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41.
林涌 《数字社区&智能家居》2009,(17)
僵尸网络Botnet是一种攻击者利用互联网秘密建立的可以集中控制的计算机群,由于数量巨大,成为目前威胁互联网安全的一个重要因素。该文从僵尸网络的定义出发,探讨了僵尸网络的组成、分类和典型代表,分析了僵尸网络的工作过程,以及可能产生的危害,并提出相关问题的解决方法思路。 相似文献
42.
根据新型军械装备损坏程度具有不确定性的特点,提出了基于D-S证据理论的新型军械装备损坏程度评估方法,并求出了新型军械装备损坏程度区分.通过对典型新型军械装备损坏程度的评估,验证了该方法的有效性和实用性. 相似文献
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44.
Peter Dabnichki 《Mathematics and computers in simulation》2011,82(3):471-482
Computational fluid mechanics (CFD) has made substantial progress on modelling a variety of important problems in industry. However, there is still lack of reliable methods to model the motion of the body in water. This is a central issue in understanding animal and human propulsion in water not only to advance science but to explore the possibility of utilising such propulsion modes for man made vehicles. The presented work identified the added mass effect as the prime contributor to propulsive force generation. The use of boundary element method (BEM) proved very successful as it allowed reducing this dynamic problem to a quasi-static one without sacrificing accuracy in the model. The comparison between the experimental data and the simulation result was in the range of 95% (average accuracy) suggesting that the added mass effect and dynamic lift and drag are the most significant physical phenomena in propulsive force generation despite the fact that there is undoubtedly and the presence of turbulent effects that were not considered. 相似文献
45.
A.R. Seadawy 《Computers & Mathematics with Applications》2011,62(10):3741-3755
The Korteweg-de Vries (KdV) equation with higher order nonlinearity models the wave propagation in one-dimensional nonlinear lattice. A higher-order extension of the familiar KdV equation is produced for internal solitary waves in a density and current stratified shear flow with a free surface. The variational approximation method is applied to obtain the solutions for the well-known KdV equation. Explicit solutions are presented and compared with the exact solutions. Very good agreement is achieved, demonstrating the high efficiency of variational approximation method. The existence of a Lagrangian and the invariant variational principle for the higher order KdV equation are discussed. The simplest version of the variational approximation, based on trial functions with two free parameters is demonstrated. The jost functions by quadratic, cubic and fourth order polynomials are approximated. Also, we choose the trial jost functions in the form of exponential and sinh solutions. All solutions are exact and stable, and have applications in physics. 相似文献
46.
风灾防护系统对于保障军交运输安全具有重要意义。本文针对风灾防护系统应用的不足,开展了需求分析,进行了工作模块设计,并提出了预警模式判别方法和防护措施的设计。该系统的逻辑步骤和模块设计符合强风条件下行车安全多因素决定性的客观特征,其具有成本优势。 相似文献
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Garzón-Alvarado DA Martinez AM Segrera DL 《Computer methods and programs in biomedicine》2011,104(3):489-497
The cerebral cortex is a gray lamina formed by bodies of neurons covering the cerebral hemispheres, varying in thickness from 1.25 mm in the occipital lobe to 4 mm in the anterior lobe. The brain's surface is about 30 times greater that of the skull because of its many folds; such folds form the gyri, sulci and fissures and mark out areas having specific functions, divided into five lobes. Convolution formation may vary between individuals and is an important feature of brain formation; such patterns can be mathematically represented as Turing patterns. This article describes how a phenomenological model was developed by describing the formation pattern for the gyri occurring in the cerebral cortex by reaction diffusion equations with Turing space parameters. Numerical examples for simplified geometries of a brain were solved to study pattern formation. The finite element method was used for the numerical solution, in conjunction with the Newton–Raphson method. The numerical examples showed that the model can represent cerebral cortex fold formation and reproduce pathologies related to gyri formation, such as polymicrogyria and lissencephaly. 相似文献
49.
Conventional controller designs for dynamic positioning of ships and floating marine structures have so far been based on the principle on automatic positioning in the horizontal‐plane about desired position and heading co‐ordinates defined by the operator. A three degrees‐of‐freedom multivariable controller either of linear or nonlinear type, normally with feedback signals from surge, sway and yaw position and velocities, has been regarded as adequate for the control objective. For floating structures with small waterplane area such as semi‐submersibles, feedback from roll and pitch angular rotation velocity may also be included to avoid thrust‐induced roll and pitch motions that are caused by the hydrodynamic and the geometrical couplings between the horizontal and vertical planes. However, for certain marine operations this control philosophy may not be the most appropriate approach ensuring safety and cost effectiveness. For drilling and work‐over operations the main positioning objective is to minimize the bending stresses along the riser and the riser angle magnitudes at the well head on the subsea structure, and at the top joint as well. A positioning control strategy solely based on manual setting of the desired position co‐ordinates may not be the most optimal solution for these applications. In this paper a new hybrid dynamic positioning controller, that also accounts for riser angle offsets and bending stresses is proposed. It is shown that a significant reduction in riser angle magnitude can be achieved. Simulations with a drilling semi‐submersible demonstrate the effect of the proposed control strategy. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
50.
较详细地分析了影响半导体力敏传感器性能的因素;介绍了圆膜片、片方膜、短形膜片上芯片的最佳设计方法.对研制开发新型的力敏传感器有一定的指导意义. 相似文献