2,835 research outputs found

    Creating effective focus cues in multi-plane 3D displays.

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    Focus cues are incorrect in conventional stereoscopic displays. This causes a dissociation of vergence and accommodation, which leads to visual fatigue and perceptual distortions. Multi-plane displays can minimize these problems by creating nearly correct focus cues. But to create the appearance of continuous depth in a multi-plane display, one needs to use depth-weighted blending: i.e., distribute light intensity between adjacent planes. Akeley et al. [ACM Trans. Graph. 23, 804 (2004)] and Liu and Hua [Opt. Express 18, 11562 (2009)] described rather different rules for depth-weighted blending. We examined the effectiveness of those and other rules using a model of a typical human eye and biologically plausible metrics for image quality. We find that the linear blending rule proposed by Akeley and colleagues [ACM Trans. Graph. 23, 804 (2004)] is the best solution for natural stimuli

    TWEETS OF AN ARTICLE AND ITS CITATION: AN ALTMETRIC STUDY OF MOST PROLIFIC AUTHORS

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    The present study was carried to find out the association between twitter and citation pattern for scholarly articles. This study was carried out with the most prolific authors of 2014 from the four subject domain “Clinical medicine, Microbiology, Molecular Biology, and Neuroscience” and 4886 papers were identified to studied their tweets and citation counts. From the study, it was found that the articles of the most prolific authors have a strong correlation with the citation and its value ρ =.518**. The linear relationship for individual subjects was between .386** to .559**, significant at .01 level

    Stable and Metastable vortex states and the first order transition across the peak effect region in weakly pinned 2H-NbSe_2

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    The peak effect in weakly pinned superconductors is accompanied by metastable vortex states. Each metastable vortex configuration is characterized by a different critical current density J_c, which mainly depends on the past thermomagnetic history of the superconductor. A recent model [G. Ravikumar, et al, Phys. Rev. B 61, R6479 (2000)] proposed to explain the history dependent J_c postulates a stable state of vortex lattice with a critical current density J_c^{st}, determined uniquely by the field and temperature. In this paper, we present evidence for the existence of the stable state of the vortex lattice in the peak effect region of 2H-NbSe_2. It is shown that this stable state can be reached from any metastable vortex state by cycling the applied field by a small amplitude. The minor magnetization loops obtained by repeated field cycling allow us to determine the pinning and "equilibrium" properties of the stable state of the vortex lattice at a given field and temperature unambiguously. The data imply the occurence of a first order phase transition from an ordered phase to a disordered vortex phase across the peak effect.Comment: 20 pages, 10 figures. Corresponding author: S. Ramakrishna

    Violent Hard X-ray Variability of Mrk 421 Observed by NuSTAR in 2013 April

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    The well studied blazar Markarian 421 (Mrk 421, zz=0.031) was the subject of an intensive multi-wavelength campaign when it flared in 2013 April. The recorded X-ray and very high energy (VHE, E>>100 GeV) γ\gamma-ray fluxes are the highest ever measured from this object. At the peak of the activity, it was monitored by the hard X-ray focusing telescope {\it Nuclear Spectroscopic Telescope Array} ({\it NuSTAR}) and {\it Swift} X-Ray Telescope (XRT). In this work, we present a detailed variability analysis of {\it NuSTAR} and {\it Swift}-XRT observations of Mrk 421 during this flaring episode. We obtained the shortest flux doubling time of 14.01±\pm5.03 minutes, which is the shortest hard X-ray (3-79 keV) variability ever recorded from Mrk 421 and is on the order of the light crossing time of the black hole's event horizon. A pattern of extremely fast variability events superposed on slowly varying flares is found in most of the {\it NuSTAR} observations. We suggest that these peculiar variability patterns may be explained by magnetic energy dissipation and reconnection in a fast moving compact emission region within the jet. Based on the fast variability, we derive a lower limit on the magnetic field strength of B0.73δ12/3ν191/3B \ge 0.73 \delta_1^{-2/3} \, \nu_{19}^{1/3}~G, where δ1\delta_1 is the Doppler factor in units of 10, and ν19\nu_{19} is the characteristic X-ray synchrotron frequency in units of 101910^{19}~Hz.Comment: 23 pages, 5 figures, 2 tables, to appear in the Astrophysical Journa
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