3,987 research outputs found
Open Source Dataset and Machine Learning Techniques for Automatic Recognition of Historical Graffiti
Machine learning techniques are presented for automatic recognition of the
historical letters (XI-XVIII centuries) carved on the stoned walls of St.Sophia
cathedral in Kyiv (Ukraine). A new image dataset of these carved Glagolitic and
Cyrillic letters (CGCL) was assembled and pre-processed for recognition and
prediction by machine learning methods. The dataset consists of more than 4000
images for 34 types of letters. The explanatory data analysis of CGCL and
notMNIST datasets shown that the carved letters can hardly be differentiated by
dimensionality reduction methods, for example, by t-distributed stochastic
neighbor embedding (tSNE) due to the worse letter representation by stone
carving in comparison to hand writing. The multinomial logistic regression
(MLR) and a 2D convolutional neural network (CNN) models were applied. The MLR
model demonstrated the area under curve (AUC) values for receiver operating
characteristic (ROC) are not lower than 0.92 and 0.60 for notMNIST and CGCL,
respectively. The CNN model gave AUC values close to 0.99 for both notMNIST and
CGCL (despite the much smaller size and quality of CGCL in comparison to
notMNIST) under condition of the high lossy data augmentation. CGCL dataset was
published to be available for the data science community as an open source
resource.Comment: 11 pages, 9 figures, accepted for 25th International Conference on
Neural Information Processing (ICONIP 2018), 14-16 December, 2018 (Siem Reap,
Cambodia
Evidence for nonmonotonic magnetic field penetration in a type-I superconductor
Polarized neutron reflectometry (PNR) provides evidence that nonlocal
electrodynamics governs the magnetic field penetration in an extreme low-k
superconductor. The sample is an indium film with a large elastic mean free
path (11 mkm) deposited on a silicon oxide wafer. It is shown that PNR can
resolve the difference between the reflected neutron spin asymmetries predicted
by the local and nonlocal theories of superconductivity. The experimental data
support the nonlocal theory, which predicts a nonmonotonic decay of the
magnetic field.Comment: 5 pages, 4 figures, LaTex, corrected typos and figure
Magnetic and Superconducting Phase Diagram of Nb/Gd/Nb trilayers
We report on a study of the structural, magnetic and superconducting
properties of Nb(25nm)/Gd()/Nb(25nm) hybrid structures of a
superconductor/ ferromagnet (S/F) type. The structural characterization of the
samples, including careful determination of the layer thickness, was performed
using neutron and X-ray scattering with the aid of depth sensitive
mass-spectrometry. The magnetization of the samples was determined by SQUID
magnetometry and polarized neutron reflectometry and the presence of magnetic
ordering for all samples down to the thinnest Gd(0.8nm) layer was shown. The
analysis of the neutron spin asymmetry allowed us to prove the absence of
magnetically dead layers in junctions with Gd interlayer thickness larger than
one monolayer. The measured dependence of the superconducting transition
temperature has a damped oscillatory behavior with well defined
positions of the minimum at =3nm and the following maximum at =4nm;
the behavior, which is in qualitative agreement with the prior work (J.S. Jiang
et al, PRB 54, 6119). The analysis of the dependence based on Usadel
equations showed that the observed minimum at =3nm can be described by the
so called "" to "" phase transition of highly transparent S/F
interfaces with the superconducting correlation length nm in
Gd. This penetration length is several times higher than for strong
ferromagnets like Fe, Co or Ni, simplifying thus preparation of S/F structures
with which are of topical interest in superconducting
spintronics
Feasibility of study magnetic proximity effects in bilayer "superconductor/ferromagnet" using waveguide-enhanced Polarized Neutron Reflectometry
A resonant enhancement of the neutron standing waves is proposed to use in
order to increase the magnetic neutron scattering from a
"superconductor/ferromagnet"(S/F) bilayer. The model calculations show that
usage of this effect allows to increase the magnetic scattering intensity by
factor of hundreds. Aspects related to the growth procedure (order of
deposition, roughness of the layers etc) as well as experimental conditions
(resolution, polarization of the neutron beam, background etc) are also
discussed.
Collected experimental data for the S/F heterostructure
Cu(32nm)/V(40nm)/Fe(1nm)/MgO confirmed the presence of a resonant 60-fold
amplification of the magnetic scattering.Comment: The manuscript of the article submitted to Crysstalography Reports.
23 pages, 5 figure
Hard Probes in Heavy Ion Collisions at the LHC: Jet Physics
We discuss the importance of high-pT hadron and jet measurements in
nucleus-nucleus collisions at the CERN Large Hadron Collider.Comment: The writeup of the working group "Jet Physics" for the CERN Yellow
Report on "Hard Probes in Heavy Ion Collisions at the LHC", 123 pages.
Subgroup convenors: R. Baier, X.N. Wang, U.A. Wiedemann (theory) and I.P.
Lokhtin, A. Morsch (experiment). Editor: U.A. Wiedeman
Measuring Higgs boson couplings at the LHC
For an intermediate mass Higgs boson with SM-like couplings the LHC allows
observation of a variety of decay channels in production by gluon fusion and
weak boson fusion. Cross section ratios provide measurements of various ratios
of Higgs couplings, with accuracies of order 15% for 100 fb^{-1} of data in
each of the two LHC experiments. For Higgs masses above 120 GeV, minimal
assumptions on the Higgs sector allow for an indirect measurement of the total
Higgs boson width with an accuracy of 10 to 20%, and of the H-->WW partial
width with an accuracy of about 10%.Comment: 25 pages, Revtex, 1 figur
Photon Physics in Heavy Ion Collisions at the LHC
Various pion and photon production mechanisms in high-energy nuclear
collisions at RHIC and LHC are discussed. Comparison with RHIC data is done
whenever possible. The prospect of using electromagnetic probes to characterize
quark-gluon plasma formation is assessed.Comment: Writeup of the working group "Photon Physics" for the CERN Yellow
Report on "Hard Probes in Heavy Ion Collisions at the LHC", 134 pages. One
figure added in chapter 5 (comparison with PHENIX data). Some figures and
correponding text corrected in chapter 6 (off-chemical equilibrium thermal
photon rates). Some figures modified in chapter 7 (off-chemical equilibrium
photon rates) and comparison with PHENIX data adde
Atomic structure of dislocation kinks in silicon
We investigate the physics of the core reconstruction and associated
structural excitations (reconstruction defects and kinks) of dislocations in
silicon, using a linear-scaling density-matrix technique. The two predominant
dislocations (the 90-degree and 30-degree partials) are examined, focusing for
the 90-degree case on the single-period core reconstruction. In both cases, we
observe strongly reconstructed bonds at the dislocation cores, as suggested in
previous studies. As a consequence, relatively low formation energies and high
migration barriers are generally associated with reconstructed
(dangling-bond-free) kinks. Complexes formed of a kink plus a reconstruction
defect are found to be strongly bound in the 30-degree partial, while the
opposite is true in the case of 90-degree partial, where such complexes are
found to be only marginally stable at zero temperature with very low
dissociation barriers. For the 30-degree partial, our calculated formation
energies and migration barriers of kinks are seen to compare favorably with
experiment. Our results for the kink energies on the 90-degree partial are
consistent with a recently proposed alternative double-period structure for the
core of this dislocation.Comment: 12 pages, two-column style with 8 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#rn_di
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