• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.3
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• pp.210-222
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• 1994

The characteristics of flows, temperatures, and concentrations of oxygen are numerically studies in the Czochralski furnace with a uniform axial magnetic field. Important governing factors to the flow fields include buoyancy, thermocapillarity, centrifugal force, magnetic force, diffusion and segregation coefficients of the oxygen, evaporation coefficient in the form of SiO, and ablation rate of crucible wall. With an assumption that the flow fields have reached the steady state, which means that two velocity components in the meridional plane and circumferential velocity, temperatures, electric current intensity become non-transient, then unsteady concentration field of oxygen has been analyzed with an initially uniform oxygen concentration. Oxygen transports due to convection and diffusion in the Czochralski flow field and oxygen flux through the growing crystal surface has been investigated.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.6
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• pp.17-26
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• 1984

A computer program (DIFSIM: Diffusion SIMulator) was written to calculate the impurity profile, specifically boron and phosphorus, due to three different diffusion processes-predeposition, drive-in in inert ambient, and drive-in in oxidizing ambient. The vacancy mechanism including Fair and Tsai's theory for phosphDrus diffusion was widely incorporated for modeling various diffusion processes. The concentrationtependent oxidation rate was also explained using the vacancy model, while the oxidation - enhanced diffusion was mo dolled using catkins replacement mochanlsm . The simulation results using DIFSIM showed a fairly good agreement with the experimental data by adjusting some of the empirical parameters in the program. The results obtained using DIFSIM were compared with the results from SUPREM II.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.9
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• pp.1174-1184
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• 1997

Extinction characteristics of pure hydrogen-oxygen diffusion flames, at high pressures in the neighborhood of the critical pressure of oxygen, is numerically studied by employing counterflow diffusion flame as a model flame let in turbulent flames in rocket engines. The numerical results show that extinction strain rate increases almost linearly with pressure up to 100 atm, which can be explained by comparison of the chain-branching-reaction rate with the recombination-reaction rate. Since contributions of the chain-branching reactions, two-body reactions, are found to be much greater than those of the recombination reactions, three-body reactions, extinction is controlled by two-body reactions, thereby resulting in the linearity of extinction strain rate to pressure. Therefore, it is found that the chemical kinetic behaviors don't change up to 100 atm. Consideration of the pressure fall-off reactions shows a slight increase in extinction strain rate, but does not modify its linearity to pressure. The reduced kinetic mechanisms, which were verified at low pressures, are found to be still valid at high pressures and show good qualitative agreement in prediction of extinction strain rates. Effect of real gas is negligible on chemical kinetic behaviors of the flames.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.11
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• pp.1422-1436
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• 1997

Numerical investigations were conducted to study the convective phenomena of an initially stably stratified salt water solution with lateral heating in a uniformly rotating annulus. The method of investigation is the finite difference analysis of the basic conservation equation for an axisymmetric, unsteady, double-diffusive convection and calculation is made for R $a_{\eta}$=2*10$^{5}$ and Ta=10$^{7}$ ~ 2.5*10$^{8}$ . Formation of layered flow structure, merging process of layers, the corresponding temperature and concentration distributions, Nu variation with time are examined. Numerical results show that in each layer, the temperature profile looks 'S'-shaped and the concentration profile is uniform due to the convective mixing. At the interface between adjacent layers, the temperature changes smoothly but the concentration changes rapidly. As the effect of the rotation increases, the generation of rolls at hot wall, the formation and merging of layers are delayed. The average Nu shows the trend of conduction heat transferees the effect of the rotation increases.n increases.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.11
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• pp.1527-1537
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• 1997

Extinction characteristics and acoustic response of hydrogen-air diffusion flames at various pressures are numerically studied by employing counterflow diffusion flame as a model flamelet in turbulent flames in combustion chambers. The numerical results show that extinction strain rate increases linearly with pressure and then decreases, and increases again at high pressures. Thus, flames are classified into three pressure regimes. Such nonmonotonic behavior is caused by the change in chemical kinetic behavior as pressure rises. The investigation of acoustic-pressure response in each regime, for better understanding of combustion instability, shows different characteristics depending on pressure. At low pressures, pressure-rise causes the increase in flame temperature and chain branching/recombination reaction rates, resulting in increased heat release. Therefore, amplification in pressure oscillation is predicted. Similar phenomena are predicted at high pressures. At moderate pressures, weak amplification is predicted since flame temperature and chain branching reaction rate decreases as pressure rises. This acoustic response can be predicted properly only with detailed chemistry or proper reduced chemistry.

• Journal of Technologic Dentistry
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• v.39 no.4
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• pp.253-259
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• 2017

목적: 이 실험의 목적은 한국 백삼과 캐나다 백삼의 일반 성분 분석, 항산화력 측정 및 치아 우식 유발균에 미치는 항균 효과를 비교 분석하는데 있다. 방법: 한국 백삼과 캐나다 백삼의 일반 성분은 수분정량, 조지방, 조단백질, 그리고 조회분의 분야에서 측정되었다. 두 백삼을 60% 에탄올에 추출시켜 환원당과 DPPH-scavenging assay를 통해 항산화력을 측정했다. 동일 추출물을 이용, 치아 우식균인 streptococcus mutans에 대해 디스크 확산법과 최소저해농도 측정을 실시해 항균력을 측정 및 비교했다. 결과: 실험 결과, 한국 백삼과 캐나다 백삼은 유사한 조지방, 조단백질, 조회분 성분을 갖고 있었으나 수분정량에서 캐나다백삼이 우세했다. 항산화력 실험에서는 캐나다 백삼이 DPPH- scavenging 능력에서 더 높았으나 환원당 실험과 총 페놀 함량에서는 한국 백삼의 수치가 더 높았다. 디스크 확산법을 통한 항균력 실험에서는 한국 백삼이 캐나다 백삼보다 더 넓은 clearing zone을 형성하고 더 낮은 최소저해농도를 달성해 항균력에서 우세했다. 결론: 한국 백삼과 캐나다 백삼은 비슷한 일반성분과 항산화력을 가졌다. 하지만 한국백삼이 치아 우식 유발균인 streptococcus mutans에 대한 항균력에서 더 우세했다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2712-2723
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• 1994

Numerical simulation of an axisymmetric ethylene-air jet diffusion flame has been carried out in order to investigate flame dynamics and soot formation. The model solves the time-dependent Navier-Stokes equations and includes models for soot formation, chemical reaction, molecular diffusion, thermal conduction, and radiation. Numerically FCT(Flux Corrected Transport) and DOM(Discrete Ordinate Method) methos are used for convection and radiation trasport respectively. Simulation was conducted for a 5 cm/sec fuel jet flowing into a coflowing air stream. The maximum flame temperature was found to be approximately 2100 K, and was located at an axial position of approximately 5 cm from the base of the flame. The maximum soot volume fraction was about $7{\times}10^{-7}$, and was located within the high temperature region where the fuel mole fraction ranges from 0.01 to 0.1. The buoyancy-driven low-frequency(12~13 Hz) structures convected along the outer region of the flame were captured. In case without radiation trasport, the maximum temperature was higher by 150 K than in case with radiation. Also the maximum soot volume fraction reached about $8{\times}10^{-6}$. As the the hydrocarbon fuel forms many soot particles, the radiation transport becomes to play a more important role.

• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.3
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• pp.23-27
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• 2002

Ocean pollution like as oil spill and red tide have occurred considerable and executing clean-up them. Rapid prediction of polluting area is necessary that efficiency clean-up. In this study, develop the program that clean-up worker could easy predict polluted area. This paper is introduced configuration and contents of ODM(oil diffusion modelling) which constructed with GUI(Graphic User Interface) system. ODM is consisted with pre, post and main process, and constructed on window process. So, clean-up worker easy operating program and confirm the result. Studying this program, the distribution of ocean pollutant and phase of ocean movement is shown without difficulty on a computer.

• Fire Science and Engineering
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• v.16 no.4
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• pp.7-14
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• 2002

The diffusion characteristics of the smoke by effect of an ascending air movement in a local part of the room where heat generated was studied. How the smoke move in the limited parts of the room at which heat generated was studied through 3 cases altering locations of inlet and outlet of ventilated air and heat generated by CFD(Computational Fluids Dynamics) method. It was found that 1. Similar distribution of air velocity, air temperature and smoke concentration appeared in the case of upper left inlet and lower right outlet and the case of lower inlet and upper right outlet. 2. Distribution of temperature and smoke concentration was 0∼0.3, 0.06∼0.14 in the case of lower left inlet and upper right outlet. 3. the location of heat generation did not influence on the temperature distribution, but influence on the distribution of smoke concentration.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.4
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• pp.200-207
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• 1990

This study is concerned with the meandering of plume axis in oceanic waters. The process is understood that it is a consequence of the differential contribution by the multiple harmonics of local velocity field to variances of center of mass of crossplume as a function of distance from the source point. A diagnostic model is proposed which is aimed to delineate the eddying motions and furthermore the amplified meandering of plumeaxis. From the data base of dye plumes, wave lengths of meandering eddies are estimated to range between 5.5 to 60.3 (m) in coastal surface waters. A numerical simulation is conducted to predict the concentration field of meandering plume.