Anisotropic Layer Research Articles

Oscillatory modes on the onset of electrohydrodynamic instability in Maxwellian nanofluid saturated anisotropic porous layer

Oscillatory modes on the onset of electrohydrodynamic instability in Maxwellian nanofluid saturated anisotropic porous layer

Darcy–Benard–Oldroyd convection in anisotropic porous layer subject to internal heat generation

An anisotropic horizontal porous layer saturated with viscoelastic liquids of the Oldroyd-B type is explored to determine how the internal heat source affects thermal convection. As a momentum equation, a modified Darcy–Oldroyd model is used that takes into account the anisotropy of the porous layer. The energy equation is formulated in such a way that the influence of internal heat sources and anisotropy in thermal diffusivity on the stability criterion may be easily identified. The effects of anisotropy, viscoelasticity, and internal heat generation on the onset of thermal convection are investigated using linear stability analysis. It is understood that convection begins via an oscillatory mode instead of a stationary mode because viscous relaxation, thermal diffusions, and internal heat generation mechanisms compete with one another. Both steady and unsteady finite-amplitude convections are studied using nonlinear stability analysis with the truncated Fourier series method. The effect of different governing parameters on the system’s stability and on convective heat transfer is studied. The present investigation has been significantly validated by the recovery of several prior results as special situations. The findings presented in this work are anticipated to have significant implications for a number of real-world applications, including modeling of oil reservoirs, crude oil extraction, crystal growth, the pharmaceutical and medical industries, and the use of geothermal energy, among others.

Dvumernye zadachi fil'tratsii zhidkosti s granichnymi istochnikami v anizotropnom neodnorodnom sloe

We study the first and second boundary value problems and the transmission problem for the complex potential of a two-dimensional filtration flow in an anisotropic and inhomogeneous (variable permeability and thickness) porous layer. The flow sources are arbitrary discrete and can generally be located both on the boundaries and outside the boundaries. The boundaries are modeled by arbitrary smooth (piecewise smooth) closed lines, and the flow sources are singularities (isolated singular points) of the complex potential. The presence of a system of sources on the boundaries leads to a fundamentally new generalization (complication) of the boundary conditions, which are characterized by singular functions with isolated singular points. In the case of an anisotropic homogeneous (constant permeability and thickness) layer and rectilinear boundaries, the solutions of the problems are presented in closed form. In the general case, when an arbitrary smooth closed curve models a boundary with sources located on it, a generalized Cauchy type integral for the complex flow potential is used. This permitted reducing the second boundary value problem and the transmission problem to boundary singular integral equations. The problems studied are mathematical models of two-dimensional filtration processes in layered porous media, which are of interest, for example, for the practice of extracting fluids (oil, water) from natural anisotropically heterogeneous soil layers.

Detection of seismic anisotropy from seismic data recorded at SMNH01 station of KiK-net using seismic interferometry and empirical mode decomposition

This study uses deconvolution of earthquakes registered at the SMNH01 station of KiK-net, which is located in Japan, to identify the presence of: (a) anisotropic layers and (b) waves which could have been induced by motion of fluid, crack propagation and local fault activation. The SMNH01 station has a borehole which is equipped with triaxial accelerometers installed at surface and at 100 m of depth. By deconvolving seismic events registered at surface and at 100 m of depth, anisotropic layers are identified. To interpret interferograms, the following tools are utilized: (a) a one dimensional (1D) isotropic layered medium, (b) empirical mode decomposition and (c) an orthorhombic model. From the empirical mode decomposition, genuine resonances or tremors are identified along directions that are subparallel to the horizontal stress orientations that seem to bisect an effective orthogonal-conjugate fracture set. The strong changes in the amplitude of the main descending deconvolved wave could be mainly due to the combined influence of: motion of fluids through fractures on the spatial scale of meters, recurrent seismic events, evolving anisotropy, dilation and temperature variations. This wave travels from the surface of the earth to the receiver located at 100 m of depth. The detected anisotropy could be associated with the presence of layers constituted by naturally fractured basalt, which are situated beneath the soil. Such anisotropic layers could have orthorhombic symmetry or lower. This study has implications in the exploration and production of natural resources.

Active Terahertz-Beam Deflection in a Double-Sided All-Dielectric Metadevice Modulated by both Polarization Rotation and Optical Pumping

Active manipulation of the terahertz (THz) beam, especially beam deflection, is urgently required for wide THz applications. Although Pancharatnam-Berry (PB) metasurfaces can flexibly control the spatial phase distribution of circularly polarized waves, active power distribution and modulation between two conjugate spin beams are still challenging. Here, we demonstrate an all-dielectric metadevice consisting of an anisotropic metasurface layer and a PB metasurface layer etched on both sides of a silicon wafer. This structure develops a photonic spin-decoupling mechanism for spin-beam manipulation, which actively controls the power distribution between the two deflected spin beams by rotating the incident linearly polarized direction. The power-distribution ratio reaches 14.9:1 in the experiment. Moreover, the deflected beam can also be modulated by active switching via a laser pump, achieving an intensity-modulation depth of over 90%. The experimental modulation depth of the metadevice is 52% higher than that of the bare silicon wafer at the same pump power, which originates from the THz localized field enhancement and the strong dispersion effect of the PB structures. Therefore, this work provides a scheme for actively manipulating THz-beam deflection, realizing controllable wave-division multiplexing, power distribution, polarization control, and modulation.

Synthesis of a Hybrid Composed of Anisotropic Niobate Layers Modified with MoC Nanoparticles.

The hybrid composed of anisotropic niobate layers modified with MoC nanoparticles is synthesized by multistep reactions. The stepwise interlayer reactions for layered hexaniobate induce selective surface modification at the alternate interlayers, and the following ultrasonication leads to the formation of double-layered nanosheets. The further liquid phase MoC deposition with the double-layered nanosheets leads to the decoration of MoC nanoparticles on the surfaces of the double-layered nanosheets. The new hybrid can be regarded as a stacking of the two layers with anisotropically modified nanoparticles. The relatively high temperature in the MoC synthesis causes partial leaching of the grafted phosphonate groups. The exposed surface of the niobate nanosheets due to the partial leaching may interact with MoC to succeed in the hybridization. The hybrid after heating exhibits photocatalytic activity, indicating that this hybridization method can be useful for hybrid synthesis of semiconductor nanosheets and co-catalyst nanoparticles toward photocatalytic application.

Instability of a plane Poiseuille flow bounded between inhomogeneous anisotropic porous layers

Instability of a plane Poiseuille flow bounded between inhomogeneous anisotropic porous layers

Temperature Dependent Viscosity Effect on Oscillatory Mode of Darcy-Rayleigh Convection in a Double Diffusive Binary Viscoelastic Fluid Saturated Anisotropic Porous Layer

An anisotropic porous layer saturated with a viscoelastic double diffusive binary fluid is examined numerically for the onset of Darcy-Rayleigh convection. From below, the system is heated, while from above, it is cooled. The temperature-dependent viscosity was added to the double diffusive binary fluid, and the Galerkin expansion method was used to determine the critical Darcy-Rayleigh number. When their values are raised, the impacts of strain retardation, thermal anisotropy parameter and Dufour number slow the production of heat transfer and stabilise the system. When the values are increased, the stress relaxation, Darcy-Prandtl, mechanical anisotropy parameters, temperature dependent viscosity and Soret number accelerate the heat transfer process in convection, which destabilises the system

Rayleigh waves in a reservoir rocks lying on the bed of sandy rocks

An analysis of the propagation behaviour of Rayleigh waves has been carried out in anisotropic layer like reservoir rocks overlying a sandy medium. The most general case of anisotropic material i.e., of triclinic crystal has been taken. An analytical approach is incorporated in a state to obtain the solutions for layer and half-space. A closed relation of phase velocity and wave number is obtained as determinant form with weld contact boundary at the interface of lower half and the adjacent layer with the upper boundary condition as a rigid called dispersion relation. For the numerical interpretation of results, two different reservoir rocks of triclinic type have been taken. The outcomes of phase velocity and wave number have been illustrated by graphs obtained with the aid of Mathematica-7.

Asymptotic expansion of transmission eigenvalues for anisotropic thin layers

We study the asymptotic expansion of transmission eigenvalues for anisotropic thin layers. We establish a rigorous second-order expansion for simple transmission eigenvalues with respect to the thickness of the layer. The convergence analysis is based on a generalization of Osborn's Theorem to non-linear eigenvalue problems by Moskow [Nonlinear eigenvalue approximation for compact operators. J Math Phys. 2015;56(11):113512]. We also provide formal derivation in more general cases validating the obtained theoretical result.

Darcy–Brinkman Double Diffusive Convection in an Anisotropic Porous Layer with Gravity Fluctuation and Throughflow

The influence of the throughflow and gravity fluctuation on thermosolutal convection in an anisotropic porous bed with the Darcy–Brinkman effect is considered numerically. The critical Rayleigh numbers for the onset of stationary and oscillatory modes have been found via linear instability analysis. The impact of various gravitational functions in the presence of throughflow on stability is studied. The analysis has been carried out for decreasing and increasing gravity fluctuations. The convective problem has been numerically analyzed using a single-term Galerkin approach. The results show that the mechanical anisotropy parameter and Lewis number have a destabilizing effect, while the thermal anisotropy parameter, Darcy number, solutal Rayleigh number, throughflow parameter, and gravity parameter have a stabilizing effect on stationary and oscillatory convection. It is clear that the system changes in a way that makes it more stable for case (iii) gravity fluctuation and more unstable for case (iv) gravity fluctuation.

Effect of annealing on the magnetic anisotropy of GaMnAsP layers with graded P concentration

We have investigated the effect of annealing on the magnetic anisotropy of MBE-grown GaMnAs1−yPy film in which phosphorus content varies from 0% to 24% along the growth direction. Such variation is achieved by growing a series of GaMnAs1−yPy layers in which y is successively increased. Hall effects measurements on an as-grown graded film reveal that the bottom 80% of the film has in-plane easy axes, 10% has both in-plane and perpendicular easy axes, and the remaining 10% has a vertical easy axis. Such gradual change of magnetic anisotropy in the film from in-plane to perpendicular with increasing P concentration is in accordance with the continuous variation of strain from compressive to tensile as the P concentration increases the bottom of the film to tensile toward its tip surface. However, thermal annealing significantly changes the magnetic anisotropy of the graded GaMnAs1−yPy film. In particular, the intermediate region having both in-plane and perpendicular easy axes nearly disappears in the film after annealing, so the film is divided into two types of layers having either only in-plane or only perpendicular anisotropy. These dramatic changes in magnetic anisotropy of the graded GaMnAs1−yPy film introduced by annealing suggest that one can strategically use this process to realize orthogonal magnetic bilayers consisting of in-plane and perpendicular easy axes.

High moisture extrusion of meat analogues using mung bean (Vigna radiata L.) protein and flour blends: investigations on morphology, texture and rheology

SummaryHigh moisture meat analogues (HMMA) from the blends of mung bean protein isolate (MPI) and mung bean flour (MF) at different MF contents (10%, 20% and 30%) were prepared using high moisture extrusion (HME) and die texturisation. Pure MPI could not be extruded and texturised. Therefore, MF was added to improve the extrudability and to assist in the texturisation of HMMA. Rheological analysis performed under a range of simulated conditions in the cooling die demonstrated the decrease in both storage and loss moduli of the blend systems as compared to pure MPI, which explained the flow capability and extrudability of the blends during die texturisation. The effect of blend compositions on morphology and texture of the extrudates was investigated. All blend extrudates showed an anisotropic layer structure with a less pronounced velocity profile with increasing MF content. The microstructure of these extrudates revealed the presence of a multiphase system of the remaining MF fragments dispersed in a continuous protein matrix, thereby facilitating phase separation, loosening the protein structure and decreasing textural properties of HMMA as MF content increased. The results demonstrate that the blend of MPI and MF is a promising ingredient to prepare mung bean‐based HMMA with the customised texture properties.

Thermal and Mechanical Properties of Cu-Graphite Composites with Spatial Anisotropy

In the present study, we analyzed the thermal and mechanical properties of Cu-graphite composites (CGCs) with spatially anisotropic graphite layers. These composites were fabricated using a combination of electroless plating and spark plasma sintering (SPS) processes. Thermal conductivities and thermal expansion coefficients of the composites were measured using differential thermal analysis (DTA) and a laser flash method. In particular, the thermal expansion coefficients of the composites were investigated by comparative analysis, which was conducted by processing prototypes in a vertical direction with a parallel sector in the direction of the upper and lower axial pressure. The Cu reinforced with the graphite flake showed better thermal properties compared to the graphite fiber, while the graphite fiber led to better mechanical properties. This investigation was conducted to better understand the dependence of thermal properties on the morphologies of the graphite layers (i.e., flake and fiber types) in the Cu matrix. The bending strength and friction coefficient of the composites were also investigated. Taken together, the results from this work offer fruitful, yet practical information to utilize the CGCs as a thermal management material, essential for electric and electronic devices.

Layered Evolution of the Oceanic Lithosphere Beneath the Japan Basin, the Sea of Japan

AbstractThe formation of a new ocean basin provides a unique observational window into the structure and deformation of the oceanic lithosphere. This study offers a detailed 1‐D vertically polarized shear‐wave velocity model of the young Japan Basin by interpreting S receiver functions, seafloor Rayleigh wave ellipticities and phase velocities in a Bayesian trans‐dimensional framework. The models suggest a distinct discontinuity in the mid‐lithosphere. Additional analyses indicate that the upper layer is characterized by strong positive radial anisotropy, while the lower layer is more isotropic. We interpret that the upper layer was formed during the back‐arc opening at 20–15 Ma, where the olivine lattice‐preferred orientation (LPO) fabric induced by passive upwelling contributes to the positive radial anisotropy. The lower, less anisotropic layer may be solidified after the sudden cessation of the opening. Small‐scale convection (SSC) from such a major tectonic event could randomize the LPO enough to weaken radial anisotropy before cooling down the asthenosphere, leaving a radially anisotropic discontinuity in the present‐day mid‐lithosphere. The proposed layered evolution history of the lithosphere beneath the Japan Basin illuminates an important role of the small‐scale convection in modifying the structural fabrics of the asthenosphere in terms of radial anisotropy. Such an SSC‐induced radial anisotropy drop could also occur at the base of the lithosphere in regions with ongoing seafloor spreading and enhance the velocity drop of horizontally polarized shear waves. Thus, the role of SSC is non‐negligible in explaining the sharpness of the Gutenberg discontinuity detected by SS precursors beneath the oceanic lithosphere.

Non-volatile electric field-mediated magnetic anisotropy in CoZr/ PMN-PT structure

Introduction: Although electric field mediated the magnetic anisotropy in ferromagnetic/ferroelectric structure have an intense report, the angle between the magnetic uniaxial anisotropy and strain anisotropy influencing the rearrangement of the magnetic moment has not well investigated.Methods: Keithley 2410 direct current power supply was used to provide voltage through the Cu wires. Static magnetic properties of CoZr layer were measured through VSM (MicroSense EV9). Dynamic magnetic properties were obtained by FMR (JEOL JES-FA 300 spectrometer, power of 1-mW, X-band at 8.969 GHz).Results and Discussion: Electric field-mediated, room-temperature magnetic anisotropy of CoZr/Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) structures, in which easy axis of CoZr layer along either direction of [01-1] or [100] of PMN–PT, was investigated. Measured with vibrating sample magnetometer, for [01-1] easy-axis direction sample, when an electric field was applied, these directions of easy axis and hard axis remains unchanged. However, for [100] easy-axis direction sample, these directions of easy axis and hard axis were changed obviously with applying electric field, attributable to the competition between magnetic uniaxial anisotropy of CoZr layer and piezostrain anisotropy of PMN-PT substrate. Nevertheless, change of the resonance magnetic field with electric field–measured by ferromagnetic resonance–exhibited non-volatile behavior, which possibly indicates magnon-driven magnetoelectric coupling existing in CoZr/PMN–PT structures.

Onset of double diffusive surface-tension driven convection in fluid layer overlying a layer of anisotropic porous layer with soret effect

The onset of double-diffusive surface tension-driven convective motion in a fluid layer overlying a fluid-saturated anisotropic porous layer is investigated analytically in the presence of the soret effect. We considered boundaries to be insulating to temperature perturbations. The governing equation that satisfies the composite system is analyzed by the normal mode approach and solved by the regular perturbation technique for linear stability. By solving coupled equations, a mathematical expression for the critical Marangoni number is obtained. Under the effect of the anisotropy, soret parameters and the impact of various physical parameters on the start of convective motion is illustrated graphically, and the stability system is investigated.

Numerical study of beam shape adaptation by anisotropic disk covering transducer or metamaterial

Metamaterials are intensely explored for their capabilities to modify sound beams. In addition to frequency filtering, acoustic lenses offer intriguing possibilities for shaping sound beams. For the time being, the versatility of metamaterials remains limitless. In beam-shape adaptation, however, their complexity suggests that manufacturers of transducers could benefit from combining metamaterials with more conventional materials. This paper investigates the transmission of a circumscribed beam through a stratum of anisotropic material to examine the change in beam shape after transmission. The incident sound is presumed to originate from a conventional transducer, possibly coated with a metamaterial to modify the sound field, before being transmitted through the anisotropic layer. Different incident beam shapes, such as conical-like, Gaussian, and pillar beams, are investigated. While the results are not exhaustive, they demonstrate the beam shape’s adaptability.

Synthesis of a large area ReS2 thin film by CVD for in-depth investigation of resistive switching: effects of metal electrodes, channel width and noise behaviour.

The anisotropic crystal structure and layer independent electrical and optical properties of ReS2 make it unique among other two-dimensional materials (2DMs), emphasizing a special need for its synthesis. This work discusses the synthesis and in-depth characterization of a 1 × 1 cm2 large and few layered ReS2 film. Vibrational modes and excitonic peaks observed from the Raman and photoluminescence (PL) spectra corroborated the formation of a ReS2 film with a 1.26 eV bandgap. High resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns inferred the polycrystalline nature of the film, while cross-sectional field emission scanning electron microscopy (FESEM) indicated planar growth with ∼10 nm thickness. The chemical composition of the film analysed through X-ray photoelectron spectroscopy (XPS) indicated the formation of a ReS2 film with a Re : S atomic ratio of 1 : 1.75, indicating a small amount of non-stoichiometric RexSy. Following the basic characterization studies, the ReS2 film was tested for resistive switching (RS) device application in which the effects of different metal electrodes (Pt/Au and Ag/Au) and different channel widths (200, 100, and 50 μm) were studied. The highest memory window equal to 108 was obtained for the Ag/Au electrode while Pt/Au showed a memory window of 102. RS for the former was ascribed to the formation of a conducting filament (CF) because of the migration of Ag+ ions, while defect mediated charge carrier transport led to switching in the Pt/Au electrode. Furthermore, the RHRS/RLRS ratio achieved in this work (108) is also of the highest magnitude reported thus far. Furthermore, a comparison of devices with Ag/Au electrodes but with different channel widths (50, 100 and 200 μm) gave insightful results on the existence of multiple resistance states, device endurance and retention. An inverse relationship between the retention time and the device's channel width was observed, where the device with a 50 μm channel width showed a retention time of 48 hours, and the one with a 200 μm width showed stability only up to 3000 s. Furthermore, low frequency noise measurements were performed to understand the effect of defects in the low resistance state (LRS) and the high resistance state (HRS). The HRS exhibited Lorentzian noise behaviour while the LRS exhibited Lorentzian only at low current bias which converged to 1/f noise at higher current bias.

FEEDBACK CONTROL OF CHAOTIC MOTION IN AN ANISOTROPIC POROUS MEDIUM UNDER MAGNETIC EFFECT

The main purpose of this work is to provide an innovative approach for studying the chaos control of the viscoelastic fluid-saturated anisotropic porous layer under the magnetic effect and feedback control modulation. The governing flow model partial differential equations (PDEs) are transformed into ordinary differential equations (ODEs) using a powerful tool of Fourier modes and a nonlinear low-dimensional Brinkman model employed by using the truncated Galerkin method. Their results reveal the feedback gain parameter, Hartmann number, Darcy number, and the mechanical and thermal anisotropy parameters on the stabilization of thermal convection to suppress the chaos. Additionally, many real-world applications conforming to system stabilization of thermal convection are important in nuclear power energy, including turbo machinery, cooling chemical components, and electronic cooling processes. The emergence of various nonlinear flows of steady-state, periodic, and oscillatory to chaotic convection is demonstrated with the change of feedback control parameters. Also, we found that the feedback control gains parameter K value is directly proportional to the scaled Rayleigh number with the external effects on the magnetic field and anisotropic parameters. Our findings were found to be in good agreement with previous numerical results. Finally, the paper proposes the implications of using feedback control combined with magnetic effect to effectively control the chaotic system.