• 감성과학
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• 제11권1호
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• pp.105-112
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• 2008

본 연구에서는 40% 농도의 산소 공급이 난이도에 따른 덧셈과제 수행 능력, 혈중 산소 포화도, 심박동율의 변화에 어떠한 영향을 미치는지 관찰하였다. 10명의 남자와 10명의 여자 대학생이 두 가지 농도의 산소 (21%, 40%)를 흡입하면서 세 가지 난이도의 덧셈연산을 수행하였다. Rest1 (3분), Task1 (1분, 한 자리 수 덧셈), Task2 (1분, 두 자리 수 덧셈), Task3 (1분, 세 자리 수 덧셈), Rest2 (4분)의 순서로 실험이 진행되었고, 모든 구간에서 혈중 산소 포화도와 심박동율이 측정되었다. 21%에 비해 40% 농도의 산소를 공급했을 때 평균 정답률이 증가하였고, 난이도가 증가할수록 정답율의 차이가 더컸다. 21%에 비해 40%의 산소가 주어질 때 모든 구간에서 혈중 산소 포화도는 증가하였고, 심박동율은 감소하였다. 결론적으로 고농도 산소 공급이 혈중 산소 포화도를 증가시켜 인지 처리에 따른 뇌 활성화를 촉진시킬 수 있고 이로 인해 연산 수행 능력이 증가되었다는 사실을 도출 할 수 있다. 특히 난이도가 증가할수록, 즉 인지 처리의 요구가 커질수록 고농도 산소의 효과가 더 명확히 나타난다는 사실을 도출할 수 있다.

• 대한기계학회논문집B
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• 제28권1호
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• pp.9-15
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• 2004

$CO_2$ is a well-known green house gas as well as the major source of global warming. Many researchers have studied to reduce $CO_2$ emission in combustion processes. Among the method for reducing $CO_2$ emission, oxygen-enriched combustion has been proposed. Because its adiabatic flame temperature is relatively too high, existing facilities must be changed or the flame temperature in the combustion zone should be reduced. The combustion characteristics, composition in the flame zone, temperature profile and emission gases were investigated experimentally for the various oxygen-enriched ratios(OER) by the addition of $CO_2$, under constant $O_2$ flow rate. Results showed that the reaction zone was quenched and broadened as the addition of $CO_2$ was increased. The emission of NOx in flue gas was decreased as decreasing temperature in reaction zone. It was also shown that the reaction was delayed by the cooling effect. As the addition of $CO_2$ was increased, the composition of CO in the flame zone was increased due to the increase of reaction rate by increasing mixing effect of oxidant/fuel at OER=0％, but the composition of CO was decreased by quenching effect at OER=50％ and 100％.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1389-1394
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• 2003

$CO_2$ is a well-known green house gas, which is the major source of global warming. Many researchers have studied to reduce $CO_2$ emission in combustion processes. Among the method for reducing $CO_2$ emission, oxygen-enriched combustion has been proposed. But the adiabatic flame temperature is too high. So existing facilities must be changed, or the adiabatic flame temperature in the combustion zone should be reduced. The combustion characteristics, composition in the flame zone, temperature profile and emission gases were studied experimentally for the various oxygen-enriched mtios(OER) by addition of $CO_2$ under coustant $O_2$ flowrate. Results showed that the reaction zone was quenched, broadened, as addition of $CO_2$ was increased. Temperature has a large effect on the NOx emission. The emission of NOx in flue gas decreased due to the decreased temperature of reaction zone. It was also shown that the reaction was delayed by the cooling effect. As the addition of $CO_2$ was increased, the composition of CO in the flame zone increased due to the increase of reaction rate by increasing mixing effect of oxidant/fuel at OER=0, but the composition of CO decreased by quenching effect at OER=50 and 100%.

• Environmental Analysis Health and Toxicology
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• 제11권1_2호
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• pp.49-57
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• 1996

The production of reactive oxygen species on addition of hexavalent chromium (potassium dichromate, $K_2Cr_2O_7$ ) to lung cells in culture was studied using flow cytometer analysis. A Coulter Epics Profile flow cytometer was used to detect the formation of reactive oxygen species after $K_2Cr_2O_7$ was added to A549 cells grown to confluence. The cells were loaded with the dye, 2',7'-dichlorofluorescein diacetate, after which cellular esterases removed the acetate groups and the dye was trapped intracellularly. Reactive oxygen species oxidized the dye, with resultant fluorescence. Increased doses of Cr(VI) caused increasing fluorescence (10-fold higher than background at 200 gM). Addition of Cr(III) compounds, as the picolinate or chloride, caused no increased fluorescence. Electron paramagnetic resonance (EPR) spectroscopic studies indicated that three (as yet unidentified) spectral "signals" of the free radical type were formed on addition of 20, 50, 100 and 200 gM Cr(VI) to the A549 cells in suspension. Two other EPR 'signals" with the characteristics of Cr(V) entities were seen at field values lower than the standard free radical value. radical value.

• 한국세라믹학회지
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• 제34권12호
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• pp.1221-1226
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• 1997

The effects of sintering atmosphere and dopant addition on the behavior of densification and grain growth of SnO2 ceramics were investigated with consideration of defect chemistry. CoO and Nb2O5 were chosen as dopants, and oxygen and nitrogen were used for controlling of sintering atmospheres. With the decrease of oxygen partial pressure, densification was depressed due to evaporation of SnO2 ceramics. In the case of SnO2 sintering, the addition of CoO, which produced oxygen vacancy in SnO2 ceramics, led to acceleration of densification and grain growth. On the contrary, when Nb2O5 as a dopant producing Sn vacancy was added to SnO2 ceramics, densification and grain growth were simultaneously retarded. As results, it was conformed that diffusion of oxygen ions was rate determinant in densification and grain growth of SnO2 ceramics.

• 한국세라믹학회지
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• 제27권3호
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• pp.401-411
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• 1990

Deposition of diamond films on Si(100) from the mixtures of methane and hydrogen were investigated using hot W filament CVD method. The nucleation density could be increased thousandfold by surface treatment with SiC powder. Upon oxygen addition to the mixture, crystal facets became developed more clearly by selectively removing non-diamond carbons, but the film growth rate generally decreased. However, at a very high methane content(e.g. 10%), a small amount of oxygen addition has resulted in an increase in the film deposition rate presumably by promotion of methane decomposition. When the gas pressure was varied, the growth rate exhibited a maxiumum at around 20torr and the film crystallinity steadily improved with the pressure increase. The observed variation of the growth rate by oxygen addition was discussed in terms of its role in the pyrolysis and the subsequent gas phase reactions.

• 한국수소및신에너지학회논문집
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• 제27권1호
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• pp.95-105
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• 2016

Spray-dried NiO-based oxygen carriers developed for chemical looping combustion required high calcination temperatures above $1300^{\circ}C$ to obtain high mechanical strength applicable to circulating fluidized-bed process. In this study, the effect of CBB ($CaO{\cdot}BaO{\cdot}B_2O_3$) addition, as a binder, on the physical properties and oxygen transfer reactivity of spray-dried NiO-based oxygen carriers was investigated. CBB addition resulted in several positive effects such as reduction of calcination temperature and increase in oxygen transfer capacity and porosity. However, oxygen transfer rate was considerably decreased. This was more apparent when a higher amount of CBB was added and MgO was added together. From the experimental results, it is concluded that CBB added NiO-based oxygen carriers are not suitable for chemical looping combustion and a new method to reduce calcination temperature while maintaining high oxygen transfer rate of NiO-based oxygen carriers should be found out.

• Journal of Plant Biology
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• 제36권3호
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• pp.259-266
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• 1993

In Tris-iso-butanol (TIB; Tris buffer pH 8.8 and 1% iso-butanol)-treated chloroplasts, oxygen evolving activity was more inhibited than Tris-treated chloroplasts, but restored highly by 2,6-dichlorophenol-indophenol (DCPIP) and photoreactivation. To understand the mechanism of this results of TIB in photosynthetic electron transport, system, oxygen consumption and evolution of PS I and PS II were measured and protein of the chloroplasts was analysed. In Tris- and TIB-treated chloroplasts, oxygen evolving activity was increased according to the light intensity. Under 48 W·m-2 light intensity, the oxygen evolving activity in both chloroplasts were similar but as the light intensity was increased, TIB-treated chloroplasts showed higher activity. Under 240 W·m-2 light intensity, TIB-treated chloroplasts showed about 25% higher oxygen evolving activity than Tris-treated chloroplasts. Oxygen evolving activity was increased after photoreactivation in both Tris-treated and TIB-treated chloroplasts. Addition of NH4Cl increased the activity in both chloroplasts but in TIB-treated chloroplasts the increase was 30% higher than that in Tris-treated chloroplasts. In PS I, oxygen evolving activity was not inhibited by both treatments whereas in PS II, significant difference was observed between two treatments. Addition of Mn2+ and Ca2+ enhanced oxygen evolution in both Tris- and TIB-treated chloroplasts. Though enhancement was higher in TIB-treated chloroplasts. No difference was observed n protein analysis of the two thylakoid membrane.

• 한국연소학회지
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• 제3권1호
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• pp.11-19
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• 1998

The influence of oxidant addition on soot formation is investigated experimentally with ethylene, propane and mixture fuel co-flow diffusion flames. Oxidant addition into fuel shows the increase of integrated soot volume fractions for ethylene, ethylene/ethane and ethylene/methane mixture flames. However, the increase of integrated soot volume fraction with oxidant addition was not significant for propane and ethylene/propane mixture flames. This discrepancy is explained with $C_2\;and\;C_3$ chemistry at the early stage of soot formation process. The oxidant addition increases the concentration of $C_3H_3$ in the soot formation region, and therefore, enhances soot formation process. A new soot formation rate model that includes both dilution effect and chemical effect of oxygen is suggested to interpret the increase of integrated soot volume fractions with oxidant addition into ethylene. Also, the role of adiabatic flame temperature for the chemical effect of oxygen addition into fuel was reviewed. The influence of oxidant or diluent addition into fuel on soot formation process are the fuel dilution effect, the adiabatic flame temperature altering effect and/or the chemical effect of oxygen. Their relative importance could change with fuel structure and adiabatic flame temperature.

• 한국진공학회지
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• 제8권2호
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• pp.165-171
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• 1999

Diamond-like carbon(DLC) films were synthesized using the rf-plasma CVD technique with the addition of small amounts of nitrogen and oxygen to a gas mixture of $CH_4$ and $H_2$. The gas flow ratio of $CH_4$ to $H_2$ was 2.4:1, and 3% , 13.6% of nitrogen were added to the gas mixture of $CH_4$ and $H_2$ for the deposition of DLC films. The film stress tended to decrease as the nitrogen concentration increased from 3% to 13.6%, probably due to the decrease of the number of the interlink between carbon atoms. The residual stress tended to slightly decrease when 3% of oxygen was added. Scratch tests were performed to investigate the adhesion between the DLC films and the Ti intelayer after pretreating the TiN surface with direct hydrogen plasma. The adhesion was enhanced by adding nitrogen and oxygen to the $CH_4$ and $H_2$ gas mixture. The adhesion for the 3% nitrogen addition was better than that for the 13.6% nitrogen addition. The Vicker's hardness of the DLC films was measured to be 1100Hv.