• Journal of Korean Society for Quality Management
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• v.29 no.2
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• pp.46-53
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• 2001

In this paper, a preventive maintenance(PM) policy for a repairable system is considered. The failure rate model proposed by Park et at.(2000) is generalized by assuming that after each PM not only the PM slows down the degradation process of the system but also reduces down the system failure rate by a certain fixed amount. Long-run expected cost rate of the PM policy is derived and the properties of joint solution of the optimal PM period and optimal number of PM which minimizes the expected cost rate are obtained. Numerical examples for the case of a Weibull-type failure rate are given.

• International Journal of Reliability and Applications
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• v.1 no.1
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• pp.65-79
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• 2000

This research considers a system which has an ultimate terminal event such as death, critical failure, bankruptcy together with a certain indicative events (temporary malfunction, special treatment, kind of defaults) that frequently occurs before the terminal event comes to the system. Some investigation of a model for the corresponding bivariate data of the system have been done with an explanation of the situation in terms of two continuous variables instead of continuous-discrete variables and some other properties. Also an analysis has been carried out to evaluate the effect of intermediate observation of occurrence of indicative event so that the result can be used for a possible suggestion of an intermediate observing schedule.

• The Korean Journal of Applied Statistics
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• v.26 no.1
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• pp.111-118
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• 2013

In this paper we study the effect of failure detection equipment(FDE)s on system availability. A new repair scheme is considered for the step of repairing FDE which becomes out of order in the course of repairing the main system(MS). We compute and compare the availability of MS.

• International Journal of Reliability and Applications
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• v.2 no.2
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• pp.107-115
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• 2001

This paper considers some reliability indices, such as availability, average availability, reliability and steady state availability, of a redundant system with the function of switchover processing. We also derive the confidence limits for steady state availability of such system. The system, which is considered in this paper, consists of an active unit, a standby unit and a switchover device. In addition, the switchover processing is controlled by a control module. The effect of failure of the control module is taken into account to develop our reliability model for the redundant structure. Numerical examples are presented to illustrate our results.

• Journal of the Korean Data and Information Science Society
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• v.14 no.1
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• pp.113-118
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• 2003

In this paper, We assume that strengths of two components system follow a bivariate pareto distribution. And these two components are subjected to a common stress which is independent of the strength of the components. We obtain maximum likelihood estimator(MLE) for the system reliability from stress-strength relationship. Also we derive asymptotic properties of the MLE and present a numerical study.

• Communications for Statistical Applications and Methods
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• v.4 no.2
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• pp.589-610
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• 1997

When a modeling process is applied to an actual commodity market in the real world, interactions over closely related commodities through the marketing channel should also be formulated into the model to reflect the information that exists in the whole market system, otherwise unreliable estimates and test statistics may be produced by ignoring those effects. Single-equation type model in this case tends to yield inefficient estimates, and sometimes biased and inconsistent, which will mislead us. A system of equation method to examine the structure of the imported commodity market system is developed and its emtirical results are analyzed, then followed by some policy experiments and its implications.

• Journal of the Korean Data and Information Science Society
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• v.14 no.4
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• pp.837-844
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• 2003

In this paper, we obtain the estimator of system reliability for the bivariate Pareto model with bivariate type 1 censored data. We obtain the estimators and approximated confidence intervals of the reliability for the parallel system based on likelihood function and the relative frequency, respectively. Also we present a numerical example by giving a data set which is generated by computer.

• Journal of the Korean Data and Information Science Society
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• v.18 no.1
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• pp.149-159
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• 2007

The main purpose of this paper is to develop a questionnaire creation system by expert co-operation on the web. The most difficult problem in a survey is to make questionnaires. To solve this problem, we suggest the questionnaire creation system which is to create questionnaire for survey by expert collaboration. We can create the best questionnaire because it can gather and exchange to questionnaire information from experts.

• Journal of applied mathematics & informatics
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• v.26 no.5_6
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• pp.839-850
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• 2008

In this paper, the symmetric accelerated overrelaxation (SAOR) method for solving $n{\times}n$ fuzzy linear system is discussed, then the convergence theorems in the special cases where matrix S in augmented system SX = Y is H-matrices or consistently ordered matrices and or symmetric positive definite matrices are also given out. Numerical examples are presented to illustrate the theory.

• Communications for Statistical Applications and Methods
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• v.7 no.3
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• pp.927-935
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• 2000

In this paper we propose a poll system n the internet. This system expects to increase the confidence of the internet poll results by sampling theory(proportional allocation). This system provides a cross-tale and result of hypothesis test which plays an important role for decision making. These results do offer a few statistical packages(such as SAS, SPSS) in the world wide web.