基于最优分簇的能量异构无线传感器网络路由协议

为了进一步均衡网络能耗,延长网络生命周期,提出了一种基于最优分簇的能量异构无线传感器网络路由协议(OCRP).OCRP协议考虑了最优簇首数K,将待测区域划分为K个固定分区,优化了成簇过程;在簇首选择阶段,充分考虑了节点的剩余能量、整个网络的能量以及节点与基站之间的距离,改进了簇头选举机制.仿真结果表明,该协议在延长网络寿命和能量消耗方面的性能优于EH-LEACH和DEEC路由协议.     

簇首选择改进的LEACH无线传感器路由协议

针对LEACH(Low Energy Adaptive Clustering Hierarchy)协议能耗大、网络生命周期短等不足,提出一种簇首选择改进的LEACH无线传感器路由协议(M-LEACH)。首先在综合考虑节点剩余能量、网络平均剩余能量、上一轮节点消耗的能量基础上,引入加权因子选择簇首。然后根据接收信息、簇首以及传输ADV的能耗确定簇首的数量,使簇首在网络中分布均匀。最后采用仿真实验进行性能测试。结果表明,相对于LEACH协议以及其他改进的LEACH协议,M-LEACH降低了传感器网络的能耗,使整个网络能量更加均衡,延长了无线传感器网络的生命周期。     

一种分布式能量高效的WSNs非均匀分簇路由协议

针对无线传感器网络(WSNs)多跳通信方式中存在的"热区"问题,提出了一种分布式的、能量高效的非均匀分簇(DEEUC)路由协议。该协议将节点的剩余能量作为簇首选择的一个重要指标,候选簇首由上轮簇首根据簇内成员节点的剩余能量指定,候选簇首能否最终成簇首也是其能量竞争的结果。在DEEUC协议中,簇首以多跳的方式与基站进行通信并选择正向单位能耗最小的邻居簇首作为路由节点以节约能耗。仿真实验表明:DEEUC能较好地提高网络能效,延长网络生存时间。     

一种基于遗传算法的无线传感器网络LEACH路由协议的改进算法

针对LEACH协议存在的簇首数目与最优簇数目不一致,随机选择簇首,未考虑节点剩余能量、节点位置和节点密集度等问题,提出了一种基于遗传算法的新型路由算法LEACH-GEC,算法首先利用最优簇数目与遗传算法的结合对网络节点进行分簇,然后利用节点剩余能量、距簇内质心的距离、节点覆盖度和共享密钥数目等约束条件来选择簇首.仿真表明:改进后的路由算法较LEACH协议分簇更均匀,簇首选取更合理,有效延长了网络寿命,同时还可以确保簇内通信的安全性.     

一种基于剩余能量的无线传感器网络分簇协议

在无线传感器网络中,分簇技术可以实现高效的能量利用、方便的数据融合、灵活的网络扩展。簇首作为簇的中心,负责收集簇成员的数据,簇首消耗的能量远大于簇成员,因此,簇首的选择至关重要。提出了一种基于剩余能量的分簇协议（CPRE）,该协议优先选择剩余能量较多的节点作为簇首,并采用簇间转发的方式将数据发送到基站。仿真结果表明：该协议能够显著地延长网络的生存时间,其性能明显优于LEACH协议。     

基于事件驱动保持网络连通性的WSNs路由协议

为保证无线传感器网络（ WSNs）的连通性,延长网络有效工作期,提出了一种事件驱动成簇、能量高效均衡的路由协议。该协议避免了与事件无关的节点参与成簇而消耗能量,通过簇首选举的控制消息延时转发节省了网络能量,建立了综合考虑当前节点剩余能量和包含其邻居节点的平均剩余能量、当前节点到邻居节点和Sink节点距离的中继路由法则。仿真结果表明：与采用预成簇的AEEC协议和事件驱动成簇的ARPEES协议相比,所提出的路由协议推迟了首个死亡节点的出现时间,使WSNs有效工作期分别提高了4.3倍和47%。     

改进的无线传感器网络簇首选择策略及其路由算法

针对无线传感器网络中簇首能耗较大引起的能量黑洞问题,在不均匀分簇的基础上,从簇首选择和簇首更换两个方面提出相应的改进措施。在簇首选择时,将整个网络区域分为不均匀的簇,通过相关参数的设置,让每簇中能量最高的节点当选为簇首节点,网络运行时簇首维护本簇的能量信息表;在簇首更换时,采用局部更换测量,并由当前簇首在能量信息表中选择剩余能量最高的节点作为下一个簇首节点,从而改善了簇首能量效率和负载均衡。最后进行了仿真实验与对比,实验结果表明改进的路由协议能够有效提高网络性能,延长网络生命周期。     

基于分区的能耗均衡路由协议

为了均衡无线传感器网络的节点能耗,增强网络稳定性,设计并实现了一种基于分区的能耗均衡路由协议.该协议设计了一种优化的分区算法,将节点基于分区划分而形成簇,解决了先前协议中簇的个数和分布的随机性问题;在选举簇首时,综合考虑了节点剩余能量、簇内节点能耗均衡、簇内部总能耗三个方面,采用三级簇首选择机制,选择的簇首既能均衡节点能耗,又可以降低簇群总能量消耗;在数据转发时,普通节点选择距离最近的簇首,在不超过通信距离阀值时,簇首可以隔层选择下一跳簇首,有利于缓解无线传感器网络的"热区效应".仿真结果表明:相比MEET和DREEM-ME路由协议,该协议能更好地均衡节点能耗、增强网络稳定性、改善网络服务质量.     

一种能量均衡的无线传感器网络分簇路由协议

由于无线传感器网络节点能量有限,为均衡无线传感器网络节点之间的能量消耗,提高整体网络的生命周期,针对LEACH协议中簇首选举时未考虑节点剩余能量因素、随机分簇等不足,提出了一种改进的LEACH协议.改进的LEACH协议在簇首选举时,以节点的剩余能量作为重要参考依据,优化节点担任簇首的概率.仿真结果表明,与传统的LEACH协议相比,改进的LEACH协议达到了能量消耗均衡的目标,从而延长了网络的生存寿命.     

长距离带状无线传感器网络路由协议设计

带状网络的长带状特性会影响无线传感器网络路由协议的性能,导致网络出现"热区"。针对该问题,提出一种能量均衡的多跳路由协议CRLDB。该协议主要采用非均匀分簇的思想,引入备选簇首竞争半径的概念和相应的竞争策略,并加入最优簇首个数、节点剩余能量和周围邻居节点个数的簇首选择机制,使节点的剩余能量和传输能量达到平衡。NS2仿真实验结果证明,与LEACH和LEACH-C协议相比,CRLDB在网络的生存时间、整体能耗和基站收到的数据量这3个性能指标上有较大程度的提高,能更好地均衡网络的能量消耗,提高网络的生命周期。     

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).