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Articles de revues sur le sujet « Tomography and anisotropy »

Auteur : Grafiati

Publié le 10 mars 2023

Mis à jour le 31 juillet 2025

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1

Carrion, Philip, Jesse Costa, Jose E. Ferrer Pinheiro, and Michael Schoenberg. "Cross‐borehole tomography in anisotropic media." GEOPHYSICS 57, no. 9 (1992): 1194–98. http://dx.doi.org/10.1190/1.1443333.

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Anisotropy has significant effect on traveltime cross‐borehole tomography. Even relatively weak anisotropy cannot be ignored if accurate velocity estimates are desired, since isotropic traveltime tomography treats anisotropy as inhomogeneity. Traveltime data in our examples were synthetically generated by a ray‐tracing code for anisotropic media, and the computed quasi‐P‐wave traveltimes were subsequently inverted using the “dual tomography” technique (Carrion, 1991). The results of the tomographic inversion show typical artifacts due to the anisotropy, and that accurate imaging is impossible

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Koren, Zvi, Igor Ravve, Gladys Gonzalez, and Dan Kosloff. "Anisotropic local tomography." GEOPHYSICS 73, no. 5 (2008): VE75—VE92. http://dx.doi.org/10.1190/1.2953979.

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Local tomography is interactive, ray-based, residual-interval-parameter analysis for updating background anisotropic velocity parameters. The method operates directly on image gathers generated by anisotropic curved-ray Kirchhoff time migration. A locally 1D, spatially varying, vertical transversely isotropic model is assumed. The background anisotropy parameters are the instantaneous (interval) vertical compression velocity [Formula: see text] and the two Thomsen anisotropy parameters, [Formula: see text] and [Formula: see text]. The interval velocity [Formula: see text] is updated from short

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Confal, Judith M., Paola Baccheschi, Silvia Pondrelli, et al. "Reproducing complex anisotropy patterns at subduction zones from splitting intensity analysis and anisotropy tomography." Geophysical Journal International 235, no. 2 (2023): 1725–35. http://dx.doi.org/10.1093/gji/ggad329.

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SUMMARY Measurements of seismic anisotropy provide a lot of information on the deformation and structure as well as flows of the Earth's interior, in particular of the upper mantle. Even though the strong and heterogeneous seismic anisotropic nature of the upper mantle has been demonstrated by a wealth of theoretical and observational approaches , most of standard teleseismic body-wave tomography studies overlook P- and S-wave anisotropy, thus producing artefacts in tomographic models in terms of amplitude and localization of heterogeneities. Conventional methods of seismic anisotropy measurem

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4

Pratt, R. G., W. J. McGaughey, and C. H. Chapman. "Anisotropic velocity tomography: A case study in a near‐surface rock mass." GEOPHYSICS 58, no. 12 (1993): 1748–63. http://dx.doi.org/10.1190/1.1443389.

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Cross‐borehole data were acquired in the surface crown pillar of a massive sulfide ore mine. The data consist of five, two‐dimensional (2-D), cross‐borehole panels, each with approximately 900 source‐receiver pairs. The panels were located within the crown pillar at either side of and within a major subvertical fault zone that intersects the orebody. An initial analysis of the data indicates that the bedrock containing the orebody is seismically anisotropic. A rigorous analysis of the traveltimes using anisotropic velocity tomography confirms the initial assessment that anisotropy exists withi

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Zhou, Chaoguang, Junru Jiao, Sonny Lin, John Sherwood, and Sverre Brandsberg-Dahl. "Multiparameter joint tomography for TTI model building." GEOPHYSICS 76, no. 5 (2011): WB183—WB190. http://dx.doi.org/10.1190/geo2010-0395.1.

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Model building for tilted transversely isotropic media has commonly been performed by a single parameter tomography that updates the velocity in the symmetry direction, while the orientation of the symmetry axis and Thomsen parameters [Formula: see text] and [Formula: see text] are typically estimated from the migration stack and well data. Unfortunately, well data are often not available. In addition, when they are available, their lateral sampling is typically very sparse and their vertical sampling usually spans only a limited range of depths. In order to obtain spatially varying anisotropi

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Hadden, Shaun, R. Gerhard Pratt, and Brendan Smithyman. "Anisotropic full-waveform inversion of crosshole seismic data: A vertical symmetry axis field data application." GEOPHYSICS 84, no. 1 (2019): B15—B32. http://dx.doi.org/10.1190/geo2017-0790.1.

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Anisotropic waveform tomography (AWT) uses anisotropic traveltime tomography followed by anisotropic full-waveform inversion (FWI). Such an approach is required for FWI in cases in which the geology is likely to exhibit anisotropy. An important anisotropy class is that of transverse isotropy (TI), and the special case of TI media with a vertical symmetry axis (VTI) media is often used to represent elasticity in undeformed sedimentary layering. We have developed an approach for AWT that uses an acoustic approximation to simulate waves in VTI media, and we apply this approach to crosshole data.

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Michelena, Reinaldo J. "Singular value decomposition for cross‐well tomography." GEOPHYSICS 58, no. 11 (1993): 1655–61. http://dx.doi.org/10.1190/1.1443381.

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I perform singular value decomposition (SVD) on the matrices that result in tomographic velocity estimation from cross‐well traveltimes in isotropic and anisotropic media. The slowness model is parameterized in four ways: One‐dimensional (1-D) isotropic, 1-D anisotropic, two‐dimensional (2-D) isotropic, and 2-D anisotropic. The singular value distribution is different for the different parameterizations. One‐dimensional isotropic models can be resolved well but the resolution of the data is poor. One‐dimensional anisotropic models can also be resolved well except for some variations in the ver

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Gao, Zirui, Manuel Guizar-Sicairos, Viviane Lutz-Bueno, et al. "High-speed tensor tomography: iterative reconstruction tensor tomography (IRTT) algorithm." Acta Crystallographica Section A Foundations and Advances 75, no. 2 (2019): 223–38. http://dx.doi.org/10.1107/s2053273318017394.

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The recent advent of tensor tomography techniques has enabled tomographic investigations of the 3D nanostructure organization of biological and material science samples. These techniques extended the concept of conventional X-ray tomography by reconstructing not only a scalar value such as the attenuation coefficient per voxel, but also a set of parameters that capture the local anisotropy of nanostructures within every voxel of the sample. Tensor tomography data sets are intrinsically large as each pixel of a conventional X-ray projection is substituted by a scattering pattern, and projection

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Leinss, S., H. Löwe, M. Proksch, J. Lemmetyinen, A. Wiesmann, and I. Hajnsek. "Anisotropy of seasonal snow measured by polarimetric phase differences in radar time series." Cryosphere Discussions 9, no. 6 (2015): 6061–123. http://dx.doi.org/10.5194/tcd-9-6061-2015.

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Abstract. Snow settles under the force of gravity and recrystallizes by vertical temperature gradients. Both effects are assumed to form oriented ice crystals which induce an anisotropy in mechanical, thermal, and dielectric properties of the snow pack. On microscopic scales, the anisotropy could be hitherto determined only from stereology or computer tomography of samples taken from snow pits. In this paper we present an alternative method and show how the anisotropy of a natural snow pack can be observed contact- and destruction-free with polarimetric radar measurements. The copolar phase di

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10

Han, S.-M., and J.-Y. Rho. "Dependence of broadband ultrasound attenuation on the elastic anisotropy of trabecular bone." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 212, no. 3 (1998): 223–26. http://dx.doi.org/10.1243/0954411981534006.

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The effect of trabecular elastic anisotropy on broadband ultrasound attenuation (BUA) and bone mineral density (BMD) was investigated with human and bovine cubic cancellous bones. Ultrasonic parameters describing trabecular anisotropy were found from the three orthogonal ultrasound velocities. BMD was measured using quantitative computed tomography. Three elastic anisotropy ratios were compared to BUA in all three directions and to BMD. The combined effect of anisotropic characteristics and BMD was also correlated with BUA. The results showed that the anisotropy ratios were significantly relat

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Pratt, R. Gerhard, and Mark S. Sams. "Reconciliation of crosshole seismic velocities with well information in a layered sedimentary environment." GEOPHYSICS 61, no. 2 (1996): 549–60. http://dx.doi.org/10.1190/1.1443981.

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In sedimentary environments, horizontal fine layering can cause significant complications when analyzing and comparing seismic data with different frequencies and propagation directions. At the Whitchester test site, three boreholes penetrate upper Carboniferous cyclical sediments, involving interbedded carbonates, sandstones, and mudstones, with seismic velocities ranging from less than 3.0 km/s in the mudstones to over 4.5 km/s in the carbonates. Initial crosshole results from two boreholes approximately 200 m deep and 75 m apart showed a poor correlation with the borehole logs recorded in a

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Leinss, Silvan, Henning Löwe, Martin Proksch, Juha Lemmetyinen, Andreas Wiesmann, and Irena Hajnsek. "Anisotropy of seasonal snow measured by polarimetric phase differences in radar time series." Cryosphere 10, no. 4 (2016): 1771–97. http://dx.doi.org/10.5194/tc-10-1771-2016.

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Abstract. The snow microstructure, i.e., the spatial distribution of ice and pores, generally shows an anisotropy which is driven by gravity and temperature gradients and commonly determined from stereology or computer tomography. This structural anisotropy induces anisotropic mechanical, thermal, and dielectric properties. We present a method based on radio-wave birefringence to determine the depth-averaged, dielectric anisotropy of seasonal snow with radar instruments from space, air, or ground. For known snow depth and density, the birefringence allows determination of the dielectric anisot

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13

Zhang, Chao, Xiangzhuang Kong, Xian Wang, Yanxia Du, and Guangming Xiao. "A Predicting Model for the Effective Thermal Conductivity of Anisotropic Open-Cell Foam." Energies 15, no. 16 (2022): 6091. http://dx.doi.org/10.3390/en15166091.

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The structural anisotropy of open-cell foam leads to the anisotropy of effective thermal conductivity (ETC). To quantitatively analyze the effect of structural anisotropy on the anisotropy of ETC, a new predicting model for the ETC of anisotropic open-cell foam was proposed based on an anisotropy tetrakaidecahedron cell (ATC). Feret diameters in three orthogonal directions obtained by morphological analysis of real foam structures were used to characterize the anisotropy of ATC. To validate our proposed anisotropic model, the ETCs of real foam structures in three orthogonal directions predicte

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VanderBeek, Brandon P., and Manuele Faccenda. "Imaging upper mantle anisotropy with teleseismic P-wave delays: insights from tomographic reconstructions of subduction simulations." Geophysical Journal International 225, no. 3 (2021): 2097–119. http://dx.doi.org/10.1093/gji/ggab081.

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SUMMARY Despite the well-established anisotropic nature of Earth’s upper mantle, the influence of elastic anisotropy on teleseismic P-wave imaging remains largely ignored. Unmodelled anisotropic heterogeneity can lead to substantial isotropic velocity artefacts that may be misinterpreted as compositional heterogeneities. Recent studies have demonstrated the possibility of inverting P-wave delay times for the strength and orientation of seismic anisotropy. However, the ability of P-wave delay times to constrain complex anisotropic patterns, such as those expected in subduction settings, remains

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Gosselin, Jeremy M., Pascal Audet, Andrew J. Schaeffer, Fiona A. Darbyshire, and Clément Estève. "Azimuthal anisotropy in Bayesian surface wave tomography: application to northern Cascadia and Haida Gwaii, British Columbia." Geophysical Journal International 224, no. 3 (2020): 1724–41. http://dx.doi.org/10.1093/gji/ggaa561.

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SUMMARY Surface wave tomography is a valuable tool for constraining azimuthal anisotropy at regional scales. However, sparse and uneven coverage of dispersion measurements make meaningful uncertainty estimation challenging, especially when applying subjective model regularization. This paper considers azimuthal anisotropy constrained by measurements of surface wave dispersion data within a Bayesian trans-dimensional (trans-d) tomographic inversion. A recently proposed alternative model parametrization for trans-d inversion is implemented in order to produce more realistic models than previous

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Chang, Young-Fo, Wei-Zhih Chang, and Lun-Tao Tong. "Detect Multiple-Set Fractures by Crosshole Seismic Tomography for use in Environmental and Engineering Geophysics." Journal of Environmental and Engineering Geophysics 29, no. 2 (2024): 61–74. http://dx.doi.org/10.32389/jeeg22-037.

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Crosshole seismic tomography (CST) could be used to reconstruct the velocity section of media between two holes. One commonly used attribute of fractures reflected in seismic waves is the anisotropy of velocity. Therefore, in this study, the multiple symmetry axes of anisotropic media are utilized to simulate the multiple-set fractures in strata. The anisotropic algebraic reconstruction technique (AART) and anisotropic simultaneous iterative reconstruction technique (ASIRT), extensions of isotropic ART and SIRT, are developed to detect the medium with multiple symmetry axes and strong anisotro

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Shalaginov, Aleksandr, Nina Nevedrova, Aidisa Sanchaa, Ilya Shaparenko, and Petr Ponomarev. "ELECTRICAL ANISOTROPY ACCORDING TO DC METHODS IN THE BYSTROVKA FIELD AREA (SHORE RESERVOIR IN THE NOVOSIBIRSK REGION)." Interexpo GEO-Siberia 2, no. 2 (2019): 158–64. http://dx.doi.org/10.33764/2618-981x-2019-2-2-158-164.

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The article presents the results of the study of electrical anisotropy by two methods of DC (vertical electrical sounding and electrical tomography) in the area of the Bystrovka field area, on the shore of the Novosibirsk reservoir. Taking into account a priori well data, the parameters of the geoelectric model and the anisotropic characteristics of the section are determined. On the site of the study, according to the data of two methods, electrical anisotropy observed in the reference geoelectric horizon, represented by shale. In addition, the main direction of crack propagation is determine

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Bukreev, D. A., M. S. Derevyanko, A. A. Moiseev, and A. V. Semirov. "Magneto-impedance tomography of CoFeTaSiB amorphous wires." Физика металлов и металловедение 124, no. 8 (2023): 710–16. http://dx.doi.org/10.31857/s0015323023600673.

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The paper presents the results of a study of the radial distribution of the magnetic permeability of an Co66Fe4Ta2.5Si12.5B15 amorphous wire with a radius of 55 μm. The study was performed using magneto-impedance tomography in the frequency range of alternating current from 0.01 to 100 MHz. It was found that the magnetic permeability significantly depends on the radial coordinate. Wherein the inner regions of the wire have predominantly axial anisotropy, while the outer layer about 2.5 µm thick has circular anisotropy. It is shown that the magnetoelastic mechanism is not the main one in the fo

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Pandey, Biswajit. "Tomography of stellar halos: what does anisotropy in a stellar halo tell us?" Journal of Cosmology and Astroparticle Physics 2022, no. 10 (2022): 058. http://dx.doi.org/10.1088/1475-7516/2022/10/058.

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Abstract The stellar halo of the Milky Way is known to have a highly lumpy structure due to the presence of tidal debris and streams accreted from the satellite galaxies. The abundance and distribution of these substructures can provide a wealth of information on the assembly history of the Milky Way. We use some information-theoretic measures to study the anisotropy in a set of Milky Way-sized stellar halos from the Bullock & Johnston suite of simulations that uses a hybrid approach coupling semi-analytic and N-body techniques. Our analysis shows that the whole-sky anisotropy in each stel

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Rao, Ying, Yanghua Wang, Shumin Chen, and Jianmin Wang. "Crosshole seismic tomography with cross-firing geometry." GEOPHYSICS 81, no. 4 (2016): R139—R146. http://dx.doi.org/10.1190/geo2015-0677.1.

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We have developed a case study of crosshole seismic tomography with a cross-firing geometry in which seismic sources were placed in two vertical boreholes alternatingly and receiver arrays were placed in another vertical borehole. There are two crosshole seismic data sets in a conventional sense. These two data sets are used jointly in seismic tomography. Because the local sediment is dominated by periodic, flat, thin layers, there is seismic anisotropy with different velocities in the vertical and horizontal directions. The vertical transverse isotropy anisotropic effect is taken into account

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Woodward, Marta Jo, Dave Nichols, Olga Zdraveva, Phil Whitfield, and Tony Johns. "A decade of tomography." GEOPHYSICS 73, no. 5 (2008): VE5—VE11. http://dx.doi.org/10.1190/1.2969907.

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Over the past 10 years, ray-based postmigration grid tomography has become the standard model-building tool for seismic depth imaging. While the basics of the method have remained unchanged since the late 1990s, the problems it solves have changed dramatically. This evolution has been driven by exploration demands and enabled by computer power. There are three main areas of change. First, standard model resolution has increased from a few thousand meters to a few hundred meters. This order of magnitude improvement may be attributed to both high-quality, complex residual-moveout data picked as

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Yang, Eomzi, Tae Sup Yun, Kwang Yeom Kim, Seong Woo Moon та Yong-Seok Seo. "Estimation of the Structural and Geomechanical Anisotropy in Fault Gouges Using 3D Micro-Computed Tomography (μ-CT)". Sensors 20, № 17 (2020): 4706. http://dx.doi.org/10.3390/s20174706.

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Fault gouges play an important role in the shear deformation of fault zones, by causing weakness and frictional instability in structures. Previous studies have investigated the evolution of shear deformation of fault zones by observing experiments using remolded and synthetic gouge specimens at a micro-scale. However, how the spatial configuration of the rock constituents accounts for the 3D anisotropy of intact structures of fault gouges, particularly at the core-scale, is not well understood. We obtained 3D μ-CT images of directionally cored gouge specimens and performed statistical analysi

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Chen, Liang, Qiang Xiao, Wei Liang, Jingxian Hong, and Xingjiang Zou. "A time-of-flight revising approach to improve the image quality of Lamb wave tomography for the detection of defects in composite panels." Science and Engineering of Composite Materials 25, no. 3 (2018): 587–92. http://dx.doi.org/10.1515/secm-2015-0399.

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Abstract Lamb wave tomography can be used to evaluate structural integrity. The time-of-flight (TOF) data are usually recorded as input to the reconstruction algorithm. For composite materials, TOF estimation is complicated due to their anisotropy. To reduce the effects of anisotropy on image reconstruction, the TOF data of flawed plates are revised according to baseline data obtained from an unflawed plate. Tomographic images are reconstructed using the original and revised TOF data, respectively. Results show that images reconstructed using the revised TOF data have better visual quality and

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Puro, A. �. "Reconstructive tomography with weak optical anisotropy." Journal of Applied Mechanics and Technical Physics 32, no. 2 (1991): 252–55. http://dx.doi.org/10.1007/bf00858045.

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Selvakumaran, Lakshmi, and Gilles Lubineau. "Validation of Micro-Meso Electrical Relations for Laminates with Varying Anisotropy." Applied Mechanics and Materials 784 (August 2015): 435–42. http://dx.doi.org/10.4028/www.scientific.net/amm.784.435.

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For electrical impedance tomography (EIT) to be useful in monitoring transverse cracks in composites, it is imperative to establish the relation between conductivity and cracking density. Micro to meso scale homogenization has been developed for classical carbon fiber reinforced polymer (CFRP) laminate which provides such a relationship. However, we have shown in previous studies that the detectability of transverse cracks in such CFRP, which are characterized by very anisotropic electrical properties, is poor. Then, it is better to lower the electrical anisotropy, which can be achieved by var

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David, Marcelo, Omer Amran, Ron Simhi, and Franco Simini. "Time-Domain Electrical Impedance Tomography by Numerical Analysis of the Step Response." Journal of Physics: Conference Series 2008, no. 1 (2021): 012019. http://dx.doi.org/10.1088/1742-6596/2008/1/012019.

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Abstract This work describes the theoretical basis of an electrical impedance tomography imaging system based on numerical analysis of the step response. Its novelty relies on the use of time domain for rendering the tomographic images. Following the injection of a Heaviside-step current through two electrodes, the voltage-response is measured on all couple of electrodes according to the neighbouring strategy; this process is repeated on every pair of consecutive electrodes. Based on the measurements, a tomographic image is reconstructed using the Gauss-Newton-Raphson algorithm. We tested the

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Palmer, Derecke. "The measurement of weak anisotropy with the generalized reciprocal method." GEOPHYSICS 65, no. 5 (2000): 1583–91. http://dx.doi.org/10.1190/1.1444846.

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Anisotropy parameters can be determined from seismic refraction data using the generalized reciprocal method (GRM) for a layer in which the velocity can be described with the Crampin approximation for transverse isotropy. The parameters are the standard anisotropy factor, which is the horizontal velocity divided by the vertical velocity, and a second poorly determined parameter which, for weak anisotropy, is approximated by a linear relationship with the anisotropy factor. Although only one anisotropy parameter is effectively determined, the second parameter is essential to ensure that the ani

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Mastio, Nicolas, Pierre Thore, Marianne Conin, and Guillaume Caumon. "Determination of a stress-dependent rock-physics model using anisotropic time-lapse tomographic inversion." GEOPHYSICS 85, no. 4 (2020): C141—C152. http://dx.doi.org/10.1190/geo2019-0526.1.

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In the petroleum industry, time-lapse (4D) studies are commonly used for reservoir monitoring, but they are also useful to perform risk assessment for potential overburden deformations (e.g., well shearing, cap-rock integrity). Although complex anisotropic velocity changes are predicted in the overburden by geomechanical studies, conventional time-lapse inversion workflows only deal with vertical velocity changes. To retrieve the geomechanically induced anisotropy, we have adopted a reflection traveltime tomography method coupled with a time-shift estimation algorithm of prestack data of the b

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Liu, Yongsheng, and Ping Tong. "Eikonal equation-based P-wave seismic azimuthal anisotropy tomography of the crustal structure beneath northern California." Geophysical Journal International 226, no. 1 (2021): 287–301. http://dx.doi.org/10.1093/gji/ggab103.

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SUMMARY Delineating spatial variations of seismic anisotropy in the crust is of great importance for the understanding of structural heterogeneities, regional stress regime and ongoing crustal dynamics. In this study, we present a 3-D anisotropic P-wave velocity model of the crust beneath northern California by using the eikonal equation-based seismic azimuthal anisotropy tomography method. The velocity heterogeneities under different geological units are well resolved. The thickness of the low-velocity sediment at the Great Valley Sequence is estimated to be about 10 km. The high-velocity ano

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Vasco, Don W., John E. Peterson, and Ki Ha Lee. "Ground‐penetrating radar velocity tomography in heterogeneous and anisotropic media." GEOPHYSICS 62, no. 6 (1997): 1758–73. http://dx.doi.org/10.1190/1.1444276.

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A ray series solution for Maxwell's equations provides an efficient numerical technique for calculating wavefronts and raypaths associated with electromagnetic waves in anisotropic media. Using this methodology and assuming weak anisotropy, we show that a perturbation of the anisotropic structure may be related linearly to a variation in the traveltime of an electromagnetic wave. Thus, it is possible to infer lateral variations in the dielectric permittivity and magnetic permeability matrices. The perturbation approach is used to analyze a series of crosswell ground‐penetrating radar surveys c

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Kästle, E. D., I. Molinari, L. Boschi, and E. Kissling. "Azimuthal anisotropy from eikonal tomography: example from ambient-noise measurements in the AlpArray network." Geophysical Journal International 229, no. 1 (2021): 151–70. http://dx.doi.org/10.1093/gji/ggab453.

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SUMMARY Ambient-noise records from the AlpArray network are used to measure Rayleigh wave phase velocities between more than 150 000 station pairs. From these, azimuthally anisotropic phase-velocity maps are obtained by applying the eikonal tomography method. Several synthetic tests are shown to study the bias in the Ψ2 anisotropy. There are two main groups of bias, the first one caused by interference between refracted/reflected waves and the appearance of secondary wave fronts that affect the phase traveltime measurements. This bias can be reduced if the amplitude field can be estimated corr

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Peng, Chengbin (Chuck), and Jun Tang. "Automatic early arrival traveltime tomography and its applications." GEOPHYSICS 82, no. 2 (2017): U1—U11. http://dx.doi.org/10.1190/geo2016-0303.1.

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We have developed a method of macrovelocity inversion that does not require explicit picking of either common-image point gathers or first breaks. The method uses head waves, diving waves, and wide-angle reflections in seismic data (collectively early arrival energies) for accurate estimation of velocity and anisotropy parameters. In this method, seismic data are first decomposed into Gaussian packets. Packets associated with early arrival energies are selected and used as input to a tomography solver. The outputs of the solver are velocity and Thomsen’s anisotropy parameters, or any of their

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Wang, Xiaoxiang, and Ilya Tsvankin. "Ray-based gridded tomography for tilted transversely isotropic media." GEOPHYSICS 78, no. 1 (2013): C11—C23. http://dx.doi.org/10.1190/geo2012-0066.1.

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Reflection tomography in the migrated domain can help reconstruct heterogeneous, anisotropic velocity fields needed for accurate depth imaging of complex geologic structures. The presence of anisotropy, however, increases the uncertainty in velocity analysis and typically requires a priori constraints on the model parameters. Here, we develop a 2D P-wave tomographic algorithm for heterogeneous transversely isotropic media with a tilted symmetry axis (TTI) and investigate the conditions necessary for stable estimation of the symmetry-direction velocity [Formula: see text] and the anisotropy par

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Maurer, Hansruedi, Sandy Isabelle Schubert, Fritz Bächle, et al. "A simple anisotropy correction procedure for acoustic wood tomography." Holzforschung 60, no. 5 (2006): 567–73. http://dx.doi.org/10.1515/hf.2006.094.

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Abstract Anisotropy of acoustic propagation velocities is a ubiquitous feature of wood. This needs to be considered for successful application of travel time tomography, an increasingly popular technique for non-destructive testing of living trees. We have developed a simple correction scheme that removes first-order anisotropy effects. The corrected travel-time data can be inverted with isotropic inversion codes that are commercially available. Using a numerical experiment, we demonstrate the consequences of ignoring anisotropy effects and outline the performance of our correction scheme. The

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Guan, Bo, Jianghai Xia, Ya Liu, Hao Zhang, and Changwei Zhou. "Near-Surface Radial Anisotropy Tomography of Geothermal Reservoir Using Dense Seismic Nodal Array." Journal of Physics: Conference Series 2651, no. 1 (2023): 012023. http://dx.doi.org/10.1088/1742-6596/2651/1/012023.

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Abstract The development and utilization of geothermal energy has become an indispensable part in the process of urbanization in China. Near-surface tomographic imaging based on ambient noise is increasingly widely used in geothermal exploration. To construct the subsurface structure of Shear-wave velocity in Andi town, Zhejiang Province, recordings of ambient noise data of 4.7 days were recorded by a dense seismic array composed of 192 stations with an aperture of about 5 km. Analysis of array beamforming in high-frequency bands indicated the approximately uniformly distributed of noise sourc

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Barber, Quinn M., and Roger J. Zemp. "Ultrasound Scattering Anisotropy Visualization With Ultrasound Tomography." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 64, no. 2 (2017): 335–39. http://dx.doi.org/10.1109/tuffc.2016.2622898.

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Rao, Ying, and Yanghua Wang. "Crosshole seismic tomography including the anisotropy effect." Journal of Geophysics and Engineering 8, no. 2 (2011): 316–21. http://dx.doi.org/10.1088/1742-2132/8/2/016.

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Perlin, Lourenço Panosso, Roberto Caldas de Andrade Pinto, and Ângela do Valle. "Ultrasonic tomography in wood with anisotropy consideration." Construction and Building Materials 229 (December 2019): 116958. http://dx.doi.org/10.1016/j.conbuildmat.2019.116958.

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Cagáň, Jan, Jaroslav Pelant, Martin Kyncl, Martin Kadlec, and Lenka Michalcová. "Damage detection in carbon fiber–reinforced polymer composite via electrical resistance tomography with Gaussian anisotropic regularization." Structural Health Monitoring 18, no. 5-6 (2018): 1698–710. http://dx.doi.org/10.1177/1475921718820013.

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Electrical resistance tomography is a method for sensing the spatial distribution of electrical conductivity. Therefore, this type of tomography is suitable for sensing damages, which affect electrical conductivity. The utilization of resistance tomography for the structural health monitoring of carbon fiber–reinforced polymer composites is questionable owing to its low spatial resolution and the strong anisotropy of carbon fiber–reinforced polymer composites. This article deals with the employment of resistance tomography with regularization based on a Gaussian anisotropic smoothing filter fo

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Lines, Larry, Henry Tan, Sven Treitel, et al. "Integrated reservoir characterization: Beyond tomography." GEOPHYSICS 60, no. 2 (1995): 354–64. http://dx.doi.org/10.1190/1.1443771.

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In 1992, there was a collaborative effort in reservoir geophysics involving Amoco, Conoco, Schlumberger, and Stanford University in an attempt to delineate variations in reservoir properties of the Grayburg unit in a West Texas [Formula: see text] pilot at North Cowden Field. Our objective was to go beyond traveltime tomography in characterizing reservoir heterogeneity and flow anisotropy. This effort involved a comprehensive set of measurements to do traveltime tomography, to image reflectors, to analyze channel waves for reservoir continuity, to study shear‐wave splitting for borehole stress

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Tokarska, Magdalena, Ayalew Gebremariam, and Adam K. Puszkarz. "Assessment of the Influence of Fabric Structure on Their Electro-Conductive Properties." Materials 17, no. 11 (2024): 2692. http://dx.doi.org/10.3390/ma17112692.

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Electro-conductive fabrics are key materials for designing and developing wearable smart textiles. The properties of textile materials depend on the production method, the technique which leads to high conductivity, and the structure. The aim of the research work was to determine the factors affecting the electrical conductivity of woven fabrics and elucidate the mechanism of electric current conduction through this complex, aperiodic textile material. The chemical composition of the material surface was identified using scanning electron microscopy energy dispersion X-ray spectroscopy. The va

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Hamanaka, Senji, Chisato Nonomura, Thanh Binh Nguyen Thi, and Atsushi Yokoyama. "Correlation between fiber orientation distribution and mechanical anisotropy in glass-fiber-reinforced composite materials." Journal of Polymer Engineering 39, no. 7 (2019): 653–60. http://dx.doi.org/10.1515/polyeng-2018-0371.

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Abstract This study investigates the correlation between the fiber orientation distribution along the thickness and mechanical anisotropy in injection-molded products using a thermoplastic resin reinforced by short fibers. To this end, polyamide-6 samples containing 15, 30, 50, and 65 wt% of short fiberglass were compounded, and flat plates with side gates were injection-molded. The fiber orientation distribution near the center of the plates was observed via X-ray computed tomography and that along the thickness was quantified via a fiber orientation tensor. Coupon test pieces were cut from t

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Ushenko, V. A., A. Yu Sdobnov, W. D. Mishalov, et al. "Biomedical applications of Jones-matrix tomography to polycrystalline films of biological fluids." Journal of Innovative Optical Health Sciences 12, no. 06 (2019): 1950017. http://dx.doi.org/10.1142/s1793545819500172.

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Algorithms for reconstruction of linear and circular birefringence-dichroism of optically thin anisotropic biological layers are presented. The technique of Jones-matrix tomography of polycrystalline films of biological fluids of various human organs has been developed and experimentally tested. The coordinate distributions of phase and amplitude anisotropy of bile films and synovial fluid taken from the knee joint are determined and statistically analyzed. Criteria (statistical moments of 3rd and 4th orders) of differential diagnostics of early stages of cholelithiasis and septic arthritis of

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Grazzi, Francesco, Carlo Cialdai, Marco Manetti, et al. "A multi-technique tomography-based approach for non-invasive characterization of additive manufacturing components in view of vacuum/UHV applications: preliminary results." Rendiconti Lincei. Scienze Fisiche e Naturali 32, no. 3 (2021): 463–77. http://dx.doi.org/10.1007/s12210-021-00994-2.

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AbstractIn this paper, we have studied an additively manufactured metallic component, intended for ultra-high vacuum application, the exit-snout of the MACHINA transportable proton accelerator beam-line. Metal additive manufacturing components can exhibit heterogeneous and anisotropic microstructures. Two non-destructive imaging techniques, X-ray computed tomography and Neutron Tomography, were employed to examine its microstructure. They unveiled the presence of porosity and channels, the size and composition of grains and intergranular precipitates, and the general behavior of the spatial di

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Williamson, Paul R. "On resolution and uniqueness in anisotropic crosshole traveltime tomography." GEOPHYSICS 63, no. 4 (1998): 1184–89. http://dx.doi.org/10.1190/1.1444418.

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The inclusion of anisotropy in P-wave traveltime tomography has been undertaken by several authors and in all cases some loss of resolution and uniqueness compared to the isotropic problem was observed. The origin of this problem is analysed for straight‐ray tomography using the Radon transform and the projection slice theorem. This analysis shows that the separation of the anisotropy from the isotropic velocity field can only be guaranteed for the dc component. Resolution at higher spatial frequencies depends upon the spatial support of the object, that is the separation of the holes in cross

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Mochizuki, E. "Nonuniqueness of two-dimensional anisotropic tomography." Bulletin of the Seismological Society of America 87, no. 1 (1997): 261–64. http://dx.doi.org/10.1785/bssa0870010261.

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Abstract If P-wave velocity depends on azimuth, travel-time tomography is nonunique for external sources and receivers. For two dimension, travel-time data can be completely fitted in terms of isotropic P velocity. We obtain analytic expressions that specify the trade-off between anisotropy and heterogeneity.

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Ayadi, Walid, Lucien Laiarinandrasana, and Kacem Saï. "Anisotropic (Continuum Damage Mechanics)-based multi-mechanism model for semi-crystalline polymer." International Journal of Damage Mechanics 27, no. 3 (2016): 357–86. http://dx.doi.org/10.1177/1056789516679494.

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In this work, the anisotropic damage of semi-crystalline polymers is investigated. The model, developed within a thermodynamic framework, includes the following features: (i) the degree of crystallinity; (ii) the hydrostatic pressure effect; and (iii) the damage anisotropy. The adopted tensorial damage variable is based on the Continuum Damage Mechanics approach under the energy equivalence assumption. For the quantification of the anisotropy, a parameter called “shape factor” is defined as the ratio between the void mean diameter and the void mean height. This parameter is linked to the main

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Andriampenomanana, Fenitra, Andrew A. Nyblade, Michael E. Wysession, et al. "Seismic velocity and anisotropy of the uppermost mantle beneath Madagascar from Pn tomography." Geophysical Journal International 224, no. 1 (2020): 290–305. http://dx.doi.org/10.1093/gji/ggaa458.

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SUMMARY The lithosphere of Madagascar records a long series of tectonic processes. Structures initially inherited from the Pan-African Orogeny are overprinted by a series of extensional tectonic and magmatic events that began with the breakup of Gondwana and continued through to the present. Here, we present a Pn-tomography study in which Pn traveltimes are inverted to investigate the lateral variation of the seismic velocity and anisotropy within the uppermost mantle beneath Madagascar. Results show that the Pn velocities within the uppermost mantle vary by ±0.30 km s–1 about a mean of 8.10 k

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Zhu, Hejun, and Jeroen Tromp. "Mapping Tectonic Deformation in the Crust and Upper Mantle Beneath Europe and the North Atlantic Ocean." Science 341, no. 6148 (2013): 871–75. http://dx.doi.org/10.1126/science.1241335.

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We constructed a three-dimensional azimuthally anisotropic model of Europe and the North Atlantic Ocean based on adjoint seismic tomography. Several features are well correlated with historical tectonic events in this region, such as extension along the North Atlantic Ridge, trench retreat in the Mediterranean, and counterclockwise rotation of the Anatolian Plate. Beneath northeastern Europe, the direction of the fast anisotropic axis follows trends of ancient rift systems older than 350 million years, suggesting “frozen-in” anisotropy related to the formation of the craton. Local anisotropic

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Liu, Yongsheng, Iman Suardi, Xueyuan Huang, Shaolin Liu, and Ping Tong. "Seismic velocity and anisotropy tomography of southern Sumatra." Physics of the Earth and Planetary Interiors 316 (July 2021): 106722. http://dx.doi.org/10.1016/j.pepi.2021.106722.

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