Ö. Selsil

Buckling of Scroll Waves

A scroll wave in a sufficiently thin layer of an excitable medium with negative filament tension can be stable nevertheless due to filament rigidity. Above a certain critical thickness of the medium, such a scroll wave will have a tendency to deform into a buckled, precessing state. Experimentally this will be seen as meandering of the spiral wave on the surface, the amplitude of which grows with the thickness of the layer, until a breakup to scroll wave turbulence happens. We present a simplified theory for this phenomenon and illustrate it with numerical examples.

Asymptotics for the First Six Eigenfrequencies of a 1D-3D Multi-Structure

We consider vibrations of a massive three-dimensional body Ω* supported by thin cylindrical rods which are parallel to each other. We assume that the number of rods, say K, is greater than three and the junction points (where the rods are attached to Ω*) do not belong to the same straight line. We present comparisons between explicit asymptotic formulae and finite element computations to prove the efficiency of the approach.

Active Cloaking for Finite Clusters of Pins in Kirchhoff Plates

This paper considers active cloaking of a square array of evenly spaced pins in a Kirchhoff plate in the presence of flexural waves. Active sources, modeled as ideal point sources, are represented by the nonsingular Greens function for the two-dimensional biharmonic operator and have an arbitrary complex amplitude. These sources are distributed exterior to the cluster, and their complex amplitudes are found by solving an algebraic system of equations. This procedure ensures that selected multipole orders of the scattered field are successfully annulled. For frequencies in the zero-frequency stop band, we find that a small number of active sources located on a grid is sufficient for cloaking. For higher frequencies, we achieve efficient cloaking with the active sources positioned on a circle surrounding the cluster. We demonstrate the cloaking efficiency with several numerical illustrations, considering key frequencies from band diagrams and dispersion surfaces for a Kirchhoff plate pinned in a doubly per...

VIBRATIONS OF DAMAGED 1D-3D MULTI-STRUCTURES

Aslanyan, AG; Dronka, J; Mishuris, GS; Selsil, O. Vibrations of damaged 1D-3D multi-structures. Vibration Problems ICOVP 2005. Editor(s): Inan E; Kiris A. Book Series: SPRINGER PROCEEDINGS IN PHYSICS. 2007, Volume: 111, 45-50

A Thermoelasticity Problem in a Domain with an Edge Crack: Asymptotic Analysis

We consider a quasi-static problem of uncoupled thermoelasticity posed in a domain with a small edge crack perpendicular to the boundary. Real life examples leading to our problem arise naturally in, for example, fast breeder reactors, pressurised water reactor nozzles, etc. The effect of rapid changes or fluctuations on the surface of these structures is known as thermal striping and is considered as the origin of thermal fatigue damage.