• Journal of Korean Institute of Industrial Engineers
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• v.41 no.3
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• pp.233-242
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• 2015

This paper analyzes a multi-product inbound lot-sizing and outbound dispatching problem with multi-vehicle types in a third-party logistics distribution center. The product must be delivered to the customers within the delivery time window and backlogging is not allowed. Replenishing orders are shipped by several types of vehicles with two types of the freight costs, i.e., uniform and decreasing, are considered. The objective of this study is to determine the lot-size and dispatching schedules to minimize the total cost with the sum of inbound and outbound transportation and inventory costs over the entire time horizon. In this study, we mathematically derive a mixed-integer programming model and propose a genetic algorithm (GA1) based on a local search heuristic algorithm to solve large-scale problems. In addition, we suggest a new genetic algorithm (GA2) with an adjusting algorithm to improve the performance of GA1. The basic mechanism of the GA2 is to provide an unidirectional partial move of products to available containers in the previous period. Finally, we analyze the results of GA1 and GA2 by evaluate the relative performance using the gap between the objective values of CPLEX and the each algorithm.

• IE interfaces
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• v.13 no.3
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• pp.455-461
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• 2000

Logistics systems can be evaluated by how productively distribution center operates, how promptly transportation vehicle dispatches, how efficiently facility layout is, and so on. In this paper, a practical vehicle routing scheme with fixed delivery time and fixed vehicle routes is introduced. The method helps the distribution center reduce logistics cost with respect to dispatching vehicles, and satisfy the customer with pre-determined delivery time window constraints. A case study has shown that the proposed scheme not only generates a feasible schedule with time windows, but also balances material flow in warehouse.

• Journal of the Korean Operations Research and Management Science Society
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• v.27 no.1
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• pp.107-117
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• 2002

The ever-glowing demands for more responsiveness and more flexibility in manufacturing generate greater expectation for the AGV system. So far. a significant amount of research has been carried out to fulfill those requirements. However, the dynamic characteristics of manufacturing systems make it hard to solve the problem analytically. In this paper, the AGV system is analyzed in the production environments which adopt a cycle time to produce materials. The use of the cycle time could eliminate much of uncertainty Inherent In the manufacturing process so that it is possible to build the deterministic model for the AGV systems, which eventually Produce better results on the important issues such as AGV dispatching, determination of the number of AGVs, and empty vehicle travel time.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.50
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• pp.221-230
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• 1999

The important issue for intra-city truck dispatching system is to measure and store actual travel speeds between customer locations. Travel speeds(and times) in nearly all metropolitan areas change drastically during the day because of congestion in certain parts of the city road network. We propose a back-propagation neural network model to recognize the pattern of intra-city vehicle travel speeds between locations that relieve much burden for the data collection and computer storage requirements. On a real-world study using the travel speed data[1] collected in Seoul, we evaluate performance of neural network model and compare with Park & Song model[2] that employs the least square method.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.3
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• pp.16-23
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• 2011

이 논문에서는 지진이나 해일과 같은 자연재해가 발생했을 때 생존자의 수를 최대화하기 위한 응급차량의 배차 문제에 대하여 살펴본다. 이 경우에는 도로 네트워크상에서 최단거리에 있으리라 예상되는 환자부터 실어 나르는 스케줄링 규칙을 많이 이용한다. 이 스케줄링 규칙을 SEPT(Shortest Expected Processing Time) 라고 한다. 이 논문에서는 SEPT보다 효율적이라 생각되는 새로운 스케줄링 규칙을 제안한다. 이 스케줄링 규칙은 처리시간과 납기일이 확정적인 경우에 생존자의 수를 최대화시켜주는 스케줄링을 제공하는 Moore의 알고리즘을 처리시간과 납기일이 확률적인 경우로 확장한 것이다. 다음으로 이 스케줄링 규칙을 지진이 많이 발생하는 미국 캘리포니아 주 로스앤젤레스의 한 지역을 대상으로 몇 가지 생존확률 하에서 생존자의 수를 기준으로 SEPT와 비교한다. 그 결과 모든 생존확률 하에서 제안된 스케줄링 규칙이 SEPT보다 평균적으로 생존자의 수를 더 늘려주는 스케줄링을 제공한다. 그리고 많은 경우 제안된 스케줄링 규칙은 최적 스케줄링을 제공한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.216-218
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• 2007

세계 선진항만은 해운물류시장의 변화에 대응하고, 경쟁력 확보 방안으로 첨단 자동화 장비와 운영시스템 도입을 통한 자동화를 지향하고 있다. 국내 부산항 신항 또한 자동화 컨테이너터미널로 개발을 추진하고 있는 것으로 알려져 있다. 자동화 터미널은 각종 자동화 장비와 시스템이 유기적으로 구성되어 있으며, 이들의 효율적인 운영을 통해 생산성을 향상시킬 수 있다. 터미널의 안벽과 장치장 사이의 컨테이너 운송을 담당하는 이송장비는 컨테이너터미널의 핵심장비로 이의 효율적인 운영은 컨테이너터미널의 생산성과 직결되어 있다. 본 연구에서는 자동화 컨테이너터미널의 운영생산성 향상을 위한 하역장비와 이송장비의 운영방안에 대하여 연구한다. 특히 DHST(Dual Hoist Second Trolley)타입의 QC와 ASHC의 장비특성과 장비간의 연계작업을 고려하여, QC의 대기시간을 최소화하여 하역 생산성을 최대화할 수 있는 ASHC Dispatching Rule을 제시하고자 한다.

• Management Science and Financial Engineering
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• v.5 no.1
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• pp.1-25
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• 1999

There is a worldwide trend to automate the handling operations in port container terminals in an effort to improve productivity and reduce labor cost. This study iscusses how to apply an AGV(automated guided vehicle) system to the handling of containers in the yard of a port container ter-minal. The main issue of this paper is how to assign tasks of container delivery to AGVs during ship operations in an automated port container terminal. A dual-cycle operation is assumed in which the loading and the discharging operation can be performed alternately. Mixed integer linear program-ming formulations are suggested for the dispatching problem. The completion time of all the dis-charging and loading operations by a quayside crane is minimized, and the minimization of the total travel time of AGVs is also considered as a secondary objective. A heuristic method using useful properties of the dispatching problem is suggested to reduce the computational time. The perfor-mance of the heuristic algorithm is evaluated in light of solution quality and computation time.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1578-1586
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• 2015

Personal rapid transit (PRT) is getting attention as a new form of transportation. It is energy efficient and provides the high level of passenger service. In this study, the dynamic PRT dispatching and routing problem is dealt with. Passengers request transportation service on a complex network, and an operating system monitors passenger arrivals and coordinates vehicles in real time. A new online dispatching and routing algorithm is proposed, which minimizes the total travel distance of vehicles and the waiting time of passengers. The algorithm dispatches vehicles by considering multiple vehicles' state and multiple passengers at the same time. In particular, finding the shortest-time path is attempted by taking into account the future congestion on lanes. Discrete-event simulation is employed to validate the performance of the proposed algorithm. The results show the algorithm in this study outperforms others.

• Journal of Navigation and Port Research
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• v.32 no.10
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• pp.837-844
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• 2008

In an automated container terminal, various factors affect the operation of container handling equipment such as quay cranes and AGVs, and thus calculating the exact operation time is nearly infeasible. This uncertainty makes it difficult to dispatch AGVs well. In this paper, we propose a simulation-based AGV dispatching algorithm When dispatching an AGV to an operation, the proposed algorithm conducts multiple stochastic simulation for the succeeding AGV operations for the predetermined period to collect stochastic samples of the result of the dispatching. In the stochastic simulation, the uncertainty of crane operations is represented as a simple probability distribution and the operation time of a crane is determined according to this. A dispatching option is evaluated by the total delay time of quay cranes which is estimated by averaging the quay crane delay of each simulation In order to collect a sufficient number of samples that guarantee the credibility of the evaluation, we devised a high-speed simulator that simulates AGV operation The effectiveness of the proposed algorithm is validated by simulation experiments.

• Journal of Korean Institute of Industrial Engineers
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• v.16 no.2
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• pp.23-36
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• 1990

A unit-load automated guided vehicle system is considered in which a single vehicle is operated on a unidirectional path in a closed loop. The vehicle serves a manufacturing cell moving pallets from one station to another based on the "First-Encountered-First-Serve" dispatching rule. An approximation method is developed to compute the mean waiting time of an arbitrary pallet at each station. Extensive numerical experiments, performed for various problems, yield fairly good results in most of the cases compared with those obtained by simulation method.