8,248 research outputs found
Internal relaxation time in immersed particulate materials
We study the dynamics of the solid to liquid transition for a model material
made of elastic particles immersed in a viscous fluid. The interaction between
particle surfaces includes their viscous lubrication, a sharp repulsion when
they get closer than a tuned steric length and their elastic deflection induced
by those two forces. We use Soft Dynamics to simulate the dynamics of this
material when it experiences a step increase in the shear stress and a constant
normal stress. We observe a long creep phase before a substantial flow
eventually establishes. We find that the typical creep time relies on an
internal relaxation process, namely the separation of two particles driven by
the applied stress and resisted by the viscous friction. This mechanism should
be relevant for granular pastes, living cells, emulsions and wet foams
Dilepton distributions at backward rapidities
The dilepton production at backward rapidities in and collisions
at RHIC and LHC energies is investigated in the dipole approach. The results
are shown through the nuclear modification ratio considering
transverse momentum and rapidity spectra. The dilepton modification ratio
presents interesting behavior at the backward rapidities when compared with the
already known forward ones, since it is related with the large kinematical
region that is being probed. The rapidity dependence of the nuclear
modification ratio in the dilepton production is strongly dependent on the
Bjorken behavior of the nuclear structure function ratio
. The transverse momentum dependence at
backward rapidities is modified due to the large nuclear effects: at RHIC
energies, for instance, the ratio is reduced as increases,
presenting an opposite behavior when compared with the forward one. It implies
that the dilepton production at backward rapidities should carry information of
the nuclear effects at large Bjorken , as well as that it is useful to
investigate the dependence of the observables in this kinematical regime.Comment: 15 pages, 6 figures. Version published in the Phys. Rev.
Proposing a customized exokernel library to data mining
The implementation of customized system libraries in an exokernel environment is considered as a promising approach in optimizing data mining processes. Customized libraries in exokernel environments have been successfully used in optimizing other applications, and is potentially suitable to demanding applications such as data mining. A prototype, to test our hypothesis, is under construction. This work introduces data mining, the exokernel environment and describes our prototype's building strategy
Differential Geometry applied to Acoustics : Non Linear Propagation in Reissner Beams
Although acoustics is one of the disciplines of mechanics, its
"geometrization" is still limited to a few areas. As shown in the work on
nonlinear propagation in Reissner beams, it seems that an interpretation of the
theories of acoustics through the concepts of differential geometry can help to
address the non-linear phenomena in their intrinsic qualities. This results in
a field of research aimed at establishing and solving dynamic models purged of
any artificial nonlinearity by taking advantage of symmetry properties
underlying the use of Lie groups. The geometric constructions needed for
reduction are presented in the context of the "covariant" approach.Comment: Submitted to GSI2013 - Geometric Science of Informatio
Anisotropic elastic theory of preloaded granular media
A macroscopic elastic description of stresses in static, preloaded granular
media is derived systematically from the microscopic elasticity of individual
inter-grain contacts. The assumed preloaded state and friction at contacts
ensure that the network of inter-grain contacts is not altered by small
perturbations. The texture of this network, set by the preparation of the
system, is encoded in second and fourth order fabric tensors. A small
perturbation generates both normal and tangential inter-grain forces, the
latter causing grains to reorient. This reorientation response and the
incremental stress are expressed in terms of the macroscopic strain.Comment: 7 pages, 2 figures. Accepted version. [email protected]
[email protected]
Compatibility of a model for the QCD-Pomeron and chiral-symmetry breaking phenomenologies
The phenomenology of a QCD-Pomeron model based on the exchange of a pair of
non-perturbative gluons, i.e. gluon fields with a finite correlation length in
the vacuum, is studied in comparison with the phenomenology of QCD chiral
symmetry breaking, based on non-perturbative solutions of Schwinger-Dyson
equations for the quark propagator including these non-perturbative gluon
effects. We show that these models are incompatible, and point out some
possibles origins of this problem.Comment: 21 pages, uuencoded latex file, 3 postscript figures, uses epsf.sty
and epsf.tex. To be published in Phys. Lett.
Automatic speech recognition: a comparative evaluation between neural networks and hidden markov models
In this work we do a comparative evaluation between Artificial Neural Networks (RNA's) and Continuous Hidden Markov Models (CDHMM), in the framework of the recognition of isolated words, under the constrain of using a small number of features extracted from each voice signal. In order to accomplish such comparison we used two models of neural networks: the Multilayer Perceptron (MLP) and a variant of the Radial Basis (RBF), and some HMM models. We evaluated the performance of all models using two different test set and observed that the neural models presented the best results in both cases. Seeking to improve the HMM performance we developed a hybrid system, HMM/MLP, that improved the results previously obtained with all HMMs, and even those obtained with the neural networks for the all previous HMM, and even the neural nets for the hardest test set case
Translation and cultural adaptation for Brazil of the Developing Nurses\u27 Thinking model1
Objectives to translate and culturally adapt to Brazilian Portuguese the Developing Nurses\u27 Thinking model, used as a strategy for teaching clinical reasoning. Method the translation and cultural adaptation were undertaken through initial translation, synthesis of the translations, back-translation, evaluation by a committee of specialists and a pre-test with 33 undergraduate nursing students. Results the stages of initial translation, synthesis of the translations and back-translation were undertaken satisfactorily, small adjustments being needed. In the evaluation of the translated version by the committee of specialists, all the items obtained agreement over 80% in the first round of evaluation and in the pre-test with the students, so the model was shown to be fit for purpose. Conclusion the use of the model as a complementary strategy in the teaching of diagnostic reasoning is recommended, with a view to the training of nurses who are more aware regarding the diagnostic task and the importance of patient safety
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