野战有线通信系统二线全双工接口测试电路设计

野战有线通信系统全双工接口在单对线上同时收发信号,难以直接进行数据采集和测试。针对上述问题,研究了一种基于收发分离和自适应回波抵消的二线全双工接口测试方法。首先,设计电子收发分离器,实现线路上收发信号的隔离;然后,使用自适应回波抵消器,完成了近端回波干扰信号的抵消;最后,借鉴软件无线电技术和存储测试技术,构建测试系统,实现激励信号生成与数据采集。仿真和实验表明,该测试方法能够实现有效完成收发信号隔离以及回波干扰信号抵消,适用于野战有线通信系统二线全双工接口测试。     

一种基于FPGA的高速图像采集及显示电路设计

为了实现高速图像采集和显示,采用CamLink接口和DVI接口来完成视频采集和显示。详细介绍了基于FPGA采集和显示的系统组成,给出了CamLink接口采样模块和DVI显示模块的工作流程及硬件电路实现方式。该硬件电路基于CPCI总线设计,实现了计算机与图像电路之间的高速数据交换。设计中使用的FPGA是Altera公司的EP2S30F672I4,用该FPGA进行配置和验证,测试表明该设计不仅实现了图像高速采集和显示,且使图像清晰、系统稳定可靠。     

用于纳米通道单分子检测的数据采集系统的设计与实现[BT)]

针对纳米通道单分子检测系统的信号特点和对数据采集的采样精度、采样速率及实时性等要求,设计并实现了基于FPGA和USB2.0接口的数据采集系统;该系统以FPGA作为控制核心,包括数据采集模块、电压输出模块和USB接口电路模块;通过USB2.0接口与计算机连接,实现数据的实时采样和参数的在线配置;此外本系统还采取了低噪声设计;经过相关试验表明,该系统引入的噪声在1 mV内,能够稳定进行数据采集,且采集信号与电压输出信号同步传输,证明该系统能够满足纳米通道单分子检测系统对数据采集的要求.     

群路CPC收发器的硬件实现

在在对循环排列码字（CPC）的特点进行分析之后,以某通信专网的群路接口为例,介绍了一种群路CPC收发器的硬件电路设计方案,给出了CPC译码表的生成算法,着重对电路的模块划分、功能及实现方法、寄存器设计及使用方式进行了详细说明,简要分析了该电路的检测性能。该设计采用现场可编程逻辑器件（FPGA）实现,资源占用较低,具有很好的移植性,简单修改后即可用于类似接口,是一种较为通用的CPC收发电路。     

导弹电动伺服机构控制器电路设计

针对导弹电动伺服机构控制系统中无刷直流电机的三闭环控制需求,提出了一种DSP和FPGA组合设计电动伺服机构控制系统硬件设计方案,其中DSP实现复杂控制算法和实时控制程序,FPGA实现时序控制逻辑。同时还扩展了基于BU-61580总线协议芯片的1553B总线接口电路设计,以满足新型弹上总线式控制系统的接口要求。电机功率驱动电路采用智能功率模块（IPM）设计实现,位置、转速、电流信号检测分别采用绝对值编码器、旋转变压器和霍尔电流传感器设计完成。硬件调试结果表明,所设计的硬件电路工作稳定,达到了预期的设计要求。     

基于FPGA的QPSK信号干扰源设计

针对QPSK调制方式特点,设计了基于FPGA的信号干扰源,分析了系统干扰原理;利用m序列生成均匀白噪声,采用地址法完成高斯白噪声转换;以Logistic混沌映射电路作为信源,采用直接数字频率合成技术产生正弦信号作为载波,用VHDL语言设计FPGA与单片机的接口电路;在单片机控制下,用于FPGA生成干扰信号经AD9760实现数模转换;仿真和实验表明,该系统精度高,干扰参数易于控制修改,满足实际要求,并且稍加改动可生成多路同步干扰信号。     

基于FPGA的ARINC429多通道接口设计与实现

针对传统ARINC429接口集成度低、功能单一的局限性,基于FPGA技术,设计并实现了多通道的ARINC429接口电路,有效地提高了数据处理能力和集成度。在航空信号仿真平台中,完成信号的接收和处理、转换和发送,实现了通道的切换和信号的交联。     

基于FPGA的数字超声内窥镜接收系统设计

根据数字超声成像的要求和超声信号的特点,设计了由高速采样电路和FPGA正交解调电路组成的数字超声内窥镜接收系统。采样电路由AD8138和AD9235实现,对放大后的超声回波信号直接进行模数转换;FPGA利用内部RAM、乘法器、IP核和宏模块构建数字正交解调电路,提取超声回波信号的幅度;获取的幅度信息经USB2.0接口电路送入计算机显示。对玻璃杯进行的静止扫描成像实验,验证了接收系统的小信号检测能力,可以检测到信噪比约为4dB的回波信号;对玻璃杯进行的旋转扫描成像实验,表明接收系统可用于数字超声内窥镜成像。     

基于FPGA的数据采集及显示

在电力系统谐波分析中,模数转换(ADC)电路是影响系统检测性能的主要环节之一。基于NiosII的谐波分析系统具有逻辑控制能力强、信号处理实时性高、系统抗干扰能力强等特点。以Altera公司的DE2开发板为平台,实现了采样电路的硬件设计;在Quartus II中用Verilog HDL语言完成了与FPGA的接口设计,并最终实现VGA显示。     

基于FPGA的遥测系统数据存储器控制模块设计

针对当前遥感系统存储器早期控制模块存在控制效率低的问题,提出了基于FPGA的遥测系统数据存储器控制模块设计。根据模块总体设计方案,设计模块结构和功能。其中模块结构是由自体测试接口模块、低速读写控制模块、高速流读写控制模块组成的,以SATA2.0接口为存储介质设计控制器,构建不同帧,进行数据间传输转换。设计稳态触发接口电路,达到高速流读写控制触发目的。根据软件主流程,在组合逻辑中插入寄存器使逻辑延迟,实现FPGA时序控制。采用分时操作方法,对命令层中控制器读写模式进行控制,实现传输层完成帧的控制收发。由实验结果可知,该模块最高控制效率优于传统模块,为数据高效存储提供支持。     

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。     

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。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).