• 품질경영학회지
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• 제18권2호
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• pp.9-17
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• 1990

This paper deals with a FOQ( ; fixed-order quantity) model for spare-part inventory control. In a spare-part inventory problem, stock depletion arises not from external market demand but from internal demand resulting from failures of parts in use. The problem differs from the classical inventory problem in that the demand for a failed part never arises more during stockout period, since the unit remains inoperative when stockout occurs until the failed part is replaced by new one. In the problem under consideration, n identical units are operating simultaneously and failed one is replaced immediately by new one if on-hand spares remain. In order to replenish spares, an order with quantity Q is placed whenever the number of on-hand spares falls to levels. The average annual cost of operating the spare-part inventory system is derived under the assumption that both lifetime of a part and replenishment lead-time distributions are exponential.

• 한국기후변화학회지
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• 제7권4호
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• pp.485-492
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• 2016

For reporting national greenhouse gas inventory in forest sector, the forest growing stock from the National Forest Inventory (NFI) system has used as activity data sources. The National Forest Inventory system was changed from rotation system by province to annual system by 5 years across the country. The forest growing stocks based on the new inventory system produced a different trend compared to the previous estimations. This study was implemented to recalculate previous forest growing stocks for time series consistency at a national level. The recalculation of forest growing stock was conducted in an overlap approach by the IPCC guideline. In order to support the more consistency data, we used calibration factors between applied stand volumes in 1985 and 2012, respectively. As a result, the time series of recalculated forest growing stock was to be consistency using the overlap approach and the calibration factor with the lower middle/middle site index. According to the applied overlap period, however, we will recalculate activity data using more complete data from national forest inventory system.

• 대한산업공학회지
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• 제5권1호
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• pp.59-66
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• 1979

The objective of this paper is to develop a stochastic inventory system model under the so-called continuous-review policy with a Poisson one-at-a-time demand process, iid customer inter-arrival times {Xi}, backorders allowed, and constant procurement lead time $\gamma$. The distributions of the so-called inventory position process {$IP_{(t-r)}$} and lead time demand process {$D_{(t-r,t)}$} are formulated in terms of cumulative demand by time t, {$N_t$}. Then, for the long-run expected average annual inventory cost expression, the "ensemble" average is estimated, where the cost variations for stock ordering, holding and backorders are considered stationary.

• 산업경영시스템학회지
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• 제27권4호
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• pp.110-116
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• 2004

ABC analysis is the process of dividing inventory items into three classes according to their monetary usage so that managers can focus on items that have the highest monetary usage value, and has been widely used in practice since its development in 1950. However, the original criterion, monetary usage value, can no longer be the only rational criterion. Applying Analytic Hierarchy Process, we develop a new method to classify inventory items by considering such operationally/strategically important criteria as annual dollar usage, lead time, supplier's capacity, defective rate, difficulty of purchasing and unit price. A case study is performed applying the method to the field data from a company which produces electrochemical products.

• 한국환경복원기술학회지
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• 제18권5호
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• pp.61-72
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• 2015

This study was reviewed the national greenhouse gas inventory report (NIR) of Annex I countries and estimated national greenhouse gas inventory on wetlands in Korea. Annex I countries submitted National Inventory Report which are focused on land converted to wetlands category and wetland remaining wetland (mainly peat lands) because IPCC did not suggest a formal methodology on flooded land. So we conducted a study on estimating of national greenhouse gas inventory in wetland (flooded land). The total annual $CO_2-eq.$ emission of wetland remaining wetland (flooded land) was ranged from 99.9 Gg $CO_2-eq.$ to 237.1 Gg $CO_2-eq.$ from 1990 to 2012. The $CO_2-eq.$ emissions was declined after peaking in 1995, however, it slightly increasing in recently years. The latest total $CO_2-eq.$ emission from flooded land was 117.7 Gg $CO_2-eq.$ in 2012 which was covered only 0.00002% of national GHG inventory. This means that flooded land is not key-category in Korea. We will consider an improvement for emissions of flooded land, if IPCC suggest formal or complementary methodology.

• International Journal of Advanced Culture Technology
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• 제8권3호
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• pp.300-306
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• 2020

This study analyzes the distributor's inventory model in a two-stage supply chain consisting of the supplier, the distributor and the end customer. The supplier will allow a credit period before the distributor settles the account with him in order to stimulate the demand for the product he produces. It is also assumed that the distributor pays the shipping cost for the order and hence, the distributor's ordering cost consists of a fixed ordering cost and the shipping cost that depend on the order quantity. The availability of the delay in payments from the supplier enables discount of the distributor's selling price from a wider range of the price option in anticipation of increased customer's demand. As a result, the availability of a credit transaction leads to an increase in inventory levels. On the other hand, in the case of deteriorating products in which the utility of the product perish over time, the deterioration rate with time plays a role in reducing inventory levels. In this regard, we analyze the effect of the length of the credit period and the degree of product deterioration on the distributor's inventory level. For the analysis, we formulate the distributor's annual net profit and analyze the effect of the length of credit period and deterioration rate of the product on inventory policy numerically.

• 한국산림과학회지
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• 제95권6호
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• pp.690-695
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• 2006

본 연구는 개인휴대 단말기(PDA)를 이용하여 임목자원 조사를 위한 산림조사 시스템을 개발하는데 그 목적이 있다. 본 연구에서 개발한 PDA용 산림조사 소프트웨어는 산림청 고시 지원 측정법과 4차 전국산림자원조사용 전국산림조사요령에 근거하여 제작되었다. 산림조사 소프트웨어는 GPS를 활용하여 표본점의 위도, 경도, 해발고도 등의 위치정보를 기록할 수 있도록 하였다. 34가지 수종, 각 수종 별 18 직경급, 수종 본수, 각 직경급별 수고 데이터, 수피의 두께 및 연년생장량 등의 항목을 입력할 수 있으며, 형수값 또는 재적식을 활용하여 단목재적 및 누적재적을 출력할 수 있다. 산림조사 소프트웨어는 울진군 산림조합과 논산 산림조합의 작업자를 대상으로 적용시험을 실시하여 시간절감 효과가 큰 것을 확인하였다. 본 연구에서 개발한 PDA를 활용한 산림조사 소프트웨어를 활용하여 효율적인 산림조사가 가능하므로 조사 및 관리비용을 절감할 수 있으며, 노동생산성을 크게 향상시킬 수 있을 것이다.

• 대한산업공학회지
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• 제24권1호
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• pp.127-136
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• 1998

This paper presents a stochastic partial backorder inventory model for the situation in which demand follows normal distribution and back order ratio during that stockout period decreases exponentially according to the length of backorder period. In the paper, an objective function is formulated to minimize the average annual cost, which is the sum of the ordering, carrying, time-proportional backordering, and lost sales cost. And then sensitivity analysis for various exponential backorder ratios and standard deviations of leadtime demand are presented. The inventory model in the paper is reduced to a backorder model and lost sales model, when backorder ratio is 1 and 0, respectively.

• 품질경영학회지
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• 제17권1호
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• pp.11-18
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• 1989

A one-upper level warehouse n-Iower level retailer inventory distribution model is discussed. This paper presents the parallel-type inventory structure using an order-up-to-level invertory control system for analyzing the approximation of the expected units back ordered and the measure of service. We find that the total expected backorder units in system can substitute the expected back orders in the last two periods for the expected back orders in total periods. The rate of total expected back orders which is the measure of disservice, is given by dividing the improved units of total expected backorder into the total demand during an order cycle. The average annual total cost in system is obtained by considering the results, but from the viewpoint of this study the cost analysis is not described.

• 한국경영과학회지
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• 제31권2호
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• pp.113-127
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• 2006

We consider an integrated supply chain model in which multiple suppliers replenish items for a single buyer's demand. Also the buyer specifies a basic replenishment cycle and the suppliers replenish the items only at those time intervals. Namely, we propose a model to study and analyze the benefit by coordinating supply chain inventories through the basic replenishment cycle time. The objective of this model is to minimize the total relevant annual cost of the integrated inventory model. After developing proposed coordinated models, we suggest heuristics for searching the solutions of our models. Finally, numerical and computational experiments for each policy are carried out to evaluate the benefits of those models and the compensation policy is addressed to share the benefits.