Sökning: "a posteriori error estimation"

Visar resultat 6 - 10 av 36 avhandlingar innehållade orden a posteriori error estimation.

1. 6. Adaptive finite element methods for parameter estimation problems in partial differential equations

   Författare :Tao Feng; Mittuniversitetet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; parameter estimation; ¯nite element approximation; adaptive ¯nite element methods; a posteriori error estimates; least squares.; MATHEMATICS; MATEMATIK;

   Sammanfattning : Physical and chemical phenomena are often described by a system of partial di®erential equations. These equations usually involve unknown parameters, which cannot be measured directly but which can be adjusted to make the model predictions match the observed data. LÄS MER

3. 7. 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

4. 8. Multiscale Methods and Uncertainty Quantification

   Författare :Daniel Elfverson; Axel Målqvist; Frédéric Legoll; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; multiscale methods; finite element method; discontinuous Galerkin; Petrov-Galerkin; a priori; a posteriori; complex geometry; uncertainty quantification; multilevel Monte Carlo; failure probability; Beräkningsvetenskap med inriktning mot numerisk analys; Scientific Computing with specialization in Numerical Analysis;

   Sammanfattning : In this thesis we consider two great challenges in computer simulations of partial differential equations: multiscale data, varying over multiple scales in space and time, and data uncertainty, due to lack of or inexact measurements.We develop a multiscale method based on a coarse scale correction, using localized fine scale computations. LÄS MER

5. 9. Automation of Computational Mathematical Modeling

   Författare :Anders Logg; Göteborgs universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; computational mathematical modeling; automation; adaptivity; multi-adaptivity; individual time steps; dual problem; a priori; a posteriori; model reduction; individual time steps;

   Sammanfattning : This thesis concerns the Automation of Computational Mathematical Modeling (CMM), involving the key steps of automation of (i) discretization, (ii) discrete solution, (iii) error control, (iv) modeling, and (v) optimization. The automation of (i)--(ii) is realized through multi-adaptive Galerkin methods on general discretizations of space-time with time steps variable in space. LÄS MER

7. 10. Channel Estimation and Self-Interference Suppression for MIMO Relaying Systems

   Författare :Panagiota Lioliou; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; estimation; expectation-maximization EM ; half-duplex; Bayesian; multiple-input multiple-output MIMO ; Cramer-Rao Bound CRB ; full-duplex; relays; performance analysis; Kalman filter KF ; self-interference.; Amplify-and-forward AF ; least squares LS ;

   Sammanfattning : Recently, the introduction of relaying nodes in wireless channels has been identified as a promising technique for providing broader coverage, higher transmission rates, and increased reliability. Moreover, when the concept of relaying systems is combined with that of multiple-input multiple-output (MIMO) technology, thesystem performance can be further improved by exploiting the spatial dimension. LÄS MER