• 산업경영시스템학회지
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• 제42권4호
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• pp.16-22
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• 2019

After Dantzig and Rasmer introduced Vehicle Routing Problem in 1959, this field has been studied with numerous approaches so far. Classical Vehicle Routing Problem can be described as a problem of multiple number of homogeneous vehicles sharing a same starting node and having their own routes to meet the needs of demand nodes. After satisfying all the needs, they go back to the starting node. In order to apply the real world problem, this problem had been developed with additional constraints and pick up & delivery model is one of them. To enhance the effectiveness of pick up & delivery, hub became a popular concept, which often helps reducing the overall cost and improving the quality of service. Lots of studies have suggested heuristic methods to realize this problem because it often becomes a NP-hard problem. However, because of this characteristic, there are not many studies solving this problem optimally. If the problem can be solved in polynomial time, optimal solution is the best option. Therefore, this study proposes a new mathematical model to solve this problem optimally, verified by a real world problem. The main improvements of this study compared to real world case are firstly, make drivers visit every nodes once except hub, secondly, make drivers visit every nodes at the right time, and thirdly, make drivers start and end their journey at their own homes.

• 한국경영과학회지
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• 제23권4호
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• pp.187-201
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• 1998

In ATM networks with high capacity, the effect of failures on transmission links or nodes can be catastrophic, so that the issue of survivability is of great importance. In this paper. we consider the routing problem for working and backup virtual paths(VPs). To accomplish a higher survivability. routing the two kinds of VPs should be taken into account at the same time because backup VP routing depends on the working VP routing. A coevolutionary algorithm is employed to solve the problem for simultaneously routing of working and backup VPs. To develop an efficient coevolutionary algorithm for the problem. structure of populations, encoding method, neighborhood, and genetic operators are studied in this paper. The results of extensive experiments are reported. The performance comparison of the proposed algorithm with a conventional genetic algorithm and existing heuristics shows that our approach is promising.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1731-1737
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• 2007

차량운용문제 혹은 열차반복문제는 수송계획, 열차운행계획에서 작성된 열차운행시각에 기초하여 편성유형 또는 차종에 따라 주어진 제약조건(선회조건, 검수조건, 기지복귀조건 등)을 반영하여 최적의 차량운용 다이아, 운용순서를 구성하는 문제이다. 일반적으로 이 문제는 집합분할(Set Partition)문제로 모델링하여 열생성(Column Generation) 기법을 사용하여 제약조건에 맞는 운용을 생성하였다. 하지만, 본 연구에서는 지하철과 같이 열차운행의 빈도는 높고 물리적 네트웍은 간단하며 시종착역의 수가 적을 경우 많은 대안 경로(Alternative Routing)들이 생성되는 특징 및 일반 철도와는 다른 역에서의 공간적 제약에 따른 차량 선회 제약을 고려하여 차량운용수를 최소화할 수 있는 지하철 차량운용 문제에 대한 수학적인 모델을 제시하고자 한다. 먼저, 차량선회제약만을 고려하여 최소비용 흐름 모형으로 네트워크 모형을 구성하였다. 최소비용 흐름 모형을 결과로 생성된 운용을 바탕으로 각 운용의 운행거리를 정규화(Normalize)하는 휴리스틱 기법을 제안하였다. 또한, 이 방법론을 실제와 유사한 지하철 열차 스케줄에 적용하였고 약 14%의 차량소요 감소 및 최대 영업거리 약 11%, 표준영업거리편차 약 5% 감소를 통하여 본 연구결과의 유용성을 확인하였다.

• 한국경영과학회지
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• 제12권1호
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• pp.34-44
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• 1987

The general vehicle routing problem has been studied by many researchers such as Christofides, et al. and Laporte, et al., but only limited effort has been devoted to developing the optimal algorithms. The purpose of this paper is to develop a branch and bound algorithm which determines the optimal vechicle routes and the optimal number of vehicles concurrenetly for the asymmetrical vehicle routing problem. In order to enhance the efficiency, this algorithm emphasizes the followings ; First, an efficient primal-dual approach is developed to solve subproblems which are called the specialized transportation problem, formed by relaxing the illegal subtour constraints from the vehicle routing problem, second, an improved branching scheme is developed to reduce the number of candidate subproblems by adequate utilization of vehicle capacity restrictions.

• Journal of Communications and Networks
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• 제16권6호
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• pp.656-666
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• 2014

In delay tolerant networks (DTNs), delay is inevitable; thus, making better use of buffer space to maximize the packet delivery rate is more important than delay reduction. In DTNs, epidemic routing is a well-known routing protocol. However, epidemic routing is very sensitive to buffer size. Once the buffer size in nodes is insufficient, the performance of epidemic routing will be drastically reduced. In this paper, we propose a buffer scheme to optimize the performance of epidemic routing on the basis of the Lagrangian and dual problem models. By using the proposed optimal buffer scheme, the packet delivery rate in epidemic routing is considerably improved. Our simulation results show that epidemic routing with the proposed optimal buffer scheme outperforms the original epidemic routing in terms of packet delivery rate and average end-to-end delay. It is worth noting that the improved epidemic routing needs much less buffer size compared to that of the original epidemic routing for ensuring the same packet delivery rate. In particular, even though the buffer size is very small (e.g., 50), the packet delivery rate in epidemic routing with the proposed optimal buffer scheme is still 95.8%, which can satisfy general communication demand.

• Management Science and Financial Engineering
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• 제18권1호
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• pp.27-37
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• 2012

This paper is motivated by a military cargo-plane routing problem which is a pickup-and-delivery problem in which load splits and node revisits are allowed (PDPLS). Although this recent evolution of a VRP-model enhances the efficiency of routing, a solution method is more of a challenge since the node revisits entail closed walks in modeling vehicle routes. For such a case, even a compact IP-formulation is not available and an effective method had been lacking until Nowak et al. (2008b) proposed a heuristic based on a tabu search. Their method provides very reasonable solu-tions as demonstrated by the experiments not only in their paper (Nowak et al., 2008b) but also in ours. However, the computation time seems intensive especially for the class of problems with dynamic transportation requests, including the military cargo-plane routing problem. This paper proposes a more scalable algorithm hybridizing a tabu search for pricing subproblem paused as a single-vehicle routing problem, with a column generation approach based on Dantzig-Wolfe decomposition. As tested on a wide variety of instances, our algorithm produces, in average, a solution of an equiva-lent quality in 10~20% of the computation time of the previous method.

• 산업경영시스템학회지
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• 제45권4호
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• pp.134-141
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• 2022

Transportation in urban area has been getting hard to fulfill the demand on time. There are various uncertainties and obstacles related with road conditions, traffic congestions, and accidents to interrupt the on-time deliveries. With this situation, the last mile logistics has been a keen issue for researchers and practitioners to find the best strategy of the problem. A way to resolve the problem is to use parcel lockers. Parcel locker is a storage that customers can pick up their products. Transportation vehicles deliver the products to parcel lockers instead of all customer sites. Using the parcel lockers, the total delivery costs can be reduced. However, the inconvenience of customer has to increase. Thus, we have to optimal solution to balance between the total delivery costs and customers' inconvenience. This paper formulates a mathematical model to find the optimal solution for the vehicle routing problem and the location problem of parcel lockers. Experimental results provide the viability to find optimal strategy for the routing problem as well as the location problem.

• 한국산학기술학회논문지
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• 제10권9호
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• pp.2340-2349
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• 2009

본 논문에서는 주기적 모니터링 센서 네트워크의 핫 스팟 문제를 해결하기 위한 호핑 라우팅 기법을 제안한다. 제안한 호핑 라우팅 기법은 네트워크의 모든 노드들의 에너지 소비 형태가 예측 가능한 부하 균등 경로를 구성한다. 부하 균등 라우팅 경로는 동일한 영역내 노드들의 부하 균형을 이루는 수평 호핑 전송 기법과 서로 다른 영역에 있는 노드 사이에 부하 균형을 이루는 수직 호핑 전송 기법으로 구할 수 있다. 수직 호핑 전송에 필요한 직접 전송횟수는 센서 노드의 에너지 소비 모델을 통해서 부하 균형을 이룰 수 있는 값을 도출하였다. 시뮬레이션을 통해서 제안한 호핑 라우팅 기법이 핫 스팟 문제를 효과적으로 해결함을 보였으며 기존 라우팅 기법 중에서 멀티 홉 전송 방식과 직접 전송 방식 그리고 클러스터링 기법과 비교 평가를 통해서 호핑 라우팅 기법의 효율성을 제시하였다.

• 디지털산업정보학회논문지
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• 제5권3호
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• pp.59-67
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• 2009

This paper proposes a improved bitmap routing protocol, which finds the best energy efficient routing path by minimizing the network overheads and prolongs the overall network lifetime. Jung proposed a bitmap scheme for sensor networks. His scheme uses a bitmap table to represent the connection information between nodes. However, it has a problem that the table size is depends on the number of nodes in the sensor networks. The problem is very serious in the sensor node with a limited memory. Thereby, this paper proposes a improved bitmap routing protocol to solve the problem in Jung's scheme. Proposed protocol over the memory restricted sensor network could optimize the size of bitmap table by applying the deployed network property. Proposed protocol could be used in the diversity of sensor networks due to it has minimum memory overheads.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.1248-1251
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• 2002

Logistics optimization problems related with vehicle routing such as warehouse locating, track scheduling, customer order delivery, wastage pickup etc. are very interesting and important issues to date. Many Vehicle Routing and Scheduling Systems (VRSS) have been developed/proposed to optimize the logistics problems. But majority of them are dedicated to a particular problem and are unable to handle the real world spatial data directly. The system developed for one problem may not be suitable for others due to inter-problem constraint variations. The constraints may include geographical, environmental and road traffic nature of the working region along with other constraints related with the problem. So the developer always needs to modify the original routing algorithm in order to fulfill the purpose. In our study, we propose a general-purpose platform by combining GIS road map and Database Management System (DBMS), so that VRSS can interact with real world spatial data directly to solve different kinds of vehicle routing problems. Using the features of our developed system, the developer can frequently modify the existing algorithm or create a new one to serve the purpose.