18,135 research outputs found
Evaluation of normalisation methods for uniaxial bias extension tests on engineering fabrics
An investigation has been conducted to evaluate the performance of normalisation methods for the uniaxial bias extension test. The predictions of two published theories for rate-independent behaviour are examined and a third heuristic method is proposed. Using hypothetical test data, the predictions of the two rate-independent theories are shown to be equivalent for specimen dimensions of high aspect ratio; in this case the predictions can be well-represented using the simple heuristic formula. The predictions diverge for specimens of low aspect ratio, when specimens are sheared to very high shear angles. In order to examine the significance of this divergence on real data, results from tests on several different engineering fabrics are normalised. Differences in the predictions of the normalisation methods are observed and the question of the significance of these differences is discussed. The paper also examines the applicability of rate-independent theory for normalising rate-dependent materials
A staggered fermion chain with supersymmetry on open intervals
A strongly-interacting fermion chain with supersymmetry on the lattice and
open boundary conditions is analysed. The local coupling constants of the model
are staggered, and the properties of the ground states as a function of the
staggering parameter are examined. In particular, a connection between certain
ground-state components and solutions of non-linear recursion relations
associated with the Painlev\'e VI equation is conjectured. Moreover, various
local occupation probabilities in the ground state have the so-called
scale-free property, and allow for an exact resummation in the limit of
infinite system size.Comment: 21 pages, no figures; v2: typos correcte
The AMBRE Project: Stellar parameterisation of the ESO:FEROS archived spectra
The AMBRE Project is a collaboration between the European Southern
Observatory (ESO) and the Observatoire de la Cote d'Azur (OCA) that has been
established in order to carry out the determination of stellar atmospheric
parameters for the archived spectra of four ESO spectrographs.
The analysis of the FEROS archived spectra for their stellar parameters
(effective temperatures, surface gravities, global metallicities, alpha element
to iron ratios and radial velocities) has been completed in the first phase of
the AMBRE Project. From the complete ESO:FEROS archive dataset that was
received, a total of 21551 scientific spectra have been identified, covering
the period 2005 to 2010. These spectra correspond to ~6285 stars.
The determination of the stellar parameters was carried out using the stellar
parameterisation algorithm, MATISSE (MATrix Inversion for Spectral SynthEsis),
which has been developed at OCA to be used in the analysis of large scale
spectroscopic studies in galactic archaeology. An analysis pipeline has been
constructed that integrates spectral reduction and radial velocity correction
procedures with MATISSE in order to automatically determine the stellar
parameters of the FEROS spectra.
Stellar atmospheric parameters (Teff, log g, [M/H] and [alpha/Fe]) were
determined for 6508 (30.2%) of the FEROS archived spectra (~3087 stars). Radial
velocities were determined for 11963 (56%) of the archived spectra. 2370 (11%)
spectra could not be analysed within the pipeline. 12673 spectra (58.8%) were
analysed in the pipeline but their parameters were discarded based on quality
criteria and error analysis determined within the automated process. The
majority of these rejected spectra were found to have broad spectral features
indicating that they may be hot and/or fast rotating stars, which are not
considered within the adopted reference synthetic spectra grid of FGKM stars.Comment: 28 pages, 28 figures, 9 table
Improved +He potentials by inversion, the tensor force and validity of the double folding model
Improved potential solutions are presented for the inverse scattering problem
for +He data. The input for the inversions includes both the data of
recent phase shift analyses and phase shifts from RGM coupled-channel
calculations based on the NN Minnesota force. The combined calculations provide
a more reliable estimate of the odd-even splitting of the potentials than
previously found, suggesting a rather moderate role for this splitting in
deuteron-nucleus scattering generally. The approximate parity-independence of
the deuteron optical potentials is shown to arise from the nontrivial
interference between antisymmetrization and channel coupling to the deuteron
breakup channels. A further comparison of the empirical potentials established
here and the double folding potential derived from the M3Y effective NN force
(with the appropriate normalisation factor) reveals strong similarities. This
result supports the application of the double folding model, combined with a
small Majorana component, to the description even of such a loosely bound
projectile as the deuteron. In turn, support is given for the application of
iterative-perturbative inversion in combination with the double folding model
to study fine details of the nucleus-nucleus potential. A -He tensor
potential is also derived to reproduce correctly the negative Li quadrupole
moment and the D-state asymptotic constant.Comment: 22 pages, 12 figures, in Revte
Deep Learning for Vanishing Point Detection Using an Inverse Gnomonic Projection
We present a novel approach for vanishing point detection from uncalibrated
monocular images. In contrast to state-of-the-art, we make no a priori
assumptions about the observed scene. Our method is based on a convolutional
neural network (CNN) which does not use natural images, but a Gaussian sphere
representation arising from an inverse gnomonic projection of lines detected in
an image. This allows us to rely on synthetic data for training, eliminating
the need for labelled images. Our method achieves competitive performance on
three horizon estimation benchmark datasets. We further highlight some
additional use cases for which our vanishing point detection algorithm can be
used.Comment: Accepted for publication at German Conference on Pattern Recognition
(GCPR) 2017. This research was supported by German Research Foundation DFG
within Priority Research Programme 1894 "Volunteered Geographic Information:
Interpretation, Visualisation and Social Computing
A determination of the fragmentation functions of pions, kaons, and protons with faithful uncertainties
We present NNFF1.0, a new determination of the fragmentation functions (FFs)
of charged pions, charged kaons, and protons/antiprotons from an analysis of
single-inclusive hadron production data in electron-positron annihilation. This
determination, performed at leading, next-to-leading, and
next-to-next-to-leading order in perturbative QCD, is based on the NNPDF
methodology, a fitting framework designed to provide a statistically sound
representation of FF uncertainties and to minimise any procedural bias. We
discuss novel aspects of the methodology used in this analysis, namely an
optimised parametrisation of FFs and a more efficient minimisation
strategy, and validate the FF fitting procedure by means of closure tests. We
then present the NNFF1.0 sets, and discuss their fit quality, their
perturbative convergence, and their stability upon variations of the kinematic
cuts and the fitted dataset. We find that the systematic inclusion of
higher-order QCD corrections significantly improves the description of the
data, especially in the small- region. We compare the NNFF1.0 sets to other
recent sets of FFs, finding in general a reasonable agreement, but also
important differences. Together with existing sets of unpolarised and polarised
parton distribution functions (PDFs), FFs and PDFs are now available from a
common fitting framework for the first time.Comment: 50 pages, 22 figures, 5 table
The AMBRE Project: Stellar Parameterisation of the ESO:UVES archived spectra
The AMBRE Project is a collaboration between the European Southern
Observatory (ESO) and the Observatoire de la Cote d'Azur (OCA) that has been
established in order to carry out the determination of stellar atmospheric
parameters for the archived spectra of four ESO spectrographs.
The analysis of the UVES archived spectra for their stellar parameters has
been completed in the third phase of the AMBRE Project. From the complete
ESO:UVES archive dataset that was received covering the period 2000 to 2010,
51921 spectra for the six standard setups were analysed. The AMBRE analysis
pipeline uses the stellar parameterisation algorithm MATISSE to obtain the
stellar atmospheric parameters. The synthetic grid is currently constrained to
FGKM stars only.
Stellar atmospheric parameters are reported for 12,403 of the 51,921 UVES
archived spectra analysed in AMBRE:UVES. This equates to ~23.9% of the sample
and ~3,708 stars. Effective temperature, surface gravity, metallicity and alpha
element to iron ratio abundances are provided for 10,212 spectra (~19.7%),
while at least effective temperature is provided for the remaining 2,191
spectra. Radial velocities are reported for 36,881 (~71.0%) of the analysed
archive spectra. Typical external errors of sigmaTeff~110dex,
sigmalogg~0.18dex, sigma[M/H]~0.13dex, and sigma[alpha/Fe]~0.05dex with some
reported variation between giants and dwarfs and between setups are reported.
UVES is used to observe an extensive collection of stellar and non-stellar
objects all of which have been included in the archived dataset provided to OCA
by ESO. The AMBRE analysis extracts those objects which lie within the FGKM
parameter space of the AMBRE slow rotating synthetic spectra grid. Thus by
homogeneous blind analysis AMBRE has successfully extracted and parameterised
the targeted FGK stars (23.9% of the analysed sample) from within the ESO:UVES
archive.Comment: 19 pages, 16 figures, 11 table
- …