• 한국ITS학회 논문지
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• 제15권3호
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• pp.60-67
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• 2016

환승누적함수에서 환승회수가 증가되면 환승비용에 대한 개별적인 환승의 영향이 선형 또는 비선형적으로 증가된다. 이 함수는 버스 또는 철도와 같이 대중교통노선에서 경로를 선택하는 승객의 행태를 효과적으로 설명한다. 이 함수로 통행시간이 더 소요되더라도 환승이 적은 대중교통노선을 선택하는 일반적인 상황의 구현이 가능하다. 그러나 환승누적함수가 포함되는 통행비용은 비가산성비용으로 최적경로탐색을 위해서 경로열거라는 어려운 상황을 포함한다. 본 연구는 환승누적함수를 고려하여 최적경로를 탐색하는 효과적인 방안을 제안하였다. 이를 위해 우선 환승누적함수가 포함되는 경우 경로탐색과정에서 나타나는 최적경로역전 현상을 설명하였다. 또한 복수의 경로를 탐색해서 최소의 비용경로를 최적경로로 선택하는 경험적인 방안을 제안하였다. 유입링크기반 전체경로삭제기법을 복수경로탐색기법으로 채택하여 알고리즘의 경로최적조건의 증명성에 기반하여 K개의 경로를 탐색하는 방안을 제안하였다. 환승계수를 도입하는 사례연구를 통하여 제안된 방안의 실제 교통망에 대한 활용성을 논의하였다.

• ETRI Journal
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• 제38권4호
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• pp.714-723
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• 2016

Considerable attention has been given to processing graph data in recent years. An efficient method for computing the node proximity is one of the most challenging problems for many applications such as recommendation systems and social networks. Regarding large-scale, mutable datasets and user queries, top-k query processing has gained significant interest. This paper presents a novel method to find top-k answers in a node proximity search based on the well-known measure, Personalized PageRank (PPR). First, we introduce a distribution state transition graph (DSTG) to depict iterative steps for solving the PPR equation. Second, we propose a weight distribution model of a DSTG to capture the states of intermediate PPR scores and their distribution. Using a DSTG, we can selectively follow and compare multiple random paths with different lengths to find the most promising nodes. Moreover, we prove that the results of our method are equivalent to the PPR results. Comparative performance studies using two real datasets clearly show that our method is practical and accurate.

• 대한기계학회논문집A
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• 제27권5호
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• pp.681-687
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• 2003

Terrain surfaces have to be modeled in very detail and wheel-surface contacting geometry must be well defined in order to obtain proper ground-reaction and friction forces fur realistic simulation of off-road vehicles. Delaunay triangulation is one of the most widely used methods in modeling 3-dimensional terrain surfaces, and the T-search is a relevant algorithm for searching resulting triangular polygons. The T-search method searches polygons in a successive order and may not allow real-time computation of off-road vehicle dynamics if the terrain is modeled with many polygons, depending on the computer performance used in the simulation. The dynamic T-search, which is proposed in this paper, combines conventional T-search and the concept of the dynmaic-window search which uses reduced searching windows or sets of triangular surface polygons at each frame by taking advantage of the information regarding dynamic charactereistics of a simulated vehicle. Numerical tests show improvement of searching speeds by about 5% for randomly distributed triangles. For continuous search following a vehicle path, which occurs in actual vehicle simulation, the searching speed becomes 4 times faster.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.87-89
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• 2002

This paper presents a new approach using an Improved branch exchange (IBE) technique to maximize the voltage stability as well as loss minimization in radial power systems. A suitable voltage stability index (VSI) for optimal routing algorithm is developed using novel methods both a critical transmission path based on a voltage phasor approach and an equivalent impedance method. Furthermore, the proposed algorithm can automatically detect the critical transmission path to be reached to a critical load faced with voltage collapse due to additional real or reactive leading. To develop an effective optimization technique, we also have applied a branch exchange algorithm based on a newly derived index of loss change. The proposed IBE algorithm for VSI maximization can effectively search the optimal topological structures of distribution feeders by changing the open/closed states of the sectionalizing and tie switches. The proposed algorithm has been tested with the various radial power systems to show its favorable performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권9호
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• pp.4606-4623
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• 2019

Nowadays modern cities develop in a very rapid speed. Buildings become larger than ever and the interior structures of the buildings are even more complex. This drives a high demand for precise and accurate indoor navigation systems. Although the existing commercially available 2D indoor navigation system can help users quickly find the best path to their destination, it does not intuitively guide users to their destination. In contrast, an indoor navigation system combined with augmented reality technology can efficiently guide the user to the destination in real time. Such practical applications still have various problems like position accuracy, position drift, and calculation delay, which causes errors in the navigation route and result in navigation failure. During the navigation process, the large computation load and frequent correction of the displayed paths can be a huge burden for the terminal device. Therefore, the navigation algorithm and navigation logic need to be improved in the practical applications. This paper proposes an improved navigation algorithm and navigation logic to solve the problems, creating a more accurate and effective augmented reality indoor navigation system.

• 한국멀티미디어학회논문지
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• 제23권4호
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• pp.517-524
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• 2020

Recently, many researches have been conducted to automatically recognize license plates of vehicles and use the analyzed information to manage stolen vehicles and track the vehicle. However, such a system must eventually be investigated by people through direct monitoring. Therefore, in this paper, the system of tracking a vehicle is implemented by sharing the information analyzed by the vehicle image among cameras registered in the IoT environment to minimize the human intervention. The distance between cameras is indicated by the node and the weight value of the weighted-graph, and the eigenvector centrality is used to select the camera to search. It demonstrates efficiency by comparing the time between analyzing data using weighted graph searching algorithm and analyzing all data stored in databse. Finally, the path of the vehicle is indicated on the map using parsed json data.

• 한국정보처리학회논문지
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• 제6권5호
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• pp.1342-1350
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• 1999

A new design procedure for micro cellular coverage prediction is presented here on this paper, which contains a new propagation analysis algorithm based on processing of vector data representing roads and buildings which mainly affect the propagation phenomena in micro-cell environments. The propagation analysis algorithm presented here has been developed to aim at the practical application for micro-cellular systems such as PCS or CE-2. As all the vectors used here are of closed poly lines, i.e., polygons, a simplified ray path search technique can be developed not only to determine if the calculation points are on the road polygons and but also to calculate the amount of blockage by buildings. The result shows a capability of predicting path loss with an RMS error of 5dB or lower.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 G
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• pp.3042-3044
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• 1999

This paper presents a method for solving the path planning problem for robot manipulators. The technique allows manipulators to move from a specified starting point to a goal without colliding with objects in two dimensional environment. Approximate cell decomposition with a greedy depth-first search algorithm is used to guide the end effector though Cartesian space and genetic algorithms are used to solve the joint variable for the robot manipulators.

• 대한교통학회지
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• 제22권2호
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• pp.131-143
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• 2004

최적경로 알고리즘에서 링크표지를 활용하면 도시가로망 상에 나타나는 유턴이나 피턴과 같은 주행했던 교차로를 다시 주행하는 통행에 대한 설명이 가능하다. 본 연구에서는 링크표지기법을 표지갱신기반 다수경로탐색알고리즘으로 확대하는 것이 목적이다. 이를 위해 도시가로망에서 발생하는 운전자의 합리적 통행행태를 링크기반으로 개념화하고, 이들 행태가 반영되도록 링크표지갱신 다경로 알고리즘을 제안하였다. 소규모 네트워크 테스트를 통하여 알고리즘의 수행과정과 결과의 적정성을 확인하였다. 대규모 네트워크 컴퓨터 수행을 통해 해의 퇴화현상을 파악하고 소수의 대안경로 정보제공에 활용 가능한 (K-1)차원 알고리즘을 제안하였다. 결론적으로 제안된 다수경로 알고리즘으로 링크표지기법이 제공하는 합리적 통행행태의 고려가 다수의 경로에도 가능해졌을 뿐만 아니라, 효율적인 대안경로 제공의 활용단계를 위해 한단계 전진되었다.

• 한국경영과학회지
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• 제30권1호
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• pp.1-15
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• 2005

In this paper, we deal with a mesh network design problem arising from the deployment of WDM for the optical internet. The mesh network consists of mesh topology for satisfying traffic demand while minimizing the cost of WDM, OXC, and fiber cables. The problem seeks to find an optimal routing of traffic demands in the network such that the total cost is minimized. We formulate the problem as a mixed-integer programming model and devise a tabu search heuristic procedure. Also we develop an optical internet design system that implements the proposed tabu search heuristic procedure. We demonstrate the computational efficacy of the proposed algorithm, compared with CPLEX 8.0.