星间光通信中局部波前畸变对捕获精度的影响

提出了一种针对反射式光学天线的简单椭圆高斯模型来描述局部波前畸变,研究了星间光通信中局部波前畸变对捕获精度的影响。理论分析和仿真结果表明:局部畸变半径、畸变深度以及畸变位置是影响捕获精度的主要因素;捕获偏差随着畸变半径以及畸变中心相对于光束中心的距离的增大而增大;随局部畸变深度的增加呈周期性振荡衰减变化,且振荡周期和峰值对应的畸变深度不依赖于其它畸变参数。对口径为240 mm的反射式接收天线系统,当遮挡比为0.15时,局部畸变引起的捕获偏差近似可达0.5 μrad。为了减小捕获偏差,所需的光学元件的加工精度应远高于0.25λ。     

第三讲 图像信息处理

图像是人类传递信息的重要媒体,图像信息处理又是信息科学的重要研究分支.目前,起源于20世纪20年代的数学图像处理技术已成为工程学、计算机科学、信息科学、统计学、物理、化学、生物学、医学甚至社会科学等领域中各学科之间学习和研究的对象.文章全面综述了图像处理理论与技术的起源、涵盖的内容、对人类的重要意义及发展趋势.以期读者对图像信息处理有一个全面的理解.     

电子式互感器高频数据采集与传输方案

针对当前电力系统电子式互感器采样率偏低,难以满足行波测距装置准确定位电力故障的问题,提出了电子式互感器高频信号采集与传输方案;电子式互感器内部为Rogowski 线圈,电网电流信号被其微分作用转换为小电压信号并附加了90°超前相差,设计积分电路补偿该相差;设计采样率为2 MSps的高频信号采集电路,FPGA通过LVDS接口读取采样数据,并进行幅值处理,最后利用大容量FIFO(先入先出单元)进行缓存;由于百兆网数据传输速率有限,利用FPGA设计吉比特光纤以太网传输特定格式报文,把电流数据传输至电力行波测距装置;解决了积分电路由于运放输入偏置电压带来的积分饱和问题,以及高速ADC输入量程小于输入信号幅值等技术难点;试验结果表明,高频信号采集及传输方案能够满足行波测距装置百米级别的测距精度要求,具有一定工程应用价值。     

Feedback control of quantum system

Feedback is a significant strategy for the control of quantum system. Information acquisition is the greatest difficulty in quantum feedback applications. After discussing several basic methods for information acquisition, we review three kinds of quantum feedback control strategies: quantum feedback control with measurement, coherent quantum feedback, and quantum feedback control based on cloning and recognition. The first feedback strategy can effectively acquire information, but it destroys the coherence in feedback loop. On the contrary, coherent quantum feedback does not destroy the coherence, but the capability of information acquisition is limited. However, the third feedback scheme gives a compromise between information acquisition and measurement disturbance.     

High Speed Image Acquisition ＆ Neutral Particle Count Systems and the RTX Research

In HL-2A tokamak experiment, high speed image acquisitoin system grabs images and shows them in real-time. It provides serial images of discharge to help scientists a lot to analyse the experiment. Neutral particle count system counts the number of neutral particles radiated from fusion plasmas. It provides the data to calculate the ion energy.     

Spin label study of phase morphology and polymer segmental motion in poly(acrylic acid)–poly(ethylene oxide) complex

The ESR lineshapes of nitroxide radical end‐labeled on poly(ethylene oxide) (SLPEO) for the pure polymer and for different weight ratio complexes with poly(acrylic acid) (PAA) were studied as a function of temperature. For SLPEO one spectral component was detected in the entire temperature range, indicating that the spin label was in the homogeneous phase domain. For all PAA–PEO complexes two spectral components with different rates of motion, a ‘fast’ and a ‘slow’ component, were observed, which indicates the existence of microheterogeneity at the molecular level: the more mobile the PEO‐rich microphase, the more rigid is the PAA‐rich microphase. On the other hand, the SLPEO polymer segmental motion was restricted owing to the hydrogen bond interaction between the carboxyl proton in PAA and the ether oxygen in PEO. This restriction was exacerbated with increasing the PAA content in the complex, which could be further substantiated through the calculated S and τ_c values. Copyright © 2003 John Wiley & Sons, Ltd.     

A novel high-resolution interference spectrometer

A novel precision wavemeter is presented with a resolution of better than 0·01 nm. A Sagnac interferometer with two diffraction gratings forms the basis of the instrument. Using spatial heterodyning techniques and a CCD camera/frame grabber data acquisition system allows fast computer control and power spectrum analysis. The mode structure and mode hopping characteristics of a typical laser diode were examined as a function of diode injection current.     

Informational acquisition and cognitive models

Life forms must organize information into cognitive models reflecting the outside environment, and in a complex and changing environment a life form must constantly select and organize this mass of information to avoid slipping into a chaotic cognitive state. The task of developing and maintaining adaptive cognitive models can be understood through two processes, crucial to regulating the interconnections between environmental elements. The inclusion and exclusion of information follows a process designated by P and the process by which cognitive models change is designated by K. Higher order concepts are created by reducing the interconnections between elements to a minimal number to avoid cognitive chaos. © 2004 Wiley Periodicals, Inc. Complexity 9:31–37, 2004     

A microcomputer system for mass spectrometer control and data acquisition

A microcomputer system has been designed for semi-automatic operation of a solid source mass spectrometer used for geochronological studies. It sequentially steps the magnetic field through pre-selected values, reads the digitized ion currents for a given time and temporarily stores the data which can be transferred to a paper tape or directly to a desk top calculator for further analysis. The unit is relatively inexpensive, made of readily available components and can be adapted to many laboratory automation tasks