共查询到16条相似文献,搜索用时 78 毫秒
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入侵检测是对计算机网络和计算机系统的关键节点的信息进行收集和分祈。由于高速网络和交换式网络的普遍应用,以分布式拒绝服务攻击为代表的新型攻击方式的出现和发展,以及现有入侵检测系统效率低下、误报率和漏报率较高的问题无法得到有效解决等问题,目前入侵检测技术正处于发展的关键时期。协议分析是网络入侵检测技术中的一种关键技术,但不能解决对于包含在多个数据包中的攻击。针对这一问题,本文提出了基于状态协议分析的检测技术,构建一个有限自动机(Finite Automata,简称FA)来约束网络,并用由正则表达式产生的语言来描述一系列的正常的状态转化,充分利用协议的状态信息检测入侵。 相似文献
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概率赋范空间有限维的特征 总被引:2,自引:0,他引:2
在概率赋范空间中给出了Riesz定理,研究了依概率范数收敛与依坐标收敛的关系,证明了概率赋范空间有限维的充要条件,并以实例说明了定理的意义。 相似文献
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朱玉山 《中国计量学院学报》1999,(2)
在〈 H ;H〉与〈 H;H〉双同态的条件下 ,本文给出了反映〈 H ;H〉中的 A-盈满子集与〈 H;H〉中的 A-盈满子集的关系的几个结果 相似文献
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特征值问题迭代伽略金法与Rayleigh商加速 总被引:3,自引:0,他引:3
该文讨论特征值问题非协调有限元和混合有限元的加速计算方法。基于迭代伽略金法和Rayleigh商加速技巧,我们建立了特征值问题Wilson非协调有限元和Ciarlet-Raviart混合有限元的加速计算方案。这些新方案把在细网格上解一个特征值问题简化为在粗网格上解一个特征值问题和在细网格上解一个线性方程。文中证明了新方案的计算结果仍然保持了渐近最优精度阶,并用数值实验验证了理论结果。 相似文献
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对解2阶椭圆特征值问题的线性有限元法,本文考虑了一种计算简单的有限元亏量校正方案。基于插值校正和Rayleigh商给出了新的校正特征值。理论分析表明该校正特征值或者达到二次元的精度阶或者当网格直径充分小时下逼近准确特征值,并用数值实验验证了理论结果。 相似文献
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基于随机集理论的多目标跟踪研究进展 总被引:1,自引:0,他引:1
基于随机有限集理论的多目标跟踪方法,能够避免数据关联步骤的困扰,能够较好地解决复杂环境中目标数目未知且随时间变化的多目标跟踪问题.本文分析基于数据关联和基于随机集理论的多目标跟踪方法,阐明基于随机集理论的多目标跟踪方法的特点和优点,对目标状态提取、航迹关联、更准确的滤波算法,以及复杂条件下的PHDF算法等关键问题进行总结和评述,并指出该领域今后的研究热点. 相似文献
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P. Ortiz E. Sanchez 《International journal for numerical methods in engineering》2001,50(12):2727-2740
The partition of unity finite element method (PUFEM) is explored and improved to deal with practical diffraction problems efficiently. The use of plane waves as an external function space allows an efficient implementation of an approximate exterior non‐reflective boundary condition, improving the original proposed by Higdon for general diffraction problems. A ‘virtually’ analytical integration procedure is introduced for multi‐dimensional high‐frequency problems which exhibits a dramatic decrease in the number of operations for a given error compared with standard integration methods. Suitable conjugate gradient type solvers for the whole range of wavenumbers are used, including such cases in which PUFEM can produce nearly singular matrices caused by ‘round‐off’ limits. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Thomas‐Peter Fries Ted Belytschko 《International journal for numerical methods in engineering》2010,84(3):253-304
An overview of the extended/generalized finite element method (GEFM/XFEM) with emphasis on methodological issues is presented. This method enables the accurate approximation of solutions that involve jumps, kinks, singularities, and other locally non‐smooth features within elements. This is achieved by enriching the polynomial approximation space of the classical finite element method. The GEFM/XFEM has shown its potential in a variety of applications that involve non‐smooth solutions near interfaces: Among them are the simulation of cracks, shear bands, dislocations, solidification, and multi‐field problems. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Abstract In order to eliminate the irrelevant data being transferred from disks into memory, many database machines adopt a data filter to filter out the irrelevant data on‐the‐fly. This paper proposes a new DFSA (Deterministic Finite State Automata) based pattern matcher to be implemented as the data filter. It can perform various searching operations, including fixed and variable length don't care patterns. The architecture of this pattern matcher is relatively simple and can be easily implemented by off‐the‐shelf LSI chips. In our design, it only requires one 16K×8 SRAM and five LSI chips for a given state transition table of 128 states. A test has been conducted to compare the performance of dBASE III and our data filter. The result shows that the data filter is, on average, five times better than the performance of dBASE III. 相似文献