Anisotropic Characteristics Research Articles

Testing a proposed planarity tool for studying satellite systems

Context. The existence of planes of satellite galaxies has been identified as a long-standing challenge to ΛCDM cosmology because satellite systems in cosmological simulations that are as extremely flattened and as strongly kinematically correlated as the observed structures are rare. Aims. We investigate a recently proposed new metric for measuring the overall degree of planarity of a satellite system that was used to claim consistency between the Milky Way satellite plane and ΛCDM. Methods. We studied the behavior of the planarity metric under several features of anisotropy that are present in ΛCDM satellite systems but are not related to satellite planes. Specifically, we considered the impact of oblate or prolate distributions, the number of satellites, the clustering of satellites, and radial and asymmetric distributions (lopsidedness). We also investigated whether the metric is independent of the orientation of the studied satellite system. Results. We find that all of these features of anisotropy lead to the metric to infer an increased degree of planarity, even though none of them has any direct relation to satellite planes. The metric is also highly sensitive to the orientation of the studied system (or chosen coordinate system): There is almost no correlation between the reported degrees of planarity of the metric for identical random systems rotated by 90°. Conclusions. Our results demonstrate that the new proposed metric is not suited for measuring the overall planarity in satellite systems. Consequently, no consistency of the observed Milky Way satellite plane with ΛCDM can be inferred using this metric.

Development of in-situ anisotropic deformation characteristics detection equipment for loess hole

Development of in-situ anisotropic deformation characteristics detection equipment for loess hole

Experimental study of deformation induced by high-pressure methane adsorption and desorption: Insights into anisotropy and hysteresis characteristics

Experimental study of deformation induced by high-pressure methane adsorption and desorption: Insights into anisotropy and hysteresis characteristics

Multi-dimensional anisotropic feature interaction with machine learning to predict the thermal conductivity of A2B2O7-type high-entropy ceramics

Multi-dimensional anisotropic feature interaction with machine learning to predict the thermal conductivity of A2B2O7-type high-entropy ceramics

Temperature evolution and thermoelastic behavior of epoxy-impregnated REBCO HTS composite coils studied using a heat-force bi-directional coupling quench model

Quench and mechanical behavior are the key issues for the safe operation of epoxy-impregnated (Re)Ba2Cu3Ox (REBCO) pancake coil. The contribution of strain energy to the temperature field during heat propagation and the effect of temperature changes on the mechanical behaviour in the force field are considered. In the paper, the bi-directional coupling differential equations of heat conduction and elastic equilibrium are proposed, and their bi-directional coupling solution is realized using finite element method. The model is not based on homogenization assumption considering separately the anisotropic characteristics of each layer in a REBCO composite tape. In addition, the REBCO tape after quench is defined as a parallel circuit model in the finite element model. During the quench, the current is distributed between the superconducting (REBCO) and metal (copper, silver and Hastelloy) layers according to their resistance. The results show that for the self-field conditions, the strain-energy contribution that is taken into account in the heat-force bi-directional coupling model causes a 3 % smaller overall temperature of the coil, which is still necessary to consider for the quench behavior of highly sensitive superconducting coils. Another important result is that thermal stresses are the major contribution to the internal stress state of the coil in self-field, whereas under the background magnetic field of 5 T, the radial stress inside the coil has reached the strength range of peeling delamination.

Deformation damage mechanism and strength criterion of columnar jointed rock mass under true triaxial condition

To accurately understand the anisotropic mechanical properties of columnar jointed basalt distributed in the Baihetan Hydropower Station, indoor true triaxial loading physical model tests were conducted with different joint angles (β = 0°–90°) to study the strength deformation and failure mode of columnar jointed rock mass (CJRM). The results indicate that the strength anisotropy characteristics of CJRM under different stress environments are significant. The peak strength shows a U-shaped (σ2 = 2 MPa, σ2 = 4.5 MPa), W-shaped (σ2 = 3 MPa), and linearly increasing (σ2 = 5 MPa) rule of change. The increments in peak strength of CJRM varied significantly with the intermediate principal stresses, with average increments of 29.0% (σ2/σ3 = 1.5), 48.8% (σ2/σ3 = 2.25), and 45.4% (σ2/σ3 = 2.5); ε3 increases and then decreases with the change of inclination angle β, and the shear expansion phenomenon increases, ε2 decreases and then increases with the β, and the deformation characteristics of CJRM are that the expansion deformation transforms into compression deformation. The increase in σ2 shifts the rock features from moderate anisotropy to low anisotropy. According to the damage characteristics, the CJRM are classified according to three damage modes: (a) structurally controlled, (b) stress-controlled, and (c) stress-structurally controlled. Finally, Mogi–Coulomb strength criterion and Drucker–Prager strength criterion, which are applicable to true triaxial stress conditions, were used to verify the experimental results. The Mogi–Coulomb strength criterion fitted the strength parameters c and φ values, which showed a high degree of agreement with the in situ test results on site, indicating good applicability. The research results can scientifically and accurately predict and evaluate the stability of the Baihetan project.

Study on the measurement method of internal strain in carbon fiber laminate

Abstract Aiming at the characteristics of orthotropic anisotropy, multiangle and multilayer of carbon fiber composites, based on the relevant theories of mechanics of materials and mechanics of composites, a method of calculating the strain in the main direction of each ply inside the carbon fiber composite laminate by using the strain measured in the reverse order of the surface layer is proposed. In this study, carbon fiber composite laminates with different lay-up angles and thicknesses are selected as test objects, and the accuracy of the strain gauge measurement and rotational axis calculation method is verified by comparing the measured values of extensometer with those of the carbon fiber strain gauge that are different in the surface pasting direction. HyperMesh finite element software was used to simulate and solve the strain values in the main direction of the internal layers and compared with the strain in the main direction of the internal layers based on the surface strain measurement, which proved the validity of the method of calculating the strain in the main direction of the internal layers based on the surface strain measurement in inverse sequence.

Integration of Asymmetric Multi-Path Hollow Structure and Multiple Heterogeneous Interfaces in Fe3O4@C@NiO Nanoprisms Enabling Ultra-Low and Broadband Absorption.

A reasonable construction of hollow structures to obtain high-performance absorbers is widely studied, but it is still a challenge to select suitable materials to improve the low-frequency attenuation performance. Here, the Fe3O4@C@NiO nanoprisms with unique tip shapes, asymmetric multi-path hollow cavity, and core-shell heteroepitaxy structure are designed and synthesized based on anisotropy and intrinsic physical characteristics. Impressively, by changing the load of NiO, the composites achieve strong absorption, broadband, low-frequency absorption: the reflection loss of -55.8 dB and the absorption bandwidth of 9.9 GHz covers both low and high frequency (2.9-6.1 and 11.3-18 GHz). The constructed anisotropic hollow and heterointerface nanoprisms can optimize impedance matching for low-frequency absorption (3.8-7.9 GHz) almost completely covering the 5G band. Especially, the influence of hollow path on the interface polarization and ferromagnetic coupling behavior is revealed through the simulation of electric and magnetic field distribution using the High-Frequency Structure Simulator (HFSS). In addition, HFSS simulation shows that the Radar Cross-Sectional (RCS) value of the absorber at any angle is <-10 dB m2, which meets the complex requirements in practical application. This research paves a new way for the development of efficient low-frequency absorbers based on composition and structure design.

Interaction effects of anisotropic roughness interface and component shape characteristics on fatigue life of thermal barrier coatings

Interaction effects of anisotropic roughness interface and component shape characteristics on fatigue life of thermal barrier coatings

Wet Anisotropic Etching Characteristics of Si{111} in KOH-Based Solution.

Wet chemical etching of silicon has been a topic of significant interest due to its importance in microelectromechanical systems (MEMS), nanotechnology, and semiconductor device fabrication. Many kinds of MEMS components (e.g., cavity, diaphragm, cantilever, etc.) are fabricated through wet anisotropic etching-based silicon bulk micromachining of {100} and {110} oriented silicon wafers. Wet anisotropic etching of silicon is primarily carried out using alkaline solutions such as potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), etc. The etching rate of Si{111} crystal planes is significantly slower compared to other planes like Si{100} and Si{110} as a result of its atomic structure and surface properties. Therefore, the Si{111} crystal plane is of particular interest owing to its unique properties and potential applications. In this work, we report the wet anisotropic etching characteristics of Si{111} in KOH with addition of isopropyl alcohol (IPA). Surface morphology of the etched Si{111} surfaces was examined using confocal laser scanning microscopy (CLSM). In all experimental scenarios, the Si{111} crystal surface gives rise to triangular etch pits, the size and depth of these etch pits are contingent upon the etching time. Following your advice, we revised the abstract phrase "become more sharper" in the summary and quantified the angle data of the triangle. The entire statement has been specifically modified to Furthermore, when the additive IPA is incorporated into the etchant, the corners of these triangular etch pits on the surface transitions from rounded to sharp (with each angles of approximately 60°), indicating that the overall shape of these triangular etch recesses approaches that of an equilateral triangle. In addition, the theory of crystal cleavage is introduced to explain the formation mechanism of surface triangular flat-bottom etch pits during the etching process of Si{111} crystal planes. At the same time, the relevant experiments on Si{111} samples with a SiO2 mask layer on the surface have been completed, and the results verify the correctness of the analysis of the relevant mechanism. The relevant results and mechanism presented in this article are of large significance for engineering applications in both academic and industrial laboratories.

Direct Ink Writing 3D Printing Polytetrafluoroethylene/Polydimethylsiloxane Membrane with Anisotropic Surface Wettability and Its Application in Oil-Water Separation.

Biological surfaces with physical discontinuity or chemical heterogeneity possess special wettability in the form of anisotropic wetting behavior. However, there are several challenges in designing and manufacturing samples with anisotropic wettability. This study investigates the fabrication of PTFE/PDMS grid membranes using Direct Ink Writing (DIW) 3D printing for oil-water separation applications. The ink's rheological properties were optimized, revealing that a 60% PTFE/PDMS composite exhibited the ideal shear-thinning behavior for 3D printing. Our research investigated the interplay between various printing parameters like the extrusion air pressure, layer thickness, feed rate, and printing speed, which were found to influence the filament dimensions, pore sizes, and hydrophobic properties of the grid membrane. Two distinct grid structures were analyzed for their wettability and anisotropic hydrophobic characteristics. The grid membranes achieved up to 100% oil-water separation efficiency in specific configurations. Separation efficiency was shown to be dependent on factors like intrusion pressure, grid architecture, and the number of layers. This study underscores the potential of DIW 3D printing in creating specialized surfaces with controlled wettability, particularly superhydrophobicity and anisotropy, paving the way for advanced environmental applications such as efficient oil-water separation.

In-Plane Anisotropy in van der Waals NiTeSe Ternary Alloy.

The anisotropic properties of materials profoundly influence their electronic, magnetic, optical, and mechanical behaviors and are critical for a wide range of applications. In this study, the anisotropic characteristics of Ni-based van der Waals materials, specifically NiTe2 and its alloy NiTeSe, utilizing a combination of comprehensive scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations, are explored. Unlike 1T-NiTe2, which exhibits trigonal in-plane symmetry, the substitution of Te with Se in NiTe2 (resulting in the NiTeSe alloy) induces a pronounced in-plane anisotropy. This anisotropy is clear in the STM topographs, which reveal a distinct linear order of charge distribution. Corroborating these observations, ARPES measurements and DFT calculations reveal an anisotropic Fermi surface centered at the point, which is notably elongated along the ky direction, leading to directional variations in in-plane carrier velocities. Consequently, the Fermi velocity is highest along the kx direction where the linear charge distribution aligns in real space and is lowest along the ky direction. These findings offer valuable insights into the tunability of anisotropic properties in ternary transition metal dichalcogenide systems, highlighting their potential applications in the development of anisotropic electronic and optoelectronic devices.

Review of the Microstructural Impact on Creep Mechanisms and Performance for Laser Powder Bed Fusion Inconel 718.

Inconel 718 (IN718) is a polycrystalline nickel-based superalloy and one of the most widely used materials in the aerospace industry owing to its excellent mechanical performances at high temperatures, including creep resistance. Interest in additively manufactured components in aerospace is greatly increasing due to their ability to reduce material consumption, to manufacture complex parts, and to produce out-of-equilibrium microstructures, which can be beneficial for mechanical behavior. IN718's properties are, however, very sensitive to microstructural features, which strongly depend on the manufacturing process and subsequent heat treatments. Additive manufacturing and, more specifically, Laser Powder Bed Fusion (LPBF) induces very high thermal gradients and anisotropic features due to its inherently directional nature, which largely defines the microstructure of the alloy. Hence, defining appropriate manufacturing parameters and heat treatments is critical to obtain appropriate mechanical behavior. This review aims to present the main microstructural features of IN718 produced by LPBF, the creep mechanisms taking place, the optimal microstructure for creep strength, and the most efficient heat treatments to yield such an optimized microstructure.

Integration and Application of a Fabric-Based Modified Cam-Clay Model in FLAC3D

In order to consider the effect of fabric anisotropy in the analysis of geotechnical boundary value problems, this study proposes a modified model based on a fabric-based modified Cam-clay model, which can account for the anisotropic response of soil. The major modification of the original model aims to simplify the equations for numerical implementation by replacing the SMP strength criterion with the Lade’s strength criterion. This model comprehensively considers the inherent anisotropy, induced anisotropy, and three-dimensional strength characteristics of soil. The model is first numerically implemented using the elastic trial–plastic correction method, and then it is encapsulated into the FLAC3D 6.0 software, and tested through conventional triaxial, embankment loading, and tunnel excavation experiments. Numerical simulation results indicate that considering anisotropy and three-dimensional strength in geotechnical engineering analysis is necessary. By accounting for the interaction between microstructure and macroscopic anisotropy, the model can more accurately represent soil behavior, providing significant advantages for geotechnical analysis.

Anisotropic Raman Scattering and Lattice Orientation Identification of 2M-WS2.

Anisotropic materials with low symmetries hold significant promise for next-generation electronic and quantum devices. 2M-WS2, which is a candidate for topological superconductivity, has garnered considerable interest. However, a comprehensive understanding of how its anisotropic features contribute to unconventional superconductivity, along with a simple, reliable method to identify its crystal orientation, remains elusive. Here, we combine theoretical and experimental approaches to investigate angle- and polarization-dependent anisotropic Raman modes of 2M-WS2. Through first-principles calculations, we predict and analyze the phonon dispersion and lattice vibrations of all Raman modes in 2M-WS2. We establish a direct correlation between their anisotropic Raman spectra and high-resolution transmission electron microscopy images. Finally, we demonstrate that anisotropic Raman spectroscopy can accurately determine the crystal orientation and twist angle between two stacked 2M-WS2 layers. Our findings provide insights into the electron-phonon coupling and anisotropic properties of 2M-WS2, paving the way for the use of anisotropic materials in advanced electronic and quantum devices.

Differential evolution of the anisotropic fracture characteristics of laminated rock under monotonic and fatigue loading

Differential evolution of the anisotropic fracture characteristics of laminated rock under monotonic and fatigue loading

Unlocking the mechanical, thermodynamic and thermoelectric properties of NaSbS2: A DFT scheme.

The present study focuses on the ground state mechanical, acoustic, thermodynamic and electronic transport properties of NaSbS2 polymorphs using the density functional theory (DFT) and semi-classical Boltzmann transport theory. The mechanical stability of the polymorphs is affirmed by the calculated elastic tensor. The calculated elastic properties asserted that all the polymorphs exhibit soft, brittle, anisotropic nature containing dominant covalent bonding. The 2D polar graphs are used to describe the anisotropic characteristic of the elastic parameters. The estimated value of Young's modulus and lattice thermal conductivity suggested that the polymorphs could be suitable for thermal barrier coating. Heat capacity, melting temperature, thermal conductivities, Grüneisen parameter, and thermal expansion coefficient of the polymorphs have also been studied to demonstrate thermodynamic behavior. The predicted lower values of lattice thermal conductivity declared that NaSbS2 polymorphs exhibit excellent electrical conductivity and transport properties. The estimated Seebeck coefficient (S), power factor (PF) and figure of merit (ZT) suggested that n-type triclinic and monoclinic, as well as p-type trigonal NaSbS2, are better for thermoelectric applications. The optimal carrier concentration for monoclinic structure is 1021cm-3 for T<750K, while it becomes 1020cm-3 for T>750K. It is also found that the optimal carrier concentration of the trigonal is 1021cm-3, whereas it is 1020cm-3 for triclinic structures. Therefore, it can be stated that NaSbS2 polymorphs possess excellent thermoelectric features, making them a promising choice for thermoelectric (TE) applications.

Pressure induced structural, anisotropy and thermal characteristics of MgIn2S4

The structural parameter, elastic anisotropy, and thermal properties of cubic MgIn2S4 under pressures is examined using first principles techniques. The determined lattice constant exhibits a high level of concurrence with the values reported in existing literature. Based on the mechanical characteristics, there is an observed enhancement in both ductility and anisotropy of MgIn2S4 under increased pressure. The investigation focuses on the thermal characteristics, encompassing the impact of temperature and pressure on key parameters such as Debye temperature, Grüneisen constant et al.

Strain Control of Third Harmonic Generation in Nb2SiTe4 Driven by Tuneable Anisotropic Characteristics

AbstractStrain engineering constitutes one of the main control knobs for material properties. The material's crystal and band structure can be strongly modified by mechanical strain, thus tailoring the electronic and photonic properties toward specific applications. However, the strain control of the higher‐order nonlinear optical (NLO) processes in crystals characterized by in‐plane anisotropy remains mostly unexplored. It is demonstrated that 2D ternary Nb2SiTe4 crystals provide an excellent platform for tuning NLO properties with uniaxial strain due to the inherently anisotropic band structure around the fundamental bandgap in the near‐infrared region. Resonant conditions between the interband excitations and third harmonic signals are realized, a record‐high third‐order susceptibility of 2.43 × 10−18m2/V2 is observed, exceeding by over an order of magnitude the values reported for commonly used NLO crystals. The measurements of the third harmonic intensity as a function of the linear polarization revealed that the anisotropic characteristics of Nb2SiTe4 can be tuned into qualitatively different regimes by the application of a uniaxial strain along the principal crystallographic axes. Notably, with increasing strain, the characteristic anisotropic direction can be reoriented. The findings provide unique perspectives for applying the modulation of the broadband NLO properties enabled by anisotropic materials in optoelectronics and all‐optical devices.

Investigation of Dielectric Anisotropy and Electrical Modulus-Impedance Properties of PCBM/E7 Composite for Organic Electronic Devices Applications

This study investigates the dielectric anisotropy and electrical modulus-impedance properties of a PCBM/E7 composite material for organic electronic devices applications. The research examines a specially fabricated cell combining nematic liquid crystal E7 with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) semiconductor. Through comprehensive analysis of dielectric anisotropy, AC conductivity, electrical modulus, and impedance characteristics under varying frequencies and applied voltages (-6.0V to +6.0V), the study reveals distinct behavioral regions and multiple relaxation processes. Key findings include frequency-dependent dielectric anisotropy transitions, enhanced AC conductivity at higher frequencies and voltages, and voltage-modulated impedance characteristics. The observed dual-peak phase angle response suggests multiple relaxation mechanisms, indicating the composite's potential for voltage-tunable electrical properties in advanced optoelectronic applications.