• Progress in Superconductivity
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• 제4권1호
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• pp.27-31
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• 2002

MgB$_2$samples have been prepared by a stoichiometry mixture of Mg and B inside stainless steel tubes(Commercial Stainless Steel Tube Enveloping Technique). XRD data show that there are no second phases like MgO. The transition temperature of specimens is 37.5 K with a sharp transition width of ΔTc within 1K. From magnetic hysteresis measurement, flux jump was shown up to 15K, which was higher than that of samples by other methods. We have concluded that the flux jump is mainly affected by impurities and second phases.

• Progress in Superconductivity
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• 제9권1호
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• pp.11-17
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• 2007

Magnetization studies have been carried out on $MgB_2$ polycrystalline samples in the temperature range of 5 - 44 K and in the magnetic field up to 7 Tesla. The critical current density was calculated from hysteresis loops using the Bean's critical state model, and the highest value of $J_c$ at 20 K was $2.7{\times}10^5\;A/cm^2$ at 2 Tesla. The hysteresis loops were carefully examined to determine the temperature and magnetic field range where flux jumps appeared. The first jump occurred typically at 1 Tesla. Due to the strong pinning, we observed the presence of flux jump below H = 1 Tesla at temperature below 30 K.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2002년도 High Temperature Superconductivity Vol.XII
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• pp.33-33
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• 2002

• Journal of applied mathematics & informatics
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• 제32권5_6호
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• pp.761-781
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• 2014

An exponentially accurate nonconforming spectral element method for elasticity systems with discontinuities in the coefficients and the flux across the interface is proposed in this paper. The method is least-squares spectral element method. The jump in the flux across the interface is incorporated (in appropriate Sobolev norm) in the functional to be minimized. The interface is resolved exactly using blending elements. The solution is obtained by the preconditioned conjugate gradient method. The numerical solution for different examples with discontinuous coefficients and non-homogeneous jump in the flux across the interface are presented to show the efficiency of the proposed method.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2009년도 Korea Superconductivity Society Meeting 2009
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• pp.34-34
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• 2009

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2007년도 High Temperature Superconductivity Vol.XVII
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• pp.43-43
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• 2007

• 대한토목학회논문집
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• 제43권6호
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• pp.749-762
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• 2023

천수 방정식 흐름률 계산에 근사 Riemann 해법을 채택한 수심 적분 모형을 도수 실험에 적용하였다. 도수 때문에 단일 수로에서 서로 다른 흐름 양상이 동시에 나타나므로 흐름 저항에 대해 수심이나 유속에 무관한 Manning 조도 계수보다는 흐름 조건을 반영할 수 있는 Weisbach 저항 계수를 채택하였다. 모의 결과는 실험 결과에 잘 부합되었으며, Weisbach 계수로부터 환산한 Manning 계수는 사류 구간과 상류 구간에서 각 각 적절하게 설정되고 있음을 확인하였다. 도수 실험과 비교에서 정수압 가정에 기반한 천수 방정식의 한계가 드러나 비정수압 천수 흐름 모형 도입의 필요성이 높아졌다.

• International Journal of Aeronautical and Space Sciences
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• 제11권3호
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• pp.193-200
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• 2010

Through experimental investigations utilizing hypersonic shock tunnel-coaxial thermocouples as well as blow down hypersonic wind tunnel-temperature sensitive paints, the heat flux and the temperature over a protuberance were measured and analyzed. The experimental data were subsequently compared to heat flux data that was obtained by using blow down hypersonic wind tunnel and heat flux gauges. According to the comparison, both sets of data illustrated correlation with one another. The measured heat flux was large when the height of the protuberance was large. Experimental results show that heat flux measurements taken at higher locations were greater than those taken at lower locations. For high protuberances, a severe jump in the heat flux was observed, ranging in values within 0.6-0.7 of the height of the protuberances. However, when the protuberance was sufficiently short, a rise in the heat flux was rarely observed as the protuberance was totally submerged under the separation region.

• 한국환경과학회지
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• 제22권2호
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• pp.173-185
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• 2013

In order to clarify the impact of wildfire and its thermal forcing on atmospheric wind and temperature patterns, several numerical experiments were carried out using three dimensional atmospheric dynamic model WRF with wildfire parametrization module SFIRE. Since wind can accelerate fire spread speed, the moving speed of fireline is faster than its initial values, and the fireline tends to move the northeast, because of the wind direction and absolute vorticity conservation law associated with driving force induced by terrain. In comparison with non-fire case, the hydraulic jump that often occurs over downwind side of mountain became weak due to huge heat flux originated by surface wildfire and wind pattern over downwind side of mountain tends to vary asymmetrically with time passing. Therefore temporal variation of wind pattern should be catched to prevent the risk of widfire.

• 대한기계학회논문집B
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• 제23권1호
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• pp.43-57
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• 1999

The fluid flow and heat transfer in a thin liquid film are investigated numerically. The flow Is assumed to be two-dimensional laminar and surface tension is considered. The most important characteristics of this flow is the existence of a hydraulic jump through which the flow undergoes very sharp and discontinuous change. Arbitrary Lagrangian-Eulerian(ALE) method is used to describe moving free boundary and a modified SIMPLE algorithm based on streamline upwind Petrov-Galerkin(SUPG) finite element method is used for time marching iterative solution. The numerical results obtained by solving unsteady full Navier-Stokes equations are presented for planar and radial flows subject to constant wall temperature or constant wall heat flux, and compared with available experimental data. It Is discussed systematically how the inlet Reynolds and Froude numbers and surface tension affect the formation of a hydraulic jump. In particular, the effect of temperature dependent fluid properties is also discussed.