18,603 research outputs found
Automatic landmark extraction from a class of hands using growing neural gas
A new method for automatically building statistical shape models from a set of training examples and in particular from a class of hands. In this method, landmark extraction is achieved using a self-organising neural network, the Growing Neural Gas (GNG), which is used to preserve the topology of any input space. Using GNG, the topological relations of a given set of deformable shapes can be learned. We describe how shape models can be built automatically by posing the correspondence problem on the behaviour of self-organising networks that are capable of adapting their topology to an input manifold, and due to their dynamic character to readapt it to the shape of the objects. Results are given for the
training set of hand outlines, showing that the proposed
method preserves accurate models
Discovery of a deep Seyfert-2 galaxy at z = 0.222 behind NGC 300
We report on the unveiling of the nature of the unidentified X-ray source
3XMM J005450.3-373849 as a Seyfert-2 galaxy located behind the spiral galaxy
NGC 300 using Hubble Space Telescope data, new spectroscopic Gemini
observations and available XMM-Newton and Chandra data. We show that the X-ray
source is positionally coincident with an extended optical source, composed by
a marginally resolved nucleus/bulge, surrounded by an elliptical disc-like
feature and two symmetrical outer rings. The optical spectrum is typical of a
Seyfert-2 galaxy redshifted to z=0.222 +/- 0.001, which confirms that the
source is not physically related to NGC 300. At this redshift the source would
be located at 909+/-4 Mpc (comoving distance in the standard model). The X-ray
spectra of the source are well-fitted by an absorbed power-law model. By tying
between the six available spectra, we found a variable index
running from ~2 in 2000-2001 years, to 1.4-1.6 in the 2005-2014
period. Alternatively, by tying , we found variable absorption columns
of N_H ~ 0.34 x cm in 2000-2001 years, and 0.54-0.75 x
cm in the 2005-2014 period. Although we cannot distinguish
between an spectral or absorption origin, from the derived unabsorbed X-ray
fluxes, we are able to assure the presence of long-term X-ray variability.
Furthermore, the unabsorbed X-ray luminosities of 0.8-2 x 10 erg
s derived in the X-ray band are in agreement with a weakly obscured
Seyfert-2 AGN at .Comment: MNRAS, accepte
Exploiting the increasing correlation of space constrained massive MIMO for CSI relaxation
In this paper, we explore low-complexity transmission in physically-constrained massive multiple-input multiple-output (MIMO) systems by means of channel state information (CSI) relaxation. In particular, we propose a strategy to take advantage of the correlation experienced by the channels of neighbour antennas when deployed in tightly packed antenna arrays. The proposed scheme is based on collecting CSI for only a subset of antennas during the pilot training stage and, subsequently, using averages of the acquired CSI for the remaining closely-spaced antennas. By doing this, the total number of radio frequency (RF) chains, for both CSI acquisition and data transmission, and the baseband signal processing are reduced, hence simplifying the overall system operation. At the same time, this impacts the quality of the channel estimation produced after the CSI acquisition process. To characterize this tradeoff, we explore the impact that the number of antennas with instantaneous CSI has on the performance, signal processing complexity, and energy efficiency of time-division duplex (TDD) systems. The analytical and simulation results presented in this paper show that the application of the proposed strategy in size-constrained antenna arrays is able to significantly enhance the energy efficiency against systems with full CSI availability, while approximately preserving their average performance
Simultaneous analysis of elastic scattering and transfer/breakup channels for the 6He+208Pb reaction at energies near the Coulomb barrier
The elastic and alpha-production channels for the 6He+208Pb reaction are
investigated at energies around the Coulomb barrier (E_{lab}=14, 16, 18, 22,
and 27 MeV). The effect of the two-neutron transfer channels on the elastic
scattering has been studied within the Coupled-Reaction-Channels (CRC) method.
We find that the explicit inclusion of these channels allows a simultaneous
description of the elastic data and the inclusive alpha cross sections at
backward angles. Three-body Continuum-Discretized Coupled-Channels (CDCC)
calculations are found to reproduce the elastic data, but not the
transfer/breakup data. The trivially-equivalent local polarization potential
(TELP) derived from the CRC and CDCC calculations are found to explain the
features found in previous phenomenological optical model calculations for this
system.Comment: 7 pages, 6 figures (replaced with updated version
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