Impacts of anisotropy coefficient and porosity on the thermal conductivity and P-wave velocity of calcarenites used as building materials of historical monuments in Morocco

It is essential to study the porosity,thermal conductivity,and P-wave velocity of calcarenites,as well as the anisotropy coefficients of the thermal conductivity and P-wave velocity,for civil engineering,and conservation and restoration of historical monuments.This study focuses on measuring the thermal conductivity using the thermal conductivity scanning(TCS)technique and measuring the P-wave ve-locity using portable equipment.This was applied for some dry and saturated calcarenite samples in the horizontal and vertical directions(parallel and perpendicular to the bedding plane,respectively).The calcarenites were selected from some historical monuments in Morocco.These physical properties were measured in the laboratory to find a reliable relationship between all of these properties.As a result of the statistical analysis of the obtained data,excellent linear relationships were observed between the porosity and both the thermal conductivity and porosity.These relationships are characterized by relatively high coefficients of determination for the horizontal and vertical samples.Based on the thermal conductivity and P-wave velocity values in these two directions,the anisotropy coefficients of these two properties were calculated.The internal structure and the pore fabric of the calcarenite samples were delineated using scanning electron microscopy(SEM),while their chemical and mineral compositions were studied using the energy dispersive X-ray analysis(EDXA)and X-ray diffraction(XRD)techniques.

Highly Tunable Perpendicular Magnetic Anisotropy and Anisotropic Magnetoresistance in Ru-Doped La_(0.67)Sr_(0.33)MnO_(3)Epitaxial Films

As a prototypical half-metallic ferromagnet,La_(0.67)Sr_(0.33)MnO_(3)(LSMO)has been extensively studied due to its versatile physical properties and great potential in spintronic applications.However,the weak perpendicular magnetic anisotropy(PMA)limits the controllability and detection of magnetism in LSMO,thus hindering the realization of oxide-based spintronic devices with low energy consumption and high integration level.Motivated by this challenge,we develop an experimental approach to enhance the PMA of LSMO epitaxial films.By cooperatively introducing 4d Ru doping and a moderate compressive strain,the maximum uniaxial magnetic anisotropy in Ru-doped LSMO can reach 3.0×10^(5)J/m^(3)at 10 K.Furthermore,we find a significant anisotropic magnetoresistance effect in these Ru-doped LSMO films,which is dominated by the strong PMA.Our findings offer an effective pathway to harness and detect the orientations of magnetic moments in LSMO films,thus promoting the feasibility of oxide-based spintronic devices,such as spin valves and magnetic tunnel junctions.

Anisotropic time-dependent behaviors of shale under direct shearing and associated empirical creep models

Understanding the anisotropic creep behaviors of shale under direct shearing is a challenging issue.In this context,we conducted shear-creep and steady-creep tests on shale with five bedding orientations (i.e.0°,30°,45°,60°,and 90°),under multiple levels of direct shearing for the first time.The results show that the anisotropic creep of shale exhibits a significant stress-dependent behavior.Under a low shear stress,the creep compliance of shale increases linearly with the logarithm of time at all bedding orientations,and the increase depends on the bedding orientation and creep time.Under high shear stress conditions,the creep compliance of shale is minimal when the bedding orientation is 0°,and the steady-creep rate of shale increases significantly with increasing bedding orientations of 30°,45°,60°,and 90°.The stress-strain values corresponding to the inception of the accelerated creep stage show an increasing and then decreasing trend with the bedding orientation.A semilogarithmic model that could reflect the stress dependence of the steady-creep rate while considering the hardening and damage process is proposed.The model minimizes the deviation of the calculated steady-state creep rate from the observed value and reveals the behavior of the bedding orientation's influence on the steady-creep rate.The applicability of the five classical empirical creep models is quantitatively evaluated.It shows that the logarithmic model can well explain the experimental creep strain and creep rate,and it can accurately predict long-term shear creep deformation.Based on an improved logarithmic model,the variations in creep parameters with shear stress and bedding orientations are discussed.With abovementioned findings,a mathematical method for constructing an anisotropic shear creep model of shale is proposed,which can characterize the nonlinear dependence of the anisotropic shear creep behavior of shale on the bedding orientation.

Investigating the elliptic anisotropy of identified particles in p-Pb collisions with a multi-phase transport model

The elliptic azimuthal anisotropy coefficient(v_(2))of the identified particles at midrapidity(|η|<0.8)was investigated in p-Pb collisions at√s_(NN)=5.02 TeV using a multi-phase transport model(AMPT).The calculations of differential v_(2)based on the advanced flow extraction method of light flavor hadrons(pions,kaons,protons,andΛ)in small collision systems were extended to a wider transverse momentum(p_(T))range of up to 8 GeV/c for the first time.The string-melting version of the AMPT model provides a good description of the measured p_(T)-differential v_(2)of the mesons but exhibits a slight deviation from the baryon v_(2).In addition,we observed the features of mass ordering at low p_(T)and the approximate number-of-constituentquark(NCQ)scaling at intermediate p_(T).Moreover,we demonstrate that hadronic rescattering does not have a significant impact on v_(2)in p-Pb collisions for different centrality selections,whereas partonic scattering dominates in generating the elliptic anisotropy of the final particles.This study provides further insight into the origin of collective-like behavior in small collision systems and has referential value for future measurements of azimuthal anisotropy.

Enhanced prediction of anisotropic deformation behavior using machine learning with data augmentation

Mg alloys possess an inherent plastic anisotropy owing to the selective activation of deformation mechanisms depending on the loading condition.This characteristic results in a diverse range of flow curves that vary with a deformation condition.This study proposes a novel approach for accurately predicting an anisotropic deformation behavior of wrought Mg alloys using machine learning(ML)with data augmentation.The developed model combines four key strategies from data science:learning the entire flow curves,generative adversarial networks(GAN),algorithm-driven hyperparameter tuning,and gated recurrent unit(GRU)architecture.The proposed model,namely GAN-aided GRU,was extensively evaluated for various predictive scenarios,such as interpolation,extrapolation,and a limited dataset size.The model exhibited significant predictability and improved generalizability for estimating the anisotropic compressive behavior of ZK60 Mg alloys under 11 annealing conditions and for three loading directions.The GAN-aided GRU results were superior to those of previous ML models and constitutive equations.The superior performance was attributed to hyperparameter optimization,GAN-based data augmentation,and the inherent predictivity of the GRU for extrapolation.As a first attempt to employ ML techniques other than artificial neural networks,this study proposes a novel perspective on predicting the anisotropic deformation behaviors of wrought Mg alloys.

Anisotropic shearing mechanism of Kangding slate:Experimental investigation and numerical analysis

The shear mechanical behavior is regarded as an essential factor affecting the stability of the surrounding rocks in underground engineering.The shear strength and failure mechanisms of layered rock are significantly affected by the foliation angles.Direct shear tests were conducted on cubic slate samples with foliation angles of 0°,30°,45°,60°,and 90°.The effect of foliation angles on failure patterns,acoustic emission(AE)characteristics,and shear strength parameters was analyzed.Based on AE characteristics,the slate failure process could be divided into four stages:quiet period,step-like increasing period,dramatic increasing period,and remission period.A new empirical expression of cohesion for layered rock was proposed,which was compared with linear and sinusoidal cohesion expressions based on the results made by this paper and previous experiments.The comparative analysis demonstrated that the new expression has better prediction ability than other expressions.The proposed empirical equation was used for direct shear simulations with the combined finite-discrete element method(FDEM),and it was found to align well with the experimental results.Considering both computational efficiency and accuracy,it was recommended to use a shear rate of 0.01 m/s for FDEM to carry out direct shear simulations.To balance the relationship between the number of elements and the simulation results in the direct shear simulations,the recommended element size is 1 mm.

Major methods of seismic anisotropy

Seismic anisotropy reveals that seismic wave velocity, amplitude, and other physical properties show variations in different directions, which can be divided into lattice-preferred orientation(LPO) and shape-preferred orientation(SPO) according to its physical mechanisms. The main methods for studying seismic anisotropy include shearwave splitting analysis, P-wave travel time inversion and surface-wave tomography, etc. There are some differences and correlations among these methods. Seismic anisotropy is an important way to reveal the dynamic processes of crust-mantle evolution, and it is significant for monitoring crustal stress changes and improve seismic exploration studies. With the help of long-term observation, the application of machine learning techniques and combining inversion based on multiple phases would become potential developments in seismic anisotropy studies. This may improve the understanding of complex seismic anisotropic models, such as multiple layers anisotropy with an oblique axis of symmetry.

Investigation of reflection anisotropy induced by micropipe defects on the surface of a 4H-SiC single crystal using scanning anisotropy microscopy

Optical reflection anisotropy microscopy mappings of micropipe defects on the surface of a 4H-SiC single crystal are studied by the scanning anisotropy microscopy(SAM)system.The reflection anisotropy(RA)image with a'butterfly pattern'is obtained around the micropipes by SAM.The RA image of the edge dislocations is theoretically simulated based on dislocation theory and the photoelastic principle.By comparing with the Raman spectrum,it is verified that the micropipes consist of edge dislocations.The different patterns of the RA images are due to the different orientations of the Burgers vectors.Besides,the strain distribution of the micropipes is also deduced.One can identify the dislocation type,the direction of the Burgers vector and the optical anisotropy from the RA image by using SAM.Therefore,SAM is an ideal tool to measure the optical anisotropy induced by the strain field around a defect.

Remnant Paleoproterozoic Subduction or Lithospheric Drip Initiation at the Yilgarn Craton Margin:Constraints from P-wave Tomography

The Paleoproterozoic was a critical time in whether modern-style plate tectonics had become globally dominant(e.g.,Wan et al.,2020).The Capricorn Orogen witnessed the assembly of the Pilbara and Yilgarn Cratons and an exotic microcontinent,the Glenburgh Terrane,to form the West Australia Craton(WAC)through two collisional orogenic events,the 2215–2145 Ma Ophthalmian and 2005–1950 Ma Glenburgh Orogenies(Johnson et al.,2013;Fig.1).Compared to other Proterozoic orogenic belts in Australia,the Capricorn Orogen preserves‘complete'opposing continental margin successions,together with intervening arc fragments associated with oceanic closure and foreland basins associated with collisional loading(Cawood et al.,2009).

Anisotropic metal–insulator transition in strained VO_(2)(B) single crystal

Mechanical strain can induce noteworthy structural and electronic changes in vanadium dioxide, imparting substantial scientific importance to both the exploration of phase transitions and the development of potential technological applications. Unlike the traditional rutile(R) phase, bronze-phase vanadium dioxide [VO_(2)(B)] exhibits an in-plane anisotropic structure. When subjected to stretching along distinct crystallographic axes, VO_(2)(B) may further manifest the axial dependence in lattice–electron interactions, which is beneficial for gaining insights into the anisotropy of electronic transport.Here, we report an anisotropic room-temperature metal–insulator transition in single-crystal VO_(2)(B) by applying in-situ uniaxial tensile strain. This material exhibits significantly different electromechanical responses along two anisotropic axes.We reveal that such an anisotropic electromechanical response mainly arises from the preferential arrangement of a straininduced unidirectional stripe state in the conductive channel. This insulating stripe state could be attributed to the in-plane dimerization within the distorted zigzag chains of vanadium atoms, evidenced by strain-modulated Raman spectra. Our work may open up a promising avenue for exploiting the anisotropy of metal–insulator transition in vanadium dioxide for potential technological applications.

Dielectric anisotropy in liquid crystal mixtures with nematic and smectic phases

The modulation of dielectric anisotropy(△ε)is pivotal for elucidating molecular interactions and directing the alignment of liquid crystals.In this study,we combine liquid crystals with opposing dielectric anisotropies to explore the impact of varying concentrations on their properties.We report the sign-reversal of△εin both the nematic and smectic A phases of these mixed liquid crystals,alongside a dual-frequency behaviour across a broad temperature spectrum.Our research further quantifies the influence of mixture ratios under various temperatures and electric field frequencies.This exploration may pave the way for the discovery of new physical phenomena.

Quantitative characterizations of anisotropic dynamic properties in organic-rich shale with different kerogen content

Understanding the quantitative responses of anisotropic dynamic properties in organic-rich shale with different kerogen content(KC)is of great significance in hydrocarbon exploration and development.Conducting controlled experiments with a single variable is challenging for natural shales due to their high variations in components,diagenesis conditions,or pore fluid.We employed the hot-pressing technique to construct 11 well-controlled artificial shale with varying KC.These artificial shale samples were successive machined into prismatic shape for ultrasonic measurements along different directions.Observations revealed bedding perpendicular P-wave velocities are more sensitive to the increasing KC than bedding paralleling velocities due to the preferential alignments of kerogen.All elastic stiffnesses except C_(13)are generally decreasing with the increasing KC,the variation of C_(1) and C_(33)on kerogen content are more sensitive than those of C_(44)and C_(66).Apparent dynamic mechanical parameters(v and E)were found to have linear correlation with the true ones from complete anisotropic equations independent of KC,which hold value towards the interpretation of well logs consistently across formations,Anisotropic mechanical parameters(ΔE and brittlenessΔB)tend to decrease with the reducing KC,withΔB showing great sensitivity to KC variations.In the range of low KC(<10%),the V_(P)/V_(S) ratio demonstrated a linearly negative correlation with KC,and the V_(P)/V_(S) ratio magnitude of less than 1.75may serve as a significant characterization for highly organic-rich(>10%)shale,compilation of data from natural organic rich-shales globally verified the similar systematic relationships that can be empirically used to predict the fraction of KC in shales.

Investigation of anisotropic strength criteria for layered rock mass

Layered rock mass is a type of engineering rock mass with sound mechanical anisotropy,which is generally unfavorable to the stability of underground works.To investigate the strength anisotropy of layered rock,the Mohr-Coulomb and Hoek-Brown criteria are introduced to establish the two transverse isotropic strength criteria based on Jaeger's single weak plane theory and maximum axial strain theory,and parameter determination methods.Furthermore,the sensitivity of strength parameters(K 1,K 2,and K 3)that are used to characterize the anisotropy strength of non-sliding failure involved in the strength criteria and confining pressure are investigated.The results demonstrate that strength parameters K 1 and K 2 affect the strength of layered rock samples at all bedding angles except for the bedding angle of 90°and the angle range that can cause the shear sliding failure along the bedding plane.The strength of samples at any bedding angle decreases with increasing K 1,whereas the opposite is for K 2.Except for bedding angles of 0°and 90°and the bedding angle range that can cause the shear sliding along the bedding plane,K 3 has an impact on the strength of rock samples with other bedding angles that the specimens'strength increases with increase of K 3.In addition,the strength of the rock sample increases as confining pressure rises.Furthermore,the uniaxial and triaxial tests of chlorite schist samples were carried out to verify and evaluate the strength criteria proposed in the paper.It shows that the predicted strength is in good agreement with the experimental results.To test the applicability of the strength criterion,the strength data of several types of rock in the literature are compared.Finally,a comparison is made between the fitting effects of the two strength criteria and other available criteria for layered rocks.

The Origin of Cosmic Structures Part 6: CMB Anisotropy

In a recent series of papers, we introduced a new model of nucleosynthesis in which the matter content of the universe came into existence at a time of about 4 × 10-5 s. At that time, a small percentage of the vacuum energy was converted into neutron/antineutron pairs with a very small excess of neutrons. This process was regulated by an imprint that was established in the vacuum during an initial Plank-era inflation. Immediately after their inception, annihilation and charge exchange reactions proceeded at a very high rate and ran to completion after an interval of about 10-11 s. By then, all the antibaryons had disappeared thereby establishing the matter/antimatter asymmetry of the universe. What remained were very high densities of mesons and leptons, somewhat lower densities of protons and neutrons, and finally, the very high density of photons that eventually became the CMB. The density of matter so created varied from one location to another in such a manner as to account for all cosmic structures and because the energy density of the photons varied in proportion to that of the matter, the CMB-to-be came into existence with an anisotropic spectrum already in place. For structures, the size of galaxy clusters, the initial anisotropy magnitudes were on the order of 25%. In this paper, we will follow the subsequent evolution of the photons and show that this model predicts with accuracy the temperature of the warmest anisotropies in the observed CMB spectrum. .

Data-driven modeling on anisotropic mechanical behavior of brain tissue with internal pressure

Brain tissue is one of the softest parts of the human body,composed of white matter and grey matter.The mechanical behavior of the brain tissue plays an essential role in regulating brain morphology and brain function.Besides,traumatic brain injury(TBI)and various brain diseases are also greatly influenced by the brain's mechanical properties.Whether white matter or grey matter,brain tissue contains multiscale structures composed of neurons,glial cells,fibers,blood vessels,etc.,each with different mechanical properties.As such,brain tissue exhibits complex mechanical behavior,usually with strong nonlinearity,heterogeneity,and directional dependence.Building a constitutive law for multiscale brain tissue using traditional function-based approaches can be very challenging.Instead,this paper proposes a data-driven approach to establish the desired mechanical model of brain tissue.We focus on blood vessels with internal pressure embedded in a white or grey matter matrix material to demonstrate our approach.The matrix is described by an isotropic or anisotropic nonlinear elastic model.A representative unit cell(RUC)with blood vessels is built,which is used to generate the stress-strain data under different internal blood pressure and various proportional displacement loading paths.The generated stress-strain data is then used to train a mechanical law using artificial neural networks to predict the macroscopic mechanical response of brain tissue under different internal pressures.Finally,the trained material model is implemented into finite element software to predict the mechanical behavior of a whole brain under intracranial pressure and distributed body forces.Compared with a direct numerical simulation that employs a reference material model,our proposed approach greatly reduces the computational cost and improves modeling efficiency.The predictions made by our trained model demonstrate sufficient accuracy.Specifically,we find that the level of internal blood pressure can greatly influence stress distribution and determine the possible related damage behaviors.

Study on the low mechanical anisotropy of extruded Mg-Zn-Mn-Ce-Ca alloy tube in the compression process

In this study,the extruded Mg-Zn-Mn-Ce-Ca alloy tube with a low compression anisotropy along the ED,45ED and TD was prepared.The effect of the second phases,initial texture and deformation behavior on this low mechanical anisotropy was investigated.The results revealed that the alloy tube contains the high content(Mg1-xZnx)11Ce phase and the low content of Mg12Ce phase.These second phases are respectively incoherent and coherent with the Mg matrix,and their influence can be ignored.Additionally,the alloy tube exhibited a weak basal fiber texture,where the c-axis was aligned along the 0°∼30°tilt from TD to ED.Such a texture made the initial deformation(at 1.0%∼1.6%strain)of the three samples controlled by comparable basalslip.As deformation progressed(1.6∼9.0%strain),larger amounts of ETWs nucleated and gradually approached saturation in the three samples,re-orienting the c-axis to a 0°∼±30°deviation with respect to the loading directions.Meanwhile,the prismatic and pyramidal<c+a>slips replaced the dominant deformation progressively until fracture.Eventually,the similar deformation mechanisms determined by the weak initial texture in the three samples contribute to the comparable strain hardening rates,resulting in the low compressive anisotropy of the alloy tube.

Anisotropy measurements and characterization of the Qingshankou shale

Qingshankou shale(Gulong area,China)exhibits strong acoustic anisotropy characteristics,posing significant challenges to its exploration and development.In this study,the five full elastic constants and multipole response law of the Qingshankou shale were studied using experimental measurements.Analyses show that the anisotropy parametersϵandγin the study region are greater than 0.4,whereas the anisotropy parameterδis smaller,generally 0.1.Numerical simulations show that the longitudinal and transverse wave velocities of these strong anisotropic rocks vary significantly with inclination angle,and significant differences in group velocity and phase velocity are also present.Acoustic logging measures the group velocity in dipped boreholes;this differs from the phase velocity to some extent.As the dip angle increases,the longitudinal and SH wave velocities increase accordingly,while the qSV-wave velocity initially increases and then decreases,reaching its maximum value at a dip of approximately 40°.These results provide an effective guide for the correction and modeling of acoustic logging time differences in the region.

Enhanced magnetic anisotropy and high hole mobility in magnetic semiconductor Ga_(1-x-y)Fe_(x)Ni_(y)Sb

(Ga,Fe)Sb is a promising magnetic semiconductor(MS)for spintronic applications because its Curie temperature(T_(C))is above 300 K when the Fe concentration is higher than 20%.However,the anisotropy constant Ku of(Ga,Fe)Sb is below 7.6×10^(3)erg/cm^(3)when Fe concentration is lower than 30%,which is one order of magnitude lower than that of(Ga,Mn)As.To address this issue,we grew Ga_(1-x-y)Fe_(x)Ni_(y)Sb films with almost the same x(≈24%)and different y to characterize their magnetic and electrical transport properties.We found that the magnetic anisotropy of Ga_(0.76-y)Fe_(0.24)Ni_(y)Sb can be enhanced by increasing y,in which Ku is negligible at y=1.7%but increases to 3.8×10^(5)erg/cm^(3)at y=6.1%(T_(C)=354 K).In addition,the hole mobility(μ)of Ga_(1-x-y)Fe_(x)Ni_(y)Sb reaches 31.3 cm^(2)/(V∙s)at x=23.7%,y=1.7%(T_(C)=319 K),which is much higher than the mobility of Ga_(1-x)Fe_(x)Sb at x=25.2%(μ=6.2 cm^(2)/(V∙s)).Our results provide useful information for enhancing the magnetic anisotropy and hole mobility of(Ga,Fe)Sb by using Ni co-doping.

Analytical solutions to the precession relaxation of magnetization with uniaxial anisotropy

Based on the Landau-Lifshitz-Gilbert(LLG)equation,the precession relaxation of magnetization is studied when the external field H is parallel to the uniaxial anisotropic field H_(k).The evolution of three-component magnetization is solved analytically under the condition of H=nH_(k)(n=3,1 and 0).It is found that with an increase of H or a decrease of the initial polar angle of magnetization,the relaxation time decreases and the angular frequency of magnetization increases.For comparison,the analytical solution for H_(k)=0 is also given.When the magnetization becomes stable,the angular frequency is proportional to the total effective field acting on the magnetization.The analytical solutions are not only conducive to the understanding of the precession relaxation of magnetization,but also can be used as a standard model to test the numerical calculation of LLG equation.

Estimation of the anisotropy of hydraulic conductivity through 3D fracture networks using the directional geological entropy

With an extension of the geological entropy concept in porous media,the approach called directional entrogram is applied to link hydraulic behavior to the anisotropy of the 3D fracture networks.A metric called directional entropic scale is used to measure the anisotropy of spatial order in different directions.Compared with the traditional connectivity indexes based on the statistics of fracture geometry,the directional entropic scale is capable to quantify the anisotropy of connectivity and hydraulic conductivity in heterogeneous 3D fracture networks.According to the numerical analysis of directional entrogram and fluid flow in a number of the 3D fracture networks,the hydraulic conductivities and entropic scales in different directions both increase with spatial order(i.e.,trace length decreasing and spacing increasing)and are independent of the dip angle.As a result,the nonlinear correlation between the hydraulic conductivities and entropic scales from different directions can be unified as quadratic polynomial function,which can shed light on the anisotropic effect of spatial order and global entropy on the heterogeneous hydraulic behaviors.