Discussion of “The asymmetry of stress in granular media”: [J.P. Bardet and I. Vardoulakis,Int. J. Solids Struct. 2001, Vol. 38, No. 2, pp. 353–367]

The discussion concerns a recently proposed definition of average stress for granular materials, one which can manifest asymmetry in the absence of surface couples, body couples, and contact couples. The average stress was derived from a new postulate that employs virtual work terminology. The discussion shows that the postulate leads to a non-unique average stress and to a non-unique stress asymmetry.     

L.A.S. and Negative Schwarzian Derivative Do Not Imply G.A.S. in Clark’s Equation

It has been conjectured that a locally attracting equilibrium of Clark’s equation \(x_{n+1}=\alpha x_n + (1-\alpha )h(x_{n-k})\) is also globally attracting whenever h is a unimodal or decreasing map with negative Schwarzian derivative. The main aim of this paper is to show that the conjecture is false when \(k\ge 3\). This is done by studying the (Neimark–Sacker) bifurcation at the parameter \(\alpha \) where the locally attracting equilibrium of the equation becomes unstable. Our results, on the other hand, reinforce the validity of the conjecture in the cases \(k=1,2\).     

Addendum to: Symmetry classification of quasi-linear PDE’s. II: an exceptional case

This short note completes the symmetry analysis of a class of quasi-linear partial differential equations considered in the previous paper (Nonlinear Dynamics 51: 309–316, 2008): it deals with an “exceptional” Lie point symmetry which is admitted only if the involved parameters are fixed by precise relationships. The peculiarity of this symmetry is enhanced by the fact that, combined with the presence of a conditional symmetry of “weak” type, it leads to a family of solutions which include, as a particular case, a relevant solution of the Grad–Schlüter–Shafranov equation, well known in plasma physics.     

G.I.泰勒及其影响

G.I泰勒(Geoffrey Ingram Taylor)是英国皇家学会的会员、功勋获得者,本世纪物理学泰斗。他的工作总是在流体力学。固体力学的研究及其在航空学、化学工程、气象学、机械工程、金属物理、海洋学方面应用的最重要的环节上。他具有独特的研究风格,他对于其考虑的几乎所有问题都具有深刻的洞察力。同时,他 ...     

I.I.Glass教授来华访问

加拿大多伦多大学宇航研究所(UTIAS)著名空气动力学家I.I.Glass教授偕夫人应中国力学学会中国气动力研究与发展中心等单位邀请于1985年4月30日至5月31日第二次来我国访问。Glass教授先后在中国科学院力学研究所,北京航空学院,中国气动力研究与发展中心,西北工业大学,中国科技大学,南京航 ...