12,763 research outputs found
Near-IR internetwork spectro-polarimetry at different heliocentric angles
The analysis of near infrared spectropolarimetric data at the internetwork at
different regions on the solar surface could offer constraints to reject
current modeling of these quiet areas.
We present spectro-polarimetric observations of very quiet regions for
different values of the heliocentric angle for the Fe I lines at 1.56 micron,
from disc centre to positions close to the limb. The spatial resolution of the
data is 0.7-1". We analyze direct observable properties of the Stokes profiles
as the amplitude of circular and linear polarization as well as the total
degree of polarization. Also the area and amplitude asymmetries are studied.
We do not find any significant variation of the properties of the
polarimetric signals with the heliocentric angle. This means that the magnetism
of the solar internetwork remains the same regardless of the position on the
solar disc. This observational fact discards the possibility of modeling the
internetwork as a Network-like scenario. The magnetic elements of internetwork
areas seem to be isotropically distributed when observed at our spatial
resolution.Comment: Sorry, this is the version with the correct bibliography. Some
figures had to be compressed. Accepted for publication in A&
Optimized LTE Data Transmission Procedures for IoT: Device Side Energy Consumption Analysis
The efficient deployment of Internet of Things (IoT) over cellular networks,
such as Long Term Evolution (LTE) or the next generation 5G, entails several
challenges. For massive IoT, reducing the energy consumption on the device side
becomes essential. One of the main characteristics of massive IoT is small data
transmissions. To improve the support of them, the 3GPP has included two novel
optimizations in LTE: one of them based on the Control Plane (CP), and the
other on the User Plane (UP). In this paper, we analyze the average energy
consumption per data packet using these two optimizations compared to
conventional LTE Service Request procedure. We propose an analytical model to
calculate the energy consumption for each procedure based on a Markov chain. In
the considered scenario, for large and small Inter-Arrival Times (IATs), the
results of the three procedures are similar. While for medium IATs CP reduces
the energy consumption per packet up to 87% due to its connection release
optimization
An upgraded drift-diffusion model for evaluating the carrier lifetimes in radiation-damaged semiconductor detectors
A near-IR line of Mn I as a diagnostic tool of the average magnetic energy in the solar photosphere
We report on spectropolarimetric observations of a near-IR line of Mn I
located at 15262.702 A whose intensity and polarization profiles are very
sensitive to the presence of hyperfine structure. A theoretical investigation
of the magnetic sensitivity of this line to the magnetic field uncovers several
interesting properties. The most important one is that the presence of strong
Paschen-Back perturbations due to the hyperfine structure produces an intensity
line profile whose shape changes according to the absolute value of the
magnetic field strength. A line ratio technique is developed from the intrinsic
variations of the line profile. This line ratio technique is applied to
spectropolarimetric observations of the quiet solar photosphere in order to
explore the probability distribution function of the magnetic field strength.
Particular attention is given to the quietest area of the observed field of
view, which was encircled by an enhanced network region. A detailed theoretical
investigation shows that the inferred distribution yields information on the
average magnetic field strength and the spatial scale at which the magnetic
field is organized. A first estimation gives ~250 G for the mean field strength
and a tentative value of ~0.45" for the spatial scale at which the observed
magnetic field is horizontally organized.Comment: 42 pages, 17 figures, accepted for publication in the Astrophysical
Journal. Figures 1 and 9 are in JPG forma
Channel Gain Cartography via Mixture of Experts
In order to estimate the channel gain (CG) between the locations of an
arbitrary transceiver pair across a geographic area of interest, CG maps can be
constructed from spatially distributed sensor measurements. Most approaches to
build such spectrum maps are location-based, meaning that the input variable to
the estimating function is a pair of spatial locations. The performance of such
maps depends critically on the ability of the sensors to determine their
positions, which may be drastically impaired if the positioning pilot signals
are affected by multi-path channels. An alternative location-free approach was
recently proposed for spectrum power maps, where the input variable to the maps
consists of features extracted from the positioning signals, instead of
location estimates. The location-based and the location-free approaches have
complementary merits. In this work, apart from adapting the location-free
features for the CG maps, a method that can combine both approaches is proposed
in a mixture-of-experts framework.Comment: 5 pages, 2 figures, accepted in Globecom 202
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