Linux抢占式内核的研究与实现

随着Linux操作系统的成功应用,尤其是在嵌入式实时应用领域,Linux实时性能的提高成为一个很重要的因素.系统核心的可抢占性是决定系统实时性能的一个重要条件,而Linux的核心是不可抢占的,通过将Linux的内核改造为可抢占式内核,可缩短系统的响应延时,提高Linux的实时性.分析了几种实现抢占式内核的方法,介绍了一种实现Linux可抢占式内核的方法,并对其实现细节进行了详细的说明.     

Linux 2.6内核进程调度分析

Linux操作系统是一种支持多任务、多用户和多处理器的现代通用操作系统。2.6内核的Linux支持O(1)级进程调度算法,支持可抢占内核,相比于2.4内核具有更好的实时性能。文中基于Linux 2.6.10内核源代码,分析了Linux 2.6内核的进程调度系统。并在详细介绍关键数据结构的基础上,阐述了进程调度算法的原理,并对实时进程的支持作了分析。     

基于LTP的Linux内核测试方法研究

内核作为Linux最关键的部分,其稳定性决定了系统的稳定性.Linux版本升级频繁,应用范围不断扩大,功能不断增强,但层出不穷的补丁程序为内核引入了诸多问题.因此,做好充分的内核测试是确保内核稳定的火键.LinuxTest Project(简称LTP)为测试内核开发了一套测试集,通过自动化测试方法对内核进行有针对性的压力测试,从而验证内核的稳定性、可靠性和健壮性.     

基于软盘的Linux

基于软盘的Linux是嵌入式Linux的基础,要使一张软盘能够完成基本硬件的初始化并进入到和DOS相似的提示符界面,就需要在这张软盘中包含Linux系统启动的内核和基本的根(root)文件系统,本文介绍了在Linux系统下(redhat 6.x或S.U.S.E Linux)下制做Linux软盘的步骤。     

基于MPC8248的嵌入式Linux系统的研究与实现

首先介绍了嵌入式PowerPC处理器MPC8248的主要特征和嵌入式Linux系统.借助于Embedded Planet公司提供的一套BSP(board support package)开发套件着重阐述了如何开发嵌入式Linux系统,主要包括主机/目标系统配置、交叉编译和调试环境的建立、PPCBoot的修改、Linux内核的裁减与移植以及文件系统的制作,并且实现了实时Linux扩展--RTAI.Linux系统对于PowerPC处理器具有良好的支持性能.基于MPC8248的嵌入式Linux系统提供了一个小体积、低功耗、接口丰富的开发平台,为变电站通信网络和系统的开发打下了一个坚实的基础.     

面向数控设备的嵌入式操作系统NC-Linux

文章以电火花(EDM)数控设备为例，分析了基于Linux平台的数控嵌入(式)系统软件结构，提出了数控嵌入(式)操作系统的一种设计方案。该系统以PC机为硬件平台，数控嵌入式操作系统中同时存在Linux内核和NC核两个内核。NC核完成数控设备的实时控制功能，并可以抢占Linux内核和Linux进程的处理机时间，Linux内核和Linux进程仅在NC核放弃处理机时运行，从而实现了对EDM数控设备的强实时控制；同时，运行在用户态的外围数控软件可以获得所有Linux系统的支持。     

Linux目标代码内核补丁的机理和应用

该文介绍了基于目标代码(二进制编译文件)为Linux运行时系统内核内存映像打补丁以修改内核的原理和方法,并给出了一个示例场景和程序以说明其应用。掌握该方法对于内核开发、系统调试和系统安全都具有重要的实用价值。     

RTLinux对Linux关中断的解决方案

Linux操作系统启用禁止中断的原因有两个:1)操作系统为了保护重要的系统程序代码暂停接受中断;2)Linux内核的进程经常关闭中断以尽快完成自己的任务.在这两种情况下,都可能导致高优先级实时进程的中断发生系统也无法响应中断,从而使得系统实时性能降低.双内核解决方案能够有效地解决Linux内核的关中断问题.它在Linux内核之下插入一个实时子内核,使Linux工作在实时内核的控制下,让实时子内核处理实时任务而Linux内核处理普通任务.     

Linux内核进程调度算法的分析、研究与改进

本文分析了Linux2.4内核的主要数据结构、进程调度原理及O(n)算法。针对Linux2.4设计缺陷和调度算法上的不足之处,本文改进了Linux2.4内核调算法,修改了内核中和调度有关的数据结构,并将Linux2.4内核调度算法的时间复杂度从O(n)级改进到O(1)级。最后通过实验测试得到的数据证明了改进后的内核进程调度使系统负载更加均衡。     

Linux系统启动盘制作关键技术的探讨

本文通过对一种Linux系统启动盘制作方法的介绍,详细地论述了在制作Linux系统启动盘时,Linux文件系统的创建、内核的选择及系统整合技术.     

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).