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Fault-tolerant computer system with three symmetric computers
World
Abstracts
on Microelectronics
Minimumexpectedlossestimatorsofreliabilityandparameters of certain lifetime distributions. V. M. RAO TUMMALA and P. T. SATHE. IEEE Trans. Reliab. R-27, (4) 283 (October 1978). The estimators ofreliability and parameters of certain lifetime distributions which are widely used in reliability, repairability, and maintainability are obtained by using a different form of loss function and minimizing the Sexpected loss with respect to the posterior distribution. These estimators are called MEL0 estimators. The applications. and the comparison between MELO, Bayes, and Maximum likelihood estimators are discussed. Top-down algorithm for obtaining prime implicant sets of non-coherent fault trees. HIROMITSU KUMAMOTO and ERNEST J. HENLEY. IEEE Trans. Reliab. R-27, (4) 242 (October 1978). An algorithm for finding all the prime implicant sets is given for non-coherent fault trees involving gates other than simple AND and OR, e.g., EOR and NOT. The sets are a generalization of min cut sets and can be used in quantitative and/or qualitative system reliability analysis. The algorithm is a top-down analysis and avoids sum of product expressions of top event, which usually involve a large number of terms. Each step of the algorithm is clearly defined and it is proven that all prime implicant sets can be obtained. The algorithm is efficient, and rather complicated trees can be handled manually. Availability of a special 2-unit series system. TOM Y. LIANG. IEEE Trans. Reiiab. R-21. (4) 294 (October 1978). This paper deals with some availability problems of a special 2-unit series system. The purpose is threefold: (I) To point out an interesting, practical situation of 2-unit series system in which failure of one unit shuts off the other, but not vice versa. (2) To dispel an erroneous notion that all availability expressions. ranging from the one extreme of “neither shutting off the other at failure” to the other extreme of “both shutting off the other at failure”, depend only on the means of the random quantities involved. A case is shown where the availability depends on the Laplace transform of a distribution as well as on the means. (3) To establish the credibility of the two extreme cases as the tight upper and lower bounds for the intermediate cases in most practical applications. All random variables are assumed solution uses supplementary variables.
s-independent.
The
Optimum ordering policies with lead time for an operating unit in preventive maintenance. NAOTO KAYO and SHLJNJI OSAKI. IEEE Trans. Rrliah. R-27, (4) 270 (October 1978). An ordering policy allows a spare, delivered after a constant lead time, to be put into inventory. Under certain conditions there exists a finite and unique ordering policy maximizing the cost effectiveness, which balances the system effectiveness and the cost and is defined as [s-availability]![s-expected cost rate]. Two criteria for preventive maintenance. P. K. W. CHAN and T. DOWNS. IEEE Trans. Reliab. R-27, (4) 272 (October 1978). The purposes of this paper are to model the effects of imperfect maintenance. and from the model to derive conditions under which preventivemaintenance is beneficial. The criteria are derived via: (1) maximization of the steady state availability and (2) minimization of the s-expected cost per unit time over an infinite time span when the maintenance times are non-zero. Life data analysis for units inspected once for failure (quantal-response data). WAYNE NELSON. IEEE Tmzs. Rdiab. R-27, (4) 274 (October 1978). This expository paper describes simple graphical and advanced maximum likelihood methods for estimating the life distribution of units that are inspected once and found failed or running.
and Reliability
307
FATRAM-A
core efficient cut-set algorithm. D. M. N. H. MARSHALL. IEEE Trans. Reliab. R-27, (4) 250 (October 1978). Many algorithms have been developed for determining minimal cut sets for logic models (in particular. fault trees). Although these methods are theoretically correct, computer implementation of these algorithms proves them less efficient than is desirable. This paper presents a new method for determining the minimal cut sets. which makes more efficient use of computer memory. The gates are resolved in a deterministic manner according to the following rules: (1) AND gates and OR gates with gate inputs are resolved: and (2) OR gates with only basic event inputs are resolved last. Other computer techniques provide increased efficiency for implementing this method. The FATRAM algorithm for finding minimal cut sets for fault trees does use computer core memory effectively. The use of stacks (last-in first-out arrays) for the AND and OR gates has also increased the efficiency of the program. The use of dynamic storage makes the program more flexible. RASMUSON and
Fault-tolerant computer system with three symmetric computers. HIROKAZU IHARA. KAZUHIKO FUKCOKA, YUTAKA KUBO and SHIGEO YOKOTA. Pror. IEEE 66, (10) 1160 (October 1978). Many computer systems have turned increasingly tocontrol systems, requiring more sophisticated machinery over an ever-widening range. The reliability of the system should be carefully considered in all its aspects. The concept of a control segment is introduced against local malfunctions or failures in order to save the system from going down. This paper also describes the fault tolerant control computer system with dual operation aimed at getting the failsafe feature of the control output and complex operation features for maintenance and improvement of the system. Three“off-the-shelf’computersareconnectedsymmetrically by three special hardwares and configuration programs not only in hardware, but also softw-are configuration. Degradation techniques in software and hardware are introduced to prevent the system from stoppage. The actual running record shows 99.99 percent operating availability for three years in the case of the command and control system for a railway which is described here. A rapid algorithm for reliability optimization of parallel redundant systems. A. D. NARASIMHALC and H. SIVARAMAKRISHNAN. IEEE Trans. Reliab. R-21, (4) 261 (October 1978). A rapid method is proposed for optimization of reliability of multiconstraint parallel redundant systems. The constraints need not be linear. This method providesgood starting values. which areclose to the boundary of the feasible region. for the number of redundant units in each subsystem. No proof has been presented to establish the optimality obtained by this method. Yet for examples tried out this method provrdes optimal or near optimal solutions. On product reliability under random held loads. K. V. BURY. IEEE Trans. Rrliab. R-27, (4) 258 (October 1978). This paper presents a simple design problem to illustrate the relationship between product reliability and design strength for the case where product failure is due to a single overload in a sequence of loads applied during the mission of the product. A case study of C.mmp, Cm*, and C.vmp: Part IIPredicting and calibrating reliability of multiprocessor systems. DANIEL P. SIEWIOREK, VITTAL KINI, ROSTAM JOOBBANI and HAROLD BELLIS. Proc. IEEE 66, (10) 1200 (October 1978). This paper focuses on measurement and modeling of hard failures in multiprocessors. The failure rate predictions of the Military Standardization Handbook
Abstracts
on Microelectronics
Minimumexpectedlossestimatorsofreliabilityandparameters of certain lifetime distributions. V. M. RAO TUMMALA and P. T. SATHE. IEEE Trans. Reliab. R-27, (4) 283 (October 1978). The estimators ofreliability and parameters of certain lifetime distributions which are widely used in reliability, repairability, and maintainability are obtained by using a different form of loss function and minimizing the Sexpected loss with respect to the posterior distribution. These estimators are called MEL0 estimators. The applications. and the comparison between MELO, Bayes, and Maximum likelihood estimators are discussed. Top-down algorithm for obtaining prime implicant sets of non-coherent fault trees. HIROMITSU KUMAMOTO and ERNEST J. HENLEY. IEEE Trans. Reliab. R-27, (4) 242 (October 1978). An algorithm for finding all the prime implicant sets is given for non-coherent fault trees involving gates other than simple AND and OR, e.g., EOR and NOT. The sets are a generalization of min cut sets and can be used in quantitative and/or qualitative system reliability analysis. The algorithm is a top-down analysis and avoids sum of product expressions of top event, which usually involve a large number of terms. Each step of the algorithm is clearly defined and it is proven that all prime implicant sets can be obtained. The algorithm is efficient, and rather complicated trees can be handled manually. Availability of a special 2-unit series system. TOM Y. LIANG. IEEE Trans. Reiiab. R-21. (4) 294 (October 1978). This paper deals with some availability problems of a special 2-unit series system. The purpose is threefold: (I) To point out an interesting, practical situation of 2-unit series system in which failure of one unit shuts off the other, but not vice versa. (2) To dispel an erroneous notion that all availability expressions. ranging from the one extreme of “neither shutting off the other at failure” to the other extreme of “both shutting off the other at failure”, depend only on the means of the random quantities involved. A case is shown where the availability depends on the Laplace transform of a distribution as well as on the means. (3) To establish the credibility of the two extreme cases as the tight upper and lower bounds for the intermediate cases in most practical applications. All random variables are assumed solution uses supplementary variables.
s-independent.
The
Optimum ordering policies with lead time for an operating unit in preventive maintenance. NAOTO KAYO and SHLJNJI OSAKI. IEEE Trans. Rrliah. R-27, (4) 270 (October 1978). An ordering policy allows a spare, delivered after a constant lead time, to be put into inventory. Under certain conditions there exists a finite and unique ordering policy maximizing the cost effectiveness, which balances the system effectiveness and the cost and is defined as [s-availability]![s-expected cost rate]. Two criteria for preventive maintenance. P. K. W. CHAN and T. DOWNS. IEEE Trans. Reliab. R-27, (4) 272 (October 1978). The purposes of this paper are to model the effects of imperfect maintenance. and from the model to derive conditions under which preventivemaintenance is beneficial. The criteria are derived via: (1) maximization of the steady state availability and (2) minimization of the s-expected cost per unit time over an infinite time span when the maintenance times are non-zero. Life data analysis for units inspected once for failure (quantal-response data). WAYNE NELSON. IEEE Tmzs. Rdiab. R-27, (4) 274 (October 1978). This expository paper describes simple graphical and advanced maximum likelihood methods for estimating the life distribution of units that are inspected once and found failed or running.
and Reliability
307
FATRAM-A
core efficient cut-set algorithm. D. M. N. H. MARSHALL. IEEE Trans. Reliab. R-27, (4) 250 (October 1978). Many algorithms have been developed for determining minimal cut sets for logic models (in particular. fault trees). Although these methods are theoretically correct, computer implementation of these algorithms proves them less efficient than is desirable. This paper presents a new method for determining the minimal cut sets. which makes more efficient use of computer memory. The gates are resolved in a deterministic manner according to the following rules: (1) AND gates and OR gates with gate inputs are resolved: and (2) OR gates with only basic event inputs are resolved last. Other computer techniques provide increased efficiency for implementing this method. The FATRAM algorithm for finding minimal cut sets for fault trees does use computer core memory effectively. The use of stacks (last-in first-out arrays) for the AND and OR gates has also increased the efficiency of the program. The use of dynamic storage makes the program more flexible. RASMUSON and
Fault-tolerant computer system with three symmetric computers. HIROKAZU IHARA. KAZUHIKO FUKCOKA, YUTAKA KUBO and SHIGEO YOKOTA. Pror. IEEE 66, (10) 1160 (October 1978). Many computer systems have turned increasingly tocontrol systems, requiring more sophisticated machinery over an ever-widening range. The reliability of the system should be carefully considered in all its aspects. The concept of a control segment is introduced against local malfunctions or failures in order to save the system from going down. This paper also describes the fault tolerant control computer system with dual operation aimed at getting the failsafe feature of the control output and complex operation features for maintenance and improvement of the system. Three“off-the-shelf’computersareconnectedsymmetrically by three special hardwares and configuration programs not only in hardware, but also softw-are configuration. Degradation techniques in software and hardware are introduced to prevent the system from stoppage. The actual running record shows 99.99 percent operating availability for three years in the case of the command and control system for a railway which is described here. A rapid algorithm for reliability optimization of parallel redundant systems. A. D. NARASIMHALC and H. SIVARAMAKRISHNAN. IEEE Trans. Reliab. R-21, (4) 261 (October 1978). A rapid method is proposed for optimization of reliability of multiconstraint parallel redundant systems. The constraints need not be linear. This method providesgood starting values. which areclose to the boundary of the feasible region. for the number of redundant units in each subsystem. No proof has been presented to establish the optimality obtained by this method. Yet for examples tried out this method provrdes optimal or near optimal solutions. On product reliability under random held loads. K. V. BURY. IEEE Trans. Rrliab. R-27, (4) 258 (October 1978). This paper presents a simple design problem to illustrate the relationship between product reliability and design strength for the case where product failure is due to a single overload in a sequence of loads applied during the mission of the product. A case study of C.mmp, Cm*, and C.vmp: Part IIPredicting and calibrating reliability of multiprocessor systems. DANIEL P. SIEWIOREK, VITTAL KINI, ROSTAM JOOBBANI and HAROLD BELLIS. Proc. IEEE 66, (10) 1200 (October 1978). This paper focuses on measurement and modeling of hard failures in multiprocessors. The failure rate predictions of the Military Standardization Handbook