• The Journal of Natural Sciences
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• v.9 no.1
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• pp.89-93
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• 1997

Polyorganophosphazenes bearing various hydrophilic and hydrophobic side groups were synthesized. These polymers were crosslinked by three methods. The side groups were (2-methoxyethoxy)ethoxy, 2,2,2-trifluoroethoxy, phenyloxy, ethyl ester of alanin. Polymers synthesized in this study were crosslinked by gamma ray irradiation, UV irradiation, and UV irradiation in the presence of crosslinker and photosensitizer. Polymers crosslinked by UV irradiation in the presence of crosslinker and photosenitizer yielded hydrogels of highest elasticity. All hydrogels had lower critical separation temperature behavior.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.1
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• pp.17-20
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• 2004

We derive specific heat gap at the critical temperature as an exact anylitical function of applied magnetic field by using the thermodynamics. And we calculate numerical value of specific heat gap for some superconductors with the derived results and discuss the physical meaning. And it will be discussed that gap of specific heat discontinuity under certain magnetic field intensity become zero at the critical temperature.

• Journal of Energy Engineering
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• v.10 no.3
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• pp.294-298
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• 2001

A research for transmutation reactor is in progress to transmute high radioactive isotopes into low radioactive ones. In this study, thermal-hydraulic and structural analysis was performed to design liquid metal target system that would be used in subcritical transmutation reactor. Diffuse plate installation was considered to enhance cooling of window. And thermal-structural analysis of window was performed varying window thickness, beam power, and coolant flow rate to determine target system design valuers. It is ensured that maximum window temperature and stress would be acceptable in the design condition.

• Journal of ILASS-Korea
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• v.9 no.4
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• pp.83-89
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• 2004

Vaporization characteristics of a liquid heptane droplet in high-pressure and temperature flow field are numerically studied. Variable thermodynamic and transport properties and high-pressure effects are taken into account in order to consider real gas effects. Droplet Vaporization in convective environments was investigated on the basis of droplet vaporization in quiescent and convective environment. In quiescent environments, droplet lifetime is directly proportional to pressure at the subcritical temperature range but it is inversely proportional to pressure at the supercritical temperature range. In convective environment, droplet deformation becomes stronger by increasing Reynolds number due to increase of velocity while droplet deformation is relatively weak at a higher pressure for the same Reynolds number cases.

• Electrical & Electronic Materials
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• v.5 no.2
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• pp.175-181
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• 1992

Y-Ba-Cu-O계 보다 화학적 내구성이 좋은 Bi-Sr-Ca-Cu-O계 초전도체 wire를 중합 binder와 초전도체 파우더를 혼합하여 sol-gel법으로 제조하였다. 여러가지 혼합비와 열처리 조건하에서 제조한 wire의 특성분석 결과 Bi$_{2}$Sr$_{2}$Ca$_{2}$Cu$_{3}$O계 초전도체와 binder의 최적 혼합율은 22.25%이었고 가열비는 0.33.deg.C/min로 500.deg.C까지는 Ar gas와 $O_{2}$ gas분위기로 열처리하고 500.deg.C에서 835.deg.C까지는 $O_{2}$ gas분위기에서 40h동안 열처리하였을때 임계온도 98K를 갖는 초전도 선재를 얻을 수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.468-468
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• 2015

일반적으로 겨울철 강수는 기온에 따라 강우와 강설로 분류된다. 특히 기온이 임계온도보다 낮을 경우, 강수는 강설의 형태로 지표면에 도달하여 적설되어진다. 겨울철 산간에 적설된 눈은 봄철이 되어 기온이 상승함에 따라 융설(snowmelt)이 발생하여 유역의 유출에 기여한다. 이러한 융설은 기온이 영하로 내려가는 11-4월에 해당하는 갈수기에 유출량 등의 수문성분에 영향을 미치고 있다. 특히 제주유역의 경우, 고도에 따른 강수량, 기온의 차이가 매우 크므로 강설, 융설 현상의 시공간적인 발생에 대한 연구가 더욱 요구된다. 따라서, 본 연구에서는 제주유역의 강설, 융설 발생의 시공간적인 평가를 위해서 융설모의가 가능한 SWAT-K를 한천유역에 적용하여, 그 결과를 분석하였다. 융설모의 이론을 검토하고, 실제 대상유역에 융설을 고려하기 위한 매개변수를 설정하고, 월별, 소유역별로 강설, 융설 발생현황을 평가하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1095-1105
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• 2005

Numerical analysis has been carried out to investigate transient turbulent convective heat transfer in a vertical tube for supercritical water near the thermodynamic critical point. Heat transfer and fluid flow in the tube we strongly coupled due to the large variations of thermodynamic and transport properties such as density, specific heat, and turbulent viscosity. As pressure in the tube approaches to the critical pressure, the properties variation with time becomes larger. Heat transfer coefficient rapidly decreases along the tube near the pseudocritical temperature at the tube wall for $P_R<1.2$. Stanton number variation with time is largely reduced in the region of gas-like phase in comparison with Nusselt number. Turbulent viscosity ratio close to the wall increases near the pseudocritical temperature and it gradually decreases with time.

• Electrical & Electronic Materials
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• v.4 no.3
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• pp.201-210
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• 1991

본 논문에서는 (B $i_{1-x}$ P $b_{x}$)$_{2}$S $r_{2}$C $a_{2}$C $u_{3.6}$ $O_{y}$ (x=0~0.5)로 조성된 분말의 최적 하소온도를 결정하고 시편의 최적 소결온도를 규명하기 위하여 열분석을 하였다. 또 단일상의 고온 초전도체를 제작하기 위하여 열처리 온도, 시간 및 Pb 함량 변화에 따라 제작된 시편의 미세구조, 조성, 전기저항 및 전류밀도를 측정하여 상호 연관성을 종합적으로 분석, 검토하여 상변이에 관한 원인을 규명하고자 하였다. 또한 실용화 전 단계로서 임계특성 해석을 위하여 성형조건을 변화시켜 시편을 제작, 전류밀도값을 측정하였다.였다.다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.4
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• pp.358-369
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• 1995

Surface structure and adhesion by the reaction between thin metal films and SiC were studied at temperatures between 550 and $1450^{\circ}C$ for various times. The reaction with the formation of various silicides was initially observed above $850^{\circ}C$ for SiC/Co system and $650^{\circ}C$ for SiC/Ni system. The cobalt reacted with SiC and consumed completely at $1050^{\circ}C$ for 0.5 h and the nickel at $950^{\circ}C$ for 2 h. The observed CoSi phase in SiC/Co and Ni$_2$Si phase in SiC/Ni are thermodynamically stable in the reaction zone up to 125$0^{\circ}C$ and $1050^{\circ}C$ respectively. Carbon was crystallized as graphite above $1450^{\circ}C$ for SiC/Co reaction surface and $1250^{\circ}C$ for SiC/Ni. The critical loads of the thin metal films on SiC substrate were qualitatively compared in terms of the scratch test method. At temperatures between 850 and $1050^{\circ}C$, relatively higher values of 20~33 N were observed for SiC/Ni couples.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.10
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• pp.653-658
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• 2016

A study on the measurement of critical heat flux using the transient inverse heat conduction method in spray cooling was performed. The inverse heat conduction method estimates the surface heat flux or temperature using a measured interior temperature history. The effects of the measuring time interval and location of temperature measurement on the measurement of critical heat flux were primarily investigated. The following results were obtained. The estimated critical heat flux decreased as the time interval of temperature measurement increased. Meanwhile, the effect of measurement location on critical heat flux was not significant. It was also found, from the experimental results, that the critical superheat increased as the measurement location of thermocouple neared the heat transfer surface.