• 경영과학
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• 제31권3호
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• pp.13-26
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• 2014

This paper considers an integrated one-vendor multi-buyer production-inventory model where the vendor manufactures multiple products in lot at their associated finite production rates. In the model, it is allowed for each product to be shipped in lot to the buyers even before the whole product production is not completed yet. Each product lot is dispatched to the associated buyer in a number of shipments. The buyers consume their products at fixed rates. The objective is to the production and shipment schedules in the integrated system, which minimizes the total cost per unit time. The total cost consists of production setup cost, inventory holding cost and shipment cost. For the model, an iterative optimal solution procedure with shipment consolidation policy incorporated. It is then tested through numerical experiments to show how efficient and effective the shipment consolidation policy is.

• 산업경영시스템학회지
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• 제44권4호
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• pp.32-42
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• 2021

The printing process can have to print various colors with a limited capacity of printing facility such as ink containers that are needed cleaning to change color. In each container, cleaning time exists to assign corresponding inks, and it is considered as the setup cost required to reduce the increasing productivity. The existing manual method, which is based on the worker's experience or intuition, is difficult to respond to the diversification of color requirements, mathematical modeling and algorithms are suggested for efficient scheduling. In this study, we propose a new type of scheduling problem for the printing process. First, we suggest a mathematical model that optimizes the color assignment and scheduling. Although the suggested model guarantees global optimality, it needs a lot of computational time to solve. Thus, we decompose the original problem into sequencing orders and allocating ink problems. An approximate function is used to compute the job scheduling, and local search heuristic based on 2-opt algorithm is suggested for reducing computational time. In order to verify the effectiveness of our method, we compared the algorithms' performance. The results show that the suggested decomposition structure can find acceptable solutions within a reasonable time. Also, we present schematized results for field application.

• 산업공학
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• 제12권1호
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• pp.121-131
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• 1999

In this article, a simulation model of a microwave oven assembly line is developed to identify system parameters to improve the system performances such as work-in-process inventories, production lead time, mean earliness, mean tardiness and in-time completion rate. System parameters investigated include dispatching rules, lot sizing, setup time reduction, demand increase, productivity improvement, production scheduling, hardware characteristics, etc. The model has been developed using SIMAN simulation language which has been demonstrated to be a powerful tool to simulate complex manufacturing systems. We have suggested the results obtained to improve the system performances of an existing production line.

• 산업경영시스템학회지
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• 제43권4호
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• pp.23-32
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• 2020

Many small and medium-sized manufacturing companies process various product types to respond different customer orders in a single production line. To improve their productivity, they often apply batch processing while considering various product types, constraints on batch sizes and setups, and due date of each order. This study introduces a batch scheduling heuristic for a production line with multiple product types and different due dates of each order. As the process times vary due to the different batch sizes and product types, a recursive equation is developed based on a flow line model to obtain the upper bound on the completion times with less computational complexity than full computation. The batch scheduling algorithm combines and schedules the orders with same product types into a batch to improve productivity, but within the constraints to match the due dates of the orders. The algorithm incorporates simple and intuitive principles for the purpose of being applied to small and medium companies. To test the algorithm, two case studies are introduced; a high pressure coolant (HPC) manufacturing line and a press process at a plate-type heat exchanger manufacturer. From the case studies, the developed algorithm provides significant improvements in setup frequency and thus convenience of workers and productivity, without violating due dates of each order.

• 제어로봇시스템학회논문지
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• 제18권8호
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• pp.731-737
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• 2012

In this paper the usage of Bluetooth in networked control systems is described. ACL links and commonly used serial port profile built on top of ACL links are analyzed and their problems such as unpredictable latency are discovered. SCO link packet scheduling, latency estimation and setup procedure are examined. SCO link is suggested as proper link for NCS, due to its low latency and low variance. Smith predictor use for latency compensation is described and its impact on control performance is estimated. A number of experiments on DC motor position control are performed and control performance of system utilizing SCO link with and without Smith predictor is proved to be higher than control performance of system utilizing ACL link.

• 한국경영과학회지
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• 제23권2호
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• pp.187-200
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• 1998

This paper presents an original approach for solving short-term power scheduling in extended power system with two fuels in a unit and a limited fuel using Lagrangian relaxations. The underlying model incorporates the full set of costs and constraints including setup, production, ramping, and operational status, and takes the form of a mixed integer nonlinear control problem. Moreover, the mathematical model developed includes two fuels in a unit and a limited fuel, regulation reserve requirements of prespecified group of units. Lagrangian relaxation is used to disaggregate the model by generator into separate subproblems which are then solved with a nested dynamic program including empirical knowledges. The strength of the methodology lies partially in its ability to construct good feasible solutions from information provided by the dual. Thus, the need for branch-and-bound is eliminated. In addition, the inclusion of two fuels in a unit and a limited fuel provides new insight into the limitations of current techniques. Computational experience with the proposed algorithm indicates that Problems containing up to 23 units including 8 unit used two fuels and 24 time periods can be readily solved in reasonable times. Duality gaps of less than 4％ were achieved.

• 산업경영시스템학회지
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• 제23권54호
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• pp.13-26
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• 2000

Machining route selection to produce parts should be based on shop flow information because of input data at scheduling tasks and is one of the main problem in process planning. This paper addresses the problem of machining route selection in multi-stage process with machine group included a similar function. The model proposed is formulated as 0-1 integer programing considering the relation of parts and machine table size, avaliable time of each machine for planning period, and delivery date. The objective of the model is to minimize the sum of processing, transportation, and setup time for all parts. Genetic algorithm approach is developed to solve this model. The efficiency of the approach is examined in comparison with the method of branch and bound technique for the same problem. Also, this paper is to solve large problem scale and provide it if the multiple machining routes are existed an optimal solution.

• 한국컴퓨터정보학회논문지
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• 제15권8호
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• pp.181-192
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• 2010

본 논문에서는 연속제조 생산방식을 취하는 제조업에서 기계고장이 발생하여 생산 일정이 실시간으로 변경되어 야 하는 환경에서도 적용 가능한 dispatching 방법을 개발한다. 개발된 dispatching 방법은 생산지연으로 인한 재료의 재가열 비용과 설치비용, 잔여납기일을 고려하여 지표를 개발하고, 지표의 값이 가장 작은 재료에 우선순위를 부여하여 기계에 할당하는 방식을 취하고 있다. 개발된 dispatching방법의 우수성 입증하기 위해 SPT와 선입선출 방법을 비교대상으로 선출하고, 이들 방법을 통계적 시뮬레이션을 통해 도출된 손실비용을 비교분석한다. 통계적으로 유효성을 입증하기 위해 각 방법별로 200개의 데이터와 20번의 반복을 통해 실험을 실시하며, 실험결과 본 연구에서 제시한 방법이 비교대상 방법에 비해 유효한 손실비용의 감소효과를 보였다. 또한 본 논문에서 개발된 통계적 시뮬레이터는 대기시간에 발생 가능한 비용을 추가하거나 변경이 용이하여 불확실성을 고려한 생산일정계획부문에 유용하게 사용될 것으로 기대한다.

• 한국시뮬레이션학회논문지
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• 제20권3호
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• pp.1-10
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• 2011

본 연구에서는 반도체, 디스플레이 등과 같은 첨단 전자제품 제조 시스템에서의 공정별 기계 대수를 결정하는 용량계획 문제를 고려한다. 제조 시스템은 공정별로 동일한 병렬기계가 존재하는 혼합흐름공정의 형태를 갖고 있으며, 각 기계 마다 서로 다른 제품 종류를 연속적으로 가공할 때는 셋업 작업이 발생한다. 설비를 구매할 수 있는 예산에 제약이 있는 상황에서 제조시스템의 생산율을 최대화 할 수 있는 공정별 기계 대수 조합을 결정해 주고자 한다. 혼합흐름공정 형태의 복잡한 제조시스템을 대상으로 주문이 동적으로 도착하고 여러 가지 일정계획방법을 적용하는 것을 모델링 하기 위하여 시뮬레이션 모델을 개발하였다. 본 연구에서는 시뮬레이션 실행을 포함한 다양한 조합의 기계 대수 증감 휴리스틱 방법을 제안하여 해를 도출하였다. 제안된 방법들은 일련의 계산실험을 통하여 그 성능을 비교 평가하였다.

• Journal of Communications and Networks
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• 제14권6호
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• pp.662-671
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• 2012

Plug-in hybrid electric vehicles (PHEVs) will be widely used in future transportation systems to reduce oil fuel consumption. Therefore, the electrical energy demand will be increased due to the charging of a large number of vehicles. Without intelligent control strategies, the charging process can easily overload the electricity grid at peak hours. In this paper, we consider a smart charging and discharging process for multiple PHEVs in a building's garage to optimize the energy consumption profile of the building. We formulate a centralized optimization problem in which the building controller or planner aims to minimize the square Euclidean distance between the instantaneous energy demand and the average demand of the building by controlling the charging and discharging schedules of PHEVs (or 'users'). The PHEVs' batteries will be charged during low-demand periods and discharged during high-demand periods in order to reduce the peak load of the building. In a decentralized system, we design an energy cost-sharing model and apply a non-cooperative approach to formulate an energy charging and discharging scheduling game, in which the players are the users, their strategies are the battery charging and discharging schedules, and the utility function of each user is defined as the negative total energy payment to the building. Based on the game theory setup, we also propose a distributed algorithm in which each PHEV independently selects its best strategy to maximize the utility function. The PHEVs update the building planner with their energy charging and discharging schedules. We also show that the PHEV owners will have an incentive to participate in the energy charging and discharging game. Simulation results verify that the proposed distributed algorithm will minimize the peak load and the total energy cost simultaneously.