Sökning: "global stability"

Visar resultat 16 - 20 av 260 avhandlingar innehållade orden global stability.

1. 16. Global bifurcations and chaotic dynamics in physical applications

   Författare :Martín G. Zimmermann; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Quantum chemistry; Global bifurcations; Šil´nikov phenomenon; degenerate homoclinic orbit; onset of spatiotemporal chaos; heteroclinic cycles; orientation- and inclination-flip bifurcations; Kvantkemi; Quantum chemistry; Kvantkemi; Quantum Chemistry; kvantkemi;

   Sammanfattning : The aim of this work has been to analyse global bifurcations arising in a laser with injectedsignal and in a catalytic reaction on a surface of Pt, from the point of view of dynamicalsystems theory.The 3-dimensional ordinary differential equation which models the laser was found to contain a homoclinic orbit to a saddle-focus equilibrium, what corresponds to the Šil´nikov phenomenon. LÄS MER

3. 17. Disordered Icosahedral Boron-Rich Solids : A Theoretical Study of Thermodynamic Stability and Properties

   Författare :Annop Ektarawong; Björn Alling; Michael Widom; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Icosahedral boron-rich solids; Boron carbide; Configurational disorder; First-principles calculations; Thermodynamic stability; Superatom-special quasirandom structure;

   Sammanfattning : This thesis is a theoretical study of configurational disorder in icosahedral boron-rich solids, in particular boron carbide, including also the development of a methodological framework for treating configurational disorder in such materials, namely superatom-special quasirandom structure (SA-SQS). In terms of its practical implementations, the SA-SQS method is demonstrated to be capable of efficiently modeling configurational disorder in icosahedral boron-rich solids, whiles the thermodynamic stability as well as the properties of the configurationally disordered icosahedral boron-rich solids, modeled from the SA-SQS method, can be directly investigated, using the density functional theory (DFT). LÄS MER

4. 18. Stability analysis and control design of spatially developing flows

   Författare :Shervin Bagheri; Dan Henningson; Martin Berggren; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Global modes; transient growth; model reduction; feedback control; Fluid mechanics; Strömningsmekanik;

   Sammanfattning : Methods in hydrodynamic stability, systems and control theory are applied to spatially developing flows, where the flow is not required to vary slowly in the streamwise direction. A substantial part of the thesis presents a theoretical framework for the stability analysis, input-output behavior, model reduction and control design for fluid dynamical systems using examples on the linear complex Ginzburg-Landau equation. LÄS MER

5. 19. Stability of plane Couette flow and pipe Poiseuille flow

   Författare :Per-Olov Åsén; Gunilla Kreiss; Jonathan Goodman; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Hydrodynamic stability; plane Couette flow; pipe Poiseuille flow; direct numerical simulations; resolvent; Fluid mechanics; Strömningsmekanik;

   Sammanfattning : This thesis concerns the stability of plane Couette flow and pipe Poiseuille flow in three space dimensions. The mathematical model for both flows is the incompressible Navier--Stokes equations. Both analytical and numerical techniques are used. We present new results for the resolvent corresponding to both flows. LÄS MER

7. 20. Oversampled radial basis function methods for solving partial differential equations

   Författare :Igor Tominec; Elisabeth Larsson; Bengt Fornberg; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; radial basis function; PDE; oversampling; stability; RBF-FD; RBF-PUM; unfitted;

   Sammanfattning : Partial differential equations (PDEs) describe complex real-world phenomena such as weather dynamics,  object deformations, financial trading prices, and fluid-structure interaction.  The solutions of PDEs are commonly used to enhance the understanding of these phenomena and also as leverage to make technological improvements to consumer products. LÄS MER