New robust stability bounds of linear discrete-time systems with time-varying uncertainties

This paper presents new uncertain parameter variation bounds for linear discrete-time systems to preserve asymptotic stability. The Lyapunov method is utilized to treat both structured and unstructured uncertainties, and the results are optimized with respect to a parameter in the inequality used. When applied to examples considered by previous authors, our results give less conservative bounds.     

Measurements of the velocity of plasma spread in switched thyristors

The method employed in the measurement of plasma spreading velocity ν_s, in power thyristors and the results obtained are reported in detail. To induce ν_s to be primarily one-dimensional the thyristors wore rectangular in configuration with gate contacts to measure the arrival of the plasma, being placed at regular intervals around the rectangular (alloyed) cathode. Gold-doped devices were compared with geometrically similar thyristors nominally gold free. Values of ν_s for gold-doped thyristors were persistently, though not always, lower. The current gain of the constituent transistors has also been measured and attempts are made to correlate these to the measured ν_s values. The currant, gains, particularly of the n-p-n section, prevailing in the ‘ off ’ region of a thyristor during a switch-on transient are contrasted with those obtaining during current gain measurements and are thought to be responsible, in conjunction with the lowered life-time in the wide n-basr regoin of the p-n-p section, for the lowered ν_s values of gold-doped thyriators.     

离子液体的性质和制备方法

离子液体作为一类新型的环境友好的“绿色溶剂”,具有很多独特的性质,在很多领域有着人的应用前景。笔者综述了离子液体的合成、结构、性能等方面的研究进展。     

结构设计中电磁兼容性分析

介绍了电磁兼容工程设计中的一般思路和常见问题的工程处理方法,以及屏蔽设计计算和屏蔽设计要点。     

从鱿鱼软骨提取β-甲壳质及其结构表征与应用性能

采用海洋生物鱿鱼的软骨作为原料 ,通过简单的工艺 ,提取得到 β 甲壳质 ,并用波谱等表征技术确定了 β 甲壳质的结构。实验表明 β 甲壳质在 2 0 0℃以下是稳定的 ;80 0℃灼烧残渣质量分数可达 0 0 4% ;作为吸潮剂其某些性能优于硅胶     

用于D类放大器的ΔΣ调制器系统分析与设计

D类放大器具有效率高、功耗低的优点,已逐渐被应用到音频领域。为了克服传统D类放大器的内在缺陷,引入了ΔΣ调制技术以及闭环特性。但由于ΔΣ调制技术的系统设计对整个放大器非常重要,而且设计方法较复杂,因此需要借助于Matlab工具。分析了ΔΣ调制技术对D类放大器的非线性、噪声和EMI等性能的改善,对几种高阶ΔΣ调制器结构进行比较分析,最后制定详细的系统设计方法、步骤,并用Matlab工具进行系统建模与仿真。通过仿真结果,验证了设计系统的有效性,从而为实际电路设计提供基础。     

THE THROMBORESISTANCE OF A HEPARIN-POLYVINYL ALCOHOL HYDROGEL†

Heparin immobilized onto polyvinyl alcohol (PVA) by action of glutaraldehyde has been shown to be biologically active in a novel parallel flow arteriovenous shunt in dogs. The hepann-PVA hydrogel originally devised by Merrill and his collaborators was applied as a coaling to chromic acid etched polyethylene lubing. A pair of Y-connectors was used to divert < 2% of the flow in the AV shunt through the heparinized tube, which remained patent for longer Ihan two hours while a control tube without heparin was occluded within 30 minutes at a main shunt flow rate of ～l50mL/min. This enhanced patency was achieved without significant release from the surface, consistent with earlier experiments attributing the thromboresistance of the heparin-PVA hydrogel to the formation of a surface bound inactive thrombin-antithrombin III complex. Radiolabelled thrombin adsorbed onto beads made from the gel was readily displaced by arvinized plasma, indicating that the inactive complex was not itself permanently bound to the surface.

These results demonstrate the utility of Merrill's hydrogel for preparing materials with potential long lerm thromboresistance and for testing the validity of the hypothesized limitations to the long term use of immobilized heparin.     

陶瓷标准样品元素分布均匀性的μ-XRF检验

为实现古陶瓷化学组成的无损定量分析,研制一组陶瓷定量分析标准样品,样品中元素的含量稳定性和分布均匀性是两个重要技术指标。本文用能量色散X射线荧光光谱仪(EDXRF)对标准样品进行均匀性检验,主要分析了Al、Si、K、Ca、Ti、Mn和Fe这7种元素。利用SPSS软件对归一化处理的净峰面积计数作了相对标准偏差计算和F统计检验。结果表明:12个配方中除DY2和JDZ4需进一步分析外,其余10个配方在束斑Ф=1mm区域内元素分布均匀性较好,基本满足古陶瓷无损定量分析标准样品的均匀性要求。