光纤传感器研究

光纤传感器具有抗电磁干扰、耐事故能力强、小型化、精度高等优点。为促进光纤传感器在更多行业的应用,对光纤传感器的研究进展进行了总结。介绍了光纤传感器的基本组成和原理,概括了光纤传感器分类特征。按光纤在传感器中的作用,可分为功能型(全光纤型)光纤传感器、传光型光纤传感器和拾光型光纤传感器。按光波调制方式,可分为强度调制型光纤传感器、频率调制型光纤传感器、波长调制型光纤传感器、相位调制型光纤传感器以及偏振态调制型光纤传感器。按传感器目标分布方式,可分为点式光纤传感器、准分布式光纤传感器和分布式光纤传感器。阐述了光纤传感器在温度、位移和气体测量方面的应用现状,并讨论了未来光纤传感器的发展趋示。     

光谱吸收型光纤气体传感器的研究

研究和讨论了一种易于实现的光谱吸收型光纤气体传感器.采用LED作为光源,利用可调谐法布里-珀罗腔的选频特性进行检波,并采用谐波检测,显著提高了检测的灵敏度.同时,采用多光路设计和软件控制相结合,可在线检测多种气体,克服了以往气体传感器只能检测一种气体的缺点,大大增加了该传感器的适用性.     

光纤瓦斯传感器在煤矿瓦斯气体监测中的应用

把传感器更好地应用在工农业生产和日常生活中的安防领域是避免造成大财产损失和人员伤亡的必要条件.鉴于此,本文简述了光纤瓦斯气体传感器的基本工作原理,通过光纤瓦斯传感器和Kj系列井下监测分站配合使用监测煤矿瓦斯气体的实例对光纤瓦斯传感器的先进性和可靠性进行了论证.Kj系列井下监测分站和光纤瓦斯传感器一起连续监测矿井下的瓦斯气体浓度,和系统中的地面中心站进行通讯完成监测、警报和控制功能,监测数据的准确度大于1.5级,满足安防场所对测量的准确度要求.     

光纤气体传感器研究进展

光纤气体传感器较传统气体传感器有诸多优点,特别是在恶劣环境检测等方面.它越来越引起人们的广泛关注,并得到了深入的研究和广泛的实用化.本文对新兴出现的几种常见的光纤气体传感器类型的原理和现状以及发展的方向进行了论述.     

光纤气体传感器及其组网技术综述

综述了光纤气体传感器及其组网方式,分别介绍了波分复用、频分复用、空分复用以及码分复用的技术,并分析了各种方法的优缺点,最后讨论了光纤气体传感器的发展方向.     

检测NO 气体的双臂式光纤束传感系统的研究

本文建立了一检测有害气体的双臂式光纤束传感器系统 ,确定了传感器探头内光纤束端面上单根光纤的最佳排列方式 .对 NO气体的特性进行了研究 ,在不同浓度下 ,得到了 NO气体对光的吸收谱和某一波长下 NO气体吸收率随气体浓度、光程的变化特性 .实验结果表明在一定条件下 NO气体浓度与吸收百分比成线性关系 .该系统的响应时间仅为 5 s,恢复时间在 10 s之内     

高分子膜及其在光纤气体传感器中的应用

高分子膜具有制备简单、性能稳定以及与指示剂相容性好等特点,是光纤气体传感器中固定指示剂的优良基质材料。简单介绍了用于光纤气体传感器的高分子膜的特点、制备方法及其性能影响因素,综述了近年来基于高分子膜的光纤气体传感器的研究进展。     

新型光纤化学瓦斯传感器的研究

利用超分子化合物穴番A对瓦斯气体的吸附作用将引起光纤包层折射率发生相应改变,结合模式滤光检测技术,提出了一种新的瓦斯传感器检测方法.分析了这种光纤化学瓦斯传感器的工作原理、组成结构及光纤的涂层方法.针对传感系统进行瓦斯监测实验表明:这种传感器能实时准确地检测出甲烷气体体积分数,是一种简便,快速,灵敏的瓦斯检测办法.     

基于分布反馈式半导体激光器的光纤甲烷传感器

简介了一种基于分布反馈式半导体激光器(DFBLD)的光纤甲烷气体传感器,在甲烷气体光谱吸收的基础上,利用差分吸收技术,实现瓦斯浓度在线检测.还介绍了DFBLD工作原理,给出了初步的实验性设想.对此光纤甲烷气体传感器只要稍加改进或换上其它附件,即可测量其它多种气体的浓度,在气体浓度测量领域,具有很好的应用前景.     

光纤气体传感器的研究

介绍了一种强度调制型光纤气体传感器，它采用光通信用多模光纤，利用ＩＣ工艺中的光刻和化学腐蚀等技术，在硅片上出传感器的整体结构，这种传感器的结构简单，测量方便，重复性好，成本低，有深入研究的价值。     

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).