• Bulletin of the Korean Chemical Society
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• 제29권5호
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• pp.1051-1054
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• 2008

The entropy production in a non-equilibrium state based on the reversible Oregonator model of the Belousov-Zhabotinskii (BZ) reaction system has been studied. The reaction affinity and the reaction rate for the individual steps have been calculated by varying the concentrations of key variables in the system. The result shows a linear relationship between the reaction affinity and the reaction rate in the given concentration range. However, the overall entropy calculated on the basic assumption that the entropy in a reaction system corresponds to the summation of a product of reaction affinity and reaction rate of individual steps shows a nonlinearity of the reaction system. The results well agrees with the fact that the entropy production is not linear or complicated function in a non-linear reaction system.

• 통상정보연구
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• 제10권1호
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• pp.329-347
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• 2008

The purpose of this study is to examine the causal relationship between the exchange rate and economic growth, and to induce policy implications. In order to test whether time series data is stationary and the model is fitness or not, we put in operation unit root test, cointegration test. And we apply Granger causality based on an error correction model. The results indicate that uni-dierctional causality between exchange rate and economic growth is detected. Exchange rate impacts on economic growth, but economic growth don't impact on exchange rate. The analysis of impulse reaction function shows that the impulse of exchange rate impacts on Korean economic growth in negative direction. We can infer policy suggestion as follows: The fluctuation of exchange rate much affects economic growth, thus we must make a stable policy of exchange rate to continue economic growth.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.243-245
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• 2013

Rate equations are exactly solved for the reversible consecutive reaction of the first-order and the time-dependence of concentrations is analytically determined for species in the reaction. With the assumption of pseudo first-order reaction, the calculation applies and determines the concentration of product accurately and explicitly as a function of time in the unimolecular decomposition of Lindemann and in the enzyme catalysis of Michaelis-Menten whose rate laws have been approximated in terms of reactant concentrations by the steady-state approximation.

• 한국환경과학회지
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• 제8권2호
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• pp.241-248
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• 1999

The photocatalytic decolorization and photodegradation of wastewater contamininated with dyes such as methyleneblue tetrahydrate(MBT), methyl orange(MO), phenol red(PR) and the mixed dyes have been studied using a batch reactor in the presence of aerotropic and titania. Degussa P25 titanium oxide was used as the photocatalyst and proved to be effective for the dyes-degradation when irradiated with UV-light source emitting the wavelength of 253.7 nm in the presence of air. In addition to removing the color from the wastewater, the photocatalytic reaction simultaneously reduced the COD and optical density which suggests that the dissolved organic compounds have been photooxidized. The reaction rate of disappearance of the dyes were measured as a function of the irradiation times. The photooxidative procedure of the aquatic solution have the first order reaction-kinetics. The rate constants were increased in the order of PR < MBT < $gL^{-1}-TiO_2$ powder were irradiated with the UV -light source.

• Nuclear Engineering and Technology
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• 제31권2호
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• pp.133-138
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• 1999

Research on the etching reaction of UO$_2$ with CF$_4$/O$_2$gas mixture plasma is carried out. The reaction rates are investigated as a function of CF$_4$/O$_2$ ratio, plasma power, and substrate temperature. It is found that there exists an optimum CF$_4$/O$_2$ ratio around 4:1 at all temperatures up to 37$0^{\circ}C$ and surface analysis using XPS X-ray Photoelectron Spectroscopy) confirms the result. Peak rate at the optimum gas composition increases with increasing temperature. Highest rate obtained in this study leaches 1050 monolayers/min. at 37$0^{\circ}C$ under r. f. power of 150 W, which is equivalent to about 0.5${\mu}{\textrm}{m}$/min. The rate also increases with increasing r. f. power, thus, higher power and higher substrate temperature will undoubtedly raise the etching reaction rate much further. This reaction seems to be an activated process, whose activation energy will be derived in the following experiments.

• Elastomers and Composites
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• 제50권2호
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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.

• 한국주조공학회지
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• 제33권4호
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• pp.162-170
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• 2013

The effects of Mn content and cooling rate on the eutectic reaction of flake graphite cast irons were studied by a combined analysis of macro/micro-structure and cooling curve data. The correlation between the eutectic reaction parameter and macro/microstructure was systematically investigated. Two sets of chemical compositions with different Mn contents were designed to cast. Three types of molds for cylindrical specimens with different diameters were prepared to analyze the cooling rate effect. The difference between undercooling temperature and cementite eutectic temperature (${\Delta}T_1=T_U-T_{E,C}$), which is decreased by increasing the Mn content or increasing the cooling rate, is considered to be a suitable eutectic reaction parameter for predicting graphite morphology. According to the criterion, A-type graphite is mainly suggested to form for ${\Delta}T_1$ over $20^{\circ}C$, and D-type graphite is mainly suggested to form for ${\Delta}T_1$ below $0^{\circ}C$. Eutectic reaction time (${\Delta}T$), which is increased by increasing the Mn content and decreased by increasing the cooling rate, is regarded as a suitable eutectic reaction parameter for predicting eutectic cell size. Eutectic cell size is found to decrease in proportion to the decrease of ${\Delta}T$.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2004년도 추계학술대회
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• pp.280-283
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• 2004

Effect of H2 spillover rate as function of reduction temperature on reaction kinetics was evaluated. Reaction kinetics including yield, conversion, activation energy and selectivity of 1-butene isomerization over Pt/HxMoO/SiO were measured as reaction temperature was increased. While conversion of 1-butane was decreased, yield of iso-butene was increased. Two kinds of reaction mechanism were proposed from the change of selectivity as function of temperature.

• 한국연소학회지
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• 제16권3호
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• pp.1-11
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• 2011

The main objective of this paper is to investigate characteristic of steam reformer at various geometries and operating conditions. In this paper, the steam reforming is studied by a numerical method and three dimensional simulations were used for effective analytical study. User - Defined Function (UDF) was used to simultaneously calculate reforming and combustion reaction. And the numerical model is validated with experimental results at the same operating conditions. In order to understand the relationship between operating conditions such as gas hourly space velocity(GHSV), mass flow rate of combustor inlet, various numerical investigations are carries out for various geometries. Numerical results show that cylindrical geometry is more effective than rectangular geometry for heat transfer to reactors and reforming efficiency. As mass flow rate of combustor inlet increase, reaction occurs more faster and temperature increase with each geometry. On the other hand, reaction and hydrogen conversion decrease as mass flow rate of reactor decreases.

• 한국인쇄학회지
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• 제20권1호
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• pp.45-53
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• 2002

The removal of chelated copper from anthraquinone dyes by cementation on powdered iron was studied. The removal of chelated copper was found to be a function of solution pH, amount of NTA and iron, and reaction temperature. In the presence of NTA, reaction rate of cementation was found to be strongly dependent on reaction temperature, solution pH, amount of NTA and amount of iron powder. These experimental results can be explained successfully by the distribution of complexed copper iron in solutions.