• KSBB Journal
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• v.11 no.6
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• pp.642-648
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• 1996

The effects of EDTA(Ethylene diamine tetraacetic acid), Cu, temperature, and gas(methane and oxygen) composition on methanol production from methane with Methylosinus trichosporium were investigated. In this experiment EDTA was found to be a potential methanol dehydrogenase inhibitor since it causes methanol accumulation and 6mM was found to be optimum concentration of EDTA for methanol production. When Cu was added in culture media, the produced methanol concentration level was increased. Hence it is believed that Cu enhanced the particulate methane monooxygenase formation and consequently the addition of Cu could increase the methanol production from methane. In this experiment the optimum concentration of Cu was found to be 1mM for methanol production. When temperature was shifted down from $30^{\circ}C to 25^{\circ}C$, the methanol production level was enhanced by 50%. When the ratio of methane to oxygen in gas phase was increased to 2.3 from 1, produced methanol concentration was also enhanced by 100%.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.243.1-243.1
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• 2013

본 연구에서는 산소 분압과 열처리 온도에 따른 ITZO 박막 트랜지스터의 전기적 특성 향상을 목적으로 실험을 진행하였다. 1) ITZO 박막 증착 시 산소 분압 가변($O_2/(Ar+O_2)$ 30~40%), 열처리 온도 고정($350^{\circ}C$)과 2) ITZO 박막 증착 시 산소 분압 고정(30%), 열처리 온도($200{\sim}400^{\circ}C$)를 가변하여 실험을 진행하였다. 두 실험 모두 특성향상을 위해 산소 분위기에서 열처리를 진행하였다. 산소의 분압이 증가할수록 산소 빈자리를 채우면서 전자 농도가 감소하여 채널 전도 효과가 줄어들면서 Hump 현상이 발생하였고, 스윙이 증가, 문턱 전압이 음의 방향으로 이동하였다. 이에 $O_2/(Ar+O_2)$)의 30%에서 30%일때, 문턱전압은 1.98 V, 전계 효과 이동도는 28.97 $cm2/V{\cdot}s$, sub-threshold swing은 280 mv/dec, on-off 비율은 ~107로 가장 우수한 전기적 특성을 보였다. 또한 열처리 온도 가변 시 $400^{\circ}C$에서 전계 효과 이동도는 28.97 $cm^2/V{\cdot}s$로 $200^{\circ}C$의 전계 효과 이동도는 11.59 $cm^2/V{\cdot}s$에 비해 약 3배 증가하였고, 소자의 스위칭 척도인 sub-threshold swing은 약 180 mv/dec 감소하였다. 문턱 전압은 0.97V, on-off ratio는 약 107을 보였다. 동일한 산소 분압의 분위기에서 $400^{\circ}C$ 열처리 시 가장 우수한 전기적 특성을 보였고, 저온 공정으로 인한 플렉서블 디스플레이 투명 디스플레이 적용 가능성을 확인하였다.

• Proceedings of the Membrane Society of Korea Conference
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• 1994.10a
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• pp.38-41
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• 1994

막분리(membrane separation)법은 막 전후의 압력차, 농도차 등을 추진력(driving foroe)으로 하여 분리대상물질에 대한 막의 선택투과성 차이를 이용, 분리를 행하는 것이다. 이 분리법은 기존의 분리공정인 심냉법(cryogenic separation)과는 달리 상변환 공정이 필요없어 에너지가 적게 들고 또한 PSA(pressure swing adsorption)법에서와 같은 cycle 운전이 필요없어 연속적으로 분리가 가능하며 시스템도 간단하다. 최근 기체 막분리의 경우 수소 및 탄산가스의 회수정제, 공기중의 산소와 질소의 분리 등에 실용화되고 있다. 여기서는 공기중의 산소를 분리하여 30-40% 산소부화공기(oxygen enriched air)를 간편하게 제조할 수 있는 산소부화막장치와 연소장치에의 응용기술 및 연구결과에 대해 간략히 소개하고자 한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.2
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• pp.165-175
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• 2024

Hydrogen is being touted as one of the energy sources to combat the climate change crisis. However, hydrogen can leak into enclosed spaces, rise to the ceiling, accumulate, and cause fires and explosions if it encounters an ignition source. In particular, ships that transport hydrogen or use it as a fuel comprise multiple enclosed spaces. Therefore, the dif usion characteristics within these spaces must be understood to ensure the safe use of hydrogen. The purpose of this study is to experimentally determine the diffusion characteristics of helium, which has similar properties to hydrogen, in a closed space on board a ship, and to determine the change in the oxygen concentration along the leakage direction as the air change per hour(ACH) increases to 25, 30, 35, 40, and 45 through CFD simulation. The study, results revealed that the oxygen concentration reduction rate was 2% for leakage in the -z direction and 1% for leakage in the +x and +z directions, and the ventilation time was 15 min 30 s for leakage in the -z direction, 7 min for leakage in the +x direction, and 9 min for leakage in the +z direction, showing that differences existed in the oxygen concentration and ventilation time depending on the leakage direction. In addition, no significant difference was observed in the rate of oxygen concentration reduction and ventilation time in all leakage directions from the ACH of 35 and above in the experimental space. Therefore, because the oxygen concentration and ventilation time were not improved by increasing the ACH, 35 was noted as the optimal ACH in this experimental environment.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.233-233
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• 2014

InGaZnO 박막트랜지스터(TFT)는 기존의 널리 사용되던 비정질 실리콘보다 높은 전하이동도와 Ion/off, 우수한 균일성과 신뢰성의 장점으로 최근 AMOLED양산에 적용되기 시작 하였다. 그러나 60인치 이상의 대면적 디스플레이와 초고해상도의 성능을 동시에 만족하기 위해 10 cm2/Vs정도의 전하이동도를 가지는 InGaZnO로는 한계가 있어 30 cm2/Vs 이상의 전하이동도를 가지는 물질의 연구가 필요하다. 연구에서는 높은 전하이동도를 만족하기 위해 InO2를, 우수한 신뢰성을 가지는 SnO2를 포함하는 InZnSnO로 실험을 진행하였다. 스퍼터링 시스템에서 ITO 타겟과 ZTO 타겟을 사용하여 동시증착법으로 채널을 증착하였고, 산소 분압 변화시에 IZTO TFT 소자 특성의 의존성을 평가하였다. Ar : O2=10 : 0 일 때와 Ar : O2=7 : 3 일 때의 이동도가 각각 12.6cm2/Vs, 19.7cm2/Vs로 산소 비율이 증가함에 따라 전하이동도가 증가하였다. 기존 IGZO 산화물 반도체에서는 산소 비율이 증가하면 산소공공(VO) 농도감소로 인해 전하이동도가 감소한다. 이는 전하농도가 증가하면 전하이동도가 증가하는 percolation 전도기구로 이해할 수 있다. 그러나 본 IZTO 물질에서는 산소비율 증가에 따라 오히려 전하이동도가 증가하였는데, 이는 IZTO 반도체에 함유된 Sn 이온의 가전자상태가 +2/+4가의 상대적 비율이 산소농도에 따라 의존하기 때문인 것으로 분석되었다.

• IE interfaces
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• v.18 no.2
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• pp.178-183
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• 2005

In this study, changes in memory performance, blood oxygen saturation and heart rate according to 30% concentration oxygen supply were observed. Ten healthy male and female college students (male:$25.8{\pm}0.8$ years, female: $24.2{\pm}1.9$ years) participated in the study. The experiment was performed as Rest (1min.), Control task (1min.), Word presentation (1min.), Reaction time task (1min.), Distractor (2min.), and Word recall (1min.) and the physiological signals such as blood oxygen saturation and heart rate were measured throughout the stages. Subjects who received 30% oxygen recalled more words than those who received 21% oxygen, which shows 30% oxygen supply has influenced positively on memory cognitive performance. When 30% concentration oxygen is supplied, the blood oxygen saturation in the task phases was increased and the heart rate decreased when comparing to 21%. It means that 30% oxygen can stimulate brain activation by increasing actual blood oxygen concentration in the process of cognitive performance, and the heart rate decreases because enough oxygen is supplied to process the cognitive performance.

• KSBB Journal
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• v.23 no.6
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• pp.525-528
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• 2008

In order to compare the germination and growth rate of the sprouts soaked in highly concentrated oxygen water, it with specific amounts of oxygen dissolved was produced in a high pressure reactor by pressuring oxygen. The sprouts were observed after being soaked in $20^{\circ}C$ oxygen water with 20, 30, 40, 50 ppm of oxygen dissolved each. Results of ten days later indicate that the final germination rate of the sprout soaked in 50 ppm oxygen water was $24.6{\sim}28.6%$ higher than that of the sprout soaked in distilled water. The final growth length also measured 6-7 mm higher than the sprout soaked in distilled water, demonstrating that enough supply of oxygen to the sprout induces stability and efficiency in its growth.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.1
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• pp.91-101
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• 2012

This study's purpose is to research the antioxidant power of Calaguala (Polypodium leucotomos, PL) as an oral supplement: Calaguala, a native of Central America, is a fern which belongs to the family polypodiaceae protecting the skin from the ultraviolet and active oxygen free radicals. The total 14 volunteers, each female 7 & male 7, were divided into 2 groups, then exposed to UV for 30 min after taking Calaguala and placebo. The total antioxidant capacity (TAC) was analyzed by taking the blood samples from anticubital vein 3 hours after UV exposure. First, Calaguala siginifcantly decreased the concentration of active oxygen free radicals 4 weeks later. The concentration of active oxygen free radical in PL group declined more than placebo group, when measured 30 min and 3 hours after UV exposure. Second, Calaguala did not significantly increase TAC 4 weeks later, but significantly decreased TAC 3 hours after exposure, when compared with placebo group. Now days, the photo allergy and photo aging caused by air pollution and ozone destruction have drastically increased, and thus the amount of UV radiation reaching the earth's surface increased. The increase of active free oxygen radicals resulted in accelerating the diseases and aging. The first superficial protecting protection by reflection & dispersion and the second body internal protection by taking oral photo antioxidant such as Calaguala should be continuously researched.

• Microbiology and Biotechnology Letters
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• v.35 no.3
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• pp.226-230
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• 2007

In order to achieve high-level expression of interferon-${\alpha}1$ (IFN-${\alpha}1$) during fed-batch fermentation of recombinant E. coli, effects of oxygen supply and induction temperature on the expression of recombinant proteins were evaluated. Supplementation of oxygen and its transfer into cells is one of the most important parameters involved in the design and operation of mixing-sparging equipment for bioreactors. Generally, higher oxygen supply stimulates cell growth of aerobic microorganism and consequently the amount of products is increased. In this study, the optimum aeration strategy for the higher production of IFN-${\alpha}1$ during fed-batch fermentation of recombinant E. coli was surveyed. The growth of the cells was also monitored with four different concentrations of dissolved oxygen (DO; limiting, 20%, 35%, 50%) conditions. The DO was controlled by varying aeration rates of air and pure oxygen. Oxygen uptake rate (OUR) and specific oxygen uptake rate (SOUR) were evaluated and compared for the enhanced growth and induction of the cells and IFN-${\alpha}1$, respectively. We confirmed that increased DO by additional oxygen supply, up to 35%, can improve the production of IFN-${\alpha}1$ during the fermentation.

• Analytical Science and Technology
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• v.12 no.6
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• pp.472-477
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• 1999

It was developed the oxygen sensor of air-fuel ratio measuring system that was controlled the needed air amounts in optimum combustion according to the analysis of oxygen concentration of exhaust gas. The oxygen sensor was prepared by using gold as cathode, which the detection range for the oxygen concentration was from 0.0% to 30.0%. Response time was observed 15 to 20 sec. rapidly and selectively. It was appeared a good result in reproducibility and stability.