• 대한산업공학회지
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• 제41권5호
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• pp.447-452
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• 2015

This paper considers a two-stage make-to-stock production system. The first stage produces a single-component and the second stage produces a make-to-stock product using components. In addition to internal demands, the first stage faces external demands with the option of accepting or rejecting. To ration component inventory, the manufacturer adopts a static rule. This paper analyzes the production controls at both facilities that maximizes the manufacturer's profit. Using the Markov decision process model, we characterize the optimal production policy by two monotonic switching curves.

• 산업공학
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• 제22권4호
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• pp.368-375
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• 2009

This paper considers a two-stage supply system consisting of two make-to-stock facilities. The facility in the first stage produces a single type of component in anticipation of future demands from the market and the end item production while the facility in the second stage produces the end item in anticipation of future demands from the OEM customers. The facility in the first stage has the option of to accept or reject each incoming demand from the market. In this paper, we address the problem of how to control the exogenous component demand and how to manage the production of the end item and the component so as to maximize the system's profit subject to the system costs. In this paper, we present a heuristic policy that is the base-stock production policy combined with a linear switching curve for component demand control. Numerical study is implemented under different operating conditions of the system and it shows that the performance of the heuristic is very promising compared to that of the optimal policy for the Markov model.

• Management Science and Financial Engineering
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• 제6권1호
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• pp.37-63
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• 2000

An important objective of pull-based production control is to achieve synchronized and smooth production flow in a multi-stage system that is subject to uncertainty. To our knowledge, previous research has not generated a performance measure that captures this objective of pull-based probased production control system. This performance material with respect to the instant when the operation is required. We examine the issue of asynchronous waste in a two-stage kanban control system.

• 대한산업공학회지
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• 제24권1호
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• pp.105-113
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• 1998

This paper deals with a production line which consists of two production stages that are separated by a finite storage buffer. The inventory level in the storage buffer controls the production rate of the preceding stage. That is, the production rate becomes high (low) when the buffer inventory is low (high). We analyze the system characteristics utilizing the Markov process theory and then find an optimal control policy which maximizes a given system profit function. Also, a sensitivity analysis is made to examine the effects of various system parameters on the system performances.

• KSBB Journal
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• 제15권5호
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• pp.489-496
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• 2000

고농도 유전자 재조합 대장균을 이용하여 pyruvate dehy-drogenase complex-E2 특이성 인간 모노클론 항체의 Fab 부분을 효율적으로 생산하기 위해 회분식, 이단 연속식, 반 유 가식, two-stage cyclic fed-batch 동 여러 가지 배양 방법이 조사되었다. 먼저 플라스미드 안정성 문제를 극복하기 위해 growth stage와 production stage를 분리하는 two-phase 회분식 배양과 이단 연속식 시스템을 시도하였다 그 결과 two-phase 회분식 배양보다는 이단 연속식 배양에서의 세포농도와 항체 생산성이 우수하였다 또한 이단 연속식 배양에서의 세포 성 장과 항처l 생산성은 용존산소를 제어한 경우가 그렇지 않은 경우보다 월등하게 높았다. 그리고 plasmid 안정성에 있어서 는 실험기간 내에 거의 100%를 유지하여 높은 안정도를 보 여주었다. 유가식 공정에 적합한 공급 배지로 변형된 M9 배 지가 최적배지로 선정되었고 이 배지 중 최적의 CjN 비율을 조사한 결파 2:3으로 결정되었다. 반 유가식 시스템에서 constant feeding 전략을 사용할 경우 최적 공급속도는 $0.6g/\ell/hr$이었다. 또한 pulse에 의해 공급배지를 공급할 경우에는 총 공급 량이 같을 경우 소량으로 자주 공급해 주는 것이 공급배지를 한꺼번에 많은 양을 공급해주는 것 보다 바람직하였다. 여러 가지 feeding 전략을 조사해 본 결과 linear feeding 방법이 가장 효과적이었다. 하지만 linear feeding 방법마저도 고농도 세포배양에 한계가 있었기 때문에 pH-stat 방법을 이용한 two-stage cyclic fed-batch 시스템을 시도하여 $54 g/\ell$의 세포 를 얻을 수 있었다. 따라서 이 방법이 일단 생산성 향상을 위한 세포의 고농도 배양에는 조사한 여러 배양 시스템 중에 가장 효율적인 시스템임올 알 수 있었다 하지만 이 시스템 에서 포도당을 낮은 level로 유지할 수 있었으나, 초산의 과도한 축적으로 항체 생산성의 향상은 예상에 비해 크지 않았다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 1993년도 추계학술대회발표논문집; 서강대학교, 서울; 25 Sep. 1993
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• pp.175-184
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• 1993

Modeling the production process is a necessary and essential aspect of the production planning. This paper introduces a theoretical model of the multi-stage production process. A multi-stage production process is regarded as a network of interrelated production activities which use system exogenous inputs of goods in production and the intermediate products transfers between activities to produce final products. Our model is characterized by (1) a few of the production-related assumptions and (2) two types of elements "goods and activities" that are represented in terms of the network terminology. This model is different from the another multi-stage production models, so-called production network models in relation to the production-theoretical concept. It is not based on the concept of the production correspondence and the activity production functions, but the technology model of Koopmans. Koopmans.

• 한국미생물·생명공학회지
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• 제20권6호
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• pp.668-676
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• 1992

Alcaligenes eutrophus에 의한 poly-Beta-hydroxybuty-rate(PHB) 생산을 최적화하기 위해서 1단계에서는 성장을 최대화하고, 2단계에서는 생산을 최대화하는 이단 유가식 배양을 채택하였다. 성장단계에서 탄소원과 질소원의 최적농도는 회분식 배양 모델로부터 결정되었는데, 각기 16.64g/l와 0.54g/l이었다. 생산단계에서 질소원의 경우, 유가식 배양실험을 통해 0.07g/l가 최적인 것으로 나타났다. 탄소원의 최적농도는 모사로부터 결정되었고 이때 최적 전환시간도 함께 결정되었다. 생산공정의 제어를 위하여 시간지연을 고려한 적응비례 되먹임제어를 이용한 결과, 탄소원 농도 및 질소원농도를 최적의 상태로 유지시킬 수 있었다.

• 한국수소및신에너지학회논문집
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• 제26권3호
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• pp.247-259
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• 2015

This study was performed to investigate the application of dark $H_2$ fermentation to two-stage bioprocesses for organic waste treatment and energy production. We reviewed information about the two-stage bioprocesses combining dark $H_2$ fermentation with $CH_4$ fermentation, photo $H_2$ fermentation, microbial fuel cells (MFCs), or microbial electrolysis cells (MECs) by using academic information databases and university libraries. Dark fermentative bacteria use organic waste as the sole source of electrons and energy, converting it into $H_2$. The reactions related to dark $H_2$ fermentation are rapid and do not require sunlight, making them useful for treating organic waste. However, the degradation is not complete and organic acids remain. Thus, dark $H_2$ fermentation should be combined with a post-treatment process, such as $CH_4$ fermentation, photo $H_2$ fermentation, MFCs, or MECs. So far, dark $H_2$ fermentation followed by $CH_4$ fermentation is a promising two-stage bioprocess among them. However, if the problems of manufacturing expenses, operational cost, scale-up, and practical applications will be solved, the two-stage bioprocesses combining dark $H_2$ fermentation with photo $H_2$ fermentation, MFCs, or MECs have also infinite potential in organic waste treatment and energy production. This paper demonstrated the feasibility of two-stage bioprocesses combining dark $H_2$ fermentation as a novel system for organic waste treatment and energy production.

• Environmental Engineering Research
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• 제19권4호
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• pp.355-361
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• 2014

The wastewater treatment with a two-phase expanded granular sludge bed (EGSB) system for anaerobic degradation of acetate, benzoate, terephtalate and p-toluate from purified terephtalic acid (PTA) production was studied. The feasibility and effectiveness of the system was evaluated in terms of organic oxidation by chemical oxygen demand (COD), gas production, bacterial adaptability and stability in the granular sludge. Average removal efficiencies 93.5% and 72.7% were achieved in the EGSB reactors under volumetric loading rates of $1.0-15kg-COD/m^3/day$ and terephtalate and p-toluate of 351-526 mg/L, respectively. Gas production reached total methane production rate of 0.30 L/g-COD under these conditions in the sequential EGSB reactor system. Higher strength influent COD concentration above 4.8 g-COD/L related to field conditions was fed to observe the disturbance of the EGSB reactors.

• 한국미생물·생명공학회지
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• 제2권1호
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• pp.29-35
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• 1974

We have studied the applicability of the principles and inherent advantages of the two-stage dontinuous uclture technique to an enzyme process for the purpose of improving and optimizing the productivity of 3-ketosteroid-delta-1-dehydrogenase. By using a two-stage continuous culture system, the growth st ageand enzyme produdtion stage are separated. In each stage an optimal set of toperaing conditions was determined, and this was tested for feasibility for the period of 10 days. During this period, at least 70％ of the maximum enzyme productivity could be maintained. The important design parameters studied are: (1) optimal specific growth rate in the first stage which corresponds to the maximal cell productivity, (2) the optimal dilution rate in the second stage which in turn determines the size of second stage fermentor and the mean residence time of cells in the second stage, (3) cell concentration in both stages, add (4) the specific enzyme productivity and enzyme productivity of the second stage. In addition, by using two-stage continuous culture system we have been able to reduce or eliminate the effect of catabolite repression due to high medium concentration and the adverse effect of the solvent used to dissolve the inducer. We have found the balance between the opposing effects of induction and repression in the second stage judging from the observation that the enzyme productivity goes through a maximum.