巧用泡沫塑料球自制晶体模型

晶体结构具有重要的教学价值和功能,由于内容较抽象,学生学习起来较为吃力。采用价格低廉的泡沫塑料球与毛绒条扭扭棒为材料,由学生自制晶体模型,安全方便、简单易行,能够有效加深学生对晶体结构的理解,提升学生的学习兴趣。另外,利用泡沫塑料球与毛绒条扭扭棒还可制作许多其他化学教学常用模型,可用度高、推广性强。     

球磨六角氮化硼的特性研究

本文对同一种六角氮化硼进行了不同时间的球磨,并利用X射线衍射及拉曼光谱分析了球磨后的六角氮化硼的特性.结果表明,球磨破坏了六角氮化硼的结晶度,随着球磨时间的增加,结晶度逐渐降低,网层内硼,氮原子的sp2六角环结构基本上未受到影响.本实验特别引进X光电子衍射测试手段分析了球磨后六角氮化硼的表面特性.结果表明,球磨后六角氮化硼表面上出现了B2O3,且随着球磨时间的增加,B2O3含量逐渐增加.     

内圈离心位移对高速角接触球轴承刚度的影响

以弹性力学理论、滚动轴承动力学和沟道控制理论为基础,计算了角接触球轴承内圈在离心力作用下的径向位移,给出了计及内圈离心位移影响时,高速角接触球轴承滚动体与内、外圈的接触刚度与轴承整体的径向刚度、轴向刚度、角刚度的计算方法和相应程序。对7012/CD轴承的计算结果表明,轴承内圈外径的离心位移随转速增加而增大,在高速条件下其值较大,不容忽视;轴承内圈离心位移对内圈接触刚度和轴承径向刚度影响较大,导致内圈接触刚度和轴承径向刚度相对增大;对外圈的接触刚度、轴承轴向刚度和角刚度的影响很小;随着转速的增加与内圈离心位移的增大,对轴承内圈接触刚度与轴承径向刚度的影响会更加明显。因此,为使高速角接触球轴承的刚度分析更加精确、更加接近实际,必须考虑内圈离心位移的影响。     

A numerical simulation of suspension flow using a constitutive model based on anisotropic interparticle interactions

We report a Brownian configuration field implementation of a recent constitutive equation for suspensions, reported by Phan-Thien et al. 1999. The numerical method is a hybrid technique, which combines a modification of the Brownian configuration field method described by Hulsen et al. 1997 and the adaptive viscosity split stress formulation proposed by Sun et al. 1996. The implementation is used to examine the flow past a sphere in a tube. The relative viscosity derived from the drag force/sedimentation velocity agrees well with a well-known empiricism. In addition, the ratio of the pressure force to the drag on the sphere seems to be weakly dependent on the volume fraction, and is somewhat higher than Brenner's results of 1962, which were derived for Newtonian fluids. Received: 5 April 1999/Accepted: 27 September 1999     

等离子体辅助球磨Si-C复合负极材料及其电化学性能研究

首次采用介质阻挡放电等离子体辅助高能两次球磨制得Si-C复合材料,其结构为微纳尺度硅颗粒均匀分散于微米级碳基体上. Si-C复合电极首周期循环放电容量为1259 mAh·g^-1,20和100周期循环的容量分别为474和396 mAh·g^-1. 该电极充放电曲线和交流阻抗测试的结果表明,复合材料中的硅和碳均参与锂离子嵌/脱反应,且其电荷传导阻抗明显低于纯Si.     

THE UNIT BALL OF C*-ALGEBRA AND DIFFERENTIABILITY OF SUPPORT FUNCTION

In this paper we show that the unit ball of an infinite dimensional commutative C-algebra lacks strongly exposed points, so they have no predual. Also in the second part, we use the concept of strongly exposed points in the Frechet differentiability of support convex functions.     

基于模糊大间隔最小球分类模型的恒星光谱离群数据挖掘方法

由于人类对宇宙的认识有限,因此,如何通过对光谱数据分析发现一些新的、特殊的天体成为天文学家面临的重要课题。目前,常见特殊天体发现方法的基本思想是利用智能分类算法对离群数据进行分析。然而,当前主流分类算法大多对离群数据不敏感,分类性能甚至受离群点影响较大,因而无法完成特殊天体发现任务。鉴于此,提出基于模糊大间隔最小球分类模型的离群数据挖掘方法,该方法利用部分一般样本和离群样本建立最小球模型,并在此基础上引入模糊技术,通过降低噪声的权重,尽量减少噪声的影响。与C-SVM,SVDD,KNN等传统分类方法在SDSS恒星光谱数据集上的比较实验表明所提方法的有效性。     

钢球检测用展开轮表面微结构增摩降磨特性分析

针对钢球缺陷检测过程中,镜面钢球打滑引起的滑动摩擦导致展开轮磨损这一问题,以实现展开轮增摩降磨为目标,提出将微结构应用于钢球展开轮表面的方法.首先,应用激光微造型技术在T10A试件表面加工不同特征参数凹坑微结构,采用单因素法在MMW-1立式万能磨擦试验机上进行点接触干滑动摩擦试验;在综合考虑局部激光硬化和几何参数对磨损性能影响的基础上,结合试验数据建立基于Archard理论的微结构磨损模型;最后通过仿真技术及磨损试验验证磨损模型的正确性,进而对微结构特征参数进行优选.结果表明:在点接触干滑动摩擦工况下,提出的三种微结构表面均可以实现增摩降磨;建立的磨损模型能准确地计算磨损系数用以分析实际工况的磨损特性;优选了凹坑面积在S_2~S_4范围内的菱形微结构.提出的方法为钢球表面缺陷检测设备提供了技术支持,所建的磨损模型为干摩擦状态下凹坑微结构表面磨损程度的预测提供了理论参考.     

具有干燥功能的简易微型气体发生器

针对现有气体发生器本身不具备干燥功能等不足,利用医疗和生活中的物品--一次性注射器、输液器、圆珠笔芯等设计制作了一件自带干燥装置的微型气体发生器。     

A general strategy of in-situ warpage characterization for solder attached packages with digital image correlation method

Recently, 3-D Digital Image Correlation (DIC) is widely applied to the reliability analysis of electronic packages, which particularly characterizes the in-situ deformation of ball grid array (BGA) packages. During the image correlation procedure, many parameters influence the accuracy and data integrity of measurement result. Facet (subset) size is the principal parameter and has been studied with much effort. However, the solder balls, which are built on the substrate surface, make the scenario different with the conventional 3-D DIC experiment for the planar samples. The undulant surface generates more obstacles for the successful image correlation. In order to summarize an effective solution of 3-D DIC measurement method for solder balls attached packages, camera angle, facet size and facet step are studied with different BGA packages and different stereoscopic camera systems to achieve the best correlation quality. Also, a novel surface treatment method is introduced to guarantee the surface speckles are generated uniformly on the fluctuant surface.