基于三层交换机的校园网络防御体系探讨

高校校园网络是高校现代化建设中重要的组成部分,同样,其安全问题也受到各个方面的威胁,本文结合高校网络建设过程中校园网络的安全特点,对于基于三层交换机的校园网络防御体系进行了探讨,研究了基于三层交换机嵌入式病毒防御与信息监控系统要解决的技术问题,并依据现有的技术提出了解决方案及发展的趋势。     

Convergence analysis of geometrical multigrid methods for solving data-sparse boundary element equations

The convergence analysis of multigrid methods for boundary element equations arising from negative-order pseudo-differential operators is quite different from the usual finite element multigrid analysis for elliptic partial differential equations. In this paper, we study the convergence of geometrical multigrid methods for solving large-scale, data-sparse boundary element equations. In particular, we investigate multigrid methods for \(\mathcal{H}\)-matrices arising from the adaptive cross approximation to the single layer potential operator.     

Web服务安全性分析与研究

该文分析了目前Web服务所存在的安全问题,重点探讨了传输层和SOAP层的Web服务安全问题及安全技术,提出了SOAP加密、SOAP签名以及安全断言的安全技术,在一定程度上消除了Web服务所面临的安全威胁。     

实时信息系统的虚拟分层设计方案

本文借助软件系统分层设计的思想,提出了虚拟层的概念,并给出了一个实时信息系统虚拟分层设计方案,这为实际应用中各种规模的系列系统提供了一个组态灵活的开发方法。实践证明,这个方案取得了很好的效果,并具有很强的灵活性。     

Free and forced convection boundary layer flow through a porous medium with large suction

An analytical study is made of the free and forced convection boundary layer flow past a porous medium bounded by a semi-infinite vertical porous plate. Locally similar solutions are then obtained by a perturbation method for large suction. Solutions for the velocity and temperature distributions are shown graphically for various suction velocities and values of the driving parameter G_r/R, where G_r is the Grashof number and R_e is the Reynolds number. The corresponding values of the skin friction coefficient and the Nusselt number are finally shown in tabular form.     

Single-Iteration Training Algorithm for Multi-Layer Feed-Forward Neural Networks

A new methodology for neural learning is presented. Only a single iteration is needed to train a feed-forward network with near-optimal results. This is achieved by introducing a key modification to the conventional multi-layer architecture. A virtual input layer is implemented, which is connected to the nominal input layer by a special nonlinear transfer function, and to the first hidden layer by regular (linear) synapses. A sequence of alternating direction singular value decompositions is then used to determine precisely the inter-layer synaptic weights. This computational paradigm exploits the known separability of the linear (inter-layer propagation) and nonlinear (neuron activation) aspects of information transfer within a neural network. Examples show that the trained neural networks generalize well.     

A parameter uniform B-spline collocation method for solving singularly perturbed turning point problem having twin boundary layers

A numerical scheme is proposed to solve singularly perturbed two-point boundary value problems with a turning point exhibiting twin boundary layers. The scheme comprises B-spline collocation method on a non-uniform mesh of Shishkin type. Asymptotic bounds are established for the derivative of the analytical solution of a turning point problem. The present method is boundary layer resolving as well as second-order accurate in the maximum norm. A brief analysis has been carried out to prove the uniform convergence with respect to the singular perturbation parameter ? by decomposing the solution into smooth and singular components. Some relevant numerical examples are also illustrated to verify computationally the theoretical aspects.     

一种TCP友好的无线多跳网络拥塞控制算法

为了改进流媒体在无线多跳网络中的传输质量,提出一种TCP友好的拥塞控制算法.该算法考虑了MAC层的信道竞争,节点通过标记数据包来通知数据流它的竞争状态,数据流基于所估计的竞争状态来控制传输速率.仿真结果表明所提出的算法能更有效地利用带宽,与已存在的算法相比,有较高的吞吐量和较好的平滑性.     

U.v. absorbers in sun cosmetics 1978

A comprehensive survey has been carried out to establish which sun-screen agents are used by the cosmetics industry in Holland. During 1978, some 200 cosmetic sun preparations, composed of forty-eight brands, were purchased and analysed to determine which u.v. absorbing compounds were present. Most of those found were identified and quantified by means of thin layer chromatography and u.v. spectrometry. A basis for this work was the proposal by the European Cosmetic Manufacturers to produce a positive list of u.v. absorbers. It was felt that by carrying out this survey, some priority could be placed on the most popular materials used by the industry. When comparing those found with the European list of u.v. absorbers 1978, only twenty-four of the sixty compounds listed could be identified in the samples. The six most frequently used were found to be:

• 1 2-Ethylhexyl.p.methoxycinnamate (nineteen brands).
• 2 2-Phenylbenzimidazole.5-sulphonic acid (eleven brands).
• 3 2-Ethoxyethyl.p.methoxycinnamate (nine brands).
• 4 3 (4′Methylbenzylidene)D,D,L-camphor (seven brands).
• 5 3-Benzylidene.D,L-camphor (six brands).
• 6 2-Hydroxy.4-methoxy.benzophenone (six brands).

Usage levels varied from 0.4% up to 6.8%. Twenty-two products used a combination of two, and four products a combination of three sun-screens. Les filtres u.v. dans les produits anti-solaires 1978     

Material surface layer damage estimation for cyclic loading conditions using the nanoindenting and nanoscratching techniques

The nanoindenting method is based on the automatic measurement and recording of the force acting on the indenter (10⁻²-5 N) and the depth of indentation (10⁻²-200 μm). The scratch hardness or nanoscratching method is based on the continuous recording of resistance forces to movement of the indenter impressed into the surface. __________ Translated from Problemy Prochnosti, No. 4, pp. 132–139, July–August, 2006.