Search for dissertations about: "Geometrical Theory of Diffraction"

Showing result 1 - 5 of 9 swedish dissertations containing the words Geometrical Theory of Diffraction.

2. 1. Elastic Wave Scattering by Cracks - Interfacial Forces and High Frequency Diffraction

   Author : Gert Persson; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; ultrasonic testing; Wiener-Hopf calculations; Geometrical Theory of Diffraction; edge diffracted body waves; PEDGE; two-dimensional diffraction; geometrical elastodynamic waves;

   Abstract : This thesis treats elastic wave scattering by cracks with interfacial forces. The results are of practical interest in ultrasonic testing and includes development of numerical methods used to predict such testing. First the canonical problem of two-dimensional (2-D) diffraction from a semi-infinite crack is solved. READ MORE

4. 2. Computational electromagnetics : software development and high frequency modeling of surface currents on perfect conductors

   Author : Sandy Sefi; Jesper Oppelstrup; Francisco Saez de Adana; KTH; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; High frequency approximations; Maxwell’s equations; Method of Moments; Physical Optics; Geometrical Theory of Diffraction; Extraction Extrapolation; Numerical analysis; Numerisk analys;

   Abstract : In high frequency computational electromagnetics, rigorous numerical methods be come unrealistic tools due to computational demand increasing with the frequency. Instead approximations to the solutions of the Maxwell equations can be employed to evaluate th electromagnetic fields. READ MORE

5. 3. Thin Layers in Elastic Wave Propagation -Effective Modelling and Diffraction

   Author : Peter Bövik; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Geometrical Theory of Diffraction; elastic wave scattering; shear waves; Wienr-Hopf method; L-TV waves; applications;

   Abstract : In the present thesis, the interest is focussed on the problem of effective modelling of thin interface layers for applications in elastic wave scattering. The layers are considered to be thin compared with wavelengths involved and it is shown that when all effects to lowest order in the layer thickness are included, we get boundary conditions (BCs) which have a number of nice features, including the one of implying that no scattering occurs when the layer has material parameters identical to the ones in the matrix medium. READ MORE

6. 4. Hybrid Methods for Computational Electromagnetics in Frequency Domain

   Author : Stefan Hagdahl; Björn Engquist; Lars Pettersson; Stockholms universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Maxwell s equations; Geometrical Theory of Diffraction; Smooth Surface Diffraction; Boundary Element Method; Hybrid methods; Electromagnetic Scattering; Numerical analysis; Numerisk analys;

   Abstract : In this thesis we study hybrid numerical methods to be used in computational electromagnetics. The purpose is to address a wide frequency range relative to a given geometry. We also focus on efficient and robust numerical algorithms for computing the so called Smooth Surface Diffraction predicted by Geometrical Theory of Diffraction (GTD). READ MORE

7. 5. Hybrid methods for computational electromagnetics in the frequency domain

   Author : Stefan Hagdahl; KTH; []
   Keywords : Computational Electromagnetics; Hybrid Methods; Boundary Element Method; Geometrical Theory of Diffraction;

   Abstract : In this thesis we study hybrid numerical methods to be usedin computational electromagnetics. We restrict the methods tospectral domain and scattering problems. The hybrids consist ofcombinations of Boundary Element Methods and Geometrical Theoryof Diffraction.In the thesis three hybrid methods will be presented. READ MORE