• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 초전도 자성체
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• pp.14-16
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• 2002

Melting and re-solidification nature of $SmBa_2Cu_3O_{7-y}$ (Sm123) grains in Ba-Cu-O (Ba:Cu=3:5) liquid containing 0.7 at.% yttrium were investigated at the temperature lower than its melt point. When Sm123 grains/liquid powder compacts were heated to a temperature between two melting points of Ba-Cu-O liquid ($1000^{\circ}C$) and a Sm123 phase ($1060^{\circ}C$) and held at this temperature for appropriate time, Sm123 grains melted partly in the liquid that was formed by melting of the liquid-forming powder. During subsequent slow cooling, (Sm,Y)$Ba_2Cu_3O_{7-y}$ solidified at the outer parts of the unmelted Sm12 grains, which is distinguished from the core regions by lower $Sm_2BaCuO_5$ (211) density.

• 한국의류학회지
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• 제13권1호
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• pp.43-47
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• 1989

The microstructural changes of nylon 6 UDY, POY and FDY were compared after free-annealing through crystallinity, birefringence, and melting behavior analyses. Free-annealing was done at various temperatures $(120^{\circ}C\;,140^{\circ}C,\;160^{\circ}C,\;180^{\circ}C,\;200^{\circ}C)$ and times (15 min., 30 min., 60 min.) using vaccum oven. Crystallinity was measured by the density gradient column technique and birefringence was measured using a Nikon polarizing microscope with a quartz wedge and Senarmont compensator. Melting behavior was investigated on the basis of DSC melting corves. Crystallinites of specimens increased as the treatment temperature and time increased. Birefringence of UDY increased after annealing and increased as the treatment temperature increased. On the other hand, those of POY and FDY decreased after annealing. Especially, the changes of crystallinity and birefringence of treated POY were particularly lower than those of treated UDY and FDY. Melting peaks of untreated UDY, POY and FDY were different in the position and the shape, but little change was seen in melting peaks in spite of increasing the annealing temperature and time. UDY and FDY showed single melting peaks in all the specimens. But POY showed double melting peaks, which means the coexistences of crystals with different thermal properties.

• 한국의류산업학회지
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• 제14권6호
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• pp.1024-1031
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• 2012

The thermal bonding PET fabrics were produced through high temperature steaming (HTS) of low melting PET yarn as warp and composite fancy yarn containing low melting PET yarn as weft. The low melting PET yarn of sheath-core structure consisted of a regular PET in core portion and low melting PET in sheath portion. The composite fancy yarn consisted of regular PET yarn as inner part and effect part and low melting PET yarn as binding part. This study was carried out to investigate the melting behavior of thermal bonded PET fabric, the effect of HTS on the thermal bonding, mechanical properties, and dyeing properties. The melting peak of low melting PET yarn showed two melting peaks caused by sheath-core structure. Almost the entire thermal bonding of the fancy PET fabrics containing low melting PET yarn has formed at $200^{\circ}C{\times}3min$ of HTS. The tensile strength in warp and weft direction of the fancy PET fabrics slightly decreased as temperature of HTS increased. The total K/S value of the fancy PET fabrics decreased slightly to $180^{\circ}C{\times}3min$ of HTS, while increased slightly above $200^{\circ}C{\times}3min$ of HTS. The changes in the hue angle ($H^{\circ}$) of the thermal bonded fancy PET fabrics dyed with disperse dyes hardly ever happened.

• 대한기계학회논문집B
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• 제21권7호
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• pp.919-927
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• 1997

The main purpose of this study is to determine bifurcation as the primary instability of a glass melting furnace. Steady-state and unsteady characteristics of natural convection in the partially open cavity as appeared in a glass melting furnace is investigated by using numerical analysis. Three types of convection, such as steady laminar, unsteady periodic or unsteady quasi-periodic convection may occur according to the temperature difference between upper two isothermal surfaces along the depth of cavity in a glass melting furnace. In the temperature difference of 150-900 K between batch and free surface, the larger the temperature difference, the weaker the convection strength and unsteadiness. Since the glass viscosity is increasing exponentially in the lower temperature, the batch freezes the thermofluidic field especially below the surface of it. If the depth of cavity is 0.5 m, the bifurcation to time-dependent natural convection may occur in the range of 60-650 K. If that is 1.0 m, it may occur in the whole range of temperature difference.

• 전기학회논문지
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• 제58권9호
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• pp.1775-1777
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• 2009

BiSrCaCuO films were prepared on MgO single substerate at $885^{\circ}C$ by melt process. The films showed superconductivity above liquid nitrogen temperature (Tc= 96K). To investigate the effect of a melting temperature on the forming of the surface texturing, the samples were prepared under various temperature. The used powder was of high Tc phase. It is implies that the origin of the properties due to the heat treatment.

• 대한기계학회논문집
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• 제9권4호
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• pp.414-420
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• 1985

본 연구에서 상변화 물질은 얼음과 물을 택하였으며, 시편의 기하학적 형상은 원동형 얼음봉을 사용하였고 온도가 일정한 물속에 수평으로 잠겨진 상태에서 얼음봉 이 융해되는 현상을 가시화하고 이를 관찰하였다. 시편주위에 발생하는 자연대류현 상이 접면효과를 받지 않토록 하기 위하여 물탱크의 크기는 시편직경의 5배 이상으로 하였고 주위물의 온도는 정도가 최대인 4.deg. C 부근을 전후한 최저 2.5.deg. C에서 최고 15.deg. C 까지를 택하였다. 융해현상은 2차원 음영방법으로 가시화하고 사진으로 기록하였다. 융해되는 얼음봉의 형상은 Fourier수와 Stefan수의 곱으로 정의된 무차원시간(.zeta.)을 변수로 하여 나타내었다. 정해진 물의 온도에서 사진으로 기록된 결과를 콤퍼레이터 (comparator)를 이용하여 음영의 변화량을 구하여 각 원주각에서의 국부 Nusselt수와 평균 Nusselt수를 무차원시간에 대하여 구하였다.

• 설비공학논문집
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• 제19권12호
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• pp.883-888
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• 2007

As a starting point of investigating what molecular dynamic simulations can reveal about the nature of atomic level of heating and cooling process, argon described by the LJ potential is considered. Stepwise heating and cooling of constant rates are simulated in the NPT (constant number, pressure and temperature) ensemble. Hysteresis is found due to the superheating and supercooling. Drastic change of volume and energy is involved with phase change, but the melting point can not be obtained by simply observing the changes of these quantities. Since liquid and solid phases can co-exist at the same temperature, Gibbs free energy should be calculated to find the temperature where the Gibbs free energy of liquid is equal to that of the solid since the equilibrium state is the state of minimum Gibbs free energy. The obtained melting temperature, $T^*=0.685$, is close to that of the experiment with only 2% error.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.351-354
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• 2002

The new enhanced method of temperature control need not any reference temperature, the system itself can find the melting temperature of gallium as a reference point by dithering input heat flux. If gallium is in melting state, the latent heat of fusion works, so gallium temperature does not change on dithering input heat flux. Also, the control method can determine the state of gallium; solid, liquid, or melting state by investigating the temperature in gallium. We apply this new temperature stabilization method to stabilize a Fabry-Perot cavity, which serves as a ultimate length measurement technique. We achieved 1 mK-temperature stability and 1.5426 nm/ 95 mm-length stability over 10 hours.

• KIEAE Journal
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• 제12권4호
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• pp.97-104
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• 2012

A phase-change material is a substance with a high heat of fusion which, melting and freezing at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid. Therefore, PCMs are classified as latent heat storage (LHS) units. The purpose of this study is to analyze PCM wallboard design parameters using dynamic energy simulation. Among the factors of PCM, melting temperature, latent heat, phase change range, thermal conductivity are very important element to maximize thermal energy storage. In order to analyze these factors, EnergyPlus which is building energy simulation provided by department of energy from the U.S is used. heat balance algorithm of energy simulation is conduction finite difference and enthalpy-temperature function is used for analyzing latent heat of PCM. The results show that in the case of melting temperature, the thermal energy storage could be improved when the melting temperature is equal to indoor surface temperature. It seems that when the phase change range is wide, PCM can store heat at a wide temperature, but the performance of heat storage is languished.

• 에너지공학
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• 제11권3호
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• pp.262-268
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• 2002

The present paper investigated the effect of ultrasonic vibrations on the melting process of phase-change materials (PCM). Furthermore, the present study considered constant heat-flux boundary condition, whereas many of the previous researches had adopted constant wall-temperature condition. The results of the present study revealed that ultrasonic vibrations accompanied the effects like acoustic streaming, cavitation, and thermally-oscillating flow. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They speed up the melting process as much as 2.5 times, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, temperature and Nusselt numbers over time provided a conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.