• ETRI Journal
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• 제35권4호
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• pp.718-721
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• 2013

This letter proposes a novel calibration method for a multiport amplifier (MPA) to achieve optimum port-to-port isolation by correcting both the amplitude and phase of the calibration signals. The proposed architecture allows for the detection of the phase error and amplitude error in each RF signal path simultaneously and can enhance the calibrated resolution by controlling the analog phase shifters and attenuators. The designed $2{\times}2$ and $4{\times}4$ MPAs show isolation characteristics of 30 dB and 27 dB over a frequency range of 19.5 GHz to 22.5 GHz, respectively.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 가을 학술발표회 발표논문집
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• pp.147-149
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• 2003

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 추계학술발표회논문집(1)
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• pp.301-306
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• 1996

To predict the average liquid level under the condition of the countercurrent stratified two-phase flow in a pipe, an analytical model has been suggested. This is made by introducing the interfacial level gradient into the liquid-phase and the gas-phase momentum equations. The analytical method for the gas-phase pressure drop calculation with f$_i$ $\neq$ f$_G$ has also been described using the liquid level prediction model developed in the present study.

• Transactions on Electrical and Electronic Materials
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• 제5권4호
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• pp.158-160
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• 2004

BiSrCaCuO thick films were fabricated by plasma enhanced chemical vapor deposition, and the crystallinity and the superconducting properties were investigated. The superconductivity was achieved at 20 K with an onset temperature of around 90 K in the film prepared at 72$0^{\circ}C$. From X ray diffraction analysis, the main superconducting phase in the films was the low Tc phase at 700∼75$0^{\circ}C$ and the high Tc phase at 750 ∼ 80$0^{\circ}C$.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.799-804
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• 1989

A new method for measuring optical phase changes of reflection beam from optical mirror is proposed. The optical phase change is liable to change with varying atmosphere conditions. This optical phase changes are measured against air pressure, temperature, humidity and CO$\_$2/ concentration variations. It is clarified that the optical phase changes are most effected by humidity change.

• Journal of the Optical Society of Korea
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• 제13권2호
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• pp.251-255
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• 2009

In the non-contact 3-dimensional (3D) shape measurements, the fringe pattern projection method based on the phase-shifting technique has been considered very effective for its high speed and accuracy. The digital fringe projector in particular has great flexibility in generating fringe patterns since the patterns can be controlled easily by the computer program. In this work, we have developed a high-speed digital laser grating projection system using a laser diode and a polygon mirror, and evaluated its performance. It has been demonstrated that all the optical measurements required to find out the profile of a 3D object could be carried out within 31 ms, which confirmed the validity of our 3D measurement system. The result implies the more important fact that the speed in 3D measurement can be enhanced remarkably since, in our novel system, there is no device like a LCD or DMD whose response time limits the measurement speed.

• 한국응용과학기술학회지
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• 제25권2호
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• pp.252-256
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• 2008

We investigated phase separation by adding different concentrations of MTBE, to the mixtures of naphtha, ethanol and water. The phase separation temperatures of the Naphtha-Ethanol-Water solutions have dropped when the concentration of MTBE increases more. When adding IPA and IBA to the solutions of Gasoline-Ethanol and Gasoline base-Ethanol individually, IBA shows lower temperatures of phase separation than IPA, and it shows synergistic effect when mixtures of IPA and IBA is applied.

• ETRI Journal
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• 제23권4호
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• pp.199-201
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• 2001

The phase noise reduction in a configuration of the HEMT oscillator with a dielectric resonator coupled by a quarter-wavelength impedance inverter is investigated. Two HEMT oscillators for a satellite payload system are manufactured in the same configuration except for the coupling configuration of the dielectric resonator (DR) in order to empirically demonstrate the phase noise reduction. Experimental result shows that a phase noise reduction by 14 dB can be enhanced by increasing the characteristic impedance of a coupling microstrip impedance inverter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
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• pp.5-9
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• 1989

In this paper, while 2-or 3-phase induction motor is driven with balance and no noise driving at dynamic and steady state condition. Single-phase induction motor is driven with pulsating torque except specific driving point. So we analyze the reason of producing pulsating torque with the view of unsymmetring concept. These results are applied to the design of high efficincy, high quality single-phase induction motor.

• 한국지구과학회지
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• 제29권1호
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• pp.60-77
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• 2008

본 연구에서는 달의 위상 변화에 대한 교과서 모델과 중 고등학생이 표현하는 모델의 비교 분석을 통해 보완 모델을 제안하고자 한다. 수도권 지역의 일반계 고등학교 1, 2학년 학생 20명과 중학교 1, 2, 3학년 학생 36명을 무선 표집하고 구두 인터뷰를 통해 달의 위상 변화 모델을 그리도록 하였다. 현행 중 고등학교 교과서의 달의 위상 변화 단원에서 직접적으로 달의 위상 변화를 설명하는 모델은 대체로 한가지로 제시되어 있는 것에 비해, 학생들의 모델은 크게 6가지 유형으로 나타났다. 학생들의 모델을 분석한 결과 낮은 학년의 학생일수록 유년적 개념과 대안적 개념이 많이 포함된 모델을 가지고 있는 것으로 나타났으며, 달의 위상 변화 단원을 배운 후에도 이러한 대안적 모델을 여전히 가지고 있는 학생들이 많은 것으로 나타났다. 이것은 교과서에서 제시하고 있는 과학적 모델의 설명이 학생들의 선개념을 극복하기에 충분치 못하기 때문인 것으로 보인다. 교과서에서는 달의 위상 변화 모델이지고 있는 제한점에 대한 설명 없이 모델이 제시되어 있으며, 이런 부분이 학생들에게 대안적 개념을 유발 할 수 있는 것으로 보인다. 따라서 본 연구에서는 다양한 모델을 사용함으로써, 교과서 모델의 제한점을 보충하고 학생들의 달의 위상 변화에 대한 이해를 도울 수 있도록 보완 모델을 제안하고자 한다.