• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.517-522
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• 2004

In this paper, we have analyzed the performance enhancement of Orthogonal Frequency Division Multiplexing/Quadrature Phase Shift Keying Modulation-Digital Microwave Radio(OFDM/QPSK-DMR) system using Band Limited-Pulse Shaping Filter(BL-PSF) over microwave channel environments. For performance enhancement, the one-tap adaptive equalizer is adopted in the OFDM/QPSK-DMR system and than both BER and signature curve performance are compared with those of single carrier DMR system. Computer simulations confirm that the OFDM/QPSK-DMR system using 16 sub-carrier increase the fade margin about 2 dB over microwave channel environments and that of performance using one-tap adaptive equalizer is highly increased the fade margin as the number of sub-carriers is larger.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.75-80
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• 2015

After some period of time, the marine traffic facilities find problems caused by shellfish adhered to inside and inlet of the water column. Therefore, single-channel AFS(Anti-Fouling System) has been applied in order to minimize the deposition of shellfish. However, imbalance phenomenon of ionization of copper electrodes that are used for single-channel AFS appeared. This problem resulted in frequent replacement of anode. In this paper, multi-channel current control system has been developed, as well as the related hardware has been designed and fabricated. Further, experimental study has been undertaken to compare the application of single and multi- channel AFS. Through the sea experiments, it was possible to confirm that the copper electrode used for multi-channel AFS is uniformly ionized.

• Proceedings of the KSEEG Conference
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• 1999.04a
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• pp.248-250
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• 1999

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.347-348
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• 2014

본 논문에서는 3D TV를 위한 다채널 전류평형 단일스위치 LED 구동회로를 제안한다. 제안된 구동회로는 각각의 LED 채널의 정전류 제어를 위해 별도의 전력단을 사용하는 대신에 2차 측에 단 1개의 switch를 추가하여 하나의 채널 전류를 정전류 제어하고 나머지 다른 채널의 전류를 캐패시터의 성질을 이용한 회로를 사용함으로써 모든 채널 전류의 정전류 제어 및 전류평형이 가능한 회로이다. 추가된 switch는 ZCS(Zero Current Switching) 동작하므로 스위칭 손실을 최소화하여 고효율화 시킬 수 있다. 또한, 여러 LED 채널의 정전류 제어를 별도의 LED Driver단을 사용하지 않고 캐패시터의 성질을 이용하여 구현하기 때문에 소형화 및 저가격화가 가능하다. 최종적으로 제안된 회로의 우수성과 이론적 분석의 타당성 검증을 위해 46" LED 3D-TV 구동회로를 위한 시작품을 제작하여 고찰된 실험 결과를 제시한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.4
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• pp.59-65
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• 2022

In this paper, a digital active phased array antenna is briefly introduced and beam forming method for a dual-channel side-lobe blanking applied to blank the side-lobe of the main beam is described. Next, the antenna performance was verified from results of design and antenna near-field measurement for the antenna main beam and side-lobe blanking beam. Then, a single-channel side-lobe blanking beam forming method was proposed to reduce the number of channels than the existing system operating dual-channel side-lobe blanking beam and weight distribution for each element of the side-lobe blanking antenna was designed with the proposed method. Finally, the designed single-channel side-lobe blanking beam pattern and blanking ability were verified and compared with the dual-channel side-lobe blanking beam. In addition, by comparing/verifying the conventional dual-channel and the proposed single-channel side-lobe blanking beam patterns measured through the receiving near-field test of the digital active phased array antenna and their ability to blank side-lobe of the main beam, validity of the proposed method for forming single-channel side-lobe blanking beam was confirmed.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.2
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• pp.28-34
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• 2011

In previous reports, we investigated a selective assembly method of fabricating single-walled carbon nanotubes (SWCNTs) on a silicon-dioxide ($SiO_2$) surface by using only a photolithographic process. In this paper, we have fabricated field effect transistors (FETs) with SWCNT channels by using the technique mentioned above. Also, we have electrically measured gating effects of these FETs under different source-drain voltages ($V_{SD}$). These FETs have been fabricated for sensor applications. Photoresist (PR) patterns have been made on a $SiO_2$-grown silicon (Si) substrate by using a photolithographic process. This PR-patterned substrate have been dipped into a SWCNT solution dispersed in dichlorobenzene (DCB). These PR patterns have been removed by using aceton. As a result, a selectively-assembled SWCNT channels in FET arrays have been obtained between source and drain electrodes. Finally, we have successfully fabricated 4 FET arrays based on SWCNT-channels by using our simple self-assembly technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.79-87
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• 2013

A new modulation technique - correlative encoded FSK (CEFSK) - for use in power and bandwidth limited digital communication system is proposed. CEFSK is free of ISI and generates output signals which have a smooth and continuous phase transition and a reduced envelope fluctuation by keeping correlation between amplitude and phases of two subsequent symbols. In comparison to conventional one-bit differential detected (1DD) GFSK, the performance of the 1DD-CEFSK in a non-linearly amplified (NLA) channel impaired by additive white Gaussian noise (AWGN), ISI and IM, is analyzed via computer simulation. The simulation result shows that, in an NLA single-channel, 1DD-CEFSK provides a signal-to-noise ratio (SNR) advantage of up to 1.2dB and 0.8dB at BER of $1{\times}10^{-4}$ when input back-off (IBO) of HPA is -1.0dB and -3.0dB, respectively. For the same channel environment with multi-channel, 1DD-CEFSK outperforms 1DD-GFSK by 1.1dB in SNR, regardless of the value of IBO.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.471-479
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• 2010

The adiabatic two-phase flow in single rectangular microchannels was studied for different aspect ratios. The working fluids were liquid water and nitrogen gas. The hydraulic diameters of the rectangular microchannels were 490, 322, and $143\;{\mu}m$, and the widths of the microchannels were around $500\;{\mu}m$. The two-phase flow pattern was visualized using a high-speed camera and a long-distance microscope. This study was focused on bubble flow regimes. From the visualized images, the bubble velocity, bubble length, number of bubbles, and void fraction were evaluated. Further, the pressure drop in a single bubble was evaluated by using a unit cell model. The bubble velocity is proportional to the superficial velocity. Further, the relationship between the void fraction and the volumetric quality is linear. The pressure drop in a single elongated bubble is strongly related to the aspect ratio. Finally, the new correlation about the pressure drop of a single elongated bubble in the rectangular microchannel was proposed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.29-34
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• 2011

In this paper, we propose antenna and relay selection system by considering channel environment between nodes. Each node has multiple antennas in each hop. And, we analyze the performance of proposed system. A General MIMO system receives signals through multiple channels and obtains diversity gain. But MIMO system causes performance degradation due to poor received signals. The proposed system consider transmitters-relays channels, relays-receivers channels and select a best channel. This channel selection prevents performance degradation and increase total system's performance. Therefore, we must select best antennas and a best relay, simultaneously.

• Journal of Astronomy and Space Sciences
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• v.10 no.1
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• pp.94-102
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• 1993

We have develped a four-channel photoelectric photometer for the 61cm telescope of Sobaeksan Astronomy Observatory using optical fiber. We observed a standard star with each channel to check the efficiency difference between the channels, and found no differences. To calibrate the observing accuracy and efficiency, we have observed a short period W UMa type eclipsing binary star, BV Dra. Test observations show that the photometer is very stabel and the accuracy of the data is also increased. The observing efficiency is very increased compared with that of single channel photometer ; at least five times faster than older one in the case of one filter observation.