2,642,746 research outputs found
Detect to Track and Track to Detect
Recent approaches for high accuracy detection and tracking of object
categories in video consist of complex multistage solutions that become more
cumbersome each year. In this paper we propose a ConvNet architecture that
jointly performs detection and tracking, solving the task in a simple and
effective way. Our contributions are threefold: (i) we set up a ConvNet
architecture for simultaneous detection and tracking, using a multi-task
objective for frame-based object detection and across-frame track regression;
(ii) we introduce correlation features that represent object co-occurrences
across time to aid the ConvNet during tracking; and (iii) we link the frame
level detections based on our across-frame tracklets to produce high accuracy
detections at the video level. Our ConvNet architecture for spatiotemporal
object detection is evaluated on the large-scale ImageNet VID dataset where it
achieves state-of-the-art results. Our approach provides better single model
performance than the winning method of the last ImageNet challenge while being
conceptually much simpler. Finally, we show that by increasing the temporal
stride we can dramatically increase the tracker speed.Comment: ICCV 2017. Code and models:
https://github.com/feichtenhofer/Detect-Track Results:
https://www.robots.ox.ac.uk/~vgg/research/detect-track
May Gravity detect Tsunami ?
The present gravitational wave detectors are reaching lowest metric deviation
fields able to detect galactic and extra-galactic gravitational waves, related
to Supernova explosions up to Virgo cluster. The same gravitational wave
detector are nevertheless almost able to reveal, in principle, near field
Newtonian gravitational perturbations due to fast huge mass displacements as
the ones occurring during largest Earth-Quake or Tsunami as the last on 26nd
December 2004 in Asiatic area. Virgo and Ligo detector are unfortunately
recording on high frequencies (above tens Hz) while the signal of the Tsunami
lay at much lower range (below 0.1 Hz). Nevertheless prompt gravitational near
field deformation by the Tsunami might reach the future LISA threshold
sensitivity and frequency windows if such an array is located nearby
(3000-10000) km distances. Unfortunately the present LISA system should be
located at Lagrange point too far (1.5 million km. far away). We note however
that the later continental mass rearrangement and their gravitational field
assessment on Earth must induce, for Richter Magnitude 9-like Tsunami, a
different terrestrial inertia momentum and a different principal rotation axis.
In conclusion we remind that gravitational geodetic deviation on new precise
satellites (GOCE 2006), assisted by GPS network, might nevertheless reach in
the near future the needed threshold and accuracy to reveal Tsunami by their
prompt tidal gravity field deviations . An array of such geoid detector maybe
correlated with LISA-like satellite on Earth orbits may offer the fastest alarm
system.Comment: 8 pages, 3 figures, Vulcano Conference 2005, in Chinese Journal of
Astronomy and Astrophysic
Bell's inequalities detect efficient entanglement
We review the status of Bell's inequalities in quantum information, stressing
mainly the links with quantum key distribution and distillation of
entanglement. We also prove that for all the eavesdropping attacks using one
qubit, and for a family of attacks of two qubits, acting on half of a maximally
entangled state of two qubits, the violation of a Bell inequality implies the
possibility of an efficient secret-key extraction.Comment: 9 pages, for the Proceedings of EQIS'03 (Kyoto, Sept. 2003
Did LIGO detect dark matter?
We consider the possibility that the black-hole (BH) binary detected by LIGO
may be a signature of dark matter. Interestingly enough, there remains a window
for masses where
primordial black holes (PBHs) may constitute the dark matter. If two BHs in a
galactic halo pass sufficiently close, they radiate enough energy in
gravitational waves to become gravitationally bound. The bound BHs will rapidly
spiral inward due to emission of gravitational radiation and ultimately merge.
Uncertainties in the rate for such events arise from our imprecise knowledge of
the phase-space structure of galactic halos on the smallest scales. Still,
reasonable estimates span a range that overlaps the Gpc yr
rate estimated from GW150914, thus raising the possibility that LIGO has
detected PBH dark matter. PBH mergers are likely to be distributed spatially
more like dark matter than luminous matter and have no optical nor neutrino
counterparts. They may be distinguished from mergers of BHs from more
traditional astrophysical sources through the observed mass spectrum, their
high ellipticities, or their stochastic gravitational wave background. Next
generation experiments will be invaluable in performing these tests.Comment: 5 pages, 2 figures, updated to match version published in PR
Detect Spinons via Spin Transport
Existence of spinons is the defining property of quantum spin liquids. These
exotic excitations have (fractionalized) spin quantum number and no electric
charge, and have been proposed to form Fermi surfaces in the recently
discovered organic spin liquid candidates. However direct probes for them are
still lacking. In this paper we propose to experimentally identify the spinons
by measuring the spin current flowing through the spin liquid candidate
materials, which would be a direct test for the existence of spin-carrying
mobile excitations. By the nonequilibrium Green function technique we evaluate
the spin current through the interface between a Mott insulator and a metal
under a spin bias, and find that different kinds of Mott insulators, including
quantum spin liquids, can be distinguished by different relations between the
spin bias and spin current, In the end we will also discuss relations to
experiments and estimate experimentally relevant parameters.Comment: 7 pages with appendix, 3 figure
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