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변도영,최한규,이정원,구본철,Byeon, Do-Yeong,Choi, Han-Gyu,Lee, Jeong-Won,Gu, Bon-Cheol 한국천문학회 1996 天文學論叢 Vol.11 No.1
We have developed a 5GHz continuum receiver system. The receiver is a direct type receiver. In order to reduce the noise due to the fluctuation of the gain in the amplifiers, the system employs the Dicke switching method. We made the 5GHz low-noise amplifier and the bandpass filter. The low-noise amplifier gives ${\sim}35dB$ gain and has ${\sim}210K$ noise temperature. The bandpass filter has a passband between 4.3 and 5.4GHz. We also made switch driver, video amplifiers, phase detector, and integrator. Using a 1.8 meter offset parabolic antenna, we measured the efficiency of the system. Since the antenna does not have a driver to track objects, observations were performed with the antenna fixed. The measured noise temperature of the system is ${\sim}650K$. From the observation of the blank sky, noise level was measured. It was found that the systematic noise(${\sim}0.5K$: peak to peak value) is much larger than the thermal noise. The systematic noise is possibly related to the stability of the DC power supplied to the receiver system. Besides the noise of the system, it was found that the airplanes are the very serious noise sources. We measured the radio flux of the Sun using the developed system. The observed radio flux of the Sun is ${\sim}10^6Jy$, which is close to the known value of the quiet Sun. The test observation of the Sun shows that the angular beam size of the antenna is ${\sim}2.2^{\circ}$.
변도영 대한기계학회 2009 기계저널 Vol.49 No.10
마이크로유체역학을 이용한 유체제어 기술에 있어서 마이크로 스케일에서의 유동현상을 관찰하고 가시화하여 원리를 규명하는 기술은 유체제어 기술의 기본이라 할 수 있다. 이 중에서도 최근에 지속적으로 연구 및 응용되고 있는 마이크로 입자유속계(micro-PIV)는 구체적인 속도장을 얻을 수 있는 장점 때문에 각광받고 있다. 이 글에서는 마이크로 입자유속계의 기본원리, 연구방향 및 응용분야에 대하여 정리하였다.