• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.1-4
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• 2005

This research is to present experimental materials model of high strength concrete for prediction of fire safety of structural members based on physical properties of materials during heating up to 800$^{circ}C$. The following conclusions are drawn from this study. First of all, between 100 to 200 $^{circ}C$, the physical models of concrete such as specific heat and thermal conductivity, show visible degradation, regardless of concrete strength. Second, between 300 to 600$^{circ}C$, the physical models of the 29MPa and 49MPa concrete show degradation continually at these temperatures. Finally, beyond 600$^{circ}C$, the physical models of 49MPa strength concrete show larger degradation than 29MPa strength concrete due to rise of pore pressure and melting of the interface between aggregate and cement paste.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.517-520
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• 2005

This study is basic experiment for estimating influence of strength by curing temperature of concrete's heat of hydration and estimate relationship of compressive strength development by initial curing temperature factor, and then asume temperature factor which influence compressive strength development and for showing basic document of quality control. According to the result of cement mortar by the curing temperature factor high-curing temperature shows high strength on 3 day compare with low curing-temperature, shows higher strength than the piece of high curing temperature.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.357-362
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• 2001

The purpose of this study is to investigate the effect of nitriding on the fatigue strength and fatigue life of turbine rotor steel (ICr-lMo-0.25V), and acquire data on the fatigue strength of nitrided turbine rotor steel at high temperature (538$^{\circ}C$). Specimens were nitrided with various layer thicknesses (160$\mu$m, 270$\mu$m and 290$\mu$m) using the nitemper method. A microstructure analysis, microhardness test, surface roughness test, and fracture surface analysis were also carried out at room temperature in order to investigate the mechanical properties of the nitrided specimens.

• Journal of Ocean Engineering and Technology
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• v.18 no.2
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• pp.64-69
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• 2004

The characteristics of the probability distribution for mechanical properties, e.g. tensile strength, reduction of area, and elongation, for STS304 stainless steel in elevated temperature are investigated. Tensile test is performed by constant crosshead speed controls with 1mm/min. The probability distribution function of measured mechanical properties seems to follow $\alpha$ 3-parameter Weibull, and shows a slight dependence on the temperature. When the temperature is raised, the shape parameter a is increased, but both the scale parameter $\beta$ and location parameter v are decreased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.34-35
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• 2014

In this study, the effects of high temperatures on the compressive strength and elastic modulus of HPC with pp and jute fiber (jute fiber addition ratio: 0.075 vol%; length: 12 mm; PP fiber addition ratio: 0.075 vol%; length: 12 mm) were experimentally investigated. The work was intended to clarify the influence of elevated temperatures ranging from 20 to 500℃ on the material mechanical properties of HPC at 80 MPa.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.68-71
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• 2010

극심한 고온 및 고압 환경에 노출되기 쉬운 항공우주 구조물에서 발생하는 기계적 삭마 현상을 해석하기 위하여 영역/경계 분할법을 적용한 삭마 해석 모델을 제안하였다. 영역 및 경계는 상변화 현상에 의한 비선형 거동을 하는 삭마 부영역과 선형 거동을 하는 선형 열탄성 부영역, 공유면, 경계 공유면으로 분할하였다. 삭마 재료 내부의 열분해 반응은 엔탈피 방법을 이용하였으며, 표면 침식 반응은 공기역학적 전단 응력과 삭마 재료의 전단 강도를 기반으로 매칭 기법을 이용하였다. 화학적 및 열적 삭마는 고려하지 않았으며, 간단한 수치 해석을 통해서 기본적인 기계적 삭마 특성을 분석하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.703-706
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• 2004

This study is basic experiment for estimating influence of strength by curing temperature of concrete's heat of hydration and estimate relationship of compressive strength development by initial curing temperature factor, and then asume temperature factor which influence compressive strength development and for showing basic document of quality control. According to the result of cement mortar by the curing temperature factor high-curing temperature shows high strength on 3 day compare with low curing-temperature, shows higher strength than the piece of high curing temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.13-16
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• 2001

반도체 동작시에 파워 손실을 최소화하는 것은 2000년대의 에너지, 산업전자, 정보통신 산업분야에서의 가장 주요한 요구 사항중의 하나이다. 실리콘계 반도체 소자들은 완전히 새로운 구동기구의 소자가 개발되지 않는 한, 실리콘 재료의 낮은 열 전도율이나 낮은 절연파괴전계와 같은 물리적 특성한계 때문에 이러한 요구를 만족시키는 것이 불가능한 실정이다. 따라서 21세기를 위한 대안으로 고열전도율의 WBG(Wide Band-Gap) 물질 그 중에서도 탄화규소(SiC) 반도체가 제시되고 있다. SiC 반도체는 실리콘에 비하여 밴드 갭(band gap: E$_{g}$)이 높을 뿐만이 아니라 절연파괴강도(E$_{B}$)가 한 자릿수 이상 그리고 전자의 포화 drift 속도, v$_{s}$ 및 열전도도 k가 3배 가량 크다. 따라서 SiC는 고온 동작 내지는 고내압, 대전류, 저손실 반도체를 제작하는데 아주 유리하다. 본고에서는 응용성이 넓고, 단결정 제조가 비교적 용이한 SiC 반도체의 기술현황 에 대하여 살펴보고자 한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.4
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• pp.339-345
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• 2008

The heat exchanger tube in nuclear power plants is mainly fabricated from nonferromagnetic material such as a copper, titanium, and inconel alloy, but the moisture separator & reheater tube in the turbine system is fabricated from ferromagnetic material such as a carbon steel or ferrite stainless steel which has a good mechanical properties in harsh environments of high pressure and temperature. Especially, the moisture separator & reheater tubes, which use steam as a heat transfer media, typically employ a tubing with integral fins to furnish higher heat transfer rates. The ferromagnetic tube typically shows superior properties in high pressure and temperature environments than a nonferromagnetic material, but can make a trouble during the normal operation of power plants because the ferrous tube has service-induced damage forms including a steam cutting, erosion, mechanical wear, stress corrosion cracking, etc. Therefore, nondestructive examination is periodically performed to evaluate the tube integrity. Now, the remote field testing(RFT) technique is one of the solution for examination of ferromagnetic tube because the conventional eddy current technique typically can not be applied to ferromagnetic tube such as a ferrite stainless steel due to the high electrical permeability of ferrous tube. In this study, we have designed RFT probes, calibration standards, artificial flaw specimen, and probe pusher-puller necessary for field application, and have successfully carry out RFT examination of the moisture separator & reheater tube of nuclear power plants.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.7
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• pp.70-75
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• 2005

In this study, experimental investigations were conducted on NOx emission characteristics with fuel swirl flow in swirl combustor. Many types of vanes, which altered air and fuel swirl angles, were employed to verify the mixing processes. For strong air swirl, fuel counter-swirl resulted in relatively large turbulent intensity, high energy to the high frequency region and narrow width of high temperature region compared with co-swirl condition. These effects of fuel counter-swirl resulted in low NOx emission characteristics at strong air swirl condition. And NOx reduction mechanism was also discussed.