28,651 research outputs found
3D-BEVIS: Bird's-Eye-View Instance Segmentation
Recent deep learning models achieve impressive results on 3D scene analysis
tasks by operating directly on unstructured point clouds. A lot of progress was
made in the field of object classification and semantic segmentation. However,
the task of instance segmentation is less explored. In this work, we present
3D-BEVIS, a deep learning framework for 3D semantic instance segmentation on
point clouds. Following the idea of previous proposal-free instance
segmentation approaches, our model learns a feature embedding and groups the
obtained feature space into semantic instances. Current point-based methods
scale linearly with the number of points by processing local sub-parts of a
scene individually. However, to perform instance segmentation by clustering,
globally consistent features are required. Therefore, we propose to combine
local point geometry with global context information from an intermediate
bird's-eye view representation.Comment: camera-ready version for GCPR '1
An exactly solvable phase transition model: generalized statistics and generalized Bose-Einstein condensation
In this paper, we present an exactly solvable phase transition model in which
the phase transition is purely statistically derived. The phase transition in
this model is a generalized Bose-Einstein condensation. The exact expression of
the thermodynamic quantity which can simultaneously describe both gas phase and
condensed phase is solved with the help of the homogeneous Riemann-Hilbert
problem, so one can judge whether there exists a phase transition and determine
the phase transition point mathematically rigorously. A generalized statistics
in which the maximum occupation numbers of different quantum states can take on
different values is introduced, as a generalization of Bose-Einstein and
Fermi-Dirac statistics.Comment: 17 pages, 2 figure
Automatic summarization of rushes video using bipartite graphs
In this paper we present a new approach for automatic summarization of rushes video. Our approach is composed of three main steps. First, based on a temporal segmentation, we filter sub-shots with low information content not likely to be useful in a summary. Second, a method using maximal matching in a bipartite graph is adapted to measure similarity between the remaining shots and to minimize inter-shot redundancy by removing repetitive retake shots common in rushes content. Finally, the presence of faces and the motion intensity are characterised in each sub-shot. A measure of how representative the sub-shot is in the context of the overall video is then proposed. Video summaries composed of keyframe slideshows are then generated. In order to evaluate the effectiveness of this approach we re-run the evaluation carried out by the TREC, using the same dataset and evaluation metrics used in the TRECVID video summarization task in 2007 but with our own assessors. Results show that our approach leads to a significant improvement in terms of the fraction of the TRECVID summary ground truth included and is competitive with other approaches in TRECVID 2007
Neutralino dark matter stars can not exist
Motivated by the recent "Cosmos Project" observation of dark-matter
concentrations with no ordinary matter in the same place, we study the question
of the existence of compact objects made of pure dark matter. We assume that
the dark matter is neutralino, and compare its elastic and annihilation cross
sections. We find that the two cross sections are of the same order of
magnitude. This result has a straightforward and important consequence that
neutralinos comprising a compact object can not achieve thermal equilibrium. To
substantiate our arguments, by solving Oppenheimer-Volkoff equation we
constructed a model of the star made of pure neutralinos. We explicitly showed
that the condition for the thermal equilibrium supported by the Fermi pressure
is never fulfilled inside the star. This neutralino state can not be described
by the Fermi-Dirac distribution. Thus, a stable neutralino star, which is
supported by the Fermi pressure, can not exist. We also estimated that a stable
star can not contain more than a few percents of neutralinos, most of the mass
must be in the form of the standard model particles.Comment: published in JHE
Analytical and numerical studies of central galactic outflows powered by tidal disruption events -- a model for the Fermi bubbles?
Capture and tidal disruption of stars by the supermassive black hole in the
Galactic center (GC) should occur regularly. The energy released and dissipated
by this processes will affect both the ambient environment of the GC and the
Galactic halo. A single star of super-Eddington eruption generates a subsonic
out ow with an energy release of more than erg, which still is not
high enough to push shock heated gas into the halo. Only routine tidal
disruption of stars near the GC can provide enough cumulative energy to form
and maintain large scale structures like the Fermi Bubbles. The average rate of
disruption events is expected to be ~ yr, providing
the average power of energy release from the GC into the halo of dW/dt ~
3*10 erg/s, which is needed to support the Fermi Bubbles. The GC black
hole is surrounded by molecular clouds in the disk, but their overall mass and
filling factor is too low to stall the shocks from tidal disruption events
significantly. The de facto continuous energy injection on timescales of Myr
will lead to the propagation of strong shocks in a density stratified Galactic
halo and thus create elongated bubble-like features, which are symmetric to the
Galactic midplane.Comment: 11 pages, 5 figures. The title and abstract have been changed.
Accepted by Astrophysical Journa
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