• 대한지하수환경학회지
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• 제7권2호
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• pp.73-88
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• 2000

강원도 북동부지역에서 산출되는 탄산약수에 대한 지구화학적 연구를 수행하였다. 탄산약수는 화학적으로 Na-$HCO_3$형, Na-Ca-$HCO_3$형, Ca-$HCO_3$형으로 구분된다. 탄산수의 지화학적 특성은 심부기원으로부터 이산화탄소의 공급을 받은 지하수가 주변암석과의 반응을 통하여 탄산수를 형성하였고, 탄산수들의 상이한 유형은 탄산수를 형성하는 심부환경이 다른 조건에 기인하는 것으로 사료된다. 특히, 물-암석반응에서 온도환경에 따른 사장석의 용해도 차이는 탄산수의 지화학적 특성을 결정짓는데 중요한 역할을 하였을 것으로 판단된다. 온도조건이 높을수록 알바이트와 아노사이트간의 용해도차이는 감소하므로, 높은 Na/Ca비를 갖고 있는 화강암내 사장석의 화학조성을 고려할 때, 높은 온도환경에서의 물 -암석반응은 상대적으로 낮은 온도환경에 비해 높은 Na/Ca비를 갖는 탄산수를 형성한다. 지질온도계의 적용결과는 Na-$HCO_3$형의 경우 약15$0^{\circ}C$의 심부저장지의 온도를 보이는 반면, Ca-$HCO_3$형은 상대적으로 낮은 온도를 보여주고 있다. 일반적인 지열구배를 고려한다면, Na-$HCO_3$형의 탄산수는 Ca-$HCO_3$형에 비해 깊은 심도에서 형성되었을 것으로 해석할 수 있다.

• 한국재료학회지
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• 제3권5호
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• pp.459-465
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• 1993

SOG박막 밑에 층간 절연박으로 사용하는 PECVD산화막을 Si rich산화막으로 만들어 줌으로써 실리콘 dangling bond가 수소원자나 수분과 결합하여 SOG박막으로 부터 침투되는 수소원자나 수분의 확산을 억제하므로서 소작 열화되는 것을 방지한다. 이러한 Si rich산화막의 기본 특성을 알아보기 위하여 LF/HF power비와 $SiH_4/N_2O$ gas유량비를 변화시켜서 박막 특성을 조사하였다. 저주파 power만 변화시킨 경우, 증착속도가 감소하고 굴절율과 압축응력에 증가하며 FTIR에서 3300$\textrm{cm}^{-1}$~3800$\textrm{cm}^{-1}$영역의 수분에 의한 peak이 감소하는 것으로 보아 박막이 치밀해짐을 알 수 있고, $SiH_{4}$기체유량을 증가시킨 경우엔 증착속도, 굴절율, 식각속도는 증가하나 압축응력은 감소한다. FTIR에서 Si-O-Si peak의 세기가 감소하고 낮은 파수영역으로 이동하며, AES분석 결과에서 일반적인 oxide(Si:0=1:1.98)에서 보다 Si:O비가 1:1.23으로 낮아 PECVD산화 막내의 Si danling bond가 증가했음을 알 수 있었다.

• 대한화학회지
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• 제24권1호
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• pp.1-7
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• 1980

메탄올, 에탄올 및 에탄올-물 혼합용매중에서 메틸클로로휘메이트, 메틸티올클로로휘메이트, 메틸티오노클로로휘메이트 및 메틸디티오클로로휘메이트의 가용매분해반응에 대한 속도상수를 전기전도도법으로 구하고 활성화 파라미터를 계산하였다. 결과로 메틸클로로휘메이트는 항상 $S_N2$ 메카니즘으로 반응하며, 가수분해 순위는 $CH_3S(CS)Cl>CH_3S(CO)Cl>CH_3O(CS)Cl>CH_3O(CO)Cl$ 로 $S_N1$ 반응성이 감소하고, 메탄올에서는 $CH_3S(CS)Cl$은 $S_N1$으로, 기타는 $S_N2$로 반응하고, 에탄올에서는 모두 $S_N2$로 반응하나 아직도 메틸클로로디티오휘메이트는 $S_N1$ 반응성이 어느정도 작용함을 알았다. 또한 에탄올-물 혼합용매에서 물함량이 큰 부분에서는 티오치환체의 $S_N1$ 반응성이 증가하며 메틸클로로디티오휘메이트는 $S_N1$으로 반응함을 알았다. 에탄올-물 혼합용매중에서 $S_N1$ 반응성의 순위는 가수분해속도의 순위와 같았다.

• 한국수소및신에너지학회논문집
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• 제14권2호
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• pp.155-170
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• 2003

$Cu-Ce/{\gamma}-Al_2O_3$ based catalysts were prepared and tested for selective oxidation of CO in a $H_2$-rich stream(1% CO, 1% $O_2$, 60% $H_2$, $N_2$ as balance). The effects of Cu loading and weight ratio(=Cu/(Cu+Ce)) upon both activity and selectivity were investigated upon the change in temperatures, It was also examined how the activity and selectivity of catalysts were varied with the presence of $CO_2$ and $H_2O$ in the reactant feed. Among the various Cu-Ce catalysts with different catalytic metal composition, Cu-Ce(4 : 16 wf%) /${\gamma}-Al_2O_3$ catalyst showed the highest activity(>$T_{99}$) and selectivities(50-80%) under wide range of temperatures($175-220^{\circ}C$). However, in the Cu-Ce(4 : 16 wt%)/ ${\gamma}-Al_2O_3$, the presence of $CO_2$ and $H_2O$ in the reactant feed decreased the activity and the maximum activity(>$T_{99}$) in terms of reaction temperature moved by about $25^{\circ}C$ toward higher temperature, the $T_{>99}$ window was seen between $210-230^{\circ}C$ (selectivity 50-75%). From $CO_2-/H_2O-TPD$, it can be concluded that the main cause for the decrease in catalytic activity may be attributed to the blockage of the active sites by competitive adsorption of water vapor and $CO_2$ with the reactant at low temperatures.

• 대한기계학회논문집B
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• 제31권10호
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• pp.855-859
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• 2007

Hydrogen as an energy carrier in fuel cell offers perhaps the largest potential benefits of reduced emissions of pollutants and greenhouse gases. The generation of high-purity hydrogen from hydrocarbon fuels is essential for efficient operation of fuel cell. Reduction of carbon monoxide to an acceptable level of 10ppm involves high temperature and low temperature water gas shift (WGS), followed by selective oxidation of residual carbon monoxide. The WGS reactor was designed and tested in this study to produce hydrogen-rich gas with CO to less than 5000 ppm. In the water gas shift operation, gas emerges from the reformer is taken through a high temperature shift (HTS) catalyst to reduce the CO concentration to about $2{\sim}4%$ followed to about 5000 ppm via a low temperature shift (LTS) catalyst.

• Journal of Microbiology and Biotechnology
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• 제8권2호
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• pp.134-140
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• 1998

Eubacterium limosum KIST612 was cultured on phosphate-buffered basal medium (PBBM) with carbon monoxide (CO) as the sole energy and carbon source. The initial growth rate of this strain was approximately 0.17~0.25 $h^-1$/ and the $K_s$ value for dissolved substrate was 0.14 mM. CO was limiting during the growth of the bacterium when the CO partial pressure was less than 0.6 atm (0.5 mM dissolved CO). The bacterial growth rate was reduced in the presence of acetate. When sufficient CO was supplied using a gas-lift reactor, the acetate concentration went up to 90 mM in 116 h. Based on these findings, it is suggested that a pressurized reactor be used to develop a process to convert CO-rich gases into multi-carbon compounds.

• 청정기술
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• 제24권1호
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• pp.50-54
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• 2018

본 연구에서는 디에틸렌트리아민(diethylenetriamine, DETA) 수용액에 물리흡수제인 N-메틸-2-피롤리돈(N-methyl-2-pyrrolidone, NMP)을 도입한 저수계 흡수제에서 이산화탄소 포집에 따른 흡수제의 상분리 현상을 고찰하였다. 2 M DETA 수용액에서 NMP 조성이 30 wt%를 초과하면 $CO_2$ 흡수에 따라 흡수제의 상이 분리되는데 그 이유는 DETA-카바메이트 이온종의 NMP에 대한 낮은 용해도로 설명할 수 있다. 흡수제 내에서 NMP의 조성이 증가함에 따라 상분리 된 흡수제의 상층과 하층의 이산화탄소 로딩 차이가 커지고 하층의 부피가 감소하게 된다. 2 M DETA + NMP + 물 혼합 흡수제를 이용하여 충진탑에서의 이산화탄소 포집을 실시할 경우 흡수제 내 NMP조성이 40 wt%에 이르면 흡수속도가 줄어드는 것으로 확인되었다. 이는 이산화탄소 흡수에 따른 점도 증가로 인한 흡수제 액막에서의 물질전달 저항 때문으로 해석된다. DETA + NMP + 물로 구성된 저수계 흡수제를 이산화탄소 포집에 적용하면 상분리에 따른 이산화탄소-rich 상 부피 감소로 재생에너지를 낮출 수 있을 것으로 기대된다.

• 한국환경과학회지
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• 제17권12호
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• pp.1307-1314
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• 2008

Hydrogen gas is used as a fuel for the proton exchange membrane fuel cell (PEMFC). Trace amount of carbon monoxide present in the reformate $H_2$ gas can poison the anode of the PEMFC. Therefore, preferential oxidation (PROX) of CO is essential for reducing the concentration of CO from a hydrogen-rich reformate gas. In this study, conventional Pt/$Al_2O_3$ catalyst was prepared for the preferential oxidation of CO. The effects of catalyst preparation method, additive, and hydrogen on the performances of PROX reaction of CO were investigated. Water treatment and addition of Ce enhanced catalytic activity of the Pt/$Al_2O_3$ catalyst at low temperature below $100^{\circ}C$.

• Asian-Australasian Journal of Animal Sciences
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• 제25권6호
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• pp.861-868
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• 2012

During two years, four samples per year were collected in Vietnam from rice bran, cassava residue, brewer's grain, tofu residue, soybean meal, coconut cake, sweet potato vines and water spinach for chemical analysis and assessment of water holding capacity (WHC). The selected feedstuffs represent fibre-rich plant sources and agro-industry co-products commonly used in pig feeding in Vietnam. The content (g/kg DM) of crude protein (CP), ether extract (EE) and non-starch polysaccharides (NSP) varied between feedstuffs and ranged from 21 to 506 for CP, from 14 to 118 for EE and from 197 to 572 for NSP. Cassava residue had a high starch content of 563 g/kg DM, while sweet potato vines, water spinach, coconut cake and soybean meal had a high content of sugars (63-71 g/kg DM). The content of individual neutral sugars varied between feed ingredients, with the highest content of arabinose, galactose and glucose in tofu residue, the highest content of xylose in brewer's grain and the highest content of mannose in coconut cake. The content of uronic acid was high for cassava residue, tofu residue, sweet potato vines and water spinach (57-88 g/kg DM). The content of soluble non-cellulosic polysaccharides (S-NCP) was positively correlated ($r^2$ = 0.82) to the WHC. The content (g/kg DM) of CP, NDF, neutral sugars, total NSP, total NCP, S-NCP and total dietary fibre in tofu residue, water spinach and coconut cake varied (p<0.05) between years. In conclusion, diet formulation to pigs can be improved if the variation in chemical composition of the fibre fraction and in WHC between potential feed ingredients is taken into account.

• Preventive Nutrition and Food Science
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• 제22권2호
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• pp.131-137
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• 2017

Maximum production of isoquercetin and quercetin simultaneously from rutin by subcritical water hydrolysis (SWH) was optimized using the response surface methodology. Hydrolysis parameters such as temperature, time, and $CO_2$ pressure were selected as independent variables, and isoquercetin and quercetin yields were selected as dependent variables. The regression models of the yield of isoquercetin and quercetin were valid due to the high F-value and low P-value. Furthermore, the high regression coefficient indicated that the polynomial model equation provides a good approximation of experimental results. In maximum production of isoquercetin from rutin, the hydrolysis temperature was the major factor, and the temperature or time can be lower if the $CO_2$ pressure was increased high enough, thereby preventing the degradation of isoquercetin into quercetin. The yield of quercetin was considerably influenced by temperature instead of time and $CO_2$ pressure. The optimal condition for maximum production of isoquercetin and quercetin simultaneously was temperature of $171.4^{\circ}C$, time of 10.0 min, and $CO_2$ pressure of 11.0 MPa, where the predicted maximum yields of isoquercetin and quercetin were 13.7% and 53.3%, respectively. Hydrolysis temperature, time, and $CO_2$ pressure for maximum production of isoquercetin were lower than those of quercetin. Thermal degradation products such as protocatechuic acid and 2,5-dihydroxyacetophenone were observed due to pyrolysis at high temperature. It was concluded that rutin can be easily converted into isoquercetin and quercetin by SWH under $CO_2$ pressure, and this result can be applied for SWH of rutin-rich foodstuffs.