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1
Stiskalek, Richard, John Veitch und Chris Messenger. „Are stellar-mass binary black hole mergers isotropically distributed?“ Monthly Notices of the Royal Astronomical Society 501, Nr. 1 (21.11.2020): 970–77. http://dx.doi.org/10.1093/mnras/staa3613.
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ABSTRACT The Advanced LIGO and Advanced Virgo gravitational wave detectors have detected a population of binary black hole mergers in their first two observing runs. For each of these events, we have been able to associate a potential sky location region represented as a probability distribution on the sky. Thus, at this point we may begin to ask the question of whether this distribution agrees with the isotropic model of the Universe, or if there is any evidence of anisotropy. We perform Bayesian model selection between an isotropic and a simple anisotropic model, taking into account the anisotropic selection function caused by the underlying antenna patterns and sensitivity of the interferometers over the sidereal day. We find an inconclusive Bayes factor of 1.3: 1, suggesting that the data from the first two observing runs are insufficient to pick a preferred model. However, the first detections were mostly poorly localized in the sky (before the Advanced Virgo joined the network), spanning large portions of the sky and hampering detection of potential anisotropy. It will be appropriate to repeat this analysis with events from the recent third LIGO observational run and a more sophisticated cosmological model.
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Rongkonusa, Melisa, Gerald Tamuntuan und Guntur Pasau. „Analisis Anisotropi Suseptibilitas Magnetik Batuan Beku Lengan Utara Sulawesi“. Jurnal MIPA 6, Nr. 1 (02.05.2017): 8. http://dx.doi.org/10.35799/jm.6.1.2017.15846.
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Telah dilakukan penelitian untuk menentukan pola anisotropi suseptibilitas magnetik dan status singkapan batuan beku dari pola yang diperoleh. Pengukuran anisotropi suseptibilitas magnetic dilakukan pada lima sampel batuan beku dari Sulawesi Utara menggunakan Bartington MS2B. Arah pengukuran sampel disesuaikan dengan desain Tauxe. Hasilnya menunjukkan bahwa suseptibilitas maksimum terdistribusi disekitar arah utara dan timur. Sedangkan suseptibilitas intermediet dan minimum terdistribusi disekitar Utara-Timur dan Timur-Selatan. Elipsoida suseptibilitas cenderung prolate atau lebih lonjong. Batuan beku yang dianalisis merupakan kelompok batuan terobosan yang mekanisme lelehannya terjadi secara vertikal.A research has been conducted to determine the anisotropic pattern of magnetic susceptibility and the status of igneous rocks exposure from the obtained pattern. We have measured the anisotropy of magnetic susceptibility on five samples of igneous rock from North Sulawesi by Bartington MS2B. The position of samples were adjusted according to the Tauxe’s design. The result shows that the maximum susceptibility is distributed around northward and eastward, while the intermediate and minimum susceptibility are distributed around nortward-eastward and eastward-southward. The susceptibility ellipsoid tends to be prolate or more oval. This shows that the igneous rocks that have been analyzed are group of intrusive rocks which melting mechanism occurs through vertical fracture.enetie
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Liu, Honglei, Wenhao Shi und Tianhong Yang. „Numerical Modeling on Anisotropy of Seepage and Stress Fields of Stratified Rock Slope“. Mathematical Problems in Engineering 2020 (07.04.2020): 1–10. http://dx.doi.org/10.1155/2020/4956025.
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Stratified rock mass is a common rock mass structure and distributed widely on the earth’s crust. High-density distribution of stratified structural planes in the stratified rock mass has a great influence on the mechanics properties of the rock mass, such as anisotropy of stress and seepage. Therefore, anisotropy is the inherent characteristic that must be considered in the stratified rock mass as well as the stratified rock slope stability. According to the anisotropic characteristics of stratified rock mass, an anisotropic seepage-stress coupled model for the mechanical behavior of stratified rock slope is proposed based on the anisotropy elasticity theory. The model is validated by simulating seepage and stress fields of an idealized slope using the finite element method. The deformation and stress-dependent permeability of the slope are predicted and compared well with the previous study, thus confirming its capability in characterizing the response of rock slope that is dominantly affected by rock anisotropy. Finally, the model is used to simulate the anisotropic properties of a stratified rock slope of Fushun west open-pit mine, China. The simulation is in good agreement with the actual measurement, which means the proposed model is capable of simulating anisotropic properties of the stratified rock slope.
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Abbasnejadfard, Morteza, Morteza Bastami und Afshin Fallah. „Investigation of anisotropic spatial correlations of intra-event residuals of multiple earthquake intensity measures using latent dimensions method“. Geophysical Journal International 222, Nr. 2 (21.05.2020): 1449–69. http://dx.doi.org/10.1093/gji/ggaa255.
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SUMMARY Considering spatial correlation of multiple earthquake intensity measures (IMs) is of particular importance in loss assessment of spatially distributed assets. This subject has been investigated in previous studies under the assumption of isotropy. Considering the fact that the assumption of isotropy is not valid in general, the present study employs a non-separable covariance model based on latent dimensions method to investigate anisotropic properties of spatial correlations and cross-correlations of intra-event residuals of multiple earthquake IMs. This method leads to the generation of valid covariance matrix in order to model anisotropic spatially distributed multivariate random fields. Two sets of IMs are considered in this study; the first set consists of peak ground intensity values (acceleration, velocity, and displacement), and the second set consists of spectral accelerations at three different periods. Data of 10 earthquake events in California and Japan are utilized in this study to estimate parameters of marginal and cross-covariance models. Moreover, parameters of covariance model of regional site condition, which is considered as average shear wave velocity of top 30 m of soil profile (Vs30), are obtained in order to investigate the effect of local sited conditions on spatial correlations of IMs. It is shown that maximum range and anisotropy ratio of covariance models of intra-event residuals of IMs are correlated with those of Vs30 values. Also, it is observed that the anisotropy direction of residuals of IMs is consistent with anisotropy direction of Vs30 values. Finally, predictive models are proposed to obtain marginal and cross-covariance functions for different earthquake IMs considering anisotropy.
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Li, Wei, Douglas R. Schmitt, Maria Tibbo und Changchun Zou. „A program to calculate the state of stress in the vicinity of an inclined borehole through an anisotropic rock formation“. GEOPHYSICS 84, Nr. 5 (01.09.2019): F103—F118. http://dx.doi.org/10.1190/geo2018-0097.1.
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A borehole existing in any geologic formation concentrates the far-field tectonic and overburden stresses amplifying the magnitudes of certain stress components near the borehole. It is important to understand the magnitudes and patterns of this stress concentration because these lead to damage and can even collapse the borehole if sufficiently strong. The solution of the stress distributed near a borehole can be complicated considering the elastic anisotropy of rocks. We have developed programs (ASCIB3D) in MATLAB and Python to model the stress distribution around an inclined borehole in an arbitrarily oriented anisotropic medium. The program is built on the Lekhnitskij-Amadei solution. The input orientation of the far-field stresses and the elastic stiffness matrix of the medium into the program are geology angles instead of the rotation angles shown in previous studies, making the code more convenient for users. The sign convention for the inverse function, which is ignored in previous studies, is discussed in detail. The results indicate that the program ASCIB3D is a useful tool for modeling the stress distributed around an inclined borehole in the anisotropic formation and analyzing the effect of anisotropy and borehole inclination on stress distribution. The inclination and azimuth of the borehole and the anisotropy of the rocks affect the orientation and strength of the stress concentration.
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Kumar, Rajneesh, und Raj Rani Gupta. „Deformation due to various sources in a fibre-reinforced anisotropic generalized thermoelastic medium“. Canadian Journal of Physics 87, Nr. 2 (Februar 2009): 179–87. http://dx.doi.org/10.1139/p09-017.
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The present investigation is concerned with the deformation of a fibre-reinforced, anisotropic, generalized thermoelastic medium subjected to mechanical and thermal sources acting on the plane surface. Close-form solutions for stresses and temperature distribution are derived using Laplace transforms for time and Fourier transforms for space. As an application of the approach concentrated, uniformly distributed, and linearly distributed sources are taken. A numerical inversion technique is applied to obtain the solution in the physical domain. Effects of anisotropy and thermal relaxation are shown graphically on the resulting quantities.
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Trach, V. M., A. V. Podvornyi und N. B. Zhukova. „Stability of non-thin anisotropic cylindrical shells in spatial position under distributed lateral pressure“. Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics, Nr. 2 (2023): 152–55. http://dx.doi.org/10.17721/1812-5409.2023/2.26.
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A three-dimensional approach to solving the problem of stability of non-thin cylindrical anisotropic layered shells under distributed lateral pressure is proposed. Based on the modified Hu-Washizu variational principle, a three-dimensional system of homogeneous differential stability equations is obtained for the calculation of shells, the anisotropy of which is characterized by a material with one plane of elastic symmetry. The solution of the three-dimensional system was carried out using the Bubnov-Galerkin methods and numerical discrete orthogonalization. The influence of an increase in the number of cross-laid layers of the same thickness on the stability of an anisotropic cylindrical shell is studied. The results of the solution are presented by graphs and their analysis is given.
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Wang, Bitao, Michele Cappellari und Yingjie Peng. „Physical explanation for the galaxy distribution on the (λR, ε) and (V/σ, ε) diagrams or for the limit on orbital anisotropy“. Monthly Notices of the Royal Astronomical Society: Letters 500, Nr. 1 (Januar 2020): L27—L31. http://dx.doi.org/10.1093/mnrasl/slaa176.
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ABSTRACT In the (λR, ε) and (V/σ, ε) diagrams for characterizing dynamical states, the fast-rotator galaxies (both early type and spirals) are distributed within a well-defined leaf-shaped envelope. This was explained as due to an upper limit to the orbital anisotropy increasing with galaxy intrinsic flattening. However, a physical explanation for this empirical trend was missing. Here, we construct Jeans Anisotropic Models (JAM), with either cylindrically or spherically aligned velocity ellipsoid (two extreme assumptions), and each with either spatially constant or variable anisotropy. We use JAM to build mock samples of axisymmetric galaxies, assuming on average an oblate shape for the velocity ellipsoid (as required to reproduce the rotation of real galaxies), and limiting the radial anisotropy β to the range allowed by physical solutions. We find that all four mock samples naturally predict the observed galaxy distribution on the (λR, ε) and (V/σ, ε) diagrams, without further assumptions. Given the similarity of the results from quite different models, we conclude that the empirical anisotropy upper limit in real galaxies, and the corresponding observed distributions in the (λR, ε) and (V/σ, ε) diagrams, are due to the lack of physical axisymmetric equilibrium solutions at high β anisotropy when the velocity ellipsoid is close to oblate.
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MALARZ, K. „A SIMPLE SOLID-ON-SOLID MODEL OF EPITAXIAL FILM GROWTH: SUBMONOLAYER SUBSTRATE COVERAGE“. International Journal of Modern Physics C 11, Nr. 08 (Dezember 2000): 1561–66. http://dx.doi.org/10.1142/s0129183100001449.
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In this work, we investigate the influence of substrate temperature on the surface morphology for substrate coverage below one monolayer. The model of film growth is based on random deposition enriched by limited surface diffusion. Also, anisotropy in the growth is involved. We found from computer simulations for the simple cubic lattice and solid-on-solid model that the surface morphology changes with increasing temperature from isotropically distributed isolated small islands through anisotropic 1D stripes to larger 2D anisotropic islands and again randomly distributed single atoms. The transition is also marked in height–height correlation function dependence on temperature as directly seen by snapshots from simulations. The results are in good qualitative agreement with already published results of kinetic Monte Carlo simulations as well as with some experimental data.
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Vélez, José A., Georgios P. Tsoflias, Ross A. Black, Cornelis J. Van der Veen und Sridhar Anandakrishnan. „Distribution of preferred ice crystal orientation determined from seismic anisotropy: Evidence from Jakobshavn Isbræ and the North Greenland Eemian Ice Drilling facility, Greenland“. GEOPHYSICS 81, Nr. 1 (01.01.2016): WA111—WA118. http://dx.doi.org/10.1190/geo2015-0154.1.
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Preferred crystal orientation fabrics (COFs) within an ice sheet or glacier are typically found from ice cores. We conducted experiments at the North Greenland Eemian Ice Drilling (NEEM) facility ice core location, where COF data were available at Jakobshavn Isbræ west Greenland, to test if COF can be determined seismically. We used observations of anisotropic seismic wave propagation on multioffset gathers and englacial imaging from a 2D reflection profile. Anisotropy analysis of the NEEM data yielded mean c-axes distributed over a conical region of 30° to 32° from vertical. No internal ice seismic reflectors were imaged. Direct COF measurements collected in the ice core agreed with the seismic observations. At Jakobshavn Isbræ, we used a multioffset gather and a 2D reflection profile, but we lacked ice core data. Englacial reflectors allowed the determination of ice column interval properties. Anisotropy analysis found that the upper 1640 m of the ice column consisted of cold ([Formula: see text]) and mostly isotropic ice with c-axes distributed over a conical region of 80° from vertical. The lower 300 m of the ice column was characterized by warm ([Formula: see text]) ice with COF. These observations were consistent with complex ice fabric development and temperature estimations over the same region of Jakobshavn Isbræ. This study demonstrated that the ice sheet and glacier ice anisotropy information can be gained from seismic field observations.
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Thomopoulos, Stavros, Gregory M. Fomovsky, Preethi L. Chandran und Jeffrey W. Holmes. „Collagen Fiber Alignment Does Not Explain Mechanical Anisotropy in Fibroblast Populated Collagen Gels“. Journal of Biomechanical Engineering 129, Nr. 5 (15.02.2007): 642–50. http://dx.doi.org/10.1115/1.2768104.
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Many load-bearing soft tissues exhibit mechanical anisotropy. In order to understand the behavior of natural tissues and to create tissue engineered replacements, quantitative relationships must be developed between the tissue structures and their mechanical behavior. We used a novel collagen gel system to test the hypothesis that collagen fiber alignment is the primary mechanism for the mechanical anisotropy we have reported in structurally anisotropic gels. Loading constraints applied during culture were used to control the structural organization of the collagen fibers of fibroblast populated collagen gels. Gels constrained uniaxially during culture developed fiber alignment and a high degree of mechanical anisotropy, while gels constrained biaxially remained isotropic with randomly distributed collagen fibers. We hypothesized that the mechanical anisotropy that developed in these gels was due primarily to collagen fiber orientation. We tested this hypothesis using two mathematical models that incorporated measured collagen fiber orientations: a structural continuum model that assumes affine fiber kinematics and a network model that allows for nonaffine fiber kinematics. Collagen fiber mechanical properties were determined by fitting biaxial mechanical test data from isotropic collagen gels. The fiber properties of each isotropic gel were then used to predict the biaxial mechanical behavior of paired anisotropic gels. Both models accurately described the isotropic collagen gel behavior. However, the structural continuum model dramatically underestimated the level of mechanical anisotropy in aligned collagen gels despite incorporation of measured fiber orientations; when estimated remodeling-induced changes in collagen fiber length were included, the continuum model slightly overestimated mechanical anisotropy. The network model provided the closest match to experimental data from aligned collagen gels, but still did not fully explain the observed mechanics. Two different modeling approaches showed that the level of collagen fiber alignment in our uniaxially constrained gels cannot explain the high degree of mechanical anisotropy observed in these gels. Our modeling results suggest that remodeling-induced redistribution of collagen fiber lengths, nonaffine fiber kinematics, or some combination of these effects must also be considered in order to explain the dramatic mechanical anisotropy observed in this collagen gel model system.
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Izzati Khalidah Khalid, Nor Fadzillah Mohd Mokhtar und Nurul Hafizah Zainal Abidin. „Thermogravitational Convection in a Controlled Rotating Darcy-Brinkman Nanofluids Layer Saturated in an Anisotropic Porous Medium Subjected to Internal Heat Source“. Journal of Advanced Research in Numerical Heat Transfer 14, Nr. 1 (11.10.2023): 70–90. http://dx.doi.org/10.37934/arnht.14.1.7090.
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Thermogravitational convection in a controlled rotating Darcy-Brinkman nanofluids layer saturated in an anisotropic porous medium heated from below is Thermogravitational convection in a controlled rotating Darcy-Brinkman nanofluids layer saturated in an anisotropic porous medium heated from below is investigated. The presence of a uniformly distributed internal heat source and considers the Brinkman model for different boundary conditions: rigid-rigid, free-free, and lower-rigid and upper-free are considered. The effect of a control strategy involving sensors located at the top plate and actuators positioned at the bottom plate of the nanofluids layer is analysed. Linear stability analysis based on normal mode technique is employed. The resulting eigenvalue problem is solved numerically using the Galerkin method implemented with Maple software. The model used for the nanofluids associates with the mechanisms of Brownian motion and thermophoresis. The influences of the internal heat source strength, mechanical anisotropy parameter, modified diffusivity ratio, nanoparticles concentration Darcy-Rayleigh number and nanofluids Lewis number are found to advance the onset of convection. Conversely, the Darcy number, thermal anisotropy parameter, porosity, rotation, and controller effects are observed to slow down the process of convective instability.investigated. The presence of a uniformly distributed internal heat source and considers the Brinkman model for different boundary conditions: rigid-rigid, free-free, and lower-rigid and upper-free are considered. The effect of a control strategy involving sensors located at the top plate and actuators positioned at the bottom plate of the nanofluids layer is analysed. Linear stability analysis based on normal mode technique is employed. The resulting eigenvalue problem is solved numerically using the Galerkin method implemented with Maple software. The model used for the nanofluids associates with the mechanisms of Brownian motion and thermophoresis. The influences of the internal heat source strength, mechanical anisotropy parameter, modified diffusivity ratio, nanoparticles concentration Darcy-Rayleigh number and nanofluids Lewis number are found to advance the onset of convection. Conversely, the Darcy number, thermal anisotropy parameter, porosity, rotation, and controller effects are observed to slow down the process of convective instability.
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Newman, Daniel, John Lindsay und Jaclyn Cockburn. „Measuring Hyperscale Topographic Anisotropy as a Continuous Landscape Property“. Geosciences 8, Nr. 8 (28.07.2018): 278. http://dx.doi.org/10.3390/geosciences8080278.
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Several landforms are known to exhibit topographic anisotropy, defined as a directional inequality in elevation. The quantitative analysis of topographic anisotropy has largely focused on measurements taken from specific landforms, ignoring the surrounding landscape. Recent research has made progress in measuring topographic anisotropy as a distributed field in natural landscapes. However, current methods are computationally inefficient, as they require specialized hardware and computing environments, or have a limited selection of scales that undermines the feasibility and quality of multiscale analyses by introducing bias. By necessity, current methods operate with a limited set of scales, rather than the full distribution of possible landscapes. Therefore, we present a method for measuring topographic anisotropy in the landscape that has the computational efficiency required for hyperscale analysis by using the integral image filtering approach to compute oriented local topographic position (LTP) measurements, coupled with a root-mean-square deviation (RMSD) model that compares directional samples to an omnidirectional sample. Two tools were developed: One to output a scale signature for a single cell, and the other to output a raster containing the maximum anisotropy value across a range of scales. The performances of both algorithms were tested using two data sets containing repetitive, similarly sized and oriented anisotropic landforms, including a dune field and a drumlin field. The results demonstrated that the method presented has the robustness and sensitivity to identify complex hyperscale anisotropy such as nested features (e.g., a drumlin located within a valley).
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Li, Xiangchun, Zhenxing An, Qi Zhang, Xiaolong Chen, Xinwei Ye und Suye Jia. „Analysis of Resistivity Anisotropy of Loaded Coal Samples“. Advances in Materials Science and Engineering 2020 (04.06.2020): 1–13. http://dx.doi.org/10.1155/2020/9016583.
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In this paper, an experimental study of the variation of resistivity of coal samples in different bedding directions at 1 MHz frequency was performed by establishing an experimental system for resistivity testing of coal under triaxial stress. The low-pressure nitrogen gas adsorption (LP-N2GA) experiment and scanning electron microscopy (SEM) were obtained to analyze the pore-fracture structural characteristics of coal samples and the influence on resistivity anisotropy. Furthermore, the fundamental cause of anisotropy of coal resistivity is expounded systematically. The results show that the resistivity of loaded coal decreased first before increasing. The ionic conductance and the high degree of metamorphism slow down the decrease of resistivity. The distribution of pore and fracture structures is anisotropic. The connected pores and fractures are mainly distributed along the parallel bedding direction. The weak plane of bedding, diagenetic fractures, and plane fracture structures of parallel bedding result in the increase of fractures in the direction of vertical bedding, so increasing the potential barrier. Therefore, the resistivity in the vertical bedding direction is higher than that of the parallel bedding. Loading coal resistivity anisotropy degree is a dynamic change trend; the load increases anisotropy significantly under axial pressure, and the degree of anisotropy has a higher discreteness under confining pressure. It is mainly the randomness of the internal pore-fracture compaction, closure, and development of the heterogeneous coal under the confining pressure; the more rapid the decline in this stage, the larger the stress damage degree.
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Zhao, Mengzhuo, Hu Zhang, Cancan Chen, Chenxia Wang, Yan Liu, Juan Li und Tiejun Cui. „The Classification of Reflectance Anisotropy and Its Application in Albedo Retrieval“. Atmosphere 13, Nr. 8 (26.07.2022): 1182. http://dx.doi.org/10.3390/atmos13081182.
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The land surface albedo reflects the ability of the surface to reflect solar radiation and is a critical physical variable in the study of the Earth’s energy budget and global climate change. Algorithms for the retrieval of albedo usually require multi-angle measurements due to surface anisotropy. However, most of the satellites cannot currently provide sufficient and well-distributed observations; therefore, the accuracy of remotely sensed albedo is constrained. Based on the Moderate-Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF) and albedo product (MCD43A1), this study proposed a method to further subdivide reflectance anisotropy and build an updated database of BRDF archetype, using both the Anisotropic Flat Index (AFX) and Perpendicular Anisotropic Flat Index (PAFX). The BRDF archetypes were used to fit the corresponding MODIS BRDF, and the optimal number of BRDF archetype categories was determined according to the tendency of fitting error. The effect of surface anisotropy and observation noise on albedo retrieval were explored based on simulated MODIS reflectance. Finally, the BRDF archetype A2P2 was taken as prior knowledge to retrieve albedo from a different number of MODIS observations, and the result was validated by the high-quality MODIS albedo product. The results show that the fitting error between BRDF archetypes and MODIS BRDF shows a rapid decline when introducing the PAFX in the classification process. A 3-by-3 matrix of BRDF archetypes, which occupy 73.44% and 70.13% of the total decline in the red and NIR band, can be used to represent the characteristics of reflectance anisotropy. The archetype A2P2 may be used as prior knowledge to improve the albedo retrieval from insufficient observations. The validation results based on MODIS observations show that the archetype A2P2-based albedo can reach root-mean-square errors (RMSEs) of no more than 0.03.
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Zheng, Kun, Yu Miao, Tong Li, Shuang-Long Yang, Li Xi, Yang Yang, Dun Zhao und De-Sheng Xue. „Anti-function solution of uniaxial anisotropic Stoner–Wohlfarth model“. Chinese Physics B 31, Nr. 4 (01.04.2022): 040202. http://dx.doi.org/10.1088/1674-1056/ac401e.
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The anti-trigonometric function is used to strictly solve the uniaxial anisotropic Stoner–Wohlfarth (SW) model, which can obtain the relation of the angle α(θ) between the magnetization (the anisotropy field) and the applied magnetic field. Using this analytic solution, the hysteresis loops of uniaxial anisotropic SW particles magnetized in typical directions could be numerically calculated. Then, the hysteresis loops are obtained in randomly distributed SW particle ensembles while ignoring the dipole interaction among them with the analytic solution. Finally, the correctness of the analytic solution is verified by the exact solutions of remanence, switching field, and coercivity from the SW model. The analytic solution provides an important reference for understanding the magnetizing and magnetization reversal processes of magnetic materials.
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Hasheminejad, S. M., und M. Maleki. „Effect of Interface Anisotropy on Elastic Wave Propagation in Particulate Composites“. Journal of Mechanics 24, Nr. 1 (März 2008): 79–93. http://dx.doi.org/10.1017/s1727719100001581.
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ABSTRACTThe scattering of time harmonic plane longitudinal and transverse elastic waves in a composite consisting of randomly distributed identical isotropic spherical inclusions embedded in an isotropic matrix with anisotropic interface layers is examined. The interface region is modeled as a spherically isotropic shell of finite thickness with five independent elastic constants. The Frobenius power series solution method is utilized to deal with the interface anisotropy and the effect of random distribution of particulates in the composite medium is taken into account via a recently developed generalized self-consistent multiple scattering model. Numerical values of phase velocities and attenuations of coherent plane waves as well as the effective elastic constants are obtained for a moderately wide range of frequencies, particle concentrations, and interface anisotropies. The numerical results reveal the significant dependence of phase velocities and effective elastic constants on the interface properties. They show that interface anisotropy can moderately depress the effective phase velocities and the elastic moduli, but leave effective attenuation nearly unaffected, especially at low and intermediate frequencies. Limiting cases are considered and good agreements with recent solutions have been obtained.
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Pedersen, Pauli, und Niels L. Pedersen. „Distributed material density and anisotropy for optimized eigenfrequency of 2D continua“. Structural and Multidisciplinary Optimization 51, Nr. 5 (16.11.2014): 1067–76. http://dx.doi.org/10.1007/s00158-014-1196-6.
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KALASHEV, O. E., V. A. KUZMIN und D. V. SEMIKOZ. „ULTRA HIGH ENERGY COSMIC RAYS: PROPAGATION IN THE GALAXY AND ANISOTROPY“. Modern Physics Letters A 16, Nr. 39 (21.12.2001): 2505–15. http://dx.doi.org/10.1142/s0217732301005990.
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We considered propagation of Ultra High Energy Cosmic Rays (UHECR) through the galaxy. We investigated models with sources of UHECR distributed in the same way as Cold Dark Matter (CDM) in a self-consistent way, taking into account both extra-galactic and Galactic contributions. Using a very simple toy model of galactic magnetic field we showed that in the case of galactic origin of UHECRs the anisotropy can reach considerable values. In the case of extragalactic UHECRs origin, the anisotropy appears to be nonvanishing only for electron and photon components due to synchrotron losses, but it can hardly be reassured. The reason is an extremely low flux of UHE electrons and a too low level of γ-ray anisotropy.
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Gao, Jianhong, Xiaoxiang Yang und Lihong Huang. „A Numerical Model to Predict the Anisotropy of Polymer Composites Reinforced with High-Aspect-Ratio Short Aramid Fibers“. Advances in Polymer Technology 2019 (02.07.2019): 1–12. http://dx.doi.org/10.1155/2019/5484675.
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Some fiber types have a high aspect ratio and it is very difficult to predict their composites using traditional finite element (FE) modeling. In this study, an FE model was developed to predict the anisotropy of composites reinforced by short aramid fibers. Three fiber distribution types were studied as follows: perfectly aligned, normally distributed, and randomly distributed fibers. The elastic constants were obtained, and, for different alignment angles and parameters in the fiber orientation distribution function, their numerical results were compared to those of the Mori–Tanaka model. Good agreement was obtained; thus, the employed FE model is an excellent and simple method to predict the isotropy and anisotropy of a composite with high-aspect-ratio fibers. Therefore, the FE model was employed to predict the orientation distribution of a composite fiber with a nonlinear matrix. The predicted and experimental results agree well.
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Shevtsova, Maria, Evgenia Kirillova, Eugeny Rozhkov, Valery Chebanenko, Sergey Shevtsov, Jiing Kae Wu und Shun Hsyung Chang. „Piezoelectric Based Lamb Waves Generation and Propagation in Orthotropic CFRP Plates: II. Influence of Interfacial Stress Distribution“. Materials Science Forum 962 (Juli 2019): 227–35. http://dx.doi.org/10.4028/www.scientific.net/msf.962.227.
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This paper investigates the Lamb wave generation by the surface bonded circular piezoelectric (PZT) actuator and wave propagation within the orthotropic Carbon Fiber Reinforced Plastic (CFRP) plate considering the anisotropy of the elastic and damping properties of the materials; existence of the adhesive layer; and dependence of the interfacial stress distribution on the surface between host plate and actuator, on the anisotropy of the plate material, and on the excited frequency, wavelength and plate thickness. This part of our investigation includes FE based study of the shear stress distribution on the interface between circular PZT actuator and surface of orthotropic CFRP plate, and its dependence on the excited wavelength and plate thickness. The anisotropic elastic and damping properties of the plate material, which are used in the implemented finite element (FE) model, have been preliminary determined in the first part of our investigation. We compare the behavior of the wave generation, propagation and attenuation that are studied using this model with the similar dependencies obtained at the simulation of the non-dissipating plate excited by the periodical radially oriented force, which is distributed along the circumference bounding the actuator, i.e. 3D pin-force excitation case. The proposed results can be used at the design of SHM for the composite structures with the structural anisotropy and damping, and at making a reasonable choice of the frequency, type, dimensions and optimum placement of the actuators and sensors.
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Безверхний, А. И., А. Д. Таланцев, Ю. Е. Калинин, А. В. Ситников, В. A. Никитенко, О. В. Коплак, О. С. Дмитриев und Р. Б. Моргунов. „Магнитная анизотропия многослойных гетероструктур [(Co-=SUB=-41-=/SUB=-Fe-=SUB=-39-=/SUB=-B-=SUB=-20-=/SUB=-)-=SUB=-x-=/SUB=-(SiO-=SUB=-2-=/SUB=-)-=SUB=-100-x-=/SUB=-/Bi-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=-]-=SUB=-47-=/SUB=-“. Физика твердого тела 61, Nr. 2 (2019): 266. http://dx.doi.org/10.21883/ftt.2019.02.47124.235.
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AbstractMagnetic anisotropy values are obtained for [(Co_41Fe_39B_20)_ x (SiO_2)_100 – _ x /Bi_2Te_3]_47 heterostructures consisting of SiO_2 alternating layers, CoFeB nanoparticles distributed in them, and Bi_2Te_3 layers with ferromagnetic resonance and magnetometry. The heterostructures have anisotropy of ~10^6 erg/cm^3, which orients the magnetic moment in films plane. The films are not solid, but they disintegrate into CoFeB nanoparticles with an average diameter of 5 nm during deposition, which corresponds to the blocking magnetization temperature of ~30 K during their saturation magnetization of M _ S = 720 emu/cm^3. The relationship between anisotropy constant and thickness of the layers of the heterostructures is nonmonotonic due to competition between surface and bulk anisotropies of the ferromagnetic granules, which the films are made of.
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Ikelle, L. T., S. K. Yung und F. Daube. „2-D random media with ellipsoidal autocorrelation functions“. GEOPHYSICS 58, Nr. 9 (September 1993): 1359–72. http://dx.doi.org/10.1190/1.1443518.
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The integration of surface seismic data with borehole seismic data and well‐log data requires a model of the earth which can explain all these measurements. We have chosen a model that consists of large and small scale inhomogeneities: the large scale inhomogeneities are the mean characteristics of the earth while the small scale inhomogeneities are fluctuations from these mean values. In this paper, we consider a two‐dimensional (2-D) model where the large scale inhomogeneities are represented by a homogeneous medium and small scale inhomogeneities are randomly distributed inside the homogeneous medium. The random distribution is characterized by an ellipsoidal autocorrelation function in the medium properties. The ellipsoidal autocorrelation function allows the parameterization of small scale inhomogeneities by two independent autocorrelation lengths a and b in the horizontal and the vertical Cartesian directions, respectively. Thus we can describe media in which the inhomogeneities are isotropic (a = b), or elongated in a direction parallel to either of the two Cartesian directions (a > b, a < b), or even taken to infinite extent in either dimension (e.g., a = infinity, b = finite: a 1-D medium) by the appropriate choice of the autocorrelation lengths. We also examine the response of seismic waves to this form of inhomogeneity. To do this in an accurate way, we used the finite‐difference technique to simulate seismic waves. Special care is taken to minimize errors due to grid dispersion and grid anisotropy. The source‐receiver configuration consists of receivers distributed along a quarter of a circle centered at the source point, so that the angle between the source‐receiver direction and the vertical Cartesian direction varies from 0 to 90 degrees. Pulse broadening, coda, and anisotropy (transverse isotropy) due to small scale inhomogeneities are clearly apparent in the synthetic seismograms. These properties can be recast as functions of the aspect ratio [Formula: see text] of the medium, especially the anisotropy and coda. For media with zero aspect ratio (1-D media), the coda energy is dominant at large angles. The coda energy gradually becomes uniformly distributed with respect to angle as the aspect ratio increases to unity. Our numerical results also suggest that, for small values of aspect ratio, the anisotropic behavior (i.e., the variations of pulse arrival times with angle) of the 2-D random media is similar to that of a 1-D random medium. The arrival times agree with the effective medium theory. As the aspect ratio increases to unity, the variations of pulse arrival times with angle gradually become isotropic. To retain the anisotropic behavior beyond the geometrical critical angle, we have used a low‐frequency pulse with a nonzero dc component.
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Thiessen, Ryan, und Thomas Hillen. „Anisotropic Network Patterns in Kinetic and Diffusive Chemotaxis Models“. Mathematics 9, Nr. 13 (02.07.2021): 1561. http://dx.doi.org/10.3390/math9131561.
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For this paper, we are interested in network formation of endothelial cells. Randomly distributed endothelial cells converge together to create a vascular system. To develop a mathematical model, we make assumptions on individual cell movement, leading to a velocity jump model with chemotaxis. We use scaling arguments to derive an anisotropic chemotaxis model on the population level. For this macroscopic model, we develop a new numerical solver and investigate network-type pattern formation. Our model is able to reproduce experiments on network formation by Serini et al. Moreover, to our surprise, we found new spatial criss-cross patterns due to competing cues, one direction given by tissue anisotropy versus a different direction due to chemotaxis. A full analysis of these new patterns is left for future work.
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Watazu, Akira, Ichinori Shigematsu, Xin Sheng Huang, Kazutaka Suzuki und Naobumi Saito. „Noncombustible Magnesium Alloy Processed by Rotary-Die Equal Channel Angular Pressing Method“. Materials Science Forum 544-545 (Mai 2007): 419–22. http://dx.doi.org/10.4028/www.scientific.net/msf.544-545.419.
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Noncombustible Mg-8Al-2Ca rods were processed by RD-ECAP. The magnesium alloy rod had Mg matrix and Al2Ca second phase. Grains with about 20 μm in diameter were observed in the matrix of the raw materials. The grains in matrix had no anisotropy. On the other hand, positions of second phase particles had anisotropy and the second phase particles formed lines. The samples processed by RD-ECAP had no crack and the samples had 20mm diameter. Grains in matrix of the 4 pass RD-ECAP sample had no anisotropy and the grains had under about 5 μm in diameter. The second phase particles had round shapes and were uniformly distributed as compared with the raw material rod. Therefore, the RD-ECAP is useful for forming noncombustible Mg-8Al-2Ca alloy with fine-grains.
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Abrashkevych, Yurii, Hryhorii Machyshyn, Oleksandr Marchenko, Maksym Balaka und Olena Zhukova. „Mechanical strength increasing of abrasive reinforced wheel“. Strength of Materials and Theory of Structures, Nr. 108 (30.05.2022): 295–308. http://dx.doi.org/10.32347/2410-2547.2022.108.295-308.
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The mechanical strength of unreinforced abrasive wheels is determined by centrifugal and bending forces, but their distribution during reinforcement is unknown. It was assumed that the stresses are distributed evenly, but a comparison of calculations on the theory of elasticity and real characteristics on a special stand showed complete discrepancy. Tensile tests of the wheels made it possible to compare the stresses results in the circumferential and radial directions. Was found that the reinforced wheel is an anisotropic body. Anisotropy can be reduced by displacing one reinforcement mesh relatively to the other by angle of 45°. In this paper, a mathematical model of the stress-strain state of the abrasive reinforced wheel was developed, taking into account the anisotropy of its properties. To determine the centrifugal forces, the theory of elasticity for an orthotropic body is applied. The bending forces that arise in the working wheel were determined during solving the problem of the distribution of deformations in the anisotropic annular plate rigidly fixed along the inner contour. As a result of experimental studies, it was found that stresses reach 8...23 MPa, which can be compared with the ultimate strength of the wheel matrix. The elastic module of the wheel matrix is noticeably greater than the elastic module of the reinforcing mesh, which practically does not perceive the load at the initial stage. The developed mathematical model of the strength indicators for abrasive reinforced wheels makes it possible to predict their reliability and safe operation.
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Sukhov, A., K. D. Usadel und U. Nowak. „Ferromagnetic resonance in an ensemble of nanoparticles with randomly distributed anisotropy axes“. Journal of Magnetism and Magnetic Materials 320, Nr. 1-2 (Januar 2008): 31–35. http://dx.doi.org/10.1016/j.jmmm.2007.05.001.
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Tao, Renchun, Munetaka Arita, Satoshi Kako und Yasuhiko Arakawa. „Optical anisotropy of m -plane nitride air-gap distributed Bragg reflector microcavities“. physica status solidi (c) 11, Nr. 3-4 (Februar 2014): 840–43. http://dx.doi.org/10.1002/pssc.201300476.
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Chizhik, Alexander, Paula Corte-Leon, Valentina Zhukova, Julian Gonzalez, Przemyslaw Gawronski, Juan Mari Blanco und Arcady Zhukov. „Determination of Magnetic Structures in Magnetic Microwires with Longitudinally Distributed Magnetic Anisotropy“. Sensors 23, Nr. 6 (13.03.2023): 3079. http://dx.doi.org/10.3390/s23063079.
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We studied the magnetic properties of a glass-covered amorphous microwire that was stress-annealed at temperatures distributed along the microwire length. The Sixtus-Tonks, Kerr effect microscopy and magnetic impedance techniques have been applied. There was a transformation of the magnetic structure across the zones subjected to annealing at different temperatures. The annealing temperature distribution induces the graded magnetic anisotropy in the studied sample. The variety of the surface domain structures depending on the longitudinal location has been discovered. Spiral, circular, curved, elliptic and longitudinal domain structures coexist and replace each other in the process of magnetization reversal. The analysis of the obtained results was carried out based on the calculations of the magnetic structure, assuming the distribution of internal stresses.
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Allen, Rebecca, und Shuyu Sun. „Computing and Comparing Effective Properties for Flow and Transport in Computer-Generated Porous Media“. Geofluids 2017 (2017): 1–24. http://dx.doi.org/10.1155/2017/4517259.
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We compute effective properties (i.e., permeability, hydraulic tortuosity, and diffusive tortuosity) of three different digital porous media samples, including in-line array of uniform shapes, staggered-array of squares, and randomly distributed squares. The permeability and hydraulic tortuosity are computed by solving a set of rescaled Stokes equations obtained by homogenization, and the diffusive tortuosity is computed by solving a homogenization problem given for the effective diffusion coefficient that is inversely related to diffusive tortuosity. We find that hydraulic and diffusive tortuosity can be quantitatively different by up to a factor of ten in the same pore geometry, which indicates that these tortuosity terms cannot be used interchangeably. We also find that when a pore geometry is characterized by an anisotropic permeability, the diffusive tortuosity (and correspondingly the effective diffusion coefficient) can also be anisotropic. This finding has important implications for reservoir-scale modeling of flow and transport, as it is more realistic to account for the anisotropy ofboththe permeability and the effective diffusion coefficient.
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Kumar, Sandeep, Y. K. Kim, T. Kang, Min Sup Hur und Moses Chung. „Evolution of magnetic field in a weakly relativistic counterstreaming inhomogeneous e−/e+ plasmas“. Laser and Particle Beams 38, Nr. 3 (24.07.2020): 181–87. http://dx.doi.org/10.1017/s0263034620000233.
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AbstractThe nonlinear evolution of electron Weibel instability in a symmetric, counterstream, unmagnetized electron–positron e−/e+ plasmas is studied by a 2D particle-in-cell (PIC) method. The magnetic field is produced and amplified by the Weibel instability, which extracts energy from the plasma anisotropy. A weakly relativistic drift velocity of 0.5c is considered for two counterstreaming e−/e+ plasma flows. Simulations show that in a homogeneous e−/e+ plasma distribution, the magnetic field amplifies exponentially in the linear regime and rapidly decays after saturation. However, in the case of inhomogeneous e−/e+ plasma distribution, the magnetic field re-amplifies at post-saturation. We also find that the amount of magnetic field amplification at post-saturation depends on the strength of the density inhomogeneity of the upstream plasma distribution. The temperature calculation shows that the finite thermal anisotropy exists in the case of an inhomogeneous plasma distribution which leads to the second-stage magnetic field amplification after the first saturation. Such density inhomogeneities are present in a variety of astrophysical sources: for example, in supernova remnants and gamma-ray bursts. Therefore, the present analysis is very useful in understanding these astrophysical sources, where anisotropic density fluctuations are very common in the downstream region of the relativistic shocks and the widely distributed magnetic field.
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Jiménez-Mejía, Raúl E., Rodrigo Acuna Herrera und Pedro Torres. „Analysis of Spatially Doped Fused Silica Fiber Optic by Means of a Hamiltonian Formulation of the Helmholtz Equation“. Advances in Materials Science and Engineering 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/5806947.
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This paper discusses an alternative method for calculating modal parameters in optical fibers such as propagation constants, transverse distributions, and anisotropy, due to linear and nonlinear phenomena acting as perturbations caused by doped silica regions. This method is based on a Hamiltonian formulation of the Helmholtz equation and the stationary perturbation theory, which allows a full-vectorial description of the electric field components when linear anisotropic inhomogeneities and Kerr nonlinearity are included. Linear and nonlinear parameters can be found for each propagating mode, and its accuracy has been successfully tested when compared to numerical calculations from the vector finite element method, and the results are published in the literature. This method facilitates the calculation of the spatial-distributed perturbation effects on individual electric field components for each propagating mode.
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Kito, Shinsuke, Jiuk Jung, Tetsuo Kobayashi und Yoshihiko Koga. „Fiber tracking of white matter integrity connecting the mediodorsal nucleus of the thalamus and the prefrontal cortex in schizophrenia: A diffusion tensor imaging study“. European Psychiatry 24, Nr. 5 (Juni 2009): 269–74. http://dx.doi.org/10.1016/j.eurpsy.2008.12.012.
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AbstractThe goal of this study was to detect abnormalities in white matter integrity connecting the mediodorsal nucleus of the thalamus and the prefrontal cortex using fiber-tracking technique. Diffusion tensor imaging was acquired in 20 patients with schizophrenia and 20 normal comparison subjects. Fiber tracking was performed on the anterior thalamic peduncle, and the tractography was used to determine the cross-sectional area, mean fractional anisotropy, and standard deviation of fractional anisotropy for every step separately in the right and left hemispheres. Compared with normal subjects, patients showed a significant reduction in the cross-sectional area of the left anterior thalamic peduncle. There were no significant differences for the mean fractional anisotropy bilaterally between the two groups, but significant differences for the standard deviation of fractional anisotropy in both hemispheres. Reduction in the cross-sectional area of the left anterior thalamic peduncle suggests the presence of the failure of left-hemisphere lateralization. In schizophrenic patients a significant increase of the standard deviation of fractional anisotropy raise the possibility that the inhomogeneity of white matter integrity, which is densely or sparsely distributed by site. These findings might provide further evidence for disruption of white matter integrity between the thalamus and the prefrontal cortex in schizophrenia.
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Zhang, Yuangui, Bangrang Di, Feng Gao und Lei Li. „Effects of Background Porosity on Seismic Anisotropy in Fractured Rocks: An Experimental Study“. Applied Sciences 13, Nr. 14 (20.07.2023): 8379. http://dx.doi.org/10.3390/app13148379.
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Fractures are widely distributed in the subsurface and are crucial for hydrocarbon, CCS, offshore infrastructure (windfarms), and geothermal seismic surveys. Seismic anisotropy has been widely used to characterize fractures and has been shown to be sensitive to background matrix porosities in theoretical studies. An understanding of the effects of background porosity on seismic anisotropy could improve seismic characterization in different fractured reservoirs. Based on synthetic rocks with controlled fractures, we conducted laboratory experiments to investigate the influence that background porosity has on P-wave anisotropy and shear wave splitting. A set of rocks containing the same fracture density (0.06) with varying porosities of 15.3%, 22.1%, 26.1% and 30.8% were constructed. The P- and S-wave velocities were measured at 0.5 MHz as the rocks were water saturated. The results show that when porosity increased from 15.3% to 22.1%, P-wave anisotropy and shear wave splitting exhibited slight fluctuations. However, when porosity continued to increase to 30.8%, P-wave anisotropy declined sharply, whereas shear wave splitting stayed nearly constant. The measured results were compared with predictions from equivalent medium theories. Qualitative agreements were found between the theoretical predictions and the measured results. In the Eshelby–Cheng model, an increase in porosity reduces fracture-induced perturbation in the normal direction of the fracture, resulting in lower P-wave anisotropy. In the Gurevich model, an increase in porosity can reduce the compressional stiffness in parallel directions to a larger extent than that in perpendicular directions, thus leading to lower P-wave anisotropy.
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Chaddock, Christopher A., Gareth J. Barker, Nicolette Marshall, Katja Schulze, Mei Hua Hall, Adele Fern, Muriel Walshe et al. „White matter microstructural impairments and genetic liability to familial bipolar I disorder“. British Journal of Psychiatry 194, Nr. 6 (Juni 2009): 527–34. http://dx.doi.org/10.1192/bjp.bp.107.047498.
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BackgroundSubtle abnormalities in frontal white matter have been reported in bipolar disorder.AimsTo assess whether impaired integrity of white matter tracts is associated with bipolar disorder and genetic liability for the disorder.MethodA total of 19 patients with psychotic bipolar I disorder from multiply affected families, 21 unaffected first-degree relatives and 18 comparison individuals (controls) underwent diffusion tensor imaging. Whole brain voxel-based analyses compared fractional anisotropy between patients and relatives with controls, and its relationship with a quantitative measure of genetic liability.ResultsPatients had decreased fractional anisotropy compared with controls in the genu of the corpus callosum, right inferior longitudinal fasciculus and left superior longitudinal fasciculus. Increased genetic liability for bipolar disorder was associated with reduced fractional anisotropy across distributed regions of white matter in patients and their unaffected relatives.ConclusionsDisturbed structural integrity within key intra- and interhemispheric tracts characterises both bipolar disorder and genetic liability for this illness.
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Liu, Xiwu, Zhiqi Guo, Qibin Zhang, Yuwei Liu und Haifeng Chen. „Rock physical characterisation of microstructural fabrics and elastic anisotropy for a shale oil reservoir“. Journal of Geophysics and Engineering 17, Nr. 2 (10.02.2020): 377–89. http://dx.doi.org/10.1093/jge/gxz123.
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Abstract Rock physics models are constructed to describe elastic anisotropy of various fabrics in shales. A method is developed to invert elastic properties of the clay mixture in shales. Inversion results indicate that the clay mixture has abnormally low Vs and consequently leads to a very high Vp/Vs ratio, which is related to the presence of the soft interparticle medium in the clay mixture. Accordingly, a model is constructed to describe anisotropy clay mixture that consists of layering distributed illite-smectite particles, and a more compliant interparticle medium that has a bulk modulus similar to that of water and smaller nonzero shear modulus. Rock physical modelling indicates that an increase in the fraction of the soft interparticle medium (f-soft) leads to a dramatic increase in Vp/Vs ratios of the clay mixture. Meanwhile, the fraction of illite (f-illite) also shows a significant impact on elastic anisotropy of the clay mixture. Accordingly, a rock physical inversion scheme is further proposed to estimate the parameters f-soft and f-illite. Finally, based on these inverted parameters, elastic anisotropy values of various fabrics at different scale, including illite-smectite platelet, clay mixture, solid matrix of shale and shale rock, are computed by the constructed rock physics model. The estimated anisotropy parameters reveal lamination textures and can help in the evaluation of mechanical properties of shale reservoirs. Also, the obtained anisotropy parameters can provide an accurate velocity model for seismic modelling, seismic data processing and inversion.
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Cundi, M. „Numerical Analysis of Test Embankment on Soft Ground Using Multi-Laminate Type Model with Destructuration / Analiza Numeryczna Nasypu Drogowego Posadowionego Na Gruncie Słabonosnym Z Zastosowaniem Modelu Wielopłaszczyznowego Z Destrukturyzacja“. Archives of Civil Engineering 57, Nr. 1 (01.03.2011): 27–44. http://dx.doi.org/10.2478/v.10169-011-0004-6.
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Abstract A multi-laminate constitutive model for soft soils incorporating structural anisotropy is presented. Stress induced anisotropy of strength, which is present in multi-laminate type constitutive models, is augmented by directionally distributed overconsolidation. The model is presented in the elastic-plastic version in order to simulate strength anisotropy of soft clayey soils and destructuration effects. Performance of the model is shown for some element tests and for the numerical simulation of a trial road embankment constructed on soft clays at Haarajoki, Finland. The numerical calculations are completed with the commercial finite element code capable to perform coupled static/consolidation analysis of soils. Problems related to the initiation of in situ stress state, conditions of preconsolidation, as well as difficulties linked to estimation of the model parameters are discussed. Despite simple assumptions concerning field conditions and non-viscous formulation of the constitutive model, the obtained final results are of a sufficient accuracy for geotechnical practice.
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Chamberlain, Samuel R., Katherine Derbyshire, Richard E. Daws, Brian L. Odlaug, Eric W. Leppink und Jon E. Grant. „White matter tract integrity in treatment-resistant gambling disorder“. British Journal of Psychiatry 208, Nr. 6 (Juni 2016): 579–84. http://dx.doi.org/10.1192/bjp.bp.115.165506.
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BackgroundGambling disorder is a relatively common psychiatric disorder recently re-classified within the DSM-5 under the category of ‘substance-related and addictive disorders'.AimsTo compare white matter integrity in patients with gambling disorder with healthy controls; to explore relationships between white matter integrity and disease severity in gambling disorder.MethodIn total, 16 participants with treatment-resistant gambling disorder and 15 healthy controls underwent magnetic resonance imaging (MRI). White matter integrity was analysed using tract-based spatial statistics.ResultsGambling disorder was associated with reduced fractional anisotropy in the corpus callosum and superior longitudinal fasciculus. Fractional anisotropy in distributed white matter tracts elsewhere correlated positively with disease severity.ConclusionsReduced corpus callosum fractional anisotropy is suggestive of disorganised/damaged tracts in patients with gambling disorder, and this may represent a trait/vulnerability marker for the disorder. Future research should explore these measures in a larger sample, ideally incorporating a range of imaging markers (for example functional MRI) and enrolling unaffected first-degree relatives of patients.
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Scherwath, Martin, Anne Melhuish, Tim Stern und Peter Molnar. „Pn anisotropy and distributed upper mantle deformation associated with a continental transform fault“. Geophysical Research Letters 29, Nr. 8 (April 2002): 16–1. http://dx.doi.org/10.1029/2001gl014179.
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Chen, D. X., und L. Pascual. „Magnetization and incremental susceptibilities of ferromagnets with angularly distributed uniaxial anisotropy above remanence“. IEEE Transactions on Magnetics 39, Nr. 1 (Januar 2003): 510–18. http://dx.doi.org/10.1109/tmag.2002.806340.
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BUCKINGHAM, A. D., und Y. TANTIRUNGROTECHAI. „Predicting the proton shielding anisotropy in HF···CO2: a use of distributed magnetizabilities“. Molecular Physics 96, Nr. 8 (20.04.1999): 1225–29. http://dx.doi.org/10.1080/00268979909483067.
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TANTIRUNGROTECHAI, A. D. BUCKINGHAM, Y. „Predicting the proton shielding anisotropy in HF...CO2: a use of distributed magnetizabilities“. Molecular Physics 96, Nr. 8 (20.04.1999): 1225–29. http://dx.doi.org/10.1080/002689799164757.
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Brainerd, Tereasa G., und Masaya Yamamoto. „Satellite galaxies in the Illustris-1 simulation: anisotropic locations around relatively isolated hosts“. Monthly Notices of the Royal Astronomical Society 489, Nr. 1 (12.08.2019): 459–69. http://dx.doi.org/10.1093/mnras/stz2102.
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ABSTRACT We investigate the locations of satellite galaxies in the z = 0 redshift slice of the hydrodynamical Illustris-1 simulation. As expected from previous work, the satellites are distributed anisotropically in the plane of the sky, with a preference for being located near the major axes of their hosts. Due to misalignment of mass and light within the hosts, the degree of anisotropy is considerably less when satellite locations are measured with respect to the hosts’ stellar surface mass density than when they are measured with respect to the hosts’ dark matter surface mass density. When measured with respect to the hosts’ dark matter surface mass density, the mean satellite location depends strongly on host stellar mass and luminosity, with the satellites of the faintest, least massive hosts showing the greatest anisotropy. When measured with respect to the hosts’ stellar surface mass density, the mean satellite location is essentially independent of host stellar mass and luminosity. In addition, the satellite locations are largely insensitive to the amount of stellar mass used to define the hosts’ stellar surface mass density, as long as at least 50–70 per cent of the hosts’ total stellar mass is used. The satellite locations are dependent upon the stellar masses of the satellites, with the most massive satellites having the most anisotropic distributions.
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Bezrodna, I., V. Svystov und D. Bezrodny. „ANALYSIS OF ACOUSTIC ANISOTROPY PARAMETERS OF PYROXENE-MAGNETITE ROCKS OF THE PISCHANKA STRUCTURE“. Visnyk of Taras Shevchenko National University of Kyiv. Geology, Nr. 1 (88) (2020): 40–45. http://dx.doi.org/10.17721/1728-2713.88.06.
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The analysis of the results of acoustic properties of rocks study of Pischans`ka iron-ore structure is presented. The aim of the work is to establish the features of the distribution of acoustic properties and parameters of acoustic anisotropy in samples of core rocks selected from the well No. 3 of the Pischans`ka structure to determine the nature of its occurrence. A sample of 35 samples from the depth range 144-273 m is divided into 3 groups of rocks, namely: magnetite-pyroxene, quartz-magnetitepyroxene and biotite-amphibole crystalline shales. Based on an invariant polarization method, a number of acoustic laboratory measurements have been carried out. The values of the measured phase velocities "quasi-longitudinal" and two "quasi-transverse" waves at the stage of measurements showed significant acoustic anisotropy of the rocks. The ranges of the measured speeds of the collection samples are 7661 ÷ 5046 m / s for longitudinal waves and 4232 ÷ 2648 m/s for transverse ones. The difference in values measured for each of the sides of the cubic rhombic dodecahedron is from 100 to 800 m / s and from 0 to 500 m/s for Vp and Vs, respectively. The parameters of an acoustic ellipsoid were calculated, on the basis of which the division of samples into 3 main groups has been performed, according to the acoustic texture: acoustically linear, shale and rhombic. Separately, a group of samples with a more complex texture was discovered. The analysis of coefficients of anisotropy by different methods is carried out: longitudinal, transverse and relative acoustic anisotropy. Most of the samples are characterized by low or average acoustic anisotropy (from 2 to 7 %). A group of highly anisotropic rocks (11–14 %), represented by samples of biotite-amphibole crystalline silicates, is singled out. According to the parameters of the acoustic tensor of most samples, the transverse isotropic type of symmetry inherent to samples from the depth intervals 174–220 m and 222–232 m, while the smaller part is rhombic, is inherent. Differences in the parameters of anisotropy of samples can be explained by the significant heterogeneity of their textures, namely: micro cracks, minerals of various sizes, shapes and orientations. The results of the research show that the acoustic properties of the samples are quite heterogeneously distributed along the investigated depth range. This indicates the difficult conditions for the formation of rocks at different depths and the presence of different types of deformations, which accompanied the formation of the Pischans`ka structure.
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Zhu, Wei, Luanxiao Zhao und Rui Shan. „Modeling effective elastic properties of digital rocks using a new dynamic stress-strain simulation method“. GEOPHYSICS 82, Nr. 6 (01.11.2017): MR163—MR174. http://dx.doi.org/10.1190/geo2016-0556.1.
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We have developed a dynamic stress-strain simulation methodology to compute effective elasticity on digital rocks in a wide range of frequency based on the rotated staggered grid finite-difference method. The primary advantage of this simulator lies in characterizing the anisotropic behavior of complex porous rocks by setting specified boundary conditions along specified directions: The edges perpendicular to the propagating wave are applied with a strain boundary condition, and the edges parallel to the propagating wave are applied with a periodic boundary condition. The accuracy of the simulator is validated by comparing the simulating results in microinhomogeneous porous media containing randomly distributed inclusions and aligned oriented cracks, with that obtained by effective medium theories of self-consistent approximation in isotropic and anisotropic domains. This dynamic simulator can successfully capture anisotropic magnitude of rocks containing needle-like inclusions with different degrees of alignment. For real digital rock saturated with viscoelastic fluids, it is able to predict the dependence of velocities and attenuating factors on the frequency. We found that the magnitude of dispersion increases with the increase of pore fluid viscosity. Therefore, this method offers a robust and effective tool to compute effective elastic properties and anisotropy for real complex porous rocks.
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Yan, Li Zhen, Yong An Zhang, Bai Qing Xiong, Zhi Hui Li, Xi Wu Li, Hong Wei Liu, Shu Hui Huang, Hong Wei Yan und Kai Wen. „Annealing on Anisotropy and Mechanical Properties of an Al-Mg-Si Alloy“. Materials Science Forum 941 (Dezember 2018): 1077–82. http://dx.doi.org/10.4028/www.scientific.net/msf.941.1077.
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Intermediate annealing on anisotropy and mechanical properties of an Al-0.78Mg-0.90Si-0.65Zn-0.16Cu (wt. %) alloy was investigated by tensile test, optical microscope (OM) and electron back-scattered diffraction (EBSD). The results indicated that alloy sheet displayed various microstructure after without intermediate annealing, intermediate annealing treatment at 350°C for 2 h, 450°C for 2 h and 500°C for 5 min. Compared with the alloy without intermediate annealing, the alloy exhibited equiaxed grain with 35.0µm after annealing at 500°C for 5 min, grain orientation of the alloy was distributed randomly, and plastic strain ratio value of 45° direction was more than 0.6. The anisotropy of the sheet was significantly reduced. Annealing at 500°C for 5 min was suitable for the production process of automobile body sheets.
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Lin, Che-Yu, Bayode E. Owolabi und Chao-An Lin. „Polymer-turbulence interactions in a complex flow and implications for the drag reduction phenomenon“. Physics of Fluids 34, Nr. 4 (April 2022): 043106. http://dx.doi.org/10.1063/5.0086686.
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We present direct numerical simulation data for turbulent duct flow of a finite-extensibility non-linear elastic dumbbell model with the Peterlin approximation (FENE-P) fluid in the high drag reduction regime. While the secondary flow pattern is qualitatively similar to that in a Newtonian fluid, its magnitude is significantly reduced, resulting in a less uniformly distributed velocity profile and hence smaller gradients at the wall. The Reynolds stress tensor in the polymer-laden flow was found to be increasingly anisotropic with most of the turbulent kinetic energy retained in the streamwise component, [Formula: see text]. We introduce a novel approach for investigating polymer stretching using the anisotropy invariant map of the polymer stress tensor and observe the persistence of both uniaxial and biaxial extension. Analysis of the transport equation for the mean kinetic energy indicates that polymer stretching and relaxation is a highly dissipative process; hence, the introduction of an additional channel for dissipation in a flow is key to drag reduction.
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Chen, Dongchang, und You Wang. „Revealing Hidden Structural Anisotropy in Cation-Disordered Rock Salts“. ECS Meeting Abstracts MA2022-02, Nr. 3 (09.10.2022): 255. http://dx.doi.org/10.1149/ma2022-023255mtgabs.
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Cation disordered rock salts (DRX), a new class of cathode materials for Li ion batteries, have attracted lots of attention in recent years, due to their fascinatingly simple cubic structure, highly diverse composition, and great electrochemical performance. As cations in DRX are randomly distributed in a long-range, how the cations (Li and transition metal) are arranged in a shorter range is an intriguing question for the community of cathode materials research. In this work, we study the vibrational structure of a series of DRXs with well controlled compositions and revealed significant anisotropy of cation arrangements. Based on the results, we propose a scheme that describes how the structural anisotropy could exist in rock salt structures but shows an overall cubic Fm-3m diffraction pattern. Furthermore, we raise a model of Li transport based on the scheme we proposed, which complements the theory of Li percolation in DRX. The electrochemical behavior of the cathodes used in the study supports the model.
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Guan, Bo, Jianghai Xia, Ya Liu, Hao Zhang und Changwei Zhou. „Near-Surface Radial Anisotropy Tomography of Geothermal Reservoir Using Dense Seismic Nodal Array“. Journal of Physics: Conference Series 2651, Nr. 1 (01.12.2023): 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 sources. We applied seismic interferometry to retrieve both Rayleigh and Love waves. We used two-station analysis to obtain dispersion images and the corresponding high-quality dispersion curves were extracted by automated codes. 3-D tomographic results down to a depth of 1.6 km of S-wave velocity structure and radial anisotropy parameters were obtained using direct surface wave radial anisotropy tomography method. The anomalies of S-wave velocity and radial anisotropy parameters were combined to infer the storage of geothermal reservoir in Andi town. Furthermore, the accuracy of our results was verified by the borehole data.
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Shuai, Da, Alexey Stovas, Jianxin Wei, Bangrang Di und Yang Zhao. „Effective elastic properties of rocks with transversely isotropic background permeated by a set of vertical fracture cluster“. GEOPHYSICS 86, Nr. 3 (18.03.2021): C75—C87. http://dx.doi.org/10.1190/geo2019-0619.1.
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The linear slip theory is gradually being used to characterize seismic anisotropy. If the transversely isotropic medium embeds vertical fractures (VFTI medium), the effective medium becomes orthorhombic. The vertical fractures, in reality, may exist in any azimuth angle that leads the effective medium to be monoclinic. We apply the linear slip theory to create a monoclinic medium by only introducing three more physical meaning parameters: the fracture preferred azimuth angle, the fracture azimuth angle, and the angular standard deviation. First, we summarize the effective compliance of a rock as the sum of the background matrix compliance and the fracture excess compliance. Then, we apply the Bond transformation to rotate the fractures to be azimuthally dependent, introduce a Gaussian function to describe the fractures’ azimuth distribution assuming that the fractures are statistically distributed around the preferred azimuth angle, and average each fracture excess compliance over the azimuth. We investigate the influence of the fracture azimuth distribution domain and angular standard deviation on the effective stiffness coefficients, elastic wave velocities, and anisotropy parameters. Our results show that the fracture cluster parameters have a significant influence on the elastic wave velocities. The fracture azimuth distribution domain and angular standard deviation have a bigger influence on the orthorhombic anisotropy parameters in the [Formula: see text] plane than in the [Formula: see text] plane. The fracture azimuth distribution domain and angular standard deviation have little influence on the monoclinic anisotropy parameters responsible for the P-wave NMO ellipse and have a significant influence on the monoclinic anisotropy parameters responsible for the S1- and S2-wave NMO ellipse. The effective monoclinic can degenerate into the VFTI medium.