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A design method for field service centres
World Abstracts on Microelectronics and Reliability Monte Carlo study are presented to demonstrate the favorable risk behavior of the EB estimator as a Bayes estimator if the sample size is large. Goodness-of-fit test-statistics on Gaussian and exponential reliability data. DUAN WEI and C. Y. CHEN. IEEE Trans. Reliab. R-32, 492 (1983). The paper presents three statistics for testing s-normality and one statistic for testing exponentiality in system reliability data. The distributions of these statistics were approximated by using Monte Carlo simulation. The power of these statistics is investigated with respect to several alternatives. For testing small sample s-normality, two of them, namely, the newly proposed Lilliefors type statistic and sample skewness coefficient have very good power. Stochastic behaviour of a single server n-unit pulverizer system with common-cause failures and general maintenance. J. NATESAN and A. K. S. JARDINE. Microelectron. Reliab. 24, 1045 (1984). A single server n-unit active redundant pulverizer system is studied under the assumption that the repair time distribution of a unit is general while the failure time distribution is exponential. The active redundant pulverizers may fail due to common-cause failures. The following system characteristics are obtained by observing the system at suitable regenerative epochs: (a) s-expected number of repairs in (o,t] ; (b) s-expected frequency of failures in (o,t]. The special case model when n = 2 is discussed with repair time distribution being both exponential and two-stage Erlangian. The plots of expected number of repairs and expected frequency of failures are shown. A classification system for reliability models. TONY BENDELL. IEEE Trans. Reliab. R-33, 160 (1984). There has been little attempt to introduce a general classification system for reliability models analogous to those in other areas of applied probability, notably queueing systems. Thus there has been an unavoidable confusion in the literature and considerable unnecessary duplication of investigative effort. This paper argues the case for a classification system analogous to that in use for queues; identifies necessary features of such a system; and proposes a partial classification system. To be successful such a system must not only be a relatively convenient summary of diverse models, but must have the general support of the reliability community. Reliability enhancement through optimal burn-in. WAY Kuo. IEEE Trans. Reliab. R-33, 145 (1984). Burn-in is an important screening method used in predicting, achieving, and enhancing field reliability. Although electronics burn-in has been studied qualitatively, no comprehensive quantitative approach exists for determining optimal burn-in periods. This paper presents a cost-optimization model from a system viewpoint, with burn-in periods for the components as the decision variables. This model is applied to an electronic product recently developed which uses many ICs. State-of-the-art ICs have high early-failure rates and long infant mortality periods. Proper use of burn-in reduces early failure rates and reduces system deployment costs. The total cost to be minimized is formulated as a function of the mean costs of the component, device burn-in, shop repair, and field repair, which in turn are functions of the mean number of failures during and after burn-in. Component and system reliability are constraints that have to be satisfied. The early device failures are assumed to have a Weibull distribution. The formulated problem, with failure rates and cost factors, is optimized. Some basic properties of reliability and cost functions are discussed. A design method for fidd service centres. LAMBERTO PESCATORI and GIOVANNI ZARONE. A lta Frequenza LIII, 213
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(1984). Resources allocation for field service is considered. The relevancy of the problem to the industrial activity is focused and the performance of a periodically manned service centre is analyzed. The basic parameters of the service are defined and the general theoretical framework is outlined. A method, developed by the authors, for manpower allocation when a specified set of operational constraints is defined, is presented. The model is described and some numerical results are provided. AFTP fault tree analysis program. RICHARD A. PULLEN. IEEE Trans. Reliab. R-33, 171 (1984). Evaluation of the cut sets of large s-coherent and non-coherent fault trees presents a severe computational problem. The computer program, AFTP has been used to evaluate the important minimal cut and path sets of large fault trees containing many hundreds of gates. The computational advantages of a Boolean algebra, bottom-up approach are emphasised. Program summary Name: AFTP (Advanced Fault Tree Program) Developed by: R. A. Pullen, Nuclear Services, SIA Ltd., Manchester Program development completion date: 1983 July Techniques employed: Bottom-up Boolean Algebra Rationale for a modified Duane model. BEY LITTLEWOOD. IEEE Trans. Reliab. R-33, 157 (1984). The Duane model for reliability growth involves a rate function which is an inverse power law and has an "infinite" value at t = 0. The model is usually motivated entirely empirically. Here a probalistic rationale is proposed via a reliability growth model involving the removal of design faults. This rationale results in a modified power law rate, finite at the origin. A wider class of rate functions should be investigated for N H P P models of reliability growth. The Pioneer 10/11 program: from 1969 to 1994. CHARLES F. HALL. IEEE Trans. Reliab. R-32, 414 (1983). The Pioneer 10/11 program began in the summer of 1969 and had as its objective the exploration of the Asteroid Belt--that region between Mars and Jupiter and the exploration of Jupiter. Two flight spacecraft were built--Pioneer 10 and Pioneer 11. Pioneer 10 was launched in 1972 March, passed by Jupiter in 1973 December, and continued on a trajectory that will allow it to escape the solar system. Thus Pioneer 10 became the first man-made object to pass successfully through the Asteroid Belt, to encounter Jupiter, and to escape from the solar system. Pioneer 11 was launched in 1973 April and passed by Jupiter in 1974 December. As a result of Jupiter's influence on its trajectory, it turned around at Jupiter, crossed back through the solar system, then beyond the orbits of Mars and Jupiter, and then encountered Saturn in 1979 September. This encounter was beyond the original objectives and was made possible by the long life and reliability of the spacecraft. Pioneer 11 became the first man-made object to encounter Saturn. At present, Pioneer 11 is also on a solar-escape trajectory although in the opposite direction from Pioneer 10. Calculations of systems unreliability by algebraic manipulation of failure event. S. HASANUDDIN AHMAD and A. T. M. JAMIL. Microelectron. Reliab. 24, 793 (1984). Computations of reliability of a given system is an important field of research in reliability engineering. There are many techniques available in the literature. Some of these are based on Boolean algebra's relations. In these papers unions of events have been reduced to give the reliability of a system. Reduction of union of events involve a lot of work and give rise to a large number of terms. In this paper we have adopted a different approach. We first set up some simple algebraic lemmas on intersections and give their proofs. Next we represent the system failure event as the intersection of paths failure events. By applying our lemmas on this intersection of events step by step we are
1163
(1984). Resources allocation for field service is considered. The relevancy of the problem to the industrial activity is focused and the performance of a periodically manned service centre is analyzed. The basic parameters of the service are defined and the general theoretical framework is outlined. A method, developed by the authors, for manpower allocation when a specified set of operational constraints is defined, is presented. The model is described and some numerical results are provided. AFTP fault tree analysis program. RICHARD A. PULLEN. IEEE Trans. Reliab. R-33, 171 (1984). Evaluation of the cut sets of large s-coherent and non-coherent fault trees presents a severe computational problem. The computer program, AFTP has been used to evaluate the important minimal cut and path sets of large fault trees containing many hundreds of gates. The computational advantages of a Boolean algebra, bottom-up approach are emphasised. Program summary Name: AFTP (Advanced Fault Tree Program) Developed by: R. A. Pullen, Nuclear Services, SIA Ltd., Manchester Program development completion date: 1983 July Techniques employed: Bottom-up Boolean Algebra Rationale for a modified Duane model. BEY LITTLEWOOD. IEEE Trans. Reliab. R-33, 157 (1984). The Duane model for reliability growth involves a rate function which is an inverse power law and has an "infinite" value at t = 0. The model is usually motivated entirely empirically. Here a probalistic rationale is proposed via a reliability growth model involving the removal of design faults. This rationale results in a modified power law rate, finite at the origin. A wider class of rate functions should be investigated for N H P P models of reliability growth. The Pioneer 10/11 program: from 1969 to 1994. CHARLES F. HALL. IEEE Trans. Reliab. R-32, 414 (1983). The Pioneer 10/11 program began in the summer of 1969 and had as its objective the exploration of the Asteroid Belt--that region between Mars and Jupiter and the exploration of Jupiter. Two flight spacecraft were built--Pioneer 10 and Pioneer 11. Pioneer 10 was launched in 1972 March, passed by Jupiter in 1973 December, and continued on a trajectory that will allow it to escape the solar system. Thus Pioneer 10 became the first man-made object to pass successfully through the Asteroid Belt, to encounter Jupiter, and to escape from the solar system. Pioneer 11 was launched in 1973 April and passed by Jupiter in 1974 December. As a result of Jupiter's influence on its trajectory, it turned around at Jupiter, crossed back through the solar system, then beyond the orbits of Mars and Jupiter, and then encountered Saturn in 1979 September. This encounter was beyond the original objectives and was made possible by the long life and reliability of the spacecraft. Pioneer 11 became the first man-made object to encounter Saturn. At present, Pioneer 11 is also on a solar-escape trajectory although in the opposite direction from Pioneer 10. Calculations of systems unreliability by algebraic manipulation of failure event. S. HASANUDDIN AHMAD and A. T. M. JAMIL. Microelectron. Reliab. 24, 793 (1984). Computations of reliability of a given system is an important field of research in reliability engineering. There are many techniques available in the literature. Some of these are based on Boolean algebra's relations. In these papers unions of events have been reduced to give the reliability of a system. Reduction of union of events involve a lot of work and give rise to a large number of terms. In this paper we have adopted a different approach. We first set up some simple algebraic lemmas on intersections and give their proofs. Next we represent the system failure event as the intersection of paths failure events. By applying our lemmas on this intersection of events step by step we are