Size-Dependent Adhesion Strength of a Single Viscoelastic Fiber

Nano-fibrillar adhesives can adhere strongly to surfaces as a gecko does. The size of each fiber has significant effects on the adhesion enhancement, especially on rough surfaces. In the present study, we report the size effects on the normal and shear strength of adhesion for a single viscoelastic fiber. It is found that there exists a limited region of the critical sizes under which the interfacial normal or tangential tractions uniformly attain the theoretical adhesion strength. The region for a viscoelastic fiber under tension with similar material constants to a gecko's spatula is 135-255 nm and that under torque is 26.5-52 nm. This finding is significant for the development of artificial biomimetic attachment systems.

凹腔非定常特性的数值模拟

采用基于Menter SST两方程湍流模型的DES方法, 数值模拟开式凹腔在跨声速条件下的非定常流动特性.计算凹腔底部和后壁面上的点的声压级频谱以及总声压级, 证明在第二噪声模态上的声压级最大

Period-doubling bifurcations of the thermocapillary convection in a floating half zone

This study experimentally explored the fine structures of the successive period-doubling bifurcations of the time-dependent thermocapillary convection in a floating half zone of 10 cSt silicone oil with the diameter d (0)=3.00 mm and the aspect ratio A=l/d (0)=0.72 in terrestrial conditions. The onset of time-dependent thermocapillary convection predominated in this experimental configuration and its subsequent evolution were experimentally detected through the local temperature measurements. The experimental results revealed a sequence of period-doubling bifurcations of the time-dependent thermocapillary convection, similar in some way to one of the routes to chaos for buoyant natural convection. The critical frequencies and the corresponding fractal frequencies were extracted through the real-time analysis of the frequency spectra by Fast-Fourier-Transformation (FFT). The projections of the trajectory onto the reconstructed phase-space were also provided. Furthermore, the experimentally predicted Feigenbaum constants were quite close to the theoretical asymptotic value of 4.669 [Feigenbaum M J. Phys Lett A, 1979, 74: 375-378].

宏观尺寸弯曲石英管对中低能电子束的导向作用

研究了宏观尺寸的弯曲圆柱形石英管对1100,1300和1500eV3种能量电子束的导向作用,并对实验结果与相同材质和尺寸的直管的情形进行了分析对比。实验中利用一个位置灵敏法拉第筒对从石英管出射的电子束进行探测,获得从管道中出射的电子束流强度在位置灵敏法拉第筒各道上的分布,其结果显示宏观尺寸石英管对电子束存在导向作用。与慢速高电荷态离子和绝缘毛细管相互作用的物理过程类似,这种导向效应是由电荷在管壁内表面自组织充电引起的。实验还发现,入射电子束流的强度越强,其导向作用越明显,这与微观尺寸毛细管对慢速高电荷态离子的导向作用不同。石英管导向能力与管的尺寸、形状及材料之间的关系还有待进一步的系统研究。

超重核合成理论模型简介

介绍并讨论了研究超重核合成的主要理论模型以及近年来在研究重核熔合机制和超重核合成理论模型方面的进展。