• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.2
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• pp.93-99
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• 1998

Parabolic approximation and sponge layer are applied as open boundary condition for elliptic finite difference wave model. Generalized conjugate gradient method is used as a solution procedure. Using parabolic approximation a large part of spurious reflection is removed at the spherical shoal experiment and sponge layer boundary condition needs more than 2 wave lengths of sponge layer to give similar results. Simulating the propagation of waves on a rectangular harbor, it is identified that iterative scheme can be applied easily for the non-rectangular computational region.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.04a
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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.

• Proceeding of EDISON Challenge
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• 2015.03a
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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.

• Journal of the Korean Magnetics Society
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• v.15 no.4
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• pp.217-220
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• 2005

The electronic structure and magnetism of Fe chain along the [110] direction on Ag(001) were investigated by using the all-electron full-potential linearized augmented plane wave (FLAPW) method within generalized gradient approximation (GGA). The magnetic moment of Fe atom in Fe chain is calculated to be $3.02\;{\mu}_B$, which is slightly larger than that ($2.99\;{\mu}_B$) of the Fe[110] chain on Cu(001). The reduced coordination number for the Fe chain induced the Fe-d band narrowing and exchange-splitting enhancement, which are responsible for the large magnetic moment of the Fe chain. The calculated band width of the Fe-d band and the exchange-splitting are 1.7 eV and 3.2 eV, respectively.

• Journal of the Korean Magnetics Society
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• v.23 no.4
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• pp.117-121
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• 2013

In this study we investigated magnetism and magnetostriction of B2-structured FeX (X = Al, Si, Ni, Ga, Ge, and Sn) using a first-principles method, in order to survey the possibility of developing a transition metal based magnetostriction material. The Full-potential Linearized Augmented Plane Wave method was employed for solving the Kohn-Sham equation within the generalized gradient approximation for exchange-correlation interaction between electrons. FeX alloys are stabilized in ferromagnetic states except for the FeSi and FeGe alloys. Magnetostrcition coefficients of FeX (X = Al, Ni, Ga, and Sn) were calculated to be -5, +6, -84, -522ppm, respectively. It is noteworthy that the magnetostriction coefficient (-522ppm) of FeSn is larger than that (+400ppm) of Gafenol.

• Nuclear Engineering and Technology
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• v.53 no.2
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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.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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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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• v.6 no.2
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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.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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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.

• Journal of the Chungcheong Mathematical Society
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• v.29 no.1
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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.