• KIEAE Journal
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• 제13권1호
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• pp.159-165
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• 2013

Recently buildings are being constructed on the downtown area. In most building construction sites on the downtown area, the need for adequate material inventories are critical in order to avoid project delays and cost increases due to inappropriate deliveries of key materials. However immoderate material inventories cause increasing inventory cost. Therefore, we need a proper management material inventories. This research re-establishes the existing safety stock and analyzes relationship between safety stock and service level. It suggests an economical re-order point based on safety stock considering service level, various demand and delivery time.

• 대한안전경영과학회지
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• 제14권2호
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• pp.137-145
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• 2012

본 연구는 공급자(supplier), 소매상(retailer) 그리고 고객(customer)으로 구성된 2 단계 공급사슬에서 소매상의 관점에서 소매상의 최적 재고정책 결정에 관한 문제를 다루었다. 공급자는 수요 증대를 목적으로 소매상의 주문량에 따라 다단계로 일정기간동안 제품 판매대금에 대한 지불 연기(외상)를 허용하고, 고객의 수요는 소매상의 제품 재고량에 영향을 받는다는 가정 하에 재고 모형을 설계하였다. 모형 분석을 통하여 소매상의 이익을 최대화하는 최적 주문량 결정 방법을 제시하였고, 예제를 통하여 그 제시된 해법의 타당성을 보였다.

• 대한안전경영과학회지
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• 제9권4호
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• pp.121-127
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• 2007

CSP(Concurrent Spare Parts) is supplied with the procurement of new equipment or weapon system and is used to sustain the equipment without resupply during the initial coverage period. This study is concerned with a problem of determining the near optimal inventory level of the spare parts, especially Concurrent Spare Parts. For this, we utilize the mixed periodic and continuous review polices considering the CSP and (r,Q) Policies concurrently in a two-echelon distribution system. We propose the mathematical model to minimize the total cost which is composed with ordering cost, purchasing cost, holding cost, and stickout cost. If the mixed policy is compared to other policies(CSP, (r,Q)), the proposed methodology performs well and is best policy in the equipment maintenance expenses.

• 산업경영시스템학회지
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• 제21권47호
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• pp.87-99
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• 1998

This study is concerned with a problem of determining the optimal requirements level of the spare parts, especially Concurrent Spare Parts(CSP). CSP is supplied with the procurement of new equipment system, and is used to sustain the equipment without resupply during the initial coverage period. We consider this situation as a multiechelon inventory model with several bases and one depot. And we assume a equipment system which consists of many types of parts would grounded if one of the parts fail. Also this multiechelon CSP problem is considering a time-varing (dynamic) environment. We develop a computational procedure to find the optimal number of spare parts minimizing the total expected cost, while achieving the required system availability. Finally we present a simple example of suggested method.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.382-386
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• 1998

The objectives of this study are to reveal relationship between tree physiology and spectral reflectance on effects of artificial acid rain and to obtain basic data on optimal wave length for forest of LRC sensor on KOMPSAT-2. Three pH levels of artificial acid rain - control, pH4.5 and pH3.0 - were applied to Pinus and Quercus species. Three types of the acid rain were spraied at the amount of 500m1 in every two days. Spectral reflectance data was collected once in a month by using GER 1500 (350~2500nm) or Ll 1800(300~1100nm) Spectroradiometer. The data was measured three times in a pH level. The results of this study are as follows; in April, the spectral reflectance of Pinus species was high in order at the level of pH3.0, control and pH4.5; in May, control, pH3.0 and pH4.5; in June, control, pH4.5 and pH3.0. That of Quercus species was high in the order of control, pH4.5 and pH3.0 in May; in June, control, pH3.0 and pH4.5, especially, within infrared wave length range, control, pH4.5 and ph3.0.

• 산업경영시스템학회지
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• 제13권21호
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• pp.25-28
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• 1990

In this paper we consider the one-period inventory model in which it is required to determine the selling quantity which maximizes the probability of realizing a predetermined level of profit L. The Assumptions used in this paper are willing to accept the rel life considerations, which are thestochasic supply, the discounted selling price and the discounted purchasing cost for the over-supply etc.

• 제어로봇시스템학회논문지
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• 제9권5호
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• pp.407-412
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• 2003

An effective methodology is .reported for determining the optimal capacity (lot-size) of batch processing and storage networks which include material recycle or reprocessing streams. We assume that any given storage unit can store one material type which can be purchased from suppliers, be internally produced, internally consumed and/or sold to customers. We further assume that a storage unit is connected to all processing stages that use or produce the material to which that storage unit is dedicated. Each processing stage transforms a set of feedstock materials or intermediates into a set of products with constant conversion factors. The objective for optimization is to minimize the total cost composed of raw material procurement, setup and inventory holding costs as well as the capital costs of processing stages and storage units. A novel production and inventory analysis formulation, the PSW(Periodic Square Wave) model, provides useful expressions for the upper/lower bounds and average level of the storage inventory hold-up. The expressions for the Kuhn-Tucker conditions of the optimization problem can be reduced to two subproblems. The first yields analytical solutions for determining batch sizes while the second is a separable concave minimization network flow subproblem whose solution yields the average material flow rates through the networks. For the special case in which the number of storage is equal to the number of process stages and raw materials storage units, a complete analytical solution for average flow rates can be derived. The analytical solution for the multistage, strictly sequential batch-storage network case can also be obtained via this approach. The principal contribution of this study is thus the generalization and the extension to non-sequential networks with recycle streams. An illustrative example is presented to demonstrate the results obtainable using this approach.

• 대한산업공학회지
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• 제25권2호
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• pp.274-281
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• 1999

In this paper, we determine the required storage capacity of a unit-load automated storage/retrieval system(AS/RS) under random storage assignment(RAN) and n-class turnover-based storage assignment(CN) policies. For each of the storage policies, an analytic model to determine the optimal storage capacity of the AS/RS is formulated so that the total cost related to storage space and space shortage is minimized while satisfying a desired service level. A closed form of optimal solutions for the RAN policy is derived from the model. For the CN policy, an optimal storage capacity is shown to be determined by applying the existing iterative search algorithm developed for the full turnover-based storage(FULL) policy. Finally, an application of the approach to the standard economic-order-quantity inventory model is provided.

• 대한산업공학회지
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• 제1권1호
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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.

• 한국국방경영분석학회지
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• 제24권2호
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• pp.146-161
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• 1998

This article develops model of the nonstationary state behavior of the multiechelon spare parts provisioning systems. This study is concerned with a problem of determining the near optimal requirements level of the spare parts, especially Concurrent Spare Parts(CSP). CSP is supplied with the procurement of new equipment system, and is used to sustain the equipment without resupply during the initial coverage period. We consider this situation as a multiechelon inventory model with several bases and one depot. And we assume an equipment system which consists of many types of parts would grounded if one of the parts fail. Also this multiechelon CSP problem is considering the nonstationary poisson failure process and nonstationary exponential repair process in a dynamic environment. We develop an efficient computational procedure to find the near optimal number of spare parts minimizing the total expected cost, while achieving the required system availability. Finally we present a simple example of suggested method.