轴向变速运动弦线的非线性振动的稳态响应及其稳定性

研究具有几何非线性的轴向运动弦线的稳态横向振动及其稳定性．轴向运动速度为常平均速度与小简谐涨落的叠加．应用Hamilton原理导出了描述弦线横向振动的非线性偏微分方程．直接应用于多尺度方法求解该方程．建立了避免出现长期项的可解性条件．得到了近倍频共振时非平凡稳态响应及其存在条件．给出数值例子说明了平均轴向速度、轴向速度涨落的幅值和频率的影响．应用Liapunov线性化稳定性理论,导出倍频参数共振时平凡解和非平凡解的不稳定条件．给出数值算例说明相关参数对不稳定条件的影响．     

复合材料层板饱和裂纹间距的试凑法(cut-and-try)

本文首次通过三维有限元法计算分析出90°层中横向裂纹的饱和间距值,为预测饱和裂纹间距提供了一条新途径.     

Shear effects on large amplitude forced vibration of symmetrically laminated rectilinearly orthotropic circular plates

I.IntroductionPlatesandshells'consistingoflaminatedcompositematerialsareimportantstructuralmembersinmodernengineering.Thustheresearchfornonlinearproblemsoftheseplatesandshellshasbecomeincreasinglyimportantl'~II].Especially.therehasalreadybeensomeresearchworktlz--lslonthenonlinearproblemoflaminatedcircularplates.Buttheeffectsoftransversestiearonthenonlinearvibrationoftheplateshavenotbeeddiscussedbecauseofthedifficultyofnonlinearmathematics.However,itisexpectedthatthesheareffectsonlaminatedcom…     

Bending of functionally graded piezoelectric rectangular plates

By introducing two displacement functions as well as two stress functions, two independent state equations with variable coefficients are derived from the three-dimensional theory equations of piezoelasticity for transverse isotropy. A laminated approximation is used to transform the state equations to those with constant coefficients in each sub-layer. The bending problem of a functionally graded rectangular plate is then analyzed based on the state equations. Numerical results are presented and the effect of material gradient index is discussed. Supported by the National Natural Sciences Foundation of China (No. 10002016).     

Modeling of transverse shears of piecewise homogeneous composite bars using an iterative process with account of tangential loads

A nonclassical model for the stress-strain state of a piecewise homogeneous composite bar is proposed. The model is based on an iterative process and takes into account the deplanation of cross sections of the bar caused by transverse shears. Based on the shear strains of some particular approximation, higher approximation models are constructed. The model accounts for both the normal and tangential loads.Presented at the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 4, pp. 487–500, July–August, 2000.     

杆系结构受横向冲击载荷下弹性波传播的实验研究

利用 Ｓ Ｈ Ｐ Ｂ装置,用空气枪加载就 ３５ Ｃｒ Ｍｎ Ｓｉ钢组成的 Ｌ型杆系结构受横向冲击载荷作用的弹性波传播进行了实验研究,给出了一些力学现象,并与轴向冲击的实验进行了对比,得到了有益的结论。     

What Are the Conditions for Exponential Time-Cubed Echo Decays?

Diffusion of precessing spins through a constant field gradient is well-known to produce two distinctive features: an exp(-bt(3)) decay of the echo amplitude in response to two pulses and a much slower decay of the Carr-Purcell echo train. These features will appear whenever the spin frequency is described by a continuous random-walk. The present work shows that this may also occur in the presence of motions with long correlation times tau(c)-continuous Gaussian frequency noise with an exponential autocorrelation has the correct properties over time durations smaller than tau(c). Thus, time-cubed echo decays will occur in situations other than physical diffusion. The decay rate of the Carr-Purcell echo train is shown to vary with the pulse spacing tau whenever the correlation time tau(c) is long; the slower Carr-Purcell decay compared to the two-pulse echo decay is not unique to diffusion. Simulations are presented that display time-cubed decays. The simulations confirm two important criteria: the echo time must be less than tau(c) and the frequency noise must consist of nearly continuous variations, as opposed to step-like changes. These criteria define the range of physical parameters for which time-cubed decays will be observable.     

Experimental Analysis of Optical Trapping System Using Tapered Hemispherically Lensed Optical Fiber

We describe the operation and performance of an optical fiber trap realized using a tapered hemispherically lensed optical fiber. Axial and transverse trapping forces exerted on a microsphere are experimentally analyzed to corroborate the optical trapping using an optical fiber. Experimental results are as follows. (i) Transverse force F_tr acting on a sphere is a restoring force that acts to pull the microsphere back to the center of trap. (ii) Axial force F_ax always acts to push a sphere in the direction of the beam away from the trapping fiber end. (iii) Vector sum of F_tr and F_ax acting on a sphere gives a restoring force directed back to the stable point. (iv) Transverse force F_tr plays a significant role in trapping a micro-sized object by means of an optical fiber.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED TECHNOLOGIES (NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Physics and Mombusho Grant-in Aid for Scientific Research on Priority Areas “Near-field Nano-optics” Project, sponsored by Japan Society for the Promotion of Science.     

横观各向同性体三维裂纹的瞬态扩展

讨论一对集中力作用下横观各向同性体三维裂纹的瞬态扩展问题,其解答构成三维裂纹瞬态扩展问题的基本解。求解方法是基于积分变换技术,将混合边值问题化为Wiener-Hopf型积分方程,求得了裂纹所在平面应力和位移的封闭形式解。进一步利用Abel定理和Cagniard-de Hoop方法,求得了动态应力强度因子的精确解。最后通过数值结果揭示了横观各向同性材料三维扩展裂纹尖端场的动态特性。     

基于关联度的高阶集合流关联分析方法

基于关联度概念,建立了可以分别检测高阶集合流的方位角关联、横向动量模关联和横向关联的新方法.采用新方法分别分析了1.2A GeV Ar+BaI₂碰撞的Bevalac流光室4π实验事件中末态粒子分布的方位角关联与粒子横向动量模的关联对高阶集合流关联的贡献.研究表明:对于这组碰撞实验,末态粒子分布的方位角关联相对横向动量模的关联在高阶集合流关联中起主要作用;末态粒子横向动量模的关联不但可以使粒子群高阶关联的强度有所增加,而且还为在更为狭窄的区间上确定集合流集体性的范围提供了重要信息.