Age-dependent highly reliable systems provide small amount of statistical information and for that reason classical frequentist methods cannot be applied due to their asymptotical assumptions. However, Bayesian methods, due to their ability to naturally couple all sources of information (including expert subjective opinions) and not rely on asymptotic assumptions, are attractive approach to solve small sample problems in age-dependent reliability modelling. In this thesis Bayesian paradigm and its applicability were presented and general methodology to analyse previously mentioned problem was obtained. Methodology successfully was applied for two real data samples: failures in European natural gas grid and electrical Instrumentation and Control components. It was concluded that presented approach is able to easily investigate small samples in nonlinear age-dependent models. Also, analysis showed that different model goodness-of-fit approaches can provide different inferences and that sometimes it can fail due to nonlinearities and heteroscedasticity present in data. For that reason Bayesian posterior model averaging procedure were applied and concluded that it gives more reliable and better calibrated results than would be in one model case. Also adaptive Metropolis superiority over classical Metropolis – Hastings algorithm for highly correlated parameters and nonlinearities in model was validated. / Nuo amžiaus priklausomos aukšto patikimumo sistemos suteikia labai mažai statistinių duomenų ir dėl šios priežasties klasikiniai dažninistiniai metodai negali būti taikomi, nes jie remiasi asimptotinėmis prielaidomis. Tačiau Bajesiniai metodai, dėl jų savybės natūraliai sujungti visus informacijos resursus (įskaitant ir subjektyvią ekspertinę nuomonę) ir nesiremti asimptotinėmis prielaidomis yra patraukli paradigma, tinkama spręsti mažų imčių problemas nuo amžiaus priklausomo patikimumo modeliavime. Šiame darbe pristatomas Bajesinis požiūris ir jo pritaikymas bei buvo sudaryta bendra metodologija, kaip analizuoti anksčiau minėtą problemą. Metodologija buvo sėkmingai pritaikyta dviems realioms sistemoms analizuoti: gedimai Europos gamtinių dujų tinkluose bei elektriniuose kontrolės komponentuose, naudojamuose atominėse elektrinėse. Padaryta išvada, kad sudaryta metodologija yra tinkama analizuoti mažoms imtims netiesiniuose nuo laiko priklausomuose modeliuose. Be to, analizė parodė, kad skirtingi modelio tikimo metodai gali vesti į skirtingas išvadas apie modelius ir kartais šie metodai gali neveikti dėl heteroskedastiškumo duomenyse. Dėl šios priežasties atlikta Bajesinio posteriorinio vidurkinimo procedūra, kurios rezultatas yra patikimesnis ir geriau kalibruotas, nei kad vieno modelio atveju. Taip pat nustatytas adaptyvaus Metropolis algoritmo pranašumas lyginant su Metropolis-Hastings algoritmu analizuojant labai koreliuotus parametrus bei netiesinius modelius.

<p>This is a qualitative study, the aim of which is to explore experiences influencing the<br /> academic performance of 1st Year nursing students at the Western Cape College of Nursing,<br /> South Africa, during 2008 when the College was confronted with unprecedented failure rates<br /> among 1st Year students. It describes the College‟s collaboration with a higher education<br /> institution and the changes that emanated from this collaboration. The influence of<br /> situational factors on 1st Year nursing students is explored. These include the legacy of the<br /> inequality of past learning opportunities, institutional factors which hamper students‟ sense of<br /> belonging, and the social and academic integration of students into their learning<br /> environment. The methodology used in the process of exploring these factors included focus<br /> group discussions with students and in-depth interviews with staff in order to explore their<br /> respective perceptions of the problem. From this it is hoped that the quality of human<br /> resources for health will be enhanced.</p>

Neste trabalho é proposta uma nova distribuição de quatro parâmetros denominada distribuição log-logística exponenciada geométrica, baseada em um mecanismo de dupla ativação para modelar dados de tempo de vida. Para esta nova distribuição, foi realizado um estudo da função de densidade de probabilidade, da função de distribuição acumulada, da função de sobrevivência e da função de taxa de falha, a qual apresenta formas que podem modelar dados de tempo de vida, tais como: forma crescente, decrescente, unimodal, bimodal e forma de U. Obteve-se expansões da função de densidade, expressões para os momentos de probabilidade ponderada, função geradora de momentos, desvios médios e as curvas de Bonferroni e de Lorenz. Considerando dados censurados, foi utilizado o método de máxima verossimilhança para estimação dos parâmetros. Analogamente também é proposto um modelo de regressão baseado no logaritmo da distribuição log-logística exponenciada geométrica com dupla ativação, que é uma extensão dos modelos de regressão logística exponenciada e logística. Este modelo pode ser usado na análise de dados reais, por fornecer um melhor ajuste que os modelos de regressão particulares, logística exponenciada e logística. Finalmente, são apresentados duas aplicações para ilustrar a utilização da nova distribuição. / In this work, we propose a new distribution with four parameters the so called exponentiated log-logistic geometric distribution based on a double mechanism of activation for modeling lifetime data. For this new distribution, we study the density function, cumulative distribution, survival function and the failure rate function which allows major harzad rates: increasing, decreasing, bathtub, unimodal and bimodal failure rates. We also obtain the density function expansions and the expressions for the probability-weighted moments, moment generating function, mean deviation and Bonferroni and Lorenz curves. Considering censored data, we use the maximum likelihood method for estimating the parameters. Similarly, we also propose the regression model based on the logarithm of the exponentiated log-logistic geometric distribution with double activation, which is an extension of the exponential logistic and logistic regression models. This new model could be widely used in the analysis of real data to provide a better fit than exponetial logistic and logistic regression models. Finally, two applications are presented to illustrate the application of the new distribution.

Submitted by BKAB Setor Proc. Técnicos FGV-SP (biblioteca.sp.cat@fgv.br) on 2013-03-11T18:02:42Z No. of bitstreams: 1 1199800362.pdf: 8051235 bytes, checksum: c9d6556eec7041191caa611c6f49b134 (MD5) / This study aims at investigate the current situation o f franchising system in Brazil and give a better comprehension of the reasons why franchisees defected from their franchising networks. Firstly, a theoretical framework is presented. Afterwards, the results of a exploratory research based on Case Studies methodology on eleven ex-franchisees from different networks. The goal is to identify the factors that caused insatisfaction with the franchise and the main reasons for defection. Lastly, the limitations and the contributions of the study, as well as some sugestions for future studies. / Este estudo procura investigar a atual situação do sistema de franquias no Brasil e propiciar uma maior compreensão das razões que levaram franqueados a desligarem-se de suas redes de franquias. Em primeiro lugar, apresenta-se um referencial teórico. Em seguida, são apresentados os resultados de uma pesquisa exploratória, baseada no Estudo de Casos, realizada junto a onze ex-franqueados de diferentes redes de franquias. Objetiva-se identificar os fatores que geraram a insatisfação com a franquia e os principais motivos de desligamento da rede. Por fim, são apresentadas as limitações e contribuições do estudo, bem como sugestões para estudos futuros.

European Commission (2011) aims to reduce the greenhouse gas emission sby 85-95% by 2050 in comparison to 1990’s levels. Wave energy could be an important step to archiving this goal. This report aims to develop a quantitative risk assessment for the Uppsala University's wave energy converter. Failure rates have been collected from various databases and reports and have been processed accordingly in order to implement them in the risk analysis. CAPEX, OPEX and possible downtime windows have been estimated. A fault tree analysis (FTA) has estimated the total unavailability, unreliability and downtime. Furthermore an economical assessment model using Monte Carlo and the unreliability data from the FTA has been developed, estimating the expected LCOE and OPEX/WEC for parks consisting of 20, 100, and 200 WECs (wave energy converters). The result show that the O-ring seal has the largest impact on both the unavailability, and the economy of the OPEX/WEC. Second biggest contributor is the translator bearing failure. The study also shows that the CAPEX cost has to be reduced to make the LCOE competitive in comparison to other renewable sources. A comparison between the system unavailability and unreliability has also been done in terms of different component parameters.

Thesis (M. Ed.) -- University of Limpopo, 2019 / The comparatively high failure rate in South African rural and township secondary schools is a matter of great concern. This study set out to establish what factors are contributing to the low matric pass rate in our secondary schools, in order to identify possible solutions. The study provides an overview, informed by a review of local and international research literature, of the educational and social factors that hinder school performance. The two secondary schools in Motupa Circuit selected for this study had underperformed for the previous five years, below the benchmark of a sixty percent pass rate. The study population consisted of school management teams, teachers, school governing bodies and grade 12 repeating learners. The study followed a qualitative approach, with a case study research design in which the inquiry process was based on interviews and observation. The theory of educational productivity was used to discuss the social and emotional influences of classroom management, parental support, and interaction between teachers and learners. Analysis of the data collected led to findings that served as the basis for the recommendation that all stakeholders, from departmental officials downwards to communities and parents, join hands and work together to address and correct all the ills. The findings revealed minimal support from departmental officials and school management teams. Poor management and instructional leadership are seen as some of the ills that affect academic results. The lack of involvement of parents in supporting the schools serves to demotivate teachers in their daily work. The study also revealed that non-completion of the syllabus and the poor monitoring of written work were a bane to our rural schools. Lastly, social life outside the classrooms contributed to derailing our learners? progress. The study recommends that the DBE develop and support SMT?s by enhancing their skills of management and leadership, so as to empower teachers at all levels. Career guidance in grade 9 was a necessary step towards guiding learners on their choice of subjects.

Master’s thesis is focused on the technical systems reliability analysis. The first part of the thesis contains the description of the most commonly used reliability parameters and random variable probability distributions. Reliability of a human operator is described in the separate chapter. In the next part of the thesis are mentioned different types of reliability diagrams and methods of reliability analysis. Reliability analysis using Monte Carlo approach is described in the extra chapter. In the thesis are described several software tools, which can be used for systems reliability analysis. Design of PLC system with a human operator is done in the thesis. Reliability analysis using Monte Carlo approach is done on the designed PLC system. Results of Monte Carlo approach are compared with analytically calculated values and with values from reliability software.

The present thesis deals with power transformers, oil and dry, their properties and structures, and subsequently faults that occur in oil transformers. First, the disorders discussed in general and then a comparison of individual samples transformer failures that have occurred in recent years in the Moravian-Silesian and Olomouc regions. Finally, I analyze the failures and the most common encountered, I suggested solutions to reduce their incidence.

Within this thesis was carried out a reconnaissance of water distribution network of the city of Slavkov u Brna. The reconnaissance consists of: age analysis of piping materials; water losses evaluation; failure rate evaluation. Then was done a condition assessment of water supply network according to a chosen methodology. Using CARE-W LTP RSM software were projected a few technical-economic alternatives of rehabilitation of water network of the city of Slavkov u Brna. Then was prepared a project of rehabilitation of chosen section of water network. The work resulted in recommendations for the owner and operator of the water network of the city of Slavkov u Brna.

The interruption cost for one hour of a petrochemical plant is 33 times higher than that of the average interruption cost for industrial plants across all industries. In addition to the high cost of loss of production, interruptions to the operations of petrochemical and gas-toliquid plants pose safety and environmental hazards. Thus it is necessary to better understand the reliability requirements of petrochemical and gas-to-liquid plants. This study investigated the reliability of electrical distribution networks used in petrochemical and gas-to-liquid plants compared to those used in other industrial plants. A model was developed that can be used to establish the adequacy of the reliability of a distribution network in terms of the components and network topologies used. This model was validated against data that had been collected by the IEEE and applied to an actual petrochemical plant. Over 19 years’ worth of data regarding the trips that have occurred on the distribution network of an existing petrochemical plant was collected and manipulated in order to calculate the reliability indices associated with the equipment used to make up thisRecommended Practice for the Design of Reliable Industrial and Commercial Power Systems. The cost of loss of production and the capital costs associated with increased reliability were calculated for a section of the existing petrochemical plant. The reliability associated with different network topologies that could possibly be used to supply power to this section of the plant were modelled using an appropriate software package. The resulting total cost of ownership over the life of the plant associated with each topology was then calculated in order to establish which network topology is the most appropriate for petrochemical and gas-to-liquid plants. It was concluded the components that affect the reliability of an industrial distribution network are different to those that affect a utility distribution network. These components were listed and compared. It was found that the reliability indices that were calculated for the components that affect the reliability of a petrochemical plant were similar to those provided by the IEEE. 17 out of 20 of the indices that were calculated were within the required factor of deviation. Generally the failure rates of components used in petrochemical plants were very similar to those given in the IEEE Gold Book, while the MTTR’s for the components used in petrochemical plants were found to be slightly better than those given in the IEEE Gold Book. The effect of network topology was found to be significant, with small changes in the topology of a network resulting in large variations in the reliability of the network. It was also found that the most appropriate type of network topology to use in the design of the electrical distribution network of a petrochemical plant is the dual radial network. This is the most conservative of the commonly used network topologies and is the one that is currently used in the existing plant that was studied. Due to the high cost of loss of production in petrochemical plants it was established that any incremental improvement in the reliability of the dual radial network would be beneficial to the total cost of ownership of such a plant. Such incremental improvement of the reliability of the distribution network could be cost effectively achieved by adopting a conservative maintenance strategy and the establishment of a conservative spares inventory. Before this study was undertaken, there was no literature around the reliability of electrical distribution networks that focused specifically on petrochemical and gas-to-liquid plants. This study produced a set of reliability indices and a model that electrical engineers can use in the reliability analysis of petrochemical and gas-to-liquid plants. Furthermore it shows that, because the cost of loss of production in petrochemical plants is so high, the most conservative distribution network design and maintenance philosophies should always be used. distribution network. These reliability indices were compared to those given by the IEEE / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / unrestricted