• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.156-157
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• 1998

It is a diffcult and challenging pproblem to control the growth of eppitaxial films. Heteroeppitaxy is esppecially idfficult because of the lattice mismatch between sub-strate and depposited layers. This mismatch leads usually to a three dimensional(3D) island growth. But the use of surfactants such as As, Sb, and Bi can be beneficial in obtaining high quality heteroeppitaxial films. In this study medium energy ion scattering sppectroscoppy(MEIS) was used in order to reveal the growth mode of Ge on Si(001) and the strain of depposited film without and with dynamically supplied atomic hydrogen at the growth thempperature of 35$0^{\circ}C$. It was ppossible to control the growth mode from layer-by-layer followed by 3D island to layer-by-layer by controlling the hydrogen flux. In the absent of hydro-gen the film grows in the layer-by-layer mode within the critical thickness(about 3ML) and the 3D island formation is followed(Fig1). The 3D island formation is suppressed by introducing hydrogen resulting in layer-by-layer growth beyond the critical thickness(Fig2) We measured angular shift of blocking dipp in order to obtain the structural information on the thin films. In the ppressence of atomic hydrogen the blocking 야 is shifted toward higher scattering angle about 1。. That means the film is distorted tetragonally and strained therefore(Fig4) In other case the shift of blocking dipp at 3ML is almost same as pprevious case. But above the critical thickness the pposition of blocking dipp is similar to that of Si bulk(Fig3). It means the films is relaxed from the first layer. There is 4.2% lattice mismatch between Ge and Si. That mismatch results in about 2。 shift of blocking dipp. We measured about 1。 shift. This fact could be due to the intermixing of Ge and Si. This expperimental results are consistent with Vegard's law which says that the lattice constant of alloys is linear combination of the lattic constants of the ppure materials.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.779-788
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• 2008

In this present study, the three dimensional shell elements analysis method for exact distortional behavior of multicell trapezoidal box girders subjected to an eccentric loading is proposed. In order to perform the independent distortional analysis using shell elements, it is necessary to calculate exact distortional forces. In this study, the force-decomposition equation for applied eccentric load acting on multicell trapezoidal box girder is derived and the equation based on static force equilibrium and superposition theory decompose the eccentric load to the loads cause flexture, torsion and distortion. So by using this force-decomposition equation and shell element analysis, each behavior can be easily analysis independently. This independent analysis method is very useful to physically understand each major behavior of multicell box girder, especially distortional phenomenon. Furthermore, it may be also very useful for designer to perform the independent distortional analysis for diaphragm design using simple 3D shell elements model without preliminary complex calculation for distortional constants.

• Journal of the Korean Magnetics Society
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• v.24 no.2
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• pp.35-40
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• 2014

We investigate magnetism and magnetocrystalline anisotropy of CoFe thin films, using VASP code in GGA. In this study Co-terminated and Fe-terminated 5-layer CoFe thin films are employed. The Co-terminated CoFe thin film shows two total energy minima at 2-dimensional lattice constants of $2.45{\AA}$ and $2.76{\AA}$. The film of $2.45{\AA}$ has fcc-like structure and the film of $2.76{\AA}$ has bcc-like structure similarly to a bulk CoFe alloy. And the fcc-like film is more stable by the energy difference of about 160 meV compared to the bcc-like film. The Fe-terminated CoFe film shows very complicated behaviour of total energy which is suspected to be closely related to its complex magnetic structure. The Co-terminated CoFe film of $2.76{\AA}$ shows perpendicular magnetocrystalline anisotropy (MCA), while the film of 2.45 does parallel MCA. The Fe-terminated CoFe film also exhibits similar MCA behaviour.

• Journal of the Korean Magnetics Society
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• v.23 no.1
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• pp.1-6
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• 2013

Spin-orbit coupling (SOC) effect is known to be the physical origin for various exotic magnetic phenomena in the low-dimensional systems. Recently, SOC also draws lots of attention in the study on magnetically doped thermoelectric alloys to determine their properties as the thermoelectric application as well as the topological insulator via the exact electronic structures determination near the Fermi level. In this research, aiming to investigate the spin-orbit coupling effect on the structural properties such as the lattice constants and the bulk modulus of the most widely investigated thermoelectric host material, $Bi_2Te_3$, we carried out the first-principles electronic structure calculation using the all-electron FLAPW (full-potential linearized augmented plane-wave) method. Employing both the local density approximation (LDA) and the generalized gradient approximation (GGA), the structural optimization is achieved by varying the in-plane lattice constant fixing the perpendicular lattice constant and vice versa, to find that the SOC effect increases the equilibrium lattices slightly in both directions while it markedly reduces the bulk modulus value implying the strong orientational dependence, which are attributed to the material's intrinsic structural anisotropy.

• Analytical Science and Technology
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• v.13 no.4
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• pp.494-503
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• 2000

A 21-residue peptide corresponding to amino acids 84-104 of $p16^{INK4A}$, the tumor suppressor, has been synthesized and its structure was studied by Circular Dichroism, $^1H$ NMR spectroscopy and molecular modeling. A p16-derived peptide (84-104 amino acids) forming stable complex with CDK4 and CDK6 inhibits the ability of CDK4/6 to phosphorylate pRb in vitro, and blocks cell-cycle progression through G1/S phase as shown in the function of the full-length p16. Its NMR spectral data including NOEs, $^3J_{NH-H{\alpha}}$ coupling constants, $C_{\alpha}H$ chemical shift, the average amplitude of amide chemical shift oscillation and temperature coefficients indicate that the secondary structure of a p16-derived peptide is similar to that of the same region of full-length p16, which consists of helix-turn-helix structure. The 3-D distance geometry structure based on NOE-hased distance and torsion angle restraints is characterized by ${\gamma}$-turn conformation between residues $Gly^{89}-Leu^{91}$(${\varphi}_{i+1}=-79.8^{\circ}$, ${\varphi}_{i+1}=60.2^{\circ}$) as evidenced in a single crystal structure for the corresponding region of p18 or p19, but is undefined at both the N and C termini. This compact and rigid ${\gamma}$-turn region is considered to stabilize the structure of p16-derived peptide and serve as a site recognizing cyelin dependent kinase, and this well-defined ${\gamma}$-turn structure could be utilized for the design of anti-cancer drug candidates.