• Journal of Electrical Engineering and Technology
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• 제6권6호
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• pp.867-873
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• 2011

A navigation mesh (NavMesh) is a suitable tool for the representation of a three-dimensional game world. A NavMesh consists of convex polygons covering free space, so the path can be found reliably without detecting collision with obstacles. The main disadvantage of a NavMesh is the huge state space. When the $A^*$ algorithm is applied to polygonal meshes for detailed terrain representation, the pathfinding can be inefficient due to the many states to be searched. In this paper, we propose a method to reduce the number of states searched by using visibility tests to achieve fast searching even on a detailed terrain with a large number of polygons. Our algorithm finds the visible vertices of the obstacles from the critical states and uses the heuristic function of $A^*$, defined as the distance to the goal through such visible vertices. The results show that the number of searched states can be substantially reduced compared to the $A^*$ search with a straight-line distance heuristic.

• 한국통신학회논문지
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• 제37권4B호
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• pp.236-244
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• 2012

무선 네트워크에서 최소 에너지 브로드캐스트 문제는 네트워크에 배치된 모든 노드가 브로드캐스팅과정에서 데이터 전송에 사용되는 에너지를 최소화하는 문제이다. 본 논문은 무선 센서 네트워크에서 최소 에너지 브로드캐스트 문제를 효과적으로 해결할 수 있는 메타휴리스틱 기법인 타부서치 알고리즘을 제안한다. 보다 효과적인 해 검색을 위해 제안된 알고리즘은 새로운 이웃해 생성방식과 복구함수를 적용한다. 제안된 알고리즘의 성능평가는 배치된 모든 노드로의 브로드캐스팅 시 전송 에너지와 알고리즘 실행시간 관점에서 기존의 알고리즘과 비교를 하였으며, 실험 결과에서 제안된 알고리즘이 최소 에너지 브로드캐스트 문제에 효과적으로 적용됨을 보여준다.

• 한국통신학회논문지
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• 제14권3호
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• pp.249-262
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• 1989

본 논문에서는 이동에지와 휴리스틱 탐색을 이용하여 움직이는 물체의 경계를 추출하는 간단한 방법을 제안한다. 실제 연속 영상에서 효율적으로 이동에지를 검출하는 방법을 제안하였으며, 그 결과 나타난 이동에지를 따라 간단한 휴리스틱 탐색을 수행하게 된다. 이상의 과정에서 나타나지 않은 움직이는 물체의 경계를 앞서 찾아간 신들의 끝점들로부터 휴리스틱하게 추출한다. 세 종류의 실제 연속영상에 제안한 방법을 적용하여 본 결과 적은 계산량으로 움직이는 물체의 경계검출이 가능함을 보였다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제8권2호
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• pp.195-205
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• 2002

승무일정계획이란 특정 기간동안 운행할 차량들을 대상으로 각 차량마다 필요로 하는 승무원을 배정하는 계획을 말한다. 최적 승무일정계획의 수립은 일반적으로 가능한 모든 종류의 개별 근무표들을 생성한 다음 이들을 대상으로 투입 승무원의 수가 최 소화 될 수 있는 최적조합을 선정하는 방식으로 이루어지고 있다. 근무표 최적조합의 선정을 위한 종래의 기법들은 주로 선형계획법에 기반을 두고 있으나, 목적함수에 선형식으로 표현하기 어려운 요소가 포함되어 있을 경우 적용이 어렵다는 문제가 있다. 본 논문은 선형식으로 표현하기 어려운 목적함수를 포함할 뿐만 아니라 동원 가능한 승무원의 수가 제한되어 있는 경우에도 계획 수립이 가능하도록, 기존의 정수계획법에 휴리스틱 탐색기법을 결합하는 방안을 제시한다. 휴리스틱 탐색은 정수계획법에 의해 일차로 도출된 계획의 불완전한 부분을 교정하기 위해 반복적 개선 탐색을 수행하는 방식으로 이루어진다. 기존의 방법으로 해결이 어려운 실제 현장의 승무일정계획 문제를 대상으로 한 실험 결과, 본 논문의 방법은 전문가의 수작업 결과보다 더 좋은 수준의 계획을 빠른 시간 내에 수립할 수 있음을 확인하였다.

• 정보기술과데이타베이스저널
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• 제6권2호
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• pp.71-86
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• 1999

The performance of relational database is measured by the number of disk accesses necessary to transfer data from disk to main memory. The paper proposes to vertically partition relations into fragments and to allow attribute replication to reduce the number of disk accesses. To reduce the computational time, heuristic search method using genetic algorithm is used. Genetic algorithm used employs a rank-based-sharing fitness function and elitism. Desirable parameters of genetic algorithm are obtained through experiments and used to find the solutions. Solutions of attribute replication and attribute non-replication problems are compared. Optimal solutions obtained by branch and bound method and by heuristic solutions(genetic algorithm) are also discussed. The solution method proposed is able to solve large-sized problems within acceptable time limit and shows solutions near the optimal value.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.351-358
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• 2005

Many methods have been developed and are in use for structural size optimization problems, In which the cross-sectional areas or sizing variables are usually assumed to be continuous. In most practical structural engineering design problems, however, the design variables are discrete. This paper proposes an efficient optimization method for structures with discrete-sized variables based on the harmony search (HS) meta-heuristic algorithm. The recently developed HS algorithm was conceptualized using the musical process of searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient search so that derivative information is unnecessary In this paper, a discrete search strategy using the HS algorithm is presented in detail and its effectiveness and robustness, as compared to current discrete optimization methods, are demonstrated through a standard truss example. The numerical results reveal that the proposed method is a powerful search and design optimization tool for structures with discrete-sized members, and may yield better solutions than those obtained using current method.

• 대한기계학회논문집A
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• 제27권5호
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• pp.798-806
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• 2003

Structural optimization has been carried out in continuous or discrete design space. Methods for continuous design have been well developed though they are finding the local optima. On the contrary, the existing methods for discrete design are extremely expensive in computational cost or not robust. In this research, an algorithm using tabu search is developed fur the discrete structural designs. The tabu list and the neighbor function of the Tabu concepts are introduced to the algorithm. It defines the number of steps, the maximum number for random searches and the stop criteria. A tabu search is known as the heuristic approach while genetic algorithm and simulated annealing algorithm are attributed to the stochastic approach. It is shown that an algorithm using the tabu search with random moves has an advantage of discrete design. Furthermore, the suggested method finds the reliable optimum for the discrete design problems. The existing tabu search methods are reviewed. Subsequently, the suggested method is explained. The mathematical problems and structural design problems are investigated to show the validity of the proposed method. The results of the structural designs are compared with those from a genetic algorithm and an orthogonal array design.

• 융합신호처리학회논문지
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• 제3권2호
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• pp.89-95
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• 2002

글로벌 라우팅(global routing)은 VLSI 설계 과정중의 하나로, 네트리스트의 모든 네트들을 연결하기 위하여 각 네트들을 라우팅 영역(routing area)에 할당시키는 문제이며, 글로벌 라우팅에서 최적의 해를 얻기 위해 maze routing 알고리즘, line-probe 알고리즘, shortest path 기반 알고리즘, Steiner tree 기반 알고리즘등이 이용된다. 본 논문에서는 라우팅 그래프에서 최단 경로 Steiner tree 탐색방법인 weighted network heuristic(WNH)과 이를 기반으로 하는 글로벌 라우팅 유전자 알고리즘(genetic algorithm; GA)을 제안하였으며, 제안한 방식을 시뮬레이티드 어닐링(SA) 방식과 비교, 분석하였다.

• Structural Engineering and Mechanics
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• 제62권6호
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• pp.749-758
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• 2017

In structural mechanics, traditional analyses methods usually employ matrix operations for obtaining displacement and internal forces of the structure under the external effects, such as distributed loads, earthquake or wind excitations, and temperature changing inter alia. These matrices are derived from the well-known principle of mechanics called minimum potential energy. According to this principle, a system can be in the equilibrium state only in case when the total potential energy of system is minimum. A close examination of the expression of the well-known equilibrium condition for linear problems, $P=K{\Delta}$, where P is the load vector, K is the stiffness matrix and ${\Delta}$ is the displacement vector, it is seen that, basically this principle searches the displacement set (or deformed shape) for a system that minimizes the total potential energy of it. Instead of using mathematical operations used in the conventional methods, with a different formulation, meta-heuristic algorithms can also be used for solving this minimization problem by defining total potential energy as objective function and displacements as design variables. Based on this idea the technique called Total Potential Optimization using Meta-heuristic Algorithms (TPO/MA) is proposed. The method has been successfully applied for linear and non-linear analyses of trusses and truss-like structures, and the results have shown that the approach is much more successful than conventional methods, especially for analyses of non-linear systems. In this study, the application of TPO/MA, with Harmony Search as the selected meta-heuristic algorithm, to cables net system is presented. The results have shown that the method is robust, powerful and accurate.

• 산업경영시스템학회지
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• 제29권3호
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• pp.62-69
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• 2006

Vehicle routing problem with time windows is determined each vehicle route in order to minimize the transportation costs. All delivery points in geography have various time restriction in camparision with the basic vehicle routing problem. Vechicle routing problem with time windows is known to be NP-hard, and it needs a lot of computing time to get the optimal solution, so that heuristics are more frequently developed than optimal algorithms. This study aims to develop a heuristic method which combines guided local search with a tabu search in order to minimize the transportation costs for the vehicle routing assignment and uses ILOG programming library to solve. The computational tests were performed using the benchmark problems.