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Attenuation

The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform

Mircea Calomfirescu – 1st expert on this subject based on the ideXlab platform

  • theoretical and experimental studies of lamb wave propagation in attenuative composites
    The 14th International Symposium on: Smart Structures and Materials & Nondestructive Evaluation and Health Monitoring, 2007
    Co-Authors: Mircea Calomfirescu, Axel S Herrmann

    Abstract:

    This paper presents a theoretical model for anisotropic wave Attenuation in composites. The model has been implemented in a software called FIBREWAVE in order to predict dispersion and Attenuation of S 0 , A 0 and SH 0 Lamb wave modes. The required input data are the complex stiffness matrix coefficients of the unidirectional plies of the laminate, which have been measured by a laser interferometry method. Complex stiffness data for an unidirectional CFRP laminates are moreover presented. Satisfactory agreement has been observed between predicted and experimental group velocities and wave Attenuations.

Guy Cloutier – 2nd expert on this subject based on the ideXlab platform

  • a frequency shift method to measure shear wave Attenuation in soft tissues
    IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, 2017
    Co-Authors: Simon Bernard, Siavash Kazemirad, Guy Cloutier

    Abstract:

    In vivo quantification of shear-wave Attenuation in soft tissues may help to better understand human tissue rheology and lead to new diagnostic strategies. Attenuation is difficult to measure in acoustic radiation force elastography because the shear-wave amplitude decreases due to a combination of diffraction and viscous Attenuation. Diffraction correction requires assuming a cylindrical wavefront and an isotropic propagation medium, which may not be the case in some applications. In this paper, the frequency-shift method, used in ultrasound imaging and seismology, was adapted for shear-wave Attenuation measurement in elastography. This method is not sensitive to diffraction effects. For a linear frequency dependence of the Attenuation, a closed-form relation was obtained between the decrease in the peak frequency of the gamma-distributed wave amplitude spectrum and the Attenuation coefficient of the propagation medium. The proposed method was tested against a plane-wave reference method in homogeneous agar–gelatin phantoms with 0%, 10%, and 20% oil concentrations, and hence different Attenuations of 0.117, 0.202, and 0.292 $\text {Np}\cdot \text {m}^{-1}$ /Hz, respectively. Applicability to biological tissues was demonstrated with two ex vivo porcine liver samples (0.79 and 1.35 $\text {Np} \,\cdot \, \text {m}^{-1}$ /Hz) and an in vivo human muscle, measured along (0.43 $\text {Np}\,\cdot \, \text {m}^{-1}$ /Hz) and across (1.77 $\text {Np}\cdot \text {m}^{-1}$ /Hz) the tissue fibers. In all cases, the data supported the assumptions of a gamma-distributed spectrum for the source and linear frequency Attenuation for the tissue. This method provides tissue Attenuation, which is relevant diagnostic information to model viscosity, in addition to shear-wave velocity used to assess elasticity. Data processing is simple and could be performed automatically in real time for clinical applications.

  • A Frequency-Shift Method to Measure Shear-Wave Attenuation in Soft Tissues
    IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, 2017
    Co-Authors: Simon Bernard, Siavash Kazemirad, Guy Cloutier

    Abstract:

    In vivo quantification of shear-wave Attenuation in soft tissues may help to better understand human tissue rheology and lead to new diagnostic strategies. Attenuation is difficult to measure in acoustic radiation force elastography because the shear-wave amplitude decreases due to a combination of diffraction and viscous Attenuation. Diffraction correction requires assuming a cylindrical wavefront and an isotropic propagation medium, which may not be the case in some applications. In this paper, the frequency-shift method, used in ultrasound imaging and seismology, was adapted for shear-wave Attenuation measurement in elastography. This method is not sensitive to diffraction effects. For a linear frequency dependence of the Attenuation, a closed-form relation was obtained between the decrease in the peak frequency of the gamma-distributed wave amplitude spectrum and the Attenuation coefficient of the propagation medium. The proposed method was tested against a plane-wave reference method in homogeneous agar-gelatin phantoms with 0%, 10%, and 20% oil concentrations, and hence different Attenuations of 0.117, 0.202, and 0.292 Np · m-1/Hz, respectively. Applicability to biological tissues was demonstrated with two ex vivo porcine liver samples (0.79 and 1.35 Np · m-1/Hz) and an in vivo human muscle, measured along (0.43 Np · m-1/Hz) and across (1.77 Np · m-1/Hz) the tissue fibers. In all cases, the data supported the assumptions of a gamma-distributed spectrum for the source and linear frequency Attenuation for the tissue. This method provides tissue Attenuation, which is relevant diagnostic information to model viscosity, in addition to shear-wave velocity used to assess elasticity. Data processing is simple and could be performed automatically in real time for clinical applications.

Axel S Herrmann – 3rd expert on this subject based on the ideXlab platform

  • theoretical and experimental studies of lamb wave propagation in attenuative composites
    The 14th International Symposium on: Smart Structures and Materials & Nondestructive Evaluation and Health Monitoring, 2007
    Co-Authors: Mircea Calomfirescu, Axel S Herrmann

    Abstract:

    This paper presents a theoretical model for anisotropic wave Attenuation in composites. The model has been implemented in a software called FIBREWAVE in order to predict dispersion and Attenuation of S 0 , A 0 and SH 0 Lamb wave modes. The required input data are the complex stiffness matrix coefficients of the unidirectional plies of the laminate, which have been measured by a laser interferometry method. Complex stiffness data for an unidirectional CFRP laminates are moreover presented. Satisfactory agreement has been observed between predicted and experimental group velocities and wave Attenuations.