (Nokia 3310) is used as a transmitting station from which the user sends text messages that contain commands and instructions to receiver GSM handset that is integrated into the developed system. The received SMS is stored in the Subscriber’s Identifying Module (SIM) memory of the phone; then, extracted by the microcontroller and processed accordingly to operate appliances via the power switching module. The brief description of individual module in the system is as follows: A. User GSM Handset: Mobile phone through which communication takes place via GSM network. The user sends command through the set to control and monitor electrical appliances in form of SMS. Making call to the system’s dedicated line also allows user to make enquiries about the status of the system. B. Receiver GSM Handset: The mobile phone (Nokia 3310) integrated into the developed system is used to receive calls and the SMS sent by the owner and then to transmit the status of electrical appliance to the user’s mobile phone. C. Battery Charger: This comprises 230V-15V step-down transformer, high-current bridge rectifier, and LM317-based voltage regulator circuit. The regulator’s output is designed to have a constant value of 13.8V. This constant voltage keeps a 12V, 7 Ah sealed lead-acid battery on float charge. This is very important to provide power back-up for the system in case of power outage. D. Microcontroller: This is an 8-bit high-performance RISC microcontroller from Microchip Technology. The microcontroller is selected since it has an enhanced USART which can be configured at baud rate of 115200 bps, large Flash Program and data memory. To read a message, the microcontroller sends the appropriate FBUS command to the Receiver GSM handset (Nokia 3310). The handset then responds with the message and the microcontroller will store the message in the RAM. The microcontroller sends another FBUS command to delete the message, in order to free mobile memory, after which the message is interpreted and the instruction from user is extracted. Based on the received instruction, the appropriate controlling signals are then sent to the relay driver and the system status is updated. Also, the microcontroller sends a command to the Nokia 3310 to query the phone if there is an incoming call. If there is an incoming call, the caller’s mobile number will be extracted and the call is subsequently terminated. The mains status (mains utility availability) is then sent via an SMS to the extracted callers’ mobile number.

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E. Relay driver: The relay driver is controlled by the microcontroller. It allows a low- power circuit to switch a relatively high current on/off according to the command sent through the SMS. The relay driver is basically ULN2003A, which is a monolithic high voltage and high current Darlington transistor arrays. It consists of seven NPN Darlington pairs that feature high-voltage outputs with common-cathode clamp diode for switching inductive loads. It is used to drive the relay circuits which switches different appliances connected to the interface. F. Liquid Crystal Display: The Liquid Crystal Display (LCD) is used to indicate the last message received from the user, and therefore indicate the cause of the operation performed by the microcontroller and also its inclusion makes the overall system user-friendly. G. Zero Crossing Detector: This is basically a step-down transformer with a small bridge rectifier. The output of the rectifier is attenuated using a potential dividing network. The scaled rectified mains supply is fed to the microcontroller through an Operational Amplifier that is configured as voltage follower, to determine availability of utility supply. Thus when the users try to call the mobile number integrated into the system, the system send an SMS to indicate mains status automatically. The complete circuit diagram of the control system is as shown in Figure 3. FIRMWARE OVERVIEW The system operates as depicted in the flowchart of Figure 2. Decode & Delete SMS

Baud Rate Initialization Phone Initialization

Start

Control Device 1

YES

Extract Caller’s Number & Terminate the call Check availability of Mains Supply

Control Device 2 NO

Device 1 ON/OFF

Get HW/SW

Wait for Timeout

YES

Any Incoming Call?

Acknowledgemen t + HW/SW frame received ?

YES

Device 2 ON/OFF

B Send Mains Status to Caller

YES Control Device 3

Get SMS From SIM

YES

Device 3 ON/OFF

YES

Device 4 ON/OFF

SMS RECEIVED?

YES

Control Device 4

Figure 2 – Program Flow Chart of the GSM Based Remote Control System NOKIA FBUS INTERFACE The firmware for this system was developed using high level language tool in C that is-MPLAB C18. The program is structured to extract the sent message from the Nokia 3310 at a regular interval

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and processes it to control the specific appliances connected to the system. The Nokia 3310 has the F Bus connection that can be used to interface a phone to a microcontroller. Hence, the Nokia F-Bus protocol has been used to communicate with the mobile phone. This bus allows exchange of sent and received SMS messages between the microcontroller and the connected mobile phone. K1

U2 ULN2003_DIP16

D1 1BH62 2

D12

VDD

230V

IRON_CORE_XFORMER

MDA990-2

U7 LM7812CT

C8 4.7mF

LINE VOLTAGE

12V

1 2 3 4 5 6 7

IN1 IN2 IN3 IN4 IN5 IN6 IN7

COM

VDD

VREG

C5 1µF

COMMON

12V

OUT1 OUT2 OUT3 OUT4 OUT5 OUT6 OUT7 GND

VCC

U3 Nokia_3310

LINE VOLTAGE

R4 R17 10kΩ 1000Ω5% 5%

VCC 5V

CURR

VREG

C4 1µF VDD

2 3

R13 330Ω 5%

LTL-293SJW

12V

VCC 5V

R15

1 2 3 4 5 6 7 8 9 10 11 12 13 14

LCD U4

28 27 26 25 24 23 22 21 20 19 18 17 16 15

1 2 3 4 5 6 7 8

16 15 14 13 12 11 10 9

JHD162ALCD

14 13 11

R10 10kΩ 5%

C12 1µF

U6D

R9 100kΩ 5%

PIC18F2550

LED3

COMMON

R19 330Ω 5% U8 LM7805CT

K3 16 15 14 13 12 11 10

10kΩ 5% LM324AN

D11 5V Zeners

X1 C2 30pF

C1 30pF

HC-49/U_25MHz

Figure 3. Complete Circuit Diagram of a GSM-Based Home Appliances Control System FIRMWARE DEVELOPMENT AND CONSTRUCTION Firmware Development The Microchip MPLAB Integrated Development Environment (IDE) was used for the firmware development. MPLAB IDE is a Windows Operating System (OS) software program that runs on a PC and contains all the components needed to design and deploy embedded systems applications. A development system for embedded controllers is a system of programs running on a desktop PC to help write, edit, debug and program code - the intelligence of embedded systems applications into a microcontroller. Procedures required for developing an embedded controller application are as follows: i. Create the high level design. From the features and performance desired, decide which PIC Microcontroller Unit or dsPIC Digital Signal Processor device is best suited to the application, then design the associated hardware circuitry. After determining which peripherals and pins control the hardware, write the firmware that will control the hardware parts of the embedded application. A language tool such as an assembler, which is directly translatable into machine code, or a compiler that allows a more natural language for creating programs, is then used to write and edit code. ii. Compile, assemble and link the software using the assembler

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and/or compiler and linker to convert code into binary number - machine code for the PIC MCUs. This machine code will eventually become the firmware (code programmed into the microcontroller). iii. Test the code. Generally a complex program does not work exactly the way imagined, therefore "bugs" must be removed from the design to get desired results. The debugger allows one to see the program execute, related to the source code written. iv. "Burn" the code into a microcontroller and verify that it executes correctly in the finished application. Construction The programmed microcontroller was tested in a breadboard with its associated sensing/control circuits. Extensive tests were performed on all the components used in each of the subsystems to ensure that they are working reliably. Having worked satisfactorily, the microcontroller and the associated components were then transferred and soldered on veroboard following light duty soldering techniques; and the entire board was properly connected to accessories. Soldering has been firmly done to reduce loose connection and short circuit. All safety measures are taken to prevent electric hazard. The whole arrangement was then housed in a plastic enclosure as shown in Figure 4.

Figure 4 .GSM-Based remote control system RESULT AND DISCUSSION When the system is powered several tests were carried out to ensure proper accomplishment of the intended result. The system was designed to receive SMS text (commands) from user handset via a receiver handset connected to the microcontroller circuit. These tests were carried out by sending SMS to the receiver handset. The SMS in the receiver are retrieved by the microcontroller and processed to carry out specific task stated in the SMS instruction. The system then replies by sending an SMS to user mobile phone reporting the current status of the appliances. The incoming message is displayed on the LCD by the microcontroller upon completion of the requested task and the message is erased in the connected mobile phone. | 79 |

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Table 1 shows the summary of the typical commands sent by the users and the corresponding responses by the control system. When a command like “Oscotech13 Turn ON Device 1 WOR” is issued, the device(s) corresponding to the number(s) indicated in the command is turned ON. In the commands in Table 1, all messages start with Oscotech13; this is the configured password for this particular system. It is expected that the password is known to only the authorized user. The password can only be changed from the firmware. Then Turn ON or Turn OFF can be issued to respectively turn on or off a specific device. Multiple devices can be controlled by using “&“. The last WR or WOR represent WITH REPLY or WITHOUT REPLY respectively. The commands are case-insensitive and spaces between words do not interfere with command interpretation. Table 1: Test result Commands from user mobile phone Oscotech13 Turn On Device 1 WOR Oscotech13 Turn OFF Device 1 WR Oscotech13 Turn ON Device 1&2&3 WR Oscotech13 Turn OFF Device 4&5&6 WOR Oscotech13 Turn OFF Device 2&3&7 WR Oscotech13 Turn ON Device 1&4&6&7 WOR Oscotech13 Turn ON ALL WOR Oscotech13 Turn OFF ALL WR

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[4.] [5.]

[6.] [7.] [8.] [9.]

Operations carried out by Status report to user the microcontroller mobile phone Device 1 is turned ON

NO REPLY

Device 1 is turned OFF Device 1 status is OFF Device 1, 2 and 3 are Device 1, 2 and 3 turned ON status are ON Device 2, 3 and 5 are Device 2, 3 and 5 turned OFF status are ON Device 2, 3 and 7 are Device 2, 3 and 7 turned OFF status are OFF Device 1,4, 6 and 7 are NO REPLY turned ON Device 1,2,3,4,5 6 and 7 NO REPLY are turned ON Device 1,2,3,4,5 6 and 7 Device 1,2,3,4,5 6 and are turned OFF 7 status are OFF

[10.] [11.] [12.] [13.] [14.]

http://www.thaieei.com/ Daniel W. Lewis (2004). “Fundamental of embedded software” Prentice hall of India Delgado, A. R., Picking, R., & Grout, V. (2006). Remote-controlled home automation systems with different network technologies. Proceedings of the 6th International Network Conference (INC 2006), University of Plymouth, 11-14 July 2006, pp. 357-366. Retrieved from http://www.newi.ac.uk/ Heckman, D. (2008), A Small World. Smart Houses and the Dream of the Perfect day, Duke University Press, London, UK Krishna Kant (2007) “Microprocessor and microcontroller” EASTERN COMPANY EDITION NEW DELHI Mazidi, M. Ali, (2007). The 8051 Microcontroller and embedded System, Second Edition Prentice Hall. India, New Delhi Neng-Shiang Liang; Li-Chen Fu; Chao-Lin Wu; (2002). “An integrated, flexible, and Internet-based control architecture for home automation System in the Internet era,” Proceedings ICRA 2002. IEEE International Conference on Robotics and Automation, Vol. 2, pp. 1101 –1106 R.S. Sedha, (2002). A Text Book of Applied Electronics, S. Chand and Company Ltd., New Delhi Rifat Shahriyar, Enamul Hoque, S.M. Sohan, Iftekhar Naim; (2008). Remote Controlling of Home Appliances using Mobile Telephony, International Journal of Smart Home, Vol. 2, No. 3, July, 2008 Sedra and Smith, (1999) Microelectronic Circuits, fourth edition, Oxford University Press Tan, H.G.R, Lee, C.H, and Mok, V.H.(2007). Automatic Power Meter Reading System using GSM Network. In: 8th International Power Engineering Conference (IPEC), Singapore William Stalling (2005) “Wireless communication and networks”, 2nd edition, Prentice hall of India

CONCLUSION This paper presents a low cost, user- friendly, secured, ubiquitously accessible, auto-configurable, remotely controlled solution for automation of homes. From convenience of a simple handset phone, a user is able to control and monitor nearly any electrical appliances. This allows users to control their home appliances from anywhere in the world; and to be assured that their appliances are not left running when they have left home. REFERENCES

[1.] AbdWahab, M.H., Mohd, S.Z. and Fazliza M.N. (2007). Integrated Billing System through GSM Network. In Proceeding of third International Conference on Robotics, Vision, Information and Signal Processing [2.] Ahmed, V., Ladhake, S. A. & Thakare, R. D. (2008). Micro-controller based Remote Monitoring using Mobile through Spoken Commands. Journal of Networks, 3(2), 58-63. Retrieved from http://www.academypublisher.com/ [3.] Alkar, A. Z. &Buhur, U. (2005). An Internet Based Wireless Home Automation System for Multifunctional Devices. IEEE Consumer Electronics, 51(4), 1169-1174. Retrieved from

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809

Tarik El OUAFY, 2. Abdelilah CHTAINI, 3. Hassan OULFAJRITE, 4. Rachida NAJIH 1.

CARBON PASTE ELECTRODE MODIFIED WITH CLAY FOR ELECTROCHEMICAL DETECTION OF COPPER (II) USING CYCLIC VOLTAMMETRY 1-4.

Equipe d’Electrochimie Moléculaire et Matériaux Inorganiques, Faculté des Sciences et Techniques de Beni Mellal, Université Sultan Moulay Slimane. 523, Beni Mellal, MOROCCO

Abstract: This paper reports on the use of carbon paste electrode modified with clay (Clay-CPE) and cyclic voltammetry (CV) for analytical detection of trace copper (II) in Na2SO4 0.1M. The electroanalytical procedure for determination of the Cu(II) comprises two steps: the chemical accumulation of the analyze under open-circuit conditions followed by the electrochemical detection of the preconcentrated species using cyclic voltammetry. The electrochemical responses obtained by CV at Clay-CPE were found to be analytically suitable to develop a method for the determination of copper at low concentration levels. Keywords: Modified electrodes; Cyclic voltammetry; Clay; Cu(II).

INTRODUCTION Recently, rapid industrialization and urbanization led to the contamination of air, soil and water. The determination of pollution by heavy metals such as copper, mercury, lead, zinc and cadmium is of special concern because of the formation of complexes with proteins [1] and their high toxicity [2-4]. The heavy metal ions are hazardous to ecosystems and can cause serious danger to human population because of their accumulation in organs including liver, heart, brain etc. [5]. For this reason, up to now, several methods including atomic absorption spectrometry, UV-Vis spectroscopy, colorimetric analysis, ion chromatography, inductively coupled plasma mass spectrometry and electroanalytical techniques have been proposed for the determination of heavy metals [6,7]. Among these techniques, electrochemical sensors have great potential for environmental and biological monitoring of toxic metal ions in drinking or waste water and biological samples as blood, urine etc. due to their portability and field-applicability, excellent sensitivity, automation, rapid analysis, low power consumptions and inexpensive equipment [8-11]. Electrochemical determination of copper has been performed with mercury-coated platinum microelectrodes [12], glassy carbon electrode modified with glyoxime [13], polyphenols [14], phenanthroline [15,16] derivatives and poly-4-nitroaniline [17]. In addition to this, the design of electrodes with controllable surface properties can be achieved using self-assembled monolayers (SAMs), which become popular in the formation of well defined functional surfaces [18–20]. The advantages of SAMs include simplicity of preparation, versatility, stability, reproducibility and possibility to introduce different chemical functionalities [21, 22]. As an alternative to environmentally unfriendly mercury- [12] and bismuth- [23] based

electrodes several papers related to the detection of metal ions [4, 7, 24, 25,30-31] including Cu(II) ions [26-29] using SAM-modified electrodes have been published recently. To enhance the preconcentration of metal ions, in this paper, a promising approach to the monitoring of Cu(II) ions was proposed. It was based on clay modified carbon paste electrode. The peak currents of Cu(II) ions were evaluated by cyclic voltammetry within a wide concentration range, with high selectivity, stability and sensitivity suitable for investigation of real samples. It was shown that the proposed sensor has great implications in the determination of Cu(II) ions in tape water even in the presence of some interfering ions. EXPERIMENTAL Apparatus and software Voltammetric experiments were performed using a voltalab potentiostat (model PGSTAT 100, Eco Chemie B.V., Utrecht, The Netherlands) driven by the general purpose electrochemical systems data processing software (voltalab master 4 software) run under windows 2007. The three electrode system consisted of a chemically modified carbon paste electrode as the working electrode a saturated calomel electrode (SCE) serving as reference electrode, and platinum as an auxiliary electrode. Electrodes Modified electrodes were prepared by mixing a carbon powder and the desired weight of clay. The body of the working electrode for voltammetric experiments was a PTFE cylinder that was tightly packed with carbon paste. The geometric area of this electrode was 0.1256cm2. Electrical contact was made at the back by means of a bare carbon.

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

Procedure The initial working procedure consisted of measuring the electrochemical response at Clay-CPE at a fixed concentration of Copper ion Cu(II). Standard solution of Copper was added into the electrochemical cell containing 100 mL of supporting electrolyte. The mixture solution was kept for 20 s at open circuit and deoxygenated by bubbling pure nitrogen gas prior to each electrochemical measurement. The cyclic voltammetry was recorded in the range from -0.8 V to 0.7 V. Optimum conditions were established by measuring the peak currents in dependence on all parameters. All experiments were carried out under ambient temperature. In order to insure the inert effect of Clay electrode during the experiment, the potential of 0mV was chosen in presence or in absence of accumulated copper. All other conditions were as described in the Voltammetric part. RESULTS AND DISCUSSION Cyclic voltammetry of Cu(II) Cyclic voltammogram in 0.1 mol L-1 Na2SO4 (at the pH 7) (Fig. 1) shows cathodic and anodic peaks, which makes it possible to determine this cation. The cyclic voltammograms were obtained for the Clay-CPE in the presence of Cu(II) and without Cu(II). There were no redox peaks in the CV of the Clay-CPE without Cu(II) (Fig. 1a). The Clay-CPE interacting with of Cu(II) showed an anodic peak at -0.05 V and cathodic peak at -0.3V versus calomel reference electrode (Fig. 1b).

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Figure 2: Effects of accumulation time on oxidation peak currents of 0.31 mmol L−1 Cu(II) (pH 7) at Clay-CPE, supporting electrolyte is Na2SO4 0.1M.

Voltammetric analysis of electrodeposit As shown in Fig. 1, a voltammetric curve of the Clay-CPE preconcentrated for 5 min in Na2SO4 (0.1 M) with a scan rate of 100 mV s-1. It may be noted the presence of a cathodic peak and anodic peak, the peak potentials were attributed to Cu(II) behaviour in Na2SO4 0.1 M. An tampon medium was selected as suitable for relegate of Cu(II) according to Eq. (1). Cu(II) species leached out from the clay at the electrode/solution interface can be detected directly by reduction Eq. (2). Clay-CPE-Cu(II) Clay-CPE + Cu(II) (1) Pb(0) (2) Cu(II) + 2 eEffect of scan rate The influences of scan rate on the oxidation peak potential (Ep) and, peak current (Ip) and the reduction peak potential (Ec) and, peak current (Ic) of copper, (0.1M Na2SO4, pH=7) were studied by cyclic voltammetry. The figure 3 shows both the anodic and the cathodic peak currents linearly increase with the scan rate over the range of 40 to 120 mVs-1, suggesting that the electrons transfers for copper at the clay modified CPE is adsorption controlled reaction. The cathodic peak shifted towards negative potential with increased in scan rate, the anodic peak shifted towards positive potential with increased in scan rate. The figure 4 shows the linear relationship between the scan rate anodic peak and cathodic peak currents of copper at ClayCPE.

Figure 1: CV recorded for 0.31 mM Cu(II) at pH 7 at bare Clay-CPE (a) and Clay-CPE/Cu(II) (b), scan rate 100 mV/s, preconcentration time (tp)=5min.

Influence of accumulation time The effect of the accumulation time is investigated (Figure 2), this significantly affects the oxidation peak current of Cu(II). The peak current of 0.31 mmol L−1 Cu(II) increases greatly within the first 5min. Further increase in accumulation time does not increase the amount of Cu(II) at the electrode surface owing to surface saturation, and the peak current remains constant. This phenomenon is due to the cavity structure of clay-CPE that improves the ability of the electrode to adsorb electroactive Cu(II). Maybe this is attributed to the saturated adsorption of Cu(II) on the Clay-CPE surface. Taking account of sensitivity and efficiency, accumulation time was 5 min in the following experiments.

Figure 3: CV acquired on Clay-CPE with 1.86 mM Cu(II) in the buffer solution at different scan rates from 40 to 120 mV.s-1.

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electrochemical reaction. The Figure 7 a shows the cyclic voltammograms of the Cu(II) at different PH. The current of the peak depend on the solution PH. The anodic peak potential shifted towards negative side and cathodic peak potential Epc shifted towards more positive potential. The figure 8 shows the graph of different pH versus peak current, it could be confirmed that the current density decreases with increased pH.

Figure 4: Plot of peaks area versus scan rate

Calibration graph In order to obtain an analytical curve for the developed sensor, we carried out cyclic voltammograms for oxidation and reduction of Cu(II) at different concentrations in 0.1mol L−1 Na2SO4 (pH=7) at a sweep rate of 100 mVs-1. Figure 5 shows the CV curves of different concentration of Cu(II) at Clay/CPE was increased from 0.31 mM to 1.55 mM. Both the anodic and cathodic peak current increases linearly with the concentration of Cu(II). It was also observed that the cathodic peak potential shift towards negative values and anodic peak potential shift towards positive side. This kind of shift in Ep in the cathodic and anodic direction with increasing concentration of the Cu(II) indicates that the product of Cu(II) are adsorbed over the electrode surface. The figure 6 shows the linear relationship between the concentration anodic peak and cathodic peak currents of copper at Clay-CPE.

Figure 7: Effect of pH on the oxidation and the reduction of Cu(II) at the Clay modified CPE

Figure 8: Plot of the relationship between solution pH and the oxidation and reduction peak Current

PRACTICAL APPLICATION In order to evaluate the performance of Clay-modified carbon paste electrode by practical analytical applications, the determination of Cu(II) was carried out in tap water without any pretreatment. The analytical curves were obtained by CV experiments in supporting electrode (Figure 9). It was founded that the peaks currents increase linearly versus Cu(II) added into the tap water (Figure 10).

Figure 5: Cyclic Voltammograms of different concentration of Cu(II) (0.31mM to 1.55mM) at Clay-CPE in 0.1 M Na2SO4, Scan rate 100 mV/s.

Figure 6: Plot of peaks area versus added concentration of Cu(II).

Influences of pH In a first step, the effect of pH on electrode response was investigated. In most cases, the solution pH is important to the | 83 |

Figure 9: Cyclic Voltammograms of different concentration of Cu(II) at Clay/CPE in 100ml tap water, Scan rate 100 mV/s

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Fascicule 1 [January – March] Tome VIII [2015]

Figure 10: Plot of peaks area versus added concentration of Cu(II)

CONCLUSION Cyclic voltammetry analysis utilizing the clay modified carbon paste electrode for the determination of copper dissolved in aqueous solutions has been demonstrated. The use of CV is faster and more sensitive than other, conventional, techniques. Besides, the use of clay modified carbon paste electrode enables direct analysis of tap water sample without treatment of the sample. This extra advantage could reduce the cost of the analysis and the time taken, hence resulting in improvements in analytical sensitivity. REFERENCES

[1.] J. Petrlova, S. Krizkova, O. Zitka, J. Hubalek, R. Prusa, V. Adam, J. Wang, M. Beklova, B. Sures, R. Kizek, Sens. Actuators B 2007, 127, 112. [2.] H. Zhao, Y. Jiang, Y. Ma, Z. Wu, Q. Cao, Y. He, X. Li, Z.Yuan, Electrochim. Acta 2010, 55,2518. [3.] M. Cauchi, C. Bessant, S. Setford, Electroanalysis 2008, 20, 2571. [4.] E. Malel, J. K. Sinha, I. Zawisza, G. Wittstock, D. Mandler, Electrochim. Acta 2008, 53, 6753. [5.] D. Bagal-Kestwal, M. S. Karve, B. Kakade, V. K. Pillai, Biosens. Bioelectron. 2008, 24, 657. [6.] S. Senthilkumar, R. Saraswathi, Sensor. Actuators B, Chem. 2009, 141, 65. [7.] D. Burshtain, D. Mandler, J. Electroanal. Chem. 2005, 581, 310. [8.] W. Yantasee, B. Charnhattakorn, G. E. Fryxell, Y. Lin, C. Timchalk, R. S. Addleman, Anal. Chim. Acta 2008, 620, 55. [9.] S. Betelu, C. Vautrin-Ul, A. Chausse, Electrochem. Commun. 2009, 11, 383. [10.] M. Badihi-Mossberg, V. Buchner, J. Rishpon, Electroanalysis 2007, 19, 2015. [11.] B. Liu, L. Lu, M. Wang, Y. Zi, Electroanalysis 2008, 20, 2363. [12.] M. A. Baldo, S. Daniele, I. Ciani, C. Bragato, J. Wang, Electroanalysis 2004, 16, 360. [13.] Y. Oztekin, Z. Yazicigil, T. Duran, H. Dumrul, E. Guler, O. Kocyigit, Clean Soil, Air, Water, 2010, 38, 921. [14.] Y. Oztekin, Z. Yazicigil, A. Ramanaviciene, A. Ramanavicius, Sensor. Actuators B, Chem.2011, 152, 37. [15.] Y. Oztekin, Z. Yazicigil, Electrochim. Acta 2009, 54, 7294. [16.] Y. Oztekin, Z. Yazicigil, A. O. Solak, Z. Ustundag, Z. Kilic, S. Bilge, Surf. Interf. Anal. 2011, 43, 923. [17.] Y. Oztekin, M. Tok, H. Nalvuran, S. Kiyak, T. Gover, Z. Yazicigil, A. Ramanaviciene, A. Ramanavicius, Electrochim. Acta 2010, 56, 387.

[18.] A. Kausaite-Minkstimiene, A. Ramanaviciene, J. Kirlyte, A. Ramanavicius, Anal. Chem. 2010, 82, 6401. [19.] A. Kausaite-Minkstimiene, A. Ramanaviciene, A. Ramanavicius, Analyst 2009, 134, 2051. [20.] Y. Oztekin, A. Ramanaviciene, A. Ramanavicius, Sens. Actuators B. DOI: 10.1016/j.snb.2011.01.018, in press. [21.] A. Kausaite, M. Van Dijk, J. Castrop, A. Ramanaviciene, J. P. Baltrus, J. Acaite, Biochem. Mol.Bio.Edu. 2007, 35,57. [22.] M. Sheffer, V. Vivier, D. Mandler, Electrochem. Commun. 2007, 9, 2827. [23.] S. B. Hocevar, J. Wang, R. P. Deo, B. Ogorevic, Electroanalysis 2002, 14, 112. [24.] E. Chow, J. J. Gooding, Electroanalysis 2006, 18, 1437. [25.] B. Zeng, X. Ding, F. Zhao, Electroanalysis 2002, 14, 651. [26.] R. S. Freire, L. T. Kubota, Electrochim. Acta 2004, 49, 3795. [27.] L. M. Niu, H. Q. Luo, N. B. Li, L. Song, J. Anal. Chem. 2007, 62, 470. [28.] R. K. Shervedani, S. A. Mozaffari, Anal. Chem. 2006, 78, 4957. [29.] M. H. Mashhadizadeh, H. Khani, A. Foroumadi, P. Sagharichi, Anal. Chim. Acta 2010, 665, 208. [30.] M.A. El Mhammedi, M. Achak, M. Bakasse, A. Chtaini, Chemosphere 76 (2009) 1130–1134 [31.] M. El Mhammedi, M. Achak, A. Chtaini., J. of Hazardouz Materials, 161(2009)55-61

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ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering Tome VIII [2015] Fascicule 1 [January – March] ISSN: 2067 – 3809 1.

Jana POLÁČKOVÁ, 2.Petr SAJDL, 3.Jana PETRŮ , 4.Daniela MARUŠÁKOVÁ

EFFECT OF CHEMICAL REGIMES ON OXIDE LAYERS OF MATERIALS IN POWER ENGINEERING 1-4

Department of Power Engineering, Institute of Chemical Technology, Technická 5, Praha 6 166 28, CZECH REPUBLIC

Abstract: Nowadays most commonly used materials in power engineering are stainless steels. Temperatures and pressures in systems are currently increased to achieve higher efficiency. In some plants are applied even supercritical values. This paper is focused on improvement of corrosion protection possibilities. Except new materials (titanium, nickel superalloys), different types of surface treatments or layers are used to reduce problems caused by corrosion. If passive film is formed on treated surface, e.g. nitrided, there can appear differences in its properties. The oxidic layers are common, however in operation of water-steam cycles in power plants arise problems like exfoliation, bigger porosity or disparity of passive layer. Consequence is larger corrosion rate, which leads up to degradation of the material and failure of equipment. In experimental section were created oxidic layers in laboratory conditions and was monitored the behavior of materials used in power industry. Thereafter were evaluated their properties and composition, which permits to analyze what terms are for given materials most suitable. Samples were exposed in autoclave in terms of different cycle chemistry and then analyzed by method of ESCA, X-ray diffraction and metallography. Keywords: corrosion, chemical regimes, oxide layers

INTRODUCTION Water treatment in steam-water cycles of power stations especially should ensure functional equipment as long time as possible. Because the construction is made practically only of metallic materials, there is a need to prevent corrosion damage. The choice of suitable chemical regime and its correct regulation are in this issue essential aspect. Appropriately treated environment can considerably reduce material degradation. Dissolved substances increase solution conductivity and promote electrochemical cells formation, which participate at mechanisms of e.g. pitting and crevice corrosion. Species of the reactions taking place on metal surface are thickly affected by pH of environment. This is associated with CO2 content regulation, which causes solutions acidification and subsequently leads to surface corrosion formation at values pH < 6. Oxygen content has to be controlled as well. It can be cause of pitting corrosion. Moreover is necessary to consider impurities and additives properties, water and steam temperature, velocity and mechanical load of the equipment. Due to loading turbines construction both tensile and cyclic part of strain, comes up a fatigue corrosion formation risk, frequently initiated by pitting or crevice corrosion. Above that is important to consider blades erosion damage by water droplets cavitation and deposits creation. They can exfoliate from the surface and are dangerous not only for direct parts of the turbine, but can cause also regulation elements failure by clogging them. Oxidic layers are often used steam turbines corrosion protection type. To be functional, is important to watch their state and prevent

undesirable changes, which can be caused by wrong steam quality and inappropriate supply water treatment [1, 2, 3]. RESTRICTION OF STEAM TURBINES CORROSION USING SURFACE TREATMENTS Surface treatments are effective method to reduce corrosion damage because they constitute solid barrier between the environment and metal. Most commonly are used oxidic layers, organic coatings, electroplating and thermic and vacuum surface treatments. In this group can be included nitriding as well. However, this technique isn’t applied directly as corrosion protection. Metal surface saturation by nitrogen has as a result very tough layer of fine particles alloying elements nitrides. The purpose of nitriding is surface hardness and abrasion resistance increasing while metals original properties remain. This treatment has been carried out on one of tested materials in experimental section [4, 5, 6]. EXPERIMENTAL To compare corrosion behavior, three types of material for steam turbines construction were tested. The first is martensitic stainless steel X 12 CrNiMoV 12-3 (1.4938) produced by company Böhler. Specimens were taken from a low pressure turbine blade, which was working in Wilson line area. There occurred problems with oxidic layer exfoliation. Next two samples types are made from nickel superalloy Nimonic 901. Beside nickel (40 – 45 %) it contains approximately 30 % iron and 11 – 14 % chrome. In experiment were tested basic material without surface treatment and nitrided material. Each specimen

ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering

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except nitrided ones was grinded before testing. Samples designation RESULTS AND DISCUSSION overview is in Table 1. Numbers are the same as expositions. After all expositions there was dark grey colored oxide layer on each sample surface. On several places occurred in small amount orange Table 1: Designation of samples corrosion products (hematite Fe2O3). The best properties showed Material Designation samples after third exposition. All layers were unbroken but thin 1.4938 (blade) L1 enough. L2 L3 On steel (designation L) were formed very fine layers. Nimonic 901 Nimonic 901 basic NZ1 nitrided samples (NN1 – NN3) showed in every exposition terms NZ2 relatively coherent and compact oxidic layers. Only by NN2 occurred NZ3 exfoliation. Nimonic 901 basic samples (NZ1 – NZ3) were covered Nimonic 901 nitrided NN1 with a passive layer but not such undivided as on nitrided set. NN2 NN3 On Figure 1 is survey spectrum of sample NZ3 after 15 minutes sputtering with significant iron and oxygen peaks. Figure 2 shows the All samples were exposed in the autoclave simulating steam turbines same samples fitted spectrum. operation conditions. Three experiments were performed. Terms were set to locate specimens in the superheated steam environment and their summary is below in tables 2 – 4. Volumetric flow of water was circa 4.6 ml/min. Expositions were implemented due to materials behaviour in terms of different chemical regimes comparison. Table 2: 1st exposition T [°C] p [MPa] τ [h] pH Degassed water Table 3: 2nd exposition

T [°C] p [MPa] τ [h] pH Degassed water

Table 4: 3rd exposition

T [°C] p [MPa] τ [h] pH Degassed water

570 6 59 < 10 Yes 570 4 66 F value, followed by the Immersion speed and the least effect is seen on Radial distance because of its least F-value of 6.1804. Interactions between the input parameters were not significant having p values >0.05.

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Diagnostic plots of oil quenched steel sample The quality of the model devloped was further tested using different diagnostic plots such as normal probability curve, residuals vs predicted, outliers and predicted against actual plots. The normal probability plot of the residuals for temperature distribution shown in Figure 2 reveal that the residuals are falling on the straight line, which means the errors are distributed normally. All the above consideration indicates an excellent adequacy of the regression model. The residual values were plotted against the individual run indicating minimum difference between the experimental data and the predicted data as shown in Figure 3. 3.00

Table 4: ANOVA for response surface quadratic model of oil quenched steel p-value Prob> F