Modélisation théorique d'écoulements pulses de fluides non newtoniens en conduites viscoélastiques poreuses et anisotropes

A theoretical study concerning the pulsatile flow of an inelastic fluid through anisotropic porous viscoelastic pipes is presented. The objective is to investigate the effects of porosity, conicity in pause, anisotropy and viscoelasticity of pipe wall material for a generalized Casson fluid. An implicit difference method is used to solve the equations, and to determine the axial and radial velocity profiles, the pressure, the flow rate and the flow rate filtration distributions, the transverse rotation and the wall axial and radial displacement. This study, considered as a step in the modelling of flow in blood vessels, may also contribute to other important fields such as water desalination or gel filtration.     

Estimations homogénéisées pour les composites hyperélastiques et applications aux élastomères renforcés

This Note is concerned with the development of variational estimates for the effective stored-energy function of hyperelastic composites undergoing finite deformations. It makes use of a suitable generalization of the “second-order procedure” of Ponte Castañeda, the key idea being the introduction of an optimally chosen “linear thermoelastic comparison composite”, which can then be used to convert available homogenization estimates for linear systems directly into new estimates for hyperelastic composites. The resulting estimates are known to be exact to second order in the contrast. An application is given for particle-reinforced rubbers.     

Non-monotonie numérique de courbes de dispersion en élasticité linéaire

This study concerns the behaviour of dispersion curves stemming from a problem of guided waves in a plane elastic medium that is invariant by translation in one spatial direction and stratified with respect to the other one. We formulate an equivalent problem in a bounded domain using transparent boundary conditions. The dispersion curves that are shown are not monotonous, a phenomenon not yet been encountered but suspected.     

Fonctionnalisations régio et stéréospécifiques successives en méta et en ortho des η6-arènetricarbonylchrome

The η⁶-1-methoxy-2,3-dimethylbenzenetricarbonylchrome and the η⁶-1-dimethylamino-2,3-dimethylbenzenetricarbonylchrome are chemically functional on the methyl group 3 first; the methyl group 2, which is less reactive, is functional later. The η⁶-1-dimethylamino-5,6,7,8-tetrahydronaphthalenetricarbonylchrome is difunctional on positions 5 then 8 using two different electrophiles.     

Formulation du contact avec adhérence en élasticité non linéaire entre deux solides déformables

Within the framework of finite deformations and using an approach to the kinematics of contact due to A. Curnier, Q.C. He and J.J. Téléga, we propose a spatial thermodynamic formulation for the problem coupling unilateral condition, friction and adhesion. The adhesion is characterized by its intensity introduced by M. Frémond. In the case of frictionless contact between an hyperelastic body and a plane rigid support, with a particular `static' law for the evolution of the intensity of adhesion, the problem can be reduced to a minimization one for which we can show the existence of a solution.     

Régimes pseudo-son et acoustique en turbulence compressible

Results of a model for compressible turbulence proposed in a companion note are presented in the case of a statistically stationary isotropic field. The model is first validated by comparison with a direct numerical simulation. The results are then analyzed at higher Reynolds numbers. At low Mach number, two regimes are detected: a pseudo-sound regime occurring in the turbulent part of the spectrum and an acoustic regime appearing at much smaller wave-numbers. In the pseudo-sound regime, the spectrum of the dilatational velocity is found to scale as K⁻³. In the acoustic part of the spectrum, the model is found to agree with classical models in acoustics. Results obtained at higher Mach number are also presented and the differences between the present model and a previous EDQNM theory (Eddy Damped Quasi-Normal Markovian theory) are shortly discussed.     

Réduction et dosage des arséniates en présence de catalyseurs,en particulier le rhénium

The reduction of arsenates to arsenites is normally slow, but is accelerated in the presence of catalysts the use of alkali perrhenate or iodide permits a quantitative reduction by stannous chloride. A method of determination using the latter reducing agent has been developed.     

Instabilité et décrochage tournant en grille d'aubes

Rotating stall is a fundamental hydrodynamic instability which is encountered in most hydraulic and aeraulic turbomachinery. It appears to exist only with cascades that considerably slow down the fluid flow and occurs in the form of rotating structures in which the flow rate may be negative. The paper analyses this instability and its transitions in a simple two-dimensional configuration using a multi-domain numerical scheme and solver. The space-time variation of the flow rates occurring for an angle of attack increasing by steps shows first standing waves, then intermittent and permanent travelling waves of limited amplitude, corresponding to blade stall. At higher angles of attack, a high amplitude wave propagates a single structure (cell) with a negative flow rate, corresponding to stalling of the cascade.     

Dépendance du coefficient homogénéisé par rapport à la forme des inclusions dans un matériau composite

In case of a two components material with a matrix reinforced by a large number of inclusions, we describe explicitely the dependence of the homogenized coefficients in function of the inclusions shape.     

Polymérisation et post-polymérisation de l'acrylate de méthyle en milieu précipitant

The radiation initiated polymerization of methyl acrylate was investigated under precipitating conditions in n-hexane In 10 and 25% monomer solutions, the conversion curves are auto-accelerated and post-polymerization is observed in the dark. The initial rate of this post-polymerization steadily increases with the degree of conversion reached during irradiation, suggesting that trapped growing chains are responsible for the effect. The post-polymerization was followed at 23, 40 and 60°. From the results, it is concluded that chain termination is negligible under such conditions. The addition of methanol to the monomer solutions results in decreased rates and in a reduction of the extent of auto-acceleration. No influence of any “matrix effect” could be detected in these systems.     

Dosages coulométriques à courant constant et en solution non agitée

Accurate evalution of “transition times” occurring during constant current electrolysis in non-stirred media may be used analytically. An apparatus has been devised for such a purpose.The method has been applied to various practical problems and stress is laid on its potentialities and main features.Under favourable conditions, determinations are performed in less than one minute, with an accuracy of about 0.2%.     

Catalyse homogéné: synthèse d'organométalliques σ-acétylèniques catalysée par le cuivre(I)

Copper(I) iodide in triethylamine catalyses the synthesis of σ-alkyne organometallics from phenylacetylene and organometallic halides.     

Etudes micro-analytiques des ions oxyhalogénés par chromatographie et absorption infrarouge

Résumé L'auteur étudie l'analyse des chlorates, bromates, iodates par chromatographie sur papier, sur colonne et par absorption infrarouge.

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Summary A study is described of the analysis of chlorates, bromates, and iodates by chromatography on paper, on column, and by infra red absorption.

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Zusammenfassung Es wird über analytische Untersuchungen der Chlorate, Bromate und Jodate durch Papierchromatographie, Säulenchromatographie und Infrarotabsorption berichtet.