• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.249-252
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• 2002

The change of critical current with a crack formation in a Bi-2223/Ag tape was studied by experimental and numerical analyses. Critical current of Bi-2223/Ag tape was measured with a continuous DC-power supply. The current-voltage relation of a Bi-2223/Ag tape is measured by the four point method. Numerical method is used to solve two dimensional heat conduction equation. By comparing the experimental and numerical results, the validity of numerical method is verified.

• Journal of the Korean Vacuum Society
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• v.2 no.4
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• pp.507-514
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• 1993

The solid state reaction of Mo/Si multilayer thin films produced by RF magnetron sputtering technique was examine dusing differential scanning calorimetry (DSC) and x-ray diffraction, and explained in view of two concepts, effective drivig force and effective heat of formation. In constant scanning rate DSC, there were two exothermic peks which corresponded to the formation of h-MoSi2 and t-MoSi2 , respectively. The activation energyfor theformation of h-MoSi2 was 1.5eV , and that of t-MoSi2 was 7.8eV. Nucleation wa stherate controlling mechanism for each of the silicide formation. Amorphous phase was not formed , which was consistent withtheprediction by the concept of effective driving force. h-MoSi2 the first crystalline phase, was considered to have lower interfacial free energy than t-MoSi2 and by increasing temperature it was transformed into more stable t-MoSi2.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.267-273
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• 2001

In this study, welding phenomena involved in formation of penetrators during high frequency electric resistance welding were investigated. High speed cinematography of the process revealer that a molten bridge between neighboring skelp edges forms at apex point and travels along narrow gap toward to welding point at a speed ranging from 100 to 400 m/min. The bridge while moving along the narrow gap swept away oxide containing molten metal from the gap, providing oxide-free surface for a forge-welding at upsetting stand frequency of the budge formation, travel distance and speed of the bridge were affected by the heat input rate into strip. The travel distance and its standard deviation were found to have a strong relationship with the weld defect density. Based on the observation, a new mechanism of the penetrator formation during HF ERW process is proposed.

• Journal of the Korean Ceramic Society
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• v.28 no.6
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• pp.495-501
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• 1991

This study is intended to make defect-free region, denuded zone at the silicon wafer surface for semiconductor device substrates. In this experiment, initial oxygen concentration of starting material CZ-grown silicon wafer, various heat treatment combinations, denuding ambient and the amounts of oxygen reduction were measured, and then denuded zone (DZ) formation and depth were investigated. In Low/High anneal (DZ formation could be achieved), the optimum temperature for Low anneal was 700$^{\circ}C$∼750$^{\circ}C$. In case of High anneal, with the time increased, DZ depth was increased at 1000$^{\circ}C$, 1150$^{\circ}C$ respectively, but on the contrary, DZ depth was decreased at low temperature 900$^{\circ}C$. As well, out-diffusion time below 2 hours was unsuitable for effective Gettering technique even though the temperature was high, and DZ formation could be achieved when initial oxygen concentration was only above 14 ppm in silicon wafer.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.332-333
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• 2007

The effect of asymmetric rolling on the recrystallization texture of an AA 3003 Aluminum alloy was investigated by X-ray diffraction. It was found that the texture of asymmetrically rolled sheets prior to subsequent heat treatment promoted the formation of the <111>//ND textures, and remained after heat treatment at $275^{\circ}C$ during 20 min in salt bath condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.1
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• pp.50-60
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• 1998

As a method to develop an enhanced heat transfer fluid, the fine particles of a phase-change material were mixed with a conventional heat transfer fluid. Paraffin, which can be obtained easily in domestic market, was used for the phase-change material and water was used as a carrier fluid. Fine liquid particles of paraffin were formed in water as an emulsion by using an emulsifier, and they were cooled rapidly to become solid particle, resulting in paraffin slurry. The average diameter of produced solid particles was inversely proportional to the amount of the added emulsifier, which was theoretically proved. The produced paraffin slurry was tested thermally in heat transfer test section having a constant-heat-flux boundary condition. The test section was made of a circular stainless-steel pipe, which was directly heated by the power supply having a maximum of 50 Volts-500 Amperes. DSC(Differential scanning calorimeter) tests showed that two kinds of phase change were involved in the melting of paraffin, and it was explained in two different ways. A five- region-melting model was developed by extending the conventional three-region-melting model, and was used to obtain the local bulk mean temperatures of paraffin slurry in the heating test section. The local heat transfer coefficient showed a maximum where the bulk mean temperature of the paraffin slurry reached at the melting temperature of paraffin.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.5
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• pp.179-183
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• 2008

Employing screen printing technology, aluminum is applied to the back side of the n-type silicon wafer to see the effect of the heat treatment parameters on the Voc of the solar cell, Heat treatment at $850^{\circ}C$ produces the highest Voc among various heat treatment conditions. Heat treatment at the temperatures higher than $850^{\circ}C$ results in lower Voc, which is due to the destruction of the Al-Si alloy emitter layer. The destruction of Al-Si layer observed to be caused by the vigorous movement of silicon atoms toward aluminum layer during the heat treatment.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.289-292
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• 1999

The charateristic of hydration reaction was studied in CaO-Al2O3-SiO2 system glass. As a result, the rate of heat liberation curves of synthestized glass becomes fixed after having increased by degrees. And it is decreasing after having increased suddenly. It was found that the total heat liberation with hydration for synthesized glass has a close relationship with the formation amount of ettringite.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.201-203
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• 2000

In this study, effect of welding parameters on the defect density in the weldments produced by high frequency electric resistance welding process. The defect density measured by X-ray radiography showed a W-type curve as a function of heat input rate. The mechanisms of the such behavior were discussed based on the chemical compositions of the oxides formed at the weldments.

• Journal of the Korean Society of Combustion
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• v.13 no.1
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• pp.1-9
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• 2008

Emission characteristics of NOx and CO with heat loss under high efficiency combustion conditions of $CH_4$/Air prmixed flame were examined numerically using detailed-kinetic chemistry. The one-dimensional combustor length was fixed 5cm, and the equivalence ratio was varied from 0.75 to 0.95. To consider the effects of heat loss on NOx and CO formation, the radiative heat loss rate and combined heat loss rate of conductive and convective heat transfer are included. The following conclusions were drawn. In order to reduce the NOx and CO emission level simultaneously, the temperature of product gases must be reduced under 1,800K as soon as possible but kept over 1,300K during the residence time which is needed to converge CO to $CO_2$.