• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.158-161
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• 2000

In this paper, we propose a new technique to compensate for the VCO nonlinearity using only the returned beat signal whose spectrum contains the internal reflections and the targets simultaneously. In the case of a distance measurement system using single antenna, the reflections from the circulator and the antenna are much larger than the return signal from target. The beat signal by these reflections is at much lower frequency than that of the target, and the VCO nonlinearity can be compensated leer using these signals. Indoor experiments were carried out and the results show marked improvement in the shape of range profile arid the range resolution.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.102-103
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• 2000

최근 광통신 시스템에서는 파장분할다중화(WDM) 방식의 도입으로 인해, 한 개의 레이저 신호를 입사시켜 여러 개의 레이저 신호를 발생시켜 광원으로 사용하는 연구가 활발히 진행되어 왔다. Park et al.[1]은 Erbium Doped Fiber Laser(EDFL)에서 1.1nm 파장간격으로 24라인을 얻었고, Yamashita et al.[2]은 내부 에탈론 구조를 가진 EDFL에서 0.8nm 간격으로 17라인, D.Yu et al.[3]은 반사형 거울과 Circulator를 사용한 Brillouin/Erbium Fiber Laser(BEFL)에서 0.08nm 간격으로 30라인, G.J.Cowle et al.[4]은 Injection-Seed Locking을 이용한 BEFL.에서 0.09nm 간격으로 12라인 그리고 N.S.Kim et al.[5]은 내부 되먹임을 이용한 BEFL에서 0.09nm 간격으로 4라인을 각각 발생시켰다. 여기서 중요한 요소로는 발생된 레이저 신호의 안정성, 각 신호들 간의 파장간격, 레이저 신호의 수 그리고 Peak Intensity 간의 차이 등이 있는데 각 연구방식에 따라 다양한 결과를 보여준다. 본 실험에서는 향상된 되먹임 구조를 가진 BEFL에서 다파장 발생에 관한 연구를 하였다. (중략)

• Korean Membrane Journal
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• v.2 no.1
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• pp.60-63
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• 2000

The effect of Candida rugosa and steapsin lipase cleaning was investigated for ultrafiltration polyethersulphone membrane (30,000 dalton MWCO) fouled with the semi-synthetic type cutting oil. The experimental by the water circulator. The enzyme cleaning effect was measured with respect to temperature, cleaning time and enzyme concentration. The optimum cleaning condition for the system was 25$^{\circ}C$ and 2 hour cleaning with 1,000 unites/mL steapsin solution. The pure water flux improvement by the steapsin solution cleaning was about 17% at the optimum cleaning condition.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.405-412
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• 2000

A natural air in-bin grain dryer with a grain circulator was developed for on farm use. Natural air drying test for rough rice was carried out to evaluate drying rate, uniformity of moisture content distribution in grain bed and energy consumption. It took 10 days to dry 8 ton of paddy rice from 21.9%(w.b) to 16.7%(w.b) moisture contents using the prototype dryer. The average drying rate was 0.52%/day. The uniformity of moisture content after drying was superior to the conventional natural air dryer where is grains were not circulated during drying periods. The dryer performance evaluation index was 738.3KJ/(kg.water), which was more effective than that of grain circulation t)pe hot air dryer(3,500-5,000 KJ/kg.water).

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.105-110
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• 2007

A tunable band-pass filter of fiber Bragg gratings incorporating the Sagnac loop interferometer configuration is presented. The proposed band-pass filter with extinction ratio 20 dB has practical advantages in terms of price and performance in comparison with the conventional band-pass filter using a circulator.

• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.21-25
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• 2017

Background: We are developing L-band and S-band microwave dielectric absorption systems aiming novel dosimetry using DNAs, such as plasmid DNA and genomic DNA, and microwave technology. Materials and Methods: Each system is composed of a cavity resonator, analog signal generator, circulator, power meter, and oscilloscope. Since the cavity resonator is sensitive to temperature change, we have made great efforts to prevent the fluctuation of temperature. We have developed software for controlling and measurement. Results and Discussion: By using this system, we can measure the resonance frequency, f, and ${\Delta}Q$ (Q is a dimensionless parameter that describes how under-damped an oscillator or resonator is, and characterizes a resonator's bandwidth relative to its center frequency) within about 3 minutes with high accuracy. Conclusion: This system will be expected to be applicable to DNAs evaluations and to novel dosimetric system.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1711-1712
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• 2007

액체탱크의 레벨을 정밀측정하는 데 FMCW(Frequency Modulated Continuous Wave)를 이용하고자 한다. 우리는 1GHz 대역폭으로 Sweep하는 Frequency Source Module을 개발하여 테스트 중이다. 개발한 송수신 모듈은 주파수의 송수신을 위한 주요부품들로 구성되는데, VCO(Voltage Controlled Oscillator), 서큘레이터(Circulator), 필터(Filter), 전력분배기(Power Divider), PLL(Phase Locked Loop)제어부, 믹서, 증폭기 등이 그것이다. 이들 부품들이 위치한 RF Board와, 패치로 구성한 안테나를 이용하여 마이크로웨이브 신호를 송수신할 수 있으며, 송수신한 신호 간의 차주파수(beat frequency)성분을 측정하면 거리정보를 획득할 수 있다. 차주파수의 아날로그신호는 DSP를 이용하여 FFT를 수행하여 주파수 성분을 찾아 거리계산을 하도록 개발하였다. 거리 측정의 성능에 영향을 미치는 가장 큰 요소는 안정된 주파수를 만들어 낼 수 있느냐 하는 것이다. 본 논문에서는 제작한 VCO 모듈을 비롯한 개발 중인 각 모듈들을 소개하였다. 향후 VCO의 선형성 개선과, 난반사에 대한 Echo Cancel 알고리듬을 적용하여 제품의 상용화를 목표로 한다.

• Macromolecular Research
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• v.16 no.6
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• pp.544-548
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• 2008

An HPLC column with a self-contained temperature control device was constructed for preparative temperature programmed interaction chromatography. Two Peltier plates were attached to a large bore column ($120{\times}22\;mm$ i.d.) and the column temperature was controlled by PID mode feed back control. At a flow rate of 1.5 mL/min, the column temperature could be increased and decreased at a rate as high as $50^{\circ}C/min$ and $10^{\circ}C/min$, respectively, which is much faster than using a column jacket and bath/circulator. The rapid heating and cooling rates allows a high repetition rate of chromatographic fractionation. The performance of the temperature controllable column was demonstrated successfully by the fractionation of homo-polymer precursors from diblock copolymers.

• Journal of the Optical Society of Korea
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• v.7 no.2
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• pp.64-66
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• 2003

The optical gain and noise figure improved double-pass two-stage EDFA using a mirror, circulator, and gain-flattening filters is proposed. By double passing the pump light and removing the ASE propagating into the input part, the signal gain of 5 ㏈ and noise figure of 2.1 ㏈ are improved compared to the conventional single- and double-pass EDFA With gain-fattening filters in the second stage of EDFA, we obtain an improved flat gain with a gain flatness less than 1 ㏈ over 33-nm wavelength range at the 980-nm pump power of 86 ㎽.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.10
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• pp.769-778
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• 2017

In this paper, a self-interference signal cancellation(SIC) circult for In-band Full-Duplex has been developed and tested in RF/analog region. By use of this SIC circuit, a FM two-way radio has been developed working at FRS(Family Radio Service) band. The two-way radio device is transmitting the FM modulated signal and demodulating the wanted FM signal at the same time. A circulator is used to enable a single antenna to transmit and receive simuultaenously. The receiver circuit needs to cancel out the self-interference signal due to the transmit signal. A vector modulator(VM) is used to control the phase and magnitude of the esitmated signal. And in-phase and quadrature correlators are used to figure out the optimal coefficients of the VM to remove the self-interference signal according to the change of channel environment. In this work, SA58646 has been used as the FM transceiver, and the system is tested with a frequency of 465 MHz and a bandwidth of 12.5 kHz FM signal. The output power is 17.2 dBm at the antenna port, and the self intererence signal level is measured -49.2 dBm at the receiver end. Therefore the SIC level is measured by 66.4 dB.