• 한국해안해양공학회지
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• 제10권2호
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• pp.93-99
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• 1998

타원형 유한차분모형에서 개방 경계조건으로 포물선 근사식과 스폰지층 경계를 사용하여 모형의 개량을 도모하였다. 수치기법은 GCG(Generalized conjugate gradient)기법을 사용하였고 구형해저실험에서 포물형 근사식을 사용하여 부적절한 반사파를 상당 부분 제거할 수 있었다. 스폰지층 경계의 경우 2파장 이상의 스폰지층을 사용할 때 포물형 근사식과 유사한 결과를 얻을 수있었다. 직사각형 항만에 대한 실험을 통하여 임의 형상의 대상 해역에도 쉽게 모형을 적용할 수 있음을 확인하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
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• pp.95-102
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• 1994

A path-switching strategy by combining the use of generalized inverse and line search is proposed. A reliable predictor for the tangent vector to bifurcation path is first computed by using the generalized inverse approach. A line search in the direction of maximum gradient of total potential at the point of intersection between the above predictor and a constant loading plane introduced in the vicinity of the detected bifurcation point is then carried out for the purpose of obtaining an improved approximation for a point on bifurcation path. With this approximation obtained, an actual point on bifurcation path is then computed through iteration on the constant loading plane.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.400-404
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• 2015

2차원 물질인 metal mono chalcogenides(MMC) 중 GaS와 GaSe를 대상으로 하여 층과 층 사이의 van der Waals(vdW) 상호작용을 density functional theory(DFT) 계산을 이용해 연구하였다. Local density approximation(LDA)와 generalized gradient approximation (GGA)의 두 가지 다른 exchange correlation functional을 이용하고, 또한 두 개의 층 사이에 작용하는 van der Waals 상호작용을 고려한 LDA-D2, GGA-D2 계산을 수행하였다. 이와 같은 네 가지 방법으로 층간거리를 바꾸어 binding energy curve를 계산하였다. 그 결과 GGA-D2계산이 MMC의 층간 상호 작용을 가장 잘 기술하였다.

• 한국자기학회지
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• 제15권4호
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• pp.217-220
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• 2005

제일원리적 에너지 띠 계산 방법인 전 전자 총 퍼텐셜 선형보강평면파동(all-electron full-potential linearized augmented plane ave) 방법에 일반기울기근사(generalized gradient approximation)를 채용하여 Ag(001) 표면 위에 [110] 방향으로 놓인 Fe 선의 전자구조와 자성을 이론적으로 연구하였다. Fe 선의 원자당 자기모멘트는 $3.02\;{\mu}_B$로 Cu(001) 위에 놓인 Fe[110] 선의 값($2.99\;{\mu}_B$) 보다 약간 컸다. Fe 선의 자기모멘트가 상당히 증가한 것은 이웃한 결합수가 줄어들고 그 결과로 Fe-d 전자상태의 띠폭이 줄어들어 국소화 되고 스핀분리가 증가하였기 때문이다. Fe-d 전자상태의 띠 폭은 약 1.6eV였으며 스핀분리는 약 3.2 eV였다.

• 한국자기학회지
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• 제23권4호
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• pp.117-121
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• 2013

본 연구에서는 대표적인 강자성 금속인 Fe에 비자성 원소가 치환된 비교적 단순한 B2 구조의 FeX(X = Al, Si, Ni, Ga, Ge, Sn) 합금의 자기변형계수를 제일원리계산으로 수행하여 Fe 기반 합금이 희토류 원소 기반 자기변형 물질인 Terfenol을 대체할 수 있는 가능성을 탐색하였다. 계산방법으로 자성 연구에 가장 적합한 것으로 알려져 있는 총퍼텐셜 선형보강 평면파(Full-potential Linearized Augmented Plane Wave; FLAPW) 방법을 사용하였으며 일반화 물매근사(generalized gradient approximation: GGA)을 도입하여 전자 상호간의 교환-상관 퍼텐셜을 기술하였다. B2 구조의 FeX(X = Al, Si, Ni, Ga, Ge, Sn)의 합금들 중에 FeSi와 FeGe은 비자성 상태가, 그 외 나머지 합금은 강자성 상태가 안정된 것으로 계산되었다. FeAl, FeNi, FeGa, FeSn의 자기변형계수 는 각각 -5, +6, -84, -522ppm으로 계산되어 FeSn은 큰 자기변형을 가질 수도 있음을 예측하였다.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.592-602
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• 2021

Thorium compounds have attracted immense scientific and technological attention with regard to both fundamental and practical implications, owing to unique chemical and physical properties like high melting point, high density and thermal conductivity. Hereby, we investigate the mechanical and thermodynamic stability and report on the structural, electronic and magnetic properties of new silicon-doped cubic ternary thorium phosphides ThSi_xP_1-x (x = 0, 0.25, 0.5, 0.75 and 1). The first-principles density functional theory procedure was adopted within full-potential linearized augmented plane wave (FP-LAPW) method. The exchange and correlation potential terms were treated within Generalized-Gradient-Approximation functional modified by Perdew-Burke-Ernzerrhof parameterizations. The proposed compounds showed mechanical and thermodynamic stable structure and hence can be synthesized experimentally. The calculated lattice parameters, bulk modulus, total energy, density of states, electronic band structure and spin magnetic moments of the compounds revealed considerable correlation to the Si substitution for P and the relative Si/P doping concentration. The electronic and magnetic properties of the doped compounds rendered them non-magnetic but metallic in nature. The main orbital contribution to the Fermi level arises from the hybridization of Th(6d+5f) and (Si+P)3p states. Reported results may have potential implications with regard to both fundamental point of view and technological prospects such as fuel materials for clean nuclear energy.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.269-269
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• 2013

Usingvan der Waals (vdW) energy-corrected density-functional theory without or with self-consistent screening (SCS) effects, we calculate the adsorption energy of acetylene, ethylene and benzene on Si(100). We find that vdW interactions without SCS effects increase the adsorption energy by 0.23, 0.30, and 0.64 eV for adsorbed $C_2H_2$, $C_2H_4$, and $C_6H_6$ on Si(100), respectively. However, if SCS effects are included, this increase of the adsorption energy is reduced as 0.19, 0.24, and 0.54 eV for the three adsorption systems, respectively. The resulting adsorption energy for each system is between the values computed using the local-density approximation and the generalized-gradient approximation.

• Interaction and multiscale mechanics
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• 제6권2호
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• pp.107-125
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• 2013

A strain smoothing meshfree formulation with stabilized conforming nodal integration is presented for modeling the consolidation process in saturated porous media. In the present method, nodal strain smoothing is consistently introduced into the meshfree approximation of strain and pore pressure gradient variables associated with the saturated porous media. Meanwhile, in order to achieve a consistent numerical implementation, a smoothing approximation of the meshfree shape function within a nodal representative domain is also proposed in the stiffness construction. The resulting discrete system of equations is all expressed in smoothed nodal measures that are very efficient for numerical evaluation. Subsequently the space-time fully discrete equations are further established by the generalized trapezoidal rule for time integration. The effectiveness of the proposed meshfree consolidation analysis method is systematically illustrated by several benchmark problems.

• 한국진공학회지
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• 제12권S1호
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• pp.60-62
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• 2003

In this study we report the results of ab initio first-principles calculations to investigate the possibility of metamagnetic behavior in Fe$_3$Al alloy. We used the WIEN2k package of full-potential linearized-augmented- plane-wave method within the local-spin-density approximation to the density-functional theory. The exchange-correlation functional is the generalized-gradient approximation of Perdew-Burke-Ernzerhof. The theoretical lattice constant, which is about 0.5% smaller than the experimental one, is obtained by minimizing the total energy. If the volume decreases about 9 % from the equilibrium, the total magnetic moment decreases abruptly from 4.6 $\mu_{B}$/f.u. to 4.0 $\mu_{B}$/f.u. Since this change is considerably large (∼14%), it is possible to measure by a simple high-pressure experiment at about 180 kbar.

• 충청수학회지
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• 제29권1호
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• pp.59-71
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• 2016

To obtain more accurate approximation of the true images in the deblurring problems, the weighted global generalized cross validation(GCV) function to the inverse problem with multiple right-hand sides is suggested as an efficient way to determine the regularization parameter. We analyze the experimental results for many test problems and was able to obtain the globally useful range of the weight when the preconditioned global conjugate gradient linear least squares(Gl-CGLS) method with the weighted global GCV function is applied.