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。     

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。     

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。     

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。     

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。     

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.     

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     

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.     

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.     

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.