基于K均值聚类的随机网络拓扑模型

路由算法仿真通常采用Waxman随机网络拓扑模型,但其生成的网络拓扑图存在网络节点疏密不当、度数难以控制、难以生成连通图等问题.针对以上不足加以完善,提出了一种基于K均值聚类的随机网络拓扑模型KRTG.其仿真实验的结果表明,使用该模型避免了出现两个节点间距离过近的情况,节点分布均匀且疏密得当,边的分布也比较均衡,能生成节点度数适当的连通图,为QoS组播路由算法的仿真工作打下了基础.     

ZigBee网络拓扑可视化再现算法研究

基于Zig Bee的网络拓扑结构在网络性能分析、网络节点部署、节点压力测试、安全监控等方面起着重要作用。但是在拓扑结构可视化时,由于网络拓扑图可视化模型会出现点覆盖、边交叉和图形拥塞,导致算法复杂度高、耗时陡增,影响可视化效果。为了解决以上问题,并满足实时在线显示需求,提出了一种基于坐标变换-虚拟节点模型的Zig Bee Tree-Star型网络拓扑结构可视化再现算法。该算法能够自适应节点变化。在节点数量较少时,层次算法模型对节点进行布局规划;当节点数量较多时,虚拟节点模型对布局进行扩展延伸。该算法对Zig Bee网络管理具有较高的参考价值。试验表明,该算法所需时间复杂度与空间复杂度低,可解决大量边交叉导致的布局混乱问题,并能适应Zig Bee网络大规模节点的实时可视化需求。     

继电控制线路的网络拓扑图的生成与再次抽取

继电控制线路原理图可以抽象为网络拓朴图。该文介绍了一种由继电控制线路原理图的几何图形生成网络拓扑图的算法,并且根据对继电控制线路分析的需要,去除了原拓扑图中的无效边和无效节点,对原拓扑图进行了再次抽取,使得整个拓扑图的结构大为简化,这样就可以大大提高时拓扑图进行分析和运算的速度,该文的结果在继电控制线路的计算机辅助设计与分析中有重要意义。     

基于斥力-张力模型的网络拓扑图布局算法

针对网络管理系统中网络拓扑图的自动布局问题，提出了一种新的算法。赋予拓扑图的顶点和边不同的物理性质(质量、张力、斥力等)，各个顶点在力的相互作用下不断运动，直至最终达到力的平衡，同时完成了拓扑图的自动布局。     

基于WSN的拓扑图自动布局方法优化与实现

无线传感器网络(WSN,wireless sensornetwork)拓扑结构的良好布局对其网络管理具有重要意义。为此,优化并实现了一种基于扩展力学模型的WSN拓扑布局方法。首先,完善了基于力学模型拓扑布局方法中的平衡检测算法,实现对WSN拓扑结构图的平衡检测;其次,加入碰撞检测算法,保证拓扑结构图中的节点处于画布有效范围内;最后,引入拓扑图居中算法优化整体布局效果。通过仿真实验以及真实WSN环境下测试证明,优化后的拓扑布局算法适用于WSN,尤其是对中小规模WSN拓扑布局效果最佳。     

一种新的因特网拓扑的序列分析方法:dM序列分析方法

网络拓扑研究的一项重要内容是分析网络拓扑的特征并生成满足这些特征的拓扑图。拓扑图特征的dK序列分析技术是一种系统化的拓扑分析技术,它能够以不同的精度描述拓扑图的特征,随着d的增加,其生成的拓扑图能够在各种重要的拓扑度量方面越来越接近原始拓扑图,因而对因特网拓扑研究具有重要意义。dK序列分析技术的问题在于状态数较多,生成算法复杂,当d>2时没有直接的生成算法。本文提出了一种新的基于邻接图分布的拓扑图特征的序列分析技术:dM序列分析技术。与dK序列分析技术相比,dM序列分析技术具有状态数少、生成算法简单的优势,因此更适合于大规模拓扑图如因特网AS拓扑的研究。     

基于粗糙图的图卷积神经网络算法

图卷积神经网络在解决节点分类问题时,使用拓扑图刻画节点间关系,并根据该拓扑图进行节点特征更新.然而,传统的拓扑图只能刻画节点之间的确定关系(即连接边权重为固定值),忽略真实世界中广泛存在的不确定性.这些不确定性不仅影响节点之间的关系,同时影响模型最终的分类性能.为了克服该缺陷,文中提出基于粗糙图的图卷积神经网络算法.首先,使用上下近似理论和传统拓扑图的边理论构造粗糙边,在粗糙边中使用成对出现的最大-最小关系值刻画节点之间的不确定关系,从而构建粗糙图.然后,设计基于粗糙图的可端到端训练的神经网络架构,将使用粗糙权重系数训练后的粗糙图输入图卷积神经网络,使用这些不确定信息更新节点特征.最后,根据这些学习的节点特征进行节点分类.在真实数据上的实验表明,文中算法可提高节点分类的准确率.     

基于三角构成规则的加权有向网络拓扑生成算法

针对加权无向图的网络拓扑模型难以表征真实网络环境下节点间有向性的问题,提出了基于三角构成规则的加权有向网络拓扑生成算法,依据概率优先选择节点的邻居节点进行有向性加边,通过网络边权的动态演化实现节点间的不对称性增长。并利用该算法进行了仿真实验。实验表明,基于三角构成的加权有向网络拓扑算法生成的网络拓扑结构符合真实环境下的网络拓扑结构所体现出来的拓扑特性,同时具有较好的聚类系数可控性。     

一种园区级网络拓扑图布局算法

以SeeLink NMS网管系统的研发工作为基础,通过分析几种常见的网络拓扑图布局算法,针对园区级网络的特点,综合分而制之思想与环型布局思想,改进设计出一种适合园区级网络的拓扑图布局算法,并在SeeLink NMS中得以实现。     

绘制动态图的IGP模型

针对可视化领域中动态图的绘制问题,提出一种新颖的可视化模型来绘制动态图.首先采用多层次方法生成初始静态图并对所有节点进行初始分区;当下一时刻的图数据来临后,先对新增节点使用重心合并排序算法的变体以确保其具有良好的初始位置,在此过程中,当有额外的附加边添加时,通过附加边长度调整算法重新调整附加边的大小以保证图的美观性;再引入"等级"的概念以提高图结构的稳定性,等级越高的节点越难以移动;最后对有变化的节点进行重新分区以简化力导向算法的排斥力计算,同时通过简化后的力导向算法优化布局.采用平均位移和总能量作为评价布局标准,用文中模型和力导向算法、节点牵制算法在Sync和Newcomb数据集上进行实验的结果表明,该模型具有较高的性能,可获得良好的布局效果.     

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).