• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.9
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• pp.71-80
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• 2007

This paper presents a new push-push VCO technique that extracts a second harmonic output signal from a capacitive commonnode in a negativegm oscillator topology. The generation of the $2^{nd}$ harmonics is accounted for by the nonlinear current-voltage characteristic of the emitter-base junction diode causing; 1) significant voltage clipping and 2) different rising and falling time during the switching operation of core transistors. Comparative investigations show the technique is more power efficient in the high-frequency region that a conventional push-push technique using an emitter common node. Prototype 12GHz and 17GHz MMIC VCO were realized in GaInP/GaAs HBT technology. They have shown nominal output power of -4.3dBm and -5dBm, phase noise of -108 dBc/Hz and -110.4 dBc/Hz at 1MHz offset, respectively. The phase noise results are also equivalent to a VCO figure-of-merit of -175.8 dBc/Hz and -184.3 dBc/Hz, while dissipate 25.68mW(10.7mA/2.4V) and 13.14mW(4.38mA/3.0V), respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.449-456
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• 2012

Herein, we design a wideband $8{\times}8$ waveguide Butler matrix in order to use in a multi-port amplifiers(MPAs) at Ka-band. To achieve the broadband characteristic, we design a binomial 6-slot 3 dB directional coupler which is used to configure the $8{\times}8$ Butler matrix. The measured results of the fabricated $8{\times}8$ Butler matrix have low insertion loss of less than 0.3 dB, good return loss of over 26 dB and high isolation of over 35 dB within the design bandwidth of 3 GHz.

• The Journal of the Acoustical Society of Korea
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• v.14 no.4
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• pp.29-37
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• 1995

A resonant frequency of piezoelectric transducer depends remarkably on the electric impedance connected to the vibrator. In this paper, using this effect of frequency controllable two layered PZT ultrasonic transducer is designed and its acoustic characteristics are analyzed by a new transmission model equivalent circuit. The theoretical and the experimental results of the electric impedance effect on the resonant frequency variation were compared and both results showed a good consistency each other. The resonant frequency has been controlled continuously in the wide frequency range of 180kHz~580kHz and the effective attenuations were less than 7dB in the frequency range of 330kHz~470kHz.

• Journal of the Korean Magnetics Society
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• v.27 no.1
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• pp.30-34
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• 2017

In this report, we calculated the angular dependence of exchange bias ($H_{ex}$) by using single domain model in exchange coupled ferromagnetic (F)/antiferromagnetic (AF) bilayers, which results with AF thickness ($t_{AF}$) were used for the analysis of measured ones in NiFe/MnIr bilayers. Angular dependence of $H_{ex}$ calculated at $t_{AF}$ > $t_c$ showed typical unidirectional behaviors, however, calculated one at $0.5t_c$ < $t_{AF}$ < $t_c$ showed peculiar angular behaviors by fixed AF spins at specified angle near ${\theta}_H=90^{\circ}$. Angular dependence of $H_{ex}$ measured in NiFe/MnIr (20 nm) bilayers showed typical unidirectional behaviors. However, measured one in NiFe/MnIr (4 nm) bilayers showed mixed behaviors including both of unidirectional and peculiar angular behaviors, which was explained by the grain size distribution of polycrystalline MnIr.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1173-1174
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• 2015

내연 발전기(50 MW, 13.8 kV) 출력단자에서 차단기까지 연결된 13.8 kV XLPE(cross-linked polyethylene) 케이블에서 운전중에 절연파괴로 인해 지락이 발생하였다. XLPE 케이블의 건전성을 확인하기 위해 절연저항과 절연진단 시험을 수행하였다. 교류전압을 1~10 kV까지 증가하면서 XLPE 케이블의 유전정접 측정결과 A상과 C상은 0.1%로 일정하게 측정되었다. 반면에 B상의 유전정접은 1 kV에서 0.54%, 2 kV에서 0.68%, 3 kV에서 0.82%, 4 kV에서 1.12%로 증가하였다. 그리고 교류전압을 약 4.3 kV 인가 중에 진단장비가 차단되었다.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.35-37
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• 2005

본 논문은 FTTH 의 본격적인 사업에 앞서 순수한 광선희망에서의 반사손실의 영향을 파악하고 문제점 도출 및 해결방안을 찾고자 시스템적인 요소를 제외하고 시험을 하였다. E-PON 광선로망의 반사손실 측정값을 위하여 1 단분기(1*32)에서의 SC/PC, SC/APC, 2 단분기(1*4/1*8)에서의 SC/PC, SC/APC 의 4 가지 형태로 구성하여 측정하였고 SC/PC 커넥터 사용시 단자내가입자단의 공기중에 노출되는 채널수가 많을수록 일정한 패턴을 보이며 반사손실 특성이 저하되었다.

• Electrical & Electronic Materials
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• v.6 no.5
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• pp.407-416
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• 1993

무산소동을 안정화 모재로한 Cu/Nb-Ti 빌렛트를 제작한 다음 간접 열간방식의 압출에 의해 얻어진 봉재를 인발한 후 신선과 열처리를 반복하여 단심 및 다심 Nb-Ti 초전도 선재를 제조하였다. 가공 조직을 조사한 결과, 단심 선재의 경우 Nb-Ti 심의 단면이 균일하게 가공된 것을 확인하였으며 다심선재의 경우는 신선가공에 의하여 다소 불균질한 필라멘트부분이 관찰되었다. 4.2K, 자장하에서 4단자법으로 직선형 단척시료의 임계전류를 측정하여 가공 열처리 조건에 따른 임계전류밀도의 자장특성을 조사하였는데 열처리시간을 길게하고 가공도를 높인 시료일수록 자장하의 임계전류밀도가 높게 나타나는 것을 확인하였다. 4.2K, 5T 자장하에서 각각 4 x $10^{5}$A/$cm^{2}$ 및 2 x $10^{5}$A/$cm^{2}$의 임계전류밀도를 나타내는 Nb-Ti 단심 및 다심 초전도선재를 제작 할 수 있었다.있었다.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.632-635
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• 2009

본 연구에서는 국내의 전압실태를 파악하고 산업체에 미치는 영향을 분석하기 위하여, 전압측정과 설문조사를 병행하였다. 먼저 전압측정을 위하여 수도권과 비수도권의 중규모 도시를 대상으로 측정지점과 대상선로를 선정하였다. 여기에서는 공장지역을 공급하는 4개의 배전용변전소의 주 변압기(M.Tr)와 5개의 고압선로(D/L)를 선정하여, 주 변압기의 직하전압(송출전압)과 말단의 수용가 단자전압을 5분간 평균치로 설정하여 측정하였다. 한편 설문조사 대전, 충남지역을 대상으로 산업체별로 전화와 설문지를 가지고 방문조사를 수행하여 분석하였다. 본 연구에서는 전압실태의 평가를 엄격하게 하기 위하여, 장거리의 고압선로이거나 부하변동이 심한 최악의 조건을 가지는 고압선로를 대상선로로 선정하였으며, 또한 선로전압조정장치(SVR)가 포함된 선로를 선정하여 고압선로 상에서의 전압조정에 대한 영향도 평가하도록 하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.6
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• pp.371-380
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• 2023

To calculate seismic fragility, it is important to select input earthquake ground motions that can properly express the characteristics of the target site. This study analyzed the seismic fragility of a single-degree-of-freedom (SDOF) model based on input earthquake ground motions in strong and low-to-moderate seismic regions. As a first step, a total of four sets of input earthquake ground motions were selected,: two sets measured near or far from overseas strong earthquake records and two sets exhibiting the characteristics of low-to-moderate earthquake regions in South Korea. A nonlinear SDOF model for three natural periods was applied to the target structure, and incremental dynamic analysis was used for fragility analysis. In addition, four damage states were defined, and seismic fragility results for each natural period of the nonlinear SDOF model for the four aforementioned input earthquake ground motion sets were obtained for each damage state.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.625-628
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• 2005

Silencers are extensively used for reducing noise in an exhaust system of internal combustion Engine and fluid machineries. The prediction and measurement of the transmission loss as the acoustic performance of silencers are important in early design stage. In the measurement of transmission loss, the semi-anechoic terminations are general used for reducing unwanted effects by reflecting wave. However it is very hard to remove reflecting wave perfectly. So the research about the error made by reflecting wave is important. The analysis about errors made by reflections and modification techniques are proposed. For an application example, the diesel particulate filter (DPF) is chosen. The transmission loss of DPF is measured with and without considerations of reflecting wave.