• 대한기계학회논문집B
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• 제27권10호
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• pp.1393-1400
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• 2003

Ignition of hydrogen and oxygen in the "third limit" is theoretically investigated in the stagnation point flow with activation energy asymptotics. With the steady-state approximations of H, OH, O and HO$_2$, a two-step reduced kinetic mechanism is derived for the regime lower than the crossover temperature T$_{c}$ at which the rates of production and consumption of all radicals are equal. Appropriate scaling of Damkohler number successfully provides the explicit relationship between pressure, temperature and strain rate at ignition. It is shown that, compared with those for the counterflow, ignition temperatures for the stagnation point flow are considerably increased with increasing the system pressure. This is because ignition in the "third limit" is characterized by the production of reduction of $H_2O$$_2$, which is reduced by wall effect. Strain rate substantially affects ignition temperature because key reaction rates of $H_2O$$_2$ are comparably with its transport rate, while the mixture temperature and the hydrogen composition do not significantly affect ignition temperature.e.

• 한국결정성장학회지
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• 제17권6호
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• pp.231-237
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• 2007

For an aspect ratio (transport length-to-width) of 5, Pr=3.34, Le=0.078, Pe=4.16, Cv=1.01, $P_B=50$ Torr, only thermally buoyancy-driven convection ($Gr=4.83{\times}10^5$) is considered in this study in spite of the disparity in the molecular weights of the component A ($Hg_2Cl_2$) and B which would cause thermally and/or solutally buoyancy-driven convection. The crystal growth rate and the maximum velocity vector magnitude are decreased exponentially for $3{\le}Ar{\le}5$, for (1) adiabatic walls and (2) the linear temperature profile, with a fixed source temperature. This is related to the finding that the effects of side walls tend to stabilize convection in the growth reactor. The rate for the linear temperature profiles walls is slightly greater than for the adiabatic walls far varied temperature differences and aspect ratios. With the imposed thermal profile, a fixed source region, both the rate and the maximum velocity vector magnitude increase linearly with increasing the temperature difference for $10{\le}{\Delta}T{\le}50K$.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.219-222
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• 2005

Recently, the interest of the engine capacity and environment of the atmosphere is increasing, so the researches for the engine capacity have been conducted for a long time. But the internal environment of an automotive engine is very severe. A piston is exposed to combustion gas of over $2000^{\circ}C$ and strong friction is occurred by high speed motion in the cylinder. The fraction between piston and wall of the cylinder causes the increase of temperature in the engine. The temperature of the engine has an effect on the engine capacity. If the temperature is high, the capacity of the engine is low. So we have to maintain the optimum temperature. To maintain the optimum temperature, the enough flow rate of the engine oil is needed. The oil jet is used to control the flow rate of the engine oil and supply the engine oil to the piston and cylinder. The purpose of this study is to check the mass flow rate of the engine oil and the characteristics of internal flow of the oil jet. Flow pattern of the engine oil is very important because it concludes the loss in the oil jet. This study is the previous research about the oil jet and we will consider the movement of the ball check valve to get more accuracy result.

• Carbon letters
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• 제10권3호
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• pp.181-189
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• 2009

Activated carbon spheres (ACS) were prepared at different heating rates by carbonization of the resole-type phenolic beads (PB) at $950^{\circ}C$ in $N_2$ atmosphere followed by activation of the resultant char at different temperatures for 5 h in $CO_2$ atmosphere. Influence of heating rate on porosity and temperature on carbon structure and porosity of ACS were investigated. Effect of heating rate and temperature on porosity of ACS was also studied from adsorption isotherms of nitrogen at 77 K using BET method. The results revealed that ACS have exhibited a BET surface area and pore volume greater than $2260\;m^2/g$ and $1.63\;cm^3/g$ respectively. The structural characteristics variation of ACS with different temperature was studied using Raman spectroscopy. The results exhibited that amount of disorganized carbon affects both the pore structure and adsorption properties of ACS. ACS were also evaluated for structural information using Fourier Transform Infrared (FTIR) Spectroscopy. ACS were evaluated for chemical composition using CHNS analysis. The ACS prepared different temperatures became more carbonaceous material compared to carbonized material. ACS have possessed well-developed pores structure which were verified by Scanning Electron Microscopy (SEM). SEM micrographs also exhibited that ACS have possessed well-developed micro- and meso-pores structure and the pore size of ACS increased with increasing activation temperature.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.311-316
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• 2005

The experimental study for an operational characteristics and performance of the sodium heat pipe were carried out. For an experiment. the heat pipe which is 1000mm length and 25.4mm diameter of stainless steel container with 50 mesh of screen wick using sodium as a working fluid is manufactured and tested as functions of heat flow rate, inclined angle and operating temperature. The test results are as follows. During the start-up. frontal start up was observed because of the vapor density increasing as increased the hot zone. Also, the heat pipe showed uniform temperature over than $420^{\circ}C$ of the operating temperature. The average heat transfer coefficient increased as the heat flux and the vapor temperature increase, and the range of the total thermal resistance was 0.075-0.04 $^{\circ}C/W$ at the 12-53.55 $kW/m^2$ of heat flux and $500-750^{\circ}C$of operating temperature. The maximum heat flow rate was 750W at the 10 degree of top heating mode.

• 한국세라믹학회지
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• 제26권3호
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• pp.323-330
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• 1989

Wear restance titanium carbonitride (TiCN) films were deposited on the SKH9 tool steels and WC-Co cutting tools by plasma assisted chemical vapor deposition (PACVD) using a gaseous mixture of TiCl4, CH4, N2, H2 and Ar. The effects of the deposition temperature and RF(Radio Frequency) power on the deposition rate, chlorine content and crystallinity of the deposited layer were studied. The experimental results showed that the stable and adherent films could be obtained above the deposition temperature of 47$0^{\circ}C$ and maximum deposition rate was obtained at 485$^{\circ}C$. The deposition rate was much affected by RF power and maximum at 40W. The crystallinity of the deposited layer was improved with increasing the deposition temperature and RF power. The TiCN films deposited by PACVD contained much chlorine. The chlorine content in the TiCN films was affected by deposition conditions and decreased with improving the crystallinity of the deposited layer. The deposited TiCN films deposited at the deposition temperature of 52$0^{\circ}C$ and RF power of 40W had an uniform surface with very fine grains of about 500$\AA$ size. The microhardness of the deposited layer was 2,300Kg/$\textrm{mm}^2$.

• 한국수소및신에너지학회논문집
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• 제6권1호
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• pp.35-41
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• 1995

The MmNi-based alloy electrode was studied for use as a negative electrode in Ni-MH battery. Alloys with $MmNi_5-_xM_x$(M=Co,Al,Mn) composition were synthesized, and their electrode charateristics of activation rate, temperature dependence, electrode capacity and cycle life were investigated. With increasing Al content and decreasing Mn content in the alloys, the discharge capacity increased while the cycle life decreased. As x in $MmNi_5-_xM_x$ increased from 1.5 to 2.0, decreasing the Ni content, the discharge capacity, the low temperature property and the rate capability decreased. However its cycle life was improved. Increasing Co content resulted in a prolonged cycle life and decrease of high rate discharge capacity. It can be concluded that the most promising alloy in view of discharge capacity and cycle life is $MmNi_{3.5}Co_{0.7}Al_{0.5}Mn_{0.3}$.

• Journal of Pharmaceutical Investigation
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• 제19권3호
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• pp.145-154
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• 1989

Methyl methacrylate-butyl methacrylate copolymer (MMBM)-povidone (PVP) films were investigated as a potential topical drug delivery system for the controlled release of econazole nitrate as a model drug. The effect of changes in film composition, drug concentration, film thickness, pH and temperature of release medium on the in vitro release of econazole nitrate were studied. The release rate constant was found to be increased with increasing povidone content in dry films. Drug release followed zero-order kinetics in the initial stage and then release rate increased gradually with time, espicially in the films having larger proportions of PVP. The release rate was found to be dependent on drug content, film thickness, the pH and temperature of release medium. Antimicrobial test showed that microbial growth was inhibited markedly with increasing proportions of PVP in films. Also drug content and film thickness affected the antimicrobial activity.

• 한국세라믹학회지
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• 제33권4호
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• pp.441-447
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• 1996

Sb doped SnO2(ATO:Antinomy doped Tin Oxide) thin films were prepared by a DC magnetron spttuering method using oxide target and the deposition characteristics were investigated. The experimental conditions are as follows :Ar flow rate : 100 sccm oxygen flow rates ; 0-100 sccm deposition temperature ; 250 -40$0^{\circ}C$ DC sputter powder ; 150~550 W and sputtering pressure ; ; 2~7 mTorr. Deposition rate greatly depends not on the deposition temperature but on the reaction pressure oxygen flow rate and sputter power,. when the sputter powder is low ATO thin films with (110) preferred orientation are deposited. And when the sputter power is high (110) prefered orientation appeares with decreasing of oxygen flow rate and increasing of suputte-ring pressure.

• 산업기술연구
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• 제20권B호
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• pp.77-86
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• 2000

In order to observe the pattern forming of copper plate and chemical corrosion reaction, a study on the effect of the process parameters on the formation of micro-pattern by a photochemical etching of copper plate was carried out. The results are as follows : 1) Etching rate increases as the concentration of etchant increases under the regular condition of the temperature by the increasing of diffusion rate to surface. 2) Etching rate increases as the temperature of etchant increases by the fast acting of the material delivery of diffusion to surface under the regular condition of concentration. 3) It was found that etching speed increases as the material delivery of convection rising increased when the aeration speed of etchant increases. This result was from the fact acted by the material delivery of convection rising rather than material delivery of diffusion to the surface.