基于FPGA的10G以太网并行CRC设计

为了解决10G以太网通信链路中大规模数据并行CRC校验的实时处理问题,提出了一种基于级联结构的并行CRC校验方法。通过传统CRC编码结构推导出任意延拓序列的CRC校验方法,设计了针对任意延拓序列的CRC校验模块。在校验算法实现中针对传统异或逻辑进行了并行电路改进,降低了电路处理时延。搭建了实验环境对所设计模块进行了验证,实验结果表明,该方法可以有效满足10G以太网接入系统CRC校验要求。     

Modbus通信协议中CRC校验的快速C语言算法

本文主要讨论了Modbus通信协议的RTU帧格式中常用的错误校验方法,即循环冗余校验法(CRC)。提出了Modbus协议反转CRC校验的方法,推导了反转CRC校验快速计算表格,并用C语言实现了基于快速查表算法的循环冗余校验程序。     

CRC算法在计算机网络通信中的应用

在计算机网络通信中,为了降低数据通信线路传输的误码率,可以采用一种差错检测控制--循环冗余码校验(CRC).介绍了CRC算法的原理、CRC算法的校验规则、CRC算法分析、CRC算法程序设计.由于CRC算法采用软件校验的方法,不需要设计另外的硬件电路,校验速度非常快,提高了计算机网络通信的速度和报文传输的准确性.     

10G以太网接口并行CRC校验的一种简化算法

在10G以太网接口设计中,64位并行数据的CRC校验是其设计难点之一,常见的一些方法在对其进行CRC32校验时,会因为以太网帧不一定结束在64比特边界,导致进行校验处理时需要同时包含8,16,24,32,40,48,56,64位的校验单元。本文提出了一种只需64位的校验单元即可实现其CRC校验的方法。     

CRC校验的C语言实现

本文对CRC校验原理作了简单介绍,并介绍通过查表法实现CRC校验的方法,并给出了实现查表法的C函数和部分CRC的余式表.     

CRC算法在计算机网络通信中的应用

在计算机网络通信中，为了降低数据通信线路传输的误码率，可以采用一种差错检测控制——循环冗余码校验（CRC）。介绍了CRC算法的原理、CRC算法的校验规则、CRC算法分析、CRC算法程序设计。由于CRC算法采用软件校验的方法，不需要设计另外的硬件电路，校验速度非常快，提高了计算机网络通信的速度和报文传输的准确性。     

字节型CRC算法分析与实现

循环冗余码校验CRC是计算机网络通信中最常采用的数据校验方法之一,CRC方法能够很好地降低数据传输的误码率。本文分析了CRC算法的原理和CRC算法的校验规则,针对字节型CRC算法,提出一种直观、紧凑、易于理解的表驱动字节型算法描述,给出了严格的数学证明,通过实例详细演绎了算法的实现过程。同时,设计了相关的类汇编语言CRC-ITU算法,简要讨论了使用F(x)/G(x)的直接余式作为监督码的方法。     

一种用于UHF RFID系统循环冗余校验的新算法

基于ISO18000—6C协议标准的UHFRFID系统中的读写器和标签之间的通信,采用CRC5和CRC16循环冗余校验。目前UHFRFID系统中,收发数据的循环冗余校验都采用按位校验法,本文根据已有的循环冗余查表校验法,提出一种适用于ISO18000—6C协议标准的新型循环冗余校验算法,极大地提高了循环冗余校验效率,非常适合用于嵌入式实时系统通信。实验结果表明,该算法将CRC5校验的效率提高了17％,将CRC16校验的效率提高了27％以上。     

快速CRC校验及其实现

在数据信息传输中,检错能力最佳要算循环冗余校验码(简称CRC校验)。但CRC校验最突出的问题是校验时间长,从而影响数据信息的传输速度。本文介绍的快速CRC校验法,比现有一般的CRC校验提高速度7～8倍。     

CRC校验在USB控制器设计中的实现

USB协议提供了强大的错误处理功能,其中包括对传送数据进行CRC校验。发送器在位填充前产生CRC,接收器在位填充去除后对CRC进行译码。如果CRC译码失败,忽略该包。本文首先分析USB中CRC校验的数学原理,然后给出硬件设计方案,包括串行CRC设计和并行CRC设计。     

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).