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A truncated sequential test for constant failure rate
340
World Abstracts on Microelectronics and Reliability
second. The method combines radiation shielding techniques with three sequential tests using krypton-85. The test program has succeeded in detecting a significant number of leaky components on electronic boards for a high reliability space application.
A failure analysis technique for locating the fail site in MOSFET (LSI) logic chips with sputtered SIO2 passivation. A. A. VIELE. Proc. IEEE Reliability Physics Symposium. April 2-4, 1974. p. 16. This paper describes a technique used successfully to locate the fail site in MOSFET (LSI) Logic Chips. It is used to analyze modules or chips which fail functionally during electrical test. Signal tracing is employed to locate the fail site while dynamically exercising the chip. This technique emphasizes the analysis of AC fails (timing problems) and chips with sputtered SiO2 (Quartz) passivation. A new approach to fault locating T1 repeatered lines. S. GHOSH. Telecommunications. November 1974. p. 39. Since the introduction of digital transmission of voice signals in the early 1960's, the D/T1 digital carrier system has grown to be the most widely used exchange area carrier system in the national telephone network. The T1 line has always been regarded as the weakest link in the whole system, primarily because it is part of the outside plant sometimes stretching over many miles of open countryside. Therefore, the engineering practice for maintenance of T1 line has been directed towards providing facilities that permit easy and quick identification of a faulty repeater or line section from the central office.
Graph representation and diagnosis for multiunit faults. H. NAKANO and Y. NAKANISHI. IEEE Trans. Reliab. R-23, 320 (1974). A method using graph theory is proposed for the detection and the location of a multiunit fault in a system. The method requires only a slight increase in the number of internal monitoring terminals over the number required for the l-unit fault diagnosis. A graph representation of a system initially leads to a rectangular diagnostic matrix. An algorithm is developed for constructing a square reachability matrix from the diagnostic matrix. A graph derived from the reachability matrix permits diagnosis of multiunit faults.
A truncated sequential test for constant failure rate. A. SALVIA and R. SUICH. IEEE Trans. Reliab. R-24, 77 (1975). This paper presents a truncated sequential procedure for testing if the failure rate of a device is constant versus a linearly increasing failure rate. A number of items, N, are placed on test and their failure times are recorded sequentially. After each observation one decides either to accept or reject a constant failure rate or to wait for another observation. Simulation under various parametric conditions yields information on the initial choice of N, average sample sizes, and points on the OC curve. Selection of the various parametric conditions is discussed. An example illustrates the use of the test.
Appro~fimately optimum confidence bounds on seriesand parullel-system reliability for systems with binomial subsystem data. N. R. MANN. IEEE Trans. Reliab. R-23, 295 (1974). A method is derived for obtaining either randomized or nonrandomized lower confidence bounds on the reliability of independent series or parallel systems when subsystem data are binomially distributed. Both types of confidence bounds agree with published values of optimum confidence bounds to within about a unit in the second significant figure. In using the method derived for obtaining nonrandomized confidence bounds there is no difficulty with the number of subsystems in the system or of a requirement of equal sample sizes, as with the
standard method of obtaining the optimum bounds. Existence of subsystems for which no failures are observed also presents no difficulty, in contrast to the maximumlikelihood and likelihood ratio approximations. Numerical comparisons are made between optimum confidence bounds and those based on other approximating methods.
Numerical solution and inference for interval-reliability of repairable components. R. L. RACICOT. IEEE Trans. Reliab. R-24, 57 (1975). The renewal and intervalreliability functions for repairable components are solved for given general probability distribution of renewal interarrival times. Two powerful numerical methods are (1) A finite difference approach wherein the renewal equation is written in discrete form and then the resulting system of algebraic equations is solved recursively. (2) Transforms of the renewal equation are treated and Fourier series expansions are used. The Fourier series approach has a wider range of applicability than finite difference in that it can be used to solve the complete renewal problem. A new equivalent form of the interval-reliability integral equation leads to a computationally faster scheme (by a factor of 10) and a simplified approximate solution for high reliability components. A numerical solution for confidence intervals has also been generated for the average interval-reliability of a component within a system, given component failure data, using a pseudoBayesian approach. The goal is to choose priors that lead to classical limits and not the usual Bayesian limits. The intervals yield close-to-exact frequency limits depending on sample size, Weibull shape parameter and the true reliability.
Determination of reliability using event-based Monte Carlo simulation. S. J. KAMAT and M. W. RILEY. IEEE Trans. Reliab. R-24, 73 (1975). The reliability of a system can be found analytically, given the time-to-failure distribution for each element and the system configuration. Such analysis becomes increasingly difficult as the complexity of a system increases. This paper presents a Monte Carlo simulation procedure to estimate the reliability of a complex system with relative ease. A computer program, written in FORTRAN IV G Level code for an IBM 360/65 computer, finds all minimal tie-sets from the system configuration, which is provided as a coded reliability flow graph. Each replication in the simulation involves a search through the minimal tie-sets to identify the success or failure of the system for each value of the required time of satisfactory performance. The reliability of the system is then estimated as a tabulated function of time.
Availability models ot maintained systems. F. A. TILLMAN and S. CHATTERJEE. IEEE Trans. Reliab. R-24, 69 (1975). The concept of availability includes reliability as well as preventive and corrective maintenance. An availability model which includes both aspects of this problem is proposed in this paper. The model includes the following decision variables: 1. failure rates and repair rates of individual units 2. the time period for perfect-preventive maintenance for a given mission time 3. the optimal failure and repair rates as a function of design costs, corrective and preventive maintenance costs. The objective is to minimize the design and operating costs where the availability requirements are satisfied. An example is solved for a system with n subsystems in series where two units in parallel comprise each subsystem. The general approach is applicable to solving other complex availability problems.
World Abstracts on Microelectronics and Reliability
second. The method combines radiation shielding techniques with three sequential tests using krypton-85. The test program has succeeded in detecting a significant number of leaky components on electronic boards for a high reliability space application.
A failure analysis technique for locating the fail site in MOSFET (LSI) logic chips with sputtered SIO2 passivation. A. A. VIELE. Proc. IEEE Reliability Physics Symposium. April 2-4, 1974. p. 16. This paper describes a technique used successfully to locate the fail site in MOSFET (LSI) Logic Chips. It is used to analyze modules or chips which fail functionally during electrical test. Signal tracing is employed to locate the fail site while dynamically exercising the chip. This technique emphasizes the analysis of AC fails (timing problems) and chips with sputtered SiO2 (Quartz) passivation. A new approach to fault locating T1 repeatered lines. S. GHOSH. Telecommunications. November 1974. p. 39. Since the introduction of digital transmission of voice signals in the early 1960's, the D/T1 digital carrier system has grown to be the most widely used exchange area carrier system in the national telephone network. The T1 line has always been regarded as the weakest link in the whole system, primarily because it is part of the outside plant sometimes stretching over many miles of open countryside. Therefore, the engineering practice for maintenance of T1 line has been directed towards providing facilities that permit easy and quick identification of a faulty repeater or line section from the central office.
Graph representation and diagnosis for multiunit faults. H. NAKANO and Y. NAKANISHI. IEEE Trans. Reliab. R-23, 320 (1974). A method using graph theory is proposed for the detection and the location of a multiunit fault in a system. The method requires only a slight increase in the number of internal monitoring terminals over the number required for the l-unit fault diagnosis. A graph representation of a system initially leads to a rectangular diagnostic matrix. An algorithm is developed for constructing a square reachability matrix from the diagnostic matrix. A graph derived from the reachability matrix permits diagnosis of multiunit faults.
A truncated sequential test for constant failure rate. A. SALVIA and R. SUICH. IEEE Trans. Reliab. R-24, 77 (1975). This paper presents a truncated sequential procedure for testing if the failure rate of a device is constant versus a linearly increasing failure rate. A number of items, N, are placed on test and their failure times are recorded sequentially. After each observation one decides either to accept or reject a constant failure rate or to wait for another observation. Simulation under various parametric conditions yields information on the initial choice of N, average sample sizes, and points on the OC curve. Selection of the various parametric conditions is discussed. An example illustrates the use of the test.
Appro~fimately optimum confidence bounds on seriesand parullel-system reliability for systems with binomial subsystem data. N. R. MANN. IEEE Trans. Reliab. R-23, 295 (1974). A method is derived for obtaining either randomized or nonrandomized lower confidence bounds on the reliability of independent series or parallel systems when subsystem data are binomially distributed. Both types of confidence bounds agree with published values of optimum confidence bounds to within about a unit in the second significant figure. In using the method derived for obtaining nonrandomized confidence bounds there is no difficulty with the number of subsystems in the system or of a requirement of equal sample sizes, as with the
standard method of obtaining the optimum bounds. Existence of subsystems for which no failures are observed also presents no difficulty, in contrast to the maximumlikelihood and likelihood ratio approximations. Numerical comparisons are made between optimum confidence bounds and those based on other approximating methods.
Numerical solution and inference for interval-reliability of repairable components. R. L. RACICOT. IEEE Trans. Reliab. R-24, 57 (1975). The renewal and intervalreliability functions for repairable components are solved for given general probability distribution of renewal interarrival times. Two powerful numerical methods are (1) A finite difference approach wherein the renewal equation is written in discrete form and then the resulting system of algebraic equations is solved recursively. (2) Transforms of the renewal equation are treated and Fourier series expansions are used. The Fourier series approach has a wider range of applicability than finite difference in that it can be used to solve the complete renewal problem. A new equivalent form of the interval-reliability integral equation leads to a computationally faster scheme (by a factor of 10) and a simplified approximate solution for high reliability components. A numerical solution for confidence intervals has also been generated for the average interval-reliability of a component within a system, given component failure data, using a pseudoBayesian approach. The goal is to choose priors that lead to classical limits and not the usual Bayesian limits. The intervals yield close-to-exact frequency limits depending on sample size, Weibull shape parameter and the true reliability.
Determination of reliability using event-based Monte Carlo simulation. S. J. KAMAT and M. W. RILEY. IEEE Trans. Reliab. R-24, 73 (1975). The reliability of a system can be found analytically, given the time-to-failure distribution for each element and the system configuration. Such analysis becomes increasingly difficult as the complexity of a system increases. This paper presents a Monte Carlo simulation procedure to estimate the reliability of a complex system with relative ease. A computer program, written in FORTRAN IV G Level code for an IBM 360/65 computer, finds all minimal tie-sets from the system configuration, which is provided as a coded reliability flow graph. Each replication in the simulation involves a search through the minimal tie-sets to identify the success or failure of the system for each value of the required time of satisfactory performance. The reliability of the system is then estimated as a tabulated function of time.
Availability models ot maintained systems. F. A. TILLMAN and S. CHATTERJEE. IEEE Trans. Reliab. R-24, 69 (1975). The concept of availability includes reliability as well as preventive and corrective maintenance. An availability model which includes both aspects of this problem is proposed in this paper. The model includes the following decision variables: 1. failure rates and repair rates of individual units 2. the time period for perfect-preventive maintenance for a given mission time 3. the optimal failure and repair rates as a function of design costs, corrective and preventive maintenance costs. The objective is to minimize the design and operating costs where the availability requirements are satisfied. An example is solved for a system with n subsystems in series where two units in parallel comprise each subsystem. The general approach is applicable to solving other complex availability problems.