针对地球自转影响的星载正侧面阵雷达杂波补偿方法

对于星载正侧面阵雷达,地球自转会导致地面杂波的多普勒分布发生展宽,使得杂波协方差矩阵估计不准确,致使空时自适应处理(STAP)的杂波抑制性能下降.针对该问题,本文提出了一种杂波补偿方法.该方法利用星载雷达的轨道参数对地球自转分量进行估计,然后对杂波数据进行多普勒补偿.该方法能够减轻由于地球自转引起的杂波多普勒分布展宽,...     

利用直接数据域的双基机载雷达地面动目标检测方法

双基机载雷达的杂波存在严重的距离依赖性,从距离上获得的样本不能够准确估计杂波加噪声协方差矩阵,从而导致空时自适应处理(STAP)的杂波抑制性能严重下降。针对该问题,提出了利用直接数据域(DDD)的双基机载雷达地面动目标检测方法。因为DDD算法是在单个距离门对目标滤除后进行空时平滑来获得足够多的样本,所以不需要对双基雷达杂波距离依赖性进行补偿。仿真实验验证了该方法的有效性。     

机载双基地雷达STAP分析

空时自适应处理(STAP)是机载雷达信号处理中的一项关键技术,近年来机载双基地雷达STAP的研究成为热点.机载双基地雷达表现出复杂的杂波特性,即严重的杂波距离相关性,导致传统STAP方法杂波抑制性能严重下降.为此,本文首先对现有解决机载双基地雷达STAP面临的杂波距离相关性问题的典型方法的机理和特点进行了分析,然后对各...     

一种全谱域的机载前视阵雷达杂波补偿方法

机载前视阵雷达近程不同距离门杂波的方位-多普勒分布不同,导致杂波具有强烈的距离依赖性,从而使得杂波噪声协方差矩阵估计不准确,空时自适应处理（STAP）的杂波抑制性能严重下降。针对该问题,提出了一种全谱域的杂波距离依赖性补偿方法。以雷达先验参数知识为基础重构各距离门的杂波协方差矩阵,对重构的杂波协方差矩阵向参考距离门进行一定变换,进而实现全谱域的补偿。仿真实验结果证明了该方法的有效性。     

多通道SAR杂波抑制技术研究

主要研究了几种典型的多通道SAR杂波抑制技术:相位中心偏置(DPCA)技术、沿航迹干涉(ATI)技术和空时自适应处理(STAP)技术,探讨了对机载单天线SAR实际数据应用复图像域DPCA、ATI杂波抑制技术和空间频率域STAP杂波抑制技术实现运动目标检测,并给出一些实际数据的实验结果。     

机载雷达杂波抑制优化与性能分析

为了有效分析机载雷达杂波抑制特性和提高目标检测性能.建立了天线行子阵和列子阵的天线发射方向图模型,同时采用空时自适应处理(Space Time Adaptive Processing,STAP)的机载雷达杂波分析方法,根据目标的导向矢量和杂波与噪声的协方差矩阵建立了杂波功率谱的数学模型,选取不同的脉冲重复频率仿真分析了杂波的特征值谱和改善因子以及杂波空时谱.仿真结果表明:低脉冲重复频率和中脉冲重复频率使杂波谱扩散;随着脉冲重复频率的减少,杂波的相关度减少;STAP法适合高脉冲重复频率的情形,为抑制雷达杂波提供了依据.     

一种基于子孔径SAR的地面运动目标检测方法

针对UHF波段运动目标检测中信号弱、杂波展宽严重等问题,提出一种基于子孔径SAR技术的杂波抑制方法。首先通过SAR成像实现运动目标的粗聚焦,再通过距离-方位拓展局部STAP实现杂波抑制,避免了运动目标越距离单元和方位散焦带来的信号损失。最后,通过仿真结果验证了算法的有效性。     

低重频采样SAR系统中地面运动目标参数估计

低脉冲重复频率(pulse repetition frequency,PRF)采样合成孔径雷达(synthetic aperture radar,SAR)系统中运动目标回波信号存在Doppler谱模糊和Doppler中心频率模糊,这给运动目标参数估计带来了很大困难.由于杂波相消后的运动目标可以看作空间稀疏信号,基于压缩感知理论,本文提出一种低PRF采样SAR系统中的运动目标参数估计的新方法.首先采用基于Keystone变换的稀疏走动校正方法来实现包络走动校正和估计出引起整数倍PRF Doppler频率偏移的垂直航向速度分量,利用压缩感知(compressed sensing,CS)理论进行稀疏信号重建,将Doppler谱模糊的运动目标参数估计问题转化为求解优化方程稀疏解,最后利用优化方法获得运动目标的速度以及方位位置.仿真实验和实测数据都验证了本文方法的有效性.     

基于通道对消处理的 SAR 快速运动目标检测技术研究磁

论文深入研究了基于通道对消处理的 SAR 快速运动目标检测、定位和速度估计技术。基于双通道杂波对消对快速运动目标信号的的影响,提出将通道对消后的残差 SAR 图像反变换回距离压缩方位时域,通过 Radon 变换计算距离走动的斜率,得到径向速度估计,再利用 keystone 变换完成运动目标的距离走动校正。基于图像熵最小化准则,采用参数搜索法实现方位向聚焦,同时获得切向速度估计值,在实现二维聚焦的基础上完成快速运动目标检测,最后对所提出的快速运动目标检测方法进行了仿真验证。     

非正侧视机载雷达一种改进的多普勒频移算法

非正侧机载雷达的杂波分布随距离变化而变化,各距离单元的杂波分布不再满足独立同分布条件,导致统计型STAP处理器性能下降。多普勒频移（Doppler Warping,DW）算法沿主波束方向对杂波非均匀进行了补偿,但在其余方向上杂波非均匀依然存在,因而性能较差。提出了一种改进的非正侧视机载雷达杂波抑制算法——修正的多普勒频移法（Modified Doppler Warping,MDW）,先通过多普勒频移法使各距离单元的杂波谱在主波束方向重合,再沿多个多普勒通道使参考单元和检测单元的杂波谱保持一致,进一步消除非正侧视机载雷达的杂波非均匀程度。仿真结果表明,与原有方法相比,该方法的杂波抑制性能有明显提高,且运算量增加不多,是一种具有工程应用价值的方法。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

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。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

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。     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。