催化燃烧型甲烷传感器的研究

在分析传统催化燃烧型甲烷传感器的基础上,实验验证了催化燃烧原理,并设计了基于脉冲式恒温供电技术和闭环反馈系统的恒温检测桥路。通过实验得到了良好的效果。     

催化燃烧型甲烷传感器恒温检测桥路的研究

催化燃烧型甲烷传感器的激活是传感器使用的关键问题。文章验证了催化燃烧原理,并分析了甲烷传感器的二值性问题。针对激活和二值性问题,设计了基于脉冲式恒温供电技术和闭环反馈系统的恒温检测桥路。通过实验取得了良好的效果。     

瓦斯探测器零点校正技术的研究

针对目前广泛使用的瓦斯探测器漂移大、成本高、维护周期短等问题,提出了基于恒温控制电路的瓦斯探测器的定时自动零点校正方法。该方法以催化燃烧式气体传感器为对象,采用恒温控制电路为传感器供电,以零点漂移的理论分析和大量实验研究工作为依据,解决了该类探测器长期未能解决的零点稳定性问题。采用模拟电子开关配合电阻网络实现数字电位器设计,节约了成本。实验结果表明:采用恒温控制电路的零点校正后的残留偏差比未经校正的输出值减少了近1个数量级,为设计具有自动定时调零功能的瓦斯探测器提供了技术支持。     

催化燃烧式LNG传感器自校准技术的研究

为了提高催化燃烧式LNG传感器的测量精度和传感器工作寿命与稳定性,研发了新型的恒温检测电路,并在此基础之上进行了零点漂移和灵敏度自动校准技术的理论分析和实验研究。实验数据表明：该技术有效地解决了该类传感器长期存在的零点漂移与灵敏度下降的问题,为设计具有自动校准功能的可燃气体变送器提供了依据。     

基于LightGBM-Stacking模型融合的多传感器甲烷检测系统

利用多传感器检测技术结合集成学习方法，设计了一种基于LightGBM-Stacking模型融合的多传感器甲烷检测系统，其中分别使用恒压供电式催化燃烧型传感器、两路脉冲供电式催化燃烧型传感器和热传导型传感器相结合的方式达到全范围检测的目的。实验结果表明，相比使用单一算法模型，本文所提出的LightGBM-Stacking集成模型在甲烷预测的准确率、均方根误差及决定系数等指标上均有更好的表现。     

恒温瓦斯检测模型动态分析及控制

恒温检测是通过控制检测元件中的电流达到控制元件工作温度的目的.检测电流会随着温度的波动而波动,普通恒温检测电路通过闭环控制需要经过很长时间才能达到稳定.为解决长时间振荡问题,在恒温瓦斯检测原理及载体催化元件性能分析的基础上,建立了恒温瓦斯检测的数学模型并设计出一种PID控制器.其控制效果明显好于闭环控制.仿真及实验结果表明,带PID控制器的恒温瓦斯检测系统只需3 s便能检测出瓦斯浓度,其稳定性和快速性明显优于一般恒温瓦斯检测系统.     

基于RBF神经网络的单一催化传感器检测混合气体研究

根据催化传感器在不同的工作温度下具有不同气体检测灵敏度的特点,提出基于恒温检测与RBF神经网络的单一热催化传感器检测可燃混合气体的新方法.采用动态学习算法的RBF神经网络建立了多种可燃气体分析的数学模型.通过对甲烷,一氧化碳和氢气三种气体混合的样本进行实验,结果表明所研究的方法可以较好地实现单一催化传感器对多种可燃混合气体的分析.     

恒温检测方法在检测混合气体中的应用

根据催化燃烧气体传感器的敏感机理,讨论了催化燃烧气体传感器检测电桥在恒压源供电情况下的输出与补偿元件和敏感元件电阻变化之间的关系;应用补偿元件和敏感元件的电阻与其工作温度变化的关系及热平衡方程,推导出了催化燃烧气体传感器输出与被测气体浓度之间的关系,且得出催化燃烧气体传感器的输出是线性的;提出了采用n个催化燃烧气体传感器分别工作在不同温度下,根据每个传感器的输出计算出由n种气体组成的混合气体中的各组分浓度的方法。试验结果表明,应用该方法检测混合气体各组分浓度时,最大检测相对误差小于10%,且相对误差与浓度没有严格的依赖关系。     

催化燃烧式瓦斯传感器技术研究进展

首先分析了催化燃烧式瓦斯传感器的工作原理,然后综述了催化燃烧式瓦斯传感器的标定与补偿技术现状,最后指出,综合考虑催化燃烧式瓦斯传感器的稳定性和一致性,探索研究在初始不一致和工作过程不稳定的双重作用下,传感器数据的变化规律,通过智能信息处理的方法予以动态补偿,将是下一步需要研究的主要方向。     

催化燃烧式瓦斯传感器技术研究进展

首先分析了催化燃烧式瓦斯传感器的工作原理,然后综述了催化燃烧式瓦斯传感器的标定与补偿技术现状,最后指出,综合考虑催化燃烧式瓦斯传感器的稳定性和一致性,探索研究在初始不一致和工作过程不稳定的双重作用下,传感器数据的变化规律,通过智能信息处理的方法予以动态补偿,将是下一步需要研究的主要方向。     

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).