• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.218-221
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• 2004

The electronic state of ZnO doped with Al, Ga and In, which belong to III family elements in periodic table, was calculated using the density functional theory. In this study, the program used for the calculation on theoretical structures of ZnO and doped ZnO was Vienna Ab-initio Simulation Package (VASP), which is a sort of pseudo potential method. The detail of electronic structure was obtained by the describe variational $X{\alpha}(DV-X{\alpha})$(DV-Xa) method, which is a sort of molecular orbital full potential method. The optimized crystal structures obtained by calculations were compared to the measured structure. The density of state and energy levels of dopant elements was shown and discussed in association with properties.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권4호
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• pp.513-528
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• 2013

A floating Oscillating Water Column (OWC) wave energy converter, a Backward Bent Duct Buoy (BBDB), was simulated using a state-of-the-art, two-dimensional, fully-nonlinear Numerical Wave Tank (NWT) technique. The hydrodynamic performance of the floating OWC device was evaluated in the time domain. The acceleration potential method, with a full-updated kernel matrix calculation associated with a mode decomposition scheme, was implemented to obtain accurate estimates of the hydrodynamic force and displacement of a freely floating BBDB. The developed NWT was based on the potential theory and the boundary element method with constant panels on the boundaries. The mixed Eulerian-Lagrangian (MEL) approach was employed to capture the nonlinear free surfaces inside the chamber that interacted with a pneumatic pressure, induced by the time-varying airflow velocity at the air duct. A special viscous damping was applied to the chamber free surface to represent the viscous energy loss due to the BBDB's shape and motions. The viscous damping coefficient was properly selected using a comparison of the experimental data. The calculated surface elevation, inside and outside the chamber, with a tuned viscous damping correlated reasonably well with the experimental data for various incident wave conditions. The conservation of the total wave energy in the computational domain was confirmed over the entire range of wave frequencies.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.740-745
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• 2005

This study is intended to build a controller of redundant manipulators with the simultaneous abilities of trajectory tracking and obstacle avoidance without any preparations of path planning to achieve full automation even for one production of one kind, while keeping the avoidance ability high and keeping its shape away from object to reduce the possibility that the manipulator crashes to the object. To evaluate the avoidance ability of the intermediate link, we proposed a scalar value of Avoidance Manipulability Shape Index(AMSI), which is independent of the obstacle's shape. On the other hand, the danger to crash to the obstacle is depending on the shape of the obstacle, which could be evaluated by the potential field set around the obstacle. This paper proposes control method of the manipulator's shape based on the AMSI to simultaneously avoid obstacles and keep the avoidance ability high with potential.

• 한국농공학회지
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• 제44권1호
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• pp.81-92
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• 2002

The purpose of this paper, the 2nd stage of this study. is to test the applicability of the potential centrality evaluation model (PCEM) to a case study area. To verify the practical applicabilities of the PCEM, an administrative area of Ucheon-myeon, Hoengseong-gun, Gangwon-do was selected as a study area. Full data on the human environments of total 72 villages within the study area were surveyed. Data on the natural environments were collected through GIS analysis from digital maps developed far this study. The highest PCI (Potential Centrality Index) score was shown at Uhang village of which one being 841 (total score being 1,000), the real single center village of the study area. The evaluation results on potential centeralities of all the villages in the study area would provide decision-makers with more precised information for selection of center villages for development project.

• 대한수학회논문집
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• 제15권1호
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• pp.155-172
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• 2000

Mode interactions at Unstable fluid interfaces induced by a shock wave (Richtmyer-Meshkov Instability) are studied both analytically and numerically. The analytical approach is based on a potential flow model with source singularities in incompressible fluids of infinite density ratio. The potential flow model shows that a single bubble has a decaying growth rates at late time and an asymptotic constant radius. Bubble interactions, bubbles of different radii propagates with different velocities and the leading bubbles grow in size at the expense of their neighboring bubbles, are predicted by the potential flow model. This phenomenon is validated by full numerical simulations of the Richtmyer-Meshkov instability in compressible fluids for initial multi-frequency perturbations on the unstable interface.

• Journal of Magnetics
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• 제18권4호
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• pp.375-379
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• 2013

The electronic and the magnetic properties of (001) surface of $KCaN_2$ half-metallic compound with full-Heusler structure are studied with the use of a full-potential linearized augmented plane wave method. Two possible terminations of the surface are considered and only the one with N atoms in the topmost layer is found to retain the half-metallic properties of the bulk. The magnetic properties of N-terminated surface are enhanced compared with the properties of the bulk. The calculated magnetic moments on the N atoms in the $KCaN_2$ are 1.26 ${\mu}_B$ in the bulk and 1.90 ${\mu}_B$ at the surface. The subsurface metal atoms are also slightly polarized. In the surface terminated with metal atoms, not only the half-metallicity is destroyed, but also the magnetic properties of the system are weakened.

• 천문학회보
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• 제36권1호
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• pp.49.1-49.1
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• 2011

Utilizing single-epoch spectra and the empirical relation between the size of the broad-line region and AGN continuum luminosity, the so-called single-epoch method has been widely used for estimating AGN black hole masses. However, the systematic uncertainties and the potential biases of this method are not well examined. Taking the full advantage of the high-quality homogeneous spectra from the Lick AGN Monitoring Project (LAMP), we investigate in detail the uncertainties of single-epoch mass estimates by comparing with the reverberation-mapping results. We find that the uncertainty due to AGN variability is less than 0.1 dex, while there is a systematic offset between single-epoch masses and reverberation masses. Particularly, narrow-line Seyfert 1 galaxies show that the Hbeta line widths measured from single-epoch (or mean) spectra are systematically larger than those from rms spectra, indicating a potential bias of single-epoch masses. We will present the detailed measurement method, the test of virial assumption, and the systematic uncertainties.

• Journal of Magnetics
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• 제13권1호
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• pp.7-10
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• 2008

The structural and magnetic properties of functionalized carbon chains doped with 4d transition metals, such as Ru, Rh, and Pd, were investigated using the full-potential linearized augmented plane wave (FLAPW) method. The carbon nanowire doped with Ru exhibited a ferromagnetic ground state with a sizable magnetic moment, while those doped with Rh and Pd had nonmagnetic ground states. For the Ru-doped chain, the density of states at the Fermi level showed large spin polarization, which suggests that the doped nanowire could be used for spintronic applications.

• Bulletin of the Korean Chemical Society
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• 제33권11호
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• pp.3597-3600
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• 2012

Thrombin binding aptamter (TBA-15) is a 15-mer guanine-rich oligonucleotide. This DNA apamer specifically binds to the thrombin protein involved in blood coagulation. Using extensive umbrella sampling molecular dynamics simulation method at all atom level, we investigated the potential of mean force (PMF) upon pulling the DNA aptamer from the binding mode of aptamer/thrombin complex. From this calculation, the free energy cost for a full dissociation of this aptamer/protein complex is 17 kcal/mol, indicating a substantial binding affinity of TBA-15. Interestingly, this PMF reveals noticeable plateau regions along the pulling coordinate. Possible structural changes of this complex in the plateau were investigated in details.

• Journal of Magnetics
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• 제14권4호
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• pp.137-143
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• 2009

The convergence behavior of the all-electron full-potential linearized augmented plane-wave (FLAPW) method with the explicit orthogonalization (XO) scheme is tested on ferromagnetic bulk body-centered-cubic Fe. Applying a commonly used criterion relating the plane-wave and angular momentum cutoffs, $l_{max}\;=\;R_{MT}K_{max}$, where $R_{MT}$ is the muffin-tin (MT) sphere radius and $K_{max}$ is the plane-wave cutoff for the basis - the total energy is converged and stable for $K_{max}R_{MT}$ = 10. The total energy convergence dependence on the star-function cutoff, $G_{max}$, is minimal and so a $G_{max}$ of 3$K_{max}$ or a large enough $G_{max}$ is a reasonable choice. We demonstrate that the convergence with respect to $l_{max}$ or a fixed large enough $G_{max}\;and\;K_{max}$ are independent, and that $K_{max}$ provides a better measure of the convergence than $R_{MT}K_{max}$. The dependence of the total energy on $R_{MT}$ is shown to be small if the core states are treated equivalently, and that the XO scheme is able to treat systems with significantly smaller $R_{MT}$ than the standard LAPW method. For converged systems, the calculated lattice parameter, bulk modulus, and magnetic moments are in excellent agreement with the experimental values.