• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.112-118
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• 2001

Magnetic field is commonly used in low temperature processing plasmas to enhance the performance of the plasma reactors. E$\times$B magnetron or surface multipole configuration is the most popular. However, the properties of capacitively coupled rf plasma confined by axial static magnetic field have rarely been studied. With these background, the effect of magnetic field on the characteristics of capacitively coupled 13.56 MHz/40 KHz argon plasma was studied, Ion saturation current, electron temperature and plasma potential were measured by Langmuir probe and emissive probe. At low pressure region (~10 mTorr), ion current increases by a factor of 3-4 due to reduction of diffusion loss of charged particles to the wall. Electron temperature slightly increases with magnetic field for 13.56 MHz discharge. However, for 40 KHz discharge, electron temperature decreased from 1.8 eV to 0.8 eV with magnetic field. It was observed that the magnetic field induces large temporal variation of the plasma potential. Particle in cell simulation was performed to examine the behaviors of the space potential. Experimental and simulation results agreed qualitatively.

• Journal of the Korean Society for Railway
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• v.8 no.4
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• pp.348-353
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• 2005

In designing the structures of railway rolling stocks, deterministic methods associated with the concept of a safety factor have been traditionally used. The deterministic approaches based on the mean values of applied loads and material properties have been used as safety verification for the design of rolling-stock car body structures. The uncertainties in the applied loading for the high speed train and the strength of new materials in the rolling stocks require the application of probabilistic approaches to ensure fatigue safety in the desired system. Pressure loadings acting on the car body when the train passes through tunnels show reflected pressure waves for high-speed trains and they may cause a fatigue failure in vehicle bodies. Use of new material technology as body structures also introduces uncertainties in the material strength. A probabilistic approach is more adaptable in designing reliable structures when the pressure waves from the tunnels pounds and new material technology is adopted. In this paper, it is proposed that a fatigue design and assessment method based on a reliability which deals with the loading variations on a railway vehicle due to the pressure reflected in tunnels and the strength variations of material. Equation for the fatigue reliability index has been formulated to calculate the reliability assessment of a vehicle body under fluctuating pressure loadings in a tunnel. Considered in this formulation are the pressure distribution characteristics, the fatigue strength distribution characteristics, and the concept of stress-transfer functions due to the pressure loading.

• The Korean Journal of Financial Management
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• v.12 no.1
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• pp.129-143
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• 1995

우리 나라의 금융기관들은 금융환경(金融環境)의 급격한 변화 속에서 일대 전환기를 맞고 있다. 대내적으로는 금리자유화를 비롯한 금융자율화(金融自律化)의 추진, 금융산업의 개편 등의 금융구조 조정이 진행되고 있고, 대외적으로는 국내금융시장에 대한 개방압력(開放壓力)이 가중되고 있다. 본 연구의 목적(目的)은 이상의 다양한 금융환경의 변화 중에서 1991년과 1993년에 실시된 1,2단계 금리자유화조치가 은행의 경영위험에 어떠한 영향을 미쳤는지를 증권시장(證券市場)의 반응을 통하여 규명하고자 한다. 구체적으로 일반적인 예상과 같이 금리자유화로 인하여 은행의 위험이 증가하였는지 아니면 금리자유화가 은행의 자금조달과 운용에 있어서 자율성과 유연성을 확보해 주어서 오히려 은행위험을 감소시켰는지를 실증적으로 검증한다. 주가자료를 이용하는 증권시장의 반응을 통한 은행위험의 분석은 은행에 관련된 재무정보를 신속하고 충분히 반영하는 효율적 시장이며 회계자료를 이용하여 은행위험을 추정하는 방법이 부적절하다는 가정하에서 합리화된다. 은행 위험은 은행감독 당국의 관심대상인 총위험과 은행주식 투자자의 관심대상인 체계적 위험의 두요소를 대상으로 한다. 본 연구의 증권시장반응을 통한 실증분석결과에 의하면 금리자유화조치 이후 은행의 위험은 예상과는 달리 증가하지 않은 것으로 나타났다. 은행총위험은 증가하지 않았으며 체계적 위험은 오히려 2차 금리자유화 이후 하락하는 결과를 보여준다. 이는 금리자유화 조치가 은행의 자금조달과 운영에 있어서 운신의 폭을 넓혀줌으로써 금리 변동폭 증대로 인한 위험증가를 상쇄함을 의미한다. 이러한 결과는 미국의 금리자유화조치에 관련된 대부분의 연구결과와 일치한다. 또한 위험은 개별은행의 재무특성에 따라서 상이한 변화를 보여주었다. 특히 자산규모가 작은 후발은행의 경우 자금조달과 운영의 측면에서의 제한이 완화됨으로써 위험이 감소함을 보여준다. 따라서 정부당국자는 금리자유화의 긍정적 효과를 극대화하는 방향으로 적극적으로 금리자유화를 추진하는 것이 바람직하다.

• Journal of computational fluids engineering
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• v.21 no.4
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• pp.61-70
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• 2016

Dong-tan Station, shared by high-speed railway and urban express railway, is a very complicated underground station having 6 tracks together with barrier and shafts between them, therefore it seems very hard to investigate the aerodynamic effects including the pressure variation and train gust in the station when a high-speed train runs through it. In this study, the aerodynamic effects on the structures and platform passengers when a high-speed train runs through an underground station have been studied using Computational Fluid Dynamics. STAR-CCM+ has been employed for numerical simulation based on Navier-Stokes equation and 2-equation turbulence model and moving mesh scheme supported by STAR-CCM+ has also been used to represent the relative motion between a train and station. Based on the simulation results, the unsteady flow fields in the underground station induced by the high-speed train have been analyzed and the pressures on the PSDs and pressure variation at the platform have quantitatively assessed.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.6
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• pp.453-460
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• 2017

In order to investigate propulsion efficiency and cavitation characteristics for expanded area ratio variation of the 8800TEU class container propeller, a series of performance tests were conducted at Large Cavitation Tunnel (LCT) and Towing Tank (TT) in KRISO. The cavitation test of the existing propellers (KP1029 & KP1030) was conducted using FRP model ship in LCT. On the basis of LCT test results, it was required to design propeller with better propulsion efficiency and cavitation performance. Two propellers (KP1171 & KP1172) with decreased expanded area ratio were designed on the basis of KP1029 propeller. The new design propellers showed higher efficiency than KP1029 and reasonable cavitation performance. In the future, they will be applied as the standard propeller for the propeller design of the large container ship. Through the performance test and prediction results for the new design propellers, it is thought that high-load propeller with better propulsion efficiency and cavitation performance will be developed constantly.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.2
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• pp.197-204
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• 2018

In the present study, unsteady flow analysis has been conducted to investigate the blade forces and wake flow around a hybrid street-lamp having a vertical-axis small wind turbine and a photovoltaic panel. Uniform velocities of 3, 5 and 7 m/s are applied as inlet boundary condition. Relatively large vortex shedding is formed at the wake region of the photovoltaic panel, which affects the increase of blade torque and wake flow downstream of the wind turbine. It is found that blade force has a good relation to the variation of the angle of attack with the rotation of turbine blades. Variations in the torque on the turbine blade over time create a cyclic fluctuation, which can be a source of turbine vibration and noise. Unsteady fluctuation of blade forces is also analyzed to understand the nature of the vibration of a small wind turbine over time. The detailed flow field inside the turbine blades is analyzed and discussed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.12
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• pp.1035-1044
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• 2013

Because of the high specific stiffness and strength inherent in the sandwich structure composed of facesheet that resists in-plane loads and a core that resists out-of-plane loads, it is often used for large and light-weighted structures. However, inevitably the increased flexibility allows greater deformation-based disturbances in the structures. Thus, it is necessary to analyze the structural safety. To obtain more accurate analytical results, the input disturbances must more closely simulate real load conditions; to improve accuracy, non-linear elements such as gust effects were considered. In addition, the structural safety was analyzed for the iso-grid sandwich panel structure using fluid-structure interactions. For a more realistic simulation, flow velocity fields, which consider the effects of irregular gust fluctuation, were generated and the coupled field was analyzed by mapping the pressure and displacement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.157-164
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• 2017

A parallel slide gate valve (PSGV) is located between the heat recovery steam generator (HRSG) and the steam turbine in a combined cycle power plant (CCPP). It is used to control the flow of steam and runs with repetitive operations such as startups, load changes, and shutdowns during its operation period. Therefore, it is necessary to evaluate the fatigue damage and the structural integrity under a large compressive thermal stress due to the temperature difference through the valve wall thickness during the startup operations. In this paper, the thermal-structural analysis and the fatigue life evaluation of a 16-inch PSGV, which is installed on the HP steam line, is performed according to the fatigue life assessment method described in the ASME B&PVC VIII-2; the method uses the equivalent stress from the elastic stress analysis.

• The Journal of the Acoustical Society of Korea
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• v.37 no.4
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• pp.163-173
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• 2018

This paper performed the prediction of the acoustic loads applied to the surface of the flight vehicle during flight. Acoustic loads during flight arise from the pressure fluctuations on the surface of body. The conventional method of predicting the acoustic loads in flight uses semi-empirical method derived from theoretical and experimental results. However, there is a limit in obtaining the flow characteristics and the boundary layer parameters of the flight vehicle which are used as the input values of the empirical equation through experiments. Therefore, in this paper, we use the hybrid method which combines the results of CFD (Computational Fluid Dynamics) with semi-empirical methods to predict the acoustic loads acting on flight vehicle during flight. For the flight vehicle with cone-cylinder-flare shape, acoustic loads were estimated for the subsonic, transonic, supersonic, and Max-q (Maximum dynamic pressure) condition flight. For the hybrid method, two kind of boundary layer edge estimation methods based on CFD results are compared and the acoustic loads prediction results were compared according to empirical equations presented by various researchers.

• Journal of Veterinary Clinics
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• v.29 no.3
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• pp.203-206
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• 2012

Treatment for heart failure is directed to reduce atrial volume overload by diuretic agents, to lessen ventricular pressure overload by vasodilatory agents and to increase myocardial performance through inotropic agents. Of those cardiac therapeutics, diuretic agents are the most important to control heart failure in dogs, although long-term use often causes detrimental side-effects such as acute renal failure and electrolyte abnormalities. Thus, this study was designed to find a new diuretic agent from medicinal herbs which has better diuretic effect and less unfavorable complications in dogs. In a preliminary study performed with 5 normal healthy dogs, the extract from Akebia quinata Decaisne showed mild to moderate diuretic effect (0.3-0.5 potency of furosemide 2 mg/kg) and minimal changes in serum chemistry and electrolyte. Although the study population was not large enough and study period was not sufficient enough, this study found a good alternative diuretic agent which can replace or reduce the use of furosemide in dogs with heart failure.