• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.93-96
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• 2009

In the cathode channel of a PEM fuel cell, the local concentration of oxygen near the gas diffusion layer (GDL) decreases in streamwise direction due to chemical reactions, which degrades the efficiency of the oxygen consumption and overall fuel cell efficiency. We numerically studied the influence of the swirling flow generated by a slanted groove mixer (SGM) on the concentration distribution of oxygen. We found that the swirling flow can increase the concentration of oxygen near the GDL, and subsequently improves the oxygen consumption rate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.117-121
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• 1992

Zinc oxide thin films were obtained from zinc acetate-2-water and oxygen by photo-CVD method. (1) The formation of ZnO films sarts from 100[$^{\circ}C$] and the deposition rate increases with increasing substrate temperature. (2) The rate of deposition was also affected by flow rates of O$_2$(reaction gas) and N$_2$(Carrier gas). (3) The deposition rate decreases with increasing O$_2$mole rate. (4) The transmission of the films was independent of oxygen mole rate and it was largely affected substrate temperature. (5) The electric resistivity of th films was largely varied at oxygen mole rate 10[%] and above 20[%], a plateau was encountered. Also, it increases with increasing substrate temperature. As the results, at substrate temperature: 200[$^{\circ}C$]; O$_2$gas mole rate:10[%]; reation time:10[min] pressure: 10$\^$-2/[atm], deposition rate; transmittance; resistivity were 780[A$\^$0/; 94[%]; 7${\times}$10$\^$-2/[$\Omega$$.$cm] respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.3
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• pp.210-222
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• 1994

The characteristics of flows, temperatures, and concentrations of oxygen are numerically studies in the Czochralski furnace with a uniform axial magnetic field. Important governing factors to the flow fields include buoyancy, thermocapillarity, centrifugal force, magnetic force, diffusion and segregation coefficients of the oxygen, evaporation coefficient in the form of SiO, and ablation rate of crucible wall. With an assumption that the flow fields have reached the steady state, which means that two velocity components in the meridional plane and circumferential velocity, temperatures, electric current intensity become non-transient, then unsteady concentration field of oxygen has been analyzed with an initially uniform oxygen concentration. Oxygen transports due to convection and diffusion in the Czochralski flow field and oxygen flux through the growing crystal surface has been investigated.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.508-508
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• 1996

;The growth of films have considerable interest in the field of superlattice structured multi-layer epitaxy led to realization of new devices concepts. Molecular beam epitaxy (MBE) with in situ observation by reflection high-energy electron diffraction (RHEED) is a key technology for controlled layered growth on the atomic scale in oxide crystal thin films. Also, the combination of radical oxygen source and MBE will certainly accelerate the progress of applications of oxides. In this study, the growth process of single crystal films using by MBE method is discussed taking the oxide materials of Bi-Sr-Ca-Cu family. Oxidation was provided by a flux density of activated oxygen (oxygen radicals) from an rf-excited discharge. Generation of oxygen radicals is obtained in a specially designed radical sources with different types (coil and electrode types). Molecular oxygen was introduced into a quartz tube through a variable leak valve with mass flowmeter. Corresponding to the oxygen flow rate, the pressure of the system ranged from $1{\;}{\times}{\;}10^{-6}{\;}Torr{\;}to{\;}5{\;}{\times}{\;}10^{-5}$ Torr. The base pressure was $1{\;}{\times}{\;}10^{-10}$ Torr. The growth of Bi-oxides was achieved by coevaporation of metal elements and oxygen. In this way a Bi-oxide multilayer structure was prepared on a basal-plane MgO or $SrTiO_3$ substrate. The grown films compiled using RHEED patterns during and after the growth. Futher, the exact observation of oxygen radicals with MBE is an important technology for a approach of growth conditions on stoichiometry and perfection on the atomic scale in oxide. The oxidization degree, which is determined and controlled by the number of activated oxygen when using radical sources of two types, are utilized by voltage locked loop (VLL) method. Coil type is suitable for oxygen radical source than electrode type. The relationship between the flux of oxygen radical and the rf power or oxygen partial pressure estimated. The flux of radicals increases as the rf power increases, and indicates to the frequency change having the the value of about $2{\times}10^{14}{\;}atoms{\;}{\cdots}{\;}cm^{-2}{\;}{\cdots}{\;}S^{-I}$ when the oxygen flow rate of 2.0 seem and rf power 150 W.150 W.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.4
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• pp.93-98
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• 2014

In this study, control of oxidizer mass flow rate and verification of control system were performed for hybrid rocket thrust control application. Oxidizer flow control system consists of ball valve and stepping motor where gaseous oxygen was used for oxidizer at feeding pressure of 10, 20 and 30 bar. According to experimental results, the oxidizer mass flow rate showed a relatively linear increment as ball valve open angle increases regardless of feeding pressure. In addition, the level of the oxidizer flow rate was kept almost constant at each sequence of flow control with ball valve during the 20 seconds of operation.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.742-750
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• 1999

Nanosized TiO2 powders were synthesized using the chemical vapor conduensation (CVC) process with various precursor feeding rates (0.37 and 0.752 ml/min) and oxygen flow rates(1-2slm) conditions and powder characteristics were investigated in terms of formation of nanosized powder varying with the above processing conditions. For this study the main thermodynamic and fluid dynamic factors -supersaturation ratio collision frequency and residence time-were theoretically established and compared to the characteristics of formed TiO2 powder. The loosely combined anatase phase powders (including less than 3%of rutile phase) having 20-30nm crystallite size were obtained at overall conditions. The particle size and th degree of agglomeration for a precursor flow rate of 0.376 ml/min turn out to be smaller than for a flow rate of 0.742ml/min. And the decreasing of particles size and particle size distribution were observed with increasing oxygen flow rate as the residence time and collision frequency were reduced by increasing oxygen flow rate,. It appears that further scrutiny is needed to elucidate the influence of the individual thermodynamic and kinetic parameters mdependently.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.12
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• pp.868-873
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• 2011

Oxygen transfer rate generally determines the performance of an aerobic wastewater treatment process that treats high strength wastewater such as food wastewater, animal wastewater and landfill leachate. In this paper, OUR and $K_L{\cdot}a$ were evaluated by using Jet Loop Reactor (JLR) according to the concentration of a mixed liquor volatile suspended solid (MLVSS), oxygen (air) flow rate and energy input as the variable of the operating conditions. Also, a nonlinear regression model was proposed by the statistical methods with the calculated $K_L{\cdot}a$. As a results, in case of applying the high strength wastewater which has to maintain high MLVSS, the energy input and the air flow rate are major parameters oxygen transfer rate in JLR. Finally, the final nonlinear regression model had been developed as a function of E/V, $Q_g$, and ${\mu}_c$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.5
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• pp.373-379
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• 2013

Mg-doped zinc tin oxide (ZTO:Mg) thin films were prepared on glasses by rf magnetron sputtering. $O_2$ was introduced into the chamber during the sputtering. The optical properties of the films as a function of oxygen flow rate were studied. The crystal structure, elementary properties, and depth profiles of the films were investigated by X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS), respectively. Bottom-gate transparent thin film transistors were fabricated on $N^+$ Si wafers, and the variation of mobility, threshold voltage etc. with the oxygen flow rate were observed.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.4 no.1
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• pp.121-131
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• 2000

Melt flow, heat and mass transfer of oxygen have been analyzed numerically in the process of Czochralski single crystal growth of silicon under the influence of misaligned cusp magnetic fields. Since the silicon melt in a crucible for crystal growth is of high temperature and of highly electrical-conducting, experimentation method has difficulty in analyzing the behavior of the melt flow. A set of simultaneous nonlinear equations including Navier-Stokes and Maxwell equations has been used for the modelling of the melt flow which can be regarded as a liquid metal. Together with the melt flow which forms the Marangoni convection, a flow circulation is observed near the comer close both to the crucible wall and the free surface. The melt flow tends to follow the magnetic lines instead of traversing the lines. These flow characteristics helps the flow circulation exist. Mass transfer characteristics influenced by the melt flow has been analyzed and the oxygen absorption rate to the crystal has been calculated and turned out to be rather uniform than in the case of an aligned magnetic field.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.179-182
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• 2005

Test of liquid oxygen sub-cooling by helium injection, which is one of the method of temperature conditioning of cryogenic propellant in liquid propulsion rocket, is performed. The sub-cooling effect at different He injection flow rate with the same initial liquid oxygen mass is compared. Test results showed liquid oxygen temperature decrease of $5\sim6^{\circ}C$ under test condition. And the required time for cooling is inversely proportional to He injection flow rate.