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Bucket Brigade를 기반으로 한 분산자율형 조립셀 운영전략
구평회(Pyung Hoi Koo) 대한산업공학회 2015 대한산업공학회지 Vol.41 No.4
A bucket-brigade is a way of transporting items where items are passed from one person to the next. The operation of the bucket brigade imitates the cooperative behavior of ants when brood, food or other resources are moved. Koo (2009) presented a bucket brigade-based assembly cell where each worker follows a simple rule: perform assembly operations on a product until the next worker downstream takes it over; then go back to the previous worker upstream to take over a new assembly job. In this way, the flow line is self-balanced without any predetermined job assignment. However, there are some productivity losses related to hand-off and blocking. This paper examines the hand-off and blocking losses and presents a new bucket brigade-based assembly cell where working areas for each assembler is restricted with the help of buffer interfaces. Simulation experiments are used to validate the performance of the new assembly system.
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.
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.
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.
평균납기지연 최소화를 위한 배치생산공정의 실시간 로딩전략
구평회(Pyung-Hoi Koo) 대한산업공학회 2014 대한산업공학회지 Vol.40 No.2
This paper provides a real-time loading strategy for batch processing machines in which a number of jobs are simultaneously processed as a batch. The batch processing machines can be seen in both manufacturing industries (e.g., semiconductor, automobile and metal working) and service industries (transportation vehicles, mail shipment and theme park). This paper focuses on batch processing machines in semiconductor manufacturing. We present a look-ahead loading strategy for tardiness minimization where future arrivals and due dates are taken into consideration. Simulation tests are performed on the presented strategy and some existing loading heuristics under various production settings with different traffic intensities and forecasting errors. Experimental results show that our strategy provides the performance of good quality.
부품공급자-생산자로 이루어진 공급망에서 생산능력 투자위험을 고려한 공급계약 방안 연구
구평회(Pyung-Hoi Koo) 대한산업공학회 2021 대한산업공학회지 Vol.47 No.6
When a new product is developed and introduced in markets, production capacity should be invested before mass production is initiated. Capacity building is often capital intensive and requires a long lead time. This paper addresses a supply contract problem for capacity investment in a two-echelon supply chain consisting of a component supplier and a final-product manufacturer. Since the demand is uncertain at the time of capacity decision-making, the supplier often builds the capacity in a conservative way to prevent possible capital losses due to excess capacity. A possible solution to this under-capacity building problem is that the manufacturer shares the investment risk with the supplier. In this paper, a capacity cost-sharing contract is introduced, and the contract parameters are examined. The attitude of suppliers to risk is discussed, and a new contract procedure is presented for a supply chain with a risk-averse supplier. With a numerical example, the effect of the contract parameters on system performance is investigated.