• 한국양식학회지
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• 제18권1호
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• pp.45-51
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• 2005

황복 치어를 대상으로 염분과 수온이 변화되었을 때 나타나는 생리적 변화를 대사지표인 산소 소비율과 암모니아 질소 배설률을 측정하여 그 영향정도를 알아보고자 하였다. 염분 2, 12, 22 및 32 psu에서 2 개월간 순치 사육한 황복(체장 9.5$\pm$0.9 cm, 체중 18.7$\pm$5.4g)의 산소소비율과 암모니아 질소 배설률은 사육염분에 대하여 포물선식으로 나타낼 수 있어서 각각 $Y=-0.0873X^2+0.6384X-0.690$ 와 $Y=-2.1667X^2+7.1672X+31.999$로 표시할 수 있었다. 산소소비율과 질소배설률은 사료섭취과 관련하여 일주기성을 나타내어 산소소비는 사료섭취 3시간 후에, 암모니아 질소 배설은 사료섭취 4시간 후에 각각 높은 값을 나타내었다. 염분 2, 12, 22 및 32 psu에서 사육하던 황복을 갑자기 염분을 달리하였을 때 산소소비율과 암모니아 질소 배설률은 저염분(2. 12 psu)으로 옮긴 경우가 정상염분(32 psu)으로 옮긴 경우 보다 각 염분별 사육군간에 유의적인 차이를 보였다. 염분변화에 대한 생리적 보상으로 에너지 소비 경향을 산소소비량 대 암모니아 질소 배설량간의 원자비(O:N비)로 대사 기질을 판단할 때 많은 에너지를 소비하지 않는 것으로 나타났다. 사료효율 및 성장으로 본 황복에 적정 염분은 22 psu로 나타났다.

• 한국수산과학회지
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• 제36권3호
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• pp.254-262
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• 2003

Effect of the air distributor pore size for the removal of aquacultural waste, such as protein, total suspended solids (TSS), chemical oxygen demand (COD), turbidity and total ammonia nitrogen (TAN) from sea water was investigated by using foam separator. With the increase of pore size of air distributor, removal rates and efficiency of protein decreased. Removal rate by commercial air stone was in the range between the removal rates by G2 and G4 sintered glass discs. Within the range of pore size distributor from Gl to G4, the removal efficiency of protein were ranged from 21 to $42\%.$ The changes of removal rates and efficiencies of TSS, COD and turbidity were similar to proteins. TAN was removed by stripping. The pore size of air distributor for a higher overall oxygen mass transfer coefficient and saturation efficiency provided the condition for higher protein removal rate. Also the foam separator could be used as an aerator.

• 항공우주기술
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• 제10권1호
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• pp.54-62
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• 2011

추진제탱크 가압가스 요구량 예측을 위해 개발된 수치해석 모델을 사용하여 운용조건에 따른 가압가스 요구량 변화를 살펴보았다. 한국형발사체 1단 산화제탱크의 개념설계 결과를 기준 모델로 정하였고, 산화제탱크로 유입되는 가압가스의 온도, 산화제의 체적유량, 산화제탱크 길이 대 직경의 비를 운용 변수로 선정하였다. 가압가스 요구량 및 질량유량, collapse factor, 얼리지 온도분포를 예측하였고, 그 결과 가압가스의 온도가 가압가스 요구량에 가장 큰 영향을 미침을 확인하였다. 또한 얼리지에 대한 에너지 분석을 통하여 추진제탱크의 가압효율을 계산하였고, 유입된 가압가스 에너지 중 추진제탱크 벽면을 통한 열손실이 가장 큼을 확인하였다.

• 공업화학
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• 제33권1호
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• pp.96-102
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• 2022

고분자전해질막 연료전지의 반응물인 수소와 산소는 기체 상태이므로, 반응물이 원활히 전달될수록 작동 전압의 손실을 줄일 수 있다. 높은 전류밀도 영역에서 산소 물질 전달이 전압 손실을 좌우하므로, 환원극 유로의 형상 변경에 대한 연구들이 진행되어 왔다. 환원극 유로 형상 중에서 유로를 막는 블록은 반응물을 다공성 매질인 기체확산층으로 강제 대류 하도록 사용되었다. 본 연구에서는 간단한 단 채널의 연료전지 모델에 블록을 배치하였다. 전산 유체역학을 사용하였고, 공기 공급 유량을 달리하였을 때 블록으로 인한 강제 대류 효과가 전압-전류 곡선과 국부 전류 밀도에 대한 영향을 연구하였다. 기체확산층으로의 강제 대류 현상을 통하여 적은 공기 공급 유량으로도 높은 전류 밀도를 얻을 수 있었다. 다수의 블록을 직렬로 배치한 경우에 1개의 블록만 배치한 것보다 강제 대류 효과를 증가시켜 높은 전류밀도를 얻을 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제25권11호
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• pp.1819-1826
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• 2015

Poly(ε-ʟ-lysine) (ε-PL) is a novel bioactive polymer secreted by filamentous bacteria. Owing to lack of a genetic system for most ε-PL-producing strains, very little research on enhancing ε-PL biosynthesis by genetic manipulation has been reported. In this study, an effective genetic system was established via intergeneric conjugal transfer for Streptomyces albulus PD-1, a famous ε-PL-producing strain. Using the established genetic system, the Vitreoscilla hemoglobin (VHb) gene was integrated into the chromosome of S. albulus PD-1 to alleviate oxygen limitation and to enhance the biosynthesis of ε-PL in submerged fermentation. Ultimately, the production of ε-PL increased from 22.7 g/l to 34.2 g/l after fed-batch culture in a 5 L bioreactor. Determination of the oxygen uptake rate, transcriptional level of ε-PL synthetase gene, and ATP level unveiled that the expression of VHb in S. albulus PD-1 enhanced ε-PL biosynthesis by improving respiration and ATP supply. To the best of our knowledge, this is the first report on enhancing ε-PL production by chromosomal integration of the VHb gene in an ε-PL-producing strain, and it will open a new avenue for ε-PL production.

• Journal of Photoscience
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• 제3권1호
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• pp.23-28
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• 1996

To investigate the structure and function of photosystem I, cartridge mutagenesis technique was used to inactivate the psaB gene of photosystem I. From the screen, many strains which have potential defects in photosystem I were generated. Biochemical analysis revealed that B2, one of the mutant, had a reduced amount of chlorophyll. Electron transfer activitx from photosystem II to photosystem I as oxygen uptake was the rate of 64 % of wild type. Also B2 showed a decreased photosystem I activity when measured by 77 K fluorescence emission spectrum. Particularly, immunodetection analysis showed that the B2 had reduced amount of PsaA/PsaB, but a normal range of PsaC and PsaD. Here we present a photoheterotrophic mutant for psaB gene as a unique model strain for future study of structural/functional relationship and biogenesis of photosystem I.

• 한국레이저가공학회지
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• 제16권2호
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• pp.16-18
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• 2013

In this paper, we fabricated breathable films on the use of microwave oven by using UV nanosecond laser micromachining, and the number of micro-grooves on the film is controlled for different oxygen transfer rate(OTR). As different number of micro-groove, the breath films of 100,000cc, 120,000cc, and 150,000cc can be fabricated. The breath film package of 120,000cc is used for the experiment of steaming a sweet potato. At the result, the sweet potato is well-cooked with enough moisture in the package not bursted.

• KSBB Journal
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• 제5권3호
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• pp.207-214
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• 1990

Growth properties of carrot hairy roots transformed by Agrobacterium rhizogenes were compared in flask and bioreactor. Oxygen transfer coefficient KLa was measured during the cultivation in bioreactor. In flask cultures, initially sucrose 30g/l was nearly exhausted after 20days. pH was dropped from initially 5.8 to 4.79 after 4 days, but it is stable after that time. Finally, after 28 days, hairy roots were grown about twelve times. In view of the results studied optimum conditions, hairy roots were maintained high growth rates in sucrose 50g/l, pH 5.8, total nitrogen 60mM. Also in bioreactor cultures, fixed stainless sieve in bottom and aerated 0.31 vvm, the results of cultivation by the use of sucrose 50g/l had grown about twenty-eight times and pH variations were liked in flask. As a results, growth rate of 1.756g fresh weight/day/g inoculum in bioreactor were higher about three times than 0.57g fresh weight/day/g inoculum in flask culture. KLa values were showed a tendency to decrease from 0.209 min-1 to 0.068 min-1.

• Rapid Communication in Photoscience
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• 제4권3호
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• pp.73-75
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• 2015

Cr(VI) reduction was successfully achieved in the presence of cationic micelles (CMs) under visible light illumination. Micelle formation of cationic surfactants seems to be critical in Cr(VI) reduction. Cr(VI) was reduced very fast above the critical micelle concentration (cmc) of CTAB solutions, but was not reduced at all either below or around the cmc of CTAB. The reduction rate of Cr(VI) was enhanced in the absence of dissolved oxygen, supporting that the removal of Cr(VI) should be achieved via a reductive pathway. When CTAB was substituted by Brij 35 or SDS, the reduction of Cr(VI) was negligible. This indicates that the electrostatic interaction between Cr(VI) and headgroups of surfactants is important in the visible light-induced Cr(VI) reduction in micellar solutions.

• 한국주조공학회지
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• 제11권6호
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• pp.482-490
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• 1991

This study presents the wear characteristics of Ti alloys (Pure Ti, Ti-6Al-4V, Ti-5Al-2.5Sn) fabricated by centrifugal precision casting in an Ohara dental titanium casting machine. It was found that the hardness of the surface region is higher than that of the interior region. It is considered that the oxygen adsorption in the surface region during casting, leads to the interstitial solid solution hardening. Wear resistance incerases in the order of pure Ti, Ti-6Al-4V, Ti-5Al-2.5Sn alloys. The interior hardness value increases in the same order. The specific wear rate increases with applied load and increases monotonously with sliding speed. The Fe transfer from the counterpart material was observed on the worn surface of the Ti-5Al-2.5Sn alloy. Oxidative wear occurs at low sliding speeds and mechanical fracture wear occurs at high sliding speeds.