• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.482-484
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• 2005

The Modulation Transfer Function (MTF) is commonly used to characterize the spatial quality of imaging systems. This work is the attempt to measure the MTF at Nyquist frequency of the satellite imaging system what has 1m spatial resolution for KOMPSAT-2 image using the edge function. Artificial tarp targets are used in this study. A type of this tarp edge consists of two adjacent uniform bright and dark sides commonly used to test the performance of an optical system in edge function. The results from this work demonstrate the potential applicability of this method to estimate the response characteristics for KOMPSAT-2 that is scheduled to be launched.

• 대한전자공학회논문지
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• 제19권6호
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• pp.67-79
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• 1982

가우스 잡음의 출현시 PWM 시스템의 안정도가 연구되었다. 일반 시스템은 종래의 서술 함수 방법을 이용할 때 비선형 소자와 선형 소자로 나누어진다. 등가 어드미턴스 개념이 이 시스템의 비선형 소자의 전달 특성을 구하는데 사용되었다. 이 논문에서는 가우스 잡음만이 존재하는 경우 자기 발진 조건이 유도되었고 그 결과를 컴퓨터 시뮬레이션으로 분석하였다. The stability of general pulse-width modulation system with Gaussian random disturbance was discussed . General system is divided into nonlinear and linear elements using the conventional describing function method. The concept of the equivalent admittance was used to find the transfer characteristic of the nonlinear element of the system. In this paper the self-sustained oscillation condition in the autonomous system was derived and the results was analyzed with computer simulation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.150-155
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• 2006

Speech intelligibility is investigated on a conference room-window glass coupled system. Using MLS(Maximum Length Sequency) signal as a sound source, acceleration and velocity responses of the window glass are measured by accelerometer and laser doppler vibrometer. MTF(Modulation Transfer Function) is used to identify the speech transmission characteristics of the room and window system. STI(Speech Transmission Index) is calculated by using MTF and speech intelligibility of the room and the window glass is estimated. Speech intelligibilities by the acceleration signal and the velocity signal are compared and the possibility of the wiretapping is investigated. Finally, intelligibility of the conversation sound is examined by the subjective test.

• 한국소음진동공학회논문집
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• 제17권4호
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• pp.363-369
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• 2007

The purpose of the study is to obtain acoustical information to prevent eavesdropping of the glass window. Speech intelligibility was investigated on the vibration sound detected from the glass window of a conference room. Objective test using speech transmission index(STI) was performed to estimate quantitatively the speech intelligibility. STI was determined based on tile modulation transfer function(MTF) of the room-glass window system. Using Maximum Length Sequency(MLS) signal as a sound source, impulse responses of the glass window and MTF were determined by signals from accelerometers and laser doppler vibrometer. Finally, speech intelligibility of the interior sound and window vibration were compared under different sound pressure levels and amplifier gains to confirm the effect of measurement condition on the speech intelligibility.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.649-654
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• 2007

Eavesdropping prevention performance is evaluated on a commercial window shaker, which is used to prevent a glass window from eavesdropping. Speech transmission index (STI) is introduced in order to estimate quantitatively the speech intelligibility of the sound detected on the glass window. Objective test by IEC standard using modulation transfer function (MTF) is performed to determine STI. Using Maximum Length Sequency (MLS) signal as a sound source, MTF is measured by accelerometers and laser doppler vibrometer. STI under different level of disturbing wave are compared to confirm the disturbing effect on the speech intelligibility.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.551-556
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• 2008

Possibility of the remote eavesdropping through window glass is investigated using a laser sensor. Various thicknesses and types of glass windows are excited by maximum length sequency (MLS) signal and the vibration sound is detected by a laser doppler vibrometer. Intelligibility of the detected sound is evaluated using the speech transmission index (STI), which is based on the modulation transfer function (MTF). In order to identify the disturbing effect, different level of disturbing wave is generated by an outside speaker and a window shaker attached on the glass window. On the different thickness of glass windows, decrease effect of the speech intelligibility is analysed.

• 한국소음진동공학회논문집
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• 제17권9호
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• pp.888-894
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• 2007

The speech sound is detected by the vibration measurement of the window glass. In this study, we investigate the effect of the disturbing waves by background noise and window shaker excitation on the speech intelligibility of the detected sound. Based upon Modulation Transfer Function(MTF), speech intelligibility of the sound is objectively estimated by Speech Transmission Index(STI) As the level of the disturbing wave varies, variation of the speech intelligibility is examined. Experimental result reveals how STI is influenced by the level and frequency characteristics of the disturbing wave. By using a customized window shaker for disturbing sound, we evaluate the efficiency and the frequency characteristics of the anti-eavesdropping system. The purpose of the study is to provide useful information to prevent the eavesdropping through the window glass.

• 한국연소학회지
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• 제14권4호
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• pp.48-53
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• 2009

This paper describes the forced flame response in a turbulent premixed gas turbine combustor. The fuel was premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. To impose the inlet flow velocity, a siren type modulation device was developed using an AC motor, rotating and static plates. Measurements were made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The test results showed that flame length as well as geometry was strongly dependent upon modulation frequency in addition to operating conditions such as inlet velocity. Convection delay time between the velocity perturbation and heat release fluctuations was calculated using phase information of the transfer function, which agreed well with the results of flame length measurements. Also, basic characteristics of the flame nonlinear response shown in the current test conditions were introduced.

• 산업기술연구
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• 제27권A호
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• pp.55-60
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• 2007

Possibility of the eavesdropping is investigated on a conference room-glass window coupled system. Speech intelligibility analysis is performed on the eavesdropping sound of the glass window. Using MLS(Maximum Length Sequency) signal as a sound source, acceleration and velocity responses of the glass window are measured by accelerometer and laser doppler vibrometer. MTF(Modulation Transfer Function) is used to identify the speech transmission characteristics of the room and window system. STI(Speech Transmission Index) is calculated by using MTF and speech intelligibility of the vibration sound is estimated. Speech intelligibilities by the acceleration signal and the velocity signal are compared.

• 한국광학회지
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• 제6권3호
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• pp.173-177
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• 1995

칼날주사방법을 이용한 CCD의 MTF 측정장치를 제작하고 일차원 CCD의 MTF특성을 측정하였다. 주사방향에 수직인 직선과 칼날이 이루는 각도에 따른 CCD MTF 측정값의 변화는 $1^{\circ}$ 미만의 작은 각도변화에 의해서도 MTF값이 크게 변함을 알 수 있었으며 CCD의 MTF 측정값은 간섭필터와 텅스텐 필라멘트가 조합된 파장에 따라 다른 값을 나타내었다. 또한 광원의 색온도 변화에 의한 CCD의 MTF특성과 CCD 화소들의 균일성을 조사하였다.