• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.7-11
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• 2007

This paper considers a shipment planning of products from manufacturers to a third-party warehouse for demands with production time windows where a demand must be replenished in its time window. The underling lot-sizing model also assumes cargo delivery cost in each inbound replenishment to the warehouse. For this model, an optimal O($nT^4$) is presented where n is the number of demands and T is the length of the planning horizon.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.548-555
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• 2003

Customer satisfaction level is usually measured in terms of price, quality, customization, after-sale-service, product variety etc. Each finn sets up a distinctive production/marketing strategy to gain competitive advantage by prioritizing the customer satisfaction measures. The market differentiation strategy directly results in supply chain performance such as lead time, inventory, customer fill rate and market share. Product proliferation desirable in customization sense often conflicts the economies of scale effect in production side. This paper focuses the relationship between product variety and market share. Specifically, we investigate how introduction of new product affects the current market share, i.e.,) formation of customer preference and provide some insight into the optimal range of product variety.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.61-64
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• 2000

This paper analyzes a dynamic lot-sizing problem, in which the order size of multiple products and a single container type are simultaneously considered. In the problem, each order (product) placed in a period is immediately shipped immediately by containers in the period and the total freight cost is proportional to the number of each container type employed. Also, it is assumed that backlogging is not allowed. The objective of this study is to determine the lot-sizes and the shipping policy that minimizes the total costs, which consist of ordering costs, inventory holding costs, and freight costs. Because this problem is NP-hard, we propose a heuristic algorithm with an adjustment mechanism, based on the optimal solution properties. The computational results from a set of simulation experiment are also presented.

• Management Science and Financial Engineering
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• v.17 no.2
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• pp.23-37
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• 2011

In this paper, we address a layout design problem for determining an optimal 4-class-based dedicated linear storage layout in a class of unit load storage systems. Assuming that space requirement for a class is the sum of the maximum inventory levels of products assigned to the class, and that one-way travel time is a linear function of storage index, we formulate a 4-class-based dedicated linear storage problem PTL[4] and provide an exact splitting algorithm with $O(n{\lceil}logn{\rceil})$. Our algorithms could be applied to more than a 4-class-based dedicated storage layout problem with slight modification in order to reduce computational execution time.

• Korean Management Science Review
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• v.11 no.1
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• pp.91-106
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• 1994

In mixed model assembly lines, products are assembled seqeuntially that have different combination of options specified by customers. In just in time (JIT) environment, production smoothing becomes an important issue for sub-lines which supply the necessary parts to each workstation of the assembly line. Another important issue is to avoid line stopping caused by work overload in workstations. To find a sequence which minimizes the costs associated with line stoppage and the option parts inventory level, a nonlinear mixed integer programming is formulated. Recognizing the limit of the Branch and Bound technique in large sized problems, a heuristic solution procedure is proposed. The performance of the heuristic is compared with the Branch and Bound technique through randomly generated test problems. The computational results indicate that on the average the heuristic solutions deviate approximately 3.6% from the optimal solutions.

• Journal of the Korean Operations Research and Management Science Society
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• v.29 no.1
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• pp.101-112
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• 2004

Customer satisfaction level is usually measured in terms of price, qualify, customization, after-sale-service, product variety etc. Each firm sets up a distinctive production/marketing strategy to gain competitive advantage by Prioritizing the customer satisfaction measures. The market differentiation strategy directly results in supply chain performance such as lead time, inventory, customer fill rate and market share. Product proliferation desirable in customization sense often conflicts the economies of scale effect in production side. This paper focuses the relationship between product variety and market share. Specifically, we investigate how introduction of new product affects the current market share, i.e., formation of customer preference and provide some insight into the optimal range of product variety.

• Journal of the Korean Operations Research and Management Science Society
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• v.31 no.2
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• pp.57-67
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• 2006

One of challenging issues of market oriented manufacturing organization is product proliferation. However, increasing product variety not only incurs additional direct and indirect production cost, but also aggravates production system performance such as inventory level, customer lead time and fill rate. Recently, as one of the most beneficial strategic choices to menage the risks associateed with product variety and uncertain sales, special attention is focused on the product/process redesign to delayed product differentiation. In this paper, we develop an analytical model to demonstrate the existence of an optimal level of product differentiation, which can be used to provide theoretical basis in establishing market oriented SCM strategy.

• Journal of the Korean Operations Research and Management Science Society
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• v.39 no.2
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• pp.97-109
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• 2014

This paper considers a reverse supply chain with simultaneous recovery of used products and manufacturing of brand-new ones. Recovered products are downgraded and have to be sold in a market different from that of brand-new products at a different price. In case of a shortage of recovered product inventory, a brand-new item, if available, can be offered at the price of a recovered product. In other words, one-way demand substitution is allowed. We address the joint decision of when to manufacture brand-new product, when to recover returned product, and how to control demand substitution to maximize the hybrid production system's profits. To this end, we propose a Markov decision Process model and investigate the structure of the optimal policy. Performance comparison is numerically implemented between the models with and without downward demand substitution option under different operating conditions of the system parameters.

• Journal of Korean Institute of Industrial Engineers
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• v.1 no.1
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• pp.41-56
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• 1975

In the past the pattern of business down-trend usually appeared in the form of, first, decrease in facility investment, then decrease in inventory level, followed by reduced level of consumption. But the pattern nowadays is becoming just the opposite, that is, first, consumption decrease, then inventory level increase, followed by restriction of facility investment. Also in the past, the greater effort was placed in strengthening of hardware areas through optimization and modernization of production means on the premise of sales. But lately software areas take most of the main effort to establish production mean with sales as its objective. Under these circumstances one of the real problems facing production activities today is the conflicting relationship between sales and production functions. This occurs due to differences of their view points. Then, in order to achieve maximum profit at the least cost, which is the ultimate objective of a production activity, the need arises to effectively coordinate sales demand and plant production capacity. For this purpose strong control means and function must be devised. In our case study example we illustrate a management technique for a combined planning function, of optimal coordination of product mixes utilizing a computerized linear programming model as control means of attaining maximum profit. It is hoped that this example help achieve some of corporate objectives.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.3
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• pp.204-209
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• 2012

본 논문은 전국적인 소매업체의 각 지점별 고객 수요가 불확실한 상황에서 고객 서비스 목표 수준을 충족하는 최적재고 수준을 결정하는 문제에 대해 연구하였다. 이를 위해 전국에 분포한 지점에서 물품을 판매하는 베스트바이, 월마트, 혹은 시어스와 같은 전국적인 소매업체 관점에서 사용할 수 있는 핵심 관리 지표(KPI)로서 ISR(In-Stock Ratio)를 정의하였으며, 전국적인 소매업체가 평균 ISR로 정의되는 고객 서비스 목표 수준을 충족하면서 각 지점 보유 재고의 총합을 최소화할 수 있는 최적화 모델을 수립하였다. 본 논문은 해당 모델에 항상 최적해가 존재함을 증명하고 해당 최적해를 Karush-Kuhn-Tucker 조건을 사용하여 고객 수요의 확률분포의 형태에 상관없이 일반화된 형태로 표현하였다. 또한 본 논문은 고객 수요가 정규분포와 같은 특정 확률분포를 따르는 경우에 대해 연구하였으며, 이 경우에 대한 최적 재고수준을 나타내는 식을 도출하였다. 마지막으로 본 논문에서는 상기 기술된 상황에 대한 수리적인 예제를 통하여 최적재고 수준과 확률분포 파라미터들간의 관계를 분석하였다.