Quasi-static versus dynamic failure instabilities in fluid-saturated porous mediaModes de rupture sous conditions quasi-statiques et dynamiques dans les milieux poreux saturés

Using a linear perturbation approach, we show that under quasi-static conditions, unbounded growth of perturbations coincides with localization under drained or undrained conditions. Under dynamic loadings, unbounded growth is related either to the emergence of stationary discontinuities (and these are set by drained conditions) or to the appearance of the flutter phenomenon (acceleration waves). For associative behaviour the inception of unbounded growth is always set (under both static and dynamic conditions) by the singularity of the drained acoustic tensor. It is only for non-associative flow that unbounded growth may correspond to undrained localization in quasi-static conditions and to flutter under dynamic conditions. To cite this article: A. Benallal, C. Comi, C. R. Mecanique 330 (2002) 339–345.     

Experimental evidence of energy pumping in acousticsMise en évidence expérimentale de pompage énergétique en acoustique

This Note presents an experimental vibro-acoustic set-up that aims to reproduce the energy pumping phenomenon between an acoustic medium and an essentially nonlinear oscillator. It shows a one-way irreversible transfer of energy between the first acoustic mode in a tube and a thin visco-elastic membrane. To cite this article: B. Cochelin et al., C. R. Mecanique 334 (2006).     

Analysis of viscoelastic contact with normal compliance,friction and wear diffusionAnalyse d'un problème viscoélastique avec compliance normale,frottement et diffusion d'usure

We consider a quasistatic problem of frictional contact between a viscoelastic body and a moving foundation. The contact is with wear and is modeled by normal compliance and a law of dry friction. The novelty in the model is that it allows for the diffusion of the wear debris over the potential contact surface. Such kind of phenomena arise in orthopaedic biomechanics and influence the properties of joint prosthesis. We derive a weak formulation of the problem and state that, under a smallness assumption on the problem data, there exists a unique weak solution for the model. To cite this article: M. Shillor et al., C. R. Mecanique 331 (2003).     

A two scale method for modulated vibration modes of large,nearly repetitive,structuresUne méthode asymptotique à deux échelles pour les modes de vibrations modulés des longues structures presque répétitives

Nearly repetitive structures can present at least two kinds of vibration modes: localized modes and modulated ones. In this Note, the multiple scale method is applied to characterize a packet of modulated modes. In this respect, only small size problems are to be solved: periodic problems posed on a few basic cells and amplitude equations, which define a sort of homogenized model for this type of modes. It is established that the influence of the non-repetitive part of the structure is accounted by a boundary condition. To cite this article: E.M. Daya et al., C. R. Mecanique 331 (2003).     

Continuum modeling for the modulated vibration modes of large repetitive structuresModèle continu pour les modes de vibrations modulés des longues structures répétitives

By homogenization theory, one can predict the vibrations of long repetitive structures in the low frequency range. Beyond this range, many modes have a modulated shape. Based on a multiple scale analysis, a continuum model is presented, that is able to account for this class of modes. This model involves a real coefficient that can be computed from the finite element resolution of problems defined on a few basic cells. An application in 2D elasticity is presented. To cite this article: E.M. Daya et al., C. R. Mecanique 330 (2002) 333–338.     

Magnetoelastic domain wall wave in a ferromagnet

We show that in a magnetically and elastically uniaxial ferromagnetic insulator, a new type of inhomogeneous elastic wave may propagate along a 180° domain wall. A numerical example is given.     

6─或8─脂代─7─氧香豆素与二氢呋喃香豆素的NMR，MS研究

对从重齿毛当归（ＡｎｇｅｌｉｃａｐｕｂｅｓｃｅｎｓＭａｘｉｍｆ．ｂｉｓｅｒｒａｔａＳｈａｎｅｔＹｕａｎ）根及根茎中分得的１２种６－或８－脂代－７－氧－香豆素和８种二氢呋喃香豆素衍生物进行了１Ｈ和１３ＣＮＭＲ分析研究．结合文献．做出规律性总结．运用２ＤＮＭＲ技术．对文献中当归醇类化合物碳谱中的个别错误归属给予了纠正，并首次探讨了此类化合物的ＭＳ裂解途径．     

浙产山胡椒根挥发油化学成分的研究

采用水蒸汽蒸馏法提取挥发油,气相色谱-质谱联用法结合计算机检索对浙产山胡椒根挥发油的化学成分进行分析和鉴定,用气相色谱面积归一法计算各组分的相对百分含量。从山胡椒根的挥发油中,分析并鉴定出17种化合物。主要含1,2,3,3a,4,5,6,7-八氢-1,4-二甲基-7-(1-甲基乙烯基)-奥艹、4,6,6-三甲基-2-(3-甲基-1,3-丁二烯基)-3-氧杂环-辛烷、愈创木醇、1,2,3,5,6,7,8,8a-八氢-1,4-二甲基-7-(1-甲基乙烯基)-奥艹,它们占挥发油总量的84.75%。