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Reliability, IEEE Transactions on

Issue 4 • Date Oct. 1989

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Displaying Results 1 - 23 of 23
  • Comment on "An improved Abraham-method for generating disjoint sums

    Page(s): 422 - 424
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    The authors' earlier algorithm (see ibid., vol.R-36, p.70-74, Apr. 1987) yields relatively short disjoint sum forms of the structure functions of coherent binary systems. In the present paper, it is shown that, in applying this algorithm, still shorter disjoint sum forms can be obtained by proper arrangement of the path sets. This is demonstrated by some examples.<> View full abstract»

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  • Comments on "Queuing model of a bi-level Markov service-system and its solution using recursion

    Page(s): 428 - 429
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    The commenter claims that the efficient solution technique of M. Alam and V. Mani (see ibid., vol.37, p.427-433, Oct. 1988) is easier to derive and generalize in matrix notation. The authors demonstrated that this technique is a matrix analog of the solution technique for the M/M/1/N queue.<> View full abstract»

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  • Treatment of catastrophic events in availability assessment

    Page(s): 506 - 507
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    The authors discuss how catastrophic events, viz. rare failure events that violently affect the system, should be treated when assessing availability. In a general statistical framework, the problem treated is related to that of using the mean of a random variable to predict the actual value of the random variable. The discussion is based on experience gained from several availability studies of oil and gas production and transportation systems View full abstract»

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  • A model for system reliability with common-cause failures

    Page(s): 406 - 410
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    A model for the analysis of systems subject to common-cause failures is proposed. The system consists of a finite number of components that are subject to: (1) statistically independent failures, and (2) external failure causes (they need not be mutually statistically independent) for groups of components. Applications to fault-tree analysis and network reliability problems are discussed View full abstract»

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  • A new estimation approach based on periodic inspection

    Page(s): 436 - 439
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    The authors present a novel approach for estimating the failure-time distribution using count data, the number of failures per interval, from periodic inspection of a standby redundant system. The procedure is based on a result for stationary renewal processes that related the forward recurrence time to the interevent time distribution. The procedure performed well in a simulation study for five Weibull distributions and is general enough to work for any failure-time distribution View full abstract»

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  • Availability evaluation of flow networks with varying throughput-demand and deferred repair

    Page(s): 499 - 505
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    The author presents some simple formulas for availability of flow networks with several levels of performance and variable throughput demands. The system comprises highly available independent components. Two main types of component failure are considered: (1) those where the corresponding repair can be deferred to a more convenient time, and (2) all other failures. This more convenient time is set to a fixed date in the present model. This model is relevant to gas/oil production and transportation systems. Such availability concepts as throughput, demand, and onstream are discussed; the throughput availability is usually the most important. The computation of these measures can be time consuming; therefore, efficient algorithms and formulas are vital. The calculations are fast, so that sensitivity of various factors can be studied easily. The calculations show which components are contributing the most to unavailability View full abstract»

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  • Optimal replacement policies for k-out-of-n systems

    Page(s): 462 - 467
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    The authors study a discrete-time, infinite-horizon, dynamic programming model for the replacement of components in a binary k -out-of-n:F system. The goal is to trade off the component replacement and system failure costs. Under the criterion of minimizing the long-run average cost per period, it is optimal to follow a critical component policy (CCP), viz., a policy specified by a critical component set and the rule: replace a component if and only if it is failed and is in the critical component set. Computing an optimal CCP is a binary nonlinear programming problem, which can be solved by searching through a set with O(nk-1) points. This approach to finding an optimal CCP is practical when k is small. In particular, assuming s-independent components, it requires O(n2k-1) calculations. The authors analyze in detail the two most important cases with small k: the series (1-out-of-n:F) system and the 2-out-of-n:F system View full abstract»

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  • Some tests for comparing reliability growth/deterioration rates of repairable systems

    Page(s): 440 - 443
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    The author presents some optimal tests for comparing the reliability growth/deterioration rate of repairable systems. Failures are assumed to follow a nonhomogeneous Poisson process with log-linear intensity. A numerical example is included View full abstract»

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  • On/off cycling under multiple stresses

    Page(s): 494 - 498
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    The authors describe an experiment, a model, and an analytic method for on/off vs. continuous policy evaluation. The methodology was developed and verified through experimentation. An experimental life-test of small DC motors was designed and performed; it involved on/off cycling vs. continuous operation under multiple stresses. A stress-factor reliability model based on the two-parameter Weibull proportional-hazards life distribution was fitted to the data. The analysis provides an estimate of the model parameters for the life distribution of the DC motors under two operating policies, while under multiple stresses. The characteristic life was related to the explanatory covariates: voltage, on/off cycling, and load. Due to the proportional hazards (common Weibull shape) nature of the model, acceleration factors were calculated to relate the stress levels. The reliability model was extended to develop a simple rule to aid in a decision between on/off cycling and continuous-run policies (to achieve higher reliability). The proposed model (with covariates) allows a much broader approach to reliability modeling than the usual Weibull model (without covariates) because it predicts the reliability under various environmental combinations View full abstract»

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  • Generalized reliability results for 1-out-of-n:G repairable systems

    Page(s): 468 - 471
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    The author examines a class of 1-out-of-n:G systems consisting of n nominally identical units in parallel redundancy serviced by a single repair facility. Assuming constant failure rates and general repair distributions permits the problem of finding the Laplace transform of the time-to-system-failure distribution and the mean time-to-system-failure to be reduced to solving a closed-form system of (n-1) by (n-1) linear equations, for n at least 4. Numerical results are presented using a model of a satellite maintenance service View full abstract»

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  • Recursive solution technique in a multi-server bi-level queueing system with server breakdowns

    Page(s): 416 - 421
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    The authors present a multiserver, first-come first-served queuing system that alternates between two modes of system operation. In one mode, all s servers are available, and in the other mode, only s-1 servers are available for serving the customers. This is due to breakdown of one of the servers. The random variables representing the system with s servers and s-1 servers have exponential distributions. In such a system, the steady-state birth/death equations are coupled because of the two modes of operation. A recursive solution is presented for computing the steady-state probabilities of such a system. Once these probabilities are known, the performance measures of interest can be easily obtained. Two practical examples validate the results and show the utility of this method. A distinct advantage of the recursive technique is that it is much faster and requires much less memory than the existing nonrecursive techniques. In a bilevel situation, the system performance measures are always bounded by two independent queuing systems with s and s-1 servers. A procedure has been outlined for extension to multiple modes of system operation View full abstract»

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  • A Bayes approach to simultaneous evaluation of similar assemblies

    Page(s): 483 - 484
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    Simultaneous qualification testing of similar electronic-assembly designs that have the same reliability objectives lends itself to a Bayes approach. The author presents a method for obtaining the number of units to be put on test (test units) and the number of survivors required for this problem. The Bayes approach can reduce the total number of test units. The similarity of any two assemblies can be qualified using projected failure rates of components common to each design and components that differ between them. Under binomial sampling, survival probabilities follow the conjugate beta distribution. Two systems of linear equations are developed. Their solutions are vectors that describe, for each design: (1) the number of test units, and (2) the minimum number of survivors to demonstrate the reliability objective View full abstract»

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  • Fitting a multivariate failure time distribution

    Page(s): 444 - 448
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    A class of continuous multivariate distributions is reviewed. It is derived in a survival/reliability context, where the dependence is modeled as random effects, viz, by an unobserved covariate common to the components in a system and assumed to follow a positive stable distribution. Accounting for censored data is straightforward. The class is well fitted to proportional hazard models, and distributions of minima are simple. An important subfamily is the multivariate Weibull distributions. The theory is illustrated with an example View full abstract»

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  • Multistate consecutively-connected systems

    Page(s): 472 - 474
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    G. Shanthikumar (ibid., vol.R-36, p.546-550, Dec. 1987) has proposed a system called the consecutively connected system, which is a generalization of the consecutive-k-out-of-n:F system. He gave an O(n2) algorithm for computing the reliability of the consecutively connected system. In the present work, the authors further generalize it by assuming that the components are multistate. They give an O(Kn) algorithm for computing the reliability of the multistate system where K(K<n) is the maximum number of states for a component. They discuss the difficulties of obtaining corresponding algorithms for circular systems and two-way communication, although for two-state components they are able to extend the Shanthikumar algorithm to circular systems View full abstract»

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  • Lifetime distribution of circular consecutive-k-out-of-n:F systems with exchangeable lifetimes

    Page(s): 460 - 461
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    A recursive algorithm for computing the lifetime distribution of a circular consecutive-k-out-of-n:F system with statistically exchangeable component lifetimes is presented. The result applies to a load-sharing model View full abstract»

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  • Bounds on the reliability of binary coherent systems

    Page(s): 425 - 427
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    The structure function of a binary coherent system is approximated by using only a few of its minimal path sets and minimal cut sets. These two incomplete structure functions are represented as disjoint sums. The average of each is a lower and upper bound, respectively, for the system reliability. The usefulness of these bounds is demonstrated on example networks View full abstract»

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  • Optimal relayed mobile communication systems

    Page(s): 457 - 459
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    Recently, D.T. Chiang and R.F. Chiang (1986) considered a relayed mobile communication system with evenly spaced mobile relay stations (spacecraft) moving at the same speed from an origin towards a destination. Such a system can be considered as a consecutive-k-out-of-n line. They gave equations for computing the mean number of stations needed for a successful relay and studied the optimal choice of k to minimize the mean number. In the present work, the authors show that it is always better to replace a consecutive-k-out-of-n line by a consecutive-1-out-of- n line, but with k redundancy. The problem of choosing an optimal k still has no closed-form solution, but it is much more tractable than the original problem studied by Chiang and Chiang. Exact solutions are provided for a wide range of parameters View full abstract»

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  • An algorithmic approach to increased reliability through standby redundancy

    Page(s): 430 - 435
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    The authors address the issue of optimal redundancy allocation, viz, improving the reliability of a system by adding cold-standby spares, through an algorithmic approach that uses the unique characteristics of an assumed underlying failure distribution. Although the approach applies to systems with mixed parallel and series configurations, the discussion is limited to a series system of components. The lifetime distributions of individual parts are of the phase type. This class of probability distributions is chosen for its ease of numerical implementation. The formulation of the reliability enhancement problem is applied, and several heuristic design algorithms are examined View full abstract»

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  • MTBF of a complex binary coherent system

    Page(s): 411 - 415
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    It is noted that there has yet been no detailed study of the relationships between the MTBF (mean time between failures) of a system and the sequences of component failures, except for the case of a series system where every component failure causes a system failure. The author defines MTBF anew and derives relationships between the properties of the MTBF of a binary coherent system and the properties of the sequences of component failures, assuming that the lifetime distributions of the components are either new-better-than-used (NBU) exponential or increasing failure rate (IFR). Lower bounds of MTBF that can be used to predict the MTBF and to decide whether the system would satisfy the MTBF requirement are derived View full abstract»

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  • Relayed communication via parallel redundancy

    Page(s): 454 - 456
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    A communication is described where relay stations are moving in groups of k stations. If all k stations of a group fail, then all groups of k stations ahead of the failed k stations as well as the k failed stations are lost. The objective is to have one station reach the destination with all groups having at least one station in good condition. It is shown that this second communication system requires fewer stations on the average than the system of D.T. Chiang and R.-F. Chiang (1986). The probability distribution of the numbers of stations required in the Chiang-Chiang communication system is also examined View full abstract»

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  • A practical end-of-life model for semiconductor devices

    Page(s): 485 - 493
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    The authors derive a model of active semiconductor device aging to predict end of mission life device parameters by extrapolating from early environmental and electrical test measurements. Beginning from mass action kinetics first principles, the model develops an envelope average of physico-chemical damage reaction kinetics of limited source amounts of contaminating reactants. Corroborating experimental and test data are included View full abstract»

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  • Shrinkage estimation of threshold parameter of the exponential distribution [reliability theory]

    Page(s): 449 - 453
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    The authors study the usual preliminary test estimator of the threshold parameter of the exponential distribution in censored samples. The optimal levels of significance and their corresponding critical values for the preliminary test are obtained. The optimal values of shrinkage coefficients for a preliminary test shrinkage estimator are also obtained on the basis of the minimax regret criterion View full abstract»

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  • Effects of redundancy management on reliability modeling

    Page(s): 475 - 482
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    Two methods are investigated for incorporating the effects of fault detection and isolation (FDI) decision errors and redundancy management (RM) policy into reliability models for a simple single-component-dual-redundant system. These two methods are combinatorial analysis and Markov chain modeling. Reliability analysts have traditionally chosen the classical combinatorial approach. However, the authors show that the existence of time-ordered event sequences resulting from the interaction of FDI decision errors with the RM policy considerably complicates the construction of the combinatorial model. An error analysis illustrates that a simplified combinatorial model, which ignores these time-ordered event sequences, inaccurately predicts the system reliability. The Markov modeling technique is an excellent alternative to the combinatorial approach because it easily and accurately accounts for time-ordered event sequences such as those present in fault-tolerant systems 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