• 한국응용과학기술학회지
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• 제25권4호
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• pp.418-428
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• 2008

Transesterification of fat of Tra catfish with methanol in the presence of the KOH catalyst yields fatty acid methyl esters (FAME) and glycerol (GL). The effects of the reaction temperature and reaction time on rate constants and kinetic order were investigated. Three regions were observed. In the initial stage, the immiscibility of the Tra fat and methanol limited the reaction rate, hence this region was controlled by the mass transfer. Subsequent to this region, produced FAME like a co-solvent made the reaction mixture homogeneous, therefore the conversion rate increased rapidly so it was controlled by the kinetic parameters of the reaction until the equilibrium was approached in the final slow region. A second-order kinetic mechanism was proposed involving second regions for the forward reaction. The rate determining step for the overall KOH catalyzed-methanolysis of Tra fat was the conversion of triglycerides (TG) to diglycerides (DG). This rate constant was increased from 0.003 to $0.019min^{-1}$ when the reaction temperature was increased from 35 to $60^{\circ}C$. Its calculated activation energy was 14.379 ($kcal.mol^{-1}$).

• Bulletin of the Korean Chemical Society
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• 제31권4호
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• pp.835-839
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• 2010

The rate constants of solvolyses of 2,2,2-trichloro-1,1-dimethylethyl chloroformate ($\underline{I}$) in 33 solvents can be well correlated using the extended Grunwald-Winstein equation, with incorporation of the $N_T$ solvent nucleophilicity scale and the $Y_{Cl}$ solvent ionizing scale, with sensitivities towards changes in the scale having values of $1.42\;{\pm}\;0.09$ for l and $0.39\;{\pm}\;0.05$ for m, respectively. The activation enthalpies are ${\Delta}H^{\neq}\;=\;12.3$ to $14.5\;kcal{\cdot}mol^{-1}$ and the activation entropies are -28.2 to $-35.5\;cal{\cdot}mol^{-1}{\cdot}K^{-1}$, consistent with the proposed bimolecular reaction mechanism. The kinetic solvent isotope effect of 2.14 in MeOH/MeOD is in accord with a bimolecular mechanism, probably assisted by general-base catalysis.

• Bulletin of the Korean Chemical Society
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• 제6권4호
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• pp.196-202
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• 1985

A Very Low Pressure Reactor (VLPR) is constructed for the kinetic study of atom-molecule bimolecular elementary reactions. The basic principles and the versatility of the method are described. By using the VLPR technique the forward (k1) and the reverse (k-1) rate constants for Br atom reaction with trimethylsilane are studied; Br + $(CH_3)_3$SiH k1 ${\leftrightarrow}$ k-1 HBr + $(CH_3)_3$Si. From the kinetic data and the entropy estimation the bond dissociation energy for Si-H bond in trimethylsilane is calculated to be 90.1 kcal/mole $({\pm}1.1$ kcal/mole). The Arrhenius parameters for k1 are found to be log A = 10.6 l/mole·sec, $E_a$ = 4.4 kcal/mole respectively. For the comparison purpose analogous reaction for carbon compound ; Br + $(CH_3)_3$CH ${\rightarrow}$ HBr + $(CH_3)_3$C was also studied. The corresponding rate constant and equilibrium constant at $25^{\circ}C$ are found to be 2.67 ${\times}$ $10^6l$/mole${\cdot}$sec and 160 respectively.

• 한국염색가공학회:학술대회논문집
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• 한국염색가공학회 2004년도 추계학술발표회 논문집
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• pp.172-176
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• 2004

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
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• pp.505-508
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• 1989

A computer simulation code of UV preionized discharge KrF laser is developed, including time dependent circuit equations, boltzmann equations, and plasma kinetic equations for various atomic and molecular species. Rate constants for electron collision processes are calculated with a boltzmann equations as a function of E/N. In this study, we studied mainly the $KrF^*$ formation process, relaxation process, and the 248nm absorption process as a function of charging voltage.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2779-2781
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• 2009

• Journal of Pharmaceutical Investigation
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• 제21권4호
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• pp.231-236
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• 1991

The molecular nature of aspirin hydrolysis was studied using cyclodextrin as a biomimetic model for esterase. Cyclodextrin was selected for this purpose because it meets the necessary requirements for the hydrolysis study, Dissociation constants and catalytic rates were obtained under alkaline conditions by the kinetic method.

• Bulletin of the Korean Chemical Society
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• 제17권2호
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• pp.158-162
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• 1996

The steady-state emission and fluorescence lifetimes of 1,3-dipyrenylpropane were measured in silicate sol-gel and xerogel matrices. In sol solution, the fluorescence emission spectra of monomer and excimer resemble those in hydrocarbon solvents. In gel and xerogel condition, however, the fluorescence spectra exhibit significant change, largely confirming the intramolecular motions in gel pores are influenced by microviscosity. The rate constants for intramolecular excimer formation were obtained from the measured fluorescence lifetimes and the rate processes for excimer forming in silicate sol-gel are described by a simple kinetic scheme.

• 산업식품공학
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• 제15권3호
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• pp.214-220
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• 2011

중고압 하에서 $\beta$-glucosidase효소반응을 물리화학적 관점에서 연구하였다. 모델 기질 (p-nitrophenyl-${\beta}$-D-glucopyranoside)에 대한 $\beta$-glucosidase 효소의 작용에 대한 압력 효과를 실험 하였다. 즉, 압력 조건(25MPa, 50 MPa, 75 MPa, 100 MPa)과 시간 (10분, 60분, 1시간, 6시간, 24시간, 40시간)의 처리 조건에서 효소 활성도를 분광학적인 표준방법에 따라 측정하였다. 효소-기질 반응의 단계를 크게 kinetic 구간과 평형 구간으로 구분하여 물리화학적 모델을 적용하여, 정 역반응속도 상수, 평형상수, 압력에 의한 부피 감소 등을 산출하였다. 대기압에서 100MPa까지 압력이 증가할수록 효소-기질 반응의 생성물이 더 많이 형성되었으며 전형적인 kinetic 구간과 평형 구간이 나타났다. 압력, 시간, 생성물농도 등의 데이터로부터 kinetic 구간과 평형에서의 생성물 예측 모델을 완성하였다. 결론적으로 중고압 처리에 의하여 효소-기질 반응이 촉진됨을 알 수 있었고, 임의의 압력 및 시간 조건에 따른 생성물의 농도를 예측할 수 있게 되었다.

• 한국가스학회지
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• 제27권1호
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• pp.78-85
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• 2023

구리가 함침된 하이드로탈사이트 촉매의 고유 키네틱 데이터를 이용하여 메탄올 수증기 개질 반응의 고정층 반응기 Computational Fluid Dynamics(CFD) 시뮬레이션을 수행하였다. 이전 연구결과로부터 얻어진 20wt%의 구리가 함침된 하이드로탈사이트 촉매의 활성화 에너지는 97.4 kJ/mol, 전 지수 인자는 5.904 × 10¹⁰를 이용하였다. 그리고 고유의 키네틱 데이터를 사용하여 반응온도 (200-450 ℃) 및 메탄올과 물의 몰비 변화에 따른 전환율을 관찰하였다. 또한 위의 키네틱 상수를 power law 모델을 사용하여 Axial 2D Symmetry 시뮬레이션을 통해 상용반응기(I.D. 0.05 - 0.1 m, Length 1 m)의 열 및 물질유동해석을 예측하였다.