Sökning: "Arnoldi"

Visar resultat 16 - 20 av 20 avhandlingar innehållade ordet Arnoldi.

1. 16. Krylov methods for nonlinear eigenvalue problems and matrix equations

   Författare :Giampaolo Mele; Elias Jarlebring; Raf Vandebril; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Numerical Analysis; Numerisk analys;

   Sammanfattning : Nonlinear eigenvalue problems (NEPs) arise in many fields of science and engineering. Such problems are often defined by large matrices, which have specific structures, such as being sparse, low-rank, etc. Like the linear eigenvalue problem, the eigenvector appears in a linear form, whereas the eigenvalue appears in a nonlinear form. LÄS MER

3. 17. Adaptive Solvers for High-Dimensional PDE Problems on Clusters of Multicore Processors

   Författare :Magnus Grandin; Sverker Holmgren; Michael Thuné; Michael Bader; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; adaptive mesh refinement; anisotropic refinement; exponential integrators; Lanczos algorithm; hybrid parallelization; time-dependent Schrödinger equation; Scientific Computing; Beräkningsvetenskap;

   Sammanfattning : Accurate numerical solution of time-dependent, high-dimensional partial differential equations (PDEs) usually requires efficient numerical techniques and massive-scale parallel computing. In this thesis, we implement and evaluate discretization schemes suited for PDEs of higher dimensionality, focusing on high order of accuracy and low computational cost. LÄS MER

4. 18. Towards an adaptive solver for high-dimensional PDE problems on clusters of multicore processors

   Författare :Magnus Gustafsson; Sverker Holmgren; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Scientific Computing; Beräkningsvetenskap;

   Sammanfattning : Accurate numerical simulation of time-dependent phenomena in many spatial dimensions is a challenging computational task apparent in a vast range of application areas, for instance quantum dynamics, financial mathematics, systems biology and plasma physics. Particularly problematic is that the number of unknowns in the governing equations (the number of grid points) grows exponentially with the number of spatial dimensions introduced, often referred to as the curse of dimensionality. LÄS MER

5. 19. Transition Properties of f-electrons in Rare-earth Optical Materials

   Författare :Daniel Åberg; Börje Johansson; Sverker Edvardsson; Lidia Smentek; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Physics; rare-earth ions; oscillator strengths; correlation; crystal field; f-electrons; Fysik; Physics; Fysik;

   Sammanfattning : The main purpose of this thesis is to theoretically study energy levels and intra-electronic transition intensities for various f-electron systems. The f-f electronic dipole transitions are parity-forbidden for a free ion but become non-zero when the ion is subject to a crystal-field. LÄS MER

7. 20. Numerical Solution of Ill-posed Cauchy Problems for Parabolic Equations

   Författare :Zohreh Ranjbar; Lars Eldén; Per Christian Hansen; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; MATHEMATICS; MATEMATIK;

   Sammanfattning : Ill-posed mathematical problem occur in many interesting scientific and engineering applications. The solution of such a problem, if it exists, may not depend continuously on the observed data. For computing a stable approximate solution it is necessary to apply a regularization method. LÄS MER