• 한국자동차공학회논문집
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• 제7권5호
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• pp.107-120
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• 1999

Catalytic converters are the most fascinating and complicated chemical reactors. They are most often operated in the transient state with respect to composition, flow rate, temperature, etc. The mathermatical model developed in this work accounts for simultaneous heat and mass transfer, chemical reaction, and multi dimensional flow characteristics to analyze the light-off performance of monolithic catalytic converter with comparable mass flow rate. To validate the mathematical model, comparison between experimental and numerical results has been performed. The numerical results show a good agreement with experimental data. It is forund that inflow rate shows major effect on the characteristics of termal response of catalytic converter.

• 한국자동차공학회논문집
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• 제12권5호
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• pp.79-84
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• 2004

We evaluated the reduction performance of NOx storage catalyst and TWC for lean-burn natural gas engine by the model gas. The method of unsteady state reaction was used to compare with reduction performances of NOx storage catalyst and TWC. It was found that the effective parameter was rich spike duration, temperature of the model gas. In the presence of $CO_2$ and $H_2O$ in the reaction mixture was decreased the NOx reduction performance.

• 한국자동차공학회논문집
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• 제5권1호
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• pp.101-109
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• 1997

A tool for the dynamic simulation and design technique of the excavator plays an important role in the prediction of dynamic behavior of the excavator in the initial design stage. In this paper, a flexible multibody dynamic analysis model including track of the crawler type excavator is developed using DADS and ANSYS. Through the driving simulation of the excavator travelling over rough road track, frequency characteristics of the upper frame and cabin are obtained, and the reaction forces acting on the track rollers are also presented for the fatigue life estimation. The effect of boom vibration modes on the joint reaction forces and accelerations is presented from the swing simulation.

• 한국세라믹학회지
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• 제32권11호
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• pp.1246-1254
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• 1995

A numerical model for fabrication and deposition of ultrafine SiO2 particles were proposed in the simplified horizontal MCVD apparatus using tube furnace reactor. The model equations such as energy and mass balance equations and the 0th, 1st and 2nd moment balance equations of aerosols were considered in the reactor. The phenomena of SiCl4 chemical reaction, SiO2 particle formation and coagulation, diffusion and thermophoresis of SiO2 particles were included in the aerosol dynamic equation. The profiles of gas temperature, SiCl4 concentration and SiO2 particle volume were calculated for standard conditions. The concentrations, sizes and deposition efficiencies of SiO2 particles were calculated, changing the process conditions such as tube furnace setting temperature, total gas flow rate and inlet SiCl4 concentration.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1145-1152
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• 2013

The rate constant of alkaline fading of methyl green ($ME^{2+}$) was measured in the presence of non ionic (TX-100), cationic (DTAB) and anionic (SDS) surfactants. $ME^{2+}$ hydrolyses and fades in neutral water and in this work we search the effects of surfactants on its fading rate. The rate of reaction showed remarkable dependence on the electrical charge of the used surfactants. It was observed that the reaction rate constant decreased in the presence of DTAB and SDS and increased in the presence of TX-100. Binding constants of $ME^{2+}$ to TX-100, DTAB and SDS and the related thermodynamic parameters were obtained by classical (or stoichiometric) model. The results show that binding of $ME^{2+}$ to TX-100 and DTAB are two-region and that of SDS is three-region. Also, the binding constants of $ME^{2+}$ to surfactant molecules in DTAB/TX-100 and SDS/TX-100 mixed solutions and their stoichiometric ratios were obtained.

• 한국응용과학기술학회지
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• 제20권2호
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• pp.154-164
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• 2003

This paper has applied a simple model to the mass transfer mechanism of Cr(VI) with crownether in a batch-type, supported liquid membrane module. Concentration at pH 3 are as follows : 0.012 kmol/$m^3{\le}$18-crown-6${\le}$0.036 kmol/$m^3$ and 20 g/$m^3{\le}$ Cr(VI)${\le}$500 g/$m^3$. The measured values of forward- and backward-reaction rate constants between Cr(VI) and 18-crown-6 were used to simulate the model with the mass conservation equation and associated boundary conditions. Comparison between the experimental and simulated facilitated factor of Cr(VI) transport led to classification of reaction regions.

• Archives of Pharmacal Research
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• 제18권6호
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• pp.376-380
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• 1995

Monocyte adhesion involves specific cell surface receptors, integrins and results in cell differentiation. We have studied expression and regulation of integrin .${\alpha}_5{\beta}_1$ during differntiation of U937 as in vitro model. To determine expression of integrin ${\alpha}_5{\beta}_1$ during differentiation of U937 as in vitro model. To determine expression of integrin ${\alpha}_5{\beta}_1$ genes by RT-PCR (reverse transcription and polymerase chain reaction) method. We determined expression of integrin ${\alpha}_5{\beta}_1$ genes by RT-PCE (reverse transcription and polymerase chain reaction) method. We found that expression of integrin .alpha.5.betha.1 was greatly increased during PMA-induced differentiation of U937 cells and also found that PMA-induced expression of integrin ${\alpha}_5{\beta}_1$ was inhibited by colchicine, microtubule depoly merizing agent. These results indicate that microtubular integrity is associated with expression of integrin. ${\alpha}_5{\beta}_1$ during PMA-induced differentiation of U937 cells.

• KCI Concrete Journal
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• 제11권3호
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• pp.175-180
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• 1999

In order to predict the onset of the corrosion of steel bars in concrete, a mathematical model was presented to observe the diffusion of chloride ion in aqueous phase, the adsorption and desorption of chloride ions to and from the surface of solid phase of concrete, and the chemical reaction or chloride ions with solid phase. The finite element method was employed to carry out the numerical analysis. The chlorides enetrating through the wall of the concrete structure from the external environment and the chlorides contained in the concrete admixture were confirmed to be two important factors to determine the onset of the corrosion of steel bars.

• Bulletin of the Korean Chemical Society
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• 제21권7호
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• pp.701-704
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• 2000

Fluorene and carbazole-containing distyrylarylene model and polymeric fluorophores were prepared by reacting 2,7-dibromo-9-butylfluorene and 3,6-dibromo-9-butylcarbazole with styrene and divinylbenzene using the Heck reaction for the chemiluminesc ence. The UV-vis absorbance, photoluminescence (PL) as well as the chemiluminescence (CL) characteristics of the model and polymeric fluorophores were measured. Sodium salicylate-catalyzed reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide produced a strong chemiluminescent blue light emission with 439-489 nm in the presence of the fluorophore. The wave-length of CL light was similar to that of photoluminescence. The chemiluminescent intensity was decayed according to the exponential equation.The glow of CL maintained more than 12 hr and was visible with naked eye.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.316-320
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• 2008

A light rail transit, using a linear induction motor, is generally composed with reaction plates along railroad track and the three phase primary on the vehicle. This linear induction motor is driven to keep clearance between the primary and the secondary of the ground for preventing any contact. Therefore efficiency and power factor is very low. In addition, the reaction plate installed on the ground throughout entire railway is impossible to keep uniform gap and it may cause system deterioration. In this paper, A rotary-type small-scale model of a linear induction motor for various characteristic analysis is designed. Thrust force, normal force and input current of the model by air-gap variation have been analyzed by using a Finite Element Method (FEM). The effects of air-gap variation on system performance have been considered by analysis results.