Micromechanism study on electronic and magnetic properties of silicene regulated by oxygen

Silicene, a two-dimensional (2D) silicon counterpart of graphene with attractive electronic properties, has attracted increasing attention. Understanding of its interaction with oxygen is of fundamental importance for nano-electronics in silicon-based technology. Here, we have systematically studied the structural, electronic and magnetic properties of silicene with oxygen atoms adsorption by using an unbiased structure search method coupled with First-principles calculations. The results show that the most favorable oxygen adsorption site on silicene surface is bridge site and oxygen atoms tend to chemisorb on silicene. A detailed analysis of the electronic band structure and density of state (DOS) suggests that there is a band gap opening near Fermi level after oxygen adsorption, which lead to pristine silicene changing from a gapless semiconductor to a direct or indirect bandgap semiconductor. The important finding is that two and six oxygen atoms adsorbed silicene are more advantageous due to the relatively large direct band gaps at the K point. The calculated magnetic moments and spin density isosurfaces reveal that the total magnetic moments are mostly localized on silicene sheet. This finding provides new insights for further materials design based on two-dimensional silicon systems.     

6自由度液压机器人的自抗扰控制

为提高6自由度液压机器人电液驱动系统的控制性能,针对电液位置伺服系统的非线性和不确定性,建立了6自由度液压机器人后臂电液位置伺服系统的数学模型,提出了3阶自抗扰控制方案,通过对系统内扰和外扰进行估计和补偿,实现对位置的控制。仿真结果表明,所设计的自抗扰控制器不仅能满足系统对快速性和准确性的要求,而且还能有效抑制负载突变或未知扰动对系统性能的影响,与传统PID控制相比,其具有更强地鲁棒性和抗扰动能力,能满足6自由度液压机器人控制系统动态性能的基本要求。     

两种油溶性离子液体与进口添加剂的摩擦学性能对比

目的 对比研究合成的油溶性离子液体(IL)N/P、P/P与传统极压抗磨添加剂IR 349、IR 353和FM 3606对85W/90 GL–5齿轮油摩擦学性能的影响。方法 以IL和传统极压抗磨剂为添加剂,加剂量为1%,在85W/90基础上制备5种润滑剂,空白样85W/90作为对照,通过同步热分析仪测试其热分解温度,采用点面往复摩擦形式在SRV–Ⅳ摩擦机上对其减摩抗磨性能进行研究,采用四球摩擦机测试其极压承载能力。通过环境扫描电子显微镜(ESEM)、三维轮廓扫描仪、X射线光电子能谱仪(XPS)对各润滑剂润滑后对应的磨斑进行微观形貌表征并对其元素组成进行分析。结果 IL的加入在很大程度上提高了85W/90的热分解温度。在50 ℃条件下,含有IL添加剂的齿轮油表现出更为优异的减摩抗磨性能,在150 ℃条件下,含IL添加剂的齿轮油与含传统极压抗磨剂的齿轮油抗磨性能相当,而前者减摩性能更为优异。极压承载能力测试表明,所合成的IL在一定程度上改善了85W/90的油膜强度。根据XPS分析结果推测,IL添加剂在外界应力(热应力、机械应力)下分解后,与金属表面反应并生成具有良好润滑效果的边界薄膜。结论 2种油溶性IL可明显改善齿轮油的摩擦学性能,可部分替代一系列进口添加剂,为后续进一步发展绿色、高性能润滑添加剂提供了一定思路,但IL的润滑机制仍值得深入探讨。     

Human-machine cooperative control for ethylene production

A new intelligent control approach, human-machine cooperation, is applied to the ethylene production process. A two-dimensional visual model obtained by pattern recognition technology is used to supervise the plant and a cooperative control strategy is proposed.