• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.172-174
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• 2005

A ZVZCS(Zero-Voltage and Zero-Current-Switching) Three-Level DC/DC Convertor reducing voltage stress of auxiliary circuit is proposed. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 2kW 40kHz IGBT based experimental circuit.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1432-1434
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• 2005

Single-stage converters are simpler and less expensive than convention two-stage converters. It can be a challenge, however, to design single-stage converters to satisfy certain key criteria such as input power factor, primary-side do bus voltage, and output voltage ripple. This is especially true for higher power single-stage AC/DC TTFC(Two-Transistor Forward Converter).

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.52.4-52
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• 1998

• The Pure and Applied Mathematics
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• v.5 no.1
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• pp.1-3
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• 1998

Let f : X longrightarrow Y be quasi-open. We show that: (1) If A $\subset$ X is open, f│A is quasi-open, (2) f : X longrightarrow f(X) is quasi-open. (3) And let $f_{\alpha}/,:X_{\alpha}$, longrightarrow $Y_{\alpha}$ be quasi-open. Then $\Pi f_{\alpha}, : \Pi X_{\alpha}$ longrightarrow $\Pi Y_{\alpha}$/ defined by {$x_{\alpha}$} longrightarrow {$f_{\alpha},({\chi}_{\alpha}$)}, is quasi-open. (4) Lastly, if $f_{i}: X_{i}$ longrightarrow Y are quasi-open, i = 1,2, then F: $X_1 \bigoplus X_2$ longrightarrow Y, defined by $F({\chi})=f_i({\chi})$, ${\chi} \in X_i$, is also quasi-open.

• Bulletin of the Korean Chemical Society
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• v.8 no.1
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• pp.6-9
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• 1987

The study of the $Na_3YSi_3O_9$ structure, by x-ray diffraction and infrared spectrum, showed that $Na_3YSi_3O_9$ is similar to $Na_4CaSi_3O_9$ except for its being pseudo-cubic instead of cubic. The peaks in the x-ray diffraction pattern of $Na_3YSi_3O_9$ could therefore be indexed on the basis of the $Na_4CaSi_3O_9$ cell. Also, modified $Na_3MSi_3O_9$ (M = Lu, Yb, Tm, Er, Y, Ho, Dy, Gd, Eu, and Sm) type compounds were synthesized by introducing excess sodium, decreasing M(III) concentration, and substituting small amount of phosphorus for silicon. The unit cell parameters of the composition $Na_{3.2}M_{0.7}Si_{2.9}P_{0.1}O_{8.7}$ were estimated from x-ray powder diffraction patterns using the Cohen method.

• Journal of the Semiconductor & Display Technology
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• v.9 no.2
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• pp.15-20
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• 2010

This paper deals with minimizing layout area of FPGA design. FPGAs are becoming increasingly important in the design of ASICs since they provide both large scale integration and user-programmability. This paper describes a method to obtain tight bound on the worst-case increase in area when drivers are introduced along many long wires in a layout. The area occupied by minimum-area embedding for a circuit can depend on the aspect ratio of the bounding rectangle of the layout. This paper presents a separator-based area-optimal embeddings for FPGA graphs in rectangles of several aspect ratios which solves the longest path problem in the constraint graph.

• Journal of Magnetics
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• v.7 no.4
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• pp.156-159
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• 2002

We have investigated the escape rate of nano-magnetic particle with a magnetic field applied along the easy axis. The model studied here is described by the Hamiltonian H=$K_1\hat{S}{_z^2}$ ＋ $K_2\hat{S}{_y^2}$ ＋ $g{\mu}_bB$ $\hat{S}_x(K_1>K_2>0)$ and the escape rate was calculated with in the semiclassical approximation. We have obtained a diagram for orders of the phase transition depending on the anisotropy constant and the external field. For $K_2$/$K_1>$0.85 the present model reveals the existence of the first order transition within the quantum regime.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.168-169
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• 2003

We have determined the orientational distribution functions (OBFs) at both air and substrate isotropic interfaces of a chiral chitosan bio-polymer film by the measurements of surface second-harmonic generation (SHG). It was shown that the simultaneous SHG analysis of both interfaces, based on the macroscopic and microscopic relations, provides all the informations on the nonlinear optical (NLO) activity. (omitted)

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.539-545
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• 2000

This paper describes the design method of the magnetic system to maximize the magnetic flux leakage (MFL) in non-destructive testing (NDT) system. The defect signals in MFL type NDT system mainly depends on the change of the magnetic leakage flux in the region of defect. The characteristics of the B-H curves are analyzed and the design method to define the operating point in B-H curves for the maximum leakage is performed. The computed MFL signal by nonlinear finite element method is verified by measurement using Hall sensors mounted on the 6 legs PIG in the 8 inches test tube with defects. The rhombic defects could be successfully composed from the defect signals.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.3
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• pp.445-452
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• 1987

In this paper, a model for characteristics in the AlxGa1-xAs layer of MODFET's is presented. The characteristics of conduction band in the AlxGa1-xAs layer is analyzed with the Fermi-Dirac statistics. And using the conduction band energy which is calculated with the numerical calculation method (false-Positon method), the variations of the electric-field distribution, the ionized donor concentration, and the two-dimensional electron gas density with gate voltage are calculated, respectively. The channel formation process for the parasitic MESFET operation in the MOD structure is also analyzed, and the characteristics in the AlxGa1-xAs layer is analytically modeled. The throretical results describe well the general characteristics in the MOD structure.