谈局域网硬件维护及网络安全

局域网作为小范围网络,其功能体现在信息资源的共享、相互间的信息资源交换、负荷分担协同工作等方面。因此,局域网的安全管理和维护就显得尤为重要。     

常用边缘检测方法分析与比较

论文对几种常用的图像边缘检测算法进行了分析,实际上这几种方法都在我们的生活生产乃至国防中得到了广泛的应用。论文在分析的基础上,进一步进行了比对说明,指出了它们各自的特点。     

逻辑系统Gdel,Luk,L*中命题真度值的分布

分别研究了Gdel,Luk,L*逻辑系统中公式的真度的分布情况,得到了公式的真度集均为[0,1]∩Q的重要结论。     

一种新的基于非测距的无线传感器网络三维定位算法

针对无线传感器网络在空间、海洋等三维场景下的应用,提出了一种基于非测距的分布式三维定位算法(DRFP-3D).该算法无需测量节点间的实际距离,只需要锚节点广播它们自身的信标信息,在锚节点一跳通信范围内的未知节点接收并存储监听到的信标信息,并根据这些信息估计自身位置.与现有的基于非测距的三维定位算法相比,该算法的通信开销和定位误差均比较小,且对网络拓扑结构具有一定的鲁棒性.仿真结果表明,在500 m×500 m×50 m的三维空间内,随机放置20个锚节点,ANR=4,就能对97%的节点进行定位,其平均定位误差仅为20%左右.     

一种主动感知的纹理图像检索方法(英文)

基于Contourlet变换和支持向量机提出了一种新的纹理图像检索方法。在这种方法中,能量和广义高斯分布参数被用做Contourlet子带图像的特征。通过这种表示,提出了由一类和二类支持向量机组成的两阶段检索算法来完成感知相似性测度。通过具有640个纹理图像的VisTex库和具有1760个纹理图像的Brodatz库证明了所提方法的有效性。实验结果表明,对于这两个纹理库,新的纹理图像检索方法的平均检索率分别达99.38%和98.07%。     

基于灰度-梯度共生矩阵的车轮踏面缺陷聚类分析北大核心CSCD

车轮作为列车走行部的关键部件之一,其踏面产生缺陷后会直接影响到列车的运行安全。为了能够在检测时准确识别车轮踏面缺陷不同类型,提出一种基于灰度-梯度共生矩阵的纹理特征提取方法,对踏面图像的灰度和梯度特征分析之后,根据灰度-梯度共生矩阵提取踏面图像纹理特征矢量,再结合K-均值(K-means)聚类优化算法对踏面缺陷特征量进行聚类,从而将踏面缺陷类型进行分类,并将分类结果用可视化数据显示。实验结果表明,采用上述所提方法,对车轮踏面缺陷不同类型的分类识别精度达96%以上。     

Some peculiarities of electric discharge between a solid electrode and technical water

We present the results of experimental study of the electric discharge between metal electrodes of various geometry and technical water within the pressure range of 8 × 10³–10⁵ Pa at the saw-tooth voltage generator frequency, f = 40 MHz, and the interelectrode distance, l = 3–30 mm. We consider transfer of the streamer discharge into spark one depending on the geometry of the metal electrode and its material. We investigate the electrical characteristics of the discharge between the plate electrode and the technical water within a wide pressure range. The essential influence of the streamer discharge type on the ozone release within the investigated parameters range is discovered.     

Dynamic flow‐based particle splitting in smoothed particle hydrodynamics

In this work, a dynamic procedure for local particle refinement to be used in smoothed particle hydrodynamics (SPH) is presented. The algorithm is able to consistently produce successive levels of particle splitting in accordance to a flow‐based criterion. It has been applied together with accurate and robust formulations for variable spatial resolution in the framework of a semi‐implicit, truly incompressible scheme for SPH. Different test cases have been considered to assess the capabilities and advantages of the proposed procedure, namely, the laminar flow around circular and square obstacles in a plane channel for various regimes. Such flow cases entail the simulation of attached and separated shear layers, recirculating flow, vortex shedding and surface discontinuities. The results obtained for two levels of particle splitting have demonstrated that significant improvements may be obtained with respect to uniform particle spacing solutions in a variety of situations, thus presenting an excellent trade‐off between accuracy and computational cost. Copyright © 2015 John Wiley & Sons, Ltd.     

对接圆柱壳结构的频响函数子结构混合建模方法研究

以建立精确的对接圆柱壳结构动力学模型为目标,为解决对接圆柱壳结构实验模型存在的界面转角自由度信息缺失的问题,提出了频响函数子结构混合建模方法,采用界面刚性等效方法进行界面转角自由度信息的近似估计,并将其与有限元频响结果进行对比分析,验证了该方法在圆柱壳结构中的计算精度。同时,根据子结构频响函数获取方式、界面自由度的不同,采用子结构频响函数综合方法进行多种工况下的混合建模。结合对接圆柱壳结构的振动特性,对比分析不同工况下的混合建模结果。结果表明：考虑界面转角自由度信息后,可有效提高对接圆柱壳结构的混合建模精度。     

Fracture of solids by radiation pulses as a method of ensuring safety in space

To determine the optimum conditions of fracturing or altering the trajectory of dangerous space objects (large iron or rock space bodies, threatening to collide with the Earth), and also destroy space debris in the space around the Earth, the author presents a mathematical formulation of the problem of calculating the dynamic strength of solids under the effect of high-energy loading pulses. The results of numerical modeling are compared with the experimental data for the formulation of cupola-shaped swollen areas on the rear surface of a metallic plate subjected to laser radiation. The change in the fracture mechanisms (front and rear spallation) with increasing energy of the effect has been detected. Recommendations are given for optimizing the pulsed laser effect on dangerous space objects to ensure the fragmentation or change their orbit.Expanded form of the document presented at the International Conference Space Protection of the Earth≓ (SPE'94, Snezhinsk, Russian, September 26–30, 1994).Translated from Problemy Prochnosti, No. 3, pp. 31–51, March, 1996.