Is Universe a big pattern? Comment on Newell and Venkataramani's essay

This note is motivated by the contribution of Alan Newell to this thematic issue of C. R. Mécanique honoring Pierre Coullet. The point of this comment is to show that some ideas in Newell and Venkataramani's essay are already there in the present theory of the ultimate structure of our Universe, although formulated in a completely different way. In particular, the relationship between the structure of the Universe at small scale and the nagging question of the missing mass is present in both theories, whereas a precise link between the observations and either theory is yet to be found.     

Cristallisation induite par écoulement ou par déformation d'un polymère – une approche thermodynamique

We present in this note a model of flow induced crystallization of a thermoplastic. The thermomechanical context of this model is that of generalized standard materials. We show first that it is possible to express by a variable change the traditional quiescent laws of crystallization (Avrami kinetic) in this standard formalism. We show then that a simple addition of the potentials of viscoplastic flow to the crystallization potentials, makes it possible to describe strain induced crystallization.     

Condition d'explosion par impact de détonation

We study the induction of an explosion in a homogeneous substance solicited by a shock resulting from the impact of a planar autonomous detonation. We obtain the explosion time and a condition for initiation as a constraint on the length of the detonating charge.     

Changements de structure provoqués par l'écoulement

Résumé De même que la structure conditionne les propriétés rhéologiques, l'état d'écoulement d'un système peut être un facteur déterminant de sa structure par suite des réarrangements moléculaires qu'il provoque. On étudie le cas d'un liquide pur à fortes interactions intermoléculaires et celui des suspensions colloïdales et solutions macromoléculaires. Les calculs sont développés dans des cas types où l'écoulement entraîne des changements de phase ou des variations de l'état d'agrégation. L'étude rhéologique ou rhéooptique de tels systèmes permet la détermination expérimentale des énergies d'interaction intermoléculaires. On en donne des exemples.

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Zusammenfassung Ebenso wie die Struktur die Theologischen Eigenschaften beeinflußt, kann der Fließzustand eines Systems ein maßgebender Faktor seiner Struktur als Folge der molekularen Umordnung, die er erzeugt, sein. Es wird der Fall einer reinen Flüssigkeit mit starken intermolekularen Wechselwirkungen sowie der kolloiden Suspensionen und makromolekularen Lösungen untersucht. Die Rechnungen sind für typische Fälle durchgeführt, bei denen das Fließen Phasenänderungen und Änderungen des Aggregatzustandes hervorruft. Die rheologische und rheooptische Untersuchungen solcher Systeme erlaubt eine experimentelle Bestimmung der zwischenmolekularen Wechselwirkungsenergien, wie an Beispielen gezeigt wird.

     

小问题? (39)

125.均质矩形物体ABCD置于斜面上,以跨过滑轮的细绳与重为W的另一物体相连。设物体ABCD重为P,宽AB=a,高BC=4a,与斜面间的摩擦系数μ=0.4,斜面斜率为3/4,细绳的AE段为水平(图1,图中未按比例)。不计滑轮摩擦,求使物体 ...     

消息与动态 (39)

应用自行研制的新的表面热膜,在低速风洞中进行的翼型的流动显示试验在南京航空学院气动所取得了初步成功。这种显示方法是将表面热膜粘贴在模型表面上,与 ...     

Écoulement turbulent dans une cavité rotor–stator fermée de grand rapport d'aspect

A direct numerical simulation is combined with laboratory study to describe the turbulent flow in an annular high speed rotor–stator cavity. Comparisons are made for a turbulent flow characterized by a Reynolds number $\mathit{Re}=\Omega R_2^2/\nu =9.5\times {10}^4$ in a shrouded cavity of large aspect ratio $G=(R_2?R_1)/h=18.32$, where $R_1$ and $R_2$ are the inner and outer radii of the rotating disk, and h is the inter-disk space. A close agreement is found between the computed results and the experimental data for the mean and turbulent fields.? To cite this article: S. Poncet, A. Randriamampianina, C. R. Mecanique 333 (2005).     

Fissuration multiple par corrosion sous contrainte : Modélisation du comportement mécanique par une méthode d'homogénéisation

Stress Corrosion Cracking (SCC) phenomenon is characterised by initiation and propagation of surface cracks frequently multiple. In order to model the mechanical behaviour of such materials we propose, as for composites, the use of homogenization techniques. Two materials are considered, first one corresponding to the cracked external volume and the second to the internal safe material. The cracked volume is considered as a two phase material, i.e., elastic matrix containing elliptical voids. The overall behaviour of the equivalent material is obtained applying the usual homogenization rules. Comparison between simulations and experimental results is done.     

Mouvements propres d'un système à 1 D.D.L. avec amortissement viscoélastique

In this note, one considers a 1-d.o.f. oscillator consisting of a mass and a viscoelastic spring, the rheology of which is represented by a generalized so-called Biot's model with $2n+1$ parameters. It is proved that its $n+2$ independent eigenmotions are of the following nature: two eigenmotions damped with or without oscillations (as in the case of classical viscous damping) and n eigenmotions damped without oscillations which are induced by the viscoelastic rheology. To cite this article: P. Muller, C. R. Mecanique 333 (2005).     

Mesure de la température de gouttelettes en combustion par fluorescence induite par laser à deux couleurs : résultats préliminaires et perspectives

Two color laser-induced fluorescence technique is able to measure mean temperature of flying droplets, in the evaporation regime without combustion. This paper presents preliminary results about the use of this technique in reactive media.     

Topological classification of affine mappings from ℝ<Superscript>2</Superscript> into ℝ<Superscript>2</Superscript>

We investigate affine mappings from ℝ² into ℝ² and establish necessary and sufficient conditions for the topological conjugacy of these mappings. Translated from Neliniini Kolyvannya, Vol. 11, No. 4, pp. 472–480, October–December, 2008.