702 research outputs found
Evolutionary Algorithms for Community Detection in Continental-Scale High-Voltage Transmission Grids
Symmetry is a key concept in the study of power systems, not only because the admittance and Jacobian matrices used in power flow analysis are symmetrical, but because some previous studies have shown that in some real-world power grids there are complex symmetries. In order to investigate the topological characteristics of power grids, this paper proposes the use of evolutionary algorithms for community detection using modularity density measures on networks representing supergrids in order to discover densely connected structures. Two evolutionary approaches (generational genetic algorithm, GGA+, and modularity and improved genetic algorithm, MIGA) were applied. The results obtained in two large networks representing supergrids (European grid and North American grid) provide insights on both the structure of the supergrid and the topological differences between different regions. Numerical and graphical results show how these evolutionary approaches clearly outperform to the well-known Louvain modularity method. In particular, the average value of modularity obtained by GGA+ in the European grid was 0.815, while an average of 0.827 was reached in the North American grid. These results outperform those obtained by MIGA and Louvain methods (0.801 and 0.766 in the European grid and 0.813 and 0.798 in the North American grid, respectively)
Simple Method for the Elimination of Polarization Noise in BOTDA Using Balanced Detection and Orthogonal Probe Sidebands
Polarization noise arises in Brillouin optical timedomain
analysis due to the strong polarization sensitivity of stimulated
Brillouin scattering. To avoid this noise, it turns out to be
indispensable to perform some kind of polarization scrambling,
either in the pump pulse, the probe signal or both. This is usually
achieved using polarization scrambling/switching systems, which,
being mechanical, tend to be not as robust as it would be desirable.
In this paper, we propose a completely passive system,with no moving
parts, to eliminate polarization noise in a BOTDA. It is based
on the use of passive depolarization of the pump pulse together
with balanced detection among orthogonally polarized Stokes and
anti-Stokes bands of the probe signal. The setup requires no alignment
readjustment over time and provides a performance similar
to a conventional BOTDA using scrambler.Ministerio de Economía y CompetitividadComunidad de MadridEuropean Commissio
Balanced detection in Brillouin optical time domain analysis
We propose the use of balanced detection in Brillouin Optical Time Domain Analysis (BOTDA) sensors. Balanced detection can be effectively accomplished among the Stokes and anti-Stokes bands in the probe signal. This type of detection leads to a doubling of the trace amplitude and at least a √2 increase in signal to noise ratio over the conventional configuration. Moreover, it leads to a complete cancellation of the common-mode noise in the probe signal, including relative intensity noise in Raman-assisted configurations. We show all these benefits both theoretically and experimentallyMinisterio de Ciencia e InnovaciónComunidad de MadridEuropean Commissio
Estimación de la localización de un vehículo usando un sistema de visión por computador
El proyecto presentado hace parte de un proyecto más grande conocido como el Proyecto "Optimus" del Grupo de Investigación Sirius de la Universidad Tecnológica de Pereira. "Optimus" busca darle a un automóvil completa autonomía para que se desplace por ambientes rurales o urbanos sin ayuda humana. En este momento el proyecto "Optimus" no cuenta con un mecanismo de localización válido que le permita conocer su ubicación y orientación en un marco de referencia determinado con su ciente con fiabilidad, debido a que dispone únicamente de la estimación de la localización provista por un GPS y una unidad de medida inercial, la cual no es lo suficientemente adecuada para un vehículo autónomo
Unexpected non-local effects in dual-probe-sideband BOTDA
Until now, non-local effects in dual-probe-sideband Brillouin Optical Time Domain Analysis (BOTDA) systems have been considered negligible if the probe power is below the Stimulated Brillouin Scattering (SBS) threshold. In this paper, we show the appearance of non-local effects even below the SBS threshold. The pump pulse experiences a frequencydependent spectral deformation that affects the readout process differently in the gain and loss configurations. The main conclusion of our study is that the measurements in gain configuration are more robust to this non-local effect than the loss configuration. These results are of particular interest for manufacturers of long-range BOTDA systems.European CommissionMinisterio de Economía y CompetitividadComunidad de Madri
Non-local effects in dual-probe-sideband Brillouin optical time domain analysis
According to recent models, non-local effects in dual-probesideband
Brillouin Optical Time Domain Analysis (BOTDA) systems
should be essentially negligible whenever the probe power is below the
Stimulated Brillouin Scattering (SBS) threshold. This paper shows that
actually there appear non-local effects in this type of systems before the
SBS threshold. To explain these effects it is necessary to take into account a
full spectral description of the SBS process. The pump pulse experiences a
frequency-dependent spectral deformation that affects the readout process
differently in the gain and loss configurations. This paper provides a simple
analytical model of this phenomenon, which is validated against compelling
experimental data, showing good agreement. The main conclusion of our
study is that the measurements in gain configuration are more robust to this
non-local effect than the loss configuration. Experimental and theoretical
results show that, for a total probe wave power of ~1 mW (500 μW on each
sideband), there is an up-shifting of ~1 MHz in the Brillouin Frequency
Shift (BFS) retrieved from the Brillouin Loss Spectrum, whereas the BFS
extracted from the measured Brillouin Gain Spectrum is up-shifted only
~0.6 MHz. These results are of particular interest for manufacturers of longrange
BOTDA systems.European CommissionMinisterio de Economía y CompetitividadComunidad de MadridUniversidad de Alcal
Nota preliminar sobre la estratigrafía y el contenido en conodontos del Prídolí-Lochkoviense inferior en la unidad de els Castells (Pirineo central)
Instituto Geológico Minero de España; DGE PB95-104
Therapeutic potential of melatonin counteracting chemotherapy-induced toxicity in breast cancer patients: a systematic review
The purpose of this systematic review is to provide an overview of the existing knowledge on the therapeutic potential of melatonin to counteract the undesirable effects of chemotherapy in breast cancer patients. To this aim, we summarized and critically reviewed preclinical- and clinical-related evidence according to the PRISMA guidelines. Additionally, we developed an extrapolation of melatonin doses in animal studies to the human equivalent doses (HEDs) for randomized clinical trials (RCTs) with breast cancer patients. For the revision, 341 primary records were screened, which were reduced to 8 selected RCTs that met the inclusion criteria. We assembled the evidence drawn from these studies by analyzing the remaining gaps and treatment efficacy and suggested future translational research and clinical trials. Overall, the selected RCTs allow us to conclude that melatonin combined with standard chemotherapy lines would derive, at least, a better quality of life for breast cancer patients. Moreover, regular doses of 20 mg/day seemed to increase partial response and 1-year survival rates. Accordingly, this systematic review leads us to draw attention to the need for more RCTs to provide a comprehensive view of the promising actions of melatonin in breast cancer and, given the safety profile of this molecule, adequate translational doses should be established in further RCTs
Limits of BOTDA Range Extension Techniques
Brillouin-based temperature and strain sensors
have attracted great attention of both the academic and
industrial sectors in the past few decades due to their ability to
perform distributed measurements. Particularly, Brillouin
Optical Time Domain Analysis (BOTDA) systems have been
applied in many different scenarios, proving particularly useful
in those requiring especially wide coverage ranging extremely
long distances, such as in civil structure monitoring, energy
transportation or environmental applications. The extension of
the measuring range in these sensors has therefore become one of
the main areas of research and development around BOTDA. To
do so, it is necessary to increase the Signal to Noise Ratio (SNR)
of the retrieved signal. So far, several techniques have been
applied in order to achieve this goal, such as pre-amplification
before detection, pulse coding or Raman amplification. Here, we
analyze these techniques in terms of their performance limits and
provide guidelines that can assist in finding out which is the best
configuration to break current range limitations. Our analysis is
based on physical arguments as well as current literature results.European CommissionMinisterio de Economía y CompetitividadUniversidad de Alcal
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