Sökning: "wave equation"

Visar resultat 11 - 15 av 208 avhandlingar innehållade orden wave equation.

1. 11. Approximating Stochastic Partial Differential Equations with Finite Elements: Computation and Analysis

   Författare :Andreas Petersson; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Lévy process; Lyapunov equation; white noise; finite element method; multilevel Monte Carlo; Monte Carlo; multiplicative noise; asymptotic mean square stability; stochastic heat equation; covariance operator; weak convergence; generalized Wiener process; numerical approximation; stochastic wave equation; Stochastic partial differential equations;

   Sammanfattning : Stochastic partial differential equations (SPDE) must be approximated in space and time to allow for the simulation of their solutions. In this thesis fully discrete approximations of such equations are considered, with an emphasis on finite element methods combined with rational semigroup approximations. LÄS MER

3. 12. Efficient Simulation of Wave Phenomena

   Författare :Martin Almquist; Ken Mattsson; Gianluca Iaccarino; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; finite difference method; high-order accuracy; stability; summation by parts; simultaneous approximation term; quantum mechanics; Dirac equation; local time-stepping; Beräkningsvetenskap med inriktning mot numerisk analys; Scientific Computing with specialization in Numerical Analysis;

   Sammanfattning : Wave phenomena appear in many fields of science such as acoustics, geophysics, and quantum mechanics. They can often be described by partial differential equations (PDEs). As PDEs typically are too difficult to solve by hand, the only option is to compute approximate solutions by implementing numerical methods on computers. LÄS MER

4. 13. The Finite Element Method for Fractional Order Viscoelasticity and the Stochastic Wave Equation

   Författare :Fardin Saedpanah; Göteborgs universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; finite element method; continuous Galerkin method; linear viscoelasticity; fractional calculus; fractional order viscoelasticity; weakly singular kernel; stability; a priori error estimate; a posteriori error estimate; stochastic wave equation; additive noise; Wiener process; strong convergence.; linear viscoelasticity;

   Sammanfattning : This thesis can be considered as two parts. In the first part a hyperbolic type integro-differential equation with weakly singular kernel is considered, which is a model for dynamic fractional order viscoelasticity. In the second part, the finite element approximation of the linear stochastic wave equation is studied. LÄS MER

5. 14. Material distribution-based topology optimization for wave propagation problems

   Författare :Ahmad Hasnain Bokhari; Eddie Wadbro; Martin Berggren; Roland Herzog; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; topology optimization; material distribution; wave propagation problems; Helmholtz equation; acoustics; electromagnetics; plasmonics;

   Sammanfattning : This thesis employs material distribution-based topology optimization for wave propagation problems. In the material distribution approach, we define a material indicator function that models the presence and absence of material in a design domain. LÄS MER

7. 15. A Fast Method for Solving the Helmholtz Equation Based on Wave Splitting

   Författare :Jelena Popovic; Olof Runborg; Elisabeth Larsson; KTH; []
   Nyckelord :Helmholtz equation; high fequency waves;

   Sammanfattning : In this thesis, we propose and analyze a fast method for computing the solution of the Helmholtz equation in a bounded domain with a variable wave speed function. The method is based on wave splitting. The Helmholtz equation is first split into one--way wave equations which are then solved iteratively for a given tolerance. LÄS MER