Sökning: "numerical analysis"

Visar resultat 31 - 35 av 1416 avhandlingar innehållade orden numerical analysis.

  1. 31. Numerical methods for waveguide modelling

    Författare :Christer Johansson; Björn Engquist; Per Lötstedt; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Waveguide; finite element; hp-adaptivity; helmholtz; maxwell; Numerical analysis; Numerisk analys;

    Sammanfattning : Waveguides are used to transmit electromagnetic signals. Their geometry is typically long and slender. This particular shape can be used in the design of efficient computational methods. Only special modes are transmitted and eigenvalue and eigenvector analysis becomes important. LÄS MER

  3. 32. Subspace Computations via Matrix Decompositions and Geometric Optimization

    Författare :Lennart Simonsson; Axel Ruhe; Linköpings universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Mathematics; Numerical Analysis; Rank-revealing UTV; Jacobi-Davidson algorithm; Decomposition; Grassmann type algorithms; Numerical analysis; Numerisk analys;

    Sammanfattning : This thesis is concerned with the computation of certain subspaces connected to a given matrix, where the closely related problem of approximating the matrix with one of lower rank is given special attention. To determine the rank and obtain bases for fundamental subspaces such as the range and null space of a matrix, computing the singular value decomposition (SVD) is the standard method. LÄS MER

  4. 33. Analysis and numerical methods for multiscale problems in magnetization dynamics

    Författare :Lena Leitenmaier; Olof Runborg; Carlos Garcia-Cervera; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Numerical Analysis; Numerisk analys;

    Sammanfattning : This thesis investigates a multiscale version of the Landau-Lifshitz equation and how to solve it using the framework of Heterogeneous Multiscale Methods (HMM). The Landau-Lifshitz equation is the governing equation in micromagnetics, modeling magnetization dynamics. LÄS MER

  5. 34. Stable High-Order Finite Difference Methods for Aerodynamics

    Författare :Magnus Svärd; Jan Nordström; Thomas Hagstrom; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; finite difference methods; high-order accuracy; summation-by-parts; stability; energy estimates; finite volume methods; Numerical analysis; Numerisk analys; Scientific Computing; Beräkningsvetenskap; Numerical Analysis;

    Sammanfattning : In this thesis, the numerical solution of time-dependent partial differential equations (PDE) is studied. In particular high-order finite difference methods on Summation-by-parts (SBP) form are analysed and applied to model problems as well as the PDEs governing aerodynamics. LÄS MER

  7. 35. Runge–Kutta Time Step Selection for Flow Problems

    Författare :Karl Hörnell; Per Lötstedt; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Runge-Kutta; stepsize selection; optimization; flow problems; numerical analysis; Numerical Analysis; Numerisk analys;

    Sammanfattning : Optimality is studied for Runge-Kutta iteration for solving steady-state and time dependent flow problems. For the former type an algorithm for determining locally optimal time steps is developed, based on the fact that the squared norm of the residual produced by an m-stage scheme is a 2m-degree polynomial, the coefficients of which can be computed from scalar products of Krylov subspace vectors. LÄS MER