• Title/Summary/Keyword: Dynamic Programming

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Thrust Generation on Flapping-Aifoil by Dynamic Stall (동적 실속을 이용한 Flapping-Airfoil의 추력 발생)

  • Lee Jung Sang;Kim Chongam;Rho Oh-Hyun
    • 한국전산유체공학회:학술대회논문집
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    • 2002.10a
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    • pp.35-40
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    • 2002
  • This paper deals with a thrust generation on flapping-airfoil by dynamic stall. Dynamic stall refers to a series of complicated aerodynamic phenomena accompanied by a stall delay in unsteady motion. In most cases, once it occurs, the dynamic stall may lead to an abrupt fluctuation of aerodynamic forces. An inverse $k\acute{a}rm\acute{a}n$ vortex has been considered as a main reason for a thrust generation. In this paper, however, we have found out that a thrust is closely related to reduced frequency and leading edge vortex in addition to inverse Karman vortex. In order to certify our opinion, picking and plunging motions were calculated with the parameter of amplitude and frequency by using the unsteady, incompressible Navier-Stokes flow solver with a two-equation turbulence model. For more efficient computation, it is parallelized by MPI programming method.

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A Link-Based Label Correcting Multi-Objective Shortest Paths Algorithm in Multi-Modal Transit Networks (복합대중교통망의 링크표지갱신 다목적 경로탐색)

  • Lee, Mee-Young;Kim, Hyung-Chul;Park, Dong-Joo;Shin, Seong-Il
    • Journal of Korean Society of Transportation
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    • v.26 no.1
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    • pp.127-135
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    • 2008
  • Generally, optimum shortest path algorithms adopt single attribute objective among several attributes such as travel time, travel cost, travel fare and travel distance. On the other hand, multi-objective shortest path algorithms find the shortest paths in consideration with multi-objectives. Up to recently, the most of all researches about multi-objective shortest paths are proceeded only in single transportation mode networks. Although, there are some papers about multi-objective shortest paths with multi-modal transportation networks, they did not consider transfer problems in the optimal solution level. In particular, dynamic programming method was not dealt in multi-objective shortest path problems in multi-modal transportation networks. In this study, we propose a multi-objective shortest path algorithm including dynamic programming in order to find optimal solution in multi-modal transportation networks. That algorithm is based on two-objective node-based label correcting algorithm proposed by Skriver and Andersen in 2000 and transfer can be reflected without network expansion in this paper. In addition, we use non-dominated paths and tree sets as labels in order to improve effectiveness of searching non-dominated paths. We also classifies path finding attributes into transfer and link travel attribute in limited transit networks. Lastly, the calculation process of proposed algorithm is checked by computer programming in a small-scaled multi-modal transportation network.

Intelligent Optimal Route Planning Based on Context Awareness (상황인식 기반 지능형 최적 경로계획)

  • Lee, Hyun-Jung;Chang, Yong-Sik
    • Asia pacific journal of information systems
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    • v.19 no.2
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    • pp.117-137
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    • 2009
  • Recently, intelligent traffic information systems have enabled people to forecast traffic conditions before hitting the road. These convenient systems operate on the basis of data reflecting current road and traffic conditions as well as distance-based data between locations. Thanks to the rapid development of ubiquitous computing, tremendous context data have become readily available making vehicle route planning easier than ever. Previous research in relation to optimization of vehicle route planning merely focused on finding the optimal distance between locations. Contexts reflecting the road and traffic conditions were then not seriously treated as a way to resolve the optimal routing problems based on distance-based route planning, because this kind of information does not have much significant impact on traffic routing until a a complex traffic situation arises. Further, it was also not easy to take into full account the traffic contexts for resolving optimal routing problems because predicting the dynamic traffic situations was regarded a daunting task. However, with rapid increase in traffic complexity the importance of developing contexts reflecting data related to moving costs has emerged. Hence, this research proposes a framework designed to resolve an optimal route planning problem by taking full account of additional moving cost such as road traffic cost and weather cost, among others. Recent technological development particularly in the ubiquitous computing environment has facilitated the collection of such data. This framework is based on the contexts of time, traffic, and environment, which addresses the following issues. First, we clarify and classify the diverse contexts that affect a vehicle's velocity and estimates the optimization of moving cost based on dynamic programming that accounts for the context cost according to the variance of contexts. Second, the velocity reduction rate is applied to find the optimal route (shortest path) using the context data on the current traffic condition. The velocity reduction rate infers to the degree of possible velocity including moving vehicles' considerable road and traffic contexts, indicating the statistical or experimental data. Knowledge generated in this papercan be referenced by several organizations which deal with road and traffic data. Third, in experimentation, we evaluate the effectiveness of the proposed context-based optimal route (shortest path) between locations by comparing it to the previously used distance-based shortest path. A vehicles' optimal route might change due to its diverse velocity caused by unexpected but potential dynamic situations depending on the road condition. This study includes such context variables as 'road congestion', 'work', 'accident', and 'weather' which can alter the traffic condition. The contexts can affect moving vehicle's velocity on the road. Since these context variables except for 'weather' are related to road conditions, relevant data were provided by the Korea Expressway Corporation. The 'weather'-related data were attained from the Korea Meteorological Administration. The aware contexts are classified contexts causing reduction of vehicles' velocity which determines the velocity reduction rate. To find the optimal route (shortest path), we introduced the velocity reduction rate in the context for calculating a vehicle's velocity reflecting composite contexts when one event synchronizes with another. We then proposed a context-based optimal route (shortest path) algorithm based on the dynamic programming. The algorithm is composed of three steps. In the first initialization step, departure and destination locations are given, and the path step is initialized as 0. In the second step, moving costs including composite contexts into account between locations on path are estimated using the velocity reduction rate by context as increasing path steps. In the third step, the optimal route (shortest path) is retrieved through back-tracking. In the provided research model, we designed a framework to account for context awareness, moving cost estimation (taking both composite and single contexts into account), and optimal route (shortest path) algorithm (based on dynamic programming). Through illustrative experimentation using the Wilcoxon signed rank test, we proved that context-based route planning is much more effective than distance-based route planning., In addition, we found that the optimal solution (shortest paths) through the distance-based route planning might not be optimized in real situation because road condition is very dynamic and unpredictable while affecting most vehicles' moving costs. For further study, while more information is needed for a more accurate estimation of moving vehicles' costs, this study still stands viable in the applications to reduce moving costs by effective route planning. For instance, it could be applied to deliverers' decision making to enhance their decision satisfaction when they meet unpredictable dynamic situations in moving vehicles on the road. Overall, we conclude that taking into account the contexts as a part of costs is a meaningful and sensible approach to in resolving the optimal route problem.

A stereo matching algorithm in pixel-based disparity space image (화소기반 변이공간영상에서의 스테레오 정합)

  • 김철환;이호근;하영호
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.6C
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    • pp.848-856
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    • 2004
  • In this paper, a fast stereo matching algorithm based on pixel-wise matching strategy, which can get a stable and accurate disparity map, is proposed. Since a stereo image pair has small differences each other and the differences between left and right images are just caused by horizontal shifts with some order, the matching using a large window will not be needed within a given search range. However, disparity results of conventional pixel-based matching methods are somewhat unstable and wrinkled, the principal direction of disparities is checked by the accumulated cost along a path on array with the dynamic programming method. Experimental results showed that the proposed method could remove almost all disparity noise and set a good quality disparity map in very short time.

Tumor boundary extraction from brain MRI images using active contour models (Snakes) (스네이크를 이용한 뇌 자기 공명 영상에서 종양의 경계선 추출)

  • Ryeong-Ju Kim;Young-Chul Kim;Heung-Kook Choi
    • Journal of the Institute of Convergence Signal Processing
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    • v.4 no.2
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    • pp.1-6
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    • 2003
  • The study is to automatically or semi-automatically detect the accurate contour of tumors or lesions using active contour models (Snakes) in the MRI images of the brain. In the study we have improved the energy-minimization problem of snakes using dynamic programming and have utilized the values of the canny edge detector by the image force to make the snake less sensitive in noises. For the extracted boundary, the inside area, the perimeter and its center coordinates could be calculated. In addition, the multiple 2D slices with the contour of the lesion wore combined to visualized the shape of the lesion in 3D. We expect that the proposed method in this paper will be useful to make a treatment plan as well as to evaluate the treatments.

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On-line signature verification method using Gabor filter (Gabor 필터를 이용한 온라인 서명 검증 기법)

  • 이종현;김성훈;김재희
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.41 no.3
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    • pp.129-137
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    • 2004
  • This paper presents a signature verification method that uses Gabor filter in computing similarity between signatures. In computing similarity to compare two on-line signatures, the temporal relationship between two signatures should be computed in advance. However, conventional point matching method using DP(dynamic programming) matching consumes much computation. In this paper, we propose a fast method for computing the temporal relationship between two on-line signatures by using the phase output of Gabor Inter applied on the on-line signature signals. Two similarity measures are defined in the method: Temporal Similarity and Temporally Arranged Feature Profile Similarity. With the proposed method, Ive could compare signatures 30 times faster than conventional method using DP matching.

TLDP: A New Broadcast Scheduling Scheme for Multiple Broadcast-Channel Environments (TLDP: 다중 방송 채널 환경을 위한 새로운 방송 스케쥴링 기법)

  • Kwon, Hyeok-Min
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.11 no.2
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    • pp.63-72
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    • 2011
  • Broadcast-based data dissemination has become a widely accepted approach of communication in the mobile computing environment. However, with a large set of data items, the expected delay of receiving a desired data increases due to the sequential nature of the broadcast channel. With the objective of minimizing this wait time, this paper explores the problem of data broadcast over multiple channels. In traditional approaches, data items are partitioned based on their access probabilities and allocated on multiple channels, assuming flat data scheduling per channel. If the data items allocated on the same channel are broadcast in different frequencies based on their access probabilities, the performance will be enhanced further. In this respect, this paper proposes a new broadcast scheduling scheme named two level dynamic programming(TLDP) which can reflect a variation of access probabilities among data items allocated on the same channel.

Optimal Design of Datention System using Incremental Dynamic Programming (동적계획법을 이용한 유수체계의 최적설계)

  • 이길성;이범희
    • Water for future
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    • v.28 no.1
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    • pp.153-168
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    • 1995
  • The purpose of this study is to develop an efficient model for the least cost design of multisite detention systems. The IDP (Incremental Dynamic Programming) model for optimal design is composed of two sub-models: hydrologic - hydraulic model and optimization model. The objective function of IDP is the sum of costs; acquisition cost of the land, construction cost of detention basin and pumping system. Model inputs include channel characteristics, hydrologic paramenters, design storm, and cost function. The model is applied to the Jung- Rang Cheon basin in Seoul, a watershed with detention basins in multiple branching channels. The application results show that the detention system can be designed reasonably for various conditions and the model can be applied to multi-site detention system design.

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The Flood Control of the Namgang and Andong Reservoir System by an Optimization Procedure (최적화(最適化) 기법(技法)에 의한 남강(南江)-안동(安東)댐의 홍수조절(洪水調節))

  • Kim, Sheung Kown;Yoon, Yong Nam;Lee, Sung Yoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.8 no.1
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    • pp.49-60
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    • 1988
  • The use of an Incremental Dynamic Programming (IDP) for real-time flood control operation is investigated. The optimization model has been applied for the Namgang and Andong hypothetical flood control system in the Nakdong river basin. The objective of the operation is defined to minimize the maximum flow at the confluence of downstreams from the two reservoirs. The results are compared to the direct summation of the flood routing results from individual flood control simulation run. It shows that peak flow at the confluence is reduced markedly by reducing peak outflows from individual reservoirs and by balancing the time of the peak release between the two reservoirs.

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Predictive Morphological Analysis of Korean with Dynamic Programming (동적 프로그래밍기법에 근거한 예측중심의 한국어 형태소 분석)

  • 김덕봉;최기선
    • Korean Journal of Cognitive Science
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    • v.4 no.2
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    • pp.145-180
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    • 1994
  • In this paper,we present an efficient morphological analysis model for Korean which produces from an input word all the feasible sequences of morphemes in the word.This model is deterministic in applying spelling rules,and has few redundant computations in processing complex and ambiguous words.This is the effect of three types of new techniques:first,a new method for interpreting speilling rules;second,predictive rule applications which restrict to the spelling rules suitable for the input word;third,the use of dynamic programming which enables the analyzer to avoid recomputing analyzed substring in case the input word is morphologically ambiguous.our model has been experimented with 413,975 word randomly selected from the corpus of Korean elementary textbooks.Experimental results show that our model guarantees fast and reliable processing.