• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.49-56
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• 1999

A material was formulated with Phenol novolac and HEXA only. The cure kinetics and thermal characteristics of phenol novolac with various HEXA contents were peformed by differential scanning calorimetry and thermal gravimetric analysis. All kinetic parameters of the curing reaction including the reaction order, activation energy, and rate constant were calculated and reported. The results indicate that the curing reaction goes through an autocatalytic kinetic mechanism. The friction and wear characteristics of this material were determined using friction material testing machine. The friction coefficient of phenol novolac with various HEXA contents was determined using the PV(pressure & velocity) factor. The most stable and highest friction coefficient with a various pressure and velocity condition was found at HEXA 10 wt.% material. The specific wear rate per unit sliding distance with a various HEXA contents was reported.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.145-148
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• 2003

The batch experiments showed that 0.515mM 4-chlorophenol and its oxidation intermediates could be totally decomposed within 60 minutes by 1g/L steelers' dust and 0.485mM hydrogen peroxide at pH 2.7. The rate constants in the simplified kinetic model proposed in this study were estimated by fitting to the experimental data obtained in $H_2O$$_2$/steelers' dust system. Using the estimated kinetic rate constants, the simulation of 4-chlorophenol, ferrous iron, hydrogen peroxide, and hydroxyl radical concentration was performed. The predicted concentrations of 4-chlorophenol and hydrogen peroxide corresponded to the actual concentrations.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.E3
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• pp.117-124
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• 2001

The present paper examined the kinetics of photocatalytic degradation of volatile organic compounds (VOCs) including gaseous trichloroethylene (TCE) and acetone. In this study, we examined the effects of the initial concentration of VOCs and the light intensity of ultra-violet (UV). A batch photo-reactor was specifically designed for this work. The photocatalytic degradation rate increased with the initial concentration of VOCs but remained almost constant beyond a certain concentration. It matched well with the Langmuir-Hinshelwood (L-H) kinetic model. When the effect of light intensity was concerned, it was found that photocatalytic degradation occurs in two regimes with respect to light intensity.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.91-94
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• 2003

Kinetic studies of the reaction of O-methyl-S-phenylthiocarbonates with benzylamines in methanol at 45.0 ℃ have been carried out. The reaction proceeds by a stepwise mechanism in which the rate-determining step is the breakdown of the zwitterionic tetrahedral intermediate, $T^{\pm}$, with a hydrogen-bonded four-center type transition state (TS). These mechanistic conclusions are drawn based on (ⅰ) the large magnitude of ${\rho}_X\;and\;{\rho}_Z$, (ⅱ) the normal kinetic isotope effects $(k_H/k_D\;>\;1.0)$ involving deuterated benzylamine nucleophiles, (ⅲ) the positive sign of ${\rho}_{XZ}$ and the larger magnitude of ${\rho}_{XZ}$ than that for normal $S_N2$ processes, and lastly (ⅳ) adherence to the reactivity-selectivity principle (RSP) in all cases.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.137-140
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• 2011

The aminolysis reactions of phenyl N-benzyl thiocarbamate with benzylamines in acetonitrile at $50.0^{\circ}C$ are investigated. The reactions are first order in both the amine and the substrate. Under amine excess, pseudo-first coefficient ($k_{obs}$) are obtained, plot of $k_{obs}$ vs free amine concentration are linear. The signs of ${\rho}_{XZ}$ (< 0) are consistent with concerted mechanism. Moreover, the variations of $\rho_X$ and $\rho_Z$ with respect to the sustituent in the substrate and large ${\rho}_{XZ}$ value indicate that the reactions proceed concerted mechanism. The normal kinetic isotope effects ($k_H/k_D$ = 1.3 ~ 1.5) involving deuterated benzylamine nucleophiles suggest a hydrogen-bonded, four-centered-type transition state. The activation parameters, ${\Delta}H^\ddagger$ and ${\Delta}S^\ddagger$, are consistent with this transition state structure.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.827-831
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• 1995

Kinetic studies on the reactions of five secondary acylic alkyl arenesulfonates with anilines are carried out in acetonitrile at 65.0 ℃. The magnitude of ρXZ determined (ρXZ=0.12-0.13) is slightly greater than that for the alicyclic series (ρXZ=0.11) under the same experimental condition. Ab initio MO results are found to support the slightly tighter transition state expected from the greater magnitude of ρXZ for the acyclic series. Despite the small variations, the magnitude of ρXZ and the theoretical transition state tightness remain relatively constant for the secondary carbon centers. Secondary kinetic isotope effects involving deuterated aniline nucleophiles show a successively smaller kH/kD(<1.0) value for a more sterically crowded reaction center carbon. This is in accord with the later transition state for bond-making predicted by the Bell-Evans-Polanyi principle for the more endothermic nucleophilic substitution reaction. Further support is provided by the results of the AM1 MO calculations on the reactions of secondary alkyl benzenesulfonates with chloride nucleophile.

• Bulletin of the Korean Chemical Society
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• v.15 no.6
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• pp.502-506
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• 1994

The results of kinetic studies on the reactions of 2-phenyl-l-propyl arenesulfonates with anilines and benzylamines in methanol at $55.0^{\circ}C$ are reported. The transition state variation with the substituents in the nucleophile (X) and leaving group (Z) is in accord with that expected from a negative ${\sigma}_{XZ}$ value. A stronger nucleophile and nucleofuge lead to a greater extent of bond-making and -breaking. Somewhat greater magnitude of ${\sigma}_{XZ}$ compared to the nearly constant value for the similar processes at a primary carbon atom has been interpreted to result from a partial contribution of the concurrent frontal displacement path.

• Food Engineering Progress
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• v.13 no.1
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• pp.70-73
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• 2009

The yield stress of stirred yogurt was measured by the vane viscometer at different pre-shearing conditions, such as pre-shear speed, pre-shear time, and wait time, and temperature (12-38${^{\circ}C}$). The yield stress ranged from ~17.6 to 10 Pa and from 34.2 to 11.9 Pa, depending on the pre-shearing conditions and temperature, respectively. The preshear speed and the wait time significantly affected the yield stress. The temperature dependence of the yield stress was described by the Eyring's kinetic model. The linear function of the temperature on the yield stress was limited at the 22${^{\circ}C}$, and at the above 22${^{\circ}C}$, the yield stress was maintained to be a constant (~12.5 Pa).

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.11-19
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• 2000

In order to predict the performance of biological wastewater treatment plant, the kinetic parameters and stoichiometric coefficient must be known. The theories and experimental procedures for determining the biological kinetic parameters were discussed in this study. Respirometric analysis in the batch reactor was carried out for the experimental assessment of kinetic parameters. A simple procedure to estimate kinetic parameters of heterotrophs and autotrophs under aerobic condition was presented. The difficulties in the interpretation of COD and VSS measurements encouraged the conversion of respirometric data to growth data. Maximum specific growth rate, yield coefficient, half saturation constant and decay rate of heterotrophic biomass were obtained from OUR(Oxygen Uptake Rate) data. Maximum specific growth rate of autotrophic biomass was obtained from the increase of nitrate concentration. The aim of this paper is to estimate the kinetic parameters of heterotrophic and autotrophic biomass by means of the respirometric analysis of activated sludge behavior in the batch reactors. These procedures may be used for the activated sludge modeling with complex kinetic parameters.

• Journal of Environmental Science International
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• v.1 no.2
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• pp.59-69
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• 1992

In order to predict the distribution of chemical species of copper and cadmium in water, conditional stability constant and complexation capacity between copper or cadmium and natural aquatic sediment have been determined in a shallow lake in Haman, Kyungnam. Kinetic parameters were calculated by Langmuir isotherm equation. Conditional stability constant was log $K_{cuSed}=4.78 and log K_{cdSed}=4.45$. Complexation capacity was $1.70{\times}10^{-4}$moles/g for copper and $5.54{\times}10^{-5}$moles/g for cadmium. Accuracy of experimental values of conditional stability constant was checked by comparing the calculated concentration of the metals with the measured one. Relatively good agreement between these values was obtained. Relative errors were 8.9% for copper and 6.5% for cadmium. Data of the measured conditional stability constant were put into data base of MINEQL computer program, and concentration of various chemical species of copper and cadmium in a model aquatic system was calculated. Aquatic sediment was associated with copper at the concentration of $10^{-5M}(0.059g/\ell)$10-5M(0.059g/l) and with cadmium at the concentration of $10^{-6M}(0.018g/\ell)$, and it significantly influenced on the distribution of chemical species of the metals. This result showed that prediction of chemical species of the heavy metals in an aquatic system should be taken into account the influence of the sediment.