• Bulletin of the Korean Chemical Society
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• 제17권4호
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• pp.365-373
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• 1996

Time profile of the transient grating signal induced by a nanosecond pulsed laser excitation of methyl red is investigated in alcohols and toluene at several solvent temperatures. The signal decays biexponentially with well-separated time constants; the faster decay is identified as due to thermal diffusion of the solvents and the slower one as mainly due to translational diffusion of the solute. The measured translational diffusion constants of methyl red in toluene are close to a hydrodynamic prediction with a slip boundary condition while those in alcohols are larger by 30% and increase slightly with the size of alcohols. We compare the results with modified hydrodynamic models.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.941-942
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• 2011

A thermal equivalent circuit of IPMSM considering eddy current loss of PM and core loss of rotor is proposed. This thermal equivalent model is represented by the thermal resistances and thermal capacitances. In order to determine the factor of each parameter, a heating test is processed. Additionally, the eddy current loss of PM is calculated by a transient 3D finite element analysis. Finally, this thermal equivalent model is verified by a temperature test in a 25kW 12-pole/18-slot IPMSM with varying load.

• Nuclear Engineering and Technology
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• 제32권2호
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• pp.169-179
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• 2000

A detailed numerical analysis of the evolution of thermal stratification in a curved piping system in a nuclear power plant is performed. A finite volume based thermal-hydraulic computer code has been developed employing a body-fitted, non-orthogonal curvilinear coordinate for this purpose. The cell-centered, non-staggered grid arrangement is adopted and the resulting checkerboard pressure oscillation is prevented by the application of momentum interpolation method. The SIMPLE algorithm is employed for the pressure and velocity coupling, and the convection terms are approximated by a higher-order bounded scheme. The thermal-hydraulic computer code developed in the present study has been applied to the analysis of thermal stratification in a curved duct and some of the predicted results are compared with the available experimental data. It is shown that the predicted results agree fairly well with the experimental measurements and the transient formation of thermal stratification in a curved duct is also well predicted.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.145-150
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• 2015

This paper described the medium voltage high temperature superconducting cable thermal simulation and its application. New simulation method for HTS cable modeling using PSCAD/EMTDC is introduced in this paper. The developed simulation method consists of electrical model part and thermal model part. In electrical model part, power loss and thermal capacitance can be calculated in each layer, then the temperature of each layer can be calculated by power loss and thermal capacitance in thermal model part. This paper also analyzes the electrical and thermal characteristic in the case of normal operating condition and transient including single line to ground fault and line to line ground fault using new simulation method.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2001년도 동계 학술대회 논문집
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• pp.219-227
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• 2001

• Journal of Welding and Joining
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• 제26권6호
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• pp.36-41
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• 2008

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 추계학술발표회요약집
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• pp.348.2-348
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• 2001

• 콘크리트학회논문집
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• 제13권3호
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• pp.268-276
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• 2001

본 논문은 고온에서의 콘크리트 재료모델을 연구하였다. 콘크리트 응력-변형률 곡선은 온도가 증가함에 따라 그 형태가 변한다. 온도에 따른 콘크리트 재료거동의 변화를 나타내기 위하여 변형된 Saenz 제안식을 이용하여 응력-변형률 관계를 표시하였다. 고온에서의 급격한 변형률의 증가현상을 설명하기 위하여, 콘크리트의 변형률 성분을 순수 열팽창 변형률, 열적크리프 변형률, 과도 변형률 및 역학적 변형률로 구분하여 나타내었다. 열적크리프 변형률은 Baily-Norton의 장기크리프 곡선 식을 수정.제안하여 1축 실험 결과를 온도, 시간 및 응력의 함수로 표현하였고, 또한 유효응력 및 유효변형률 개념을 도입하여 다차원에서도 적용할 수 있는 모델을 제시하였다. 과도 변형률을 제안하여 다공탄성 거동을 가정한 콘크리트 내에 포함된 공극 및 수분의 작용을 역학적 거동의 영향을 분석하고자 하였다. 마지막으로, 본 논문에서 제시한 고온에서의 콘크리트 재료모델을 이용한 해석결과를 실제 화재실험자료와 비교하였다.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.19-26
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• 2020

Small nuclear reactor features higher power capacity, longer operation life than conventional power sources. It could be an ideal alternative of existing power source applied for special equipment for terrestrial or underwater missions. In this paper, a 25kWe heat pipe cooled reactor power source applied for multiple use is preliminary designed. Based on the design, a thermal-hydraulic analysis code for heat pipe cooled reactor is developed to analyze steady and transient performance of the designed nuclear reactor. For reactor design, UN fuel with 65% enrichment and potassium heat pipes are adopted in the reactor core. Tungsten and LiH are adopted as radiation shield on both sides of the reactor core. The reactor is controlled by 6 control drums with B₄C neutron absorbers. Thermoelectric generator (TEG) converts fission heat into electricity. Cooling water removes waste heat out of the reactor. The thermal-hydraulic characteristics of heat pipes are simulated using thermal resistance network method. Thermal parameters of steady and transient conditions, such as the temperature distribution of every key components are obtained. Then the postulated reactor accidents for heat pipe cooled reactor, including power variation, single heat pipe failure and cooling channel blockage, are analyzed and evaluated. Results show that all the designed parameters satisfy the safety requirements. This work could provide reference to the design and application of the heat pipe cooled nuclear power source.

• 대한기계학회논문집B
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• 제28권6호
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• pp.688-696
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• 2004

Nonlinear dynamic behavior of diffusive-thermal instability in diluted CH$_4$/O$_2$ diffusion flames is numerically investigated by adopting detailed chemistry and transport. Counterflow diffusion flame is adopted as a model flamelet. Particular attention is focused on the pulsating-instability regime, which arises for Lewis numbers greater than unity, and the instability occurs at high strain rate near extinction condition in this flame configuration. Once a steady flame structure is obtained for a prescribed value of initial strain rate, transient solution of the flame is calculated after a finite amount of strain-rate perturbation is imposed on the steady flame. Transient evolution of the flame depends on the initial strain rate and the amount of perturbed strain rate. Basically, the dynamic behaviors can be classified into two types, namely non-oscillatory decaying solution and diverging solution leading to extinction. The peculiar oscillatory solution, which has been found in the previous study adopting one-step chemistry and constant Lewis numbers, is net observed in this study, which is attributed to both convective flow and preferential diffusion effects.