RESUMEN
A new rotational field planar eddy current probe is proposed. The probe is combined with two orthogonal driver traces and a pickup coil that includes two-circular sector windings with series connection. Rotational eddy currents are induced by driver traces of the same amplitude and frequency, but fed with 90° phase different alternating exciting currents. An experimental demonstration using prototypes of the probes and artificial defects showed that the probe with a two-circular sector pickup coil is more sensitive for detecting the short defects than the probe with a circular pickup coil.
RESUMEN
Strange attractors can be observed in chaotic and hyperchaotic systems. Most of the dynamical systems hold a finite number of attractors, while some chaotic systems can be controlled to present an infinite number of attractors by generating infinite equilibria. Chaos can also be triggered in some dynamical systems that can present hidden attractors, and the attractors in these dynamical systems find no equilibria and the basin of attraction is not connected with any equilibrium (the equilibria position meets certain restriction function). In this paper, Hamilton energy is calculated on the chaotic systems with different types of attractors, and energy modulation is used to control the chaos in these systems. The potential mechanism could be that negative feedback in energy can suppress the phase space and oscillating behaviors, and thus, the chaotic, periodical oscillators can be controlled. It could be effective to control other chaotic, hyperchaotic and even periodical oscillating systems as well.
RESUMEN
Alterations of individual neurons dynamics and associated changes of the activity pattern, especially the transition from tonic firing (single-spikes) to bursts discharges (impulse groups), play an important role for neuronal information processing and synchronization in many physiological processes (sensory encoding, information binding, hormone release, sleep-wake cycles) as well as in disease (Parkinson, epilepsy). We have used Hodgkin-Huxley-type model neurons with subthreshold oscillations to examine the impact of noise on neuronal encoding and thereby have seen significant differences depending on noise implementation as well as on the neuron's dynamic state. The importance of the individual neurons' dynamics is further elucidated by simulation studies with electrotonically coupled model neurons which revealed mutual interdependencies between the alterations of the network's coupling strength and neurons' activity patterns with regard to synchronization. Remarkably, a pacemaker-like activity pattern which revealed to be much more noise sensitive than the bursting patterns also requires much higher coupling strengths for synchronization. This seemingly simple pattern is obviously governed by more complex dynamics than expected from a conventional pacemaker which may explain why neurons more easily synchronize in the bursting than in the tonic firing mode.
