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981.
We consider a weakly dissipative quasilinear system of PDEs, governingthe unsteady one-dimensional motion of a relaxing gas, and investigatethe effects ofhigher order terms and the source term, present in the differentialsystem, on the wave motion associated with it. The undisturbed stateof the medium, which is assumed to be uniform and at restadmits mixed nonlinearity, i.e., the quadratic nonlinearity parameter inherent in the system changes sign depending on the basestate. The method of multiple scales is employed to determine theevolution equation governing small perturbations to the state where is of O(), and the effects of nonlinearity arenoticeable over times of order O(–2). 相似文献
982.
In this paper we examine the conditions for surface topography evolution and crack growth/fracture during the cyclic actuation
of polysilicon microelectromechanical systems (MEMS) structures. The surface topography evolution that occurs during cyclic
fatigue is shown to be stressassisted and may be predicted by linear perturbation analyses. The conditions for crack growth
(due to pre-existing or nucleated cracks) are also examined within the framework of linear elastic fracture mechanics. Within
this framework, we consider pre-existing cracks in the topical SiO2 layer that forms on the Si substrate in the absence of passivation. The thickening of the SiO2 that is normally observed during cyclic actuation of Si MEMS structures is shown to increase the possibility of stable crack
growth by stress corrosion cracking prior to the onset of unstable crack growth in the SiO2 and Si layers. Finally, the implications of the results are discussed for the prediction of fatigue damage in silicon MEMS
structures. 相似文献
983.
N. N. Myagkov 《Journal of Applied Mechanics and Technical Physics》2003,44(2):249-254
Nonlinear wave processes in shockloaded elastoplastic materials are modeled. A comparison of the results obtained with experimental data and numerical solutions of exact systems of dynamic equations shows that the model equations proposed qualitatively describe the stressdistribution evolution in both the elasticflow and plasticflow regions and can be used to solve one and twodimensional problems of pulsed deformation and fracture of elastoplastic media. 相似文献
984.
S. V. Stebnovskii 《Fluid Dynamics》2003,38(6):832-838
The possibility of the fragmentation of a liquid piston moving with variable acceleration, due to air jets forming on its free surface and penetrating inward, is established experimentally. The liquid piston acceleration regimes in which air jets capable of penetrating into the liquid are formed from initial perturbations on its free surface are theoretically analyzed. 相似文献
985.
A second-order asymptotic expression for the profile of a capillary-gravity wave traveling over the charged surface of an ideal incompressible fluid is calculated analytically. Two types of steady-state profiles of nonlinear periodic capillary-gravity waves are found. For a certain fixed dimensionless surface charge the shape of the tops of the nonlinear waves changes: from blunt to pointed for short waves and from pointed to blunt for long waves. 相似文献
986.
Shape bifurcation of an elastic wafer due to surface stress 总被引:1,自引:0,他引:1
IntroductionSurfacestressisresponsibleformanymesoscopicalphenomenainmaterialsandthushasbeenstudiedextensively[1~ 5 ].Althoughtheabsolutevalueofsurfacestressofasolidcurrentlycannotbeobtainedbyexperiments,themethodformeasuringitschangehasbeenwellestablished .Theprincipleisratherclear.Whenthesurfacestressononesurfaceofawafer,eitherfreestandingorclampedatoneend ,changesduetocertainreasonssuchasadsorption ,thedifferencebetweenthesurfacestressonthissurfaceandthatontheoppositeoneresultsinabendingmom… 相似文献
987.
We study the self-diffusion of adatom on Pt(100) surface by molecular dynamics. The metal is modeled by the surface embedded-atom potential. Besides the conventional concerted exchange mechanism, a new exchange mechanism in which an ad-dimer diffuses by a concerted motion of three atoms is observed. The importance is that it could become a dominant diffusion mechanism in some cases. 相似文献
988.
Shinzo Watanabe 《Acta Appl Math》2000,63(1-3):441-464
We study asymptotic winding properties of Brownian motion paths on Riemann surfaces by obtaining limit laws for stochastic line integrals along Brownian paths of meromorphic differential 1-forms (Abelian differentials). 相似文献
989.
Augusto Nobile 《Geometriae Dedicata》2000,80(1-3):1-27
First, a modern presentation of the theory of the Halphen transform is given. This method associates to a plane projective curve C, once a general conic has been chosen, another birationally equivalent plane curve, whose singularities are simpler than those of C. Repeating, a curve is obtained whose only singularities are nodes. Next, it is studied how to apply this process to a family of plane curves. With this technique it is possible to transform a given family (with irreducible general member) into one where, generically, the curves are nodal. Finally, it is studied a similar process, called the Halphen–Picard transformation, for surfaces in three-space. By suitably reiterating this procedure, a surface can be transformed into a birationally equivalent one (in the same projective space), such that the sections with planes in a general pencil are, generically, nodal curves. 相似文献
990.
Matthieu Fradelizi 《Proceedings of the American Mathematical Society》2000,128(9):2735-2744
We define the sectional bodies associated to a convex body in and two related measures of symmetry. These definitions extend those of Grünbaum (1963). As Grünbaum conjectured, we prove that the simplices are the most dissymmetrical convex bodies with respect to these measures. In the case when the convex body has a sufficiently smooth boundary, we investigate some limit behaviours of the volume of the sectional bodies.