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Analysis of limitations in divided-pulse nonlinear compression and amplification
No full textInternational audienceWe analyze quantitatively physical effects that limit the coherent combining efficiency in highly nonlinear divided-pulse fiber-based setups such as parabolic amplifiers or nonlinear temporal compression experiment. The impact of differential dispersion and non-equal replicas power is assessed using numerical simulations and compared with experimental demonstrations. We also point out optimization strategies to minimize the impact of these effects on the performance of ultrafast fiber sources
Getting the most out of it: optimal experiments for parameter estimation of microalgae growth models
No full textInternational audienceMathematical models are expected to play a pivotal role for driving microalgal production towards a profitable process of renewable energy generation. To render models of microalgae growth useful tools for prediction and process optimization, reliable parameters need to be provided. This reliability implies a careful design of experiments that can be exploited for parameter estimation. In this paper, we provide guidelines for the design of experiments with high informative content based on optimal experiment techniques to attain an accurate parameter estimation. We study a real experimental device devoted to evaluate the effect of temperature and light on microalgae growth. On the basis of a mathematical model of the experimental system, the optimal experiment design problem was formulated and solved with both static (constant light and temperature) and dynamic (time varying light and temperature) approaches. Simulation results indicated that the optimal experiment design allows for a more accurate parameter estimation than that provided by the existing experimental protocol. For its efficacy in terms of the maximum likelihood properties and its practical aspects of implementation, the dynamic approach is recommended over the static approach
Measurement of prompt psi(2S) to J/psi yield ratios in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV
No full textSubmitted to Phys. Rev. Lett; see paper for full list of authorsThe ratio between the prompt psi(2S) and J/psi yields, reconstructed via their decays into muon pairs, is measured in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV. The analysis is based on PbPb and pp data samples collected by CMS at the LHC, corresponding to integrated luminosities of 150 inverse microbarns and 5.4 inverse picobarns, respectively. The double ratio of measured yields, (N[psi(2S)]/N[J/psi])[PbPb] / (N[psi(2S)]/ N[J/psi])[pp], is computed in three PbPb collision centrality bins and two kinematic ranges: one at midrapidity, abs(y)<1.6, covering the transverse momentum range 6.
A symbolic model for timed concurrent constraint programming
No full textInternational audienceConcurrent Constraint Programming (ccp) is a model for concurrency where agents interact with each other by telling and asking constraints (i.e., formulas in logic) into a shared store of partial information. The ntcc calculus extends ccp with the notion of discrete time-units for the specification of reactive systems. Moreover, ntcc features constructors for non-deterministic choices and asynchronous behavior, thus allowing for (1) synchronization of processes via constraint entailment during a time-unit and (2) synchronization of processes along time-intervals. In this paper we develop the techniques needed for the automatic verification of ntcc programs based on symbolic model checking. We show that the internal transition relation, modeling the behavior of processes during a time-unit (1 above), can be symbolically represented by formulas in a suitable fragment of linear time temporal logic. Moreover, by using standard techniques as difference decision diagrams, we provide a compact representation of these constraints. Then, relying on a fixpoint characterization of the timed constructs, we obtain a symbolic model of the observable transition (2 above). We prove that our construction is correct with respect to the operational semantics. Finally, we introduce a prototypical tool implementing our method
On the distance-profile of random rooted plane graphs
No full textInternational audienceWe study the distance-profile of the random rooted plane graph Gn with n edges (by a plane graph we mean a planar map with no loops nor multiple edges). Our main result is that the profile and radius of Gn (with respect to the root-vertex), rescaled by (2n) 1/4 , converge to explicit distributions related to the Brownian snake. A crucial ingredient of our proof is a bijection we have recently introduced between rooted outer-triangular plane graphs and rooted eulerian triangulations, combined with ingredients from Chassaing and Schaeffer (2004), Bousquet-Mélou and Schaeffer (2000), and Addario-Berry and Albenque (2013). We also show that the result for plane graphs implies similar results for random rooted loopless maps and general maps
Bessel beam propagation in transparent solids for micromachining applications : theory, simulations and experiments
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Ultra-short pulse laser-induced damage thresholds of broadband high-reflective and low dispersive coatings
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Contraindre les distributions de partons dans les noyaux grâce au boson W produit dans les collisions pPb à 5,02 TeV avec CMS
No full textMeasurements of W bosons produced in pPb collisions at nucleon-nucleon centre-of-mass energy √{s_{ℕ}}=5.02 TeV are presented in the muon plus neutrino decay channel. The data sample of 34.6 nb-1 integrated luminosity was collected by the CMS detector. The W boson differential cross sections, lepton-charge asymmetry and forward/backward asymmetry are computed as a function of the lepton pseudorapidity, for muons of transverse momentum higher than 25 GeV/c. These observables are compared to two sets of parton distributions (PDF). One of two assumes nuclear modifications (EPS09) while the other is simply a superposition of free proton PDF CT10). Some of the observables deviate from expectations based on unmodified and currently available nuclear PDF. One in particular slightly deviates from both predictions which may indicates dependence of nuclear PDF as a function of the valence quark flavor.Les mesures de bosons W produits en collisions pPb à une énergie dans le centre de masse de 5,02 TeV sont présentées dans le canal de désintégration muonique. Les données collectées par le détecteur CMS représentent une luminosité intégrée de 34,6 nb-1. Les sections efficaces de production ainsi que plusieurs asymétries sont mesurées en fonction de la pseudo-rapidité du muon, pour des muons ayant tous une impulsion transverse supérieure à 25 GeV/c. Ces observables sont comparées à deux paramétrisations de distributions partoniques (PDF). La première (CT10) ne considère pas de modifications nucléaires sur les PDF et les PDF de noyaux sont donc une superposition de PDF de protons libres. La seconde (EPS09) tient compte de modifications nucléaires. Les mesures obtenues confirment légèrement certaines modifications et une observable en particulier, dévie des deux paramétrisations. Les données pourraient indiquer une dépendance des PDF nucléaires en fonction de la saveur du quark de valence
Full-Field Measurements on Low-Strained Geomaterials Using Environmental Scanning Electron Microscopy and Digital Image Correlation: Improved Imaging Conditions
No full textInternational audienceFull-field strain measurement at microscale on geomaterials by means of hydromechanical in situ testing and imaging in an environmental scanning electron microscope and digital image correlation techniques is a challenging task because of both low magnitude of investigated strains (typically of the order of 10−3) and unfavourable imaging conditions. In view of improving strain measurement accuracy, three major sources of measurement errors are evaluated, and methods to minimise their effects are proposed. First, a fast and simple procedure to accurately quantify image noise is proposed and subsequently used to optimise various environmental scanning electron microscope setting parameters, such as dwell time, spot size, working distance and chamber pressure. Second, a specific procedure to limit magnification fluctuations to a sufficiently low level is described. Finally, digital image correlation systematic errors are quantified on real images, and several ways to reduce their amplitude are compared. The combination of these improvements finally allows us to reach an appropriate accuracy for overall strain measurements and characterisation of microscale heterogeneities