• International Journal of Advanced Culture Technology
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• v.8 no.3
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• pp.292-299
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• 2020

This paper presents an evaluation criteria of an information system availability for guaranteeing availability (service target level) from the perspective of the SLA contract and its technical point of view. In order to verify the effectiveness for information system failure and availability guarantee measures, three cases were examined. In summary, the failure time was reduced by 32% ~ 62% after applying the availability guarantee measure, verifying the excellence in the evaluation of an information system availability.

• 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.

• Journal of the Korea Safety Management & Science
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• v.8 no.5
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• pp.253-264
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• 2006

This paper is to derive three reliability and eight maintainability measures after organizing total time. I propose inherent availability,.achieved availability and operational availability with the new and useful reliability and maintainability measures above. Especially, inherent availability measure extends the repairable system reliability models.

• 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 Applied Reliability
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• v.16 no.4
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• pp.295-304
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• 2016

Purpose: This paper presents an application of Markov Process to reliability and availability analysis. In order to do that of analysis, we set up a specific case of Tablet PC and it's usage scenario. The case has it some spares and maintenance and repair processes. Methods: Different configurations of the tablet PC and as well as their functions are defined. The system configuration and calculated failure rates of components are modeled from Windchill Quality Solution. Two models, without a spare and with spare, are created and compared using Markov Process. The Matlab numerical analysis is used to simulate and show the change of state with time. Availability of the system is computed by determining the time the system stays in different states. Results: The mission availability and steady-state condition availability in accordance with the mission are compared and the availability of the system with spares have improved availability than without spares. Simulated data shows that downtime of the system increased which results in greater availability through the consideration of spares. Conclusion: There's many techniques and methods to do reliability and availability analysis and mostly are time-independent assumptions. But Markov Process, even though its steady-state and ergodic properties, can do time analysis any given time periods.

• Journal of Astronomy and Space Sciences
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• v.15 no.2
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• pp.485-497
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• 1998

To estimate the availability of the MCE for KOMPSAT I, mathematical models of H/W and S/W availability, the availability estimating methods for parallel and redundant system were presented. Furthermore, to improve and estimate the MCE system availability, we analyzed the computational procedure of redundant methods, and we also included effective switch choosing methods in this paper. The analytical results of the MCE system availability were estimated as follows: - 0.995216 not considering system redundancy, - 0.9955165 considering system redundancy, and -0.9963991 for the time of system real time operation.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.155-158
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• 1998

The KOMPSAT system incorporates multiple missions designed to provide various applications in the field of Korean peninsula observation covering land, sea and coastal zones. The missions are Korea cartography (1:25,000 scale maps of the Korean peninsula), biological oceanography and science instrument accommodation. The operational availability of KOMPSAT TTC system should be predicted more accurately because its failure has a significant influence on satellite command and tracking and on satellite data collection. In this paper, system availability structure of KOMPSAT TTC system are made and availability of KOMPSAT TTC system is analyzed aspect to the system operation in accordance with logistic condition.

• Communications for Statistical Applications and Methods
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• v.10 no.1
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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.

• 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.