• 한국경영과학회지
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• 제4권1호
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• pp.25-31
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• 1979

We consider the optimal ordering policy for a single-product two-stage inventory system where the main assumptions are as follows: (i) constant continuous demand only at stage 2, (ii) constant input (production) rate at stage 1, (iii) instantaneous delivery (transportation) from stage 1 to stage 2, (iv) backlogging is allowed only at stage 2, (v) an infinite planning horizon. Costs considered are ordering and linear holding costs at both stages, and linear shortage cost only at stages 2. By solving 9 different case problems, we have observed the general from of the optimal ordering policies for our model which minimizes the total cost per unit time. It is noticeable from this observation that the questionable but more often than not adopted assumption by many authors in determining the optimal potimal policy for multistage inventory systems, that the ordering (lot) sizes at each stage remain constant thruout the planning horizon, is not valid.

• 한국미생물·생명공학회지
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• 제17권4호
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• pp.343-348
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• 1989

L. erythrorhizon 세포를 polyurethane foam과 함께 증식시킬 경우 shikonin 유도체가 polyurethane에 효과적으로 흡착됨과 동시에 polyurethane을 사용하지 않은 경우와 비교하여 shikonin 생산량이 현저히 증가하였다. 이 같은 증가는 세포를 polyurethane pore에 고정하여 증식시킴으로써 원활한 세포간 접촉을 유지하고 세포 내에 shikonin 농도를 저하시켜shikonin 생성에 좋은 조건을 제공함에 기인한 것으로 생각되었다. 공정의 생산성을 높이기 위하여 여러가지 배양시스템이 검토되었는데, indole-3-acetic acid(1.75mg/ι)와 kinetin(0.1mg/ι)을 함유하는 Schenk-Hildebrandt 배지 (SHIK 배지) 시스템이 가장 효과적이었다. p-Chlorophenoxyacetic acid (2.0 mg/ι)와 kinetin (0.1 mg/ι)를 함유하는 Schenk-Hildebrandt 배지 (SHND 배지) 시스템에 비교하여 SHIK 배지 시스템에서 Shikonin 생성량은 약 4.5배 증가하였다. Polyurethane을 세포를 고정화하는 지지체로 사용할 경우에는 현재 행하여지고 있는 2단계 배양보다 1단계 배양이 더욱 효과적이며 경제적으로도 매우 유리할 것으로 판단되었다.

• 대한산업공학회지
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• 제17권1호
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• pp.29-35
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• 1991

This paper deals with a production-inventory model for two-stage batch production system. We propose a lot-sizing scheme which combines the integer multiple lot requirements (IMLR) policy and the integer split lot requirements (ISLR) policy. An iterative search procedure for optimal decision variables is presented and numerical examples are solved to illustrate the validity of the model. The results show that the proposed scheme outperforms the existing policies.

• 한국미생물·생명공학회지
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• 제19권2호
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• pp.171-178
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• 1991

The two-stage enzyme reactor, packed with cyclodextrin glucanotransferase (CGTase) immobilized on Amberite IRA 900, coupled with ultrafiltration membrane was investigated for continuous production of cyclodextrin (CD). 5% (w/v) of soluble starch was partially cyclized, in the 0.1 l first-stage immobilized enzyme reactor, up to CD conversion yield of 10% (w/w) at retention time of 0.56hr and 1.5 units of immobilized CGTase/1g of carrier. In the second stage main immobilized enzyme reactor capacity of 1.5 l, the maximum CD conversion yield of 39% (w/v) was achieved at retention time of 2.8hr and 0.47 unit of CGTase/1 g of carrier. Unreacted residual dextrin was fractionated with ultrafiltration membrane, and then, recycled into the second-stage main bioreactor to increase the CD conversion yield. The most suitable membrane size and the volume concentration ratio (concentrate: filterate) for recycling of unreacted residual dextrin were found to be 5K dalton and 4:6, respectively. CD conversion yield was increased about 3~4% upon co-immobilization of pulluanase along with CGTase. Spent Amberite IRA 900 can be reutilized consecutively more than 3 times for immobilization of CGTase after regeneration.

• Journal of Plant Biotechnology
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• 제3권1호
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• pp.1-5
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• 2001

Traditional culture technology of medicinal plants mainly depends on the field culture, which has many problems. With progress of modern culture technology, it has become possible to produce valuable secondary metabolites from medicinal plants. In this paper, we discuss about the pigment and saikosaponin production from too medicinal plants, Carthamus tinctorius and Bupleurum falcatum, through bioreactor culture system. A two-stage bioreactor culture system was established for the production of yellow and red pigments and saikosaponins by cell suspension cultures of Carthamus tinctorius and Bupleurum falcatum. In Carthamus tinctorius, balloon type airlift bioreactors and column type airlift bioreactors were employed for the tell culture and for the pigment production, respectively. The greatest pigment production was obtained on White medium supplemented with 4 mg/L kinetin, high levels of sucrose concentration and photosynthetic photon flux. In Bupleurum falcatum, adventitious roots were cultured in balloon type airlift bioreactors and the root growth was greatest on SH medium containing 5 mg/L IBA and 0.2 mg/L kinetin. HPLC analysis showed that the contents of main active saikosaponins a, c, and d in adventitious roots were almost the same as those in field cultured root.

• 품질경영학회지
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• 제24권1호
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• pp.20-31
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• 1996

A pure zero-one integer program is formulated for determining where to assign the inspection stations in a multi-stage production system. The objective fuction is formulated to minimize the overall inspection costs. One of the major characteristics of this system is that an assigned inspection station is to inspect only the items produced in previous manufacturing stages. Each inspection station can be assigned to any possible inspection stage between two manufacturing stages. Error-free and screening inspection policy is assumed in this system and the defective items found in any inspection station will be reworked at once. The integer programming model presented in this paper has the advantages in the ease of modeling and modifiing as compared with the existing dymanamic programming methods. The solutions of the model can be easily obtained by the commercially available softwares like LINDO and GAMS.

• 산업경영시스템학회지
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• 제18권36호
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• pp.167-174
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• 1995

The Dynamic programming method are developed for determining where to assign the inspection efforts in serial multi-stage production systems. The objective function is formulated to minimize the inspection and repairing costs. One of the major assumptions in this systems is that every assigned inspection stations should inspect the only items produced in manufacturing stages after the previous inspction station. The inspection stations can be assigned at every possible inspection stage after the manufacturing stages. Two type error is considered and screening inspection policy is assumed in this system and the defective items detected in tile inspection stations will be repaired or scraped by the defective types.

• 공업화학
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• 제22권3호
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• pp.286-290
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• 2011

본 연구에서는 W시에서 운영하는 RDF 생산시설의 펠렛 RDF를 이용하여 RDF의 가스화 반응으로 합성가스를 생산하였다. 생산된 RDF 촤를 소각로에 투입하여 연소과정에서 발생되는 열을 가스화로의 간접열원으로 이용하는 2단 가스화시스템 공정을 개발하였다. RDF의 가스화 반응 시간에 따른 합성가스 발생 비율과 잔재물(촤)의 발열량 분석 등을 통하여 2단 가스화시스템 공정에서의 합성가스 생산 최적 운전조건을 연구하였다. 가스화로의 외부 열원 공급에 필요한 에너지 비용 저감을 위해 최적의 촤 체류시간을 도출하였다.

• 대한임베디드공학회논문지
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• 제17권2호
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• pp.77-83
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• 2022

In this paper, the two-stage object detection approach is proposed to implement a deep learning-based label inspection system on edge computing environments. Since the label printed on the products during the production process contains important information related to the product, it is significantly to check the label information is correct. The proposed system uses the lightweight deep learning model that able to employ in the low-performance edge computing devices, and the two-stage object detection approach is applied to compensate for the low accuracy relatively. The proposed Two-Stage object detection approach consists of two object detection networks, Label Area Detection Network and Character Detection Network. Label Area Detection Network finds the label area in the product image, and Character Detection Network detects the words in the label area. Using this approach, we can detect characters precise even with a lightweight deep learning models. The SF-YOLO model applied in the proposed system is the YOLO-based lightweight object detection network designed for edge computing devices. This model showed up to 2 times faster processing time and a considerable improvement in accuracy, compared to other YOLO-based lightweight models such as YOLOv3-tiny and YOLOv4-tiny. Also since the amount of computation is low, it can be easily applied in edge computing environments.

• 상하수도학회지
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• 제30권3호
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• pp.271-278
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• 2016

Recently, reverse osmosis (RO) is the most common process for seawater desalination. A common problem in both RO and thermal processes is the high energy requirements for seawater desalination. The one energy saving method when utilizing the osmotic power is utilizing pressure retarded osmosis (PRO) process. The PRO process can be used to operate hydro turbines for electrical power production or can be used directly to supplement the energy required for RO desalination system. This study was carried out to evaluate the performance of both single-stage PRO process and two-stage PRO process using RO concentrate for a draw solution and RO permeate for a feed solution. The major results, were found that increase of the draw and feed solution flowrate lead to increase of the production of power density and water permeate. Also, comparison between CDCF and CDDF configuration showed that the CDDF was better than CDCF for stable operation of PRO process. In addition, power density of two-stage PRO was lower than the one of single-stage. However, net power of two-stage PRO was higher than the one of single-stage PRO.