26,764 research outputs found
Photo Enhancement On Mobile Devices Using Deep Neural Networks
In recent years, the return of the usage of Artificial Neural Networks has lead to the
greatest improvements in the field of Artificial Intelligence, due to the huge diversity
of different applications that deep learning models has in a large variety of research
fields, and also the evolution of information processing systems capacity. This thesis
aims to study which deep neural networks models are most suitable for photo
enhancement, to generate images with certain desired characteristics.
Model selection has been done by comparing the both supervised, Convolutional
Neural Networks, and unsupervised models, Generative Adversarial Networks. It has
been demonstrated that Generative Adversarial Networks have great potential by
showing results that compete with the state of the art. The chosen model is a
Generative Adversarial model which outperforms the rest in terms of a combination
of enhancement quality and time taken in the process. Moreover, since the model is
compatible with mobile devices it has been integrated and evaluated in a BQ
smartphone, to proof its viability on mobile devices.Doble Grado en Ingeniería Informática y Administración de Empresa
A Precise Water Abundance Measurement for the Hot Jupiter WASP-43b
The water abundance in a planetary atmosphere provides a key constraint on
the planet's primordial origins because water ice is expected to play an
important role in the core accretion model of planet formation. However, the
water content of the Solar System giant planets is not well known because water
is sequestered in clouds deep in their atmospheres. By contrast, short-period
exoplanets have such high temperatures that their atmospheres have water in the
gas phase, making it possible to measure the water abundance for these objects.
We present a precise determination of the water abundance in the atmosphere of
the 2 short-period exoplanet WASP-43b based on thermal
emission and transmission spectroscopy measurements obtained with the Hubble
Space Telescope. We find the water content is consistent with the value
expected in a solar composition gas at planetary temperatures (0.4-3.5x solar
at 1 confidence). The metallicity of WASP-43b's atmosphere suggested
by this result extends the trend observed in the Solar System of lower metal
enrichment for higher planet masses.Comment: Accepted to ApJL; this version contains three supplemental figures
that are not included in the published paper. See also our companion paper
"Thermal structure of an exoplanet atmosphere from phase-resolved emission
spectroscopy" by Stevenson et a
Phase-sensitive detection of Bragg scattering at 1D optical lattices
We report on the observation of Bragg scattering at 1D atomic lattices. Cold
atoms are confined by optical dipole forces at the antinodes of a standing wave
generated by the two counter-propagating modes of a laser-driven high-finesse
ring cavity. By heterodyning the Bragg-scattered light with a reference beam,
we obtain detailed information on phase shifts imparted by the Bragg scattering
process. Being deep in the Lamb-Dicke regime, the scattered light is not
broadened by the motion of individual atoms. In contrast, we have detected
signatures of global translatory motion of the atomic grating.Comment: 4 pages, 4 figure
PMU-Based ROCOF Measurements: Uncertainty Limits and Metrological Significance in Power System Applications
In modern power systems, the Rate-of-Change-of-Frequency (ROCOF) may be
largely employed in Wide Area Monitoring, Protection and Control (WAMPAC)
applications. However, a standard approach towards ROCOF measurements is still
missing. In this paper, we investigate the feasibility of Phasor Measurement
Units (PMUs) deployment in ROCOF-based applications, with a specific focus on
Under-Frequency Load-Shedding (UFLS). For this analysis, we select three
state-of-the-art window-based synchrophasor estimation algorithms and compare
different signal models, ROCOF estimation techniques and window lengths in
datasets inspired by real-world acquisitions. In this sense, we are able to
carry out a sensitivity analysis of the behavior of a PMU-based UFLS control
scheme. Based on the proposed results, PMUs prove to be accurate ROCOF meters,
as long as the harmonic and inter-harmonic distortion within the measurement
pass-bandwidth is scarce. In the presence of transient events, the
synchrophasor model looses its appropriateness as the signal energy spreads
over the entire spectrum and cannot be approximated as a sequence of
narrow-band components. Finally, we validate the actual feasibility of
PMU-based UFLS in a real-time simulated scenario where we compare two different
ROCOF estimation techniques with a frequency-based control scheme and we show
their impact on the successful grid restoration.Comment: Manuscript IM-18-20133R. Accepted for publication on IEEE
Transactions on Instrumentation and Measurement (acceptance date: 9 March
2019
Mach Bands: How Many Models are Possible? Recent Experiemental Findings and Modeling Attempts
Mach bands are illusory bright and dark bands seen where a luminance plateau meets a ramp, as in half-shadows or penumbras. A tremendous amount of work has been devoted to studying the psychophysics and the potential underlying neural circuitry concerning this phenomenon. A number of theoretical models have also been proposed, originating in the seminal studies of Mach himself. The present article reviews the main experimental findings after 1965 and the main recent theories of early vision that have attempted to discount for the effect. It is shown that the different theories share working principles and can be grouped in three clsses: a) feature-based; b) rule-based; and c) filling-in. In order to evaluate individual proposals it is necessary to consider them in the larger picture of visual science and to determine how they contribute to the understanding of vision in general.Air Force Office of Scientific Research (F49620-92-J-0334); Office of Naval Research (N00014-J-4100); COPPE/UFRJ, Brazi
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