• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1767-1770
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• 2009

The Henry (nitroaldol) reaction proceeds under mild conditions with catalytic amount of tetramethylethylenediamine (TMEDA) to afford $\beta$-nitro alkanol in considerably excellent yield. Structurally diverse aldehydes react with nitromethane in presence of 0.3 equiv of TMEDA under solvent-free condition at rt. The low catalytic loading and mild reaction condition are the key features of the catalytic method.

• Journal of Microbiology and Biotechnology
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• v.19 no.12
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• pp.1596-1602
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• 2009

A lipase-catalyzed esterification reaction of (S)-naproxen ethyl ester by CALB (Candida antarctica lipase B) enzyme was performed in supercritical carbon dioxide. Experiments were performed in a high-pressure cell for 10 h at a stirring rate of 150 rpm over a temperature range of 313.15 to 333.15 K and a pressure range of 50 to 175 bar. The productivity of (S)-naproxen ethyl ester was compared with the result in ambient condition. The total reaction time and conversion yields of the catalyzed reaction in supercritical carbon dioxide were compared with those at ambient temperature and pressure. The experimental results show that the conversion and reaction rate were significantly improved at critical condition. The maximum conversion yield was 9.9% (216 h) at ambient condition and 68.9% (3 h) in supercritical state. The effects of varying amounts of enzyme and water were also examined and the optimum condition was found (7 g of enzyme and 2% water content).

• Communications of the Korean Mathematical Society
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• v.14 no.2
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• pp.441-447
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• 1999

A free boundary problem is derived from a singular limit system of a reaction diffusion equation whose reaction terms are bistable type. In this paper, we shall consider a free boundary problem with two layers satisfying the zero flux boundary condition and shall show that the Hopf bifurcation can not occur as a parameter varies.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.5 s.236
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• pp.617-624
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• 2005

An analysis of the effects of $CO_{2}$ on fundamental combustion characteristics was performed in Oxygen enriched condition by comparing the laminar burning velocities, flame structures, fuel oxidation paths. Fictitious $CO_{2}$ was introduced to discriminate the chemical reaction effects of $CO_{2}$ from the thermal effects. PREMIX code was utilized to evaluate the laminar burning velocities. OPPDIF code was utilized to investigate the flame structure and fuel oxidation path variation. The contributions of thermal effects on laminar burning velocities are dominant at lowly oxygen-enriched condition but those of chemical reaction effects become dominant at highly oxygen-enriched condition. Chemical reaction effects caused the additional flame temperature decrease besides thermal effects and oxygen-leakage increase in non-premixed flame. Specific fuel oxidation path and CO production path is enhanced in spite of overall decrement of fuel consumption rate by chemical reaction effects of$CO_{2}$.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.121-127
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• 2004

It is necessary to supply external carbon source for enhancement of biological nitrogen removal from domestic wastewater with low influent C/N ratio. Sulfide was chosen as a cost effective electron donor and reaction stoichiometry for autotrophic denitrification was investigated by conducting bench-scale experiments in this study. Higher sulfur to nitrogen (S/N) ratio than the calculated value from theoretical reaction stoichiometry was required when the anoxic reactor was operated at open condition because dissolved oxygen introduced by surface aeration reacted with sulfide with ease. In addition, higher sulfate production and lower yield of microorganism could be observed under the same condition. It was possible to obtain reliable reaction stoichiometry for autotrophic denitrification by establishing pure anoxic condition. Linear relationship between bacterial growth and consumption of nitrate, sulfide, alkalinity, and sulfate production enabled to derive a relatively correct reaction stoichiometry for autotrophic denitrification when sulfide was used as an electron donor.

• Journal of Powder Materials
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• v.23 no.2
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• pp.143-148
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• 2016

A microfluidic reactor with computer-controlled programmable isocratic pumps and online detectors is employed as a combinatorial synthesis system to synthesize and analyze materials for fabricating CdSe quantum dots for various applications. Four reaction condition parameters, namely, the reaction temperature, reaction time, Cd/Se compositional ratio, and precursor concentration, are combined in synthesis condition sets, and the size of the synthesized CdSe quantum dots is determined for each condition. The average time corresponding to each reaction condition for obtaining the ultraviolet-visible absorbance and photoluminescence spectra is approximately 10 min. Using the data from the combinatorial synthesis system, the effects of the reaction conditions on the synthesized CdSe quantum dots are determined. Further, the data is used to determine the relationships between the reaction conditions and the CdSe particle size. This method should aid in determining and selecting the optimal conditions for synthesizing nanoparticles for diverse applications.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.1
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• pp.41-47
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• 2003

Recently, interest in utilization plan of recycling paper have been enhanced. Therefore, this research aimed to develop the manufacture process of cellulose acetate using old newsprint by acetosolv pulping process. And the manufactured cellulose acetate was also analyzed, especially based on chemical properties. The summarized results in this research were as follows; Reaction time, kind and amount of catalyst, and ratio of liquor to material were varied during acetosolv pulping process of old newsprint. Ratio of liquor to material did not give the significant difference in reaction product. Delignification rate was increased with increasing reaction time during acetosolv pulping, but yield and degree of substitution decreased with increasing reaction time. Sulfuric acid are better catalyst than hydrochloric acid in acetosolv pulping process for old newsprint, and optimal addition amount of catalyst was 1% based on reaction material. Delignification, yield, and degree of substitution were influenced by the catalyst and reaction time. Under pulping condition of $120^{\circ}C$ in 1/12 liquor to material ratio and 60min, degree of substitution was about 0.7. The acetylation reaction was not completely caused by these reaction condition. The examination of the FT-IR spectra revealed that absorption band(1200$\textrm{cm}^{-2}$, 1,750$\textrm{cm}^{-1}$) caused by carbonyl group were confirmed.

• Preventive Nutrition and Food Science
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• v.15 no.4
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• pp.304-308
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• 2010

Boiled-type shrimp flavor was developed using Maillard reaction to reduce or mask fish odor or off-flavor in seafood. Model systems were created using enzymatic hydrolysate of shrimp and adding precursor compounds to increase flavor quality and stability. Amino acid precursors of cysteine and methionine and sugar precursors such as glucose, xylose, ribose and sucrose were tried and their flavor qualities were tested by sensory evaluation. After the optimal precursors were determined, the optimum reaction condition was investigated using pHs of 5, 6, 7, and 8 and reaction times of 1, 2 and 3 hours. The best precursors for boiled-type shrimp flavor were methionine and sucrose. The optimum reaction condition was pH 8.0 and a one hour reaction time.

• KSBB Journal
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• v.22 no.4
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• pp.228-233
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• 2007

The high cost and lack of vegetable oil are limiting the expansion of biodiesel production. The purpose of research was to investigate the potential of animal fats as biodiesel feedstock. In this paper, transesterification using alkali catalyst and methanol was performed to reaction, we carried out experiments that it was changed variables as reaction temperature, methanol molar ratio, catalyst types, amount of catalyst and reaction time. The optimum reaction condition for biodiesel production was reaction temperature 65$^{\circ}C$, potassium hydroxide 1.0% (w/w), oil to methanol molar ratio 1:15 and reaction time 20 min. In this reaction condition, the contents of fatty acid methyl ester was reached to about 98.7%. Also, properties of biodiesel were measured to correspond to domestic quality standard of acid values, density and viscosity.

• Journal of the Korean Mathematical Society
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• v.47 no.6
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• pp.1317-1328
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• 2010

In this paper, we study the properties of positive solutions for the reaction-diffusion equation $u_t$ = $\Delta_u+{\int}_\Omega u^pdx-ku^q$ in $\Omega\times(0,T)$ with nonlocal nonlinear boundary condition u (x, t) = ${\int}_{\Omega}f(x,y)u^l(y,t)dy$ $\partial\Omega\times(0,T)$ and nonnegative initial data $u_0$ (x), where p, q, k, l > 0. Some conditions for the existence and nonexistence of global positive solutions are given.