Inhomogeneous Layer Research Articles

THROUGHGOING FLUID-CONDUCTING STRUCTURES: CONCEPTUALIZATION, TERMINOLOGY, TYPES, PROPERTIES, AND THE ROLE IN FLUID CIRCULATION

In this paper the review and analysis of global data on throughgoing fluid-conducting structures is performed, the problematic issues of related concepts and terminology are considered, typification of structures by various criteria is proposed and their role in fluid circulation and in lithogenesis and evolution of sedimentary basins is accessed. Such structures are ubiquitous and are an integral part of the drainage system of the upper crust, although the intensity of their distribution and impact on fluid circulation vary widely and increase drastically in certain geological and geodynamic conditions. At the local and subregional scales, throughgoing structures and related phenomena show uneven, clustered distribution. The key role of throughgoing structures in fluid circulation, including the migration of hydrocarbons and pollutants, is determined by their intersecting and throughgoing nature with respect to layered inhomogeneities, including sealing (low permeability) horizons, and by usually much higher permeability than that of the host rocks. The vertical nature of structures and localized vertical fluid flow across lateral lithological and hydrodynamic boundaries cause the formation of thermal and geochemical anomalies and disequilibrium of the water-rock system, accompanied by the interaction of conduit fluids with host rocks and reservoirs and by alteration of the rocks that contain them. This determines the leading role of throuhgoing structures in superimposed lithogenesis and ore mineralization. The fluid conductivity of throughgoing structures is variable over time because it depends on their origin, stages of their formation and secondary changes. In this regard, the comparison of this ability between morphogenetic varieties of throughgoing structures is generally difficult, although the most effective in this respect are structures of karstic origin. For structures of fluidodynamic type, the greatest permeability and intensity of fluid flows through the conduits are characteristic of the periods of their formation and immediately after them, as well as of the periods of activation, which are usually associated with tectonic events.

Influence of the stratopause wind and temperature stratification on the waveform of the infrasound signal from the August 4, 2020 beirut explosion

The waveform of the infrasound signal received at a distance of 2398 km (infrasound station IS48) from the epicenter of the powerful explosion in Beirut, which occurred on August 4, 2020, is analyzed and modeled by using ray trace and pseudo-differential parabolic equation (PDPE) methods. Given a high temporal variability of the effective sound speed in the stratopause predicted by the European ECMWF model, we assumed that within the stratopause layer the increase in effective sound speed with increasing height is very small, on the order of 1 m/s. We also took into account the fine-scale layered structure of wind velocity and temperature in the real atmosphere, which is not taken into account in the ECMWF model. Accounting for the scattering of infrasound by strongly anisotropic (layered) inhomogeneities of the effective sound speed by using the PDPE wave method allowed us to explain for the first time the appearance of “fast” stratospheric arrivals, their time durations, time period between successive arrivals (about 110 s) and the waveform of the entire observed signal. [This work was supported by the Russian Science Foundation, Grant No 21-17-00021.]

Transverse oscillations and damping of magnetic flux tubes with a thick transitional layer

ABSTRACT In this paper, the magnetohydrodynamic kink waves and their damping are investigated in a thin coronal flux tube model. The thickness of the inhomogeneous transitional layer is of the order of the tube’s radius. The governing equations are solved analytically in all regions of the tube except for the thin dissipative layer. The dispersion relation is derived and solved numerically. The oscillation frequency does not vary much when varying the thickness of the transitional layer. When the transitional layer is thin, the damping rate of the kink wave increases significantly with the increase in the thickness of the transitional layer; however, when the transitional layer is thick, the damping rate does not vary much with the increase in the thickness of the transitional layer. For small values of the thickness of the transitional layer, our results are in agreement with results obtained in the thin tube, thin boundary approximation. In flowing tubes, the effect of flow on the damping rate of the waves depends on the direction of the wave propagation and plasma flow. The resonant instability of the kink waves in flux tubes with flowing transitional layer has been investigated.

Geometric 3-D inversion of airborne time-domain electromagnetic data with applications to kimberlite pipes prospecting in a complex medium

We consider an approach to solving 3-D inverse problems of airborne time-domain electromagnetic (TD-EM) survey in complex geoelectrical conditions, when the responses of target objects in the measured signal are relatively small and mixed with responses of rugged topography, 3-D inhomogeneities in overburden layers, and other interfering 3-D objects. For parameterization of the geoelectrical model of the geological medium, global and local structures are used. A block structure is a grid with large cells whose boundaries can move during the inversion process. Block structures are characterized by two types of parameters: geometric and physical. Geometric parameters include the coordinates of the boundaries of blocks in block structures, which are used for recovering local bodies or 3-D inhomogeneities within the layers, and physical parameters are the conductivities inside the blocks. In addition, the geometric parameters include displacements of control points, which are used for describing curved surfaces. The functional employed for inversion includes regularizing terms that allow controlling the self-crossing of geometric boundaries and extension of physical parameters beyond the boundaries of the allowed values range. Regularization coefficients are calculated adaptively at each iteration of the nonlinear 3-D inversion. In order to separate the responses of 3-D inhomogeneities located under the overburdens from those of 3-D inhomogeneities inside the overburdens, we propose to carry out 3-D inversion in two stages. At the first stage, over a shortened time range, we recover the conductivity distribution using global block structures and the shape of the boundaries of the overburden layers using control points. At the second stage, the entire time range is used. In those places where the significant residuals remained at late times, local block structures are employed to recover local objects (including target ones) under the overburden layers. This enables us to define quite accurately the position in plan, top border depth, and type of 3-D inhomogeneities, which are located under the overburdens, at the second stage of geometric inversion. To calculate 3-D time-domain electromagnetic fields, we use the vector finite element method implemented on optimized non-conforming hexahedral meshes with the possibility of adjoining the faces of several finite elements to the face of one finite element. The workability of the proposed approaches is demonstrated on synthetic airborne TD-EM data as well as on experimental airborne data, which are obtained as a result of methodical work over the kimberlite pipe deposit. The proposed geoelectrical model parameterization and the approach to 3-D inversion allow the discovery of relatively small 3-D target objects, when many non-target objects, including 3-D inhomogeneities in the overburdens, give several times greater responses in the measured signals.

Thermal sensitivity and barrier height inhomogeneity in thermally annealed and un-annealed Ni/n-6H-SiC Schottky diodes

The Ni/n-6 H-SiC Schottky barrier diodes (SBDs) have been fabricated. Then, they have been thermally annealed at 700 oC for 2 min. Their forward bias voltage versus measurement temperature (V-T) curves in 100–500 K range have been studied to determine the thermal sensitivity at current levels from 1.0 nA to 100 µA for as-deposited SBD and from 10 pA to 1.0 µA for the annealed SBD. The V-T curves of both SBDs have exhibited the linear behavior at the mentioned current levels. The thermal sensitivity coefficient (α) calculated from the slope of the V-T curves has ranged from 2.15 mV/K at 1.0 nA to 1.79 mV/K at 10 μA for the un-annealed diode, and from 1.75 mV/K at 10 pA to 1.27 mV/K at 1.0 μA for the annealed diode. Furthermore, the α versus current level (I) graph of the un-annealed diode has given a straight line from 1.0 nA to 10 μA. The linearity of the V-T and α -I graphs is a very crucial factor for a good thermal sensor in the thermal sensitivity. It can be said that the un-annealed diode can operate adequately as a temperature sensor in the range of 100–500 K and of 1.0 nA-10 μA, considering studies in literature. The annealed diode did not exhibit a linear α versus current level curve. This has been ascribed to the formation of a highly resistive inhomogeneous layer at the Ni/n-6 H-SiC interface due to thermal annealing to 700 °C. The interfacial inhomogeneity has been explained by Gaussian distribution of the barrier heights.

Simulation of spatial strain inhomogeneities in lithium-ion-cells due to electrode dilation dependent on internal and external cell structures

Electrochemical-mechanical interactions, especially pressure-induced ones, have been identified to be a cause for lithium-plating in lithium-ion cells. Mechanically induced porosity inhomogeneities in the separator layers due to electrode expansion during charging especially lead to cell internal balancing currents and can cause localized plating. To identify cell-format and cell-material dependent mechanical weak spots, a layer-resolved mechanical simulation of different cell types and cell-material combinations is presented in this work. The simulation results show distinctive layer strain patterns for different cell-types that coincide with localized lithium-plating found in post-mortem cells. Additionally, the effects of cell bracing in battery modules is investigated and a method to mitigate the increased layer strain due to bracing counterforces is proposed that also increases cell energy density for hardcase-type automotive cells.

Impact of skull sutures, spongiform bone distribution, and aging skull conductivities on the EEG forward and inverse problems

Objective. Source imaging is a principal objective for electroencephalography (EEG), the solutions of which require forward problem (FP) computations characterising the electric potential distribution on the scalp due to known sources. Additionally, the EEG-FP is dependent upon realistic, anatomically correct volume conductors and accurate tissue conductivities, where the skull is particularly important. Skull conductivity, however, deviates according to bone composition and the presence of adult sutures. The presented study therefore analyses the effect the presence of adult sutures and differing bone composition have on the EEG-FP and inverse problem (IP) solutions. Approach. Utilising a well-established head atlas, detailed head models were generated including compact and spongiform bone and adult sutures. The true skull conductivity was considered as inhomogeneous according to spongiform bone proportion and sutures. The EEG-FP and EEG-IP were solved and compared to results employing homogeneous skull models, with varying conductivities and omitting sutures, as well as using a hypothesised aging skull conductivity model. Main results. Significant localised FP errors, with relative error up to 85%, were revealed, particularly evident along suture lines and directly related to the proportion of spongiform bone. This remained evident at various ages. Similar EEG-IP inaccuracies were found, with the largest (maximum 4.14 cm) across suture lines. Significance. It is concluded that modelling the skull as an inhomogeneous layer that varies according to spongiform bone proportion and includes differing suture conductivity is imperative for accurate EEG-FP and source localisation calculations. Their omission can result in significant errors, relevant for EEG research and clinical diagnosis.

Anticlassical approximation in the problem of electromagnetiv wave reflection from an inhomogeneous medium

Expressions are derived for the reflection coefficients ofelectromagnetic waves with p and s type polarizations from asemi-infinite dielectric medium having an inhomogeneous layer. Theinfluence of the layer was taken into account by the method of perturbationtheory in a quadratic approximation of the layer thickness. A method isproposed for converting expressions derived using perturbation theory intoother expressions that give more accurate values of the reflectioncoefficient. The angular dependences of the reflection coefficient obtainedby the developed method are compared with those obtained by the numericalsolution of electrodynamic equations. Requirements for the layercharacteristics are formulated to minimize the error of the analyticalsolution. Keywords: dielectric medium, inhomogeneous layer, electromagnetic wavereflection coefficient, analytical calculation, perturbation theory.\

Антиклассическое приближение в задаче об отражении электромагнитной волны от неоднородной среды

Expressions are derived for the reflection coefficients of electromagnetic waves with "p" and "s" type polarizations from a semi-infinite dielectric medium having an inhomogeneous layer. The influence of the layer was taken into account by the method of perturbation theory in a quadratic approximation of the layer thickness. A method is proposed for converting expressions derived using perturbation theory into other expressions that give more accurate values of the reflection coefficient. The angular dependences of the reflection coefficient obtained by the developed method are compared with those obtained by the numerical solution of electrodynamic equations. Requirements for the layer characteristics are formulated to minimize the error of the analytical solution.

On deep-sea acoustic inhomogeneities in the bottom layers in the Sea of Okhotsk and in the Sea of Japan

On deep-sea acoustic inhomogeneities in the bottom layers in the Sea of Okhotsk and in the Sea of Japan

Far-End Crosstalk Modeling and Prediction for Stripline With Inhomogeneous Dielectric Layers (IDLs)

Far-end crosstalk (FEXT) is a critical factor that limits signal integrity performance in high-speed systems. The FEXT level is sensitive to the dielectric inhomogeneity of the stripline in fabricated printed circuit boards (PCB). The dielectric of the stripline is manufactured with multiple inhomogeneous dielectric layers (IDLs) of various resin and glass fiber bundles. A marginal difference in the dielectric permittivity of the IDLs can lead to a significant change FEXT level. In this paper, a practical FEXT modeling methodology for striplines is proposed by introducing the extraction method for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\bm{\varepsilon }}}_{\bm{r}}$</tex-math></inline-formula> of IDLs. The new stripline model is constructed with three IDLs comprised of core, prepreg, and resin pocket, to improve the model accuracy. With the cross-sectional geometry and measured S-parameters of the coupled striplines, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bm{\ }}{{\bm{\varepsilon }}}_{\bm{r}}$</tex-math></inline-formula> of IDLs can be extracted. In addition, an analytical model to predict the FEXT polarity and magnitude of the stripline caused by the inhomogeneity is proposed targeted for pre-layout application. The proposed models have been verified using measurement. The proposed models can provide useful analysis methodology and design guidelines to mitigate the FEXT level in high-speed systems, especially for high-volume PCB tests in the pre-layout and post-layout stages.

Reflection and Transmission of a Polarized Vortex Beam by an Inhomogeneous Anisotropic Plane Layer

Reflection and Transmission of a Polarized Vortex Beam by an Inhomogeneous Anisotropic Plane Layer

Site-specific water dynamics in the first hydration layer of an anti-freeze glyco-protein: a simulation study.

Antifreeze glycoproteins (AFGPs) inhibit ice recrystallization by a mechanism remaining largely elusive. The dynamics of AFGPs' hydration water and its involvement in the antifreeze activity, for instance, have not been identified conclusively. We herein, by simulation and theory, examined the picosecond site-specific water dynamics in the first hydration layer of a solvated AFGP8. Using a hydrogen bond switch event-based treatment, we strictly excluded the non-first layer water contribution. The observed water dynamics is much more retarded and inhomogeneous compared to the result of other commonly adopted treatments with non-first layer water contributions included. A molecular jump model analysis, with the cross-correlation between hydrogen bond switch molecular frames included, further indicates that excluding the non-first layer water contribution enhances the slow component in water dynamics, which couples strongly with the local environment. Further comparison with the structured ubiquitin protein revealed that, although the overall relaxation time distributions are similar between two proteins, a significant portion (>30%) of water hydrogen bond switching processes on the AFGP8 surface are considerably slower since they are trapped between the disaccharides and other protein regions. AFGP8 therefore resembles much the situation of an enzyme binding cleft or a DNA groove, where considerable slowdown of hydration water dynamics is observed due to the confinement. When bound to the ice surface, these slow, disordered water molecules may become a factor hindering the ice growth.

Spectral Dyadic Green’s Function for Multilayer Periodic Bi-Anisotropic Media

A computational technique for evaluating the spectral dyadic Green’s function utilized in the analysis of multilayer structures composed of periodic bi-anisotropic layers is presented. The Green’s function is achieved with the help of a fully vectorial rigorous matrix formulation based on a generalized transmission line (TL) formulation of Maxwell’s equations. This matrix formulation simplifies the mathematics involved in the modeling of the coupled diffraction orders within a periodic bi-anisotropic layer. To examine the soundness of this modeling, the extracted Green’s function is used in an integral equation for the analysis of metallic gratings on homogeneous/inhomogeneous anisotropic and chiral materials. The resulting integral equation is then solved by the Method of Moments (MoM) formulated in terms of sub-domain basis and Galerkin’s test functions. As verification, several examples are analyzed and the results obtained by this method are compared with those available in the literature or obtained by EM-solvers. The efficiency assessment of this method is carried out by considering its convergence rate and cost-time in terms of truncation orders. It is revealed not only the metallic grating with inhomogeneous periodic bi-anisotropic layers can be analyzed by this method but also analysis time, memory, and CPU occupancies are decreased in comparison with commercial EM-solvers.

Recognition of Volumetric Scattering of Lunar Regolith Media in the PSR via Fully Polarimetric SAR Data

Data of fully polarimetric synthetic aperture radar (full pol-SAR) onboard Chandrayaan-2 make it feasible to analyze the geometric and physical properties of the lunar soil layer. A specific mission of Chandrayaan-2 is to investigate if there is water-ice in the regolith of the PSR (Permanently Shadowed Region). Volatile substances are likely to accumulate in the ancient regolith media. Volumetric scattering of the regolith media might indicate specific characteristics of the regolith. Scattering from surface rocks should be excluded. Such flat regions are difficult to identify in digital elevation model. In this paper, Chandrayaan-2 full-pol data at L band are used for this purpose. The co-pol and cross-pol scattering coefficients and decomposition parameters, such as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha $</tex-math></inline-formula> , degree of polarization, and circular polarization ratio of lunar surface are studied. High-order scattering from rough surface is numerically simulated and analyzed by the bidirectional analytical ray tracing code. It is found that rocky rough surface causes high co-pol scatterings. High-order scatterings of the rough surface and volumetric scatterers can enhance cross-pol scattering. Criteria are proposed to select volume scatterings at flat regions at Mare Serenitatis and a PSR crater. Regions with weak co-pol backscattering in a PSR crater at (85.9°N, 111.7°E) are classified as flat surface. It is found that a flat region with weak co-pol and high cross-pol terms appears different from surrounding regions. The enhanced cross-pol is likely to be caused by volumetric inhomogeneity in the regolith. This unusual region shows its inhomogeneous soil layer, and deserve further study.

Simulation of Microwave Remote Sensing of the Ocean

The paper considers simulation of microwave remote sensing of the ocean. The direct and inverse problems of diffraction of a plane electromagnetic wave on a periodic inhomogeneous layer of finite thickness are considered. The computer program is developed, that allows to model the process of active and passive radiometry of the free surface or of the near-surface layer of the ocean. The program is validated by comparison with the analytical result for the case of a periodically repeating planar layered structure. High accuracy of calculations is shown. The results of a number of calculations for the needs of passive and active radiometry of the surface and of the medium consisting of layers with sinusoidal boundaries are presented.

Modeling of rubber-cord layers under quasi-static loading

Modeling a pneumatic tire with a strong change in shape causes the problem of choosing an adequate model for rubber-cord plies. Generally, the classical method of asymptotic homogenization is not suitable due to physical and geometrical nonlinearity for the strain up to 15 %. The known models used for simulation the entire tire as well as rubber-cord plies are analyzed. A choice is made in favor of modeling the plies using the stress anisotropic potential, which is an anisotropic function of the strain tensor invariants. The relationship of such a constitutive law with a quasi-linear constitutive equation in terms of stress and strain differentials is indicated. A convenience of these two types of constitutive equations in terms of numerical implementation is also given. A modification of the effective properties definition for an inhomogeneous layer is explained. The difference from the standard effective moduli definition is clarified. The arrangement of the cords is supposed to be approximately periodic and all cords to be equivalent to the effective fiber. Two models of a rubber-cord plies are described under such assumption. These are a model of an orthotropic material and a model of a transversely isotropic material. Computational experiments, which make it possible to determine the material parameters of anisotropic potentials, are pointed out. Real tests with a sample of rubber ply under slow quasi-static loading were conducted. Significant hysteresis was detected. It is shown that an additive model combining a hyper elastic material with Maxwell viscoelastic model provides good accuracy in stress dependence on the strain rate. The numerical procedure developed to calculate solution to the quasi-static problem of tire deformation is described. It is implemented in home-made computer code. A numerical example on the tire simulation is given. That is so-called breaking test, in which strong deformation is achieved and the developed model is applied to.

Formation by high power ultrasound of aggregated emulsions stabilised with milk protein concentrate (MPC70)

In this work, oil-in-water emulsions stabilised by milk protein concentrate (MPC70) were investigated. The MPC70 concentration was kept constant at 5% (close to the protein content found in skim milk) and the oil volume fraction was varied from 20 to 65%. Sonication was performed at 20 kHz and at a constant power of 14.4 W for a total emulsion volume of 10 mL. Under certain oil concentration (≥35%) and sonication times (≥3s) the emulsion aggregated and formed high-viscosity pseudo plastic materials. However, the viscosity behaviour of the emulsion made with 35% oil reverted to that of a liquid if sonicated for longer times (≥15 s). Confocal laser scanning microscopy showed clearly that the oil droplets are aggregated under the sonication conditions and oil concentrations indicated above. An attempt to explain this behaviour through a simple model based on the bridging of oil droplets by the MPC70 particles and, taking into account the oil droplet and MPC70 particle sizes as well as the oil volume fraction, was made. The model fails to describe in details the aggregation behaviour of these emulsions, likely due to the inhomogeneous protein layer, where both free caseins and casein micelles are adsorbed, and to the packing of the oil droplets at concentrations ≤55%. Nonetheless, this work demonstrates the potential of ultrasound processing for the formation of dairy emulsions with tailored textures.

On the use of complex stretching coordinates in generalized finite difference method with applications in inhomogeneous visco-elasto dynamics

In the study, in conjunction with perfectly matched layer (PML) analysis, an approach is proposed for the evaluation of complex derivatives directly in terms of complex stretching coordinates of points in PML. For doing this within the framework of generalized finite difference method (GFDM), a difference equation is formulated and presented, where both the function values and coordinates of data points might be complex. The use of the proposed approach is considered in the analysis of inhomogeneous visco-elasto-dynamic system and assessed through three example problems analyzed in Fourier space: the composite and inhomogeneous tube, layer and impedance problems. The GFDM results obtained for the tube and layer problems compare very closely and coincide almost exactly with the exact solution. In the impedance problems, rigid surface or embedded footings resting on a composite inhomogeneous half-space are considered. The influences of various types of inhomogeneities, as well as, of various geometric shapes of PML-(physical region) interfaces on impedance curves are examined.

Reflection and transmission of P-waves at a very rough interface between two isotropic elastic solids

This paper deals with the reflection and transmission of P-waves at a very rough interface between two isotropic elastic solids. The interface is assumed to oscillate between two straight lines. By mean of homogenization, this problem is reduced to the reflection and transmission of P-waves through an inhomogeneous orthotropic elastic layer. It is shown that a P incident wave always creates two reflected waves (one P wave and one SV wave), however, there may exist two, one or no transmitted waves. Expressions in closed-form of the reflection and transmission coefficient have been derived using the transfer matrix of an orthotropic elastic layer. Some numerical examples are carried out to examine the reflection and transmission of P-waves at a very rough interface of tooth-comb type, tooth-saw type and sin type. It is found numerically that the reflection and transmission coefficients depend strongly on the incident angle, the incident wave frequency, the roughness and the type of interfaces.