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Reliability and availability analysis of systems operating in multiple environments
World Abstracts on Microelectronics and Reliability CHMT-6 (4), 510 (December 1983). Low voltage failure in multilayer ceramic capacitors is now generally accepted to be associated with an electrochemical dissolution of electrode materials in a humid environment and subsequent migration and deposition of material between electrodes of opposite polarity. This migration is particularly related to surface cracks or linked porosity. A novel screening technique for chip capacitors has been developed at Standard Tele-
3. C I R C U I T
AND
SYSTEMS
RELIABILITY,
Cumulative sum control charts for the mean of an exponential distribution using extremes. H. R. SINGHand GAURI SHANKAR. QR J. (India) 97 (September 1983). In this paper Cumulative Sum Control Charts have been developed for the mean of an exponential population by considering (1) minimum number of samples of size m and (2) maximum of the ordered observations of a single Type II censored sample. These are useful where quality characteristic is measured by product life. Event tree modeling on a small computer. JAMESM. KOREN, GEORGE B. ROTHBARTand BLAKEF. PUTNEY. Proc. a. Reliab. Maintainab. Syrup. 330 (1984). An event tree analysis program has been written for the IBM Personal Computer allowing the reliability engineer to graphically construct, edit, store and analyze system reliability using the event tree methodology. The system is cost-effective, easy to use ("userfriendly"), and is similar to an electronic spreadsheet in that it computes and displays reliability parameters and probability results as the tree is constructed or modified. The user may quickly perform "what-if" operations, obtain results, and receive hardcopy graphics and tables on both a dotmatrix printer or pen plotter. The benefit to the reliability community is that event tree analyses may be completed more quickly, conveniently and accurately than with previous methods. Maintenance processors for mainframe computers. TzE-SHIU LIU. IEEE Spectrum, 36 (February 1984). Special-purpose computers supervise the proper operation of their host computer to improve reliability and reduce down time. Stochastic behaviour of a standby redundant system with three modes. S. M. GUPTA, N. K. JAISWAL and L. R. GOEL. Microelectron. Reliab. 23 (2), 329 (1983). This paper discusses the stochastic behaviour of a two-unit cold standby redundant system in which each unit works in three different modes normal, partial failure and total failure. Failuretime distributions of units are exponential, whereas repairtime distributions are arbitrary. Explicit expressions for the Laplace-Stieltjes transforms of the distribution function of the first passage time, mean time to system failure and steady state availability of the system are obtained. A few particular cases are discussed. Analysis of l-out-of-n:G adjustable operating system. P SARMAHand A. D. DHARMADHIKARI"Microelectron. Reliab. 23 (3), 477 (1983). This paper deals with the analysis of a single unit Adjustable Operating system supported by ( n - 1) inactive standbys and a repair facility. Various operating characteristics are studied, viz. transit probabilities, failure time distribution and mean time to failure of the system, availability of the system at time t, s-expected number of failures of the system in (0, t], s-expected number of repairs in (0, t]. Results are obtained in terms of L.S. transforms. A few special cases are studied for n = 3. Modified periodic preventive maintenance policies. TOSHIO NAKAGAWA, KENJIRO NISHI and YOSHIYA SAWA. Microelectron. Reliab. 23 (5), 945 (1983). This paper proposes four preventive maintenance policies where the unit is scheduled
989
communication Laboratories (STL) that can detect the structural defects that are likely to give rise to low voltage failure. The technique is rapid and nondestructive, and is particularly suited to on-line production testing of chips as well as being suitable for goods inward inspection by the customer. Encapsulated capacitors can also be screened and information is then obtained concerning the quality of the encapsulation. MAINTENANCE
AND
REDUNDANCY
to be maintained preventively or to be repaired only at periodic times kT (k = 1,2,...): If a failure occurs during [(k - 1)T, kT], then (A) the unit remains failed, (B) the failed unit undergoes only minimal repair, (C) the failed unit is replaced by a spare unit, and (D) the failed unit is repaired instantaneously. The expected cost rates for each model are obtained and the optimal policies are discussed. Nonparametric tests for testing the homogeneity of k(>2) exponential, Gamma and Weibull populations using censored data. A. R. PADMANABHAN and N. SINGH. Microelectron. Reliab. 23 (5), 953 (1983). In this paper, nonparametric tests based on censored data are proposed for testing the equality of scale parameters of k(>2) populations, which are (1) either exponential with identical (but possibly unknown) location parameters (2) or Weibull with identical (but possibly unknown) location and shape parameters (3) or which belong to lognormal or gamma family. A numerical example at the end illustrates the application of the theoretical results developed in this paper. Reliability and availability analysis of systems operating in multiple environments. B. S. DHILLON and J. NATESAN. Microelectron. Reliab. 23 (5), 883 (1983). This paper presents two newly developed stochastic models which can represent engineering systems operating in different types of environments. Laplace transforms of the state probabilities, system reliability and availability equations are developed. In addition, steady-state availability and mean-time-to-failure expressions are developed and their plots are shown. Analysis of series deviance in a parallel state transition diagram and applications to fault tolerant computing. FABRIZIO LOMBARDI and STEVE RATHEAL. Microelectron. Reliab. 23 (5), 963 (1983). In this paper the effect of deviance on a parallel state transition diagram is analyzed. The attributes of deviance are identified by a modification in the system characterization which resembles the effects of fault/ failure on a fault tolerant system operation. The steady state availabilities of two deviances are determined and the applicability of these results to static and dynamic N Modular Redundancy Systems, is presented. Managing test-procedures to achieve reliable software. PETER KUBAT and HARVEY S. KOCH. IEEE Trans. Reliab. R-32 (3), 299 (August 1983). Quantitative decision-making procedures are proposed to aid software project managers to manage effectively the testing stage during software project developmont. The module and integration testing phases are thoroughly investigated. Decision procedures which maximize the reliability and/or minimize some cost-benefit objective subject to a time and/or budget constraint are suggested. These procedures optimally allocate test time to the modules for module testing and select the optimal data mixture for integration testing. Testing of computer software is a major component of the software development effort. An efficient allocation of computer time among various modules during testing can appreciably improve reliability and shorten the testing stage. Using decision models presented in this paper, a project manager can effectively allocate test time during module
3. C I R C U I T
AND
SYSTEMS
RELIABILITY,
Cumulative sum control charts for the mean of an exponential distribution using extremes. H. R. SINGHand GAURI SHANKAR. QR J. (India) 97 (September 1983). In this paper Cumulative Sum Control Charts have been developed for the mean of an exponential population by considering (1) minimum number of samples of size m and (2) maximum of the ordered observations of a single Type II censored sample. These are useful where quality characteristic is measured by product life. Event tree modeling on a small computer. JAMESM. KOREN, GEORGE B. ROTHBARTand BLAKEF. PUTNEY. Proc. a. Reliab. Maintainab. Syrup. 330 (1984). An event tree analysis program has been written for the IBM Personal Computer allowing the reliability engineer to graphically construct, edit, store and analyze system reliability using the event tree methodology. The system is cost-effective, easy to use ("userfriendly"), and is similar to an electronic spreadsheet in that it computes and displays reliability parameters and probability results as the tree is constructed or modified. The user may quickly perform "what-if" operations, obtain results, and receive hardcopy graphics and tables on both a dotmatrix printer or pen plotter. The benefit to the reliability community is that event tree analyses may be completed more quickly, conveniently and accurately than with previous methods. Maintenance processors for mainframe computers. TzE-SHIU LIU. IEEE Spectrum, 36 (February 1984). Special-purpose computers supervise the proper operation of their host computer to improve reliability and reduce down time. Stochastic behaviour of a standby redundant system with three modes. S. M. GUPTA, N. K. JAISWAL and L. R. GOEL. Microelectron. Reliab. 23 (2), 329 (1983). This paper discusses the stochastic behaviour of a two-unit cold standby redundant system in which each unit works in three different modes normal, partial failure and total failure. Failuretime distributions of units are exponential, whereas repairtime distributions are arbitrary. Explicit expressions for the Laplace-Stieltjes transforms of the distribution function of the first passage time, mean time to system failure and steady state availability of the system are obtained. A few particular cases are discussed. Analysis of l-out-of-n:G adjustable operating system. P SARMAHand A. D. DHARMADHIKARI"Microelectron. Reliab. 23 (3), 477 (1983). This paper deals with the analysis of a single unit Adjustable Operating system supported by ( n - 1) inactive standbys and a repair facility. Various operating characteristics are studied, viz. transit probabilities, failure time distribution and mean time to failure of the system, availability of the system at time t, s-expected number of failures of the system in (0, t], s-expected number of repairs in (0, t]. Results are obtained in terms of L.S. transforms. A few special cases are studied for n = 3. Modified periodic preventive maintenance policies. TOSHIO NAKAGAWA, KENJIRO NISHI and YOSHIYA SAWA. Microelectron. Reliab. 23 (5), 945 (1983). This paper proposes four preventive maintenance policies where the unit is scheduled
989
communication Laboratories (STL) that can detect the structural defects that are likely to give rise to low voltage failure. The technique is rapid and nondestructive, and is particularly suited to on-line production testing of chips as well as being suitable for goods inward inspection by the customer. Encapsulated capacitors can also be screened and information is then obtained concerning the quality of the encapsulation. MAINTENANCE
AND
REDUNDANCY
to be maintained preventively or to be repaired only at periodic times kT (k = 1,2,...): If a failure occurs during [(k - 1)T, kT], then (A) the unit remains failed, (B) the failed unit undergoes only minimal repair, (C) the failed unit is replaced by a spare unit, and (D) the failed unit is repaired instantaneously. The expected cost rates for each model are obtained and the optimal policies are discussed. Nonparametric tests for testing the homogeneity of k(>2) exponential, Gamma and Weibull populations using censored data. A. R. PADMANABHAN and N. SINGH. Microelectron. Reliab. 23 (5), 953 (1983). In this paper, nonparametric tests based on censored data are proposed for testing the equality of scale parameters of k(>2) populations, which are (1) either exponential with identical (but possibly unknown) location parameters (2) or Weibull with identical (but possibly unknown) location and shape parameters (3) or which belong to lognormal or gamma family. A numerical example at the end illustrates the application of the theoretical results developed in this paper. Reliability and availability analysis of systems operating in multiple environments. B. S. DHILLON and J. NATESAN. Microelectron. Reliab. 23 (5), 883 (1983). This paper presents two newly developed stochastic models which can represent engineering systems operating in different types of environments. Laplace transforms of the state probabilities, system reliability and availability equations are developed. In addition, steady-state availability and mean-time-to-failure expressions are developed and their plots are shown. Analysis of series deviance in a parallel state transition diagram and applications to fault tolerant computing. FABRIZIO LOMBARDI and STEVE RATHEAL. Microelectron. Reliab. 23 (5), 963 (1983). In this paper the effect of deviance on a parallel state transition diagram is analyzed. The attributes of deviance are identified by a modification in the system characterization which resembles the effects of fault/ failure on a fault tolerant system operation. The steady state availabilities of two deviances are determined and the applicability of these results to static and dynamic N Modular Redundancy Systems, is presented. Managing test-procedures to achieve reliable software. PETER KUBAT and HARVEY S. KOCH. IEEE Trans. Reliab. R-32 (3), 299 (August 1983). Quantitative decision-making procedures are proposed to aid software project managers to manage effectively the testing stage during software project developmont. The module and integration testing phases are thoroughly investigated. Decision procedures which maximize the reliability and/or minimize some cost-benefit objective subject to a time and/or budget constraint are suggested. These procedures optimally allocate test time to the modules for module testing and select the optimal data mixture for integration testing. Testing of computer software is a major component of the software development effort. An efficient allocation of computer time among various modules during testing can appreciably improve reliability and shorten the testing stage. Using decision models presented in this paper, a project manager can effectively allocate test time during module