24,923 research outputs found
Direct and Inverse Computational Methods for Electromagnetic Scattering in Biological Diagnostics
Scattering theory has had a major roll in twentieth century mathematical
physics. Mathematical modeling and algorithms of direct,- and inverse
electromagnetic scattering formulation due to biological tissues are
investigated. The algorithms are used for a model based illustration technique
within the microwave range. A number of methods is given to solve the inverse
electromagnetic scattering problem in which the nonlinear and ill-posed nature
of the problem are acknowledged.Comment: 61 pages, 5 figure
Multiscale Finite Element Modeling of Nonlinear Magnetoquasistatic Problems Using Magnetic Induction Conforming Formulations
In this paper we develop magnetic induction conforming multiscale
formulations for magnetoquasistatic problems involving periodic materials. The
formulations are derived using the periodic homogenization theory and applied
within a heterogeneous multiscale approach. Therefore the fine-scale problem is
replaced by a macroscale problem defined on a coarse mesh that covers the
entire domain and many mesoscale problems defined on finely-meshed small areas
around some points of interest of the macroscale mesh (e.g. numerical
quadrature points). The exchange of information between these macro and meso
problems is thoroughly explained in this paper. For the sake of validation, we
consider a two-dimensional geometry of an idealized periodic soft magnetic
composite.Comment: Paper accepted for publication in the SIAM MMS journa
An efficient steady-state analysis of the eddy current problem using a parallel-in-time algorithm
This paper introduces a parallel-in-time algorithm for efficient steady-state
solution of the eddy current problem. Its main idea is based on the application
of the well-known multi-harmonic (or harmonic balance) approach as the coarse
solver within the periodic parallel-in-time framework. A frequency domain
representation allows for the separate calculation of each harmonic component
in parallel and therefore accelerates the solution of the time-periodic system.
The presented approach is verified for a nonlinear coaxial cable model
Coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures
Accomplishments are described for the first year effort of a 5-year program to develop a methodology for coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures. These accomplishments include: (1) the results of the selective literature survey; (2) 8-, 16-, and 20-noded isoparametric plate and shell elements; (3) large deformation structural analysis; (4) eigenanalysis; (5) anisotropic heat transfer analysis; and (6) anisotropic electromagnetic analysis
A nested hybridizable discontinuous Galerkin method for computing second-harmonic generation in three-dimensional metallic nanostructures
In this paper, we develop a nested hybridizable discontinuous Galerkin (HDG)
method to numerically solve the Maxwell's equations coupled with the
hydrodynamic model for the conduction-band electrons in metals. By means of a
static condensation to eliminate the degrees of freedom of the approximate
solution defined in the elements, the HDG method yields a linear system in
terms of the degrees of freedom of the approximate trace defined on the element
boundaries. Furthermore, we propose to reorder these degrees of freedom so that
the linear system accommodates a second static condensation to eliminate a
large portion of the degrees of freedom of the approximate trace, thereby
yielding a much smaller linear system. For the particular metallic structures
considered in this paper, the resulting linear system obtained by means of
nested static condensations is a block tridiagonal system, which can be solved
efficiently. We apply the nested HDG method to compute the second harmonic
generation (SHG) on a triangular coaxial periodic nanogap structure. This
nonlinear optics phenomenon features rapid field variations and extreme
boundary-layer structures that span multiple length scales. Numerical results
show that the ability to identify structures which exhibit resonances at
and is paramount to excite the second harmonic response.Comment: 31 pages, 7 figure
- …