by Kit-ching To. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 64-67). / Abstract also in Chinese. / Chapter Chapter 1 --- Overview --- p.1 / Chapter Chapter 2 --- Geometric Process Model --- p.6 / Chapter 2.1 --- Introduction --- p.6 / Chapter 2.2 --- Some Properties of Geometric Process --- p.7 / Chapter 2.3 --- Geometric Process Model for the Exponential Distribution --- p.13 / Chapter Chapter 3 --- Analysis of Warranty Policy by a Geometric Process Model --- p.16 / Chapter 3.1 --- Introduction --- p.16 / Chapter 3.2 --- Consumer's Policy --- p.17 / Chapter 3.2.1 --- N-Repair Warranty Policy --- p.19 / Chapter 3.2.2 --- n-Renewal Warranty Policy --- p.23 / Chapter 3.2.2.1 --- Modified n-Renewal Warranty Policy --- p.25 / Chapter 3.2.3 --- Optimal Policy to Consumer --- p.29 / Chapter 3.3 --- Manufacturer's Policy --- p.33 / Chapter 3.3.1 --- Optimal Policy to Manufacturer --- p.36 / Chapter 3.4 --- Numerical Examples --- p.38 / Chapter Chapter 4 --- Analysis of a Repairable M/M/l Queueing System by a Geometric Process Model --- p.45 / Chapter 4.1 --- Introduction --- p.45 / Chapter 4.2 --- Model --- p.46 / Chapter 4.2.1 --- Some Reliability Indices --- p.53 / Chapter 4.2.1.1 --- Availability --- p.53 / Chapter 4.2.1.2 --- Rate of Occurrence of Failures (ROCOF) --- p.54 / Chapter 4.3 --- Numerical Method --- p.56 / Chapter 4.3.1 --- Results --- p.58 / Bibliography --- p.64

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / Microfiche copy available in Archives and Engineering. / Vita. / Bibliography: leaves 252-261. / by Mircea Grigoriu. / Ph.D.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / Ph.D.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / Ph.D.

The reliability of the main cable of a suspension bridge is crucial to the reliability of the entire bridge. Throughout the life of a suspension bridge, its main cables are subject to corrosion due to various factors, and the deterioration of strength is a slowly evolving and dynamic process. The goal of this research is to find the pattern of how the strength of steel wires inside a suspension bridge cable changes with time. Two methodologies are proposed based on the analysis of five data sets which were collected by testing pristine wires, artificially corroded wires, and wires taken from three suspension bridges: Severn Bridge, Forth Road Bridge and Williamsburg Bridge. The first methodology is to model wire strength as a random process in space whose marginal probability distribution and power spectral density evolve with time. Both the marginal distribution and the power spectral density are parameterized with time-dependent parameters. This enables the use of Monte Carlo methods to estimate the failure probability of wires at any given time. An often encountered problem -- the incompatibility between the non-Gaussian marginal probability distribution and prescribed power spectral density -- which arises when simulating non-Gaussian random processes using translational field theory, is also studied. It is shown by copula theory that the selected marginal distribution imposes restrictions on the selection of power spectral density function. The second methodology is to model the deterioration rate of wire strength as a stochastic process in time, under Ito's stochastic calculus framework. The deterioration rate process is identified as a mean-reversion stochastic process taking non-negative values. It is proposed that the actual deterioration of wire strength depends on the deterioration rate, and may also depend on the state of the wire strength itself. The probability distribution of wire strength at any given time can be obtained by integrating the deterioration rate process. The model parameters are calibrated from the available data sets by matching moments or minimizing differences between probability distributions.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 160-163. / by Mostafa Hamed Ammar. / M.S.

Orientador: Prof. Dr. Julio Carlos Teixeira / A expansão da energia eólica no Brasil é fato nos últimos 20 anos e está consagrada com sua participação da matriz energética nacional. Este trabalho desenvolve um modelo de cálculo de Energia Anual Produzida (EAP), considerando a taxa de falhas e o tempo no qual o equipamento permanece sem gerar energia, indisponibilidade ou downtime. Para identificar o efeito das falhas na energia gerada é necessário um banco de dados ainda não disponibilizado no Brasil. O trabalho utilizou valores de referências ¿ benchmarks - de países com diferentes condições climáticas, que empregam diferentes tecnologias, confiabilidades e diferentes tempos de reparo. A partir deste modelo desenvolvido, foi feita a avaliação da EAP e de alguns indicadores de eficiência, considerando diferentes regimes de ventos, taxa de falhas e downtimes. Os resultados mostraram que as perdas devido às taxas fixas e variáveis para ventos brandos, em torno de 6 m/s, são equivalentes, se comportam linearmente com aumento de ventos e são relativamente pequenas se comparadas com as de velocidades mais altas onde as perdas aumentam de forma significativa. A análise desses resultados aponta que a taxa de falhas interfere de forma significativa na estimativa do fator de capacidade e na disponibilidade. Nas condições analisadas, as diferenças entre os indicadores estimados e aqueles que consideram downtimes, superam 2,6%. Essa diferença pode ser tanto maior quanto menor for a confiabilidade ou quanto maior for o tempo de reparo esperado para o parque eólico. Os resultados do trabalho mostram que a indisponibilidade tende a ser reduzida com as manutenções preventivas dos subconjuntos da turbina, e se ocorrerem no período úmido, ocasionarão perdas menores do que se comparadas ao período seco, na proporção de quase 30% nas condições simuladas. Os resultados mostraram também que valores de benchmarks provocam diferentes impactos na EAP. Portanto, conhecer o valor típico brasileiro do MTBF ¿ Tempo Médio Entre Falhas, qual o subsistema é mais confiável e outras informações referentes às condições nacionais, criará condições para uma estimativa mais realista da EAP. Na mesma analogia, conhecendo-se os tempos médios de reparos desses subsistemas - MTTR, e dos demais tempos decorrentes para realização da manutenção, pode-se planejar políticas e práticas adequadas de manutenabilidade para os parques eólicos implantados no Brasil. / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Energia, 2014. / The wind energy expansion has been a fact over the last 20 years in Brazil and it is consolidated as an integral part of the national energy grid. This paper presents a method of calculation of the EAP (annual energy production) considering failure rates and downtime. In order to assess the impact of the energy failures a database, which is not available in Brazil, would be needed. Benchmarks from countries with different climates, different technologies, reliability and recovery time were used. EAP (annual energy production) and some efficiency indicators were assessed through this model, considering different wind patterns, failure rates and downtime. Losses due to fixed and variable rates of light wind, approximately 6 m/s, are equivalent, behave linearly with wind increase and are relatively small when compared to higher speeds, where losses go up and diverge. The outcome assessment shows that the failure rates interfere significantly with the estimate of availability and capacity factors. Under the conditions assessed, the difference between estimated indicators and downtime, is over 2.6%. The lower the reliability or the longer recovery time is, the higher this difference will be. The outcome shows that unavailability tends to be reduced with preventive maintenance of the turbine subsystems, and if it happens in wet seasons, losses are lower compared to dry seasons, nearly 30% under the simulated conditions. The results also showed that benchmark figures have different impacts on EAP. Therefore, knowing the Brazilian typical MTBF (average time between failures) or which subsystem is more reliable will provide conditions to a more accurate and optimized estimate of the EAP. In addition, knowing the average time of recovery of these subsystems (MTTR) as well as the time taken on maintenance might enable us to plan new maintenance practices and policies.

Consideration of diagnosability in product design promises to increase product quality by reducing maintenance time without increasing cost or decreasing reliability. Methods for investigating the diagnosability of mechanical and electro-mechanical systems are described and are applied to the Bleed Air Control System (BACS) on the Boeing 747-400. The BACS is described and a diagnostic model is developed using information from the system Failure Modes and Effects Analysis. Emphasis is placed on the relationships between the system's functions and its components. Two metrics for the evaluation of system diagnosability and two metrics for the evaluation of component diagnosability are defined. These metrics emphasize diagnostic ambiguity and are combined with the probability of different system failures to weight the effects of each failure. Three modified systems are produced by reassigning functions from one component to another. The resulting effects on the system and component diagnosability are evaluated. We show that by changing these relationships system diagnosability can be improved without adding sensors or other components. / Graduation date: 1994

J.D. Birdwell, D.A. Castanon and M. Athans. / Bibliography: leaf 8. / Caption title. Supported in part by the Fannie and John Hertz Foundation. / NASA Ames Grant NGL-22-099-124 AFOSR Grant 77-3281

Thesis (M.S.)--Mississippi State University. Department of Aerospace Engineering. / Title from title screen. Includes bibliographical references.