Sökning: "Electromagnetic Theory"

Visar resultat 21 - 25 av 126 avhandlingar innehållade orden Electromagnetic Theory.

  1. 21. Hybrid Methods for Computational Electromagnetics in Frequency Domain

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

    Sammanfattning : 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). LÄS MER

  3. 22. Gravitational perturbations in plasmas and cosmology

    Författare :Mats Forsberg; Gert Brodin; Michael Bradley; Christopher Clarkson; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; general relativity; cosmology; gravitational waves; plasma; electromagnetic waves; nonlinear waves; Plasma physics; Plasmafysik; Theory of relativity; gravitation; Relativitetsteori; gravitation; Cosmology; Kosmologi; teoretisk fysik; Theoretical Physics;

    Sammanfattning : Gravitational perturbations can be in the form of scalars, vectors or tensors. This thesis focuses on the evolution of scalar perturbations in cosmology, and interactions between tensor perturbations, in the form of gravitational waves, and plasma waves. LÄS MER

  4. 23. Relativistic theory of laser-induced magnetization dynamics

    Författare :Ritwik Mondal; Peter M. Oppeneer; Jan Rusz; Olle Eriksson; Paul-Antoine Hervieux; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Relativistic quantum electrodynamics; magneto-optics; spin-orbit coupling; ultrafast demagnetization; inverse Faraday effect; magnetic inertia; Gilbert damping; Fysik; Physics;

    Sammanfattning : Ultrafast dynamical processes in magnetic systems have become the subject of intense research during the last two decades, initiated by the pioneering discovery of femtosecond laser-induced demagnetization in nickel. In this thesis, we develop theory for fast and ultrafast magnetization dynamics. LÄS MER

  5. 24. Interaction between Electromagnetic Waves and Localized Plasma Oscillations

    Författare :Jan-Ove Hall; Thomas Leyser; Jan Trulsen; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Space and plasma physics; space physics; plasma physics; radio waves; ionospheric modification; density depleations; field-aligned irregularities; lower hybrid solitary structures; lower hybrid cavities; Z mode waves; magnetosonic waves; scattering; mode conversion; Rymd- och plasmafysik; Space physics; Rymdfysik;

    Sammanfattning : This thesis treats interaction between electromagnetic waves and localized plasma oscillations. Two specific physical systems are considered, namely artificially excited magnetic field-aligned irregularities (striations) and naturally excited lower hybrid solitary structures (LHSS). LÄS MER

  7. 25. Mathematical modeling of electromagnetic disturbances in railway system

    Författare :Farid Monsefi; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Drift och underhållsteknik; Operation and Maintenance; Industrial Electronics; Industriell elektronik;

    Sammanfattning : By introduction of modern electronics into railway system, new challenges in understanding the electric and electromagnetic behavior of these systems arise. In this thesis, electromagnetic modeling of electric networks above dielectric and perfect electrically conducting surfaces are studied. LÄS MER