6,726 research outputs found

    Effects of interedge scattering on the Wigner crystallization in graphene nanoribbons

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    We investigate the effects of coupling between the two zigzag edges of graphene nanoribbons on the Wigner crystallization of electrons and holes using a combination of tight-binding, mean field Hubbard and many-body configuration interaction methods. We show that the thickness of the nanoribbon plays a crucial role in the formation of Wigner crystal. For ribbon widths smaller than 16 \mbox{\AA}, increased kinetic energy overcomes the long-range Coulomb repulsion and suppresses the Wigner crystallization. For wider ribbons up to 38 \mbox{\AA} wide, strong Wigner localization is observed for even number of electrons, revealing an even-odd effect also found in Coulomb blockade addition spectrum. Interedge correlations are found to be strong enough to allow simultaneous crystallization on both edges, although an applied electric field can decouple the two edges. Finally, we show that Wigner crystallization can also occurs for holes, albeit weaker than for electrons.Comment: Accepted for publication in PR

    On the period function of Newtonian systems

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    We study the existence of centers of planar autonomous system of the form (S)x˙=y,y˙=−h(x)−g(x)y−f(x)y2.(S) \quad \dot x=y,\qquad \dot y = -h(x) - g(x)y - f(x)y^2. We are interested in the period function TT around a center 0. A sufficient condition for the isochronicity of (S) at 0 is given. Such a condition is also necessary when f,g,hf,g,h are analytic functions. In that case a characterization of isochronous centers of system (S) is given. Some applications will be derived. In particular, new families of isochronous centers will be describedComment: 16 page

    Subharmonic solutions for nonautonomous sublinear first order Hamiltonian systems

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    In this paper, the existence of subharmonic solutions for a class of non-autonomous first-order Hamiltonian systems is investigated. We also study the minimality of periods for such solutions. Our results which extend and improve many previous results will be illustrated by specific examples. Our main tools are the minimax methods in critical point theory and the least action principle. {\bf Key words.} Hamiltonian systems. Critical point theory. Least action principle. Subharmonic solutions.Comment: 17 page

    3D Camouflaging Object using RGB-D Sensors

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    This paper proposes a new optical camouflage system that uses RGB-D cameras, for acquiring point cloud of background scene, and tracking observers eyes. This system enables a user to conceal an object located behind a display that surrounded by 3D objects. If we considered here the tracked point of observer s eyes is a light source, the system will work on estimating shadow shape of the display device that falls on the objects in background. The system uses the 3d observer s eyes and the locations of display corners to predict their shadow points which have nearest neighbors in the constructed point cloud of background scene.Comment: 6 pages, 12 figures, 2017 IEEE International Conference on SM

    Computation of canonical correlation and best predictable aspect of future for time series

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    The canonical correlation between the (infinite) past and future of a stationary time series is shown to be the limit of the canonical correlation between the (infinite) past and (finite) future, and computation of the latter is reduced to a (generalized) eigenvalue problem involving (finite) matrices. This provides a convenient and essentially, finite-dimensional algorithm for computing canonical correlations and components of a time series. An upper bound is conjectured for the largest canonical correlation

    Intraoperative bronchial stump air leak control by Progel® application after pulmonary lobectomy

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    Diffuse tracheobronchial calcification is a physiological condition associated with advanced age, especially in women. A calcified bronchus can be fractured during major lung resections (lobectomy, bilobectomy, and pneumonectomy), exposing patients to intraoperative air leakage and broncho-pleural fistula (BPF) occurrence. We retrospectively evaluated the use of Progel® application on the suture line of bronchial stump after pulmonary lobectomy analysing the intraoperative air leak and BPF occurrence. Between January 2014 and December 2014, Progel® was applied in 11 patients who presented intraoperative bronchial fractures after suture resection by mechanical staplers and air leak from bronchial stump, in order to treat air leakage. Patients were 7 men and 4 women, aged between 56 and 81 years (mean age 71.2 ± 12.1 years). Surgical procedures included 6 upper lobectomies (4 right, 2 left), 1 bilobectomy and 4 lower lobectomies (3 right, 1 left). Mean hospital stay was 4.5 ± 2.6 days (2-8 days). None of the patients had postoperative air leakage. No Progel® application-related complications occurred. No other major complications occurred. No mortality occurred. Progel® proved to be useful in treating intraoperative air leakage during major lung resections, particularly those occurring as a result of fracture of the bronchus from a mechanical stapler

    Push clocks: a new approach to charge-coupled devices clocking

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    A new approach to charge-coupled device clocking has been developed—dynamic push clocks. With dynamic push clocks, the charge is transferred by pushing it from one storage site to another. The push clock approach results in a larger signal dynamic range, larger signal-to-noise ratio, and better performance at both high and low frequencies

    Nonlinearity in Single Photon Detection: Modeling and Quantum Tomography

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    Single Photon Detectors are integral to quantum optics and quantum information. Superconducting Nanowire based detectors exhibit new levels of performance, but have no accepted quantum optical model that is valid for multiple input photons. By performing Detector Tomography, we improve the recently proposed model [M.K. Akhlaghi and A.H. Majedi, IEEE Trans. Appl. Supercond. 19, 361 (2009)] and also investigate the manner in which these detectors respond nonlinearly to light, a valuable feature for some applications. We develop a device independent model for Single Photon Detectors that incorporates this nonlinearity
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