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Reliability, IEEE Transactions on

Issue 2 • Date June 1991

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Displaying Results 1 - 21 of 21
  • Comments on "Diagnostic-strategy selection for a series system" by J.A. Nachlas et al

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (92 KB)  

    The authors comment on the work of J.A. Nachlas et al. (see ibid., vol.39, no.3, p.273-80, 1990) that presents diagnostic strategies for series systems with both perfect and imperfect testing. Their comment concerns the results given for the perfect-test case. They hold that the proof of the theorem which provides a simple optimal test sequence is incomplete and give a necessary criterion for an optimal strategy.<> View full abstract»

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  • Scalability analysis in gracefully-degradable large systems

    Page(s): 189 - 197
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    The scalability of large degradable homogeneous multiprocessors is analyzed. The objective is to assess the limitations, imposed by reliability considerations, on the number of processors. The analysis of the mean-time-to-failure and the mission-time shows that, for a given value of the coverage factor, there exists a value of the number of processors at which these measures are maximal. As the system size is increased beyond this value, the reliability of the system becomes a rapidly decreasing function of the number of processors. For computations with linear speed-up, the amount of reliable computational work is constant for large system-sizes. When the speed-up is not linear, this amount is a decreasing function of the number of processors. Therefore, for large system-sizes and same technology, increasing the number of processors results in a decrease of the average amount of reliable computational work the system can deliver. Graceful degradation in large fault-tolerant systems is not scalable View full abstract»

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  • A generalized reduction method for the connectedness probability of stochastic networks

    Page(s): 198 - 204
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    The connectedness probability of a stochastic network is computed by a generalized approach to network reduction. The approach is based on separating-vertex-sets and on introducing more than one replacement graph. Computational aspects are discussed, and examples are presented View full abstract»

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  • Piecewise exponential estimator of the survivor function

    Page(s): 134 - 139
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    A method for estimating the survivor function of a life distribution from a set of censored data is presented. The method is illustrated and it is explained how to calculate the survivor function from a censored data set. The estimator is compared with the well-known Kaplan-Meier estimator, using a set of data observed in a real engineering situation. The advantages and disadvantages of the method are discussed View full abstract»

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  • Robustness of a semi-parametric proportional intensity model

    Page(s): 161 - 164
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    The Prentice, Williams, Peterson (PWP) semiparametric model for the failure processes of repairable systems involves regression on explanatory variables across strata defined by the failure-event count. A heuristic method is developed for assessing the robustness of the PWP model, where the true underlying process is nonhomogeneous Poisson with power-law intensity function. The PWP model performed well for large samples and increasing rates of occurrence of failures and poorly for small samples and decreasing rates of occurrence of failures View full abstract»

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  • A reliability simulation approach for use in the design process

    Page(s): 177 - 181
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    A simulation model for use in the engineering design process is reported. The simulation model facilities reliability modeling by design engineers and reliability analysts early in the design process. The model applies to preliminary feasibility and design tradeoff studies. The authors describe the model, focus on applications to mission reliability analysis, and give a case study for the voice-communication system of the F-16 fighter aircraft View full abstract»

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  • Approximate MLEs for the location and scale parameters of the extreme value distribution with censoring

    Page(s): 146 - 151
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    For the extreme value distribution, the maximum likelihood method does not provide explicit estimators for the location and scale parameters. A method of deriving explicit estimators by approximating the likelihood function is provided. The authors derive the asymptotic variances, covariance, and conditional bias of these estimators, and show that they are almost as efficient as the maximum likelihood estimators and just as efficient as the best linear unbiased and the best linear invariant estimators. Two examples illustrate this method of estimation View full abstract»

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  • A maintenance policy for repairable systems based on opportunistic failure-rate tolerance

    Page(s): 237 - 244
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    An opportunistic hazard rate replacement policy for a repairable system with several types of units is presented. A unit is repaired at failure when the hazard rate falls in (0, L-u). A unit is replaced at failure when the hazard rate falls in (L-u , L). An operating unit is replaced when its hazard rate reaches L. When a unit is replaced because its hazard rate reaches L, all operating units with their hazard rates falling in (L-u, L) are replaced. The long-run mean cost rate as a function of L and u is derived. Optimal L and u are obtained to minimize the total maintenance cost rate. Application and analysis of results are demonstrated through a numerical example. The maintenance model is designed for a system with multitype units. Each type has its own increasing hazard rate. Units are repaired or replaced depending on their hazard rate at a failure or active replacement of another unit. The repair interval, replacement limit, and replacement tolerance are determined to yield the optimal total maintenance cost rate View full abstract»

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  • Incorporating the effects of time estimation into human-reliability analysis for high-risk situations

    Page(s): 247 - 254
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    A modeling framework for predicting the effects of discrepancies between subjective and objective measures of elapsed time on performance of human-machine interaction tasks in high-risk situations is presented. Following a review of the major theories and experimental research findings in time estimation, the importance of time estimation in terms of its potential for affecting human performance in critical human-machine system operations is discussed. The authors' approach for dealing with time-related task demands is to describe the ongoing dynamic processes during task performance that are associated with temporal estimation, and to assess their effects on human reliability. This is accomplished through a conceptual framework that is depicted and discussed in terms of several task features and information-processing mechanisms, and that implicitly recognizes the experimental evidence concerning human time-estimation performance. This concept is illustrated through special cases that are formulated and analyzed in terms of their potential for contributing to human error as a function of time-estimation considerations View full abstract»

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  • A class of tests for testing an increasing failure-rate-average distribution with randomly right-censored data

    Page(s): 152 - 156
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    For testing exponentiality versus (nonexponential) increasing failure rate average (IFRA) alternatives (which are nonexponential) using the randomly right censored data, a class of test statistics based on a functional of the Kaplan-Meier estimator is proposed. The asymptotic relative efficiencies of tests from this class with respect to other test statistics are derived. The efficiency loss due to censoring is studied. The proposed tests are applied to published survival data View full abstract»

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  • Some thought-experiments in reliability

    Page(s): 131 - 132
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    Five thought-experiments are presented which address the relationships between life distributions and physical processes. These relationships are sources of basic misconceptions in the reliability literature View full abstract»

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  • K-terminal reliability of hierarchical networks

    Page(s): 218 - 225
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    A class of networks called hierarchical networks is described, and it is shown how reliability can be computed efficiently in a hierarchical network. In particular, an algorithm for the K-terminal problem is described for computing the probability that a set of k nodes (k>1) can communicate through the network. The algorithm complexity is polynomial with a small degree. The exact degree depends on the distribution of the nodes that desire to communicate and the external gateways View full abstract»

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  • Optimal accelerated life-time plans that minimize the maximum test-stress

    Page(s): 166 - 172
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    The author proposes a variation of the optimum accelerated life test plans described by Nelson and others, and shows how to minimize the maximum test-stress that is required, subject to meeting a certain standard-deviation limit on the estimate. Previous optimal life-test plans have shown how to minimize the standard-deviation of the estimated product life, subject to a given maximum test-stress View full abstract»

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  • A nonparametric approach to progressive stress accelerated life testing

    Page(s): 173 - 176
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    Progressive-stress accelerated life testing in which the stress on an unfailed item increases linearly with test time when the time transformation function is a version of the inverse power law is considered. The approach is nonparametric in that not many assumptions are made about life distribution. A testing pattern is introduced, and it is explained how to draw inferences from progressive stress tests. An estimator of life distribution at the usual stress level is proposed View full abstract»

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  • Approximate MLEs for the location and scale parameters of the half-logistic distribution with type-II right-censoring

    Page(s): 140 - 145
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    For the half-logistic distribution the maximum likelihood method does not provide an explicit estimator for the scale parameter based on either complete or right-censored samples. The authors provide a simple method of deriving an explicit estimator by approximating the likelihood function. The bias and variance of this estimator are studied, and it is shown that this estimator is as efficient as the best linear unbiased estimator. An example to illustrate the method is presented View full abstract»

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  • Factoring and reductions for networks with imperfect vertices

    Page(s): 210 - 217
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    Factoring and reductions are effective methods for computing the K-terminal reliability of undirected networks, but they have been applied mostly to networks with perfect vertices. However, in real problems, vertices may fail as well as edges. Imperfect vertices can be factored like edges, but the complexity then increases exponentially with their number. A technique has been developed to account for the failure of vertices with small additional cost, using a modified method of factoring and reductions. This technique is very easy to integrate into a factoring algorithm. It consists of factoring not on a single element (e.g., a single edge) but on a set of elements (e.g., an edge and its endpoints). The problem is that random variables associated with the elements of the network are no longer independent. This can be handled by choosing factoring edges that have at least one perfect endpoint. This technique leaves the factoring algorithm practically unchanged. The only difference is that some supplementary probability values are kept for the imperfect vertices of the original and the induced graphs. For algorithms using simple reductions, it has negligible computational cost View full abstract»

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  • A note on minimal repair

    Page(s): 245 - 246
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    The cumulative function for the number of failures for a unit which is subjected to minimal repair after each failure is a nonstationary Poisson process. In this note, a simple method for obtaining this result is presented. A conditional probability approach is used for the derivation View full abstract»

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  • Interdependence between safety-control policy and multiple-sensor schemes via Dempster-Shafer theory

    Page(s): 182 - 188
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    The Dempster-Shafer (D-S) theory has been gaining popularity in fields where incomplete knowledge is a factor. The author explores the application of the D-S theory in system reliability and safety. Inappropriate application of the D-S theory to safety-control policies can degrade plant safety. This is proven in two phases: (1) a unified combination rule for fusing information on plant states given by independent knowledge sources such as sensors or human operators is developed; and (2) combination rules cannot be chosen in an arbitrary manner, i.e., the best choice of combination rules depends on whether the safety-control policy is fault-warning or safety-preservation View full abstract»

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  • Temperature-dependent standard deviation of log(failure time) distributions

    Page(s): 157 - 160
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    The distributions of failure times at accelerated life-test temperatures are often analyzed assuming a constant-σ model, where σ is the standard deviation of log(failure times). Recent experimental and theoretical studies of laser degradation, time-dependent dielectric breakdown, and electromigration suggest that σ is temperature-dependent. The author derives a general relationship for temperature-dependent σ from the Arrhenius relation. The relationship is used to analyze published electromigration data. The analysis suggests that the correlation coefficient between the activation energy and log(pre-exponential factor in the Arrhenius relation) close to -1. An example illustrates the use of the relationship to validate the electromigration design rule of a hypothetical microcircuit technology. The author argues that assuming a constant σ could result in an invalid design rule View full abstract»

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  • Modeling a shared-load k-out-of-n:G system

    Page(s): 205 - 209
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    A Markov model for analyzing the reliability and availability of an n-unit shared-load repairable k-out-of-n:G system with imperfect switching is presented. The equations for both time-dependent and steady-state system availability are given. An inverse Laplace transform is used to solve the simultaneous differential equations for the nonrepairable case. A generalized analytic function for system reliability is obtained. Examples are provided to demonstrate the model and the impact of a load-sharing strategy on the reliability. The load-sharing strategy can improve system reliability and availability, if the controller and switching parameters are adequate. The proposed approach and solution are helpful to system engineers and reliability analysts View full abstract»

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  • Rainbow Net analysis of VAXcluster system availability

    Page(s): 226 - 236
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    A system modeling technique, Rainbow Nets, is used to evaluate the availability and mean-time-to-interrupt of the VAXcluster. These results are compared to the exact analytic results showing that reasonable accuracy is achieved through simulation. The complexity of the Rainbow Net implemented for the VAXcluster does not increase as the number of processors increases, but remains constant. This is unlike a Markov model which increases in size exponentially. The constancy is achieved by using tokens with identity attributes (items) that can have additional attributes associated with them (features) which can exist in multiple states. The time to perform the simulation increases, but this is a polynomial increase rather than exponential. With Rainbow Nets, there is no restriction on distributions used for transition firing times. This freedom allows real situations to be modeled more accurately by choosing the distribution which best fits the system performance. This eliminates the need to make the many simplifying assumptions that are typically required to keep analytic calculations from becoming intractable View full abstract»

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Aims & Scope

IEEE Transactions on Reliability is concerned with the problems involved in attaining reliability, maintaining it through the life of the system or device, and measuring it.

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Meet Our Editors

Editor-in-Chief
Way Kuo
City University of Hong Kong