2,325 research outputs found
Handcrafted and learning-based tie point features-comparison using the EuroSDR RPAS benchmark datasets
The identification of accurate and reliable image correspondences is fundamental for Structure-from-Motion (SfM) photogrammetry. Alongside handcrafted detectors and descriptors, recent machine learning-based approaches have shown promising results for tie point extraction, demonstrating matching success under strong perspective and illumination changes, and a general increase of tie point multiplicity. Recently, several methods based on convolutional neural networks (CNN) have been proposed, but few tests have yet been performed under real photogrammetric applications and, in particular, on full resolution aerial and RPAS image blocks that require rotationally invariant features. The research reported here compares two handcrafted (Metashape local features and RootSIFT) and two learning-based methods (LFNet and Key.Net) using the previously unused EuroSDR RPAS benchmark datasets. Analysis is conducted with DJI Zenmuse P1 imagery acquired at Wards Hill quarry in Northumberland, UK. The research firstly extracts keypoints using the aforementioned methods, before importing them into COLMAP for incremental reconstruction. The image coordinates of signalised ground control points (GCPs) and independent checkpoints (CPs) are automatically detected using an OpenCV algorithm, and then triangulated for comparison with accurate geometric ground-truth. The tests showed that learning-based local features are capable of outperforming traditional methods in terms of geometric accuracy, but several issues remain: few deep learning local features are trained to be rotation invariant, significant computational resources are required for large format imagery, and poor performance emerged in cases of repetitive patterns
Mobility induces global synchronization of oscillators in periodic extended systems
We study synchronization of locally coupled noisy phase oscillators which
move diffusively in a one-dimensional ring. Together with the disordered and
the globally synchronized states, the system also exhibits several wave-like
states which display local order. We use a statistical description valid for a
large number of oscillators to show that for any finite system there is a
critical spatial diffusion above which all wave-like solutions become unstable.
Through Langevin simulations, we show that the transition to global
synchronization is mediated by the relative size of attractor basins associated
to wave-like states. Spatial diffusion disrupts these states and paves the way
for the system to attain global synchronization
The AGN nature of 11 out of 12 Swift/RXTE unidentified sources through optical and X-ray spectroscopy
The Swift Burst Alert Telescope (BAT) is performing a high Galactic latitude
survey in the 14-195 keV band at a flux limit of ~10^{-11} erg cm^{-2} s^{-1},
leading to the discovery of new high energy sources, most of which have not so
far been properly classified. A similar work has also been performed with the
RXTE slew survey leading to the discovery of 68 sources detected above 8 keV,
many of which are still unclassified. Follow-up observations with the Swift
X-ray Telescope (XRT) provide, for many of these objects, source localization
with a positional accuracy of few arcsec, thus allowing the search for optical
counterparts to be more efficient and reliable. We present the results of
optical/X-ray follow-up studies of 11 Swift BAT detections and one AGN detected
in the RXTE Slew Survey, aimed at identifying their counterparts and at
assessing their nature. These data allowed, for the first time, the optical
classification of 8 objects and a distance determination for 3 of them. For
another object, a more refined optical classification than that available in
the literature is also provided. For the remaining sources, optical
spectroscopy provides a characterization of the source near in time to the
X-ray measurement. The sample consists of 6 Seyfert 2 galaxies, 5 Seyferts of
intermediate type 1.2-1.8, and one object of Galactic nature - an Intermediate
Polar (i.e., magnetic) Cataclysmic Variable. Out of the 11 AGNs, 8 (~70%)
including 2 Seyferts of type 1.2 and 1.5, are absorbed with NH > 10^{22}
cm^{-2}. Up to 3 objects could be Compton thick (i.e. NH > 1.5 x 10^{24}
cm^{-2}), but only in one case (Swift J0609.1-8636) does all the observational
evidence strongly suggests this possibility.Comment: 50 pages, including 16 figures and 7 tables. Accepted for publication
in Ap
Magnon Heat Transport in doped
We present results of the thermal conductivity of and single-crystals which represent model systems for the
two-dimensional spin-1/2 Heisenberg antiferromagnet on a square lattice. We
find large anisotropies of the thermal conductivity, which are explained in
terms of two-dimensional heat conduction by magnons within the CuO planes.
Non-magnetic Zn substituted for Cu gradually suppresses this magnon thermal
conductivity . A semiclassical analysis of
is shown to yield a magnon mean free path which scales
linearly with the reciprocal concentration of Zn-ions.Comment: 4 pages, 3 figure
Persistent systemic microbial translocation, inflammation, and intestinal damage during Clostridioides difficile infection
Background. Clostridioides difficile infection (CDI) might be complicated by the development of nosocomial bloodstream infection (n-BSI). Based on the hypothesis that alteration of the normal gut integrity is present during CDI, we evaluated markers of microbial translocation, inflammation, and intestinal damage in patients with CDI. Methods. Patients with documented CDI were enrolled in the study. For each subject, plasma samples were collected at T0 and T1 (before and after CDI therapy, respectively), and the following markers were evaluated: lipopolysaccharide-binding protein (LPB), EndoCab IgM, interleukin-6, intestinal fatty acid binding protein (I-FABP). Samples from nonhospitalized healthy controls were also included. The study population was divided into BSI+/BSI- and fecal microbiota transplantation (FMT) +/FMT- groups, according to the development of n-BSI and the receipt of FMT, respectively. Results. Overall, 45 subjects were included; 8 (17.7%) developed primary n-BSI. Markers of microbial translocation and intestinal damage significantly decreased between T0 and T1, however, without reaching values similar to controls (P < .0001). Compared with BSI-, a persistent high level of microbial translocation in the BSI+ group was observed. In the FMT+ group, markers of microbial translocation and inflammation at T1 tended to reach control values. Conclusions. CDI is associated with high levels of microbial translocation, inflammation, and intestinal damage, which are still present at clinical resolution of CDI. The role of residual mucosal perturbation and persistence of intestinal cell damage in the development of n-BSI following CDI, as well as the possible effect of FMT in the restoration of mucosal integrity, should be further investigated
GARFIELD + RCo Digital Upgrade: a Modern Set-up for Mass and Charge Identification of Heavy Ion Reaction Products
An upgraded GARFIELD + Ring Counter (RCo) apparatus is presented with
improved performances as far as electronics and detectors are concerned. On one
side fast sampling digital read out has been extended to all detectors,
allowing for an important simplification of the signal processing chain
together with an enriched extracted information. On the other side a relevant
improvement has been made in the forward part of the setup (RCo): an increased
granularity of the CsI(Tl) crystals and a higher homogeneity in the silicon
detector resistivity. The renewed performances of the GARFIELD + RCo array make
it suitable for nuclear reaction measurements both with stable and with
Radioactive Ion Beams (RIB), like the ones foreseen for the SPES facility,
where the Physics of Isospin can be studied.Comment: 13 pages, 19 figures - paper submitted to Eur. Phys. J.
Meat quality of Nellore cattle finished in feedlot fed with diets containing agroindustrial co-products or not.
Synchronization of Coupled Systems with Spatiotemporal Chaos
We argue that the synchronization transition of stochastically coupled
cellular automata, discovered recently by L.G. Morelli {\it et al.} (Phys. Rev.
{\bf 58 E}, R8 (1998)), is generically in the directed percolation universality
class. In particular, this holds numerically for the specific example studied
by these authors, in contrast to their claim. For real-valued systems with
spatiotemporal chaos such as coupled map lattices, we claim that the
synchronization transition is generically in the universality class of the
Kardar-Parisi-Zhang equation with a nonlinear growth limiting term.Comment: 4 pages, including 3 figures; submitted to Phys. Rev.
Low thermal conductivity of the layered oxide (Na,Ca)Co_2O_4: Another example of a phonon glass and an electron crystal
The thermal conductivity of polycrystalline samples of (Na,Ca)Co_2O_4 is
found to be unusually low, 20 mW/cmK at 280 K. On the assumption of the
Wiedemann-Franz law, the lattice thermal conductivity is estimated to be 18
mW/cmK at 280 K, and it does not change appreciably with the substitution of Ca
for Na. A quantitative analysis has revealed that the phonon mean free path is
comparable with the lattice parameters, where the point-defect scattering plays
an important role. Electronically the same samples show a metallic conduction
down to 4.2 K, which strongly suggests that NaCo_2O_4 exhibits a glass-like
poor thermal conduction together with a metal-like good electrical conduction.
The present study further suggests that a strongly correlated system with
layered structure can act as a material of a phonon glass and an electron
crystal.Comment: 5 pages 3 figures, to be published in Phys. Rev.
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