Sökning: "a posteriori error estimators"

Visar resultat 1 - 5 av 10 avhandlingar innehållade orden a posteriori error estimators.

  1. 1. Time-domain Reconstruction Methods for Ultrasonic Array Imaging : A Statistical Approach

    Författare :Fredrik Lingvall; Tadeusz Stepinski; Karl-Jörg Langenberg; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Signalbehandling; Ultrasonic array imaging; synthetic aperture imaging; maximum a posteriori estimation; linear minimum mean squared error estimation; SAFT; Bayesian image reconstruction; Signalbehandling; Signal processing; Signalbehandling; Signal Processing; signalbehandling;

    Sammanfattning : This thesis is concerned with reconstruction techniques for ultrasonic array imaging based on a statistical approach. The reconstruction problem is posed as the estimation of an image consisting of scattering strengths. LÄS MER

  3. 2. Mathematical analysis and approximation of a multiscale elliptic-parabolic system

    Författare :Omar Richardson; Adrian Muntean; Alfred Schmidt; Karlstads universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Two-scale modelling; two-scale Galerkin approximation; inverse Robin estimates; elliptic-parabolic system; a priori analysis; a posteriori error estimators; Matematik; Mathematics;

    Sammanfattning : We study a two-scale coupled system consisting of a macroscopic elliptic equation and a microscopic parabolic equation. This system models the interplay between a gas and liquid close to equilibrium within a porous medium with distributed microstructures. We use formal homogenization arguments to derive the target system. LÄS MER

  4. 3. Maximum a posteriori deconvulution of ultrasonic data with applications in nondestructive testing : Multiple transducer and robustness is

    Författare :Tomas Olofsson; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Materials science; Ultrasonic pulse-echo testing; nondestructive testing; maximum a posteriori estimation; linear minimum mean squared error estimation; robust filtering; multivariable filtering; sparse deconvolution; Materialvetenskap; Materials science; Teknisk materialvetenskap; Signal Processing; signalbehandling;

    Sammanfattning : In the thesis, various aspects of deconvolution of ultrasonic pulse-echo signals in nondestructive testing are treated. The deconvolution problem is formulated as estimation of a reflection sequence which is the impulse characteristic of the inspected object and the estimation is performed using either maximum a posteriori (MAP) or linear minimum mean square error (MMSE) estimators. LÄS MER

  5. 4. A Two-stage Numerical Procedure for an Inverse Scattering Problem

    Författare :John Bondestam Malmberg; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; coefficient inverse problem; inverse scattering; backscattering data; approximate global convergence; finite element method; adaptivity; a posteriori error analysis; a posteriori error analysis;

    Sammanfattning : In this thesis we study a numerical procedure for the solution of the inverse problem of reconstructing location, shape and material properties (in particular refractive indices) of scatterers located in a known background medium. The data consist of time-resolved backscattered radar signals from a single source position. LÄS MER

  7. 5. Aspects of adaptive mesh refinement in the spectral element method

    Författare :Nicolas Offermans; Philipp Schlatter; Ananias Tomboulides; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Error estimators; mesh refinement; adaptivity; spectral element method; algebraic multigrid method; NACA4412; periodic hill case.; Engineering Mechanics; Teknisk mekanik;

    Sammanfattning : This thesis deals with the improvement of the efficiency of numerical simulations in computational fluid dynamics. Some of the limitations of current algorithms on future exascale supercomputers are addressed with the main goal of using adaptive mesh refinement for the simulation of turbulent and three-dimensional flows. LÄS MER