二维条码技术及其在电子邮票中的应用

PDF417二维条码具有信息容量大、保密性好、纠错能力强等优点,特别适合于电子商务中物流配送对电子邮票的需求。文章在分析电子邮票的需求和二维条码的特点基础上,建立了基于PDF417二维条码技术的电子邮票服务系统。     

彩色三维PDF417条码的设计

在所有类型的二维条码中,二维PDF417条码的应用范围最广,但随着经济的快速发展,条码应用范围的进一步扩大,二维PDF417条码承载信息的能力已不能满足人们的要求,因此本文以三维条码理论为基础,设计彩色三维PDF417条码,并研究了三维PDF417条码识别。     

基于SPIHT图像压缩算法的PDF417二维条码研究

介绍PDF417二维条码的基本概念和编码方法,针对PDF417条码存储空间有限的问题,提出将SPIHT图像压缩算法结合PDF417条码技术,将人脸图像编码到二维条码中。研究表明,通过此方法可以有效地保证在指定字节数情况下达到高质量的压缩图像,应用到证书中可以解决证书的防伪保密问题。     

针式打印机PDF417二维码的设计与实现

本文介绍了PDF417二维条码的特点和编码原理,针对汉字编码特性,采用高效的拆分迭代编码算法来实现压缩,完成了在针式打印机系统直接生成二维码打印的设计和实现.经验证,可以准确无误地实现PDF417二维条码的编码和打印.     

税务申报的全新方式--二维条码PDF417在税务申报中的应用

二维条码PDF417是二十世纪九十年代初由美国Symbol公司发明的,它是一种机器可以识读的条码,由于具备普通一维条码无法比拟的优越性,因此它一经问世,就受到了广大用户的青睐.我国1997年12月正式颁布二维条码国家标准<四一七条码>,它标志着PDF417条码在我国的应用步入正规有序的发展阶段.     

基于LabVIEW的二维条码识别

PDF417型二维条码是一种多层、可变长度、具有高容量和纠错能力的二维条码,但由于图像的采集过程中容易受到各种噪声干扰,使得条码的识别率不高。本文利用LabVIEW虚拟仪器软件平台提供的IMAQ Vision模块,通过实验分析比较各种滤波及边缘检测的方法,提出一套完整的针对PDF417型二维条码的识别方法。结果表明,该方法能有效的滤除噪声,检测完整的边缘,提高检测精度。     

基于Reed-Solomon算法的PDF417码纠错研究

PDF417二维条码采用Reed-Solomon码作为纠错码，很好地解决了因条码破损和污染造成的识读问题。在介绍PDF417二维条码和RS纠错码的基础上，详细阐述了RS码的译码原理，包括伴随式的计算、错误位置多项式的计算、错误位置的确定和错误值的计算等。最后分析了RS码译码的算法复杂性。     

基于PDF417条码的信息隐藏方法

信息隐藏技术是信息安全研究领域最新热点之一,PDF417条码是中应用十分广泛的二维条码之一,将信息隐藏技术与二维条码技术相结合就产生了基于二维条码的信息隐藏技术.现有技术目前存在着信息嵌入算法复杂和隐藏信息量较小等问题.根据PDF417二维条码自身结构特点,对其组成条空进行适量的微调,将信息隐藏进条码当中.理论分析和实验结果表明该方法可以有效抵御打印扫描攻击,具有嵌入算法简单、安全性好、鲁棒性高、信息隐藏量大等优点.     

PDF417二维条码肖像图片压缩编码的优化算法研究

针对PDF417二维条码存储空间有限的问题，提出了一种基于小波变换的有损图像压缩算法，通过这个算法，可以将静态图片信息加入PDF417条码中，并能够满足在指定字节数情况下保证高质量地压缩图像，该文在分析小波变换等算法理论的基础上，详细介绍了PDF417二维条码肖像图片压缩编码的优化算法及该算法的实验结果与美国Symbol公司的PC2VQ算法结果对比。     

基于PDF417条码结构变换的信息隐藏方法

描述了一种在PDF417二维条码这种特殊二值图像中嵌入隐藏信息的新算法,该方法结合人的视觉特性,根据PDF417二维条码自身的特殊结构,在条码容许误差范围内通过改变视觉不易察觉部分的像素值,来实现条码图像的信息嵌入。在算法实现复杂度,嵌入信息容量,抗攻击特性三个方面进行深入分析,通过实验验证,将已转换为比特流的隐藏信息嵌入到条码图像,证明了该算法的可行性、正确性。     

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).