• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 가을 학술발표회 논문집
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• pp.76-83
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• 1995

Estimation of blasting behavior of explosives is prerequisite in the numerical analysis of blasting works. In this study, blasting pressure is estimated by the finite difference method using the Flux-Corrected Transport Algorithm. To formulate the behavior of blasting gas, the mass conservation equation, the moment conservation equation, the energy conservation equation and the ideal gas state equation are used. The simplified species conservation equation is included to simulate the behavior of reacting explosives. To verify the calculation, the Sod's shock tube problem, the strong shock problem and the reacting problem we used. Numerical results show that the shock wave can be captured by means of the FCT algorithm in the reacting and nonreacting states.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제17권1호
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• pp.29-45
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• 2013

Central schemes offer a simple and versatile approach for computing approximate solutions of nonlinear systems of hyperbolic conservation laws. However, there are large numerical dissipation in case of contact discontinuity. We study semi-discrete central upwind scheme by changing flux functions to reduce the numerical dissipation and we perform numerical computations for various problems in case of contact discontinuity.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제23권3호
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• pp.211-236
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• 2019

This paper is devoted to the study and investigation of the Runge-Kutta discontinuous Galerkin method for a system of differential equations consisting of two hyperbolic conservation laws. The numerical coupling flux which is used at a given interface (x = 0) is the upwind flux. Moreover, in the linear case, we derive optimal convergence rates in the $L_2$-norm, showing an error estimate of order ${\mathcal{O}}(h^{k+1})$ in domains where the exact solution is smooth; here h is the mesh width and k is the degree of the (orthogonal Legendre) polynomial functions spanning the finite element subspace. The underlying temporal discretization scheme in time is the third-order total variation diminishing Runge-Kutta scheme. We justify the advantages of the Runge-Kutta discontinuous Galerkin method in a series of numerical examples.

• 보존과학회지
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• 제36권4호
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• pp.236-243
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• 2020

In this study, an accelerated aging experiment for fabric and paper was conducted using two light emitting diode(LED) sources with different wavelength characteristics, and the discoloration under each lighting type was examined. Hanji(Korean traditional paper) and related textiles showed more discoloration under blue LEDs, while the blue wool standard showed more discoloration under white LEDs. This, indicated that the deterioration varied depending on the sample color. The the effect of the light source on artifact deterioration was primarily related to the total radiation flux(expressed in mill watts), rather than the total luminous flux(expressed in lumens). In addition, the discoloration of the investigated artifacts was dependent on the color rendering of the lighting.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권4호
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• pp.477-482
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• 2012

This paper describes a new rotor position sensorless control method for SRM drives based on an improved simplified flux linkage method. In the traditional simplified flux linkage method, every phases take turns conduction and current chopping control method is used. Every phases take turns conduction means turning on the incoming working phase while turning off the working phase. This conduction mode causes coupling between turn-on and turn-off angles, which goes against optimal efficiency or torque ripple minimization with sensorless speed control. In the improved simplified flux linkage method, turn-off angle is calculated by flux loop, the turn-on angle can be given arbitrarily and has no relations with the turn-off angle, and the current chopping control method is used. The speed and rotor position can be estimated then. Finally, a sensorless SRM speed control system and an experiment platform with DSP are built and validity of this method is confirmed.

• 보존과학회지
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• 제34권2호
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• pp.77-85
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• 2018

유물에 대한 조명의 변색 영향을 파악하기 위해서는 유물을 구성하는 재질에 대한 빛의 반응특성을 우선 분석하여야 한다. 본 연구에서는 회화유물의 채색층을 구성하는 대표적인 전색제인 동물성 아교와 린시드유를 대상으로 하였으며, 파장 특성이 다른 White LED와 Blue LED 조명을 사용한 가속열화실험을 통해 변색 영향 정도를 확인하였다. 실험 결과, 동물성 아교 및 린시드유는 Blue LED 조명을 사용한 가속열화실험 조건에서 변색이 두드러지게 나타났으며, 두 종류의 LED 조명 중에서 전복사속(mW) 값이 큰 Blue LED에서 재질 변색 정도가 크게 나타났다. 이상의 결과로, 동물성 아교 및 린시드유 등 회화유물 전색제의 변색에 미치는 광원의 영향은 전광선속(lm)보다 전복사속(mW)이 주요하게 작용함을 파악하였다.

• 대한수학회보
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• 제52권6호
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• pp.1945-1962
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• 2015

This paper is mainly concerned with the formation of delta standing wave for the scalar conservation law with a linear flux function involving discontinuous coefficients by using the self-similar viscosity vanishing method. More precisely, we use the self-similar viscosity to smooth out the discontinuous coefficient such that the existence of approximate viscous solutions to the delta standing wave for the Riemann problem is established and then the convergence to the delta standing wave solution is also obtained when the viscosity parameter tends to zero. In addition, the Riemann problem is also solved with the standard method and the instability of Riemann solutions with respect to the specific small perturbation of initial data is pointed out in some particular situations.

• 한국환경과학회지
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• 제16권1호
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• pp.73-79
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• 2007

The purpose of this study is to clarify the effect of mountain-valley wind on heat island formed in urban area which is located around valley mouth. The meteorological observations were carried out over the Dalbi-valley under a clear summer pressure patterns, and some consideration were tried from the results. In order to make clear the climatological characteristics and air-mass modification process of the mountain-valley wind over the valley, the meteorological observations were done simultaneously at two points. The observational points were located at the breast and valley mouth parts, respectively. The results were as follows: First, it was found that the valley wind was observed through the daytime, and it was replaced by a mountain wind after sunset. Second, the heat budget is also investigated with observation data. The sensible heat flux over the breast of Dalbi-valley reached to about $200 W/m^2$ during daytime, which is a little more than one third of net radiation. On the other hand, the sensible heat flux represented negative values during nighttime. But the sensible heat flux over the valley mouth covered by asphalt showed plus value(about $20{\sim}30 W/m^2$) during the nighttime.

• Progress in Superconductivity
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• 제1권2호
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• pp.99-104
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• 2000

The e.m.f. induced by a normal spot moving in a superconducting foil has been investigated by using the simulation and the experiment of a simple superconducting Power Supply. The induced e.m.f. has been derived theoretically from the magnetic field distribution within the spot. It is the sum of a DC component induced constantly by the Faraday's law during the spot's movement and a pulse component induced periodically by the flux conservation law at every electrical degrees 2$\pi$ radians. The DC component of the output voltage appears slightly nonlinear to the rotating speed, having values greater than the linear approximation values. The theoretical interpretation has been verified through experiment.

• Nuclear Engineering and Technology
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• 제25권2호
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• pp.233-236
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• 1993

상 변화가 없고 압력 변화가 없는 일차원 이상 유동에 있어서 드리프트 플럭스 모델자 2-유체 모델 사이의 상관 관계가 연구되었다. 증기 보존식은 드리프트 플럭스를 통하여 운동량 보존식에 의존한다는 사실에 기초하여 관계가 얻어졌다. 2-유체 모델로부터 출발하여 트리프트 플럭스의 파라미터의 함수로 표현된 계면 마찰식을 얻었다. 또한 기공 전달식을 유도함으로써 드리프트 플럭스는 2-유체 모델의 마찰력과 상호 관계가 있음을 보였다.