• Journal of Korean Society for Quality Management
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• v.27 no.3
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• pp.79-93
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• 1999

The common accelerated life test(ALT) consists of test methods applying a constant stress, higher than the use condition stress, to items. There we, however, situations for which a progressive stress ALT, in which the stress on a test item is continuously increased with time, Is more convenient to perform testing and simpler in analyzing data than a constant stress ALT. When a product under constant stress s follows a Weibull distribution with parameters $\theta$(5) and $\beta$, maximum likelihood(ML) estimators of parameters involved in the model are obtained and their asymptotic distributions are derived under stress bounded ramp tests in which the stress is increased linearly from use condition stress to the stress upper bound. The optimum test plans are also found which minimize the asymptotic variance of the ML estimator of the log mean life at design constant stress. For selected values of the design parameters, tables useful for finding optimal test plans are given. The effect of the pre-estimates of design parameters is studied.

• Journal of Korean Society for Quality Management
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• v.22 no.1
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• pp.169-178
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• 1994

Nonparametric tests for comparing two treatments when data are subject to unequal patterns of censorship are discussed. Best precedence test proposed by Slud can be viewed as a nice alternative test comparing with weighted log-rank tests, not to mention the advantage of short experimental period. This research revises some missing parts of Slud's test and examines the asymptotic power of it under the nonproportional hazard alternatives through the simulation. The simulation studies show best precedence test has reasonable power in the sense of robustness under nonproportional hazard alternatives and could be recommended at such situation.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.82-84
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• 2000

통화시간에 대한 할인율 적용 혹은 짧은 통화에 요금을 부과하지 않은 정책 등 마케팅활동의 효과분석 및 마케팅전략을 수립하는데 있어서 통화시간 분석은 매우 중요하다. 기존연구들은 설명변수의 도입이 편리한 비례위험함수(proportional hazard function) 을 활용해 왔다. 그러나 이 방법은 추정이 용이하지 않다는 약점을 갖고 있다. 특히 통화행태를 설명하기위해 다양한 설명변수를 도입하는 경우, 기존에 상용화된 통계패키지로 추정하는데 한계점을 갖고 있다. 본 연구에서는 추정의 용이성에 초점을 맞추어, 실무자들이 손쉽게 통화시간에 대한 마케팅 노력의 효과를 분석할 수 있는 분석방법론을 제시하고, 제시된 분석방법을 이용하여 판촉활동 (요금할인)이 통화대기시간과 통화시간에 미치는 영향을 실증분석 하고 있다.

• Proceedings of the Korean Society for Information Management Conference
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• 2004.08a
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• pp.61-66
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• 2004

본 연구에서는 시소러스를 구축하기 위해 필요한 디스크립터 수집원으로써 이용자 로그데이터를 분석하여 후보 디스크립터의 외형적 특성을 분석하였다. 분석대상인 이용자 로그데이터는 국내 검색엔진가운데 야후와 라이코스를 대상으로 하였다. 분석결과, 이용자들은 대부분 검색어로써 명사와 복합명사를 사용하였으며, 조사 '의'이외에는 다른 품사로 이루어진 검색어는 거의 존재하지 않음을 알 수 있었다. 또한 검색어로써 이용자들은 고유명사(외국어 포함)를 많이 사용함으로써, 국내외 지침에서 권고하는 고유명사의 최소한 사용지침과 실제 이용자 사이의 이용행태와의 차이를 알 수 있었다. 따라서 국내외 시소러스 개발지침을 수용하면서, 이용자 중심의 시소러스를 개발하기 위해서는 전거어나 유사어 사전을 대등관계와 연동하여 개발하는 것을 고려해야 한다.

• Journal of the Korean Operations Research and Management Science Society
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• v.39 no.4
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• pp.1-17
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• 2014

The functions of stocking and releasing in logistics center consist of three major procedure such as receiving, shipping and stock managements. Each process includes various sub-processes which are complicatedly connected with each other. Furthermore, lots of operators execute various tasks in the different sub-processes, simultaneously. It makes difficult to standardize, monitor, and analyze the processes. This paper proposed the quantitative methodology using process mining approach to discover and analyze receiving and shipping processes. For this purpose, the PDA operation log data is analyzed to build a realistic process model. The deduced model has been compared with official process model. In addition, task assignment and social networks analysises are carried out by utilizing process mining tools. Also, it has been proposed how to improve the processes with the analytical simulation model based on the results of process mining.

• Korea Information Processing Society Review
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• v.17 no.2
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• pp.18-29
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• 2010

In this paper, we surveyed SSO based security management including the knowledge domain of the area of cloud and its relevant components. Cloud computing refers to the delivery of software and other technology services over the Internet by a service provider. SSO refers to the ability to log on to a single security system once, rather than logging on separately to multiple security systems. Existing SSO solutions in cloud computing environment suggest several methods. SSO-based security Issues illustrate these key items in cloud computing environment such as risks and security vulnerabilities of SSO. SSO supports for multiple and different domains in cloud computing environment.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.10a
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• pp.93-95
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• 1996

A replication server is considered to be one of the most effective tools to cope with the problems that may be caused by the complex data replications in distributed database systems. In the distributed environment, locking a table is inevitable and it is the main reason to coerce the system practically. This paper presents an Asynchronous Replicator Scheme (ARS) that basically utilizes the system log as files named differential files to refresh the distributed data files with complicated queries, and that it prevents (normally, huge) base tables from being locked. We take join operations as the complicated queries, not only because the join operation covers almost all the operations, but also because it is one of the most time-consuming and data intensive operations in query processings.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.381-384
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• 2000

This paper proposes a method of estimating the lifetime distribution at use condition for constant stress accelerated lift tests when extrinsic failure mode as well as intrinsic one exists. A mixture of two log-normal distributions is introduced to describe these failure modes and it is assumed that a linear relation exists between the location parameter and stress. An estimation procedure using the expectation and maximization algorithm is proposed and a numerical example is given.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.39-41
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• 2002

Management of internal Internet servers is increasingly becoming an important task. According to meet this requirement, they use service log analysis tools and network monitoring tools. But these are not enough to produce advanced management information considering contents of Internet services. Therefor we propose a system and let it detect Internet server systems existing in internal network and individuate those systems with providing profile. Internet server profile includes system's basic information, network traffic information, and Internet service usage information.

• Journal of Korean Society for Quality Management
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• v.30 no.2
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• pp.130-151
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• 2002

This paper investigates the relation between the Process capability index(PCI) and the quality assurance level under various conditions. The effect of the off-targetness of the process mean, deviation from the nomality, the estimation error, and tile measurement error on the quality assurance level is evaluated. Various distributions such as the Student-t, the chi-square, the gamma, the Weibull, and the log-normal distributions are considered to evaluate the deviation from the nomality. The quality levels under abnormal conditions turn out to be severely different from that under the standard condition. We provide tables and graphs of the quality assurance level on various abnormal conditions. In order for the industry users to use the PCI properly, they should refer to the tables and graphs, especially when they are not certain about the standard assumptions on which the PCI depends.