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Fouque C.,CNRS Pascal Institute | Bonnifait P.,Compiègne University of Technology
IEEE Transactions on Intelligent Transportation Systems | Year: 2012

Map matching means determining the location of a mobile with respect to a road network description stored in a digital map. This problem is usually addressed using Global Positioning System (GPS)-like fixes. Unfortunately, there are many situations in urban areas where few satellites are visible because of outages due to tall buildings. In this paper, map matching is solved using raw GPS measurements (pseudoranges and Doppler measurements), avoiding the necessity to compute a global position. The problem is formalized in a general Bayesian framework to handle noise, which can perform multihypothesis map matching when there is not enough information to make unambiguous decisions. This tightly coupled GPS-map fusion has to simultaneously cope with identifying the road and estimating the mobile's position on that road. A marginalized particle filter is proposed to efficiently solve this hybrid estimation problem. Real experimental results are reported to show that this approach can be initialized with fewer than four satellites. It can also track the location with only two satellites once the road selection has been solved. © 2011 IEEE.

Tercas H.,CNRS Pascal Institute | Solnyshkov D.D.,CNRS Pascal Institute | Malpuech G.,CNRS Pascal Institute
Physical Review Letters | Year: 2013

We consider a one-dimensional gas of half-solitons in a spinor Bose-Einstein condensate. We calculate the topological interaction potential between the half-solitons. Using a kinetic equation of the Vlasov-Boltzmann type, we model the coupled dynamics of the interacting solitons. We show that the dynamics of the system in the gaseous phase is marginally stable and spontaneously evolves toward a Wigner crystal. © 2013 American Physical Society.

Nozahic V.,CNRS Pascal Institute | Amziane S.,CNRS Pascal Institute
Composites Part A: Applied Science and Manufacturing | Year: 2012

The engineering of ultra-lightweight lignocellulosic concretes has been considered from the point of view of mechanical, physical or thermal characteristics. Several works underlined interfaces as the weakest part of these composites. This study is devoted to the first interface creation step: the adhesion process. Sunflower stem aggregate properties useful for the study of adhesion are determined. The effects of one chemical treatment and two coatings are analyzed. A new technique to qualify aggregate/binder adhesion during the binder structuring is experimented. Relationships are made between sunflower aggregate properties and adhesion quality. The results show the interest of the new adhesion measurement technique. Ca(OH) 2 treatment, paraffin wax coating and 5 min water pre-wetting improved sunflower/binder interfacial shear stress respectively by 66.3%, 67% and 33%. © 2012 Elsevier Ltd. All rights reserved.

Lhuillier M.,CNRS Pascal Institute
International Journal of Computer Vision | Year: 2011

Recently, it was suggested that structure-from-motion be solved using generic tools which are exploitable for any kind of camera. The same challenge applies for the automatic reconstruction of 3D models from image sequences, which includes structure-from-motion. This article is a new step in this direction. First, a generic error model is introduced for central cameras. Second, this error model is systematically used in the 3D modeling process. The experiments are carried out in a context which has rarely been addressed until now: the automatic 3D modeling of scenes using a catadioptric camera. © 2010 Springer Science+Business Media, LLC.

Nalitov A.V.,CNRS Pascal Institute | Solnyshkov D.D.,CNRS Pascal Institute | Malpuech G.,CNRS Pascal Institute
Physical Review Letters | Year: 2015

We demonstrate that honeycomb arrays of microcavity pillars behave as an optical-frequency two-dimensional photonic topological insulator. We show that the interplay between the photonic spin-orbit coupling natively present in this system and the Zeeman splitting of exciton polaritons in external magnetic fields leads to the opening of a nontrivial gap characterized by a C=±2 set of band Chern numbers and to the formation of topologically protected one-way edge states. © 2015 American Physical Society.

Nalitov A.V.,CNRS Pascal Institute | Malpuech G.,CNRS Pascal Institute | Tercas H.,CNRS Pascal Institute | Solnyshkov D.D.,CNRS Pascal Institute
Physical Review Letters | Year: 2015

We study the spin-orbit coupling induced by the splitting between TE and TM optical modes in a photonic honeycomb lattice. Using a tight-binding approach, we calculate analytically the band structure. Close to the Dirac point, we derive an effective Hamiltonian. We find that the local reduced symmetry (D3h) transforms the TE-TM effective magnetic field into an emergent field with a Dresselhaus symmetry. As a result, particles become massive, but no gap opens. The emergent field symmetry is revealed by the optical spin Hall effect. © 2015 American Physical Society.

Lhuillier M.,CNRS Pascal Institute
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2012

Two problems occur when bundle adjustment (BA) is applied on long image sequences: large calculation time and drift (or error accumulation). In recent work, the calculation time is reduced by local BAs applied in an incremental scheme. The drift may be reduced by fusion of GPS and Structure-from-Motion. An existing fusion method is BA minimizing a weighted sum of image and GPS errors. This paper introduces two constrained BAs for fusion which enforce an upper bound for the reprojection error. These BAs are alternatives to the existing fusion BA which does not guarantee a small reprojection error and requires a weight as input. Then, the three fusion BAs are integrated in an incremental Structure-from-Motion method based on local BA. Last, we will compare the fusion results on long monocular image sequences and low cost GPS. © 2012 IEEE.

Review publications show the advantages of using quantum Monte Carlo (QMC) methods when bonding interactions are modified and consequently, where the electron correlation energy varies and needs to be evaluated accurately. This article considers a model efficient metal catalyst for reactions of carbon monoxide. The ultimate aim is to help design industrially useful catalysts, since the reaction with water produces hydrogen gas selectively, that is, a clean fuel and a sustainable energy source. To narrow the gap between the industrial process and calculation, a model of platinum/oxide is studied. It is mimicked here by copper with and without adsorbed oxygen. Periodicity as well as a validated pseudo-potential are used to limit the number of active electrons considered. A suitable code to carry out this task is CASINO. Furthermore, this code scales linearly to 100,000 processors and possesses a shared memory facility so that it is well-suited to runs on the Blugene/P. It has been in production on such computers since early in 2011. A mixed plane-wave/exponential type orbitals (ETO) basis is used for the systems studied. Plane waves are well-suited to periodic solid substrates and a linear combination of ETOs for molecules. The atomic orbitals have direct physical interpretation, i.e., Coulomb Sturmians and hydrogen-like orbitals. Their radial nodes are shown to be essential in obtaining the vitally important accurate QMC trial wave-functions. Until 2008, ETO products on different atoms were difficult to manipulate for the evaluation of two-electron integrals. Coulomb resolutions provide an excellent approximation that reduces these integrals to a sum of one-electron overlap-like integral products that each involve orbitals on at most two centers. They are thus readily evaluated. Only these integrals need to be re-evaluated to change basis functions. In this article, QMC-VMC variational optimisation is used with a quasi analytic two-electron and nucleus correlation factor. The QMC diffusion Monte Carlo methodology is applied to adsorbed carbon monoxide and some of its reactions. © 2011 Wiley Periodicals, Inc.

Granet G.,CNRS Pascal Institute
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2012

Both of them divide the computational domain into nonoverlapping subdomains and replace the spatial derivative in the Helmoltz equation by a differentiation matrix at the Chebyshev collocation points. The authors of the second reference claim that their method is more robust and accurate because they match the Fourier coefficient at the interfaces between the layers and drop some computed eigenmodes. We challenge these two ideas. Instead, we numerically demonstrate that by keeping all computed eigenmodes and by also numerically computing eigenmodes in homogeneous regions, the pseudospectral method performs better. © 2012 Optical Society of America.

Granet G.,CNRS Pascal Institute
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2014

The B-spline modal method (BMM) as applied to lamellar gratings analysis is revisited, and a new implementation is presented. The main difference with our previous work is that we now take into account discontinuities by putting a spline with a degenerate knot on them. Our new approach is compared with other implementations of the BMM and is shown to be superior in terms of numerical convergence. © 2014 Optical Society of America.

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