• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.301-309
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• 2008

In this study, the effect of formaldehyde to phenol (F/P) molar ratios, catalyst wt%, and reaction temperature on the chemical structure was studied utilizing a two-level full factorial experimental design. The effect of three variables on the chemical structure was analyzed by using three-way ANOVA of SPSS. Concentration of methyrol-substituted phenols after 300 min addition reaction increased with higher the F/P mole ratio, lower the reaction temperature and lower the catalyst wt%. Resol catalysed by barium hydroxide showed higher addition of formaldehyde onto ortho positions of phenolic rings. A simplified elementary reaction model for resole type phenolic resin formation which do not consider the dissociation of phenolic compounds and the fraction of formaldehyde in the form of methylene glycol was proposed and compared with Zavitsas' type models. Elementary reaction model showed error of 2.79% compared to the error of 3.27% in Zavitsas' type models. It was thought that the elementary reaction model could be used to predict the behavior of addition reaction in resol formation.

• Elastomers and Composites
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• v.50 no.2
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• pp.92-97
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• 2015

A study on reaction kinetics for a PTMG/TDI prepolymer with 2,2'-dichloro-4,4'-methylenedianiline (MOCA), of which formulations may be generally used for fabricating high performance polyurethane elastomers, was peformed using non-isothermal differential scanning calorimetry (DSC). A number of thermograms were obtained at several constant heating rates, and analysed using Flynn-Wall-Ozawa (FWO) isoconversional method for activation energy, $E_a$ and extended-Avrami equation for reaction order, n. Urea formation reaction of the present system was observed to occur through the simple exothermic reaction process in the temperature range of $100{\sim}130^{\circ}C$ for the heating rate of $3{\sim}7^{\circ}C/min$. and could be well-fitted with generalized sigmoid function. Though activation energy was nearly constant as $53.0{\pm}0.5kJ/mol$, it tended to increase a little at initial stage, but it decreases at later stage by the transformation into diffusion-controlled reaction due to the increased viscosity. Reaction order was evaluated as about 2.8, which was somewhat higher than the generally well-known $2^{nd}$ order values for the various urea reactions. Both the reaction order and reaction rate explicitly increased with temperature, which was considered as the indication of occurring the side reactions such as allophanate or biuret formation.

• Bulletin of the Korean Chemical Society
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• v.25 no.8
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• pp.1217-1224
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• 2004

We have calculated the probability of HBr formation and energy disposal of the reaction exothermicity in HBr produced from the reaction of gas-phase bromine with highly covered chemisorbed hydrogen atoms on a Si (001)-(2 ${\times}$1) surface. The reaction probability is about 0.20 at gas temperature 1500 K and surface temperature 300 K. Raising the initial vibrational state of the adsorbate(H)-surface(Si) bond from the ground to v = 1, 2 and 3 states causes the vibrational, translational and rotational energies of the product HBr to increase equally. However, the vibrational and translational motions of product HBr share most of the reaction energy. Vibrational population of the HBr molecules produced from the ground state adsorbate-surface bond ($v_{HSi}$ =0) follows the Boltzmann distribution, but it deviates seriously from the Boltzmann distribution when the initial vibrational energy of the adsorbate-surface bond increases. When the vibration of the adsorbate-surface bond is in the ground state, the amount of energy dissipated into the surface is negative, while it becomes positive as vHSi increases. The energy distributions among the various modes weakly depends on surface temperature in the range of 0-600 K, regardless of the initial vibrational state of H(ad)-Si(s) bond.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.205-214
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• 2002

The reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on a silicon surface is studied by use of the classical trajectory approach. Especially, we have focused on the mechanism changes with the hydrogen surface coverage difference. On the sparsely covered surface, the gas atom interacts with the preadsorbed hydrogen atom and adjacent bare surface sites. In this case, it is shown that the chemisorption of H(g) is of major importance. Nearly all of the chemisorption events accompany the desorption of H(ad), i.e., adisplacement reaction. Although much less important than the displacement reaction, the formation of $H_2(g)$ is the second most significant reaction pathway. At gas temperature of 1800 K and surface temperature of 300 K, the probabilities of these two reactions are 0.750 and 0.065, respectively. The adsorption of H(g) without dissociating H(ad) is found to be negligible. In the reaction pathway forming $H_2$, most of the reaction energy is carried by $H_2(g)$. Although the majority of $H_2(g)$ molecules are produced in sub-picosecond, direct-mode collisions, there is a small amount of $H_2(g)$ produced in multiple impact collisions, which is characteristic of complex-mode collisions. On the fully covered surface, it has been shown that the formation of $H_2(g)$ is of major importance. All reactive events occur on a subpicosecond scale, following the Eley-Rideal mechanism. At gas temperature of 1800 K and surface temperature of 300 K, the probability of the $H_2(g)$ formation reaction is 0.082. In this case, neither the gas atom trapping nor the displacement reaction has been found.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.134-137
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• 2009

Commercially available elemental powders of Cu, Zn, Sn and Se were employed for crystallizing a stannite-type $Cu_2ZnSnSe_4$ compound by means of solid state reaction. $Cu_2ZnSnSe_4$ reaction chemistry was also modeled based on differential-thermal analysis and X-ray powder diffraction results. It was observed that Se tends to react preferably with Cu to form CuSe and $CuSe_2$ phases at low reaction temperature. The formation of $Cu_5Zn_8$ intermetallic phase was found to be the intermediate reaction path for the binary ZnSe formation. A solid state reaction at $320^{\circ}C$ reacted elemental powderst obinary selenides of CuSe, ZnSe and SnSe completely. The crystallization of $Cu_2ZnSnSe_4$ was was detected to begin at $300^{\circ}C$ and its weight fraction increased with an increase of reaction temperature, which most probably formed from the reaction between $Cu_2SnSe_3$ and ZnSe.

• Journal of Korean Society of Water and Wastewater
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• v.7 no.2
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• pp.34-38
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• 1993

An experimental study was conducted to investigate the effects of chlorine dioxide and ozone on reduction of THM(trihalomethane) formation. Precursor concentration, chlorine concentration, reaction time, pH, and temperature were governing compornents of THM formation. When other conditions are constant, THM formation increased linearly with precursor concentration increased. THM formation increased when pH increased from 5 to 9. In combined treatment with chlorine and chlorine dioxide, chlorine treatment after chlorine dioxide treatment made less THM than any other case does. Ozonation reduced THMFP(THM formation potential) of THM precursor. THMFP decreased exponentially with reaction time increased. Also biodegradability of humic acid was enhanced by ozonation.

• Journal of the Korean Ceramic Society
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• v.20 no.4
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• pp.297-304
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• 1983

In this study a Comparative investigation of the effect of $K_2SO_4$ and $CaSO_4$ on the formation of calcium silicate was made. $K_2SO_4$ had little effect on C3S formation. More than 4.0wt% of CaSO4 hindered the reaction of $C_2S$ and CaO so $C_3S$ formation was restrained by forming the reaction rim around $C_2S$ Particles. And activation energy for $C_3S$ formation was calculated around to be 40kcal/mol irespective of the amount of $K_2SO_4$.

• Journal of Food Hygiene and Safety
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• v.2 no.4
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• pp.191-196
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• 1987

Erythrosine used as a colouring agent in drugs, cosmetics and foods in Korea, was examined for its effects on murine immune system and methemoglobin formation. As immunotoxicologic assay parameters, we adopted circulating leukocytes and immunoorgan weights for pathotoxicology, IgM plaque forming cells and arthus reaction for humoral immunity, delayed hypersensitivity reaction of cell mediated immunity and carbon clearacnce for macrophage function. Erythrosine's effects were observed as follows; 1. Ery throsine showed no significant effects on circulating leulocyte counts and relative immunoorgan weight. 2. Erythrosine diminished IgM plaque forming cells. 3. Erythrosine decreased arthus reaction, in the dose dependent manner. 4. Erythrosine had no significant effect on delayed hypersensitivity. 5. Phagocytic and corrected phagocytic index were not affected. 6. Methemoglobin content was similar in the test and control groups.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.95-101
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• 1995

Experiments have been conducted to investigate the characteristics of formaldehyde and nitrous oxide formation from the catalytic reaction of methane. Catalysts used in the experiment were Pd. Pd/Pt/Rh loaded on ${\gamma}-Al_2O_3$ and ${\gamma}-Al_2O_3-La_2O_3$ monolith. In the catalytic reaction of methane. as the concentration of NO, $O_2$ and $CH_4$ increased, the formaldehyde emission was increased. The concentration of $N_2O$ increased as NO and CO increased. It was also found that the formaldehyde emission was produced by the gas reaction of methane in high temperature above 950K.

• Journal of Photoscience
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• v.9 no.3
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• pp.57-63
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• 2002

A homopolymer containing anthracene groups, poly[6-(9-anthryloxy)hexyl methacrylate] (PAn) was prepared and the effect of oxygen on its photochemical reaction was studied by UV and IR absorption spectroscopy in order to understand its photochemical behavior. Photochemical reaction of the PAn in THF solution under an atmosphere of air resulted in the formation of endoperoxide at the beginning stage of reaction followed by photodimerization reaction after all the oxygen was consumed, whereas photodimerization and endoperoxide formation took place concomitantly in the film state. The photoreversible reaction of the anthracene photodimer groups in the polymer by photolysis with 254 nm UV light was not efficient. The IR absorption spectral changes of the PAn film upon irradiation indicate that various photooxidation products were produced in the atmosphere of air.