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A practical method of optimizing system life cycle costs vs availability
World Abstracts on Microelectronics and Reliability ance into electronic systems has become more difficult due to system complexity. Design automation offers an alternative to traditional approaches of managing the complexity problem. This alternative depends almost exclusively on the computer and is implemented via a set of tightly or loosely integrated programs.
Some aspects of the need for redundancy in telecommunication transmission systems. B. TIGERMAN and L. M. ERICSSON. Microelectron. Reliab. 17, 129 (1978). The high inherent reliability of the electronic equipment as well as the greatly simplified replacement of functional units makes all duplication superfluous in a multiplex terminal on the apparatus level. An economically justifiable availability of a telecommunication network can be achieved, however, by appropriate planned transmission systems with automatic or manual re-routing possibilities in combination with an adequate maintenance and well-considered stock of spares. Fault trees revisited. W. A. WOLFE. Microelectron. Reliab. 17, 117 (1978). Embedded in a fault tree is a vast amount of information. In this paper methods to extract this information are reviewed. Method of reliability analysis of control systems for nuclear power plants. SAMIR BASU and RAIDIS ZEMDEGS. Microelectron. Reliab. 17, 105 (1978). High reliability is one of the main objectives of the design and operation of Control Systems in Nuclear Power Plants. This paper presents a method of reliability analysis for these systems using various reliability techniques and engineering judgement. The stepby-step analysis includes system study, field data, failure mode and effect analysis, common mode failures, fault trees, human factors, reliability targets, and design reviews. To illustrate this method, the Liquid Zone Control System for C A N D U nuclear reactor control is used. The microprocessor failure rate predictions. B. HALIL. Microelectron: Reliab. 17, 211 (1978). A discrepancy is observed for the LSI failure rate model of the MIL-HDBK-217B Handbook between a large gate count LSI device failure rate and the same device modelled by its parts namely MSI and SSI devices. A modified model is presented to show a close relationship in failure rates of small gate count LSI devices and to modify the results of higher gate count LSI devices using MIL-HDBK-217B data. Reliability of large equipment and systems of nuclear power plants. M. F. HASHM1. Microelectron. Reliab. 17, 99 (1978). Reliability studies have to be system-oriet~ted. However, malfunction and failures of equipment in one system could have a serious effect on an interfacing system or large equipment. The type of coordination done for functional design of system interface needs to be carried out in reliability engineering as well. Some ideas for evaluation and improvement of reliability of large equipment are offered and illustrated with some examples. Estimating software reliability from test data. ELDRED NELSON. Microelectron. Reliab. 17, 67 (1978). Recent work on software reliability associates correct execution of a test case with a statistical inference that the program will execute correctly for a specified subset of inputs. Test cases can be designed so that their associated subsets cover the entire input domain, allowing reliability estimates to be made for expected operational use profiles. Structuring software development for reliability. SOL J. GREENSPAN and CLEMENT L. McGOWAN. Microelectron. Reliah. 17, 75 (1978). Software system development is viewed as a series of discrete ordered activities that produce successively more constrained models of the system by binding in additional system aspects. Treating the system aspects as
561
separate concerns allows software engineering techniques that control production cost and enhance reliability to be applied to each step. The greatest gains, however, are due to the reliability and traceability of the system over its lifetime. Anessential tool is a structured system description technique.
Operating system redundancy on an active, a stand-by or a passive basis. KLAAS B. KLAASSEN, JACQUES C. L. VAN PEPPEN and HENDRIK J. JANSEN. Microelectron, Reliab. 17, 35 (1978). When applying redundancy, the system designer may find himself facing the dilemma of weighting the better life prospects of passive redundant hardware against the lower system complexity in the case of active redundant hardware. This dilemma is analyzed here by comparing the MTTF and the reliability obtained with active, stand-by and passive redundancy. The analysis makes use of Markov diagrams and a generalized reliability mode/ that embraces all three types of redundancy and covers all types of failure which can occur in practice. A practical method of optimizing system life cycle costs vs availability. ROBERT B. WERDEN. Microelectron. Reliab. 17, 1 {1978). The effect will be shown, on availability and life cycle costs by equipment reliability, maintainability, system configuration and technician response time to equipment failures. Guidelines will be given to assist the project manager in determining best system parameters for minimizing life cycle costs for a particular application.
System diagnosis with FLIP. P. DESMARAISand S. WILLIAMS. Microelectron. Reliab. 17, 47 (1978). This paper presents a graphical technique implemented as a computer program called FLIP, whose main function is to select a minimal set of test points required to achieve 1--distinguishability of failures in a system. In support of diagnostic test activities, fault signatures are also generated for every system failure, where the level of fault isolation is defined by the graphical model drawn of the system or subsystem. The paper shall first outline the theoretical basis upon which FLIP was developed, then briefly describe the various capabilities of the program, and finally discuss a specific application to electronic system diagnosis. The time dependent failure rate of a system consisting of three 50%-units in active parallel. G. W. E. NIEUWHOF. Microelectron. Reliab. 17, 53 (1978). This paper deals with an investigation of the failure rate time function of the above system. The general equation of the failure rate function is derived by using the Boolean expression of the fault tree diagram for the system. Particular attention is given to the case of three identical units with constant failure rate. This last system is compared with a system which consists of two 100~o-units in active parallel.
Effect of reliability programs on life cycle cost--a case history. ROLAND G. BERTSCHY. Microelectron. Reliab, 17, 9 (1978). A case history is presented of the impact that implementation of a Reliability (R) program had on the Life Cycle Cost (LCC) of the TACAN Test Set, AN/ARM-135(A). An analysis is made of the reliability activities performed and the effect of resulting corrective actions on the total program LCC. The relative worth of each activity is explored. On optimizing maintainabilityrNATHAN JOHNSON, JR. Microelectron. Reliab. 17, 4l (1978). The probability concept allows the equations and generalizations of reliability to be mapped to maintainability through the avenue created by the unschedule maintenance action, thereby offering an additional feature for existing maintainability measures. An example is presented to clarify the usefulness of the concept--corrective maintenance is anticipated at stated risks, spare parts allocated, degrading subsystems are identified and repair time distributions optimized.
Some aspects of the need for redundancy in telecommunication transmission systems. B. TIGERMAN and L. M. ERICSSON. Microelectron. Reliab. 17, 129 (1978). The high inherent reliability of the electronic equipment as well as the greatly simplified replacement of functional units makes all duplication superfluous in a multiplex terminal on the apparatus level. An economically justifiable availability of a telecommunication network can be achieved, however, by appropriate planned transmission systems with automatic or manual re-routing possibilities in combination with an adequate maintenance and well-considered stock of spares. Fault trees revisited. W. A. WOLFE. Microelectron. Reliab. 17, 117 (1978). Embedded in a fault tree is a vast amount of information. In this paper methods to extract this information are reviewed. Method of reliability analysis of control systems for nuclear power plants. SAMIR BASU and RAIDIS ZEMDEGS. Microelectron. Reliab. 17, 105 (1978). High reliability is one of the main objectives of the design and operation of Control Systems in Nuclear Power Plants. This paper presents a method of reliability analysis for these systems using various reliability techniques and engineering judgement. The stepby-step analysis includes system study, field data, failure mode and effect analysis, common mode failures, fault trees, human factors, reliability targets, and design reviews. To illustrate this method, the Liquid Zone Control System for C A N D U nuclear reactor control is used. The microprocessor failure rate predictions. B. HALIL. Microelectron: Reliab. 17, 211 (1978). A discrepancy is observed for the LSI failure rate model of the MIL-HDBK-217B Handbook between a large gate count LSI device failure rate and the same device modelled by its parts namely MSI and SSI devices. A modified model is presented to show a close relationship in failure rates of small gate count LSI devices and to modify the results of higher gate count LSI devices using MIL-HDBK-217B data. Reliability of large equipment and systems of nuclear power plants. M. F. HASHM1. Microelectron. Reliab. 17, 99 (1978). Reliability studies have to be system-oriet~ted. However, malfunction and failures of equipment in one system could have a serious effect on an interfacing system or large equipment. The type of coordination done for functional design of system interface needs to be carried out in reliability engineering as well. Some ideas for evaluation and improvement of reliability of large equipment are offered and illustrated with some examples. Estimating software reliability from test data. ELDRED NELSON. Microelectron. Reliab. 17, 67 (1978). Recent work on software reliability associates correct execution of a test case with a statistical inference that the program will execute correctly for a specified subset of inputs. Test cases can be designed so that their associated subsets cover the entire input domain, allowing reliability estimates to be made for expected operational use profiles. Structuring software development for reliability. SOL J. GREENSPAN and CLEMENT L. McGOWAN. Microelectron. Reliah. 17, 75 (1978). Software system development is viewed as a series of discrete ordered activities that produce successively more constrained models of the system by binding in additional system aspects. Treating the system aspects as
561
separate concerns allows software engineering techniques that control production cost and enhance reliability to be applied to each step. The greatest gains, however, are due to the reliability and traceability of the system over its lifetime. Anessential tool is a structured system description technique.
Operating system redundancy on an active, a stand-by or a passive basis. KLAAS B. KLAASSEN, JACQUES C. L. VAN PEPPEN and HENDRIK J. JANSEN. Microelectron, Reliab. 17, 35 (1978). When applying redundancy, the system designer may find himself facing the dilemma of weighting the better life prospects of passive redundant hardware against the lower system complexity in the case of active redundant hardware. This dilemma is analyzed here by comparing the MTTF and the reliability obtained with active, stand-by and passive redundancy. The analysis makes use of Markov diagrams and a generalized reliability mode/ that embraces all three types of redundancy and covers all types of failure which can occur in practice. A practical method of optimizing system life cycle costs vs availability. ROBERT B. WERDEN. Microelectron. Reliab. 17, 1 {1978). The effect will be shown, on availability and life cycle costs by equipment reliability, maintainability, system configuration and technician response time to equipment failures. Guidelines will be given to assist the project manager in determining best system parameters for minimizing life cycle costs for a particular application.
System diagnosis with FLIP. P. DESMARAISand S. WILLIAMS. Microelectron. Reliab. 17, 47 (1978). This paper presents a graphical technique implemented as a computer program called FLIP, whose main function is to select a minimal set of test points required to achieve 1--distinguishability of failures in a system. In support of diagnostic test activities, fault signatures are also generated for every system failure, where the level of fault isolation is defined by the graphical model drawn of the system or subsystem. The paper shall first outline the theoretical basis upon which FLIP was developed, then briefly describe the various capabilities of the program, and finally discuss a specific application to electronic system diagnosis. The time dependent failure rate of a system consisting of three 50%-units in active parallel. G. W. E. NIEUWHOF. Microelectron. Reliab. 17, 53 (1978). This paper deals with an investigation of the failure rate time function of the above system. The general equation of the failure rate function is derived by using the Boolean expression of the fault tree diagram for the system. Particular attention is given to the case of three identical units with constant failure rate. This last system is compared with a system which consists of two 100~o-units in active parallel.
Effect of reliability programs on life cycle cost--a case history. ROLAND G. BERTSCHY. Microelectron. Reliab, 17, 9 (1978). A case history is presented of the impact that implementation of a Reliability (R) program had on the Life Cycle Cost (LCC) of the TACAN Test Set, AN/ARM-135(A). An analysis is made of the reliability activities performed and the effect of resulting corrective actions on the total program LCC. The relative worth of each activity is explored. On optimizing maintainabilityrNATHAN JOHNSON, JR. Microelectron. Reliab. 17, 4l (1978). The probability concept allows the equations and generalizations of reliability to be mapped to maintainability through the avenue created by the unschedule maintenance action, thereby offering an additional feature for existing maintainability measures. An example is presented to clarify the usefulness of the concept--corrective maintenance is anticipated at stated risks, spare parts allocated, degrading subsystems are identified and repair time distributions optimized.