空间光通信中轨道短时预报

瞄准、捕获和跟踪(PAT)技术是星间光通信的关键技术之一,高精度卫星轨道短时预报能有效实现PAT.首先在EGM96地球引力场模型下建立了卫星状态动力方程和预报方程,然后改进基于数值算法的扩展卡尔曼滤波算法对卫星轨道短时预报,最后以champ卫星星载GPS实时定轨数据为卡尔曼滤波器观测数据进行仿真实验:预报卫星位置误差约亚米级,速度误差约0.05m/s;卫星位置和速度的均方差估计趋于稳定,在一定程度上能很好地克服离散误差和模型误差对轨道估计精度的影响.PAT瞄准精度约1.6 μrad.预报轨道精度能满足空间光通信PAT技术要求.     

论OA系统的文档类型

本文论述了在开发OA系统过程中,如何选择合适的文档类型。文中给出了具体方案,并对文档类型的标准化及未来的发展趋势进行了分析。     

时滞依赖不确定线性系统的鲁棒H_∞控制

针对一类不确定性不满足匹配条件的具有时滞依赖不确定线性系统,研究了鲁棒H∞控制器的设计问题.基于线性矩阵不等式方法,通过构造合适的Lyapunov函数,给出了鲁棒H∞状态反馈控制器存在的充分条件,并通过求解相应的线性矩阵不等式完成了控制器的设计.仿真结果表明,所设计的控制器对所有容许的不确定性不仅使闭环系统渐近稳定,又能保证闭环系统满足一定的H∞性能指标,具有较好的抑制扰动的效果.     

A less conservative method for designing H∞ filters for linear time‐delay systems

This paper focuses on H_∞ filtering for linear time‐delay systems. A new Lyapunov–Krasovskii functional (LKF) is constructed by uniformly dividing the delay interval into two subintervals, and choosing different Lyapunov matrices on each subinterval. Based on this new LKF, a less conservative delay‐dependent bounded real lemma (BRL) is established to ensure that the resulting filtering error system is asymptotically stable with a prescribed H_∞ performance. Then, this new BRL is equivalently converted into a set of linear matrix inequalities, which guarantee the existence of a suitable H_∞ filter. Compared with some existing filtering results, some imposed constraints on the Lyapunov matrices are removed through derivation of the sufficient condition for the existence of the filter. Numerical examples show that the results obtained in this paper significantly improve the H_∞ performance of the filtering error system over some existing results in the literature. Copyright © 2008 John Wiley & Sons, Ltd.     

Digital‐to‐analog converter with gamma correction on glass substrate for TFT‐panel applications

Abstract— Low‐temperature polysilicon (LTPS) technology has a tendency towards integrating all circuits on glass substrate. However, the poly‐Si TFTs suffered poor uniformity with large variations in the device characteristics due to a narrow laser process window for producing large‐grained poly‐Si TFTs. The device variation is a serious problem for circuit realization on the LCD panel, so how to design reliable on‐panel circuits is a challenge for system‐on‐panel (SOP) applications. In this work, a 6‐bit R‐string digital‐to‐analog converter (DAC) with gamma correction on glass substrate for TFT‐panel applications is proposed. The proposed circuit, which is composed of a folded R‐string circuit, a segmented digital decoder, and reordering of the decoding circuit, has been designed and fabricated in a 3‐μm LTPS technology. The area of the new proposed DAC circuit is effectively reduced to about one‐sixth compared to that of the conventional circuit for the same LTPS process.     

Granular Rough Theory: A representation semantics oriented theory of roughness

The present work is an archival paper for a series of contributions proposed in last few years on building a theory of roughness over pure mereological relations among information granules. There are five major efforts taken in the present paper: (1) emphasizing on the representational semantics of theory of roughness: to approximately represent a class of entities characterized by some aspects in terms of entity collections described at other aspects; (2) defining a representation model Granular Representation Calculus (GrRC) to synthesize complex information systems from information granules; (3) establishing notion of Granular Rough Theory (GrRT) over information granules operated in terms of GrRC; (4) extending GrRC/GrRT to various computational environments such as multi-agent systems and ontological computing environments; (5) exploring pragmatic aspects of GrRC/GrRT in implementing prototypes with data model and object programming orientations, and proposing an Ontology-Driven Web Information System as a granular-rough computational Web intelligence framework over GrRC/GrRT.     

虚拟机检测技术研究

虚拟机在反恶意软件研究领域的应用越来越普遍。虚拟机检测技术对恶意软件的作者或反恶意软件的研究人员都具有重要的意义。首先简述了虚拟机检测技术的意义,然后介绍了虚拟机检测技术的理论基础,接着描述了现有的虚拟机检测技术的基本思想,分析了其优缺点,最后在总结现有成果的基础上,指出了未来的研究重点和方向。     

基于模糊定性趋势分析的故障诊断方法研究

趋势能够反映过程重要参数的运行状态和发展趋向;利用定性趋势分析进行故障诊断时,趋势固有的定性特性使得趋势分类的界限变得模糊,带来诊断的模糊性和规则知识库的组合爆炸等一系列问题;将模糊理论与定性趋势分析相结合,给出了趋势提取及基于模糊逻辑的趋势匹配算法,研究了一种基于模糊定性趋势分析的故障诊断方法来有效地解决这些问题;实例分析表明,基于模糊定性趋势分析的故障诊断方法能大大缩小规则知识库的规模,提高定性趋势分析故障诊断的准确性和实时性,及时发现和预测控制过程的早期故障。     

基于自动检焦信号梯度信息的自适应平滑算法研究

近年来随着航空相机技术不断发展,高分辨率相机将成为未来航空相机的发展趋势;但环境的变化会使光学系统的性能发生显著的、随机的变化,因此,欲在恶劣的环境条件下获得最佳分辨率,必须使相机具有很高的检焦精度,然而由于测量元件及电源等的噪声的存在,大大影响了检焦信号精度;基于中值滤波和梯度信息的平滑滤波算法,介绍了一种新的自适应平滑算法,该算法有效地抑制扰动信号,更为真实的突现出峰值信号,从而大大提高了检焦精度;该方法大大减小了随机干扰对检焦结果的影响,提高了检焦精度,从而每次都能获得较为清晰的图像。     

基于二维小波变换的车牌边缘检测的研究

在Matlab环境下运用基于二维小波变换边缘检测方法提取车牌信息的边缘。实验证明这种方法对车牌边缘信息提取的效果比传统的边缘提取算子提取车牌信息边缘的效果要好,特别是对伪边缘和图片噪声的过滤作用比较明显。