198 research outputs found

    Unified radio and network control across heterogeneous hardware platforms

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    Experimentation is an important step in the investigation of techniques for handling spectrum scarcity or the development of new waveforms in future wireless networks. However, it is impractical and not cost effective to construct custom platforms for each future network scenario to be investigated. This problem is addressed by defining Unified Programming Interfaces that allow common access to several platforms for experimentation-based prototyping, research, and development purposes. The design of these interfaces is driven by a diverse set of scenarios that capture the functionality relevant to future network implementations while trying to keep them as generic as possible. Herein, the definition of this set of scenarios is presented as well as the architecture for supporting experimentation-based wireless research over multiple hardware platforms. The proposed architecture for experimentation incorporates both local and global unified interfaces to control any aspect of a wireless system while being completely agnostic to the actual technology incorporated. Control is feasible from the low-level features of individual radios to the entire network stack, including hierarchical control combinations. A testbed to enable the use of the above architecture is utilized that uses a backbone network in order to be able to extract measurements and observe the overall behaviour of the system under test without imposing further communication overhead to the actual experiment. Based on the aforementioned architecture, a system is proposed that is able to support the advancement of intelligent techniques for future networks through experimentation while decoupling promising algorithms and techniques from the capabilities of a specific hardware platform

    Bifurcations of discrete breathers in a diatomic Fermi-Pasta-Ulam chain

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    Discrete breathers are time-periodic, spatially localized solutions of the equations of motion for a system of classical degrees of freedom interacting on a lattice. Such solutions are investigated for a diatomic Fermi-Pasta-Ulam chain, i. e., a chain of alternate heavy and light masses coupled by anharmonic forces. For hard interaction potentials, discrete breathers in this model are known to exist either as ``optic breathers'' with frequencies above the optic band, or as ``acoustic breathers'' with frequencies in the gap between the acoustic and the optic band. In this paper, bifurcations between different types of discrete breathers are found numerically, with the mass ratio m and the breather frequency omega as bifurcation parameters. We identify a period tripling bifurcation around optic breathers, which leads to new breather solutions with frequencies in the gap, and a second local bifurcation around acoustic breathers. These results provide new breather solutions of the FPU system which interpolate between the classical acoustic and optic modes. The two bifurcation lines originate from a particular ``corner'' in parameter space (omega,m). As parameters lie near this corner, we prove by means of a center manifold reduction that small amplitude solutions can be described by a four-dimensional reversible map. This allows us to derive formally a continuum limit differential equation which characterizes at leading order the numerically observed bifurcations.Comment: 30 pages, 10 figure

    Integration of WiFi ToF Positioning System in the Open, Flexible and Adaptive WiSHFUL Architecture

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    We integrate a prototype WiFi Time-of-Flight (ToF) ranging and po- sitioning system in the WiSHFUL software platforms and hardware radios for experimental prototyping. Users can have access to ToF measurements as well as computed positions through uni ed pro- gramming interfaces that make possible to investigate innovative positioning and networking solutions

    Subacute dislocation of the elbow following Galeazzi fracture-dislocation of the radius: A case report

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    <p>Abstract</p> <p>Introduction</p> <p>The Galeazzi fracture-dislocation was originally described by Sir Astley Cooper in 1822 but was named after Italian surgeon Ricardo Galeazzi in 1934. It is an injury classified as a radial shaft fracture with associated dislocation of the distal radioulnar joint and disruption of the forearm axis joint. The associated distal radioulnar joint injury may be purely ligamentous in nature, tearing the triangular fibrocartilaginous complex, or involve bony tissue (that is, ulnar styloid avulsions) or both. We report this case because of the rare association of posterior dislocation of the elbow along with Galeazzi fracture-dislocation. To the best of our knowledge, this has not been previously reported in the English literature.</p> <p>Case presentation</p> <p>A 26-year-old Caucasian man presented to our department after a fall from a motorbike. He sustained a closed, isolated Galeazzi fracture-dislocation of the right forearm and no associated elbow injuries, and this necessitated open reduction and internal fixation of the radius. Post-operative radiographs films were satisfactory. However, clinical and radiological evidence of ipsilateral elbow dislocation was noted at a five-week follow-up, subsequently requiring open reduction of the joint and collateral ligament repair. Our patient was noted to have full elbow and forearm function at three months.</p> <p>Conclusions</p> <p>Although the Galeazzi fracture-dislocation has been classically described as involving only the distal radioulnar joint, traumatic forces can be transmitted to the elbow via the interosseous membrane of the forearm. This can lead to instability of the elbow joint. Therefore, we recommend that, in every case of forearm fracture, both elbow and wrist joints be assessed clinically as well as radiologically for subluxation or dislocation.</p

    Automatic Music Transcription: Breaking the Glass Ceiling

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    Automatic music transcription is considered by many to be the Holy Grail in the field of music signal analysis. However, the performance of transcription systems is still significantly below that of a human expert, and accuracies reported in recent years seem to have reached a limit, although the field is still very active. In this paper we analyse limitations of current methods and identify promising directions for future research. Current transcription methods use general purpose models which are unable to capture the rich diversity found in music signals. In order to overcome the limited performance of transcription systems, algorithms have to be tailored to specific use-cases. Semi-automatic approaches are another way of achieving a more reliable transcription. Also, the wealth of musical scores and corresponding audio data now available are a rich potential source of training data, via forced alignment of audio to scores, but large scale utilisation of such data has yet to be attempted. Other promising approaches include the integration of information across different methods and musical aspects

    Isochronism and tangent bifurcation of band edge modes in Hamiltonian lattices

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    In {\em Physica D} {\bf 91}, 223 (1996), results were obtained regarding the tangent bifurcation of the band edge modes (q=0,πq=0,\pi) of nonlinear Hamiltonian lattices made of NN coupled oscillators. Introducing the concept of {\em partial isochronism} which characterises the way the frequency of a mode, ω\omega, depends on its energy, ϵ\epsilon, we generalize these results and show how the bifurcation energies of these modes are intimately connected to their degree of isochronism. In particular we prove that in a lattice of coupled purely isochronous oscillators (ω(ϵ)\omega(\epsilon) strictly constant), the in-phase mode (q=0q=0) never undergoes a tangent bifurcation whereas the out-of-phase mode (q=πq=\pi) does, provided the strength of the nonlinearity in the coupling is sufficient. We derive a discrete nonlinear Schr\"odinger equation governing the slow modulations of small-amplitude band edge modes and show that its nonlinear exponent is proportional to the degree of isochronism of the corresponding orbits. This equation may be seen as a link between the tangent bifurcation of band edge modes and the possible emergence of localized modes such as discrete breathers.Comment: 23 pages, 1 figur

    Transform Autism Education - Final Report

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    The Transform Autism Education (TAE) project focused on the domain of ‘good autism practice’ in the education of pupils with autism in the UK, Greece and Italy with the overall objectives to:• Research good autism practice in education.• Create professional development programmes in Greece and Italy.• Enhance the knowledge and practice of school staff.• Facilitate the inclusion of autistic children in primary schools in those countries.Funded by the European Commission through Erasmus Plus Key Action 2, Strategic Partnerships scheme, and led by Principal Investigator Dr. Karen Guldberg, the project involved a range of Greek, Italian and UK partners. It employed the Autism Education Trust (AET) collaborative training schemes in the UK as a founding model. While the requirements of each country were distinct, and so necessitated careful adaptations of the materials to their specific needs, what united all aspects of the project was a desire to improve the educational inclusion of autistic children, as well as their general experiences in school and their outcomes
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