Viscosity of nonelectrolyte liquid mixtures. III Binary mixtures of methyl methacrylate with hydrocarbons,haloalkanes, and alkylamines

Measurements of the viscosity and the density are reported for 14 binary mixtures of methyl methacrylate (MMA) with hydrocarbons, haloalkanes, and alkylamines at 303.15 K. The viscosity data have been correlated with equations of Grunberg and Nissan, of McAllister, and of Auslaender. Furthermore, excess viscosity In and excess Gibbs energy of activationG* ^E of viscous flow have been calculated and have been used to predict molecular interactions occurring in present binary mixtures. The results show the existence of specific interactions in MMA + aromatic hydrocarbons, MMA + haloalkanes, and MMA + primary amines.     

A μ-H∞ control strategy for decreasing torque fluctuation of electro-hydraulic integrated braking system in mode switching

Due to the difference of time-domain response between hydraulic braking and regenerative braking, as well as changes of equivalent parameters and operating parameters during braking mode switching, it is liable to cause torque fluctuation, which affects braking safety and vehicle ride comfort. First, the uncertainties of vehicle load and frictional coefficient model are investigated. Second, the hybrid system theory is applied to provide state transfer condition for mode switching strategy. Finally, the control strategy that utilizes regenerative braking torque to compensate for difference of the required braking torque is designed, and a new μ-H_∞ control algorithm through D-K iteration is presented to improve the robust performance. The proposed μ-H_∞ control strategy is examined under various braking situations, and the results indicate that (1) the μ-H_∞ controller have the advantage of robustness performance, the amplitude of regenerative braking is decreased by 6.14%, and the steady-state error of hydraulic braking is decreased by 5.26% over the H_∞, and (2) under the braking mode switching, the designed compensation control strategy has the performance of fast and accurate tracking of the desired torque, and the steady-state error does not exceed 3.5%.     

Near-field scanning optical microscope probe analysis

In this article results of a comparison of two NSOM probe characterization methods are presented. Scanning electron microscopy analysis combined with electromagnetic field modeling using the finite difference in time domain method are compared with measured far-field radiation diagrams of NSOM probes. It is shown that measurement of far-field radiation diagrams can be an efficient tool for daily checking of the NSOM probes quality. Moreover, it is shown that the inner probe geometry has large influence on the directional radiation of an NSOM probe and the far-field radiation diagram can be used as a simple method to distinguish between different probe geometries.     

Communication—Processor Tradeoffs in a Limited Resources PRAM

   Abstract. We consider a simple restriction of the PRAM model (called PPRAM), where the input is arbitrarily partitioned between a fixed set of p processors and the shared memory is restricted to m cells. This model allows for investigation of the tradeoffs/ bottlenecks with respect to the communication bandwidth (modeled by the shared memory size m ) and the number of processors p . The model is quite simple and allows the design of optimal algorithms without losing the effect of communication bottlenecks. We have focused on the PPRAM complexity of problems that have

嵌入式Web服务器下μClinux移植研究

以开发嵌入式Web服务器为目标,搭建了移植μClinux需要的开发环境和设计移植的流程,并对μClinux移植进行裁减和分析。bootloader、μClinux内核和只读的romfs文件系统烧到Flash中的分析研究及μClinux内核和根文件系统的烧到Flash详细过程描述。     

基于μClinux的嵌入式导盲系统

提出一种为盲人或视弱人群提供导航的基于盲道识别的嵌入式系统的设计方案。结合高性能定点DSP ADSP-BF533 和视频解码芯片SAA7113,设计图像处理硬件平台,移植嵌入式操作系统并给出算法实现与优化方法。实验结果表明,该系统在自然盲道情况下达到必需的处理实时性和判断的准确性要求,可较好地服务于盲人的独立出行。     

µTESLA广播认证协议优化研究

广播认证是无线传感器网络能够正常工作的重要保证.μTESLA协议凭借其低成本高效率的加密技术和认证框架,在一定程度上符合了无线传感器网络的特点和安全需求.深入研究了μTESLA协议的实现过程,并针对广播周期交界处易出现的广播数据包无法正常认证的问题,提出了"认证漂移"的概念和一种基于阈值的多重认证机制(M-μTESLA).研究结果表明,该机制有效改善了μTESLA协议的性能.     

一种新型可编程多轴控制器PMAC的设计

通过SOPC Builder搭建出的NiosⅡ微处理器软核及外围设备控制器作为可编程多轴控制器硬件平台,本文较详细地介绍基于μC／OS-Ⅱ的多轴控制器的软件设计思想。系统将μC／OS-Ⅱ与片上可编程技术SOPC的特点充分结起来,很好地解决了可编程多轴控制器PMAC（Programmable Multi -Axis controller）的程序结构复杂以及实时性差难题。实验结果表明,改善了传统系统软件单任务顺序机制,系统安全性、实时性都得到了显著的提高。     

基于过水断面面积的长江口南支放宽率计算及变化特征分析

河槽放宽率是保持潮汐河口河槽稳定性的主要参数之一。在利用河槽宽度计算放宽率的基础上,提出了以过水断面面积为主要参数计算的天然河口放宽率,能更真实地反映河槽沿程过水能力是否增强以及增强的幅度。1917-2006年长江口南支河槽自白峁沙至吴淞口的放宽率计算结果表明:整体上,近100年来放宽率呈减小之势,与南支河槽不断冲刷相适应,且白峁沙、扁担沙、中央沙、浏河沙等主要沙洲的生长也起到了缩窄河宽,减小河道过水断面面积,缩小放宽率的作用;放宽率在1979年出现最小值,与七丫口-5 m槽宽为历年最窄及充分发挥其节点作用有关;放宽率在2006年增至1.21%,与三峡工程蓄水后流域供沙大幅度减少,南支河槽主要沙体受到侵蚀,特别是中央沙和浏河沙侵蚀最为严重,使石洞口-吴淞口区域过水断面面积增大有关。     

基于m伪随机序列的车内空传噪声传递特性辨识

根据车内空气传播噪声的源-路径-接受者模型,提出了传递路径函数的m序列相关辨识方法。仿真结果表明:该方法具有很好的噪声抗干扰性能。采用复杂可编程逻辑器件CPLD为核心器件,连接外围电路,设计了移位时钟频率可调、长度可选的m序列发生器。利用m序列发生器进行实车对比实验,结果表明:m序列方法的测试误差比白噪声法小1/3,辨识精度高;测试环境的本底噪声能提高40dB(A),抗干扰性好。