• Biotechnology and Bioprocess Engineering:BBE
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• 제6권1호
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• pp.1-5
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• 2001

The potential use of spin filter device to retain Propionibacterium acidipropionici in the bioreactor under continuous mode of fermentation, and improve acid productivity, was examined. The yield of propionic acid based on lactose concentration was 51% in batch and 54% in continuous (dilution rate = 0.05 h(sup)-1) operation. The yield in continuous fermentation with cell retention using spin filter of 10 micron size (dilution rate = 0.05 h(sup)-1) was even higher at 70% (w/w). The volumetric productivity under batch and continuous mode of operation were 0.312g L(sup)-1 h(sup)-1 and 0.718g L(sup)-1 h(sup)-1 respectively. Continuous fermentation with cell retention demonstrated even higher volumetric productivities at 0.98g L(sup)-1 h(sup)-1 with out clogging problems. It could be used for utilization of cheese whey to produce propionic acid at higher yield and productivities.

• Journal of Forest and Environmental Science
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• 제23권1호
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• pp.11-19
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• 2007

이 연구에서는 소경목 및 불량목 등 목재폐잔재가 발생하는 산지에서 이들을 활용하여 목탄 목초액을 생산할 수 있는 이동식 조립식 탄화로를 개발하고 실용화하는 데 필요한 경제성을 분석하였다. 경제성분석을 위해서 B/C율을 사용하였고 가격과 이자율의 변화에 따른 감응도 분석을 하였다. 우리나라 실정에 맞는 이동식 조립식 탄화로의 형태는 운전, 탄화시간, 제품의 질, 수집능력 등을 고려했을 때 원통형인 것으로 나타났다. 적정 규모는 3단 규모에 총중량 400 kg, 크기는 2(직경) ${\times}$ 2.4 m(높이), 1 Batch 당 탄재량은 1,500 kg, 목탄생산량은 300 kg, 목초액은 $45{\ell}$, 탄화소요시간은 48-52시간, 장치의 수명은 5년이다. 탄화로의 수익성분석결과 1대를 설치하고 Batch를 100회(300일), 80회 (24일), 70회(210일)로 할 경우 어느 경우라도 B/C율이 1보다 큰 것으로 나타났다. 수익이 발생하는 시점은 100회 및 80회는 모두 4년, 70회는 5년부터인 것으로 나타났다. 그러나 발생하는 수익액이 작아 최소 2대를 운용해야 하는 것으로 나타났다. 산지에서 생산되는 제품가격은 최소 목탄은 kg당 750원, 목초액은 ${\ell}$당 700원이 되어야 매년 수익이 발생하여 경제성이 있는 것으로 나타났다.

• 한국세라믹학회지
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• 제24권1호
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• pp.1-8
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• 1987

The validity of Alyavdin-Chujyo's Equation was re-examined over the broader milling conditions that those previously examined. Ordinary ball mill grinding with a laboratory scale batch mill (133mmø×144mm length) were selected as the grinding methods. The results show that in ball milling the Alyavdin-Chunjyo's Equation can be applicable over wide grinding time and size range with few exceptions. The validity of which are examined and discussed. The theoretical consideration of the relation between Alyavdin-Chujyo's Equation and size distributiion equation, such as Rosin-Rammler's law, was tried, and it is found that, under the condition of alyardin-Chujyo's relation, the Rosin-Rammler size distribution law can hold.

• Management Science and Financial Engineering
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• 제13권2호
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• pp.47-77
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• 2007

This paper considers a scheduling problem where a customer orders multiple products(jobs) from a production facility. The objective is to minimize the sum of the order(batch) completion times. While a machine can process only one job at a time, multiple machines can simultaneously process jobs in a batch. Although each job has a unique processing time, we consider the case where batch processing times are identical. This simplification allows us to develop heuristics with improved performance bounds. This problem was motivated by a real world problem encountered by foreign electronics manufacturers. We first establish the complexity of the problem. For the two parallel machine case, we introduce two simple but intuitive heuristics, and find their worst case relative error bounds. One bound is tight and the other bound goes to 1 as the number of orders goes to infinity. However, neither heuristic is superior for all instances. We extend one of the heuristics to an arbitrary number of parallel machines. For a fixed number of parallel machines, we find a worst case bound which goes to 1 as the number of orders goes to infinity. Then, a tighter bound is found for the three parallel machine case. Finally, the heuristics are empirically evaluated.

• 대한산업공학회지
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• 제34권4호
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• pp.481-488
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• 2008

This paper deals with a scheduling problem for two-machine flow shop, in which the preceding machine is a batch processing machine that can process a number of jobs simultaneously. To minimize makespan of the system, we present a mixed integer linear programming formulation for the problem, and using this formulation, it is shown that an optimal solution for small problem can be obtained by a commercial optimization software. However, since the problem is NP-hard and the size of a real problem is very large, we propose a number of heuristic algorithms including genetic algorithm to solve practical big-sized problems in a reasonable computational time. To verify performances of the algorithms, we compare them with lower bound for the problem. From the results of these computational experiments, some of the heuristic algorithms show very good performances for the problem.

• 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.

• 한국분말재료학회지
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• 제10권6호
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• pp.395-405
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• 2003

In the conventional metallothermic reduction (MR) process for obtaining tantalum powder in batch-type operation. it is difficult to control morphology and location of deposits. On the other hand, a electronically mediated reaction (EMR) process is capable to overcome these difficulties and has a merit of continuous process, but it has the defect that the reduction yield is poor. MR-EMR combination process is a method that is able to overcome demerits of MR and EMR process. In this study, a MR-EMR combination process has been applied to the production of tantalum powder by sodium reduction of $K_2$TaF$_{7}$. The total charge passed through external circuit and average particle size (FSSS) were increased with increasing reduction temperature. The proportion of fine particle (-325 mesh) was decreased with increasing reduction temperature. The yield was improved from 65% to 74% with increasing reduction temperature. Considering the charge, impurities, morphology, particle size and yield, an reduction temperature of 1,123 K was found to be optimum temperature for MR-EMR combination process.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1859-1864
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• 2004

An effective methodology is reported for the optimal design of multisite batch production/transportation and storage networks under uncertain demand forecasting. We assume that any given storage unit can store one material type which can be purchased from suppliers, internally produced, internally consumed, transported to or from other plant sites and/or sold to customers. We further assume that a storage unit is connected to all processing and transportation stages that consume/produce or move 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. A batch transportation process can transfer one material or multiple materials at once between plant sites. The objective for optimization is to minimize the probability averaged total cost composed of raw material procurement, processing setup, transportation 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. The expressions for the Kuhn-Tucker conditions of the optimization problem can be reduced to two sub-problems. The first yields analytical solutions for determining lot 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 given demand forecast scenario. The result of this study will contribute to the optimal design and operation of large-scale supply chain system.

• 한국미생물·생명공학회지
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• 제31권1호
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• pp.46-50
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• 2003

젓갈에서 분리된 Lactococcus lactis SA72균주로부터 유용 박테리오신인 lacticin SA72의 생산을 최적화하기 위해 배양용 배지 및 배양조건을 검토하였다. 유산균의 대표적인 배양 배지인 BHI, MRS, Ml7배지에 대해서 검토한 결과, 이중 MRS배지가 최적 배지로 결정되었다. 이 MRS배지에 0.5% glucose를 첨가한 경우, 더 높은 활성을 얻을 수 있었다. pH의 영향을 검토하였을 때는, 초기 pH에서는 pH 7이었고, 발효조에서의 배양기간 동안 pH 6으로 조절할 때가 높은 활성을 보였다. 배양온도는 $32^{\circ}C$로 유지할 때가 활성이 우수하였다. 회분식 배양에서는 최대 3,200AU/m1을 얻을 수 있었으며, 유가식 배양으로 10g/1 glucose를 주기적으로 공급하였을 때 , 약 6,400 AU/ml로 가장 높은 활성을 얻을 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제26권2호
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• pp.356-363
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• 2016

Human papillomavirus (HPV), a non-enveloped, double-stranded DNA tumor virus, is a primary etiological agent of cervical cancer development. As a potential tool for prophylactic vaccination, the development of virus-like particles (VLPs) containing the HPV16 L1 capsid protein is highly desired. In this study, we developed a high-level expression system of the HPV16 L1 in Escherichia coli for the purpose of VLP development. The native gene of HPV16 L1 has many rare codons that cause the early termination of translation and result in the production of truncated forms. First, we optimized the codon of the HPV16 L1 gene to the preferable codons of E. coli, and we succeeded in producing the full-size HPV16 L1 protein without early termination. Next, to find the best host for the production of HPV16 L1, we examined a total of eight E. coli strains, and E. coli BL21(DE3) with the highest yield among the strains was selected. With the selected host-vector system, we did a fed-batch cultivation in a lab-scale bioreactor. Two different feeding solutions (complex and defined feeding solutions) were examined and, when the complex feeding solution was used, a 6-fold higher production yield (4.6 g/l) was obtained compared with that with the defined feeding solution.