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Estimation of mission reliability from multiple independent grouped s censored samples
046
World Abstracts on Microeleclronics and Reliability
f h e approximation techniques for unavailability estimates for phased missions contained in this paper are useful for mdnstrial applications. The techniques are implcmentable and existing computer programs such as MOCUS, PREP, and KITT can be used for the analysis although snch use is not ctIicient at this time. These programs arc currently being modified, for elticient use in phased mission problems, at the Idaho National Engineering Laboratory, MOCUS, PREP, and KITT are obtainable from the Argonne Code Center: 9700 South Cass Avenue: Argonne. IL 60439 USA.
of test data from the improved system. A decision to make the improvements can be based on the estimated increase in reliability. The procedures used for estimating changes can also bc adapted to estimating reliability using data from a test program conducted in stages. For this case. a sample is taken at each stage and changes are made so that all newly identified failure modes which are correctable are eliminated from the system. Simulation is used to study reliability estimators both when .just one sample is taken and when sampling is conducted m stages.
An improved management approach to upgrade avionic system reliability. LARRY S. KLIWNS. IEEE Trans. Reliab.
Automatic testing of integrated circuits. H. P. BET~E. Elec-
23 (April 1977). This paper presents an improved reliability-program management-approach for upgrading avionic system reliability. Management of the program was by means of an improvement control plan that included continuousl~ updated field performance data, the improvements planned, and projections of the numerical reliability increase with the changes incorporated. The use of special teams working concurrently to improve design, parts, and manufacturing processes is discussed. Presented are measured field results that veri~ the cflcctiveness of these improvement efl\~rts.
tron. Power p. 380 (May 1977). If it is true that integrated circuits are the main elements in every modern electronic system, it must also be true that the testing of these components is of prime importance, not only to the manufacturer, but also to the user. Yet, conventional methods, based on the oscilloscope and the trace recorder, are no longer adequate. The question whether an integrated circuit is good or bad is subject to views and interpretations determined by a number of economic and applicationoriented rules. Automatic equipment should be capable of meeting every test requirement. A multitude of technologies and the system user's divergent interests demand problem-oriented test solutions if testing is to remain an economic proposition.
Predicting in-plant test failures. E. R. CARRUBBA. IEEE Trans. Reliab. R-26, (1) 29 (April 1977~. This paper presents an approach for prediction of in-plant test failures so that appropriate cost planning can be undertaken. The approach is based on the technique of multiple regression analysis. The primary independent variables include equipment complexity, reliability program emphasis, and test program severity. As a guideline in estimating the number of in-plant test failures, a Test Failure Estimator (TFE) graph is provided. The results of this analysis showed a high degree of correlation between the number of test failures experienced and the combined effect of equipment complexity and test program severity. Statistical tests confirmed that both the multiple correlation coefficient and the degree of explained variance are s-significant at a high probability level. Thus, this multiple regression analysis 11 verifies a s-significant correlation between the independent variables and in-plant test failures and 2) demonstrates the feasibility of using these variables to predict the number of in-plant test failures. This area still needs more study. In the meantime, thc TFE graph can be used as a guideline in estimating the number of in-plant test failures.
A class of distributions useful in life testing and reliability. Z. GOVINDARAJULA.IEEE Trans. Reliab. R-26, (1) 67 (April 1977). A new class of distributions having a finite range that will be useful in life testing and reliability is proposed. Methods of estimating the unknown parameters are studied. Explicit expressions for lower moments of order statistics in complete random samples of any size are given. A uniformly most powerful test is derived for the "shape" parameter assuming the location and scale parameters known. An asymptotically optimal test procedure is also suggested when the location and scale parameters are unknown.
"'What ifs'" for nuclear plants. W. C. GANGLOFF. IEEE Spectrum p. 53 (June 1977). Hundreds of thousands of electrical and electronic components are imbedded in the systems that operate and monitor a typical nuclear power generating station. To predict the reliability of systems containing these components and the risks involved in operating these stations, the nuclear power industry is slowly but snrely accepting reliability analysis. Using these techniques, the analyst systematically challenges the design by asking a series of "'what if" questions, concerning potential component failures, always probing for design weaknesses. Many utilities are now employing such methods in reliability analyses directed to improving the availability of their power-generating facilities and thus increasing the energy output obtained for each collar invested in these facilities. Using qualitative and, more recently, quantitative techniques, reliability analysis is gradually becoming a regular, day-to-day tool of nuclear power plant design.
Estimation of mission reliability from multiple independent grouped s censored samples. J. EDWARD B1LIKAM and ALBERT H. MOORF. IEEE Trans. Reliab. R-26, (1) 57 (April 1977). Aircraft or missiles are flown for missions of varying durations. Data are collected at the end of each mission which indicate the mission duration and whether the equipment failed. The data are considered as multiple s-independent grouped censored samples with failure times unknown. The underlying failure model considered is the 2-parameter Weibull distribution. Maximum likelihood estimates are derived. The exponential distribution is used for comparison. Monte Carlo simulations are used to compare s-efficiency of estimates for grouped data with estimates if failure times were known. The asymptotic variance-covariance matrix was computed lbr the sampling conditions studied and was used to obtain lower s-confidence bounds on the system reliability.
Estimating reliability growth. DALE E OLSEN. IEEE Trans. Reliab. R-26, (1) 50 (April 1977). Test programs are con-
Predicting the cost impact of system improvements. RHODA
ducted to identify system failure modes and to estimate reliability. If the system can be changed so that some of the identified failure modes are eliminated and new failure modes are not introduced, the reliability of the system is improved. This paper examines small-sample techniques for estimating the change in reliability without the benefit
L. MORRIS. Proc. IEEE Reliab. Mamtainab. Syrup, Philadelphia. Jan. 18 20, 1977. p. 286. This paper is the result of a study undertaken in order to find one or more elements in proposed system improvements which are related to the life cycle costs of those improvements in such a way as to be predictive of those costs.
World Abstracts on Microeleclronics and Reliability
f h e approximation techniques for unavailability estimates for phased missions contained in this paper are useful for mdnstrial applications. The techniques are implcmentable and existing computer programs such as MOCUS, PREP, and KITT can be used for the analysis although snch use is not ctIicient at this time. These programs arc currently being modified, for elticient use in phased mission problems, at the Idaho National Engineering Laboratory, MOCUS, PREP, and KITT are obtainable from the Argonne Code Center: 9700 South Cass Avenue: Argonne. IL 60439 USA.
of test data from the improved system. A decision to make the improvements can be based on the estimated increase in reliability. The procedures used for estimating changes can also bc adapted to estimating reliability using data from a test program conducted in stages. For this case. a sample is taken at each stage and changes are made so that all newly identified failure modes which are correctable are eliminated from the system. Simulation is used to study reliability estimators both when .just one sample is taken and when sampling is conducted m stages.
An improved management approach to upgrade avionic system reliability. LARRY S. KLIWNS. IEEE Trans. Reliab.
Automatic testing of integrated circuits. H. P. BET~E. Elec-
23 (April 1977). This paper presents an improved reliability-program management-approach for upgrading avionic system reliability. Management of the program was by means of an improvement control plan that included continuousl~ updated field performance data, the improvements planned, and projections of the numerical reliability increase with the changes incorporated. The use of special teams working concurrently to improve design, parts, and manufacturing processes is discussed. Presented are measured field results that veri~ the cflcctiveness of these improvement efl\~rts.
tron. Power p. 380 (May 1977). If it is true that integrated circuits are the main elements in every modern electronic system, it must also be true that the testing of these components is of prime importance, not only to the manufacturer, but also to the user. Yet, conventional methods, based on the oscilloscope and the trace recorder, are no longer adequate. The question whether an integrated circuit is good or bad is subject to views and interpretations determined by a number of economic and applicationoriented rules. Automatic equipment should be capable of meeting every test requirement. A multitude of technologies and the system user's divergent interests demand problem-oriented test solutions if testing is to remain an economic proposition.
Predicting in-plant test failures. E. R. CARRUBBA. IEEE Trans. Reliab. R-26, (1) 29 (April 1977~. This paper presents an approach for prediction of in-plant test failures so that appropriate cost planning can be undertaken. The approach is based on the technique of multiple regression analysis. The primary independent variables include equipment complexity, reliability program emphasis, and test program severity. As a guideline in estimating the number of in-plant test failures, a Test Failure Estimator (TFE) graph is provided. The results of this analysis showed a high degree of correlation between the number of test failures experienced and the combined effect of equipment complexity and test program severity. Statistical tests confirmed that both the multiple correlation coefficient and the degree of explained variance are s-significant at a high probability level. Thus, this multiple regression analysis 11 verifies a s-significant correlation between the independent variables and in-plant test failures and 2) demonstrates the feasibility of using these variables to predict the number of in-plant test failures. This area still needs more study. In the meantime, thc TFE graph can be used as a guideline in estimating the number of in-plant test failures.
A class of distributions useful in life testing and reliability. Z. GOVINDARAJULA.IEEE Trans. Reliab. R-26, (1) 67 (April 1977). A new class of distributions having a finite range that will be useful in life testing and reliability is proposed. Methods of estimating the unknown parameters are studied. Explicit expressions for lower moments of order statistics in complete random samples of any size are given. A uniformly most powerful test is derived for the "shape" parameter assuming the location and scale parameters known. An asymptotically optimal test procedure is also suggested when the location and scale parameters are unknown.
"'What ifs'" for nuclear plants. W. C. GANGLOFF. IEEE Spectrum p. 53 (June 1977). Hundreds of thousands of electrical and electronic components are imbedded in the systems that operate and monitor a typical nuclear power generating station. To predict the reliability of systems containing these components and the risks involved in operating these stations, the nuclear power industry is slowly but snrely accepting reliability analysis. Using these techniques, the analyst systematically challenges the design by asking a series of "'what if" questions, concerning potential component failures, always probing for design weaknesses. Many utilities are now employing such methods in reliability analyses directed to improving the availability of their power-generating facilities and thus increasing the energy output obtained for each collar invested in these facilities. Using qualitative and, more recently, quantitative techniques, reliability analysis is gradually becoming a regular, day-to-day tool of nuclear power plant design.
Estimation of mission reliability from multiple independent grouped s censored samples. J. EDWARD B1LIKAM and ALBERT H. MOORF. IEEE Trans. Reliab. R-26, (1) 57 (April 1977). Aircraft or missiles are flown for missions of varying durations. Data are collected at the end of each mission which indicate the mission duration and whether the equipment failed. The data are considered as multiple s-independent grouped censored samples with failure times unknown. The underlying failure model considered is the 2-parameter Weibull distribution. Maximum likelihood estimates are derived. The exponential distribution is used for comparison. Monte Carlo simulations are used to compare s-efficiency of estimates for grouped data with estimates if failure times were known. The asymptotic variance-covariance matrix was computed lbr the sampling conditions studied and was used to obtain lower s-confidence bounds on the system reliability.
Estimating reliability growth. DALE E OLSEN. IEEE Trans. Reliab. R-26, (1) 50 (April 1977). Test programs are con-
Predicting the cost impact of system improvements. RHODA
ducted to identify system failure modes and to estimate reliability. If the system can be changed so that some of the identified failure modes are eliminated and new failure modes are not introduced, the reliability of the system is improved. This paper examines small-sample techniques for estimating the change in reliability without the benefit
L. MORRIS. Proc. IEEE Reliab. Mamtainab. Syrup, Philadelphia. Jan. 18 20, 1977. p. 286. This paper is the result of a study undertaken in order to find one or more elements in proposed system improvements which are related to the life cycle costs of those improvements in such a way as to be predictive of those costs.