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Hittade 4 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. Solitary waves and enhanced incoherent scatter ion lines

    Författare :Jonas Ekeberg; Lars Eliasson; Kristof Stasiewicz; Jan Trulsen; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; plasma waves and instabilities; nonlinear phenomena; solitons and solitary waves; ionosphere; Sun: corona; incoherent scatter radar; MHD; plasmavågor och instabiliteter; ickelinjära fenomen; solitoner och solitära vågor; jonosfär; solen: korona; inkoherent spridningsradar; MHD; Geocosmophysics and plasma physics; Geokosmofysik och plasmafysik; Space physics; Rymdfysik; Plasma physics; Plasmafysik; Non-linear dynamics; chaos; Icke-linjär dynamik; kaos; fysik; Physics; rymd- och plasmafysik; Space and Plasma Physics;

    Sammanfattning : This thesis addresses solitary waves and their significance for auroral particle acceleration, coronal heating and incoherent scatter radar spectra. Solitary waves are formed due to a balance of nonlinear and dispersive effects. LÄS MER

  3. 2. Splitting schemes for nonlinear parabolic problems

    Författare :Tony Stillfjord; Matematik LTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : This thesis is based on five papers, which all analyse different aspects of splitting schemes when applied to nonlinear parabolic problems. These numerical methods are frequently used when a problem has a natural decomposition into two or more parts, as the computational cost may then be significantly decreased compared to other methods. LÄS MER

  4. 3. Development and Application of Non-linear Mid-infrared Laser Spectroscopy for Combustion Diagnostics

    Författare :Zhiwei Sun; Förbränningsfysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Degenerate four-wave mixing; Polarization spectroscopy; Mid-infrared; Non-linear laser spectroscopy; Laser diagnostics; Combustion; Flame; HITRAN; Concentration; Temperature; Fysicumarkivet A:2012:Sun;

    Sammanfattning : The work reported in this thesis involved the development and application of two novel infrared non-linear laser techniques, namely mid-infrared polarization spectroscopy (IRPS) and mid-infrared degenerate four-wave mixing (IR-DFWM) to combustion diagnostics. These two techniques meet the needs of species concentration detection in combustion environments, especially for those species lacking accessible electronic (one-photon) transitions in the ultraviolet (UV) or visible spectral region. LÄS MER

  5. 4. Backward and Forward Nonlinear Optical Processes in Potassium Titanyl Phosphate

    Författare :Kjell Martin Mølster; Fredrik Laurell; Valdas Pasiskevicius; Ulf L. Österberg; Stefano Taccheo; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; QPM; PPKTP; Nonlinear Optics; Backward second-harmonic; BWOPO; OPO; parametric devices; QPM; Ickelinär Optik; BWOPO; OPO; PPKTP; QPM; kvasifasematching; ikkelinæer optikk; bakovervendt parametrisk oscillator; optisk parametrisk oscillator; PPKTP; Optics and Photonics; Optik och fotonik; Physics; Fysik;

    Sammanfattning : Second-order nonlinear optical processes generate radiation across a broad spectrum, including UV and the far-infrared. In this thesis, new light sources in the near(NIR) and mid infrared (MIR) using three-wave mixing geometries in periodically poled potassium titanyl phosphate (PPKTP) is studied. LÄS MER