单壁碳纳米管手性角对声子振动频率的影响

报道了用卷曲法对一系列手性单壁碳纳米管计及卷曲效应声子振动谱的计算结果.基于实际的数值计算，讨论了Brillouin区中心Γ点手性管晶格振动模的分类；得出了其12个非简并的本征频率与手性和管径的关系. 关键词： 单壁碳纳米管 手性管 振动模式     

直线加速运动动态黑洞的熵

选取超前爱丁顿坐标,采用薄膜brickwall模型,计算Kinnersley度规表述的直线加速运动动态黑洞的熵.通过此方法,可以给出视界面上每一点的温度和熵密度.这一结果表明,熵与视界面积成正比的结论,不仅适用于整个视界,也适用于视界面上的局部;不仅适用于稳态黑洞,也适用于动态黑洞.在薄膜趋于视界面时,其厚度也趋于零,薄膜本身成为视界面,黑洞熵就是视界面上量子态的熵 关键词： 熵 加速黑洞 薄膜brickwall模型     

Screening of aU(1) ×U(1) dyon by a domain wall in a double axion model

The screening of the electric-like charge degrees of freedom of aU(1) ×U(1) dyon by an axion-like domain wall is discussed. Depending on the combination of degenerate minima at the interior and exterior boundary of the spherical domain wall a multiplicity of “screened generated electric-likeU(1) ×U(1) charges” are generated in the region exterior to the domain wall. Such a result demonstrates how aU(1) ×U(1) dyon-domain wall configuration may generate multiplicate phenomena in the early universe from a singleU(1) ×U(1) source.     

Translation and rotation of spheres settling in square and circular conduits: Experiments and numerical predictions

The terminal settling velocities and rotation rates of spherical particles settling in circular and square conduits were investigated experimentally and numerically with the aim to benchmark the numerical predictions using the boundary element method. Spheres were allowed to settle in viscous Newtonian fluid under conditions such that only hydrodynamic forces exerted an appreciable effect. The terminal settling velocities and the rotation rates were measured as a function of the size and density of the falling sphere, the drop position of the sphere in the conduit and the dimensions and geometry of the containing vessel or conduit. The experimental measurements were subjected to an exacting error analysis and compared with fully three-dimensional boundary element calculations. We found that the results of the experiments and numerical simulations showed remarkable agreement within the bounds of experimental error.     

管材无模扩径壁厚变化数学模型研究

对管材无模扩径变形速度场及壁厚变化规律进行了理论及实验研究.分析了管材无模扩径的变形模型、速度场以及壁厚变化的影响因素及影响规律,采用上限法确定了管材无模扩径速度场及壁厚变化数学模型.     

Influence of multiwall carbon nanotubes on morphology and electrical conductivity of PP/ABS blends

Polypropylene (PP) and acrylonitrile‐butadiene‐styrene (ABS) blends with multiwall carbon nanotubes (MWNT) were prepared by melt mixing. PP/ABS blends without MWNT revealed coarse co continuous structures on varying the ABS content from 40 to 70 wt %. Bulk electrical conductivity of the blends showed lower percolation threshold (0.4–0.5 wt %) in the 45/55 co continuous blends whereas the percolation threshold was between 2 and 3 wt % in matrix‐particle dispersed morphology of 80/20 blends. Interestingly, droplet size was observed to decrease with addition of MWNT above percolation threshold in 80/20 blends. Further, the bulk electrical conductivity was found to be dependent on the melt flow index of PP. The non‐polar or weakly polar nature of blends constituents resulted in the temperature independent dielectric constant, dielectric loss, and DC electrical conductivity. Rheological analysis revealed the formation of 3D network‐like structure in 80/20 PP/ABS blends at 3 wt % MWNT. An attempt was made to understand the relationship between rheology, morphology, and electrical conductivity of these blends. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2286–2295, 2008     

The Asymmetric Exclusion Process Revisited: Fluctuations and Dynamics in the Domain Wall Picture

We investigate the total asymmetric exclusion process by analyzing the dynamics of the shock. Within this approach we are able to calculate the fluctuations of the number of particles and density profiles not only in the stationary state but also in the transient regime. We find that the analytical predictions and the simulation results are in excellent agreement.     

A note on the periodic motion of a visco-elastic fluid in a radially non-symmetric constricted tube

An approximate solution for the problem of fluid flow through a rigid tube with a mild constriction is given. It is assumed that the fluid is visco-elastic (Maxwell fluid) and the constriction is non-symmetric with respect to the radial distance. A theoretical result is given for the wall shear stress and numerical solutions are shown graphically for different values of the relaxation time and the shape parameter of the constriction profile.     

锥形血管入口区域内管壁与血液的耦合运动

本文研究了锥形血管入口区域内血管壁与血液间的耦合问题。对具有锥度角的弹性血管入口区域内的管壁运动和血液流动建立的相互耦合作用的数学模型，在满足相应的边界条件下求得了一组血液流动的速度分布公式、压力分布公式以及管壁运动公式，得出了一些重要的结论。