245 research outputs found
Avalanches and clusters in planar crack front propagation
We study avalanches in a model for a planar crack propagating in a disordered
medium. Due to long-range interactions, avalanches are formed by a set of
spatially disconnected local clusters, the sizes of which are distributed
according to a power law with an exponent . We derive a scaling
relation between the local cluster exponent and the
global avalanche exponent . For length scales longer than a cross-over
length proportional to the Larkin length, the aspect ratio of the local
clusters scales with the roughness exponent of the line model. Our analysis
provides an explanation for experimental results on planar crack avalanches in
Plexiglas plates, but the results are applicable also to other systems with
long-range interactions.Comment: 7 pages, 6 figures, accepted for publication in Physical Review
Distributed Localization Algorithms for Wireless Sensor Networks: From Design Methodology to Experimental Validation
Recent advances in the technology of wireless electronic devices have made possible to build
ad–hoc Wireless Sensor Networks (WSNs) using inexpensive nodes, consisting of low–power
processors, a modest amount of memory, and simple wireless transceivers. Over the last years,
many novel applications have been envisaged for distributed WSNs in the area of monitoring, communication, and control. Sensing and controlling the environment by using many
embedded devices forming a WSN often require the measured physical parameters to be associated with the position of the sensing device. As a consequence, one of the key enabling
and indispensable services in WSNs is localization (i.e., positioning).
Moreover, the design of various components of the protocol stack (e.g., routing and Medium
Access Control, MAC, algorithms) might take advantage of nodes’ location, thus resulting in
WSNs with improved performance. However, typical protocol design methodologies have
shown signiï¬cant limitations when applied to the ï¬eld of embedded systems, like WSNs. As
a matter of fact, the layered nature of typical design approaches limits their practical usefulness for the design of WSNs, where any vertical information (like, e.g., the actual node’s
position) should be efï¬ciently shared in such resource constrained devices. Among the proposed solutions to address this problem, we believe that the Platform–Based Design (PBD)
approach Sangiovanni-Vincentelli (2002), which is a relatively new methodology for the design of embedded systems, is a very promising paradigm for the efï¬cient design of WSNs
Automatic Personal Identification System for Security in Critical Services: Two Case Studies based on a Wireless Biometric Badge
Roughness and multiscaling of planar crack fronts
We consider numerically the roughness of a planar crack front within the
long-range elastic string model, with a tunable disorder correlation length
. The problem is shown to have two important length scales, and the
Larkin length . Multiscaling of the crack front is observed for scales
below , provided that the disorder is strong enough. The asymptotic
scaling with a roughness exponent is recovered for scales
larger than both and . If , these regimes are separated
by a third regime characterized by the Larkin exponent .
We discuss the experimental implications of our results.Comment: 8 pages, two figure
AngioJet thrombectomy for the treatment of coronary artery aneurysm after failed thrombolysis in acute myocardial infarction
Acute myocardial infarction (AMI) is caused by thrombus formation over a disrupted plaque occluding an epicardial coronary artery. Mechanical thrombectomy is effective in removing thrombus burden from native vessels and saphenous vein grafts. Here we report a case of an aneurysmatic dilatation of an infarct-related artery (IRA) referred to our Institute for rescue PCI, after failed fibrinolysis, successfully treated with only rheolytic thrombectomy (AngioJet, Possis Medical, Minneapolis, Minnesota, USA) without the need for adjunctive balloon or stent implantation
Sound and light from fractures in scintillators
Prompted by intriguing events observed in certain particle-physics searches
for rare events, we study light and acoustic emission simultaneously in some
inorganic scintillators subject to mechanical stress. We observe
mechanoluminescence in , and ,
in various mechanical configurations at room temperature and ambient pressure.
We analyze how the light emission is correlated to acoustic emission during
fracture. For , we set a lower bound on the energy of
the emitted light, and deduce that the fraction of elastic energy converted to
light is at least
Demo: Automatic Personal Identification System for Security in Critical Services: A Case Study
ISBN: 978-1-4503-0718-5International audienceThe demonstration proposal moves from the capabilities of a wireless biometric badge [4], which integrates a localization and tracking service along with an automatic personal identification mechanism, to show how a full system architecture is devised to enable the control of physical accesses to restricted areas. The system leverages on the availability of a novel IEEE 802.15.4/Zigbee Cluster Tree network model, on enhanced security levels and on the respect of all the users' privacy issues
- …