• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.175.1-175.1
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• 2014

Despite growing interest in Ge as a possible alternative to Si, reliable data on Ge surface has been relatively scarce. Using low temperature scanning tunneling microscopy (STM), we investigate band-bending effects of localized charge traps at Ge(001) surface at 78 K. For this investigation, we prepared nearly defect-free Ge(001) surface by keeping the background pressure to < $1{\times}10^{-10}$ mbar during outgassing. Ge(001) surfaces this obtained exhibit a flat-band condition, and deposition of charge traps induce a distinct, sharp boundary between pinned and depinned surface area in the constant current mode STM images. We will show the tip-surface interaction plays an essential role in producing the boundary, and discuss about the conditions that enable the pinning effect.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.3
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• pp.263-268
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• 2012

It is important to know the mechanism of cell membrane fluctuation because it can be readout for the nanomechanical interaction between cytoskeleton and plasma membrane. Traditional techniques, however, have drawbacks such as probe contact with the cell surface, complicate analysis, and limit spatial and temporal resolution. In this study, we developed a new system for non-contact measurement of nano-scale localized-cell surface dynamics using modified-scanning ion-conductance microscopy. With 2 nm resolution, we determined that endothelial cells have local membrane fluctuations of ~20 nm, actin depolymerization causes increase in fluctuation amplitude, and ATP depletion abolishes all membrane fluctuations.

• Smart Structures and Systems
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• v.18 no.1
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• pp.1-16
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• 2016

Model Order Reduction (MOR) denotes the theory by which one tries to catch a model of order lower than that of the real model. This is conveniently pursued in view of the design of an efficient structural control scheme, just passive within this paper. When the nonlinear response of the reference structural system affects the nature of the reduced model, making it dependent on the visited subset of the input-output space, standard MOR techniques do not apply. The mathematical theory offers some specific alternatives, which however involve a degree of sophistication unjustified in the presence of a few localized nonlinearities. This paper suggests applying standard MOR to the linear parts of the structural system, the interface remaining the original unreduced nonlinear components. A case study focused on the effects of a helicopter land crash is used to exemplify the proposal.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.58-58
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• 2003

The envelope glycoprotein of HIV, gp41, mediates the membrane fusion with human cells. The extracellular domain of gp41 has two helical regions. The N-terminus helical region (N-helix) forms trimeric coiled coil, interacts with the C-terminus helical region (C-helix) of gp41 to form a stable helical bundle structure. In this study, we have shown that the N-helix of gp41 has membrane interacting and disrupting abilities. It was localized into the interface of the lipidic phase and head group of the membrane. In contrast, the N-helix region with membrane fusion defective mutations could not bind to membrane. In addition, the N-helix bound on the membrane was released from the membrane by the C-helix, and the complex of the N- and C-helix did not interact with membrane. These results suggested that the membrane binding ability of the N-helix is necessary for the fusion activity of gp41, and such property is possibly controlled by the C-helm.

• Journal of Integrative Natural Science
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• v.1 no.1
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• pp.5-13
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• 2008

본 논문은 국지적 상호작용 하에서 행위자들간에 특성의 차이에 근거한 구별짓기가 협조적 행위의 진화에 미치는 영향을 분석한다. 이 논문에서는 이러한 구별짓기의 성향이 왜, 그리고 어떤 메커니즘을 통해서 진화해나가는지를 보이고자 시도할 것이다. 아울러 구별짓기 성향과 함께 내부인과 외부인을 향한 행동을 다르게 함으로써 어떻게 내부인에 대한 이타적 협조행동을 발생시키는지, 더 나아가 구별짓기의 근거가 되는 행위자들의 여러 특성들(생물학적 혹은 문화적)은 어떻게 변화해 나가고 이들 특성의 변화가 구별짓기와 협조적 행동에 어떤 효과를 가져오는지를 살펴보고자 한다. 더 나아가 본 논문에서는 구별짓기가 협조적 행위의 진화에 영향을 미치는 과정을 장/단기로 구분함으로써 구별짓기의 효과를 보다 명확히 규명하고자 한다.

• Journal of Korean Vacuum Science & Technology
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• v.2 no.1
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• pp.13-19
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• 1998

We have calculated the electronic structure of impurity atoms in metal host by using the tight binding model in the recursion method. For a self-consistent calculation, we assumed that the effect of impurity introduction was localized only at the impurity site and its neighbours. We calculated the Madelung term by limiting the contribution to Vm of the charge perturbations to the first shell around the impurity with Evjen technique. The calculated local density of states and charge transfer values have been compared with the experimental values for a single impurity in metal host. We fund that d-reso-nance state came from the repulsive interaction between impurity d-state and host band, and the position of d-resonance state depended on the difference of valence electrons between the host and the impurity. the results also showed that the charge transfer value between an impurity and host metal was comparable to the ionicity difference between them.

• Structural Engineering and Mechanics
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• v.51 no.5
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• pp.809-821
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• 2014

The truss based steel bridge structures usually consists of gusset plates which lose their load carrying capacity and rigidity under the effect of repeated and dynamics loads. This paper is focused on modeling the nonlinear material behavior of the gusset plates of the Truss Based Bridges subjected to dynamics loads. The nonlinear behavior of material is characterized by a damage coupled elsto-plastic material models. A truss bridge finite element model is established in Abaqus with the details of the gusset plates and their connections. The nonlinear finite element analyses are performed to calculate stress and strain states in the gusset plates under different loading conditions. The study indicates that damage initiation occurred in the plastic deformation localized region of the gusset plates where all, diagonal, horizontal and vertical, truss member met and are critical for shear type of failure due tension and compression interaction. These findings are agreed with the analytical and experimental results obtained for the stress distribution of this kind gusset plate.

• Bulletin of the Korean Chemical Society
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• v.14 no.6
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• pp.740-743
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• 1993

By considering both electron-electron and electron-lattice interactions, the effect of charge transfer on the bond structure and electronic states of $C_{60}$ is studied without configuration limitation. The results show that the electron-electron interaction does not eliminate the layer structure of the bond distortion and the self-trapping of transferred electrons. For charged ${C_{60}}^{2-}$, there exist two localized electronic states, which possess laminar wave functions, and four nonequivalent groups of carbon atoms, which induce a fine-structure in the NMR spectrum line.

• Journal of the Semiconductor & Display Technology
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• v.9 no.3
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• pp.1-4
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• 2010

First-principles calculations based on spin density functional theory are performed to study the spin-resolved electronic properties of AlN doped with a Cu concentration of 6.25%-18.75%. The ferromagnetic state is more energetically favorable state than the antiferromagnetic state or the nonmagnetic state. For $Al_{0.9375}Cu_{0.0625}N$, a global magnetic moment of 1.26 mB per supercell, with a localized magnetic moment of 0.75 $m_B$ per Cu atom is found. The magnetic moment is reduced due to an increase in the number of Cu atoms occupying adjacent cation lattice position. For $Al_{0.8125}Cu_{0.1875}N$, the magnetism of the supercell disappears by the interaction of the neighboring Cu atoms. The nonmagnetic to ferromagnetic phase transition is found to occur at this Cu concentration. The range of concentrations that are spin-polarized should be restricted within very narrow.

• Korean Journal of Metals and Materials
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• v.48 no.2
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• pp.163-168
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• 2010

We here describe the laser-direct patterning of nanostructured metal thin films. This method involves light-matter interaction in which a pulsed laser beam impinging on the film generates a thermoelastic force that plays a role to detach the film from the substrate or underlying layers. A moderate cohesion of the nanostructured film enables localized desorption of the material upon irradiation by a spatiallymodulated laser beam, giving good fidelity with the transfered pattern. This photoresist-free process provides a simple high-resolution scheme for patterning metal thin films.