径向可开启板式结构几何协调性研究

介绍了一种新型开合结构--径向可开启板式结构.针对它在几何协调性方面存在的缺陷,分析了这种结构的基本构成并给出基本几何方程;运用欧式几何分析方法研究了开启时具有圆形开口的结构各单元之间的拓扑关系,得到了临界方程和限制方程,据此绘制了一些常用参数下的临界曲线和限制曲线,以便设计者选用;给出了两种开启时可形成梅花形开口或多边形开口的新型结构,解决了特定参数下屋面设计的几何协调性问题.研究结果为径向可开启板式结构的设计提供了有价值的参考.     

Magnetic Properties of （Sm, Tb）FeCo/Cr/TbFeCo Trilayers with Perpendicular Anisotropy

A series of （Sm, Tb）FeCo/Cr/TbFeCo trilayers with perpendicular anisotropy was prepared by RF magnetron sputtering, and the effect of Cr interlayer thickness on magnetic properties and interlayer exchange coupling was investigated. All the samples showed strong out-of-plane anisotropy but their hysteresis loops displayed two types ： singlephase and double-phase, indicating that interlayer exchange coupling and magnetic properties varied with the thickness of Cr interlayer. Both saturation field Hs and （1-Mr/Ms） curves indicated that interlayer exchange coupling oscillated between antiferromagnetic and ferromagnetic with a period of 1.6 nm, and the oscillation strength attenuated with increasing Cr interlayer thickness. After being annealed at 450℃ for 25 min, the hysteresis loops of all the samples became single-phase type and coercivity Hc decreased greatly, which could be attributed to the decrease of effective anisotropy in （Sm, TbFeCo） grains.     

具有折展与变刚度特征的NOTES手术器械臂

自然腔道手术(Natural orifice transluminal endoscopic surgery,NOTES)具有恢复快、创伤小、疼痛轻等优点,在临床应用潜力巨大。为适应人体复杂腔道环境,NOTES中常采用长器械臂为手术工具提供通路及支撑。现有的器械臂往往尺寸较大且刚度低,不能满足NOTES的要求。提出一种可折展、变刚度的器械臂,采用编织结构作为骨架实现径向折展,同时借助包覆在编织结构交叉点处的热熔胶实现刚度调节。建立了器械臂的数学模型,得到了柔态和刚态下的刚度解析表达式。试验结果表明,通过加热及冷却热熔胶,器械臂可以实现刚柔两态转化,其刚度比接近20,并且转换时间小于30 s,同时可以实现约2倍的径向展开比。