Free Vibration Analysis of Laminated Composite Beams Using Differential Quadrature Method

IntroductionFiber- reinforced composite materials have foundnumerous applications in many engineering fieldsdue to their outstanding engineering properties,such as high strength- to- weight ratio and highstiffness- to- weight ratio.Specially,compositebeams are widely used in the aerospace industry,automobile industry,robotics and sportingappliances.The dynamic characteristics of thesestructures are of greatimportance in the design andservice process.　 As acknowledged by some researchers[1] ,t…     

12-磷钼酸对苯乙烯自由基阻聚反应动力学影响的研究

用膨胀计法研究了12-磷钼酸的自由基阻聚反应动力学，实验证明，在苯乙烯自由基聚合过程中12-磷钼酸确实抑制了聚合反应速率，动力学数据表明，苯忆烯自由基聚合反应速率的改变值与12-磷钼酸浓度的0.16次幂成正比。     

系数间断的Stefan型自由边界问题

本文讨论一维系数间断的Stefan型自由边界问题(1.1)～(1.11).分别证明其弱解与强解的存在性.     

论自发过程

用熵增原理分析讨论了对自发过程的各种现行叙述法和定义,给出了自发过程的严格定义,分析了自由能判据和自由焓判据的实质.     

关于直译和意译新定义的研究

给出了直译和意译的新定义,它体现了直译和意译的本质特征,较好地划清了二者之间的界限。     

Bacterial suicide through stress

Outside of the laboratory, bacterial cells are constantly exposed to stressful conditions, and an ability to resist those stresses is essential to their survival. However, the degree of stress required to bring about cell death varies with growth phase, amongst other parameters. Exponential phase cells are significantly more sensitive to stress than stationary phase ones, and a novel hypothesis has recently been advanced to explain this difference in sensitivity, the suicide response. Essentially, the suicide response predicts that rapidly growing and respiring bacterial cells will suffer growth arrest when subjected to relatively mild stresses, but their metabolism will continue: a burst of free-radical production results from this uncoupling of growth from metabolism, and it is this free-radical burst that is lethal to the cells, rather than the stress per se. The suicide response hypothesis unifies a variety of previously unrelated empirical observations, for instance induction of superoxide dismutase by heat shock, alkyl-hydroperoxide reductase by osmotic shock and catalase by ethanol shock. The suicide response also has major implications for current [food] processing methods. Received 29 March 1999; received after revision 14 May 1999; accepted 17 May 1999