• Applied Biological Chemistry
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• 제40권1호
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• pp.18-22
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• 1997

Bifidobacterium longum을 고농도 배양하기 위하여 최적 생육 조건을 조사하고 cross-flow filtration으로 생육 저해 대사산물인 lactic acid와 acetic acid를 제거하면서 균체 순환 배양을 사용하였다. 회분 배양에서는 탄소원으로 glucose를 50 g/l 농도로 사용하고 초기 pH 6.5인 경우 생육이 가장 높았다. B. longum을 cross-flow filtration으로 12시간 배양한 결과, 희석속도 $0.31h^{-1}$에서 최대 균체농도에 도달하여 16.4g/l의 건조균체량을 얻었으며 이로써 회분 배양시 보다 약 4배 높은 균체를 생산하였다.

• 대한기계학회논문집B
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• 제24권12호
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• pp.1596-1607
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• 2000

The optimal design of auto-catalyst needs a good compromise between the pressure drop and flow uniformity in the substrate. One of the effective methods to achieve this goal is to use the concept of radially variable cell density. But this method has not been examined its usefulness in terms of chemical behavior and conversion performance. In this work, two-dimensional performance prediction of catalyst coupled with turbulent reacting flow simulation has been used to evaluated the benefits of this method n the flow uniformity and conversion efficiency. The results showed that two cell combination of 93cpsc and 62 cpsc was the most effective for improved pressure drop and conversion efficiency due to balanced space velocity and efficient usage of geometric surface area of channels. It was also found that large temperature difference between the bricks in case that the edge of the frontal face of brick has too much lower cell density(less than 67% of cell density of the center of the brick). This study has also demonstrated that the present computational results show the better prediction accuracy in terms of CO, HC and NO conversion efficiencies compared to those of conventional 1-D adiabatic model by comparison with experimental results.

• KSBB Journal
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• 제6권4호
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• pp.395-402
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• 1991

A new process was developed to degrade PVA(polyvinyl alcohol) in desize wastewater. Two symbiotic bacteria of Pseudomonas strain G5Y and PW were immobilized on the media by adsorption. A natural zeolite was chosen as the best media considering cell adhesion capacity, sedimentation rate, and material cost. PVA and COD removal efficiencies of this system for synthetic wastewater were 84% and 85% at the retention time of 6 hr, when the volumetric loading rate was PVA 8g/L·day and COD 8g/L·day, and cell density was 19,775 mg/L. In case of desire wastewater, they were 78% and 72% at the retention time of 6 hr, respectively, when the volumetric loading rate was PVA 8g/L·day and COD 13.2g/L·day, and cell density was 32,899mg/L. In case of desize wastewater, PVA and COD removal efficiencies were lower than synthetic wastewater, but cell density of the desize wastewater was lower than that of the synthetic wastewater, because there were insufficiency of necessary nutrition and variety of desize materials in the desize wastewater. A pilot test was successfully performed showing 88% and 82%, PVA and COD removal efficiencies at the retention time of 24 hr, when volumetric loading rate were 4.7 PVA g/L·day and COD 6.9g/L·day, and cell density was 12,,324 mg/L.

• 한국동물학회지
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• 제33권1호
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• pp.22-27
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• 1990

본 연구는 옴개구리의 위저부 점막을 전자현미경으로 관찰한 결과, 내분비세포의 분비 과립의 크기, 형태, 전자밀도 및 세포의 형태에 따라서 다음과 같이 3종류의 세포를 분류하였다. 제 I 형 : 전자밀도가 높고 원형 또는 난원혀으이 과립을 가지며, 과립내용물과 한계막 사이의 편제하거나 공포상으로 출현하였다. 과립의 크기는 직경이 300-500nm였다. 제 II 형 : 구형 또는 난원형의 과립을 가지며, 전자밀도는 낮거나 높게 나타나며, 한계막과 과립내용물 사이에는 좁은 halo를 나타내었다. 과립의 크리는 직경이 110-230nm였다. 제 III 형 : 신장된 난원형 또는 다형태성의 과립을 가지며, 전자밀도는 낮거나 중등도이며 과림가 내용물 사이에는 명확한 halo를 형성하고 세포질내에는 미세섬유들이 풍부하게 출현하였다. 과립의 크기는 직경이 50-200nm였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권6호
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• pp.564-570
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• 2005

In the present study, the protective effects of Bcl-2 over-expression in a suspension culture (without any adaptation) and spent medium (low nutrient and high toxic metabolite conditions) were investigated. In the suspension culture without prior adaptation, the viability of the control cell line fall to 0% by day 7, whereas the Bcl-2 cell line had a viability of 65%. The difference in the viability and viable cell density between the Bcl-2 and control cell lines was more apparent in the suspension culture than the static culture, and became even more apparent on day 6. Fluorescence microscopic counting revealed that the major mechanism of cell death in the control cell line in both the static and suspension cultures was apoptosis. For the Bcl-2 cell lines, necrosis was the major mode of cell death in the static culture, but apoptosis became equally important in the suspension culture. When the NS0 6A1 cell line was cultured in spent medium taken from a 14 day batch culture, the control cell line almost completely lost its viability by day 5, whereas, the Bcl-2 still had a viability of 73%. The viable cell density and viability of the Bcl-2 cell line cultivated in fresh medium were 2.2 and 2.7 fold higher, respectively, than those of the control cultures. However, the viable cell density and viability of the Bcl-2 cultivated in the spent medium were 8.7 and 7.8 fold higher, respectively, than those of the control cultures. Most of the dead cells in the control cell line were apoptotic; whereas, the major cell death mechanisms in the Bcl-2 cell line were necrotic.

• 한국가금학회지
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• 제27권1호
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• pp.63-71
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• 2000

The testis is an extremely heterogeneous organ, containing numerous compartments types. Morphometric studies were performed of 3 avian species (pigeon, pheasant and chicken) to determine volume density absolute volume, numerical density, total number of serminiferous tubule components, and sperm production, especially those related to the Sertoli cell, and to make comparisons among the species. Volume density of seminiferous tubule components per testis was determined by point counting method. Testis volume and sperm production were measured by routine techniques. Numerical density (the number of cells per unit volume of testis) of seminiferous tubule components per testis was determined by morphometry (Floderus method). The volume density of seminiferous tubules per testis was 91.58, 92.18 and 94.21% in pigeon, pheasant, and chicken, respectively. The volume density of spermatogonium, spermatocyte, spermatid, spermatozoon, and Sertoli cell did not produce significant changes in the three species. The absolute volume of spermatogonium, spermatocyte, spermatid, and Sertoli cell showed significant changes in the three species (p<0.05). The average volume of Sertoli cell ranged from 758.34(pheasant) to 1,212.9 ㎛$^3$(chicken) and was not significantoy different in the three species(p>0.05). The number of Sertoli cells per testis showed significant differences in the three species : 34.52 $\times$10(sup)6, 186.82$\times$10(sup)6, 810.62$\times$10(sup)6 in pigeon, pheasant, and chicken, respectively(p<0.05). The sperm production was significantly different in the three species : 3,018$\times$10(sup)6, 993.9$\times$10(sup)6, and 8.9$\times$10(sup)6 in chicken, pheasant, and pigeon, respectively(p<0.05). These results suggest that number of Sertoli cells may be more important than Sertoli cell size in explaining the difference in sperm production among the three species.

• Current Photovoltaic Research
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• 제9권1호
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• pp.6-10
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• 2021

The mesh mask screen, which is generally used for screen printing metallization of silicon solar cell, requires high squeegee pressure and low printing speed. These requirements are acting as a limiting factor in production yield in photovoltaic industries. In order to improve the productivity, a metal mask, which has high durability and high printing speed, has been researched. In this paper, the characteristics of each solar cell, in which electrodes were formed by using a metal mask and a mesh mask, were analyzed through recombination current density. In particular, the metal-induced recombination current density (Jom) representing the recombination of the emitter-metal interface was calculated using the shading method, and the resulting efficiency and open-circuit voltage were analyzed through the diode equation. As a result of analyzing the proportion of the metal-induced recombination current density to the total emitter recombination current density, it was analyzed that the reduction of the metal-induced recombination current density through the metal mask is an important factor in reducing the total recombination current density of the solar cell.

• 해양환경안전학회지
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• 제28권7호
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• pp.1209-1215
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• 2022

선택적 촉매 환원법(SCR)은 질소산화물(NO_x)을 저감하는 매우 효율적인 방법으로 알려져 있으며 발생된 질소산화물(NO_x)을 질소(N₂)와 수증기(H₂O)로 환원시키는데 촉매 작용을 한다. 질소산화물(NO_x) 저감 성능을 결정하는 요소 중 하나인 촉매는 셀 밀도가 증가하면 촉매효율이 증가하는 것으로 알려져 있다. 본 연구에서는 실습선 세계로호에 설치되어 있는 발전 기관의 배기가스 조건을 모사한 실험장치를 통하여 100CPSI(60Cell)촉매의 부하에 따른 질소산화물(NO_x) 저감 성능을 확인하고 세계로호에 설치되어 있는 25.8CPSI(30Cell) 촉매의 기존 연구 자료와의 비교를 통해, 셀 밀도가 질소산화물(NO_x)의 저감에 미치는 영향에 대하여 고찰하였다. 실험용 촉매는 셀 밀도만 변화를 주었고 형태는 벌집형(honeycomb), 조성물질은 V₂O₅-WO₃-TiO₂를 동일하게 사용하여 제작하였다. 실험결과 100CPSI(60Cell) 촉매의 질소산화물(NO_x) 농도 저감율은 평균적으로 88.5%이며 IMO specific NOx 배출량은 0.99g/kwh로 IMO Tier III NOx 배출기준을 만족하였다. 25.8CPSI(30Cell) 촉매의 경우, 질소산화물(NO_x) 농도 저감율은 78%, IMO specific NOx 배출량은 2.00g/kwh 이었다 두 촉매의 NOx 농도 저감율과 IMO specific NOx 배출량을 비교하였을 때, 100CPSI(60Cell)촉매가 25.8CPSI(30Cell) 촉매보다, NOx 농도 저감율은 10.5% 높고 IMO specific NOx 배출량은 약 2배 적은 것을 확인하였다. 따라서 촉매의 셀 밀도를 높임으로써 효율적인 탈질효과를 기대할 수 있으며 향후 실선 테스트를 통하여 검증한다면 촉매의 부피 저감을 통한 제작 비용을 줄이고 협소한 선박 기관실을 효율적으로 사용하기 위한 실용적인 자료로서 기대된다.

• 전기화학회지
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• 제9권4호
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• pp.151-157
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• 2006

A two-dimensional numerical model to study the performance of anode-supported flat-tube solid oxide fuel cell (SOFC) far the cross section of the cell in the flow direction of the fuel and air flows is developed. In this model a mass and charge balance, Maxwell-Stefan equation as well as the momentum equation by using, Darcy's law are applied in differential form. The finite element method using FEMLAB commercial software is used for meshing, discritization and solving the system of coupled differential equations. The current density distribution and fuel consumption as well as water production are analyzed. Experimental data is used to verify a predicted voltage-current density and power density versus current density to judge on the model accuracy.

• Applied Science and Convergence Technology
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• 제23권1호
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• pp.27-33
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• 2014

We have studied photovoltaic characteristics of single-junction GaAs solar cells with/without an $MgF_2/ZnS$ anti-reflective coating (ARC) illuminated by low-density concentration (<10 suns). By the ARC deposition, the short-circuit current density ($J_{SC}$) and the fill factor (FF) are increased by $5mA/cm^2$ and 5% at a standard illumination (1 sun), respectively, and the resulted conversion efficiency is enhanced by 45%. In contrast with the cell with no ARC showing a rapid degradation with increasing concentration power, the efficiency of ARC-deposited cell remains almost constant as ($17.7{\pm}0.3$)% regardless of the concentration. It informs that ARC treatment is very effective in GaAs concentrator solar cells.