Sökning: "finite differences"

Visar resultat 21 - 25 av 141 avhandlingar innehållade orden finite differences.

  1. 21. Adaptive finite element/difference methods for time-dependent inverse scattering problems

    Författare :Larisa Beilina; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : In this thesis we develop adaptive hybrid finite element/difference methods for inverse time-domain acoustic and elastic scattering, where we seek to find the location and form of a (small) unknown object inside a large homogeneous body from measured wave-reflection data. We formulate the inverse problem as an optimal control problem, where we seek to reconstruct unknown material coefficients with best least squares wave fit to data. LÄS MER

  3. 22. Testing and finite element modeling of wooden stairs and bridge decks

    Författare :Anna Pousette; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Träteknik; Wood Technology;

    Sammanfattning : Development of new products in the joinery industry has traditionally been based on testing of prototypes. Computer-aided design tools and finite element analysis can supplement traditional prototype testing and improve the product development process. LÄS MER

  4. 23. Simulation of Electro-Optic Modulators by a Time-Domain Beam-Propagation Method

    Författare :Elin Solberg; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; time-domain beam-propagation method; finite element method; tensor products; computational electromagnetics; photonics; electro-optic modulators; finite element method;

    Sammanfattning : Electro-optic modulators (EOMs) are components which convert electric signals to optical ones. They are needed, e.g., at the transmitter end of fiber-optic communication systems and in time-stretch analog-to-digital converters. LÄS MER

  5. 24. Efficient Adaptive Algorithms for an Electromagnetic Coefficient Inverse Problem

    Författare :John Bondestam Malmberg; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; coefficient inverse problem; inverse scattering; Maxwell’s equations; approximate global convergence; finite element method; adaptivity; ; a posteriori error analysis;

    Sammanfattning : This thesis comprises five scientific papers, all of which are focusing on the inverse problem of reconstructing a dielectric permittivity which may vary in space inside a given domain. The data for the reconstruction consist of time-domain observations of the electric field, resulting from a single incident wave, on a part of the boundary of the domain under consideration. LÄS MER

  7. 25. Low Speed Energy Conversion from Marine Currents

    Författare :Karin Thomas; Mats Leijon; Cameron Johnstone; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Electrical power technology; Direct Drive Generator; Finite Element Method; Marine Current Energy; Synchronous Generator; Permanent Magnet; Tidal Current Energy; Elkraftteknik; Engineering physics; Teknisk fysik;

    Sammanfattning : The focus of this thesis is research on the performance of very low speed direct drive permanent magnet generators for energy conversion from marine and tidal currents. Various aspects involved in the design of these generators and their electromagnetic modelling using the finite element simulations are presented. LÄS MER