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Maintainability application to system effectiveness quantification
WORLD
ABSTRACTS
ON MICROELECTRONICS
tion by linear codes, was adopted. Other techniques for automatic replacement of fault units are also considered.
*Highly reliable computing systems. B. RANDALL. Newcastle upon Tyne Univ., U.K., July (1971), pp. 43. H E L D - B Y - N L L , TR-20-NLL-8724-9. Provides an overview of some of the problems of obtaining high reliability from complex computing systems and describes several systems of interest in this regard. T h e problems of hardware and software reliability and of designing a system that can continue to provide reliable service in the presence of hardware failures and software errors are discussed.
Maintainability application to system effectiveness q u a n t i f i c a t i o n . E. L. PETERSON, IEEE Tram. Relish. R-20, No. ! (1971), p. 3. A new mathematical technique has been developed in the description of approaches for maintainability applications to system effectiveness quantification. It promises to have high utility because the method itself is completely independent of the probability density function for downtime. This is particularly important where combinations of more than one malfunction are sufficiently important to warrant inclusion in the system effectiveness equation. T h e potential sensitivity of each term can be quickly estimated by referring to a table for the individual terms of the Poisson formula. This method's mathematical simplicity lends itself to hand computational techniques for small quantities of equipment. It is also easily computerized for more complicated systems. R e l i a b i l i t y c o n s i d e r a t i o n s i n design trade s t u d i e s . R. L. EXSNER. Proc. Ann. Syrup. Reliab., Washington D.C., U.S.A., IEEE Cat. No. 71C 2-R, 12-14 January (1971), p. 98. Reliability analysis is an essential input when trade studies are undertaken to select the most attractive designs for various components of a system. This analysis involves both technical and practical considerations--technical considerations related to the interfacing and interaction of components (and their failure modes), and practical considerations related to the level of detail and completeness of the analysis. This paper identifies and amplifies those considerations and provides illustrations of their implementation in trade studies on components of the nuclear engine for rocket vehicle application nuclear subsystem. D e s i g n o f adaptive procedures for fault detection and isolation. M. COliN and G. Oar. 1EEE Tram. Relish. R-20, No. 1 (1971), p. 7. An algorithm is presented for designing minimum-expected-cost test trees for detecting and isolating single faults in a system. A test is specified by the subset of components that must be good for the test to pass, and with each test is associated a fixed cost. Each component is assumed to have an a pr/ori probability of failure. T h e test tree specifies an adaptive testing procedure that detects a failure and isolates the faulty component while minimizing the expected cost of testing.
AND
RELIABILITY
115
Discrete renewal processes. M. MUNTNFJ~. IEEE Tram. Reliab. R-20, No. 2 (1971), p. 46. Discrete renewal processes until recently have not been applied to the mathematical modeling of physical processes. Analyses of such renewal processes have proceeded on the basis of generating functions but the results are often too complicated to be of use. This paper presents an alternative approach to discrete renewal theory and calculates many of the more complex statistics of such processes.
*Reliability and switching technique of integrated switching circuit with complementary M O S F E T t r a n s i s t o r s . (In German.) W. SCHAMBECK. Deutsche Forschungs-u. Versuchsamtalt Luft-u. Raumf. Germany, November (1970), pp. 29. P-176598, S O N D E R DRUCK-100. T h e reliability of complementary M O S integrated circuits (C-MOS-circuits) is covered. T h e failure mechanisms which have been found for pchannel MOS-circuits show that the major reasons for failure are: defects in the oxide, the metallization, in bonding and in electrical overstress and poor handling. Examinations of the metallization and the bonds in C - M O S circuits made by RCA as well as Solid State Scientific show that no such difficulties have to be suspected. New input-protection circuits give sufficient protection against transient and static overvoltages. E v a l u a t i o n o f c o n d i t i o n a l f a i l u r e density from h a z a r d r a t e . S. G. Loo. IEEE Tram. Reliab. R-20, No. 2 (1971), p. 87. Further to the recent discussion regarding the concepts of hazard rate and conditional failure density, it is shown that the latter may be expressed in terms of the former. Moreover, six functions, namely, failure time distribution function, failure time density, reliability function, hazard rate, conditional failure distribution and conditional failure density, are shown to be equivalent to the extent that if one of them is known, the other five are completely determined. T h e results are summarized in a table. * F a u l t i s o l a t i o n c o m p u t e r m e t h o d s . R. F. GARzI^. Computer Sciences Corp., Huntsville, Ala., U.S.A., February 0971), pp. 161. P-174547, NASA-CR-1758. NAS-8-18405 TR-1. T e n computer methods for fault isolation, three of them employing two different techniques, are presented. In some cases computer applicatior~ are included, with some comments on the results of them. It is felt that some of the methods could be modified and improved to make them into practical tools. Others which assume ideal situations are impractical in a real environment.
Reliability of special redundant systems considering exchange time and repair t i m e . T. ]TO and C. KAw^cucm. 1EEE Tram. Rellab. R-20, No. 1 (1971), p. 11. T h e reliability of a two-out-of-three parallel redundant system having a limited n u m b e r of standby spare units is derived when the exchange of the failed unit for a spare unit is not instantaneous, T h e reliability can be represented in the form of a failure
ABSTRACTS
ON MICROELECTRONICS
tion by linear codes, was adopted. Other techniques for automatic replacement of fault units are also considered.
*Highly reliable computing systems. B. RANDALL. Newcastle upon Tyne Univ., U.K., July (1971), pp. 43. H E L D - B Y - N L L , TR-20-NLL-8724-9. Provides an overview of some of the problems of obtaining high reliability from complex computing systems and describes several systems of interest in this regard. T h e problems of hardware and software reliability and of designing a system that can continue to provide reliable service in the presence of hardware failures and software errors are discussed.
Maintainability application to system effectiveness q u a n t i f i c a t i o n . E. L. PETERSON, IEEE Tram. Relish. R-20, No. ! (1971), p. 3. A new mathematical technique has been developed in the description of approaches for maintainability applications to system effectiveness quantification. It promises to have high utility because the method itself is completely independent of the probability density function for downtime. This is particularly important where combinations of more than one malfunction are sufficiently important to warrant inclusion in the system effectiveness equation. T h e potential sensitivity of each term can be quickly estimated by referring to a table for the individual terms of the Poisson formula. This method's mathematical simplicity lends itself to hand computational techniques for small quantities of equipment. It is also easily computerized for more complicated systems. R e l i a b i l i t y c o n s i d e r a t i o n s i n design trade s t u d i e s . R. L. EXSNER. Proc. Ann. Syrup. Reliab., Washington D.C., U.S.A., IEEE Cat. No. 71C 2-R, 12-14 January (1971), p. 98. Reliability analysis is an essential input when trade studies are undertaken to select the most attractive designs for various components of a system. This analysis involves both technical and practical considerations--technical considerations related to the interfacing and interaction of components (and their failure modes), and practical considerations related to the level of detail and completeness of the analysis. This paper identifies and amplifies those considerations and provides illustrations of their implementation in trade studies on components of the nuclear engine for rocket vehicle application nuclear subsystem. D e s i g n o f adaptive procedures for fault detection and isolation. M. COliN and G. Oar. 1EEE Tram. Relish. R-20, No. 1 (1971), p. 7. An algorithm is presented for designing minimum-expected-cost test trees for detecting and isolating single faults in a system. A test is specified by the subset of components that must be good for the test to pass, and with each test is associated a fixed cost. Each component is assumed to have an a pr/ori probability of failure. T h e test tree specifies an adaptive testing procedure that detects a failure and isolates the faulty component while minimizing the expected cost of testing.
AND
RELIABILITY
115
Discrete renewal processes. M. MUNTNFJ~. IEEE Tram. Reliab. R-20, No. 2 (1971), p. 46. Discrete renewal processes until recently have not been applied to the mathematical modeling of physical processes. Analyses of such renewal processes have proceeded on the basis of generating functions but the results are often too complicated to be of use. This paper presents an alternative approach to discrete renewal theory and calculates many of the more complex statistics of such processes.
*Reliability and switching technique of integrated switching circuit with complementary M O S F E T t r a n s i s t o r s . (In German.) W. SCHAMBECK. Deutsche Forschungs-u. Versuchsamtalt Luft-u. Raumf. Germany, November (1970), pp. 29. P-176598, S O N D E R DRUCK-100. T h e reliability of complementary M O S integrated circuits (C-MOS-circuits) is covered. T h e failure mechanisms which have been found for pchannel MOS-circuits show that the major reasons for failure are: defects in the oxide, the metallization, in bonding and in electrical overstress and poor handling. Examinations of the metallization and the bonds in C - M O S circuits made by RCA as well as Solid State Scientific show that no such difficulties have to be suspected. New input-protection circuits give sufficient protection against transient and static overvoltages. E v a l u a t i o n o f c o n d i t i o n a l f a i l u r e density from h a z a r d r a t e . S. G. Loo. IEEE Tram. Reliab. R-20, No. 2 (1971), p. 87. Further to the recent discussion regarding the concepts of hazard rate and conditional failure density, it is shown that the latter may be expressed in terms of the former. Moreover, six functions, namely, failure time distribution function, failure time density, reliability function, hazard rate, conditional failure distribution and conditional failure density, are shown to be equivalent to the extent that if one of them is known, the other five are completely determined. T h e results are summarized in a table. * F a u l t i s o l a t i o n c o m p u t e r m e t h o d s . R. F. GARzI^. Computer Sciences Corp., Huntsville, Ala., U.S.A., February 0971), pp. 161. P-174547, NASA-CR-1758. NAS-8-18405 TR-1. T e n computer methods for fault isolation, three of them employing two different techniques, are presented. In some cases computer applicatior~ are included, with some comments on the results of them. It is felt that some of the methods could be modified and improved to make them into practical tools. Others which assume ideal situations are impractical in a real environment.
Reliability of special redundant systems considering exchange time and repair t i m e . T. ]TO and C. KAw^cucm. 1EEE Tram. Rellab. R-20, No. 1 (1971), p. 11. T h e reliability of a two-out-of-three parallel redundant system having a limited n u m b e r of standby spare units is derived when the exchange of the failed unit for a spare unit is not instantaneous, T h e reliability can be represented in the form of a failure