可信软件代码中程序标注的使用及类型验证     

赵洋  徐晓刚  张功萱  张容 《武汉大学学报(信息科学版)》2010,(5)

程序标注技术能够勾勒程序代码中的各种数据属性和软件行为,提出了使用许可类型系统作为沟通程序标注和程序代码的桥梁,从程序代码的角度分析和验证了程序的安全性,进而提升了整个软件系统的可靠性和可维护性。  相似文献   

Lead isotope evidence for recent uranium mobility in geological formations of Brazil: implications for radioactive waste disposal     

《Applied Geochemistry》1999,14(2):197-221

Lead–lead isotope data from whole rock samples are used to investigate the recent (last few million years) mobility of U and Th. The method is based on the comparison of the calculated present day U and Th concentrations required to yield the Pb isotope composition in the samples with the actual present day concentrations of U and Th obtained by direct measurement. The geological formations studied include the Neoproterozoic carbonate sediments of the Bambuı́ Group, Archean/Paleoproterozoic granite–greenstone terrain of the Contendas–Mirante Complex and a Proterozoic ortho-gneisses hosting U deposit in Lagoa Real. All these formations are in the São Francisco Craton, Brazil. The data show high U mobility in the carbonate sediments and in the deformed ortho-gneisses set in a ductile shear zone. Infiltration of groundwater through fault zones seems to have facilitated the U mobility. The Pb isotope approach is a useful technique complementing U-series disequilibrium studies and may be included for site characterization studies for radioactive waste disposal.  相似文献   

无线Ad Hoc网络拓扑控制研究     

李华峰  徐延贵  钱焕延 《中国海洋大学学报(自然科学版)》2008,(Z1)

由节点位置和传输范围确定的无线网络拓扑结构对网络性能有着重大影响。拓扑控制通过调节节点的传输功率,能够优化网络的性能,减少节点的功率消耗,延长网络的生存时间。拓扑控制算法按其优化目标可以分为基于几何结构和基于能量有效性2类,前者主要以某些几何结构为基础构建网络拓扑,后者主要关注网络的能量有效性。文中综述了Ad Hoc网络拓扑控制的研究现状,介绍了一些典型拓扑控制算法的原理及最新进展。  相似文献   

On the Numerical Stability of Some Symplectic Integrators     

《Chinese Astronomy and Astrophysics》2007,31(2):172-186

In this paper, we analyze the linear stabilities of several symplectic integrators, such as the first-order implicit Euler scheme, the second-order implicit mid-point Euler difference scheme, the first-order explicit Euler scheme, the second-order explicit leapfrog scheme and some of their combinations. For a linear Hamiltonian system, we find the stable regions of each scheme by theoretical analysis and check them by numerical tests. When the Hamiltonian is real symmetric quadratic, a diagonalizing by a similar transformation is suggested so that the theoretical analysis of the linear stability of the numerical method would be simplified. A Hamiltonian may be separated into a main part and a perturbation, or it may be spontaneously separated into kinetic and potential energy parts, but the former separation generally is much more charming because it has a much larger maximum step size for the symplectic being stable, no matter this Hamiltonian is linear or nonlinear.  相似文献   

多种信息融合的实时在线多目标跟踪     

刘忠耿  练智超  冯长驹 《南京气象学院学报》2017,9(6):656-660

多目标跟踪算法在目标发生遮挡、目标快速运动时容易跟踪失败,而且无法从失败中恢复跟踪.针对该问题,首先利用目标的外观信息、运动信息和形状信息多种信息融合的目标特征表示,准确地计算目标间的相似性,使同一目标之间相似性距离尽量小,不同目标间的相似性距离尽量大;其次,基于判别能力强大的相关滤波器和卡尔曼预估器结合的单目标跟踪器可以在目标遮挡、快速运动中准确地跟踪目标.实验结果表明,多目标跟踪算法能够实时准确地跟踪被遮挡的目标和快速运动的目标.  相似文献   

基于虚拟仪器的水下目标二维角估计     

刘伟  王昌明  张自嘉  包建东 《海洋测绘》2008,28(1):49-51

利用LabVIEW软件，通过8通道数据采集卡和均匀圆阵对水下目标的噪声进行采集和处理。结合一维直线阵波束形成理论，实现了对水下目标二维方向角估计实验研究和算法验证。实验证明利用虚拟仪器方便地实现了对水声信号的采集、处理，以及在方位估计时，为传感器布阵和算法的确定提供参考。  相似文献   

高校网络信息应用分类研究     

刘正勇  邱均平 《中国海洋大学学报(自然科学版)》2008,(Z1)

传统分类法是1种重要的信息组织方式,目前的网络环境对传统信息分类法提出了新的要求。DDC,LCC,UDC等传统分类工具在对网络资源组织时,存在着自身优势和局限性,传统分类法在未来的发展中应该遵循一定的原则,对构建统一的网络资源分类法提出了建议。  相似文献   

Measurements of ocean wave spectrum from airborne radar at small incidence angles   总被引：1，自引：0，他引：1  

REN Lin  PAN Delu  MAO Zhihua 《海洋学报(英文版)》2011,30(1):40-46

This paper proposes the retrieval method of ocean wave spectrum for airborne radar observations at small incidence angles, which is slightly modified from the method developed by Hauser. Firstly, it makes use of integration method to estimate total mean square slope instead of fitting method, which aims to reduce the affects of fluctuations superposed on normalized radar cross-section by integration. Secondly, for eliminating the noise spectrum contained in signal spectrum, the method considers the signal spectrum in certain look direction without any long wave components as the assumed noise spectrum, which would be subtracted from signal spectrum in any look direction for linear wave spectrum retrieval. Estimated ν from the integration method are lower than the one from fitting method and have a standard deviation of 0.004 between them approximately. The assumed noise spectrum energy almost has no big variations along with the wave number and is slightly lower to the high wave number part of signal spectrum in any look direction, which follows that the assumption makes sense. The retrieved directional spectra are compared with the buoy records in terms of peak wavelength, peak direction and the significant wave height. Comparisons show that the retrieved peak wavelength and significant wave height are slightly higher than the buoy records but don’t differs significantly (error less than 10%). For peak direction, the swell waves in first case basically propagate in the wind direction 6 hours ago and the wind-generated waves in second case also propagate in the wind direction, but the 180? ambiguity remains. Results show that the modified method can carry out the retrieval of directional wave spectrum.  相似文献   

舷侧阵CBF和OBF的阵增益比较     

何云峰  宋高顺  焦君圣 《海洋技术学报》2011,30(3)

以舷侧阵作为研究对象,首先介绍了常规波束形成器(CBF)和最佳波束形成器(OBF)的波束输出信号模型,然后推导了信号+噪声场合下的阵增益表达式,比较了在不同信号频率和不同信号源方向角下,CBF和OBF的阵增益,最后在增加了有指向性的CW干扰后,分析了此场合下的阵增益,并比较了不同的信号频率下,干扰源方向角的变化对两类波束形成器阵增益的影响。  相似文献   

利用FY-2F数据检测快速发展对流     

汪柏阳  覃丹宇  刘传才 《遥感学报》2015,19(5):836-843

快速发展对流RDC(Rapid Developing Convection)是灾害性天气发生的先兆。如何利用卫星遥感技术快速捕捉到RDC信息,是天气临近预报非常关注的内容。随着中国FY-2F气象卫星快速扫描工作模式的业务化,可提供时间分辨率为6 min,空间分辨率为5 km的多通道快速扫描数据,这使得利用卫星检测RDC业务化成为可能。本文根据FY-2F多通道快速扫描数据的特点,设计了一种快速发展对流检测方法。该方法主要根据云顶快速降温率CTC(Cloud Top Cooling rate)的多通道判识,设计了带有3个测试的CTC过滤器,过滤之后得到每个RDC的局部亮温极小值点,然后以该点为中心对周围像元进行漫水填充,得到快速发展对流体。对2013年8月(94°E—129°E,11°N—26°N)的扫描数据进行试验验证,结果表明,本文方法对RDC检测的准确率POD、误报率FAR和临界成功指数CSI分别为0.89、0.15和0.77,能够较为准确地检测快速发展对流。  相似文献