30,761 research outputs found

    electron-positron-photon plasma around a collapsing star

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    We describe electron-positron pairs creation around an electrically charged star core collapsing to an electromagnetic black hole (EMBH), as well as pairs annihilation into photons. We use the kinetic Vlasov equation formalism for the pairs and photons and show that a regime of plasma oscillations is established around the core. As a byproduct of our analysis we can provide an estimate for the thermalization time scale.Comment: 8 pages, 4 figures, to appear in the Proceedings of QABP200

    Stress intensity factor in a tapered specimen

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    The general problem of a tapered specimen containing an edge crack is formulated in terms of a system of singular integral equations. The equations are solved and the stress intensity factor is calculated for a compact and for a slender tapered specimen, the latter simulating the double cantilever beam. The results are obtained primarily for a pair of concentrated forces and for crack surface wedge forces. The stress intensity factors are also obtained for a long strip under uniform tension which contains inclined edge cracks

    Interaction between a crack and a soft inclusion

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    With the application to weld defects in mind, the interaction problem between a planar-crack and a flat inclusion in an elastic solid is considered. The elastic inclusion is assumed to be sufficiently thin so that the thickness distribution of the stresses in the inclusion may be neglected. The problem is reduced to a system of four integral equations having Cauchy-type dominant kernels. The stress intensity factors are calculated and tabulated for various crack-inclusion geometries and the inclusion to matrix modulus ratios, and for general homogeneous loadiong conditions away from the crack-inclusion region

    The influences of the galactic cosmic ray on the atmospheric ozone

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    The relationship between the yearly variations of cosmic ray intensity and ozone in the atmosphere, and the ozone disturbance initiated by the Forbush decrease of 1965-1976 is analyzed. The data on cosmic ray intensity were selected from the records of the super neutron monitor at Deep River station and the ionization chamber at Beijing station. Ozone data were taken from Resolute (Canada), Bismark (N. Dakota, USA), Kagoshima (Japan), and Kodaikanal (India). The statistical results show that ozone is prominently modulated and disturbed by the 11 year variation and the Forbush decrease in the galactic cosmic ray

    Visual Dynamics: Probabilistic Future Frame Synthesis via Cross Convolutional Networks

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    We study the problem of synthesizing a number of likely future frames from a single input image. In contrast to traditional methods, which have tackled this problem in a deterministic or non-parametric way, we propose a novel approach that models future frames in a probabilistic manner. Our probabilistic model makes it possible for us to sample and synthesize many possible future frames from a single input image. Future frame synthesis is challenging, as it involves low- and high-level image and motion understanding. We propose a novel network structure, namely a Cross Convolutional Network to aid in synthesizing future frames; this network structure encodes image and motion information as feature maps and convolutional kernels, respectively. In experiments, our model performs well on synthetic data, such as 2D shapes and animated game sprites, as well as on real-wold videos. We also show that our model can be applied to tasks such as visual analogy-making, and present an analysis of the learned network representations.Comment: The first two authors contributed equally to this wor

    Mechanical modulation of single-electron tunneling through molecular-assembled metallic nanoparticles

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    We present a microscopic study of single-electron tunneling in nanomechanical double-barrier tunneling junctions formed using a vibrating scanning nanoprobe and a metallic nanoparticle connected to a metallic substrate through a molecular bridge. We analyze the motion of single electrons on and off the nanoparticle through the tunneling current, the displacement current and the charging-induced electrostatic force on the vibrating nanoprobe. We demonstrate the mechanical single-electron turnstile effect by applying the theory to a gold nanoparticle connected to the gold substrate through alkane dithiol molecular bridge and probed by a vibrating platinum tip.Comment: Accepted by Phys. Rev.
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