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To achieve high-precision calculation of the electromagnetic field of layered media and to ensure that the apparent resistivity calculation and sensitivity are not affected by numerical errors, this paper implements high-precision calculation of the layered electromagnetic field based on the weighted average (WA) extrapolation method. Firstly, the 1D electromagnetic field expression of an arbitrary attitude field source is obtained by using the magnetic vector potential; then, the WA extrapolation technique is introduced to achieve the high-precision and fast solution of the Hankel transform, and the effects of the number of Gaussian points and the number of integration intervals on the accuracy are investigated. The theoretical model test shows that, compared with the open-source Dipole1D, the algorithm proposed in this paper has wider adaptability, and can achieve high-precision calculation of electric and magnetic dipole sources with higher efficiency. Compared with the epsilon algorithm studied by previous researchers, the WA extrapolation method proposed in this article can improve the convergence rate by approximately 20% under the same conditions. It can obtain high-precision numerical solutions with less integration time. The relative accuracy can reach the order 10 − 10 , and its computational efficiency is significantly better than the existing epsilon algorithm. Finally, we used two cases of marine controlled source electromagnetic method to show the application. The sensitivity and Poynting vectors are calculated, which provides a technical tool for a deep understanding of physical mechanisms in layered media. [ABSTRACT FROM AUTHOR]

A general theory for solving electromagnetic diffraction problems with impenetrable/penetrable wedges immersed in/made of an arbitrary linear (bianistropic) medium is presented. This novel and general spectral theory handles complex scattering problems by using transverse equations for layered planar and angular structures, the characteristic Green function procedure, the Wiener–Hopf technique, and a new methodology for solving GWHEs. The technique has been proven effective for analyzing problems involving wedges immersed in isotropic media; in this study, we extend the theory to more general cases while providing all necessary mathematical tools and corresponding validations. We obtain generalized Wiener–Hopf equations (GWHEs) from spectral functional equations in angular regions filled by arbitrary linear media. The equations can be interpreted with a network formalism for a systematic view. We recall that spectral methods (such as the Sommerfeld–Malyuzhinets (SM) method, the Kontorovich–Lebedev (KL) transform method, and the Wiener–Hopf (WH) method) are well-consolidated, fundamental, and effective tools for the correct and precise analysis of electromagnetic diffraction problems constituted by abrupt discontinuities immersed in media with one propagation constant, although they are not immediately applicable to multiple-propagation-constant problems. To the best of our knowledge, the proposed mathematical technique is the first extension of spectral analysis to electromagnetic problems in the presence of angular regions filled by complex arbitrary linear media, thereby providing novel mathematical tools. Validation through fundamental examples is proposed. [ABSTRACT FROM AUTHOR]

In recent years, much attention has been paid to integrated photonics devices based on nonlinear media. A generalization of the transfer matrix method to problems in plane-parallel layered media with quadratic and cubic nonlinearity is proposed. The incident radiation can be either a monochromatic wave or a non-monochromatic pulse. Previously, such problems could only be solved using grid methods. The proposed approaches significantly expand the range of applicability of matrix methods and are drastically superior in efficiency to the well-known grid methods. [ABSTRACT FROM AUTHOR]

The scattering of electromagnetic radiation by a layered periodic diffraction grating is an important model in engineering and the sciences. The numerical simulation of this experiment has been widely explored in the literature and we advocate for a novel interfacial method which is perturbative in nature. More specifically, we extend a recently developed High-Order Perturbation of Surfaces/Asymptotic Waveform Evaluation algorithm to utilize a stabilized numerical scheme which also suggests a rigorous convergence result. An implementation of this algorithm is described, validated, and utilized in a sequence of challenging and physically relevant numerical experiments. [ABSTRACT FROM AUTHOR]

Inversion of surface‐wave free fields is of great importance in providing seismic excitations for the finite element (FE) analysis of soil–structure interaction (SSI) systems. In the case of layered media, the propagating surface waves are characterized by their unique dispersion property, resulting in dispersive multi‐mode surface wavefields. Available studies primarily focus on only the fundamental mode and neglect the influence of higher modes, which fail to identify the real structural response characteristics. To enhance the precision of seismic excitations for SSI systems situated in layered media, a multi‐mode inversion method for dispersive surface‐wave free fields is proposed in this study. The proposed method employs the energy flow density to characterize the participation volume of dispersive modes, and further calculates corresponding modal participation factors by combining with the dispersion curve and dynamic‐stiffness matrix (DSM) method. The modal participation factors are then utilized to assign the ground surface components of each mode and invert respective single‐mode surface‐wave free fields. Based on the mode superposition theory, all the single‐mode surface‐wave free fields are finally superimposed to construct the multi‐mode wavefields. The accuracy of the proposed method is thoroughly verified and validated across various types of layered media. Furthermore, the engineering application of the proposed method is illustrated by performing the FE analysis on an SSI example. The analysis results highlight the significant participation of surface waves' higher modes in structural seismic responses, particularly in the weak‐interbed type media. [ABSTRACT FROM AUTHOR]

When an impactor strikes a layered target, both the impactor and the target experience waves. The waves produced travel and engage in interactions with other waves as well as the interfaces in the impactor-target system. For the impact problems on a layered mediumwith periodic properties and layered elastic media of Goupillaud-type (each layer has the same wave travel time), researchers have presented an analytical solution for stress variation with position and time within the target. However, the solution for an elastic media not satisfying the above conditions is not available in the literature. The present study fills this gap and finds the behaviour of a generalized layered medium to an impact problem. The response of the material at any position inside the layered medium is found by solving the interaction between waves, interfaces, and boundaries. The mass, momentum balance and constitutive relationship are solved to get the exact analytical expressions for particle velocity and stress for each possible wave interaction happening in the impactor and the layered medium. The expressions are utilized in a computer program to study the impact behaviour of a layered media. The code tracks each wave as it travels through the system and identifies those interactions that occur in the shortest time, uses the stress and velocity expression for that interaction, and updates the state of the material. When stress produced at the impact surface is tensile in nature, the impactor and target can be separated. The work can be applied to both finite and semi-infinite impactors and targets, and the layered medium does not necessarily have to be a periodic layered media or a Goupillaud-type medium. [ABSTRACT FROM AUTHOR]

The effective thermal characteristics of composite materials used in the theory of solid-state cooling are studied. Two classes of composites are considered: layered structures consisting of a large number of nano-sized layers and two-phase granular composites. It is assumed that the interfaces between media are imperfect. The Kapitza temperature jump occurs at the interfaces. The effective characteristics of layered structures are obtained using the matrix homogenization method. The homogenization of the characteristics of granular composites is based on the Bruggeman approach. Formulas taking into account the influence of the interlayer Kapitza resistance on the homogenized thermal characteristics of the structure are obtained. Expressions for average values of heat sources are derived. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Computational Mechanics / Jisuan Lixue Xuebao is the property of Chinese Journal of Computational Mechanics Editorial Office, Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A general theory for solving electromagnetic diffraction problems with impenetrable/penetrable wedges immersed in/made of an arbitrary linear (bianistropic) medium is presented. This novel and general spectral theory handles complex scattering problems by using transverse equations for layered planar and angular structures, the characteristic Green function procedure, the Wiener–Hopf technique, and a new methodology for solving GWHEs. The technique has been proven effective for analyzing problems involving wedges immersed in isotropic media; in this study, we extend the theory to more general cases while providing all necessary mathematical tools and corresponding validations. We obtain generalized Wiener–Hopf equations (GWHEs) from spectral functional equations in angular regions filled by arbitrary linear media. The equations can be interpreted with a network formalism for a systematic view. We recall that spectral methods (such as the Sommerfeld–Malyuzhinets (SM) method, the Kontorovich–Lebedev (KL) transform method, and the Wiener–Hopf (WH) method) are well-consolidated, fundamental, and effective tools for the correct and precise analysis of electromagnetic diffraction problems constituted by abrupt discontinuities immersed in media with one propagation constant, although they are not immediately applicable to multiple-propagation-constant problems. To the best of our knowledge, the proposed mathematical technique is the first extension of spectral analysis to electromagnetic problems in the presence of angular regions filled by complex arbitrary linear media, thereby providing novel mathematical tools. Validation through fundamental examples is proposed.

A piecewise-homogeneous medium, consisting of anisotropic layers, is excited by a primary spherical sound wave due to a point source lying in the exterior of the medium or in one of its layers. The direct scattering problem is formulated by means of a modified scalar Helmholtz equation incorporating the anisotropic characteristics of the problem. The T-matrix of the problem is determined analytically by means of a suitable coordinate transformation. Then, the acoustic fields in all layers are obtained. Finally, specific reductions to special cases are presented. [ABSTRACT FROM AUTHOR]

In the framework of mean field approximation, we consider a spin system consisting of two interacting sub-ensembles. The intra-ensemble interactions are ferromagnetic, while the inter-ensemble interactions are antiferromagnetic. We define the effective number of the nearest neighbors and show that if the two sub-ensembles have the same effective number of the nearest neighbors, the classical form of critical exponents ( α = 0 , β = 1 / 2 , γ = γ ′ = 1 , δ = 3 ) gives way to the non-classical form ( α = 0 , β = 3 / 2 , γ = γ ′ = 0 , δ = 1 ), and the scaling function changes simultaneously. We demonstrate that this system allows for two second-order phase transitions and two first-order phase transitions. We observe that an external magnetic field does not destroy the phase transitions but only shifts their critical points, allowing for control of the system's parameters. We discuss the regime when the magnetization as a function of the magnetic field develops a low-magnetization plateau and show that the height of this plateau abruptly rises to the value of one when the magnetic field reaches a critical value. Our analytical results are supported by a Monte Carlo simulation of a three-dimensional layered model. [ABSTRACT FROM AUTHOR]

This work is concerned with operators of the type A = -c A acting in domains fi := fi0 x (0,H) C Rd x Rc The diffusion coefficient c >0 depends on one coordinate y e (0, H) and is bounded but may be discontinuous. This corresponds to the physical model of "layered media," appearing in acoustics, elasticity, optical fibers. Dirichlet boundary conditions are assumed. In general, for each s > 0, the set of eigenfunctions is divided into a disjoint union of three subsets: Fng (non-guided), Fg (guided) and Fres (residual). The residual set shrinks as s ! 0: The customary physical terminology of guided/non-guided is often replaced in the mathematical literature by concentrating/non-concentrating solutions, respectively. For guided waves, the assumption of "layered media" enables us to obtain rigorous estimates of their exponential decay away from concentration zones. The case of non-guided waves has attracted less attention in the literature. While it is not so closely connected to physical models, it leads to some very interesting questions concerning oscillatory solutions and their asymptotic properties. Classical asymptotic methods are available for c (y) e C2 but a lesser degree of regularity excludes such methods. The associated eigenfunctions (in Fng) are oscillatory. However, this fact by itself does not exclude the possibility of "flattening out" of the solution between two consecutive zeros, leading to concentration in the complementary segment. Here we show it cannot happen when c(y) is of bounded variation, by proving a "minimal amplitude hypothesis." However the validity of such results when c(y) is not of bounded variation (even if it is continuous) remains an open problem. [ABSTRACT FROM AUTHOR]

Srivastava and Yeh (1991, https://doi.org/10.1029/90WR02772) derived an exact solution to the linearized Richards equation (LRE) for two‐layer medium infiltration using the Laplace transform (LT) method with a particular initial condition assumed, making the most pioneering contribution to the derivation of exact solutions to the layered‐medium LRE (i.e., ES‐LMLREs). However, the LT method is unsuitable for deriving an ES‐LMLRE that considers either an arbitrary initial condition or an arbitrary number of layers, or both, preventing further progress in developing ES‐LMLREs. Adopting a new solution strategy, namely a conjunctive use of the variable separation method and the transfer matrix method, we develop a novel exact layered‐medium‐LRE infiltration solution, overcoming the above difficulties. First, the proposed solution is successfully validated against the Srivastava‐Yeh solution. As a feature‐demonstration example, a layered‐medium water absorption process is simulated, and our solution well captures how the heterogeneity of hydraulic parameters affects the dynamics of this process. Moreover, the proposed solution is a valuable benchmark for related numerical models. Key Points: An exact solution for transient infiltration in layered media that enjoys flexibility in initial condition and layer number is presentedThe new analytical solution can analyze the moisture absorption process from the water table in initially dry layered soilsThe proposed solution can serve as a valuable benchmark for related numerical models [ABSTRACT FROM AUTHOR]

The scattering of linear waves by periodic structures is a crucial phenomena in many branches of applied physics and engineering. In this paper we establish rigorous analytic results necessary for the proper numerical analysis of a class of high-order perturbation of surfaces/asymptotic waveform evaluation (HOPS/AWE) methods for numerically simulating scattering returns from periodic diffraction gratings. More specifically, we prove a theorem on existence and uniqueness of solutions to a system of partial differential equations which model the interaction of linear waves with a periodic two-layer structure. Furthermore, we establish joint analyticity of these solutions with respect to both geometry and frequency perturbations. This result provides hypotheses under which a rigorous numerical analysis could be conducted on our recently developed HOPS/AWE algorithm. [ABSTRACT FROM AUTHOR]

The high-resolution range profiles (RPs) of 3-D objects buried in layered media are investigated. In order to simulate the RPs efficiently, wideband scattered fields are calculated by a method of moments (MoM) based fast algorithm, i.e. characteristic basis function method (CBFM). To achieve fast frequency sweep, an adaptive frequency sampling strategy (AFS) is implemented to accelerate the broadband simulation. Then by using the inverse discrete Fourier transform (IDFT), RPs of the object are obtained. To validate the proposed approach, range locations are predicted qualitatively based on the ray theory. Moreover, the ray approach also enables the physical interpretation of the scattering mechanisms corresponding to the peaks, for example, the specular reflection, the edge diffraction, and the higher-order effects. Since different scattering centers (SCs) dominate in different directions, the RPs are aspect dependent. Furthermore, the RPs are also dependent on the lossy and dispersive effects of the layered medium. Numerical results demonstrate that the peaks are significantly reduced when the layered medium is lossy, especially those due to the higher-order interactions between the object and the interfaces. [ABSTRACT FROM AUTHOR]

An asymptotic expansion of layered Green's function is examination in a spatial domain and parametric approach is proposed by determining a small parameter to derive the shortened form of Green's function for 3- and 4-layered structures. For qualitative testing and comparison of the exact Green's function and asymptotic shortened Green's functions associated with the measurement and source point in the same layer, we performed numerical calculations. [ABSTRACT FROM AUTHOR]

A number of actual problems of integrated photonics are reduced to an oblique incidence of radiation on a plane-parallel scatterer. For such problems, an approximate method of integrating the Maxwell equations along the beam propagation direction is proposed. As a result, the original two-dimensional problem is reduced to a one-dimensional one, and recently proposed one-dimensional bicompact schemes are used to solve it. This approach provides a significant reduction of computational costs compared to traditional two-dimensional methods such as finite differences and finite elements. To verify the proposed method, calculations of test and applied problems with known exact reflection spectra are carried out. [ABSTRACT FROM AUTHOR]

• Elastic response of surface-loaded layered 1D hexagonal quasicrystal is investigated. • Fourier transform and stiffness methods are adopted to derive complete analytical solution. • Effects of arrangement and thickness of coating layers are explored. • Strong phonon-phason coupling in predicted solutions is addressed. • Application of multi-layer scheme to model FGQ coating layer is highlighted. This study aims to investigate the elastic response of a two-dimensional, surface-loaded substrate coated by a multi-layered system consisting of one-dimensional hexagonal quasicrystal materials. A linear elasticity theory for quasicrystals is adopted to simulate phonon and phason elastic fields. First, a set of governing differential equations for each layer is established in terms of the phonon and phason displacements. The general solution for a generic layer is constructed through the Fourier transform method in a closed form in the transform space. This solution is then utilized to formulate a layer stiffness equation. Adopting a direct stiffness method along with continuity along the layer interfaces, a stiffness equation for the multi-layered coated substrate is derived. An efficient quadrature is adopted to evaluate all involved integrals resulting from Fourier integral inversion. After verification with benchmark cases, the capability of the derived solutions are demonstrated by investigating the influence of various parameters such as layer thickness, layer arrangement, and loading conditions on the predicted response. Finally, applications of the developed multi-layer scheme to tackle a functionally graded quasicrystal layer are elucidated. [ABSTRACT FROM AUTHOR]

A piecewise-homogeneous medium, consisting of anisotropic layers, is excited by a primary spherical sound wave due to a point source lying in the exterior of the medium or in one of its layers. The direct scattering problem is formulated by means of a modified scalar Helmholtz equation incorporating the anisotropic characteristics of the problem. The T-matrix of the problem is determined analytically by means of a suitable coordinate transformation. Then, the acoustic fields in all layers are obtained. Finally, specific reductions to special cases are presented.

Nowadays, many wireless applications require the exchange of electromagnetic waves through propagation environments that look like to stratified media to some extent. This may concern both natural scenarios, e.g., air/vegetation/ground, and artificial structures, like meta-materials, photonic devices, solar cells or systems-on-chip. The characterization of the layered propagation channel is therefore important for the design and deployment of effective devices and systems. To this aim, the Dyadic Green Function method has been often leveraged, although its use is usually limited to simple sources, like short dipoles or current elements. Furthermore, it seems unsuited to assess the dispersive properties of the channel, which are known to become important when high data-rate must be conveyed. In this paper, a ray-based approach to propagation inside layers is proposed. As the layered environment can be quite reverberating, a great number of rays may be needed, to the extent that the corresponding computational burden might be hardly afforded by general purpose ray tracing tools. Therefore, the ray tracing engine here presented is specifically conceived for the layered case, and mostly relies on analytical formulation. The accuracy of the model is checked against measurement carried out at chip scale at optical frequency, as a reference study case.

A detailed Volume Integral Equation (VIE) formulation for planar plasmonic nano structures with finite thickness in flat multi-layers medium is presented. The boundary condition along the localized metallic objects is expressed in terms of the unknown polarization current flowing through these objects in the form of an integral equation, which is solved using the Method of Moments (MoM). The Green's functions associated with a layered medium of practical importance are expressed in the spectral domain. The corresponding spatial domain Green's functions are obtained using the Discrete Complex Images Method (DCIM). Special treatment for the spectral function's asymptote at high spectral values is performed. The presented formulation is applied on different plasmonic structures immersed inside layered media. The structures include nano-rod and nano-patch excited by an incident plane wave. In addition, a simple band-stop filter based on quarter-wavelength stubs is considered. This filter is fed with a couple of plasmonic transmission lines. The obtained current distributions and S-parameters are compared with those obtained using a commercial full-wave electromagnetic simulator, namely CST Microwave Studio. A very good agreement is observed. The proposed integral equation formulation enjoys high degree of stability, numerical efficiency, and accuracy.

We investigate indentation of a linear viscoelastic half-space with periodically distributed heterogeneities by a smooth, rigid, axisymmetric indenter of an arbitrary profile. For this, we first show how such materials may be homogenized directly in the time-domain to yield a homogeneous,anisotropic, linear viscoelastic medium. For the layered half-space that we then focus upon homogenization leads to a transversely isotropic, homogeneous, viscoelastic medium. We then replace the layered half-space in the original indentation problem by its homogenized counterpart. For axisymmetric indenters, for loadings in which the contact area is non-decreasing, we solve this indentation problem analytically by extending the correspondence principle of Graham (in Q Appl Math 26:167–174, 1968. https://doi.org/10.1090/qam/99860). Finally, we compare the results of homogenization with direct finite element computations of both displacement and force controlled indentation tests. We find that the contact pressure, the depth of penetration and the displacement of the top surface of the layered half-space are well approximated by those obtained through homogenization, and the approximation improves as the layer thickness is reduced, which is precisely when FE computations become harder. The latter aspect makes the development of the present approach useful. [ABSTRACT FROM AUTHOR]

We investigate indentation by a smooth, rigid, spherical indenter of a heterogeneous half-space made up of layers of two different linear-elastic materials arranged periodically, parallel to the free surface. We utilize homogenization theory to approximate the heterogeneous material by a linear-elastic, homogeneous, but transversely isotropic material. This replaces the original system by an analytically tractable indentation problem, whose solution is then compared with that of the former obtained through the finite element (FE) method. We find that the contact pressure obtained through homogenization is a good approximation to that on the layered half-space, and the approximation improves if (1) the layer thickness is reduced, or (2) the indented force is augmented, or (3) the two layers exhibit closer elastic response. We demonstrate that the difference between the pressures obtained from FE and homogenization has an upper bound that depends only upon the materials' Poisson's ratio, the ratio of their Young's moduli, and their volume fractions. We then show that the penetration depth of the indenter in the layered half-space converges to that in the homogenized material as the layers become thinner. Finally, we find that the homogenized material captures well the discontinuous variation of von Mises stress in the layered medium. [ABSTRACT FROM AUTHOR]

In this work, we present a novel analytical model for the magnetic field in through-the-Earth (TTE) communications. The modeling approach is based on dyadic Green’s functions to compute impressed and scattered fields in a multilayered structure. Its performance is assessed through comparisons with previous models, measurements, and simulations of magnetic field. The great advantages of the proposed approach in relation to the previous ones are its flexibility in the positioning and direction of antennas and the unlimited number of layers of soil. Moreover, this approach can be more accurate than classical ones in scenarios where the soil has a high conductivity below the antenna in an uplink scenario. [ABSTRACT FROM AUTHOR]

A matrix basis formulation is introduced to represent the 3 × 3 frequency domain dyadic Green's functions of Maxwell's equations in 3-dimensional layered media. The formulation can be used to decompose the Maxwell's Green's functions into independent TE and TM components, each satisfying a scalar Helmholtz equation. Moreover, the interface transmission conditions for the electromagnetic fields can be reduced to decoupled conditions for the matrix basis coeffcients at interfaces. Numerical results for the electric and magnetic dyadic Green's functions for a 10-layer medium show the capability of the proposed formulation. [ABSTRACT FROM AUTHOR]

Ultrasonic phased array testing is commonly employed for inspecting curved structures. Conventional plane wave imaging techniques, based on delay-and-sum in the time-domain, offer high image quality and inspection accuracy but suffer from low frame rates due to their high computational complexity. In this work, an efficient wavenumber-domain imaging method that combines non-stationary wavefield extrapolation and f - k migration is proposed for curved structure inspection. Special emission focal laws are designed to generate a sequence of steered plane waves through the curved interface. The raw data is then extrapolated to the top boundary of the region of interest, followed by f - k migration to reconstruct images with high time efficiency. Simulation and experimental evaluations demonstrate a time reduction by a factor of up to 32.24 compared to conventional time-domain plane wave image reconstruction with equivalent image quality, highlighting its potential for monitoring flaws in real-time. • Wavefield extrapolation and f-k migration are combined to achieve high efficiency. • A frame rate of up to 18 fps is attainable without any detriment to image quality. • The frame rate is improved by a factor of 32.24 compared to the conventional PWI-TFM. [ABSTRACT FROM AUTHOR]

The current study examines the propagation of surface waves in an asymmetric rotating doubly coated nonhomogeneous half space. The coating layers are assumed to be made of different homogeneous isotropic materials, while the overlaying nonhomogeneous half space layer is considered to be of exponentially varying material properties. The consequential exact vibrational displacements and dispersion relation are determined analytically, in addition to the approximate validation of the dispersion relation via the application of an asymptotic procedure within the long wave limit. Two cases of unloaded and loaded end surface scenarios are analyzed by examining the posed fundamental modes. More precisely, an elastic Winkler foundation was considered in the case of a mechanically loaded end surface condition and was found to proliferate the transition between having a fundamental mode over the frequency axis to the wave number axis as the angular velocity increased. Moreover, the rotational effect was found to have a direct impact on the surface wave propagation with a long wave and low frequency. Aside from that, an increase in the nonhomogeneity parameter resulted in propagation with a relatively long frequency. [ABSTRACT FROM AUTHOR]

We present a method for low-cost fabrication of polydimethylsiloxane (PDMS) tissue simulating phantoms with tunable scattering spectra, spanning visible, and near-infrared regimes. These phantoms use optical polishing agents (aluminum oxide powders) at various grit sizes to approximate in vivo tissue scattering particles across multiple size distributions (range: 17 to 3  μm). This class of tunable scattering phantoms is used to mimic distinct changes in wavelength-dependent scattering properties observed in tissue pathologies such as partial thickness burns. Described by a power-law dependence on wavelength, the scattering magnitude of these phantoms scale linearly with particle concentration over a physiologic range [μs′=(0.5 to 2.0  mm−1)] whereas the scattering spectra, specific to each particle size distribution, correlate to distinct exponential coefficients (range: 0.007 to 0.32). Aluminum oxide powders used in this investigation did not detectably contribute to the absorption properties of these phantoms. The optical properties of these phantoms are verified through inverse adding-doubling methods and the tolerances of this fabrication method are discussed.

Thin dielectric or conductive structures are very common in many applications. Modeling such structures in the finite-element method can require a very dense mesh near the structures, which increases the computation cost and degrades the mesh quality. In this work, the surface current boundary condition is incorporated into the framework of the spectral-element spectral-integral method to efficiently model thin structures with double periodicity embedded in layered media. The thin structures are viewed as zero-thickness surfaces, and no dense mesh is required. Furthermore, a fast and convenient formulation is developed to evaluate the tangential field in the background of doubly periodic structures. Numerical experiments demonstrate the accuracy and efficiency of the proposed method by comparing with various reference solvers. [ABSTRACT FROM AUTHOR]

This paper presents an analytical solution to the mixed boundary value problem for a dynamic rigid rectangular plate on the surface of a layered transversely isotropic half-space. For the contact problem, the mixed boundary conditions at the surface are converted into linear equations by means of Bessel series expansions. Solving these linear equations can get the expression of the contact stress, which can be further utilized to obtain the stresses and displacements of this model by the analytical layer element method of layered media. Additionally, the contact stresses can be used to evaluate the vertical and rocking compliances of a rectangular plate. A good agreement with existing solutions verifies the accuracy of the proposed method, and numerical examples are carried out to investigate the effect of angular frequency, length-to-width ratios, transverse isotropy and the stratification of media. [ABSTRACT FROM AUTHOR]

In this work we solve a problem of a solid infinitely long cylinder composed of three layers of different materials. The current problem occurs in the context of fractional order thermoelasticity theory. The problem is solved using a direct approach together with the Laplace transform technique. A numerical method based on Fourier expansion is used to obtain the inverse transform. The results are represented graphically and discussed. [ABSTRACT FROM AUTHOR]

The real-time evaluation for non-destructive air-coupled ultrasonic testing of panel materials is a big task for several industries. To make these tests more and more accurate, efficient and reliable calculation methods from ultrasonic holography are essential. In the past, we presented the spec-radiation method as a fast and accurate method for such tasks. The spec-radiation method calculates the sound field utilizing data from a measurement plane at another parallel or tilted plane, especially the sound field at the surface of a panel. This can be used to detect flaws. There is a limitation of the current method: using the data on the panel surface limits the accuracy of the detected flaws. A big step forward could be expected if the sound field in the material were known. As a first step, we developed the spec-radiation method forward to consider multiple material layers. For now, we made the major assumption that all layers have fluid-like properties. Hence, transversal waves were neglected. This extension of the spec-radiation method was validated utilizing an experiment. We present that flaws in the panel material can be detected with higher accuracy at a similar speed compared to our former approach. [ABSTRACT FROM AUTHOR]

Electromagnetic simulation plays an essential role in formation conductivity determination by electromagnetic well-logging tools, especially when the nonvertical borehole and invasion zones are present in a layered earth. A hybrid finite-element boundary integral (FEBI) method is suitable for such well-logging simulations. The usage of layered medium Green’s functions allows the simulation background to be a planar stratified medium to characterize the earth formation. However, conventional FEBI using the Rao–Wilton–Glisson (RWG) basis function produces inaccurate results due to the low-frequency breakdown of the boundary integral equation solution. The new contribution of this work is to apply the loop-tree (LT) basis functions in the FEBI method to reduce the numerical error at low frequencies. Such an LT-FEBI method can handle all specific requirements of well-logging simulations at low frequencies. A direct solver is applied to make it more efficient to obtain logging curves with multiple source locations. The LT-FEBI simulation results are validated in several numerical examples, including a challenging well-logging model with a deviated borehole and invasion zones in the Oklahoma formation having 28 layers. [ABSTRACT FROM AUTHOR]

Copyright of Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil is the property of University of Puerto Rico and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A number of actual problems of integrated photonics are reduced to an oblique incidence of radiation on a plane-parallel scatterer. For such problems, an approximate method of integrating the Maxwell equations along the beam propagation direction is proposed. As a result, the original two-dimensional problem is reduced to a one-dimensional one, and recently proposed one-dimensional bicompact schemes are used to solve it. This approach provides a significant reduction of computational costs compared to traditional two-dimensional methods such as finite differences and finite elements. To verify the proposed method, calculations of test and applied problems with known exact reflection spectra are carried out.

A number of simple models containing frequency‐independent elements have been presented to simulate unbounded soil in dynamic soil‐structure interaction problems. Most of the existing models were established through a traditional top‐down strategy with significant computational complexities. This study develops an alternative method based on a bottom‐up strategy, in which the optimal element layout is determined by an adaptive refinement procedure considering finite modularized units. This innovation eliminates the need for lengthy procedures to establish simple models. The proposed three‐parameter model is used to simulate the layered soil for rigid foundations undergoing vertical vibration. The accuracy of the model is validated by comparing the magnified responses obtained when a foundation is subjected to harmonic forces with those obtained via theoretical solutions and advanced numerical simulations. The proposed model is found to effectively simulate a layered half‐space and a soil layer on rock. Compared to two existing models, the proposed model performs better and has fewer parameters and a higher degree of adaptivity. Therefore, the adaptivity of simple models obtained using the proposed method may allow simulation of a variety of layered soil systems. [ABSTRACT FROM AUTHOR]

The problem of target detection and localization in layered media can be solved by the mixed TR–RTM. The highlight of this paper is on multilayer media, where the target is harder to detect than in double-layered media, due to the interference of multiple interface reflection signals. The core idea of the TR–RTM mixed method, namely the RTM isochronism principle, is applied for the three cases. Typically, a target under a TR–RTM process can form a mountain-like acoustic field distribution. For the interface whose reflected signal is an interference, the acoustic field distribution is disordered and inhomogeneous, with a smaller amplitude. The TR–RTM greatly improves the signal-to-interference ratio, where the position of the summit is the just position of the target, thus, detecting and localizing the target. [ABSTRACT FROM AUTHOR]

Spectral properties of the modes supported by plasmonic waveguides in planarly layered media are studied by the method of Multiple MultiPoles (MMP). It is shown that the most important entities in the mode analysis are the wavenumbers of the upper and lowermost layers and the wavenumbers of the guided waves supported by the layered medium. These wavenumbers introduce branch points and associated branch cuts on the complex plane where the out-of-plane wavenumbers of the modes are searched. These branch points and associated cuts make the mode analysis in layered media more demanding than the mode analysis in homogeneous media, where there is only one branch point and associated branch cut related to the wavenumber of the homogeneous medium. Several numerical examples are given to address the differences introduced by the layered media in the mode analysis and guidelines that can be used in any well-known computational electromagnetics method are provided. [ABSTRACT FROM AUTHOR]

In this paper, vertical vibrations of a group of flexible strip foundations on multilayered transversely isotropic poroelastic soils are presented. The dynamic interaction problem is studied by employing a variational approach based on the discretization of the strip-soil contact region. Exact stiffness matrices for each layer and the half-plane are explicitly derived in the Fourier transform space for the first time to determine the influence functions required in the variational scheme. A set of numerical results for the vertical displacement and the bending moment of the foundations are presented to illustrate the influence of governing parameters such as anisotropic properties, foundation rigidity, and distance between strips on the dynamic interaction between foundations. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Signal Processing is the property of Journal of Signal Processing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)