Wall effects on the transportation of a cylindrical particle in power-law fluids

The present work deals with the numerical calculation of the Stokes-type drag undergone by a cylindrical particle perpendicularly to its axis in a power-law fluid. In unbounded medium, as all data are not available yet, we provide a numerical solution for the pseudoplastic fluid. Indeed, the Stokes-type solution exists because the Stokes’ paradox does not take place anymore. We show a high sensitivity of the solution to the confinement, and the appearance of the inertia in the proximity of the Newtonian case, where the Stokes’ paradox takes place. For unbounded medium, avoiding these traps, we show that the drag is zero for Newtonian and dilatant fluids. But in the bounded one, the Stokes-type regime is recovered for Newtonian and dilatant fluids. We give also a physical explanation of this effect which is due to the reduction of the hydrodynamic screen length, for pseudoplastic fluids. Once the solution of the unbounded medium has been obtained, we give a solution for the confined medium numerically and asymptotically. We also highlight the consequence of the confinement and the backflow on the settling velocity of a fiber perpendicularly to its axis in a slit. Using the dynamic mesh technique, we give the actual transportation velocity in a power-law “Poiseuille flow”, versus the confinement parameter and the fluidity index, induced by the hydrodynamic interactions

Interactions hydrodynamiques en fluide non newtonien et conséquences sur le transport de particules sphériques

Pour contribuer à la compréhension des interactions hydrodynamiques, à faible nombre de Reynolds, exercées sur une particule par les parois d'un tube où elle est axialement positionnée, les équations du mouvement sont exprimées en formulation fonction de courant et de la vorticité pour être réécrites en coordonnées curvilignes orthogonales. Ces équations sont résolues par la méthode des différences finies. La génération du maillage est effectuée en utilisant la méthode des singularités. La précision des résultats a permis d'évaluer les facteurs de correction de la force totale et de ses composantes de pression et de viscosité. L'analyse des résultats montre, contrairement à ce que l'on obtient en régime dilué, une prédominance des forces de pression sur celles de viscosité évoluant dans un rapport qui ne dépend pas de n en régime de lubrification. Quant au rapport des vitesses de sédimentation en milieu confiné et illimité, celui-ci s'avère ne dépendre que du confinement

Variable binding, symmetric monoidal closed theories, and bigraphs

This paper investigates the use of symmetric monoidal closed (SMC) structure for representing syntax with variable binding, in particular for languages with linear aspects. In our setting, one first specifies an SMC theory T, which may express binding operations, in a way reminiscent from higher-order abstract syntax. This theory generates an SMC category S(T) whose morphisms are, in a sense, terms in the desired syntax. We apply our approach to Jensen and Milner's (abstract binding) bigraphs, which are linear w.r.t. processes. This leads to an alternative category of bigraphs, which we compare to the original.Comment: An introduction to two more technical previous preprints. Accepted at Concur '0

Utilisation de matrices de dissimilarité multiples pour la classification de documents

International audienceThis paper introduces a clustering algorithm that is able to partition objects taking into account simultaneously their relational descriptions given by multiple dissimilarity matrices. These matrices could have been generated using different sets of variables and a fixed dissimilarity function, using a fixed set of variables and different dissimilarity functions or using different sets of variables and dissimilarity functions. This method, which is based on the dynamic hard clustering algorithm for relational data, is designed to provided a partition and a prototype for each cluster as well as to learn a relevance weight for each dissimilarity matrix by optimizing an adequacy criterion that measures the fit between clusters and their representatives. These relevance weights change at each algorithm iteration and are different from one cluster to another. Experiments aiming at obtaining a categorization of a document data base demonstrate the usefulness of this partitional clustering method.Cet article introduit l'algorithme de classification donné dans CarvhaloLechevallier:2007:SFC capable de partitionner des objets en prenant en compte de manière simultanée plusieurs matrices de dissimilarité qui les décrivent. Ces matrices peuvent avoir été générées en utilisant différents ensembles de variables et une fonction de dissimilarité unique, un ensemble de variables donné et différentes fonctions de dissimilarité ou bien différents ensembles de variables et de fontions de dissimilarité. Cette méthode, basée sur l'algorithme de nuées dynamiques est conçu pour fournir une partition et un prototype pour chaque classe tout en découvrant une pondération pertinante pour chaque matrice de dissimilarité en optimisant un critère d'adéquation entre les classes et leurs représentants. Ces pondérations changent à chaque itération de l'algorithme et sont différentes pour chacune des classes. Ce papier se focalise sur une expérience utilisant un ensemble de documents, dont nous connaisssons une classification donnée a priori par des experts servant de référence, et montre l'utilité de cette méthode de partitionnement

A dependent nominal type theory

Nominal abstract syntax is an approach to representing names and binding pioneered by Gabbay and Pitts. So far nominal techniques have mostly been studied using classical logic or model theory, not type theory. Nominal extensions to simple, dependent and ML-like polymorphic languages have been studied, but decidability and normalization results have only been established for simple nominal type theories. We present a LF-style dependent type theory extended with name-abstraction types, prove soundness and decidability of beta-eta-equivalence checking, discuss adequacy and canonical forms via an example, and discuss extensions such as dependently-typed recursion and induction principles

A prototype personal aerosol sampler based on electrostatic precipitation and electrowetting-on-dielectric actuation of droplets

This is an Open Access article, distributed under the terms of the Open Government Licence. http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved. The version of record (T. G. Foat, et al, 'A prototype personal aerosol sampler based on electrostatic precipitation and electrowetting-on-dielectric actuation of droplets', Journal of Aerosol Science, Vol. 95, pp. 43-53, May 2016) is available online at doi: https://doi.org/10.1016/j.jaerosci.2016.01.007.An electrostatic precipitator (ESP) based personal sampler with a laboratory based electrowetting-on-dielectric (EWOD) concentrator could provide a high concentration rate personal aerosol sampler system. A prototype system has been developed based on the concept of a lightweight personal ESP collecting aerosol particles onto a hydrophobic surface followed by the use of an EWOD actuated droplet system to transfer the deposited sample into a microlitre size water droplet.A personal sampler system could provide military or civilian personnel with a wide area biological monitoring capability supplying information on who has been infected, what they have been infected with, how much material they were exposed to and possibly where and when they were infected. Current commercial-off-the-shelf (COTS) personal sampler solutions can be bulky and use volumes of water to extract the sample that are typically a thousand times greater than the proposed method.Testing of the prototype ESP at a sample flow rate of 5Lmin-1 demonstrated collection efficiencies greater than 80% for sodium fluorescein particles larger than 4μm diameter and of approximately 50% at 1.5μm. The ESP-EWOD system collection efficiency measured for Bacillus atrophaeus (BG) spores with an air sample flow rate of 20L min-1 was 2.7% with a concentration rate of 1.9×105 min-1. This was lower than expected due to the corona ions from the ESP affecting the hydrophobicity of the collection surface and hence the EWOD efficiency. However, even with this low efficiency the concentration rate is more than an order of magnitude higher than the theoretical maximum of the best current COTS personal sampler. For an optimised system, ESP-EWOD system efficiency should be higher than 32% with a comparable increase in concentration rate.Peer reviewe

A formalized general theory of syntax with bindings

We present the formalization of a theory of syntax with bindings that has been developed and refined over the last decade to support several large formalization efforts. Terms are defined for an arbitrary number of constructors of varying numbers of inputs, quotiented to alpha-equivalence and sorted according to a binding signature. The theory includes a rich collection of properties of the standard operators on terms, such as substitution and freshness. It also includes induction and recursion principles and support for semantic interpretation, all tailored for smooth interaction with the bindings and the standard operators