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Visar resultat 1 - 5 av 36 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. Atomic Influences in Stellar Spectroscopy

    Författare :Krister Nielsen; Atomfysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; magnetic and optical properties; supraconductors; magnetic resonance; relaxation; Kondenserade materiens egenskaper:elektronstruktur; spectroscopy; rymdvetenskap; kosmisk kemi; Astronomi; Astronomy; spektroskopi; magnetisk resonans; supraledare; magnetiska och optiska ; egenskaper elektriska; space research; cosmic chemistry; stellar magnetic fields; branching fractions; spectral line structure; Fysicumarkivet A:2002:Nielsen; Condensed matter:electronic structure; line blending; electrical;

    Sammanfattning : This thesis is a description of how knowledge of atomic physics can be used in a stellar spectrum analysis. Stellar investigations are spectroscopically performed based on wavelengths, intensities and spectral line structure. LÄS MER

  3. 2. Wind turbine simulations using spectral elements

    Författare :Elektra Kleusberg; Dan Henningson; Philipp Schlatter; Stefan Ivanell; Johan Meyers; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; wind turbine; wakes; wake interaction; computational fluid dynamics; actuator line method; spectral elements; free-stream turbulence; Engineering Mechanics; Teknisk mekanik;

    Sammanfattning : Understanding the flow around wind turbines is a highly relevant research question due to the increased interest in harvesting energy from renewable sources. This thesis approaches the topic by means of numerical simulations using the actuator line method and the incompressible Navier–Stokes equations in the spectral element code Nek5000. LÄS MER

  4. 3. Rare-gas Clusters Studied by Electron Spectroscopy : Structure of Heterogeneous Clusters and Effects of Electron Scattering on Auger Decay

    Författare :Marcus Lundwall; Olle Björneholm; Gunnar Öhrwall; Maxim Tchaplyguine; Thomas Möller; Uppsala universitet; []
    Nyckelord :Physics; Nano-particles; Clusters; Heterogeneous clusters; Core-shell clusters; XPS; UPS; AES; Electron scattering; Radial structure; Surface structure; Surface sensitivity; Synchrotron radiation; Ne; Ar; Kr; Xe; Fysik;

    Sammanfattning : In this Thesis experimental studies of nano-clusters using synchrotron radiation based photoelectron (UPS and XPS) and Auger Electron Spectroscopy (AES) are presented. The investigations may be divided into two parts where the first reports on the structure of heterogeneous two component clusters, and the second concerns electronic decay processes. LÄS MER

  5. 4. Sparse Modeling of Grouped Line Spectra

    Författare :Ted Kronvall; Statistical Signal Processing Group; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; line spectra; parameter estimation; convex optimization; group-sparsity; block-sparsity; dictionary learning; ADMM; adaptive penalty; total variation; multi-pitch estimation; chroma; audio processing; TDOA; near-field localization; amplitude modulation;

    Sammanfattning : This licentiate thesis focuses on clustered parametric models for estimation of line spectra, when the spectral content of a signal source is assumed to exhibit some form of grouping. Different from previous parametric approaches, which generally require explicit knowledge of the model orders, this thesis exploits sparse modeling, where the orders are implicitly chosen. LÄS MER

  7. 5. Sunspot structure and dynamics

    Författare :Luc Rouppe van der Voort; Wolfgang Schmidt; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; Astronomi; Astronomy; astronomi;

    Sammanfattning : Fundamental physical processes occur on small spatial scales in the solar atmosphere and high-spatial-resolution observations are necessary to test theoretical models. This thesis presents high-spatial-resolution observations of sunspots obtained with the Swedish solar telescopes on La Palma: the Swedish Vacuum Solar Telescope (SVST) and its successor the Swedish 1-m Solar Telescope (SST). LÄS MER