• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.281-288
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• 1993

We have investigated the output characteristics and optimal conditions of a multi-stage amplifier system of Rhodamine 6G dye laser. The parameters in this simulation work were the beam diameter of the dye laser oscillator, the size of dye cell, the dye concentration, the number of stages in the amplifier system, and the pumping energy ratio of each amplifier at given pump energy. As a result, the output energy 10 mJ and the conversion efficiency of 40% in the two stage amplifier system were obtained with the pumping energy of 25mJ and the oscillator energy of 0.01 mJ.

• Journal of Energy Engineering
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• v.9 no.2
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• pp.138-145
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• 2000

고체재료의 열확산계수나 열전도계수와 같은 열물성을 비접촉식 방법으로 측정하기 위하여 광열변위법에 대한 이론적인 해석을 수행하였다. 가열빔의 파형을 코사인파, 삼각파 그리고 사각파로 가정하여 2차원 열전도 방정식과 열탄성 방정식의 엄밀해를 구하였고, 이를 가열빔으로부터 직접 구한 실제파의 결과와 비교하였다. 코사인파의 결과가 다른 파형에 비하여 실제파와 가장 유사한 것으로 보아 비교적 해석이 복잡한 실제파를 코사인파로 가정하여도 무방하다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.2
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• pp.27-38
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• 2002

A new self-consistent mathematical model for semiconductor quantum well device was developed. The model was based on the direct solution of the Boltzmann transport equation, coupled to the Schrodinger and Poisson equations. The solution yielded the distribution function for a two-dimensional electron gas(2DEG) in quantum well devices. To solve the Boltzmann equation, it was transformed into a tractable form using a Legendre polynomial expansion. The Legendre expansion facilitated analytical evaluation of the collision integral, and allowed for a reduction of the dimensionality of the problem. The transformed Boltzmann equation was then discretized and solved using sparce matrix algebra. The overall system was solved by iteration between Poisson, Schrodinger and Boltzmann equations until convergence was attained.

• Journal of the Korean Magnetics Society
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• v.6 no.5
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• pp.281-286
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• 1996

For the accurate analysis of motional characteristics of electrical machines, it is needed to solve the motion equations together with the electromagnetic field equations. In this paper the sequential coupling of systems, the spring mass system and the electromagnetic system, is adopted. The induced current and the magnetic fields are calculated by finite element method(FEM) with given speed. And then, with the computed elec-tromagnetic force, the mechanical equations are solved by the Runge-Kutta method. The above two processes are repeated sequentially to obtain the time domain solutions. The resultant values are applied to the energy conservation law to prove the usefulness of the proposed sequential method.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.498-498
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• 2012

직류 아크 토치를 이용하여 열플라즈마를 발생시키는 방법은 전극의 구성에 따라 크게 비이송식(non-transferred)과 이송식(transferred)의 2가지 형태로 나눌 수 있다. 1950년대 H. Maecker 등에 의해 이론적 기초가 형성되기 시작한 이송식 아크 플라즈마 발생장치는 처리 대상물질을 전극으로 사용하여 양극에서의 에너지 전달을 직접 이용할 수 있으므로 열효율이 매우 높기 때문에 이를 이용한 고출력 토치에 관한 활발한 연구가 지속되고 있다. 본 연구에서는 대기압 아르곤 자유연소아크 방전에 의해 발생되는 열플라즈마의 열유동 특성을 수치적으로 해석하기 위하여 아크 기둥의 온도, 압력 및 속도 특성을 Navier-Stokes 방정식과 Maxwell 방정식을 연계 계산하였다. 또한 아크-전극 상호작용(arc-electrode interaction) 모델링을 통한 양극(anode)인 처리 대상물질로의 에너지 플럭스 유입을 고려하여 전극 내부의 온도분포를 계산하였다. 해석결과를 검증하기 위하여 음극과 양극 사이 플라즈마 기둥(column)의 중심축 온도는 Haddad & Farmer(1984)의 실험데이터와 비교하였고, 양극으로의 에너지 플럭스 및 온도분포 데이터는 Bini 등(2006)의 실험 및 해석데이터와 비교하여 만족스런 일치를 확인하였다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2007.11a
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• pp.269-275
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• 2007

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.1
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• pp.81-87
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• 1994

The mild slope equation has been directly derived from the energy equation, and the relation between energy equation and Green's first and second identities was also clarified. It is shown here that the mild slope equation of elliptic type in the wave-current interaction has to have the same form as the one derived by Berkhoff (1972), and its physical meaning was investigated through analytical solutions.

• Water for future
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• v.29 no.6
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• pp.217-224
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• 1996

In this paper, the evaluation of diameter, global velocity, global roughness coefficients of the water distribution pipes are examined by using pressure and flowrate measurements in selected points of the network. The selected pipe network parameters are determined through reformulation of the continuity and energy equation. Additional energy equation is considered to analyze the coefficient matrix. The resulting nonlinear equations are solved by using Newton Raphson method. Three computer models with complex pipe system are used to demonstrate these procedures. The computed results of hydraulic parameters show good agreements with KYPIPE2 flow analysis model.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.2
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• pp.11-15
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• 2009

This paper is concerned with the elastic buckling of thin-walled arches that are subjected to uniform bending. Nonlinear strain-displacement relations with the initial curvature are substituted into the second variation of the total potential energy to obtain the energy equation including initial curvature effects. The approximation for initial curvature effects that the bending normal strain distribution is linear across the cross section is applied consistently in the derivation process. The closed form solution is obtained for flexural-torsional buckling of arches under uniform bending and, it is compared with the previous theoretical results.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.3
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• pp.174-180
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• 2010

The inhomogeneous Helmholtz equation is introduced for variable water depth and potential function and separation of variables are introduced for the derivation. Only harmonic wave motions are considered. The governing equation composed of the potential function for irrotational flow is directly applied to the still water level, and the inhomogeneous Helmholtz equation for variable water depth is obtained. By introducing the wave amplitude and wave phase gradient the governing equation with complex potential function is transformed into two equations of real variables. The transformed equations are the first and second-order ordinary differential equations, respectively, and can be solved in a forward marching manner when proper boundary values are supplied, i.e. the wave amplitude, the wave amplitude gradient, and the wave phase gradient at a side boundary. Simple spatially-centered finite difference numerical schemes are adopted to solve the present set of equations. The equation set is applied to two test cases, Booij’ inclined plane slope profile, and Bragg’ wavy bed profile. The present equations set is satisfactorily verified against other theories including the full linear equation, Massel's modified mild-slope equation, and Berkhoff's mild-slope equation etc.