基于AT89S51单片机的PWM专用信号发生器的设计

介绍一种脉冲涡流无损检测系统所使用的多波形专用PWM信号发生器的设计.该信号发生器以单片机为核心控制单元,通过对外围芯片的控制来实现对输出波形的频率、电压幅值、占空比的连续调节,并能对运行信号参数进行实时显示.经实验验证,该信号发生器便于观察和调节,完全满足脉冲涡流检测系统所需激励信号的要求.     

一种高速率Chirp-UWB信号发生器的设计与实现

Chirp超宽带通信系统使用满足UWB定义的Chirp信号作为数据传输的载体,起到了扩频效果,具有CSS和UWB的优点,其处理增益大、传输距离远、功率谱密度低、抗衰落能力和抗截获能力强,获得广泛研究与关注。Chirp-UWB信号发生器是实现该通信系统的关键技术之一,采用DA+锁相环(PLL)技术,设计并实现了Chirp-UWB信号,详细分析了其设计过程与原理。试验表明,设计的信号发生器在≥2Mb/s调制数率的驱动下,能够产生稳定可靠的Chirp-UWB信号,该发生器具有电路结构简单、易于编程控制、扩展性好以及实用性强等优点,能够满足远距离高速率无线传输数据的要求。     

基于AT89S51单片机的PWM专用信号发生器的设计

介绍一种脉冲涡流无损检测系统所使用的多波形专用PWM信号发生器的设计。该信号发生器以单片机为核心控制单元,通过对外围芯片的控制来实现对输出波形的频率、电压幅值、占空比的连续调节,并能对运行信号参数进行实时显示。经实验验证,该信号发生器便于观察和调节,完全满足脉冲涡流检测系统所需激励信号的要求。     

数字通信原理的虚拟实验室系统的设计与实现

本文提出了基于CORBA技术的网上虚拟实验系统模型，该模型以Java Applet作为客户端，CORBA作为中间通信桥梁，能够集成JavaBean、Matlab、COM／DCOM作为计算后台，大大提高了专业虚拟实验室的开发效率。基于这个平台，开发了通信原理实验需要的信号发生器、信号叠加器、滤波器以及示波器四种设备。同时，通信原理虚拟实验室为学生提供了学习通信原理的实验环境，学生能够在互联网上根据需要完成各种通信原理实验。     

基于实时频谱分析的便携式射频通信干扰器设计

针对传统电子干扰器系统复杂、体积大、功耗高的缺点,文章设计了一种基于FXI规范的射频通信干扰器,FXI规范在FMC信号定义的基础之上,针对虚拟仪器领域的应用,定义了FXI模块的结构尺寸和FXI接口的专有信号组,提高了虚拟仪器模块的功能密度,从而实现了模块化、小型化和轻量化的设计目的。该射频通信干扰器内部同时集成了频谱仪模块和射频信号发生器模块,通过采用硬件逻辑实现射频信号的实时跟踪和干扰信号的实时合成,从而实现对高跳速射频通信信号的跟踪和干扰,用户可针对短波通信、超短波通信和微波通信扩展不同的模块,来实现在不同使用场景中的应用。经过测试,该射频通信干扰器的各项指标可满足使用要求,可进一步推广至电子对抗、无人机干扰等技术领域。     

网络化虚拟信号发生器设计

本设计采用NI PCI-6024E数据采集卡,运用虚拟仪器及其相关技术于多通道数据采集系统的设计.该信号发生器系统具有数据同时采集、采集数据实时显示、存储与管理、报警记录等功能,最后使用Web技术实现了虚拟信号发生器的远程访问,其是虚拟仪器在测控领域的一次成功尝试,能够高效的实现各种测控任务.     

复杂电磁环境中的常规通信信号的实时分选

为了能够从复杂电磁环境中提取常规通信信号的有效参数,研究了一种基于单天线接收的常规通信信号的实时分选方法。该方法由窄带信号检测、参数估计、信号跟踪三部分组成。提出了一种适用于高斯色噪声背景的窄带信号检测与参数估计的方法,给出了一种能够实时跟踪常规通信信号的算法。仿真结果表明,当信噪比高于0 dB时,窄带信号检测方法的正确率为92%以上,分选算法能够从复杂电磁环境中提取常规通信信号的有效参数,具有一定的工程实用价值。     

基于FPGA的多功能信号发生器的设计

本系统主要是以FPGA基础上实现的多功能信号发生器,该信号发生器主要能够实现正弦波、三角波、方波的信号输出。主要是以现场可编程门阵列FPGA为主要部件,实现直接数字频率合成器DDS的设计。     

基于Labview的虚拟函数信号发生器的设计

基于专业虚拟仪器开发工具Labview,设计了一虚拟函数信号发生器.该虚拟函数信号发生器能够产生正弦波、三角波、方波、锯齿波等波形,频率动态范围较宽且可微调.     

多功能函数信号发生器设计

目前市场上的信号发生器产生的波形种类较少,主要有方波、正弦波、锯齿波,且信号发生器价格昂贵,而试验室等多种场合可能需要用到更复杂的波形来作为模拟试验的输入。针对该问题,设计了基于STM32的函数信号发生器。该信号发生器采用D/A转换,通过软件来实现对信号的类型、频率、电压等的控制。信号发生器以STM32作为控制核心,外部接入键盘,通过键盘的输入来实现对波形和频率的快速改变;利用函数库math.h,不仅能输出使用较多的正弦波、方波、锯齿波、三角波,还能输出指数函数、对数函数等任意函数的模拟信号,也可以产生频率、电压随时间变化的波形。试验表明:该信号发生器设计简单,能够实现对信号的波形、频率等的灵活控制,系统稳定可靠,输出信号失真小。该发生器具有低成本、低功耗的特点,能够应用在试验室等场合中。     

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.     

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.     

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.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

正~~     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate