Derivatives on the isotropic tensor functions

The derivative of the isotropic tensor function plays an important part in continuum mechanics and computational mechanics, and also it is still an opening problem. By means of a scalar response function f(Λ_i, I ₁, I ₂) and solving a tensor equation, this problem is well studied. A compact explicit expression for the derivative of the isotropic tensor function is presented, which is valid for both distinct and repeated eigenvalue cases. Throughout the analysis, the formulation holds for general isotropic tensor functions without need to solve eigenvector problems or determine coefficients. On the theoretical side, a very simple solution of a tensor equation is obtained. As an application to continuum mechanics, a base-free expression for the Hill’s strain rate is given, which is more compact than the existent results. Finally, with an example we compute the derivative of an exponent tensor function. And the efficiency of the present formulations is demonstrated. We dedicate this work with deep respect and admiration to the memory of Prof. Gao Yuchen.     

宽孔距微差爆破机理及其合理的孔距与排距

本文以爆破漏斗理论为基础,通过分析密集系数m炮孔孔距与排距之比的变化所引起的爆破几何条件、岩石破碎机理的变化,说明宽孔距微差爆破对改善破碎质量是由于临空面的增加,发育的爆破裂隙系,最小抵抗线的减小,应力降低区域的消失,附加破碎概率的增加和爆方单耗的微小增加。合理的m值以大于4(至少应大于3)小于8为好。     

酯交换反应对PBT／PC共混体系相容性及热行为的影响

研究了ＰＢＴ、ＰＣ间的酯交换反应及共混体系的相容性和热行为。ＩＲ结果表明，在熔融共混过程中ＰＢＴ、ＰＣ间发生了酯交换反应，磷酸三苯酯可在一定程度上抑制酯交换反应的进行，但是当温度过高或共混时间过长时，ＴＰＰ的作用减弱甚至消失。     

中国学者参与IUTAM组织和中国申办ICTAM的历程

国际理论与应用力学联合会（International Union of Theoretical and Applied Mechanics,简称IUTAM）是国际力学界最具权威的非政府学术组织,是国际科学理事会(International Council for Science,简称 ICSU、国科联)的国际科学联合成员。国际理论与应用力学联合会的会员（Adhering Organization）由代表国家级的相关组织或学会组成。经国务院和中国科协批准,1980年中国力学学会正式向IUTAM提出申请,并被IUTAM接纳成为该组织的国家会员。     

中国科协第235次青年科学家论坛简介————-极端复杂测试环境下实验力学的机遇与挑战

由中国科协主办、中国力学学会和北京交通大学共同承办的``中国科协第235次青年科学家论坛'于2011年5月27$\sim$29日在北京交通大学召开.本次论坛的主题为``极端复杂测试环境下实验力学的机遇与挑战', 论坛主席由北京交通大学王正道、中国科学技术大学龚兴龙、国家特种设备检测研究院丁克勤和清华大学冯雪共同担任.      

ELASTIC WAVE LOCALIZATION IN TWO-DIMENSIONAL PHONONIC CRYSTALS WITH ONE-DIMENSIONAL QUASI-PERIODICITY AND RANDOM DISORDER

The band structures of both in-plane and anti-plane elastic waves propagating in two-dimensional ordered and disordered （in one direction） phononic crystals are studied in this paper. The localization of wave propagation due to random disorder is discussed by introducing the concept of the localization factor that is calculated by the plane-wave-based transfer-matrix method. By treating the quasi-periodicity as the deviation from the periodicity in a special way, two kinds of quasi phononic crystal that has quasi-periodicity （Fibonacci sequence） in one direction and translational symmetry in the other direction are considered and the band structures are characterized by using localization factors. The results show that the localization factor is an effective parameter in characterizing the band gaps of two-dimensional perfect, randomly disordered and quasi-periodic phononic crystals. Band structures of the phononic crystals can be tuned by different random disorder or changing quasi-periodic parameters. The quasi phononic crystals exhibit more band gaps with narrower width than the ordered and randomly disordered systems.