4,814 research outputs found
First-Order Transition in XY Fully Frustrated Simple Cubic Lattice
We study the nature of the phase transition in the fully frustrated simple
cubic lattice with the XY spin model. This system is the Villain's model
generalized in three dimensions. The ground state is very particular with a
12-fold degeneracy. Previous studies have shown unusual critical properties.
With the powerful Wang-Landau flat-histogram Monte Carlo method, we carry out
in this work intensive simulations with very large lattice sizes. We show that
the phase transition is clearly of first order, putting an end to the
uncertainty which has lasted for more than twenty years
Phase Transition in Heisenberg Fully Frustrated Simple Cubic Lattice
The phase transition in frustrated spin systems is a fascinated subject in
statistical physics. We show the result obtained by the Wang-Landau flat
histogram Monte Carlo simulation on the phase transition in the fully
frustrated simple cubic lattice with the Heisenberg spin model. The degeneracy
of the ground state of this system is infinite with two continuous parameters.
We find a clear first-order transition in contradiction with previous studies
which have shown a second-order transition with unusual critical properties.
The robustness of our calculations allows us to conclude this issue putting an
end to the 20-year long uncertainty.Comment: submitted for publicatio
Partially obscured human detection based on component detectors using multiple feature descriptors
This paper presents a human detection system based on component detector using multiple feature descriptors. The contribution presents two issues for dealing with the problem of partially obscured human. First, it presents the extension of feature descriptors using multiple scales based Histograms of Oriented Gradients (HOG) and parallelogram based Haar-like feature (PHF) for improving the accuracy of the system. By using multiple scales based HOG, an extensive feature space allows obtaining high-discriminated features. Otherwise, the PHF is adaptive limb shapes of human in fast computing feature. Second, learning system using boosting classifications based approach is used for training and detecting the partially obscured human. The advantage of boosting is constructing a strong classification by combining a set of weak classifiers. However, the performance of boosting depends on the kernel of weak classifier. Therefore, the hybrid algorithms based on AdaBoost and SVM using the proposed feature descriptors is one of solutions for robust human detection.This paper presents a human detection system based on component detector using multiple feature descriptors. The contribution presents two issues for dealing with the problem of partially obscured human. First, it presents the extension of feature descriptors using multiple scales based Histograms of Oriented Gradients (HOG) and parallelogram based Haar-like feature (PHF) for improving the accuracy of the system. By using multiple scales based HOG, an extensive feature space allows obtaining high-discriminated features. Otherwise, the PHF is adaptive limb shapes of human in fast computing feature. Second, learning system using boosting classifications based approach is used for training and detecting the partially obscured human. The advantage of boosting is constructing a strong classification by combining a set of weak classifiers. However, the performance of boosting depends on the kernel of weak classifier. Therefore, the hybrid algorithms based on AdaBoost and SVM using the proposed feature descriptors is one of solutions for robust human detection
Effect of Disorder in the Frustrated Ising FCC Antiferromagnet: Phase Diagram and Stretched Exponential Relaxation
We study the phase transition in a face-centered-cubic antiferromagnet with
Ising spins as a function of the concentration of ferromagnetic bonds
randomly introduced into the system. Such a model describes the spin-glass
phase at strong bond disorder. Using the standard Monte Carlo simulation and
the powerful Wang-Landau flat-histogram method, we carry out in this work
intensive simulations over the whole range of . We show that the first-order
transition disappears with a tiny amount of ferromagnetic bonds, namely , in agreement with theories and simulations on other 3D models. The
antiferromagnetic long-range order is also destroyed with a very small
(). With increasing , the system changes into a spin glass and
then to a ferromagnetic phase when . The phase diagram in the space
() shows an asymmetry, unlike the case of the Ising spin glass
on the simple cubic lattice. We calculate the relaxation time around the
spin-glass transition temperature and we show that the spin autocorrelation
follows a stretched exponential relaxation law where the factor is equal to
at the transition as suggested by the percolation-based theory.
This value is in agreement with experiments performed on various spin glasses
and with Monte Carlo simulations on different SG models
On the deformation morphology of bulk metallic glasses underneath a Vickers indentation
16th International Symposium on Metastable, Amorphous and Nanostructured Materials, Beijing, PEOPLES R CHINA, JUL 05-09, 2009International audienceThe techniques commonly used for observing the deformation mechanisms underneath a Vickers indentation in metallic glasses (chemical etching, bonded interface) induce artefacts such as cracks or semi-circular shear-bands. We propose an alternative technique based on the propagation of indentation corner cracks through a pre-existing imprint, which is possible in metallic glasses such as iron-based compositions. With this procedure, only radial shear-bands are observed. Comparisons between the chemical etching or the bonded interface techniques and the new technique are made. (C) 2010 Elsevier B.V. All rights reserved
Charm mass corrections to the bottomonium mass spectrum
The one-loop corrections to the bottomonium mass spectrum due to the finite
charm mass are evaluated in the framework of the relativistic quark model. The
obtained corrections are compared with the results of perturbative QCD.Comment: 6 pages, references added, version to be published in Phys. Rev.
Sound-Dr: Reliable Sound Dataset and Baseline Artificial Intelligence System for Respiratory Illnesses
As the burden of respiratory diseases continues to fall on society worldwide,
this paper proposes a high-quality and reliable dataset of human sounds for
studying respiratory illnesses, including pneumonia and COVID-19. It consists
of coughing, mouth breathing, and nose breathing sounds together with metadata
on related clinical characteristics. We also develop a proof-of-concept system
for establishing baselines and benchmarking against multiple datasets, such as
Coswara and COUGHVID. Our comprehensive experiments show that the Sound-Dr
dataset has richer features, better performance, and is more robust to dataset
shifts in various machine learning tasks. It is promising for a wide range of
real-time applications on mobile devices. The proposed dataset and system will
serve as practical tools to support healthcare professionals in diagnosing
respiratory disorders. The dataset and code are publicly available here:
https://github.com/ReML-AI/Sound-Dr/.Comment: 9 pages, PHMAP2023, PH
The Threshold t-tbar Cross Section at NNLL Order
The total cross section for top quark pair production close to threshold in
e+e- annihilation is investigated. Details are given about the calculation at
next-to-next-to-leading logarithmic order. The summation of logarithms leads to
a convergent expansion for the normalization of the cross section, and small
residual dependence on the subtraction parameter nu. A detailed analysis of the
residual nu dependence is carried out. A conservative estimate for the
remaining uncertainty in the normalization of the total cross section from QCD
effects is . This makes precise extractions of the strong
coupling and top width feasible, and further studies of electroweak effects
mandatory.Comment: 33 pages, 11 figs, a program to produce the cross section will be
available soo
Characterization of Extracellular Polymeric Substances (Eps) Produced by \u3ci\u3eCloacibacterium normanense\u3c/i\u3e Isolated from Wastewater Sludge for Sludge Settling and Dewatering
In this study, extracellular polymeric substances (EPSs) producing strain was isolated from municipal wastewater sludge (MWWS). Growth profile and the EPS production by Cloacibacterium normanense using wastewater sludge as raw material in shake flask fermentation for 96 h were investigated. The highest concentration of S-EPS (13.0 ± 0.8 g/L) and C-EPS (0.3 ± 0.1 g/L) were attained at 48 h of fermentation. S-EPS revealed higher flocculation activity (94.2%) and dewaterability (59.9%) than other types of EPS in kaolin suspension. The dewaterability of MWWS with 2 g suspended solids (SS)/L was improved by 37.6% using 0.02 ± 0.01 g/L of S-EPS and 600 mg/L of Al2(SO4)3. The study showed a promising approach of new isolated strain to produce high concentration EPS in sludge with high flocculation activity as well as good settlin
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