基于DSP5402的雷达测速系统硬件、软件设计

文章主要研究了一种基于DSP5402的测速系统,说明了雷达测速的原理,并设计了相应的具体实现方案,包括硬件设计和软件设计以及它们的实现。雷达测速是一种直接测量速度的方法,可以得到列车实际的运行速度。根据多普勒频移效应原理,在发射波和反射波之间产生频差,通过测量频差可以计算出机车的运行速度。该系统以DSP芯片作为数据处理核心,最终实验结果表明：该系统方案稳定可靠,满足雷达测速系统的准确以及实时性要求。     

基于GPS/BD机动参试设备角度标校方法研究

针对机动参试的高精度测速设备标校存在的问题,利用GPS/BD卫星导航定位系统进行方向测量,具有设备简单、体积小、成本低、初始化时间短、精度高、无积累误差、不受地理条件影响等优点.设计了双天线GPS/BD系统进行雷达设备角度标校方法,在完成雷达角度标校的同时还可进行站址坐标的测量,降低了雷达设备对测量场地的要求,为实现真正意义上的机动参试奠定了基础.经某高精度测速设备试验表明,该方法标校精度与传统的方位标校方法相当,但标校效率提高,过程得以最大程度简化.     

基于Nios Ⅱ的机车速度信号处理片上系统设计

介绍频率等精度测量原理,并应用于基于Nios Ⅱ的机车速度信号等精度采集与防滑、防空转控制片上系统的设计中.试验证明,完全满足机车双闭环调速控制系统对速度反馈信号的要求,同时在此基础上实现的机车防(滑)空转保护控制,实际应用效果良好.     

雷达角度电视跟踪系统

雷达角度电视跟踪系统采用ＣＣＤ摄象机作为目标传感器,用软硬件结合方法测定目标坐标,再与雷达电轴位置相比较,输出目标角度误差信号,输入雷达天线驱动系统,使天线向减小目标角度误差方向运动,实现雷达天线对目标的角度自动跟踪。目标在电视视野中的位置测量是关键技术,本文着重阐述电视跟踪系统中目标坐标的录取方法。     

基于RSSI盲估计的MUAV双天线跟踪系统设计

天线实时精确地跟踪无人机飞行方向,是有效保证无人机扩展战术网络覆盖范围、提高通信带宽和质量的关键所在。设计了一款基于信号接收强度(RSSI)盲估计跟踪的双天线跟踪系统,使天线主波束时刻对准中继无人机,提高了地面定向天线对中继无人机的初始捕获速度,实现动态跟踪,确保通信信号强度处于优值。实验结果表明,相比单天线系统,该系统捕获灵敏度和跟踪速度明显提高。     

基于图像处理技术的井下机车速度测定方法

针对传统的使用传感器测定井下机车速度存在的故障率及成本高的问题,提出了一种基于图像处理技术的新的测速方法。该方法通过对图像进行模板匹配求取模板质心坐标,利用模板质心坐标在前后连续两张图片中的变化求得模板在图像中的移动距离;将该移动距离通过比例系数转换为机车实际的行驶距离,再根据两张图像的时间差计算出机车速度。实验表明,该方法可实时确定机车速度,性能较可靠。     

一种目标速度精确测量的新方法

提出了一种CW雷达目标速度测量的新方法,该方法运用离散多项相位变换法先获得目标加速度,然后利用该值对雷达回波进行加速度补偿并基于FFT和插值FFT获得速度值。又考虑到经过雷达信号处理机后得到的速度值存在波动和野值,运用自适应卡尔曼滤波进行处理,剔除野值。相比于传统的测速方法,该方法提高了测量精度,同时也较好地消除了雷达系统噪声,提高了测速系统的稳定性。计算机仿真和外场实测数据处理结果表明了该方法的有效性。     

自适应波束形成算法的现状与发展动态

近十年自适应波束形成算法在通信、雷达、声纳、生物医学工程等科技领域中得到了极为广泛的应用.在实际应用中,如果信号源、天线阵列出现误差,传统的自适应波束形成算法性能将会下降.但是对于稳健的自适应波束形成算法,环境及天线阵列的误差和不确定性是必须要考虑的关键问题.这里对稳健的自适应波束形成算法的研究现状与发展动态进行了较为详细的评述.     

船摇陀螺前馈的转换公式推导及船摇隔离效果分析

随着高频段(X频段乃至Ka频段)天线在航天测控中的不断应用,由于波束非常窄,对捕获跟踪低轨的高动态目标,这将是一个新的技术难点,而在远望号测量船上,加之船摇的影响,窄波束捕获跟踪问题将更加突出；如果船摇隔离度不够,会导致船摇残差过大而导致目标丢失,为了提高跟踪精度,一般采用中心机前馈或陀螺前馈进行速度补偿,等效于提高了系统的加速度误差常数(Ka值)；与中心机前馈相比,陀螺前馈在测量精度、实时性方面存在优势,在船载雷达伺服系统中得到推广应用；文章主要讨论前馈陀螺的两种安装形式、转换公式以及在船载雷达伺服系统中的应用效果。     

基于电感式传感器的非接触测速定位方法研究

对一种新型的电感式传感器装置进行了研究，简单介绍了传感器的基本原理及结构、相关DSP数字信号处理系统，并对测速定位的精度进行了理论分析，得出了其性能参数，通过实验室试验装置验证，与理论计算值相一致。此传感器不仅可用于齿槽状转子的速度测量，还可应用于长定子构造的直线电机的速度、距离的测量上，具有较高的精度和测量范围，以及良好的实际应用价值。     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).