气体传感器阵列中特征参数的提取与优化

用一组厚膜金属氧化锡气体传感器阵列对气味进行分析和识别 ,其中最重要、最难的因素是传感器特征提取技术和特征参数的优化 ,使所用的传感器阵列能快速准确地识别不同气味。然而 ,目前尚无令人满意的方法。本文中研制了适用于传感器阵列反应的试验装置 ,在获得传感器与食醋挥发气体反应的整个过程的数据的基础上 ,提取了传感器与食醋散发的气体反应的特征值。利用分辨率来提取 ,以确定所提取的特征参数是否最优 ,从而决定该特征值在以后模式识别中是否有用。再对那些分辨率指数大的特征参数进行主成分分析和神经网络分析 ,主成分分析结果表明不同醋之间区分得比较开 ,神经网络的识别正确率达到 10 0 %。显然这一方法也可用于解决其它形式传感器阵列问题。     

食醋分类中气体传感器阵列的一种优化方法

利用13只气体传感器、1只温度传感器和1只湿度传感器构成的初始测试系统,对3种不同品种的食醋进行测试。运用小波包的三尺度分解来提取测试结果的分析特征向量,并借助主成分分析(PCA)技术,对传感器阵列进行了优化,得到由5只传感器构成的优化阵列。利用RBF神经网络,对原阵列和优化后阵列的鉴别效果进行比较,结果表明:优化后传感器阵列能将3种不同品种的食醋成功区分开,并且鉴别效果也得到明显改善。     

基于PCA与BP混合神经网络算法的电子鼻系统

为了对食物品质进行非接触式评价,基于6种费加罗金属氧化物气体传感器阵列,通过由数据采集模块和微处理器模块组成的硬件设计方案,设计并研制了可对被测食物进行实时、无损检测的电子鼻系统。在软件设计方案上,该系统采用主成分分析(PCA)和反向传播(BP)混合神经网络模式,通过LabVIEW对气体"指纹信息"数据库进行分析。实验结果表明:该设计的电子鼻系统可以很好地区分不同种类的食醋,并提供了一种对食醋品质评价的便利方法。     

基于小波特征提取的气体传感器温度调制模式研究

为了有效提取传感器对被测气体的响应特征,通过对单个微热板式气体传感器在不同温度调制模式下,对3种可燃性气体的动态响应信号结合主成分分析(PCA)和概率神经网络(PNN)进行分析和测试,利用小波变换对温度调制下传感器的动态响应信号进行小波特征提取。结果表明:提取的小波特征系数能较好地反映被测气体的信息。     

气体传感器特征参数分析

特征参数在气体传感器的描述、气体/气味分类、识别和量化中起着关键作用。对从气体传感器响应曲线中直接提取的典型客观特征的统计性能进行了分析。通过一个自动测试系统测试了一个微热板式气体传感器阵列对不同浓度的CO、CH4和NO2三种气体的响应,获得了一系列的响应曲线。从曲线中提取客观的稳态和动态特征进行分析,建立了一个有效的特征子集,并通过一个神经网络进行了验证。实验结果说明,使用该特征子集为输入参数的神经网络收敛速度快,误差性能小,验证了提取的特征子集的合理性。     

基于卟啉传感器阵列系统的肺癌标志物识别算法

卟啉传感器阵列系统可以检测肺癌呼出气体中特定的标志性气体,不同标志性气体检测输出的差值图谱不一样.介绍了一种结合反向传播(BP)神经网络和主成分分析(PCA)的肺癌标志性气体种类识别算法,并将其应用在卟啉传感器阵列系统中.通过计算卟啉传感器阵列中各点的主成分得分选出敏感点,保留各气体敏感点的值,并组成识别模板作为BP神经网络的输入层,达到去除冗余数据的目的.通过实验对比聚类分析结果、未降维数据的BP神经网络识别结果及已经PCA降维后的数据作为输入的BP神经网络识别结果,证明提出的算法可以更加精确地识别不同的肺癌标志性气体.     

基于声表面波传感器阵列的气体鉴别算法研究

声表面波(SAW)传感器阵列具有体积小、功耗低、反应灵敏等优点,在食品检测、环境治理、气体鉴别等领域有广泛的应用前景。结合声表面波传感器阵列的原理及特点,建立和优化了声表面波传感器阵列的数学模型,并对数据进行预处理、主成分分析（PCA）以及BP神经网络分析处理,实现了对气体的鉴别分类,取得了好的实验结果。     

用于食醋品质预评价的电子鼻研究

设计了面向食用醋品质预评价的电子鼻系统,它包括:由5种TGS系列和1种MQ系列半导体氧化物气体传感器构建的传感器阵列、以LPC2138微处理器为核心的采集电路等硬件部分。通过USB接口将所采集的数据上传至计算机,利用上位机LabVIEW软件进行数据采集的实时显示,并利用主成分分析(PCA)法和线性判别式分析(LDA)法对数据进行分析。使用该设计的电子鼻对生活中常见的5种食醋进行测量,并对食醋种类、配料关系进行了分析。结果表明,电子鼻技术在食醋品质预评价中是可行的。     

电子鼻技术在食醋识别中的应用

利用由10个掺杂纳米氧化锌厚膜气敏传感器组成的阵列对9种食醋和乙酸溶液进行了测量.并通过主元分析、聚类分析和概率神经网络对数据进行了分析和识别.主元分析表明不同的食醋在品牌、种类、酸度等方面具有一定的相似性.聚类分析进一步研究了食醋种类之间的相似程度.利用概率神经网络对所测试的食醋进行了识别,有较高的识别率.分析表明电子鼻技术是食醋分析和识别的一种具有发展前途的实用技术.     

主成分分析与神经网络结合的黄山毛峰茶品质检测

研究了利用主成分分析与BP神经网络结合的方法对黄山毛峰茶进行品质检测。首先应用主成分分析法对反映茶叶香气信息的原始特征变量进行分析,提取出前5个主成分,再以这些主成分作为BP神经网络的输入,建立3层BP神经网络预测模型。试验结果表明,该模型相对于未经过主成分分析的BP神经网络模型,建模效率大大提高,判别准确率也由92.5%提高到97.5%。说明主成分分析与BP神经网络结合应用于黄山毛峰茶品质检测是有效的。     

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).