Estimation of total attenuation and scatterer size from backscattered ultrasound waveforms

2005 ◽  
Vol 117 (3) ◽  
pp. 1431-1439 ◽  
Author(s):  
Timothy A. Bigelow ◽  
Michael L. Oelze ◽  
William D. O’Brien
Keyword(s):  
Total Attenuation ◽  
Scatterer Size

Conductivity and scattering Q in GPR data: Example from the Ellenburger dolomite, central Texas

Geophysics ◽  
2012 ◽  
Vol 77 (4) ◽  
pp. H63-H78 ◽  
Author(s):  
Hussein Harbi ◽  
George A. McMechan
Keyword(s):  
Dielectric Relaxation ◽  
Synthetic Data ◽  
Total Attenuation ◽  
Frequency Independent ◽  
Scattering Spectra ◽  
Central Texas ◽  
The Difference ◽  
Scattering Contribution ◽  
Ground Penetrating ◽  
Scatterer Size

Total attenuation ([Formula: see text]) in ground-penetrating radar (GPR) data is a composite of intrinsic and scattering attenuations ([Formula: see text] and [Formula: see text]). For nonmagnetic materials, [Formula: see text] is a combination of the effects of real conductivity and dielectric relaxation. The attenuation for real conductivity [Formula: see text] in the GPR frequency band is a function of frequency while the dielectric relaxation is frequency-independent. These frequency behaviors allow separation of the attenuation types by attributing and fitting the [Formula: see text] decay shape with frequency to the conductivity, and by attributing the magnitude of [Formula: see text] to the sum of conductivity and dielectric relaxation attenuations at each frequency. Total attenuation is calculated from GPR data using spectral ratios, and [Formula: see text] is obtained by fitting a smooth lower bound to [Formula: see text]; the difference between [Formula: see text] and [Formula: see text] estimates the scattering contribution [Formula: see text]. Scatterer size spectra are evaluated using [Formula: see text] for 2D, and [Formula: see text] for 3D, propagation (where [Formula: see text] is wavenumber and [Formula: see text] is the scatterer size). We illustrate with 2D synthetic data and three field 2D crosshole profiles from an outcrop of an Ellenburger collapsed paleocave environment in central Texas. Between the three pairs of holes, we estimate the breccia sizes from the scattering spectra [Formula: see text]. To image the anisotropic electrical conductivity distributions, we use simultaneous iterative reconstruction tomography. There is a correlation between the low wavenumber features of the results of the current conductivity tomography and those in previous velocity tomography, and with surface data results that are predicted and calculated from GPR data attributes. Low- and high-conductivity zones tend to follow either the GPR facies distributions, lithological boundaries, or the larger of the fractures. Correlations are not visible where the breccias are finer because these tend to be more randomly oriented, and/or below the resolution of the GPR data.

scholarly journals In vivo attenuation and equivalent scatterer size parameters for atherosclerotic carotid plaque: Preliminary results

Ultrasonics ◽  
2009 ◽  
Vol 49 (8) ◽  
pp. 779-785 ◽  
Author(s):  
Hairong Shi ◽  
Tomy Varghese ◽  
Carol C. Mitchell ◽  
Matthew McCormick ◽  
Robert J. Dempsey ◽  
...  
Keyword(s):  
Carotid Plaque ◽  
Preliminary Results ◽  
Scatterer Size

scholarly journals Radiometric Performance Evaluation of FY-4A/AGRI Based on Aqua/MODIS

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1859
Author(s):  
Bo Zhong ◽  
Yingbo Ma ◽  
Aixia Yang ◽  
Junjun Wu
Keyword(s):  
Near Infrared ◽  
Spectral Response ◽  
Convective Cloud ◽  
Radiation Level ◽  
High Attenuation ◽  
Total Attenuation ◽  
Attenuation Rate ◽  
Calibration Facility ◽  
Deep Convective Cloud ◽  
Directional Reflectance

Fengyun-4A (FY-4A) is the first satellite of the Chinese second-generation geostationary orbit meteorological satellites (FY-4). The Advanced Geostationary Radiation Imager (AGRI), onboard FY-4A does not load with high-precision calibration facility in visible and near infrared (VNIR) channel. As a consequence, it is necessary to comprehensively evaluate its radiometric performance and quantitatively describe the attenuation while using its VNIR data. In this paper, the radiometric performance at VNIR channels of FY-4A/AGRI is evaluated based on Aqua/MODIS data using the deep convective cloud (DCC) target. In order to reduce the influence of view angle and spectral response difference, the bi-directional reflectance distribution function (BRDF) correction and spectral matching have been performed. The evaluation result shows the radiometric performance of FY-4A/AGRI: (1) is less stable and with obvious fluctuations; (2) has a lower radiation level because of 24.99% lower compared with Aqua/MODIS; 3) has a high attenuation with 9.11% total attenuation over 2 years and 4.0% average annual attenuation rate. After the evaluation, relative radiometric normalization between AGRI and MODIS in VNIR channel is performed and the procedure is proved effective. This paper proposed a more reliable reference for the quantitative applications of FY-4A data.

2G-5 Methods for Improvement on Liver Scatterer Size Estimates

2006 ◽  
Author(s):  
W. Liu ◽  
J. A. Zagzebski ◽  
A. L. Gerig ◽  
T. Varghese ◽  
E. C. Marquez ◽  
...  
Keyword(s):  
Scatterer Size ◽  
Size Estimates

Intrinsic and Scattering Attenuations in the Crust of the Racha Region, Georgia

2019 ◽  
Vol 14 (02) ◽  
pp. 2050006
Author(s):  
Ia Shengelia ◽  
Nato Jorjiashvili ◽  
Tea Godoladze ◽  
Zurab Javakhishvili ◽  
Nino Tumanova
Keyword(s):  
Time Window ◽  
Frequency Range ◽  
Quality Factors ◽  
Lapse Time ◽  
Intrinsic Attenuation ◽  
Total Attenuation ◽  
Relative Contribution ◽  
Normalization Methods ◽  
Coda Normalization ◽  
Back Scattering

Three hundred and thirty-five local earthquakes were processed and the attenuation properties of the crust in the Racha region were investigated using the records of seven seismic stations. We have estimated the quality factors of coda waves ([Formula: see text]) and the direct [Formula: see text] waves ([Formula: see text]) by the single back scattering model and the coda normalization methods, respectively. The Wennerberg’s method has been used to estimate relative contribution of intrinsic ([Formula: see text]) and scattering ([Formula: see text]) attenuations in the total attenuation. We have found that [Formula: see text] and [Formula: see text] parameters are frequency-dependent in the frequency range of 1.5–24[Formula: see text]Hz. [Formula: see text] values increase both with respect to lapse time window from 20[Formula: see text]s to 60[Formula: see text]s and frequency. [Formula: see text] and [Formula: see text] parameters are nearly similar for all frequency bands, but are smaller than [Formula: see text]. The obtained results show that the intrinsic attenuation has more significant effect than scattering attenuation in the total attenuation. The increase of [Formula: see text] with lapse time shows that the lithosphere becomes more homogeneous with depth.

Sign in / Sign up

Export Citation Format

Share Document