Vanadium dioxide (VO2) exhibits exceptional phase transition characteristics that enable dynamic manipulation of electromagnetic wave. In this study, a novel design bilayer isotropic metasurface is introduced. It leverages insulating-to-metallic VO2 to broadband holography for terahertz For the metallic VO2, upper antennas reflect incident wave and generate hologram. insulating reflected by lower gold same hologram generated with frequency doubling. Working frequencies designed holograms are...

We present an efficient nonconformal-mesh discontinuous Galerkin (DG) method for elastic wave propagation in viscous media. To include the attenuation and dispersion due to quality factor time domain, several sets of auxiliary ordinary differential equations (AODEs) are added. Unlike conventional partial equation-based algorithm, this new is highly parallel with its lossless counterpart, thus requiring much less storage consumption. Another superior property AODE-based DG that a novel exact...

We present a node-based discontinuous Galerkin (DG) pseudospectral time domain (PSTD) algorithm, with adaptive nonconformal unstructured meshes, for 3-D large-scale Maxwell's equations. This algorithm is combination of new DG and PSTD method, where spectral accuracy achieved via the while serves as stable coupling multiple domains hexahedra. Time marching efficient because mass matrix in DG-PSTD exactly diagonal. The scheme low-storage scalable stiffness localized into small shared matrix....

Non‐invasive photoacoustic tomography (PAT) of mouse brains with intact skulls has been a challenge due to the skull's strong acoustic attenuation, aberration, and reverberation, especially in high‐frequency range (>15 MHz). In this paper, we systematically investigated impacts murine skull on wave propagation PAT image reconstruction. We studied aberration impedance mismatch at boundaries mode conversion between longitudinal shear wave. The wave's reverberation within was for both modes....

A high-order discontinuous Galerkin (DG) method with nonconformal meshes is developed to accurately simulate large-scale poroelastic wave propagation in 3-D isotropic media. An exact upwind flux succinctly derived serve as an accurate coupling solver for the DG algorithm. Specifically, eigenvalue problem Riemann solution effectively reduced from rank of 13 4. Furthermore, this new numerical gives more explicit physical insight, which indicates three-type waves media: two P and one S wave....

We present a mesh skeleton-enhanced discontinuous Galerkin (DG) method, i.e., hybridizable DG, to solve the 3-D highly nonlinear semiconductor drift-diffusion model. This DG algorithm is remedy but significant extension of classical where only degrees freedom on skeleton are involved as globally coupled problem, thus reducing global dimension from 2-D and 1-D. Furthermore, high-order nodal basis functions over tetrahedra easily obtained, meticulous designs circumvented for complex modeling....

In this paper, full mechanisms of dissipation and dispersion in poro-viscoelastic media are accurately simulated time domain. Specifically, four Q values first proposed to depict a medium: two for the attenuation bulk shear moduli solid skeleton, one modulus pore fluid, other solid-fluid coupling. By introducing several sets auxiliary ordinary differential equations, factors efficiently incorporated high-order discontinuous Galerkin algorithm. Consequently, mathematical sense, Riemann...

This paper first presents machine learning inversion of resistivity profiles from multi-frequency electromagnetic measurements on undulating terrain surfaces based synthetic data training by the mixed spectral element method (MSEM). The combines several advanced technologies with various merits. A semi-regular mesh generation is designed and developed for adaption to complex measured data, proposed meshing technology also suitable modeling different models under same terrain. By simulating...

A three-dimensional high-order reverse-time migration (3-D HO-RTM) method is proposed to perform subsurface electromagnetic imaging with an ultra-wideband radar (UWBR) system consisting of a multi-input and multi-output antenna array. By using UWBR collect temporal scattering signals, targets can be detected, the image obtained by methods such as back-propagation method, frequency-wavenumber technique, time-reversal mirror, method. The HO-RTM based on finite-difference time-domain (HO-FDTD)...

An efficient and accurate hybrid spectral element-spectral integral (SESI) method is proposed to simulate electromagnetic (EM) scattering by objects in multiregion cylindrically layered media. The field each of the multiple regions with scatterers can be solved element (SEM), while (SIM) used as an exact boundary condition for adjacent multilayered This between electric surface current density cylindrical layer obtained using a recursive formula SIM. inverse matrix Toeplitz arising from SIM...

This article proposes a novel method for calculating radar cross-sections (RCSs) that combines the spectral element and integral method, allowing RCS calculations at any position in free space or half-space. approach replaces field source with an incident using scattered equation of enabling arbitrary placement without being limited by computational domain. By applying superposition theorem volume equivalence principle, objects is obtained through equations, eliminating limitations on...

As one of the most important nondestructive characterization techniques, electromagnetic (EM) methods can be used in subsurface fracture detection, especially for hydraulic evaluation unconventional petroleum exploration and development. The multiscale nature long but extremely thin 3-D fractures is difficult conventional EM modeling such as finite element method (FEM) numerical simulation. problem becomes even more challenging when effects tilted borehole, casing, planar stratified media...

A new mixed finite-element time-domain (FETD) method is developed to eliminate the low-frequency breakdown phenomenon in conventional when solving electrically small transient problems. Constructed by Gauss's law and current continuity equation, divergence constraint equation incorporated into wave for electric field form of a Lagrange multiplier. Curl-conforming vector basis functions nodal are chosen spatial discretization implicit Newmark-beta algorithm adopted time integration. It shown...

Traditional time-domain finite-element and spectral-element methods are known to suffer from the so-called low-frequency breakdown problem, where system matrix can become ill-conditioned, results be unstable for electrically fine structures. In this article, a new mixed (SETD) (FETD) proposed overcome problem by constraint equations tree-cotree splitting. Two forms of gradient matrices or null space stiffness high-order basis functions calculated construct equations. Then, directly applied...