• Journal of Korea Society of Digital Industry and Information Management
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• v.17 no.1
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• pp.25-34
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• 2021

Availability is one of the important factor for developing weapon system, because it indicates the mission capability and sustainable life cycle management of weapon system. Recently, as weapon system becomes more advanced and more complex, availability estimation becomes more important to reduce the life cycle cost of weapon system. Modeling and simulation(M&S) is useful method to describe the availability of complex weapon system applying operational environment and maintenance plan. Especially agent based model(ABM) has the strength to describe interactions between agents and environments in complex system. Therefore, this paper presents the availability estimation of weapon system using agent based model. The sample data of part list and reliability analysis is applied to build availability estimation model. User agent and mechanic agent are developed to illustrate the behavior of operation and maintenance using formal specification. Storage reliability is applied to describe failure of each parts. The experimental result shows that this model is quite useful to estimate availability of weapon system. This model may estimate more reasonable availability, if full scale data of weapon system and real field data of operation is provided.

• Korean Journal of Human Ecology
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• v.23 no.1
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• pp.15-29
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• 2014

The purposes of this study were to explore the effect of mother-child emotional availability on preschooler's preschool adjustment and mediating effect of preschooler's effortful control on the relationship between mother child emotional availability and preschooler's preschool adjustment. 222 preschoolers(110 boys, 112 girls, aged 5) and their mothers participated in this study. Mother child emotional availability was assessed by Emotional Availability Scale(Biringen, et al., 1998). Preschooler's effortful control was measured by the Child Behavior Questionnaire(Rothbart, et al., 1994). Preschooler's school adjustment was measured by Teacher Rating Scale of School Adjustment: TRSSA(Buhs & Ladd, 2001). Data were analyzed using descriptive statistics, correlations, and structural equation modeling analysis. The major results of this study were as follows; First, Mother-child emotional availability effected on preschooler's preschool adjustment. Second, Mother-child emotional availability effected on preschooler's effortful control. Third, Preschooler's effortful control effected on preschooler's preschool adjustment. Forth, preschooler's effortful control mediated the effect of mother-child emotional availability on preschooler's preschool adjustment. That was, the more mother-child were emotionally available to each other, the more preschooler's effortfully control their attention and behavior, which in turn contributed to preschooler's preschool adjustment. In conclusion, mother-child emotional availability affect on preschooler's preschool adjustment and preschoolers control mediates the relationship between mother-child emotional availability and preschool adjustment.

• Journal of Applied Reliability
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• v.14 no.1
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• pp.1-9
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• 2014

One important measure of performance for a repairable system is steady-state availability. In this paper, a method to estimate and establish confidence interval for the steady-state availability under Weibull lifetime and lognormal repair time distributions is proposed. Also, bias and mean squared error of a point estimator for an availability are investigated. In addition, a procedure to derive the sample size and critical value for availability demonstration test is presented and illustrated with a numerical example.

• Journal of the Korean Society of Systems Engineering
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• v.14 no.1
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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 Korean Society for Quality Management
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• v.41 no.3
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• pp.413-421
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• 2013

Purpose: System availability and life cycle cost are often used to evaluate the system performance and is influenced by the operation and maintenance characteristic. In this paper, we propose the method to improve life cycle cost and satisfy the target availability through redundancy allocation. Methods: We consider the redundancy is available at all items in multi level system. Thus, we assume that sub-assembly, module, components can be duplicated. Simulation and genetic algorithm are employed to optimize redundancy allocation. Results: Target availability is higher, the life cycle cost is increased. In addition, the items for redundancy are selected at higher level in multi level system if target availability is higher. Conclusion: We could know that target availability affects the duplication number of items and the selection of redundancy items. For further study, we will consider new optimization algorithms to compare with the proposed GA algorithm and improve optimization performance.

• Journal of Information Processing Systems
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• v.8 no.2
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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.

• Journal of Applied Reliability
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• v.5 no.4
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• pp.465-486
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• 2005

A unreliable network system results in unsatisfied performance. A performance criterion of a network is throughput and availability. One of the most compelling technological advances of this decade has been the advent of deploying wireless networks of heterogeneous smart sensor nodes for complex information gathering tasks, The advancement and popularization of wireless communication technologies make more efficiency to network devices with wireless technology than with wired technology. Recently, the research of wireless sensor network has been drawing much attentions. In this paper, We evaluate throughput and availability of wireless sensor network, which have hierarchical structure based on clustering and estimate the maximum hroughput, average throughput and availability of the network considering several link failure patterns likely to happen at a cluster consisted of sensor nodes. Also increasing a number of sensor nodes in a cluster, We analysis the average throughput and availability of the network.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.4
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• pp.471-478
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• 2014

Navy forces of ROK asked for more than 90% operational availability in the requirement document of combat ship. This study proposes the evaluation methodology of operational availability with the evaluation process, calculation formula, analysis of operational test data. As the case study, the developed methodology is proved to apply for 00 batch-I naval ship using the data to be acquired during the operational test period. The operational availability by test data was 90.03%, and it was satisfied with objective value 90%. The paper will contribute not only to establish the evaluation methodology of operational availability for combat ship but also other general weapon system.

• Proceedings of the Safety Management and Science Conference
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• 2007.04a
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• pp.309-322
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• 2007

This paper shows application guide of dependability data from the field, life cycle costing, and maintainability. Moreover, this study introduces mathematical expressions and predictions for reliability, availability and maintainability. This paper also shows compliance test procedures for steady-state availability, and application of Markov techniques.

• Journal of the Korean Society for Railway
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• v.14 no.2
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• pp.87-93
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• 2011

This work describes an availability model of highly available systems to achieve Five-9's availability. Modern railway systems have raised users' expectations of powerful "always on" services. The crucial characteristics of these highly available services are essential to many modern businesses area, such as telecommunications, railway systems, information operations, Web-based businesses, and so on. The architecture-based model of system availability is useful to assess the feasibility of meeting a high availability target. The Markov model approach is straightforward for relative system engineers to adapt when they model highly available system failure and the failure recovery process. This work proposed the improved availability model through UML2.0. It is shown that the architecture-based model of system availability is a good reasonable by its application of the railway systems.