• Journal of Microbiology and Biotechnology
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• 제14권6호
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• pp.1200-1210
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• 2004

Metabolic flux analysis was established by adapting previous stoichiometric model developed during growth with cellulose to cell grown with cellobiose for further direct comparison of the bacterial metabolism. In carbon limitation with cellobiose, a shift from acetate-ethanol fermentation to ethanol-lactate fermentation is observed and the pyruvate overflow is much higher than with cellulose. In nitrogen limitation with cellobiose, the cellodextrin and exopolysaccharide overflows are much higher than on cellulose. In carbon and nitrogen saturation with cellobiose, the cellodextrin, exopolysaccharide, and free amino acids overflows reach the highest levels observed but all remain limited on cellulose. By completely shunting the cellulosome, the use of cellobiose allows to reach much higher carbon consumption rates which, in return, highlights the metabolic limitation of C. cellulolyticum. Therefore, the physical nature of the carbon source has a profound impact on the metabolism of C. cellulolyticum and most probably of other cellulolytic bacteria. For cellulolytic bacteria, the use of soluble carbon substrate must carefully be taken into consideration for the interpretation of results. Direct comparison of metabolic flux analysis from cellobiose and cellulose revealed the importance of cellulosome, phosphoglucomutase and pyruvate-ferredoxin oxidoreductase in the distribution of carbon flow in the central metabolism. In the light of these findings, future directions for improvement of cellulose catabolism by this bacterium are discussed.

• Journal of Advanced Marine Engineering and Technology
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• 제29권6호
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• pp.662-670
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• 2005

With highly oxygenated fuels the smoke emissions decreased sharply and linearly with increases in the fuel oxygen content and entirely disappeared at an oxygen content of $38wt-\%$ even at stoichiometric mixture conditions The NOx also decreased monotonically with increases in oxygen content. and thermal efficiency slightly improved because of a reduction in cooling loss and improvement in the degree of constant volume combustion. The mechanisms of the significant reductions in emissions and improvement in engine performance were analyzed with a bottom view type DI diesel engine. Together with direct flame images, flame images were taken through an optical fetter passing only two wavelengths for use in 2-D two-color analysis. The results showed that luminous flame decreased significantly with increases in oxygen content and was not detected for neat dimethoxy methane(DMM). The decrease in flame luminosity with highly oxygenated fuels corresponds with decreases in soot and cooling losses, including those due to heat radiation. The 2-D two-color flame analysis indicated that the high temperature flame and high KL factor areas apparently decreased with increasing fuel oxygen content. These results correspond strongly with decreases in NOx. smoke. and cooling loss with increases in oxygen content.

• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 The 4th Korea-Italy Workshop
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• pp.81-85
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• 2003

PU block polymers are constituted by sequences of constitutional units CU which are : a diisocyanate T, a polyol or a polyamine V, an extensor E .Due to the CU different solubility parameters ,hard and soft micro domains are formed;they can aggregate into different phases. A linear PU can be described by two parameters R=T/N and $R_{E}$=(R-1)V/E.A stoichiometric model is proposed which gives the general formula of all the possible PU: X((TV)$_{k}$(TE)$_{n}$)$_{m}$X , where k and m can be calculated from the experimental molecular weights respectively of pre polymer and polymer and n= R-1.Physical properties depend on PU composition and on nature of CU. I.R. analysis is useful for discovering the hydrogen bonds location : DSC gives informations on the presence of the different phases .PALS analysis shows that nano cavities become tighter on increasing n. A series of particular Pus ,obtained from :TDI, a low molecular weight polyol, a cyclic extensor, at different R and RE was prepared and analysed. These PU are amorphous, monophasic and appear to be good candidates for membranes.nes.nes.

• Journal of Microbiology and Biotechnology
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• 제12권2호
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• pp.258-267
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• 2002

A flux determination methodology has been built which enables to develop constrained stoichiometric relationships and metabolic balances. The analysis differs from those developed for anaerobic growth conditions in that cell mass formation is a significant sink for carbon. When combined with experimental measurements, a determined system of equations results yielded tricarboxylic acid (TCA) cycle and glycolytic fluxes. The methodology was implemented to determine the fluxes of E. coli B/r and K12, and it was found that as the growth rate in a glucose minimal medium increased, the cells became increasing glycolytic and the TCA fluxes either leveled off or declined. The pattern identified for the TCA fluxes corresponded to ${\alpha}$-ketoglutarate dehydrogenase's induction-repression pattern, thereby suggesting that the induction-repression of the enzyme could result in significant flux changes. When the minimum flux solution was contrasted to the glycolytic and TCA fluxes determined, two observations were made. First, the minimum flux could provide the cell's biosynthetic ATP requirements. Second, at a high growth rate in a glucose medium, the excess glycolytic flux exceeded that of the TCA cycle, which appeared to more closely match the biosynthetic needs.

• 한국결정성장학회지
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• 제8권3호
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• pp.387-387
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• 1998

본 연구에서는 기상화학 증착법으로 성장되는 GaN 후막에 대한 열역학적 전사모사를 수행하고 이를 실험결과와 비교, 검토하였다. 열역학적계산은 화학양론적 연산방식을 이용하여 수치 해석하였으며, 모사의 변수로써 온도범위는 400∼1500K, 기상비율은 $(GaCl_3)/[GaCl_3+NH_3],(N_2)/(GaCl_3+NH_3)$를 취하였다. GaN의 성장온도 범위는 이론적인 계산이 실험결과보다 훨씬 낮은 450∼750K으로 예측되었다. 성장온도에서 모사결과와 실험결과와의 차이는 GaN의 기상 에픽텍시 성장이 박막성장의 높은 활성화 에너지 때문에 반응속도론적으로 국한된 영역 내에서 발생한다는 것을 나타낸다.

• 한국결정성장학회지
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• 제8권3호
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• pp.388-395
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• 1998

본 연구에서는 기상화학 증착법으로 성장되는 GaN 후막에 대한 열역학적 전사모사를 수행하고 이를 실험결과와 비교, 검토하였다. 열역학적계산은 화학양론적 연산방식을 이용하여 수치 해석하였으며, 모사의 변수로써 온도범위는 400~1500K, 기상비율은 $(GaCl_3)/[GaCl_3+NH_3],(N_2)/(GaCl_3+NH_3)$를 취하였다. GaN의 성장온도 범위는 이론적인 계산이 실험결과보다 훨씬 낮은 450~750K으로 예측되었다. 성장온도에서 모사결과와 실험결과와의 차이는 GaN의 기상 에픽텍시 성장이 박막성장의 높은 활성화 에너지 때문에 반응속도론적으로 국한된 영역 내에서 발생한다는 것을 나타낸다.

• 대한기계학회논문집B
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• 제24권11호
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• pp.1513-1522
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• 2000

In this study, the burning velocities of LFG and LFG mixed fuels have been numerically determined. C3 reaction mechanism involving 92 species and 621 reactions was adopted in the calculation. The computed burning velocities using C3 mechanism show good agreements with experimental data. Based on numerical results, the maximum burning velocities of LFG and LFG mixed fuels were correlated as a function of CH$_4$ and LFG component percentage at stoichiometric conditions. In addition, the correlations of burning velocities of LFG and LFG mixed fuels were obtained over a wide range of the equivalence ratio. The numerical results are well agreed with the burning velocity correlations. The burning velocity correlations for LFG and LFG mixed fuels suggested in this study can be applied to the practical utilization of LFG.

• 한국표면공학회지
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• 제30권4호
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• pp.223-230
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• 1997

Tungsten oxide and nickel oxide thin films were deposited onto ITO(Indium Tin Oxide) transparent glass by the E-beam evaporation and were used as a cathode and an anode for the EC(Electrochromic) smart window, respectively. Stoichiometric structures of the deposited films were investigated by the implementation of XPS(X-ray Photoelectron Spectroscopy) analysis and the results were $WO_{2.42}$ and $NiO_{0.44}$. This oxygen deficincy might affect affect the transparency of the thin films. The electrolyte for the EC smart windows was PAN-$LiCIO_4$ conducting polymer. EC(Ethylene Carbonate)and PC(Propylene Carbonate) were added as plasticizer to enhance ion conductivity. When the weight ratio of the EC : PC was 3 : 1, transmission difference and cycle life performance were tested. Polymer EC windows showed 40% $\Delta$T at 1.5V operating volage for 3,200 cycles. Structural degradation was observed by the SIMS(Secondary Ion Mass Spectroscopy) analysis and it was confirmed that structural degradation of polymer caused by the solvent evaporation was the main cause to degrade EC smart windows.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.407-410
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• 2002

Thermal oxidations of 3C-SiC thin-films grown on Si(100) by APCVD(atmospheric pressure chemical vapor deposition) were carried out. The oxidations of 3C-SiC were performed at $1100^{\circ}C$ for 1~6 hr in wet and dry $O_2$ ambient, respectively. Ellipsometry was used to determine the thickness and index of refraction of oxide films. The oxide thickness vs. the oxidation time follows the general relationship used for the thermal oxidation of Si. The surface roughness was analyzed by using AFM(atomic force microscopy). The surface roughness of oxidized 3C-SiC was rougher than before oxidation. The thermal oxide was found to be $SiO_2$ by XPS(X-ray photoelectron spectroscopy) analysis. Auger analysis showed them to be homogeneous with near stoichiometric composition.

• Bulletin of the Korean Chemical Society
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• 제22권7호
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• pp.703-708
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• 2001

K2NiF4-type organic-based perovskites of the (C4H9NH3)2FexPb1-xCl4 (x=0.00, 0.25, 0.50, and 0.75) system have been synthesized using a low-temperatu re solution method under a flowing argon gas. When stoichiometric butylamine, iron chloride, and lead chloride are mixed, a yellow solution are obtained from slow cooling of 90 to -10 $^{\circ}C.$ The final product is a plate-like yellow crystal. The X-ray crystallographic analysis has been carried out using XRD in the range of $5^{\circ}{\leq}$ 2${\theta}$ ${\leq}80^{\circ}.$ The local symmetry around the absorbing Pb atom of the samples has been determined by the EXAFS spectroscopic study. The crystals assign to orthorhombic system by the XRD analysis. The FT-IR spectra are analyzed in the range of 600 to 3300 cm-1 . DSC and TGA are measured to detect thermal stability between 30 and 300 $^{\circ}C.$ Two endothermic peaks are detected in all samples. The electrical conductivity has been measured using the four-probes technique for the (C4H9NH3)2FexPb1-xCl4 system in 300-460 K. Photoluminescence phenomenon was also investigated at room-temperature.