磁力驱动器涡流损失的研究

对磁力驱动器金属隔离套在交变磁场中引起的涡流损失进行了理论计算 ,并与实测结果进行了对比。指出合理选择金属隔离套的相关参数 ,可以有效控制涡流损失的大小     

Controller design for nonlinear systems using the Contoured Robust Controller Bode plot

In this paper, we develop the Contoured Robust Controller Bode (CRCBode) plot and demonstrate its use in the design of robust controllers for nonlinear single‐input single‐output (SISO) systems. The CRCBode plot shows contours (level sets) of a robust performance quantity on the Bode magnitude and phase plots of the controller. An iterative frequency domain loop‐shaping design approach is employed to eliminate all intersections of the controller frequency response with certain ‘forbidden regions,’ indicating that a standard SISO robust stability and performance criterion is satisfied. Nonlinearities are accounted for by avoiding the maximum forbidden regions over a structured uncertainty set consisting of linearizations of the system dynamics about several operating points. We demonstrate this technique by designing and experimentally verifying a flow‐rate controller for a butterfly‐valve based liquid cooling system, which is robust to valve nonlinearities and flow disturbances. Finally, we compare this compensator with one generated using an automated H _∞ synthesis algorithm and discuss the advantages of the CRCBode approach. Copyright © 2013 John Wiley & Sons, Ltd.     

Nonaqueous poly(methyl methacrylate) dispersions: radical dispersion polymerization in the presence of AB block copolymers of polystyrene and poly(dimethyl siloxane)

Well defined AB block copolymers of polystyrene (PS) and poly(dimethyl siloxane) (PDMS) have been prepared with PS molecular weights in the range 8 800 to 43 600 and PDMS molecular weights in the range 2 400 to 48 000. Provided the PS and PDMS molecular weights have a ratio within the range 0.5 to 4.0, these block copolymers stabilize particles of poly(methyl methacrylate) in n-alkanes. The particle size over the range 0.1 to 0.5 μm may be varied by performing dispersion polymerizations of methyl methacrylate as a function of monomer content of the seed stage and as a function of the concentration, molecular weight and composition of the block copolymer. From silicon analyses of the poly(methyl methacrylate) particles, values of the surface area stabilized per PDMS chain were established. The results indicate complete surface coverage of the particles.     

Solvent-free oxidation of benzyl alcohol using titania-supported gold–palladium catalysts: Effect of Au–Pd ratio on catalytic performance

The oxidation of benzyl alcohol with molecular oxygen under solvent-free conditions has been investigated using a range of titania-supported Au–Pd alloy catalysts to examine the effect of the Au–Pd ratio on the conversion and selectivity. The catalysts have been compared at high reaction temperature (160 °C) as well as at 100 °C, to determine the effect on selectivity since at lower reaction temperature the range of by-products that are formed are limited. Under these conditions the 2.5 wt.% Au–2.5 wt.% Pd/TiO₂ was found to be the most active catalyst, whereas the Au/TiO₂ catalyst demonstrated the highest selectivity to benzaldehyde. Toluene, formed via either a hydrogen transfer process or an oxygen transfer process, was observed as a major by-product under these forcing conditions.     

多无限远目标模拟装置光轴共面测试技术研究

提出一种基于激光准直五棱镜回转扫描和CCD技术的非接触检测方法,通过检测三块立板平面度来实现对多无限远目标模拟装置光轴共面度的高精度非接触测量。给出误差评定方法,同时对仪器精度进行分析,通过实验测得共面度为0.039mm,满足精度要求。     

基于RS-SVM的建筑施工项目安全预警模型

针对目前建筑施工项目安全风险管理的现状,应用粗集理论对建筑施工项目的安全因素进行预处理,将处理后的信息结构作为支持向量机的输入数据进行训练和预测,构建建筑施工项目安全风险预警模型,并在小样本条件下,与BP神经网络进行对比分析。结果表明,RS-SVM预测模型的最小均方根误差为0.011 5,BP神经网络的均方根误差为0.070 7,RS-SVM预警模型的预测精度、泛化能力明显优越于BP神经网络学习方法。     

红外测速光幕靶改进及测量精度分析

为提高XGK-2002型红外测速光幕靶的测量精度及安装调试速度,提出采用双辅助激光器实现光源和接收精确对准的光幕靶改进方案.在现有红外测速光幕靶工作原理及结构基础上,对光源和接收对准中存在的问题进行了探讨,分析了其影响.提出了在光幕靶两端分别设置一激光器实现对准的光幕靶改进方案,并从测时误差及靶距误差两方面对改进后测量精度进行了分析.结果表明,改进后的光幕靶可快速、直观的实现光源和接收的对准,测试精度及安装可靠性提高,改进后测速精度可达到1‰.     

基于二氨基苯基卟啉的新型聚酰亚胺的合成与表征

卟啉类化合物的结构特征使其在很多领域受到广泛的关注,现在通常在卟啉上做修饰以获得更优的性能。以氨基苯基取代的卟啉化合物作为二胺单体和均苯四甲酸二酐为二酐单体,以苯甲酸为溶剂,通过反应合成粗产品新型的聚酰亚胺材料,用丙酮和氯仿洗涤得到纯产品,并进一步合成了Zn-卟啉聚酰亚胺。采用傅里叶红外吸收光谱、紫外-可见吸收光谱对产物进行了结构表征,对主要的紫外光谱、红外光谱吸收带进行了经验归属,以及原料与产物的对比分析,初步确定了合成产物的结构。结果表明,聚合产物是以卟啉骨架结构为主要聚合单元的聚酰亚胺类共聚物。     

一种高效的基于身份的部分盲签名方案*

提出了一个新的基于身份的部分盲签名方案,证明了所提方案的完整性、部分盲性和不可伪造性,并比较了所提方案与现有方案的计算代价,比较结果显示所提方案是目前效率较高的基于身份的部分盲签名方案。     

环氧涂层/镀锌板电极系统腐蚀电化学行为

利用EIS研究环氧型有机涂层的腐蚀电化学行为。在浸泡初期阻抗谱是一个时间常数的单容抗弧,阻抗值基本不变,此时漆膜能够阻止介质渗入。在浸泡中期阻抗值随时间逐渐增大,原因为镀锌钢板表面预处理层的铬酸盐自修复作用以及铬酸盐转化膜溶解物和腐蚀产物沉积堵塞漆膜微孔隙,阻止介质渗入到达镀锌钢板表面,导致阻抗值变大。后期,预处理膜完全溶解破坏,金属基体腐蚀反应加快,阻抗值变小.