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Abstract: The master’s thesis discusses different approaches how to assure the quality and reliability of high voltage contactors in automotive industry. In the beginning, the history of the development is described, followed by basic knowledge about materials and magnetic theory used in relays. The main part of the thesis is tests defying to qualify the relays for usage in automotive industry. There are different tests, divided in different groups. Second important part is reliability prediction according to standards used in this area of business. Reliability prediction and calculation of failure rate on different contactors are described in last chapters. Calculation also included influence of different factors on life span of the parts. In conclusion, the results are commented and proposal for development is given based on results of the research.
Keywords: Automotive industry, high voltage contactors, testing, reliability, failure rate
Published: 07.02.2018; Views: 862; Downloads: 80
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Abstract: The purpose of the study was to assess internal consistency by calculating coefficient alpha. It presents the variation in coefficient alpha, depending on questionnaire length and the homogeneity or heterogeneity of the questionnaire. The maximum possible value for coefficient alpha was also calculated by the item elimination method. The study included 99 children aged 10. The children completed The Athletic Coping Skills Inventory - 28 (ACSI-28; Smith et al., 1995), which contains seven constructs: coping with adversity, coachability, concentration, confidence and achievement motivation, goal setting and mental preparation, peaking under pressure and freedom from worry. The results confirmed that the values of the alpha coefficient vary depending on the number and composition of items and the sample size. In terms of item structure, homogeneous constructs yielded lower values for the alpha coefficient (in a range from .48 to .61) than the questionnaire with all the constructs (alpha = .79), despite higher inter-item correlations. In terms of the number of items, the longer test generated higher alpha coefficients (alpha= .79) than the shorter test (half-sets of items = .60, .73, .69, .70). A higher overall value (alpha= .83) can be achieved by item elimination.
Keywords: coefficient alpha, internal consistency, reliability
Published: 20.09.2017; Views: 460; Downloads: 69
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Abstract: This paper examines the reliability of the operation of cableway systems in Slovenia, which has major impact on the quality of service in the mountain tourism, mainly in wintertime. Different types of cableway installations in Slovenia were captured in a sample and fault tree analysis (FTA) was made on the basis of the obtained data. The paper presents the results of the analysis. With these results it is possible to determine the probability of faults of different types of cableways, which types of faults have the greatest impact on the termination of operation, which components of cableways fail most, what is the impact of age of cableways on the occurrence of the faults. Finally, an attempt was made to find if occurrence of faults on individual cableway installation has also impact on traffic on this cableway due to reduced quality of service.
Keywords: service quality, reliability, fault tree analysis, faults, quality, ski-tows, chairlifts, aerial ropeways, cableways
Published: 05.06.2017; Views: 782; Downloads: 315
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Keywords: analysis, ejector, heat flow, oscillation, reconstruction, reliability of production, pump system, motive steam, turbine condenser
Published: 10.07.2015; Views: 1112; Downloads: 33
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Abstract: Only recently have methodical tools adequate to design real-time systems been formally introduced in design methodologies. Naturally, they were present fromthe beginning, but due to the large diversity of embedded systemsć areas of deployment, specially dedicated formalisms have been developed and used. High-level language programming and integration of modeling formalisms into design methods eased the development of more complex real-time applications. With the emerging object-oriented programming languages and design methods, their integration into larger information systems has become more transparent. It was the UML methodology, however, which eventually merged also the design methods and concepts of real-time systems into a consistent whole. It took a large consortium and a long process to persuade industry of the benefits the new integral methodology can offer. On the other hand, there are some trade-offs, and there are some features not completely covered, yet. Here, a different, more straightforward approach to program and design (embedded) real-time systems is presented. Since it emerged from the real-time community, it includes most features relevant there. Independent of the UML profile for schedulability, performance and time specification, a profile was devised for use in PEARL-oriented UML design. The strengths of the mentioned language and design methods for QoS-oriented design of (embedded) real-time systems are emphasised throughout this article.
Keywords: real time systems, embedded systems, quality of service, co-design, co-simulation, safety, dependability, security, timeliness, determinism, readiness, reliability, portability, flexibility, specification PEARL, UML profiles, patterns
Published: 31.05.2012; Views: 1945; Downloads: 108
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