预条件的平方Smith法求解大型Sylvester矩阵方程

提出了一种预条件的平方Smith算法求解大型连续Sylvester矩阵方程,该算法利用交替方向隐式迭代(ADI)来构造预条件算子,将原方程转换为非对称Stein方程,并在Krylov子空间中应用平方Smith法迭代产生低秩逼近解。数值实验表明,与已知的Jacobi迭代法等算法相比,该算法有更好的迭代效率和收敛精度。     

无线传感器网络中抗共谋的自愈组密钥分配方案

针对现有基于双向Hash链技术的自愈组密钥分配方案不能抵抗撤销节点和新加入节点的共谋攻击问题,并进一步提高现有方案的性能,提出了一种适用于无线传感器网络的有效的抗共谋攻击的自愈组密钥分配方案。方案对传统的双向Hash链进行了结构性改造,在有撤销节点的会话中,用随机值替换前向密钥,使得已被撤销节点无法和新加入节点共谋获取它们未被授权的会话密钥,消除了共谋攻击对网络构成的安全威胁,更适用于俘获节点攻击高发的网络环境。方案还考虑了在实际网络环境中,并不是在每一个会话都有节点被撤销这一个实际情况,减少了通信开销和能量消耗。安全性和性能分析与仿真结果表明,方案在保证更好安全性的同时,降低了通信开销。     

无线视频传感器网络有向感知K覆盖控制算法研究

作为无线视频传感器网络的一个研究热点,有向覆盖控制理论引起了很多研究者的广泛关注,但是有向K覆盖问题还未得到深入研究.由于最大K有向覆盖问题属于NP-complete问题,所以难以在多项式时间内得到求解,因此设计了一种简单的分布式启发式算法,在一跳邻居范围内对传感器节点的感知方向进行协同调度,使得目标集合被有向K覆盖的时间最大.最后通过仿真比较了有向感知K覆盖DS-K-Coverage算法、贪婪算法Greedy-Algorithm、随机覆盖算法Random-Coverage的覆盖性能.     

Extreme value analysis of streamflow time series in Poyang Lake Basin, China

Extreme meteorological and hydrological events may cause major disasters and heavy social and economic losses.Therefore,more and more studies have focused on extreme hydro-meteorological events in various climates and geographic regions.Based on nearly 50 years of observed records of the Poyang Lake Basin,the occurrence and changing trends of extreme streamflow indices,including the annual maximum flow,annual peak-over-threshold flows,and low flows,were analyzed for ten hydrological stations.The results indicate that most annual maximum flows occurred from April to July,highly attributed to the Southeast Asian summer monsoons,whereas the annual minimum flows were concentrated between January and February.As for the low flow indices (the annual minimum flow,annual minimum 7-d flow,and annual minimum 30-d flow),a significant increasing trend was detected in most parts of the Poyang Lake Basin.The trends illustrate the potential effects of climate change and human activities on the hydrological cycle over the Poyang Lake Basin.     

针对地质灾害检测的视频传感器覆盖的一种新算法*

在实际地质灾害监测工程中,为了使视频传感器这一有向传感器最大化覆盖,提出了一种全新的资源掠夺算法。该算法将相邻的节点看成树干上的叶片,利用树叶为争夺阳光而具有的特点使节点覆盖具有最大覆盖面积、最小的覆盖重合区域。从区域覆盖角度对算法进行仿真分析,证明了算法的可行性并且相对于传统算法覆盖效果好且高效,在相关应用中将有很大的优势。     

A Multi-parameter Approach to Automated Building Grouping and Generalization

This paper presents an approach to automated building grouping and generalization. Three principles of Gestalt theories, i.e. proximity, similarity, and common directions, are employed as guidelines, and six parameters, i.e. minimum distance, area of visible scope, area ratio, edge number ratio, smallest minimum bounding rectangle (SMBR), directional Voronoi diagram (DVD), are selected to describe spatial patterns, distributions and relations of buildings. Based on these principles and parameters, an approach to building grouping and generalization is developed. First, buildings are triangulated based on Delaunay triangulation rules, by which topological adjacency relations between buildings are obtained and the six parameters are calculated and recorded. Every two topologically adjacent buildings form a potential group. Three criteria from previous experience and Gestalt principles are employed to tell whether a 2-building group is ‘strong,’ ‘average’ or ‘weak.’ The ‘weak’ groups are deleted from the group array. Secondly, the retained groups with common buildings are organized to form intermediate groups according to their relations. After this step, the intermediate groups with common buildings are aggregated or separated and the final groups are formed. Finally, appropriate operators/algorithms are selected for each group and the generalized buildings are achieved. This approach is fully automatic. As our experiments show, it can be used primarily in the generalization of buildings arranged in blocks.

指纹连续分类基于遗传算法的实现

首先介绍了一种基于指纹方向图分区和遗传算法的连续分类方案。根据各种典型指纹类别的拓扑特性而引进了一组动态分区模板和代价函数用于引导方向图分区,并将寻找最佳匹配划分的过程转化成一个N维向量空间的函数优化问题,然后给出了该问题基于遗传算法的求解过程。最后,讨论了遗传算法的优越性。     

烟台—淄博输油管道穿河工程对河道防洪影响

结合烟台港西港区至淄博重质液体化工原料输送管道穿越潍河的防洪影响评价项目,简要介绍了穿河输油管道防洪评价的基本内容和方法,对因输油管道建设对河道防洪造成的影响进行了防洪分析计算和综合评价,对影响河道防洪安全的问题提出了相应的建议。     

基于功率匹配的水平定向钻节能控制系统研究

以节能为出发点,通过对水平定向钻功率匹配的分析,研究了将液压泵的最大功率曲线设定在发动机的输出功率曲线之上的功率匹配原理.控制系统检测外负载的变化,输出控制信号调节液压泵的排量,使液压泵在外负载大幅变化时仍可以完全吸收发动机输出的功率,确保发动机维持在设定的转速下运行,实现了充分发挥发动机功率和节能的目的.建立了水平定向钻AMESim仿真模型,研究了PID控制器在节能控制系统上的应用.仿真及试验结果表明,发动机转速波动均控制在50 r.min-1内,有效地减少了功率损失.     

SPOTE随钻测井系统的试验研究

为验证SPOTE随钻测井系统功能进行了机械密封室内压力试验、电子硬件及程序室内联调测试。制定了实钻试验方案,确定了循环系统参数、钻进参数、MWD工作参数。分析了SPOTE随钻测井系统获取的数据,与ELIS电缆复测试验数据比较,随钻地层自然伽马和电阻率测井数据与电缆测井数据一致性良好,表明SPOTE系统定向参数测量精确,同时将随钻测井曲线与Trip-log测井曲线对比,也验证了仪器有较好的测量重复性。