MICRO MECHANICAL ANALYSIS OF 3-D WOVEN COMPOSITES

A micro mechanical model is carried out to predict micro stresses and macro elastic properties of 3-D woven composites. A unit cell is composed of two phases. One is fiber yarn and the other is resin or fiber yarn in transverse. The additional shearing introduced by bending of fiber yarn is considered. The method to determine the microstructure is also discussed. This model is applied to the analysis of a 3-D woven graphite/epoxy composite. Micro stresses of the cell are studied, and then macro modulus is obtained by employing the average method. The predictions agree well with experimental results.

展示文化底蕴 服务广大群众——辽宁省博物馆新馆建设体会

2004年11月12日，辽宁省博物馆经过精心打造，向社会推出了“清宫散佚书画国宝展”、“中国古代碑志展”、“清宫瓷器展”、“辽代陶瓷展”、“中国古代货币展”、“明清工艺品展”等七大展览，以崭新的面貌呈现在广大观众面前。开馆以来，每天参观者都不下3000人，海内外朋友纷至沓来，市民也排着“长龙”观看展览，每天闭馆的时间一延再延，场面热烈，盛况空前。回顾开馆的过程，辽博始终坚持“三贴近”原则，履行“宣传展示，服务社会”的职能，围绕开馆形式如何求新、展览设计如何求精、宣传推介如何求广、服务质量如何求优等方面做了一些有益的探索。

Quantitative determination of PFC3D microscopic parameters

It is important to calibrate micro-parameters for applying partied flow code(PFC)to study mechanical characteristics and failure mechanism of rock materials.Uniform design method is firstly adopted to determine the microscopic parameters of parallel-bonded particle model for three-dimensional discrete element particle flow code(PFC3D).Variation ranges of microscopic of the microscopic parameters are created by analyzing the effects of microscopic parameters on macroscopic parameters(elastic modulus E,Poisson ratio v,uniaxial compressive strengthσc,and ratio of crack initial stress to uniaxial compressive strengthσci/σc)in order to obtain the actual uniform design talbe.The calculation equations of the microscopic and macroscopic parameters of rock materials can be established by the actual uniform design table and the regression analysis and thus the PFC3D microscopic parameters can be quantitatively determined.The PFC3D simulated results of the intact and pre-cracked rock specimens under uniaxial and triaxial compressions(including the macroscopic mechanical parameters,stress−strain curves and failure process)are in good agreement with experimental results,which can prove the validity of the calculation equations of microscopic and macroscopic parameters.

Estimation of Geodetic Parameters with VLBI Data of Last 5 Years

The meaning to research the potential of VLBI for geodetic applications is summarized. And the observation models and their related parameters of geodetic interest are investigated. Then, the principle and method of using the random model in VLBI data processing are investigated. With the world wide VLBI data from 2000-2004, the conditions to compute the parameters of geodetic interest are introduced, and so are the computing methods and processes. And the computed resuits of the parameters of geodetic interest are analyzed.

Dark energy and fate of the Universe

We explore the ultimate fate of the Universe by using a divergence-free parametrization for dark energy w（z）=w0＋wa, [In（2 ＋ z） / （1 ＋ z） - In 2] . Unlike the Chevallier-Polarski-Linder parametrization, this parametrization has well behaved, bounded behavior for both high redshifts and negative redshifts, and thus can genuinely cover many theoretical dark energy models. Alter constraining the parameter space of this parametrization by using the current cosmological observations, we find that, at the 95.4% confidence level, our Universe can still exist at least 16.7 Gyr before it ends in a big rip. Moreover, for the phantom energy dominated Universe, we find that a gravitationally bound system will be destroyed at a time t = P√2｜ 1 ＋ 3w（ 1）] / [6π] 1 ＋ w（-1）｜], where P is the period of a circular orbit around this system, before the big rip.

Effect of triple-phase contact line on contact angle hysteresis

Recent studies have shown that the triple-phase contact line has critical effect on the contact angle hysteresis of surfaces.In this study,patterned surfaces with various surface structures of different area fractions were prepared by electron etching on a silicon wafer.The advancing angle,receding angle and hysteresis angle of these surfaces were measured.Our experimental results showed that while the geometry of microstructure and contact line have a minor effect on the advancing angle,they have a significant effect on the receding angle and thus the hysteresis angle.We have shown that the effect of microstructure and the contact line can be described by a quantitative parameter termed the triple-phase line ratio.The theoretical predictions were in good agreement with our experimental results.

From strangelets to strange stars:a unified description

The conventionally separated treatments for strangelets and strange stars are now unified with a more comprehensive theoretical description for objects ranging from strangelets to strange stars. After constraining the model parameter according to the Witten–Bodmer hypothesis and observational mass–radius probability distribution of pulsars, we investigate the properties of this kind of objects. It is found that the energy per baryon decreases monotonically with increasing baryon number and reaches its minimum at the maximum baryon number, corresponding to the most massive strange star. Due to the quark depletion,an electric potential well is formed on the surface of the quarkpart. For a rotational bare strange star, a magnetic field with the typical strength in pulsars is generated.