366 research outputs found

    Push & Pull: autonomous deployment of mobile sensors for a complete coverage

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    Mobile sensor networks are important for several strategic applications devoted to monitoring critical areas. In such hostile scenarios, sensors cannot be deployed manually and are either sent from a safe location or dropped from an aircraft. Mobile devices permit a dynamic deployment reconfiguration that improves the coverage in terms of completeness and uniformity. In this paper we propose a distributed algorithm for the autonomous deployment of mobile sensors called Push&Pull. According to our proposal, movement decisions are made by each sensor on the basis of locally available information and do not require any prior knowledge of the operating conditions or any manual tuning of key parameters. We formally prove that, when a sufficient number of sensors are available, our approach guarantees a complete and uniform coverage. Furthermore, we demonstrate that the algorithm execution always terminates preventing movement oscillations. Numerous simulations show that our algorithm reaches a complete coverage within reasonable time with moderate energy consumption, even when the target area has irregular shapes. Performance comparisons between Push&Pull and one of the most acknowledged algorithms show how the former one can efficiently reach a more uniform and complete coverage under a wide range of working scenarios.Comment: Technical Report. This paper has been published on Wireless Networks, Springer. Animations and the complete code of the proposed algorithm are available for download at the address: http://www.dsi.uniroma1.it/~novella/mobile_sensors

    Quantum Characterization of a Werner-like Mixture

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    We introduce a Werner-like mixture [R. F. Werner, Phys. Rev. A {\bf 40}, 4277 (1989)] by considering two correlated but different degrees of freedom, one with discrete variables and the other with continuous variables. We evaluate the mixedness of this state, and its degree of entanglement establishing its usefulness for quantum information processing like quantum teleportation. Then, we provide its tomographic characterization. Finally, we show how such a mixture can be generated and measured in a trapped system like one electron in a Penning trap.Comment: 8 pages ReVTeX, 8 eps figure

    Synthesis and characterization of entangled mesoscopic superpositions for a trapped electron

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    We propose a scheme for the generation and reconstruction of entangled states between the internal and external (motional) degrees of freedom of a trapped electron. Such states also exhibit quantum coherence at a mesoscopic level.Comment: 4 pages, 1 figure, RevTeX (twocolumn

    The Pauli Equation for Probability Distributions

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    The "marginal" distributions for measurable coordinate and spin projection is introduced. Then, the analog of the Pauli equation for spin-1/2 particle is obtained for such probability distributions instead of the usual wave functions. That allows a classical-like approach to quantum mechanics. Some illuminating examples are presented.Comment: 14 pages, ReVTe

    Contractive Schroedinger cat states for a free mass

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    Contractive states for a free quantum particle were introduced by Yuen [Yuen H P 1983 Phys. Rev. Lett. 51, 719] in an attempt to evade the standard quantum limit for repeated position measurements. We show how appropriate families of two- and three component ``Schroedinger cat states'' are able to support non-trivial correlations between the position and momentum observables leading to contractive behavior. The existence of contractive Schroedinger cat states is suggestive of potential novel roles of non-classical states for precision measurement schemes.Comment: 24 pages, 7 encapsulated eps color figures, REVTeX4 style. Published online in New Journal of Physics 5 (2003) 5.1-5.21. Higher-resolution figures available in published version. (accessible at http://www.njp.org/

    The complementarity effect of exporting, importing and R&D on the productivity of Ukrainian MNEs

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    After two decades of research on Emerging Market Multinational Enterprises (EMNE), the debate still concerns the antecedents and strategies of their foreign expansion. However, much less has been said on the effects of international participation on their productivity. Building on insights from the Resource-Based View of the firm and agency theory, we develop hypotheses on the presence of complementarities among export, import and R&D and their impact on productivity. Our empirical analyses on a panel of 23,000 time-year observations of Ukrainian MNEs over the period 2000–2006, confirm that: (i) EMNEs benefit from complementarities stemming from the assimilation and integration of knowledge from international external sources (import and export) with internal knowledge (own R&D investment); (ii) the effect is more pronounced for private-owned enterprises (POEs) rather than state-owned enterprises (SOEs), and (iii) especially when they trade with partners in/from advanced markets
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