一种无线传感器网络预配置对密钥的改进方案*

针对预配置对密钥管理方案存在的缺点,引入一个临时初始密钥和混沌加密算法,提出一种预配置随机对密钥的改进方案。该方案能够使加密密钥随机地改变,且可以更新密钥,提高了网络抗破译的能力,实现了对称和非对称密钥体制的结合。分析表明该方案在安全性、密钥连通性、内存需求和密钥协商的计算量等方面有一定的优势,易于在Mica2节点上软件实现。     

上海电网中长期负荷预测

介绍了上海电网概况,分析了网供负荷特性,以及近期影响上海地区负荷的因素,并使用不同的预测方法给出了中长期负荷和用电量的方案.最后针对上海地区的特点,提出了提高负荷预测准确性和应对本地区电网严峻形势的对策和建议.     

基于蚁群算法的遥感图像聚类方法

聚类分析是遥感图像非监督分类的有效方法,蚁群算法具有离散性和并行性的特点,蚂蚁觅食行为、蚂蚁堆积尸体行为和基于蚂蚁自我聚集行为的聚类算法是目前研究较为广泛的3种基于蚂蚁的仿生聚类算法.为验证上述3种算法的有效性,在对这3种聚类算法进行研究的基础上,针对遥感图像进行了聚类实验.实验结果表明,基于蚂蚁的聚类方法对图像的聚类分析是有效的,较传统的k均值和模糊C均值算法有一定优越性.     

海洋平台灰预测和支持向量机的逆控制

导管架式海洋平台在随机波浪等外载荷作用下极易产生有害振动,且其动力响应具有极强的非线性和时变性,采用被动控制方法和基于精确数学模型的主动控制方法控制海洋平台的有害振动很难达到理想的控制效果.结合灰预测和支持向量机的优点,提出了基于灰预测和支持向量机的自适应逆控制方法,并将其与动态刚度阵法相结合应用于导管架式海洋平台的振动主动控制中.数值算例分析表明,该控制方法可有效地控制波浪和风载荷作用下引起导管架式平台的有害振动,并能解决由于控制信号传输等原因引起的时滞问题.     

Method of change management based on dynamic machining error propagation

In multistage machining processes(MMPs),the final quality of a part is influenced by a series of machining processes,which are complex correlations.So it is necessary to research the rule of machin-ing error propagation to ensure the machining quality.For this issue,a change management method of quality control nodes(i.e.,QC-nodes) for machining error propagation is proposed.A new framework of QC-nodes is proposed including association analysis of quality attributes,quality closed-loop control,error tracing...     

Experiments and reaction characteristics of liquid phase simultaneous removal of SO<Subscript>2</Subscript> and NO

Experiments of simultaneous removal of SO₂ and NO from simulated flue gas, using NaClO₂ solution as the absorbent, were carried out in a self-designed bubble reactor, and high simultaneous removal efficiencies of SO₂ and NO were obtained under the optimal experimental conditions. The mechanism of simultaneous removal based on NaClO₂ acid solutions was proposed by analyzing the removal products. Possibility and limitation of the desulfurization and denitrification using NaClO₂ acid solutions were calculated by thermodynamic methods. Experimental results of reaction kinetics for simultaneous desulfurization and denitrification indicated that the oxidation-absorption processes of SO₂ and NO were divided into two zones, namely the fast and slow reaction zones. In the slow reaction zones both were zero order reactions, and in the fast reaction zones, the reaction order, rate constant and activation energy of SO₂ reaction with absorbent were 1.4, 1.22 (mol·L⁻¹)^−0.4·s⁻¹ and 66.25 kJ·mol⁻¹, respectively, and 2, 3.15×10³ (mol·L⁻¹) ⁻¹·s⁻¹, and 42.50 kJ·mol⁻¹ for NO reaction, respectively. Supported by the National High-Tech Research and Development Program of China (“863” Project) (Grant No. 2007AA061803)     

Restraint of mid-spatial frequency error in magneto-rheological finishing (MRF) process by maximum entropy method

In order to restrain the mid-spatial frequency error in magnetorheological finishing (MRF) process, a novel part-random path is designed based on the theory of maximum entropy method (MEM). Using KDMRF-1000F polishing machine, one flat work piece (98 mm in diameter) is polished. The mid-spatial frequency error in the region using part-random path is much lower than that by using common raster path. After one MRF iteration (7.46 min), peak-to-valley (PV) is 0.062 wave (1 wave =632.8 nm), root-mean-square (RM...     

Effects of irrigation efficiency on chemical transport processes

Irrigation practices greatly affect sustainable agriculture development. In this study, we investigated the effects of irrigation efficiency on water flow and chemical transport in soils, which had significant impact on the environment. Field dye staining experiments were conducted at different soils with various irrigation amount. Image analysis was conducted to study the heterogeneous flow patterns and their relationships with the irrigation efficiency. Irrigation efficiency and its environmental effects were evaluated using various indictors, including application efficiency, deep percolation ratio, storage efficiency, and uniformity. Under the same irrigation condition, soil chemical distributions were more heterogeneous than soil water distributions. The distributions were mainly affected by soil texture, initial soil water content, and irrigation amount. Storage efficiency, irrigation uniformity, and deep percolation ratio increased with irrigation amount. Since the chemical distribution uniformity was lower than the water uniformity, the amount of chemical leaching increased sharply with decrease of irrigation uniformity, which resulted in high environmental risks of groundwater pollution.     

纯电动汽车经济性比较与分析

对纯电动汽车和传统燃油汽车进行全寿命周期成本的比较和分析,并通过敏感性分析找出影响纯电动汽车成本的关键因素,直观地反映纯电动汽车经济性的优势与不足,分析结果表明,对纯电动汽车的研究开发和推广应用具有指导意义.     

支持MPLS流量工程的选播路由

对选播服务的网络负载均衡做了研究,提出一种支持多协议标签交换（MPLS）流量工程的选播路由算法（ART）．ART基于最小冲突路由机制,通过MPLS约束路由的标记分发协议（CR LDP）建立1条从选播服务器到客户方向的标记交换路径（LSP）,并预留带宽资源．仿真结果表明,ART能平衡网络的负载,在选播服务中实现网络资源的优化利用,并且在传输服务数据流时,能减少时延及数据包的丢失．