• 동력기계공학회지
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• 제10권4호
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• pp.71-77
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• 2006

This study introduces the seismic qualification of safety related equipments for nuclear power plants to verify the possibility of resonance in regard to the operating speed and the structural integrity due to external piping nozzle loads as well as seismic dynamic loads using El-Centro earthquake, which was occurred in the 1940's previously. As a first step, it is necessary to investigate the natural frequency of the vertical mixed flow pump in order to determine whether static or dynamic equipment comparing with seismic cut-off frequency, 33hz. Also the normal mode analysis was carried out with the introduction of seismic redesign straint at the middle of vertical pump to increase the natural frequency. In terms of structural integrity, the application of static analysis with normal, upset and faulted nozzle loads event was presented for the comparison of material allowable stress. Also the dynamic analysis was performed to show the design adequacy through the application to the case of El-Centro earthquake.

• Current Optics and Photonics
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• 제5권2호
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• pp.141-146
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• 2021

We have evaluated the suppression effect of atmospheric-turbulence-induced optical scintillation in terrestrial free-space optical (FSO) communication systems using a gain-saturated erbium-doped fiber amplifier (EDFA). The variation of EDFA output signal power has been measured with different amounts of gain saturation and modulation indices of the optical input signal. From the measured results, we have found that the peak-to-peak power variation was decreased drastically below 2 kHz of modulation frequency, in both 3-dB and 6-dB gain compression cases. Then, the power spectral density (PSD) of optical scintillation has been calculated with Butterworth-type transfer function. In the calculation, different levels of atmospheric-turbulence-induced optical scintillation have been taken into account with different values of the Butterworth cut-off frequency. Finally, the suppression effect of optical scintillation has been estimated with the measured frequency response of the EDFA and the calculated PSD of the optical scintillation. From our estimated results, the atmospheric-turbulence-induced optical scintillation could be suppressed efficiently, as long as the EDFA were operated in a deeply gain-saturated region.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.249-252
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• 2000

A new Smart rower IC's based on the Partial SOI technology was designed for such applications as mobile communication systems, high-speed HDD systems etc. A new methodology of integrating a 0.8${\mu}{\textrm}{m}$ BiCMOS compatible Smart Power technology, high voltage bipolar device, high speed SAVEN bipolar device, LDD NMOSFET and a new LDMOSFET based on the Partial SOI technology is presented in this paper. The high voltage bipolar device has a breakdown voltage of 40V for the output stage of analog circuit. The optimized Partial SOI LDMOSFET has an off-state breakdown voltage of 75 V and a specific on- resistance of 0.249mΩ.$\textrm{cm}^2$ with the drift region length of 3.5${\mu}{\textrm}{m}$. The high-speed SAVEN bipolar device shows cut-off frequency of about 21㎓. The simulator DIOS and DESSIS has been used to get these results.

• 한국광학회지
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• 제26권3호
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• pp.162-167
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• 2015

본 논문에서는 적외선 파장대에서 렌즈의 변조전달함수(MTF)를 칼날 주사방식으로 측정하는 적외선 MTF 측정장치를 구성하고 평가하였다. 측정장치는 물체부, 평행광을 만들어주는 시준부, 형성된 상을 분석하는 분석부로 나뉜다. 광원으로는 텅스텐 필라멘트 광원을 사용하였으며 중적외선 영상을 검출하기 위해 MCT를 사용하였다. 이 장치를 사용하여 ZnSe 재질의 f 수가 5인 표준렌즈의 MTF를 중적외선 파장대인 $3{\sim}5{\mu}m$에서 측정하고 Zemax 프로그램을 통해 계산한 이론값과 측정값 차이를 비교하여 차단주파수(Cut-off frequency)인 50 1/mm까지 전구간에서 ${\pm}0.035$이내임을 확인하였다. 또한 측정값의 신뢰도를 확인하기 위한 A형 측정불확도를 계산한 결과 MTF의 대표 공간 주파수인 20 1/mm에서 0.002으로 동일한 조건 하에서 측정 시 측정값의 변화가 거의 없음을 알 수 있었다.

• 한국항행학회논문지
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• 제13권1호
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• pp.41-47
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• 2009

이 논문에서는 마이크로스트립을 이용하여 차단주파수가 10.2 GHz인 계단형 임피던스 구조의 저역 통과 여파기를 설계하고, 차단주파수 3.2 GHz인 병렬 스터브를 이용한 고역 통과 여파기를 설계하여 서로 결합하고 삽입하여 소형화하는 방식으로 UWB 대역을 포함하는 대역통과여파기를 설계, 제작하였다. 설계에 사용된 기판의 유전율은 2.2, 높이 0.508mm, loss tangent 0.0009이고, 대역통과 여파기의 넓이는 약 3 cm의 소형으로 제작되었다. 통과 대역에서의 측정 결과 -10 dB 대역폭은 7.5 GHz, -3dB 이하의 삽입손실의 특성을 보였다. 이 연구의 결과 UWB 통신 시스템과 MIC/MMIC, RFIC 시스템에 충분히 이용될 수 있을 것이다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권5호
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• pp.315-320
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• 2000

This paper presents the fabrication and test of a micropump with an electromagnetic actuator and a pair of aluminum flap valves. The actuator consists of a solenoid coil, a permanent magnet and an actuator diaphragm. The actuator diaphragm is fabricated by the spin coating of silicone rubber. The valve are passive ones and are fabricated by micromachining. The deflection of the fabricated actuator diaphragm is measured with a laser vibrometer. The deflection of the actuator diaphragm is proportional to the input current. The measured deflection of the fabricated diaphragm is $400 \mum$,/TEX> when the input is 118 mApp, and the cut-off frequency is 50 Hz. The maximum flow rate of the fabricated micropump with the electromagnetic actuator is about 5$0 \muell/min$ at 5 Hz when the input current and the duty ratio of the square was are 118 mApp and 50%, respectively.

• ETRI Journal
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• 제19권2호
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• pp.48-58
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• 1997

Using high quality high-$T_c$ superconducting (HTS) YBCO thin films, we designed and fabricated 3-pole, 5-pole, and 7-pole lowpass filters consisting of microstrip transmission lines and open-stub lines. We measured the microwave response of the filters in the temperature range of T=85 K to 27 K. AtT=30 K, the observed inband insertion loss was 0.14dB and 0.02dB for the 5-pole and 7-pole filters, respectively. The cut-off frequency was 4.7 GHz for the 5-pole filter and 7.9GHz for the 7-pole filter. To the authors' knowledge, the measured inband insertion losses are the best values reported so far for the open-stub line type HTS multipole lowpass filters. The skirt property of the 5-pole filter showed a large improvement over that of the 3-pole filter as predicted from the simulation. We found that, to obtain a stable performance, the HTS multipole lowpass filters should be operated at the temperatures between 60% and 70% of $T_c$.

• ETRI Journal
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• 제35권3호
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• pp.538-541
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• 2013

A compact microstrip lowpass filter (LPF) with an elliptic function response is proposed. A high equivalent capacitance and inductance between the structures of the resonator result in the sharp transition band of 0.04 GHz from 4 GHz to 4.04 GHz with an attenuation level of -3 dB and -20 dB, respectively. To improve the LPF rejection band, multiple open stubs are connected to the proposed resonator. A filter with a 3-dB cut-off frequency at 4 GHz is designed, fabricated, and measured, and agreement between the measured and simulated results is achieved. The results show that a stopband bandwidth of 131% with a suppression level better than -20 dB is obtained while achieving a compact size with a wide stopband.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1469-1478
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• 2014

Use of acetonitrile in electrolytes promotes better operation of supercapacitors. Recent efforts show that electrolytes containing acetonitrile can also function in a wide range of operating temperatures. Therefore, this paper addresses the dielectric relaxation processes, structure and dynamic properties of the bulk acetonitrile at various temperatures. Systems of acetonitrile were modeled using canonical ensemble and simulated by employing Molecular Dynamics method. Results show that interactions among the molecules were correlated within a cut-off radius while parallel and anti-parallel arrangements are observed beyond this radius at relatively high and low temperatures respectively. Furthermore, effects of C-C-N and C-H bending modes were greatly appreciated on the power spectral density of time rate change of dipole-dipole correlations whereas frequency shifts were observed on all modes at the lowest temperature under consideration. Linear variations with temperature were depicted for reorientation times and self-diffusion coefficients. Shear viscosity was also computed with a good accuracy within a certain range of the temperature as well.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.82-85
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• 2002

A compact rail to rail CMOS voltage follower is presented. The circuit is based on the symmetrical class AB voltage follower and can operate under supply voltages of ${\pm}$ 1.5 V. The proposed circuit has power dissipation of 5.2㎽ under quiescent condition and can drive ${\pm}$1.25 V to 250$\Omega$ load with a total harmonic distortion of less than 0.5 percent and cut off frequency of 237 ㎒. Although simple, the proposed circuit enables the output transistors to drive load efficiently.