Examinando por Autor "Taboada, Jose M."

Mostrando 1 - 10 de 10

A Discontinuous Galerkin Combined Field Integral Equation Formulation for Electromagnetic Modeling of Piecewise Homogeneous Objects of Arbitrary Shape
(Institute of Electrical and Electronics Engineers, 2021-07-26) Martin, Victor F.; Landesa, Luis; Obelleiro, Fernando; Taboada, Jose M.
We present a novel discontinuous Galerkin surface integral equation approach, based on the electric and magnetic current combined field integral equations (JMCFIE), for the electromagnetic analysis of arbitrarily shaped piecewise homogeneous objects. In the proposed scheme, nonoverlapping boundary surfaces and interfaces between materials can be handled independently, without any continuity requirement through multimaterial junctions and tear lines between surfaces in contact. The use of nonconformal meshes provides improved flexibility for CAD prototyping and tessellation. The proposed formulation can readily address nonconformal multi-material junctions, where three or more material regions meet. The continuity of the electric surface current across the junction contours is enforced by the combination of the boundary conditions implicit in the JMCFIE formulation and the weakly imposed interior penalty between the contacting surfaces within each region. This completely avoids the cumbersome junction problem, which no longer requires any special treatment. Numerical experiments are included to validate the accuracy and demonstrate the great versatility of the proposed JMCFIE-DG formulation for the management and solution of complex composite objects with junctions.
A Domain Decomposition Scheme with an Efficient Multitrace Multiresolution Preconditioner for the Simulation of Complex Composite Problems
(International Union of Radio Science, 2023) Martin, Victor F.; Taboada, Jose M.; Vipiana, Francesca
In this work we present a multitrace method including an automatic and multilevel quasi-Helmholtz decomposition integrated with the domain decomposition method for the solution of arbitrary complex geometries composed of piecewise homogeneous composite objects. A numerical experiment demonstrates the flexibility of the proposed approach for the solution of large multi-scale objects composed of multiple materials.
A Multi-Resolution Preconditioner for Nonconformal Meshes in the MoM Solution of Large Multiscale Structures
(Institute of Electrical and Electronics Engineers, 2023-04-26) Martin, Victor F.; Taboada, Jose M.; Vipiana, Francesca
The paper presents a multi-resolution preconditioner able to improve the solution convergence, via the method of moments and the multilevel fast multipole algorithm, in the case of non-conformal meshes applying the multi-branch Rao-Wilton-Glisson basis functions. The proposed preconditioner enables, for the first time, an automatic multi-level quasi-Helmholtz decomposition on non-conforming meshes, including also the generation of the topological (global) loop functions. Moreover, the generation of the proposed preconditioning schemeis fully parallelized in a multicore shared-memory enviroment. Numerical results show the great flexibility of this approach for the solution of electrically-large multi-scale objects including hrefinement discretizations.
A novel MultiResolution Preconditioner Including Piecewise Homogeneous Dielectric Objects
(Institute of Electrical and Electronics Engineers, 2023) Martin, Victor F.; Solis, Diego M.; Taboada, Jose M.; Vipiana, Francesca
An extensive literature demonstrates the capabilities of the hierarchical quasi-Helmholtz decomposition multiresolution preconditioner both to address the breakdowns for the surface integral equations and to improve the convergence in multiscale problems, until now only applied to perfect electrical conductors. In this work we present a novel methodology based on this efficient preconditioner able to solve arbitrary complex geometries composed of piecewise homogeneous composite objects, that automatically satisfies the boundary conditions. To the authors’ knowledge, this is the first work where a multilevel quasi-Helmholtz decomposition is applied to objects with dielectric junctions without the need of a weak enforcement of the continuity or a number-of-unknown-reduction scheme. Numerical examples demonstrate the efficiency of the proposed approach for the solution of complex problems involving multiple materials (dielectric and conductors).
Accurate EMC Engineering on Realistic Platforms using an Integral Equation Domain Decomposition Approach
(Institute of Electrical and Electronics Engineers, 2019-11-06) Solis, Diego M.; Martin, Victor F.; Araujo, Marta G.; Larios, David; Obelleiro, Fernando; Taboada, Jose M.
This article investigates the efficiency, accuracy and versatility of a surface integral equation (SIE) multisolver scheme to address very complex and large-scale radiation problems including multiple scale features, in the context of realistic electromagnetic compatibility (EMC)/electromagnetic interference (EMI) studies. The tear-and-interconnect domain decomposition (DD) method is applied to properly decompose the problem into multiple subdomains attending to their material, geometrical, and scale properties, while different materials and arbitrarily shaped connections between them can be combined by using the so-called multiregion vector basis functions. The SIE-DD approach has been widely reported in the literature, mainly applied to scattering problems or small radiation problems. Complementarily, in this article, the focus is placed on realistic radiation problems, involving tens of antennas and sensors and including multiscale ingredients and multiple materials. Such kind of problems are very demanding in terms of both convergence and computational resources. Throughout two realistic case studies, the proposed SIE-DD approach is shown to be a powerful electromagnetic modeling tool to provide the accurate and fast solution which is indispensable to rigorously accomplish real-life EMC/EMI studies.
Additive-Free Synthesis of (Chiral) Gold Bipyramids from Pentatwinned Nanorods
(American Chemical Society, 2024-10-17) Bevilacqua, Francisco; Girod, Robin; Martin, Victor F.; Obelleiro-Liz, Manuel; Vinnacombe-Willson, Gail A.; Van Gordon, Kyle; Hofkens, Johan; Taboada, Jose M.; Bals, Sara; Liz-Marzán, Luis M.
The production of colloidal metal nanostructures with complex geometries usually involves shape-directing additives, such as metal ions or thiols, which stabilize high-index facets. These additives may however affect the nanoparticles’ surface chemistry, hindering applications, e.g., in biology or catalysis. We report herein the preparation of gold bipyramids with no need for additives and shape yields up to 99%, using pentatwinned Au nanorods as seeds and cetyltrimethylammonium chloride as surfactant. For high-growth solution:seed ratios, the bipyramids exhibit an unusual “belted” structure. Three-dimensional electron microscopy revealed the presence of high-index {117}, {115}, and {113} side facets, with {113} and {112} facets at the belt. Belted bipyramids exhibit strong near-field enhancement and high extinction in the near-infrared, in agreement with electromagnetic simulations. These Ag-free bipyramids were used to seed chiral overgrowth using 1,1′-binaphthyl-2,2′-diamine as a chiral inducer, with g-factor up to 0.02, likely the highest reported for bipyramid seeds so far.
Domain Decomposition Method (DDM).
(Scitech Publishing, 2024) Martin, Victor F.; Hong-Wei, Gao; Solis, Diego M.; Taboada, Jose M.; Peng, Zhen
This chapter concerns the use of domain decomposition (DD) methods for the surface integral equation (SIE)-based solution of time-harmonic electromagnetic wave problems. DD methods have attracted significant attention for solving partial differential equations. These methods are appealing due to their ability to obtain effective, efficient preconditioned iterative solution algorithms. They are also attractive because of their inherently parallel nature, an important consideration in keeping with current trends in computer architecture.
Influence of Geometrical Parameters on the Optical Activity of Chiral Gold Nanorods
(Wiley, 2023-03-08) Obelleiro-Liz, Manuel; Martin, Victor F.; Solis, Diego M.; Taboada, Jose M.; Obelleiro, Fernando; Liz-Marzán, Luis M.
Chiral metal nanoparticles (NPs) offer a powerful means of inducing and harnessing optical activity. However, due to the incomplete knowledge of the underlying growth mechanisms, there is still limited control over the achievable morphological detail and, consequently, over the resulting optical activity. Therefore, theoretical modeling is needed to guide experimental development toward optimizing the plasmonic chiroptical response. Toward filling this gap, herein an extensive parametric analysis is presented, via computer-aided-design (CAD) models and full-wave electrodynamic simulations, which aims at systematically analyzing the influence of structural changes on the plasmonic circular dichroism (CD) spectra of rod-shaped gold NPs comprising helical indentations on achiral nanorod cores. From this analysis, interesting patterns in the plasmon-mediated resonant behavior are identified and cause–effect relationships are drawn that may serve as a go-to recipe for the understanding and fabrication of these NPs and their applications, such as spectroscopic (bio)detection including CD spectral shifts and surface-enhanced Raman optical activity.
Multiresolution Preconditioners for Solving Realistic Multi-Scale Complex Problems
(Institute of Electrical and Electronics Engineers, 2022-02-21) Solis, Diego M.; Martin, Victor F.; Taboada, Jose M.; Vipiana, Francesca
In this work, the hierarchic multiresolution (MR) preconditioner is combined with the multilevel fast multipole algorithm-fast Fourier transform (MLFMA-FFT) and eficiently parallelized in multicore computers for computing electromagnetic scattering and radiation from complex problems exhibiting deep multi-scale features. The problem is formulated using the thin-dielectric-sheet (TDS) approximation for thin dielectric materials and the electric and combined field integral equations (EFIE/CFIE) for conducting objects. The parallel MLFMA-FFT is tailored to accommodate the MR hierarchical functions, which provide vast improvement of the matrix system conditioning by accurately handling multi-scale mesh features in different levels of detail. The higher (coarser) level hierarchical functions are treated by an algebraic incomplete LU decomposition preconditioner, which has been ef ciently embedded into the parallel framework to further accelerate the solution. Numerical examples are presented to demonstrate the precision and eficiency of the proposed approach for the solution of realistic multi-scale scattering and radiation problems.
The Multi-resolution preconditioner
(Scitech Publishing, 2024) Vipiana, Francesca; Martin, Victor F.; Taboada, Jose M.
The purpose of this chapter is to provide the main guidelines for an efficient implementation of the multi-resolution (MR) preconditioner for the electromagnetic (EM) analysis of perfect electric conductor (PEC) structures of arbitrary 3-D shape via the method of moments (MoM) applied to the electric field integral equation (EFIE) and to the combined field integral equation (CFIE). The chapter is structured in four main parts. First, the generation of the MR basis functions as a linear combination of the standard basis functions is described. Second, the generation of a multi-level set of meshes, starting from the usual mesh, is reported: the MR functions are defined on each level of the generated set of meshes. These two parts are essential to implement the proposed preconditioner. Then, the third part is dedicated to the insertion of the MR preconditioner into the solution algorithm, together with the description of some implementation tricks. Finally, numerical results, where the MR preconditioner is applied to complex realistic 3-D structures, are reported and commented. The expected property of the MR preconditioner is an improvement of the convergence rates of iterative solvers, with a limited computational cost for its generation and application. The proposed preconditioner can be applied to realistic structures with arbitrary topological complexity.