ECK2007模型与其他密钥协商协议模型安全强弱关系的形式化证明

比较了安全性模型Extended Canetti＆Krawczyk 2007（ECK 2007）与其他4个安全模型（Bellare＆Rogaway 1993（BR93）,Bellare＆Rogaway 1995（BR95）,Bellare,Pointcheval＆Rogaway 2000（BPR 2000）和Canetti＆Krawczyk 2001（CK2001））的不同点,并形式化地分析了这些模型之间的强弱关系,对模型间存在的蕴含关系提供了形式化证明,对非蕴含关系提供了反例。     

Carbon sequestration in the agricultural soils of Europe

In this review, technical and economically viable potentials for carbon sequestration in the agricultural soils of Europe by 2008-2012 are analysed against a business-as-usual scenario. We provide a quantitative estimation of the carbon absorption potential per hectare and the surface of agricultural land that is available and suitable for the implementation of those measures, their environmental effects as well as the effects on farm income. Realistically, agricultural soils in EU-15 can sequester up to 16-19 Mt C year⁻¹ during the first Kyoto commitment period (2008-2012), which is less than one fifth of the theoretical potential and equivalent to 2% of European anthropogenic emissions. We identified as most promising measures: the promotion of organic inputs on arable land instead of grassland, the introduction of perennials (grasses, trees) on arable set-aside land for conservation or biofuel purposes, to promote organic farming, to raise the water table in farmed peatland, and—with restrictions—zero tillage or conservation tillage. Many options have environmental benefits but some risk of increasing N₂O emissions. For most measures it is impossible to determine the overall impact on farm profitability. Efficient carbon sequestration in agricultural soils demands a permanent management change and implementation concepts adjusted to local soil, climate and management features in order to allow selection of areas with high carbon sequestering potential. Some of the present agricultural policy schemes have probably helped to maintain carbon stocks in agricultural soils.     

基于MPLS/BGP电子政务网L2VPN应用与实现

 各厅局通过ATM,F/R,VPDN,Ethernet等方式接入电子政务网,通过分析比较各种基于MPLS的L2VPN技术,构建基于MPLS/BGP的L2VPN,分析改进的Kompella方式的实现过程和原理,实现Kompella和Martini方式的互联互通问题。     

基于异构数据集成技术的农业信息综合管理网络平台开发

针对中国当前农业无线监测中农业信息化标准尚未建立,监测终端各不相同,监测系统数据结构兼容性差的问题,该文围绕异构数据规范化设计和管理,开发了面向差异化农业信息监测终端的一体化网络平台。根据异构网络数据特点,将不同监测终端上传的数据格式标准化;基于XML(extensible markup language)和Visual Basic 6.0开发了标准化网管数据接口,将不同终端数据按照通讯协议的标准格式解析、存储数据;基于PHP、My SQL数据库和服务器及网站网页技术设计并搭建了远程监测平台。利用开沟机监测终端进行田间试验,监测耕深和跟踪机具,试验表明:网管数据接口能实时接收并正确解析终端数据;监测平台可实现远程数据的曲线显示、数据导出和控制终端的远程控制、轨迹绘制的功能;通过导出数据的轨迹和平台显示轨迹对比,轨迹精确。该研究解决了监测系统异构数据及终端硬件差异问题,把单机测控应用扩展至广域网,可应用于农机信息的远程实时监测和远程控制,对现代化农业信息化共享有着重要作用。     

能量高效的农田无线传感器网络拓扑关联路由算法

针对农田无线传感器网络节点分布不均、能量约束严格等特点,提出了一种能量高效的簇头选择方法TBCS-EA,在以剩余能量进行簇头选择的基础上根据节点拓扑位置、拓扑密度等进行加权,使距离sink较近的节点与密集区节点大概率成为簇头,提高成簇能量使用效率。针对现有成簇算法频繁进行簇头选举,算法开销大等问题,提出了一种能量逼近式簇头轮换机制,节点连续担任簇头并以某一目标进行能量逼近,在达到逼近目标后进行根据簇内信息指定新簇头,减少簇头选择的次数与协议开销。仿真与实验结果表明,TBCS-EA算法的网络生命周期约为LEACH的2.2倍,CHCS的1.5倍,从节点能量曲线看能耗均衡效果与CHCS相当,明显优于LEACH。结果显示TBCS-EA综合性能较之于现有算法有明显提升。     

广西山区茶园无线网络监测系统设计

针对广西山区茶园设计了依靠节点自组织特性自动构建零通信费的ZigBee无线网络监测系统,能够定时采集茶园的空气温湿度、土壤温湿度和光照等参数。该系统除协调器外全部使用路由节点,种植区按蜂窝状划分,每个路由监测节点均布置在蜂窝中心,有效提高了监测系统可靠性。在种植区与监控中心之间的非种植区设计了路由中继节点,用于接力传送茶园监测数据至监控中心内的协调器。节点硬件电路包括核心板与底板,核心板设计了CC2530与RFX2401射频功放,底板设计了传感器处理模块、电源模块及调试接口。深入分析了Z-stack协议栈基于事件处理的多任务构架下用户程序设计方法。完成了山区茶园基于ZigBee技术的无线监控网络设计,实现了茶叶种植区内空气温、湿度及土壤温、湿度,光照参数,CC2530供电电压和工作温度的周期采集和传输。通过实际运行,整个系统稳定可靠。     

奶牛场无线传感器网络设计研究

针对奶牛养殖场数据采集时不易实现检测区域的完全覆盖和铺设线缆繁琐的问题,设计了由高性能、低功耗单片机ATmega32L和无线通信模块CRM2400CNC,建立奶牛养殖场无线传感器网络。同时,重点讨论了系统结构、传感器节点的硬软件设计和通信协议等关键问题,结合奶牛场的实际对系统结构的简化进行了研究,并提出了一种新的适合动态网络的跨层技术。试验结果表明,该系统具有结构简单、成本低、功耗低等特点。     

无线传感器网络在现代农业中的应用

阐述了无线传感器网络在现代农业中应用的优势、研究现状、应用前景以及应用时需注意的关键问题。     

Functions for estimating belowground and whole tree biomass of birch in Norway

Obtaining accurate estimates of national belowground and whole tree biomass is important to better understand the global carbon cycle and to quantify biomass stocks and changes. However, the availability of individual tree belowground biomass functions is generally low due to the difficulty of extracting roots. Allometric birch (Betula pubescens Ehrh. and Betula pendula Roth) biomass functions were derived from 67 trees for belowground and whole tree biomass using diameter at breast height (dbh) and height as the independent variables. The sampled trees spanned a dbh range from 4.0 to 45.5?cm and the functions provided a good fit to the data (RMSE?=?14.2?kg for BG and 40.7?kg for whole tree with dbh as predictor). Belowground, total stem, live crown, and dead branch biomass comprised 29.2%, 52.2%, 18.1%, and 0.5% of the whole tree biomass, respectively. Observed root-to-shoot ratios were between 0.21 and 0.88 with a mean of 0.42. Comparisons with existing belowground birch biomass functions from Fennoscandia indicated considerable differences in estimates between existing functions. The derived data-set for belowground birch biomass is the largest in Fennoscandia and the developed functions are likely the best available for estimating national birch biomass stock and stock change in Norway.     

基于WSN的油菜生长环境数据采集系统

针对传统作物生长环境数据获取手段实时性差、劳动强度大以及部署微型自动气象站和商用Zigbee产品成本高、开放性较差等问题，设计并实现了一种基于WSN的油菜生长环境数据采集系统。提出了轻量级的能量感知路由协议CLFP，并给出了软硬件的相关设计方法。仿真和大田试验结果表明，系统温度采集精度最高可达0.01 ℃，测湿精度达±5%，光强采集范围为1~65 535 lx，可并发的数据传输达到36路，可满足农业现场环境数据的较高测量要求。在标称电源供电情况下，系统实际有效生存周期超过142 d，由于采用AT89C51和nRF2401作为基础硬件平台，成本低廉，有助于大规模部署和应用。