• Journal of Korean Association for Spatial Structures
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• v.1 no.2 s.2
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• pp.85-92
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• 2001

The structural behaviors of anisotropic laminated shells are quite different from that of isotropic shells, Also, the classical theory of shells based on neglecting transverse shear deformation is invalid for laminated shells. Thus, to obtain the more exact behavior of laminated shells, effects of shear deformation should be considered in the analysis. As the length of x-axis or y-axis is increase, the effects of transverse shear deformation are decrease because the stiffness for the axis according to the increasing of length is large gradually. In this paper, the governing equations for anisotropic laminated shallow shell including the effects of shear deformation are derived. And then, by using Navier's solutions for shallow shells having simple supported boundary, extensive numerical studies for anisotropic laminated shallow shells were made to investigate the effects of shear deformation for 3 typical shells. Also, static analysis is carried out for cross-ply laminated shells considering the effects of various geometrical parameters, e,g., the shallowness ratio, the thickness ratio and the ratio of a(length of x-axis)-to-b(length of y-axis). The results are compared with existed one and show good agreement.

• Macromolecular Research
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• v.12 no.6
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• pp.564-572
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• 2004

Modem applications could benefit from multifunctional materials having anisotropic optical, electrical, thermal, or mechanical properties, especially when coupled with locally controlled distribution of the directional response. Such materials are difficult to engineer by conventional methods, but the electric field-aided technology presented herein is able to locally tailor electroactive composites. Applying an electric field to a polymer in its liquid state allows the orientation of chain- or fiber-like inclusions or phases from what was originally an isotropic material. Such composites can be formed from liquid solutions, melts, or mixtures of pre-polymers and cross-linking agents. Upon curing, a 'created composite' results; it consists of these 'pseudofibers' embedded in a matrix. One can also create oriented composites from embedded spheres, flakes, or fiber-like shapes in a liquid plastic. Orientation of the externally applied electric field defines the orientation of the field-aided self-assembled composites. The strength and duration of exposure of the electric field control the degree of anisotropy created. Results of electromechanical testing of these modified materials, which are relevant to sensing and actuation applications, are presented. The materials' micro/nanostructures were analyzed using microscopy and X-ray diffraction techniques.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1035-1038
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• 2007

We designed and manufactured a 1.8T high temperature superconducting(HTS) insert coil for a NMR magnet operated at 4.2 K. Suitable HTS superconductor and HTS coil were carefully designed and developed. We have selected multi-filamentary Bi2223 conductor fabricated by American Superconductor Corporation(AMSC). The selected conductor consists of Bi2223 filaments of 55, silver stabilizer and stainless steel reinforcement tapes. Therefore, it shows good hoop strength as well as compression tolerance. The conductor has a tape cross-section of 0.31mm x 4.8mm. the Bi2223 conductor shows large anisotropy of critical current. The critical current of conductor in magnetic field parallel to the flat surface are much higher than that in magnetic field perpendicular. The HTS coil has an inner diameter of 78 mm, an outer diameter of 127 mm and a coil length of 600 mm. In this paper, the detailed design, fabrication and test results on the HTS insert coil are presented.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.771-776
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• 2000

Fine grid calculations are reported for the developing turbulent flow in a straight duct and a curved duct of square cross-section with a radius of curvature to hydraulic diameter ratio ${\delta}=R_c/H_H=3.357$ and a bend angle of 180 deg. A sequence of modeling refinements is introduced; the replacement of wall function by a fine mesh across the sublayer and a low Reynolds number second moment closure up to the near wall sublayer in which the non-linear return to isotropy model and the cubic-quasi-isotropy model for the pressure strain are adopted; and the introduction of a multiple source model for the exact dissipation rate equation. Each refinement is shown to lead to an appreciable improvement in the agreement between measurement and computation.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.471-474
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• 2002

Three-ring types liquid crystalline compounds having fluoro and isothiocyanate substituent were synthesized and their physical and electro-optical properties were measured to evaluate the applications to active matrix VA liquid crystal displays. The tetrakis(triphenylphosphine)palladium(0) catalyzed cross coupling of aryl boronic acids with aryl halides is used to prepare trans-4'-Alkoxy-2,3-difluoro-3'-isothiocyanato-4-(4-alkylcyclohexyl}-biphenyl series. The synthesized compounds showed the nematic liquid crystalline phase and the negative dielectric anisotropy. The prepared mixtures showed faster response time and lower threshold voltage than their host mixture.

• Korean Journal of Computational Design and Engineering
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• v.7 no.2
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• pp.96-101
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• 2002

Rapid Prototyping (RP) technology has been advanced to fabricate initial prototypes from various materials. Stratasys′ Fused Deposition Modeling (FDM) is one of the typical RP processes that provide functional prototypes of ABS plastic. In order to predict the behavior of final ABS parts, it is critical to understand the material properties of the raw FDM process material, and the effect that FDM build parameters have on the FDM part. In this paper, we seek to characterize the properties of ABS parts fabricated by the FDM 1650. Using the Design of Experiment (DOE) approach, the process parameters of FDM, such as raster orientation, air gap, bead width, color, and model temperature were examined. Tensile strengths of crisscross specimens, 〔45°/-45°〕, cross specimens, 〔0°/90°〕, and directionally fabricated tensile specimens (〔0°〕 and 〔90°〕) were measured and compared with the injection molded FDM-ABS P400 material. For the FDM parts made with a -0.003"air gap, the typical tensile strength ranged between 50 percent and 83 percent of the strength of injection molded ABS P400. From the experiments, a couple of build rules for designing FDM parts were obtained.

• Nuclear Engineering and Technology
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• v.49 no.6
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• pp.1114-1124
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• 2017

Acceleration/preconditioning strategies available in the SCEPTRE radiation transport code are described. A flexible transport synthetic acceleration (TSA) algorithm that uses a low-order discrete-ordinates ($S_N$) or spherical-harmonics ($P_N$) solve to accelerate convergence of a high-order $S_N$ source-iteration (SI) solve is described. Convergence of the low-order solves can be further accelerated by applying off-the-shelf incomplete-factorization or algebraic-multigrid methods. Also available is an algorithm that uses a generalized minimum residual (GMRES) iterative method rather than SI for convergence, using a parallel sweep-based solver to build up a Krylov subspace. TSA has been applied as a preconditioner to accelerate the convergence of the GMRES iterations. The methods are applied to several problems involving electron transport and problems with artificial cross sections with large scattering ratios. These methods were compared and evaluated by considering material discontinuities and scattering anisotropy. Observed accelerations obtained are highly problem dependent, but speedup factors around 10 have been observed in typical applications.

• Journal of the Korean Physical Society
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• v.73 no.10
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• pp.1541-1545
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• 2018

We study lattice thermal conductivity of $Sb_2Te_3$ using molecular dynamics simulations. The interatomic potentials are fitted to reproduce total energy and elastic constants, and phonon properties calculated using the potentials are in reasonable agreement with first-principles calculations and experimental data. Our calculated lattice thermal conductivities of $Sb_2Te_3$ decrease with temperature from 150 K to 500 K. The in-plane lattice thermal conductivity of $Sb_2Te_3$ is higher than cross-plane lattice thermal conductivity of $Sb_2Te_3$, as in the case of $Bi_2Te_3$, which is consistent with the anisotropy of the elastic constants.

• Earthquakes and Structures
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• v.5 no.2
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• pp.161-205
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• 2013

We study seismically induced, anti-plane strain wave motion in a non-homogeneous geological region containing tunnels. Two different scenarios are considered: (a) The first models two tunnels in a finite geological region embedded within a laterally inhomogeneous, layered geological profile containing a seismic source. For this case, labelled as the first boundary-value problem (BVP 1), an efficient hybrid technique comprising the finite difference method (FDM) and the boundary element method (BEM) is developed and applied. Since the later method is based on the frequency-dependent fundamental solution of elastodynamics, the hybrid technique is defined in the frequency domain. Then, an inverse fast Fourier transformation (FFT) is used to recover time histories; (b) The second models a finite region with two tunnels, is embedded in a homogeneous half-plane, and is subjected to incident, time-harmonic SH-waves. This case, labelled as the second boundary-value problem (BVP 2), considers complex soil properties such as anisotropy, continuous inhomogeneity and poroelasticity. The computational approach is now the BEM alone, since solution of the surrounding half plane by the FDM is unnecessary. In sum, the hybrid FDM-BEM technique is able to quantify dependence of the signals that develop at the free surface to the following key parameters: seismic source properties and heterogeneous structure of the wave path (the FDM component) and near-surface geological deposits containing discontinuities in the form of tunnels (the BEM component). Finally, the hybrid technique is used for evaluating the seismic wave field that develops within a key geological cross-section of the Metro construction project in Thessaloniki, Greece, which includes the important Roman-era historical monument of Rotunda dating from the 3rd century A.D.

• Journal of the Korean Magnetics Society
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• v.14 no.5
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• pp.163-168
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• 2004

We prepared ultra thin film structure of Si(100)/ $SiO_2$(200 nm)/Ta(5 nm)/Ni$_{80}$Fe$_{20/(l～15 nm)}$Ta(5 nm) using an inductively coupled plasma(ICP) helicon sputter. Magnetic properties and cross-sectional microstructures were investigated with a superconduction quantum interference device(SQUID) and a transmission electron microscope(TEM), respectively. We report that NiFe films of sub-3 nm thickness show the B$_{bulk}$ = 0 and B$_{surf}$=-3 ${\times}$ 10$^{-7}$(J/$m^2$). Moreover, Curie temperature may be lowered by decreasing thickness. Coercivity become larger as temperature decreased with 0.5 nm - thick Ta/NiFe interface intermixing. Our result implies that effective magnetic properties of magnetoelastic anisotropy, saturation magnetization, and coercivity may change abruptly in nano-thick films. Thus we should consider those abrupt changes in designing nano-devices such as MRAM applications.