• ETRI Journal
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• v.27 no.3
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• pp.312-318
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• 2005

Mid-span spectral inversion (MSSI) has to utilize high optical pump power, for its operation principle is based on a nonlinear optical wavelength conversion. In this paper, a low pump-power operation of MSSI-based chromatic dispersion compensation (CDC) has been achieved successfully, for the first time to our knowledge, by introducing a noise pre-reduction scheme in cascaded wavelength conversions with periodically poled $LiNbO_3$ waveguides at a relatively low operation temperature. As preliminary studies, phase-matching properties and operation-temperature dependence of the wavelength converter (WC) were characterized. The WC pumped at 1549 nm exhibited a wide conversion bandwidth of 59 nm covering the entire C-band and a conversion efficiency of -23.6 dB at 11 dBm pump power. CDC experiments were implemented with 2.5 and 10 Gb/s transmission systems over 100 km single-mode fiber. Although it is well-known that the signal distortion due to chromatic dispersion is not critical at a 2.5 Gb/s transmission, the clear recovery of eye patterns was identified. At 10 Gb/s transmission experiments, eye patterns were retrieved distinctly from seriously distorted ones, and notable improvements in bit-error rates were acquired at a low pump power of 14 dBm.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.57-62
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• 2004

This paper deals with a waypoint trajectory following problem for the tilt-rotor UAV under development in Korea (TR-KUAV). In this problem, dynamic model inversion based on the linearized model and Sigma-Phi neural network with adaptive weight update are involved to realize the waypoint following algorithm for the vehicle in the helicopter flight mode (nacelle angle=0 deg). This algorithms consists of two main parts: outer-loop system as a command generator and inner-loop system as stabilizing controller. In this waypoint following problem, the position information in the inertial axis is given to the outer-loop system. From this information, Attitude Command/Attitude Hold logic in the longitudinal channel and Rate Command/Attitude Hold logic in the lateral channel are realized in the inner-loop part of the overall structure of the waypoint following algorithm. The nonlinear simulation based on the TR-KUAV is carried out to evaluate the stability and performance of the algorithm. From the numerical simulation results, the algorithm shows very good tracking performance of passing the waypoints given. Especially, it is observed that ACAH/RCAH logic in the inner-loop has the satisfactory performance due to adaptive neural network in spite of the model error coming from the linear model based inversion.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.459-462
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• 2002

We report viewing angle characteristics of the Ultra-FFS TFT-LCD. The FFS mode is known to exhibit both a wide viewing angle and high transmittance, owing to the approximated in-plane rotation of the LC director. Nevertheless, in the bright state, the device shows bluish and yellowish color parallel and perpendicular to the LC director at off-normal directions since the LC director rotates onl.v in one direction, and in addition, the grey scale inversion exists in large oblique viewing angle. However, the Ultra-FFS shows no grey scale inversion and no color shift in wide viewing angle range.

• Journal of information and communication convergence engineering
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• v.17 no.4
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• pp.227-233
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• 2019

In long-haul optical communication system consisting of standard single-mode fiber spans and fiber amplifiers, such as the erbium-doped fiber amplifier, performance is deteriorated by signal distortion due to chromatic dispersion and nonlinearity of the fiber. A combination of dispersion management and optical phase conjugation is an effective technique to compensate for the distortion. In an optical link configured by this combination, a dispersion map mainly affects the compensation of the distorted optical signals. This paper proposes new dispersion maps configured by the decaying or expanding distribution of residual dispersion per span (RDPS) in a dispersion-managed link combined with a midway optical phase conjugator. The effect of the proposed dispersion maps on the compensation for distorted 24 channel × 40 Gbps wavelength-division multiplexed signals was assessed through numerical simulation. It was confirmed that all the proposed dispersion maps are most appropriate for the compensation and, furthermore, for the flexibility of link configuration than conventional links.

• Journal of Advanced Information Technology and Convergence
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• v.8 no.2
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• pp.59-67
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• 2018

The minimum power supply voltage of a typical bandgap current reference (BGCR) is limited by operating temperature and input common mode range (ICMR) of a feedback amplifier. A new BGCR using a bandgap voltage generator (BGVG) is proposed to minimize the effect of temperature, supply voltage, and process variation. The BGVG is designed with proportional to absolute temperature (PTAT) characteristic, and a feedback amplifier is designed with weak-inversion transistors for low voltage operation. It is verified with a $0.18-{\mu}m$ CMOS process with five corners for MOS transistors and three corners for BJTs. The proposed circuit is superior to other reported current references under temperature variation from $-40^{\circ}C$ to $120^{\circ}C$ and power supply variation from 1.2 V to 1.8 V. The total power consumption is $126{\mu}W$ under the conditions that the power supply voltage is 1.2 V, the output current is $10{\mu}A$, and the operating temperature is $20^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.53-54
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• 2006

We have studied the viewing angle control of a twist nematic liquid crystal display (TN-LCD). The TN-LCD exhibits a bad image quality along vertical direction, due to characteristics such as low contrast ratio and grey scale inversion. The proposed new TN-LCD has the function of switching between the wide viewing mode and narrow viewing angle mode using two tilted LC layers at both sides of a TN-cell Tilt angles of the two LC layers, $14^{\circ}$ and $60^{\circ}$ were required in both wide viewing angle and narrow viewing angle modes, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.452-455
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• 2002

We demonstrate the wide-viewing characteristics of a twisted nematic liquid crystal display (LCD) with self-formed micro-domains through the topographical alignment and fringe field effects of dielectric surface gratings (DSG). The mutual optical compensation between micro-domains within each pixel eliminates the contrast inversion phenomenon of TN mode without complex surface treatments.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.420-424
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• 2014

본 논문에서는 접합을 가지지 않는 Junctionless transistor (JLT)의 두께에 따른 특성 차이 및 기존의 MOSFET과의 특성 비교를 EDISON 시뮬레이터를 통해 확인을 하였다. JLT의 두께가 얇아짐에 따라 On/off 비율 측면에서 소자의 특성이 향상됨을 확인 하였으며, 기존 Inversion mode의 MOSFET과 비교하여 단 채널 효과 측면에서도 향상된 특성을 확인 할 수 있었다.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.903-913
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• 2007

In this study, the researchers compared the S-wave velocity structures obtained by two kinds of dispersion curves: phase and group dispersions from a tidal flat located in the SW coast of the Korean peninsula. The ${\tau}-p$ stacking method was used for the phase velocity and two different methods (multiple filtering technique: MFT and continuous wavelet transform: CWT) for the phase velocity. It was difficult to separate higher modes from the fundamental mode phase velocities using the ${\tau}-p$ method, whereas the separation of different modes of group velocity were easily achieved by both MFT and CWT. Of the two methods, CWT was found to be more efficient than MFT. The spatial resolutions for the inversion results of the fundamental mode for both phase and group velocities were good for only a very shallow depth of ${\sim}1.5m$. On the other hand, the spatial resolutions were good up to ${\sim}4m$ when both the fundamental and the 1st higher mode poop velocities obtained by CWT were used for S-wave inversion. This implies that the 1st higher mode Rayleigh waves contain more information on the S-wave velocity in deeper subsurface. The researchers applied the CWT method to obtain the fundamental and the 1st higher mode poop velocities of the S-wave velocity structure of a tidal flat located in SW coast of the Korean peninsula. Thea the S-wave velocity structures were compared with the borehole description of the study area.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.2
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• pp.83-88
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• 2005

The interface-states between the top silicon layer and buried oxide layer of nano-SOI substrate were developed. Also, the effects of thermal treatment processes on the interface-state distributions were investigated for the first time by using pseudo-MOSFETs. We found that the interface-state distributions were strongly influenced by the thermal treatment processes. The interface-states were generated by the rapid thermal annealing (RTA) process. Increasing the RTA temperature over $800^{\circ}C$, the interface-state density considerably increased. Especially, a peak of interface-states distribution that contributes a hump phenomenon of subthreshold curve in the inversion mode operation of pseudo-MOSFETs was observed at the conduction band side of the energy gap, hut it was not observed in the accumulation mode operation. On the other hand, the increased interface-state density by the RTA process was effectively reduced by the relatively low temperature annealing process in a conventional thermal annealing (CTA) process.