一种交换式以太网拓扑结构的发现算法

首先介绍了目前局域网拓扑发现的主要方法及存在的问题,然后提出一个基于生成树协议 地址转发表的交换式以太网物理拓扑结构的自动发现算法.算法首先利用生成树协议建立起交换机之间的连接关系,在此基础上进一步利用地址转发表建立起交换机与主机的连接关系.该算法 1)能给发现被生成树协议阻塞的连接;2)通过处理连接冲突,能够准确无误的发现网络物理拓扑结构;3)算法开销小,时间复杂度低.文中算法已成功地应用于社区宽带综合业务网络管理系统(CBISNMS)中.     

基于动态优化因子的Zigbee协议优化仿真算法

研究Zigbee无线网络协议的优化.当前的无线传感网络中以Zigbee协议为基础,传递过程存在很大的盲目性,节点分布存在较大的随机性.目前协议中,节点最优评估通信方法大多针对静态无权网络拓扑结构,一旦随机性增大,网络拓扑结构发生松动,造成非最优节点参与通信,引起协议效率低下.为了避免上述缺陷,提出了一种基于动态优化因子的Zigbee协议优化仿真算法.应用动态优化因子方法,对网络节点进行搜索,为网络协议优化提供准确的数据基础.利用簇树拓扑方法,为网络节点分配地址,从而实现Zigbee协议优化.实验结果表明,应用改进算法进行Zigbee协议优化处理,能够提高网络服务效率.     

引入证据后的贝叶斯网络信息传递方法

连接树算法是贝叶斯网络的一种应用广泛并有效的精确推理算法。在贝叶斯推理中，为了保持各个节点的一致性，势必会有信息的传递。简要介绍贝叶斯网络的连接树算法以及无证据下的信息的传递方法，对贝叶斯网络在证据进入的情况下的信息传递进行了重点的介绍，尤其是处理动态证据时的情况。     

交换式以太网物理拓扑结构的自动发现

准确及时的拓扑结构信息是网络性能监测与评估、故障发现与定位、资源分配与管理等一系列维护工作的基础 .交换式以太网是目前局域网的主要组网方式,其拓扑结构被看做为一棵拓扑树,并把网络节点之间的连接关系分为直系关系和旁系关系,给出一组判定定理用以确定网络节点之间的连接关系 .基于上述定理,提出了一个新的拓扑发现算法,该算法能够利用不完整的地址转发表构造出整个网络拓扑结构 .该算法已成功地应用于社区宽带综合业务网络管理系统(CBISNMS)中 .     

基于Hilbert曲线的双层覆盖网模型

资源定位和负栽均衡是P2P网络系统中急需解决的核心问题。本文给出的模型将连续相邻的结点组成一个无结构的结点组,结点组之间利用Chord协议连接成为一个全局结构化的环形拓扑结构,并在该拓扑结构中引入HBLS资源查找算法和动态负载均衡双层环状模型调度策略。整个方案不仅具有很好的负载平衡特性,而且为查找提供了充分的灵活性性。仿真实验表明,该模型在资源定位和负载平衡两个方面都优于原Chord。     

基于网络邻域拓扑的粒子群优化算法

探讨类无标度网、全局耦合网、环形网、随机网、星形网等邻域拓扑结构对粒子群优化算法寻优效果的影响。理论分析与实验结果显示,以类无标度网作为邻域拓扑结构的粒子群优化算法在误差范围内的寻优效果最好,收敛速度最快,可以较好地避免陷入局部最优,且网络平均度对粒子群优化算法的寻优效果有一定的影响。     

一种基于可变多簇结构的动态概率粒子群优化算法

针对传统粒子群优化算法中全连接型拓扑和环形拓扑的特点,引入了一种粒子群信息共享方式——多簇结构,进而基于多簇结构提出了动态可变拓扑策略以协调动态概率粒子群优化算法的勘探和开采能力,并从理论上分析了最优信息在各种拓扑中的传播,同时从图论角度分析了几种经典拓扑以及动态可变多簇结构的统计特性.通过典型的Benchmark函数优化问题测试并比较了几种经典拓扑以及可变拓扑在高斯动态粒子群优化算法中的性能.实验结果表明,基于多簇结构的可变拓扑策略在求解复杂优化问题时优势明显,可以有效地避免算法陷入局部最优,在保证收敛速度的同时增强了算法的全局搜索能力.     

动态传感网络主节点恶意攻击检测仿真

动态传感网络是一种点对点结构的网络,有着多跳、无中心、自组织网络等特点,主节点会根据需要发生变动,导致网络拓扑结构也随之改变.传统的受恶意攻击主节点检测方法是根据固定拓扑结构设定的属性指标进行检测,针对拓扑结构经常变动的动态传感网络中受恶意攻击主节点检测准确性不高.提出利用加权平均算法的动态传感网络恶意行为检测方法,对节点的变化恶意信息进行加权,将节点特殊标记信息所携带的数据进行加权,使得各个节点的加权因子比较合理,对整个节点网络的加权平均控制在一定范围内,对恶意行为进行检测.通过对改进算法进行仿真验证,结果表明,提出的方法在入侵检测和屏蔽恶意代码攻击方面有着良好的效果.     

一种新的低压电力线网络路由器设计

低压配电网络具有物理拓扑未知和信道时变性等特征,通信可靠性问题严重制约了其在实际应用的规模。论文通过对现有电力线载波通信网络结构的分析比较,提出了适用于低压电力线窄带载波通信的树簇路由算法。首先建立树簇路由算法的协议框架,然后设计了簇生成、簇维护、骨干树生成和树维护等模块算法。最后给出了树簇路由实现策略。分析表明,树簇结合的动态路由满足了低压窄带载波通信技术条件。     

一种新的低压电力线网络路由器设计

低压配电网络具有物理拓扑未知和信道时变性等特征,通信可靠性问题严重制约了其在实际应用的规模。本文通过对现有电力线载波通信网络结构的分析比较,提出了适用于低压电力线窄带载波通信的树簇路由算法。首先建立树簇路由算法的协议框架,然后设计了簇生成、簇维护、骨干树生成和树维护等模块算法。最后给出了树簇路由实现策略。分析表明,树簇结合的动态路由满足了低压窄带载波通信技术条件。     

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).