4,457 research outputs found
A Computationally Light Pruning Strategy for Single Layer Neural Networks based on Threshold Function
Embedded machine learning relies on inference functions that can fit resource-constrained, low-power computing devices. The literature proves that single layer neural networks using threshold functions can provide a suitable trade off between classification accuracy and computational cost. In this regard, the number of neurons directly impacts both on computational complexity and on resources allocation. Thus, the present research aims at designing an efficient pruning technique that can take into account the peculiarities of the threshold function. The paper shows that feature selection criteria based on filter models can effectively be applied to neuron selection. In particular, valuable outcomes can be obtained by designing ad-hoc objective functions for the selection process. An extensive experimental campaign confirms that the proposed objective function compares favourably with state-of-the-art pruning techniques
From empty pews to empty cradles: Fertility decline among european catholics
Total fertility in the Catholic countries of Southern Europe has dropped to remarkably low rates (=1.4) despite continuing low rates female labor force participation and high historic fertility. We model three ways in which religion affects the demand for children-Through norms, market wages, and childrearing costs. We estimate these effects using new panel data on church attendance and clergy employment for 13 European countries from 1960 to 2000, spanning the Second Vatican Council (1962-65). Using nuns per capita as a proxy for service provision, we estimate fertility effects on the order of 300 to 400 children per nun. Moreover, nuns outperform priests as a predictor of fertility, suggesting that changes in childrearing costs dominate changes in theology and norms. Reduced church attendance also predicts fertility decline, but only for Catholics, not for Protestants. Service provision and attendance complement each other, a finding consistent with club models of religion
A survey on deep learning in image polarity detection: Balancing generalization performances and computational costs
Deep convolutional neural networks (CNNs) provide an effective tool to extract complex information from images. In the area of image polarity detection, CNNs are customarily utilized in combination with transfer learning techniques to tackle a major problem: the unavailability of large sets of labeled data. Thus, polarity predictors in general exploit a pre-trained CNN as the feature extractor that in turn feeds a classification unit. While the latter unit is trained from scratch, the pre-trained CNN is subject to fine-tuning. As a result, the specific CNN architecture employed as the feature extractor strongly affects the overall performance of the model. This paper analyses state-of-the-art literature on image polarity detection and identifies the most reliable CNN architectures. Moreover, the paper provides an experimental protocol that should allow assessing the role played by the baseline architecture in the polarity detection task. Performance is evaluated in terms of both generalization abilities and computational complexity. The latter attribute becomes critical as polarity predictors, in the era of social networks, might need to be updated within hours or even minutes. In this regard, the paper gives practical hints on the advantages and disadvantages of the examined architectures both in terms of generalization and computational cost
Spin Polarizabilities of the Nucleon from Polarized Low Energy Compton Scattering
As guideline for forthcoming experiments, we present predictions from Chiral
Effective Field Theory for polarized cross sections in low energy Compton
scattering for photon energies below 170 MeV, both on the proton and on the
neutron. Special interest is put on the role of the nucleon spin
polarizabilities which can be examined especially well in polarized Compton
scattering. We present a model-independent way to extract their energy
dependence and static values from experiment, interpreting our findings also in
terms of the low energy effective degrees of freedom inside the nucleon: The
polarizabilities are dominated by chiral dynamics from the pion cloud, except
for resonant multipoles, where contributions of the Delta(1232) resonance turn
out to be crucial. We therefore include it as an explicit degree of freedom. We
also identify some experimental settings which are particularly sensitive to
the spin polarizabilities.Comment: 30 pages, 19 figure
Low-energy and low-momentum representation of the virtual Compton scattering amplitude
We perform an expansion of the virtual Compton scattering amplitude for low
energies and low momenta and show that this expansion covers the transition
from the regime to be investigated in the scheduled photon electroproduction
experiments to the real Compton scattering regime.
We discuss the relation of the generalized polarizabilities of virtual
Compton scattering to the polarizabilities of real Compton scattering.Comment: 13 pages, LaTeX2e/RevTeX, no figure
Structure analysis of the virtual Compton scattering amplitude at low energies
We analyze virtual Compton scattering off the nucleon at low energies in a
covariant, model-independent formalism.
We define a set of invariant functions which, once the irregular nucleon pole
terms have been subtracted in a gauge-invariant fashion, is free of poles and
kinematical zeros.
The covariant treatment naturally allows one to implement the constraints due
to Lorentz and gauge invariance, crossing symmetry, and the discrete
symmetries.
In particular, when applied to the reaction,
charge-conjugation symmetry in combination with nucleon crossing generates four
relations among the ten originally proposed generalized polarizabilities of the
nucleon.Comment: 19 pages, LaTeX2e/RevTeX, no figures, original sections IV.-VI.
removed, to be discussed in a separate publication, none of the conclusions
change
Complete one-loop analysis of the nucleon's spin polarizabilities
We present a complete one-loop analysis of the four nucleon spin
polarizabilities in the framework of heavy baryon chiral perturbation theory.
The first non-vanishing contributions to the isovector and first corrections to
the isoscalar spin polarizabilities are calculated. No unknown parameters enter
these predictions. We compare our results to various dispersive analyses. We
also discuss the convergence of the chiral expansion and the role of the delta
isobar.Comment: 4 pp, REVTE
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Eccentricity evolution during planet-disc interaction
During the process of planet formation, the planet-disc interactions might excite (or damp) the orbital eccentricity of the planet. In this paper, we present two long (t ~ 3 Ă 10 5 orbits) numerical simulations: (a) one (with a relatively light disc, M d /M p = 0.2), where the eccentricity initially stalls before growing at later times and (b) one (with a more massive disc, M d /M p = 0.65) with fast growth and a late decrease of the eccentricity. We recover the well-known result that a more massive disc promotes a faster initial growth of the planet eccentricity. However, at late times the planet eccentricity decreases in the massive disc case, but increases in the light disc case. Both simulations show periodic eccentricity oscillations superimposed on a growing/decreasing trend and a rapid transition between fast and slow pericentre precession. The peculiar and contrasting evolution of the eccentricity of both planet and disc in the two simulations can be understood by invoking a simple toy model where the disc is treated as a second point-like gravitating body, subject to secular planet-planet interaction and eccentricity pumping/damping provided by the disc. We show how the counterintuitive result that the more massive simulation produces a lower planet eccentricity at late times can be understood in terms of the different ratios of the disc-to-planet angular momentum in the two simulations. In our interpretation, at late times the planet eccentricity can increase more in low-mass discs rather than in high-mass discs, contrary to previous claims in the literature.This work has been supported by the DISCSIM project, grant agreement 341137 funded by the European Research Council under ERC-2013-ADG. JT acknowledges support from STFC through grant ST/L000636/1. This work used the Wilkes GPU cluster at the University of Cambridge High Performance Computing Service (http://www.hpc.cam.ac.uk/), provided by Dell Inc., NVIDIA and Mellanox, and part funded by STFC with industrial sponsorship from Rolls Royce and Mitsubishi Heavy Industries. We also thank the MIAPP for hosting us for the âProtoplanetary Disks and Planet Formation and Evolutionâ topical workshop held in Munich during June 2017. All the figures were generated with the python-based package matplotlib (Hunter 2007)
Eccentricity evolution during planet–disc interaction
During the process of planet formation, the planet\u2013disc interactions might excite (or damp) the orbital eccentricity of the planet. In this paper, we present two long (t 3c 3
7 105 orbits) numerical simulations: (a) one (with a relatively light disc, Md/Mp = 0.2), where the eccentricity initially stalls before growing at later times and (b) one (with a more massive disc, Md/Mp = 0.65) with fast growth and a late decrease of the eccentricity. We recover the well-known result that a more massive disc promotes a faster initial growth of the planet eccentricity. However, at late times the planet eccentricity decreases in the massive disc case, but increases in the light disc case. Both simulations show periodic eccentricity oscillations superimposed on a growing/decreasing trend and a rapid transition between fast and slow pericentre precession. The peculiar and contrasting evolution of the eccentricity of both planet and disc in the two simulations can be understood by invoking a simple toy model where the disc is treated as a second point-like gravitating body, subject to secular planet\u2013planet interaction and eccentricity pumping/damping provided by the disc. We show how the counterintuitive result that the more massive simulation produces a lower planet eccentricity at late times can be understood in terms of the different ratios of the disc-to-planet angular momentum in the two simulations. In our interpretation, at late times the planet eccentricity can increase more in low-mass discs rather than in high-mass discs, contrary to previous claims in the literature
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