• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.585-590
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• 2004

Many machine failures are not detected well in advance due to the masking of background noise and attenuation of the source signal through the transmission mediums. Advanced signal processing techniques using adaptive filters and higher order statistics have been attempted to extract the source signal from the measured data at the machine surface. In this paper, blind deconvolution using the eigenvector algorithm (EVA) technique is used to recover a damaged bearing signal using only the measured signal at the machine surface. A damaged bearing signal corrupted by noise with varying signal-to-noise (s/n) was used to determine the effectiveness of the technique in detecting an incipient signal and the optimum choice of filter length. The results show that the technique is effective in detecting the source signal with an s/n ratio as low as 0.21, but requires a relatively large filter length.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.836-842
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• 2005

This paper presents a power supply of railway signal system using a Z-source inverter. The Z-source inverter overcomes the conceptual and theoretical barriers and limitations of the tradition voltage-source inverter and current-source inverter and provides novel power conversion concept. The Z-source inverter is a Buck-Boost inverter that has a wide range of obtainable voltage.

• 한국정밀공학회지
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• 제21권8호
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• pp.57-64
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• 2004

This study deals with the prediction of defect location which can be occurred in structure. The existing methods was very difficult to be applied to predict it, because of complex numerical formula. The triangulation method proposed in this study can predict the source location easily with small amount of data. The arrival time of wave can be directly converted into the distance between sensors. For this purpose, the propagation velocity was measured by Rayleigh wave, and the propagation behavior was analyzed. The welded workpiece is adapted to investigate for the consideration of jointed part in structure, The propagation velocity of signal was measured in welded workpiece and the revised algorithm of source location was proposed.

• Journal of Information Technology Applications and Management
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• 제24권1호
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• pp.157-167
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• 2017

This paper proposes a simple sound source localization (SSL) method based on signal energies comparison and partial cross correlation for TDOA computation. Many sound source localization methods include multiple TDOA computations in order to eliminate front-back confusion. Multiple TDOA computations however increase the methods' computation times which need to be as minimal as possible for real-time applications. Our aim in this paper is to achieve the same results of localization using fewer computations. Using three microphones, we first compare signal energies to predict which quadrant the sound source is in, and then we use partial cross correlation to estimate the TDOA value before computing the azimuth value. Also, we apply a threshold value to reinforce our prediction method. Our experimental results show that the proposed method has less computation time; spending approximately 30% less time than previous three microphone methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.467-469
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• 2001

This paper presents an efficient location estimation methodology for a partial discharge(PD) source in the power transformer. The methodology previously proposed is not suitable for locating a PD source because the ultrasonic signal with medium attenuated through the inner structure. In general, the propagation characteristic of ultrasonic signal with medium is different. Therefore, using this propagation characteristic, we can detect the location of PD source. In this paper, the proposal algorithm finds the PD source using three sensors attached to one side of the transformer without attenuation of the ultrasonic signal and applying the neural network based geometrical method. The proposed methodology demonstrates the effectiveness and validity on an experimental transformer.

• Journal of the Optical Society of Korea
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• 제12권3호
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• pp.121-125
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• 2008

We address the problem of Blind Source Separation(BSS) of superimposed signals in situations where one signal has constant or slowly varying intensities at some consecutive locations and at the corresponding locations the other signal has highly varying intensities. Independent Component Analysis(ICA) is a major technique for Blind Source Separation and the existing ICA algorithms fail to estimate the original intensities in the stated situation. We combine the advantages of existing sparse methods and Kernel ICA in our technique, by proposing wavelet packet based sparse decomposition of signals prior to the application of Kernel ICA. Simulations and experimental results illustrate the effectiveness and accuracy of the proposed approach. The approach is general in the way that it can be tailored and applied to a wide range of BSS problems concerning one-dimensional signals and images(two-dimensional signals).

• 한국음향학회지
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• 제35권5호
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• pp.331-339
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• 2016

본 논문은 음선 기반 블라인드 디컨볼루션을 이용하여 송 수신기의 상대적인 이동으로 인한 도플러 편이가 존재하는 수중 음향 채널 환경에서의 송신 신호 및 채널 임펄스 응답 추정에 대한 방법을 제시한다. 도플러 편이가 존재하는 수중 채널 환경에서 m시퀀스와 같은 도플러 효과에 민감한 탐침 신호를 사용할 경우, 도플러 왜곡에 의한 수신 신호와의 낮은 상관도에 의해 정합 필터 처리만으로는 채널 임펄스 응답 추정에 어려움이 따른다. 본 연구에서는 음선기반 블라인드 디컨볼루션을 이용하여 도플러 편이가 포함되어 있는 송신 신호의 위상을 추정한 후, 이를 수신 신호에 보상함으로써 도플러 편이가 보상된 채널 임펄스 응답 추정에 대한 방법을 제안한다. 해상실험을 통해 측정된 수신 데이터에 대하여 정합 필터만으로는 채널 임펄스 응답 추정이 어려운 반면 제안된 방법을 통한 채널 임펄스 응답 추정 시, 음선 모델에서 예측된 전달경로와 유사한 특성을 보여주는 것을 확인하였다. 또한 산란 함수를 통해 추정된 도플러를 보상한 송신 신호에 비해 음선 기반 블라인드 디컨볼루션을 이용하여 복원한 송신 신호가 더 우수한 도플러 보상효과를 나타낸다.

• 센서학회지
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• 제13권3호
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• pp.224-229
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• 2004

In this paper, we propose a new Active Noise Control (ANC) system using a teacher forced Blind Source Separation (BSS) algorithm. The Blind Source Separation based on the Independent Component Analysis (ICA) separates the desired sound signal from the unwanted noise signal. In the proposed system, the BSS algorithm is used as a preprocessor of ANC system. Also, we develop a teacher forced BSS learning algorithm to enhance the performance of BSS. The teacher signal is obtained from the output signal of the ANC system. Computer experimental results show that the proposed ANC system in conjunction with the BSS algorithm effectively cancels only the ship engine noise signal from the linear and convolved mixtures with human voice.

• 한국음향학회지
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• 제18권6호
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• pp.3-8
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• 1999

본 연구에서는 신호원에 대한 사전 정보 없이 혼합된 신호로부터 잡음 신호만을 선택적으로 제거할 수 있는 새로운 형태의 능동 소음 제거기(Active noise canceller)를 제안한다. 음성신호와 같은 동특성을 갖는 신호의 분리에 효과적으로 사용되는 동적 재귀 신경망(Dynamic recurrent neural network)을 원하는 신호원에 섞인 잡음신호를 분리하여 선택적으로 제거하기 위한 능동 소음 제거기의 전처리기로 이용한다. 능동 소음 제거기는 분리된 잡음 신호에 대한 역위상 신호를 적응적으로 발생함으로써 특정 위치에서 원하는 신호만을 선택적으로 남길 수 있도록 한다. 컴퓨터 시뮬레이션을 통하여 제안된 시스템이 선택적인 소음제거에 효과적임을 보인다.

• 음성과학
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• 제3권
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• pp.132-147
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• 1998

Previously developed methods for pitch modification have not been based on the voice source model. Therefore, the synthesized speech often sounds unnatural although it may be highly intelligible. The purpose of this paper is to analyze the alteration of a voice source signal with pitch period and to establish the pitch-modification rule based on the result of this analysis. We examine the alteration of the interval of closing phase, closed phase and open phase using the excitation waveform as the pitch increases. In comparison to the previous methods which performed directly on the speech signal, the pitch modification method based on a voice source model shows high intelligibility and naturalness. This study might benefit the application to the speaker identification and the voice color conversion. Therefore the proposed method will provide high quality synthetic speech.