• Journal of the Korea Society for Simulation
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• v.17 no.4
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• pp.61-69
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• 2008

In order to evaluate the performance of priority queues for future event list in discrete-event simulations, models representing patterns of enqueue and dequeue processes are required. The time complexities of diverse priority queue implementations can be compared using the performance models. This study aims at developing such performance models especially under the environment that a developed simulation model is used repeatedly for a long period. The developed performance model is based on multi-stage Markov process models; probabilistic patterns of enqueue and dequeue are considered by incorporating non-homogeneous transition probability. All necessary parameters in this performance model would be estimated by analyzing a results obtained by executing the simulation model. A case study with a war game simulation model shows how the parameters defined in muti-stage Markov process models are estimated.

• 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.

• Journal of the Korean Society for Railway
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• v.20 no.3
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• pp.349-355
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• 2017

Failures of railway systems can result in train delays or accidents, and therefore high reliability is required to ensure safety of railway systems. To improve reliability, railway systems are designed with redundant systems so that the standby system will continue to function normally even if the primary system fails. Generally, overall system reliability can be evaluated by the reliabilities of the parts of the whole system and the reliability of the redundant system considering common failures in case of each system is not conform physical, functional and process independent. In this study, the reliability of the hot-standby sparing system is analyzed the independent systems and dependent systems with common failures. The reliability for the standby system can be effectively analysed using Markov models, which can model the redundant configuration and the state transition.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.877-880
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• 2007

이 논문에서는 에너지 제한이 엄격한 환경에서 동작하는 무선 센서 네트워크를 위한 기회적 전송 전략을 제안한다. 본 연구는 무선 센서 네트워크의 호스트 지연에 민감한 어플리케이션을 고려하였다. 우리가 제안한 전송 전략은 시변 채널에서 지연의 제약을 받으면 채널상태가 좋을 때 전송을 시도하는 이진-결정 기반 전송 방식이다. 마코브 결정 프로세스가 전송 결정을 위한 최적 임계치를 찾는데 사용되었다. 우리의 이진-결정 기반 전송 방식은 에너지 소모의 원인인 전송실패를 가능하면 피하기 위해 채널의 질이 최적 임계 치를 넘을 때만 전송을 시작한다. 우리가 제안한 방식의 성능을 검증하기 위해 무선 페이딩 채널에서 광범위한 시뮬레이션을 수행하였다. 시뮬레이션 결과는 이진-결정 기반 전송 방식이 다른 방식보다. 35% 놓은 에너지 효율을 가지고 이로인해 네트워크 수명이 연장된다는 것을 보여준다.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.6
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• pp.459-464
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• 2001

This paper discusses a stochastic stabilization of Takagi-Sugeno(TS) fuzzy system with Markovian input delay. The finite Markovian process is adopted to model the input delary of the overall control system. It is assumed that the zero and hold devices are used for control input. The continuous-time TS fuzzy system with the Markovian input delay is discretized for easy handling delay, according, the discretized TS fuzzy system is represented by a discrete-time TS fuzzy system with jumping parameters. The stochastic stabilizibility of the jump TS fuzzy system is derived and formulated in terms of linear matrix inequalities (LNIS)

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.1
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• pp.34-43
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• 2000

Replicated data that is used for fault tolerant distributed system requires replica control protocol to maintain data consistency. The one of replica control protocols is quorum consensus method which accesses replicated data by getting majority approval. If site failure or communication link failure occurs and any one can't get quorum consensus, it degrades the availability of data managed by quorum consensus protocol. So it needs for ghost to replace the failed site. Because ghost is not full replica but process which has state information using meta data, it is important to simplify meta data. In order to maintain availability and simplify meta data, we propose a method to use cohort set as ghost's meta data. The proposed method makes it possible to organize meta data in 2N+logN bits and to have higher availability than quorum consensus only with cohort set and dynamic linear voting protocol. Using Markov model we calculate proposed method's availability to analyze availability and compare it with existing protocols.