• 대한기계학회논문집
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• 제8권1호
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• pp.18-25
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• 1984

The transition boiling of a liquid droplet on a heated flat surface was studied utilizing Kotake's model with the effects of viscosity of a thin vapor layer between the droplet and the hot plate taken into account. This problem was analyzed considering the process of the droplet evaporation which resulted in hydrodynamic instability at the liquid-vapor interface. The results of the study are as follows; (1)The effect of the viscosity in the vapor layer at the interface appears as a dimensionless number N, namely .sigma. .delta.$_{0}$ /.rho.nu.$^{2}$ (2)The time required for evaporation at the transitional region increases with the temperature difference ratio .DELTA. T$_{r}$. The rate of increase of the total evaporation time becomes larger as increasing of N$_{m}$(N number at maximum heat flux) increases.s.

• 한국진공학회지
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• 제22권2호
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• pp.105-110
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• 2013

Vapor-Liquid-Solid 방법을 이용하여 다양한 성장온도와 V/III 비율 아래 $In_xGa_{1-x}As$ 나노와이어를 실리콘 (111) 기판 위에 성장하였다. 나노와이어 성장은 화학기상증착(MOCVD)장치를 이용하였으며, 나노와이어의 구조적 특성은 주사전자현미경 및 투과전자현미경을 이용하여 분석하였다. 나노와이어의 조성비 분포를 확인하기 위하여 투과전자현미경에 장착된 Energy dispersive X-ray 분석기로 나노와이어의 길이에 따른 In과 Ga의 조성비를 측정하였다. 성장온도와 V/III 비율이 올라갈수록 In 조성비가 나노와이어 내부에서 크게 변하는 것을 확인하였는데, 이는 Vapor-Solid 방식에 의한 나노와이어 표면에서의 성장이 증가하기 때문으로 이해된다.

• 한국분무공학회지
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• 제7권3호
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• pp.18-23
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• 2002

An evaporating diesel spray of a common rail lnjector was visualized by LIEF technique. This technique makes it possible to separate the vapor and liquid phase images. The experiment was conducted in a constant volume vessel to make a high temperature and high pressure condition. Three images(vapor and liquid phase images from LIEF and a liquid phase image from Mie scattering) were taken simultaneously in one spray event. The major experimental parameters are the injection pressure and the ambient gas pressure. Also, a relative SMD distribution in a liquid phase was obtained by the ratio of the intensities of the fluorescence and the Mie scattering. The results show that the injection pressure and the ambient gas pressure have a close relation with the spray development and air-fuel muting process.

• Nuclear Engineering and Technology
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• 제41권9호
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• pp.1215-1222
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• 2009

The present work pertains to a research program to study Molten Fuel-Coolant Interactions (MFCI), which may occur in a nuclear power plant during a hypothetical severe accident. Dynamics of the hot liquid (melt) droplet and the volatile liquid (coolant) were investigated in the MISTEE (Micro-Interactions in Steam Explosion Experiments) facility by performing well-controlled, externally triggered, single-droplet experiments, using a high-speed visualization system with synchronized digital cinematography and continuous X-ray radiography. The current study is concerned with the MISTEE-NCG test campaign, in which a considerable amount of non-condensable gases (NCG) are present in the film that enfolds the molten droplet. The SHARP images for the MISTEE-NCG tests were analyzed and special attention was given to the morphology (aspect ratio) and dynamics of the air/ vapor bubble, as well as the melt drop preconditioning. Energetics of the vapor explosion (conversion ratio) were also evaluated. The MISTEE-NCG tests showed two main aspects when compared to the MISTEE test series (without entrapped air). First, analysis showed that the melt preconditioning still strongly depends on the coolant subcooling. Second, in respect to the energetics, the tests consistently showed a reduced conversion ratio compared to that of the MISTEE test series.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.384-384
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• 2012

We report nonvolatile memory properties of poly (3, 4-ethylenedioxythiophene) (PEDOT) thin films grown by vapor phase polymerization using FeCl3 as an oxidant. Liquid-bridge-mediated transfer method was employed to remove FeCl3 for generation of pure PEDOT thin films. From the electrical measurement of memory device, we observed voltage induced bipolar resistive switching behavior with ON/OFF ratio of 103 and reproducibility of more than 103 dc sweeping cycles. ON and OFF states were stable up to 104 seconds without significant degradation. Cyclic voltammetry data illustrates resistive switching effect can be attributed to formation and rupture of conducting paths due to oxidation and reduction of PEDOT. The maximum current before reset process was found to be increase linearly with increase in compliance current applied during set process.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3571-3574
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• 2011

Nano-scaled metal oxides have been attractive materials for sensors, photocatalysis, and dye-sensitization for solar cells. We report the controlled synthesis and characterization of single crystalline $TiO_2$ nanowires via a catalyst-assisted vapor-liquid-solid (VLS) and vapor-solid (VS) growth mechanism during TiO powder evaporation. Scanning electron microscope (SEM) and transmission electron microscope (TEM) studies show that as grown $TiO_2$ materials are one-dimensional (1D) nano-structures with a single crystalline rutile phase. Also, energy-dispersive X-ray (EDX) spectroscopy indicates the presence of both Ti and O with a Ti/O atomic ratio of 1 to 2. Various morphologies of single crystalline $TiO_2$ nano-structures are realized by controlling the growth temperature and flow rate of carrier gas. Large amount of reactant evaporated at high temperature and high flow rate is crucial to the morphology change of $TiO_2$ nanowire.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.935-944
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• 2003

Forced convective boiling heat transfer coefficients were predicted for an annular flow inside a horizontal tube for pure refrigerants and nonazeotropic binary refrigerant mixtures. The heat transfer coefficients were calculated based on the turbulent temperature profile in liquid film and vapor core considering the composition difference in vapor and liquid phases, and the nonlinearity in mixing rules for the calculation of mixture properties. The heat transfer coefficients of pure refrigerants were estimated within a standard deviation of 14% compared with available experimental data. For nonazeotropic binary refrigerant mixtures, prediction of the heat transfer coefficients was made with a standard deviation of 18%. The heat transfer coefficients of refrigerant mixtures were lower than linearly interpolated values calculated from the heat transfer coefficients of pure refrigerants. This degradation was represented by several factors such as the difference between the liquid and the overall compositions, the conductivity ratio and the viscosity ratio of both components in refrigerant mixtures. The temperature change due to the concentration gradient was a major factor for the heat transfer degradation and the mass flux itself at the interface had a minor effect.

• 한국분무공학회지
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• 제23권1호
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• pp.30-35
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• 2018

The objective of this study is to predict numerically the effect of intake humidification on the injected diesel fuel spray characteristics in a compression ignition engine. In this work, Wave model and Ducowicz model were applied as the break-up model and evaporation model, respectively. The amount of water vapor for the humidification was changed from 0% to 30% of injected fuel mass. The number of applied meshes was generated from 49,000 to 110,000. At the same time, the results of this work were compared in terms of spray tip penetration, SMD and equivalence ratio distributions. It was found that the cylinder temperature and cylinder pressure were decreased with increasing water vapor mass by vaporization latent heat and specific heat, however, the difference was very small. So, the spray tip penetration was not different by water vapor mass. Also, higher equivalence ratio distributions were observed with increasing water vapor mass by the improvement of fuel atomization.

• 한국가스학회지
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• 제2권3호
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• pp.37-48
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• 1998

밀폐된 초저온액화가스 저장탱크에 액화질소의 충전량을 바꾸어 가면서 시간이 경과함에 따른 탱크 내부의 여러 가지 변화에 대해 조사하였다. 탱크 내부의 압력, 온도, 액체와 기체의 비율 등의 변화는 충전된 액체의 양에 의존한다. 탱크에 충전된 액체의 양에 따라 (1)액면이 높아지면서 액화를 동반하기도 하고, (2)액면이 높아짐에도 불구하고 초기에는 액체의 기화가 일어나다가 압력이 높아지면 다시 액화가 일어나기도 하며, (3)액면은 일정하게 유지되지만 액체의 기화가 일어나기도 하며, (4)액면이 낮아짐과 동시에 액체의 기화가 일어나는 등 다양한 변화를 나타내었다. 탱크에 액체를 가득 채우면 압력이 급상승하여 매우 위험하므로 안전수칙에 따라 $90\%$ 이하 충전해야한다. 탱크가 완전히 밀폐되어 있을 경우, 탱크를 액체로 가득 채우면 불과 5일만에 80bar의 압력상승을 가져오지만, $90\%$ 충전하면 5일 동안에 겨우 1.5bar의 압력상승이 일어난다. 그러나 어느 경우이건 액체를 충전한 채 탱크를 완전히 밀폐시킨 뒤 장기간 방치하는 것은 대단히 위험하다.

• The Korean Journal of Ceramics
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• 제6권3호
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• pp.219-223
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• 2000

The ferroelectric SBT films were deposited on Pt/Ti/SiO$_2$/Si substrates by liquid injection metalorganic chemical vapor deposition (MOCVD) with single-mixture solution of Sr[Ta(OEt)$_5$(dmae)]$_2$and Bi(C$_6$ 6/H$_5$)$_3$. The Sr/Ta and Bi/Ta ratio in SBT films depended on deposition temperature and mol ratio of precursor in the single-mixture solution. At the substrate temperature of 40$0^{\circ}C$, Sr/Ta and Bi/Ta ratio were close to 0.4 and 1 at precursor mol ratio of 0.5~1.0, respectively. As-deposited film was amorphous. However, after annealing at 75$0^{\circ}C$ for 30 min in oxygen atmosphere, the diffraction patterns indicated polycrystalline SBT phase. The remanent polarization (Pr) and coercive field (Ec) of SBT film annealed at 75$0^{\circ}C$ were 4.7$\mu$C/$\textrm{cm}^2$ and 115.7kV/cm at an applied voltage of 5V, respectively. The SBT films annealed at 75$0^{\circ}C$ showed practically no polarization fatigue up to 10$^10$ switching cycles.