Sökning: "spectral interval"

Visar resultat 1 - 5 av 30 avhandlingar innehållade orden spectral interval.

  1. 1. Spectral analysis of the heart rate variability : a methodological study

    Författare :Urban Niklasson; Umeå universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Heart-rate variability; R-R interval; cardiac autonomic function; spectral analysis; IPFM model;

    Sammanfattning : Heart rate and other cardiovascular variables are not steady but fluctuate over time. The evolution of computer technology the last 2 decades has made detailed analysis of the fluctuations possible and has focused the attention to the information content of the variability. LÄS MER

  3. 2. Semi-classical approximations of Quantum Mechanical problems

    Författare :Ulf Karlsson; KTH; []
    Nyckelord :Schrödinger equation; semiclassical analysis; multi-well potential; potential wells; scale functions; spectral interval; Agmon metric; interaction matrix; hierarchical potential; Helmholtz operator; Fourier integral operator; global phase; hyperbolic;

    Sammanfattning : .... LÄS MER

  4. 3. Spectral Computed Tomography with a Photon-Counting Silicon-Strip Detector

    Författare :Mats Persson; Mats Danielsson; Hans Bornefalk; Jiang Hsieh; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Photon-counting; silicon-strip detector; spectral computed tomography; ring artifacts; fluence rate; basis material decomposition; sub-pixel information; Fysik; Physics;

    Sammanfattning : Computed tomography (CT) is a widely used medical imaging modality. By rotating an x-ray tube and an x-ray detector around the patient, a CT scanner is able to measure the x-ray transmission from all directions and form an image of the patient’s interior. LÄS MER

  5. 4. An Event-Reconstructing Silicon Detector for 1 µm Resolution Spectral Computed Tomography

    Författare :Christel Sundberg; Mats Danielsson; Julia Herzen; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; photon-counting; silicon detector; spectral computed tomography; subpixel resolution; dose efficiency; coincidence tracking; event reconstruction; fotonräknande; kiseldetektor; spektral datortomografi; subpixelupplösning; doseffektivitet; koincidensspårning; händelserekonstruktion; Fysik; Physics;

    Sammanfattning : Computed tomography (CT) is a medical imaging modality in which cross-sectional images of the human body are created using x-rays. Commercial CT scanners utilize energy-integrating detectors to measure the x-ray attenuation. However, photon-counting detectors with energy-discriminating abilities have started to emerge. LÄS MER

  7. 5. Multi-spectral analysis of fine scale aurora

    Författare :Hanna Dahlgren; Göran Marklund; Nickolay Ivchenko; Fred Sigernes; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Plasma physics; Plasmafysik; Optics; Optik;

    Sammanfattning : The Aurora Borealis is the visible manifestation of the complex plasma interaction between the solar wind and the Earth's magnetosphere and ionosphere. Ground based and in situ measurements demonstrate a prevalence of dynamic fine structure within auroral displays, with spatial scales down to tens of metres and time variations occurring on a fraction of a second. LÄS MER