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Failure prediction from interval data
306
WORLD
ABSTRACTS
ON MICROELECTRONICS
the tasks, showing how all the information for the myriad of subsystems, equipments, assemblies, and the like must be organized at the system level to provide the proper measures of system effectiveness. The tasks involved in the reliability assessment were: (1) collecting reliability data on subsystems from all available sources; (2) analyzing subsystem reliability data.
Reliability considerations in STD development. J. P. DIETZ, Proc. IEEE Reliab. Phys. Syrup., Las Vegas, U.S.A. 31 March-5 April (1971). S T D is a hybrid circuit building technique developed at the General Electric Company in which integrated circuit devices are surrounded in a thermo-plastic material and connections are made to the devices by deposited metal layers on the plastic. Some of the factors which could affect the reliability will be described and results of testing for these will be discussed.
Reliability approach to ship systems. G. W. ABSHER, JR., Proc. Ann. Symp. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C 2-R. 12-14 January (1971), p. 194. Reliability analysis procedures, when used by the ship design contractor as system engineering and subsystem design "tools", play two important roles in ship system design: (1) they, of course, "force" the design into an acceptable configuration from the standpoint of reliability conformance; and (2) more important, they provide the needed systematic basis and formalized methods for uniform consideration of all other aspects of the system design problem--including mission effectiveness, life cycle cost, producibility and logistics supportability. This paper summarizes the experience of several Navy and industrial ship system design activities in the use of reliability engineering procedures and analytical techniques as the primary basis for the system engineering approach to total ship system design.
A design procedure for discard VS repair decisions. J. BRUNO, Proc. Ann. Symp. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C 2-R. 12-14 January (1971), p. 278. This paper presents a simplified procedure using parameters which the designer can readily estimate to determine whether to design a module for discard or repair. Further, the procedure provides the designer with a method of determining the number of modules into which a unit must be partitioned to result in a cost effective throwaway design.
On simplifying mission reliability calculations. R. A. KOWALSKI,Proc. Ann. Nymp. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C 2-R. 12-14 January (1971), p. 261. This paper presents a graphical technique which simplifies mission reliability calculations for systems with redundant units. It has been used in design studies for an airborne warning and control system (AWACS) and other radar control systems. The user can quickly determine how the addition or deletion of a redundant unit will affect mission reliability. The method can also be used to optimize the choice of redundant units with respect to price, weight or some other physical
AND RELIABILITY
attribute, when such data is available. A series of examples show how the technique is applied to typical active and standby redundant configurations.
Failure prediction from interval data. J. D. JOHNSON and L. T. STEWART,Proc. Ann. Symp. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C 2-R. 12-14 January (1971), p. 356. This paper describes a solution to reliability and inventory problems of the following type: (1) The individual items in a population can be inspected for failure only at irregular times. Furthermore, the inspection times often are not predetermined. When a failure is observed at the time of inspection, it is known only that the failure occurred during the time interval since the last inspection; the exact time of failure is unknown. (2) For any given future calendar date, a confidence interval prediction for the total number of items that will have failed by that date is desired.
Monolithic m a i n m e m o r y - - n e w reliability and serviceability environment. D. H. REDFIELD,W. A. SAMSand E. G. BROWN, Proc. IEEE Reliab. Phys. Symp., Las Vegas, U.S.A. 31 March-2 April (1971). A combination of error-correcting circuitry and one-bit/card organization gives increased reliability by masking intermittents and by offering a wide range of servicing strategies. The net result will be higher system availability and lower service costs.
Prediction intervals for life testing. R. G. EASTERLING and I. J. HALL,Proc. Ann. Syrup. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C 2-R. 12-14 January (1971), p. 389. In statistical literature much attention has been devoted to confidence intervals and tolerance intervals. Another type of inferential interval which has recently drawn attention is the prediction interval. Hahn has given tables for calculating limits within which one predicts with 100 "~ per cent confidence that k future observations will fall, based on a sample of size n from a normal distribution, and Hewett and Bulgren consider similar intervals in the case of a gamma distribution. Hewett also considers prediction intervals for an exponential distribution in a context for which the prediction required is for the final result of a life test based on a portion of the results. In this paper we consider how these latter intervals can be applied to acceptance sampling.
MIL-STD-781 sequential tests: t i m e to completion. B. F. KREMP and J. E. LUPO, Proc. Ann. Symp. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C2-R. 12-14 January (1971), p. 1. Military Specification M I L STD-781 contains standard test plans for reliability qualification and reliability production acceptance tests for military and aerospace equipment. These reliability tests are mostly based on the assumption of an exponential distribution of equipment time between failures and the tests are designed to provide information about the mean time between failures (MTBF) of the equipment being tested. There are 30 basic test plans described, of which 10 are probability ratio sequential tests
WORLD
ABSTRACTS
ON MICROELECTRONICS
the tasks, showing how all the information for the myriad of subsystems, equipments, assemblies, and the like must be organized at the system level to provide the proper measures of system effectiveness. The tasks involved in the reliability assessment were: (1) collecting reliability data on subsystems from all available sources; (2) analyzing subsystem reliability data.
Reliability considerations in STD development. J. P. DIETZ, Proc. IEEE Reliab. Phys. Syrup., Las Vegas, U.S.A. 31 March-5 April (1971). S T D is a hybrid circuit building technique developed at the General Electric Company in which integrated circuit devices are surrounded in a thermo-plastic material and connections are made to the devices by deposited metal layers on the plastic. Some of the factors which could affect the reliability will be described and results of testing for these will be discussed.
Reliability approach to ship systems. G. W. ABSHER, JR., Proc. Ann. Symp. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C 2-R. 12-14 January (1971), p. 194. Reliability analysis procedures, when used by the ship design contractor as system engineering and subsystem design "tools", play two important roles in ship system design: (1) they, of course, "force" the design into an acceptable configuration from the standpoint of reliability conformance; and (2) more important, they provide the needed systematic basis and formalized methods for uniform consideration of all other aspects of the system design problem--including mission effectiveness, life cycle cost, producibility and logistics supportability. This paper summarizes the experience of several Navy and industrial ship system design activities in the use of reliability engineering procedures and analytical techniques as the primary basis for the system engineering approach to total ship system design.
A design procedure for discard VS repair decisions. J. BRUNO, Proc. Ann. Symp. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C 2-R. 12-14 January (1971), p. 278. This paper presents a simplified procedure using parameters which the designer can readily estimate to determine whether to design a module for discard or repair. Further, the procedure provides the designer with a method of determining the number of modules into which a unit must be partitioned to result in a cost effective throwaway design.
On simplifying mission reliability calculations. R. A. KOWALSKI,Proc. Ann. Nymp. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C 2-R. 12-14 January (1971), p. 261. This paper presents a graphical technique which simplifies mission reliability calculations for systems with redundant units. It has been used in design studies for an airborne warning and control system (AWACS) and other radar control systems. The user can quickly determine how the addition or deletion of a redundant unit will affect mission reliability. The method can also be used to optimize the choice of redundant units with respect to price, weight or some other physical
AND RELIABILITY
attribute, when such data is available. A series of examples show how the technique is applied to typical active and standby redundant configurations.
Failure prediction from interval data. J. D. JOHNSON and L. T. STEWART,Proc. Ann. Symp. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C 2-R. 12-14 January (1971), p. 356. This paper describes a solution to reliability and inventory problems of the following type: (1) The individual items in a population can be inspected for failure only at irregular times. Furthermore, the inspection times often are not predetermined. When a failure is observed at the time of inspection, it is known only that the failure occurred during the time interval since the last inspection; the exact time of failure is unknown. (2) For any given future calendar date, a confidence interval prediction for the total number of items that will have failed by that date is desired.
Monolithic m a i n m e m o r y - - n e w reliability and serviceability environment. D. H. REDFIELD,W. A. SAMSand E. G. BROWN, Proc. IEEE Reliab. Phys. Symp., Las Vegas, U.S.A. 31 March-2 April (1971). A combination of error-correcting circuitry and one-bit/card organization gives increased reliability by masking intermittents and by offering a wide range of servicing strategies. The net result will be higher system availability and lower service costs.
Prediction intervals for life testing. R. G. EASTERLING and I. J. HALL,Proc. Ann. Syrup. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C 2-R. 12-14 January (1971), p. 389. In statistical literature much attention has been devoted to confidence intervals and tolerance intervals. Another type of inferential interval which has recently drawn attention is the prediction interval. Hahn has given tables for calculating limits within which one predicts with 100 "~ per cent confidence that k future observations will fall, based on a sample of size n from a normal distribution, and Hewett and Bulgren consider similar intervals in the case of a gamma distribution. Hewett also considers prediction intervals for an exponential distribution in a context for which the prediction required is for the final result of a life test based on a portion of the results. In this paper we consider how these latter intervals can be applied to acceptance sampling.
MIL-STD-781 sequential tests: t i m e to completion. B. F. KREMP and J. E. LUPO, Proc. Ann. Symp. Reliab., Washington DC, U.S.A. IEEE Cat. No. 71C2-R. 12-14 January (1971), p. 1. Military Specification M I L STD-781 contains standard test plans for reliability qualification and reliability production acceptance tests for military and aerospace equipment. These reliability tests are mostly based on the assumption of an exponential distribution of equipment time between failures and the tests are designed to provide information about the mean time between failures (MTBF) of the equipment being tested. There are 30 basic test plans described, of which 10 are probability ratio sequential tests