• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.1
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• pp.93-104
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• 2007

We consider a supply chain where products are shipped to warehouse from manufacturing system to customers. Products are supplied from either in-house regular manufacturing or the secondary source such as subcontractor. The inventory in warehouse is controlled by base-stock policy, that is, whenever a demand arrives from customer, an order is released to the manufacturing system. Unsatisfied demand is backlogged. The manufacturing system is modeled as M/M/s+1/c queueing system, and the orders exceeding the given limit care blocked and lost. The steady state distribution of the outstanding orders and the throughput of the manufacturing system are functions of the level of engagement In the secondary source. There is a profit obtained from throughput and cost not only due to the engagement of the secondary source in the manufacturing system but also inventory positions. We want to maximize the total production profit minus the total cost of the production system by simultaneously determining the optimal level of engagement of the secondary source and the optimal base-stock level of the inventory. We develop two algorithms : one without guarantee of the optimal solution but with the small number of computations, the other optimal but with more computations.

• Journal of Korean Institute of Industrial Engineers
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• v.28 no.1
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• pp.1-13
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• 2002

We study a multi-component production/inventory system in which individual components are made to meet various demand types. We assume that the demands arrive according to a Poisson process, but there is a fixed probability that a demand requests a particular kit of different components. Each component is produced by a flow line with several stations. The production of each component is operated by the CONWIP control mechanism. To analyse this system, we propose an approximation method based on aggregation method. In application of the aggregation method, a product-form approximation technique as well as a matrix-geometric method is used. Comparisons with simulation show that the approximation method provides fairly good results.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.11a
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• pp.661-664
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• 2006

Under a VMI (Vendor Managed Inventory) system, the vendor holds a certain level of control over not only inbound replenishment decisions on stocking but also outbound re-supply decisions. In this situation, vendor faces a better opportunity to synchronize the inventory and transportation decisions. However, shipment consolidation can reduce transportation expenses, but delivery time about the customer comes to be long and a customer service is fallen. Thus, a stock and transportation decision must consider this correlation. This study look into the relevant literature and suggest about further research direction.

• Journal of the Korean Home Economics Association
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• v.29 no.2
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• pp.77-86
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• 1991

본 연구의 목적은 1) 집단 급식소의 재고 관리 시스템에 관한 자기학습식 Module (Self-instructional Module)을 개발하고, 2) 비동등 통계 실험연구 디자인 (Nonequivalent Control group research design)을 사용하요 자기학습식 재고 관리 시스템 Module의 교육적 효과를 평가하여, 3) 교육기관 및 집단 급식소에서의 교육용 교재로서의 타당성 여부를 검증하고자 함이다. 집단급식소의 재고 관리 시스템에 관한 자기학습식 Module을 개발하기 위해서 현재 미국 전역의 가정대학 내의 식품영양 및 급식경양학과에서 재고 관리에 관련된 교과목을 위하여 채택되어 사용되어지고 있는 주요 교과서들의 내용 분석과 급식경영학 전공 교수 3인의 판단에 기초를 두어 재고관리에 포함되어야 할 내용이 분석되었다. 포함되어져 있는 내용의 목차는 반입(receiving), 저장(storing), 출고(issuing), 재고통제(inventory control), 재고의 자산적 가치(inventory valuation) 및 재고관리 시스템의 자동화(inventory control computer system)등이다. 실험 대상은 Iowa 주립대학에서 급식정보관리 (Foodservice Management Information System) 과목을 수강하였던 88명의 학생이며, 강의를 통해 수업을 받은 통제집단 46명과, 자기 학습식 Module을 사용했던 실험집단 42명으로 구성되었다. 모든 실험 대상에게는 사전검사(Pretest)와 사후검사(posttest)를 실시하였으며 자료의 처리는 SPSS PC Package를 통계법으로 분석하였다. 연구결과는 강의 중심의 통제집단과 자기학습식 Module을 사용했던 실험집단 간의 통제 후 평균 값(posttest adjusted mean score)사이에는 유의적인 차이를 보였으며 (p<0.05), 자기 학습식 Module 그룹에 속해 있던 학생들이 더 높은 통제 후 평균값(adjusted mean score)을 보여 주었다. 그러므로, 이 실험을 통하여, 개발된 집단 급식소 재고관리 시스템에 대한 자기학습식 Module은 학생들에게 재고관리 시스템에 관한 개념과 내용의 습득력을 향상시키는데 있어서 적어도 강의식 교수법과 동일하거나 더나은 교육적 효과를 가져왔다고 판단되었다.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.2
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• pp.145-151
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• 2015

As order quantity is increased, the ordering cost per item will be cheaper due to saving of transportation and material handling costs. In this paper, two realistic assumptions such as quantity discount and budget limit are considered. Quantity discount means that all units in the order will be discounted according to the predetermined order levels. Budget limit represents that the costs for inventory investments are bounded. This paper develops a Lagrangian relaxation approach for a continuous review inventory model with a budget constraint and quantity discounts. Computational results indicate that the proposed approach provides a good solution. Sensitivity analysis is done to get some insights on budget limit and quantity discount. As budget limit or the amount of discount according to order quantity is increased, order quantity is increased, whereas reorder point is not always increased.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.05a
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• pp.441-445
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• 2004

In this paper, we deal with an inventory model of a multi-stage, serial supply chain system where a single product type and nonstationary customer demand pattern are considered. The retailer and suppliers place their orders according to an echelon-stock based replenishment control policy. We assume that the suppliers can access online information on the demand history and use this information when making their replenishment decisions. Using a reinforcement learning technique, the inventory control parameters are designed to adaptively change as the customer demand pattern is altered, in order to maintain a given target service level. Through a simulation based experiment, we verified that our approach is good for maintaining the target service level.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.4
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• pp.69-78
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• 2010

Multi-criteria ABC inventory classification is one of the most widely employed techniques for efficient inventory control, and it considers more than one criterion for categorizing inventory items into groups of different importance. Recently, Ramanathan (2006) proposed a weighted linear optimization (WLO) model for the problem of multi-criteria ABC inventory classification. The WLO model generates a set of criteria weights for each item and assigns a normalized score to each item for ABC analysis. Although the WLO model is considered to have many advantages, it has a limitation that many items can share the same optimal efficiency score. This limitation can hinder a precise classification of inventory items. To overcome this deficiency, we propose a context-dependent DEA based method for multi-criteria ABC inventory classification problems. In the proposed model, items are first stratified into several efficiency levels, and then the relative attractiveness of each item is measured with respect to less efficient ones. Based on this attractiveness measure, items can be further discriminated in terms of their importance. By a comparative study between the proposed model and the WLO model, we argue that the proposed model can provide a more reasonable and accurate classification of inventory items.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.5
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• pp.81-90
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• 2014

It is an element certainly required for the cost reduction of a company that forward and reverse logistics chain are unified and constitutes a resource closed-loop supply chain (CLSC). In this study, the inventory control which unifies inventory of distribution centers (DCs) of forward logistics and processing center of reverse logistics in the CLSC environment is proposed. The inventory system model for newly-constructed CLSC considers the JIT(Just-In-Time) delivery from the processing center to the manufacturer, including the making of decisions on whether to wait for the arrival of end-of-life products or to back-order necessary products for manufacturer when the supply of end-of-life products at the processing center via the returning center is insufficient for the demands of the manufacturers. The validity of the proposed model was verified using the genetic algorithm (GA). In order that a parameter might investigate the effect which it has on a solution, the simulation was carried out for priGA(priority-based GA) on three kinds of parameter conditions. Moreover, mhGA(modified hybrid GA) to which a parameter is adjusted for every Study on Reducing Logistics Costs and Inventory Control System according to facilities integration in the Closed-Loop Supply Chain Environment generation, the simulation was carried out to a four-kind numerical example.

• Journal of Korean Society of Rural Planning
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• v.17 no.3
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• pp.103-111
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• 2011

The purpose of this study is to review foreign scenic inventory map for the systematic management of natural scenic resources. Several foreign cases were surveyed and analyzed to apply the scenery inventory map in domestic, such as Visual Resource Management(VRM) from United States Bureau of Land Management, Scenery Management System(SMS) from USDA Forest Service and Visual Landscape Inventory(VLI) from British Columbia Ministry of Forest's, that were already established scenery inventory maps. The results are as follows. First, the characteristic of Korean landscape is quite a different from those of north american's, which is much smaller and more complex in topography and land use. So, it would be difficult to apply foreign system directly and we need more researches to our own system. The multi-stepped landscape unit system is highly recommended. Second, scenic quality could be estimated by the pre-built database, such as land forms, vegetation, hydrology and land uses. Historical and cultural attributes should be complemented. Third, existing scenic integrity could be grasped by scenic damage, landscape alteration caused by human activities and land exfoliation. Also, subjective evaluation method should be supplemented by objective criteria through further detailed studies. Finally, about landscape view conditions, landscape control points should be surveyed and established in advance, and viewing distance, viewing frequency, amount of observers and public interests should be considered.

• Journal of Korean Port Research
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• v.14 no.1
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• pp.37-45
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• 2000

Centralized safety stock in a periodic replenishment system which consists of one central warehouse and m regional warehouse can reduce backorders allocating the centralized safety stocks to regional warehouse in a certain instant of each replenishment cycle. If the central warehouse can not monitoring inventories in the regional warehouse, then we have to predetermine the instant of allocation according to demand distribution and this instant must be same for all different replenishment cycle. However, transition of inventory level in each cycle need not to be same, and therefore different instant of the allocation may results reduced shortage compare to the predetermined instant of allocation. In this research, we construct a dynamic model based on the assumption of monitoring inventories in the regional warehouse everyday, and develop an algorithm minimize shortage in each replenishment cycle using dynamic programming approach.