• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.381.2-381.2
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• 2014

In this study the amorphous carbon films were deposited by PECVD at the substrate temperature range of 250 to $600^{\circ}C$, and the process conditions of higher and lower precursor flow rate, respectively. The temperature was a main parameter to control the density and mirco-structures of carbon films, and their's properties depended with the process temperatrue are changed by controlling precursor flow rate. The precursor feeding rate affect on the plasma ion density and a deposition reactivity. This change of film properties was obtained the instrinsic stress, FT-IR & Raman analysis, refractive index (RI) and ext. coef. (k) measured by ellipsometer. In the process conditions of lower and higher flow rate of precursor it had a different intrinsic stress as a function of the substrate temperature.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.312-317
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• 2005

Electric Multiple Unit is one of the major mass public transportation systems and passengers are under the influence of indoor air quality such as air temperature, relative humidity and concentration of CO2 gas. Therefore ventilation system of Electric Multiple Unit should be designed for both healthy and comfortable environments. We survey the optimal ventilation rate and the permissible CO2 concentration in the saloon with the consideration of the cooling and heating capacity and fresh air induced from tunnel.

• Journal of Microbiology and Biotechnology
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• v.21 no.5
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• pp.519-524
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• 2011

The correlation between alcoholic fermentation rate, measured as carbon dioxide ($CO_2$) evolution, and the rate of hydrogen sulfide ($H_2S$) formation during wine production was investigated. Both rates and the resulting concentration peaks in fermentor headspace $H_2S$ were directly impacted by yeast assimilable nitrogenous compounds in the grape juice. A series of model fermentations was conducted in temperature-controlled and stirred fermentors using a complex model juice with defined concentrations of ammonium ions and/or amino acids. The fermentation rate was measured indirectly by noting the weight loss of the fermentor; $H_2S$ was quantitatively trapped in realtime using a pre-calibrated $H_2S$ detection tube which was inserted into a fermentor gas relief port. Evolution rates for $CO_2$ and $H_2S$ as well as the relative ratios between them were calculated. These fermentations confirmed that total sulfide formation was strongly yeast strain-dependent, and high concentrations of yeast assimilable nitrogen did not necessarily protect against elevated $H_2S$ formation. High initial concentrations of ammonium ions via addition of diammonium phosphate (DAP) caused a higher evolution of $H_2S$ when compared with a non-supplemented but nondeficient juice. It was observed that the excess availability of a certain yeast assimilable amino acid, arginine, could result in a more sustained $CO_2$ production rate throughout the wine fermentation. The contribution of yeast assimilable amino acids from conventional commercial yeast foods to lowering of the $H_2S$ formation was marginal.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.54-59
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• 2007

In a view of capturing $CO_2$ as a greenhouse gas, an experimental study was conducted on the combustion characteristics of pulverized coal in $O_2$/$CO_2$ environment using TGA/DSC and DTF facilities. The effects of gas composition and concentration on the processes of devolatilization and char burning experienced by coal particles in combustion furnace and on the concentration of products such as $CO_2$, CO and $NO_x$ were observed using TGA/DSC and DTF respectively. As results, it were found that the rate of devolitilation is nearly independent on the $O_2$ concentration if it is over 20% but the char burning rate is a sensitive function of $O_2$ percent, and the two rates can be controlled by $O_2$ concentration in order to be similar with those of air combustion case. It was also found that high concentration $CO_2$ can be captured by oxy-coal combustion and high concentration of CO and low value of $NO_x$ are exhausted in that case. Additionally, NO reducing reaction by CO with char as catalyst was observed and a meaningful results were obtained.

• Journal of Energy Engineering
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• v.6 no.2
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• pp.203-211
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• 1997

This study is on the separation of Global warming effect gas, CO$_2$by chemical absorption from mixture of CO$_2$-N$_2$which was modeled after flue gas of fire power plant. Investigation of optimum condition for absorbent was carried out by using sparged vessel apparatus. Through packed tower experiments, applicabilities of two absorption models were tested by comparing experimental results with theoretical values. Absorbent used in the experiments was Monoethanolamine (MEA) and gas mixture was made in the mole composition of 15% CO$_2$and 85% N$_2$. Through estimations of CO$_2$loading and CO$_2$removal efficiency, optimum concentration of absorbent was found in the range of 4-5 M. To find a rate of absorption, an enhancement factor was introduced. Values of rate of absorption were calculated by Film model and Higbie model, respectively. Higbie model showed good agreement with experimental results. Therefore, this models is considered to be applicable to the CO$_2$separation process for flue gas from fire power plant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.7
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• pp.650-654
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• 2006

[ $LiNi_{0.4}Mn_{0.3}Co_{0.3}O_2$ ] cathode material was synthesized by a mixed hydroxide method. Structural characterization was carried out using X-ray diffraction studies. Electrochemical studies were performed by assembling 2032 coin cells with lithium metal as an anode. DSC (Differential scanning calorimetry) data showed that exothermic reactions of $LiNi_{0.4}Mn_{0.3}Co_{0.3}O_2$ charged to 4.3 V versus Li started at high temperatures$(280\sim390^{\circ}C)$. The cell of $LiNi_{0.4}Mn_{0.3}Co_{0.3}O_2$ mixed cathode delivered a discharge capacity of 150 mAh/g at a 0.2 C rate. The capacity of the cell decreased with the current rate and a useful capacity of 134 mAh/g was obtained at a 2 C rate. The reversible capacity after 100th cycles was 126 mAh/g when a cell was cycled at a current rate of 0.5 C in $2.8\sim4.3V$.

• Nuclear Engineering and Technology
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• v.35 no.6
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• pp.507-514
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• 2003

Recently dry decontamination/surface-cleaning technology using plasma etching has been focused in the nuclear industry. In this study, the applicability of this new dry processing technique are experimentally investigated by examining the etching reaction of $UO_2$, Co, and Mo in r.f. plasma with the etchant gas of $CF_4/O_2$ mixture. $UO_2$ is chosen as a representing material for uranium and TRU (TRans-Uranic) compounds while metallic Co and Mo are selected because they are the principal contaminants in the used metallic nuclear components such as valves and pipes made of stainless steel or inconel. Results show that in all cases maximum etching rate is achieved when the mole fraction of $UO_2\;in\;CF_4/O_2$ mixture gas is $20\%$, regardless of temperature and r.f. power. In case of $UO_2$, the highest etching reaction rate is greater than 1000 monolayers/min. at $370^{\circ}C$ under 150 W r.f. power which is equivalent to $0.4{\mu}m/min$. As for Co, etching reaction begins to take place significantly when the temperature exceeds $350^{\circ}C$. Maximum etching rate achieved at $380^{\circ}C\;is\;0.06{\mu}m/min$. Mo etching reaction takes place vigorously even at relatively low temperature and the reaction rate increases drastically with increasing temperature. Highest etching rate at $380^{\circ}C\;is\;1.9{\mu}m/min$. According to OES (Optical Emission Spectroscopy) and AES (Auger Electron Spectroscopy) analysis, primary reaction seems to be a fluorination reaction, but carbonyl compound formation reaction may assist the dominant reaction, especially in case of Co and Mo. Through this basic study, the feasibility and the applicability of plasma decontamination technique are demonstrated.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.1
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• pp.93-101
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• 2008

The effects of $CO_2$ enrichment on growth of maize (Zea mays L.) were examined. Parameters analyzed include growth characteristics, yields, photosynthetic rates, evaporation rates and photosynthesis-related characteristics under elevated $CO_2$. The plants were grown in growth chambers with a 12-h photoperiod and a day/night temperature of $28/21^{\circ}C$ at the seedling stage and $30/23^{\circ}C$ from the silking stage. The plants were exposed to two elevated $CO_2$ of 500, 700ppm and ambient levels (350 ppm). Chalok 1 and GCB 70 germinated three days after seeding, and germination rates were faster in the elevated $CO_2$ than the control. Germination rates displayed significant differences among the $CO_2$ treatments. At the seedling stage, leaf area, top dry weight, and photosynthetic rates, and plant height indicated positive relationship with elevated $CO_2$ concentrations. At the $5{\sim}6$ leaf stage, $CO_2$ concentration also indicated positive relationship with plant height, leaf area, top dry weight, and photosynthetic rates. At the silking stage, increased plant height of Chalok 1 was noted in the $CO_2$ treatments compared to the control. No significant differences were noted for GCB 70, in which leaf area decreased but photosynthetic rates increased progressively with $CO_2$ concentration. Stomatal aperture was a little bigger in the elevated $CO_2$ than the control. $CO_2$ concentration was negatively related to stomatal conductance and transpiration rates, resulting in high water use efficiency.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.676-680
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• 1998

The relaxation process of photogenerated carriers was investigated using conductivity measurement on ZnO under He, $H_2,\; CO_2\; and\; O_2$. The process was well explained with the rate constant of reaction or recombination of hole and electron, $k_h \;and\; k_e ( k_h > k_e)$, respectively. Generally, $k_h$ increased with the pressure of the gases. The slope of $k_h$ with respect to the pressure increased in the order of $H_2{\le}He, while $k_h$ of $O_2$ was sensitive to the history of the sample. The relaxation process on ZnO which was exposed to oxygen at 298 K and 573 K was observed during the illumination at 298 K and it was found that the rate constant of hole decreased with illumination time. From the result, it was suggested that the rate constant of photogenerated excess carriers was affected by the surface barrier of the semiconductor.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.727-733
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• 2009

Effects of $Ca(OH)_2$ concentration(0.16~0.64 wt%), total volumetric flow rate(3~6 L/min) and $CO_2$ volume fraction(0.3~0.6) on morphology of the precipitated $CaCO_3$ and the mean particle size of the precipitated $CaCO_3$ were investigated in the slurry bubble column reactor. Experiments were carried out in acrylic reactor($0.11m-ID{\times}1.0m-high$) with a internal tube($0.04m-ID{\times}1.0m-high$). The calibration curve on the mass ratio of $CaCO_3$ to $Ca(OH)_2$ was obtained by FT-IR for the conversion of $Ca(OH)_2$ with the reaction time. The reaction rate of $Ca(OH)_2$ increased with increasing the volumetric flow rate of $CO_2$. From SEM images, the crystal size of $CaCO_3$ increased with increasing the reaction rate in the saturated concentration of $Ca(OH)_2$ (0.16 wt%). In addition, the crystal size of precipitated $CaCO_3$ decreased with increasing the concentration of $Ca(OH)_2$, but the mean particle size of precipitated $CaCO_3$ increased with increasing the concentration of $Ca(OH)_2$.