宽带直流放大器的增益控制设计与研究

首先进行了方案论证与比较,分析各种方案的优点缺点,最后选择亚德诺半导体公司生产的低噪声增益可控集成运算放大器AD603和电流反馈型宽带运算放大器AD811等器件设计宽带直流放大器。输入级采用两级AD603级联,输出级设计通频带0~10MHz的带宽,通过单片机可以对放大器增益进行控制。该放大器具有频带宽、功率高、增益可调、带宽可选择等特点。此外,对提高直流放大器的各种性能指标提出了多种具体措施,在要求较高的系统中具有较强的实用性。     

运算放大器特性参数偏差对控制系统稳定性的影响分析

对一种运算放大器AD8692(以下简称运放)的特性参数偏差对整机控制稳定性的影响机理进行了研究,运放在整机中用于处理器前级对位移闭环控制信号的处理,实验证明,运放特性参数偏差会引起位移信号自激振荡,进而导致整机性能下降,系统失稳。对标GJB 9147进行运放各项参数的系统测试和分析,找出了影响闭环控制稳定性的参数,并对多批运放的性能参数进行了对比测试,验证了参数分析的正确性和普适性。经实验测试提出了运放性能参数的测试筛选控制措施,对装机器件的性能控制提供了有效手段。     

基于AD9250的高速数据接口设计

AD9250是ADI公司的两路14位250MSPS数模转换器,采用JESD204B协议接口。文中分析了JESD204B协议,并基于Xilinx FPGA的GTX高速串口实现高速数据接口,将AD9250输出的串行数据转换为14位的并行采样数据。同时搭建了验证平台,对高速数据接口进行了数据传输测试验证,测试结果表明,该高速数据接口可正确接收速度高达5Gbps的采样数据。     

一种新型隔离放大器的设计

隔离放大器是在运算放大器基础上发展起来的,它具有很高的隔离模抑制比。它主要应用在自动控制、医学和核工业等领域。本篇介绍以V/F、F/V变换器为主要器件设计一种电磁隔离放大器,内置三端隔离电源。经初步试验,在功耗和噪音等参数超过BB3656技术指标。     

基于雷达的测试性设计优化方法应用研究

基于雷达等电子产品测试性要求的不断提高,对产品进行测试性设计迭代并进行测试性验证,成为对电子产品的普遍要求。由于初始设计有缺陷、覆盖故障模式不全等引起测试性设计不能满足要求,开展闭环测试、脉冲检测、隔离策略优化等测试性改进,最终选择软、硬件改进相平衡的方案,通过回归试验,获得满足指标要求的检测率和隔离率结果,优化方法促进了产品的测试性设计改进和增长。     

动态电子轨道衡数据采集系统设计

提出了一种动态电子轨道衡数据采集系统的设计方案,重点介绍了影响系统性能的称重通道的硬件设计。该系统采用可编程增益放大器AD625及二阶低通滤波电路对传感器信号进行初步处理;采用带光电隔离的模入接口卡PCI-8325B实现AD转换,并通过PCI总线将数据送入前端主机进行软件处理,处理后的数据通过网桥或Modem送往终端计算机,实现数据的统一管理。试验结果表明,该系统满足工程实际应用需要。     

隔离放大器及其应用

在某些使用电子测量仪器的場所,信号源与电子仪器之间存在着共模电压(CMV)。这种情况下如果仪器本身不采取隔离措施又不考虑浮空屏蔽,则微弱的小信号就会被强大的共模干扰淹沒,仪器将无法正常工作,甚至会损坏仪器中的器件。隔离放大器的出现从根本上解决了因共模电压的存在而引起的干扰问题,本文将以美国AD公司的产品为例,介绍隔离放大器的原理、性能及其各种应用。     

一种新型隔离放大器的设计

隔离放大器是在运算放大器基础上发展起采的，它具有很高的隔离模抑制比。它主娶应用在自动控制、医学和核工业等领域。本篇介绍以V／F、F／V变换器为主要器件设计一种电磁隔离放大器，内置三端隔离电源。经初步试验，在功耗和噪音等参数超过BB3656技术指标。     

基于AD9833的ZPW-2000R移频测试信号研究

ZPW-2000R移频自动闭塞系统是我国主推的国产新型自动闭塞系统。在此闭塞系统接收机模块的质量测试过程中,测试系统需要提供双路频率、幅值可调的高精度移频信号。本系统通过主控芯片TMS320F2812的SPI和GPIO模拟的SPI控制两片DDS芯片AD9833产生频率可调的移频信号。为了实现信号的幅值可调,本系统将AD9833输出的测试信号经高精度运算放大器进行幅值放大后输入至数模转换芯片AD7521中,通过GPIO口对AD7521的数字输入口的控制实现信号的幅值连续可调。经实验验证,本系统所产生的双路移频测试信号精度高,波形平滑稳定,从而提高了自动闭塞系统接收机模块测试的可信度。     

用于电阻类传感器校准的电子合成电阻

利用运算放大器和数模转换器等电路构成单口网络,通过编程得到输入电压及电流的比值,获得期望大小的合成电阻。这种合成电阻可以用于对电阻类传感器的测试电路或仪器的自动校准。提出了在提高电阻合成准确度、扩展桥压范围、提高极性适应能力和多通道之间的隔离等方面的解决办法,并对实验结果进行了分析,给出了实用的修正方法。     

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)

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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