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RIW with cost sharing
World Abstracts on Microelectronics and Reliability or IMPATT diode. In particular, the present approach is especially helpful when such a device is the least reliable component in the system.
An optimal decision rule for repair vs replacement. EGINHARD J. MUTH. IEEE Trans. Reliab. R-26, (3) 179 (August 1977). This paper presents a policy for either repairing or replacing a system that has failed. The policy applies to systems whose mean residual life function is decreasing. An optimal policy is developed that minimizes the cost per unit time for repair and replacement. Results are shown graphically for a particular distribution of time to failure and are motivated in terms of an automobile replacement problem. Optimal selection of sequential tests for reliability. J. M. MOGG. IEEE Trans. Reliab. R-26, (2) 116 (June 1977). Reliability test requirements exist whereby truncated sequential test methods offer management the opportunity to minimize the s-expected cost of a test by optimal selection of the blend of resources that will be consumed by the test. The models presented here are useful in the real world design of reliability tests because of the case of arriving at cost estimates and the existing availability of statistical distributional information on truncated sequential tests. The test parameters of sample size, number of spares, and duration of the test are amenable to optimization for reduction in the cost of reliability acceptance testing. When the various costs associated with the test are known, and the pdf and Sf of failures and/or time to test termination are defined, then minimum s-expected test costs are achievable. Constraints and sensitivity analysis can be applied to the models to assist the managerial decision process. Allocation of test effort for minimum variance of reliability. L. DANIEL MAXIM and HARRISON D. WEED. IEEE Trans. Reliab. R-26, (2) 111 (June 1977). This paper is concerned with the problem of determining the optimal allocation of test effort among individual components of a system. Using knowledge of the relationship between component uncertainty and system uncertainty, and component and system test costs, the test allocation is determined so as to minimize the variance of an estimator of overall system reliability. The optimal allocations for a series system and a parallel system are examined as special cases. The sensitivity of the optimal allocation is examined with respect to differences in system configuration. A variance minimization method of reliability design. R. KRISHNAN IYER and T. DOWNS. IEEE Trans. Reliab. R-26, (2) 106 (June 1977). This approach to reliability design seeks to minimize the variance on system lifetime within s-expected life and economic constraints. We consider the case where the parameters of the lifetime distribution are constant and discuss the more general case where the parameters of the lifetime distribution are random variables. The design procedure is illustrated by simple numerical examples which show that for a small increase in cost an appreciable decrease in the variance of the lifetime is obtained. We have restricted our attention to active redundancy but the extension to standby redundancy is straightforward. Maximum reliability route subject to k-improvements in a directed network. S. P. BANSALand S. KUMAR. IEEE Trans. Reliab. R-26, (2) 103 (June 1977). The network consists of links and perfect nodes. Each link has several known reliability numbers associated with it; each reliability number is related to the number of improvements made on that link. The network reliability is to be maximised subject to a constraint on the sum of the number of link improvements, by finding the appropriate route through
417
the network. Dynamic programming is used to solve the problem. A numerical example illustrates the solution.
Role of assurance technologies in M-PRT evaluation. PATRICK R, ESPOSITO. Proc. IEEE Reliab. Maintainab. Syrup., Philadelphia (Jan. 18-20, 1977) p. 472. In evaluating the performance of a transportation system, several performance factors must be considered. Naturally, in this group of factors are the assurance technologies. To evaluate the performance of the M-PRT, a year of testing was initiated in October, 1975. During this year, passenger service was carried out under normal operating conditions. Of course, significant attention was devoted to assessing and evaluating system performance. Included in the evaluation factors were: safety assessment spares usage O & M costs and, of course, the assurance technologies: reliability availability dependability maintainability. This paper deals with the assurance factors applied to the M-PRT. And, in particular, it discusses the application of assurance technologies to a case study of an advance transportation system--the M-PRT. The results of the M-PRT tests will be discussed with general observations on the system and the application of the assurance technologies to transportation systems. RIW with cost sharing. ROBERT M. SPRINGER JR. Proc. IEEE Reliab. Maintainab. Syrup., Philadelphia (Jan. 18-20, 1977) p. 391. This paper considers Reliability Improvement Warranties (RIW) with cost sharing incentive pricing as an alternative to the Fixed Firm Price (FFP) method presently used for RIW. Some contractors are concerned that the F F P method of rigid pricing of RIW contracts often places maximum economic risk on contractors in conditions of cost uncertainty, and have recommended cost sharing incentives as alternative methods of pricing. This analysis indicates that, from the government's interest, traditional cost sharing with shallow share ratios may tend to dilute the contractor's motivation to improve product reliability and control costs. If, despite this apparent disadvantage, cost sharing is used, then target costs, share ratios, and cost ceilings should be selected in such a way as to retain as much contractor cost control and reliability improvement motivation as possible. From the contractor's point of view, RIW with cost sharing involves less economic risk than the F F P RIW. If the contractor is relatively confident of the reliability of his product, either F F P or cost sharing may be desirable for him, depending on his degree of confidence. If the contractor is not confident of pre-production reliability estimates, neither method is desirable since at very low hours mean time between failure (MTBF) the contractor's costs increase exponentially. Combined environment reliability test (CERT). ALAN H. BURKHARD. Proc. IEEE Reliab. Maintainab. Syrup., Philadelphia (Jan. 18-20, 1977) p. 460. This paper outlines the basic philosophy and assumptions that have been used to formulate the environmental test conditions used in the initial test programs conducted to evaluate the merits of the combined environment reliability test (CERT) concept. General observations based upon the results of these initial tests are presented. Impact of the frequency of technician visits on facility failure rate. H. GILBERT MILLER and R. BRAFF. IEEE Trans. Reliab. R-26, (4) 245 (October 1977). A 3-state Markovchain model has been developed to analyze the relationship between the failure rate and the technician visitation
An optimal decision rule for repair vs replacement. EGINHARD J. MUTH. IEEE Trans. Reliab. R-26, (3) 179 (August 1977). This paper presents a policy for either repairing or replacing a system that has failed. The policy applies to systems whose mean residual life function is decreasing. An optimal policy is developed that minimizes the cost per unit time for repair and replacement. Results are shown graphically for a particular distribution of time to failure and are motivated in terms of an automobile replacement problem. Optimal selection of sequential tests for reliability. J. M. MOGG. IEEE Trans. Reliab. R-26, (2) 116 (June 1977). Reliability test requirements exist whereby truncated sequential test methods offer management the opportunity to minimize the s-expected cost of a test by optimal selection of the blend of resources that will be consumed by the test. The models presented here are useful in the real world design of reliability tests because of the case of arriving at cost estimates and the existing availability of statistical distributional information on truncated sequential tests. The test parameters of sample size, number of spares, and duration of the test are amenable to optimization for reduction in the cost of reliability acceptance testing. When the various costs associated with the test are known, and the pdf and Sf of failures and/or time to test termination are defined, then minimum s-expected test costs are achievable. Constraints and sensitivity analysis can be applied to the models to assist the managerial decision process. Allocation of test effort for minimum variance of reliability. L. DANIEL MAXIM and HARRISON D. WEED. IEEE Trans. Reliab. R-26, (2) 111 (June 1977). This paper is concerned with the problem of determining the optimal allocation of test effort among individual components of a system. Using knowledge of the relationship between component uncertainty and system uncertainty, and component and system test costs, the test allocation is determined so as to minimize the variance of an estimator of overall system reliability. The optimal allocations for a series system and a parallel system are examined as special cases. The sensitivity of the optimal allocation is examined with respect to differences in system configuration. A variance minimization method of reliability design. R. KRISHNAN IYER and T. DOWNS. IEEE Trans. Reliab. R-26, (2) 106 (June 1977). This approach to reliability design seeks to minimize the variance on system lifetime within s-expected life and economic constraints. We consider the case where the parameters of the lifetime distribution are constant and discuss the more general case where the parameters of the lifetime distribution are random variables. The design procedure is illustrated by simple numerical examples which show that for a small increase in cost an appreciable decrease in the variance of the lifetime is obtained. We have restricted our attention to active redundancy but the extension to standby redundancy is straightforward. Maximum reliability route subject to k-improvements in a directed network. S. P. BANSALand S. KUMAR. IEEE Trans. Reliab. R-26, (2) 103 (June 1977). The network consists of links and perfect nodes. Each link has several known reliability numbers associated with it; each reliability number is related to the number of improvements made on that link. The network reliability is to be maximised subject to a constraint on the sum of the number of link improvements, by finding the appropriate route through
417
the network. Dynamic programming is used to solve the problem. A numerical example illustrates the solution.
Role of assurance technologies in M-PRT evaluation. PATRICK R, ESPOSITO. Proc. IEEE Reliab. Maintainab. Syrup., Philadelphia (Jan. 18-20, 1977) p. 472. In evaluating the performance of a transportation system, several performance factors must be considered. Naturally, in this group of factors are the assurance technologies. To evaluate the performance of the M-PRT, a year of testing was initiated in October, 1975. During this year, passenger service was carried out under normal operating conditions. Of course, significant attention was devoted to assessing and evaluating system performance. Included in the evaluation factors were: safety assessment spares usage O & M costs and, of course, the assurance technologies: reliability availability dependability maintainability. This paper deals with the assurance factors applied to the M-PRT. And, in particular, it discusses the application of assurance technologies to a case study of an advance transportation system--the M-PRT. The results of the M-PRT tests will be discussed with general observations on the system and the application of the assurance technologies to transportation systems. RIW with cost sharing. ROBERT M. SPRINGER JR. Proc. IEEE Reliab. Maintainab. Syrup., Philadelphia (Jan. 18-20, 1977) p. 391. This paper considers Reliability Improvement Warranties (RIW) with cost sharing incentive pricing as an alternative to the Fixed Firm Price (FFP) method presently used for RIW. Some contractors are concerned that the F F P method of rigid pricing of RIW contracts often places maximum economic risk on contractors in conditions of cost uncertainty, and have recommended cost sharing incentives as alternative methods of pricing. This analysis indicates that, from the government's interest, traditional cost sharing with shallow share ratios may tend to dilute the contractor's motivation to improve product reliability and control costs. If, despite this apparent disadvantage, cost sharing is used, then target costs, share ratios, and cost ceilings should be selected in such a way as to retain as much contractor cost control and reliability improvement motivation as possible. From the contractor's point of view, RIW with cost sharing involves less economic risk than the F F P RIW. If the contractor is relatively confident of the reliability of his product, either F F P or cost sharing may be desirable for him, depending on his degree of confidence. If the contractor is not confident of pre-production reliability estimates, neither method is desirable since at very low hours mean time between failure (MTBF) the contractor's costs increase exponentially. Combined environment reliability test (CERT). ALAN H. BURKHARD. Proc. IEEE Reliab. Maintainab. Syrup., Philadelphia (Jan. 18-20, 1977) p. 460. This paper outlines the basic philosophy and assumptions that have been used to formulate the environmental test conditions used in the initial test programs conducted to evaluate the merits of the combined environment reliability test (CERT) concept. General observations based upon the results of these initial tests are presented. Impact of the frequency of technician visits on facility failure rate. H. GILBERT MILLER and R. BRAFF. IEEE Trans. Reliab. R-26, (4) 245 (October 1977). A 3-state Markovchain model has been developed to analyze the relationship between the failure rate and the technician visitation