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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean society for quality management
Journal Basic Information
Journal DOI :
The Korean Society for Quality Management
Editor in Chief :
Volume & Issues
Volume 25, Issue 4 - Dec 1997
Volume 25, Issue 3 - Sep 1997
Volume 25, Issue 2 - Jun 1997
Volume 25, Issue 1 - Mar 1997
Selecting the target year
Conditional Confidence Intervals for Accelerated Life Testing in Modified Arrhenius Model
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 1~10
In the context of accelerated life tests, procedures are given for estimating the parameters in the modified Arrhenius model and for estimating mean life at a given future stress level. The conditional confidence intervals are obtained by conditioning on ancillary statistics and pivotal quantity. Using the data of Tobias and Trindada(1986), we illustrate conditional confidence interval for parameters under use condition in the modified Arrhenius model.
A Study on the Test of Mean Residual Life with Random Censored Sample
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 11~21
The mean residual life(MRL) function gives the expected remaining life of a item at age t. In particular F is said to be an increasing intially then decreasing MRL(IDMRL) distribution if there exists a turing point
such that m(s)
m(t) for 0
t. If the preceding inequality is reversed, F is said to be a decreasing initially then increasing MRL(DIMRL) distribution. Hawkins, et al.(1992) proposed test of H0 : F is exponential versus
: F is IDMRL, and
' : F is DIMRL when turning point is unknown. Their test is based on a complete random sample
from F. In this paper, we generalized Hawkins-Kochar-Loader test to random censored data.
Stochastically Dependent Sequential Acceptance Sampling Plans
Kim, Won-Kyung ;
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 22~38
In a traditional sequential acceptance sampling plan, it is assumed that the sampled items are independent each other. In this paper, stochastically dependent sequential acceptance sampling plans are dealt when there exists dependency between sampled items. Monte-Calro algorithm is used to find the acceptance and rejection probabilities of a lot. The number of defectives for the test to be accepted and rejected in probability ratio sequential test can be found by using these probabilities. The formula for measures of performance of these sampling plans is developed. Type I and II error probabilities are estimated by simulation. This research can be a, pp.ied to sequential sampling procedures in place of control charts where there is a recognized and necessary dependency during the production processes. Also, dependent multiple acceptance sampling plans can be derived by extending this sequential sampling procedure. As a numerical example, a Markov dependent process model is given, and the characteristics of the sampling plans are examined according to the change of the dependency factor.
Markov Chain Method for Monitoring Several Correlated Quality Characteristics with Variable Sampling Intervals
Chang, Duk-Joon ;
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 39~50
Markov chain method to evaluate the properties of control charts with variable sampling intervals(VSI0 for simultaneously monitoring several correlated quality characteristics under multivariate normal process are investigated. For comparing the efficiencies and properties of multivariate control charts, we consider multivariate Shewhart, CUSUM and EWMA charts in terms of average time to signal(ATS) and average number of samples to signal(ANSS). We obtained stabilized numerical results with Markov chain method when the number of transient state is greater than 100.
A Smooth Estimation of Failure Rate Function
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 51~61
We introduce a method of estimating an unknown failure rate function based on sample data. We estimate failure rate function by a function s from a space of cubic splines constrained to be linear (or constant) in tails using maximum likelihood estimation. The number of knots are determined by Bayesian Information Criterion(BIC). Examples using simulated data are used to illustrate the performance of this method.
Variable Sampling Interval Control Charts for Number of Defectives
Cho, Gyo-Young ; Ahn, Young-Seon ; Kim, Youn-Jin ;
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 62~73
Previous VSI control chart works have been done on quality variable whose distribution is normal. But there are many situations in which hte assumption of not a, pp.opriate. Also, in many industrial processes, the interest is to monitor the number of defectives. In this paper, we will take the existing properties of VSI control chart developed for the normal distribution and a, pp.y them to the np-chart based on the discrete binomial distribution. We will consider the CUSUM chart for the number of defectives. Here, the interesting object is to compute the VSI ATS for CUSUM control chart using Markov chain a, pp.oach and to compare FSI ATS and VSI ATS.
Detection of Changes of the Population Fraction Nonconforming in the p Control Chart
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 74~85
In this paper we calculate the subgroup size necessary for detecting the change of percent defective with several detection probabilities for orginal population fraction nonconforming p, changed population fraction nonconforming
, and the ratio k=
/p in the usage of p control charts. From our calculation we can know the error level of normal a, pp.oximation in detection probability calculation and recommend the subgroup size with lower error levels of normal a, pp.oximation, and then we show the reasonable subgroup size necessary for p,
, k, and the detection probability of the change of fraction nonconforming in a process. The information that we here show in tables will be useful when p control chart users decide the subgroup size in the p control chart users decide the subgroup size in the p control chart.
Periodic Preventive Maintenance Policies when Minimal Repair Costs Vary at Failures
Joon Keun Yum ; Gi Mun Jung ; Dong Ho Park ;
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 86~95
This paper considers a repairable system, which is maintained preventively at periodic times and is minimally repaired at each failure. Most preventive maintenance policies for such repairable systems assume that the cost of minimal repair is constant regardless of its age at failure. However, it is more practical to consider the situations where the cost of minimal repair is dependent not only on its age at failue, but also on the number of preventive maintenance carried out prior to its failure. We consider the preventive maintenance carried out prior to its failure. We consider the preventive maintenance policy with age-dependent minimal repair cost. The optimal policies which minimize the expected cost rate over an infinite time span are discussed. We obtain the optimal period and number of preventive maintenance prior to replacement of the system.
A Study on A, pp.ication of Reliability Prediction & Demonstration Methods for Computer Monitor
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 96~107
The recent stream to reliability prediction is that it is totally inclusive in depth to consider even the operating and environmental condition at the level of finished goods as well as component itselves. In this study, firstly we present the reliability prediction methods by entire failure rate model which failure rate at the system level is added to the failure rate model at the component level. Secondly we build up the improved bases of reliability demonstration through a, pp.ication of Kaplan-Meier, Cumulative hazard, Johnson's methods as non-parametric and Maximum Likelihood Estimator under exponential & Weibull distribution as parametric. And also present the methods of curve fitting to piecewise failure rate under Weibull distribution, PRST (Probability Ratio Sequential Test), curve fitting to S-shaped reliability growth curve, computer programs of each methods. Lastly we show the practical for determination of optimal burn-in time as a method of reliability enhancement, and also verify the practical usefulness of the above study through the a, pp.ication of failure and test data during 1 year.
Bayes Estimate for the Reliability of Nuclear-Power Plant Emergency Diesel Generator
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 108~118
A commercial nuclear power station contains at least two emergency diesel generates(EDG) to control the risk of severe core demage during the station blackout accidents. Therefore the reliability of the EDG's to start and load-run on demend must be maintained at a sufficiently high level. Until now, a simple assessment of start and load-run success rates was used to calculate the EDG's reliability. However, this method has been found to contain many defects. Recently, the work of Martz et al.(1996) proposed the use of the Bayes estimator to find the EDG's reliability. In this paper, we will propose confidence interval for the Bayes estimator, compare the above two methods and, using practical examples, illustrate why the Bayes estimator method is more reasonable in our situation.
Analysis of Quality Loss Function(QLF) of Taguchi
Journal of the Korean society for quality management, volume 25, issue 3, 1997, Pages 119~130
In this paper, we analyze quality loss function(QLF) of Taguchi. Taguchi method of QLF gives more advanced measure process capability than classic capacity(i.e. Cp). We first discuss of QLF and Cp and give one good example of QLF. Because of simplicity of QLF, it is not good fit to a, pp.y in the real field. We suggest interval quantity-loss cost function and total loss cost(TLC) which modify QLF. Also we give one example which can be obtained in the real field.