9,435 research outputs found
Multi-View Deep Learning for Consistent Semantic Mapping with RGB-D Cameras
Visual scene understanding is an important capability that enables robots to
purposefully act in their environment. In this paper, we propose a novel
approach to object-class segmentation from multiple RGB-D views using deep
learning. We train a deep neural network to predict object-class semantics that
is consistent from several view points in a semi-supervised way. At test time,
the semantics predictions of our network can be fused more consistently in
semantic keyframe maps than predictions of a network trained on individual
views. We base our network architecture on a recent single-view deep learning
approach to RGB and depth fusion for semantic object-class segmentation and
enhance it with multi-scale loss minimization. We obtain the camera trajectory
using RGB-D SLAM and warp the predictions of RGB-D images into ground-truth
annotated frames in order to enforce multi-view consistency during training. At
test time, predictions from multiple views are fused into keyframes. We propose
and analyze several methods for enforcing multi-view consistency during
training and testing. We evaluate the benefit of multi-view consistency
training and demonstrate that pooling of deep features and fusion over multiple
views outperforms single-view baselines on the NYUDv2 benchmark for semantic
segmentation. Our end-to-end trained network achieves state-of-the-art
performance on the NYUDv2 dataset in single-view segmentation as well as
multi-view semantic fusion.Comment: the 2017 IEEE/RSJ International Conference on Intelligent Robots and
Systems (IROS 2017
Dynamics of wave equations with moving boundary
This paper is concerned with long-time dynamics of weakly damped semilinear wave equations defined on domains with moving boundary. Since the boundary is a function of the time variable the problem is intrinsically non-autonomous. Under the hypothesis that the lateral boundary is time-like, the solution operator of the problem generates an evolution process U(t, Ï„ ) : XÏ„ → Xt, where Xt are timedependent Sobolev spaces. Then, by assuming the domains are expanding, we establish the existence of minimal pullback attractors with respect to a universe of tempered sets defined by the forcing terms. Our assumptions allow nonlinear perturbations with critical growth and unbounded time-dependent external forces.Conselho Nacional de Desenvolvimento CientÃfico e TecnológicoMinisterio de EducaciónMinisterio de Ciencia e Innovació
Positive and negative electrocaloric effect in BaTiO in the presence of defect dipoles
The influence of defect dipoles on the electrocaloric effect (ECE) in
acceptor doped BaTiO is studied by means of lattice-based Monte-Carlo
simulations. A Ginzburg-Landau type effective Hamiltonian is used. Oxygen
vacancy-acceptor associates are described by fixed defect dipoles with
orientation parallel or anti-parallel to the external field. By a combination
of canonical and microcanoncial simulations the ECE is directly evaluated. Our
results show that in the case of anti-parallel defect dipoles the ECE can be
positive or negative depending on the density of defect dipoles. Moreover, a
transition from a negative to positive ECE can be observed from a certain
density of anti-parallel dipoles on when the external field increases. These
transitions are due to the delicate interplay of internal and external fields,
and are explained by the domain structure evolution and related field-induced
entropy changes. The results are compared to those obtained by MD simulations
employing an {\it{ab initio}} based effective Hamiltonian, and a good
qualitative agreement is found. In addition, a novel electrocaloric cycle,
which makes use of the negative ECE and defect dipoles, is proposed to enhance
the cooling effect
Simultaneous large deviations for the shape of Young diagrams associated with random words
We investigate the large deviations of the shape of the random RSK Young
diagrams associated with a random word of size whose letters are
independently drawn from an alphabet of size . When the letters are
drawn uniformly and when both and converge together to infinity,
not growing too fast with respect to , the large deviations of the shape of
the Young diagrams are shown to be the same as that of the spectrum of the
traceless GUE. In the non-uniform case, a control of both highest probabilities
will ensure that the length of the top row of the diagram satisfies a large
deviation principle. In either case, both speeds and rate functions are
identified. To complete our study, non-asymptotic concentration bounds for the
length of the top row of the diagrams, that is, for the length of the longest
increasing subsequence of the random word are also given for both models.Comment: Published at http://dx.doi.org/10.3150/14-BEJ612 in the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
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Line shape parameters of PH₃ transitions: Theoretical studies of self-broadened widths and line mixing effects
Line mixing effects have been calculated in various parallel and perpendicular bands of self-broadened PH₃ lines and compared with recent experimental data. The theoretical approach is an extension to symmetric tops with high inversion barrier of the formalism previously developed for NH₃ (Q. Ma and C. Boulet J. Chem. Phys. 144, 224303 (2016)). The model takes into account the non diagonality of the scattering operator within the linespace as well as, in a correct way, the double degeneracy of the j, k levels when k ≠0. Transitions between such levels should be considered as doublets whose components may be coupled by the line mixing process. It has been shown that, at low pressure, the inversion of the experimental data will strongly depend on the splitting between the two components of a doublet. When it is significant, one can measure independently both the width of one component and the intra-doublet coupling matrix element. Otherwise, one can only measure the sum of these two elements. Comparisons with measurements show that the present formalism leads to accurate predictions of the experimental line shapes
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The relaxation matrix for symmetric tops with inversion symmetry. II. Line mixing effects in the ν1 band of NH₃
Line mixing effects have been calculated in the ν1 parallel band of self-broadened NH₃. The theoretical approach is an extension of a semi-classical model to symmetric-top molecules with inversion symmetry developed in the companion paper [Q. Ma and C. Boulet, J. Chem. Phys. 144, 224303 (2016)]. This model takes into account line coupling effects and hence enables the calculation of the entire relaxation matrix. A detailed analysis of the various coupling mechanisms is carried out for Q and R inversion doublets. The model has been applied to the calculation of the shape of the Q branch and of some R manifolds for which an obvious signature of line mixing effects has been experimentally demonstrated. Comparisons with measurements show that the present formalism leads to an accurate prediction of the available experimental line shapes. Discrepancies between the experimental and theoretical sets of first order mixing parameters are discussed as well as some extensions of both theory and experiment
Line Coupling Effects in the Isotropic Raman Spectra of N2: A Quantum Calculation at Room Temperature
We present quantum calculations of the relaxation matrix for the Q branch of N2 at room temperature using a recently proposed N2-N2 rigid rotor potential. Close coupling calculations were complemented by coupled states studies at high energies and provide about 10200 two-body state-to state cross sections from which the needed one-body cross-sections may be obtained. For such temperatures, convergence has to be thoroughly analyzed since such conditions are close to the limit of current computational feasibility. This has been done using complementary calculations based on the energy corrected sudden formalism. Agreement of these quantum predictions with experimental data is good, but the main goal of this work is to provide a benchmark relaxation matrix for testing more approximate methods which remain of a great utility for complex molecular systems at room (and higher) temperatures
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