• Industrial Engineering and Management Systems
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• 제11권3호
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• pp.288-298
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• 2012

Lot sizing and shipment scheduling are two interrelated decisions made by a manufacturing plant and a third-party logistics distribution center. This paper analyzes a dynamic inbound ordering problem and shipment problem with a freight container cost, in which the order size of multiple products and single container type are simultaneously considered. In the problem, each ordered product placed in a period is immediately shipped by some freight containers in the period, and the total freight cost is proportional to the number of containers employed. It is assumed that the load size of each product is equal and backlogging is not allowed. The objective of this study is to simultaneously determine the lot-sizes and the shipment schedule that minimize the total costs, which consist of production cost, inventory holding cost, and freight cost. Because the problem is NP-hard, we propose three meta-heuristic algorithms: a simulated annealing algorithm, a genetic algorithm, and a new population-based evolutionary meta-heuristic called self-evolution algorithm. The performance of the meta-heuristic algorithms is compared with a local search heuristic proposed by the previous paper in terms of the average deviation from the optimal solution in small size problems and the average deviation from the best one among the replications of the meta-heuristic algorithms in large size problems.

• 산업경영시스템학회지
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• 제44권2호
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• pp.24-35
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• 2021

Due to increasing awareness on the treatment of end-of-use/life products, disassembly has been a fast-growing research area of interest for many researchers over recent decades. This paper introduces a novel lot-sizing problem that has not been studied in the literature, which is the service-parts lot-sizing with disassembly option. The disassembly option implies that the demands of service parts can be fulfilled by newly manufactured parts, but also by disassembled parts. The disassembled parts are the ones recovered after the disassembly of end-of-use/life products. The objective of the considered problem is to maximize the total profit, i.e., the revenue of selling the service parts minus the total cost of the fixed setup, production, disassembly, inventory holding, and disposal over a planning horizon. This paper proves that the single-period version of the considered problem is NP-hard and suggests a heuristic by combining a simulated annealing algorithm and a linear-programming relaxation. Computational experiment results show that the heuristic generates near-optimal solutions within reasonable computation time, which implies that the heuristic is a viable optimization tool for the service parts inventory management. In addition, sensitivity analyses indicate that deciding an appropriate price of disassembled parts and an appropriate collection amount of EOLs are very important for sustainable service parts systems.

• 한국구조물진단유지관리공학회 논문집
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• 제16권2호
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• pp.58-64
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• 2012

세계적인 고유가의 영향으로 석유 소비가 높은 산업의 생산성은 현저히 저하되었다. 고강도 PHC 파일 중 AC 방식은 2차례의 증기양생 공정을 거쳐 제조되고 있으며, 이는 제품의 제조원가에 심각한 상승을 초래하고 있다. 다른 형식의 파일 제조 공정인 NAC 방식은 1차례의 증기양생을 함으로써 제조 원가가 절감되는 장점이 있지만, 초기 강도가 AC 방식보다 저하되기 때문에 약3일 정도의 양생기간을 거쳐 출하되고 있으며, 양생기간에 따른 제품 재고의 증가를 피할 수 없으므로 이는 제조원가 상승의 요인으로 작용하고 있다. AC 방식은 양생 직후, 즉시 출하되며 현장 도입 (항타현장 등) 시 파손 등의 문제가 발생되지 않으나, NAC의 경우는 최소 3일의 양생기간을 거쳐 강도 80 MPa이상을 발현 후 현장에 출하된다. 따라서, NAC는 종류별 적정 재고유지 비용의 증가와 강도부족 시 현장에서 파손이 발생되는 문제점을 안고 있다. 본 연구에서는 NAC 방식의 PHC 파일에 대하여 AC 방식과 동등한 1일 강도를 발현하기 위한 배합특성 연구를 수행하였고, 원재료 변화에 따른 강도 특성도 파악하였다.

• 산업경영시스템학회지
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• 제35권3호
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• pp.77-86
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• 2012

We consider the capacitated lot-sizing and scheduling problem for a paper remanufacturing system that produces several types of corrugated cardboards. The problem is to determine the lot sizes as well as the sequence of lots for the objective of minimizing the sum of setup and inventory holding costs while satisfying the demand and the machine capacity over a given planning horizon. In particular, the paper remanufacturing system has sequence-dependent setup costs that depend on the type of product just completed and on the product to be processed. Also, the setup state at one period can be carried over to the next period. An integer programming model is presented to describe the problem. Due to the complexity of the problem, we modify the existing two-stage heuristics in which an initial solution is obtained and then it is improved using a multi-pass interchange method. To show the performances of the heuristics, computational experiments were done using the real data, and a significant amount of improvement is reported.