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New practical Bayes estimators for the 2-parameter Weibull distribution
592
World Abstracts on MIcroelectronlcs and Reliability
creasmg uncertainty in dewce parameters, smaller device dimensions, greater number of devices per chip, larger number of bits per parity check, and with smaller allowed ranges of tolerable device behavior A methodology for photovoltalc system reliabihty and economic analysis. L H STEMBER, W R Huss and M S BRIDGMAN IE E E Trans Rehab R-31 (3), 296 (1982) This paper describes the approach and progress on a 1981 study of photovoltalc (PVl system reliability being conducted by Battelle Columbus for Sandla Laboratories as part of DOE's PV Systems Definition Project Initially, the study is concerned with the functional modehng of rehablhty and maintenance of a PV system We begin with relatively general, but simple, system level reliability models that can be expanded to more detailed, lower-level forms as Input data justify Corrective maintenance is Included to permJt estimates of system avallablhty The output of these models wdl be coupled with life-cycle energy cost models and apphed to PV system designs
the probablhstlc domain and, for complex systems, ts lengthy An alternative method Is to consider the component reliability parameters to be Boolean variables rather than probablhstlc variables and to treat the whole problem as If it were Boolean This has the advantage of allowing the use of powerful Boolean reduction theorems to contain the size of the problem Unfortunately, much of this advantage is lost ,ahen conversion back into the probablhstlc domain takes place This paper presents a techmque for overcoming this disadvantage, the technique is based on analyzing and modifying the Boolean expression prior to the conversion process The technique was originally developed as an aid to faulttree analysis but it applies to general problems of reliability assessment 1 claim no orlglnallt) for the procedure The motivation to write the paper is quite simple the procedure is not as well-known as it should be either amongst practising rehablhty engineers or amongst those who teach the subject The purpose of the paper is therefore tutorial
Expected number of failures caused by protective systems Rehabilit)-related inferences for a Gamma distribution RONALD E GLASER I E E E Trans Rehab R-3112), 198 (1982) The following inferences are obtained, based on a complete random sample from a gamma distribution with unknov, n shape and scale parameters a median unbiased point estimator, and optimum s-confidence bounds and Intervals, for the shape parameter, the uniformly minimum variance unbiased estimator, and a conservative lower ~confidence bound, for rehablhty Illustrative computations and comparisons with competing techniques are presented
Redundant microcomputer-controlled 3-stage Clos network for system-availability enhancement. HSIEN-Lu HUANG I E E E Tran,s Rehab R-31(2l, 182 (1982) This paper analyzes a redundant microcomputer-controlled 3-stage Clos network to enhance system avadablhty Lower bound of number of Middle Switch Segments is established for the existence of one backup path to support each prlmar5 path which connects each pair of input/output ports to the switch network This lower bound also satisfies the strictly nonblocking condition established by Marcus In 1977 The paper proves that a full-loaded network with single loads IS the worst case for availability analysis Upper bounds on the number of 1,0 ports are established for networks of se',eral SV,ltch-card designs to enhance availability An availability model for redundant microcomputer-controlled network is presented with numerical results The approach Js unique and new
New practical Bayes estimators for the 2-parameter Weibull distribution. PASQUALE ERTO I E E E Trans Rehab R-31 (2), 194 (1982) New Bayes estimators for the 2-parameter Welbull model are proposed when both parameters are unknown In many life testing situations there IS pr,or lnformanon whmh can be reasonably quantified in terms of (1~ range of the shape parameter, and (2) anticipated value of a quantlle (reliable life) of the sampling distribution This paper directly incorporates such information into the estimation process, using a new (not completely specified) prior distribution Since analytic tractablhty is not possible, the estimates are obtained with easy numerical integration A Monte Carlo slmulatmn (carried out each time on 1000 samples and also using very poor priors) has shown that these estimators are quite ,s-unbiased and s-efficient for a large range of parameter values of poor priors
Analysis of reliability block diagrams by Boolean techniques. R G BENNFTTS IE EE Trans Rehab R-31 (2), 159 (1982) A rehablhty block diagram for complex systems is often analyzed by applying the series/parallel product laws or, where this is not possible, by using a conditional probability result lBayes theoreml In both cases the analysis is conducted m
HIROMITSU KUMAMOTO, HIROTOSHI OHTSUKA and KOICHI INOUE I E E E Ttans Rehab R-31 (2), 219 11982) s-Expected numbers of normal trips, spurious trips, and hazards are useful figures of merit for design of protective systems This paper presents formulae for these figures of merit for l-outof-I G, l-out-of-2 G, and 2-out-of-2 G configurations of the protective system with scheduled and unscheduled maintenance
Apphcation and use of acceleration factors in mtcroelectronlcs testing. DAN EPSTEIN Sohd St Technol, 116 (November 1982~ Two aspects of acceleration factors in mlcroelectromcs testing are discussed The first aspect deals with the apphcation and use of acceleration factors The second deals with the ease of developing tables of acceleration factors for any activation energy and temperature test condition by means of the personal computer There are numerous applications of acceleration factors and the user is cautioned to consider their advantages as well as their disadvantages Each use must be carefully evaluated to ensure that the proper test situation is achieved, otherwise erroneous failure modes may be induced or observed
Estimation under reliability growth assuming Gamma fadure models W J PADGETT and D T McNICHOLS I E E E Tlan~ Rehab R-31 (2), 155 (1982) Engineers often make changes during the development of a system in order to correct design weaknesses If done well, this results in rehabihty growth (an increase in rehablhty and mean hfe) as development contmues The hfetlme distribution at each stage in development is assumed to be gamma Approximate maximum likelihood estimates (MLEs) of the parameters are obtained subject to the conditions that no parameter decreases In the next stage An lteratlve procedure involving two constrained nonlinear optimization problems is proposed for obtaining the approximate MLEs The constrained optimization problems can be computed using isotonic regression, the iterations converge rather quickly The computations can be performed using common mathematical subroutine packages such as the International Mathematical and Statlstmal Libraries
A simple technique for computing network reliability. S HASANUDDIN AHMAD IEEE Trans Rehab R-31 (1), 41 11982) A tree construction techmque to compute a reliability expression of a netx~ork is derived The technique is straight forward and good for both directed and undirected graphs It gives mutually disjoint success brunches The reliability expression of each branch can be directly written by a set of rules The rehablhty of the network can then be obtained by taking the direct sum of the rehablhtIes of the branches It involves fewer multiplications than other knov, n techniques
World Abstracts on MIcroelectronlcs and Reliability
creasmg uncertainty in dewce parameters, smaller device dimensions, greater number of devices per chip, larger number of bits per parity check, and with smaller allowed ranges of tolerable device behavior A methodology for photovoltalc system reliabihty and economic analysis. L H STEMBER, W R Huss and M S BRIDGMAN IE E E Trans Rehab R-31 (3), 296 (1982) This paper describes the approach and progress on a 1981 study of photovoltalc (PVl system reliability being conducted by Battelle Columbus for Sandla Laboratories as part of DOE's PV Systems Definition Project Initially, the study is concerned with the functional modehng of rehablhty and maintenance of a PV system We begin with relatively general, but simple, system level reliability models that can be expanded to more detailed, lower-level forms as Input data justify Corrective maintenance is Included to permJt estimates of system avallablhty The output of these models wdl be coupled with life-cycle energy cost models and apphed to PV system designs
the probablhstlc domain and, for complex systems, ts lengthy An alternative method Is to consider the component reliability parameters to be Boolean variables rather than probablhstlc variables and to treat the whole problem as If it were Boolean This has the advantage of allowing the use of powerful Boolean reduction theorems to contain the size of the problem Unfortunately, much of this advantage is lost ,ahen conversion back into the probablhstlc domain takes place This paper presents a techmque for overcoming this disadvantage, the technique is based on analyzing and modifying the Boolean expression prior to the conversion process The technique was originally developed as an aid to faulttree analysis but it applies to general problems of reliability assessment 1 claim no orlglnallt) for the procedure The motivation to write the paper is quite simple the procedure is not as well-known as it should be either amongst practising rehablhty engineers or amongst those who teach the subject The purpose of the paper is therefore tutorial
Expected number of failures caused by protective systems Rehabilit)-related inferences for a Gamma distribution RONALD E GLASER I E E E Trans Rehab R-3112), 198 (1982) The following inferences are obtained, based on a complete random sample from a gamma distribution with unknov, n shape and scale parameters a median unbiased point estimator, and optimum s-confidence bounds and Intervals, for the shape parameter, the uniformly minimum variance unbiased estimator, and a conservative lower ~confidence bound, for rehablhty Illustrative computations and comparisons with competing techniques are presented
Redundant microcomputer-controlled 3-stage Clos network for system-availability enhancement. HSIEN-Lu HUANG I E E E Tran,s Rehab R-31(2l, 182 (1982) This paper analyzes a redundant microcomputer-controlled 3-stage Clos network to enhance system avadablhty Lower bound of number of Middle Switch Segments is established for the existence of one backup path to support each prlmar5 path which connects each pair of input/output ports to the switch network This lower bound also satisfies the strictly nonblocking condition established by Marcus In 1977 The paper proves that a full-loaded network with single loads IS the worst case for availability analysis Upper bounds on the number of 1,0 ports are established for networks of se',eral SV,ltch-card designs to enhance availability An availability model for redundant microcomputer-controlled network is presented with numerical results The approach Js unique and new
New practical Bayes estimators for the 2-parameter Weibull distribution. PASQUALE ERTO I E E E Trans Rehab R-31 (2), 194 (1982) New Bayes estimators for the 2-parameter Welbull model are proposed when both parameters are unknown In many life testing situations there IS pr,or lnformanon whmh can be reasonably quantified in terms of (1~ range of the shape parameter, and (2) anticipated value of a quantlle (reliable life) of the sampling distribution This paper directly incorporates such information into the estimation process, using a new (not completely specified) prior distribution Since analytic tractablhty is not possible, the estimates are obtained with easy numerical integration A Monte Carlo slmulatmn (carried out each time on 1000 samples and also using very poor priors) has shown that these estimators are quite ,s-unbiased and s-efficient for a large range of parameter values of poor priors
Analysis of reliability block diagrams by Boolean techniques. R G BENNFTTS IE EE Trans Rehab R-31 (2), 159 (1982) A rehablhty block diagram for complex systems is often analyzed by applying the series/parallel product laws or, where this is not possible, by using a conditional probability result lBayes theoreml In both cases the analysis is conducted m
HIROMITSU KUMAMOTO, HIROTOSHI OHTSUKA and KOICHI INOUE I E E E Ttans Rehab R-31 (2), 219 11982) s-Expected numbers of normal trips, spurious trips, and hazards are useful figures of merit for design of protective systems This paper presents formulae for these figures of merit for l-outof-I G, l-out-of-2 G, and 2-out-of-2 G configurations of the protective system with scheduled and unscheduled maintenance
Apphcation and use of acceleration factors in mtcroelectronlcs testing. DAN EPSTEIN Sohd St Technol, 116 (November 1982~ Two aspects of acceleration factors in mlcroelectromcs testing are discussed The first aspect deals with the apphcation and use of acceleration factors The second deals with the ease of developing tables of acceleration factors for any activation energy and temperature test condition by means of the personal computer There are numerous applications of acceleration factors and the user is cautioned to consider their advantages as well as their disadvantages Each use must be carefully evaluated to ensure that the proper test situation is achieved, otherwise erroneous failure modes may be induced or observed
Estimation under reliability growth assuming Gamma fadure models W J PADGETT and D T McNICHOLS I E E E Tlan~ Rehab R-31 (2), 155 (1982) Engineers often make changes during the development of a system in order to correct design weaknesses If done well, this results in rehabihty growth (an increase in rehablhty and mean hfe) as development contmues The hfetlme distribution at each stage in development is assumed to be gamma Approximate maximum likelihood estimates (MLEs) of the parameters are obtained subject to the conditions that no parameter decreases In the next stage An lteratlve procedure involving two constrained nonlinear optimization problems is proposed for obtaining the approximate MLEs The constrained optimization problems can be computed using isotonic regression, the iterations converge rather quickly The computations can be performed using common mathematical subroutine packages such as the International Mathematical and Statlstmal Libraries
A simple technique for computing network reliability. S HASANUDDIN AHMAD IEEE Trans Rehab R-31 (1), 41 11982) A tree construction techmque to compute a reliability expression of a netx~ork is derived The technique is straight forward and good for both directed and undirected graphs It gives mutually disjoint success brunches The reliability expression of each branch can be directly written by a set of rules The rehablhty of the network can then be obtained by taking the direct sum of the rehablhtIes of the branches It involves fewer multiplications than other knov, n techniques