Vilnius Gediminas Technical University
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Elektromagnetinių procesų tyrimas elektromagnetinėse svaidyklėse naudojant milžiniškos magnetovaržos jutiklius
No full textThe development of rails and armatures which ensure a sliding solid-to-solid contact during the whole projectile acceleration is a great challenge in the field of railgun technology. Multifaceted physics exists at the sliding contact interface: The current concentrates at the rear of the interface due to magnetic diffusion processes and the fast armature movement. Consequently, Joule heating leads to enhanced wear in this region. In this dissertation, magnetic diffusion in railguns is investigated by means of measuring magnetic fields with CMR-B-scalar sensors at static and dynamic experimental conditions. These novel sensors, based on La0.83Sr0.17MnO3 thin films exhibiting colossal magnetoresistance were adapted for the use at railguns.
It was found that these sensors are effective tools to measure the magnitude of high pulsed magnetic fields independent of the field orientation. Magnetic field distributions influenced by proximity and velocity skin effect could be measured in the harsh railgun environment. The obtained results allowed to estimate the skin depth in the rails at the sliding interface of a fast moving armature (>1500 m/s). Furthermore experiments with fixed multiple brush armatures showed that front brushes can have contact problems in case of missing contact pressure.
The dissertation consists of an Abstract, an Introduction, 6 chapters, General Conclusions, References, a List of Publications and 2 Appendices.
The introduction reveals the investigated problem, the importance of the thesis and describes the purpose and tasks of the work. Furthermore, it presents the research methodology, the scientific novelty, the practical significance of results, the defended statements and the acknowledgement.
Chapter 1 gives a literature review and introduces the field of railgun research and the idea behind this dissertation. Chapter 2 describes the experimental setups and main equipment. Chapter 3 deals with the CMR-B-scalar sensor and related metrological questions. The use of the sensor in static and dynamic coilgun experiments is presented in chapter 4. Chapter 5 deals with the investigation of magnetic diffusion and the current distribution in the rails of a railgun. Chapter 6 is about the current distribution in brush armatures.
Seven articles focusing on the subject of the discussed dissertation have been published so far: Six articles in Journals listed in the Thomson ISI Web of Science and one article in the proceedings of an international conference. Seven presentations of the subject have been given at 5 international conferences.Doctoral dissertatio
High Velocity Oxygen Liquid-Fuel (HVOLF) Spraying of WC-Based Coatings for Transport Industrial Applications
No full textIn this article, we analyse five types of coatings, in terms of their microstructure, hardness, porosity, and wear resistance, in the as-sprayed state. The coatings are WC-based (WC-FeCrAl, WC-WB-Co, and WC-NiMoCrFeCo), alloy-based (Co-MoCrSi), or nanoWC coating-based (nanoWC-CoCr). Two tests were applied to assess the wear resistance of the coatings: a dry-pot wear test with two impact angles and an abrasive test using an abrasive cloth with two grit sizes. Porosity was determined by image analysis. Vickers impression was performed on cross-sections of the coatings, in order to determine their indentation fracture toughness. The highest hardness of the tested coatings was recorded for the nanoWC coating, followed by the rest of the WC-based coatings; meanwhile, the lowest hardness was recorded for the alloy coating. Minimal porosity was achieved by the alloy coating, due to its different nature and the absence of hard particles with a higher melting point. The NanoWC coating and other WC-based coatings had a higher porosity; however, porosity did not exceed 1% for each coating. The best wear resistance was achieved by the nanoWC coating, followed by the other WC-based coatings, with the lowest obtained by the alloy coating. The same tendency was recorded when determining the indentation fracture toughness. From a microscopic point of view, the structure of the evaluated coatings is not compact; nevertheless, their properties are excellent, and they act as compact coatings under load.This article belongs to the Special Issue Application of Alloys in Transpor
Investigation of pulsating flow’s ejector
No full textDisertacijoje nagrinėjamas naujai sukurtas pulsuojančio srauto ežektorius, kuris gali būti naudojamas geležies junginiams iš vandens šalinti. Pagrindinis tyrimo objektas – naujai sukurtas optimalios mechaninės konstrukcijos pulsuojančio srauto ežektorius. Disertacijos tikslas – pritaikius pulsuojančio srauto ežektoriaus mechaninės konstrukcijos naujumą ir atsižvelgiant į atliktų pulsuojančio srauto kompleksinių teorinių ir eksperimentinių tyrimų rezultatus, sukurti pulsuojančio srauto ežektorių, gebantį pagerinti bereagenčio geležies šalinimo iš vandens technologiją. Siekiant įgyvendinti tyrimų tikslą, buvo sprendžiami šie uždaviniai: atlikta mokslinės literatūros, kurioje nagrinėjamos ežektorių konstrukcijų charakteristikos ir juose vykstantys ežektuojamo srauto hidrodinaminiai procesai, analizė. Analitiškai ištirtos pulsuojančio srauto hidrodinaminių parametrų charakteristikos. Sukurtas pulsuojančio srauto ežektoriaus prototipas, pagrįstas akustinio lauko generavimu, ežektuojamam srautui susimaišant su darbiniu skysčiu, kai kinta jų tekėjimo debitas. Eksperimentiškai ištirta sukurto pulsuojančio srauto ežektoriaus hidrodinaminių parametrų įtaka deguonies tirpumui vandenyje ir geležies koaguliavimui.
Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai ir keturi priedai.
Įvadiniame skyriuje aptariama tiriamoji problema, pristatomas darbo aktualumas, aprašoma tyrimų metodika, nurodomas darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė ir ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema paskelbtos autoriaus publikacijos ir pranešimai konferencijose bei disertacijos struktūra. Pirmajame skyriuje analizuojami pulsuojantį srautą generuojantys įrenginiai ir jų konstrukcijų analizė, procesai, vykstantys pulsuojančio srauto ežektoriuje. Skyriaus pabaigoje formuluojamos išvados ir tikslinami disertacijos uždaviniai.
Antrajame skyriuje pristatomi ežektoriaus generuojamo pulsuojančio srauto teoriniai ir analitiniai tyrimai.
Trečiajame skyriuje aprašomi pulsuojančio srauto ežektoriaus eksperimentiniai tyrimai, pateikta tyrimo metodika. Išsamiai išanalizuota generuojamų garso slėgio charakteristikų priklausomybė nuo akustinio lauko generatorių konstrukcijų. Įvertintas pulsuojančio srauto ežektoriuje vykstančių reakcijų efektyvumas.
Disertacijos tema paskelbtos devynios publikacijos: septynios – recenzuojamuose mokslo žurnaluose, dvi – kituose leidiniuose. Išradimui „Pulsuojančio srauto ežektorius“ gautas Lietuvos patentas.Daktaro disertacij
Link between Financial Management Behaviours and Quality of Relationship and Overall Life Satisfaction among Married and Cohabiting Couples: Insights from Application of Artificial Neural Networks
No full textBackground: To explain the link between household finances and the quality of the relationship between married or cohabitating partners and their life satisfaction, the Family Stress Model (FSM) was used and placed within the theoretical framework of the Couples and Finances Theory (CFT). Methods: The measures used to examine the relationship between partners were the Financial Management Behaviour Scale, the Marriage Questionnaire (KDM-2) adapted to a version for cohabitating couples, The Shared Goals and Values Scale, Harsh Start-up Scale, and the Satisfaction With Life Scale (SWLS). In order to find out the relationship between variables, artificial neural networks (ANN) were applied. The research was conducted on a sample of 500 couples living in Poland (384 married and 116 cohabitating couples). Results: The results indicate that overall life satisfaction is most influenced by fundamental, direct, current ways of dealing with the daily financial routine and by saving and investing behaviours. Credit management and insurance behaviours are the most important for the quality of the relationship between partners. Conclusions: The research shows that financial management behaviours have an impact on the quality of relationships as well as on the subjective well-being of people in a relationship, and their relationship dynamics. This finding may be used to highlight the psychological importance of financial management behaviours.This article belongs to the Special Issue The Economics of Health BehaviorsThis research was funded by the Ministry of Science and Higher Education, Republic of Poland, grant number 0057/DLG/2016/10. The APC was funded by the University of Economics and Innovation, Lublin, Poland
Corporate Governance-Based Strategic Approach to Sustainability in Energy Industry of Emerging Economies with a Novel Interval-Valued Intuitionistic Fuzzy Hybrid Decision Making Model
No full textThe sustainability in energy industry is one of the most prominent issues in emerging economies because of needs for the long-term growth of production and managerial capacity. Accordingly, corporate governance could lead to develop the sustainable production of energy industry. The purpose of this study is to define a set of criteria and dimensions for analyzing the corporate governance-based strategic approach to sustainability in the energy industry of emerging economies. For this purpose, this study provides several novelties by extending a hybrid decision making model with interval-valued intuitionistic fuzzy sets (IVIF) and defining the related criteria and dimensions of corporate governance-based strategic approach with the supported literature. IVIF decision making trial and evaluation laboratory (DEMATEL) is constructed for measuring the relative importance of criteria and dimensions. IVIF VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) is applied for ranking the corporate governance-based performance of sustainable energy industries in emerging economies. Sensitivity analysis is also used for understanding the coherence of ranking results. Analysis results illustrate that the energy industry could provide more sustainable results than the conventional managerial policies by considering the social capital of board members. Additionally, mass-economies are closely related to the sustainable production capacities of energy industry and have the best performance results for the corporate governance-based sustainable energy production strategies. The results are discussed to provide the policy recommendations by comparing analysis results of emerging economies for further studies.This article belongs to the Special Issue Current Issues in Sustainable Energy Production: Multidimensional Outlook for the Sustainable Economic GrowthThis work was sponsored in part by Science and Technology Development Plan Project of Jilin Province of China (20190601025FG), National Social Science Foundation of China (19BJL057), Social Science Foundation Project of Jilin Province of China (2019c14). This work was sponsored in part by Zhejiang Social Science Fund
(20NDQN305YB)
Research of Energy and Ecological Indicators of a Compression Ignition Engine Fuelled with Diesel, Biodiesel (RME-Based) and Isopropanol Fuel Blend
No full textThis article presents the results of a study of energy and ecological indicators at different engine loads (BMEP) adjusting the Start of Injection (SOI) of a Compression Ignition Engine fuelled with blends of diesel (D), rapeseed methyl ester (RME)-based biodiesel and isopropanol (P). Fuel blends mixed at D50RME45P5, D50RME40P10 and D50RME30P20 proportions were used. Alcohol-based fuels, such as isopropanol, were chosen because they can be made from different biomass-based feedstocks and used as additives with diesel fuel in diesel engines. Diesel fuel and its blend with 10% alcohol have almost the same thermal efficiency (BTE). In further examination of energy and ecological indicators, combustion parameters were analysed at SOI 6 CAD BTDC using AVL BOOST software (BURN subprogram). Increasing alcohol content in fuel blends led to a reduced cetane number, which prolonged the ignition delay phase and intensified heat release in the premixed combustion phase. Higher combustion temperatures and oxygen content in the fuel blends increased NOx emissions. Lower C/H ratios and higher O2 levels affected by RME and isopropanol reduced smoke emissions.This article belongs to the Special Issue Alternative Fuels and Their Application to Combustion Engine
Research on the acoustic qualities of building materials and structures and their use for noise reduction in premises
No full textDisertacijoje nagrinėjamos statybinių medžiagų ir konstrukcijų garso izoliacinės savybės. Disertacijos tikslas – natūrinėmis sąlygomis ir triukšmo slopinimo kameroje ištirti ir nustatyti konstrukcijas, kurios, kaip pastatų vidinės ir išorinės sudėtinės dalys, užtikrintų vidaus patalpų apsaugą nuo triukšmo, ir tuo pagrindu sumodeliuoti konstrukcijų garso izoliavimo rodiklius.
Šiame darbe sprendžiami keli pagrindiniai uždaviniai: statybinių medžiagų ir konstrukcijų akustinių savybių tyrimai triukšmo slopinimo kameroje ir natūrinėmis sąlygomis, matavimų rezultatų palyginimas, perspektyvių konstrukcijų garso izoliavimo rodiklių įvertinimas modeliavimo būdu.
Disertaciją sudaro įvadas, aštuoni skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašas.
Įvadiniame skyriuje pristatoma tiriamoji problema, darbo aktualumas, apibūdinamas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, nusakomas darbo mokslinis naujumas ir darbo rezultatų praktinė reikšmė, išvardijami ginamieji teiginiai. Įvadas baigiamas disertacijos tema autoriaus paskelbtų publikacijų ir pranešimų konferencijose pristatymu bei disertacijos struktūra.
Pirmajame skyriuje analizuojama su disertacijos tema susijusi literatūra. Skyriaus pabaigoje formuluojamos išvados.
Tyrimų metodikos pateiktos kiekvieno skyriaus pradžioje. Antrajame skyriuje išdiferencijuojami triukšmo slopinimo kameroje vykdyti tyrimai ir analizuojami jų rezultatai. Trečiame skyriuje referuojami ir interpretuojami fasadų ir langų garso izoliavimo tyrimų natūrinėmis sąlygomis rezultatai. Ketvirtame skyriuje analizuojami ir vertinami pertvarų akustiniai natūriniai tyrimai, lyginami jų rezultatai. Penktame skyriuje nagrinėjami ir apibendrinami perdangų smūgio garso izoliacijos tyrimai. Šeštame skyriuje išskirti pertvarų garso izoliacijos rodiklių skaičiavimai pagal masės dėsnį ir tarptautinį standartą LST EN 12354-1; šie skaičiavimai palyginami su tyrimų, atliktų triukšmo slopinimo kameroje ir natūrinėmis sąlygomis, rezultatais. Septintame skyriuje, remiantis tyrimais, aiškinamas perspektyvių pertvarų ir perdangų garso izoliacijos rodiklių modeliavimas BASTIAN programa. Aštuntame skyriuje aprašyti sukurtų žaliuzių triukšmui mažinti tyrimo rezultatai. Darbo rezultatų pagrindu 4 straipsniai paskelbti recenzuojamuose leidiniuose, įrašytuose į ISI Web of Science žurnalų sąrašą su citavimo indeksu, 2 straipsniai – recenzuojamuose leidiniuose, įrašytuose į Mokslinės informacijos instituto (MII) sąrašą (ISI Proceedings), 2 straipsniai – kituose mokslo leidiniuose.Daktaro disertacij
An Extended Shapley TODIM Approach Using Novel Exponential Fuzzy Divergence Measures for Multi-Criteria Service Quality in Vehicle Insurance Firms
No full textClassification of the divergence measure for fuzzy sets (FSs) has been a successful approach since it has been utilized in several disciplines, e.g., image segmentation, pattern recognition, decision making, etc. The objective of the manuscript is to show the advantage of the combined methodology. A comparison clearly shows the usefulness of the proposed technique over the existing ones under the fuzzy environment. This study presents novel exponential-type divergence measures with some elegant features, which can be applied to FSs. Next, a TODIM (an acronym in Portuguese for Interactive Multicriteria Decision Making) approach derived from prospect theory, Shapley function, and divergence measure for multi-criteria decision-making (MCDM) is proposed. Besides, for the reason of evaluating the dominance degree of the option, and the weights of the criteria, proposed divergence measures are implemented. Evaluating and selecting the service quality is the most important issue in management; it has a direct influence on the way the manufacturer performs its tasks. Selecting the service quality can be thought of as a problem of MCDM involving numerous contradictory criteria (whether of a quantitative or qualitative nature) for the evaluation processes. In recent years, the service quality assessment is becoming increasingly complex and uncertain; as a result, some criteria assessment processes cannot be efficiently done by numerical assessments. In addition, decision experts (DEs) may not always show full rationality in different real-life situations that need decision making. Here, a real service quality evaluation problem is considered to discuss the efficacy of the developed methods. The algorithm (TODIM based on the Shapley function and divergence measures) has a unique procedure among MCDM approaches, which is demonstrated for the first time in this paper.This article belongs to the Special Issue Uncertain Multi-Criteria Optimization Problem
An integrated Multi-Criteria Decision Making Model for Sustainability Performance Assessment for Insurance Companies
Get PDFTo stay competitive in a business environment, continuous performance evaluation based on the triple bottom line standard of sustainability is necessary. There is a gap in addressing the computational expense caused by increased decision units due to increasing the performance evaluation indices to more accuracy in the evaluation. We successfully addressed these two gaps through (1) using principal component analysis (PCA) to cut the number of evaluation indices, and (2) since PCA itself has the problem of merely using the data distribution without considering the domain-related knowledge, we utilized Analytic Hierarchy Process (AHP) to rank the indices through the expert’s domain-related knowledge. We propose an integrated approach for sustainability performance assessment in qualitative and quantitative perspectives. Fourteen insurance companies were evaluated using eight economic, three environmental, and four social indices. The indices were ranked by expert judgment though an analytical hierarchy process as subjective weighting, and then principal component analysis as objective weighting was used to reduce the number of indices. The obtained principal components were then used as variables in the data envelopment analysis model. So, subjective and objective evaluations were integrated. Finally, for validating the results, Spearman and Kendall’s Tau correlation tests were used. The results show that Dana, Razi, and Dey had the best sustainability performance.This article belongs to the Special Issue Sustainability Assessmen
Mapping International Civic Technologies Platforms
No full textThe new communication paradigm supported by Information and Communication Technology (ICT) puts end-users at the center of innovation processes, thereby shifting the emphasis from technology to people. Citizen centric approaches such as New Public Governance and Open Government in the public management research suggest that government alone cannot be responsible for creating public value. Traditional approaches to public engagement and governmental reforms remain relevant, however our research is more interested in the ability of a networked society to resolve social problems for itself, i.e., without government intervention. In seeking to gain insights into bottom up co-creation processes, this paper aims to collect and generalize information on the international civic technology platforms by focusing on three dimensions: identification of the objectives (content), classification of main stakeholder groups (actors), and definition of co-creative methods (processes). In view of a paucity of research on Civic Technologies, the content analysis will extend the understanding of this growing field and allow us to identify the patterns in their development.This article belongs to the Special Issue Feature Paper in Informatic