• Title/Summary/Keyword: NP-complete 문제

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Development of a Single Allocation Hub Network Design Model with Transportation Economies of Scale (수송 규모의 경제 효과를 고려한 단일 할당 허브 네트워크 설계 모형의 개발)

  • Kim, Dong Kyu;Park, Chang Ho;Lee, Jin Su
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.6D
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    • pp.917-926
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    • 2006
  • Transportation Economies of scale are the essential properties of hub networks. One critical property of the hub network design problem is to quantify cost savings which stem from economies of scale, the costs of operating hub facilities and opportunity costs associated with delays stemming from consolidation of traffic flows. Due to the NP-complete property of the hub location problem, however, most previous researchers have focused on the development of heuristic algorithms for approximate solutions. The purpose of this paper is to develop a hub network design model considering transportation economies of scale from the consolidation of traffic flows. The model is designed to consider the uniqueness of hub networks and to determine several cost components. The heuristic algorithms for the developed model are suggested and the results of the model are compared with recently published studies using real data. Results of the analysis show that the proposed model reflects transportation economies of scale due to consolidation of flows. This study can form not only the theoretical basis of an effective and rational hub network design but contribute to the assessment of existing and planned logistics systems.

Classification of the Seoul Metropolitan Subway Stations using Graph Partitioning (그래프 분할을 이용한 서울 수도권 지하철역들의 분류)

  • Park, Jong-Soo;Lee, Keum-Sook
    • Journal of the Economic Geographical Society of Korea
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    • v.15 no.3
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    • pp.343-357
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    • 2012
  • The Seoul metropolitan subway system can be represented by a graph which consists of nodes and edges. In this paper, we study classification of subway stations and trip behaviour of subway passengers through partitioning the graph of the subway system into roughly equal groups. A weight of each edge of the graph is set to the number of passengers who pass the edge, where the number of passengers is extracted from the transportation card transaction database. Since the graph partitioning problem is NP-complete, we propose a heuristic algorithm to partition the subway graph. The heuristic algorithm uses one of two alternative objective functions, one of which is to minimize the sum of weights of edges connecting nodes in different groups and the other is to maximize the ratio of passengers who get on the subway train at one subway station and get off at another subway station in the same group to the total subway passengers. In the experimental results, we illustrate the subway stations and edges in each group by color on a map and analyze the trip behaviour of subway passengers by the group origin-destination matrix.

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Algorithm for Maximum Degree Vertex Partition of Cutwidth Minimization Problem (절단 폭 최소화 문제의 최대차수 정점 분할 알고리즘)

  • Sang-Un Lee
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.24 no.1
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    • pp.37-42
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    • 2024
  • This paper suggests polynomial time algorithm for cutwidth minimization problem that classified as NP-complete because the polynomial time algorithm to find the optimal solution has been unknown yet. To find the minimum cutwidth CWf(G)=max𝜈VCWf(𝜈)for given graph G=(V,E),m=|V|, n=|E|, the proposed algorithm divides neighborhood NG[𝜈i] of the maximum degree vertex 𝜈i in graph G into left and right and decides the vertical cut plane with minimum number of edges pass through the vertex 𝜈i firstly. Then, we split the left and right NG[𝜈i] into horizontal sections with minimum pass through edges. Secondly, the inner-section vertices are connected into line graph and the inter-section lines are connected by one line layout. Finally, we perform the optimization process in order to obtain the minimum cutwidth using vertex moving method. Though the proposed algorithm requires O(n2) time complexity, that can be obtains the optimal solutions for all of various experimental data

A Study on QoS Improvement for Overlay Multicast Using Modified Dijkstra Algorithm (변형된 Dijkstra 알고리즘을 활용한 오버레이 멀티캐스트 QoS 향상 기법 연구)

  • Lee, Hyung-Ok;Nam, Ji-Seung;Park, Jun-Seok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.7
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    • pp.3468-3473
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    • 2013
  • Conditions that overlay multicast tree must satisfy for the real-time application system of a video-conference, an internet broadcasting is two things. First, the degree of nodes in a tree must be proper value. Second, the diameter of the multicast tree, distance between longest two users should be short. If the path between two users in the tree is long, the delay time in data transmission between two users great. So, it is not suitable to the application system such as video-conferences. In this paper, the cost of the dijkstra algorithm calculate with proposed score-function through checking the extra bandwidth, the delay and the requested bandwidth. It is composed the tree through the dijkstra algorithm.

An Optimization Model and Heuristic Algorithms for Multi-Ring Design in Fiber-Optic Networks (광전송망에서의 다중링 설계를 위한 최적화 모형 및 휴리스틱 알고리즘)

  • 이인행;이영옥;정순기
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.1B
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    • pp.15-30
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    • 2000
  • The important considerations in the design of fiber-optic networks are reliability and survivability preparing against a failure. The SDH(Synchronous Digital Hierarchy), the international standard of optical transmission, offers several network reconfiguration methods that enable network to be automatically restored from failure. One of the methods is the SHR(Self Healing Ring), which is a ring topology system. Most network providers have constructed their backbone networks with SHR architecture since it can provide survivability economically. The network architecture has eventually evolved into a multi-ring network comprised of interconnected rings. This paper addresses multi-ring network design problems is to minimize ring-construction cost. This problem can be formulated with MIP(mixed integer programming) model. However, it is difficult to solve the model within reasonable computing time on a large scale network because the model is NP-complete. Furthermore, in practice we should consider the problem of routing demands on rings to minimize total cost. This routing problem involves multiplex bundling at the intermediate nodes. A family of heuristic algorithms is presented for this problem. These algorithms include gateway selection and routing of inter-ring demands as well as load balancing on single rings. The developed heuristic algorithms are applied to some network provider's regional and long-distance transmission networks. We show an example of ring design and compare it with another ring topology design. Finally, we analysis the effect bundling.

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A Non-strict Hub Network Design for Road Freight Transportation considering Economies of Scale (규모의 경제효과를 고려한 도로화물수송의 비제약 허브네트워크 설계)

  • Kim, Nam-Ju;Kim, Yong-Jin;Kho, Seung-Young;Chon, Kyung-Soo
    • Journal of Korean Society of Transportation
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    • v.26 no.6
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    • pp.103-112
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    • 2008
  • Implementing hub networks in logistics is generally attractive and effective because of cost savings derived from economies of scale on network transportation, and objective of the hub network design problem is to decide optimal hub locations, and the transportation route of each origin-destination pair. This problem is generally a NP-complete problem not to solve easily, and it is almost impossible to find optimal solutions considering the big-sized network within a reasonable time. This research tried to find optimal logistics strategy in the given big-sized real network and the freight origin-destination data. The objective function, which was proposed by Honor and O'kelly (2001), that rewards economies of scale on network links with increase of transportation volumes, is applied. This thesis proposed the optimal hub network of korea within a reasonable time based on engineering approaches. And it is expected that this thesis can contribute to plan freight policies which can improve to have competitive power in the level of a company or nation by reducing logistic costs.

An Improved Online Algorithm to Minimize Total Error of the Imprecise Tasks with 0/1 Constraint (0/1 제약조건을 갖는 부정확한 태스크들의 총오류를 최소화시키기 위한 개선된 온라인 알고리즘)

  • Song, Gi-Hyeon
    • Journal of KIISE:Computer Systems and Theory
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    • v.34 no.10
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    • pp.493-501
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    • 2007
  • The imprecise real-time system provides flexibility in scheduling time-critical tasks. Most scheduling problems of satisfying both 0/1 constraint and timing constraints, while the total error is minimized, are NP-complete when the optional tasks have arbitrary processing times. Liu suggested a reasonable strategy of scheduling tasks with the 0/1 constraint on uniprocessors for minimizing the total error. Song et at suggested a reasonable strategy of scheduling tasks with the 0/1 constraint on multiprocessors for minimizing the total error. But, these algorithms are all off-line algorithms. In the online scheduling, the NORA algorithm can find a schedule with the minimum total error for the imprecise online task system. In NORA algorithm, EDF strategy is adopted in the optional scheduling. On the other hand, for the task system with 0/1 constraint, EDF_Scheduling may not be optimal in the sense that the total error is minimized. Furthermore, when the optional tasks are scheduled in the ascending order of their required processing times, NORA algorithm which EDF strategy is adopted may not produce minimum total error. Therefore, in this paper, an online algorithm is proposed to minimize total error for the imprecise task system with 0/1 constraint. Then, to compare the performance between the proposed algorithm and NORA algorithm, a series of experiments are performed. As a conseqence of the performance comparison between two algorithms, it has been concluded that the proposed algorithm can produce similar total error to NORA algorithm when the optional tasks are scheduled in the random order of their required processing times but, the proposed algorithm can produce less total error than NORA algorithm especially when the optional tasks are scheduled in the ascending order of their required processing times.

A case study on optimal location modeling of battery swapping & charging facility for the electric bus system (전기버스를 위한 배터리 자동 교환-충전인프라 배치 최적화 모형개발 및 적용 사례 분석)

  • Kim, Seung-Ji;Kim, Wonkyu;Kim, Byung Jong;Im, Hyun Seop
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.12 no.1
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    • pp.121-135
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    • 2013
  • This paper propose an efficient algorithm for selecting electric bus charging facility location. In nature, the optimal charging facility location problem is similar to Set Covering Problem. Set Covering Problem is the problem of covering all the rows of an $m{\times}n$ matrix of ones and zeros by a subset of columns with a minimal cost. It has many practical applications of modeling of real world problems. The Set Covering Problem has been proven to be NP-Complete. In order to overcome the computational complexity involved in seeking optimal solutions, this paper present an enhanced greedy algorithm and simulated annealing algorithm. In this paper, we apply the developed algorithm to Seoul's public bus system.

Multi-Line Driving Technology on PM OLED using Graph theory and Correlation (그래프 이론과 상관성을 이용한 PM OLED 다중선 구동 기술)

  • Lee, Gil-Jae;Lee, Chang-Hoon;Jeong, Je-Chang
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.47 no.1
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    • pp.62-72
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    • 2010
  • PM OLED is used in many applications as one of the display for the next generation. The most essential problems are the power dissipation and the short life time in applying PM OLED into a commercial application. Many efforts are made in developing the panel and in improving the circuit for expanding the current market wider. The life time in PM OLED is expanded by lessening the power dissipation of the circuit for the magnitude of the driving current is lowered. It is possible to minimize the power dissipation from improving the driving technology. The classical technology, Row-to-Row driving, is that row is selected one by one while applying the column current input individually. The multi-line driving is a new technology which is to select multiple rows simultaneously while applying the column current as a whole. However, the solution of the multi-line driving is NP-complete problem. The efficiency is dependant on the sort of picture and the driving condition. This paper presents the new efficient multi-line driving which is that the multiple lines are selected by applying column current together after grouping the simultaneous driving group applying the gnew efficient muthe coi-line dr coefficient. Bengrouping the several rows which has the higher coi-line dr coefficient, the more efficient driving is realized to present the high quality image and to lessen the power dissipation and to stretch the life time in the PM OLED.

Development of Intelligent ATP System Using Genetic Algorithm (유전 알고리듬을 적용한 지능형 ATP 시스템 개발)

  • Kim, Tai-Young
    • Journal of Intelligence and Information Systems
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    • v.16 no.4
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    • pp.131-145
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    • 2010
  • The framework for making a coordinated decision for large-scale facilities has become an important issue in supply chain(SC) management research. The competitive business environment requires companies to continuously search for the ways to achieve high efficiency and lower operational costs. In the areas of production/distribution planning, many researchers and practitioners have developedand evaluated the deterministic models to coordinate important and interrelated logistic decisions such as capacity management, inventory allocation, and vehicle routing. They initially have investigated the various process of SC separately and later become more interested in such problems encompassing the whole SC system. The accurate quotation of ATP(Available-To-Promise) plays a very important role in enhancing customer satisfaction and fill rate maximization. The complexity for intelligent manufacturing system, which includes all the linkages among procurement, production, and distribution, makes the accurate quotation of ATP be a quite difficult job. In addition to, many researchers assumed ATP model with integer time. However, in industry practices, integer times are very rare and the model developed using integer times is therefore approximating the real system. Various alternative models for an ATP system with time lags have been developed and evaluated. In most cases, these models have assumed that the time lags are integer multiples of a unit time grid. However, integer time lags are very rare in practices, and therefore models developed using integer time lags only approximate real systems. The differences occurring by this approximation frequently result in significant accuracy degradations. To introduce the ATP model with time lags, we first introduce the dynamic production function. Hackman and Leachman's dynamic production function in initiated research directly related to the topic of this paper. They propose a modeling framework for a system with non-integer time lags and show how to apply the framework to a variety of systems including continues time series, manufacturing resource planning and critical path method. Their formulation requires no additional variables or constraints and is capable of representing real world systems more accurately. Previously, to cope with non-integer time lags, they usually model a concerned system either by rounding lags to the nearest integers or by subdividing the time grid to make the lags become integer multiples of the grid. But each approach has a critical weakness: the first approach underestimates, potentially leading to infeasibilities or overestimates lead times, potentially resulting in excessive work-inprocesses. The second approach drastically inflates the problem size. We consider an optimized ATP system with non-integer time lag in supply chain management. We focus on a worldwide headquarter, distribution centers, and manufacturing facilities are globally networked. We develop a mixed integer programming(MIP) model for ATP process, which has the definition of required data flow. The illustrative ATP module shows the proposed system is largely affected inSCM. The system we are concerned is composed of a multiple production facility with multiple products, multiple distribution centers and multiple customers. For the system, we consider an ATP scheduling and capacity allocationproblem. In this study, we proposed the model for the ATP system in SCM using the dynamic production function considering the non-integer time lags. The model is developed under the framework suitable for the non-integer lags and, therefore, is more accurate than the models we usually encounter. We developed intelligent ATP System for this model using genetic algorithm. We focus on a capacitated production planning and capacity allocation problem, develop a mixed integer programming model, and propose an efficient heuristic procedure using an evolutionary system to solve it efficiently. This method makes it possible for the population to reach the approximate solution easily. Moreover, we designed and utilized a representation scheme that allows the proposed models to represent real variables. The proposed regeneration procedures, which evaluate each infeasible chromosome, makes the solutions converge to the optimum quickly.