Cambrian Hopf Algebras

Cambrian trees are oriented and labeled trees which fulfill local conditions around each node generalizing the conditions for classical binary search trees. Based on the bijective correspondence between signed permutations and leveled Cambrian trees, we define the Cambrian Hopf algebra generalizing J.-L. Loday and M. Ronco's algebra on binary trees. We describe combinatorially the products and coproducts of both the Cambrian algebra and its dual in terms of operations on Cambrian trees. We also define multiplicative bases of the Cambrian algebra and study structural and combinatorial properties of their indecomposable elements. Finally, we extend to the Cambrian setting different algebras connected to binary trees, in particular S. Law and N. Reading's Baxter Hopf algebra on quadrangulations and S. Giraudo's equivalent Hopf algebra on twin binary trees, and F. Chapoton's Hopf algebra on all faces of the associahedron.Comment: 60 pages, 43 figures. Version 2: New Part 3 on Schr\"oder Cambrian Algebra. The title change reflects this modificatio

A Monolithic Finite Element Approach to Compute Permeabilityatc Microscopic Scales in LCM Processes

International audienceIn this paper, a numerical approach for permeability determination at the mesoscopic and microscopic scales is proposed. In an eulerian framework, the computational domain (corresponding to the elementary cell) is composed of one single mesh, where the interface between the fibres (microscopic scale) or the yarns composing the fabric (mesoscopic scale) and fluid is captured through a level set approach. At the microscopic scale, Stokes equations are considered. At the mesoscopic scale, resolution of a coupled Stokes (in the fluid)Darcy (in the yarn) flow is necessary and is performed using also a mixed finite element technique, providing a single system of equations. Stabilization of the Brinkman flow is attained using the P1+/P1 element. Results on permeability computation at the microscopic scale, as well as sensitivity analysis, illustrate the methodology followed

Etudes numériques et expérimentales sur les suspensions de fibres et de sphères solides

International audienceUne méthode numérique a été développé afin de permettre le calcul du mouvement de particules solides dans un fluide en cisaillement. Les calculs sur un volume élémentaire permettent d'étudier l'évolution de l'orientation de particules allongées pour un fluide chargés en particules sphériques. Finalement, des observations expérimentales sont faites en utilisant des outils de rhéooptique

Numerical and Experimental Studies of Suspensions of Fiber and Spherical Solid Particles

Coupled Problems 2009 is one of the Thematic Conferences of the European Community in Computational Methods in Applied Sciences (ECCOMAS).International audienceThis paper is devoted the behavior of suspension of fiber-spheres particles. We pointed out by experimental and numerical observations that the Jeferry approximation is no more valid as the sphere particle concentration increases

Optical extinction in a single layer of nanorods

We demonstrate that almost 100 % of incident photons can interact with a monolayer of scatterers in a symmetrical environment. Nearly-perfect optical extinction through free-standing transparent nanorod arrays has been measured. The sharp spectral opacity window, in the form of a characteristic Fano resonance, arises from the coherent multiple scattering in the array. In addition, we show that nanorods made of absorbing material exhibit a 25-fold absorption enhancement per unit volume compared to unstructured thin film. These results open new perspectives for light management in high-Q, low volume dielectric nanostructures, with potential applications in optical systems, spectroscopy, and optomechanics

Comment rater la validation de votre algorithme d'ordonnancement

National audienceImaginons que vous veniez de développer un nouvel algorithme d’ordonnancement : félicitations ! Pourdisposer d’informations qualitatives sur votre algorithme et le comparer à d’autres vous avez décidécomme beaucoup avant vous de réaliser des simulations. Très classiquement vos simulations portentsur des jeux de données aléatoires (ici, des graphes orientés acycliques)

Étude comparative de quelques marqueurs de reformulation paraphrastique dans les articles de recherche et les articles de vulgarisation

Cette étude est menée dans le cadre d’un projet visant à mettre au jour les spécificités grammaticales des articles de recherche et des articles de vulgarisation. Il s’agit de montrer que si, comme l’ont exposé de nombreux auteurs, vulgarisation et reformulation en tant qu’activités discursives sont effectivement étroitement associées, cette corrélation fonctionnelle n’implique pas pour autant une surutilisation des marqueurs explicites de reformulation dans les textes vulgarisés. Trois marqueurs (en particulier « that is, i.e. » et « namely ») sont clairement propres aux articles de recherche. Pour rendre compte de ce résultat, nous dégageons deux paramètres, l’un formel, l’autre fonctionnel, dont les valeurs se combinent pour générer quatre grands types de reformulation : hétérogène clarifiante, hétérogène précisante, homogène clarifiante et homogène précisante. Ainsi, il apparaît que chacun des deux discours étudiés privilégie, en raison de sa visée socio-pragmatique, certaines combinaisons, tandis que chacun des marqueurs de reformulation est employé prioritairement dans un ou deux types de reformulation, ce qui explique leur fréquence dans les articles de recherche et leur relative rareté en discours vulgarisé.This study is part of a wider research project which seeks to describe the grammatical properties of research articles and popular science articles. As many authors have shown, there is a close connection between reformulation and popularization understood as discourse practices. However, this does not entail that writers of popular science make extensive use of formal markers of reformulation. In fact, the corpus analysis shows that three connectors (“that is, i.e.” and “namely”) are specific to research articles. We suggest that two parameters are relevant to account for this: (i) Is the reformulation homogeneous or heterogeneous? (ii) Is it intended as a means of making things clearer or more precise? Each genre, because of its socio-pragmatic properties, is associated with one or two kinds of reformulation. The same holds of individual markers, which explains why they are used frequently in research articles and much less so in popular science articles

Semiconductor nanostructures for spectral filtering

International audienceWe present theoretical and experimental study of nanostructured guided-mode resonant filter, made of a highly doped InAsSb grating and a GaSb waveguide