• Proceedings of the Korea Inteligent Information System Society Conference
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• 2005.05a
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• pp.222-231
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• 2005

본 논문에서는 자율 에이전트에 의해 미지의 공간을 탐사하는 실시간 그래프 탐색 알고리즘 $DFS-RTA^{\ast}$와 $DFS-PHA^{\ast}$를 제안하고 그 효율성을 비교한다. 두 알고리즘들은 모두 깊이-우선 탐색(DFS)을 기초로 하고 있으며, 직전 노드로의 빠른 후진(backtrack) 을 위해 각각 실시간 최단 경로 탐색 방법인 $RTA^{\ast}$와 $PHA^{\ast}$를 적용하는 것이 특징이다. 본 논문에서는 대표적인 3차원 온라인 게임 환경인 Unreal Tournament 게임과 지능형 캐릭터 에이전트인 KGBot를 이용한 실험을 통해 두 탐색 알고리즘의 완전성과 효율성을 분석해본다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.70-72
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• 2004

본 논문에서는 Grid 시스템에서 작업을 할당하기 위해서, 가능한 모든 작업 분할 방법을 찾는 기법에 대해 연구 하고자 한다. 즉 다수의 노드를 가진 여러 클러스터 사이에 많은 노드를 필요로 하는 작업을 할당하기 위해 변형된 깊이 우선 탐색 트리를 사용하여 작업 분할 리스트를 찾는 방법을 만들고, 그 알고리즘의 속도 및 효율을 평가하였다. 제안된 알고리즘은 전체 리스트를 검색하는 방법에 비해 속도 측면에서 빠른 효율을 보이는 것을 알 수 있다. 따라서 제안된 알고리즘은 동기화된 작업의 스케쥴링에 사용할 경우 유용할 것으로 생각된다.

• Journal of Korean Society of Transportation
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• v.23 no.8 s.86
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• pp.113-128
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• 2005

We propose a modified version of 'a Lazy Version of Eppstein's k shortest paths Algorithm(LVEA)' which can find the k shortest paths in total time O(m+ n log n+ K log K) in the worst-case. The algorithm we propose, since the Link repeated paths are all eliminated when enumerating k shortest paths, is No link repeated paths algorithm that is suitable in a transportation network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.11
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• pp.1538-1543
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• 2018

For n pairs of points (a,b) on a circle, the line segment to connect two points is called a chord. These chords define a new graph G. Each chord corresponds to a vertex of G, and if two chords intersect, the two vertices corresponding to them are connected by an edge. This makes a graph, called by a circle graph. In this paper, we deal with the problem to find the connected components of a circle graph. The connected component of a graph G is a maximal subgraph H such that any two vertices in H can be connected by a path. When the adjacent matrix of G is given, the problem to find them can be solved by either the depth-first search or the breadth-first search. But when only the information for the chords is given as an input, it takes ${\Omega}(n^2)$ time to obtain the adjacent matrix. In this paper, we do not make the adjacent matrix and develop an $O(n{\log}^2n)$ algorithm for the problem.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.160-162
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• 2004

본 논문에서는 XML 문서간의 자동 변환을 위한 효율적인 XSLT 스크립트를 생성하는 알고리즘을 제안한다. 제안된 방법은 XML DTD를 구성하는 단말 노드간의 일대일 대응관계가 주어져 있다는 가정 하에 XSLT 스크립트를 생성하는데 중점을 둔다. 제안된 알고리즘은 상향식과 하향식의 복합적인 접근 방식을 적용한다. 먼저 중간 노드간의 대응관계를 상향식으로 생성하며 하향식 깊이 우선 탐색을 적용하여 XSLT 스크립트를 생성한다. 실험결과, 제안된 방법은 기존 연구와 비교하여 XML 문서를 보다 빠르게 변환하는 XSLT 스크립트를 생성하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.730-732
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• 2005

본 논문에서는 자율적인 다수의 에이전트들이 협력하여 미지의 공간을 탐사하는 실시간 그래프 탐색 알고리즘인 MADFS를 제안하고 그 효율성을 분석한다. 이 알고리즘은 깊이-우선 탐색(DFS)에 기초한 단일 에이전트 공간 탐사 알고리즘인 dFS-RTA* 와 DFS-PHA* 를 멀티 에이전트 환경에 적합하게 에이전트 간 정보공유 방식과 방문노드 선택전략을 설계하여 확장하였다. 본 논문에서는 대표적인 3차원 온라인 게임 환경인 Unreal Tournament 게임과 지능형 캐릭터 에이전트인 KGBot를 이용한 실험을 통해 알고리즘의 완전성과 효율성을 분석해본다.

• Journal of Intelligence and Information Systems
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• v.11 no.1
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• pp.153-167
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• 2005

In this paper, we consider the problem of exploring unknown environments with a mobile robot or an autonomous character agent. Traditionally, research efforts to address the space exploration problem havefocused on the graph-based space representations and the graph search algorithms. Recently EXPLORE, one of the most efficient search algorithms, has been discovered. It traverses at most min$min(mn, d^2+m)$ edges where d is the deficiency of a edges and n is the number of edges and n is the number of vertices. In this paper, we propose DFS-RTA* and DFS-PHA*, two real-time graph search algorithms for directing an autonomous agent to explore in an unknown space. These algorithms are all built upon the simple depth-first search (DFS) like EXPLORE. However, they adopt different real-time shortest path-finding methods for fast backtracking to the latest node, RTA* and PHA*, respectively. Through some experiments using Unreal Tournament, a 3D online game environment, and KGBot, an intelligent character agent, we analyze completeness and efficiency of two algorithms.

• Journal of the Korea Society of Computer and Information
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• v.16 no.4
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• pp.127-135
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• 2011

Efficient ordering of decision variables is one of the methods that find solutions quickly in the depth first search using backtracking. At this time, development of variables ordering algorithms considering dynamic and static properties of the problems is very important. However, to exploit optimal variable ordering algorithms appropriate to the problems. In this paper, we propose a problem classifying rule which provides problem type based on variables' properties, and use this rule to predict optimal type of variable ordering algorithms. We choose frequency allocation problem as a DS-type whose decision variables have dynamic and static properties, and estimate optimal variable ordering algorithm. We also show the usefulness of problem classifying rule by applying base station problem as a special case whose problem type is not generated from the presented rule.

• The KIPS Transactions:PartA
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• v.18A no.3
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• pp.115-122
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• 2011

It is very hard to obtain a general algorithm for solution of all the constraint satisfaction optimization problems. However, if the whole problem is separated into subproblems by characteristics of decision variables, we can assume that an algorithm to obtain solutions of these subproblems is easier. Under the assumption, we propose a problem classifying rule which subdivide the whole problem, and develop backtracking algorithms fit for these subproblems. One of the methods of finding a quick solution is efficiently arrange for any order of the search tree nodes. We choose the cluster head positioning problem in wireless sensor networks in which static characteristics is dominant and interference minimization problem of RFID readers that has hybrid mixture of static and dynamic characteristics. For these problems, we develop optimal variable ordering algorithms, and compare with the conventional methods. As a result of classifying the problem into subproblems, we can realize a backtracking framework for systematic search. We also have shown that developed backtracking algorithms have good performance in their quality.

• Journal of the Korea Computer Graphics Society
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• v.17 no.2
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• pp.17-26
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• 2011

This paper presents an interactive progressive image transmission method, which enables a remote user to interactively select and transmit preferred regions from an index image. Our enhanced quadtree decomposition using PSNR-based rules and new implicit quadtree coding provide better rate-distortion performance than previous quadtree coders as well as leading bit plane methods. An adaptive traversal of child nodes is introduced for better visual display of restored images. Depth-first traversal combined with breadth-first traversal of the quadtree to accomplish interactive transmission as presented, results in a method that provides competitive performance at a low level of computational complexity. Moreover, our decoding requires only simple arithmetic which is enabling our method to be used for real-time mobile applications.