• Korean Journal of Food Science and Technology
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• v.24 no.3
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• pp.261-265
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• 1992

To improve preservation and utilization of radish juice concentrates, radish juice were concentrated by reverse osmosis(RO) and thin layer evaporator(TLE) and their rheological properties were investigated. Radish juice concentrates were considered as nowtonian fluids. The apparent viscosity of conc. 1 (Heat treatment radish juice, concentrated by TLE), conc. 2 (Raw radish juice, concentrated by TLE), conc. 3 (Heat treatment radish juice, concentrated by RO) were 0.0503, 0.0578 and 0.0655 Pa.s at 10(1/s), respectively. The yield stress of these concentrates were ranged from 0.0001 to 0.0580 Pa. The activation energy for the flow of the radish juice conc. 1 were increased from 2.7057 to $4.1159{\times}10^4KJ/kg.mol$ by increasing concentration of radish juice.

• Korean Journal of Food Science and Technology
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• v.19 no.3
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• pp.239-244
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• 1987

Rheological properties of 5% starch suspension were investigated using a capillarity tube viscometer. Nonglutinous and glutinous rice starch suspensions at $30-60^{\circ}C$, and $30-55^{\circ}C$, respectively, had no yield stress and showed dilatant flow behavior in the absence or presence of phosphate. However, flow behavior of nonglutinuous starches at $65^{\circ}C$ and glutinous starch at $60^{\circ}C$ was pseudopalastic. Flow activation energies for rice starch suspensions were 0.88-1.45 kcal/mole at $30-50^{\circ}C$ and about 45-73 kcal/mole $60-65^{\circ}C$. Flow activation energy in the presence of phosphate was 90-182 kcal/mole at $60-65^{\circ}C$. Akibare starch had the highest activation energy, and glutinous starch the lowest.

• Microbiology and Biotechnology Letters
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• v.7 no.3
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• pp.141-147
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• 1979

Naringinase from Atpergillus nidulans was immobillized on DEAE-Sephadex A-25 and its characteristics were studied. The optimal conditions for the preparation of the immobilized enzyme were as follow; optimal pH, incubation time and the suitable amount of enzyme were 6.0, 30 min. and 110 units per gram of the dried ion exchage resin, respectively. The optimal pH of the immobilized enzyme was higher than that of the native enzyme. The optimal temperature increased from 4$0^{\circ}C$ to 5$0^{\circ}C$. The heat and pH stability of the immobillized enzyme were better than those of the native enzyme. No significant difference in the Michaelis constant was detected. Activation energy of the immobilized enzyme was 7.96 Kcal/mole, and the apparent Michaelis rate equation was used to describe the action of this material. The degree of hydrolysis was dependant on the flow rate at low rate of perfusion through the column. As the flow rate increased, the value of the apparent Km decreased.

• Microbiology and Biotechnology Letters
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• v.14 no.2
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• pp.169-174
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• 1986

Cytosine deaminase was partialy purified about 10 fold from the ceil-free extract of Aspergillus fumigatus. The partialy purified enzyme was relatively stable in a pH 5.5 to 8.0, but thermo-unstable. The enzyme activity was found in a pH optimum of 7.0 and temperature optimum of 30 to 35$^{\circ}C$. The activation energy calculated to be 13,240 cal/mol. The apparent Michaelis constants Km for cytosine was found to be 1.53 mM and the molecular weight was determined to be approximately 32,000. The enzyme was strongly inhibited by 0.1 mM of Hg$^^{2+}$, Pb$^{2+}$, Cd$^{2+}$ and Fe$^{2+}$, furthermore inhibited by 1mM of ATP, UTP, o-phenanthroline and p-chloromercuribenzoate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1125-1129
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• 2008

Polypropylene (PP)/corn starch master batch(starch-MB) blends with different PP compositions of 90, 80, 70, and 60 wt% were prepared by melt compounding at $200^{\circ}C$, using lab scale Brabender mixer. The chemical structures, thermal properties and non-isothermal crystallization behavior of the PP/starch-MB blends were investigated by FT-infrared spectrometry (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). The fabrication of the PP/starch-MB blend was confirmed by the existence of hydroxy group in FT-IR spectrum. There was no district change in melting temperature and melting enthalpy, and TGA curve indicates a decrease in degradation temperature with starch-MB content. The non-isothermal crystallization process was analyzed using by Avrami equation. The Avrami exponents were in the range of 2.71-3.97 for PP and 1.48-1.99 for PP/starch-MB blonds. The activation energies calculated by Kissinger method were 233 kJ/mol for PP, 484 kJ/mol for PP90, 541 kJ/mol for PP80, 553 kJ/mol for PP70, and 422 kJ/mol for PP60.

• Polymer(Korea)
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• v.24 no.2
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• pp.168-173
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• 2000

Radical copolymerization of N-isopropylacrylamide (NIPAAM) with methyl methacrylate (MMA) was carried out in 1,4-dioxane using 2,2'-azobisisobutyronitrile (AIBN). To investigate the reactivity ratios of NIPAAM and MMA at different reaction temperatures, the copolymerization was allowed to proceed to low conversion (less than 10 wt%), and the reaction temperatures were 50, 60, and 7$0^{\circ}C$. The monomer reactivity ratios of NIPAAM and MMA were estimated by the graphical methods according to the Finemann-Ross equation. The ${\gamma}$$_1$ and ${\gamma}$$_2$ values for NIPAAM-MMA were 0.259 and 2.782 at 5$0^{\circ}C$, 0.271 and 2.819 at 6$0^{\circ}C$, and 0.286 and 2.915 at 7$0^{\circ}C$, respectively. As the reaction temperature increased, the ${\gamma}$$_1$ and ${\gamma}$$_2$ values increased. The activation energy difference was estimated by comparing the reactivity ratios at different reaction temperatures.

• Journal of the Korean Chemical Society
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• v.39 no.3
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• pp.157-162
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• 1995

The x values and electrical conductivities of the nonstoichiometric compounds $WO_{3-x}$ have been measured in the temperature range from 350 to 700$^{\circ}C$ under oxygen partial pressure of $2{\times}10_{-1}\;to\;1{\times}10_{-5}$ atm. The enthalpy of the defect formation shows an endothermic process, and the oxygen pressure dependence of the defect formation or 1/n varies from -1/5.2 to -1/5.9. The activation energy and 1/n value for the electrical conductivity are 0.24~0.29 eV and -1/4.3~-1/7.6, respectively. The Tungsten Oxide as a n-type semiconductor has predominently defect model of singly charged oxygen vacancy at low temperature, and of doubly charged oxygen vacancy at high temperature.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.395-401
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• 2014

In this work, the reaction characteristics for the non-catalytic esterification of palm fatty acid distillate were analyzed. The esterification reaction was assumed as the pseudo homogeneous $2^{nd}$ order reversible reaction and 'reaction effectiveness factor (${\eta}$)' was used to take accounts into evaporation and reaction of water and methanol, which take place simultaneously in the liquid phase. The nonlinear programming was used to derive appropriate kinetic parameters, the reaction rate constant and mass transfer coefficient, minimizing the error between experimental data and the numerical values. Based on these parameters, the apparent activation energy was calculated to be 43.98 kJ/mol.

• Korean Journal of Food Science and Technology
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• v.25 no.6
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• pp.643-648
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• 1993

A simple approximate model using equivalent time at a reference temperature ($t_{eq}$) was derived to predict quality changes caused by temperature fluctuations. The validity and effectiveness of this model have been assessed with experimental data of sucrose hydrolysis. Kinetic parameters of sucrose hydrolysis were estimated by one step method using equivalent time at a reference temperature with linearly increasing temperature profile. Sucrose hydrolysis was a first order reaction, and the activation energy was 25.84 kcal/mol. The extent of sucrose hydrolysis of liquid model system under accelerated test with sinusoidal temperature fluctuations were determined. The proposed model yielded accurate prediction with the correlation coefficient in the range of $0.92{\sim}0.99$.

• Korean Journal of Food Science and Technology
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• v.28 no.5
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• pp.877-881
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• 1996

The firming rate of cooked rice stored at $4^{\circ},\;20^{\circ}$ and $30^{\circ}C$ were analyzed. The initial and limiting firmness of cooked rice were decreased as the moisture content increased from 57.5 to 69.5%. The firming rate was inversely related to the storage temperature, but was fairly constant at moisture content between $60.5{\sim}65.9%$. The activation energy and $Q_{10}$ value for firming of cooked rice was $-4.07{\times}10^3\;cal/mole$ and 1.26, respectively. No significant difference in firming rate was observed among rice cultivars.