基于无载频脉冲式超宽带雷达的生命信号检测分析与实现

首先分析了无载频脉冲式超宽带雷达检测生命信号的检测原理,论证了基于频谱搜索检测生命信号的方法;然后介绍了一款新颖的无栽频脉冲式超宽带生命信号检测雷达系统.该雷达发射机结构简单,能产生Vp-p+为2～10 V、脉冲宽度为300～500 ps、脉冲重复频率大于10 MHz的超短脉冲.接收机利用PNP和NPN微波三极管的互补特性,产生一对平衡对称的超短门脉冲控制二极管桥的导通与截止,实现对天线接收到的信号进行采样,从而完成等效采样接收.依据人体呼吸信号的频谱特性,搜索包含具有最大功率谱的生命信号的快时间点、提取位于快时间点和不同慢时间点的雷达信号得到生命信号.实验证明,该雷达系统能实时实现人体生命信号非接触式检测.     

物联网嵌入式脉冲涡流无损检测系统研究

为了能够在线无损检测设备内部缺陷与损伤,本文设计一种物联网嵌入式脉冲涡流无损检测系统。该系统通过信号发生器产生脉冲宽度调制波经过放大后驱动探头;探头采集被测试件的缺陷与损伤信号,将含有缺陷和损伤的磁信号转换成电信号,经过调理电路后,在模数转换部分将电信号转换为数字信号传输至STM32f107内;在控制器控制下通过物联网传输至PC机,然后PC机对信号进行分析与显示。     

利用DFT技术检测连续时间信号中频率较近分量方法的研究

从信号检测的需求出发,阐述了运用离散傅里叶变换检测连续时间信号频谱的原理和具体方法。通过实例表明：利用DFT检测连续信号中频率较近的分量时,应当根据分量的频率差、窗函数主瓣的有效宽度、时域信号的抽样频率,并准确计算时域信号的抽样点数,才能获得理想的检测效果。     

基于FPGA的某型发动机超声波探测电路设计

固体火箭发动机的钢壳、绝热层、衬层、推进剂多层粘接结构的脱粘缺陷,很容易引起灾难性后果,对它的检测已经成为一项极其重要的工作,文章设计了一种基于FPGA的超声波探测电路,构建了一个可编程片上系统（SOPC）,并编写了PWM控制组件。以NiosⅡ为核心控制产生脉冲宽度、重复频率可调的超声波激励脉冲,配合高速A／D实现回波信号的采集和存储。缩短了设计周期,简化了硬件电路,为后续研究便携式超声波检测仪奠定了良好的基础。     

基于ARM和FPGA的旋转叶片振动信号仿真系统设计

设计了一种脉冲信号发生器,作为高速旋转叶片振动测量系统中的测试环节,实时模拟现场光纤传感器产生的多路脉冲信号,用以测试和验证上位机软件算法的可靠性.对旋转叶片进行数学建模,提取影响叶片振动的相关参数,计算出各传感器脉冲信号产生的时间;实现了基于ARM和FPGA的硬件方案,使用ARM进行外设的控制,使用FPGA进行主要运算和脉冲信号的输出.将该设备应用于叶片振动测量系统,能够产生准确的脉冲信号,完全满足系统高速、高精度的要求,通过自带键盘或串口输入参数,该设备具有足够的可调范围,且同时做到便携性.     

取样脉冲对平衡式取样积分微分电路性能影响

取样脉冲是影响超宽带无线电引信接收机性能的关键因素。在分析取样积分微分电路工作原理的基础上,建立了其频域和时域数学模型。结合无载波信号的时域多普勒效应,提出了基于Matlab的超宽带无线电引信接收机输出信号时域仿真方法。研究了取样脉冲宽度和幅度对电路输出波形的影响,结果表明:电路完全对称时,输出信号幅度只与取样脉冲宽度有关,但并非单调关系;非对称时,电路达到稳态前产生一个脉冲信号,脉冲幅度与取样脉冲的幅度成正比,宽度成反比。     

高精度超声波液位测量系统设计

随着工业生产中对在线液位检测技术要求的不断提升,需要更适用于工业生产、精度更高的测量设备。对基于脉冲回波法的超声波液位检测系统进行了研究和改进,介绍了其工作原理及系统结构。以STM32F407为控制器,设计了超声波信号的产生、接收、处理、采集等电路。发射电路对脉冲宽度调制(PWM)脉冲升压驱动超声波换能器产生超声波,接收电路先对信号进行限幅和滤波处理。通过放大数据将脉冲信号处理成更易分析的低频信号,利用控制器的直接内存存取(DMA)功能实现对信号的连续采集。通过辨识回波信号起始时刻,建立渡越时间与液位之间的关系。试验结果表明,在70 mm的范围内,系统误差小于1 mm。该设计为密闭容器的液位测量提供了一种高精度的检测方法,同时为工业领域的液位在线自动检测提供了参考。     

JTIDS信号的高效信道化接收及检测方法

根据联合战术信息分发系统（Joint Tactical Information Distribution System,JTIDS）信号的特点,提出一种基于多相滤波的JTIDS信号接收方法。该接收模型具有全概率接收JTIDS信号的特点,而且所需计算复杂度低。在信号接收后,通过能量检测对输出信号进行脉冲宽度检测,判断信号是否为JTIDS信号。仿真结果表明该方法在信噪比为正时具有较好的性能。     

一种简易通用的敲击触发式惯性导航系统时间同步装置设计方案

科学研究与工程实践中常需要利用多种传感器协同工作获取被测目标的动态信息,此时对不同传感器采集的数据进行时间同步是必要前提。提出了一种以“敲击-脉冲”信号为媒介的时间同步方案,通过能够在敲击瞬间产生脉冲信号的时间同步装置实现惯性导航系统等运动传感器与其他脉冲同步传感器的时间同步,并通过实验验证了其可行性和时间同步精度。与传统的硬件方案或软件方案时间同步技术相比,本方案通用性极强,开发工作量小,操作简单方便,适用于对时间同步精度要求不高的传感器或系统的快速试验评估。     

某型机载雷达信号发生器功能扩充方法研究

针对某型机载雷达信号发生器信号样式单一、载波频点对应的脉冲宽度和重复周期值较为有限的问题．利用CPLD技术重新制作信号发生器的信号调制板．增加了脉冲宽度值,重复周期值和一种抗干扰信号样式——重频参差,扩充了信号发生器的功能．最后给出仿真结果与硬件测试结果。     

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。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

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.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

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.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

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。