• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2418-2425
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• 1993

A two-dimensional transient heat transfer model for reactive gas assisted laser cutting process with a moving Gaussian heat source is developed using a numerical finite difference technique. The kerf width, melting front shape and temperature distribution were calculated by using the boundary-fitted coordinate system to handle the ejection of workpiece material and heat input from reaction and evaporation. An analytical solution for cutting front movement was adopted and numerical simulation was performed to calculate the temperature distribution and melting front thickness. To calculate the moving velocity of cutting front, the normal distribution of the cutting gas velocity was used. The kerf width was revealed to be dependent on the cutting velocity, laser power and cutting gas velocity.

• Journal of Integrative Natural Science
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• v.1 no.2
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• pp.122-126
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• 2008

The stress is an unavoidable result and a complex phenomenon in modern society. too, Human activity changes under control of the stress. The stress is a reaction to adrenalin or other stress hormones. It provides the power for fighting and the energy for going away from dangers. Because of the stress, our bodies increase the pulse, the blood pressure and the breath for more blood and more oxygen. So, in this research, we are measuring those which was increased by the stress. Also we will examine the change of HRV and APG on music. After that, in order to reduce the stress, we will design matching system that is based on the sense for music by using Zigbee.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.21-27
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• 2012

The characteristics of floc formation of the iron(Fe) ions contained in the acid mine drainage was studied for developing the process treating the acid mine drainage. The iron(Fe) ions were formed into flocs by the acid-base reaction with the added $Ca(OH)_2$. The molal ratio of iron(Fe) vs $Ca(OH)_2$ was one of major control variables in treatment; pH change, iron(Fe) ions concentration in treated drainage, DO (dissolved oxygen content). In addition, the air gave much effect on the color of the $iron(Fe)-Ca(OH)_2$ flocs and the attachment to magnet. The attaching to the magnet of the flocs formed in the air was much less than the case without air.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.3
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• pp.184-192
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• 2010

PEM fuel cell produces electric power, water and heat by the electrochemical reaction of hydrogen and oxygen. The heating value is dependent on the molar enthalpy of vaporization of product water and the performance loss. In this paper, the heating value of fuel cell stack has been studied under various stack operating temperatures to achieve more efficient heat management. A technology using the molar enthalpy of vaporization of product water is suggested to reduce heat-up time during start-up of a fuel cell vehicle.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.3
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• pp.317-324
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• 2010

It was used as measuring system to diagnose insulating condition, by which was kept a insulating resistance of inner stack and at the same time was cooled electrochemical heat of reaction of FCEV(fuel cell electric vehicle) stack that used a compressed hydrogen gas reacting with oxygen in accordance with variation on thermal degradation of nonconductive heat transfer fluid. Consequently it was developed a cylindrical multi-terminal capacitive-conductive sensor that could be attached to the internal surface of cooling system pipe to evaluate capacitance and conductivity of heat transfer fluid.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.916-920
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• 2003

Photoreactions of N-(2,4-dibromonaphthyl)arenecarboxamides in basic medium result in the intramolecular substituted products, 2-aryl-8-bromonaphthoxazoles in moderate yields and further photoreactions of the products afford the reduced products, 2-arylnaphthoxazoles. These reactions are straightforward for syntheses of naphthoxazole derivatives. Since the intramolecular photosubstitution of the bromoarenecarboxamide by the oxygen of its amide group is more effective than the photoreduction of the substituted product, 2-aryl-8- bromonaphthoxazole in basic medium, the intramolecular substituted product, 2-aryl-8-bromonaphthoxazole can be isolated. A charge-transfered excited singlet state of an imidol form of the 2-bromoarenecarboxamide is involved in the photosubstitution, whereas an excited triplet state of the 2-aryl-8-bromonaphthoxzole is closely involved in the photoreduction.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.597-600
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• 2004

Fabrication technique and performance test of catalytic micro propulsion are treated based on MEMS technology. This propulsion is designed to use hydrogen peroxide as liquid mono-propellant for attitude control of pica-satellite. The propellant is fed into the micro reactor channel and decomposed into hot gas yielding controllable thrust by catalyst. In order to increase the efficiency of the reaction that depends on the contact area of propellant and catalyst, porous surface formation on the channel accompanied by platinum particle deposition has been performed using H$_2$PtCl$_{6}$ solution as a precursor. Several thrusters were fabricated in different concentration of H$_2$PtCl$_{6}$ solution to determine the best quantity of Pt particles. For the comparison of the performance of each thruster, the volume of oxygen generated by the decomposition of hydrogen peroxide and the thrust were measured.red.

• KSBB Journal
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• v.8 no.3
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• pp.272-281
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• 1993

State varibles were estimated for fermentations of K. marxianus under various dilution rates and dissolved oxygen concentrations. The number of elementary reaction stoichiometry with fixed coefficients was determined by singular variable decomposition. Stoichiometry with feasible physical meaning was obtained by target factor analysis. States of fermentations were estimated by linear quadratic programming. The process conditions of single cell production to maximize carbon source consumption were suggested.

• Journal of Environmental Health Sciences
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• v.35 no.3
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• pp.201-208
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• 2009

Oxidation of phenol in aqueous media by electro-Fenton process using Ru-Sn-Sb/graphite electrode has been studied. Hydrogen peroxide was electrically generated by reaction of dissolved oxygen in acidic solutions containing supporting electrolyte and $Fe^{2+}$ was added in aqueous media. Phenol degradation experiments were performed in the presence of electrolyte media at pH 3. Effect of operating parameters such as current, electrolyte type (NaCl, KCl and $Na_2SO_4$) and concentration, $Fe^{2+}$ concentration, air flow rate and phenol concentration were investigated to find the best experimental conditions for achieving overall phenol removal. Results showed that current of 2 A, NaCl electrolyte concentration of 2g/l, 0.5M concentration of $Fe^{2+}$, air flow rate of 1l/min were the best conditions for mineralization of the phenol by electro-Fenton.

• Journal of the Korean Ceramic Society
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• v.31 no.4
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• pp.443-447
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• 1994

Compacts of mixed SiO2-Si powder were liquid phase sintered at 145$0^{\circ}C$ for up to 60 min in a hydrogen atmosphere. In contrast to the conventional microstructures of liquid phase sintered materials, the specimens showed that the solid phase of SiO2 formed a matrix while the liquid phase of Si was the dispersed in the solid matrix. The dispersion of liquid Si pockets was attributed to the high wetting angle of liquid Si on solid SiO2. Because of relatively high solubility of SiO2 in liquid Si at 145$0^{\circ}C$, SiO2 particles accommodated their shape via a solution-reprecipitation process. The liquid Si pockets grew by coalescing with their neighbour pockets. In the latter stage of the sintering, plate-shape grains appeared in the liquid Si pockets. The grains were SiO2 phase precipitated from the liquid Si which was oversaturated with oxygen during cooling to room temperature. By the formation and subsequent removal of the gaseous SiO phase due to the reaction between SiO2 and Si, the specimens became porous.