836 research outputs found

    A GIS TOOL FOR THE MANAGEMENT OF SEISMIC EMERGENCIES IN HISTORICAL CENTERS: HOW TO CHOOSE THE OPTIMAL ROUTES FOR CIVIL PROTECTION INTERVENTIONS

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    Abstract. Italy hosts a considerable part of the world's great art treasures. This great heritage must be protected from risks deriving from a territory characterized by hydrogeological problems and high seismicity. For these reasons, despite the preventive measures that can be foreseen, the need to face emergencies is recurrent. The main instrument to address the hydrogeological and seismic emergencies is the Municipal Civil Protection Emergency Plan. In this plan, both strategic viability and strategic buildings (whose collapse could cause significant damage to the historical, artistic and cultural heritage) must be identified.The paper proposes a methodology, using a GIS platform, useful for achieving two objectives: (1) planning of safe routes in case of critical conditions and (2) identification and planning of safety interventions, thus assigning appropriate priorities to the buildings to be restored, based not only on their relevance to road use, but also on cost considerations.</p

    Tailoring the magnetic ordering of the Cr4O5/Fe(001) surface via a controlled adsorption of C60&#160;organic molecules

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    We analyse the spinterface formed by a C60 molecular layer on a Fe(001) surface covered by a two-dimensional Cr4O5 layer. We consider different geometries, by combining the high symmetry adsorption sites of the surface with three possible orientations of the molecules in a fully relaxed Density Functional Theory calculation.We show that the local hybridization between the electronic states of the Cr4O5 layer and those of the organic molecules is able to modify the magnetic coupling of the Cr atoms. Both the intra-layer and the inter-layer magnetic interaction is indeed driven by O atoms of the two-dimensional oxide. We demonstrate that the C60 adsorption on the energetically most stable site turns the ferromagnetic intra-layer coupling into an antiferromagnetic one, and that antiferromagnetic to ferromagnetic switching and spin patterning of the substrate are made possible by adsorption on other sites

    Electron transport in carbon wires in contact with Ag electrodes : a detailed first principles investigation

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    The structure and electronic properties of carbon atom chains Cn in contact with Ag electrodes are investigated in detail with first principles means. The ideal Ag(100) surface is used as a model for binding, and electron transport through the chains is studied as a function of their length, applied bias voltage, presence of capping atoms (Si, S) and adsorption site. It is found that the metal\u2013molecule bond largely influences electronic coupling to the leads. Without capping atoms the quality of the electric contact improves when increasing the carbon atom coordination number to the metal (1, 2 and 4 for adsorption on a top, bridge and hollow position, respectively) and this finding translates almost unchanged in more realistic tip-like contacts which present one, two or four metal atoms at the contact. Current\u2013voltage characteristics show Ohmic behaviour over a wide range of bias voltages and the resulting conductances change only weakly when increasing the wire length. The effect of a capping species is typically drastic, and either largely reduces (S) or largely increases (Si) the coupling of the wire to the electrodes. Comparison of our findings with recent experimental results highlights the limits of the adopted approach, which can be traced back to the known gap problem of density-functional-theory

    Electronic structure and lifetime broadening of a quantum-well state on p(2x2) K/Cu(111)

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    We studied a quantum-well state (QWS) generated by the adsorption of one monolayer of K on Cu(111) surface by means of a first principles approach. We calculated the electronic properties of the system within the Inglesfield's embedding method, which enables us to investigate the elastic linewidth of surface states. Our findings are in good agreement with recent experimental results obtained from photoemission spectroscopy measurements for binding energy and k(vertical bar vertical bar) dispersion. We also studied the contributions to the QWS linewidth due to electron-electron many-body effects and electron-phonon scattering in Hedin's GW approach and within the Debye model, respectively. The main contribution to the linewidth is due to intraband transitions within the QWS itself, accounting for similar to 16 meV to the total width. The elastic, electron-phonon, and interband transition contributions are smaller than 3 meV each

    Contact mechanics analysis of a soft robotic fingerpad

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    The precision grasping capabilities of robotic hands is a key feature which is more and more required in the manipulation of objects in several unstructured fields, as for instance industrial, medical, agriculture and food industry. For this purpose, the realization of soft robotic fingers is crucial to reproduce the human finger skills. From this point of view the fingerpad is the part which is mostly involved in the contact. Particular attention must be paid to the knowledge of the mechanical contact behavior of soft artificial fingerpads. In this paper, artificial silicone fingerpads are applied to the last phalanx of robotic fingers actuated by tendons. The mechanical interaction between the fingerpad and a flat surface is analyzed in terms of deformations, contact areas and indentations. A reliable model of fingertip deformation properties provides important information for understanding robotic hand performance, that can be useful both in the design phase and for defining control strategies. The approach is based on theoretical, experimental, and numerical methods. The results will be exploited for the design of more effective robotic fingers for precision grasping of soft or fragile objects avoiding damages

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    Hydrogen-dimer lines and electron waveguides in graphene

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    The electronic and transport properties of graphene ribbons sandwiched between hydrogen dimer lines, of the kind recently realized by Nilsson et al., Carbon, 2012, 50, 2052, are investigated with the help of first principles methods. It is found that such lines of hydrogen atoms block conduction between neighboring channels and effectively allow the confinement of graphene charge carriers, thereby opening the possibility of imprinting nano-circuits in graphene by controlled hydrogenation

    Sticking of atomic hydrogen on graphene

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    Recent years have witnessed an ever growing interest in the interactions between hydrogen atoms and a graphene sheet. Largely motivated by the possibility of modulating the electric, optical and magnetic properties of graphene, a huge number of studies have appeared recently that added to and enlarged earlier investigations on graphite and other carbon materials. In this review we give a glimpse of the many facets of this adsorption process, as they emerged from these studies. The focus is on those issues that have been addressed in detail, under carefully controlled conditions, with an emphasis on the interplay between the adatom structures, their formation dynamics and the electric, magnetic and chemical properties of the carbon sheet

    Mixed Dark Matter from Axino Distribution

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    We study the possibility of mixed dark matter obtained through the phase space distribution of a single particle. An example is offered in the context of SUSY models with a Peccei-Quinn symmetry. Axinos in the 100 keV range can naturally have both thermal and non-thermal components. The latter one arises from the lightest neutralino decays and derelativizes at z ~ 10^4.Comment: Figures added, references fixed. Version accepted for publication on Phys. Rev. D. LaTeX. 9 pages, 3 figures, uses epsfig.st
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