考虑变量相关性的正交异性板细节疲劳可靠性评估

传统的疲劳可靠性评估方法忽略了功能函数中变量的相关性,致使计算得到疲劳可靠度指标精度降低。针对这一问题,基于既有悬索桥主梁细节应变和环境温度大样本监测数据,讨论疲劳功能函数变量之间的相关性关系。提出基于Copula函数的相关性变量的联合分布模型,解决联合概率分布建模中多重积分求解困难的问题。研究表明,受环境温度的影响,靠近顶板焊接细节的日等效应力幅和应力循环次数存在较强的相关性,Gaussian Copula函数可作为相关性变量的最优连接函数,对于U肋-顶板细节,桥梁结构服役100年时,考虑与不考虑变量相关性的可靠度指标值分别5.3和6.9,两者之间相差约1.3倍。当年交通增长率分别等于3%和5%时,可靠度指标在服役年限为94.6年和67.1年时间到达目标可靠度指标。对于U肋-U肋对接细节,考虑和不考虑变量的相关性对可靠性指标影响相对顶板细节较小。     

Multinomial-exponential reliability function: a software reliability model

The multinomial-exponential reliability function (MERF) was developed during a detailed study of the software failure/correction processes. Later on MERF was approximated by a much simpler exponential reliability function (EARF), which keeps most of MERF mathematical properties, so the two functions together makes up a single reliability model. The reliability model MERF/EARF considers the software failure process as a non-homogeneous Poisson process (NHPP), and the repair (correction) process, a multinomial distribution. The model supposes that both processes are statistically independent.The paper discusses the model's theoretical basis, its mathematical properties and its application to software reliability. Nevertheless it is foreseen model applications to inspection and maintenance of physical systems. The paper includes a complete numerical example of the model application to a software reliability analysis.     

Error bounds for the reliability index in finite element reliability analysis

This work presents an extension of the goal‐oriented error estimation techniques to the reliability analysis of a linear elastic structure. We use a first‐order reliability method in conjunction with a finite element analysis (FEA) to compute the failure probability of the structure. In such a situation the output of interest that is computed from the FEA is the reliability index β. The accuracy of this output, and thus of the reliability analysis, depends, in particular, on the accuracy of the FEA. In this paper, upper and lower bounds of the reliability index are proposed, as well as simple bounds of the failure probability. An application to linear fracture mechanics is presented. Copyright © 2011 John Wiley & Sons, Ltd.     

Maturity index on reliability: covering non-technical aspects of IEC61508 reliability certification

One of the more recent developments in the field of reliability and safety is the realisation that these aspects are not only a function of the product itself, but also of the organisation realising this product. A second development is a trend from an often predominantly qualitative analysis towards a quantitative analysis. In contrast to the (older) DIN 0801, the (more recent) IEC61508 requires, on product level, also a quantitative analysis and, on organisational level, an assessment of the lifecycle of a product by analysing the (maturity of the) relevant business processes (DIN V VDE 0801. Grundsätze für Rechner in Systemen mit Sicherheitsaufgaben, 1990; DIN V 0801. Grundlegende Sicherheitsbetrachtungen für MSR-Schutzeinrichtungen, 1994; DIN V VDE 0801 A1. Grundsätze für Rechner in Systemen mit Sicherheitsaufgaben, Änderung A1, 1994; IEC 61508 Functional Safety of electrical/electronic/programmable electronic safety-related systems, draft 4.0, 1997). The IEC standard 61508 covers: (i) technical aspects, both on a quantitative and a qualitative level; (ii) organisational aspects, both on aspects of maturity of business processes (quantitative) and on aspects of the definition and application of procedures (qualitative).This paper shows the necessity for an analysis on all aspects in a safety certification process, and presents an overview of the available tools and techniques for the various quadrants. As methods and tools for especially quadrant C are currently unavailable, this paper will propose a method to assess and improve the maturity of an organisation on reliability management: the maturity index on reliability (MIR).     

Bayesian reliability: Combining information

ABSTRACT

One of the most powerful features of Bayesian analyses is the ability to combine multiple sources of information in a principled way to perform inference. This feature can be particularly valuable in assessing the reliability of systems where testing is limited. At their most basic, Bayesian methods for reliability develop informative prior distributions using expert judgment or similar systems. Appropriate models allow the incorporation of many other sources of information, including historical data, information from similar systems, and computer models. We introduce the Bayesian approach to reliability using several examples and point to open problems and areas for future work.     

A study of operational and testing reliability in software reliability analysis

Software reliability is an important aspect of any complex equipment today. Software reliability is usually estimated based on reliability models such as nonhomogeneous Poisson process (NHPP) models. Software systems are improving in testing phase, while it normally does not change in operational phase. Depending on whether the reliability is to be predicted for testing phase or operation phase, different measure should be used. In this paper, two different reliability concepts, namely, the operational reliability and the testing reliability, are clarified and studied in detail. These concepts have been mixed up or even misused in some existing literature. Using different reliability concept will lead to different reliability values obtained and it will further lead to different reliability-based decisions made. The difference of the estimated reliabilities is studied and the effect on the optimal release time is investigated.     

Recent achievements in the reliability of InP-based HEMTs

The current understanding of reliability issues for InP HEMTs is reviewed. To date, the origin of some instability and degradation phenomena have been identified and the solutions to eliminate or mitigate them have been found. On the other hand, some degradation phenomena are quite complicated and are still under investigation. The increase of drain resistance is one of them. This might be related to the hot electron effect, but it is still an open question as to where and how it happens. Some efforts at solving this mystery, including cathodoluminescence studies, are presented.     

Specifying the reliability of measurement means

Conclusions The fraction of correction measurements, which is a use indicator for the quality of measurement means and takes their specifications into account, depends on the distributions of failure-free operating time in the presence of sudden and gradual failures and the distribution of the time of an intercheck interval, and also on the relations between these distributions. In the general case the fraction of correct measurements is determined by the integral of the joint distribution of these events. The approach explained here has permitted the consideration of a number of particular cases that are important in metrological practice.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 92–94, February, 1971.     

Optical correlation: influence of the coding of the input image

We analyze the influence of different optical coding methods of the input image in optical correlators. The noise robustness and the optical efficiency of the correlator are investigated. We show in particular that the signal-to-noise ratio is greatly dependent on the coding method. It decreases drastically for large phase modulation.     

Quantifying the reliability of dispersal paths in connectivity networks

Many biological systems, from fragmented landscapes to host populations, can be represented as networks of connected habitat patches. Links between patches in these connectivity networks can represent equally diverse processes, from individuals moving through the landscape to pathogen transmissions or successive colonization events in metapopulations. Any of these processes can be characterized as stochastic, with functional links among patches that exist with various levels of certainty. This stochasticity then needs to be reflected in the algorithms that aim to predict the dispersal routes in these networks. Here we adapt the concept of reliability to characterize the likelihood that a specific path will be used for dispersal in a probabilistic connectivity network. The most reliable of the paths that connect two patches will then identify the most likely sequence of intermediate steps between these patches. Path reliability will be sensitive to targeted disruptions of individual links that form the path, and this can then be used to plan the interventions aimed at either preserving or disrupting the dispersal along that path. The proposed approach is general, and can be used to identify the most likely dispersal routes in various contexts, such as predicting patterns of migrations, colonizations, invasions and epidemics.     

Empirical Bayes estimation in the case of exponential reliability

The empirical Bayes estimate is derived for the failure rate parameter in the exponential distribution by considering a spline density estimate for the prior density function of the parameter. The reliability function is also estimated either by using the empirical Bayes estimate of the parameter, or by obtaining the expectation of the reliability function. Numerical examples (computerized simulation) are introduced to compare the performance of this estimate with the pure (or classical) Bayes estimates obtained using symmetrical triangular and gamma prior distributions.     

Software reliability prediction: A survey

Softwares play an important role in controlling complex systems. Monitoring the proper functioning of the components of such systems is the principal role of softwares. Often, a petite fault in one of the subsystems may cause irreparable damages; therefore, it is of great importance to be able to predict software faults and estimate the reliability of softwares. In this survey, we present a classification of various methods proposed in the literature to predict software reliability. This study summarizes the results of more than 200 research papers in the field. We also discuss the challenges involved in prediction methods along with proposed partial solutions (i.e., Bayesian methods) to improve the accuracy of such predictions. Moreover, we review numerous evaluation measures introduced so far to assess the performance of prediction models, the datasets they are based on, and also the results they yield.     

An evaluation of the multi-state node networks reliability using the traditional binary-state networks reliability algorithm

A system where the components and system itself are allowed to have a number of performance levels is called the Multi-state system (MSS). A multi-state node network (MNN) is a generalization of the MSS without satisfying the flow conservation law. Evaluating the MNN reliability arises at the design and exploitation stage of many types of technical systems. Up to now, the known existing methods can only evaluate a special MNN reliability called the multi-state node acyclic network (MNAN) in which no cyclic is allowed. However, no method exists for evaluating the general MNN reliability. The main purpose of this article is to show first that each MNN reliability can be solved using any the traditional binary-state networks (TBSN) reliability algorithm with a special code for the state probability. A simple heuristic SDP algorithm based on minimal cuts (MC) for estimating the MNN reliability is presented as an example to show how the TBSN reliability algorithm is revised to solve the MNN reliability problem. To the author's knowledge, this study is the first to discuss the relationships between MNN and TBSN and also the first to present methods to solve the exact and approximated MNN reliability. One example is illustrated to show how the exact MNN reliability is obtained using the proposed algorithm.     

Use of reliability technology in the process industry

Reliability analysis has been established as a useful tool for risk analysis and the design of safety systems. During the past ten years use of advanced methods for optimal maintenance and process control based on reliability technology has been introduced. Lack of data has been a problem, but even more important has been the reluctance of personnel involved with regard to implementation of these methods. One reason for this is the complexity of the models and methods presented. In the future more emphasis should be put on the solving of problems as experienced by the industry. The following are proposed to encourage the use of reliability technology:

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  close cooperation with industry;

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  focus on specific problems as experienced by the industry rather than system modelling;

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  development of simple methods to be applied by the people who own the problem.

     

The use of models in reliability

The paper reviews the scientific and philosophical basis of the use of models in engineering, particularly in reliability engineering, and their credibility in predicting future outcomes.     

Weighted voting systems: reliability versus rapidity

The weighted voting system (WVS) consists of n units that each provide a binary decision (0 or 1) or abstain from voting. Each unit has its own individual weight. System output is 1 if the cumulative weight of all 1-opting units is at least a pre-specified fraction τ of the cumulative weight of all non-abstaining units. Otherwise, system output is 0. The system input is either 0 or 1. Every unit is characterized by probability of making decisions 0 and 1 and by probability of abstaining for each input. The system fails if its output is not equal to its input.This paper shows that if the WVS consists of units that need different time to produce their outputs, the decision time of the entire system depends on the distribution of unit weights and on the value of τ. It shows also that a tradeoff exists between the system reliability and its rapidity.An algorithm that finds the system parameters maximizing its reliability under constraint imposed on the expected system decision time is suggested. Illustrative examples are presented.     

Evaluating the reliability of prototype degradable systems

The technique introduced in this paper is a new technique for analyzing fault tolerant designs under considerable uncertainty, such as seen in unique or few-of-a-kind devices in poorly known environments or pre-prototype design analyses. This technique is able to provide useful information while maintaining the uncertainty inherent in the original specifications. The technique introduced here is a logical extension of the underlying concepts of fuzzy sets and Markov models. Although originally developed for robotic systems, the technique is more broadly applicable. This paper develops fuzzy Markov modeling and uses it to analyze a specific robot designed for hazardous waste removal and specific types of electronic systems.