• Title/Summary/Keyword: Path-Finding

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A Study on Finding the K Shortest Paths for the Multimodal Public Transportation Network in the Seoul Metropolitan (수도권 복합 대중교통망의 복수 대안 경로 탐색 알고리즘 고찰)

  • Park, Jong-Hoon;Sohn, Moo-Sung;Oh, Suk-Mun;Min, Jae-Hong
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.607-613
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    • 2011
  • This paper reviews search methods of multiple reasonable paths to implement multimodal public transportation network of Seoul. Such a large scale multimodal public transportation network as Seoul, the computation time of path finding algorithm is a key and the result of path should reflect route choice behavior of public transportation passengers. Search method of alternative path is divided by removing path method and deviation path method. It analyzes previous researches based on the complexity of algorithm for large-scale network. Applying path finding algorithm in public transportation network, transfer and loop constraints must be included to be able to reflect real behavior. It constructs the generalized cost function based on the smart card data to reflect travel behavior of public transportation. To validate the availability of algorithm, experiments conducted with Seoul metropolitan public multimodal transportation network consisted with 22,109 nodes and 215,859 links by using the deviation path method, suitable for large-scale network.

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A dynamic Shortest Path Finding with Forecasting Result of Traffic Flow (교통흐름 예측 결과틀 적용한 동적 최단 경로 탐색)

  • Cho, Mi-Gyung
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.13 no.5
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    • pp.988-995
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    • 2009
  • One of the most popular services of Telematics is a shortest path finding from a starting point to a destination. In this paper, a dynamic shortest path finding system with forecasting result of traffic flow in the future was developed and various experiments to verify the performance of our system using real-time traffic information has been conducted. Traffic forecasting has been done by a prediction system using Bayesian network. It searched a dynamic shortest path, a static shortest path and an accumulated shortest path for the same starting point and destination and calculated their travel time to compare with one of its real shortest path. From the experiment, over 75%, the travel time of dynamic shortest paths is the closest to one of their real shortest paths than one of static shortest paths and accumulated shortest paths. Therefore, it is proved that finding a dynamic shortest path by applying traffic flows in the future for intermediated intersections can give more accurate traffic information and improve the quality of services of Telematics than finding a static shortest path applying by traffic flows of the starting time for intermediated intersections.

Determination of the Shortest Transportation Path in Wartime (전시 최단수송경로 선정)

  • Yun Jong-Ok;Ha Seok-Tae
    • Journal of the military operations research society of Korea
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    • v.17 no.2
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    • pp.72-89
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    • 1991
  • In transportation network problems, it is often desirable to select multiple number of the shortect paths. On problems of finding these paths, algorithms have been developed to choose single shortest path, k-shortest paths and k-shortest paths via p-specified nodes in a network. These problems consider the time as the main factor. In wartime, we must consider availability as well as time to determine the shortest transportation path, since we must take into account enemy's threat. Therefore, this paper addresses the problem of finding the shortest transportation path considering both time and availability. To accomplish the objective of this study, values of k-shortest paths are computed using the algorithm for finding the k-shortest paths. Then availabilties of those paths are computed through simulation considering factors such as rates of suffering attack, damage and repair rates of the paths. An optimal path is selected using any one of the four decision rules that combine the value and availability of a path.

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A New Route Guidance Method Considering Pedestrian Level of Service using Multi-Criteria Decision Making Technique

  • Joo, Yong-Jin;Kim, Soo-Ho
    • Spatial Information Research
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    • v.19 no.1
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    • pp.83-91
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    • 2011
  • The route finding analysis is an essential geo-related decision support tool in a LBS(Location based Services) and previous researches related to route guidance have been mainly focused on route guidances for vehicles. However, due to the recent spread of personal computing devices such as PDA, PMP and smart phone, route guidance for pedestrians have been increasingly in demand. The pedestrian route guidance is different from vehicle route guidance because pedestrians are affected more surrounding environment than vehicles. Therefore, pedestrian path finding needs considerations of factors affecting walking. This paper aimed to extract factors affecting walking and charting the factors for application factors affecting walking to pedestrian path finding. In this paper, we found various factors about environment of road for pedestrian and extract the factors affecting walking. Factors affecting walking consist of 4 categories traffic, sidewalk, network, safety facility. We calculated weights about each factor using analytic hierarchy process (AHP). Based on weights we calculated scores about each factor's attribute. The weight is maximum score of factor. These scores of factor are used to optimal pedestrian path finding as path finding cost with distance, accessibility.

Optimization of real-time path finding for material handling of finishing work considering the logistics flow (물류량을 고려한 마감공사 자재운반의 실시간 경로탐색 최적화 연구)

  • Kim, Wansoub;Lee, Dongmin;Kim, Taehoon;Cho, Hunhee;Kang, Kyung-In
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2015.11a
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    • pp.170-171
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    • 2015
  • Resource procurement and material handling are considered as a significant part of construction project especially in large or tall building construction site. There are multiple variables that must be considered in a construction site during finishing work such as movement of materials, equipments, and workers. Therefore, it is difficult for construction workers to find the material handling path solely by intuition. The aim of this study is to propose a real-time path finding model suitable for complicated logistics flow in the field. The model explores the optimal transport path of finishing material with its basis on optimization algorithm, and it determines the direction of the Smart Sign. The proposed model is expected to be utilized for planning of efficient finishing material handling.

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A Method for finding the k Most Vital Arcs in the Shortest Path Problem (최단경로문제에서 k개의 치명호를 찾는 방법)

  • 안재근;정호연;박순달
    • Journal of the Korean Operations Research and Management Science Society
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    • v.23 no.4
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    • pp.11-20
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    • 1998
  • This paper deals with a mathematical model and an algorithm for the problem of determining k most vital arcs in the shortest path problem. First, we propose a 0-1 integer programming model for finding k most vital arcs in shortest path problem given the ordered set of paths with cardinality q. Next, we also propose an algorithm for finding k most vital arcs ln the shortest path problem which uses the 0-1 Integer programming model and shortest path algorithm and maximum flow algorithms repeatedly Malik et al. proposed a non-polynomial algorithm to solve the problem, but their algorithm was contradicted by Bar-Noy et al. with a counter example to the algorithm in 1995. But using our algorithm. the exact solution can be found differently from the algorithm of Malik et al.

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Finding a Second Best Coverage Path (차선거리유지 경로찾기)

  • Na, Hyeon-Suk;Kim, Jung-Hee
    • Journal of KIISE:Computer Systems and Theory
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    • v.35 no.8
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    • pp.385-393
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    • 2008
  • The best coverage problem is finding a path whose worst distance to the sensor-set is the best among all paths. Instead, if the user stays close to its nearest two sensors, then the stability of the wireless connection may be guaranteed. So we consider the problem of finding a second best coverage path; given the sensor set U, a starting point s and a target point t, find a path whose worst distance to the second closest sensor is minimized. This paper presents an O(n logn) -time algorithm to find such a path. We also give experimental evidence showing that the connection to the sensor-set along a second best coverage path is more stable than that along the best coverage path.

The Maximum Origin-Destination Flow Path Problem in a Directed Network (유방향 네트워크에서 최대물동량경로 문제에 관한 연구)

  • Seong Gi-Seok;Song Seong-Heon
    • Journal of the military operations research society of Korea
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    • v.18 no.2
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    • pp.151-166
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    • 1992
  • In this paper, we define a problem finding a simple path that maximizes the sum of the satisfied Origin-Destination (O-D) flows between nodes covered by that path as a Maximum O-D Flow Path Problem(MODEP). We established a formulation and suggested a method finding MODEP in a directed network. The method utilizes the constraint relaxation technique and the Dual All Integer Algorithm.

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Development of Optimal-Path Finding System(X-PATH) Using Search Space Reduction Technique Based on Expert System (전문가시스템을 이용한 최적경로 탐색시스템(X-PATH)의 개발)

  • 남궁성;노정현
    • Journal of Korean Society of Transportation
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    • v.14 no.1
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    • pp.51-67
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    • 1996
  • The optimal path-finding problem becomes complicated when multiple variables are simultaneously considered such as physical route length, degree of congestion, traffic capacity of intersections, number of intersections and lanes, and existence of free ways. Therefore, many researchers in various fields (management science, computer science, applied mathematics, production planning, satellite launching) attempted to solve the problem by ignoring many variables for problem simplification, by developing intelligent algorithms, or by developing high-speed hardware. In this research, an integration of expert system technique and case-based reasoning in high level with a conventional algorithms in lower level was attempted to develop an optimal path-finding system. Early application of experienced driver's knowledge and case data accumulated in case base drastically reduces number of possible combinations of optimal paths by generating promising alternatives and by eliminating non-profitable alternatives. Then, employment of a conventional optimization algorithm provides faster search mechanisms than other methods such as bidirectional algorithm and $A^*$ algorithm. The conclusion obtained from repeated laboratory experiments with real traffic data in Seoul metropolitan area shows that the integrated approach to finding optimal paths with consideration of various real world constraints provides reasonable solution in a faster way than others.

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A Hierarchical Graph Structure and Operations for Real-time A* Path finding and Dynamic Graph Problem (실시간 A* 길 찾기와 동적 그래프 문제를 위한 계층적 그래프 구조와 연산자)

  • Kim, Tae-Won;Cho, Kyung-Eun;Um, Ky-Hyun
    • Journal of Korea Game Society
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    • v.4 no.3
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    • pp.55-64
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    • 2004
  • A dynamic graph is suitable for representing and managing dynamic changable obstacles or terrain information in 2D/3D games such as RPG and Strategy Simulation Games. We propose a dynamic hierarchical graph model with fixed level to perform a quick A* path finding. We divide a graph into subgraphs by using space classification and space model, and construct a hierarchical graph. And then we perform a quick path fading on the graph by using our dynamic graph operators. With our experiments we show that this graph model has efficient properties for finding path in a dynamic game environment.

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