1,088 research outputs found
Joint Group Feature Selection and Discriminative Filter Learning for Robust Visual Object Tracking
We propose a new Group Feature Selection method for Discriminative
Correlation Filters (GFS-DCF) based visual object tracking. The key innovation
of the proposed method is to perform group feature selection across both
channel and spatial dimensions, thus to pinpoint the structural relevance of
multi-channel features to the filtering system. In contrast to the widely used
spatial regularisation or feature selection methods, to the best of our
knowledge, this is the first time that channel selection has been advocated for
DCF-based tracking. We demonstrate that our GFS-DCF method is able to
significantly improve the performance of a DCF tracker equipped with deep
neural network features. In addition, our GFS-DCF enables joint feature
selection and filter learning, achieving enhanced discrimination and
interpretability of the learned filters.
To further improve the performance, we adaptively integrate historical
information by constraining filters to be smooth across temporal frames, using
an efficient low-rank approximation. By design, specific
temporal-spatial-channel configurations are dynamically learned in the tracking
process, highlighting the relevant features, and alleviating the performance
degrading impact of less discriminative representations and reducing
information redundancy. The experimental results obtained on OTB2013, OTB2015,
VOT2017, VOT2018 and TrackingNet demonstrate the merits of our GFS-DCF and its
superiority over the state-of-the-art trackers. The code is publicly available
at https://github.com/XU-TIANYANG/GFS-DCF
Locating the gamma-ray emission site in Fermi/LAT blazars from correlation analysis between 37 GHz radio and gamma-ray light curves
We address the highly debated issue of constraining the gamma-ray emission
region in blazars from cross-correlation analysis using discrete correlation
function between radio and gamma-ray light curves. The significance of the
correlations is evaluated using two different approaches: simulating light
curves and mixed source correlations. The cross-correlation analysis yielded 26
sources with significant correlations. In most of the sources, the gamma-ray
peaks lead the radio with time lags in the range +20 and +690 days, whereas in
sources 1633+382 and 3C 345 we find the radio emission to lead the gamma rays
by -15 and -40 days, respectively. Apart from the individual source study, we
stacked the correlations of all sources and also those based on sub-samples.
The time lag from the stacked correlation is +80 days for the whole sample and
the distance travelled by the emission region corresponds to 7 pc. We also
compared the start times of activity in radio and gamma rays of the correlated
flares using Bayesian block representation. This shows that most of the flares
at both wavebands start at almost the same time, implying a co-spatial origin
of the activity. The correlated sources show more flares and are brighter in
both bands than the uncorrelated ones.Comment: 15 pages, 8 figures and 4 tables. Published in MNRAS. Online-only
Figure 6 is available as ancillary file with this submissio
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