• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.2
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• pp.60-66
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• 1994

The scattering problem by E-polarized plane wave with oblique incidence on a tapered resistive strip grating with infinite resistivity at strip-edges is analyzed by the method of moments in the spectral domain. Then the induced surface current density is expanded in a series of Ultraspherical polynomials of the zeroth order. The expansion coefficients are calculated numerically in the spectral domain, the numerical results of the geometricoptical reflection coefficient for the tapered resistivity in this paper are compared with those for the existing uniform resistivity. And the position of sharp variation points in the magnitude of the geometric-optical reflection coefficient can be moved by varying the incident angle and the strip spacing. It is found out that these sharp variation points are due to the transition of higher modes between the propagation mode and the evanescent mode.

• Journal of applied mathematics & informatics
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• v.18 no.1_2
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• pp.171-182
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• 2005

An analysis of the non-homogeneous term involved in the free surface condition for second order wave diffraction on a pair of cylinders is presented. In the computations of the nonlinear loads on offshore structures, the most challenging task is the computation of the free surface integral. The main contribution to this integrand is due to the non-homogeneous term present in the free surface condition for second order scattered potential. In this paper, the free surface condition for the second order scattered potential is derived. Under the assumption of large spacing between the two cylinders, waves scattered by one cylinder may be replaced in the vicinity of the other cylinder by equivalent plane waves together with non-planner correction terms. Then solving a complex matrix equation, the first order scattered potential is derived and since the free surface term for second order scattered potential can be expressed in terms of the first order potentials, the free surface term can be obtained using the knowledge of first order potentials only.

• Journal of Magnetics
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• v.1 no.1
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• pp.9-13
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• 1996

The effects of surface relaxation on surface and interface magnetism in Fe/Cr (001) are investigated using the highly precise all-electron total-energy full-potential linearized augmented plane wave method. The Fe-Cr interlayer spacing is deter-mined by total-energy calculation and it is found to be relaxed downward by 18%. For the relaxed system, the magnetic moment of surface Fe is highly suppressed to be $1.72\mu_B$compared to the unrelaxed case ($2.39\mu_B$). This reduction of magnetic moment is considered as a result of the enhanced hybridization between Fe-d and Cr-d states, which can be seen from the calculated density of states. This work suggests the importance of effect of relaxation to the surface and interface magnetism in Fe/Cr system.

• Structural Engineering and Mechanics
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• v.59 no.3
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• pp.475-502
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• 2016

Nanobeams are widely used as a structural element for nanodevices and nanomachines. The development of nano-sized machines depends on proper understanding of mechanical behavior of these nano-sized beam elements. Small length scales such as lattice spacing between atoms, surface properties, grain size etc. are need to be considered when applying any classical continuum model. In this study, Eringen's nonlocal elasticity theory is incorporated into classical beam model considering the effects of axial extension and the shear deformation to capture unique static behavior of the nanobeams under continuum mechanics theory. The governing differential equations are obtained for curved beams and solved exactly by using the initial value method. Circular uniform beam with concentrated loads are considered. The displacements, slopes and the stress resultants are obtained analytically. A detailed parametric study is conducted to examine the effect of the nonlocal parameter, mechanical loadings, opening angle, boundary conditions, and slenderness ratio on the static behavior of the nanobeam.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.455-458
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• 2002

Design methods are presented for an X-band traveling-wave slot array realized on a rectangular waveguide. An array of 21 longitudinal slots is realized on the broad wall of a rectangular waveguide. The squint of the antenna main beam is adjusted using the element spacing and the waveguide broad wall dimension. The excitation of the array is controlled by the slot offset from the waveguide center line Multiple I-plane steps are placed around last slot elements so that the second-order beam due to tile reflected wave Is minimized A waveguide-to-coaxial adapter Is designed for feeding the array antenna from a coaxial system. Results of the design show an outstanding performance of the antenna 17.1 dB gain. 36"beam 1111, and -21 dB maximum sidelobe level.evel.

• Applied Science and Convergence Technology
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• v.23 no.3
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• pp.128-133
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• 2014

We study the ballistic spin transport properties in a two-dimensional electron gas system in the presence of magnetic barriers using a transfer matrix method. We concentrate on the size-effect of the magnetic barriers parallel to a two-dimensional electron gas plane. We calculate the transmission probability of the ballistic spin transport in the magnetic barrier structure while varying the width of the magnetic barriers. It is shown that resonant tunneling oscillation is affected by the width and height of the magnetic barriers sensitively as well as by the inter-spacing of the barriers. We also consider the effect of additional electrostatic modulation on the top of the magnetic barriers, which could enhance the current spin polarization. Because all-semiconductor-based devices are free from the resistance mismatch problem, a resonant tunneling structure using the two-dimensional electron gas system with electric-magnetic modulation would play an important role in future spintronics applications. From the results here, we provide information on the physical parameters of a device to produce well-defined spin-polarized current.

• Bulletin of the Korean Chemical Society
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• v.21 no.10
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• pp.1049-1051
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• 2000

A chromia-pillared clay has been prepared by ion exchange type intercalation reaction between the sodium ion in montmorillonite and the trimeric chromium oxyformate (TCF) ion, and by subsequent heat-treatment. The structural and thermal properties have been systematically studied by thermal analysis, powder XRD, IR spec-troscopy, and XAS. The gallery height of~6.8 $\AA$ upon intercalation of the TCF ion suggests that the $Cr_3O$ plane is parallel to the aluminosilicate layers. Even though the basal spacing of TCF intercalated clay decreases slightly upon heating, the layer structure was retained up to $550^{\circ}C$ as confirmed by XRD and TG/DTA. Ac-cording to the EXAFS spectroscopic analysis, it is identified that the (Cr-Cr) distance of 3.28 $\AA$ between vertex-linked CrO6 octahedra in TCF splits into 2.64 $\AA$, 2.98 $\AA$, and 3.77 $\AA$ due to the face-, edge-, and corner-shared CrO6 octahedra after heating at $400^{\circ}C$, implying that a nano-sized chromium oxide phase was stabilized within the interlayer space of clay.

• Wind and Structures
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• v.5 no.5
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• pp.393-406
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• 2002

Aerodynamic pressures and forces were measured on a model of a solar panel containing six slender, parallel modules. Of particular importance to system design is the aerodynamically induced torque. The peak system torque was generally observed to occur at approach wind angles near the diagonals of the panel ($45^{\circ}$, $135^{\circ}$, $225^{\circ}$ and $315^{\circ}$) although large loads also occurred at $270^{\circ}$, where wind is in the plane of the panel, perpendicular to the individual modules. In this case, there was strong vortex shedding from the in-line modules, due to the observation that the module spacing was near the critical value for wake buffeting. The largest loads, however, occurred at a wind angle where there was limited vortex shedding ($330^{\circ}$). In this case, the bulk of the fluctuating torque came from turbulent velocity fluctuations, which acted in a quasi-steady sense, in the oncoming flow. A simple, quasi-steady, model for determining the peak system torque coefficient was developed.

• Current Photovoltaic Research
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• v.8 no.1
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• pp.27-32
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• 2020

CuS thin films were deposited on glass substrates at room temperature by RF magnetron sputtering. The structural and optical properties of CuS thin films grown by varying RF-power from 40 W to 100 W were studied. From the XRD analysis, we confirmed hexagonal crystal structures grown in the preferred orientation of the (110) plane in all CuS thin films, and the intensity of the main diffraction peak increased in proportion to the increase of RF-power. In the case of CuS thin film deposited at 40W, small-sized particles formed a thin and dense surface morphology with narrow pore spacing, relatively. As the power increased, the grain size and grain boundary spacing increased sequentially. The peaks for the binding energy of Cu 2p_3/2 and Cu 2p_1/2 were determined at 932.1 eV and 952.0 eV, respectively. The difference in binding energy for the Cu²⁺ states was the same at 19.9 eV regardless of process parameters. The transmittance and band gap energy in the visible region tended to decrease with increasing sputtering powers.

• Journal of the Korean Chemical Society
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• v.21 no.4
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• pp.246-255
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• 1977

The adsorption of methylmethacylate on layer silicates containing various interlayer cations has been studied by means of infrared spectroscopy and X-Ray. Several characteristic carbonyl bands of adsorbed methylmethacrylate appeared differently at the region of 1723∼1547$cm^{-1}$depending on the species of cation and the dehydration temperature. The carbonyl stretching band shifted about 190$cm^{-1}$ to lower frequencies has been observed only for polyvalent cations, which has been attributed to $>C=O{\cdot}{\cdot}{\cdot}M^{n+}$ complex formation. The band appeared at 1703∼1640$cm^{-1}$ is responsible for hydrogen bonding between carbonyl oxygen and cationic water or cationic hydroxyl group, and the degree of shift indicates good correlation with the polarizing power of the interlayer cations. However, the band appeared at 1723$cm^{-1}$ has not been correlated with the species of cation but assigned to the carbonyl stretching which reacted with the surface hydroxyl group. On the basis of interlamellar spacing, it is suggested that the molecular plane of MMA molecule is parallel to silicate layers.