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Cost analysis of a two-unit standby system with two types of repairmen
1166
World Abstracts on Microelectronics and Reliability
Reliab. Maintainab. Syrup. 82 (1985). The architecture of an expert system for the interactive data-driven construction of fault trees is presented. Parts of the system are now under realization and testing. The system intends to offer a flexible and easy-to-operate tool to the analyst in reliability assessment of complex engineered installations. The expert system is organized according to a number of knowledgebased modules that contain metarules, allow the establishment of rules, and to collect and interpret data. The construction process bases upon a representation of the elementary components given a terms of multiple-valued logical (MVL) trees and results into an MVL-tree. This tree can be analyzed directly or when requested it can be reduced to a number of binary fault trees.
Independence bounds and approximations for system availability computations. MARTIN L. SHOOMAN. Proc. A. Reliab. Maintainab. Syrup. 115 (1985). This paper discusses various simplified bounds and approximations which can be used to simplify the computation of system availability via Markov model analysis. This is especially important when the system contains many states due to: (a) a large number of elements, (b) the extra states needed to model built-in-test, (c) the extra states needed to model hardware/software interactions. These simplified formulas can also be used to check the results of a computer simulation which is the conventional way of performing such complex computations. Analysis of a two unit standby system with partial failure and two types of repairs. L. R. GOEL, ASHOK KUMAR and A. K. RASTOGI. Microeleetron. Reliab. 24, 873 (1984). A two dissimilar unit standby system is analysed. The priority unit can either be in normal or partial operative mode. When the unit fails from the partial mode, it undergoes minor repair and the unit becomes operative with different failure rate. If this unit fails again, it goes to major repair after which it works as good as new. The standby unit while in use is either operative or failed. This non priority unit fails without passing through the partial failure mode and undergoes only one type of repair with different repair time distribution. Failure and repair time distributions are negative exponential and general respectively.Regenerative technique in M R P is applied to obtain several reliability characteristics of interest to system designers. Analysis of a k-out-of-n unit system with two types of failure and preventive maintenance. L. R. GOEL and PRAVEENGUPTA. Microeleetron. Reliab. 24, 877 (1984). A k-out-of-n unit system is analysed with two types of failure: (1) failure due to change in operating characteristics and (2) catastrophic failure. Preventive maintenance of the system is allowed at random epochs. All transition rates are taken to be general. Several measures of reliability useful for system designers and operations managers have been obtained by using regenerative point technique with Markov renewal process. Some important results obtained earlier are shown as particular cases. Performance-related dependability evaluation of supercomputer systems. J. ARLAT and J. C. LAPRIE. Microelectron. Reliab. 24, 717 (1984). The paper presents an example of performance-related dependability evaluation of a supercomputer structure corresponding to an M I M D multiprocessor system intended for high speed scientific computation. The approach presented addresses the problems of deriving a model that is tractable yet representative of the behaviour of a complex system. This is achieved by means of an intensive validation study, and through the evaluation of measures of interest which account for the specific operating requirements characterizing the system under investigation: (a) maintain very high throughput over a long period of time, and (b) provide an efficient operational life-cycle.
Topological optimization of distributed computer networks subject to reliability constraints. ANTONI ZABLUDOWSKIand ANDRZEJ SOBOLSKLMicroelectron. Reliab. 24, 1023 (1984). A method of topological optimization of the networks with minimum cost subject to reliability constraints is given in this paper. The proposed optimization algorithm is based on branch and bound method. The computational results of this algorithm are discussed. On power line carrier communication (PLC). YOSEFS. SHERIF and S. S. ZAmR. Microelectron. Reliab. 24, 781 (1984). Power line carrier communication (PLC) provides significant services for the electric utilities in particular and to the industrial and consumer sectors in general. Since its inception in the early 1920's, PLC has been used for voice communication, protective relaying telemetry and supervisory control. Lately PLC has proved to render the most efficient means for distribution automation and load management. This paper is a review of literature related to PLC and its applications.
Minimizing the cost of automated board testing. JANET PAGE WALTON. Electron. Prod. 39 (September 1984). While it is simplistic to believe that the total cost of Automatic Testing can be reduced by purchasing low cost equipment, only a limited number of companies can afford the high capital cost of sophisticated ATE. On multistate coherent systems. FUMIO OH1 and TOSHIO NISHIDA. IEEE Trans. Reliab. R-33, 284 (1984). Recently, several authors have treated multistate systems and given some results. This paper summarizes the several concepts of s-coherency and shows the relationships between them. An intresting theorem for the existence of series and parallel coherent systems is presented. We have proved IFRA and NBU closure theorems under more general situation than have E1-Neweihi et al. and Ross. We discuss our IFR closure theorem.
Stochastic behaviour of a maintained system with protection system. ASHOK KUMAR,VIPIN B. KAPOORand A. K. RASTOGI. Microelectron. Reliab. 24, 869 (1984). This paper deals with the analysis of a single unit system backed by a protection system (P.S.). Both are subject to failure with exponential failure time distribution. Repair time of working unit, fault detection and inspection time of protection system are assumed to follow general distribution. The system has been investigated in detail by the help of semi-Markov process and several parameters of interest are obtained. Optimum preventive maintenance policies for a computersystem with restart. TOSHIO NAKAGAWA,KENJIRO NISHI and KAZUM1 YASUI. IEEE Trans. Reliab. R-33, 272 (1984). This paper considers a computer system where an operation is restarted when the system stops on some faults. The restart does not succeed every time. Three preventive maintenance (pm) models are considered: (A) The pm is made at the scheduled time T. (B) The pm is made at the K-th successful restart. (C) The pm is made at the next scheduled time if the total number of successes of restart exceeds K. The availabilities of each model are obtained and the optimum pm policies are discussed. Cost analysis of a two-unit standby system with two types of repairmen. VIBHA GOYAL and K. MURARI. Microelectron. Reliab. 24, 849 (1984). This paper is concerned with a twounit cold standby system with two types of repairmen. One "regular" repairman is kept for repairing the units as soon as they fail. It is assumed that sometimes he might not be able to do the repairs within some tolerable time (patience time). Another "expert" repairman, assumed to be perfect, is called on to do the repairs on the completion of this patience time or on the failure of the system, whichever is later.
World Abstracts on Microelectronics and Reliability Various measures of system effectiveness are calculated using semi-Markov processes and regenerative processes. Based on these measures, a rule is developed whether the expert repairman should be called after the system failure. Further numerical results for a case, in which repair time and patience time both have non-Markovian property, are also investigated. Then the upper bound of the cost K3, below which the expert repairman should be called immediately after the system failure and the corresponding increase in profit are calculated.
The impact of robots on product reliability. JOHN MIHALASKY. Proc. Reliab. Maintainab. Syrup. 464 (1985). With robots beginning to appear more often as industry rebuilds, there is a need to look at the impact of robots on product reliability. This paper discusses why the robots will "force" companies to buy better raw materials, do a better analysis of manufacturing methods, increase the use of in-process automatic testing and improve the products' handleability characteristics. Also discussed is how robots will allow for designing to a higher reliability level because of the improvement of manufacturing processes. Finally, there is coverage on how the use of robots will result in less scrap and rework, which should reflect itself in fewer catastrophic and early failures.
The anatomy of burn-in--an analysis. GUSTAVOST. Electron. Prod. 27 (February 1985). An in-depth analysis of the burn-in process which can reveal 70 % of chip-related early failures.
Bayes reliability assessment of a two-unit hot-standby redundant system. SUSUMUFuJn and HIROAKISANDOH.IEEE Trans Reliab. R-33, 297 (1984). This study assesses the reliability of a two-unit hot-standby redundant system with an imperfect switch. The prior knowledge of experts is used in the assessment through Bayes theorem. Bayes interval limits for the system reliability are presented. The predictive distribution of the first failure time of the system is formulated.
Computing k-out-of-n system reliability. R. E. BARLOWand K. D. HEIDTMANN.IEEE Trans. Reliab. R-33, 322 (1984). A linear-time algorithm and its short computer program in BASIC for k-out-of-n:G system reliability computation is presented.
Fractional duration before first failure--a useful index and an analytical tool. C. SINGH and J. S. DUe,GAL. Microelectron. Reliab. 24, 1077 (1984). This paper defines a new index, fractional duration before first failure and describes the methodology for its calculation. The relationship of this index to the mean time to first failure is also presented. The fractional duration before first failure is, therefore, not only a useful measure of system reliability but also provides an alternative approach to calculate mean time to first failure. The concepts and techniques are illustrated with suitable examples.
Reliability with imperfect diagnostics. ALLEN L. WHITE. Microelectron. Reliab. 24, 1069 (1984). This paper considers the reliability of systems that accumulate faults throughout their lifetime because of imperfect diagnostics. Several experiments are referenced that show the difficulty of achieving a 100 percent diagnostic level. After explaining the assumptions and constructing the reliability estimation method, the paper proceeds to a graphical trade-off analysis that considers the effect of imperfect diagnostics on three traditional ways of achieving higher reliability: lower component fault rate, more redundancy, and redundancy with reconfiguration.
1167
A new heuristic approach for redundancy optimization problem. V. DAKSHINA MURTY and K. B. MISRA. Microelectron. Reliab. 24, 1013 (1984). The present paper describes a simple heuristic approach to solve redundancy optimization problem without much of computation to help reliability designers choose an appropriate configuration. The solution technique is simpler than all previous methods and offers optimal results with a high success rate.
A Truncation methodology for evaluating large fault trees. M. MODARRESand H. DEZFULI.IEEE Trans. Reliab. R-33, 325 (1984). Probabilistic risk assessment (PRA) of a nuclear power plant often involves evaluating large fault trees (eg, trees with more than 1000 basic events and 1000 gates). It is desired to generate the dominant minimal cut sets (MCSs) in order to gain engineering insight, to estimate the top event probability, and to calculate the frequency of reactor core damage. To estimate the top event probability with computers, the usual practice has been to neglect those MCSs of the fault tree that have a probability of less than some cutoff value; the cut-off value is subjectively selected by the analyst. This method of truncation eliminates some MCSs, and thus simplifies the fault tree but does not help the analyst to estimate the truncation error. This source of uncertainty has been a concern in PRA calculations. A better method of truncation, based on both cut-set size and cut-set probability [Combined Truncation (CT) methodology] is developed and discussed in this paper. With this method, the analyst is able to estimate the maximum error that can occur in the truncation process. In the CT methodology the analyst estimates a parameter which is a function of the number of primary events in the fault tree, and the highest probability associated with the basic events in the fault tree. From that parameter value, the analyst then determines the level of truncation necessary and the associated maximum error of truncation. Application of the CT methodology has several advantages with regard to identification of dominant MCSs of large fault trees. The CT method is simple to use, provides an estimation of the maximum truncation error, and substantially reduces the CPU time for computer computations. The implementation of CT methodology requires no major changes in the current versions of fault-tree evaluation codes, and the CT method can be conveniently automated on them.
Analysis of systems subject to inspection and repair: a state-of -tbe-art survey. R. SUBRAMANYAMNAIDUand M. N. GOPALAN. Microelectron. Reliab. 24, 939 (1984). The main intent of the paper is to provide a detailed literature survey on the analysis of systems subject to inspection and repair.
Space station reliability. CLAUDER. BIRDSALLand HOWARDJ. FRANK. Proc. A. Reliab. Maintainab. Syrup. 197 (1985). This paper addresses the complex reliability issues of a permanent manned space station. Space station development concepts for a space vehicle service station demand state of the art approaches to crew safety, automation, space shuttle support, and maintenance. The paper describes a preliminary approach to application of reliability technology to future manned space systems. An effective approach to minimal cost is a difficult issue. A nearly failure free system is within the available technology, but the initial cost is high. Lower reliability, more frequent failure, more maintenance and logistic support raise operational support cost. The solution is shown to lie between the extremes of the reliability alternatives.
Digital computer systems reliability. DON O. KOVAL and HENRY F. EWASECHKO.Proc. A. Reliab. Maintainab. Syrup. 69 (1985). This paper will present the statistical characteristics of a 10 yr study on the University of Alberta's AMDAHL 470
World Abstracts on Microelectronics and Reliability
Reliab. Maintainab. Syrup. 82 (1985). The architecture of an expert system for the interactive data-driven construction of fault trees is presented. Parts of the system are now under realization and testing. The system intends to offer a flexible and easy-to-operate tool to the analyst in reliability assessment of complex engineered installations. The expert system is organized according to a number of knowledgebased modules that contain metarules, allow the establishment of rules, and to collect and interpret data. The construction process bases upon a representation of the elementary components given a terms of multiple-valued logical (MVL) trees and results into an MVL-tree. This tree can be analyzed directly or when requested it can be reduced to a number of binary fault trees.
Independence bounds and approximations for system availability computations. MARTIN L. SHOOMAN. Proc. A. Reliab. Maintainab. Syrup. 115 (1985). This paper discusses various simplified bounds and approximations which can be used to simplify the computation of system availability via Markov model analysis. This is especially important when the system contains many states due to: (a) a large number of elements, (b) the extra states needed to model built-in-test, (c) the extra states needed to model hardware/software interactions. These simplified formulas can also be used to check the results of a computer simulation which is the conventional way of performing such complex computations. Analysis of a two unit standby system with partial failure and two types of repairs. L. R. GOEL, ASHOK KUMAR and A. K. RASTOGI. Microeleetron. Reliab. 24, 873 (1984). A two dissimilar unit standby system is analysed. The priority unit can either be in normal or partial operative mode. When the unit fails from the partial mode, it undergoes minor repair and the unit becomes operative with different failure rate. If this unit fails again, it goes to major repair after which it works as good as new. The standby unit while in use is either operative or failed. This non priority unit fails without passing through the partial failure mode and undergoes only one type of repair with different repair time distribution. Failure and repair time distributions are negative exponential and general respectively.Regenerative technique in M R P is applied to obtain several reliability characteristics of interest to system designers. Analysis of a k-out-of-n unit system with two types of failure and preventive maintenance. L. R. GOEL and PRAVEENGUPTA. Microeleetron. Reliab. 24, 877 (1984). A k-out-of-n unit system is analysed with two types of failure: (1) failure due to change in operating characteristics and (2) catastrophic failure. Preventive maintenance of the system is allowed at random epochs. All transition rates are taken to be general. Several measures of reliability useful for system designers and operations managers have been obtained by using regenerative point technique with Markov renewal process. Some important results obtained earlier are shown as particular cases. Performance-related dependability evaluation of supercomputer systems. J. ARLAT and J. C. LAPRIE. Microelectron. Reliab. 24, 717 (1984). The paper presents an example of performance-related dependability evaluation of a supercomputer structure corresponding to an M I M D multiprocessor system intended for high speed scientific computation. The approach presented addresses the problems of deriving a model that is tractable yet representative of the behaviour of a complex system. This is achieved by means of an intensive validation study, and through the evaluation of measures of interest which account for the specific operating requirements characterizing the system under investigation: (a) maintain very high throughput over a long period of time, and (b) provide an efficient operational life-cycle.
Topological optimization of distributed computer networks subject to reliability constraints. ANTONI ZABLUDOWSKIand ANDRZEJ SOBOLSKLMicroelectron. Reliab. 24, 1023 (1984). A method of topological optimization of the networks with minimum cost subject to reliability constraints is given in this paper. The proposed optimization algorithm is based on branch and bound method. The computational results of this algorithm are discussed. On power line carrier communication (PLC). YOSEFS. SHERIF and S. S. ZAmR. Microelectron. Reliab. 24, 781 (1984). Power line carrier communication (PLC) provides significant services for the electric utilities in particular and to the industrial and consumer sectors in general. Since its inception in the early 1920's, PLC has been used for voice communication, protective relaying telemetry and supervisory control. Lately PLC has proved to render the most efficient means for distribution automation and load management. This paper is a review of literature related to PLC and its applications.
Minimizing the cost of automated board testing. JANET PAGE WALTON. Electron. Prod. 39 (September 1984). While it is simplistic to believe that the total cost of Automatic Testing can be reduced by purchasing low cost equipment, only a limited number of companies can afford the high capital cost of sophisticated ATE. On multistate coherent systems. FUMIO OH1 and TOSHIO NISHIDA. IEEE Trans. Reliab. R-33, 284 (1984). Recently, several authors have treated multistate systems and given some results. This paper summarizes the several concepts of s-coherency and shows the relationships between them. An intresting theorem for the existence of series and parallel coherent systems is presented. We have proved IFRA and NBU closure theorems under more general situation than have E1-Neweihi et al. and Ross. We discuss our IFR closure theorem.
Stochastic behaviour of a maintained system with protection system. ASHOK KUMAR,VIPIN B. KAPOORand A. K. RASTOGI. Microelectron. Reliab. 24, 869 (1984). This paper deals with the analysis of a single unit system backed by a protection system (P.S.). Both are subject to failure with exponential failure time distribution. Repair time of working unit, fault detection and inspection time of protection system are assumed to follow general distribution. The system has been investigated in detail by the help of semi-Markov process and several parameters of interest are obtained. Optimum preventive maintenance policies for a computersystem with restart. TOSHIO NAKAGAWA,KENJIRO NISHI and KAZUM1 YASUI. IEEE Trans. Reliab. R-33, 272 (1984). This paper considers a computer system where an operation is restarted when the system stops on some faults. The restart does not succeed every time. Three preventive maintenance (pm) models are considered: (A) The pm is made at the scheduled time T. (B) The pm is made at the K-th successful restart. (C) The pm is made at the next scheduled time if the total number of successes of restart exceeds K. The availabilities of each model are obtained and the optimum pm policies are discussed. Cost analysis of a two-unit standby system with two types of repairmen. VIBHA GOYAL and K. MURARI. Microelectron. Reliab. 24, 849 (1984). This paper is concerned with a twounit cold standby system with two types of repairmen. One "regular" repairman is kept for repairing the units as soon as they fail. It is assumed that sometimes he might not be able to do the repairs within some tolerable time (patience time). Another "expert" repairman, assumed to be perfect, is called on to do the repairs on the completion of this patience time or on the failure of the system, whichever is later.
World Abstracts on Microelectronics and Reliability Various measures of system effectiveness are calculated using semi-Markov processes and regenerative processes. Based on these measures, a rule is developed whether the expert repairman should be called after the system failure. Further numerical results for a case, in which repair time and patience time both have non-Markovian property, are also investigated. Then the upper bound of the cost K3, below which the expert repairman should be called immediately after the system failure and the corresponding increase in profit are calculated.
The impact of robots on product reliability. JOHN MIHALASKY. Proc. Reliab. Maintainab. Syrup. 464 (1985). With robots beginning to appear more often as industry rebuilds, there is a need to look at the impact of robots on product reliability. This paper discusses why the robots will "force" companies to buy better raw materials, do a better analysis of manufacturing methods, increase the use of in-process automatic testing and improve the products' handleability characteristics. Also discussed is how robots will allow for designing to a higher reliability level because of the improvement of manufacturing processes. Finally, there is coverage on how the use of robots will result in less scrap and rework, which should reflect itself in fewer catastrophic and early failures.
The anatomy of burn-in--an analysis. GUSTAVOST. Electron. Prod. 27 (February 1985). An in-depth analysis of the burn-in process which can reveal 70 % of chip-related early failures.
Bayes reliability assessment of a two-unit hot-standby redundant system. SUSUMUFuJn and HIROAKISANDOH.IEEE Trans Reliab. R-33, 297 (1984). This study assesses the reliability of a two-unit hot-standby redundant system with an imperfect switch. The prior knowledge of experts is used in the assessment through Bayes theorem. Bayes interval limits for the system reliability are presented. The predictive distribution of the first failure time of the system is formulated.
Computing k-out-of-n system reliability. R. E. BARLOWand K. D. HEIDTMANN.IEEE Trans. Reliab. R-33, 322 (1984). A linear-time algorithm and its short computer program in BASIC for k-out-of-n:G system reliability computation is presented.
Fractional duration before first failure--a useful index and an analytical tool. C. SINGH and J. S. DUe,GAL. Microelectron. Reliab. 24, 1077 (1984). This paper defines a new index, fractional duration before first failure and describes the methodology for its calculation. The relationship of this index to the mean time to first failure is also presented. The fractional duration before first failure is, therefore, not only a useful measure of system reliability but also provides an alternative approach to calculate mean time to first failure. The concepts and techniques are illustrated with suitable examples.
Reliability with imperfect diagnostics. ALLEN L. WHITE. Microelectron. Reliab. 24, 1069 (1984). This paper considers the reliability of systems that accumulate faults throughout their lifetime because of imperfect diagnostics. Several experiments are referenced that show the difficulty of achieving a 100 percent diagnostic level. After explaining the assumptions and constructing the reliability estimation method, the paper proceeds to a graphical trade-off analysis that considers the effect of imperfect diagnostics on three traditional ways of achieving higher reliability: lower component fault rate, more redundancy, and redundancy with reconfiguration.
1167
A new heuristic approach for redundancy optimization problem. V. DAKSHINA MURTY and K. B. MISRA. Microelectron. Reliab. 24, 1013 (1984). The present paper describes a simple heuristic approach to solve redundancy optimization problem without much of computation to help reliability designers choose an appropriate configuration. The solution technique is simpler than all previous methods and offers optimal results with a high success rate.
A Truncation methodology for evaluating large fault trees. M. MODARRESand H. DEZFULI.IEEE Trans. Reliab. R-33, 325 (1984). Probabilistic risk assessment (PRA) of a nuclear power plant often involves evaluating large fault trees (eg, trees with more than 1000 basic events and 1000 gates). It is desired to generate the dominant minimal cut sets (MCSs) in order to gain engineering insight, to estimate the top event probability, and to calculate the frequency of reactor core damage. To estimate the top event probability with computers, the usual practice has been to neglect those MCSs of the fault tree that have a probability of less than some cutoff value; the cut-off value is subjectively selected by the analyst. This method of truncation eliminates some MCSs, and thus simplifies the fault tree but does not help the analyst to estimate the truncation error. This source of uncertainty has been a concern in PRA calculations. A better method of truncation, based on both cut-set size and cut-set probability [Combined Truncation (CT) methodology] is developed and discussed in this paper. With this method, the analyst is able to estimate the maximum error that can occur in the truncation process. In the CT methodology the analyst estimates a parameter which is a function of the number of primary events in the fault tree, and the highest probability associated with the basic events in the fault tree. From that parameter value, the analyst then determines the level of truncation necessary and the associated maximum error of truncation. Application of the CT methodology has several advantages with regard to identification of dominant MCSs of large fault trees. The CT method is simple to use, provides an estimation of the maximum truncation error, and substantially reduces the CPU time for computer computations. The implementation of CT methodology requires no major changes in the current versions of fault-tree evaluation codes, and the CT method can be conveniently automated on them.
Analysis of systems subject to inspection and repair: a state-of -tbe-art survey. R. SUBRAMANYAMNAIDUand M. N. GOPALAN. Microelectron. Reliab. 24, 939 (1984). The main intent of the paper is to provide a detailed literature survey on the analysis of systems subject to inspection and repair.
Space station reliability. CLAUDER. BIRDSALLand HOWARDJ. FRANK. Proc. A. Reliab. Maintainab. Syrup. 197 (1985). This paper addresses the complex reliability issues of a permanent manned space station. Space station development concepts for a space vehicle service station demand state of the art approaches to crew safety, automation, space shuttle support, and maintenance. The paper describes a preliminary approach to application of reliability technology to future manned space systems. An effective approach to minimal cost is a difficult issue. A nearly failure free system is within the available technology, but the initial cost is high. Lower reliability, more frequent failure, more maintenance and logistic support raise operational support cost. The solution is shown to lie between the extremes of the reliability alternatives.
Digital computer systems reliability. DON O. KOVAL and HENRY F. EWASECHKO.Proc. A. Reliab. Maintainab. Syrup. 69 (1985). This paper will present the statistical characteristics of a 10 yr study on the University of Alberta's AMDAHL 470