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.     

PX联合装置低温热利用合理性分析

结合镇海炼化Ⅱ套催化改造,将PX联合装置的低温位热进行合理利用,形成Ⅱ套催化气分装置和PX联合装置热联合。热联合后既节约Ⅱ套催化气分装置的低压蒸汽消耗,又降低了PX装置的空气冷器电耗,达到能量合理利用的目的。     

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。     

玻璃的艺术

玻璃就像是一片凝固了的水。在室内空间中，它可以变成溶化的冰块，让我们的视线穿透它，让我们的眼睛可以看到玻璃的另一面，将室内跟室外的空间连成一体。加工后的玻璃可以从无色变成有色，把透明变成不透明，或经其他加工程序，把它原来脆弱的本质都改变。玻璃的可塑性打开了人类的梦想，就因为这一个奇妙的特性，从古至今，建筑师及艺术家都被玻璃材料这一种优美所吸引着。在现代建筑中，建筑师把玻璃当成一幅透明的墙，而艺术家则把它当成为一种雕塑的材料来运用。     

硫磺回收装置再热方式比较分析

炼油厂硫磺回收的主要工艺流程是CLAUS反应制硫法＋SCOT净化尾气法的组合工艺,硫磺回收率可以达到99.9％,尾气排放符合国家标准.在此工艺流程中,一、二级CLAUS反应器和加氢还原反应器入口过程气需要重新加热到一定温度才能进入反应器.目前,硫磺回收装置常用的再热方式有掺和法、在线炉法和蒸汽加热法等.本文通过在能耗、投资、操作难度和操作成本等方面对三种操作方式进行系统比较,得出这三种常用的再热方式的优缺点.     

基于数据挖掘和因子试验设计的聚丙烯装置生产优化

在将工艺参数优化技术用于优化某聚丙烯装置的温度、压力和反应时间等过程参数,使装置生产运行趋于平稳的基础上,采用23全因子试验设计对装置生产中的催化剂TiCl4、活化剂(C2H5)3Al和助催化剂CMMS的用量开展设计实验,通过对实验结果分析得出优化的催化剂、活化剂及助催化剂配料方案为TiCl4:(C2H5)3Al:CMMS=95g:0.9L:200g。以此配料方案进行生产试验,试验结果聚丙烯釜产量均值为3119.50kg,较试验对照期釜产量均值3033.75kg增加85.75kg,增幅达2.83%。     

三门峡水库淤积上延机理的研究

本文分析了三门峡水库渭河下游实测资料，认为前期淤积使潼关河段同流量流速降低，使渭河下游主槽过洪通过减小、洪水流速降低，而洪水是维持潼关及渭河下游动态冲淤平衡的动力，因此，前期淤积是造成渭河下游淤积上延严重的根本原因，流速降低破坏了渭河干流推移质和支流推移质进入渭河后的输沙平衡，这也是渭河下游淤积上延严重的原因之一。     

我视材料为音符

“理性”与“感性”是支配人类行为的两大元素，对室内设计师而言，这可以理解成“经意”或“漫不经心”的两种设计手法。     

Robust observer design for nonlinear uncertain systems with LQ regulators

For a class of uncertain systems with linear nominal dynamics and nonlinear uncertainties, it has been shown (Katayama and Sasaki 1987) that linear quadratic (LQ) state feedback regulators can be used to provide robust asymptotic stability. In this paper, we study the combined observer-controller design problem, based on the linear state feedback regulator proposed by Katayama and Sasaki (1987), so that only output feedback is needed. Both full-order and reduced-order observers are considered. For the full-order observer, we propose an algorithm to synthesize the robust observer gain matrix. It is shown that with the observer it is still possible to achieve robust asymptotic stability. For the reduced-order observer, some conditions are derived to guarantee the robust asymptotic stabilizability of the uncertain systems. The trade-off between the magnitudes of controller and observer gains is clear in our approach. An example is used to illustrate the design process of the robust controller with full-order as well as reduced-order observers.