• 한국공간정보시스템학회 논문지
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• 제11권4호
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• pp.39-46
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• 2009

일반적으로 휴리스틱을 이용한 알고리즘에서는 탐색 비용이 증가하는 문제가 발생할 수 있다. 휴리스틱에 의해 결정된 추정 경로에 실제 경로가 존재하지 않을 경우, 휴리스틱 가중치 값이 비슷한 2 가지 이상의 경로가 존재할 경우 탐색 비용이 증가한다. 이 논문에서는 탐색 비용 증가 문제점을 해결하기 위해 추상 그래프를 제안한다. 추상 그래프는 실제 도로를 단순화한 그래프로서, 전체 지도를 고정된 크기의 그리드 셀로 나누고, 셀과 도로 정보를 기반으로 생성된다. 경로 탐색은 추상 그래프 탐색, 실제 도로 네트워크 탐색 순으로 2단계로 수행된다. 106,254개의 간선으로 이루어진 실제 도로 네트워크 데이터에 대해서 성능 평가 실험을 수행한 결과와 탐색 비용 측면에서 그리드 셀 크기에 따라 그리드 기반 A* 알고리즘에 비해 최소 3%에서 최대 35% 좋은 성능을 보였다. 반면에 유효 셀을 제외한 영역에 대한 탐색이 이루어지지 않기 때문에, 생성된 경로의 이동 비용은 1.5~6.6% 증가하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.925-926
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• 2006

In the multi-agent system for a single task, the action selection can be made for the real-time environment by using the global coordination space, global coordination graph and MAX-PLUS algorithm. However, there are some difficulties in multi-agent system for multi-tasking. In this paper, a real-time decision making method is suggested by using coordination space, coordination graph and dynamic coordinated state of multi-agent system including many agents and multiple tasks. Specifically, we propose locally dynamic coordinated state to effectively use MAX-PLUS algorithm for multiple tasks completion. Our technique is shown to be valid in the box pushing simulation of a multi-agent system.

• Journal of Multimedia Information System
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• 제2권3호
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• pp.263-274
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• 2015

The subject of this work is the complex discrete systems simulation special features with the aid of dynamic graph models. The proposed simulation technique allows to determine the ways for tasks solutions in terms of discrete systems analysis and synthesis of various complication: one-dimensional and multidimensional, steady and unstable, with the pulse elements abnormal operating mode and others. Often complex control systems analysis and synthesis task solutions, via classical approach comes out to be insolvent, because of the computational problems. The application of graph models allows to perform clear and strict characterization and computer procedures automation. The optimal controls synthesis algorithm presented in this paper, transferring the discrete system from target initial state to target final state within the minimum time, allows to consider the zero initial conditions systems, with the initial potential energy, with the control actions limitations and complex pulse elements operating mode.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제7권5호
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• pp.177-188
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• 2018

최근 웹, 소셜 네트워크 서비스, 모바일, 사물인터넷 등의 ICT 기술의 발전으로 인해 처리 및 분석이 필요한 그래프 데이터의 규모가 급속하게 증가하였다. 이러한 대규모 그래프 데이터는 단일 기기에서의 처리가 어렵기 때문에 여러 기기에 나누어 분산/병렬 처리하는 것이 필요하다. 기존 그래프 처리 알고리즘들은 단일 메모리 환경을 기반으로 연구되어 분산/병렬 처리환경에 적용되기 힘들다. 이에 대규모 그래프의 보다 효과적인 분산/병렬 처리를 위해 정점 중심 방식의 그래프 처리 시스템들과, 정점 중심 방식의 단점을 보완한 블록 중심 방식의 그래프 처리 시스템들이 등장하였다. 이러한 시스템들은 초기 그래프 분할 상태가 전체 처리 성능에 상당한 영향을 미친다. 한 번에 최적의 상태로 그래프를 분할하는 것은 매우 어려운 문제이므로, 그래프 처리 시간에 점진적으로 그래프 분할 상태를 개선하는 여러 로드 밸런싱 기법들이 연구되었다. 그러나 기존 기법들은 대부분 정점 중심 그래프 처리 시스템을 대상으로 하여 블록 중심 그래프 처리 시스템에 적용이 어렵다. 본 논문에서는 블록 중심 그래프 처리 시스템을 대상으로 적용 가능한 로드 밸런싱 기법을 제안한다. 제안 기법은 동적으로 블록을 재배치하여 점진적으로 그래프 분할 상태를 개선시키며, 해를 찾아나가는 과정에서 지역 최적해를 벗어나기 위한 블록 분할 전략을 함께 제시한다.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.386-403
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• 2016

The safety of nuclear power plants is analyzed by a probabilistic risk assessment, and the fault tree analysis is the most widely used method for a risk assessment with the event tree analysis. One of the well-known disadvantages of the fault tree is that drawing a fault tree for a complex system is a very cumbersome task. Thus, several graphical modeling methods have been proposed for the convenient and intuitive modeling of complex systems. In this paper, the reliability graph with general gates (RGGG) method, one of the intuitive graphical modeling methods based on Bayesian networks, is improved for the reliability analyses of dynamic systems that have various operation modes with time. A reliability matrix is proposed and it is explained how to utilize the reliability matrix in the RGGG for various cases of operation mode changes. The proposed RGGG with a reliability matrix provides a convenient and intuitive modeling of various operation modes of complex systems, and can also be utilized with dynamic nodes that analyze the failure sequences of subcomponents. The combinatorial use of a reliability matrix with dynamic nodes is illustrated through an application to a shutdown cooling system in a nuclear power plant.

• Journal of Information Processing Systems
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• 제19권1호
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• pp.130-138
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• 2023

The traffic flow in an urban area is affected by the date, weather, and regional traffic flow. The existing methods are weak to model the dynamic road network features, which results in inadequate long-term prediction performance. To solve the problems regarding insufficient capacity for dynamic modeling of road network structures and insufficient mining of dynamic spatio-temporal features. In this study, we propose a novel traffic flow prediction framework called shared spatio-temporal attention convolution optimization network (SSTACON). The shared spatio-temporal attention convolution layer shares a spatio-temporal attention structure, that is designed to extract dynamic spatio-temporal features from historical traffic conditions. Subsequently, the graph optimization module is used to model the dynamic road network structure. The experimental evaluation conducted on two datasets shows that the proposed method outperforms state-of-the-art methods at all time intervals.

• 대한기계학회논문집A
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• 제20권11호
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• pp.3507-3515
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• 1996

This paper presents an attempt to find the physical structure of dynamic systems which achieves the behavior of a given system function. The scheme pursued by the paper would be regarded as synthesizing dynamic systems, and a method to synthesize them analytically is proposed by means of bond graph prototypes. The method adopts several conceptsused to synthesize networks in the electrical field, but yet deconstrates its own strengths such as the freedom from assigning causality and determining junction types. Also, itis shown that this method has further advantages in reticulating a given specification into feedforward and feedback components relative to network synthesis and the method is examined though an example to trace the outline of the analytical synthesis of dynamic systems using bond graph prototypes.

• International Journal of Aerospace System Engineering
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• 제2권1호
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• pp.47-52
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• 2015

The transient phenomenon of self-powered energy-harvesting is assessed using a bond-graph method. The bond-graph is an energy-based approach to describing physical-dynamic systems. It shows power flow graphically, which helps us understand the behavior of complicated systems in simple terms. Because energy-harvesting involves conversion of power in mechanical form to the electrical one, the bond-graph is a good tool to analyze this power flow. Although the bond-graph method can be used to calculate the dynamics of combining mechanical and electrical systems simultaneously, it has not been used for harvesting analysis. We demonstrate the usability and versatility of bond-graph for not only steady analysis but also transient analysis of harvesting.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권5호
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• pp.1976-1997
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• 2016

This paper investigates the problem of co-tier interference mitigation for dynamic small- cell networks, in which the load of each small-cell varies with the number of active associated small-cell users (SUs). Due to the fact that most small-cell base stations (SBSs) are deployed in an ad-hoc manner, the problem of reducing co-tier interference caused by dynamic loads in a distributed fashion is quite challenging. First, we propose a new distributed channel allocation method for small-cells with dynamic loads and define a dynamic interference graph. Based on this approach, we formulate the problem as a dynamic interference graph game and prove that the game is a potential game and has at least one pure strategy Nash equilibrium (NE) point. Moreover, we show that the best pure strategy NE point minimizes the expectation of the aggregate dynamic co-tier interference in the small-cell network. A distributed dynamic learning algorithm is then designed to achieve NE of the game, in which each SBS is unaware of the probability distributions of its own and other SBSs' dynamic loads. Simulation results show that the proposed approach can mitigate dynamic co-tier interference effectively and significantly outperform random channel selection.

• Journal of applied mathematics & informatics
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• 제9권1호
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• pp.77-86
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• 2002

Ford and Fulkerson have shown that a stationary maximal dynamic flow can be obtained by solving a transhipment problem associated with the static network and thereby finding the maximal temporally repeated dynamic flow. This flow is known to be an optical dynamic flow. This paper presents an algorithm for second best temporal1y repeated flows. A numerical example is presented.