A Measurement Tool for Investigating the Volcanic Activity

Video surveillance systems are consolidated techniques for monitoring eruptive phenomena in volcanic areas. Along with these systems, which use standard video cameras, people working in this field sometimes make use of infrared cameras providing useful information about the thermal evolution of eruptions. Real-time analysis of the acquired frames is required along with image storing to analyze and classify the activity of volcanoes. Human efforts are hence required to perform monitoring tasks. In this paper a new strategy is presented, which aims to improve the performance of surveillance systems in terms of human-independent image processing. The proposed methodology is based on real time thermo graphic analysis of the area considered. The tool developed provides information about the activity being monitored

Synchronization time in a hyperbolic dynamical system with long-range interactions

We show that the threshold of complete synchronization in a lattice of coupled non-smooth chaotic maps is determined by linear stability along the directions transversal to the synchronization subspace. We examine carefully the sychronization time and show that a inadequate observation of the system evolution leads to wrong results. We present both careful numerical experiments and a rigorous mathematical explanation confirming this fact, allowing for a generalization involving hyperbolic coupled map lattices.Comment: 22 pages (preprint format), 4 figures - accepted for publication in Physica A (June 28, 2010

Symmetries, Cluster Synchronization, and Isolated Desynchronization in Complex Networks

Synchronization is of central importance in power distribution, telecommunication, neuronal, and biological networks. Many networks are observed to produce patterns of synchronized clusters, but it has been difficult to predict these clusters or understand the conditions under which they form, except for in the simplest of networks. In this article, we shed light on the intimate connection between network symmetry and cluster synchronization. We introduce general techniques that use network symmetries to reveal the patterns of synchronized clusters and determine the conditions under which they persist. The connection between symmetry and cluster synchronization is experimentally explored using an electro-optic network. We experimentally observe and theoretically predict a surprising phenomenon in which some clusters lose synchrony while leaving others synchronized. The results could guide the design of new power grid systems or lead to new understanding of the dynamical behavior of networks ranging from neural to social

Complete Characterization of Stability of Cluster Synchronization in Complex Dynamical Networks

Synchronization is an important and prevalent phenomenon in natural and engineered systems. In many dynamical networks, the coupling is balanced or adjusted in order to admit global synchronization, a condition called Laplacian coupling. Many networks exhibit incomplete synchronization, where two or more clusters of synchronization persist, and computational group theory has recently proved to be valuable in discovering these cluster states based upon the topology of the network. In the important case of Laplacian coupling, additional synchronization patterns can exist that would not be predicted from the group theory analysis alone. The understanding of how and when clusters form, merge, and persist is essential for understanding collective dynamics, synchronization, and failure mechanisms of complex networks such as electric power grids, distributed control networks, and autonomous swarming vehicles. We describe here a method to find and analyze all of the possible cluster synchronization patterns in a Laplacian-coupled network, by applying methods of computational group theory to dynamically-equivalent networks. We present a general technique to evaluate the stability of each of the dynamically valid cluster synchronization patterns. Our results are validated in an electro-optic experiment on a 5 node network that confirms the synchronization patterns predicted by the theory.Comment: 6 figure

Studio della correlazione tra il tremore vulcanico e l’attività esplosiva dell’Etna nel Gennaio - Febbraio 1999 mediante il sistema VoTA (Volcanic Tremor Analyzer)

Il seguente lavoro presenta lo studio della correlazione tra il tremore vulcanico e l'attività esplosiva dell'Etna nel gennaio-febbraio 1999 effettuato mediante l’implementazione e lo sviluppo del sistema automatico per l’analisi e la visualizzazione del tremore vulcanico VoTA (Volcanic Tremor Analizer). In particolare, sono stati presi in considerazione cinque episodi eruttivi significativi dell’attività dell’Etna durante i quali il VoTA ha effettuato un’analisi on line del tremore vulcanico. Successivamente, tali dati sono stati confrontati con le immagini dell’attività eruttiva riprese dalla telecamera di sorveglianza dell’Etna, permettendo di ricavare delle correlazioni tra le diverse fasi dell’attività esplosiva ed i corrispondenti valori del tremore vulcanico