Sökning: "urban lundin"

Visar resultat 1 - 5 av 25 avhandlingar innehållade orden urban lundin.

  1. 1. Physics of Strong Correlations in Electronic Structure and Model Calculations

    Författare :Urban Lundin; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Physics; Strongly correlated electrons; Electronic structure calculations; Fysik; Physics; Fysik; fysik; Physics;

    Sammanfattning : Using field theoretical methods models of strongly correlated electrons have been investigated. Application to electronic structure calculations has been made. LÄS MER

  3. 2. Slow Transit Constipation : Aspects of Diagnosis and Treatment

    Författare :Erik Lundin; Urban Karlbom; Wilhelm Graf; Anders Dolk; Uppsala universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Surgery; colectomy; constipation; radio-opaque markers; rectal compliance; rectal sensation; scintigraphy; segmental colonic resection; segmental colonic transit; sphincter pressure; Kirurgi; Surgery; Kirurgi;

    Sammanfattning : Oral 111-Indium-DTPA colonic scintigraphy was used to assess segmental transit in 23 patients with slow transit constipation (STC) and 13 controls. The transit time did not differ between patients and controls in the right colon, whereas the patients had a consistent delay from the transverse colon and distally (P... LÄS MER

  4. 3. Kinetic Energy Storage and Magnetic Bearings : for Vehicular Applications

    Författare :Johan Abrahamsson; Hans Bernhoff; Urban Lundin; Richard Magdalena Stephan; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; flywheel; magnetic bearing; energy storage; electric vehicle; Engineering Science with specialization in Science of Electricity; Teknisk fysik med inriktning mot elektricitetslära;

    Sammanfattning : One of the main challenges in order to make electric cars competitive with gas-powered cars is in the improvement of the electric power system. Although many of the energy sources currently used in electric vehicles have sufficientlyhigh specific energy, their applicability is limited due to low specific power. LÄS MER

  5. 4. Hydropower generator and power system interaction

    Författare :Johan Bladh; Urban Lundin; Rafael Escarela-Perez; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Amortisseur windings; applied voltage test; automatic voltage regulators; damper windings; damping torque; empirical modelling; equivalent circuits; excitation control; finite element method; hydropower generators; power system restoration; power system stability; synchronous machines; self excitation; shaft torque amplification; short circuit test; single machine infinite bus; slip test; standstill frequency response test; subsynchronous oscillations; synchronising torque; synchronous generators; torsional interaction.; Engineering Science with specialization in Science of Electricity; Teknisk fysik med inriktning mot elektricitetslära;

    Sammanfattning : After decades of routine operation, the hydropower industry faces new challenges. Large-scale integration of other renewable sources of generation in the power system accentuates the role of hydropower as a regulating resource. LÄS MER

  7. 5. Grid frequency stability from a hydropower perspective

    Författare :Elin Dahlborg; Per Norrlund; Urban Lundin; Linn Saarinen; Katherine Elkington; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Frequency control; frequency stability; grid codes; hydropower; inertia; Kaplan unit; model validation; Engineering Science with specialization in Science of Electricity; Teknisk fysik med inriktning mot elektricitetslära;

    Sammanfattning : Many AC grids suffer from decreased frequency stability due to less system inertia. This has increased the risk of large-scale blackouts. This thesis and its papers address the frequency stability problem from a hydropower perspective.Grid frequency stability assessments often require accurate system inertia estimates. LÄS MER