10,112 research outputs found
Effective perihelion advance and potentials in a conformastatic background with magnetic field
An Exact solution of the Einstein-Maxwell field equations for a
conformastatic metric with magnetized sources is study. In this context,
effective potential are studied in order to understand the dynamics of the
magnetic field in galaxies. We derive the equations of motion for neutral and
charged particles in a spacetime background characterized by this class of
solutions. In this particular case, we investigate the main physical properties
of equatorial circular orbits and related effective potentials. In addition, we
obtain an effective analytic expression for the perihelion advance of test
particles. Our theoretical predictions are compared with the observational data
calibrated with the ephemerides of the planets of the Solar system and the Moon
(EPM2011). We show that, in general, the magnetic punctual mass predicts values
that are in better agreement with observations than the values predicted in
Einstein gravity alone.Comment: 11 pages, 6 figures. arXiv admin note: substantial text overlap with
arXiv:1601.0074
COSMOSOMAS Observations of the CMB and Galactic Foregrounds at 11 GHz: Evidence for anomalous microwave emission at high Galactic Latitude
We present observations with the new 11 GHz radiometer of the COSMOSOMAS
experiment at the Teide Observatory (Tenerife). The sky region between 0 deg <=
RA <= 360 deg and 26 deg <= DEC 49 deg (ca. 6500 square degrees) was observed
with an angular resolution of 0.9 deg. Two orthogonal independent channels in
the receiving system measured total power signals from linear polarizations
with a 2 GHz bandwidth. Maps with an average sensitivity of 50 microK per beam
have been obtained for each channel. At high Galactic latitude (|b|>30deg) the
11 GHz data are found to contain the expected cosmic microwave background as
well as extragalactic radiosources, galactic synchrotron and free-free
emission, and a dust-correlated component which is very likely of galactic
origin. At the angular scales allowed by the window function of the experiment,
the dust-correlated component presents an amplitude \Delta T aprox. 9-13 microK
while the CMB signal is of order 27 microK. The spectral behaviour of the
dust-correlated signal is examined in the light of previous COSMOSOMAS data at
13-17 GHz and WMAP data at 22-94 GHz in the same sky region. We detect a
flattening in the spectral index of this signal below 20 GHz which rules out
synchrotron radiation as being responsible for the emission. This anomalous
dust emission can be described by a combination of free-free emission and
spinning dust models with a flux density peaking around 20 GHz.Comment: 17 pages, 10 tables, 20 figures. Details on the COSMOSOMAS experiment
can be found at http://www.iac.es/project/cmb/cosmosomas
Comprehensive review of vision-based fall detection systems
Vision-based fall detection systems have experienced fast development over the last years. To determine the course of its evolution and help new researchers, the main audience of this paper, a comprehensive revision of all published articles in the main scientific databases regarding this area during the last five years has been made. After a selection process, detailed in the Materials and Methods Section, eighty-one systems were thoroughly reviewed. Their characterization and classification techniques were analyzed and categorized. Their performance data were also studied, and comparisons were made to determine which classifying methods best work in this field. The evolution of artificial vision technology, very positively influenced by the incorporation of artificial neural networks, has allowed fall characterization to become more resistant to noise resultant from illumination phenomena or occlusion. The classification has also taken advantage of these networks, and the field starts using robots to make these systems mobile. However, datasets used to train them lack real-world data, raising doubts about their performances facing real elderly falls. In addition, there is no evidence of strong connections between the elderly and the communities of researchers
On Grid Codes
If is finite alphabet for , the Manhattan distance is
defined in . A grid code is introduced as a subset of
. Alternative versions of the Hamming and
Gilbert-Varshamov bounds are presented for grid codes. If is a cyclic
group for , some bounds for the minimum Manhattan distance of codes
that are cyclic subgroups of are determined in terms of
their minimum Hamming and Lee distances. Examples illustrating the main results
are provided
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