• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.237-240
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• 2002

We have studied a RF energy transformation. In this paper, we introduced proximity sensor using RF energy transformation. We used 125kHz RF signal as carrier frequency and BPSK circuit, PNP proximity sensor and designed circuit to transmit to the reader through the antenna with data which sensor had acquired. Micro-controller, oscillator, power amp, FSK Modulation module are included in the circuit. Max 323 chip is applied to analog switch and used to HYP-30R10NA sensor chip.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.6-10
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• 2013

We investigate the electrical and thermal transport properties of a sesquicarbide superconductor $La_2C_3$, including electrical resistivity, thermoelectric power, and thermal conductivity. The electrical resistivity exhibits a typical metallic character with a saturation behavior at high temperatures. The thermoelectric power shows a metallic behavior with pronounced phonon-drag effect, comparable with pure metals. The broad peak of the thermal conductivity is observed in the superconducting state, which is rapidly suppressed by magnetic fields. These observations suggest that the electron-phonon scattering is significant in $La_2C_3$, which is relevant with the relatively high-$T_c$ in $La_2C_3$ through strong electron-phonon coupling with low frequency phonon modes.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.213-216
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• 1988

This paper describes design & fabrication of RF modulator using 2um Bipolar process which convert video & audio signal into high frequency VHF/UHF signals for all TV standards. This VHF/UHF RF modulator fabricated using 2um bipolar process( T max = 5GHz) shows satisfying electrical characteristics and meets all the design targets.

• The Journal of Korean Physical Therapy
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• v.11 no.3
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• pp.45-55
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• 1999

This study was compared with each 2 groups (Intermittent traction therapy alone group1: Control group and Intermittent traction therapy plus Auriculotherapy group 2: Experimental group) on 20 HIVLD(Hemiated Intervertebral Lumbar Disk) patients with sciatics Each subjects were divided to control and experimental. Each group were applied Intermittent traction therapy (HOld:25, Rest:15) for 15 minute and control group were not received auricular stimulation. However experimental groups were applied auricular stimulation simultaneosly. Auricular acupuncture points(max-17, min=13) were stimulated with low frequency. high intensity Electro-Acupunture stimulator for 20 seconds per each point. Treatment and measurements(R.P and VAS) was administered to each patient during the 10 times therapy per 2 weeks. The results were significant differences between the two groups. Experimental group appeared significantly greater than before in pain, and pain relief, and significant improvement in centralization phenomenon of radiating pain.

• Journal of Korean Physical Therapy Science
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• v.6 no.2
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• pp.977-988
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• 1999

This study compared the effects of Intermittent traction therapy alone(Group1=Control group) and Intermittent traction therapy plus Auriculotherapy (Group2=Experimental group) to 20 Sciatica patients. Subjects were assigned to two groups with each 10. The two groups received Intermittent traction therapy (Hold:25, Rest:15) for 15 minute and experimental group did received auricular stimulation. Auricular acupuncture points(max=17, min=13) were stimulated with low frequency, high intensity Electro-Acupunture stimulator for 20 seconds per a each point. Treatment and measurements(SLR and VAS) was administered to each patient during the two weeks of 10 times therapy. The results were significant differences between the two groups. Experimental group produced significantly greater pain relief, and significant improvement of limited SLR.

• Journal of electromagnetic engineering and science
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• v.14 no.4
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• pp.405-410
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• 2014

In this paper, we compare the quality of images reconstructed by a conventional delayed-sum (DS) algorithm and radiation pattern-based DS algorithm. In order to evaluate the quality of images, we apply the target-to-clutter ratio (TCR), which is commonly used in synthetic aperture radar (SAR) image assessment. The radiation pattern-based DS algorithm enhances the TCR of the image by focusing the target signals and preventing contamination of the radar scene. We first consider synthetic data obtained through GprMax2D/3D, a finite-difference time-domain (FDTD) forward solver. Experimental data of a 2-GHz bandwidth stepped-frequency signal are collected using a vector network analyzer (VNA) in an anechoic chamber setup. The radiation pattern-based DS algorithm shows a 6.7-dB higher TCR compared to the conventional DS algorithm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.497-500
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• 1999

This paper reports on the fabrication and characteristics of recessed gate GaN MESFETs fabricated using a photoelectrochemical wet etching method. The unique etching process utilizes photo-resistive mask and KOH based etchant. GaN MESFETs with successfully recessed gate structure was characterized in terms of dc and RF performance. The fabricated GaN MESFET exhibits a current saturation at $V_{DS}$ = 4 V and a pinch-off at $V_{GS}$ =-3V The peak drain current of the device is about 230mA/mm at 300 K and the value is remained almost same for 500K operation. The $f_{T}$ and $f_{max}$ from the device are 6.357Hz and 10.25 GHz, respectively.y.y.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.324-329
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• 2003

Asynchronus high speed turbo blower of 100HP class with gas bearing supports is developed. The high speed motor is cooled by air and it's RPM is controlled by high frequency inverter to adjust inlet flow rate. Product family is ranged from 50 to 200HP and covered by three frames. Highly efficient impeller is designed and proved by performance test on system. Overall measured system efficiency is 82% including motor and inverter. The motor efficiency is about 95%. It is designed to guarantee to operate at ambient temperature of 35 Deg.C and max 45 DegC. Gas bearing with high load capacity is developed to support heavy rotor on low rotational speed.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.141-149
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• 2007

Multiple-input multiple-output (MIMO) transmit pre-coding/beamforming can significantly improve system spectral efficiency. However, several obstacles prevent precoding from wide deployment in early wireless networks: The significant feedback overhead, performance degradation due to feedback delay, and the large storage requirement at the mobile devices. In this paper, we propose a precoding method that addresses these issues. In this approach, only 3 or 6 bits feedback is needed to select a precoding matrix from a codebook. There are fifteen codebooks, each corresponding to a unique combination of antenna configuration (up to 4 antennas) and codebook size. Small codebooks are prestored and large codebooks are efficiently computed from the prestored codebook, modified Hochwald method and Householder reflection. Finally, the feedback delay is compensated by channel prediction. The scheme is validated by simulations and we have observed significant gains comparing to space-time coding and antenna selection. This solution was adopted as a part of the IEEE 802.16e specification in 2005.

• Journal of Communications and Networks
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• v.5 no.1
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• pp.65-72
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• 2003

Internet roundtrip delay/time (RTT) prediction plays an important role in detecting packet losses in reliable transport protocols for traditional web applications and determining proper transmission rates in many rate-based TCP-friendly protocols for Internet-based real-time applications. The widely adopted autoregressive and moving average (ARMA) model with fixed-parameters is shown to be insufficient for all scenarios due to its intrinsic limitation that it filters out all high-frequency components of RTT dynamics. In this paper, we introduce a novel parameter-varying RTT model for Internet roundtrip time prediction based on the information theory and the maximum entropy principle (MEP). Since the coefficients of the proposed RTT model are updated dynamically, the model is adaptive and it tracks RTT dynamics rapidly. The results of our experiments show that the MEP algorithm works better than the ARMA method in both RTT prediction and RTO estimation.