• 조명전기설비학회논문지
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• 제27권7호
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• pp.45-51
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• 2013

This study is to discuss simulation results with 51 principal chemical reactions in non-thermal plasma space under atmospheric pressure, and the ambient gas was mainly composed of oxygen and nitrogen molecules. The initial density of O and OH radicals under the ambient temperature of 300K is largely generated in comparison with other higher temperature, and the density of O radical decreased from $20{\mu}s$ according to increase the temperature. The initial density of OH radical seemed to decrease steeply at the initial stage. By increasing the initial density of $H_2O$ molecules, O radical's effect was few and the density of OH radical was largely generated about 2 times. In addition, ozone density was increased as increasing the density of O radical, but it was decreased as increasing the density of $H_2O$. In case of the temperature more than 300K, $NO_2$ tend to be removed, but NO was increased than the initial density.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.5-6
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• 2009

In this paper, plasma ion implant is performed with $PH_3$ gas diluted by helium gas on P-type Si wafer (100). Spike Rapid Thermal Processing(RTP) annealing performed for 30~60 sec from $800\;^{\circ}C$ to $1000\;^{\circ}C$ in $N_2+O_2$ ambient. Crystalline defect is analyzed by Transmission Electron Microscope(TEM) and Double crystal X-ray Diffraction(DXRD). Contact resistivity($\rho c$), contact resistance(Rc) and sheet resistance(Rs) are analyzed by measuring Transfer Length Method(TLM) using 4155C analysis. As annealing temperature increase, Rs decrease and ${\rho}c$ and Rc increase at temperature higher than $850\;^{\circ}C$. We achieve low Rs, ${\rho}c$ and Rc with Plasma ion implant and spike RTP.

• 한국입자에어로졸학회지
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• 제8권4호
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• pp.161-172
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• 2012

Three-dimensional numerical simulation using a computational fluid dynamics (CFD) was carried out in order to investigate the formation and dispersion of the plume discharged from the stack of a thermal power station. The simulation was based on the standard ${\kappa}{\sim}{\varepsilon}$ turbulence model and a finite-volume method. Warm and moist exhaust from a power plant stack forms a visible plume as entering the cold ambient air. In the simulation, moisture content, emission velocity and temperature of the flue gas, air temperature and wind speed were dealt with the main parameters to analyze the properties of the plume composed mainly of water vapor. As a result of the simulation, the plume could be more apparent in cold winter due to a big difference of latent heat capacity. At no wind condition, the white plume rises 120 m upward from the top of the stack, and expands to 40 m around from the stack in cold winter after flue gas heat recovery. The influencing distance of relative humidity will be about 100 m to 400 m downstream from the stack with a cross wind effect. The decrease of flue gas temperature by heat recovery of thermal energy facilitates the formation of the plume and restrains its dispersion. Wind speed with vertical distribution affects the plume dispersion as well as the density.

• International Journal of Air-Conditioning and Refrigeration
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• 제16권3호
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• pp.77-82
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• 2008

For heat pumps used in a cold region, it is very important to obtain appropriate heating capacity. Several studies using a variable speed compressor and an additional heater have been performed to enhance heating capacity at low ambient temperatures. However, for outdoor temperature conditions below $-15^{\circ}C$, it is still difficult to obtain enough heating capacity above the rated value. In recent studies, the application of gas injection technique into a two-stage heat pump yielded noticeable heating performance improvement at low temperature conditions. In this study, the heating performance of a two-stage gas injection heat pump with a rated capacity of 3.5 kW was measured and analyzed by varying refrigerant charge amount and EEV opening at the standard heating condition. The heating performance of the two-stage gas injection heat pump was compared with that of a two-stage non-injection heat pump. The heating capacity and COP of the two-stage gas injection heat pump were improved by 2-10% at the optimal charging condition over those of the two-stage non-injection heat pump.

• 에너지공학
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• 제9권3호
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• pp.261-268
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• 2000

A heat transfer correlation to predict the vaporization of a water droplet in highly superheated steam during a loss-of-coolant accident(LOCA) of a nuclear power plant is provided. Vaporization of liquid fuel or water droplets in superheated air or steam and subsequent interface heat transfer between a liquid droplet and superheated gas is typically correlated by way of a Nusselt number as a function of Reynolds number, Prantl number, and in some cases including mass transfer number. Presently available correlations and experimental data of the evaporation of liquid droplets in air or steam are analyzed and a new Nusselt number correlation is proposed taking Schmidt number into consideration in order to account for binary diffusion of the vapor as well, Nu$\_$f/(1+B)$\^$0.7/=2+0.53Sc$\_$f/$\^$-1/5/Re$\_$M/$\^$$\sfrac{1}{2}$/Pr$\_$f/$\^$$\sfrac{1}{3}$/ for which properties are evaluated at film condition except the density of Reynolds number evaluated at ambient condition. Diverse correlations for various combinations of liquid and gas species are put into single equation. The blowing correction factor of (1+B)$\^$0.7/ is confirmed appropriate, and a criterion to distinguish so-called high- and low-temperature condition of ambient gas is set forth.

• 한국환경농학회지
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• 제28권2호
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• pp.106-112
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• 2009

The increased $CO_2$ and temperature (700 ${\mu}$mol.$mol^{-1}$ $CO_2$ and $30^{\circ}C$) was compared with ambient growth conditions (400 ${\mu}$mol.$mol^{-1}$ $CO_2$ and $25^{\circ}C$) in hot pepper. Gas exchange measurements, including net photosynthesis ($P_{net}$) and stomatal conductance ($g_s$), were taken according to treatment in fields of peppers grown in Suwon and Asan during 2008. The increased treatment $P_{net}$ by 35-45% throughout the season and was statistically significant in t-tests (p < 0.001); however, it did not significantly affect $g_s$. In addition, the gas exchange parameters in sun and shade leaves were measured. The difference between the sun and shade leaves was much greater than that between the elevated and ambient treatments, especially at harvest. Four commercial cultivars of hot pepper, Chunhasangsa, Ryukang, Manitta, and Olympic, were also compared by ANOVA. Chunhasangsa had the highest $P_{net}$, which decreased by 30% from the vegetative to the harvest stage. Based on a factorial design, the effect of the increased $CO_2$ and temperature was assessed based on the temperature, $CO_2$, and their interaction effects. Orthogonal contrasts showed that the effects of temperature on $P_{net}$ and $g_s$ were significant, whereas $CO_2$ and their interactions were not.

• 한국항공우주학회지
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• 제31권7호
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• pp.85-93
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• 2003

주위 압력변화에 따른 공기중에 놓인 탄화수소 연료 액적의 기화에 관한 수치적 연구를 일차원 기화모델을 사용하여 수행하였다. 주위 압력은 대기압에서 임계압력이상까지 변화시켰다. 높은 압력에서 실기체 효과를 고려하기 위해 수정 Soave-Redich-Kwong상태 방정식을 사용하였으며 임계온도 근방과 초임계상태에서는 비이상기체 열역학 및 전달 물성치를 고려하였다. 계산의 타당성을 위해 계산 결과와 사토의 실험결과를 비교하였고 비교적 잘 일치하였다. 아임계 온도에서는 압력증가에 따라 액적수명은 증가하였으며 초임계온도에서는 압력증가에 따라 액적수명은 감소하였다. 고압에서는 액상에 용해되는 질소의 용해도는 무시할 수 없고 온도와 압력이 높을수록 용해도는 증가하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.303-306
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• 2009

High temperature solid oxide fuel cells (SOFCs) offer a clean, pollution-free technology to electrochemically generate electricity at high efficiencies. Solid oxide fuel cells in several different designs have been investigated; these include planar and tubular geometries. The tubular type cell is widely researched due to it have advantages about thermal expansion and sealing issues. Unfortunately, lab scale tubular cell for testing has thermal expansion and sealing problems. The previous Jig for lab scale tubular cell testing has many sealing problems. When we feed fuel gas to jig inlet, ceramic glue sealant has amount of gas expansion pressure, because temperature of feeding gas changes ambient temperature to high temperature ($700{\sim}900^{\circ}C$). Furthermore, when we carry out long time test, something like degradation test, crack of ceramic glue sealant due to weakness of mechanical properties can make stop working the test. Additionally, we reduce setting process for assembling, because micanite is not required drying or debinding process.

• Journal of Advanced Marine Engineering and Technology
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• 제32권5호
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• pp.707-716
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• 2008

The objective of this study was to analyze the effect of mixed fuel composition and mass fraction on spray inner structure in evaporating transient spray under the variant ambient conditions. Spray structure and spatial distribution of liquid phase concentration were investigated using a thin laser sheet illumination technique on the three component mixed fuels. A pulsed Nd:YAG laser was used as a light source. The experiments were conducted in a constant volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector. Used fuel contains i-octane($C_8H_{18}$), n-dodecane($C_{12}H_{26}$) and n-hexadecane($C_{16}H_{34}$) that were selected as low-, middle- and high-boiling point fuel, respectively. Experimental conditions are 42 MPa, 72 MPa and 112 MPa in injection pressure, $5\;kg/m^3$, $15kg/m^3$ and $30kg/m^3$ in ambient gas density, 300 K, 500 K, 600 K and 700 K in ambient gas temperature, 300 K and 368 K in fuel temperature and different fuel mass fraction. Experimental results indicated that the multi-component fuels made two phase region mixed vapor and liquid so that it would are helpful to improve combustion, for the fuels of high boiling point component could accelerate evaporation very much according as low boiling point fuel was added to high boiling point fuel.

• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1746-1755
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• 2003

Operating characteristics of a triple pressure reheat HRSG are analyzed using a commercial software package (Gate Cycle by GE Enter Software). The calculation routine determines all the design parameters including configuration and area of each heat exchanger. The off-design calculation part has the capability of simulating the effect of any operating parameters such as power load, process requirements, and operating mode, etc., on the transient performance of the plant. The arrangement of high-temperature and intermediate-temperature components of the HRSG is changed, and its effect on the steam turbine performance and HRSG characteristics is examined. It is shown that there could be a significant difference in HRSG sizes even though thermal performance is not in great deviation. From the viewpoint of both economics and steam turbine performance, it should be carefully reviewed whether the optimum design point could exist. Off-design performance could be one of the main factors in arranging components of the HRSG because power plants operate at various off-design conditions such as ambient temperature and gas turbine load, etc. It is shown that different heat exchanger configurations lead to different performances with ambient temperature, even though they have almost the same performances at design points.