泥石流反粒径分布的一种定性解释

假设泥石流中的粗颗粒（如石块等）以跳跃的方式前进，通过分析单个颗粒在定常充分发展的流场中的运动，给出了单一起跳速度下以及具有一定分布的起跳速度下，颗粒数密度随高度的分布，并给出了起跳粒径有分布时颗粒的平均粒径随高度的分布，定性地解释了泥石流中的反粒径分布现象。

Theoretical investigation of epitaxial deformation and the hcp-bcc transition of alkali metals

The deformation of alkali metals K, Rb, and Cs under epitaxial deformation is studied via the ab initio pseudopotential plane wave method using the local-density approximation. Under loading from the stable fee phase, metastable stares along directions [001], [111], and [201] are identified. One metastable state, presented at direction [201], has a very low symmetry in contrast to the planes [001] and [201]. Our results show that the softening direction and sequences of growth is significantly affected by the existence of the metastable states and magnitude of the energy barrier. The resulting softening sequences from soft to hard are [201], [110], [001], and [111] under biaxial compression and [001], [111], [201], and [110] under biaxial tension. An orthorhombic deformation path is used to investigate the fact, that the structure of the alkali films K and Cs evolve from the quasihexagonal structure into the (110)-oriented bcc structure, observed by experiments.