完备化ANCF薄板单元及在钢板弹簧动力学建模中的应用

绝对节点坐标方法已在多体系统动力学研究中广泛应用, 但常用来描述板壳类结构的薄板单元, 由于梯度不完备而无法直接用于带有初始弯曲参考构型的柔性体变形描述. 为避免全参数板单元建立车辆钢板弹簧模型时存在的严重截面闭锁问题, 拟采用薄板单元用于板簧建模. 为此, 探索了将现有绝对节点坐标薄板单元纳入一般连续介质力学弹性力表达的方法, 采用中面上单位法向量作为单元厚度方向的梯度向量, 从而得到了完备化的薄板单元及其描述初始弯曲构型时消除初应变的方法. 在此基础上通过定义簧片的未变形构型, 在钢板弹簧中引入可控的预应力, 实现对钢板弹簧装配过程的准确模拟. 通过数值算例验证了本方法的正确性. 建立了车辆钢板弹簧模型, 通过建立在簧片上的局部坐标系实现接触点的跨单元搜索, 并采用惩罚函数法和平滑化的库伦摩擦模型施加簧片间的接触力. 引入参考节点的概念建立了整合车身与吊耳及其机构运动关系的刚柔耦合模型.}}      

钴掺杂二氧化锡纳米粉的光致发光和磁学性质

研究了钴掺杂对二氧化锡纳米粉的光致发光性质和磁学性质的影响,发现钴掺杂对发光带的位置影响很小,但紫外发光带与蓝色发光带的强度之比随掺杂含量的增加而下降.当钴掺杂含量达到0.02时,样品中的铁磁性被完全破坏.讨论了样品中的磁相互作用的机理,认为掺杂离子的不均匀分布、自旋极化子与掺杂离子之间的耦合都可能导致反铁磁性的相互作用,这种反铁磁性的作用破坏了铁磁性. 关键词： 钴掺杂二氧化锡 光致发光 磁学性质     

基于Unity3D的全息照相与全息干涉法虚拟仿真平台

全息照相和全息干涉法研究需要对实验仪器进行精准的控制和调整,同时实验现象的观察与测量依赖于干板的成像效果。而虚拟仿真实验能够弥补实验现象的观察与测量而出现的问题,同时也能够准确体验操作过程,获得更为理想的实验效果。我们基于Unity3D搭建虚拟仿真实验平台,由单色光干涉理论计算得到干板透射率分布,通过再进行实时渲染出实验效果以便学生研究全息照相与全息干涉法实验。借助虚拟仿真平台,可以使实验教学更加轻松,让学生更加直观地理解实验,同时得到更高的实验成功率与更好的实验效果。     

外延铁电薄膜相变温度的尺寸效应

考虑外延钙钛矿型铁电薄膜内的等效应力、表面晶格变化和表面电荷引起的退极化效应等机电耦合边界条件,利用铁电薄膜系统的动态金茨堡-朗道方程(DGL),系统分析和讨论了外延铁电薄膜相变温度与临界相变厚度的尺寸效应.结果表明,铁电薄膜相变温度与临界相变厚度完全依赖于各种与薄膜厚度相关的力电耦合边界条件.也给出了BaTiO₃外延铁电薄膜相变温度在各种边界条件下随厚度的变化,从结果看出,本文的分析与结论更符合实验数据. 关键词： 尺寸效应 外延铁电薄膜 相变温度 力电耦合边界     

C/SiC纳米管异质结电子结构的第一性原理研究

采用基于密度泛函理论的第一性原理计算,对扶手椅型(4,4)和(6,6)及锯齿型(8,0)和(10,0)C/SiC纳米管异质结的电子结构进行了研究.结果表明两类异质结结构都表现为半导体特性.扶手椅型纳米管异质结形成了Ⅰ型异质结,电子和空穴都限制在碳纳米管部分.锯齿型纳米管异质结中价带顶主要分布在碳纳米管部分及C/SiC界面处,而导带底均匀分布在整个纳米管异质结上.这两种异质结结构在未来纳米器件中具有潜在的应用价值. 关键词： C/SiC纳米管异质结 第一性原理 电子结构     

激光诱导光学材料后表面损伤的数值模拟

 采用3维时域有限差分方法和完全匹配吸收层,模拟了长方体缺陷在熔石英前后表面时对入射激光为TM波的调制作用,绘出了截面上的电场强度分布及最大电场强度随熔石英深度变化的曲线,并进行了比较和分析。结果表明：缺陷在前表面上时,后表面附近的最大电场强度2.522 41 V/m大于缺陷附近的1958 83 V/m;缺陷在后表面上时,材料中的最大电场强度为2.799 38 V/m,且出现在后表面附近。无论该缺陷在前表面还是在后表面,最大电场强度都是出现在后表面附近,表明光学材料的后表面在一定程度上更容易被损伤。     

离子注入掺杂锐钛矿TiO2薄膜的光学性能

 在玻璃基体上,采用射频磁控溅射方法在不同的基体温度下制备了TiO₂薄膜,然后在薄膜中注入注量分别为5×1016, 1×1017和5×1017/cm2的N离子以制备N掺杂的TiO₂薄膜。X射线衍射结果表明：制备出的TiO₂薄膜为锐钛矿型。X射线光电子能谱研究结果表明：注入的N离子与TiO₂晶粒相互作用,形成了含氮的TiO_xN_2-x化合物,从而改变了TiO₂薄膜的吸收边;随N离子注量增加,吸收边移动更明显;同时,由于氮离子注入产生的辐照缺陷使TiO₂薄膜在紫外和可见光区的吸收也明显增强。     

熔石英表面损伤修复点的损伤概率

针对3个光斑尺寸的CO2激光辐照尺寸小于400 m损伤点后得到的修复点,从4个方面对损伤修复点经355 nm激光辐照后的损伤概率分别进行研究。结果表明,根据修复光斑尺寸或损伤点尺寸分别讨论修复点的损伤概率,更能反映修复点的抗激光损伤能力。通过分别讨论可以看出,采用小光斑CO2激光辐照损伤点或者修复尺寸小于200 m的损伤点,修复成功率超过90%。同时,可以通过损伤修复点的激光损伤阈值都服从正态分布的规律来预测修复点的损伤概率。     

Incident laser modulation of a repaired damage site with a rim in fused silica rear subsurface

Local CO2 laser treatment has proved to be an effective method to prevent the 351-nm laser-induced damage sites in a fused silica surface from exponentially growing, which is responsible for limiting the lifetime of optics in high fluence laser systems. However, the CO2 laser induced ablation crater is often surrounded by a raised rim at the edge, which can also result in the intensification of transmitted ultraviolet light that may damage the downstream optics. In this work, the three-dimensional finite-difference time-domain method is developed to simulate the distribution of electrical field intensity in the vicinity of the CO2 laser mitigated damage site located in the exit subsurface of fused silica. The simulated results show that the repaired damage sites with raised rims cause more notable modulation to the incident laser than those without rims. Specifically, we present a theoretical model of using dimpled patterning to control the rim structure around the edge of repaired damage sites to avoid damage to downstream optics. The calculated results accord well with previous experimental results and the underlying physical mechanism is analysed in detail.     

Fabrication processing effects on the microstructure and morphology of erbium film

The effect of substrate temperature on the microstructure and the morphology of erbium film are systematically investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). All the erbium films are grown by electron-beam vapor deposition (EBVD). A novel preparation method for observing the cross-section morphology of the erbium film is developed. The films deposited at 200°C have (002) preferred orientation, and the films deposited at 450°C have a mixed (100) and (101) texture, due to the different growth mechanisms of surface energy minimization and recrystallization, respectively. The peak positions and the full widths at half maximum (FWHMs) of erbium diffraction lines (100), (002), and (101) shift towards higher angles and decrease with the increasing substrate temperature in a largely uniform manner, respectively. Also, the lattice constants decrease with increasing temperature. The transition in the film stresses can be used to interpret the changes in peak positions, FWHMs, and lattice constants. The stress is compressive for the as-growth films, and is counteracted by the tensile stress formed during the process of temperature cooling to room temperature. The tensile stress mainly originates from the difference in the coefficients of thermal expansion of the substrate-film couple.