969 research outputs found
Delayed-feedback chimera states: Forced multiclusters and stochastic resonance
A nonlinear oscillator model with negative time-delayed feedback is studied
numeri- cally under external deterministic and stochastic forcing. It is found
that in the unforced system complex partial synchronization patterns like
chimera states as well as salt-and-pepper like soli- tary states arise on the
route from regular dynamics to spatio-temporal chaos. The control of the
dynamics by external periodic forcing is demonstrated by numerical simulations.
It is shown that one-cluster and multi-cluster chimeras can be achieved by
adjusting the external forcing frequency to appropriate resonance conditions.
If a stochastic component is superimposed to the determin- istic external
forcing, chimera states can be induced in a way similar to stochastic
resonance, they appear, therefore, in regimes where they do not exist without
noise.Comment: 6 pages of paper with references + tex style file + 5 figure
Synthesis of memristive one-port circuits with piecewise-smooth characteristics
A generalized approach for the implementation of memristive two-terminal
circuits with piesewise-smooth characteristics is proposed on the example of a
multifunctional circuit based on a transistor switch. Two versions of the
circuit are taken into consideration: an experimental model of the
piecewise-smooth memristor (Chua's memristor) and a piecewise-smooth memristive
capacitor. Physical experiments are combined with numerical modelling of the
discussed circuit models. Thus, it is demonstrated that the considered circuit
is a flexible solution for synthesis of a wide range of memristive systems with
tuneable characteristics.Comment: 3 pages, 3 figure
Euler potentials for the MHD Kamchatnov-Hopf soliton solution
In the MHD description of plasma phenomena the concept of magnetic helicity
turns out to be very useful. We present here an example of introducing Euler
potentials into a topological MHD soliton which has non-trivial helicity. The
MHD soliton solution (Kamchatnov, 1982) is based on the Hopf invariant of the
mapping of a 3D sphere into a 2D sphere; it can have arbitrary helicity
depending on control parameters. It is shown how to define Euler potentials
globally. The singular curve of the Euler potential plays the key role in
computing helicity. With the introduction of Euler potentials, the helicity can
be calculated as an integral over the surface bounded by this singular curve. A
special programme for visualization is worked out. Helicity coordinates are
introduced which can be useful for numerical simulations where helicity control
is needed.Comment: 15 pages, 12 figure
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