84 research outputs found
Identification of Two categories of optically bright gamma-ray bursts
We present the results of a systematical analysis of the intrinsic optical
afterglow light curves for a complete sample of gamma-ray bursts (GRBs)
observed in the period from Feb. 1997 to Aug. 2005. These light curves are
generally well-sampled, with at least four detections in the band. The
redshifts of all the bursts in the sample are available. We derive the
intrinsic band afterglow lightcurves (luminosity versus time within the
cosmic proper rest frame) for these GRBs, and discover a fact that they
essentially follow two universal tracks after 2 hours since the GRB triggers.
The optical luminosities at 1 day show a clear bimodal distribution, peaking at
1.4*10^{46} ergs~s^{-1} for the luminous group and 5.3*10^{44} ergs~s^{-1} for
the dim group. About 75% of the GRBs are in the luminous group, and the other
25% belong to the dim group. While the luminous group has a wide range of
redshift distribution, the bursts in the dim group all appear at a redshift
lower than 1.1.Comment: 10 pages, 2 figures, emulateapj style, accepted for publication by
ApJ Letter
TiEV: The Tongji Intelligent Electric Vehicle in the Intelligent Vehicle Future Challenge of China
TiEV is an autonomous driving platform implemented by Tongji University of
China. The vehicle is drive-by-wire and is fully powered by electricity. We
devised the software system of TiEV from scratch, which is capable of driving
the vehicle autonomously in urban paths as well as on fast express roads. We
describe our whole system, especially novel modules of probabilistic perception
fusion, incremental mapping, the 1st and the 2nd planning and the overall
safety concern. TiEV finished 2016 and 2017 Intelligent Vehicle Future
Challenge of China held at Changshu. We show our experiences on the development
of autonomous vehicles and future trends
One for More: Selecting Generalizable Samples for Generalizable ReID Model
Current training objectives of existing person Re-IDentification (ReID)
models only ensure that the loss of the model decreases on selected training
batch, with no regards to the performance on samples outside the batch. It will
inevitably cause the model to over-fit the data in the dominant position (e.g.,
head data in imbalanced class, easy samples or noisy samples). %We call the
sample that updates the model towards generalizing on more data a generalizable
sample. The latest resampling methods address the issue by designing specific
criterion to select specific samples that trains the model generalize more on
certain type of data (e.g., hard samples, tail data), which is not adaptive to
the inconsistent real world ReID data distributions. Therefore, instead of
simply presuming on what samples are generalizable, this paper proposes a
one-for-more training objective that directly takes the generalization ability
of selected samples as a loss function and learn a sampler to automatically
select generalizable samples. More importantly, our proposed one-for-more based
sampler can be seamlessly integrated into the ReID training framework which is
able to simultaneously train ReID models and the sampler in an end-to-end
fashion. The experimental results show that our method can effectively improve
the ReID model training and boost the performance of ReID models
Spectral and temporal analysis of the joint Swift/BAT-Fermi/GBM GRB sample
Using the gamma-ray bursts simultaneously detected by Swift/BAT and Fermi/GBM
we performed a joint spectral and temporal analysis of the prompt emission data
and confirm the rough correlation between the BAT-band photon index Gamma_BAT
and the peak spectral energy Epeak. With the redshift known sub-sample, we
derived the isotropic gamma-ray energy E_gamma,iso and also confirm the
E_gamma,iso - Epeak,rest relation, with a larger scatter than the Amati sample
but consistent with GBM team analyses. We also compare the T_90 values derived
in the GBM band with those derived in the BAT band and find that for long GRBs
the BAT T_90 is usually longer than the GBM T_90, while for short GRBs the
trend reverses. This is consistent with the soft/hard nature of long/short GRBs
and suggests the importance of an energy-dependent temporal analysis of GRBs.Comment: 18 pages, 9 figures, 3 tables, MNRAS accepted, spectral fits updated,
conclusions unchange
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