微机械电容式加速度计检测电路设计

通过对MEMS电容式加速度计的差分电容检测电路优缺点的比较,结合直流充放电检测方法和交流测量方法的优点,设计了微分检测电路,用方波作为载波。该电路由方波信号发生器、微分电路、全波整流电路和滤波电路组成。经试验验证:可检测到10-16F的差分电容,且其非线性度小于±1%FS,可作为MEMS电容式加速度计的后续处理电路。     

基于Verilog-A的电容式MEMS加速度计模型

本文分析了传统MEMS电容式加速度计模型的不足,根据三明治结构电容式加速度计的特点,考虑了寄生电容和热机械噪声的影响,建立了用Verilog-A硬件描述语言实现的模型。该模型与主流集成电路设计环境相兼容,具有很强的可移植性。模拟验证结果表明,该模型如实反映了MEMS电容式加速度计的工作状态,能够为设计单片集成的微弱电容检测电路提供有效的帮助。     

厚膜混合集成电容式加速度计

设计了电容式加速度计的信号检测电路,与电容式加速度计敏感单元进行联调和测试,并进行了标定。为减小体积,提高电容式加速度计的检测精度,采用厚膜混合集成工艺,将检测电路和电容式加速度计敏感单元集成于一体,并进行了电路测试和性能测试。测试数据表明,其测试精度提高了一个数量级,线性度和温度特性均有很大的改善。     

微机械电容式加速度传感器测试电路研究

在测量硅微电容式加速度传感器时,由于器件信号的微弱和寄生电容的干扰,提高加速度的稳定性和分辨率非常困难.针对这种情况,作者分析对比开关性和调制解调型两种常见微弱电容检测方法优缺点,并提出了一种微电容检测的改进电路,用此电路对电容式加速度传感器进行了测试.数据表明,微加速度计灵敏度为1.63 V/gn,可以检测到10-17F量级的电容值.     

非硅MEMS电容式微加速度计的测控电路设计

为了提高MEMS微加速度计的量程和抗过载能力,设计了基于UV-LIGA技术的非硅MEMS电容式微加速度计。针对该加速度计,设计了基于相敏解调的差分电容测控电路。检测通道主要由前置级电荷积分放大电路、带通滤波电路、相敏解调器、低通滤波以及电平转换电路组成,反馈通道由低通滤波和加法电路组成。完成了微加速度计测控电路的调试和检测通道的标定实验,实验表明:检测通道的量程约为±6 pF,灵敏度为89.3 mV/pF,线性度为2.59%,满足加速度计检测通道的要求。     

基于电容桥的差动电容检测方法

数字闭环石英挠性加速度计系统主要由石英挠性加速度计表头和数字检测电路组成,其极限精度取决于差动电容检测电路的灵敏度。针对数字闭环石英挠性加速度计前端差动电容检测的需求,给出了一种基于电容桥的差动电容检测方法。利用数字电路产生高频方波进行单载波调制,同时利用交流电容桥结构对载波信号进行处理,并设计后续的差分放大电路对载波信号进一步处理最终实现对微弱差动电容变化的检测。经过实验验证,检测电路对电容的检测最终实现最小分辨率约为1. 8 f F(对应加速度变化1μgn)。     

一种用于MEMS陀螺的高精度电容读出电路的设计

针对电容式MEMS陀螺,设计了一种高精度CMOS接口读出电路。从理论上分析了接口寄生电容、器件的不匹配对接口电路的影响,采用连续时间电压读出方式的检测方法,设计了一款带有输入输出共模反馈的低噪声全差分电荷运算放大器,输入输出共模电压稳定在2.5V,输入端的噪声电压为9nV。载波调制技术用来消除低频闪烁噪声。在Cadence中对设计的接口电路进行仿真分析,并采用PCB电路板进行了实验。结果显示所提出的接口电路不仅消除了大部分寄生电容的影响,抑制了大部分的耦合信号和噪声信号,而且减小了由于器件的不匹配产生的失调电压对电容分辨率的影响,电路Cadence仿真的电容分辨率可达0.13aF/(Hz)~1/2,能满足惯导级的需求。     

电容式加速度计的数字化处理电路及其与模拟电路的比较

介绍了对一种电容式MEMS加速度计处理电路的数字化工作,并对数字式加速度计系统的各个组成模块进行了分析,并与模拟处理电路的相应模块进行比较,给出了制约数字和模拟加速度计性能的因素.实验测试结果表明,数字式加速度计的零偏稳定性达到了0.21 mgn,相对模拟加速度计的零偏稳定性(1.02 mgn)提高了约5倍,噪声降低了3/5,数字式加速度计系统的性能有了很大的改进.这是由于数字系统采用了先进的解调算法,使得载波的信噪比有所提高,相位噪声有所降低.     

基于低温共烧陶瓷的微机械差分电容式加速度计的研究

低温共烧陶瓷（LTCC）技术是实现电子设备小型化、高密度集成化的主流封装/组装集成技术,可适用于耐高温、耐受恶劣环境下的特性要求。报道了以LTCC为结构材料设计、制作的一种MEMS差分电容式加速度计。该器件的敏感质量、4根悬臂梁结构都内嵌于LTCC多层基板,质量块和上下盖板之间通过印刷电极组成差分电容对;高精度电容检测芯片表贴于LTCC基板表面,将差分电容信号转化为电压信号。论文讨论了微机械LTCC加速度计的设计与制备、检测电路和性能测试。LTCC的高密度多层布线减小了互连线的长度和相关耦合寄生电容;基于集成芯片的检测电路解决了分立式检测电路的引起噪声大、电路复杂等问题。测试结果表明：该加速度计结构灵敏度较高,小载荷情况下表现出良好的线性关系,灵敏度约为30.3 mV/gn。     

中国微米纳米-基于低温共烧陶瓷的微机械差分电容式加速度计的研究

低温共烧陶瓷（LTCC）技术是实现电子设备小型化、高密度集成化的主流封装/组装集成技术,可适用于耐高温、耐受恶劣环境下的特性要求。本文报道了以LTCC为结构材料设计、制作的一种MEMS差分电容式加速度计。该器件的敏感质量、四根悬臂梁结构都内嵌于LTCC多层基板,质量块和上下盖板之间通过印刷电极组成差分电容对;高精度电容检测芯片表贴于LTCC基板表面,将差分电容信号转化为电压信号。论文讨论了微机械LTCC加速度计的设计与制备、检测电路和性能测试。LTCC的高密度多层布线减小了互连线的长度和相关耦合寄生电容;基于集成芯片的检测电路解决了分立式检测电路的引起噪声大、电路复杂等问题。测试结果表明：该加速度计结构灵敏度较高,小载荷情况下表现出良好的线性关系,灵敏度约为30.3mV/g。     

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).