采用混合粒子群算法的星图识别方法

为提高大视场高灵敏度星敏感器的星图识别速度和识别成功率,提出了一种基于混合粒子群算法的星图识别方法,该方法首先根据星图中星点的灰度信息确定候选识别主星集合;然后选择该集合中的一个星点为圆心,以一定角距为半径画圆,将圆内的所有星点构成特征数据集合;然后利用混合粒子群算法对圆内的星点进行快速路径寻优;最后利用最优路径长度进行索引,并利用最优路径中前三个星点间的角距以及它们的星等信息进行匹配识别;实验结果表明,与现有识别方法相比,该方法具有高的识别率,良好的实时性和鲁棒性,且所需的导航星库容量小.     

一种静态星模拟器的设计与星点位置修正方法

为了实现对高精度星敏感器的地面标定,设计了一种大视场静态星模拟器,其星间角距精度要求优于20(″).采用星点分划板作为核心显示器件来模拟星图,通过设计大视场小畸变光学系统使模拟星图成平行光出射,在星敏感器入瞳位置产生星图.为保证星点板的星图模拟精度,提出了一种星点位置的修正方法.实验结果表明,经过星点位置修正后的静态星...     

基于双星敏感器的船体姿态测量系统设计

提出了一种基于双星敏感器的船体姿态测量系统。本系统采用两台大视场高精度CCD星敏感器,一台指向船艉,一台指向左舷,组合定姿达到提高横摇角测量精度的目的。选用TH7888A作为CCD传感器,成像后经实时图像处理器提取星点目标位置、灰度信息传给数据处理计算机,通过星图识别、姿态确定获取地心惯性坐标系下视轴指向,经岁差、章动、极移、船位、蒙气差等修正,获得惯导地平系下姿态矩阵。依据标定的星敏感器与甲板坐标系安装矩阵,解算船体姿态角,将两台星敏感器解算的姿态角进行融合,达到获取三个高精度船体姿态角的目的。实验表明,该系统航向、纵摇及横摇测角精度分别达到8.46″、7.16″及5.11″,测量精度高、自主性强且能不随时间漂移。     

多视场星敏感器近地轨道自主定位导航方法

传统航天器自主天文导航需要星敏感器、红外地平仪、磁强计等多种敏感器采集导航数据,增加了航天器的成本和复杂度。利用多视场星敏感器的特点,分别对恒星与地球进行成像,在完成姿态测量的同时,得到地心矢量信息,从而进行自主天文导航。首先建立地球几何模型,结合航天器轨道参数与多视场星敏感器的安装布局,实现各个视场内地球边缘的成像模拟,使用Steger 算法提取地球边缘。综合考虑地球扁率的影响,对不同视场中观测到的地球边缘进行拟合得到精确地心矢量,最后进行基于星光角距的直接敏感地平导航仿真。仿真结果表明,在一个视场观测恒星,另外两个视场观测地球边缘的布局情况下,地心矢量精度和导航位置精度分别达到0.017 2（1）和190 m（1）。     

采用扩展外部编程方法优化设计APS星敏感器光学系统

星敏感器是目前精度最高的姿态测量仪器,光学系统是其重要的组成部分.首先介绍星敏感器的工作原理.讨论星图识别过程中星像位置提取算法和星图识别算法.剖析光学系统的像差校正、成像特性要求.基于特殊的像质要求,兼顾优化速度,提出运用ZEMAX扩展外部编程以约束光线的优化设计方案.通过编写外部约束条件程序,使用动态数据交换技术实现外部程序和ZEMAX软件的通信,达到星敏感器光学系统的优化设计的目的.然后针对设计指标焦距f=43.56 mm,入瞳直径D=27.3 mm,全视场角为20°的APS星敏感器光学系统,采用该方案优化设计.得到的星敏感器光学系统,所有光学面都是球面,材料选用普通玻璃,具有像方远心的特点,系统成像质量满足星图识别要求.仿真表明:运用ZEMAX扩展外部编程优化设计星敏感器光学系统的方案快速有效.     

三视场定位定向设备的视场确定

为了提高三视场定位定向设备可靠性,建立三视场系统功能的基本约束条件测试模型,以模型为依据对可见光波段的视场进行优化分析。首先,分析了设备正常完成工作时采用组合星图识别和简单星图识别所需的必要条件,并建立这两种识别方式关于视场大小的概率分布模型。从原理和实验数据两个方面说明了三视场结构识别三角形概率分布不能通过单视场的概率分布简单推导获取的原因。,给出用蒙特卡洛法求取此概率分布和视场最优值的方法。然后,通过仿真分析得出了两种识别方法关于视场大小的概率分布,在分析两种识别方法仿真数据的基础上,取识别概率为1时视场大小为其优化值。实验结果表明:以组合星图识别为工作基础的三视场定位定向设备有更好的可靠性,优化的视场大小为4.2253.168 75。它满足三视场定位定向设备识别条件可靠性要求。     

多视场星敏感器结构布局优化

星敏感器是应用于航天器的重要的姿态测量器件.多视场星敏感器与传统单视场星敏感器相比,在测量精度及可靠性方面具有明显优势,是星敏感器技术发展的重要方向.如何对多视场星敏感器的安装结构进行优化布局,获得最佳的姿态测量效果,是多视场星敏感器在设计与应用过程中需要首先解决的关键问题.从测量精度出发,对多视场星敏感器的结构布局进...     

适用于星敏感器的星跟踪算法研究

为了解决全天球识别中星像坐标提取速度慢的问题,提高空间飞行器姿态确定的实时性,提出了一种新的星跟踪算法.该算法根据星敏感器在一次全天球识别后能够获得一定先验信息的特点,利用星敏感器在上一时刻采集的星图中已识别观测星的信息来获取星敏感器下一时刻采集的星图中待识别观测星的信息.仿真结果表明该算法不但提高了星像坐标提取的速度.也由此提高了星敏感器的姿态更新率,从而避免了由于全天球识别导致的误匹配.     

一种基于星点特征不变原理的快速星图识别方法

星图识别算法是星敏感器输出姿态的关键技术。根据星图从天球坐标系转换到星敏感器坐标系过程中存在特征值不变的原理,结合视场和星等需求建立了导航星表。并根据星图识别要求设计了对应的快速识别算法。针对特征表维数多的特点,采用K向量法提高搜索效率,同时采用并行计算的思想进一步提高搜索速度。采用Matlab编程实现了算法,并进行了仿真。结果表明,算法的识别效率可达97.8%,平均搜索时间可达14.4ms,能够满足准确率高、识别速度快的要求。     

L2范式距离的星图识别方法

在Hausdorff距离的基础上,提出一种不依赖于星敏感器的旋转方向和焦距等因素的星图识别方法。在构造Hausdorff距离的数据点集合时,采用基于L2范数对应的相对欧氏距离作为集合元素,解决星敏感器滚动对星图识别的影响;另一方面,由于受星敏感器焦距的影响,星敏感器图像与标准参考图也会存在误差。在构造标准数据点元素时,考虑到如果一个数据点集包含另一个数据点集,在这两个数据点集之间至少有两个数据点之间的L2范式距离是相同的。对L2范式Hausdorff距离进行比例化处理,每个集合中的相对空间距离除以本集合中最小的相对空间距离,构成一种新的数据点集。这种方法不需要对星敏感器图像由于焦距不同进行标定,避免了星敏感器焦距对星图识别的影响。给出了距离的计算公式和实现步骤,并给出了实验结果。结果表明:在星敏感器转动、尺度变换等情况下,该算法可以正确得到星图识别结果,从而获得星敏感器的姿态信息。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks