• Journal of Korea Multimedia Society
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• v.8 no.10
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• pp.1322-1328
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• 2005

The circulation flows passing through the Ekman boundary layer on the rotating disk and transfer the angular momentum into the interior region of the container. Consequently, the circulation enhances the momentum transfer and the interior fluid is divided by a propagating shear front. This investigation focuses on computer vision and image processing technique for analysis of Non-Newtonian Fluids. To visualize marching velocity shear front for the transient flow, a particular shaped particles and light are used. To validate the proposed method, quantitative image are compared with the optical data acquired by a direct measurement of LDV (Laser Doppler Velocimetry).

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.3
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• pp.186-197
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• 2012

In order to understand hydrodynamic and water quality changes on the Saemangeum reservoir in accordance to inner development plan, intensive numerical simulations using EFDC have been done. Due to inner dike construction and proposed dredging plans, stratification might occur and yield flow field change. It should be noticed that very conditional gate operation schedule adjusting target water elevation of -1.5 meter causes severe stratification and hence plays an important role in poor water qualities. By using random walk particle tracking residence simulations, it is found that hydrodynamic characteristics depends greatly on riverine inflow conditions. It is also inferred that the northern part of the Mangyeong reservoir behaves as a dead zone and acts as major reasoning of water quality deterioration owing to benthic flux from long-term residing settled sediment.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.596-603
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• 2020

In this study, a mathematical model for optimal operation of the fusion fuel cycle is developed based on scheduling approach. The fusion fuel cycle consists of a system for storing and supplying deuterium and tritium, and receiving and separating process after the fusion reaction. Except that tritium is a radioactive material, most of these processes consist of catalytic reactions and separation process. For these reasons, it is possible to apply scheduling approach which is also widely utilized to chemical plants to derive the optimal operating scenarios. The developed model determined the optimal regeneration cycle to minimize the amount of tritium inside the vacuum pumps. Based on the characteristics of various device in the fusion reactor, the optimal tritium plant operation scenario is evaluated. The formulated model was applied to the actual tokamak scenario and utilized to analyze the fuel flow and balance of ITER fuel cycle.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.10a
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• pp.83-96
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• 2005

PVC is the thermoplastic offering excellent material properties. PVC is used in wide variety of applications, however, it causes environmental problems when it is discarded because of its high chlorine content. Since dechlorination reaction of PVC is taking place relatively low temperature compared to the pyrolysis temperature of plastics, study on the dechlorination reaction has been carried out as a pre-treatment process. Twin screw reactor which shows excellent mixing capabilities is employed. Experimental variables are first and second reactor temperature, PVC content in mixed plastics, viscosity of mixed plastics, feeding rate, rotational speed of the second reactor. Over 90% of dechlorination rate can be obtained under proper operation conditions. Chlorine gas evolved from reactor is absorbed in water and can be recovered as a hydrochloric acid. Analysis had been done on chlorine flows by taking material balance over reactor.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2011.10a
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• pp.5-5
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• 2011

최근에 고령화 사회에 접어들면서 건강하게 활동하며 수명을 다하는 것이 중요한 연구과제가 되고 있다. 이 때문에 영양, 운동, 스트레스, 환경 등과 관련하여 암, 당뇨병, 고혈압, 비만, 동맥경화 등 생활습관병의 극복이 사회문제가 되고 있는 실정이다. 지금까지 고려인삼의 대표적인 동물실험 및 임상학적 연구결과를 종합하여 보면 성인의 난치성 만성질환에 대해서 치료제보다는 질병을 예방하고 회복촉진에 보다 큰 효과 있음을 확인할 수 있다. 이는 인삼이 식품과 의약품의 중간에 위치한 식품의약품(Nutraceutical)의 용도로 활용할 수 있음을 시사한다. 현재까지 인삼제품에 표시되는 기능성의 내용은 약 3,000여편 이상의 약리효능에 관련된 논문이 발표되었다 하더라도 "피로회복, 면역력 증진, 혈소판 응집 억제를 통한 혈액흐름에 도움이 됩니다"이며 이외의 기능성 표시는 현재로서 원칙적으로 불가한 것으로 되어 있다. 그러나 시험물질의 규격화 및 임상시험의 검토기준을 만족시키는 과학적 자료제출에 의한 개별 평가 후 표시내용의 확대가 가능하다. 고려인삼의 다양한 성분 중 ginsenoside는 주요 약효성분으로 인정을 받고 있으며 현재 품질관리의 지표성분으로 활용되고 있다. 이러한 개별 ginsenoside의 약리작용을 보면 서로 유사 또는 상반된 효과를 보여주는 성분들이 공존하고 있어 인삼의 다양한 약리효과와 일맥상통하는 것으로 보고되고 있다. 아울러, ginsenoside는 인삼의 부위 별로 현격한 차이를 보여주기 때문에 소재의 규격화는 매우 중요하다고 판단된다. 따라서, 인삼제품 개발의 가장 중요한 조건은 의약품에 가까운 기능성식품으로 세계적인 제품을 만들기 위해서는 표준화가 선행되어야 한다. 이와 같은 조건을 잘 충족시키는 제품이 스위스 "파마톤의 진사나(백삼추출물, G115)" 제품으로 생각할 수 있다. 따라서, 고려인삼의 수출시장 확대 및 세계적인 제품을 위해서는 진사나에 필적할 수 있는 새로운 홍삼의 표준화된 추출물을 도출하는 것이 무엇보다 급선무라 생각한다. 아울러 고려인삼의 특장점 발굴을 위한 표준화 된 추출분획물, 활성성분 및 효능과 연계한 새로운 고부가가치 창출제품(식품/의약품)개발에 주력해야 할 것이다.

• Journal of the Korean earth science society
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• v.27 no.5
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• pp.569-578
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• 2006

The distribution and kinematic information of the continuum, $H{\alpha},\;H{\beta}$, [O III], & [N II] images based on spectroscopic data secured with the OASIS at the Hawaii CFHT 3.6m telescope have been analyzed to study the physical characteristics of NGC 5728. The three bright regions-northwestern knot, southeastern knot, and the nucleus-exist within a $15"{\times}12"$ sky area which seem to indicate gas flows along the northwestern or western direction from the nucleus. We find that the center of a 10" diameter ring is at the northwestern knot, not at the galactic center. To further analyze the formation mechanism of such a ring, the kinematics of the nucleus and knot have been studied and the central structure of the Active Galactic Nuclei has been investigated by comparing various emission images.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.847-853
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• 2016

Here has been examined a 3-dimensional computational fluid dynamics (CFD) modeling in order to investigate the performance analysis of proton exchange membrane (PEM) fuel cells with serpentine flow fields. The present CFD model considers the isothermal transport phenomena in a fuel cell involving mass, momentum transport, electrode kinetics, and potential fields. Co-current flow patterns for a PEMFC are considered for various geometries in the single straight cell. Current density distribution from the calculated distribution of oxygen and hydrogen mass fractions has been determined, where the activation overpotential has been also calculated within anode and cathode. CFD results showed that profiles differ from those simulations subjected to each the calculated activation overpotential. It is interesting that the present serpentine flow field shows the specific distribution of current density with respect to the aspect ratio of depth to width and the ratio of reaction area for various serpentine geometries. Simulation results were considered reasonable with the other CFD results reported in literature and global comparisons of the PEMFC model.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.4
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• pp.306-317
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• 1995

Abstract Gallium arsenide crystal is usually grown from the melt by the horizontal Bridgman method. We constructed pseudo - steady - state model for crystal growth of GaAs which inclue melt, crystal and the free interface. Mathematical equations of the model were solved for flow, temperature, and concentration field in the melt and temperature field in the crystal. The location and shape of the interface were also solved simultaneously. In 2 - dimensional model, the shape of the interface is flat with adiabatic thermal boundary condition, but it becomes curved with completely conducting thermal boundary condition. In 3 - dimensional model, the interface is less curved than 2 - dimensional case and the flow intensity is similar to that of 2 - dimensional case. With the increase of flow intensity vertical segregation shows maximum value in both 2 - and 3 - D model. However, the maximum value occurs in lower flow intensity in 2 - D model because the interface is more curved for the same flow intensity.

• Atmosphere
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• v.25 no.3
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• pp.473-482
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• 2015

In this study, street canyons with a higher downwind building (so called, step-up street canyons) are considered for understanding characteristics of flow and reactive pollutants' dispersion as a basic step to understand the characteristics in wider urban areas. This study used a CFD_NIMR_SNU coupled to a chemistry module just including simple $NO_X-O_3$ photochemical reactions. First, flow characteristics are analyzed in step-up street canyons with four aspect ratios (0.33, 0.47, 0.6, 0.73) defined as ratios of upwind building heights to downwind building height. The CFD_NIMR_SNU reproduced very well the main features (that is, vortices in the street canyons) which appeared in the wind-tunnel experiment. Wind speed within the street canyons became weak as the aspect ratio increased, because volume of flow incoming over the upwind building decreased. For each step-up street canyon, chemistry transport model was integrated up to 3600 s with the time step of 0.5 s. The distribution patterns of $NO_X$ and $O_3$ were largely dependent on the mean flow patterns, however, $NO_X$ and $O_3$ concentrations were partly affected by photochemical reactions. $O_3$ concentration near the upwind lower region of the street canyons was much lower than background concentration, because there was much reduction in $O_3$ concentration due to NO titration there. Total amount of $NO_X$ in the street canyons increased with the aspect ratio, resulting from the decrease of mean wind intensity.

• Journal of Soil and Groundwater Environment
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• v.7 no.3
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• pp.103-114
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• 2002

Knowledge of soil water retention characteristic is essential for many problems involving water flow and organic solute transport in unsaturated soils. A physico-empirical approach based on the translation of the particle-size distribution (PSD) into a corresponding water retention curve has been accomplished by others using the concept that the pore-size distribution is directly related to PSD. This approach implies that details of a PSD curve may affect the estimation of water retention characteristic (WRC). To determine whether the WRC estimation using the Arya-Paris model could be affected by the selection of a PSD model, four PSD models with one to four fitting parameters were used. The Jaky model with only one fitting parameter had greater WRC estimation ability than other models with greater number of fitting parameters. The better performance of the Jaky model may be explained by the effect of soil structure in field soils.