基于参数空间法的飞行器再入控制研究

针对空天飞行器再入段环境变化剧烈、气动参数变化范围大的特点,采用参数空间方法来设计其控制系统;首先建立飞行器控制系统的数学模型,鉴于飞行器再入过程中对攻角有着严格的要求,设计了以攻角反馈为被控信号的三回路自动驾驶仪结构,然后根据参数空间方法求出对应的控制器参数,最后基于Matlab/Simulink的非线性仿真表明,所设计的控制系统在大气密度偏差±30%、气动力/力矩系数各偏差±20%的组合偏差情况下仍具有较好的鲁棒稳定性和跟踪性能。     

光电火控系统指向精度CCD非接触测量方法研究

为满足某光电火控系统中二维转台指向精度的高精度测量需求,提出了一种利用CCD图像的非接触测量方法;以静态指向精度为测量对象,构建了CCD图像测量系统,系统分辨力为0.44mrad,采用视频序列的数字图像自动拼接方法得到单幅宽视场全景图,通过图像快速匹配方法得到转台的方位像素坐标值,对转台的指向精度进行了测量;测量实验结果表明:转台的指向精度为0.5mrad,满足指向精度2mrad的设计要求。     

有源电光调制式高功率瞬态电场传感器的研制

瞬态电场防护及应用技术的研究离不开瞬态电场测试系统;文中基于有源电光调制法,研制了一种高功率瞬态电场传感器;通过建立该传感器的等效电路模型,并借助CST仿真建模,分别从频域和时域角度分析了传感器的接收特性,并得到了一致的结果;最后利用脉冲噪声模拟器和吉赫兹横电磁波小室对研制的传感器性能进行了测试;结果表明:接收天线为单极子天线,天线负载采用高阻时响应电压与被测电场场强成正比;研制的传感器带宽为10kHz～314MHz,可用于纳秒级高功率瞬态电场的时域测试。     

存储系统细粒度加密安全设计

存储系统会有成百上千的存储设备和大量的数据。其中有相当部分敏感数据需要加密存储,然而现有的存储系统只能对整个文件进行加密,而不能对文件某一部分进行加密。尽管其实现方法比较简单,但它会导致系统额外的开销并且极大的影响系统性能。本文提出了存储系统的一种文件细粒度加密方案,它可以充分利用分布式存储内在的特性,有效地利用元数据信息对文件内多个任意大小的数据块进行加密。用户还可以根据数据块的保密级别对不同的数据块定义不同的加密算法以满足需要。对于广泛存在的视频、地图、档案等大文件实现不同粒度加密策略,可减少文件中不必要的数据加密操作,极大提高存储系统的性能。     

Delay‐dependent stability for Markovian genetic regulatory networks with time‐varying delays

This paper is concerned with the problem of stochastic stability analysis for a class of genetic regulatory networks with Markovian jump parameters and time‐varying delays. A delay‐dependent stability criterion is derived by using a novel mode‐dependent Lyapunov functional. The derived stability criterion is expressed in terms of linear matrix inequalities and is less conservative than the existing ones in the literature. A numerical example is provided to demonstrate the effectiveness of the proposed stability criterion. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Growth characteristics of β-SiC by chemical vapour deposition

A twin-plane re-entrant corner effect (TPRE) in growth of chemical vapour deposited (CVD) -SiC is described by the film and particles of gas-phase homogeneous nucleation. The structural morphology has been characterized by scanning electron microscopy and transmission electron microscopy. Morphological characteristics of the deposited crystals, such as triangularity, hexagons or facets have been explained in terms of the re-entrant corner effect at twin junctions, which were proposed as preferential growth sites for perfect crystals. For real deposits, screw dislocations and/or the re-entrant corner effect are not expected to be compatible. The majority of chemical vapour deposited SiC crystals have a high defect density comprised of {111} twins and dislocations associated with the process variables. Infrared transmission spectra and electron spectroscopy of chemical analysis indicated that the major chemical bonds of CVD -SiC were Si-C and C-H bonds. The positions of the 1s or 2p corelevel peaks for deposits are described.     

Piezoelectric and acoustic properties of potassium titanyl phosphate (KTP) and its isomorphs

The bulk elastic and piezoelectric properties of potassium titanyl phosphate (KTP) and some of its family members such as RbTiOPO(4 ) (RTP) and RbTiOAsO(4) (RTA) have been determined. The piezoelectric, elastic, and dielectric matrix (P-E-D) of KTP has been completely characterized. Values for the temperature dependence of the expansion coefficients and elastic constants have been obtained, and the effects of variations in dielectric constant on coupling coefficient determined. The major diagonal elements of the piezoelectric and elastic matrices of RTP and RTA were measured as were the thermal expansion coefficient of all the KTP isomorphs, KTP in the temperature range 25-80 degrees C, is shown to have a combination of large coupling coefficients (up to k(t)=38% for hydrothermally grown KTP) and medium temperature dependence coefficients of elastic constant (as low as 40 p.p.m./ degrees C for tau(c33) for hydrothermally grown KTP) that makes it attractive for many piezoelectric applications.     

软件单元测试应用研究及案例分析

单元测试是软件测试过程的第一站,高质量的单元测试是软件质量保证的必要条件,本文就单元测试的概念、测试类型及规程作了简单的阐述,同时就单元测试进行了案例分析。     

基于大湾区外环的柔性直流互联方案

面对日益严峻的短路电流超标、交直流交互影响、第三道防线难以有效设置等问题,广东等多直流馈入受端电网分区构网需求迫切。为协调分区与系统稳定、网架可靠性等方面的矛盾,支撑区内电力消费增长和大规模清洁能源接入,提出了建设大湾区外环的设想,并对广东电网大湾区外环覆盖范围、分区划分和外环容量选择等关键问题进行了具体论证,形成了基于大湾区外环的柔性直流互联构网方案。经仿真分析,该方案符合安全标准,可提升广东电网容量至预期水平且有效应对了短路电流超标、交直流交互影响突出、第三道防线难以有效设置等问题。