Avancerad sökning

Visar resultat 1 - 5 av 10 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Wave Propagation in Structural Elements - Direct and Inverse Problems in the Time Domain

   Författare :Peter Folkow; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; integro-differential equations; non-uniform beams; wave splitting; wave propagator; finite difference; Timoshenko beam; imbedding; Mindlin plate; inverse problem; viscoelastic damping; nonlinear rod; transient wave propagation; Green function;

   Sammanfattning : The subject of this thesis is direct and inverse wave propagation problems in structural elements. The considered structures are beams, plates and rods. The models for the beams and the plates are based on linear theory, while the rods are assumed to be nonlinear. The greater part of the work concerns the Timoshenko beam. LÄS MER

3. 2. Modified Stencils for Boundaries and Subgrid Scales in the Finite-Difference Time-Domain Method

   Författare :Jon Häggblad; Björn Engquist; Olof Runborg; Björn Sjögreen; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; FDTD; Yee; Staircasing;

   Sammanfattning : This thesis centers on modified stencils for the Finite-Difference Time-Domain method (FDTD), or Yee scheme, when modelling curved boundaries, obstacles and holes smaller than the discretization length.  The goal is to increase the accuracy while keeping the structure of the standard method, enabling improvements to existing implementations with minimal effort. LÄS MER

4. 3. A hybrid finite element method for electromagnetics with applications in time-domain

   Författare :DAVID DEGERFELDT; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Nitsche s method; antenna arrays; NASA almond; edge elements; scattering; explicit-implicit time-stepping; Maxwell s equations; Finite Element Method; mass lumping; stability analysis; Finite-Differences Time-Domain; periodic structures; shape and material optimization;

   Sammanfattning : In this thesis, a new hybrid method that combines the Finite Element Method (FEM) with the Finite-Difference in Time-Domain (FDTD) method is presented. Tetrahedrons in the unstructured FEM region are connected directly to thehexahedrons in the structured FDTD region. LÄS MER

5. 4. Investigation of New Concepts and Solutions for Silicon Nanophotonics

   Författare :Zhechao Wang; Lech Wosinski; Kresten Yvind; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Planar integrated circuit; silicon photonics; slot waveguide; finite-difference time-domain; waveguide grating coupler; ring resonator; polarization diversity scheme; polarization beam splitter; polarization rotator; hybrid silicon laser; epitaxial lateral overgrowth; chemical-mechanical polishing.; Optics; Optik;

   Sammanfattning : Nowadays, silicon photonics is a widely studied research topic. Its high-index-contrast and compatibility with the complementary metal-oxide-semiconductor technology make it a promising platform for low cost high density integration. LÄS MER

7. 5. Optimization for scattering and radiation problems based on a stable FEM-FDTD hybrid method

   Författare :Tomas Halleröd; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; finite-difference time-domain; finite element method; array antennas; electric and magnetic losses; pattern synthesis; shape and material optimization; explicit-implicit time-stepping; scattering;

   Sammanfattning : In this thesis, a stable hybrid method combining the finite-elementmethod (FEM) and the finite-difference time-domain (FDTD) scheme forMaxwell's equations in two dimensions with both electric and magneticlosses is presented. It combines the flexibility of the FEM with theefficiency of the FDTD scheme. LÄS MER