Preparation and properties of a novel bone repair composite: nano-hydroxyapatite/chitosan/carboxymethyl cellulose

Nano-hydroxyapatite/chitosan/carboxymethyl cellulose (n-HA/CS/CMC) composites with weight ratios of 70/10/20, 70/15/15 and 70/20/10 were prepared through a co-solution method. The properties of the composites were characterized by means of burn-out test, IR, XRD, TEM and universal material testing machine. The degradation and bioactivity were also investigated by in vitro test in a simulated body fluid (SBF) for 8 weeks. The results showed that n-HA particles were dispersed uniformly in organic phase, and strong chemical interactions formed among the three phases. Moreover, the composites were similar to natural bone in morphology and size. In addition, the compressive strength was improved compared with n-HA/CS composite. The biodegradation rate was controllable by altering weight ratio of the CS/CMC. Meanwhile, the composites could induce apatite particles to deposit in SBF. All the above results indicate that the novel composites of n-HA/CS/CMC have a promising prospect used for bone repair materials in view of the good mechanical property, adjustable biodegradation rate and bioactivity in SBF. Additionally, the study would provide a good guide to exploit clinical application of natural cellulose.     

用不对称醚作调节剂合成苯乙烯-异戊二烯-丁二烯橡胶的反应动力学

以苯乙烯(St)、异戊二烯(Ip)和丁二烯(Bd)为单体,正丁基锂(n-BuLi)为引发荆,乙基乙二醇叔丁基醚(BET)为结构调节剂,合成了线型无规结构的苯乙烯-异戊二烯-丁二烯橡胶(SIBR),进行了聚合反应动力学研究,并与以四氢呋喃(THF)为结构调节剂的体系进行了比较.结果表明,BET的加入提高了聚合反应速率;随反应温度的升高和BET/n-BuLi(摩尔比)的增大,聚合反应速率加快,尤其是St的反应速率提高显著;BET调节聚合速率的能力明显高于THF.     

三角网格表面等残留高度刀轨生成算法

针对截平面法规划的三角网格表面的刀轨长度较长、加工表面残留高度不均匀的问题,提出一种基于改进截平面法的等残留高度刀轨生成算法.首先在估算刀触点轨迹线垂直方向曲率半径的基础上,计算刀触点轨迹投影线并对其进行修正,去除其中冗余的投影点;然后由修正后的刀触点轨迹投影线构造驱动表面,利用驱动表面和网格表面迭代计算刀触点轨迹线;最后由刀触点轨迹线计算无干涉刀轨.与截平面法生成的刀轨进行比较分析的结果表明,文中算法生成的刀轨长度较小且获得的残留高度保持均匀,适合于三角网格表面表示的复杂表面的精加工.     

贮氢合金组成对电极性能的影响

本文研究了混合稀土MmBx贮氢合金B组分的钴含量和Mm(Ni_(0.70)Co_(0.16)Mn_(0.08)Al_(0.06))_x的配比数x对P-C-T曲线平衡氢压、放电容量和电池的循环使用寿命的影响。     

DGS00-180型给水泵振动分析及处理

运用振动机理分析,查明了DG500—180给水泵轴瓦振动的主要原因是该泵导叶套与叶轮轮毂的碰磨,采取将导叶套、叶轮轮毂配合间隙适当放大的方法,成功解决了同类型4台给水泵轴瓦振动,对于其它多级水泵的振动消除具有重要的参考价值。     

一种新型啮合式磁吸传动系统的电磁有限元分析

介绍一种新型的啮合式磁吸传动系统,它将电动机和减速机结合在一起,结构和制造工艺简单、传动比大、成本低、可靠性高。在分析其结构和工作原理的基础上,建立有限元分析模型,采用磁矢量势分析方法（MVP）对这种磁吸传动系统进行二维静态仿真,得到了系统的静态性能,并分析了磁势、工作气隙、材料等各种因素对该系统传动性能的影响。将计算结果与现有电机产品进行比较,得出该系统的优缺点。