• 한국측량학회지
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• 제25권1호
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• pp.1-8
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• 2007

최근 주상복합형의 주거공간, 지하철, 대형쇼핑몰 등 건물내부가 복잡하고 대규모인 공간에서 머무르는 시간과 기회가 날로 증가하고 있다. 건물이 복잡할수록 건물 내에서 사람들이 원하는 목적지에 도착하기까지 보다 많은 시행착오를 겪으면서 이동하게 된다. 시행착오를 줄이고, 보다 빠르게 이동하기 위해서는 최단경로를 탐색하여 제공하는 시스템이 필요하게 된다. 이러한 대규모 공간 내에서의 최적이동경로에 대한 정보는 특히 화재나 정전, 테러위협과 같은 응급상황에서 더욱 필요로 하게 된다. 이에 본 연구에서는 Raster GIS기반의 데이터구조 상에서 $A^*$알고리즘을 사용한 최단경로 탐색기법을 비교, 분석하고자 한다. 평상시에는 건물내부에서의 위치 이동시에 필요한 최단 경로를 제공하고, 응급상황에서는 탐색시간을 최소화하여 대피 경로를 제공하는 방안을 제시하였으며, 이를 캠퍼스 건물을 이용하여 예시하였다.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.92-99
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• 2024

To minimize the cumulative radiation dose, various path-finding approaches for single agent have been proposed. However, for emergence situations such as nuclear power plant accident, these methods cannot be effectively utilized for evacuating a large number of workers because no multi-agent method is valid to conduct the mission. In this study, a novel algorithm for solving the multi-agent path-finding problem is proposed using the conflict-based search approach and the objective function redefined in terms of the cumulative radiation dose. The proposed method can find multi paths that all agents arrive at the destinations with reducing the overall radiation dose. To verify the proposed method, three problems were defined. In the single-agent problem, the objective function proposed in this study reduces the cumulative dose by 82% compared with that of the shortest distance algorithm in experiment environment of this study. It was also verified in the two multi-agent problems that multi paths with minimized the overall radiation dose, in which all agents can reach the destination without collision, can be found. The method proposed in this study will contribute to establishing evacuation plans for improving the safety of workers in radiation-related facilities.

• Management Science and Financial Engineering
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• 제12권2호
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• pp.87-110
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• 2006

In a hierarchical road network, all roads can be classified according to their attributes such as speed limit, number of lanes, etc. By splitting the whole road network into the subnetworks of the highlevel and low-level roads, we can reduce the size of the network to be calculated at once, and find a path in the way that drivers usually adopt when searching out a travel route. To exploit the hierarchical property of road networks, we define a convenient path and propose an algorithm for finding convenient paths. We introduce a parameter indicating the driver's tolerance to the difference between the length of a convenient path and that of a shortest convenient path. From this parameter, we can determine how far we have to search for the entering and exiting gateway. We also propose some techniques for reducing the number of pairs of entries and exits to be searched in a road network. A result of the computational experiment on a real road network is given to show the efficiency of the proposed algorithm.

• 로봇학회논문지
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• 제13권2호
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• pp.142-149
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• 2018

$RRT^*$ (Rapidly exploring Random $Tree^*$) based algorithms are widely used for path planning. Informed $RRT^*$ uses $RRT^*$ for generating an initial path and optimizes the path by limiting sampling regions to the area around the initial path. $RRT^*$ algorithms have several limitations such as slow convergence speed, large memory requirements, and difficulties in finding paths when narrow aisles or doors exist. In this paper, we propose an algorithm to deal with these problems. The proposed algorithm applies the image skeletonization to the gridmap image for generating an initial path. Because this initial path is close to the optimal cost path even in the complex environments, the cost can converge to the optimum more quickly in the proposed algorithm than in the conventional Informed $RRT^*$. Also, we can reduce the number of nodes and memory requirement. The performance of the proposed algorithm is verified by comparison with the conventional Informed $RRT^*$ and Informed $RRT^*$ using initial path generated by $A^*$.

• Management Science and Financial Engineering
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• 제10권1호
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• pp.53-75
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• 2004

Most existing studies on time-dependent networks have been focused on finding a minimum delay path given a departure time at the origin. There, however, frequently happens a situation where users can select any departure time in a certain time interval and want to spend as little time as possible on traveling the networks. In that case. the delay spent on traveling networks depends on not only paths but also the actual departure time at the origin. In this paper, we propose a new problem in time-dependent networks whose objective is to find an optimal departure time given possible departure time interval at the origin. From the optimal departure time, we can obtain a path with minimum delay among all paths for possible departure times at the origin. In addition, we present an algorithm for finding an optimal departure time by enumerating trees which remain shortest path tree for a certain time interval.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2732-2734
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• 2000

This paper proposes a path planning algorithm for mobile robots. To generate a minimum-distance path for mobile robots, we use the Genetic Algorithm(GA) and Visibility Graph. After finding a minimum-distance path between a start and a goal point, the path is revised to find the smooth subminimum-distance path by a path-smoothing algorithm. Simulation results show that the proposed algorithms are effective.

• 한국정보과학회논문지:데이타베이스
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• 제36권5호
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• pp.405-410
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• 2009

본 논문에서는 기존 k-최근접 객체 검색의 효율성을 개선하고 도로 네트워크에의 응용을 용이하게 하기 위하여 질의 점으로부터 k개의 정적 객체까지의 경로를 효과적으로 탐색할 수 있는 방법을 제안한다. 제안한 방법은 우선, k-최근접 이웃 질의 방법을 이용하여 후보 정적 객체들을 선정한 후 이들 후보 객체들의 위치 정보를 이용하여 최단 경로를 탐색한다. 일대다 경로탐색을 위하여 A* 알고리즘을 개선하여 반복된 일대일 경로탐색에 따르는 중복된 노드 스캔을 제거한다. 또, 계산된 결과를 이용하여 질의점으로부터 네트워크 거리상으로 가까운 k개의 정적 객체들의 위치를 재정렬하여 반환한다. 성능평가 실험 결과, 제안한 방법은 기존 방법들인 INE, post-Dijkstra, 그리고 $na{\ddot{i}}ve$ method에 비해 정확성이 100%로 매우 높게 나타났으며, 노드 탐색 시간은 $1.3{\sim}3.0$배로 향상된 성능을 보였다.

• 한국정보통신학회논문지
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• 제13권11호
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• pp.2367-2372
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• 2009

최근 단말기 기반의 경로 탐색에서도 동적인 정보를 반영하기 위한 연구가 진행되고 있다. 제시하는 대부분의 알고리즘은 $A^*$알고리즘을 기반으로 한다. 휴리스틱을 이용한 알고리즘에서는 탐색 비용이 증가하는 문제가 발생할 수 있다. 추상 그래프는 실제 도로 네트워크를 단순화한 그래프로, 휴리스틱 의존성과 탐색 비용을 줄이기 위해 제안된 방법이다. 이 논문에서는 생성방법이 다른 두 가지의 추상 그래프를 이용하여 성능 평가하였다. 추상 그래프는 생성 방법에 따라 동일 특성 노드 합병을 통한 추상 그래프($AG^H$)와 연결 노드 합병을 통한 추상 그래프($AG^C$)로 구별된다. 성능 실험 결과 생성 비용과 노드 접근 비용 측면에서 $AG^C$가 좋은 성능을 보였지만, 탐색된 경로의 이동시간측면에서는 $AG^H$가 좋은 성능을 보였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.337-340
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• 1999

At each iteration, the path is either extended by adding a new node, or contracted by deleting its terminal node. When the destination becomes the terminal node of the path, the algorithm terminate. In the process of finding the shortest path to given destination, the algorithm visits other node, there by obtaining a shortest path from the origin to them. We show here that when the auction algorithm is applied to this equivalent program with some special rules for choosing the initial object prices and the person submitting a bid at each iteration, one obtains the generic form of the $\varepsilon$-relaxation method. Thus, the two methods are mathematically equivalent

• 대한전기학회논문지:시스템및제어부문D
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• 제54권3호
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• pp.148-155
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• 2005

A seam-line determination algorithm is proposed to determine image border-line in mosaicing using the transformation of gray value differences and dynamic programming. Since visually good border-line is the one along which pixel differences are as small as possible, it can be determined in association with an optimal path finding algorithm. A well-known effective optimal path finding algorithm is the Dynamic Programming (DP). Direct application of the dynamic programming to the seam-line determination causes the distance effect, in which seam-line is affected by its length as well as the gray value difference. In this paper, an adaptive cost transform algorithm with which the distance effect is suppressed is proposed in order to utilize the dynamic programming on the transformed pixel difference space. Also, a figure of merit which is the summation of fixed number of the biggest pixel difference on the seam-line (SFBPD) is suggested as an evaluation measure of seamlines. The performance of the proposed algorithm has been tested in both quantitively and visually on various kinds of images.