Sökning: "Greens functions"

Visar resultat 16 - 20 av 54 avhandlingar innehållade orden Greens functions.

  1. 16. Development of new techniques for the numerical modelling of railway track dynamics. Application to rolling noise assessment

    Författare :Blas Blanco; Leif Kari; Ernesto García-Vadillo; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Track modelling; Timoshenko element; local deformation; distributed supports; moving Green s functions; rolling noise;

    Sammanfattning : The numerical modelling is widely employed for the prediction of the railway track dynamic behaviour, which is of utmost importance for the characterisation of the undesired medium-high frequency phenomena, such as corrugation, wheel-out-of-roundness and noise emission. This study is devoted to the improvement of railway track numerical modelling, the efficient resolution of the problem in the time domain and the assessment of rolling noise for different approaches of the track modelling. LÄS MER

  3. 17. Mesoscopic superconductivity : quasiclassical approach

    Författare :Marek Ožana; Andrei Shelankov; Dierk Rainer; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; mesoscopic superconductivity; quasiclassical theory; boundary conditions; multi-layer structures; Gor kov equations; quasiclassical Green s function; Green s function on classical trajectories;

    Sammanfattning : This Thesis is concerned with the quasiclassical theory of meso-scopic superconductivity. The aim of the Thesis is to introduce the boundary conditions for a quasiclassical Green’s function on partially transparent interfaces in mesoscopic superconducting structures and to analyze the range of applicability of the quasiclassical theory. LÄS MER

  4. 18. Quantitative Modeling of Gain in Quantum Cascade Lasers under Operational Intensities

    Författare :David Winge; Matematisk fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; non-linear response; quantum cascade lasers; modelling; Non-equilibrium Green s functions; Gain clamping; Fysicumarkivet A:2016:Winge; kvantkaskadlaser; terahertz; infrarött; Halvledarfysik; spektroskopi; simulering;

    Sammanfattning : This thesis adresses modeling of quantum cascade lasers using non-equilibrium Green’s functions. Focus lies on the quantitative modeling of the gain when the systems are exposed to strong laser fields, as under realistic opertional conditions. LÄS MER

  5. 19. Neutronics in reactors with propagating perturbations

    Författare :Anders Jonsson; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; one-group theory; Green s function; Molten Salt Reactors; two-group theory; neutron noise; propagating perturbations;

    Sammanfattning : This thesis contains several studies of the properties of neutron noise, primarily in Molten Salt Reactors and other reactors with propagating perturbations. Both one- and two-group diffusion theory are employed to investigate the differences that arise from the movement of the fuel. LÄS MER

  7. 20. Lineshape in Quantum Cascade Lasers - Temperature, Screening and Broadening

    Författare :Rikard Nelander; Matematisk fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Quantum Cascade Lasers; quantum wells; spectral lineshape; Non-Equilibrium Green s Functions; screening; temperature dependence;

    Sammanfattning : This dissertation deals with the optical properties of Quantum Cascade Lasers (QCLs). Studies are performed using transport calculations employing the theory of Non-Equilibrium Green's Functions, and screening is studied within the Random Phase Approximation. Focus is put on the temperature dependent effects in THz QCLs. LÄS MER