Sökning: "wave operator"

Visar resultat 11 - 15 av 46 avhandlingar innehållade orden wave operator.

  1. 11. Non-invasive imaging for improved cardiovascular diagnostics : Shear wave elastography, relative pressure estimation, and tomographic reconstruction

    Författare :David Marlevi; Matilda Larsson; Reidar Winter; Massimiliano Colarieti-Tosti; Kathryn Nightingale; KTH; Karolinska Institutet; Karolinska Institutet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Medical imaging; Cardiovascular disease; Atherosclerosis; Hemodynamics; Ultrasound; Shear Wave Elastography SWE ; Magnetic Resonance Imaging MRI ; 4D flow MRI; Relative Pressure; Virtual Work-Energy; micro-Computed Tomography micro-CT ; Tomographic reconstruction; Pre-clinical imaging; Medicinsk avbildning; Hjärt-kärlsjukdomar; Ateroskleros; Hemodynamik; Ultraljud; Skjuvvågselastografi SWE ; Magnetresonanstomografi MRI ; 4D flödes-MRI; Tryckfall; Virtuellt flöde; mikro-Datortomografi mikro-CT ; Tomografisk rekonstruktion; Preklinisk avbildning; Medicinsk teknologi; Medical Technology;

    Sammanfattning : Throughout the last century, medical imaging has come to revolutionise the way we diagnose disease, and is today an indispensable part of virtually any clinical practice. In cardiovascular care imaging is extensively utilised, and the development of novel techniques promises refined diagnostic abilities: ultrasound elastography allows for constitutive tissue assessment, 4D flow magnetic resonance imaging (MRI) enables full-field flow mapping, and micro-Computed Tomography (CT) permits high-resolution imaging at pre-clinical level. LÄS MER

  3. 12. Directional Decomposition in Anisotropic Heterogeneous Media for Acoustic and Electromagnetic Fields

    Författare :B. Lars G. Jonsson; KTH; []
    Nyckelord :directional wave-field decomposition; wave splitting; spectral reduction; aourstic anisotropy; electromagnetic anisotropy; generalized eigenvalue problem;

    Sammanfattning : Directional wave-field decomposition for heterogeneousanisotropic media with in-stantaneous response is establishedfor both the acoustic and the electromagnetic equations.We derive a sufficient condition for ellipticity of thesystem's matrix in the Laplace domain and show that theconstruction of the splitting matrix via a Dunford-Taylorintegral over the resolvent of the non-compact, non-normalsystem's matrix is well de ned. LÄS MER

  4. 13. The Back-scattering Problem in Three Dimensions

    Författare :Robert Lagergren; Matematik (naturvetenskapliga fakulteten); []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; back-scattering; Schrödinger operator; inverse scattering; Mathematics; Matematik;

    Sammanfattning : In this thesis we study the (inverse) back-scattering problem for the Schr"odinger operator in $R^3$. We introduce the back-scattering transform $B(v)$ of a real-valued potential $vin C_0^infty(R^3)$, and prove that the back-scattering data associated to $v$ determine $B(v)$. LÄS MER

  5. 14. Quantum dynamics of spin active and d-wave Josephson junctions

    Författare :Jens Harro Michelsen; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Josephson effect; macroscopic quantum tunneling; high-temperature superconducvity; superconducting junctions; spin-active junctions; nonequilibrium superconductivity; Andreev bound states;

    Sammanfattning : Conventional tunnel Josephson junctions form the basic building blocks of superconducting electronics. Their operation is based on comparatively simple dynamics where the superconducting phases across the junctions is the only dynamical degree of freedom. LÄS MER

  7. 15. Analysis of boundary and interface closures for finite difference methods for the wave equation

    Författare :Siyang Wang; Gunilla Kreiss; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Scientific Computing; Beräkningsvetenskap;

    Sammanfattning : We consider high order finite difference methods for the wave equations in the second order form, where the finite difference operators satisfy the summation-by-parts principle. Boundary conditions and interface conditions are imposed weakly by the simultaneous-approximation-term method, and non-conforming grid interfaces are handled by an interface operator that is based on either interpolating directly between the grids or on projecting to piecewise continuous polynomials on an intermediate grid. LÄS MER