• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.121-122
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• 2006

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.67-68
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• 2006

• Proceedings of the KIEE Conference
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• 1983.07a
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• pp.28-30
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• 1983

• Proceedings of the Optical Society of Korea Conference
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• 1997.08a
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• pp.49-49
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• 1997

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.190-191
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• 2002

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.3-17
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• 1999

Torsion shear tests under various stress paths were performed to study the behavior of sand during large stress reversal. The stress paths can be classified into the clockwise and the counterclockwise according to torque applied to specimen, and the directions of plastic strain incremental on the stress paths including large stress reversal are compared with the direction of stress state and stress incremental. From test results, the isotropic hardening theory using the principle of St. Venant desirably showed that direction of plastic strain incremental coincided with stress state on primary loading part and nearby failure point, but it might result in a rough approximation on part of unloading and reloading by stress reversal.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.5
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• pp.460-469
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• 2010

This paper presents the analysis of a time reversal process for $A_0$ Lamb wave mode($A_0$ mode) on a rectangular plate. The dispersion characteristic equation of the $A_0$ mode is approximated using the Timoshenko beam theory. A virtual sensor array model is developed to consider the effects of reflections occurring on the plate boundary on the time reversal process. The time reversal process is formulated in the frequency domain using the virtual sensor array model. The reconstructed signal is obtained in the time domain through an inverse fast Fourier transform. The validity of the proposed method is demonstrated through the comparison to the numerical simulation results computed by the finite element analysis.

• Korean Journal of Optics and Photonics
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• v.19 no.6
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• pp.408-415
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• 2008

The characteristics of a ferroelectric-domain inverted grating fabricated by applying a high-voltage pulse at room temperature in Ti-diffused channel waveguides in z-cut $LiNbO_3$ (Ti:PPLN) were examined for channel waveguide quasi phase-matched secondharmonic generation devices. The fabrication conditions of uniform periodic domain-inversion were examined. Ti:PPLN with period ${\Lambda}=16.6{\mu}m$ for SHG were fabricated and the performances were measured. A normalized SHG efficiency as high as 473 (%/W) was obtained with 49 mm interaction length.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.9
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• pp.1-5
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• 1999

In this paper, we proposed a novel branch-line coupler using filp-chip technology. The proposed coupler consists of CPW and inverted microstrip. The CPW is on the GaAs flip-chip substrate, and the inverted microstrip is on the alumina main substrate. The ground plane of the CPW is used as a ground plane of the inverted microstrip. And both the transmission lines are connected by solder bump with each other. The characteristics of thisstructure was calculated by FDTD method. The S21, S31 are -3dB and the phase difference is $90^{\circ}$. The calculated characteristics are the same as those of the regular branch-line coupler. This structure can be applied for various kinds of devices using flipchip technology.

• Journal of Broadcast Engineering
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• v.11 no.3 s.32
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• pp.326-335
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• 2006

Design criteria far a block code which guarantees minimized PAPR of the OFDM signals are proposed in this paper. Encoding procedure of the minimum PAPR codes (MPC) is composed of searching a seed codeword, circular shifting the register elements, and determining codeword inversion. It is shown that the PEP is invariant to the circular shift of register elements and codeword inversion. Based on such properties, systematic encoding rule for MPC is proposed. In addition proposed encoding rule can reduced greatly the size of look up table for MPC.