Sökresultat

Filtyp

Din sökning på "*" gav 531496 sökträffar

Residual-based adaptive refinement for meshless eigenvalue solvers

The concept of an adaptive meshless eigenvalue solver is presented and implemented for two-dimensional structures. Based on radial basis functions, eigenmodes are calculated in a collocation approach for the second-order wave equation. This type of meshless method promises highly accurate results with the simplicity of a node-based collocation approach. Thus, when changing the discrete representat

Eigenvalue analysis and longtime stability of resonant structures for the meshless radial point interpolation method in time domain

A meshless collocation method based on radial basis function (RBF) interpolation is presented for the numerical solution of Maxwell's equations. RBFs have attractive properties such as theoretical exponential convergence for increasingly dense node distributions. Although the primary interest resides in the time domain, an eigenvalue solver is used in this paper to investigate convergence properti

Complex dispersion relation calculations with the symmetric interior penalty method

A high-order discontinuous Galerkin method for calculations of complex dispersion relations of two-dimensional photonic crystals is presented. The medium is characterized by a complex-valued permittivity and we relate for this absorptive system the spectral parameter to the time frequency. We transform the non-linear eigenvalue problem for a Lorentz material in air into a non-Hermitian linear eige

On the spectrum of a holomorphic operator-valued function with applications to absorptive photonic crystals

We study electromagnetic wave propagation in a periodic and frequency dependent material characterized by a space- and frequency-dependent complex-valued permittivity. The spectral parameter relates to the time-frequency, leading to spectral analysis of a holomorphic operator-valued function. We apply the Floquet transform and show for a fixed quasi-momentum that the resulting family of spectral p

On a method to reduce uncertainties in bulk property measurements of two-component composites

For two-component composites, we address the inverse problem of estimating the structural parameters and decrease measurement errors in bulk property measurements. A measurement of the effective permittivity at one frequency gives microstructural information about the composite that is used in cross-property bounds to estimate the effective permittivity at other frequencies. We use this informatio

Meshless eigenvalue analysis for resonant structures based on the radial point interpolation method

Meshless methods are a promising field of numerical methods recently introduced to computational electromagnetics. The potential of conformal and multi-scale modeling and the possibility of dynamic grid refinements are very attractive features that appear more naturally in meshless methods than in classical methods. The Radial Point Interpolation Method (RPIM) uses radial basis functions for the a

On the spectrum of an operator pencil with applications to wave propagation in periodic and frequency dependent materials

We study wave propagation in periodic and frequency dependent materials when the medium in a frequency interval is characterized by a real-valued permittivity. The spectral parameter relates to the quasi momentum, which leads to spectral analysis of a quadratic operator pencil where frequency is a parameter. We show that the underlying operator has a discrete spectrum, where the eigenvalues are sy

Computations of lossy Bloch waves In two-dimensional photonic crystals

In this article we compute lossy Bloch waves in two-dimensional photonic crystals with dispersion and material loss. For given frequencies these waves are determined from non-linear eigenvalue problems in the wave vector. We applied two numerical methods to a demanding test case, a photonic crystal with embedded quantum dots that exhibits very strong and anamolous dispersion. The first method is b

Inverse bounds of two-component composites

A method is presented for estimating microstructural parameters from permittivity measurements of two-component composites. This structural information is described by a particular positive measure in the Stieltjes integral representation of the effective permittivity. The dependence on the geometrical structure can be reduced to the problem of calculating the moments of the measure. We present a

Inverse bounds and bulk properties of complex-valued two-component composites

The bulk properties of composites are known to depend strongly on the microstructure. This dependence can be quantified in terms of a representation introduced by D. Bergman, which factorizes the geometry dependence from the contrast. Based on this analytic representation of the effective permittivity, we present a general scheme to estimate the microstructural parameters such as the volume fracti

Bounds on effective anisotropic material parameters

A new method to estimate the micro-structural parameters of anisotropic two-phase composite material is derived. The parameters are estimated using information from measurements or from numerical experiments. The method is used to derive new bounds on the effective tensor that incorporates information from measurements of a related parameter. These new bounds are called cross-property bounds.

Bounds on the effective tensor and the structural parameters for anisotropic two-phase composite material

This paper is concerned with the estimation of macroscopic properties such as the permittivity or the thermal conductivity of a composite material from the microstructure. A new method of estimating the microstructural parameters, such as the volume fraction of anisotropic two-phase composite material, is derived. The parameters are estimated using information from measurements of the random mater

Vad händer med historien när vi kan chatta med de döda?

AI-appar Vad skulle du vilja fråga Julius Caesar, Virginia Woolf, Adolf Hitler? På senare tid har flera AI- tjänster dykt upp som tillåter användaren att samtala med avlidna kändisar. Så inleds ett nytt kapitel i den både uråldriga och fåfänga drömmen om att kommunicera med de döda.