• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.8
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• pp.969-977
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• 1999

A similarity solution of a steady laminar flow of micropolar fluids past wedges has been studied. The similarity variables found by Falkner and Skan are employed to reduce the streamwise-dependence in the coupled nonlinear boundary layer equations. Numerical solutions of the equations are then obtained using the fourth-order Runge-Kutta method and the distribution of velocity, micro-rotation, shear and couple stress across the boundary layer are obtained. These results are compared with the corresponding flow problems for Newtonian fluid past wedges with various wedge angles. Numerical results show that, keeping ${\beta}$ constant, the skin friction coefficient is lower for a micropolar fluid, as compared to a Newtonian fluid. For the case of constant material parameter K, however, the velocity distribution for a micropolar fluid is higher than that of a Newtonian fluid.

• Journal of the Korean Society of Clothing and Textiles
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• v.22 no.1
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• pp.100-107
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• 1998

Polyester filaments were dyed with disperse dye in dyebath containing water and water miscible organic solvents . acetone, 1,4-dioxane, DMF. In case of Acetone and 1,4-dioxane, the equilibrium dyeuptake was maximun at the volume fraction 0.05. The equilibrium dye uptakes were decreased as volun~e fraction of organic solvents were increased. When the volume fractions of water miscible organic solvents were varied, dye uptake was increased constantly with dyeing time. In dyebath containing water and water miscible organicsolvent, the dyeuptake was increased quickly during initial 40∼ 60 min. and slowly increased there after. The slope of Ct/Coo to t was greater in dyebath containing water and water miscible organic solvents than dyebath containing water. The differences of the slope with volulne fractions of water miscible organic solvent were not shown big.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1578-1579
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• 2011

본 논문에서는 고분자 절연체가 인가된 전압의 시간에 따라 변화하는 공간전하와 전도 전류의 영향에 대하여 조사를 하였다. 또한 극성반전에 따른 공간전하의 분포와 전도 전류에 변화에 대한 연구를 실시하였다. 기존의 공간전하 분포 측정법들은 주로 고분자 절연재료 내에서 공간전하분포의 측정만을 목표로 한 반면에 공간전하 측정법 중의 하나인 PEA(Pulsed Electro-Acoustic method)을 개선시켜 공간전하와 전도전류의 동시 측정을 가능하게 하였다. 개선된 PEA법은 시간변화에 따른 공간전하와 전기전도의 직접적인 상관관계와 미리 형성 되어 있는 공간전하가 전기전도 및 절연특성에 미치는 영향을 직접적으로 분석할 수 있는 장점을 가지고 있다. 이러한 공간전하와 전류의 동시 측정법을 이용하여 연구하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.04a
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• pp.850-853
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• 2017

본 논문은, 크롤링을 통해 얻은 비정형 데이터를 'Python'의 'KoNLPy' 라이브러리를 사용해 형태소 분석한 후 텍스트 마이닝을 통한 감성사전 구축을 목표로 하고 있으며, 형태소들의 빈도수를 기반으로 가중치로 두어 선별된 단어들을 이용해 긍정과 부정으로 나누어 카테고리화 한다. 이후, 선별한 카테고리에 단어의 극성을 판단하여 감성사전을 모델링한다. 실험을 위하여, 온라인 쇼핑몰 리뷰를 크롤링하여 비정형 데이터를 수집하고, 수집한 데이터를 분석, 가공 과정을 거쳐 정형화된 단어를 추출한다. 그 후에, 리뷰에 자주 사용되는 단어를 바탕으로 카테고리를 구성하였다. 구성된 카테고리 별로 단어의 극성을 판단하여 소비자 성향을 분석한 결과, 단순히 긍정과 부정을 표현하는 범용 감성사전보다 더 세분화된 감성 사전을 구축 할 수 있었다.

• Journal of Energy Engineering
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• v.2 no.3
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• pp.315-322
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• 1993

The generalized 23 constants of the Benedict-Webb-Rubin-Starling (BWRS) equation of state were modified to achieve accurate predictions of thermo-physical properties for polar halocarbons. Multiproperty analysis was employed to obtain an optimum set of 23 constants for individual halocarbons. The overall average absolute deviations of predicted properties for those halocarbons using the 23 constants optimized for each halocarbon with use of either an acentric factor or orientation parameters are 0.41% for density, 0.33 Kcal/kg for enthalpy and 0.39% for vapor pressure. These results show a remarkable improvement in predicting properties over the ones obtained by use of the generalized constants for all the ten halocarbons tested here.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.2
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• pp.185-191
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• 1992

In this paper, it is attempted to distinguish the charged particles and to judge the polarity by the use of Thermally Stimulated Current(TSC) and Temperature Gradient Thermally Stimulated Surface Potential Measurement(TG-TSSP)with experimental insulation material XLPE-EVA for power cables which is made by blending cross-linked polyethylene(XLPE) and ethylene-vinylacetate copolymer(EVA). In addition, it is performed to investigate the effect of EVA blending. From the experimental results, it is known that for the case of XLPE-EVA blended experimental material, the generation of space charged electric field is not obtained in the high temperature region due to the obatruction of the injection of trapping carrier by the electron and the positive hole.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.3
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• pp.196-205
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• 2008

A noble polarity inversion dc/dc power conversion circuit that has the high input-output voltage conversion ration characteristics is presented for high voltage DC power supply applications. The proposed circuit features the reduced voltage stresses of the component compared to those of the conventional ones. The operational principles of the proposed circuit is analyzed and comparative features are presented. The simulation results and experimental results are presented to verify the validity of the proposed circuit.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.199-199
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• 1999

상용의 PVC가 갖는 소수 특성을 개선하기 위해 산소, 아르곤, 수소 이온의 이온 보조 반응법을 이용하여 표면의 친수성을 증대시키고 이때 친수성 증가의 직접적 원인인 표면에너지 증가를 각각의 이온조사에 따라서 비교하였다. 이온 소스는 직경 5-cm의 cold hollow cathod ion gun을 이용하였으며 산소, 아르곤, 수소이온을 이온 조사량 5$\times$1014~1$\times$1017ions/cm2까지 변화시키고 산소의 유량을 0~8sccm까지 변화시키면서 표면 에너지 변화를 관찰하였다. 표면 에너지는 두 가지의 극성 용매인 물과 포름아마이드의 접촉각을 정적 접촉각 측정기를 이용하여 측정한 후에 이로부터 dispersion force와 polar force를 계산하여 얻었다. 계산된 결과를 보면 처리 전과후의 dispersion force의 변화는 거의 없으나 polar force는 크게 증가하였다. 이때 표면 에너지의 증가는 표면 형상의 변화와 극성을 띠는 친수성기의 증가로 여겨지며 각각의 경우에 대한 분석을 위해 AFM과 XPS 분석을 시행하여 각각의 이온에 따르는 표면 형상의 변화와 친수성기의 형성 및 상대적인 양을 비교하였다.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.154-160
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• 2008

We investigated molecular polarity by using theoretical means and comparing empirical solvent polarity. Our approach employed electrostatic potentials at the molecular surface calculated by density functional methods. A number of molecular descriptors related to molecular polarities were computed from molecular surface electrostatic potentials. Among computed molecular descriptors, the most positive electrostatic potential provided the best correlation with the empirical solvent polarities. A regression equation was developed in order to predict molecular polarities of molecules whose experimental solvent polarities were unknown. The new regression equations were utilized in estimating solvent polarities of cubane derivatives which are considered important precusors of high-energy density meterials.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.657-662
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• 1992

For describing the bipolar packed-bed electrode cell filled with graphite pellete electrode, the application of the model of equivalent circuit was studied. The ratio between the Faradaic current through bipolar electrodes and the applied current was dependent on the resistance coefficient, specific conductivity of electrolyte, and electrolyte circulation rate. The ratio of the Faradaic current through bipolar electrodes to the applied current increased with the applied current(or cell voltage), but decreased with the increase of electrolytic conductivity and circulation rate of the electrolyte.