• Membrane Journal
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• v.13 no.4
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• pp.268-282
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• 2003

Pervaporation-facilitated esterification with slow reaction regime was characterized by using a practical model based on non-perfect separation through membrane. A non-perfect separation in which the membrane is not perfectly permselective to water was applied to the model. Thus, membrane selectivity and membrane capability to remove water were included in the simulation model to explain how they influence the membrane-facilitated reaction process and improve the reactor performance. It was shown by simulation that in the reaction systems with non-perfect separation, reaction completion can hardly be achievable when any reactant at initial molar ratio=1 or the less abundant reactant at initial molar ratio>1 permeates through membrane, and the permeation of ester accelerates the forward reaction md increase reaction conversion at any instant through removal of product species like water. The volume change causes concentrating both reactants and products that affect the reaction with time in opposite ways; reactant-concentrating effect is dominant during the initial stage of reaction, increasing the reaction rate, and then concentrating product influences more reaction by decreasing the reaction rate.

• Membrane Journal
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• v.8 no.2
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• pp.86-93
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• 1998

A permeation apparatus has been devdoped which could make the on-line measurements of both flux and permeate composition. Pervaporative experiment of a single component, i.e. water was performed by using poly(vinyl alcohol) membrane crosslinked with glutaraldehyde to confirm the validity of the apparatus. In the experiment, steady-state permeation was obtained in 15 minutes and the measurement could be completed within 20 minutes. A comparison of the on-line measurement was made with the fluxes measured simultaneously by the conventional method in which the permeates were collected by liquid nitrogen. The on-line measurement by the apparatus showed an excellent agreement with the conventional measurement within a difference of $\pm$2%. From the flux data with operating time, 3 kinds of diffusion coefficients of water $D_{slope}, D_{1/2}$, and $D_t$ were determined, which were also coincident with values in a literature. It was confirmed that accurate measurements of fluxes could be obtained from the apparatus.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.8-8
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• 1998

액체 추진제를 사용하는 연소기관내의 연소 불안정 현상에 대하여 수치적인 해석을 수행하였다 비정상 다차원 다상 유동장에 대한 Eulerian-Lagrangian 방법에 기반을 두고 수학적으로 모델 하였으며 속도-압력-밀도에 대한 결합메커니즘은 개선된 PISO 알고리즘을 사용하여 처리하였다. 연소실의 기하학적 형상 및 추진제의 분무조건이 액체 연료 추진기관의 연소 불안정 현상에 미치는 영향을 체계적으로 해석하였으며 액체 추진제의 증발 특성이 연소 불안정 현상의 Driving Mechanism에 미치는 영향을 상세히 분석하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.04a
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• pp.12-13
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• 2007

OLED는 유기물을 이용한 진공 증발 증착법(Evaporation)에 의해 제조하고 있으며, 2세대 기판을 사용하고 있는 현재의 개념으로는 유기물 증착 효율이 수 %에 그치고 증착속도도 수 A/s로 상당히 낮다. OLED 제조의 생산성을 향상하기 위해서 증착속도로 10A/s이상, 제조 단가를 줄이기 위해 재료의 효율도 30% 이상으로 향상시킬 수 있었다.

• Journal of the Korean Wood Science and Technology
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• v.2 no.2
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• pp.5-7
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• 1974

1. This study indicates that above the fiber saturation point the drying rate can be increased with increasing the velocity of the air circutation, i.e., the drying rate of sample boards is proportional to the air velocity, but below the fiber saturation point, the effect of the velocity of air circulation is very low as shown in Figs. 1 and 2. 2. Under the controlled temperature and humidity in the kiln, the more the sample boards have moisture, the higher drying rate of it can be obtained. In other words, this means that even though in the case of drying various moisture content of wood, at the final drying stage, approximately the same percentage of moisture content of wood can be secured by employing the higher velocity of air circulation. 3. This study shows that the rate of drying in kiln changes distinctly at the fiber saturation point, i, e., above the fiber saturation point, the drying curve shows concave aginst the X axsis, but below the fiber saturation point, in the range from 30 percent of moisture content to 20 percent of moisture content, the curve shows convex as shown in Fig. 3. As the drying progresses, however, the drying curve shows concave again below 20 percent of moisture content. This means that inflection point of drying curve may be located clearly at the fiber saturation point, i.e., 30 percent of moisture content. As mentioned above, the 30 percent of moisture content of wood at which the inflectional point appears can be recognized as a critical point, i. e., the fiber saturation point at which all free water was removed from wood. The existence of inflectional point indicates that the evaporation of hygroscopic water in a cell wall is more difficult than the evaporation of free water in a cell cavity and the minor space of cell wall. The convex curve in the range of moisture content from 30 percent to 20 percent means that the evaporation of capillary condensed water has a tendency of the same rates of drying approximately, but as approaching to the 20 percent of moisture, the transfusion of moisture from wood becomes difficult because of having less moisture in cell wall. Below 20 percent of moisture content, the drying curve shows concave again, which means that it is difficult to remove the moisture located nearer to the surface of cellulose molecules and the surface bound water. These relations were revealed in Fig. 4. In comparison AC curve which does not have the two inflection points with BD curve which has two inflection points, i.e., Band D, they are mentioned already, by existence of the inflection points, the curve BD shows that the change of drying rate in the interval from 20 percent of moisture content to 30 percent of moisture content is not greater than in the case of the curve AC in the same interval. At the inflection point of 30 percent of moisture content, it can be noticed that the changing of the drying rate is very conspicuous. This phenomenon also can be recognized, as it is noticed by the Fig. 3, the drying rate from green to 30 percent of moisture content is very great. But the inclination of the curve is very slow from 30 percent of moisture content to 20 percent of moisture content, i.e., the inclination of the curve becomes almost horizontal lines. Acknowledgments Gratitude is expressed to Fred E. Dickinson, Professor of 'Wood Technology, School of Natural Resources, University of Michigan, USA for his suggestion to carry out this study.

• Proceedings of the KGS Conference
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• 2002.11a
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• pp.37-39
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• 2002

인간에 의한 바닷물 이용은 역사와 더불어 시작된 것이기에 새삼스러운 일은 아니다. 그렇게 생각하는 것은 자연계에서의 물 순환과정 속에 언제나 일어나는 해양환경의 증발현상이라고만 인식하고 있기 때문이다. 더구나 자연현상으로 생각해 해양수 이용이라는 생각을 안 할 뿐 이다. 물론 자연현상이므로 이용이라고 정의되지는 안는다. 육지의 담수를 공급 받기 어려운 상황에서는 해수를 담수화하여 이용하는 예는 일반화된 기술이다.(중략)

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2008.05a
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• pp.231-232
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• 2008

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.695-701
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• 2013

The suppression of a thermocapillary flow (Marangoni flow) by a nonionic surfactant is experimentally investigated for evaporating pure water droplets on hydrophobic substrates. The experiment shows that as the initial concentration of the surfactant increases, the velocity and lifetime of the flow monotonically decrease. The result confirms the no-slip boundary condition at a liquid-air interface, which is explained on the basis of the previous model regarding the effect of surfactants on the no-slip condition. Interestingly, at an initial concentration much less than a critical value, it is found that depinning of the contact line occurs during the early stage of evaporation, which is ascribed to a reduction in the contact angle hysteresis owing to the presence of the Marangoni flow.

• Korean Journal of Crystallography
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• v.3 no.2
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• pp.111-119
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• 1992

Alexandrite crystals were grown by the Czochralski method. Relationships between or ystal quality and crystal growth factors such as pulling rate, rotation rate, purity of BeO po wders and evaporation loss compensation of BeO and Cr3+/Al3+substitution ratio were investigated. As a result, 1) high purity (more than 99.99p,) of BeO, as a raw material, is requisite condition for single crystal growth, 2) evaporation loss comp ensation is also requisite for high quality crystal growth. This compensation depends on pulling rate and Cr3+/Al3+ ratio. And 3) optimum pulling and rotation rate for alexandrite growth were 0.5∼1.0mm/hr and 20∼25rpm, respectively. Ale xandrite crystals were grown to (001) direction. Various types of defects were detected by the polarizing microscope and we discussed how to remove these defects. And room tempo rature absorption and fluorescence spectra were measured.

• Fire Science and Engineering
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• v.19 no.3 s.59
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• pp.13-19
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• 2005

An experimental study is presented for extinguishing characteristics of liquid fuel fire by water mist containing sodium acetate trihydrate. To evaluate the extinguishing performance of water mist containing an additive, the evaporation characteristics of a water droplet on a heated surface was examined. The evaporation process was recorded by a charge-coupled-device camera. Also, small-scale extinguishing tests were conducted for n-heptane pool fire in ventilated space to measure flame temperature variation. The average evaporation rate of a water droplet containing an additive was lower than that of a pure water droplet at a given surface temperature due to the precipitation of salt in the liquid-film and change of surface tension. In case of using an additive, the flame temperature was lower than that of pure water at a given discharge pressure and it was because the momentum of a water droplet containing an additive was increased reducing flame size. And also dissociated metal atoms, sodium, were reacted as a scavenger of the major radical species OH^-,\;H^+$ which were generated for combustion process. Moreover, at a high pressure of 4MPa, the fire was extinguished through blowing effect as well as primary extinguishing mechanisms.