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91.
A nonlinear model associated to the motion of a membrane is considered as limit of a sequence of approximate models, for which a global existence and uniqueness theorem can be proved. The paper investigates the relationship between the solutions of the real and approximate models. 相似文献
92.
Four kinds of surfactants, sodium laurate, sodium myristate, sodium palmitate and sodium oleate were used to study the effects of surfactant coatings on the lifetime and attenuation of microbubbles. The changes in the size distribution of microbubbles prepared with these surfactants in saline were measured with a Coulter Multisizer (Coulter Electronics Ltd., Luton, UK). Frequency characteristics of ultrasonic attenuation of the microbubble suspensions were measured between 400 kHz and 6 MHz. From the changes in attenuation in the microbubble suspensions over time, it was found that the lifetime of microbubbles in a suspension also depends on the frequency of the irradiating ultrasound. The effect of surfactants on the frequency characteristics of attenuation was also studied, and characteristics of the surfactant coating, including shell elasticity and shell friction parameters were calculated from the measurement results. Microbubbles produced with sodium palmitate had the longest lifetime and the smallest average size. The shell had very little effect on the ultrasonic properties of microbubbles produced with sodium palmitate, suggesting that the sodium palmitate microbubbles behaved ultrasonically as free microbubbles. 相似文献
93.
采用AVR单片机AT90S8515作为控制核心,通过步进电机带动丝杠运动,利用光栅编码器、高精度力传感器、2个引伸计分别测量了位移、力及试件横、纵变形,在老式电子万能材料实验机上建立了新型计算机控制系统,可方便测定弹性模量和泊松比. 相似文献
94.
Mourad Bellassoued 《数学学报(英文版)》2008,24(7):1175-1192
In this paper, we shall investigate the decay property of the solutions to the initial-boundary value problem for the elastic wave equation with a local time-dependent nonlinear damping. We give some decay rate of the energy when the damping term is effective only in a neighborhood of a suitable subset of the boundary. The results obtained in this paper extend, in particular, the known results for the scalar wave equation. 相似文献
95.
This paper investigates the existence and uniqueness of solutions of some boundary value problems modeling the deformation of a membrane of revolution under a partially vanishing normal load. The frame of the membrane models we deal with is the Reissner theory of thin shells of revolution, in which strain-displacement relations are nonlinear, although it assumes a linear stress-strain relation. 相似文献
96.
97.
XIE XiaoPing & XU JinChao School of Mathematics Sichuan University Chengdu China 《中国科学 数学(英文版)》2011,(7)
We consider mixed finite elements for the plane elasticity system and the Stokes equation. For the unmodified Hellinger-Reissner formulation of elasticity in which the stress and displacement fields are the primary unknowns, we derive two new nonconforming mixed finite elements of triangle type. Both elements use piecewise rigid motions to approximate the displacement and piecewise polynomial functions to approximate the stress, where no vertex degrees of freedom are involved. The two stress finite element ... 相似文献
98.
A new multi-scale numerical model is presented using the fractal theory and adopting FEM to simulate the failure of concrete.The relation between the fractal box dimension in large scale and the damage to concrete in small scale is deduced.And the evolutionary process of elastic modulus and strength in small scale is given.Consequently,the multi-scale numerical model is proposed to describe the constitutive relation of concrete between small scale and large scale.A two-dimensional static analysis of a concrete block is performed by using this model and the calculation result is discussed.The propagation of cracks of the concrete block is also studied. 相似文献
99.
CHEMICAL STRUCTURE DEPENDENCE OF THE INTERNAL ENERGY CONTRIBUTION IN RUBBER ELASTICITY 总被引:2,自引:0,他引:2
Juan Sun Xiao-zhen Yang Polymer Physics Laboratory Center for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing China 《高分子科学》2001,(5):447-449
Conformational elasticity theory recently developed has been used to explore the internal energy contribution tothe elastic force f_e/f as a function of strain for poly(cis-1,4-isoprene) and poly(trans-1, 4-isoprene). Calculated f_e/f values arein good agreement with those obtained experimentally. Results show that behavior of f_e/f is mainly contributed by chemicalstructure, or intramolecular interaction, supporting the experimental observations, and that the internal energy contribution isstrain dependent. 相似文献
100.
A three-dimensional, explicit and exact, equilibrium solution is derived for transversely isotropic, linearly elastic bodies
in the form of a right cylinder simply supported over its lateral boundary and loaded over its end faces. This solution, which
generalizes an earlier proposal of Levinson in various respects, is to serve as a benchmark for the corresponding plate theories.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献