• Title/Summary/Keyword: Wavelet filter

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KERNEL-BASED NOISE FILTERING OF NEUTRON DETECTOR SIGNALS

  • Park, Moon-Ghu;Shin, Ho-Cheol;Lee, Eun-Ki
    • Nuclear Engineering and Technology
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    • v.39 no.6
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    • pp.725-730
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    • 2007
  • This paper describes recently developed techniques for effective filtering of neutron detector signal noise. In this paper, three kinds of noise filters are proposed and their performance is demonstrated for the estimation of reactivity. The tested filters are based on the unilateral kernel filter, unilateral kernel filter with adaptive bandwidth and bilateral filter to show their effectiveness in edge preservation. Filtering performance is compared with conventional low-pass and wavelet filters. The bilateral filter shows a remarkable improvement compared with unilateral kernel and wavelet filters. The effectiveness and simplicity of the unilateral kernel filter with adaptive bandwidth is also demonstrated by applying it to the reactivity measurement performed during reactor start-up physics tests.

Flaw Detection of Ultrasonic NDT in Heat Treated Environment Using WLMS Adaptive Filter (열처리 환경에서 웨이브렛 적응 필터를 이용한 초음파 비파괴 검사의 결함 검출)

  • 임내묵;전창익;김성환
    • The Journal of the Acoustical Society of Korea
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    • v.18 no.7
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    • pp.45-55
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    • 1999
  • In this paper, we used the WLMS(Wavelet domain Least Mean Square) adaptive filter based on the wavelet transform to cancel grain noise. Usually, grain noise occurs in changes of the crystalline structure of metals in high temperature environment. It makes the detection of flaw difficult. The WLMS adaptive filtering algorithm establishes the faster convergence rate by orthogonalizaing the input vector of adaptive filter as compared with that of LMS adaptive filtering algorithm in time domain. We implemented the WLMS adaptive filter by using the delayed version of the primary input vector as the reference input vector and then implemented the CA-CFAR(Cell Averaging- Constant False Alarm Rate) threshold estimator. CA-CFAR threshold estimator enables to detect the flaw and back echo signals automatically. Here, we used the output signals of adaptive filter as its input signal. To Cow the statistical characteristic of ultrasonic signals corrupted by grain noise, we performed run test. The results showed that ultrasonic signals are nonstationary signal, that is, signals whose statistical properties vary with time. The performance of each filter is appreciated by the signal-to-noise ratio. After LMS adaptive filtering in time domain, SNR improves to about 2-3㏈ but after WLMS adaptive filtering in wavelet domain, SNR improves to about 4-6㏈.

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A Design of Wavelet OFDM based on CIC Filter (CIC 필터를 이용한 Wavelet OFDM 설계)

  • Moon, Ki-Tak;Jang, Dong-Won;Kim, Kyung-Seok
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.2C
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    • pp.93-98
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    • 2011
  • Currently, The new communication system was very important because of the increasing demand for Internet access. One of these alternatives is the PLC. But, Power Line is not suitable for communication. So, electromagnetic wave is generated from Power Line during flow of communication information. And the electromagnetic wave is interfered with Wireless Communication Service using the same frequency range. To eliminate this interference by used Notch tilter. Wavelet OFDM in another way, while one is used. In this paper, Wavelet OFDM CIC filter used in the CMFB structure by applying a further lowering the value of the side-lobe is proposed to improve performance.

Image Restoration Based on Inverse Filtering Order and Power Spectrum Density (역 필터 순서와 파워 스펙트럼 밀도에 기초한 이미지 복원)

  • Kim, Yong-Gil;Moon, Kyung-Il
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.16 no.2
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    • pp.113-122
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    • 2016
  • In this paper, we suggest a approach which comprises fast Fourier transform inversion by wavelet noise attenuation. It represents an inverse filtering by adopting a factor into the Wiener filtering, and the optimal factor is chosen to minimize the overall mean squared error. in order to apply the Wiener filter, we have to compute the power spectrum of original image from the corrupted figure. Since the Wiener filtering contains the inverse filtering process, it expands the noise when the blurring filter is not invertible. To remove the large noises, the best is to remove the noise using wavelet threshold. Wavelet noise attenuation steps are consisted of inverse filtering and noise reduction by Wavelet functions. experimental results have not outperformed the other methods over the overall restoration performance.

Seafloor Classification Based on the Texture Analysis of Sonar Images Using the Gabor Wavelet

  • Sun, Ning;Shim, Tae-Bo
    • The Journal of the Acoustical Society of Korea
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    • v.27 no.3E
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    • pp.77-83
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    • 2008
  • In the process of the sonar image textures produced, the orientation and scale factors are very significant. However, most of the related methods ignore the directional information and scale invariance or just pay attention to one of them. To overcome this problem, we apply Gabor wavelet to extract the features of sonar images, which combine the advantages of both the Gabor filter and traditional wavelet function. The mother wavelet is designed with constrained parameters and the optimal parameters will be selected at each orientation, with the help of bandwidth parameters based on the Fisher criterion. The Gabor wavelet can have the properties of both multi-scale and multi-orientation. Based on our experiment, this method is more appropriate than traditional wavelet or single Gabor filter as it provides the better discrimination of the textures and improves the recognition rate effectively. Meanwhile, comparing with other fusion methods, it can reduce the complexity and improve the calculation efficiency.

Dynamic and Static End-milling Force Analysis According to Workpiece Geometry (가공물 형상에 따른 동적 및 정적 절삭력 성분 분석법)

  • Yang, Jae-Yong;Yoon, Moon-Chul;Kim, Byung-Tak
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.11 no.4
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    • pp.13-19
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    • 2012
  • There are many dynamic properties in measured end-milling force. So, it is difficult to predict the real static property of end-milling force. Also the behavior of end-milling force is very complex to predict with the measured one. To extract the static property from measured force, it must be filtered and its problem is closely related to a de-noising one. Also this paper presents alternative de-noising method of end-milling force using wavelet filter bank, based on the wavelet transform and its inverse one. In this paper, by comparing the measured force and its wavelet filtered one, the fundamental end-milling force property after wavelet transform is well reviewed and analyzed. This result of wavelet filtering with filter bank shows the static force of end-milling which has severe dynamic properties occurring in entry and exit state of edge emersion into the workpiece.

An Adaptive Active Noise Cancelling Model Using Wavelet Transform and M-channel Subband QMF Filter Banks (웨이브릿 변환 및 M-채널 서브밴드 QMF 필터뱅크를 이용한 적응 능동잡음제거 모델)

  • 허영대;권기룡;문광석
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.1B
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    • pp.89-98
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    • 2000
  • This paper presents an active noise cancelling model using wavelet transform and subband filter banks based on adaptive filter. The analysis filter banks decompose input and error signals into QMF filter banks of lowpass and highpass bands. Each filter bank uses wavelet filter with dyadic tree structure. The decomposed input and error signals are iterated by adaptive filter coefficients of each subband using filtered-X LMS algorithm. The synthesis filter banks make output signal of wideband with perfect reconstruction to prepare adaptive filter output signals of each subband. The analysis and synthesis niter hants use conjugate quadrature filters for Pefect reconstruction. Also, The delayed LMS algorithm model for on-line identification of error path transfer characteristics is used gain and acoustic time delay factors. The proposed adaptive active noise cancelling modelis suggested by system retaining the computational and convergence speed advantage using wavelet subband filter banks.

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Reduction of Speckle Noise in Images Using Homomorphic Wavelet-Based MMSE Filter with Edge Detection (에지 영역을 고려한 호모모르픽 웨이브렛 기반 MMSE 필터를 이용한 영상 신호의 스펙클 잡음 제거)

  • 박원용;장익훈;김남철
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.11C
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    • pp.1098-1110
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    • 2003
  • In this paper, we propose a homomorphic wavelet-based MMSE filter with edge detection to restore images degraded by speckle noise. In the proposed method, a noisy image is first transformed into logarithmic domain. Each pixel in the transformed image is then classified into flat and edge regions by applying DIP operator to the image restored by homomorphic directional MMSE filter. Each pixel in flat region is restored by homomorphic wavelet-based MMSE filter. Each pixel in edge region is restored by the weighted sum of the output of homomorphic wavelet-based MMSE filtering and that of homomorphic directional MMSE filtering. The restored image in spatial domain is finally obtained by applying the exponential function to the restored image in logarithmic domain. Experimental results show that the restored images by the proposed method have ISNR improvement of 3.3-4.0 ㏈ and ${\beta}$, a measurement parameter on edge preservation, improvement of 0.0103-0.0126 and superior subjective image quality over those by conventional methods.

fast running FIR filter structure based on Wavelet adaptive algorithm for computational complexity (웨이블렛 기반 적응 알고리즘의 계산량 감소에 적합한 Fast running FIR filter에 관한 연구)

  • Lee, Jae-Kyun;Lee, Chae-Wook
    • Proceedings of the Korea Institute of Convergence Signal Processing
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    • 2005.11a
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    • pp.250-255
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    • 2005
  • In this paper, we propose a new fast running FIR filter structure that improves the convergence speed of adaptive signal processing and reduces the computational complexity. The proposed filter is applied to wavelet based adaptive algorithm. Actually we compared the performance of the proposed algorithm with other algorithm using computer simulation of adaptive noise canceler based on synthesis speech. As the result, the frequency domain algorithm is prefer than the existent time domain. we analyzed the Wavelet algorithm, short-length fast running FIR algorithm, fast-short-length fast running FIR algorithm and proposed algorithm.

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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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