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Shrunken estimators of Weibull shape parameter from Type-II censored samples
1418
World Abstracts on Microelectronics and Reliability
Selecting the most reliable design under Type-II cen- available from a repairable system. Both a subjective sored accelerated testing. DONG-SHANG CHANG, graphical procedure and an analytic test procedure DENG-YUANHUANGand SHENG-TSAINGTSENG. I E E E based on the cumulative TTT-statistic are studied. Transactions on Reliability, 41(4), 588 (1992). Accelerated life tests (ALTs) of products and materials Predicting performability of a fault-tolerant microcomare used to obtain reliability information within a puter for process control. CRISTIANCONSTANTINESCU. reasonable time frame. However, there are no suit- I E E E Transactions on Reliability, 41(4), 558 (1992). able selection rules for selecting the best product or The performability of a gracefully degrading micromaterial as a result of the ALT. Under the type-II computer, designed for process control applications, censoring plan, this paper proposes a reasonable is evaluated. Two Markov models, (1) fault/error selection rule for an ALT using the Arrhenius model. handling, and (2) fault occurrence and repair, are The advantages of this selection rule are compared used to describe the microcomputer. They are separwith a non-ALT selection rule by using as criteria ately solved according to the behavioral decompo(a) the average ratio of time-saving in life testing, and sition/aggregation method. A numerical algorithm, (b) sample size. The tradeoff between an increased based on Laplace and Laplace-Stieltjes transforms, sample size and a shortened life testing time for the is used to derive system performability. The influALT selection procedure is feasible. ence of the permanent, intermittent, and transient faults underline the importance of the detection, Evaluating the performance of software-reliability isolation, and reconfiguration mechanisms. The effect models. THOMASDOWNS and ANTHONYSCOTT. I E E E of the parallelization algorithms, captured by various Transactions on Reliability, 41(4), 533 (1992). In this reward structures, is analyzed. The performability paper we investigate a method of quantifying the increases appreciably when global repair actions are performance of software-reliability models that was undertaken. Local repair also has a benefic influence, proposed by Littlewood. The method is essentially a but only for large amounts of required work. Finally, Kolmogorov-Smirnov goodness-of-fit test. We adding spare processing elements improves perdemonstrate that although the Littlewood method is formability. Their influence becomes visible for large rather unconventional, the standard Kolmogorov- amounts of work too. These results help the pracSmirnov tables (for the simple hypothesis) can be ticing engineer verify the effectiveness of recovery directly applied. On this basis, we show the kind of mechanisms, choose the proper parallelization algorperformance that can be anticipated from an ideal ithms, choose the best repair techniques, and find the software-reliability model. We also present a new optimum number of spare processors. performance measure which overcomes a weakness in the Littlewood method. Statistical analysis of the geometric de-eutrophication software-reliability model. OLIVIER GAUDOIN and Shrunken estimators of Weibull shape parameter from JEAN-LOuIS SOLER. I E E E Transactions on Reliability, Type--ll censored samples. M. PANDEY and U. S. 41(4), 518 (1992). The Moranda geometric deSINGH. I E E E Transactions on Reliability, 42(1), 81 eutrophication software-reliability model appears to (1993). This paper suggests a shrunken estimator of be a particular case of a class of general models with the Weibull shape parameter for failure censored proportional failure rates. The paper is devoted to a samples. This shrunken estimator is compared with detailed statistical analysis of this general model. shrunken estimators given by Bain, Singh and Statistical inference on the unknown parameters is Bhatkulikar, and Pandey. Even for sample sizes of 5 discussed. The distribution of the maximum likeliand 10 this shrunken estimator based on failure data hood estimator of the main parameter provides exact censored at only 3 and 4, respectively, can be used confidence intervals and a new reliability-growth test. with advantage when one has a reasonable guess for New explicit estimators which are based on a leastthe shape parameter. This estimator has higher squares method are proposed. The model is satisefficiency and nearness than other estimators. factorily applied to real software-error data. The geometric de-eutrophication model presents interGoodness-of-fit tests for the power-law process based esting theoretical and practical aspects: It is conon the TTT-plot. BENGTKLEFSJO and UDAYKUMAR. ceptually well founded and the parameters, which I E E E Transactions on Reliability, 41(4), 593 (1992). have useful practical interpretation, can be estimated The TTT-plot (TTT = Total Time on Test) and its by methods which provide prediction with good theoretical counterpart, the scaled TTT-transform, statistical properties. were introduced by Barlow and Campo and used for model identification of complete samples from non- On the optimal design of k--out-of-n :G subsystems. repairable units. Since then various applications of HOANG PHAM. I E E E Transactions on Reliability, TTT-plotting, intended for data from non-repairable 41(4), 572 (1992). For a k-out-of-n :G subsystem, units, have been presented. This paper illustrates how we are interested in mathematically determining the the TTT-plot can be used as a basis for goodness-of- most economical number of components in the subfit tests for the power-law process when data are system. This paper gives the optimal values of k (for
World Abstracts on Microelectronics and Reliability
Selecting the most reliable design under Type-II cen- available from a repairable system. Both a subjective sored accelerated testing. DONG-SHANG CHANG, graphical procedure and an analytic test procedure DENG-YUANHUANGand SHENG-TSAINGTSENG. I E E E based on the cumulative TTT-statistic are studied. Transactions on Reliability, 41(4), 588 (1992). Accelerated life tests (ALTs) of products and materials Predicting performability of a fault-tolerant microcomare used to obtain reliability information within a puter for process control. CRISTIANCONSTANTINESCU. reasonable time frame. However, there are no suit- I E E E Transactions on Reliability, 41(4), 558 (1992). able selection rules for selecting the best product or The performability of a gracefully degrading micromaterial as a result of the ALT. Under the type-II computer, designed for process control applications, censoring plan, this paper proposes a reasonable is evaluated. Two Markov models, (1) fault/error selection rule for an ALT using the Arrhenius model. handling, and (2) fault occurrence and repair, are The advantages of this selection rule are compared used to describe the microcomputer. They are separwith a non-ALT selection rule by using as criteria ately solved according to the behavioral decompo(a) the average ratio of time-saving in life testing, and sition/aggregation method. A numerical algorithm, (b) sample size. The tradeoff between an increased based on Laplace and Laplace-Stieltjes transforms, sample size and a shortened life testing time for the is used to derive system performability. The influALT selection procedure is feasible. ence of the permanent, intermittent, and transient faults underline the importance of the detection, Evaluating the performance of software-reliability isolation, and reconfiguration mechanisms. The effect models. THOMASDOWNS and ANTHONYSCOTT. I E E E of the parallelization algorithms, captured by various Transactions on Reliability, 41(4), 533 (1992). In this reward structures, is analyzed. The performability paper we investigate a method of quantifying the increases appreciably when global repair actions are performance of software-reliability models that was undertaken. Local repair also has a benefic influence, proposed by Littlewood. The method is essentially a but only for large amounts of required work. Finally, Kolmogorov-Smirnov goodness-of-fit test. We adding spare processing elements improves perdemonstrate that although the Littlewood method is formability. Their influence becomes visible for large rather unconventional, the standard Kolmogorov- amounts of work too. These results help the pracSmirnov tables (for the simple hypothesis) can be ticing engineer verify the effectiveness of recovery directly applied. On this basis, we show the kind of mechanisms, choose the proper parallelization algorperformance that can be anticipated from an ideal ithms, choose the best repair techniques, and find the software-reliability model. We also present a new optimum number of spare processors. performance measure which overcomes a weakness in the Littlewood method. Statistical analysis of the geometric de-eutrophication software-reliability model. OLIVIER GAUDOIN and Shrunken estimators of Weibull shape parameter from JEAN-LOuIS SOLER. I E E E Transactions on Reliability, Type--ll censored samples. M. PANDEY and U. S. 41(4), 518 (1992). The Moranda geometric deSINGH. I E E E Transactions on Reliability, 42(1), 81 eutrophication software-reliability model appears to (1993). This paper suggests a shrunken estimator of be a particular case of a class of general models with the Weibull shape parameter for failure censored proportional failure rates. The paper is devoted to a samples. This shrunken estimator is compared with detailed statistical analysis of this general model. shrunken estimators given by Bain, Singh and Statistical inference on the unknown parameters is Bhatkulikar, and Pandey. Even for sample sizes of 5 discussed. The distribution of the maximum likeliand 10 this shrunken estimator based on failure data hood estimator of the main parameter provides exact censored at only 3 and 4, respectively, can be used confidence intervals and a new reliability-growth test. with advantage when one has a reasonable guess for New explicit estimators which are based on a leastthe shape parameter. This estimator has higher squares method are proposed. The model is satisefficiency and nearness than other estimators. factorily applied to real software-error data. The geometric de-eutrophication model presents interGoodness-of-fit tests for the power-law process based esting theoretical and practical aspects: It is conon the TTT-plot. BENGTKLEFSJO and UDAYKUMAR. ceptually well founded and the parameters, which I E E E Transactions on Reliability, 41(4), 593 (1992). have useful practical interpretation, can be estimated The TTT-plot (TTT = Total Time on Test) and its by methods which provide prediction with good theoretical counterpart, the scaled TTT-transform, statistical properties. were introduced by Barlow and Campo and used for model identification of complete samples from non- On the optimal design of k--out-of-n :G subsystems. repairable units. Since then various applications of HOANG PHAM. I E E E Transactions on Reliability, TTT-plotting, intended for data from non-repairable 41(4), 572 (1992). For a k-out-of-n :G subsystem, units, have been presented. This paper illustrates how we are interested in mathematically determining the the TTT-plot can be used as a basis for goodness-of- most economical number of components in the subfit tests for the power-law process when data are system. This paper gives the optimal values of k (for