卵形杆弹对铝靶的斜侵彻

在Lagrange有限元基础上,扼要介绍了一种适用于三维斜侵彻数值模拟计算的滑移面处理技术。该方法放弃了传统滑移计算中从单元的设置,而代之以预设从节点,从而避免三维斜侵彻数值计算中主从单元的相交、滑移面的识别、修正与再定义的困难。在确保计算精度的同时,有效地提高了计算效率。卵形杆弹对铝靶侵彻的系列数值模拟计算表明,无论对于正撞击或斜撞击,本文中所获结果与实验结果都有良好的一致性,这说明本文中所述方法和所建程序的合理性和有效性,为侵彻贯穿过程的数值分析提供了一种实用和有效的手段。     

用Laplace变换法求解端点系有集中质量的弹性杆的振动问题

用Laplace变换法求解了一端为齐次边界条件,另一端系有集中质量的弹性杆的纵振动问题,推广了相关文献的结果。     

ZnO纳米线/棒阵列的水热法制备及应用研究进展

氧化锌(ZnO)纳米线/棒阵列的质量决定了所构建光电器件的性能. 为了制备出比表面积更大、垂直性更好以及无根部融合的高质量ZnO纳米线/棒阵列, 本文概述了近几年两步水热法可控制备ZnO纳米线/棒阵列的研究进展, 分别探讨了种子层、生长液和生长方法对纳米线/棒阵列形貌的影响, 详细分析了氨水、六次甲基四胺和聚乙烯亚胺对于促进纳米线/棒阵列生长的作用机理, 提出了通过微流控技术可控制备ZnO纳米线阵列提高纳米线生长效率的方法. 最后介绍了ZnO纳米线/棒阵列的形貌对于提高染料敏化太阳能电池、纳米发电机、气体传感器和场发射器件性能的重要作用, 并对未来两步水热法制备ZnO纳米线/棒阵列的发展趋势进行了展望.     

High-power high-stability Q-switched green laser with intracavity frequency doubling of diode-pumped composite ceramic Nd:YAG laser

We successfully obtain high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By use of a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

剪切场下两亲性棒状粒子对聚异丁烯/聚二甲基硅氧烷共混物相形态的影响

合成了具有两亲表面性质的棒状SiO₂粒子,借助共聚焦激光扫描显微镜研究了两亲性棒状SiO₂粒子在共混物中的选择性分布,并通过在线剪切-显微技术和流变技术研究了其对聚异丁烯/聚二甲基硅氧烷（PIB/PDMS）不相容共混物形态结构的影响.研究表明,两亲性棒状SiO₂粒子倾向于分布在两相界面处及PIB相中.分散相的剪切诱导凝聚行为强烈依赖于粒子的含量和共混物的组成比.少量两亲性SiO₂粒子会促进分散相的凝聚,而加入足够量的粒子则能抑制分散相凝聚.     

Large deflection and post-buckling analysis of non-linearly elastic rods by wavelet method

We propose a wavelet method in the present study to analyze the large deflection bending and post-buckling problems of rods composed of non-linearly elastic materials, which are governed by a class of strong non-linear differential equations. This wavelet method is established based on a modified wavelet approximation of an interval bounded L²-function, which provides a new method for the large deflection bending and post-buckling problems of engineering structures. As an example, in this study, we considered the rod structures of non-linear materials that obey the Ludwick and the modified Ludwick constitutive laws. The numerical results for both large deflection bending and post-buckling problems are presented, illustrating the convergence and accuracy of the wavelet method. For the former, the wavelet solutions are more accurate than the finite element method and the shooting method embedded with the Euler method. For the latter, both bifurcation and limit loads can be easily and directly obtained by solving the extended systems. On the other hand, for the shooting method embedded with Runge–Kutta method, to obtain these values usually needs to choose a good starting value and repeat trial solutions many times, which can be a tough task.     

Full time-domain nonlinear coupled dynamic analysis of a truss spar and its mooring/riser system in irregular wave

A new full time-domain nonlinear coupled method has been established and then applied to predict the responses of a Truss Spar in irregular wave.For the coupled analysis,a second-order time-domain approach is developed to calculate the wave forces,and a finite element model based on rod theory is established in three dimensions in a global coordinate system.In numerical implementation,the higher-order boundary element method(HOBEM)is employed to solve the velocity potential,and the 4th-order Adams-Bashforth-Moultn scheme is used to update the second-order wave surface.In deriving convergent solutions,the hull displacements and mooring tensions are kept consistent at the fairlead and the motion equations of platform and mooring-lines/risers are solved simultaneously using Newmark-integration scheme including Newton-Raphson iteration.Both the coupled quasi-static analysis and the coupled dynamic analysis are performed.The numerical simulation results are also compared with the model test results,and they coincide very well as a whole.The slow-drift responses can be clearly observed in the time histories of displacements and mooring tensions.Some important characteristics of the coupled responses are concluded.     

Love–Bishop rod solution based on strain gradient elasticity theory

In the present work, the propagation of longitudinal stress waves is investigated with a strain gradient elasticity theory given by Lam et al. In principle, the analysis of wave motion is based on the Love rod model including the lateral deformation effects, but in the same time is also taken into account the shear strain effects with Bishop?s correction. By applying Hamilton?s principle, a general explicit strain gradient elasticity solution is developed for the longitudinal stress waves, and it is compared with the special solutions based on the modified couple stress and classical theories. This work gives useful information with regard to the meaning of the three scale parameters in the strain gradient elasticity theory used here.     

In-plane and out-of-plane free vibration and stability of a curved rod in flow

This paper investigates the free vibration and stability of a curved rod in flow. The equations of the three-dimensional motions of the rod are derived by the Newtonian approach. The differential quadrature method (DQM) is introduced to formulate the discrete forms of the governing equations of the inextensible rod with clamped–clamped supports. Based on numerical calculations, the effects of several system parameters, especially the flow velocity, on the natural frequencies and stability of the system are discussed. Buckling and flutter instability are detected as the flow velocity is varied in a certain range. Moreover, a derivation of the generalized slender-body theory for such a deformable curved rod is given in Appendix A.     

TRIAL FUNCTION METHOD FOR THE LONGITUDINAL VIBRATION OF RODS WITH VARIABLE CROSS-SECTIONS

给出了一种试探函数法,并研究了变截面杆的纵振动问题. 先给出振动控制方程的特殊函数形式的试探解,然后要求此解满足控制方程,反过来确定了控制方程各种可能的系数函数（即截面变化函数）并得到了控制方程的精确解. 作为例子,给出了一种变截面杆在3 种边界条件下的频率方程,计算出了固有频率. 研究表明,试探函数法简单、直接,适合于研究变截面杆的纵振动问题. 对于杆扭转振动、薄膜振动以及管中波传播等问题,该方法同样有推广应用价值.