Observer‐based H ∞ control for networked systems with bounded random delays and consecutive packet dropouts

This paper is concerned with the H _∞ control problem for a class of systems with bounded random delays and consecutive packet dropouts that exist in both sensor‐to‐controller channel and controller‐to‐actuator channel during data transmission. A new model is developed to describe possible random delays and packet dropouts by two groups of Bernoulli distributed stochastic variables. To avoid the state augmentation, a full‐order observer‐based feedback controller is designed via LMI approach. Based on the Lyapunov theory, a sufficient condition is provided to guarantee the closed‐loop networked system to be asymptotically mean‐square stable and achieve the prescribed H _∞ disturbance‐rejection‐attenuation level. The simulation examples illustrate the effectiveness of the proposed method. Copyright © 2013 John Wiley & Sons, Ltd.     

一种通过USB接口的可靠固件升级技术

本文提出一种可靠固件升级的技术。该技术采用外部主晶振,工作异常时自动切换到校准后的内部晶振,还使用了DFU检测序列、看门狗等方法。相对于传统的固件升级技术,该技术具有抗干扰能力强、可靠、易于使用等优点。     

Spartan6芯片μC/OS-Ⅱ的可抢占式嵌套中断控制方法

介绍了Spartan6芯片搭载MicroBlaze软核的硬件平台,以及集成了μC/OS-Ⅱ操作系统的软件平台;给出了在此软硬件平台上的可抢占、可嵌套的中断机制的实现方法;灵活地运用面向底层硬件代码与操作系统代码之间的参数传递,协调了中断处理与任务调度之间的关系。阐述了方案的原理,给出了程序流程图;通过试验,验证了可抢占、可嵌套的中断机制的正确性与可行性。     

多媒体技术在高校教学中的应用

多媒体技术运用在高校音乐教学课堂中,不仅能为高校学生们营造一个生动的学习环境,吸引学生的兴趣,还能让学生直观地欣赏音乐,从而在在轻松的氛围中学习音乐知识,提高自己的音乐鉴赏水平。本文主要研究多媒体技术在高校音乐教学中的作用以及多媒体技术在高校音乐教学中的具体应用。     

成核剂对不同特性粘数PET结晶性能的影响

研究了新型复合成核剂水滑石(HT)／离聚物(Surlyn8920)／聚乙二醇(PEG)对不同特性粘数聚对苯二甲酸乙二醇酯(PET)非等温结晶性能的影响。通过差示扫描量热仪测试了PET的结晶峰温度T_(mc)和熔融峰温度(T_m)。结果表明,复合成核剂各组分及PET的质量比为0.5:3.0:3.0:100.0时,各种PET的过冷度(T_m-T_(mc))均显著减少．半结晶时间(1gt_(1／2))也明显降低。而且,复合成核剂对不同特性粘数PET结晶性能的改善是一致的。     

Crystal lattice deformation and the mesophase in poly(ethylene terephthalate) uniaxially drawn by solid-state coextrusion

The development of crystalline and mesophase structure on drawing of poly(ethylene terephthalate) (PET) has been studied. The uniaxial drawing has been done by solid-state coextrusion from 50 to 90°C. The unit-cell parameters of stress-induced crystallites in extrudates have been determined as a function of extrusion draw ratio (EDR) up to 4.4 and at an extrusion temperature (ET) above T_g, at 70 and 90°C. The higher the EDR, the longer the c-axis chain direction, the shorter the a and b axes and the smaller the unit-cell volume. In comparison with the conventional lattice parameters obtained by Bunn and Fisher, the highest elongation of the c axis is near 10%. These features imply that the lattice of stress-induced crystallites is far from the closest packing. Coextrudates made below the T_g of PET differ markedly from those made above T_g. Wide-angle X-ray diffraction (WAXD) patterns of PET extruded at 50°C (below T_g) even at high draw ratio exhibit small and/or imperfect crystallites. They appear much as a mesophase. The distance between macromolecular chains ranges from 3.2 to 5.4 Å. The shortest value in the mesophase approaches the interplanar crystal distance of 3.4 Å for the (100) crystal face, on which the benzene rings lie. The crystalline peak separation of the PET, WAXD curve has been evaluated to obtain absolute crystallinities and the content of mesophase and amorphous phase.     

基于Pro/TOOLKIT异步模式特征识别方法

对Pro／Engineer（Pro／E）二次开发工具Pro／TOOLKIT（PTC公司为Pro／E软件提供的二次开发工具包）的异步模式进行了研究，充分利用参数化技术，开发了实体模型的特征识别系统。系统可以控制Pro／E的自动启动及关闭，使其在后台运行。通过模型的调用实现实体特征的快速识别提取，为模具估价系统的智能化设计做好了准备。     

压挤成形--固化法制备0-3型压电复合材料的性能研究

详细地叙述了室温压挤成形———固化工艺制备 0 -3型压电复合材料工艺 ,使用XRD、SEM和HP42 94测试并分析了样品的结构和性能 ,并与压电陶瓷性能参数进行了对比 ;同时用这种工艺制备可以获得介电损耗小、机电耦合系数为 2 5 .11%、压电应变常数为 3 2PC N和机电品质因数可达到 3 0 2的 0— 3型压电复合材料。     

Bending behavior of an electrically activated complex forming hydrogel

Summary The complex forming poly[(ethylene glycol-co-proplene glycol)-g-acrylamide]: polyacrylic acid interpenetrating polymer network hydrogel is able to bend under electric field stimuli. pH, ionic strength gradients and voltage can influence it's bending degree. So we may improve the sample' responsive speed through manipulating those factor in the further study in order to put it into the biomedical application.     

Neutral Pd(II) and Ni(II) Acetylide Catalysts for the Polymerization of Methyl Methacrylate

Homogenous polymerization of methyl methacrylate using Pd(II)- and Ni(II)-based acetylide complexes as initiators has been investigated. M(PR'₃)₂(CCR)₂ (M=Pd, Ni; R'=PPh₃, Pn-Bu₃; R=Ph, CH₂OH, CH₂OOCCH₃, CH₂OOCPh, CH₂OOCPhOH-o) were found to be a novel type of effective initiators for the polymerization of methyl methacrylate. Among them, Pd(C CPh)₂(PPh₃)₂ (PPP) shows the highest activity in the MMA polymerization and the PMMA obtained is a syndiotactic polymer with high number-average molecular weight (M _n) of 14.1 × 10⁴. Some features and kinetic behavior of MMA polymerization initiated by PPP were studied in detail. The polymerization reaction is first-order with respect to both [PPP] and [MMA]. Radical polymerization mechanism is proposed.