• 한국가시화정보학회지
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• 제7권1호
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• pp.29-34
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• 2009

During the past three or four decades, the characteristics of turbulent flow have been studied extensively because of their scientific and academic importance. This research deals with the periodic flow oscillation without swirling flow in a 180 degree circular tube using hot wire anemometry, microphone and accelerometer. The frequency regions are observed through the structured oscillation from spectrum. This work carried out to measure the sound level for each Reynolds number, $6{\times}10^4$, $8{\times}10^4$ and $1{\times}10^5$ respectively at the test tube without swirl flow.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.632-637
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• 2012

Antenna equipment is transported being assembled to moving equipment and often subjected to vibration and shock excitation during transportation. In these circumstances, structural safety of antenna equipment must be secured. Wire rope isolators are assembled between moving equipment and antenna equipment to reduce the level of vibration and shock. In this paper, a isolator that are suitable to the system is selected and dynamic characteristics analysis of driving on antenna equipment is conducted using real system and the result is compared with response analysis. Also modal test of array-antenna pack-assembly is conducted and structural safety of that is secured by reinforcing its structure.

• 전기학회논문지
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• 제62권12호
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• pp.1700-1705
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• 2013

A second harmonic millimeter wave oscillator utilizing sub-harmonic injection-synchronization is presented. A 8.7GHz oscillator with MES-FET is designed, and is driven as a harmonic output oscillator at 17.4GHz by means of sub-harmonic injection-synchronization. The oscillator operates as a multiplier as well as a oscillator in this scheme. Adopting this method, a high sable, high frequency millimeter wave source is obtainable even though self-oscillating frequency of an oscillator is relatively low. The range of injection-synchronization is about 26MHz, and is proportional to the input sub-harmonic power. The spectrum analysis of the 2nd harmonic output frequency shows remarkably decreased the phase noise level.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.262-266
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• 2014

Military vehicle equipped with an antenna and a shelter for operating radar has a vibration exposure during driving time. This vibration would have influence on structure of military vehicle critically. In this paper, driving stability of the military vehicle is obtained through the vibration response analysis. And, vibration level of the military vehicle satisfied the military vibration specification through analysis and comparing the MIL-STD-810G. PSD and Grms data obtained by road test can be used for vibration test specification of cabinets and electronic equipment in shelter.

• Journal of Advanced Marine Engineering and Technology
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• 제33권6호
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• pp.903-911
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• 2009

During the past three or four decades, the characteristics of turbulent swirling flow have been studied extensively because of their scientific and academic importance. This research deal with the periodic flow oscillation with and without swirling flow in a 180 degree circular tube using hot wire anemometry, microphone and accelerometer. The frequency regions are observed through the structured oscillation from spectrum. This work carried out to measure the sound level by using hot wire anemometry, microphone and accelerometer for each Reynolds number, $6{\times}10^4$, $8{\times}10^4$ and $1{\times}10^5$ respectively at the entry of the test tube with and without swirl flow.

• 대한전기학회논문지:전력기술부문A
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• 제48권4호
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• pp.467-473
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• 1999

We have realized the two kinds of power line communication systems by the FSK MODEM. The first approach is the DS-SS (Direct suquence-spread spectrum) technique using 8 bits pseudo noise, the other is Convolutional coding method by the new algorithm. Their characteristics are comparied with each other by experimenting their Bit Error Rates (BER) in high level of Noise. The results have showed that two systems are useful to the application of HA (Home Automation) systems.

• 한국소음진동공학회논문집
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• 제11권6호
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• pp.163-168
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• 2001

Vibration problems occurred in an air cooled heat exchanger with axial flow fan for a petrochemical plant were investigated. Experimental field test and theoretical verification were performed. To find the main cause of the high vibration of the fan at the air inlet of the axial fan, the frequency spectrum was measured. The natural frequency of the driving support of the heat exchanger was numerically calculated. Both of the measured and the natural frequency were approximately equal to the blade passing frequency. Because it was difficult to modify the structure of the driving support during the normal operation of the plant, the blade number of the fan was increased, which greatly reduced the vibration level of the heat exchanger.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.75-81
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• 2000

Vibration problems induced by an air cooled heat exchanger with axial flow fan were investigated during the operation of a petrochemical plant. Two different studies were done; one was experimental field test and the other was theoretical verification. To find main cause of the blade passing frequency of the fan after installing additional blockage board at the air inlet of the axial fan, the frequency spectrum was measured. The vibrations of the blade passing frequency became higher. The natural frequency of driving support of the heat exchanger was theoretically calculated. It was approximately equal to the blade passing frequency. During the normal operation of the plant, it was impossible to modify the structure of the driving support. Instead, the blade number was increased to reduce vibration level. It increased the ratio of the forcing frequency to the natural frequency of the driving support over the resonance region.

• 한국통신학회논문지
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• 제34권3A호
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• pp.272-280
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• 2009

배경잡음 측정은 전파환경 조사 및 주파수 점유율의 비교기준인 임계레벨을 산출하는데 반드시 수행되어야 하는 매우 중요한 과정이다. 배경잡음 측정은 측정대상 대역에서 가급적 잡음만으로 구성된 부대역을 선정하고, 선정된 표본 부대역에 대하여 잡음전력을 측정하여 대상대역에 대한 대표값으로 사용하는 과정으로 이루어진다. 본 논문에서는 배경잡음으로 백색가우시안 잡음을 가정하고, 잡음 측정의 첫 번째 단계에서 신호가 적고 대부분 잡음으로만 구성된 대역을 선별하는데 적용될 수 있는 특이값 분해 (singular value decomposition, SVD)를 이용한 잡음대역 선정 방법을 제안한다. 기존에 널리 쓰여지는 방법인 신호강도확률분포 (amplitude probability distribution, APD) 방법과의 성능비교를 통하여 우수성을 확인하였다.

• 한국의학물리학회지:의학물리
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• 제19권4호
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• pp.219-226
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• 2008

이 연구에서는 저자들이 개발한 비정질 셀레늄층과 비정질 실리콘TFT배열을 사용하는 직접방식 디지털 X-선 영상 검출기에 대해 IEC (international electrotechnical commission)와 같은 국제표준으로 권고된 측정방법에 따라 특성을 평가하였다. 영상 성능 묘사에 사용되는 측정은 응답특성(response characteristic), 변조전달함수(MTF, modulation transfer function), 잡음전력스펙트럼(NPS, noise power spectrum), 양자검출효율(DQE, detective quantum efficiency), 양자제한 성능을 포함하고 있다. 영상특성평가 결과, 개발된 검출기의 DQE 값은 최저주파수와 최고주파수에서 각각 40%와 25%이었다. 해외 타사의 제품과 비교해서도 우월한 값을 나타내었다. 또한 MTF는 간접방식 DR, CR과 비교하면 매우 우월한 성능을 보이고 있다. 또한 양자 제한된 특성을 평가한 결과, 0.023 mR 이하에서만 제한된 특성을 보여 일반촬영용도로서 적합성을 확인할 수 있었다.