25 research outputs found
Collisional effects in the tokamap
AbstractPlasmas confined in tokamaks with non-symmetric perturbations are surrounded by a chaotic layer of magnetic field lines that guide charged particles to the tokamak wall. We use an analytical two-dimensional symplectic mapping to study the resulting fractal patterns of field line escape. However, particles may experience several collisions before escaping toward the tokamaks wall. We add a random collisional term to the field line mapping to investigate how the particle collisions modify their escape patterns
Synchronised firing patterns in a random network of adaptive exponential integrate-and-fire neuron model
Acknowledgements This study was possible by partial financial support from the following Brazilian government agencies: CNPq, CAPES, and FAPESP (2011/19296-1 and 2015/07311-7). We also wish thank Newton Fund and COFAP.Peer reviewedPostprin
Non-transitive maps in phase synchronization
Concepts from the Ergodic Theory are used to describe the existence of
non-transitive maps in attractors of phase synchronous chaotic systems. It is
shown that for a class of phase-coherent systems, e.g. the sinusoidally forced
Chua's circuit and two coupled R{\"o}ssler oscillators, phase synchronization
implies that such maps exist. These ideas are also extended to other coupled
chaotic systems. In addition, a phase for a chaotic attractor is defined from
the tangent vector of the flow. Finally, it is discussed how these maps can be
used to real time detection of phase synchronization in experimental systems
Replicate Periodic Windows in the Parameter Space of Driven Oscillators
In the bi-dimensional parameter space of driven oscillators, shrimp-shaped
periodic windows are immersed in chaotic regions. For two of these oscillators,
namely, Duffing and Josephson junction, we show that a weak harmonic
perturbation replicates these periodic windows giving rise to parameter regions
correspondent to periodic orbits. The new windows are composed of parameters
whose periodic orbits have periodicity and pattern similar to stable and
unstable periodic orbits already existent for the unperturbed oscillator. These
features indicate that the reported replicate periodic windows are associated
with chaos control of the considered oscillators
Spike timing-dependent plasticity induces non-trivial topology in the brain.
We study the capacity of Hodgkin-Huxley neuron in a network to change temporarily or permanently their connections and behavior, the so called spike timing-dependent plasticity (STDP), as a function of their synchronous behavior. We consider STDP of excitatory and inhibitory synapses driven by Hebbian rules. We show that the final state of networks evolved by a STDP depend on the initial network configuration. Specifically, an initial all-to-all topology evolves to a complex topology. Moreover, external perturbations can induce co-existence of clusters, those whose neurons are synchronous and those whose neurons are desynchronous. This work reveals that STDP based on Hebbian rules leads to a change in the direction of the synapses between high and low frequency neurons, and therefore, Hebbian learning can be explained in terms of preferential attachment between these two diverse communities of neurons, those with low-frequency spiking neurons, and those with higher-frequency spiking neurons
Fluctuation spectrum for linear gyroviscous MHD
SIGLEAlso published in Phys. Lett., A (17 Sep 1984) v. 104(8) p. 423-424 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
Hamiltonian formulation of two-dimensional gyroviscous MHD
SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman