Sökning: "wave equations differential"

Visar resultat 1 - 5 av 57 avhandlingar innehållade orden wave equations differential.

1. 1. Wave Propagation in Structural Elements - Direct and Inverse Problems in the Time Domain

   Författare :Peter Folkow; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; integro-differential equations; non-uniform beams; wave splitting; wave propagator; finite difference; Timoshenko beam; imbedding; Mindlin plate; inverse problem; viscoelastic damping; nonlinear rod; transient wave propagation; Green function;

   Sammanfattning : The subject of this thesis is direct and inverse wave propagation problems in structural elements. The considered structures are beams, plates and rods. The models for the beams and the plates are based on linear theory, while the rods are assumed to be nonlinear. The greater part of the work concerns the Timoshenko beam. LÄS MER

3. 2. Scattering on the Timoshenko Beam. Direct and Inverse Problems in the Time Domain

   Författare :Dag V. J. Billger; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; integro-differential equations; wave splitting; transient wave propagation; viscoelastic damping; wave propagators; inverse problems; scattering operators; Timoshenko beam; non-uniform beams; imbedding;

   Sammanfattning : This thesis concerns the use of time domain methods for treating direct and inverse scattering problems for flexural waves on beams. The Timoshenko equation is used throughout to describe the behaviour of such waves. LÄS MER

4. 3. Exponential integrators for stochastic partial differential equations

   Författare :Rikard Anton; David Cohen; Christian Engström; Stig Larsson; Annika Lang; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Stochastic partial differential equations; numerical methods; stochastic exponential integrator; strong convergence; trace formulas;

   Sammanfattning : Stochastic partial differential equations (SPDEs) have during the past decades become an important tool for modeling systems which are influenced by randomness. Because of the complex nature of SPDEs, knowledge of efficient numerical methods with good convergence and geometric properties is of considerable importance. LÄS MER

5. 4. 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

7. 5. Finite Difference and Discontinuous Galerkin Methods for Wave Equations

   Författare :Siyang Wang; Gunilla Kreiss; Thomas Hagstrom; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Wave propagation; Finite difference method; Discontinuous Galerkin method; Stability; Accuracy; Summation by parts; Normal mode analysis; Beräkningsvetenskap med inriktning mot numerisk analys; Scientific Computing with specialization in Numerical Analysis;

   Sammanfattning : Wave propagation problems can be modeled by partial differential equations. In this thesis, we study wave propagation in fluids and in solids, modeled by the acoustic wave equation and the elastic wave equation, respectively. LÄS MER