力学大师S.P.铁木辛柯

S.P.铁木辛柯,20世纪活跃在工程力学领域约60年,培养了几代优秀的工程师和力学家,取得了丰硕的研究成果,推动了工程力学的进展,人们尊之为力学大师.本文从学术生涯、研究成果、学术著作、学术贡献几方面简介铁木辛柯.     

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 \(k=1,2\).     

S.M.Bogdonoff教授在中国科学院力学研究所讲学

美国普林斯顿大学S.M.Bogdonoff教授于5月19日下午在力学所介绍了他们几年来在湍流边界层分离研究方面取得的进展和今后工作的展望。他们研究的主要对象是四种翼的典型外形(图1)在马赫数3和高雷诺数(10~7—10~8/米)来流条件下产生的激波湍流边界层干扰流场。研究内容主要是干扰流场的平均性质和干扰流场的非定常性。他们用煤油-烟黑油流      

W.SHOCKLEY’S EQUATION AND ITS LIMITATION

The problem of p-n junction in Ref.[1] is discussed in thispaper.We consider that Tsai Shu-tang’s view that w.Shock-ley’s equation cannot be applied to all circumstances is cor-rect,but we cannot sag,because of this,that W.Shockley’smethod of treatment and its conclusion for p-n junction arewrong.In this paper we demonstrated that W.Shockley’s e-quation merely describes ideal p-n junction model.     

W.SKOCKLEY’S EQUATION AND ITS LIMITATION

The problem of P-n junction in Ref.[1] is discussed in this paper. We consider that Tsai Shu-tang’s view that W.Shock-ley’s equation cannot be applied to all circumstances is correct, but we cannot say, because of this, that W. Shockley’s method of treatment and its conclusion for P-n junction are wrong. In this paper we demonstrated that W. Shockley’s e-quation merely describes ideal P-n junction model.     

均匀各向异性湍流后期衰变的涡性结构与J. C. Bennett禾口S. Corrsin实验

本文在以前几篇文章的基础上,假定后期各向异性湍流场是由我们以前所用的涡旋和涡球迭加所组成。假定涡旋和涡球是彼此独立的。涡旋的轴的方向在空间分布是各个方向机率相等的,而涡球的轴则在空间取某一固定方向。在平均时除了对涡旋和涡球的中心进行平均以外,还要对涡旋的轴的方向进行平均。由于涡球的轴指向某一固定方向,所以并不平均。通过这样平均,我们得到二元速度关联和三元速度关联张量。最后算出了沿某一特定方向的二元速度关联函数和三元速度关联函数的各向异性修正项和。并且作出了f(r)和k(r)的曲线与J. C. Bennett和S. corrsin的实验进行比较。二元速度关联函数f(r)仍旧是指数型的关联函数和实验比较符合,三元速度关联函数k(r)和实验符合得很好。     

On the activity of the S. P. Timoshenko institute of mechanics in 1991–2011

This paper, dedicated to the 20th anniversary of the independence of Ukraine (1991–2011), analyzes the activity of the S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, in 1991–2011. The major scientific achievements and their evaluation by the world’s scientific community are briefly reported. The scientific staff and training activity of the Institute are discussed. New books (m?n?graphs, textbooks) and publications in scientific journals are mentioned. It is shown that the scientists of the Institute participate in the establishment of the scientific information environment     

Comments on “Effects of temperature dependent fluid properties and variable Prandtl number on the transient convective flow due to a porous rotating disk by M. S. Alam,S. M. Chapal Hossain,M. M. Rahman [Meccanica (2014) 49:2439–2451]”

In this letter, we submit our comments on recently published paper titled “Effects of temperature dependent fluid properties and variable Prandtl number on the transient convective flow due to a porous rotating disk by Alam et al. (Meccanica 49: 2439–2451, 2014)”. Authors of this paper have attempted to present similarity solutions in the paper. We comment in this letter is that the similarity transformations considered in Alam et al. (Meccanica 49: 2439–2451, 2014) are not correct and thus results are leading to invalid conclusions.     

AN ANALYTICAL SOLUTION OF G.I.TAYLOR’S THEORY OF PLASTIC DEFORMATION IN IMPACT OF CYLINDRICAL PROJECTILES AND ITS IMPROVEMENT

The theory of plastic deformation in the impact of cylindrical projec-tiles on rigid targets was first introduced by G.I.Taylor(1948).The importance of this theorg lies in the fact that the dgnamic yieldstrength of the materials can be determined from the measurement ofthe plastic deformation of flat-ended cylindrical projectiles.Fromthe experimental results.we find that the dynamic gield strengthis independent of impact velocity.and that it is higher than the sta-tic yield strength in general,and several times higher than the sta-tic yield strength in certain cases.This gives an important founda-tion for the studg of elastoplastic impact problems in qeneral.How-ever,it is well known that the complexity of differential equationsin Taylor’s theory compelled us to use the troublesome numerical so-lution.In this paper,the analgtical solution of all the equationsin Taylor’s theory is given in parametrical form and the results arediscussed in detail.In the latter part of this paper,the method of calculatio     

AN ANALYTICAL SOLUTION OF G. I. TAYLOR’S THEORY OF PLASTIC DEFORMATION IN IMPACT OF CYLINDRICAL PROJECTILES AND ITS IMPROVEMENT

The theory of plastic deformation in the impact of cylindrical projectiles on rigid targets was first introduced by G. I. Taylor(1948)^[1]. The importance of this theory lies in the fact that the dynamic yield strength of the materials can be determined from the measurement of the plastic deformation of flat-ended cylindrical projectiles. From the experimental results^[2] we find that the dynamic yield strength is independent of impact velocity, and that it is higher than the static yield strength in general, and several times higher than the static yield strength in certain cases. This gives an important foundation for the study of elastoplastic impact problems in general. However, it is well known that the complexity of differential equations in Taylor’s theory compelled us to use the troublesome numerical solution. In this paper, the analytical solution of all the equations in Taylor’s theory is given in parametrical form and the results are discussed in detail.In the latter part of this paper, the method of calculation of impulse of impact is improved by considering the processes of radial’ movement of materials. The analytical solution of the improved theory shows that it gives better agreement with the experimental results than that of original Taylor’s theory.