261 research outputs found
Automatic Synchronization of Multi-User Photo Galleries
In this paper we address the issue of photo galleries synchronization, where
pictures related to the same event are collected by different users. Existing
solutions to address the problem are usually based on unrealistic assumptions,
like time consistency across photo galleries, and often heavily rely on
heuristics, limiting therefore the applicability to real-world scenarios. We
propose a solution that achieves better generalization performance for the
synchronization task compared to the available literature. The method is
characterized by three stages: at first, deep convolutional neural network
features are used to assess the visual similarity among the photos; then, pairs
of similar photos are detected across different galleries and used to construct
a graph; eventually, a probabilistic graphical model is used to estimate the
temporal offset of each pair of galleries, by traversing the minimum spanning
tree extracted from this graph. The experimental evaluation is conducted on
four publicly available datasets covering different types of events,
demonstrating the strength of our proposed method. A thorough discussion of the
obtained results is provided for a critical assessment of the quality in
synchronization.Comment: ACCEPTED to IEEE Transactions on Multimedi
Multimodal-based Diversified Summarization in Social Image Retrieval
In this paper, we describe our approach and its results for the MediaEval 2015 Retrieving Diverse Social Images task. The main strength of the proposed approach is its flexibility that permits to filter out irrelevant images, and to obtain a reli- able set of diverse and relevant images. This is done by first clustering similar images according to their textual descrip- tions and their visual content, and then extracting images from different clusters according to a measure of user’s cred- ibility. Experimental results shown that it is stable and has little fluctuation in both single-concept and multi-concept queries
Multiple Description Coding Using Data Hiding and Regions of Interest for Broadcasting Applications
We propose an innovative scheme for multiple description coding (MDC) with regions of interest (ROI) support to be adopted in high-quality television. The scheme proposes to split the
stream into two separate descriptors and to preserve the quality of the region of interest, even in case
one descriptor is completely lost. The residual part of the frame (the background) is instead modeled
through a checkerboard pattern, alternating the strength of the quantization. The decoder is provided
with the necessary side-information to reconstruct the frame properly, namely, the ROI parameters and
location, via a suitable data hiding procedure. Using data hiding, reconstruction parameters are embedded
in the transform coefficients, thus allowing an improvement in PSNR of the single descriptions at the
cost of a negligible overhead. To demonstrate its effectiveness, the algorithm has been implemented in
two different scenarios, using the reference H.264/AVC codec and an MJPEG framework to evaluate the
performance in absence of motion-compensated frames on 720p video sequences
Morphological Filter Detector for Image Forensics Applications
Mathematical morphology provides a large set of powerful non-linear image operators, widely used for feature extraction, noise removal or image enhancement. Although morphological filters might be used to remove artifacts produced by image manipulations, both on binary and graylevel documents, little effort has been spent towards their forensic identification. In this paper we propose a non-trivial extension of a deterministic approach originally detecting erosion and dilation of binary images. The proposed approach operates on grayscale images and is robust to image compression and other typical attacks. When the image is attacked the method looses its deterministic nature and uses a properly trained SVM classifier, using the original detector as a feature extractor. Extensive tests demonstrate that the proposed method guarantees very high accuracy in filtering detection, providing 100% accuracy in discriminating the presence and the type of morphological filter in raw images of three different datasets. The achieved accuracy is also good after JPEG compression, equal or above 76.8% on all datasets for quality factors above 80. The proposed approach is also able to determine the adopted structuring element for moderate compression factors. Finally, it is robust against noise addition and it can distinguish morphological filter from other filters
What is Minimal Model of 3He Adsorbed on Graphite? -Importance of Density Fluctuations in 4/7 Registered Solid -
We show theoretically that the second layer of 3He adsorbed on graphite and
solidified at 4/7 of the first-layer density is close to the fluid-solid
boundary with substantial density fluctuations on the third layer. The solid
shows a translational symmetry breaking as in charge-ordered insulators of
electronic systems. We construct a minimal model beyond the multiple-exchange
Heisenberg model. An unexpectedly large magnetic field required for the
measured saturation of magnetization is well explained by the density
fluctuations. The emergence of quantum spin liquid is understood from the same
mechanism as in the Hubbard model and in \kappa-(ET)_2Cu_2(CN)_3 near the Mott
transitions.Comment: 9 pages, 5 figure
Benchmarking van der Waals Density Functionals with Experimental Data: Potential Energy Curves for H2 Molecules on Cu(111), (100), and (110) Surfaces
Detailed physisorption data from experiment for the H_2 molecule on low-index
Cu surfaces challenge theory. Recently, density-functional theory (DFT) has
been developed to account for nonlocal correlation effects, including van der
Waals (dispersion) forces. We show that the functional vdW-DF2 gives a
potential-energy curve, potential-well energy levels, and difference in lateral
corrugation promisingly close to the results obtained by resonant elastic
backscattering-diffraction experiments. The backscattering barrier is found
selective for choice of exchange-functional approximation. Further, the DFT-D3
and TS-vdW corrections to traditional DFT formulations are also benchmarked,
and deviations are analyzed.Comment: 15 pages, 9 figure
Terrestrial exposure of a fresh Martian meteorite causes rapid changes in hydrogen isotopes and water concentrations
Determining the hydrogen isotopic compositions and H2O contents of meteorites and their components is important for addressing key cosmochemical questions about the abundance and source(s) of water in planetary bodies. However, deconvolving the effects of terrestrial contamination from the indigenous hydrogen isotopic compositions of these extraterrestrial materials is not trivial, because chondrites and some achondrites show only small deviations from terrestrial values such that even minor contamination can mask the indigenous values. Here we assess the effects of terrestrial weathering and contamination on the hydrogen isotope ratios and H2O contents of meteoritic minerals through monitored terrestrial weathering of Tissint, a recent Martian fall. Our findings reveal the rapidity with which this weathering affects nominally anhydrous phases in extraterrestrial materials, which illustrates the necessity of sampling the interiors of even relatively fresh meteorite falls and underlines the importance of sample return missions
Polarization degrees of freedom in photoinduced two-nucleon knockout from finite nuclei
The polarization degrees of freedom in photoinduced two-nucleon knockout from
finite nuclei are studied. It is pointed out that they open good perspectives
to study the dynamics of dinucleons in the medium in detail. The ()
and () angular cross sections, photon asymmetries and outgoing
nucleon polarizations are calculated for the target nuclei O and
C and photonenergies ranging from 100 up to 500 MeV. It is investigated
to which degree the two-nucleon emission reaction is dominated by
photoabsorption on proton-neutron and proton-proton
pairs in the nuclear medium. The calculations demonstrate that dominance of
wave photoabsorption in the () channel does not necessarily imply
that the reaction mechanism is similar to what is observed in deuteron
photodisintegration.Comment: 27 pages, REVTeX 3.0 with epsf.sty, 11 figures in EPS forma
Quantum scattering of neon from a nanotextured surface
Phonon exchange is the usual cause of decoherence in atom–surface scattering. By including quantum effects in the treatment of Debye–Waller scattering, we show that phonon exchange becomes ineffective when the relevant phonon frequencies are high. The result explains the surprising observation of strong elastic scattering of Ne from a Cu(100) surface nanotextured with a c(2 × 2) Li adsorbate structure. We extend a previous model to describe the phonon spectra by an Einstein oscillator component with an admixture of a Debye spectrum. The Einstein oscillator represents the dominant, high frequency vibration of the adsorbate, normal to the surface, while the Debye spectrum represents the substrate contribution. Neon scattering is so slow that exciting the adsorbate mode has a low probability and is impossible if the incident energy is below the threshold. Thus, adsorbate vibrations are averaged out. A theoretical discussion and calculation shows that under such circumstances the vibrations of a light adsorbate do not contribute to the Debye–Waller effect, with the result that Ne scattering at thermal energies is quantum mechanical and largely elastic, explaining the high reflectivity and the diffraction peaks observed experimentally
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