频域宽带阵列波束形成技术优化设计

为提高宽带相控阵系统的波束合成性能,该文针对宽带相控阵系统中的延时补偿问题,采用频域宽带阵列波束形成的方法,分析了宽带相控阵中应用交叠FFT进行时延补偿的原理和误差造成的原因;基于一个接收信号带宽为600MHz的64阵元的宽带相控阵系统,研究了子阵规模、FFT点数、交叠率、位宽、采样率等交叠FFT参数对延时精度、信号保真度和波束性能的影响,在满足工程应用的要求的同时对频域宽带阵列波束合成技术进行了优化;经研究确定子阵规模不超过9个天线阵元、FFT点数不小于512、交叠率不小于1/16、位宽不小于采用12bit时可以达到指标的要求,为交叠FFT方法应用在实际工程中提供了依据与参考,并使其工程实现复杂度降低。     

相控阵雷达波控系统研究

基于相控阵天线渡束控制的基本原理和波控系统的任务,讨论了相控阵雷达波控系统的相关问题.通过MATLAB仿真可知,依据相控阵天线雷达的方向图的可分离性,实现了对雷达波束的控制,本文采用分布式查表和程序运算相结合的方法,提高了波控运算速度.     

超声相控阵缺陷检测聚焦技术仿真分析

采用有限元方法对超声相控阵缺陷检测技术进行分析.首先介绍了超声波波束聚焦、偏转的基本原理,然后使用COMSOL有限元分析软件以及Matlab仿真程序对超声相控阵缺陷检测技术进行建模,在该模型的基础上分析了超声相控阵延时聚焦技术的实现过程与方法.在仿真过程中,通过改变阵元参数,研究其对于超声相控阵缺陷检测信号的影响,并结合物理实验进行了验证.分析结果表明,超声相控阵的延时聚焦技术减小了发射波的波幅宽度,提高了缺陷点回波信号的幅值;基于延时聚焦技术的发射信号,其波束指向性图的主波瓣波束较窄,幅值较高,旁瓣幅值降低,提高了图像分辨率以及成像质量.     

相控阵测量雷达波控系统优化设计

以某型相控阵雷达为例,从雷达波束控制的实现方法出发,对雷达波控信号完整性(SI)进行了理论分析.通过天线小阵实验,讨论了天线阵面电磁场对雷达波控信号的影响,实现了对雷达波控系统的优化设计.     

基于正弦频偏的多载波频控阵的设计与实现

针对常规频控阵(FDA)采用线性频偏增量产生的"S"形波束图在角度和距离上耦合和分辨率不够高的问题,提出一种新型频控阵——基于正弦频偏的多载波FDA.设计并建立了布阵模型,分析了信号模型,推导了在远场形成的发射波束方向图.通过MATLAB对该频控阵的仿真,结果显示该频控阵能够在目标位置处形成点状波束,在发射能量聚焦性能...     

一种基于有向均匀圆阵的宽带波束形成方法

本文提出一种基于有向均匀圆阵解决宽带波束形成问题的新方法,其基本思想是针对某一特定频率设计窄带波束形成空域滤波器,并把得到的滤波器权值直接应用于宽带信号以降低设计和处理的复杂度.在已知信号方向信息的前提下,使用线性约束的最小二乘法设计窄带空域滤波器,而有向均匀圆阵对频率变化不敏感的特性可以保证使用同一组空域滤波器权值在宽带信号所包含的不同频率上形成一致的波束与陷波点.所提出的宽带波束形成方法可以显著降低阵列信号处理时的运算复杂度,便于进行实时信号处理.     

基于PXI总线的相控阵雷达波束控制器测试系统

介绍了一种利用LabVIEW编程,基于PXI总线技术的某型相控阵雷达波束控制器的自动化测试系统。该系统采用了通用化、模块化的系统设计原则,并应用基于LabVIEW的图形化编程语言实现,设计开发了相控阵雷达波束控制器自动化测试设备,满足了大型相控阵雷达波控阵列信号测试要求。     

直升机载相控阵雷达波束波形联合自适应调度算法研究

孔径分割技术和波形捷变能力让直升机雷达可同时形成多个波束完成不同功能,并根据不同需求选择不同波形,因此对雷达资源管理提出更高的要求;综合考虑时间资源、能量资源、孔径资源的约束下,提出一种适合于多子阵直升机载相控阵雷达的波束波形联合自适应调度算法,对雷达波束和波形进行有效调度,并通过与传统自适应调度算法进行仿真对比,证明了该算法在调度能力、能量节约等方面的先进性。     

光控平面阵列建模与计算机仿真

光延时相控阵能够明显地改善普通相控阵雷达系统的带宽,然而大多数的研究和实验系统均基于光控线阵,故对光控面阵的分析和研究有着重大的现实意义.针对在平面阵列的行、列上中同时使用子阵延时、单元移相的光延时波控技术的二维扫描光控面阵,建立了光控平面阵列的数学模型,通过该数学模型完成了光控平面阵列方向图及其在不同的子阵划分和不同指向角下的计算机仿真,仿真结果表明光控平面阵的行、列子阵划分方式和指向角对阵列带宽均存在重大影响,这为进一步研究光控平面阵列奠定了重要基础.     

基于数字波束形成技术的二次雷达系统

随着计算机、集成电路技术、高速信号传输技术的进步,数字波束形成技术开始应用于相控阵雷达。提出了数字阵二次雷达是基于数字T/R组件、高速信号传输、数字信号处理等构成的系统,可以实现瞬时多波束及实时自适应处理,具有目标跟踪、远作用距离、快速识别目标以及同时完成目标搜索、识别、捕获和跟踪等功能。     

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。