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Frédéric Patat - One of the best experts on this subject based on the ideXlab platform.
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Estimation of the blood Doppler Frequency shift by a time-varying parametric approach
Ultrasonics, 2000Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric PatatAbstract:– Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performances of those methods deteriorate when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying auto-regressive method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and auto-regressive (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of frequencies tracking and of delay on the Frequency Estimate is illustrated on both simulated and in vivo Doppler signals.
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estimation of the blood doppler Frequency shift by a time varying parametric approach
Ultrasonics, 2000Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric PatatAbstract:Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performance of those methods deteriorates when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying autoregressive (AR) method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and AR (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of Frequency tracking and delay in the Frequency Estimate is illustrated for both simulated and in vivo Doppler signals.
Jean-marc Girault - One of the best experts on this subject based on the ideXlab platform.
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Estimation of the blood Doppler Frequency shift by a time-varying parametric approach
Ultrasonics, 2000Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric PatatAbstract:– Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performances of those methods deteriorate when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying auto-regressive method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and auto-regressive (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of frequencies tracking and of delay on the Frequency Estimate is illustrated on both simulated and in vivo Doppler signals.
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estimation of the blood doppler Frequency shift by a time varying parametric approach
Ultrasonics, 2000Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric PatatAbstract:Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performance of those methods deteriorates when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying autoregressive (AR) method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and AR (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of Frequency tracking and delay in the Frequency Estimate is illustrated for both simulated and in vivo Doppler signals.
Rollin H. Hotchkiss - One of the best experts on this subject based on the ideXlab platform.
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ANALYSIS OF GAUGING STATION FLOOD Frequency EstimateS IN NEBRASKA USING L-MOMENTS AND REGION OF INFLUENCE METHODS
Transportation Research Record, 1998Co-Authors: Mary Kay Provaznik, Rollin H. HotchkissAbstract:Recent advances in predicting flood magnitude and Frequency at streamgauging stations are illustrated using stream flow data from Nebraska. Prediction methods were based on statistical techniques referred to as L-moments and the region of influence method (ROI). L-moments are less sensitive to extremely high or low floods than current procedures and may provide more stable Estimates of flood Frequency. The ROI method for predicting flood Frequency does not depend on fixed hydrologic regions but uses information from all appropriate gauges in the state to form a unique region and Frequency Estimate for each site. Estimates of the 100-year flood using current procedures showed statistically significant differences from Estimates made using a generalized extreme value distribution with L-moments. Differences were due to the treatment of extreme flood events and illustrate the robust character of L-moments. L-moments were less sensitive to extreme floods as expected. Creating regions using the ROI method was ...
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Analysis of Gauging Station Flood Frequency Estimates in Nebraska Using L-Moments and Region of Influence Methods
Transportation Research Record: Journal of the Transportation Research Board, 1998Co-Authors: Mary Kay Provaznik, Rollin H. HotchkissAbstract:Recent advances in predicting flood magnitude and Frequency at streamgauging stations are illustrated using stream flow data from Nebraska. Prediction methods were based on statistical techniques referred to as L-moments and the region of influence method (ROI). L-moments are less sensitive to extremely high or low floods than current procedures and may provide more stable Estimates of flood Frequency. The ROI method for predicting flood Frequency does not depend on fixed hydrologic regions but uses information from all appropriate gauges in the state to form a unique region and Frequency Estimate for each site. Estimates of the 100-year flood using current procedures showed statistically significant differences from Estimates made using a generalized extreme value distribution with L-moments. Differences were due to the treatment of extreme flood events and illustrate the robust character of L-moments. L-moments were less sensitive to extreme floods as expected. Creating regions using the ROI method was found to be sensitive to the selection of basin attributes for assembling sites, but was not sensitive to the number of gauges initially used to create a region, nor the criterion used to eliminate a gauge from a potential region. Statistical tests revealed insignificant differences between ROI Estimates of the 100-year flood when compared with Estimates using current procedures. The similarity in Estimates is attributed to current “filtering” procedures used that reduce the impact of extreme events. The ROI method is viewed as a more objective method of achieving the same result.
H.c. So - One of the best experts on this subject based on the ideXlab platform.
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unitary puma algorithm for estimating the Frequency of a complex sinusoid
IEEE Transactions on Signal Processing, 2015Co-Authors: Cheng Qian, H.c. So, Lei Huang, Nicholas D SidiropoulosAbstract:One-dimensional (1-D) and two-dimensional (2-D) Frequency estimation for a single complex sinusoid in white Gaussian noise is a classic signal processing problem with numerous applications. It is revisited here through a new unitary principal-singular-vector utilization modal analysis (PUMA) approach, which is realized in terms of real-valued computations. The 2-D unitary PUMA is first formulated as an iteratively weighted least squares optimization problem. Recognizing that only one iteration is sufficient when 2-D unitary PUMA is initialized using least squares, a computationally attractive closed-form solution is then obtained. A variant of 2-D unitary PUMA is also developed for the 1-D case. Due to the real-valued computations and closed-form expression for the Frequency Estimate, the unitary PUMA is more computationally efficient than a number of state-of-the-art methods. Furthermore, the asymptotic variances of 1-D and 2-D unitary PUMA estimators are theoretically derived, and numerical results are included to demonstrate the effectiveness of the proposed methods.
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closed form unbiased Frequency estimation of a noisy sinusoid using notch filters
IEEE Transactions on Automatic Control, 2003Co-Authors: Sergio Maria Savaresi, Sergio Bittanti, H.c. SoAbstract:In this note, the problem of the Frequency estimation of a sinusoid embedded in white noise is considered. The approach used herein is the minimization of the sample variance of the output of constrained notch filters fed by the noisy sinusoid. In particular, this note focuses on closed-form expressions of the Frequency Estimate, which can be obtained using notch filters having an all-zeros finite-impulse response (FIR) structure. The results presented in this note are as follows: 1) it is shown that the FIR notch filters obtained from standard second-order infinite-impulse response (IIR) filters are inadequate; 2) a new second-order IIR notch filter is proposed, which provides an unbiased Estimate of the Frequency; 3) the FIR filter obtained from the new IIR filter provides a closed-form unbiased Frequency Estimate; and 4) the closed-form Frequency Estimate obtained using the new FIR notch filter asymptotically converges toward the Pisarenko harmonic decomposition estimator and the Yule-Walker estimator.
Denis Kouamé - One of the best experts on this subject based on the ideXlab platform.
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Estimation of the blood Doppler Frequency shift by a time-varying parametric approach
Ultrasonics, 2000Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric PatatAbstract:– Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performances of those methods deteriorate when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying auto-regressive method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and auto-regressive (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of frequencies tracking and of delay on the Frequency Estimate is illustrated on both simulated and in vivo Doppler signals.
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estimation of the blood doppler Frequency shift by a time varying parametric approach
Ultrasonics, 2000Co-Authors: Jean-marc Girault, Denis Kouamé, Abdeldjalil Ouahabi, Frédéric PatatAbstract:Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and Frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provides a time-Frequency representation, is limited by the intrinsic trade-off between time and Frequency resolutions. Parametric methods have then been introduced as an alternative to overcome this resolution problem. However, the performance of those methods deteriorates when high non-stationarities are present in the Doppler signal. For the purpose of accurately estimating the Doppler Frequency shift, even when the temporal flow velocity is rapid (high non-stationarity), we propose to combine the use of the time-varying autoregressive (AR) method and the (dominant) pole Frequency. This proposed method performs well in the context where non-stationarities are very high. A comparative evaluation has been made between classical (FFT based) and AR (both block and recursive) algorithms. Among recursive algorithms we test an adaptive recursive method as well as a time-varying recursive method. Finally, the superiority of the time-varying parametric approach in terms of Frequency tracking and delay in the Frequency Estimate is illustrated for both simulated and in vivo Doppler signals.