57 research outputs found
Detection of out-of-distribution samples using binary neuron activation patterns
Deep neural networks (DNN) have outstanding performance in various
applications. Despite numerous efforts of the research community,
out-of-distribution (OOD) samples remain a significant limitation of DNN
classifiers. The ability to identify previously unseen inputs as novel is
crucial in safety-critical applications such as self-driving cars, unmanned
aerial vehicles, and robots. Existing approaches to detect OOD samples treat a
DNN as a black box and evaluate the confidence score of the output predictions.
Unfortunately, this method frequently fails, because DNNs are not trained to
reduce their confidence for OOD inputs. In this work, we introduce a novel
method for OOD detection. Our method is motivated by theoretical analysis of
neuron activation patterns (NAP) in ReLU-based architectures. The proposed
method does not introduce a high computational overhead due to the binary
representation of the activation patterns extracted from convolutional layers.
The extensive empirical evaluation proves its high performance on various DNN
architectures and seven image datasets
Combating noisy labels in object detection datasets
The quality of training datasets for deep neural networks is a key factor
contributing to the accuracy of resulting models. This is even more important
in difficult tasks such as object detection. Dealing with errors in these
datasets was in the past limited to accepting that some fraction of examples is
incorrect or predicting their confidence and assigning appropriate weights
during training. In this work, we propose a different approach. For the first
time, we extended the confident learning algorithm to the object detection
task. By focusing on finding incorrect labels in the original training
datasets, we can eliminate erroneous examples in their root. Suspicious
bounding boxes can be re-annotated in order to improve the quality of the
dataset itself, thus leading to better models without complicating their
already complex architectures. We can effectively point out 99\% of
artificially disturbed bounding boxes with FPR below 0.3. We see this method as
a promising path to correcting well-known object detection datasets.Comment: 10 pages, 8 figures, submitted to CVPR 2023 Conferenc
Constraining the near-core rotation of the gamma Doradus star 43 Cygni using BRITE-Constellation data
Photometric time series of the Dor star 43 Cyg obtained with the
BRITE-Constellation nano-satellites allow us to study its pulsational
properties in detail and to constrain its interior structure. We aim to find a
g-mode period spacing pattern that allows us to determine the near-core
rotation rate of 43 Cyg and redetermine the star's fundamental atmospheric
parameters and chemical composition. We conducted a frequency analysis using
the 156-days long data set obtained with the BRITE-Toronto satellite and
employed a suite of MESA/GYRE models to derive the mode identification,
asymptotic period spacing and near-core rotation rate. We also used
high-resolution, high signal-to-noise ratio spectroscopic data obtained at the
1.2m Mercator telescope with the HERMES spectrograph to redetermine the
fundamental atmospheric parameters and chemical composition of 43 Cyg using the
software Spectroscopy Made Easy (SME). We detected 43 intrinsic pulsation
frequencies and identified 18 of them to be part of a period spacing pattern
consisting of prograde dipole modes with an asymptotic period spacing of . The near-core rotation rate was
determined to be . The
atmosphere of 43 Cyg shows solar chemical composition at an effective
temperature of 7150 150 K, a log g of 4.2 0.6 dex and a projected
rotational velocity, , of 44 4 kms. The morphology
of the observed period spacing patterns shows indications of the presence of a
significant chemical gradient in the stellar interior.Comment: 9 pages, 8 figures, accepted by A&
Investigating the origin of optical flares from the TeV blazar S4 0954+65
Aims. We aim to investigate the extreme variability properties of the TeV
blazar S4 0954+65 using optical photometric and polarisation observations
carried out between 2017 and 2023 using three ground-based telescopes.
Methods. We examined an extensive dataset comprised of 138 intraday
(observing duration shorter than a day) light curves (LCs) of S4 0954+65 for
flux, spectral, and polarisation variations on diverse timescales. For the
variable LCs, we computed the minimum variability timescales. We investigated
flux-flux correlations and colour variations to look for spectral variations on
long (several weeks to years) timescales. Additionally, we looked for
connections between optical R-band flux and polarisation degree.
Results. We found significant variations in 59 out of 138 intraday LCs. We
detected a maximum change of 0.580.11 in V-band magnitude within
2.64 h and a corresponding minimum variability timescale of
18.214.87 mins on 2017 March 25. During the course of our observing
campaign, the source brightness changed by 4 magnitudes in V and R bands;
however, we did not find any strong spectral variations. The slope of the
relative spectral energy distribution was 1.370.04. The degree of
polarisation varied from 3% to 39% during our monitoring. We observed a
change of 120 degrees in polarisation angle (PA) within 3 h on 2022
April 13. No clear correlation was found between optical flux and the degree of
polarisation.
Conclusions. The results of our optical flux, colour, and polarisation study
provide hints that turbulence in the relativistic jet could be responsible for
the intraday optical variations in the blazar S4 0954+65. However, the
long-term flux variations may be caused by changes in the Doppler factor.Comment: 9 pages, 10 figures, 4 tables, 4 appendix, Astronomy & Astrophysics
journal (in press
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