• Title, Summary, Keyword: Noise Filter

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A Study on the Combining Circuit of New Active EMI Filter (새로운 능동EMI필터의 결합회로에 관한 연구)

  • Choi, Min-Whan;Shin, Dong-Seok;Lee, Dong-Ho;Park, Chong-Yeun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.29 no.6
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    • pp.78-89
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    • 2015
  • Conventional EMI filters have tried to use an active EMI filter as a series by the series connection of two EMI filters for CM and DM noise. However, the proposed filter is formed into one circuit by using the active EMI filter which is able to filter CM and DM noise components together. As a result, the active EMI filter showed the outstanding quality in mass and volume under 50% and electric characteristics have been compared to the passive EMI filter in approximately 150kHz~10MHz. Furthermore, the proposed circuit has simple circuit components by comparing with the series EMI filters, and electrical characteristics are similar. The noise have been attenuated to maximum 20dBuV.

Online estimation of noise parameters for Kalman filter

  • Yuen, Ka-Veng;Liang, Peng-Fei;Kuok, Sin-Chi
    • Structural Engineering and Mechanics
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    • v.47 no.3
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    • pp.361-381
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    • 2013
  • A Bayesian probabilistic method is proposed for online estimation of the process noise and measurement noise parameters for Kalman filter. Kalman filter is a well-known recursive algorithm for state estimation of dynamical systems. In this algorithm, it is required to prescribe the covariance matrices of the process noise and measurement noise. However, inappropriate choice of these covariance matrices substantially deteriorates the performance of the Kalman filter. In this paper, a probabilistic method is proposed for online estimation of the noise parameters which govern the noise covariance matrices. The proposed Bayesian method not only estimates the optimal noise parameters but also quantifies the associated estimation uncertainty in an online manner. By utilizing the estimated noise parameters, reliable state estimation can be accomplished. Moreover, the proposed method does not assume any stationarity condition of the process noise and/or measurement noise. By removing the stationarity constraint, the proposed method enhances the applicability of the state estimation algorithm for nonstationary circumstances generally encountered in practice. To illustrate the efficacy and efficiency of the proposed method, examples using a fifty-story building with different stationarity scenarios of the process noise and measurement noise are presented.

Adaptive Switching Median Filter for Impulse Noise Removal Based on Support Vector Machines

  • Lee, Dae-Geun;Park, Min-Jae;Kim, Jeong-Ok;Kim, Do-Yoon;Kim, Dong-Wook;Lim, Dong-Hoon
    • Communications for Statistical Applications and Methods
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    • v.18 no.6
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    • pp.871-886
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    • 2011
  • This paper proposes a powerful SVM-ASM filter, the adaptive switching median(ASM) filter based on support vector machines(SVMs), to effectively reduce impulse noise in corrupted images while preserving image details and features. The proposed SVM-ASM filter is composed of two stages: SVM impulse detection and ASM filtering. SVM impulse detection determines whether the pixels are corrupted by noise or not according to an optimal discrimination function. ASM filtering implements the image filtering with a variable window size to effectively remove the noisy pixels determined by the SVM impulse detection. Experimental results show that the SVM-ASM filter performs significantly better than many other existing filters for denoising impulse noise even in highly corrupted images with regard to noise suppression and detail preservation. The SVM-ASM filter is also extremely robust with respect to various test images and various percentages of image noise.

A Mixed Nonlinear Filter for Image Restoration under AWGN and Impulse Noise Environment

  • Gao, Yinyu;Kim, Nam-Ho
    • Journal of information and communication convergence engineering
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    • v.9 no.5
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    • pp.591-596
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    • 2011
  • Image denoising is a key issue in all image processing researches. Generally, the quality of an image could be corrupted by a lot of noise due to the undesired conditions of image acquisition phase or during the transmission. Many approaches to image restoration are aimed at removing either Gaussian or impulse noise. Nevertheless, it is possible to find them operating on the same image, which is called mixed noise and it produces a hard damage. In this paper, we proposed noise type classification method and a mixed nonlinear filter for mixed noise suppression. The proposed filtering scheme applies a modified adaptive switching median filter to impulse noise suppression and an efficient nonlinear filer was carried out to remove Gaussian noise. The simulation results based on Matlab show that the proposed method can remove mixed Gaussian and impulse noise efficiently and it can preserve the integrity of edge and keep the detailed information.

Acoustic modeling of an air cleaner filter in the engine intake system (자동차 흡기계 공기 여과기 필터의 음향학적 모델)

  • Ih, Jeong-Guon;Kang, Jang-Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.114-117
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    • 2006
  • The air filter in engine intake system has a function of filtrating the dirt in the scavenging air as well as attenuating the noise. The noise attenuation within the air cleaner filter, however, has been regarded as negligible by the field engineers. In this paper, for the analysis of the acoustical performance of air filter, an acoustical model was suggested and the characteristics of air filter system were investigated. Fibrous structure of the filter element was modeled as a micro-perforated panel using the flow resistivity and porosity. The pleated geometry of the filter element was modeled as two coupled ducts that have permeable walls, in which each duct area was assumed being constant. Using such simplified geometry, a mathematical model was developed for the sound propagation within a narrow duct system. Visco-thermal effect was considered in modeling the sound propagation through such tubes; the filter box was modeled as a rigid rectangular box. By combining two models, a four-pole transfer matrix was derived. For the validation purpose, transmission loss was measured for a plastic rectangular box containing an air filter. A noticeable effect of the air filter element was observed by including the filter into the box. Comparing the predicted and measured data, we found that the predicted TL agrees well with experimental results, in particular, in magnitude and frequency at TL troughs.

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Characteristics of noise cancellation for MCG signals using wavelet packets (웨이브렛 패킷을 이용한 심자도 신호의 잡음 제거 특성)

  • 박희준;김용주;정주영;원철호;김인선;조진호
    • Progress in Superconductivity
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    • v.4 no.1
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    • pp.53-58
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    • 2002
  • Noise from electronic instrumentation is invariably present in biomedical signals, although the art of instrumentation design is such that this noise source may be negligible. And sometimes signals of interest are contaminated or degraded by signals of similar type from another source. Biomedical signals are omni-presently contaminated by these background noises that span nearly all frequency bandwidths. In the magneto-cardiogram (MCG), several digital filters have been designed for the elimination of the power-line interference, broadband white noise, surrounding magnetic noise, and baseline wondering. In addition to the introduced FIR filter, notch, adaptive filter using the least mean square (LMS) algorithm, and recurrent neural network (RNN) filter, a new filtering method for effective noise canceling in MCG signals is proposed in this paper, which is realized by the wavelet packets. The experimental results show that the proposed filter using wavelet packet performs efficiently with respect to noise rejection. To verify this, two characteristics were analyzed and compared with LMS adaptive filter, SNR of filtered signal and attractor pattern using the nonlinear dynamics.

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A Study on Composite Filters for Salt and Pepper Noise Removal (Salt and Pepper 잡음 제거를 위한 복합 필터에 관한 연구)

  • Hong, Sang-Woo;Kwon, Se-Ik;Kim, Nam-Ho
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.409-411
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    • 2016
  • Salt and pepper noise is caused by various causes such as camera malfunction, storage media memory error, and transmission channel error. Representative filters to remove salt and pepper noise include SMF(standard median filter), CWMF(center weighted median filter), and AMF(adaptive median filter). However previous filters have inadequate noise removal characteristics in high density salt-and-pepper noise environment. Therefore the study suggested a composite filter which, through noise evaluation, preserves original pixels when the central pixel is non-noise, and uses spatial weighted value mask and median when there is noise.

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EMG Signal Elimination Using Enhanced SVD Filter in Multi-Lead ECG (향상된 SVD 필터를 이용한 Multi-lead ECG에서의 EMG 신호 제거)

  • Park, Kwang-Li;Park, Se-Jin;Choi, Ho-Sun;Jeong, Kee-Sam;Lee, Kyoung-Joung;Yoon, Hyoung-Ro
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.50 no.6
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    • pp.302-308
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    • 2001
  • SVD(Singular Value Decomposition) filter for the suppression of EMG in multi-lead stress ECG is studied. SVD filter consists of two parts. In the first part, the basis vectors were chosen from the averaged singular vectors obtained from the decomposed noise-free ECG. The singular vector is computed from the stress ECG and is compared itself with basis vectors to know whether the noise exist in stress ECG. In the second part, the existing elimination method is used, when one(or two) channels is(or are) contaminated by noise. But the proposed enhanced SVD filter is used in case of having the noise in the many channels. During signal decomposition and reconstruction, the noise-free channel or the least noisy channel have the weight of 1, the next less noisy channel has the weight of 0.8. In this way, every channel was weighted by decreased of 0.2 in proportion to the amount of the added noise. For the evaluation of the proposed enhanced SVD filter, we compared the SNR computed by the enhanced SVD filter with the standard average filter for the noise-free signal added with artificial noise and the patient data. The proposed SVD filter showed better in the SNR than the standard average filter. In conclusion, we could find that the enhanced SVD filter is more proper in processing multi-lead stress ECG.

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A Study on Modified Median Filter for Impulse Noise Removal (임펄스 잡음 제거를 위한 변형된 메디안 필터에 관한 연구)

  • Lee, Kyung-Hyo;Kim, Nam-Ho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.13 no.2
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    • pp.376-381
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    • 2009
  • The image data compression, recognition, restoration, etc. are parts of the digital image processing technology. In the process by various devices, noises would be made. Because the noise could damage the image, we use the image filter to preserve the original image from the noise. The image filter used in digital image process basically has a two-dimensional structure. There an two methods of creating the filter - One is reiterating one dimension and the other is using an indivisible two-dimension image filter. The image filter is being widely used along with one-dimension filter according to each noise, and various median filters are being used to remove the impulse noise. In this paper, I suggested a powerful modified median filter, and compared with conventional filters for objective verification.

우리나라 의용생체공학의 현황과 전망

  • 이충웅
    • Journal of Biomedical Engineering Research
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    • v.10 no.2
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    • pp.83-88
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    • 1989
  • This paper is a study on the design of adptive filter for QRS complex detection. We propose a simple adaptive algorithm to increase capability of noise cancelation in QRS complex detection with two stage adaptive filter. At the first stage, background noise is removed and at the next stage, only spectrum of QRS complex components is passed. Two adaptive filters can afford to keep track of the changes of both noise and QRS complex. Each adaptive filter consists of prediction error filter and FIR filter The impulse response of FIR filter uses coefficients of prediction error filter. The detection rates for 105 and 108 of MIT/BIH data base were 99.3% and 97.4% respectively.

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