2,062 research outputs found
Temporal Relational Reasoning in Videos
Temporal relational reasoning, the ability to link meaningful transformations
of objects or entities over time, is a fundamental property of intelligent
species. In this paper, we introduce an effective and interpretable network
module, the Temporal Relation Network (TRN), designed to learn and reason about
temporal dependencies between video frames at multiple time scales. We evaluate
TRN-equipped networks on activity recognition tasks using three recent video
datasets - Something-Something, Jester, and Charades - which fundamentally
depend on temporal relational reasoning. Our results demonstrate that the
proposed TRN gives convolutional neural networks a remarkable capacity to
discover temporal relations in videos. Through only sparsely sampled video
frames, TRN-equipped networks can accurately predict human-object interactions
in the Something-Something dataset and identify various human gestures on the
Jester dataset with very competitive performance. TRN-equipped networks also
outperform two-stream networks and 3D convolution networks in recognizing daily
activities in the Charades dataset. Further analyses show that the models learn
intuitive and interpretable visual common sense knowledge in videos.Comment: camera-ready version for ECCV'1
New Hardware and Software Innovations (for Volumetric Modeling)
19 pages (includes illustrations and maps)
Continuum Variability of Deeply Embedded Protostars as a Probe of Envelope Structure
Stars may be assembled in large growth spurts, however the evidence for this
hypothesis is circumstantial. Directly studying the accretion at the earliest
phases of stellar growth is challenging because young stars are deeply embedded
in optically thick envelopes, which have spectral energy distributions that
peak in the far-IR, where observations are difficult. In this paper, we
consider the feasibility of detecting accretion outbursts from these younger
stars by investigating the timescales for how the protostellar envelope
responds to changes in the emission properties of the central source. The
envelope heats up in response to an outburst, brightening at all wavelengths
and with the emission peak moving to shorter wavelengths. The timescale for
this change depends on the time for dust grains to heat and re-emit photons and
the time required for the energy to escape the inner, optically-thick portion
of the envelope. We find that the dust response time is much shorter than the
photon propagation time and thus the timescale over which the emission varies
is set by time delays imposed by geometry. These times are hours to days near
the peak of the spectral energy distribution and weeks to months in the sub-mm.
The ideal location to quickly detect continuum variability is therefore in the
mid- to far-IR, near the peak of the spectral energy distribution, where the
change in emission amplitude is largest. Searching for variability in sub-mm
continuum emission is also feasible, though with a longer time separation and a
weaker relationship between the amount of detected emission amplitude and
change in central source luminosity. Such observations would constrain
accretion histories of protostars and would help to trace the disk/envelope
instabilities that lead to stellar growth.Comment: 25 pages, 6 figures, accepted for publication in the Astrophysical
Journa
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