Sökning: "Martin Stefan"

Visar resultat 1 - 5 av 23 avhandlingar innehållade orden Martin Stefan.

  1. 1. On Models of Quantum Plasmas and their Nonlinear Implications

    Författare :Martin Stefan; Gert Brodin; Mattias Marklund; Tito Mendonca; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : The theory of quantum plasmas dates back to the first attempts of Wigner, Moyal and others to find a suitable formalism to describe many body quantum systems, and from this foundation a rich field has emerged. A plasma is a system consisting of many charged particles, and in a quantum plasma these particles have quantum mechanical properties, such as for example spin. LÄS MER

  3. 2. Churning losses and efficiency in gearboxes

    Författare :Martin Andersson; Ulf Olofsson; Stefan Björklund; Ulf Sellgren; Bo Alfredsson; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; gears; efficiency; temperature; running-in; assembly; torque loss; surface roughness;

    Sammanfattning : Efficient transmissions systems are key to producing competitive motor vehicles that have a smaller environmental impact. Gears are the main components in vehicle transmissions and although they are already highly efficient, there is still room for improvement. LÄS MER

  4. 3. Electromagnetic dispersion modeling and analysis for HVDC power cables

    Författare :Stefan Gustafsson; Sven Nordebo; Martin Norgren; Linnéuniversitetet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; HVDC power cables; electromagnetic model; TDR measurement; sensitivity analysis; dispersion relation; propagation constant; low-frequency asymptotics;

    Sammanfattning : Derivation of an electromagnetic model, regarding the wave propagation in a very long (10 km or more) High Voltage Direct Current (HVDC) power cable, is the central part of this thesis. With an existing “perfect” electromagnetic model there are potentially a wide range of applications. LÄS MER

  5. 4. Exactly solved quantum many-body systems in one dimension

    Författare :Martin Hallnäs; Edwin Langmann; Stefan Rauch-Wojciechowski; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Physics; Fysik;

    Sammanfattning : This thesis is devoted to the study of various examples of exactly solved quantum many-body systems in one-dimension. It is divided into two parts: the first provides background and complementary results to the second, which consists of three scientific papers. LÄS MER

  7. 5. On Acute Thrombo-Embolic Occlusion of the Superior Mesenteric Artery

    Författare :Stefan Acosta; Martin Björck; Mats Ögren; Bengt Lindblad; Uppsala universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Surgery; acute thrombo-embolic occlusion; superior mesenteric artery; intestinal infarction; D-Dimer; intestinal revascularisation; population-based study; incidence; autopsy; Kirurgi; Surgery; Kirurgi;

    Sammanfattning : Acute thrombo-embolic occlusion of the superior mesenteric artery (SMA) with intestinal infarction is a lethal disease, difficult to diagnose in time, with unknown incidence and cause-specific mortality. The aim of this thesis was to characterize the disease and to develop diagnostic methods. LÄS MER