• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.55-56
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• 2008

The photo leakage currents of a conventional hydrogenated amorphous silicon(a-Si:H) thin film transistor(TFT) were investigated and analyzed in the case of illumination from various lightsources such as halogen lamp, cold cathode fluorescent lamp(CCFL) backlight, and white light emitting diode(LED) backlight The photo leakage characteristics showed the apparent differences in the leakage level and in the $I_{on}/I_{off}$ ratio in spite of the similar luminances of light sources. This leakage level is expected to be related to the wavelength of the lowest intensity peak from spectral analysis of light sources.

• 한국전기전자재료학회논문지
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• 제21권9호
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• pp.844-847
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• 2008

The photo leakage currents of a conventional hydrogenated amorphous silicon(a-Si:H) thin film transistor(TFT) were investigated and analyzed in case of illumination from various light sources such as halogen lamp, cold cathode fluorescent lamp(CCFL) backlight, and white light emitting diode(LED) backlight. The photo leakage characteristics showed the apparent differences in the leakage level and in the $I_{on}/I_{off}$ ratio in spite of the similar luminances of light sources. This leakage level is expected to be related to the wavelength of the lowest intensity peak from the spectral characteristics of light sources.

• 전자공학회논문지D
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• 제35D권4호
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• pp.40-46
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• 1998

Leakage phenomena of flip-chip structures on common GaAs and alumina main substrates are characterized using the spectral domain approach to reduce the possible chip-to-chip crosstald and transmission resonance. We have found taht the longitudinal section magnetic mode is dominant for the coplanar waveguide leakage andthe leakage can be suppreassed by properly managing the gap height and the main substrate thickness in addition to the dielectric constant. These calculation results will be helpful for designing and flip-chip packagaing of high-frequency integrated circuits.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(4)
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• pp.106-109
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• 2000

There have been proposed two types of low bit rate vocoder upto now : One is MBE type using the spectrum modeling and another is CELP type using the hybrid coding method. CELP type vocoder has mainly studied between them. Specially, much of intensity is concentrated in CELP vocoder due to the emergence of Internet Phone and PCS in a domestic. In order to improve the speech quality in CELP vocoder, in this paper, we proposed a new spectrum analysis algorithm with variable window, In CELP vocoder, the spectrum of the synthesised speech signal is distorted because the fixed size windows is used for spectrum analysis. So we have measured the spectral leakage and in order to minimize the spectral leakage have adjusted the window size. Applying this method G.723.1 ACELP, we can get SD(Spectral Distortion) reduction 0.084(dB), residual energy reduction 6.3% and MOS(Mean Opinion Score) improvement 0.1.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2010년도 춘계학술발표논문집 1부
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• pp.265-268
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• 2010

There have been proposed two types of low bit rate vocoder upto now : One is MBE type using the spectrum modeling and another is CELP type using the hybrid coding method. CELP type vocoder has mainly studied between them. Specially, much of intensity is concentrated in CELP vocoder due to the emergence of Internet Phone and PCS in a domestic. In order to improve the speech quality in CELP vocoder, in this paper, we proposed a new spectrum analysis algorithm with variable window. In CELP vocoder, the spectrum of the synthesised speech signal is distorted because the fixed size windows is used for spectrum analysis. So we have measured the spectral leakage and in order to minimize the spectral leakage have adjusted the window size. Applying this method G.723.1 ACELP, we can get SD(Spectral Distortion) reduction 0.084(dB), residual energy reduction 6.3% and MOS(Mean Opinion Score) improvement 0.1.

• ETRI Journal
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• 제31권3호
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• pp.292-297
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• 2009

The power spectral density of a signal can be estimated most accurately by using a window with a narrow bandwidth and large sidelobe attenuation. Conventional windows generally control these characteristics by only one parameter, so there is a trade-off problem: if the bandwidth is reduced, the sidelobe attenuation is also reduced. To overcome this problem, we propose using a Butterworth window with two control parameters for power spectral density estimation and analyze its characteristics. Simulation results demonstrate that the sidelobe attenuation and the 3 dB bandwidth can be controlled independently. Thus, the trade-off problem between resolution and spectral leakage in the estimated power spectral density can be overcome.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.845-850
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• 2003

Unsteady nature of a tip leakage vortex in an axial flow fan operating at a design and off-design operating conditions has been investigated by measuring the velocity fluctuation in a blade passage with a rotating hotwire probe sensor. Two hot-wire probe sensors rotating with the fan rotor were also introduced to obtain the cross-correlation coefficient between the two sensors located in the vortical flow as well as the fluctuating velocity. The results show that the vortical flow structure near the rotor tip can be clearly observed at the quasi-orthogonal planes to a tip leakage vortex. The leakage vortex is enlarged as the flow rate is decreased, thus resulting in the high blockage to main flow. The spectral peaks due to the fluctuating velocity near the rotor tip are mainly observed in the reverse flow region at higher flow rates than the peak pressure operating condition. However, no peak frequency presents near the rotor tip for near stall condition.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2004년도 추계학술발표대회논문집 제23권 2호
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• pp.35-38
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• 2004

In this paper, we investigate and analyze the problems encountered in frame-based estimation of TDOA(Time Difference of Arrival) using CPSP function. Spectral leakage occurring in framing of a speech signal by a rectangular window makes estimation of CPSP spectrum inaccurate. Framing with a Hamming window to reduce the spectral leakage effect distorts the signal due to the different weighting at temporally same sample, which make the TDOA estimation using CPSP function inaccurate. In this paper, we solve this problem by reducing the dynamic range of the spectrum of a speech signal with preemphasis. Experimental results confirm that the framing of pre-emphasized microphone output with a rectangular window shows higher success ratio of TDOA estimation than any other framing methods.

• 한국통신학회논문지
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• 제41권8호
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• pp.859-867
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• 2016

GPS(Global Positioning System)는 미국에서 군사목적으로 이용하기 위해 개발된 위치측정 시스템으로, 현재는 우리나라를 포함한 각 국에서 군용뿐만 아니라 민간에도 유용하게 쓰이고 있다. 하지만 GPS는 위성으로부터 지면에 도달하는 신호의 세기가 매우 약해서 전파방해신호(Jamming Signal)에 약하다는 단점을 가진다. 본 논문에서는 수신된 GPS 신호에 협대역의 전파방해 신호가 존재한다고 가정하고, 새로운 협대역 전파방해신호 제거 알고리즘을 제안한다. 우선, GPS 수신기에서 수신한 신호를 FFT를 이용하여 주파수 성분으로 표현하며, FFT로 인하여 발생하는 Spectral Leakage의 영향을 줄이기 위하여 Blackman-Harris window를 적용한다. Blackman-Harris window의 주파수 응답을 형태를 이용하여, 가장 큰 파워를 가지는 주파수 성분을 찾고 그 주변으로 일정한 개수의 성분을 제거하는 알고리즘을 제안하였다. 주로 쓰일만한 128~512포인트의 FFT를 사용할 시에 고정적으로 최대값 주변의 42개의 성분을 제거하는 것이 가장 최적임을 알 수 있었다.

• 한국컴퓨터정보학회논문지
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• 제10권6호
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• pp.233-238
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• 2005

CELP 계열 음성부호화기는 대략 4.8kbps의 전송률로 음질 면에서 우수한 특성을 지닌다. 이중에서 인터넷폰과 화상회의를 위해 개발되어진 G.723.1 음성부호화기는 5.3kbps ACELP와 6.3kbps MP-MLQ 이중 전송률로 구성된다. 본 논문에서는 CELP 계열 음성부호화기의 음질 개선을 위해 가변 윈도우를 이용한 새로운 스펙트럼 분석 알고리즘을 제안한다. 기존의 방법에서는 스펙트럼 분석시 고정 윈도우를 사용하기 때문에 합성음의 스펙트럼의 경우 왜곡이 발생한다. 그러므로 스펙트럼 누설을 최소화하기 위해 조절되어진 윈도우를 사용하였다. 제안한 알고리즘을 G.723.1 ACELP에 적용한 실험결과에서 스펙트럼 왜곡은 0.084dB 정도 감소, 잔차 에너지는 6.3$\%$ 감소하였으며 이에 반해 MOS는 0.1 정도 개선되었다.