• 공업화학
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• 제9권4호
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• pp.561-564
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• 1998

Stockmayer 분자 모델을 도입하여 linear spheroidal 형태의 $C_2H_4$ 기체분자를 사중극자 (quadrupole)분자로 단순화하여 $C_2H_4$ 기체의 동경분포함수 (radial distribution function)를 계산하였다. 또한 이렇게 얻어진 동경분포함수의 신뢰도를 조사하기 위해 여러 온도에서의 밀도 변화에 따른 $C_2H_4$ 기체의 압력을 계산하여 문헌에 알려진 실험치와 비교하였다. 계산에 사용된 온도는 50,100, 그리고 $150^{\circ}C$ 이었으며 조사된 밀도의 범위에 최대 약 $0.02/{\AA}^3$ (최대 압력 = 1500 atm)까지이다. 동경분포함수는 Baker와 Henderson의 섭동이론을 응용하여 Yoon, Hacura, 그리고 Baglin (YHB)에 의해 얻어진 동경분포함수의 형식을 사용하여 컴퓨터로 계산 하였으며 계산 결과는 최대 ${\pm}5%$의 오차범위내에서 실험치와 일치하였다. 이는 YHB 동경분포함수를 사용하여 압력과 같은 밀도변화에 민감한 각종 물리량을 충분히 정확하게 예측할 수 있다는 것을 나타낸다.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1703-1705
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• 2014

Bubble column reactors are considered the reactor of choice for numerous applications including oxidation, hydrogenation, waste water treatment, and Fischer-Tropsch (FT) synthesis. They are widely used in a variety of industrial applications for carrying out gas-liquid and gas-liquid-solid reactions. In this paper, the computational fluid dynamics (CFD) model is used for predicting the gas holdup and its distribution along radial and axial direction are presented. Gas holdup increases linearly with increase in gas velocity. Gas bubbles tends to concentrate more towards the center of the column and follows a wavy path.

• Bulletin of the Korean Chemical Society
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• 제19권11호
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• pp.1172-1174
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• 1998

Spatial(radial and height) distributions of excited argon species are measured for an inductively coupled plasma under five operating conditions: 1) no carrier gas, 2) carrier gas without aerosol, 3) carrier gas with desolvated aerosol, 4) carrier gas with aerosol, 5) carrier gas with aerosol and excess lithium. A complete RF power mapping of argon excited states is obtained. The excited states of argon for a typical analytical torch rapidly diffuse towards the center in the higher region of the plasma. The presence of excess lithium makes no significant change in the excited states of argon. The increase in the RF power increases the intensity of argon excited states uniformly across the radial coordinate.

• 공업화학
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• 제10권3호
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• pp.456-460
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• 1999

Stockmayer 분자 모델을 도입하여 선형분자인 CO분자를 쌍극자 분자로 단순화하여 CO 기체의 YHB 동경분포함수 (radial distribution function)를 컴퓨터로 계산하였다. 얻어진 CO 분자의 YHB 동경분포함수의 신뢰도는 여러 온도에서의 밀도 변화에 따른 CO 기체의 압력을 계산하여 조사하였다. 계산된 압력들은 문헌에 알려진 CO기체의 압력과 잘 일치하였으며 계산에 사용된 온도는 273, 298, 373 K, 그리고 조사한 밀도의 범위는 최대 약 $0.013/{\AA}^3$ (최대 압력 = 1000 atm)까지이다. 계산된 압력들이 문헌에 나타난 실험치와 잘 일치하는 것으로 나타났으므로 구해진 YHB 동정분포함수는 CO 분자의 압력과 같은 밀도변화에 민감한 각종 물리 화학적 평형 양들을 신뢰성있게 계산 및 예측할 수 있을 것으로 기대된다. 또한 이 연구에서 CO 기체의 dipole-dipole 상호작용은 약 2.5 분자직경까지 효과적으로 작용하는 것으로 나타났다.

• 대한화학회지
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• 제30권3호
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• pp.327-332
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• 1986

유도결합 플라스마 공간내의 전자밀도를 측정하였다. 전자밀도의 측정시 유도결합 플라스마의 작동조건은, (1) 냉각기체만 사용할 때, (2) 냉각기체와 운반기체만을 사용할 때, (3) 보통의 작동조건은, 즉 에아로졸을 포함한 운반기체를 사용할 때, (4) 약 88%의 에아로졸을 제거시켰을 때, 그리고 (5) 과량의 리튬을 주입시켰을 때로서 분류하였다. 보통의 작동조건에서 플라스마의 낮은 부분에서는 전자밀도가 상당히 감소하여 플라스마내의 가장 전자밀도가 큰 곳보다 약 80배 감소하였다. 이온화 방해영향을 일으키는 알칼리금속을 과량으로 넣었을 때 전자밀도의 변화는 관찰되지 않았고 유도코일의 power를 증가시키면 전자밀도도 증가하였다.

• 한국조명전기설비학회지:조명전기설비
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• 제7권2호
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• pp.31-35
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• 1993

본 논문은 t은과 10[torr]의 희유기체의 혼합기체 중에서 심하게 변조된 저압기체방전의 양광주의 반경방향 압자분포를 이론적으로 연구하였다. 전류는 깊이 50[%[로 정현파로 변조되었다. 계산결과 여기 원자의 반경방향 분포는 0차 Bessel 함수 $J_0(2.4r/R)$와 다르고 분포의 반전이 나타나는 주파수 대역도 있었다. 연립미분방정식을 풀기 위하여 FDM과 2계 Runge-Kutta method의 혼합법을 사용하였다.

• Journal of Welding and Joining
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• 제27권2호
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• pp.44-50
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• 2009

The characteristics of arc pressure, current density and heat flux distribution are important factors in understanding physical arc phenomena, which will have a marked effect on the penetration, size and shape of a weld in TIG welding. The purpose of this study is to find out the effect of the heat flux on the melting efficiency and penetration shape in TIG welding using the results of the previous investigators. The conclusions obtained permit to draw a proper method which derived the heat flux distributions by arc pressure distribution measurements, but previous researchers calculated heat flux and current distribution with the heat intensity measurements by the calorimetry. Heat flux of Ar gas arc was concentrated at the central part and distributed low from the arc axis to the radial direction, that of He mixing arc was lower than that of Ar gas, and it was wide distributed to radial direction. That showed a similar characteristic with the Nestor's by calorimetry calculated values. Throughout heat flux drawn in this study was discussed melting efficiency and penetration shape on Ar gas and He mixing gas arc.

• 천문학회지
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• 제29권1호
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• pp.63-73
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• 1996

The previous study of chemical evolution of the Galaxy is extended to the radial properties of the Galactic disk. The present model includes radial dependency of the time-dependent bimodal IMF, radial flow of material in the disk, and the change of type I supernova explosion rate with radial distance from the disk center as model parameters and observed gas and stellar density distributions and metallicity abundance gradient as observational constraints. The results of two models in this study explain the observed gas and stellar density distributions well, with the slope of the gas density gradient in the region of 4.5 kpc$Y_1$ and -0.123dex/kpc in model $Y_2$, respectively, which fit well the observed gradient of -0.l1dex/kpc. The abundance gradient reproduced in model $Y_1$ is getting flatter with decreasing radius, while that in model $Y_2$ is getting steeper, which fits better the observed abundance gradient. This result shows the necessity of exponentially increasing type I supernova explosion rate with decreasing radius in order to explain the observed abundance gradient in the disk. The fitness of observed density distribution and star formation rate distribution justifies the reliability of time-dependent bimodal IMF as a compound quantitative chemical evolution model of the Galaxy. The temporal variations of metallicity gradients for carbon, nitrogen and oxygen are also shown.

• Bulletin of the Korean Chemical Society
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• 제20권10호
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• pp.1209-1212
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• 1999

The entropies and chemical potentials of hard-sphere solutes solvated in hard-sphere solids were calculated by Monte Carlo method using the radial free-space distribution function. This method is based on calculating the entropy by comparing the free volume of a molecule with that of an ideal gas, and is applicable even when the size of solute is very large and the solvent is a solid. When the diameter of hard-sphere solute is small the solute molecule behaves as like as a fluid in solid structures, but when the diameter of solute becomes large, a fluid-to-solid phase transition takes place. The fluid-to-solid phase transition occurs at the region of the smaller size of solute with the more increase of solvent density. The least square fit values of analytical form of the radial free-space distribution functions of solute molecules are presented for future uses.

• 산업기술연구
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• 제22권A호
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• pp.9-17
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• 2002

This analysis is aimed to find out how the conditions of secondary air injection affects the residence time and the turbulence energy of flue gas and flow field in a small incinerator. A commercial code, PHOENICS, is used to simulate the flow field of an Incinerator. The computational grid system is constructed in a cartesian coordinate system In this numerical experiment, an independent numerical variable is the conditions of secondary air injection and dependants are the residence time of flue gas and the mean value of turbulence energy in a primary combustion chamber. The flow field and the distribution of turbulence energy are analysed to evaluate the residence time of flue gas and the turbulence energy The computational results say that the tangential injection of secondary air make the residence time much longer than the radial injection and that the radial injection of secondary make turbulence much stronger than the tangential injection.