Página 1 dos resultados de 24652 itens digitais encontrados em 0.027 segundos

Reliability-based evaluation of design code provisions for circular concrete-filled steel columns

BECK, Andre T.; OLIVEIRA, Walter L. A. de; NARDIM, Silvana De; ELDEBS, Ana L. H. C.
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.6%
This paper presents an investigation of design code provisions for steel-concrete composite columns. The study covers the national building codes of United States, Canada and Brazil, and the transnational EUROCODE. The study is based on experimental results of 93 axially loaded concrete-filled tubular steel columns. This includes 36 unpublished, full scale experimental results by the authors and 57 results from the literature. The error of resistance models is determined by comparing experimental results for ultimate loads with code-predicted column resistances. Regression analysis is used to describe the variation of model error with column slenderness and to describe model uncertainty. The paper shows that Canadian and European codes are able to predict mean column resistance, since resistance models of these codes present detailed formulations for concrete confinement by a steel tube. ANSI/AISC and Brazilian codes have limited allowance for concrete confinement, and become very conservative for short columns. Reliability analysis is used to evaluate the safety level of code provisions. Reliability analysis includes model error and other random problem parameters like steel and concrete strengths, and dead and live loads. Design code provisions are evaluated in terms of sufficient and uniform reliability criteria. Results show that the four design codes studied provide uniform reliability...

Reliability-based design optimization strategies based on FORM: a review

Lopez, Rafael Holdorf; Beck, André Teófilo
Fonte: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM Publicador: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.6%
In deterministic optimization, the uncertainties of the structural system (i.e. dimension, model, material, loads, etc) are not explicitly taken into account. Hence, resulting optimal solutions may lead to reduced reliability levels. The objective of reliability based design optimization (RBDO) is to optimize structures guaranteeing that a minimum level of reliability, chosen a priori by the designer, is maintained. Since reliability analysis using the First Order Reliability Method (FORM) is an optimization procedure itself, RBDO (in its classical version) is a double-loop strategy: the reliability analysis (inner loop) and the structural optimization (outer loop). The coupling of these two loops leads to very high computational costs. To reduce the computational burden of RBDO based on FORM, several authors propose decoupling the structural optimization and the reliability analysis. These procedures may be divided in two groups: (i) serial single loop methods and (ii) unilevel methods. The basic idea of serial single loop methods is to decouple the two loops and solve them sequentially, until some convergence criterion is achieved. On the other hand, uni-level methods employ different strategies to obtain a single loop of optimization to solve the RBDO problem. This paper presents a review of such RBDO strategies. A comparison of the performance (computational cost) of the main strategies is presented for several variants of two benchmark problems from the literature and for a structure modeled using the finite element method.

Análise de confiabilidade de sistemas eletrônicos complexos baseada em ensaios acelerados de vida.; Reliability analysis of complex electronic systems based on accelerated life tests.

Felix, Érico Pessoa
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/01/2007 PT
Relevância na Pesquisa
36.6%
O objetivo deste estudo é desenvolver um método para avaliar a confiabilidade de sistemas eletrônicos complexos. A análise proposta baseia-se na aplicação de ensaios de confiabilidade e de normas técnicas, bem como modelos matemáticos para estimação da vida operacional. Os ensaios de confiabilidade executados nesse estudo simulam condições operacionais mais severas que as usualmente enfrentadas pelo sistema, a fim de reduzir o tempo de execução dos ensaios. Ao longo destes, foram coletados os tempos até a falha de diversas amostras do sistema, os quais são submetidas a diferentes condições de operação. O planejamento das variáveis que aceleram os principais modos de falha de componentes eletrônicos e os perfis de solicitação empregados também são discutidos, sendo consideradas as mais importantes a temperatura e a umidade. Através da aplicação de modelos matemáticos para predição da vida nas condições normais de operação, dadas as ocorrências de falhas nas condições aceleradas, a confiabilidade e o tempo médio até a falha são determinados para a central telefônica estudada, tomada como exemplo na aplicação do método. Adicionalmente aos ensaios são desenvolvidas estimativas da confiabilidade da central telefônica através da norma militar US MIL-HDBK-217 F (1991). Os resultados destas estimativas são utilizados para comparação e confirmação dos resultados obtidos através dos ensaios. Destaca-se que os métodos descritos neste texto não são restritos a aplicação em centrais telefônicas analógicas...

Aplicação de confiabilidade na calibração de coeficientes parciais de segurança de normas brasileiras de projeto estrutural; Reliability based calibration of partial safety factors of brazilian design codes

Souza Junior, Antonio Carlos de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/02/2009 PT
Relevância na Pesquisa
36.62%
Neste trabalho é realizado o estudo dos coeficientes parciais de segurança utilizados em normas de projeto estrutural. O trabalho é fundamentado na teoria de confiabilidade estrutural, que permite uma representação explícita das incertezas envolvidas em resistências e ações, e resulta em uma estimativa quantitativa da segurança estrutural: o índice de confiabilidade. O trabalho aborda uma metodologia de calibração de norma que permite obter o conjunto de coeficientes parciais de segurança que minimiza as variações dos índices de confiabilidade das mais diversas estruturas projetadas segundo uma norma de projeto, em relação ao índice de confiabilidade alvo utilizado na calibração. Uma calibração inicial é feita utilizando um índice de confiabilidade alvo igual a 3,0, mas diferentes índices de confiabilidade também são considerados. A análise é feita para elementos estruturais de aço. A calibração é feita para dois formatos de norma distintos. No formato das normas americanas (ANSI/AISC), um conjunto de coeficientes parciais de segurança é obtido para cada expressão de combinação de ações. No formato da norma Brasileira e Européia, um único conjunto de coeficientes parciais (e de coeficientes de combinação) é obtido...

A reliability analysis approach to assist the design of aggressively scaled reconfigurable architectures

Pereira, Mônica Magalhães
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
ENG
Relevância na Pesquisa
36.67%
As computer systems are built with aggressively scaled and unreliable technologies, some implementations rely on function specialization with reconfigurable computing to increase performance by exploiting parallelism, with possible energy gains. However, the use of reconfigurable devices in general purpose computing also brings extra reliability challenges at the system level. Solutions to cope with that are generally accompanied with the addition of excessive area, performance and power overheads to the overall system. These overheads could be reduced if a more extensive analysis was performed to evaluate the best fault tolerance strategy to balance the tradeoff between reliability and the mentioned aspects. In this context, this work present a comprehensive analysis of architectural design that includes the use of reliability modeling and takes into consideration aspects such as area, performance, and power. The analysis aims to assist the design of reliability-aware reconfigurable architectures by giving some indications about what kind of redundancy should be used in order to increase reliability. In the proposed analysis, we show that communication among functional units is critical to the overall reliability of reconfigurable architectures. Therefore...

Sensibilidade a variações de perfil operacional de dois modelos de confiabilidade de software baseados em cobertura; Sensitivity to variations in the operational profile of two software reliability models based on coverage

Odair Jacinto da Silva
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/01/2014 PT
Relevância na Pesquisa
36.62%
Diversos estudos publicados indicam que a capacidade preditiva dos modelos de confiabilidade de software, que utilizam a informação da cobertura observada durante os testes, é melhor do que a capacidade preditiva dos modelos baseados no domínio do tempo. E, por isso, têm sido propostos por pesquisadores da área como uma alternativa aos modelos baseados no domínio do tempo. Entretanto, para chegar a uma conclusão sobre a superioridade desta classe de modelos é necessário avaliar a sua sensibilidade a variações do perfil operacional. Uma qualidade desejável dos modelos de confiabilidade de software é a de que sua capacidade preditiva não seja afetada por variações no perfil operacional de um software. Esta dissertação avalia, por meio de um experimento, o comportamento de dois modelos de confiabilidade de software que se baseiam na informação de cobertura do código: "Modelo Binomial Baseado em Cobertura" e "Modelo de Falhas Infinitas Baseado em Cobertura". O experimento aplica os modelos nos dados de falhas observados durante a execução de um programa em três perfis operacionais estatisticamente distintos. Adicionalmente, seis modelos de confiabilidade de software tradicionais são utilizados para estimar a confiabilidade do software utilizando os mesmos dados de falhas. Os modelos escolhidos foram: Musa-Okumoto...

On the use of NDT data for reliability-based assessment of existing timber structures

Sousa, Hélder S.; Sørensen, John D.; Kirkegaard, Poul H.; Branco, Jorge M.; Lourenço, Paulo B.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
Relevância na Pesquisa
36.65%
The objective of this paper is to address the possibilities of using non-destructive testing (NDT) data for updating information and obtaining adequate characterization of the reliability level of existing timber structures and, also, for assessing the evolution in time of performance of these structures when exposed to deterioration. By improving the knowledge upon the mechanical properties of timber, better and more substantiated decisions after a reliability safety assessment are aimed at. Bayesian methods are used to update the mechanical properties of timber and reliability assessment is performed using First Order Reliability Methods (FORM). The results show that different degrees of belief in the updating data may significantly influence the reliability level. The updating data to be used are NDT results obtained with ultrasound, resistance drilling and pin penetration equipments. The tests were conducted on chestnut wood (Castanea sativa Mill.) specimens, and were combined with tests to determine the compressive strength parallel to the grain. The uncertainty of the different NDT results is modeled by Maximum Likelihood estimates. Resistance distributions functions are considered to analyze the difference before and after updating by NDT...

Reliability and cost models of axial pile foundations

Teixeira, Ana
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 09/04/2013 ENG
Relevância na Pesquisa
36.7%
Tese de doutoramento em Engenharia Civil / Geotecnia; Pile foundations are often used for important structures, and thus, reliability evaluation is an important aspect of the design. Unlike the approach to reliability evaluation used in structural engineering, the traditional procedure used in geotechnical designs addresses uncertainties through high global or partial safety factors, mostly based on past experience. However, this approach to addressing uncertainties does not provide a rational basis for understanding their influence on design. For this reason, and because of regulation codes and social concerns (such as sustainability), geotechnical engineers need to improve their ability to deal with uncertainties and probabilities to help with decision-making. Reliability methods have become increasingly important as decision support tools. The main benefit of reliability analysis is that it provides quantitative information about the parameters (uncertainties) that most significantly influence the behaviour under study. This makes risk control, the determination of the potential causes of adverse effects on the structure, possible. In particular, the design of pile foundations still involves many limitations and uncertainties...

The reliability of the Brazilian version of the Composite International Diagnostic Interview (CIDI 2.1)

Quintana,M.I.; Andreoli,S.B.; Jorge,M.R.; Gastal,F.L.; Miranda,C.T.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2004 EN
Relevância na Pesquisa
36.64%
The objective of the present study was to determine the reliability of the Brazilian version of the Composite International Diagnostic Interview 2.1 (CIDI 2.1) in clinical psychiatry. The CIDI 2.1 was translated into Portuguese using WHO guidelines and reliability was studied using the inter-rater reliability method. The study sample consisted of 186 subjects from psychiatric hospitals and clinics, primary care centers and community services. The interviewers consisted of a group of 13 lay and three non-lay interviewers submitted to the CIDI training. The average interview time was 2 h and 30 min. General reliability ranged from kappa 0.50 to 1. For lifetime diagnoses the reliability ranged from kappa 0.77 (Bipolar Affective Disorder) to 1 (Substance-Related Disorder, Alcohol-Related Disorder, Eating Disorders). Previous year reliability ranged from kappa 0.66 (Obsessive-Compulsive Disorder) to 1 (Dissociative Disorders, Maniac Disorders, Eating Disorders). The poorest reliability rate was found for Mild Depressive Episode (kappa = 0.50) during the previous year. Training proved to be a fundamental factor for maintaining good reliability. Technical knowledge of the questionnaire compensated for the lack of psychiatric knowledge of the lay personnel. Inter-rater reliability was good to excellent for persons in psychiatric practice.

Cross-cultural adaptation and reliability analysis of the Brazilian version of Pediatric Balance Scale (PBS)

Ries,Lílian G. K.; Michaelsen,Stella M.; Soares,Patrícia S. A.; Monteiro,Vanessa C.; Allegretti,Kátia M. G.
Fonte: Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia Publicador: Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
36.62%
BACKGROUND: The Pediatric Balance Scale (PBS) was developed from a modified version of the Berg Balance Scale aiming to obtain a balance scale more appropriate for the child population. OBJECTIVES: To adapt the PBS into Brazilian-Portuguese and to evaluate the intra and inter-rater reliability of the Brazilian-Portuguese version of PBS. METHODS: To perform the cross-cultural adaptation of the American version of PBS four translators were involved, who have performed two translations and their respective back-translations. Then, a review by a multidisciplinary committee and a subsequent an assessment of the equivalence of meaning between the back-translations and the original English scale were performed by 3 and 30 healthcare professionals respectively. The intra-rater reliability of the final version of the Brazilian-Portuguese PBS was evaluated using a test-retest design with one-week interval. The Brazilian-Portuguese version of the PBS was tested twice on the same day by two different raters to test the inter-rater reliability. The inter-rater reliability, which was measured from a video of the volunteers performance, was evaluated by comparing the score given by five raters independently. Reliability was evaluated by Intraclass Correlation Coefficient (ICC). Fifteen volunteers (11±2.7 years) diagnosed with Cerebral Palsy (CP) classified at level I and II on the Gross Motor Function Classification System (GMFCS) were assessed. RESULTS: The reliability of the PBS total score for both intra-rater (ICC=0.85) and inter-rater (ICC=0.91) was excellent. The inter-rater reliability (measured from the video) for the total score was also classified as excellent (ICC=0.98). CONCLUSION: The results showed adequate reliability for the PBS for pediatric population with CP diagnostic classified at level I and II on the GMFCS.

Inter-rater reliability for movement pattern analysis (MPA): measuring patterning of behaviors versus discrete behavior counts as indicators of decision-making style

Connors, Brenda L.; Rende, Richard; Colton, Timothy J.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.62%
The unique yield of collecting observational data on human movement has received increasing attention in a number of domains, including the study of decision-making style. As such, interest has grown in the nuances of core methodological issues, including the best ways of assessing inter-rater reliability. In this paper we focus on one key topic – the distinction between establishing reliability for the patterning of behaviors as opposed to the computation of raw counts – and suggest that reliability for each be compared empirically rather than determined a priori. We illustrate by assessing inter-rater reliability for key outcome measures derived from movement pattern analysis (MPA), an observational methodology that records body movements as indicators of decision-making style with demonstrated predictive validity. While reliability ranged from moderate to good for raw counts of behaviors reflecting each of two Overall Factors generated within MPA (Assertion and Perspective), inter-rater reliability for patterning (proportional indicators of each factor) was significantly higher and excellent (ICC = 0.89). Furthermore, patterning, as compared to raw counts, provided better prediction of observable decision-making process assessed in the laboratory. These analyses support the utility of using an empirical approach to inform the consideration of measuring patterning versus discrete behavioral counts of behaviors when determining inter-rater reliability of observable behavior. They also speak to the substantial reliability that may be achieved via application of theoretically grounded observational systems such as MPA that reveal thinking and action motivations via visible movement patterns.

The inter and intra-rater reliability of age band 2 of the Movement Assessment Battery for children - second edition (MABC2)

Martin, Conor
Fonte: Department of Physiotherapy, University of Limerick Publicador: Department of Physiotherapy, University of Limerick
Tipo: Bachelor thesis; all_ul_research; ul_theses_dissertations; none
ENG
Relevância na Pesquisa
36.7%
non-peer-reviewed; Background: The MABC-2 is one of the most widely used outcome measures as means of measuring developmental delay. (Van Waelvelde et al 2006). Despite this, there is little literature surrounding the reliability of the outcome measure. Objectives: To determine the inter-rater and intra-rater reliability of the second age band of the MABC-2 Methods: 11 children (mean age 7.55 years) enrolled in second class of primary education completed the Movement Assessment Battery for Children 2 on two separate occasions. The results of these two testing sessions were used to calculate inter and intra-rater reliability. Results: Inter-rater reliability The ICC values for the inter-rater reliability were very good with only one task falling below 0.9. One task received an ICC .892, which is still considered excellent reliability. (Portney & Watkins 1993). Intra-rater reliability The ICC values for the intra-rater reliability do not appear as strong as the results for inter-rater reliability. Only two tasks had a reliability that can be considered excellent (>0.9). Three other tasks appear to have moderate intra-rater reliability(.5-.75). All other tasks fell below and ICC of 0.5 indicating poor intra-rater reliability reliability. Conclusions: The MABC-2 appears to have good inter-rater reliability but much poorer intra-rater reliability. Although there were some limitations to the methodology...

RELIABILITY AND RISK ASSESSMENT OF NETWORKED URBAN INFRASTRUCTURE SYSTEMS UNDER NATURAL HAZARDS

Rokneddin, Keivan
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
36.68%
Modern societies increasingly depend on the reliable functioning of urban infrastructure systems in the aftermath of natural disasters such as hurricane and earthquake events. Apart from a sizable capital for maintenance and expansion, the reliable performance of infrastructure systems under extreme hazards also requires strategic planning and effective resource assignment. Hence, efficient system reliability and risk assessment methods are needed to provide insights to system stakeholders to understand infrastructure performance under different hazard scenarios and accordingly make informed decisions in response to them. Moreover, efficient assignment of limited financial and human resources for maintenance and retrofit actions requires new methods to identify critical system components under extreme events. Infrastructure systems such as highway bridge networks are spatially distributed systems with many linked components. Therefore, network models describing them as mathematical graphs with nodes and links naturally apply to study their performance. Owing to their complex topology, general system reliability methods are ineffective to evaluate the reliability of large infrastructure systems. This research develops computationally efficient methods such as a modified Markov Chain Monte Carlo simulations algorithm for network reliability...

Stochastic comparisons and Bayesian inference in software reliability; Ordenaciones estocásticas e inferencia bayesiana en fiabilidad de software

Torrado Robles, Nuria
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado Formato: application/pdf
ENG
Relevância na Pesquisa
36.67%
Within the last decade of the 20th century and the first few years of the 21st century, the demand for complex software systems has increased, and therefore, the reliability of software systems has become a major concern for our modern society. Software reliability is defined as the probability of failure free software operations for a specified period of time in a specified environment. Many current software reliability techniques and practices are detailed by Lyu and Pham. From a statistical point of view, the random variables that characterize software reliability are the epoch times in which a failure of software takes place or the times between failures. Most of the well known models for software reliability are centered around the interfailure times or the point processes that they generate. A software reliability model specifies the general form of the dependence of the failure process on the principal factors that affect it: fault introduction, fault removal, and the operational environment. The purpose of this thesis is threefold: (1) to study stochastic properties of times between failures relative to independent but not identically distributed random variables; (2) to investigate properties of the epoch times of nonhomogeneous pure birth processes as an extension of nonhomogeneous Poisson processes used in the literature in software reliability modelling and...

Reliability the life cycle driver : an examination of reliability management culture and practices

Masiello, Gregory L.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xvi, 105 p. : ill. (some col.) ;
Relevância na Pesquisa
36.64%
Approved for public release; distribution is unlimited.; The importance of reliable and maintainable equipment in the hands of our service members cannot be overstated. Reliability has been identified as the life cycle cost driver for defense weapon systems. Knowing that the reliability of a weapon system directly impacts upon that system's operational capability and life cycle costs makes it of fundamental importance to the warfighter. In recognition of its importance, it is mandatory for all program managers within the Department of Defense (DoD) to ensure their program accounts for the user's reliability objectives. However, reliability failures continue to disappoint operators, maintainers and testers of DoD systems. This thesis evaluates reliability management within the acquisition process of Naval Aviation programs. Reliability, logistical, and program management personnel directly involved with the issues of reliability management provided empirical insight to help the researcher identify root causes and risk mitigation techniques that are critical to reliability optimization.; Major, United States Marine Corps

Joint Source-Channel Coding Reliability Function for Single and Multi-Terminal Communication Systems

Zhong, Yangfan
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 2246891 bytes; application/pdf
EN; EN
Relevância na Pesquisa
36.66%
Traditionally, source coding (data compression) and channel coding (error protection) are performed separately and sequentially, resulting in what we call a tandem (separate) coding system. In practical implementations, however, tandem coding might involve a large delay and a high coding/decoding complexity, since one needs to remove the redundancy in the source coding part and then insert certain redundancy in the channel coding part. On the other hand, joint source-channel coding (JSCC), which coordinates source and channel coding or combines them into a single step, may offer substantial improvements over the tandem coding approach. This thesis deals with the fundamental Shannon-theoretic limits for a variety of communication systems via JSCC. More specifically, we investigate the reliability function (which is the largest rate at which the coding probability of error vanishes exponentially with increasing blocklength) for JSCC for the following discrete-time communication systems: (i) discrete memoryless systems; (ii) discrete memoryless systems with perfect channel feedback; (iii) discrete memoryless systems with source side information; (iv) discrete systems with Markovian memory; (v) continuous-valued (particularly Gaussian) memoryless systems; (vi) discrete asymmetric 2-user source-channel systems. For the above systems...

Confiabilidade da fleximetria e goniometria na avaliação da amplitude de movimento cervical em crianças; Reliability of fleximetry and goniometry for assessing cervical range of motion among children

CHAVES, TC; NAGAMINE, HM; BELLI, JFC; DE HANNAI, MCT; BEVILAQUA-GROSSI, D; DE OLIVEIRA, AS
Fonte: Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia Publicador: Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
36.62%
OBJETIVO: Determinar a confiabilidade intra e interexaminadores e correlacionar os valores de amplitudes de movimentos (ADM) cervical obtidas por fleximetria e goniometria em crianças. MÉTODOS: Participaram deste estudo 106 crianças saudáveis, 49 meninos (8,91±2,09 anos) e 57 meninas (9,14±1,46 anos), com idades entre seis e 14 anos, assintomáticas para disfunção cervical. Dois examinadores previamente treinados e dois auxiliares avaliaram a ADM cervical. Os examinadores coletaram as medidas por fleximetria e goniometria (confiabilidade interexaminadores) e repetiram as avaliações, após uma semana (confiabilidade intra-examinador). Todas as medidas foram registradas três vezes por cada examinador e o valor médio foi considerado para análise estatística. O coeficiente de correlação intraclasse (ICC 2,1 e 2,2) foi utilizado para verificação das confiabilidades e o coeficiente de correlação de Pearson (p<0,05) foi utilizado para verificação da correlação entre as medidas obtidas por ambas as técnicas. RESULTADOS: Foram observadas confiabilidades intra-examinador moderado e excelente para a fleximetria e moderada para a goniometria. As confiabilidades interexaminadores foram moderada e excelente para a fleximetria e pobre e moderada para a goniometria. Foi verificada correlação significativa e pobre entre todas as medidas de ADM cervical obtida pelas técnicas estudadas...

Proposta de método de análise de confiabilidade de sistemas eletrônicos empregando dados de retorno em garantia. ; Proposal of reliability analysis method of electronic systems using warranty data.

Lemes, Danielli Villar
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/06/2006 PT
Relevância na Pesquisa
36.62%
Atualmente, a grande concorrência de mercado faz com que as empresas busquem maior confiabilidade e qualidade em seus produtos, aumentando assim a confiança e fidelidade de seus clientes. Além disso a diminuição dos gastos com garantia e a possibilidade de extensão da mesma é um grande diferencial de mercado, e pode ser obtido com a realização de estudos de confiabilidade dos sistemas e equipamentos. Este trabalho propõe um método para esse estudo e apresenta um caso exemplo, aplicando o método sugerido, e, propondo melhorias. O presente trabalho reúne conceitos básicos de confiabilidade, apresentando as ferramentas mais utilizadas e explana sobre análise de dados de retorno em garantia. São propostas também algumas soluções para vencer as dificuldades possíveis de serem encontradas. O método consiste em adequar os dados obtidos, de um banco de dados qualquer, para se realizar uma análise de confiabilidade partindo do conhecimento do produto através de materiais apropriados e da execução da árvore funcional, seguida da Análise de Modos e Efeitos de Falha, e, realizando a análise dos dados de garantia, classificando o tipo de registro, como suspenso, completo ou agrupado, e atribuindo a aproximação dos dados a uma distribuição estatística adequada para se calcular os parâmetros e obter a confiabilidade do equipamento ou sistema. A partir dessa análise dos dados é possível se obter relações de sazonalidade entre falhas...

Making Noncatastrophic Health Care Processes Reliable: Learning to Walk before Running in Creating High-Reliability Organizations

Resar, Roger K
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em /08/2006 EN
Relevância na Pesquisa
36.65%
Health care clinicians successfully apply proven medical evidence in common acute, chronic, or preventive care processes less than 80 percent of the time. This low level of reliability at the basic process level means that health care's efforts to improve reliability start from a different baseline from most other industries, and therefore may require a different approach. This paper describes The Institute for Healthcare Improvement's (IHI) current approach to improving health care reliability, including a useful nomenclature for levels of reliability, and a focus on improving reliability of basic health care processes before moving on to more sophisticated high reliability organization concepts. Early IHI work with a community of health care reliability innovators has identified four themes in health care settings that help to explain at least a portion of the gap in process reliability between health care and other industries. These include extreme dependence on hard work and personal vigilance, a focus on mediocre benchmark outcomes rather than process, great tolerance of provider autonomy, and failure to create systems that are specifically designed to reach articulated reliability goals. This paper describes our recommendations for the initial steps health care organizations' might take...

Pile design practice in southern Africa Part 2: Implicit reliability of existing practice

Retief,J V; Dithinde,M
Fonte: Journal of the South African Institution of Civil Engineering Publicador: Journal of the South African Institution of Civil Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2013 EN
Relevância na Pesquisa
36.65%
Limit state design has become the basis of geotechnical design codes worldwide. With the semi-probabilistic limit state design approach, load and resistance factors of (deterministic) design functions are calibrated on the basis of reliability theory. The calibration is done to obtain procedures that will ensure that a target level of reliability is exceeded under the design conditions within the scope of the design function. This is conventionally expressed in terms of the reliability index (β), which is related to the probability of failure (Pf). Acceptable existing design practice is an important source of information on appropriate levels of reliability. This paper uses the results from a pile load test database to evaluate the reliability levels implied in the current South African pile design approach. The results of the analysis indicate that the reliability index values for ultimate limit state failure of single piles implicit to present design practice vary with the pile class. However, the influence of the probability model applied is more significant. Based on conventional and standardised procedures for reliability analysis, a representative implicit reliability index value βI Rep 3.5 is obtained, corresponding to a probability of failure Pf = 2.10-4. The values for various sets of pile conditions range from βI = 3.1 (Pf = 1.10-3) to βI = 4.3 (Pf = 1.10-5). This compares well with target levels of reliability for structural and geotechnical performance of βT = 3.0 as set in SANS 10160-1:2011 Part 1 Basis of structural design. These indicative results provide a useful reference base to establish the reliability of existing and therefore acceptable South African pile design practice. It could also be interpreted as indicative of geotechnical design practice in general. The standard SANS 10160-5:2011 Part 5 Basis for geotechnical design and actions provides the framework for future calibration investigations.