• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.6
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• pp.244-251
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• 2005

The relationship between particle size of hydro-thermally synthesized barium titanate powders (BT01, BT02, BT03, BT04, BT05) and the powder properties was investigated by means of particle size, specific surface area, zeta potential, XPS, XRD and SEM. Particle size determined by laser light scattering is closely related with specific surface area and the tetragonality (c/a) obtained from XRD. The specific surface area of the samples inversely decreased with increasing particle size except BT03 powder. BT03 sample showed higher surface area than BT04 sample of equivalent particle size, which was attributed mostly to the agglomeration of particles in terms of SEM image and XRD analysis. Zeta potential increased with increasing particle size with the exception of BT02 and BT03 which showed larger minus value of zeta potential in comparison with other BT powders. Beta potential results of BT02 and BT03 are considered to be related with the dissolution of $Ba^{2+}$ ion in these powers which was examined by XPS.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.1
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• pp.27-33
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• 2005

In this study, the process parameters in ceramics powder compaction are optimized for getting high relative densities of ceramic products. To find optimized parameters, the analytic models of powder compaction are firstly prepared by 2-dimensional rod arrays with random green densities using a quasi-random multiparticle array. Then, using finite element method, the changes in relative densities are analyzed by varying the size of Al₂O₃ particle, the amplitude of cyclic compaction, and the coefficient of friction, which influence the relative density in cyclic compactions. After the analytic function of relative density associated process parameters are formulated by aid of the response surface method, the optimal conditions in powder compaction process are found by the grid search method. When the particle size of Al₂O₃ is 22.5 ㎛, the optimal parameters for the amplitude of cyclic compaction and the coefficient of friction are 75 MPa and 0.1103, respectively. The maximum relative density is 0.9390.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.1
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• pp.9-25
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• 1994

In the present study, the Reynolds-averaged Navier-Stokes equations, together with the equations of the $k-{\varepsilon}$ model of turbulence, were solved numerically in a general body-fitted coordinate system for three-dimensional turbulent flows around the six basic shapes of the magnetically levitated train(MAGLEV). The numerical computations were conducted on the MAGLEV model configurations to provide information on shapes of this type very near the elevated track at a constant Reynolds number of $1.48{\times}10^{6}$ based on the body length. The coordinate system was generated by numerically solving a set of Poisson equations. The convective transport equations were discretized using the finite-analytic scheme which employed analytic solutions of the locally-linearized equations. A time marching algorithm was employed to enable future extensions to be made to handle unsteady and fully-elliptic problems. The pressure-velocity coupling was treated with the SIMPLER-algorithm. Of particular interests were wall effect by the elevated track on the aerodynamic forces and flow characteristics of the six models calculated. The results indicated that the half-circle configuration with extended sides and with smooth curvature of sides was desirable because of the low aerodynamic forces and pitching moment. And it was found that the separation bubble was occured at wake region in near the elevated track.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.315-323
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• 1997

The sing1e crystal of cadmium sulfide was grown by vertical sublimation method. The lattice constants of CdS single crystal by extrapolation method are $a_0=4.139\AA$ and $c_0=6.719\AA$, respectively. The $Cu_2$S/CdS solar cell was fabricated using the single crystal of cadmium sulfide and the CuCl solution. The light- to- dark JV cross over effect of the $Cu_2$S/CdS solar cell was measured after annealing for 2 minutes at $250^{\circ}C$ in air atmosphere. The values of Voc, Jsc, Vop, FF, and efficiency are 0.40 volt, $4.2mA/\textrm{cm}^2$, 0.31 volt, $3.8mA/\textrm{cm}^2$, 0.68 and 3.8 %, respectively. The spectral response of the solar cell shows the peaks at 498 nm (2.49 eV) and 585 nm (2.12 eV).

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.1-8
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• 1991

The electronic and magnetic structure of Fe overlayers on W(110) is determined by means of the all-electron local spin density full potential linearized augmented plane wave (FLAPW) method with a single slab approach. Charge and spin densities, magnetic moments, contact hyperfine fields, and layer projected density of states (LDOS) are presented. For bilayer Fe coverage, we find magnetic moments to be 2.90 and 2.30 ${\mu}_B$ for the surface and subsurface Fe layers, respectively, corresponding to a 18% enhancement of the total magnetization compared with the calculated bulk value (2.22${\mu}_B$);For monolayer coverage the moment is 2.56 ${\mu}_B$ which is enhanced by 16% compared to bulk. Unusual changes in the magnetic hyperfine interaction are found in going from a monolayer to a bilayer coverage. Comparison of the results to the theoretical ones of the clean Fe(110) to discuss the hybridization and the negative pressure effects. We discuss our results by comparing them to experimental results.

• Journal of the Korean Magnetics Society
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• v.4 no.2
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• pp.154-159
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• 1994

The magneto-optical Kerr spectra(${\lambda}=250~700nm$) of amorphous RE-Co(RE=Ce, Nd, Pr, Gd, Tb, Er, Ho) are compared with those of Y-Co films. It has been found that the Kerr rotation of RE-Co is mainly due to Co in the long wavelength region, whereas at short wavelength Ce, Pr, Nd, and Gd contribute positively, and Tb, Ho, and Er contribute negatively to the Kerr rotation of RE-Co amorphous films. In the interesting energy region(1.5~5.0 eV), the magneto-optical contribution of Pr and Nd are thought to be related with $4f{\uparrow}->5d{\uparrow}$ interband transition, and the contribution of Ce and Gd might be concerned with d->p interband transition. The magneto-optical effect of Tb in the short wavelength region might be related with $4f{\downarrow}->5d{\downarrow}$ and/or $5d{\downarrow}->4f{\downarrow}$, and that of Ho and Er can be explained by $4f{\downarrow}->5d{\downarrow}$ magneto-optical interband transition.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.10
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• pp.965-971
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• 2015

This paper suggests a feature point-based Iterative Closest Point (ICP) algorithm to compensate for the disparity error in building a two-dimensional map. The ICP algorithm is a typical algorithm for matching a common object in two different images. In the process of building a two-dimensional map using the laser scanner data, warping and distortions exist in the map because of the disparity between the two sensor values. The ICP algorithm has been utilized to reduce the disparity error in matching the scanned line data. For this matching process in the conventional ICP algorithm, pre-known reference data are required. Since the proposed algorithm extracts characteristic points from laser-scanned data, reference data are not required for the matching. The laser scanner starts from the right side of the mobile robot and ends at the left side, which causes disparity in the scanned line data. By finding the matching points between two consecutive frame images, the motion vector of the mobile robot can be obtained. Therefore, the disparity error can be minimized by compensating for the motion vector caused by the mobile robot motion. The validity of the proposed algorithm has been verified by comparing the proposed algorithm in terms of map-building accuracy to conventional ICP algorithm real experiments.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.61-70
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• 2006

3-D S-wave velocity model in the southern Korean Peninsula is investigated by using the joint inversion of receiver functions and surface-wave dispersion. A peninsula average Rayleigh-wave phase velocity in the 10-150 seconds range and tomographic estimates of the Rayleigh and Love wave group velocities in the 0.5-20 seconds period range determined using a $12.5{\times}12.5\;km$ grid for the southern part of the peninsula are used for the inversion. Receiver functions were determined from broadband (STS-2), short-period (SS-1) and acceleration (Episensor) channels of 95 stations. The dense distribution of the stations in the Peninsula permits us to examine the 3-D crustal structure in detail. The inversion result shows the variation and characteristics of S-wave velocity in the crust and upper mantle of the southern Korean Peninsula very well.

• Korean Journal of Crystallography
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• v.1 no.2
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• pp.66-75
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• 1990

The Pd-Te system has been investigated by differential thermal analysis, X-ray diffration, electron probe microanalysis and reflected light microscopy. New phase relations in 0-50at% Te portion of the binary system are proposed. Eight binary phases exist in the system:Pd17Te4, Pd20Te7.PdsTe3, P477e3, P497e4, P637e2, PeTe and PaTe2. Of these, P677e3 is a newly reported phase. P4177e4 is cubic, space group Fd3c, with a=12.678(5)A. The X-ray powder data of PdsTe3, indexed on an orthorhombic cell, give a= 12.843(3), b=15.126(3), c: 11.304(2)A and those of PdTTe.1, indexed on a monoclinic cell, give a=7.444(1), b= 13.918(2) , c=8.873(2)A. p =92.46(2). Some physical and optical properties of synthetic phases in the system are also reported.

• Journal of Radiation Protection and Research
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• v.28 no.2
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• pp.87-95
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• 2003

The fabrication process and the structure of PIN semiconductor detectors have been designed optimally by simulation for doping concentration and width of p+ layer, impurities re-contribution due to annealing and the current distribution due to guard ring at the sliced edges. The characteristics to radiation response has been also simulated in terms of Monte Carlo Method. The device has been fabricated on n type, $400\;{\Omega}cm$, orientation <100>, Floating-Zone silicon wafer using the simulation results. The leakage current density of $0.7nA/cm^2/100{\mu}m$ is achieved by this process. The good linearity of radiation response to Cs-137 was kept within the exposure ranges between 5 mR/h and 25 R/h. This proposed process could be applied for fabricating a PIN semiconductor detector for measuring individual dose.