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구평회,장재진 한국경영과학회 2001 韓國經營科學會誌 Vol.26 No.1
Design and evaluation of AGV-based material handling systems are very complicated due to the randomness and the large number of variables involved. Vehicle travel time is a key parameter for designing and evaluating AGV systems. Although loaded travel time is relatively easy to estimate, determination of empty vehicle travel time is difficult due to the inherent randomness of material handling system. Most previous studies assume that the empty vehicle travel time is the same as the loaded travel time or assume very specific environments. This paper presents new vehicle travel time models for AGV-based material transport systems. The research effort is focused on the estimation of empty vehicle travel time under various vehicle dispatching policies. Simulation experiments are used to verify the proposed travel time models.
An Analytical Approach for AGV Fleet Size Determination
Koo, Pyung-Hoi,Song, Jun-Yeob,Lee, Seung-Woo 한국경영과학회 1998 한국경영과학회 학술대회논문집 Vol.- No.1
As manufacturing systems are growing in size and complexity, material flow control has become one of the key issues for system efficiency. This paper addresses a design problem involved in automated guided vehicle systems (AGVS). Of the AGVS design issues, the determination of the AGVS fleet size is the basic and important issue. Existing non-simulation approaches in determining AGV fleet size have not considered stochastic features of AGVS. This paper presents an analytical model for determining the AGV fleet size in which the stochastic characteristics are taken into consideration.
A berth planning approach with flexible quay crane assignments in seapor t container terminals
구평회 ( Pyung Hoi Koo ) 한국경영공학회 2013 한국경영공학회지 Vol.18 No.1
In seaport container terminals, the berth space is the most limited resource because of its tremendous investment and the geographical constraints associated with it. This paper addresses a berth planning problem under the assumption of multiple quay crane assignment options. Berth planning determines the berthing time and position of the container ships for loading/unloading services. An optimization model is presented for berth planning. For large problems, a heuristic procedure is proposed, which is based on a genetic algorithm. Experimental results are presented to see the performance of flexible quay crane assignment options and the proposed approach.
컨테이너터미널의 생산성 향상을 위한 하역시스템 운영방안
구평회(Pyung Hoi Koo) 한국SCM학회 2012 한국SCM학회지 Vol.12 No.2
This paper deals with operational strategies for loading/unloading in seaport container terminals. A variety of container handling facilities are cooperating with each other for loading/unloading operations. Among the logistics facilities, quay cranes, large dockside gantry cranes for loading and unloading containers from container ships, are a bottleneck resource that determines the system performance in most container terminals. The majority of the efficiency losses in the quay cranes are due to the failure of synchronization between quay cranes and yard trucks. This paper presents the concept of buffer employed for the interface between quay cranes and yard trucks for efficient use of quay cranes. For implementation of buffers, we consider buffer stations and reach stackers, which are expected to be employed in a minimum investment cost. Simulation experiments are performed to examine the performance for the new operational strategies. The managerial implications are discussed for industry applications.
구평회(Pyung-Hoi Koo),고시근(Shie-Gheun Koh) 대한산업공학회 2007 대한산업공학회지 Vol.33 No.2
All of the machines in a production line can be classified into bottleneck and non-bottleneck machines. A bottleneck is a resource whose capacity limits the throughput of the whole production facility. This paper addresses a batch sizing problem at the bottleneck machine. Traditionally, most batch sizing decisions have been made based on the EOQ (economic order quantity) model where setup and inventory costs are considered while throughput rate is assumed to be given. However, since batch size affects the capacity of the bottleneck machine, the throughput rate may not be constant. As the batch size increases, the frequency of the setup decreases. The saved setup time can be transferred to processing time, which results in higher throughput. But, the larger batch size may also result in longer lead time and larger WIP inventory level. This paper presents an alternative method to determine batch size at the bottleneck machine in a manufacturing line. A linear search algorithm is introduced to find optimal throughput rate and batch size at the same time. Numerical examples are provided to see how the proposed method works and to investigate the effects of some parameters.