A Dynamic Frictional Contact Problem with Normal Damped Response

We consider a mathematical model which describes the frictional contact between a viscoelastic body and a reactive foundation. The process is assumed to be dynamic and the contact is modeled with a general normal damped response condition and a local friction law. We present a variational formulation of the problem and prove the existence and uniqueness of the weak solution, using results on evolution equations with monotone operators and a fixed point argument. We then introduce and study a fully discrete numerical approximation scheme of the variational problem, in terms of the velocity variable. The numerical scheme has a unique solution. We derive error estimates under additional regularity assumptions on the data and the solution.     

水平管油水两相流摩擦阻力特性实验研究

本文对水平管内油水液液两相流的摩擦阻力压降特性进行了实验研究。水平管实验段由有机玻璃管制成,内径为40mm。根据油水两相流流型的不同,通过建立物理模型或对实验数据的整理得到了各种典型流型下的摩擦阻力压降计算式。揭示了摩擦阻力压降随混合物速度和体积含水率等的变化规律。     

Analytical bending solutions of elastica with one end held while the other end portion slides on a friction support

Summary Treated herein is an elastica under a point load. One end of the elastica is fully restrained against translation, and elastically restrained against rotation, while the other end portion is allowed to slide over a friction support. The considered elastica problem belongs to the class of large-deflection beam problems with variable deformed arc-lengths between the supports. To solve the governing nonlinear differential equation together with the boundary conditions, the elliptic integral method has been used. The method yields closed-form solutions that are expressed in a set of transcendental equations in terms of elliptic integrals. Using an iterative scheme, pertinent bending results are computed for different values of coefficient of friction, elastic rotational spring constant and loading position, so that their effects may be examined. Also, these accurate solutions provide useful reference sources for checking the convergence, accuracy and validity of results obtained from numerical methods and software for large deflection beam analysis. It is interesting to note that this class of elastica problem may have two equilibrium states; a stable one and an unstable one. Received 5 August 1996; accepted for publication 14 February 1997     

Fluctuations in nonequilibrium systems and broken supersymmetry

The fluctuation-dissipation theorem is not expected to hold for systems that either violate detailed balance or have time-dependent or nonpotential forces. Therefore the relation between response and correlation functions should have contributions due to the nonequilibrium nature. An explicit formula for such a contribution is calculated, which in the present derivation appears as a historydependent term. These relations are the Ward-Takahashi identities of a supersymmetric formulation of the Langevin models, and the new term results from a broken supersymmetry.     

换热器传热管在静水中的挤压膜阻尼研究

本文通过求解三维Navier-Stokes方程,导出计算挤压膜阻尼的公式,对Mulcahy所提出的模型作了改进,并提出了stokes数的间隙修正因子的概念. 改进后的挤压膜阻尼模型计及管子振幅的影响,在管子振幅很小的情况下,它与Mulcahy提出的模型相似,实际上可把Mulcahy提出的模型看成改进后模型的一个特例. 为了验证改进后的模型,对传热管在空气和静水介质中的阻尼进行了实验研究.结果表明理论计算值与实验测量值符合良好.     

Core potential of intermolecular forces applied to third virial coefficients and transport coefficients of polyatomic gases

The three-molecular cluster integrals for oxygen, nitrogen, and carbon tetrafluoride and the coefficients of viscosity and self-diffusion for nitrogen and carbon dioxide are discussed on the basis of the Kihara convex-core potential of intermolecular forces. For the equilibrium property, the relative size of the core is essential; for the transport properties, the nonspherical character of the molecule plays an important role.