• 한국안전학회지
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• 제11권1호
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• pp.27-38
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• 1996

현대 산업사회에서 네트워크나 시스템의 신뢰도는 전기, 전자, 통신, 화공, 핵공학 등에서 광범위하게 사용되고 있다. 통신의 경우 순간의 고장도 사회에 직접적으로 미치는 파급 효과가 크므로, 예측되는 부품의 고장 둥으로 인한 네트워크의 사용 가능 여부, 확률 등이 관심의 대상이 되고 있다. 이러한 문제들은 종종 신뢰도 공학의 고전적인 문제인 source to terminal problem으로 표현될 수 있으며, 이들의 문제해결을 위하여 그래프 이론과 domination 이론이 점점 중요한 비중을 차지하고 있다. 예를 들면 13개의 minimal path로 구성된 어떤 네트워크(그레프)를 관찰할 때, 신뢰도 계산을 위하여는 이들 13개 m-path의 모든 조합($2^{l3}$ -1=8191개)을 관찰하여야 하나, $\ulcorner$l$\lrcorner$에서 발표된 예제는 domination 이론을 기초로 한 topologic식을 사용하면 정확성의 상실없이 123개 항으로 감소시킬 수 있음을 보여주었다. A. Satyanarayana와 A. Prabhaker등은 $\ulcorner$1-19$\lrcorner$에서 그래프로 표현되는 시스템이나 네트워크들의 정확한 신뢰도 계산을 위하여 m-path를 사용한 domination 이론을 연구하고, 몇가지 알고리즘을 제시하였다. 하지만 어떤 네트워크를 관찰하 때 "왜 정상인가\ulcorner" 보다는 "왜 고장인가\ulcorner"를 관찰하여야 할 경우가 더 많으며, 이런 경우 m-path보다는 m-cutset을 사용한 신뢰도분석이 더 요구된다. $\ulcorner$20$\lrcorner$에서는 m-cutset을 근거로 한 네트워크(그래프)의 domination을 연구하였으나, $\ulcorner$1$\lrcorner$dml m-path를 기초로 한 경우처럼 간단한 topologic식이 성립 될 수 없음을 밝혔다.(중략)

• ETRI Journal
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• 제31권5호
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• pp.534-544
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• 2009

Finding link-disjoint or node-disjoint paths under multiple constraints is an effective way to improve network QoS ability, reliability, and so on. However, existing algorithms for such scheme cannot ensure a feasible solution for arbitrary networks. We propose design principles of an algorithm to fill this gap, which we arrive at by analyzing the properties of optimal solutions for the multi-constrained link-disjoint path pair problem. Based on this, we propose the link-disjoint optimal multi-constrained paths algorithm (LIDOMPA), to find the shortest link-disjoint path pair for any network. Three concepts, namely, the candidate optimal solution, the contractive constraint vector, and structure-aware non-dominance, are introduced to reduce its search space without loss of exactness. Extensive simulations show that LIDOMPA outperforms existing schemes and achieves acceptable complexity. Moreover, LIDOMPA is extended to the node-disjoint optimal multi-constrained paths algorithm (NODOMPA) for the multi-constrained node-disjoint path pair problem.

• 대한임베디드공학회논문지
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• 제15권1호
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• pp.25-33
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• 2020

Multipath routing protocols with unmanned aerial vehicles have been proposed to improve reliability in tactical ad hoc networks. Most of existing studies tend to establish the paths with multiple metrics. However, these approaches suffer from link loss and congestion problems according to the network condition because they apply same metric for both ground and air path or employ the simple weight value to combine multiple metrics. To overcome this limitation, in this study, we propose new routing metrics for path over unmanned aerial vehicles and use the multi-criteria decision making (MCDM) method to determine the weight factors between multiple metrics. For the case studies, we extend the ad-hoc on-demand distance vector protocol and propose a strategy for modifying the route discovery and route recovery procedure. The simulation results show that the proposed mechanism is able to achieve high end-to-end reliability and low end-to-end delay in tactical ad hoc networks.

• 품질경영학회지
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• 제47권4호
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• pp.701-711
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• 2019

Purpose: The problem of optimizing redundancy allocation in multi-level systems is considered when each item in a multi-level system has alternative items with the same function. The number of redundancy of multi-level system is allocated to maximize the reliability of the system under path set and cost limitation constraints. Methods: Based on cost limitation and path set constraints, a mathematical model is established to maximize system reliability. Particle swarm optimization is employed for redundant allocation and verified by numerical experiments. Results: Comparing the particle swarm optimization method and the memetic algorithm for the 3 and 4 level systems, the particle swarm optimization method showed better performance for solution quality and search time. Particularly, the particle swarm optimization showed much less than the memetic algorithm for variation of results. Conclusion: The proposed particle swarm optimization considerably shortens the time to search for a feasible solution in MRAP with path set constraints. PS optimization is expected to reduce search time and propose the better solution for various problems related to MRAP.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.1911-1930
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• 2017

Overlay routing has emerged as a promising approach to improve reliability and efficiency of the Internet. The key to overlay routing is the placement and maintenance of the overlay infrastructure, especially, the selection and placement of key relay nodes. Spurred by the observation that a few relay nodes with high betweenness centrality can provide more optimal routes for a large number of node pairs, we propose a resilient routing overlay network construction method by introducing Super-Relay nodes. In detail, we present the K-Minimum Spanning Tree with Super-Relay nodes algorithm (SR-KMST), in which we focus on the selection and connection of Super-Relay nodes to optimize the routing quality in a resilient and scalable manner. For the simultaneous path failures between the default physical path and the overlay backup path, we also address the selection of recovery path. The objective is to select a proper one-hop recovery path with minimum cost in path probing and measurement. Simulations based on a real ISP network and a synthetic Internet topology show that our approach can provide high-quality overlay routing service, while achieving good robustness.

• 한국정보통신학회논문지
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• 제19권7호
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• pp.1561-1567
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• 2015

모바일 애드혹 네트워크의 노드는 일반적으로 에너지의 용량이 제한된 배터리를 사용한다. 경로의 안정성을 유지하기 위해 균형 잡힌 에너지 소비가 중요하다. 본 논문에서는 애드혹 네트워크에서 데이터 전송 경로의 안정성을 향상시키는 것을 목표로 한다. 이를 위해 데이터를 전송할 수 있는 최단 전송 경로 중에서 노드 에너지 잔량의 최소값이 가장 큰 경로를 선택하는 새로운 라우팅 프로토콜을 제안한다. 에너지 잔량의 최소값이 가장 큰 경로는 다른 경로보다 상대적으로 긴 수명을 갖게 되어 데이터 전송에 안정성을 향상 시킬 수 있다. NS-3 시뮬레이터를 사용하여 제안하는 라우팅 프로토콜이 AODV와 EA-AODV보다 수명이 긴 안정적인 경로를 제공하는 것을 확인한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.235-238
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• 1990

This paper presents a method of finding the optimal path of which is considered the switching cost and the reliability index. The problem is formulated as an optimization problem and solved by the maximum flow/mimimum cut method. The objective of this paper is to find the optimal path and minimize the failure cost and switching cost. Presented method has been simulated and the results are discussed.

• Communications for Statistical Applications and Methods
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• 제13권3호
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• pp.577-585
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• 2006

This paper presents a method for reliability evaluation of a telecommunication network with variable link-capacities when the simple paths of the network are known. The LP-EM, suggested by Lee and Park (2001), identifies a composite path as a subnetwork and adds only a minimal set of links at each step which gives maximal increase on the maximum capacity flow of the subnetwork. Thereby the LP-EM reduces the possible occurrence of redundant composite paths significantly over other existing methods. Based on the LP-EM, our method further reduces the possible redundancy by identifying such simple paths that could give no increase of maximum capacity flow on the current subnetwork and excluding those simple paths from consideration in the process of constructing composite paths.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.772-775
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• 2002

The remote handling and maintenance devices in the nuclear hot ceil should be checked prior to the hot operation in view of reliability and operability. In this study, the digital mock-up is implemented to analyze and define the process equipment maintenance processes instead of real mock-up, which is very expensive and time consuming. To do this, the parts of equipment and maintenance devices are modeled in 3-D graphics, assembled, and kinematics is assigned. Also, the virtual workcell of the spent fuel management process is implemented in the graphical environment which is the same as the real environment. This simulator has the several functions for verification such as analyses for the manipulator's working area, the collision detection, the path planning and graphic simulation of the processes etc. This graphic simulator of the maintenance devices can be effectively used in designing of the maintenance processes for the hot cell equipment and enhance the reliability of the spent fuel management.

• Journal of Power Electronics
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• 제6권3호
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• pp.205-213
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• 2006

A cost-effective magnetic-coupled AC-PDP sustain driver with low switching loss is proposed. The transformer reduces current stress in the energy recovery switches which affects circuit cost and reliability. The turns-ratio can be used to adjust the sustain pulse slopes which affect gas discharge uniformity. Dividing the recovery paths prevents abrupt changes in the output capacitance and thereby switching losses of the recovery switches is reduced. In addition, the proposed circuit has a more simple structure because it does not use the recovery path diodes which also afford a large recovery current. By reducing the current stress and device count in the energy recovery circuit, the proposed driver may have decreased circuit cost and improved circuit reliability.