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How to test the reliability of instruments used in mirotremor horizontal-to-vertical spectral ratio measurements
Izidor Tasič, Franc Runovc, 2010, original scientific article

Abstract: The reliability of a horizontal-to-vertical spectral ratio (HVSR) curve depends on the results obtained by a verified seismological system. Seismic microzonation provides the basis for a site-specific risk analysis and it can be evaluated using the microtremor HVSR method, where the data are recorded using modern seismological systems. Changes in the transfer function of seismological systems affect the HVSR curve and, consequently, also its interpretation, if these changes are not detected and taken into consideration while performing the microtremor spectral calculations. The reliability of the seismic microzonation performed by such a procedure becomes questionable. An algorithm is developed with a two references system, where the influence of the transfer function on the HVSR curve by the tested system can be evaluated without any a-priori knowledge regarding the transfer functions of any of the systems. This approach is applied to a Lennartz Le-3D/5s seismometer and to a TROMINO seismological system, where two Streckeisen STS2 seismometers are used as the reference systems.
Keywords: seismic microzonation, horizontal-to-vertical spectral ratio method, ambient vibrations, microtremor, seismic system transfer function, reliability and calibration of seismic systems
Published: 11.06.2018; Views: 343; Downloads: 34
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Validation test plan for relays in avtomotive industry
Urban Cotič, 2017, master's thesis

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: 765; Downloads: 73
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Weibull decision support systems in maintenance
Khalid Aboura, Johnson Agbinya, Ali Eskandarian, 2014, original scientific article

Abstract: Background: The Weibull distribution is one of the most important lifetime distributions in applied statistics. Weibull analysis is the leading method in the world for fitting and analyzing lifetime data. We discuss one of the earliest decision support system for the assessment of a distribution for the parameters of the Weibull reliability model using expert information. We then present a different approach to assess the parameters distribution. Objectives: The studies mentioned in this paper aimed to construct a distribution of the parameters of the Weibull reliability model and apply it in the domain of Maintenance Optimization. Method: The parameters of the Weibull reliability model are considered random variables and a distribution for the parameters is assessed using informed judgment in the form of reliability estimates from vendor information, engineering knowledge or experience in the field. Results: The results are the development of modern maintenance optimization models that can be embodied in decision support systems. Conclusion: While the information management part is important in the building of maintenance optimization decision systems, the accuracy of the mathematical and statistical algorithms determines the level of success of the maintenance solution.
Keywords: Weibull distribution, reliability, inference, maintenance, expert opinion
Published: 23.01.2018; Views: 534; Downloads: 262
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Assessing reliability of a multi-dimensional scale by coefficient alpha
Ivan Šerbetar, Iva Sedlar, 2016, short scientific article

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: 388; Downloads: 67
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Internal structure of an alternative measure of burnout
Nataša Sedlar, Lilijana Šprah, Sara Tement, Gregor Sočan, 2015, original scientific article

Abstract: This study evaluates the factorial validity and reliability of the Slovenian adaptation of the Oldenburg Burnout Inventory (OLBI) in a sample of 1436 Slovenian employees of various occupations. Confirmatory factor analyses were used to evaluate alternative structural models of OLBI, and reliability of variant scales was estimated. The results reveal a different structure of the Slovenian adaptation compared with the original one and a very notable difference in reliability between positively and negatively framed items. The results could be explained with a response bias or the specific nature of burnout and work engagement that OLBI promises to assess simultaneously. Therefore, we believe that the internal structure of the original inventory needs to be reconsidered.
Keywords: burnout, Oldenburg Burnout Inventory, factor structure, reliability, psychometrics
Published: 14.07.2017; Views: 675; Downloads: 117
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Reliability analysis of operation for cableways by FTA (fault tree analysis) method
Sergej Težak, Zdravko Toš, Ivo Jurić, 2010, original scientific article

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: 687; Downloads: 282
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Increase of optical transfer medium transport capacity and consequent increase of safety and reliability of traffic
Andrej Godec, Boštjan Hernavs, 2004, review article

Abstract: Over the past few years we have been witnessing a rapid development of communication technology. The aim of this article is to find a technical solution for increasing the existent optical cable capacities. The purpose is not to replace the existing cables but to use advanced technology and to improve the economy, safety and reliability of all kinds of communications that use an optical transmission medium.
Keywords: traffic, traffic infrastructure, optical infrastructure, communications, optical multiplex, DWDM, CWDM, security, reliability, optical cables
Published: 02.06.2017; Views: 682; Downloads: 67
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QoS-oriented design of embedded systems with specification PEARL
Roman Gumzej, Wolfgang A. Halang, 2007, original scientific article

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: 1854; Downloads: 106
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