A reliability-program case-history on design review

World Abstracts on M icroelectronics and Reliability probabilities (for example, the Pearson & Hartley Biometrica Tables). Reliability characteristics of a Markov system with a mission of random duration. CttAgI.F.SE. WELLSand JOHN L. BRYANT. IEEE Trans. Reliab. R-34(4), 393 (1985). Realistic reliability measures are developed for s-coherent systems whose behavior can be modeled as a continuous-time Markov chain, and which terminate their useful life in some finite but random amount of time. An example is included to illustrate the use of the closed form expressions that are derived for these measures. Evalnating the signal-reliability of logic circuits. KYUNG-SHIK KOH. IEEE Trans. Reliab. R-34(3), 323 (1985). A different approach to the evaluation of signal reliability of digital logic circuits is presented. The method derives functional descriptions of each output of the circuit. In order to include the effect of faults in the function realized by the circuit, three binary variables are used to specify the state of each line in the circuit. This approach provides a different insight into the problem of digital system reliability. The difficulty of this method is the complexity of probability expression for a large circuit. The calculations will be lessened when we introduce the concept of bundling. But no existing method can reduce the calculations drastically. Bayes inference from failure data contaminated due to maintenance. C. A. CLAROT'n, G. KOCH and F. SPIZZICHINO. IEEE Trans. Reliab. R-34(4), 377 (1985). In operating plants, records are routinely taken on component-failures, maintenance actions, and component withdrawals. In some cases, these data are the only available information on the component reliability (proper life-tests being infeasible due to cost, duration or other considerations). For these data to be suitable for inference on the parameters of the underlying life distributions, one has to account for the homogeneityconstraints on the stopping rules and the effect of maintenance. We generalize the sampling plan proposed by Barlow & Proschan for coping with incomplete data obtained under non-homogenous stopping rules, by allowing components to be maintained. A Bayes model accounts for the effect of maintenance.

On da-inknge estimation of the exponential scale parameter. B. N. PANDEYand RAKI':SHSRIVASTAVA.IEEE Trans. Reliab. R-34(3), 224 (1985). This paper shows some simple shrunken estimators for the scale parameter of an exponential distribution and compares them with minimum MSA estimator and the estimator proposed by Pandey. We have also obtained a Bayes estimator, which is a shrinkage estimator and has smaller MSE than the estimator (sample mean) n/(n + 1) if sample size, n, is small and other restrictions apply. Reliability application of the alpha distribution. ANTHONY A. SALVIA. IEEE Trans. Reliab. R-34(3L 251 (1985). This paper describes the alpha distribution and its applicability as a model for accelerated life testing. Tables for exact lower confidence limits for reliability and quantiles, based on least-squares estimators of Weibull parameters. PASQUALE ERTO and MAURIZIO GUIDA. IEEE Trans. Reliab. R-34(3), 219 (1985). For the 2-parameter Weibull distribution, this paper gives tables to obtain exact lower s-confidence limits for reliability on the basis of the least-squares method and median plotting positions. The tables use a method based on the ancillary property of these estimators. They apply to samples of size N = 3(1)13, censored after the first m observations, m = 3(1)N. The same tables enable one to obtain lower s-confidence limits for population quantiles. The use of the tables is illustrated with a numerical example.

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On the software reliability medeis of Jelinski--Moranda and Littlewood. H. JOE and N. REID. IEEE Trans. Reliab. R-34(3), 216 (1985). This note provides an alternative formulation of the software reliability models of Jelinski-Moranda and Littlewood. The formulation is in terms of failure times rather than interfailure times; the models are then equivalent to observing the first n order statistics (n is random) from a random sample of size N. The models can be generalized by using a decreasing failure rate for the failure times. For the Jelinski-Moranda model, we comment on the maximum likelihood estimate and an improved estimate for the initial number of faults in the software. We discuss how to check the validity of the Jelinski-Moranda model. S. ESCAF: sequential complex systems are analysed with ESCAF through an add-on option. A. LAVIRON,A. BUN, J. M. LANORE and C. RIVET. IEEE Trans. Reliab. R-34(3), 229 (1985). This article presents the new possibilities afforded by S.ESCAF for analysis of sequential systems with very complex Markov diagrams. S.ESCAF is an add-on option to the commercially available desktop ESCAF unit. The user builds an electronic simulation of the studied system in a very simple manner based directly on the system diagram. A sequential events combination generator (SCG) then inputs all allowable time sequences of events to this electronic simulation--component failures, repairs, non-starts, etc. S.ESCAF analyzes the resulting output state to determine those sequences which result in system failure. Its originality lies in its ability to generate and analyze all events sequences, taking into account the order of occurrence of the events, even for complex systems. Maximum capacity is 80 events.

On some common interests among reliability, inventory, and queuing. DONALD GRO$S, DOUGLASR. MILLER and RICHARD M. SOLAND. IEEE Trans. Reliab. R-34(3), 204 (1985). Queueing networks can be used to model maintained systems. Under many conditions, closed-network queuing theory can be applied to ascertain the availability of such systems. Multi-echelon repairable-item inventory systems are one such class. Problems of common interest to the reliability, queuing, and inventory communities are highlighted, and solution techniques for these problems are presented. Optimization problems in k-out--of-n systems. Tosmo NAKAGAWA. IEEE Trans. Reliab. R-34(3), 248 (1985). A kout-of-n:G system is an important complex system and is used for mass transit and computer systems. This paper does not dicuss the availability, but considers what is the most economical k-out-of-n system when the failure rate of each element is constant. We solve two problems to minimize the mean cost-rate; (i) the optimal number of elements and (ii) the optimal replacement time before system failure. A numerical example is given. A reliability-program case-history on design review. KENJ! KITAGAWA. IEEE Trans. Reliab. R-34(3), 212 (1985). This paper summarizes the investigative results of actual design reviews as an important part of reliability program, and describes several reliability engineering efforts to achieve an effective design review. Design data packages (design documentation) which indicate the basic design program and design process are important in design reviews. When attention is concentrated on a data package, the ability of the reviewers is heightened and the results of the review are enhanced. When the design review is concerned with product reliability, then the availability and quality of : (1) a data package with established reliability level objectives and predictions, (2) a Failure Mode Effect Analysis and a Fault Tree Analysis, and (3) other data packages on product reliability and related technology or engineering, all greatly influence the results of the review. The potential weak points in a design can be revealed by

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World Abstracts on Microelectronics and Reliability

over-stress tests and the results of such tests are very useful in the reliability design review. The improved design which can withstand the adequate over-stress tests appreciably lessened customer complaints about reliability. Optimal allocation of redundant components for large systems. ROaERT L. BUL~N and CHANG YUNG LIU. IEEE Trans. Reliab. R-34 (3), 241 (1985). This paper discusses allocating redundant components subject to resource constraints so as to optimize some measure of system performance. Two new exact algorithms are presented for the case where the objective and constraint functions are stagewise separable. Both are branch and bound algorithms. The first, BLE1, is based on an underlying knapsack structure, while the second, BLE2, exploits a multiple-choice knapsack structure. BLE1 can solve problems with 100 stages and 10 constraints in just a few seconds of CPU time on an IBM 3033. For larger problems, BLH, a heuristic procedure, is proposed. The heuristic is based on the "slippery algorithm" for knapsack problems. Computational testing indicates BLH often finds the optimal solution, and when it doesn't, the solutions are quite close to optimal. Conlidenee bounds for the percentiles of a wearout failure distribution. F. BEICrl~T. IEEE Trans. Reliab. R-34(4), 356 (1985). A drifting parameter is described by a stochastic process with linear realizations. Lifetime (time to wearout failure) distributions are derived for 1- and 2-sided bounded tolerance regions. Optimum parameter adjustments are proposed. Based on random samples, s-confidence intervals for the percentiles of the lifetime distributions are constructed. A probability bound estinmdoa method in Marker reliability analysis. K. TAKARAGI, R. SASAKI and S. SHINGA1. IEEE Trans. Reliab. R-M (3), 257 (1985). In many practical systems, the uncertainty of component failure/repair rates result in uncertainty of system failure probability. Concerning a repairable system, uncertainty is evaluated as a probability bound in the Markov process. In practical analysis, the Laplace transform has the advantage of relatively less computing time than that of a numerical method, e.g. Runge Kutta. This paper proposes an algorithm for evaluating this uncertainty using the Laplace transform method. This algorithm assumes the Johnson SB distribution for systemfailure probability. Then, the mean and the variance of system-failure probability are obtained using Newton's method and an integral form for calculating parametric differentiation. Finally, the probability bounds are obtained by applying the conventional moment-matching method. A tutorial example is presented at the end of this paper. On discrete failure models. W. J. PADOETT and JOaN D. SPURRmR. IEEE Trans. Reliab. R-34(3), 253 (1985). In some situations, discrete failure "time" distributions are appropriate to model "lifetimes". For example, a discrete distribution is appropriate when a piece of equipment operates in cycles and the number of cycles prior to failure is observed. This paper provides three families of discrete parametric distributions which are versatile in fitting increasing, decreasing, and constant failure rate models to either uncensored or right-censored discrete life-test data. The maximum likelihood estimation of parameters, survival

probabilities, and mean lifetime is investigated. The MLEs can be computed by simple numerical methods. Multistme block diagrams and fault trees. ALAN P. WOOD. IEEE Trans. Reliab. R-34(3), 236 (1985). This paper shows how to model a multistate system with multistate components using binary variables. This modeling technique allows current binary algorithms for block diagrams and fault trees to be applied to multistate systems. Several multistate examples are presented, and some cases in which computational efficiency can be enhanced are discussed. A method of rapid Markov reliability calculation. K. TAKARAGI,R. SASAKIand S. SHINGAI.IEEE Trans. Reliab. R34(3), 262 (1985). Our reliability calculation method for a Markov state-transition graph enables a rapid computation by finding and cutting (removing) non-effective edges (NEEs). An NEE is an edge in a Markov state transition graph, the cut of which has little effect on the reliability calculation. NEEs can be found only by checking in a small graph, given the assumption that component failure rate is far smaller than component repair rate. NEEs are found and cut until the Markov graph is separated into two subgraphs. One subgraph is usually very small compared with the original, and the reliability can be approximately calculated on this small subgraph of the Markov graph. Proof and numerical examples are presented. Some stochastic stress.strength processes. J. EDWARD BILIKAM. IEEE Trans. Reliab. R-34(3), 269 (1985). General engineering stress-strength relationships are studied in this paper as they fit a bivariate continuous-time random process. The reliability is then classed into time bands of durability, wear, and fatigue. The particular processes are composed of extreme-value random variates with monotonic time parameters such that the stress is a stochastically increasing r.v. and the strength is a stochastically decreasing r.v. On the F-distribution for cakulatiag Bayes credible intervals for fraction noncomforming. B. J. NICHOLSON. IEEE Trans. Reliab. R-34(3), 227 (1985). A procedure is described for Bayes credible interval estimation of fraction noncomforming when an infinite population and a uniform prior distribution on the fraction nonconforming are assumed. The procedure uses survival function percentiles from the Fdistribution to derive credible-interval limits for fraction noncomforming. Reliability analysis of a non-redundant repairable multiplexing unit. A. PATTAVINA,A. ROVERtand A. LECCESF. IEEE Trans. Reliab. R-3,1(3), 275 (1985). This paper analyzes steady-state reliability measures of a modular multiplexing unit. It is based on a Markov model for the failure and repair process. In particular some reliability figures of merit are determined for a subset of the whole communication path set supported by the multiplex. The key point is a procedure for evaluating the probability that a suitable subset of communication paths can be established. The proposed methodology is applied to some examples of common time-division multiplexing units. The results are useful for the dimensioning of communication networks with reliability constraints.

4. M I C R O E L E C T R O N I C S - - G E N E R A L The role of universities ia electronic packaging engineering. J. L. PRINCE, DOUGLAS J. HAMILTON, EtLEEN M. MATZ and ZBIGNIEW J. STASZAK. Proc. IEEE 73(9), 1416 (1985). Characteristics of present and future problems and directions in Level I and Level 2 packaging are discussed. Research areas are delineated, and problems amenable to attack by

universities are suggested. An example of an existing university research program is given. Methods for universities to develop and implement courses in electronic packaging are discussed. A three-course core presently in use is described; this core can be used to provide Electronic Packaging Engineering emphasis in the