A model of biospray for the upper airways

We here deal with a model of therapeutic sprays for the upper airways. We aim to model both inhaled and injected sprays. We propose a numerical solver for the kinetic equation which underlies our model, using a particle method. Eventually, we present two numerical tests for simple geometries of the airways

Measuring Fishing Capacity with a DEA Method in the French Prawn Fishery

According to the objective of stock recovery defined at the summit of Johannesburg, the optimal management of fisheries requires adequacy between the available resource and fishing capacity. However, matching this objective with another goal of economic and social sustainability is also of major importance. Data Envelopment Analysis (DEA) methods are generally used to measure fishing capacity in order to detect the situations of overcapacity. Such methods are particularly adapted to the case of multi-specific fleets. In a fisheries management perspective, the DEA method shows a certain number of limits (sensitivity to outliers, to the sampled fleet) and must be used very carefully. In this communication, the DEA method is applied to prawn (Nephrops norvegicus) fishery in France. The fleet is quite heterogeneous in terms of species, size, fishing zones and strategies. Two homogeneous sub-samples show opposite results in terms of capacity utilisation and profitability, therefore requiring two different management policies

The Economic Results of Fishing Harbors: The Effects of an Internal or External Shock

The economic results of fishing harbours are a key issue for the sustainability of coastal economies. To deal with it, three harbour branches need to be analysed : the suppliers of goods and services, the fishing companies and the trading actors. The compatible state with constraints, various interactions and behaviours of these actors defines the harbour equilibrium . This communication introduces an evaluation model whose interest is twofold. The first one is to assess the economic value and efficiency of fishing harbours at time t. The second one is to estimate the impact that an internal or external shock may have on harbour equilibrium. As far as the methodology is concerned, some recent economic concepts such as Direct Added Value (DAV) or Economic Efficiency Rate (EER) are combined with econometric models. These new concepts are based on the distinction between the company (business management with an aim of making profits) and the firm (productive organisation). Several results can be emphasised: -For each value of landings, the contribution of the fishing harbour to the national economy is assessed both in terms of price and quantity -The threshold of economic efficiency can be estimated -The impact of a shock on both the national economy and economic efficiency of the fishing harbour is computed

Decoupling of arsenic and iron release from ferrihydrite suspension under reducing conditions: a biogeochemical model

High levels of arsenic in groundwater and drinking water are a major health problem. Although the processes controlling the release of As are still not well known, the reductive dissolution of As-rich Fe oxyhydroxides has so far been a favorite hypothesis. Decoupling between arsenic and iron redox transformations has been experimentally demonstrated, but not quantitatively interpreted. Here, we report on incubation batch experiments run with As(V) sorbed on, or co-precipitated with, 2-line ferrihydrite. The biotic and abiotic processes of As release were investigated by using wet chemistry, X-ray diffraction, X-ray absorption and genomic techniques. The incubation experiments were carried out with a phosphate-rich growth medium and a community of Fe(III)-reducing bacteria under strict anoxic conditions for two months. During the first month, the release of Fe(II) in the aqueous phase amounted to only 3% to 10% of the total initial solid Fe concentration, whilst the total aqueous As remained almost constant after an initial exchange with phosphate ions. During the second month, the aqueous Fe(II) concentration remained constant, or even decreased, whereas the total quantity of As released to the solution accounted for 14% to 45% of the total initial solid As concentration. At the end of the incubation, the aqueous-phase arsenic was present predominately as As(III) whilst X-ray absorption spectroscopy indicated that more than 70% of the solid-phase arsenic was present as As(V). X-ray diffraction revealed vivianite Fe(II)3(PO4)2.8H2O in some of the experiments. A biogeochemical model was then developed to simulate these aqueous- and solid-phase results. The two main conclusions drawn from the model are that (1) As(V) is not reduced during the first incubation month with high Eh values, but rather re-adsorbed onto the ferrihydrite surface, and this state remains until arsenic reduction is energetically more favorable than iron reduction, and (2) the release of As during the second month is due to its reduction to the more weakly adsorbed As(III) which cannot compete against carbonate ions for sorption onto ferrihydrite. The model was also successfully applied to recent experimental results on the release of arsenic from Bengal delta sediments

The Mean-Field Limit for Solid Particles in a Navier-Stokes Flow

We propose a mathematical derivation of Brinkman's force for a cloud of particles immersed in an incompressible fluid. Our starting point is the Stokes or steady Navier-Stokes equations set in a bounded domain with the disjoint union of N balls of radius 1/N removed, and with a no-slip boundary condition for the fluid at the surface of each ball. The large N limit of the fluid velocity field is governed by the same (Navier-)Stokes equations in the whole domain, with an additional term (Brinkman's force) that is (minus) the total drag force exerted by the fluid on the particle system. This can be seen as a generalization of Allaire's result in [Arch. Rational Mech. Analysis 113 (1991), 209-259] who treated the case of motionless, periodically distributed balls. Our proof is based on slightly simpler, though similar homogenization techniques, except that we avoid the periodicity assumption and use instead the phase-space empirical measure for the particle system. Similar equations are used for describing the fluid phase in various models for sprays

Celebrating Cercignani's conjecture for the Boltzmann equation

Cercignani's conjecture assumes a linear inequality between the entropy and entropy production functionals for Boltzmann's nonlinear integral operator in rarefied gas dynamics. Related to the field of logarithmic Sobolev inequalities and spectral gap inequalities, this issue has been at the core of the renewal of the mathematical theory of convergence to thermodynamical equilibrium for rarefied gases over the past decade. In this review paper, we survey the various positive and negative results which were obtained since the conjecture was proposed in the 1980s.Comment: This paper is dedicated to the memory of the late Carlo Cercignani, powerful mind and great scientist, one of the founders of the modern theory of the Boltzmann equation. 24 pages. V2: correction of some typos and one ref. adde

Modélisation, étude mathématique et simulation des collisions dans les fluides complexes

Nous nous intéressons à l'étude des aérosols (ou sprays, i.e. ensemble de particules en suspension dans un fluide environnant). La phase continue est décrite par des équations de type Navier Stokes ou Euler. La phase dispersée est décrite par une équation cinétique de type Boltzmann. Nous démontrons l'existence en temps petit d'une solution régulière pour le couplage Vlasov Euler isentropique. Nous présentons les équations précises relatives à la modélisation des collisions/coalescences/fragmentations dans un spray. Nous décrivons la simulation numérique du couplage fluide cinétique dans un code industriel (Commissariat à l'Énergie Atomique), en particulier l'ajout des phénomènes de collisions. Un deuxième modèle de fragmentation est présenté, plus pertinent dans les cas ou les particules ont un grand nombre de Weber. Enfin, nous présentons un résultat concernant, une estimation explicite de trou spectral pour les opérateurs de Boltzmann et de Landau avec potentiels durs linéarisésThis thesis deals with the study of sprays (i.e. particles in suspension in a surrounding fluid).The physical quantities are solutions of partial differential equations. The continuous phase is described by Euler or Navier Stokes type equations. The dispersed phase is described by a kinetic equation. We establish the existence for small tirne of a regular solution for the Vlasov isentropic Euler system. Next, we write clown the precise kernels corresponding to the complex phenomena of oscillations, breakup and collisions/coalescences. Then, we describe the numerical simulation of a kineticfluid coupling in an industrial code (Commissariat à l'Énergie atomique); we especially study the implementation of collisions in the code. A second model of breakup, more adapted when droplets interact with a pressure wave and have an high Weber number, is also presented. We give explicit estimates for the spectral gap of the linearized Boltzmann and Landau operators with hard potentialsCACHAN-ENS (940162301) / SudocSudocFranceF

La justice des mineurs et les affaires de terrorisme

National audienceTerrorism-related cases were marginal in the juvenile justice system for many years but now occupy a growing proportion of its activity, because of the conflict in Syria and Iraq. In criminal matters, it must deal with the cases of minors who have gone to the war zones (or wanted to do so), or who have even planned or conducted attacks on national territory. In educational assistance, it must handle the situations of children who have returned from the war zones and whose parents are under investigation (and often imprisoned). In a context marked by concern and a focus on terrorism, the juvenile justice system has difficulty upholding its specific character and modes of action, and yet these are essential to understanding and addressing these issues.Longtemps anecdotiques pour la justice des mineurs, les affaires de terrorisme occupent désormais une place plus importante dans son activité, notamment en raison du conflit en Syrie et en Irak. Au pénal, elle est saisie de dossiers de mineur(e)s s'étant rendu(e)s sur place (ou ayant souhaité le faire), voire qui ont planifié ou mené des attaques sur le territoire national. En assistance éducative, elle traite les situations d'enfants revenus de ces zones de guerre et dont les parents sont mis en examen (et souvent incarcérés). Dans un contexte marqué par l'inquiétude et la prégnance des logiques antiterroristes, elle a du mal à faire prévaloir ses spécificités et ses modes d'actions, qui pourtant constituent un atout essentiel pour appréhender et traiterces questions

Modélisation multiphysique pour la prédiction de la durée de vie d’un composite à matrice céramique autocicatrisante

Un macro-modèle est utilisé pour simuler le comportement et pour prédire la durée de vie d’un matériau composite à matrice céramique autocicatrisante. Il couple mécanique et physico-chimie afin de décrire les processus de fissuration, cicatrisation et dégradation des fibres en ambiance oxydante. Ce modèle construit à partir de micro-modélisations est en partie identifié par des essais sur constituants de base. Une illustration de ses capacités prédictives est donnée pour des hautes températures