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Reliability demonstration: purposes, practices and value
World Abstracts on Microelectronics and Reliability and explains some seasonal fluctuations in actual MTBF. Monthly and yearly fluctuations are also explored. Part 2 shows some effects of workmanship-in-repair on reliability growth. The repair procedure was changed and the reliability gradually improved over a long period of time. Part 3 treats one of the components, a wirewound potentiometer, in some detail. A failure analysis and an improvement program are described.
The set approach to determine the frequency of system failure. C. SINGH. Microelectron. & Reliab. 14, 293 (1975). The reliability block diagram may be solved by manipulating either the cut sets or the tie sets of the network. The formulae for calculating the probability of system failure using either of the approaches are well documented [1]. An exact formula for determining the frequency of system failure using cut set approach was given in [2]. This paper derives the complementary formula for the frequency of system failure using tie set approach.
Design for quality: A designer's notebook for electronic systems. H. G. FRANKLAND and MARY JANE HYDE. Qual-
ity Progress, June 1975. p. 22. Quality assurance, along with producibility and reliability, can be designed into or designed out of a product. It all starts with a blank piece of paper. The more sophisticated a design, the greater the care that must be taken to design, in quality at the outset. In electronic systems, the more complex a circuit is, the more difficult it is to build, inspect and assure good quality. Systems and circuit designers, all of whom are aware of this, will go overboard to simplify circuits. Then, once the circuit has been designed and breadboarded, it is up to the packaging design engineer to use his experience and ingenuity to come up with the most simple package possible.
Stochastic behaviour of a two-unit priority standby redundant system with repair. T. NAKAGAWA and S. OSAK1.
407
MIL-STD-781B: Effect o| a "Continue Test" decision. M. A. McGREGOR. Proc. Reliability and Maintainability Syrup. Washington D,C., p. 304, 28-30 January, 1975. All possible continue testing decisions occurring in the application of MIL-STD-781B Test Plans III and IV have been analyzed. A complete set of tables show how the probability of acceptance, and the expected test time for an accept decision are influenced when the accumulated test time and the accumulated number of failures result in a continue testing decision.
Empirical reliability models of complex structures. C. W. JOHNSON, R. E. MAXWELL and L. G. ALLRED. Proc. Reliability and Maintainability Syrup. Washington D.C., p. 323, 28-30 January, 1975. A method is presented for replacing complicated functions in Monte Carlo Simulation and Sensitivity (MCSS) analysis reliability models with functions that are more easily evaluated and which make the computer time requirements of many such analyses smaller, and thus, improve the practicality of the method.
Prediction of software reliability during debugging. P. B. MORANDA. Proc. Reliability and Maintainability Syrup. Washington D.C, p. 327, 28-30 January, 1975. Estimates of future performance of a software package are obtained from debugging data in essentially two ways. In one way the record in time of the occurrence of anomalies is used; in this paper three different mathematical models of failure rates are described, together with illustrative predictions of MTI'F and of the total error content using actual trouble report data. A second estimate of performance of a program is by its "operational reliability", which is obtained through variations of input data according to assumed probability laws. With respect to this procedure, an outline is given of the goals of some research currently being done at McDonnell Douglas Astronautics Company under Air Force Office of Scientific Research Contract AF-F44620-74-C-008.
Microelectron. & Reliab. 14, 309 (1975). A two-unit
Modelling transient faults in TMR computer systems. P.
priority standby redundant system is discussed taking account of a repairable nonpriority unit. Stochastic behavior of such a system is investigated; the distribution of the time to the system failure, the expected number of visits to the system failure during a finite interval, and the pointwise unavailability are obtained. A special case with all exponential distributions are presented in details as an example. Further the distribution of the busy period of a repairman and the distribution of the time to the system recovery are derived.
M. MERRYMAN and A. A. AVIZIENIS. Proc. Reliability and Maintainability Syrup. Washington D . C . p . 333, 28-30 January, 1975. In this paper we report the development of a technique for modeling transient faults in redundant computer systems. Transient faults are characterized by their arrival rate and their duration. Fault detection, transient recovery, and the effect of permanent faults are included. A fault occurrence/recovery status state diagram is drawn to illustrate the operational status of the system while undergoing faults. The state diagram is used to formulate the equations for the mission failure probability. The techniques are then applied to a triple modular redundant computer system.
Decision theoretic approach to the design of reliability systems. N. SINGH and G. C. JAIN. Microelectron. &
Reliab. 14, 315 (1975). Nevertheless the continual growth in research into the reliability of complex systems, questions regarding the optimal design of such systems have rarely been answered. Most works reported to date have not taken into account the difficult issues such as the existing uncertainties about the failure rates, service rates of components (or subsystems) while working on the design of various types of complex systems. The objective of this paper is to indicate the methodology to resolve such outstanding questions through the approach of decision theory. Some examples are presented in the last section. Some approaches to Bayesian reliability demonstration. R. E. SCHAFER. Proc. Reliability and Maintainability Syrup. Washington D.C., p. 253, 28-30 January, 1975. In this paper we present an overview of some reliability demonstration test plans recently developed by the Hughes Aircraft Company under RADC sponsorship.
Local-exchange renewal strategy: Maintenance man-hour requirements. C. R. J. SHURROCK and A. F. YAXLEY. The
Post Office Electrical Engrs' J. 68 (2) 77 (1975). This article describes the special studies carried out to determine the maintenance man-hour requirements/exchangesize relationships of Strowger, crossbar and electronic exchange systems for use in deriving the costings of various strategies for the renewal of local exchanges.
Reliability demonstration: purposes, practices and value. H. S. BALABAN. Proc. Reliability and Maintainability Syrup. Washington D.C., p. 246, 28-30 January 1975. Is reliability demonstration worth the cost? That question is difficult to answer quantitatively, so we have to appraise the general effects of a demonstration program for various degrees of application. Concluding that reliability demonstration is inherently very beneficial, we then suggest ways that it can be made more useful than in the past.
The set approach to determine the frequency of system failure. C. SINGH. Microelectron. & Reliab. 14, 293 (1975). The reliability block diagram may be solved by manipulating either the cut sets or the tie sets of the network. The formulae for calculating the probability of system failure using either of the approaches are well documented [1]. An exact formula for determining the frequency of system failure using cut set approach was given in [2]. This paper derives the complementary formula for the frequency of system failure using tie set approach.
Design for quality: A designer's notebook for electronic systems. H. G. FRANKLAND and MARY JANE HYDE. Qual-
ity Progress, June 1975. p. 22. Quality assurance, along with producibility and reliability, can be designed into or designed out of a product. It all starts with a blank piece of paper. The more sophisticated a design, the greater the care that must be taken to design, in quality at the outset. In electronic systems, the more complex a circuit is, the more difficult it is to build, inspect and assure good quality. Systems and circuit designers, all of whom are aware of this, will go overboard to simplify circuits. Then, once the circuit has been designed and breadboarded, it is up to the packaging design engineer to use his experience and ingenuity to come up with the most simple package possible.
Stochastic behaviour of a two-unit priority standby redundant system with repair. T. NAKAGAWA and S. OSAK1.
407
MIL-STD-781B: Effect o| a "Continue Test" decision. M. A. McGREGOR. Proc. Reliability and Maintainability Syrup. Washington D,C., p. 304, 28-30 January, 1975. All possible continue testing decisions occurring in the application of MIL-STD-781B Test Plans III and IV have been analyzed. A complete set of tables show how the probability of acceptance, and the expected test time for an accept decision are influenced when the accumulated test time and the accumulated number of failures result in a continue testing decision.
Empirical reliability models of complex structures. C. W. JOHNSON, R. E. MAXWELL and L. G. ALLRED. Proc. Reliability and Maintainability Syrup. Washington D.C., p. 323, 28-30 January, 1975. A method is presented for replacing complicated functions in Monte Carlo Simulation and Sensitivity (MCSS) analysis reliability models with functions that are more easily evaluated and which make the computer time requirements of many such analyses smaller, and thus, improve the practicality of the method.
Prediction of software reliability during debugging. P. B. MORANDA. Proc. Reliability and Maintainability Syrup. Washington D.C, p. 327, 28-30 January, 1975. Estimates of future performance of a software package are obtained from debugging data in essentially two ways. In one way the record in time of the occurrence of anomalies is used; in this paper three different mathematical models of failure rates are described, together with illustrative predictions of MTI'F and of the total error content using actual trouble report data. A second estimate of performance of a program is by its "operational reliability", which is obtained through variations of input data according to assumed probability laws. With respect to this procedure, an outline is given of the goals of some research currently being done at McDonnell Douglas Astronautics Company under Air Force Office of Scientific Research Contract AF-F44620-74-C-008.
Microelectron. & Reliab. 14, 309 (1975). A two-unit
Modelling transient faults in TMR computer systems. P.
priority standby redundant system is discussed taking account of a repairable nonpriority unit. Stochastic behavior of such a system is investigated; the distribution of the time to the system failure, the expected number of visits to the system failure during a finite interval, and the pointwise unavailability are obtained. A special case with all exponential distributions are presented in details as an example. Further the distribution of the busy period of a repairman and the distribution of the time to the system recovery are derived.
M. MERRYMAN and A. A. AVIZIENIS. Proc. Reliability and Maintainability Syrup. Washington D . C . p . 333, 28-30 January, 1975. In this paper we report the development of a technique for modeling transient faults in redundant computer systems. Transient faults are characterized by their arrival rate and their duration. Fault detection, transient recovery, and the effect of permanent faults are included. A fault occurrence/recovery status state diagram is drawn to illustrate the operational status of the system while undergoing faults. The state diagram is used to formulate the equations for the mission failure probability. The techniques are then applied to a triple modular redundant computer system.
Decision theoretic approach to the design of reliability systems. N. SINGH and G. C. JAIN. Microelectron. &
Reliab. 14, 315 (1975). Nevertheless the continual growth in research into the reliability of complex systems, questions regarding the optimal design of such systems have rarely been answered. Most works reported to date have not taken into account the difficult issues such as the existing uncertainties about the failure rates, service rates of components (or subsystems) while working on the design of various types of complex systems. The objective of this paper is to indicate the methodology to resolve such outstanding questions through the approach of decision theory. Some examples are presented in the last section. Some approaches to Bayesian reliability demonstration. R. E. SCHAFER. Proc. Reliability and Maintainability Syrup. Washington D.C., p. 253, 28-30 January, 1975. In this paper we present an overview of some reliability demonstration test plans recently developed by the Hughes Aircraft Company under RADC sponsorship.
Local-exchange renewal strategy: Maintenance man-hour requirements. C. R. J. SHURROCK and A. F. YAXLEY. The
Post Office Electrical Engrs' J. 68 (2) 77 (1975). This article describes the special studies carried out to determine the maintenance man-hour requirements/exchangesize relationships of Strowger, crossbar and electronic exchange systems for use in deriving the costings of various strategies for the renewal of local exchanges.
Reliability demonstration: purposes, practices and value. H. S. BALABAN. Proc. Reliability and Maintainability Syrup. Washington D.C., p. 246, 28-30 January 1975. Is reliability demonstration worth the cost? That question is difficult to answer quantitatively, so we have to appraise the general effects of a demonstration program for various degrees of application. Concluding that reliability demonstration is inherently very beneficial, we then suggest ways that it can be made more useful than in the past.