• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2002년도 춘계학술대회논문집
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• pp.219-223
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• 2002

Voltage and current signals during impulse tests on transformer are treated as non-stationary signals. A new method incorporating signal-processing method such as Wavelets and courier transform is proposed for failure identification. It is now possible to distinguish failure during impulse tests. The method is experimentally validated on a transformer winding. The wavelet transforms enables the detection of the time of occurrence of switching or failure events. After establishing the time of occurrence, the original waveform is split into two or more sections. The wavelet transform has ability to analysis the failure signal on time domain as well as frequency domain. Therefore, the wavelet transform is superior than courier transform to analysis the failure signal. In this paper, the fact was proved by real data which was achieved.

• 소음진동
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• 제4권3호
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• pp.337-343
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• 1994

A method of the leak detection from the pipe system by using accelerometer is proposed. The signal detected from accelerometer is proved experimentally to be a dispersive wave. Based on the experiments, a method using the narrow band pass filter and the unit impulse response function is analyzed. The method uses the characteristics of the unit impulse response function, that the function is available evenin the narrow band signal because, unlike the cross correlation, it is normalized by the auto spectrum. The accelerometer is quite easier to use than the hydrophone in adapting to the pipe system.

• Journal of Korean Society for Atmospheric Environment
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• 제23권E2호
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• pp.66-73
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• 2007

The introduction of tracer gas techniques to ventilation studies in indoor environments provides valuable information that used to be unattainable from conventional testing environments. Data acquisition systems (DASs) containing analogue-to-digital (A/D) converters are usually used to function the key role that records signals to storage in digital format. In the testing process, there exist a number of components in the measuring equipment which may produce system-based inference to the monitored results. These unwanted fluctuations may cause significant error in data analysis, especially when non-linear algorithms are involved. In this study, a pre-processor is developed and applied to separate the unwanted fluctuations (noise or interference) in raw measurements and to reduce the uncertainty in the measurement. Moving average, notch filter, FIR (Finite Impulse Response) filters, and IIR (Infinite Impulse Response) filters are designed and applied to collect the desired information from the raw measurements. Tracer gas concentrations are monitored during leakage and ventilation tests in the model test room. The signal analysis functions are introduced to carry out the digital signal processing (DSP) work. Overall the FIR filters process the $CO_2$ measurement properly for ventilation rate and mean age of air calculations. It is found that, the Kaiser filter was the most applicable digital filter for pre-processing the tracer gas measurements. Although the IIR filters help to reduce the random noise in the data, they cause considerable changes to the filtered data, which is not desirable.

• 전기전자학회논문지
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• 제26권1호
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• pp.36-42
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• 2022

본 연구에서는 전기 신호 경로로서의 인체 채널에 대해 임펄스 응답 신호를 이용한 분석 결과를 제시한다. 최근, 인체 통신(human body communications)은 착용형 또는 임플란트형 센서 디바이스 간의 통신 방법으로 인체 영역 통신망(wireless body area networks)을 구성하는 효과적인 접근방법으로 제시되고 있다. 인체 통신 시스템 설계에 중요한 지침인 인체 채널 특성 제공을 위해, 자체 제작한 채널 응답측정장치를 사용하고 용량성 커플링(capacitive coupling) 특성에 적합한 실험환경을 구축하여 측정을 수행하고 그 분석한 결과를 제시한다. 측정 신호에 대한 신호처리 과정으로 임펄스 응답을 효과적으로 추출하여, 0 MHz에서 100 MHz 사이의 주파수 분석을 통해 평균 경로 손실 약 46.8 dB를 제시하고 주파수별 경로 손실 특성을 확인할 수 있다. 또한, 본 연구는 인체 통신 시스템의 수신기 신호 대 잡음비(signal-to-noise ratio) 예측을 위한 수신기 필터의 커패시터와 저항값 변화에 따른 전체 측정 주파수와 기저 대역 신호의 검출 성능 결정에 영향을 주는 3 MHz 이하 대역에서의 상대적인 잡음 전력을 제시하였다.

• Journal of information and communication convergence engineering
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• 제5권1호
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• pp.1-6
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• 2007

In the process of the acquisition, storage, transmission of signals, noises are generated by various causes and the degradation phenomenon by noises tends to generate serious errors for the signal with information. So, in order to analyze and remove these noises, studies on numerous mathematical methods such as the Fourier transform have been implemented. And recently there have been many ongoing wavelet-based denoising algorithms representing excellent characteristics in time-frequency localization and multiresolution analysis, but the method to remove additive white Gaussian noise (AWGN) and the impulse noise simultaneously was not given. So, to reconstruct the corrupted signal by noises, in this paper a novel wavelet-based denoising algorithm was proposed and using signal-to-noise ratio (SNR) this method was compared to conventional methods.

• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.232-238
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• 2001

Fast Fourier Transformation is employed to convert the head variation of a pipeline in the time domain to the amplitude of the frequency domain. Applying method of characteristics to a pipeline provides a significant frequency range for a surge introduced from the valve modulation. Inverse Fast Fourier Transformation and a Finite Impulse Response Filter can be used to remove any possible noise existing from the significant frequency range of an unsteady condition. A filtered signal shows higher potential for the inverse calculation of leakage detection than the noise-added signal does. The respective performances of Inverse Fast Fourier Transformation and a Finite Impulse Response Filter are compared in terms of leakage detection capability. Characteristics of the frequency range for multiple leakages were investigated to validate the effectiveness of the noise control method in the frequency domain.

• Journal of Biosystems Engineering
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• 제22권1호
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• pp.41-48
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• 1997

A nondestructive quality inspection technique using acoustic impulse response method was studied to investigate the feasibility of egg shell inspection. An experimental system was built to generate impact force, to measure the response signal and to analyze the frequency spectrum. This system includes an impulse generating unit, an egg holding seat, a microphone with preamplifier, and a digital oscilloscope connected to Personal Computer by RS-232C interface. The factors such as impulse generating method, egg holding method, and sensor location were evaluated by analyzing the power spectrum density of the measured signal. The results obtained are summarized as follows : 1. From the sampled eggs, the proper conditions for detecting damaged eggs were found as followings; ceramic for the impact ball material, rubber for egg seat material, 20 degrees for an impact angle of pendulum, 10mm for the distance between egg and sensor, the sharp side for impacting part, and 180 degrees for the location of sensor. 2. Examination of the Fourier transformed analysis in beth normal and damaged eggs revealed that those factors such as the resonant frequency, a number of peak frequencies and the magnitude of power spectrum were important to detect damaged eggs.

• Journal of Information Processing Systems
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• 제9권1호
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• pp.89-102
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• 2013

The paper presents a fuzzy based impulse noise filter for both gray scale and color images. The proposed approach is based on the technique of boundary discriminative noise detection. The algorithm is a multi-step process comprising detection, filtering and color correction stages. The detection procedure classifies the pixels as corrupted and uncorrupted by computing decision boundaries, which are fuzzified to improve the outputs obtained. In the case of color images, a correction term is added by examining the interactions between the color components for further improvement. Quantitative and qualitative analysis, performed on standard gray scale and color image, shows improved performance of the proposed technique over existing state-of-the-art algorithms in terms of Peak Signal to Noise Ratio (PSNR) and color difference metrics. The analysis proves the applicability of the proposed algorithm to random valued impulse noise.

• 한국항행학회논문지
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• 제6권4호
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• pp.318-325
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• 2002

본 논문에서는 FCC에서 제정한 허용 주파수 3.1~10.6 GHz 대역 내에서 사용 가능한 모노펄스를 이용하여 PPM 변조된 TH IR 시스템 시뮬레이터를 AWGN 환경에서 설계하고 시뮬레이터를 이용하여 모노사이클 펄스 특성 및 시스템 성능을 분석하였다. 또한, 간섭 환경에 따른 시스템 성능을 알아보기 위해 다원접속 간섭과 공유 주파수 대역에 존재하는 협대역 시스템 신호를 간섭 신호로 고려하였다. 여기에서 협대역 시스템 간섭 신호는 IR 시스템 대역폭에 비해 매우 협소하고 IR 시스템보다 큰 진폭을 갖기 때문에 협대역 간섭 신호를 간섭 전력과 대역 점유율을 고려하여 IR 시스템에서 간섭 환경에 따른 시스템 성능을 분석하였다.

• 대한전자공학회논문지TC
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• 제42권12호
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• pp.165-170
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• 2005

본 논문은 임펄스 전파 채널 측정에 있어서, 사용된 초광대역 (Ultra Wideband) 안테나가 시간 및 주파수 영역에서 임펄스 전파 채널에 미치는 영향을 기술하고자 한다. 임펄스 전파 채널에서의 초광대역 안테나의 영향을 해석하기 위해, 우선 초광대역 안테나의 임펄스 응답을 구하였고, 이를 이용하여 초광대역 안테나의 영향이 배제된 임펄스 전파 채널 해석 방법을 제시하였다. 이론적 증명을 위해, 임펄스 전파 채널 측정을 위한 변형된 초광대역 코니컬 모노폴 안테나를 설계, 제작하였고 무반향 반사실에서의 전달 특성을 측정하여 초광대역 안테나의 임펄스 응답을 도출하였다. 또한, 임펄스 전파 채널 상에서의 초광대역 안테나에 대한 영향을 해석하기 위해, 무반향 반사실에서 다중경로 환경을 만들어 주파수 영역에서 벡터 회로망 분석기를 사용하여 전달 특성을 측정하였다. 주파수 영역에서 측정된 데이터는 신호 처리 과정을 거쳐 시간 영역의 신호로 변환하였다. 측정된 결과로부터, 안테나의 특성이 임펄스 전파 채널에 영향을 미침을 확인하였다. 또한, 초광대역 안테나의 임펄스 응답을 사용하여 순수하게 다중경로 채널에 의한 임펄스 응답을 구하였다.