7,349 research outputs found
Particle growing mechanisms in Ag-ZrO2 and Au-ZrO2 granular films obtained by pulsed laser deposition
Thin films consisting of Ag and Au nanoparticles embedded in amorphous ZrO2
matrix were grown by pulsed laser deposition in a wide range of metal volume
concentrations in the dielectric regime (0.08<x(Ag)<0.28 and 0.08<x(Au)<0.52).
High resolution transmission electron microscopy (TEM) showed regular
distribution of spherical Au and Ag nanoparticles having very sharp interfaces
with the amorphous matrix. Mean particle size determined from X-ray diffraction
agreed with direct TEM observation. The silver mean diameter increases more
abruptly with metal volume content than that corresponding to gold particles
prepared under the same conditions. Two mechanisms of particle growing are
observed: nucleation and particle coalescence, their relative significance
being different in both granular systems, which yields very different values of
the percolation threshold (xc(Ag)~0.28 and xc(Au)~0.52).Comment: 6 figure
Transferable Attack for Semantic Segmentation
We analysis performance of semantic segmentation models wrt. adversarial
attacks, and observe that the adversarial examples generated from a source
model fail to attack the target models. i.e The conventional attack methods,
such as PGD and FGSM, do not transfer well to target models, making it
necessary to study the transferable attacks, especially transferable attacks
for semantic segmentation. We find two main factors to achieve transferable
attack. Firstly, the attack should come with effective data augmentation and
translation-invariant features to deal with unseen models. Secondly, stabilized
optimization strategies are needed to find the optimal attack direction. Based
on the above observations, we propose an ensemble attack for semantic
segmentation to achieve more effective attacks with higher transferability. The
source code and experimental results are publicly available via our project
page: https://github.com/anucvers/TASS.Comment: Source code is available at: https://github.com/anucvers/TAS
Motion Segmentation of Truncated Signed Distance Function based Volumetric Surfaces
© 2015 IEEE.Truncated signed distance function (TSDF) based volumetric surface reconstructions of static environments can be readily acquired using recent RGB-D camera based mapping systems. If objects in the environment move then a previously obtained TSDF reconstruction is no longer current. Handling this problem requires segmenting moving objects from the reconstruction. To this end, we present a novel solution to the motion segmentation of TSDF volumes. The segmentation problem is cast as CRF-based MAP inference in the voxel space. We propose: a novel data term by solving sparse multi-body motion segmentation and computing likelihoods for each motion label in the RGB-D image space, and, a novel pair wise term based on gradients of the TSDF volume. Experimental evaluation shows that the proposed approach achieves successful segmentations on reconstructions acquired with Kinect Fusion. Unlike the existing solutions which only work if the objects move completely from their initially occupied spaces, the proposed method permits segmentation of objects when they start to move
Studies of Quantum Spin Ladders at T=0 and at High Temperatures by Series Expansions
We have carried out extensive series studies, at T=0 and at high
temperatures, of 2-chain and 3-chain spin-half ladder systems with
antiferromagnetic intrachain and both antiferromagnetic and ferromagnetic
interchain couplings. Our results confirm the existence of a gap in the 2-chain
Heisenberg ladders for all non-zero values of the interchain couplings.
Complete dispersion relations for the spin-wave excitations are computed. For
3-chain systems, our results are consistent with a gapless spectrum. We also
calculate the uniform magnetic susceptibility and specific heat as a function
of temperature. We find that as , for the 2-chain system the uniform
susceptibility goes rapidly to zero, whereas for the 3-chain system it
approaches a finite value. These results are compared in detail with previous
studies of finite systems.Comment: RevTeX, 14 figure
Comparing the estimates of effect obtained from statistical causal inference methods: An example using bovine respiratory disease in feedlot cattle
The causal effect of an exposure on an outcome of interest in an observational study cannot be estimated directly if the confounding variables are not controlled. Many approaches are available for estimating the causal effect of an exposure. In this manuscript, we demonstrate the advantages associated with using inverse probability weighting (IPW) and doubly robust estimation of the odds ratio in terms of reduced bias. IPW approach can be used to adjust for confounding variables and provide unbiased estimates of the exposure’s causal effect. For cluster-structured data, as is common in animal populations, inverse conditional probability weighting (ICPW) approach can provide a robust estimation of the causal effect. Doubly robust estimation can provide a robust method even when the specification of the model form is uncertain. In this paper, the usage of IPW, ICPW, and doubly robust approaches are illustrated with a subset of data with complete covariates from the Australian-based National Bovine Respiratory Disease Initiative as well as simulated data. We evaluate the causal effect of prior bovine viral diarrhea exposure on bovine respiratory disease in feedlot cattle. The results show that the IPW, ICPW and doubly robust approaches would provide a more accurate estimation of the exposure effect than the traditional outcome regression model, and doubly robust approaches are the most preferable overall
A new theoretical approach to improving face recognition in disorders of central vision: Face caricaturing
Damage to central vision, of which age-related macular degeneration (AMD) is the most common cause, leaves patients with only blurred peripheral vision. Previous approaches to improving face recognition in AMD have employed image manipulations designed to enhance early-stage visual processing (e.g., magnification, increased HSF contrast). Here, we argue that further improvement may be possible by targeting known properties of mid- and/or high-level face processing. We enhance identity-related shape information in the face by caricaturing each individual away from an average face. We simulate early- through late-stage AMD-blur by filtering spatial frequencies to mimic the amount of blurring perceived at approximately 10° through 30° into the periphery (assuming a face seen premagnified on a tablet computer).We report caricature advantages for all blur levels, for face viewpoints from front view to semiprofile, and in tasks involving perceiving differences in facial identity between pairs of people, remembering previously learned faces, and rejecting new faces as unknown. Results provide a proof of concept that caricaturing may assist in improving face recognition in AMD and other disorders of central vision
Faddeev-Volkov solution of the Yang-Baxter Equation and Discrete Conformal Symmetry
The Faddeev-Volkov solution of the star-triangle relation is connected with
the modular double of the quantum group U_q(sl_2). It defines an Ising-type
lattice model with positive Boltzmann weights where the spin variables take
continuous values on the real line. The free energy of the model is exactly
calculated in the thermodynamic limit. The model describes quantum fluctuations
of circle patterns and the associated discrete conformal transformations
connected with the Thurston's discrete analogue of the Riemann mappings
theorem. In particular, in the quasi-classical limit the model precisely
describe the geometry of integrable circle patterns with prescribed
intersection angles.Comment: 26 pages, 18 color figures, minor correction
Baryon Antibaryon Nonets
The baryon-antibaryon SU(3) nonets are proposed as a scheme to classify the
increased number of experimentally observed enhancements near the baryon
antibaryon mass threshold. The scheme is similar to the Fermi-Yang-Sakata
model, which was put forth about fifty years ago in explaining the mesons
observed at that time. According to the present scheme, many new
baryon-antibaryon bound states are predicted, and their possible productions in
quarkonium decays and B decays are suggested for experimental search.Comment: 5 pages, 1 figur
Mott effect at the chiral phase transition and anomalous J/Psi suppression
We investigate the in-medium modification of the charmonium break-up
processes due to the Mott effect for light (pi) and open-charm (D, D*) mesons
at the chiral/deconfinement phase transition. A model calculation for the
process J/Psi + pi -> D + \bar D* + h.c. is presented which demonstrates that
the Mott effect for the D-mesons leads to a threshold effect in the thermal
averaged break-up cross section. This effect is suggested as an explanation of
the phenomenon of anomalous J/Psi suppression in the CERN NA50 experiment.Comment: 9 pages, 3 figures; final version to appear in Phys. Lett.
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