259 research outputs found
Simulation and experimental verification of W-band finite frequency selective surfaces on infinite background with 3D full wave solver NSPWMLFMA
We present the design, processing and testing of a W-band finite by infinite and a finite by finite Grounded Frequency Selective Surfaces (FSSs) on infinite background. The 3D full wave solver Nondirective Stable Plane Wave Multilevel Fast Multipole Algorithm (NSPWMLFMA) is used to simulate the FSSs. As NSPWMLFMA solver improves the complexity matrix-vector product in an iterative solver from O(N(2)) to O(N log N) which enables the solver to simulate finite arrays with faster execution time and manageable memory requirements. The simulation results were verified by comparing them with the experimental results. The comparisons demonstrate the accuracy of the NSPWMLFMA solver. We fabricated the corresponding FSS arrays on quartz substrate with photolithographic etching techniques and characterized the vector S-parameters with a free space Millimeter Wave Vector Network Analyzer (MVNA)
Overview of Large-Scale Computing: The Past, the Present, and the Future
published_or_final_versio
Application of the multi-level time-harmonic fast multipole BEM to 3-D visco-elastodynamics
Engineering Analysis with Boundary elements (accepted, to appear)International audienceThis article extends previous work by the authors on the single- and multi-domain time-harmonic elastodynamic multi-level fast multipole BEM formulations to the case of weakly dissipative viscoelastic media. The underlying boundary integral equation and fast multipole formulations are formally identical to that of elastodynamics, except that the wavenumbers are complex-valued due to attenuation. Attention is focused on evaluating the multipole decomposition of the viscoelastodynamic fundamental solution. A damping-dependent modification of the selection rule for the multipole truncation parameter, required by the presence of complex wavenumbers, is proposed. It is empirically adjusted so as to maintain a constant accuracy over the damping range of interest in the approximation of the fundamental solution, and validated on numerical tests focusing on the evaluation of the latter. The proposed modification is then assessed on 3D single-region and multi-region visco-elastodynamic examples for which exact solutions are known. Finally, the multi-region formulation is applied to the problem of a wave propagating in a semi-infinite medium with a lossy semi-spherical inclusion (seismic wave in alluvial basin). These examples involve problem sizes of up to about boundary unknowns
Combined Field Integral Equation Based Theory of Characteristic Mode
Conventional electric field integral equation based theory is susceptible to
the spurious internal resonance problem when the characteristic modes of closed
perfectly conducting objects are computed iteratively. In this paper, we
present a combined field integral equation based theory to remove the
difficulty of internal resonances in characteristic mode analysis. The electric
and magnetic field integral operators are shown to share a common set of
non-trivial characteristic pairs (values and modes), leading to a generalized
eigenvalue problem which is immune to the internal resonance corruption.
Numerical results are presented to validate the proposed formulation. This work
may offer efficient solutions to characteristic mode analysis which involves
electrically large closed surfaces
A Coupled Hybridizable Discontinuous Galerkin and Boundary Integral Method for Analyzing Electromagnetic Scattering
A coupled hybridizable discontinuous Galerkin (HDG) and boundary integral
(BI) method is proposed to efficiently analyze electromagnetic scattering from
inhomogeneous/composite objects. The coupling between the HDG and the BI
equations is realized using the numerical flux operating on the equivalent
current and the global unknown of the HDG. This approach yields sparse coupling
matrices upon discretization. Inclusion of the BI equation ensures that the
only error in enforcing the radiation conditions is the discretization.
However, the discretization of this equation yields a dense matrix, which
prohibits the use of a direct matrix solver on the overall coupled system as
often done with traditional HDG schemes. To overcome this bottleneck, a
"hybrid" method is developed. This method uses an iterative scheme to solve the
overall coupled system but within the matrix-vector multiplication subroutine
of the iterations, the inverse of the HDG matrix is efficiently accounted for
using a sparse direct matrix solver. The same subroutine also uses the
multilevel fast multipole algorithm to accelerate the multiplication of the
guess vector with the dense BI matrix. The numerical results demonstrate the
accuracy, the efficiency, and the applicability of the proposed HDG-BI solver
Boundary integral equation methods for the elastic and thermoelastic waves in three dimensions
In this paper, we consider the boundary integral equation (BIE) method for
solving the exterior Neumann boundary value problems of elastic and
thermoelastic waves in three dimensions based on the Fredholm integral
equations of the first kind. The innovative contribution of this work lies in
the proposal of the new regularized formulations for the hyper-singular
boundary integral operators (BIO) associated with the time-harmonic elastic and
thermoelastic wave equations. With the help of the new regularized
formulations, we only need to compute the integrals with weak singularities at
most in the corresponding variational forms of the boundary integral equations.
The accuracy of the regularized formulations is demonstrated through numerical
examples using the Galerkin boundary element method (BEM).Comment: 24 pages, 6 figure
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