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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
331

Concept Study and Design of a New Torque Calibration Rig

Lidgren, Albin January 2017 (has links)
When buying a new car today, the customer often expects to get a vehiclewith high quality. Each vehicle or engine should therefore be checked toassure quality. The same goes for clutches and couplings. A powerful enginebecomes useless when a clutch slips. Reliable torque measurement istherefore essential to the automotive industry. The herewith Bachelor thesisproposes a new torque calibration rig for online torque measurement in couplingapplications.The concept encompasses a servo motor with its associated electronics, agearbox to create the high torques (3 kNm), a reference torque transducer,and mounting elements or adapters. From the concept generation phase, thethesis includes CAD-models of the torque calibration rig with mathematicalmodels leading to the calculation of the measurement uncertainty of the calibrationsystem.This work was performed at BorgWarner PowerDrive Systems AB in Landskronaduring eight weeks; the two remaining weeks were completed in Lulea.
332

Building A Profile of Inattentive Participants: Attachment Theory and Inattentive Responding

Unknown Date (has links)
Inattentive responding by research participants may decrease the reliability and validity of self-report measures. The current studies broaden the record of personality traits correlated with inattention by examining individual differences in attachment anxiety and avoidance among adults in romantic relationships. Based upon the characteristics typically exhibited by adults high on attachment avoidance, I expected an overlap between this personality trait and inattention, such that participants higher on attachment avoidance would exhibit higher levels of inattentive responding when answering self-report questions about their relationship. Two studies addressed this hypothesis using both self-report data from individuals and partner-report data from romantic couples to examine the association between a participant’s attachment avoidance and their level of inattentive responding while participating in research focusing on their romantic relationships. Self-reported attachment avoidance was associated with greater inattentive responding in both studies. However, partner-reported attachment avoidance was not significantly associated with inattentive responding in Study 2. / Includes bibliography. / Thesis (M.A.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
333

Identification errors and the control of time-delay systems

Chotai, A. January 1980 (has links)
A general scheme for time-delay control systems is presented so that with particular choice of system elements and loop gain many of the existing time-delay systems can be recovered. The effects of imperfections in the system model for time-delay systems are described and analysed. Sensitivity expressions are obtained and their relationship with the structure of time-delay systems are explored. Sensitivity Analysis for a time-delay system is extended to Adaptive Control of time-delay systems. An adaptive control system for Smith's Predictor and an LOP Optimal Control scheme are investigated analytically and by simulation. Delay-free optimal control methods are extended to systems with delay for LQP and parametric optimisation. For parametric optimal control, we explore, in particular, cases where deliberate mismatch leads to improvement, and the improvement of delay-free systems by addition of delay is also investigated. Various cases of LQP are discussed and the sub-optimality of published schemes, induced by mismatch is exposed. The method is also extended to time-varying systems with time-delay.
334

Confiabilidade dos valores de amplitude da eletromiografia de superfície durante exercícios para membro superior com carga axial e superfície estável e instável / Reliability of surface electromyography amplitude values during exercises for the upper limb with axial load and stable and unstable surfaces

Araujo, Rodrigo Cappato de 28 July 2006 (has links)
O objetivo deste estudo foi avaliar a confiabilidade intradia e interdias dos valores de amplitude da eletromiografia de superfície, dos músculos da cintura escapular e membro superior, durante a realização de 3 exercícios isométrico com a extremidade distal do segmento fixa em uma superfície estável e outra superfície instável, com descarga de peso axial controlada para o membro superior. Para tanto, 20 adultos saudáveis realizaram os exercícios push-up, bench-press e wall-press em diferentes níveis de carga (80 e 100% da carga máxima). Os valores de carga produzida por cada um dos exercícios foram registrados de maneira simultânea à eletromiografia. Os sujeitos realizaram três contrações voluntárias máximas (CVM) na posição de prova de função muscular de cada músculo, para obtenção do valor de referência para normalização dos valores de root mean square (RMS) e da integral do envoltório linear (?env). Os sujeitos foram instruídos, a realizarem de forma aleatória, 3 séries de contrações isométricas por 6 segundos em cada exercício, com intervalo de 2 minutos entre as séries e exercícios.Os sinais eletromiográficos dos músculos deltóide porção anterior e posterior, trapézio fibras superiores, serrátil anterior, peitoral maior porção clavicular, bíceps braquial porção longa e tríceps braquial porção longa foram captados por eletrodos de superfície ativos simples diferenciais, realizados em dois testes com intervalo de sete dias. Os dados foram coletados com freqüência de amostragem de 4000Hz e aplicados filtros digitais de passa baixa de 500Hz e passa alta de 20Hz. Os valores de RMS e ?env foram normalizados pelo valor máximo da amplitude eletromiográfica obtida em 1 das 3 CVM do músculo correspondente. As confiabilidades intradia e interdias foram calculadas através do coeficiente de correlação intraclasse (ICC), erro padrão da medida (SEM) e coeficiente de variação (CV). Os resultados indicaram excelente confiabilidade intradia dos valores de amplitude eletromiográfica (ICC ?0,75). A confiabilidade interdias dos valores normalizados de RMS apresentou valores variando entre bom e excelente (ICC 0,52-0,98), já os valores normalizados de ?env apresentaram valores pobres a excelente de confiabilidade (ICC 0,06-0,93). Os valores de carga produzidos durante os exercícios apresentaram excelente confiabilidade intradia e interdias (ICC ?0,97). Por fim, os resultados do presente estudo sugerem que a confiabilidade dos valores normalizados de amplitude eletromiográfica dos músculos analisados apresentam valores mais confiáveis durante os exercícios realizados com superfície estável. Já os níveis de carga empregados (80 e 100%) durante os exercícios parecem não ter influenciado nos níveis de variabilidade, talvez por serem cargas muito próximas. / The objective of the present study was to evaluate the intra and interday reliability of surface electromyography amplitude values of the scapular girdle muscles and upper limbs during the performance of 3 isometric exercises of closed kinetic chain regarding the upper limbs with the fix distal segment extremity on one stable surface and the other one on one unstable surface. In this regard, 20 healthy adults realized the exercises push-up, bench-press and wall-press with different load levels (80 and 100% maximal load). The load values produced for each exercise were recorded simultaneously to the electromyography. The individuals performed three maximal voluntary contractions (MVC) in the muscular testing position of each muscle for the obtainment of the reference value for the root mean square (RMS) normalization values and for the integrated of the linear envelope (?env). The individuals were instructed to realize at random, 3 isometric contraction series taking each exercise 6 seconds with a rest of 2 minutes between the series and the exercises. The electromyographic signals of the anterior and posterior deltoid, upper trapezius, anterior serratus, pectoralis major, biceps and triceps brachial muscle were captured by simple active differential surface electrodes, in two tests with a 7-day interval. Data were collected with a sampling frequency of 4000Hz and 500Hz low and 20Hz high passage digital filters. The RMS and ?env values were normalized by the maximal electromyographic amplitude value obtained in 1 of the 3 MVC of the corresponding muscle. The intra and interday reliabilities were calculated through the intraclass correlation coefficient (ICC), standard error measure (SEM) and coefficient of variation (CV). The results indicated an excellent intraday reliability of the electromyographic amplitude values (ICC ?0.75). The interday reliability of the RMS normalized values presented values varying between good and excellent (ICC 0.52-0.98), whereas the ?env normalized values presented poor to excellent reliability values (ICC 0.06-0.93). The load values produced during the exercises presented excellent intra and interdays reliability. Finally, the results of the present study suggest that the reliability of the electromyographic amplitude normalized values of the analyzed muscles present better values during the performance of the exercises with stable surface. However the load levels utilized during the exercises do not seem to have influenced the variability levels, eventually in view of being very close levels
335

Análise do processo de atendimento a itens não conformes no campo / not available

Salvador, Carlos Cesar 20 December 2004 (has links)
A confiabilidade do produto é um dos principais atributos da sua qualidade, porém a melhoria contínua desta confiabilidade é um objetivo inalcançável para as empresas, principalmente após o processo de globalização, no qual as empresas locais não têm como competidores apenas as empresas regionais ou nacionais, mas também as outras empresas mundiais. Outro fator importante, para o estabelecimento da confiabilidade, é o cliente que têm aumentado as suas exigências num processo contínuo, em que os aspectos de conformidade às especificações do projeto estão se tornando critério de compra. Este trabalho, através de um estudo de caso, apresenta a análise de um processo de atendimento a itens não conformes e propõe melhorias neste processo, visando agilizar a solução de problemas de campo. Para isso será avaliada a confiabilidade da empresa, desde a comunicação do cliente, passando pelo revendedor e da própria empresa, até a metodologia utilizada para a análise das falhas de campo dos produtos existentes. Os registros e informações da área de suporte e serviços, serão fundamentais para a introdução de melhorias para o procedimento atualmente em uso pela empresa. / The reliability of a product is one of the main attributes of its quality, however continuous improvement of its reliability is a never-ending journey for companies, especially those with global processes, as they must complete with other regional, national and global companies. Another important factor in determining the reliability of a product is the understanding of the critical customer requirements. Due to market globalization, consumers now have access to a greater variety of products and are better able to make comparisons between similar items. This ability drives consumers to constantly change or refine their critical requirements that ultimately influence their purchasing decisions. This case study presents an analysis of a process for monitoring product non-conformances and proposes process improvements aimed at speeding up the solution to field problems. To do this, company reliability will be analyzed in terms of the path of communication of product problems from the customer to the dealer, the dealer to the factory and from the factory to the methodology used to analyze field failures. Information from the product support and services area will be fundamental to the introduction of improvements to the current field failure processes.
336

Estudo de confiabilidade de compressores alternativos semi-herméticos de sistemas de refrigeração. / Reliability study of reciprocating compressors of refrigeration systems.

Bassetto, Izeds Felipe Facchini 27 March 2007 (has links)
Sistemas de refrigeração são sistemas reparáveis. Isto significa que os componentes destes sistemas podem sofrer manutenção várias vezes durante a vida útil do sistema como um todo. Em sistemas de refrigeração o mais conhecido é o que opera com ciclo por compressão de vapor. Neste ciclo, o compressor é o equipamento mais complexo e de maior custo. Dessa forma, deve-se tomar especial cuidado, pois além de problemas como desgaste e falta de lubrificantes, ele está sujeito a sofrer danos decorrentes do funcionamento incorreto ou falho de todos os outros componentes. Dentro dos compressores existentes, o compressor alternativo pode ser comercialmente considerado o cavalo de batalha da refrigeração industrial, dominando a faixa de capacidades inferiores a 300 kW (85 TRs). O compressor alternativo também pode ser utilizado, com vantagens, quando o controle de capacidade se faz necessário, através do procedimento de desativação dos cilindros. Este compressor possui a possibilidade de manutenção no campo de, praticamente, qualquer item construtivo. O termo confiabilidade vem do inglês \"reliability\" que é a probabilidade de um item poder desempenhar sua função requerida, por um intervalo de tempo estabelecido, sob condições definidas de uso. Testes de confiabilidade possibilitam, através de estimativa, com base em estudos de confiabilidade, caracterizar os comportamentos de confiabilidade, da probabilidade de falha e da taxa de falha em relação ao tempo de um componente ou sistema. Uma das ferramentas para permitir avaliar ações que aumentem a confiabilidade é a Análise de Modos e Efeitos de Falha ou FMEA (\"Failure Mode and Effect Analysis\"). Basicamente, esta ferramenta parte da definição das funções dos sistemas e subsistemas analisados, verificando em seguida as falhas que afetam cada função e todos os modos de falha que levam a cada falha. Para cada modo de falha, analisam-se os efeitos e define-se a necessidade de ações para reduzir a possibilidade de ocorrência deste evento, eliminá-lo ou, simplesmente controlar os efeitos indesejáveis. O objetivo deste trabalho é o estudo das principais falhas, modos de falha de compressores semi-herméticos alternativos de sistemas de refrigeração, suas ocorrências e o comportamento destes equipamentos no seu período de garantia, sob a ótica da confiabilidade. / Refrigeration systems are reparable systems. This means that one can perform maintenance actions on them several times during the system life cycle. The most common refrigeration system is the vapor compression cycle. In this cycle, the compressor is the most complex and expensive component. So, the user should take special care because , beside problems like wear and lubricant lack, the compressor can also suffer damages caused by the incorrect work or fault from the others system components. Among the compressor types, the reciprocating compressor can be considered as the most used in the industrial refrigeration, from lowers capacities to up to 300 kW. Also the reciprocating compressor has some advantages, where its cylinders can be disabled for capacity control purposes. One can perform field maintenance of almost every part for this compressor. The word reliability means the probability of some equipment can not perform its requested function for an established time period, under defined operation conditions.. One of the tools to allow actions to improve the reliability is the failure mode and effect analysis (FMEA). This tool is based on the analyzed function and sub function systems definitions seeking faults that affect each function and all fault modes that lead to every fault. For each fault mode, the effects are analyzed and the need of actions to decrease the occurrence of this event is defined, excluding or control this undesirable events. This work objective is to study the most important faults, fault modes of reciprocating semi-hermetic compressors, its occurrences and its behavior during the guarantee period under reliability point of view.
337

A general inspection-repair-replacement model for systems with unobservable states.

January 1996 (has links)
by Siu-Keung Wan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 69-70). / Chapter Chapter 1 --- Introduction and Review / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Review --- p.3 / Chapter Chapter 2 --- A general IRR model for a system with unobservable states / Chapter 2.1 --- Model and assumptions --- p.8 / Chapter 2.2 --- Long-run average cost per unit time incurred in a replacement cycle --- p.14 / Chapter Chapter 3 --- The Algorithm / Chapter 3.1 --- The key point and the local turning point of the average cost --- p.16 / Chapter 3.2 --- A finite algorithm --- p.23 / Chapter Chapter 4 --- Numerical examples and sensitivity analysis with discussion / Chapter 4.1 --- Weibull Distribution Case --- p.25 / Chapter 4.2 --- Gamma Distribution Case --- p.28 / Chapter 4.3 --- Exponential Distribution Case --- p.30 / Chapter 4.4 --- Sensitivity analysis --- p.32 / Chapter 4.5 --- Conclusion and further development --- p.38 / Figures --- p.40 / Tables --- p.46 / References --- p.69
338

Consecutive-k-OUT-OF-n: F repairable system with markov dependence of order (k-1).

January 1999 (has links)
Ng Hon Keung Tony. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 85-87). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Probability Analysis of Consecutive-k-out-of-n: F system with (k-l)-step Markov Dependence --- p.11 / Chapter 2.1 --- Model and Assumptions --- p.11 / Chapter 2.2 --- Find Out the Failure Risk of the System --- p.17 / Chapter 2.3 --- The Linear Consecutive-3-out-of-4: F Repairable system with 2-step Markov Dependence --- p.27 / Chapter 2.3.1 --- Failure risk of the system --- p.27 / Chapter 2.3.2 --- Priority repair rule --- p.32 / Chapter 2.4 --- The Circular Consecutive-3-out-of-4: F Repairable system with 2-step Markov Dependence --- p.41 / Chapter 2.4.1 --- Failure risk of the system --- p.41 / Chapter 2.4.2 --- Priority repair rule --- p.47 / Chapter Chapter 3 --- System Analysis for Linear Consecutive-3-out-of-4: F system with 2-step Markov Dependence by Laplace Transform Method --- p.57 / Chapter Chapter 4 --- Reliability Indices for Consecutive-3-out-of-4: F system with 2-step Markov Dependence by Numerical Method and Simulation Study --- p.69 / Chapter 4.1 --- Numerical Method --- p.69 / Chapter 4.1.1 --- Linear consecutive-3-out-of-4: F repairable system with 2-step Markov dependence --- p.70 / Chapter 4.1.2 --- Comparison between Laplace transform method and numerical method --- p.72 / Chapter 4.1.3 --- Circular consecutive-3-out-of-4: F repairable system with 2-step Markov dependence --- p.75 / Chapter 4.2 --- Numerical Results --- p.75 / Chapter 4.3 --- Simulation Study --- p.78 / Chapter 4.4 --- Comparison between Simulation Method and Numerical Method --- p.79 / FIGURES 1 to 7 --- p.82-84 / REFERENCES --- p.85-87
339

Strain measurement using neutron diffraction

Wang, Duan Qiang January 1996 (has links)
This thesis contains a study of improvement and application of strain measurement technique using neutron diffraction. A dedicated neutron strain scanner - ENGIN, funded by Ee. has been developed at ISIS. It has two radial collimators, allowing for the first time, measurements taken simultaneously at two orthogonal directions; uses Pawley refinement permitting both whole pattern and individual peak profile analysis and its positioner allow's specimens weighing 250 kg to be placed with an accuracy of 100 um. Strain measurement using neutron diffraction has been investigated under two extreme circumstances: very shallow (within 1 mm near surface) and very deep in materials (hundred of mm). Near-surface measurement requires both the accurate determination of the effective measurement position associated with precise location of specimen, calculation of centroid and correction for an anomalous near-surface effect. The strain measurements on a shot-peened surface in titanium alloy were carried out using the methodology mentioned above. The result is comparable to that obtained from X-ray diffraction. The latter was exploited by studying the effect of wavelength-dependent attenuation in materials. Experiments and theoretical analysis on aluminium and iron show that the effect is small for a strain scanner using radial collimator and time-of-flight technique. However, the reduction of the diffraction peak intensity, as a function of the amount of material in the beam path, reveals that great care should be taken when measuring texture as a function of depth in materials. The neutron diffraction technique was applied to several sets of engineering strain measurements. Firstly, 3-D residual stresses surrounding a cold expanded hole in a high strength aluminium alloy plate were measured. The result agrees well with that from modified Sachs' method after taking the effect of gauge volume averaging into account. Second, measurements of strain distributions in a Q-joint under zero and 30 kN load have been carried out, which provides a confirmation of the excellence of the joint design as the fastener system has completely shielded the fastener hole from deleterious tensile strains under operational loading. Finally, calibration strain measurement for an energy dispersive neutron transmission spectrometer was performed for the first time and it is found that the transmission spectrometer is feasible for strain and phase transformation measurement.
340

Software reliability prediction

Steel, Donald January 1990 (has links)
The aim of the work described in this thesis was to improve NCR's decision making process for progressing software products through the development cycle. The first chapter briefly describes the software development process at NCR, detailing documentation review and software testing techniques. The objectives and reasons for investigating software reliability models as a tool in the decision making process are outlined. There follows a short review of software reliability models, with the Littlewood and Verrall Bayesian model considered in detail. The difficulties in using this model to obtain estimates for model parameters and time to next failure are described. These estimation difficulties exist using the model on good datasets, in this case simulated failure data, and the difficulties are compounded when used with real failure data. The problems of collecting and recording failure data are outlined, highlighting the inadequacies of these collected data, and real failure data are analysed. Software reliability models are used in an attempt to quantify the reliability of real software products. The thesis concludes by summarising the problems encountered when using reliability models to measure software products and suggests future research into metrics that are required in this area of software engineering.

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