• Communications for Statistical Applications and Methods
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• 제10권1호
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• pp.191-202
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• 2003

Availability is an important measure of performance of a repairable component. In this paper, the explicit expression for the availability of a repairable component, which is subject to the policy II(Age Replacement Policy) of Barlow and Hunter (1960), is obtained and the existence of the steady state availability is shown. The steady state availabilities of the model are also obtained for the cases when the mean of the minimal repair time is increasing at a geometric rate or linearly increasing, In order to show the importance and the utility of the obtained result, we also consider an illustrative example of the repairable coherent system whose components are repairable, and the obtained results are applied to derive the steady state availability of the whole system. In this situation, we can see that the condition of the existence of the steady state availability for each component is essential. Some remarks on the optimal replacement policy that maximizes the steady state availability are also given.

• International Journal of Reliability and Applications
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• 제5권2호
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• pp.75-80
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• 2004

Relationships between inventory policy and operational availability of military equipment maintained under a logistics support system are analyzed. A continuous review inventory model with a stochastic demand typically used in a military logistics support is considered and some numerical studies are provided.

• 시스템엔지니어링학술지
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• 제14권1호
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• pp.36-43
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• 2018

The availability of the weapon system can be analyzed through state modeling and simulation using the Markov process. In this paper, show how to analyze the availability of the weapon system and can use the Markov process to analyze the system's steady state as well as the RAM at a transient state in time. As a result of the availability analysis of tracked vehicles, the inherent availability was 2.6% and the operational availability was 1.2% The validity criterion was defined as the case where the difference was within 3%, and thus it was judged to be valid. We have identified the faulty items through graphs of the number of visits per state among the results obtained through the MPS and can use them to provide design alternatives.

• Journal of Information Processing Systems
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• 제8권2호
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• pp.263-278
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• 2012

The data grid provides geographically distributed resources for large-scale applications. It generates a large set of data. The replication of this data in several sites of the grid is an effective solution for achieving good performance. In this paper we propose an approach of dynamic replication in a hierarchical grid that takes into account crash failures in the system. The replication decision is taken based on two parameters: the availability and popularity of the data. The administrator requires a minimum rate of availability for each piece of data according to its access history in previous periods, but this availability may increase if the demand is high on this data. We also proposed a strategy to keep the desired availability respected even in case of a failure or rarity (no-popularity) of the data. The simulation results show the effectiveness of our replication strategy in terms of response time, the unavailability of requests, and availability.

• 가족자원경영과 정책
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• 제17권2호
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• pp.173-194
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• 2013

The purpose of this study was to examine the association between time-income availability and health-promoting behavior (physical practice, smoking, alcohol consumption) of older males (55-69). This study attempted to shed light on health-behavior changes during the transition period of male retirement. The availability of time resources was examined by addressing the amount of weekly paid labor hours. The availability of financial resources was calculated by using the debt-income ratio. The study sample comprised 1,372 (age range 55-69) male respondents of the 2006 Korean Longitudinal Study of Aging (2006 KLOSA wave 1). The results of CHAID (CHi-squared Automatic Interaction Detection) analysis uncovered four distinctive combinations of resource types: time-money poor, time rich, money rich, time-money rich. According to logit results, these four groups had different socio-demographic profiles and different health-behavior risks. The time-money poor males were unlikely to perform physical activities needed to improve their health or to quit smoking or alcohol consumption. This group was also more likely to consume alcohol compared to the time-money resource types. In contrast, the time-money rich group was more likely to exercise longer and more frequently than the reference group (time and money poor). The time-rich types, those who have time-only resources and less money, were likely to be smokers and have problems with alcohol consumption.

• 한국시스템다이내믹스연구
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• 제11권2호
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• pp.119-138
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• 2010

This study introduces the system dynamics model that simulate total operational availability when 10 equipments made of 3 major components are serviced under the constrains of the maintenance capacity level and the number of spare parts. This simulation is designed on the base of reliability engineering concept so failures of components happens with the rule of engineering factors like the mean time between failure(MTBF) of component and the next failure time of one component is effected by the conditions of other components. We analysed availability of 10 equipments under 121 constrains and executed multiple regression analysis with the simulation result. The analysis provide the managerial insight in the service fields with operation many equipments.

• International Journal of Reliability and Applications
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• 제16권1호
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• pp.1-13
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• 2015

In this paper, we investigate reliability and availability of repairable systems with two types of failure. The first one is to one unit and the second one is to M units in parallel structure. Let failure rate and repair rate of [type1, type2] components are assumed to be exponentially distributed. The expressions of availability and reliability characteristics such as the system reliability and the mean time to failure are derived for two systems. We used several cases to analyze graphically the effect of various system parameters on the reliability system and availability system.

• 한국위성정보통신학회논문지
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• 제10권4호
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• pp.107-112
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• 2015

본 논문에서는 정지궤도 복합위성 2B에 대한 환경위성지상국 시스템의 성능지표의 하나인 가용도를 예측하기 위한 H/W 및 S/W 시스템 가용도의 수학적 모델링을 제시하고, 직렬연결 시스템에 대한 가용도 예측 방법을 제시하였다. 또한, 본 논문에서는 환경위성 지상국 시스템의 가용도 예측 결과를 산출하였으며, 그 가용도 예측 결과는 0.998072로 분석 되었다.

• 한국시뮬레이션학회논문지
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• 제21권2호
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• pp.103-112
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• 2012

전통적인 시스템 차원에서의 신뢰도 분석 모형에서 탈피하여 사용자가 인지하는 서비스 가용도에 대한 필요성이 대두되고 있다. 본 논문에서는 우선 서비스 가용도 모형에 대해 살펴보고 이의 근간을 이루는 UBG에 대하여 논하였다. 그리고 사용자 모델, 시스템 모델 및 서비스 모델을 복합적으로 고려하여 서비스 가용도를 산출하는 시뮬레이션 모델을 제안하였다. 아울러 예제를 통하여 사용자 모델의 UBG와 시스템 모델을 작성하고 이를 토대로 서비스 모델을 정의하는 일련의 과정을 보여 주었다. 그리고 시스템 모델과 UBG의 여러 파라메타들이 서비스 가용도에 미치는 영향에 대해 살펴보았다.

• 산업경영시스템학회지
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• 제23권59호
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• pp.53-67
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• 2000

In this paper we consider the CSP requirements determination problem of new equipment(machine) system. For the newly procured equipment systems, mathematical analyses are made for the system which is constructed with the consumable parts and the repairable parts to derive the associated CSP requirement determination model in mathematical expression. Based on these analyses, a mathematical model Is derived for making an optimal CSP requirement determination subject to the constraint of satisfying any given operational availability limitation. We assume that the failure of a part follows a Poisson process and the repair time has an exponential distribution. Firstly, the operational availability concept in CSP is defined and the relation between the general system availability and the operational availability is established. Secondly, the problem is formulated as the cost minimization problem that should satisfy the operational availability limitation, and then, using the generalized Lagrange multipliers method, the optimal solution procedure Is derived.