First , we extended the liberman model of collisionless rf sheath . taking into account elastic collisions and charge - exchange collisions between ions and neutral particles , we established a self - consistent model describing the dynamics of rf sheath driven by a sinusoidal current source . the effects of collisions and rf - biased source power on the instantaneous thickness of the rf sheath and the sheath electric fields were studied 首先将liberman的无碰撞射频鞘层模型进行推广，考虑了离子与中性粒子的电荷交换碰撞效应，建立了描述碰撞射频等离子体鞘层动力学特性的自洽模型，研究了碰撞效应，射频偏压，电源参数等对射频鞘层的瞬时厚度及电场分布的影响。
We have summarized a set of theoretical approach to this problem and discussed the instability of the gas cloud and the systems composed of collisionless particles in the background of dark matter . linear perturbation theory is the method to solve this problem , in which , we add the perturbation into the equilibrium state and discussed its evolution 本文研究了自引力系统的稳定性问题，总结了解决该问题的一套理论方法。并具体研究了存在暗物质背景时气体云和无碰撞粒子系统中扰动的演化情况。解决稳定性问题的方法用线性扰动理论，即在平衡态中加入扰动，研究扰动在系统中的演化情况。
The main contribution of this paper is to present an architecture of robot network control system , and develop a 3d visual system by using opengl and visual c + + 6 . 0 . furthermore , we are engaged in researches on method of robot network control with variational time - delay units and obstacle avoidance algorithm 本文研究基于internet的机器人网络控制系统的三维可视化仿真，采用opengl和visualc + + 6 . 0开发了基于虚拟现实的机器人网络控制系统，同时对带有时变滞后环节的机器人网络控制方法和无碰撞轨迹规划算法进行了研究。
