基于HMM的分布式拒绝服务攻击检测方法

文章根据分布式拒绝服务攻击（DDoS）的本质特点，提出了一种基于隐马尔可夫模型（HMM）的DDoS攻击检测方法。该方法通过IP地址信息库．保存当前常用服务的源IP地址，然后对新到数据包的IP地址用HMM建模。通过离线训练，更新IP地址信息库，优化HMM参数。在线检测时，IP地址信息库在线学习更新，HMM实时检测．并根据检测结果通过边界路由器进行积极响应。实验结果显示，该方法具有很好的检测效果，并能及时响应，保持常用服务的延续性。     

路由器防范拒绝服务攻击技术研究

拒绝服务攻击给网络安全带来了巨大的威胁，防范DDoS攻击一直是安全领域的一个重要课题。介绍了路由器防范拒绝服务攻击的技术，包括IP路径重构技术、在源端防范DDoS策略、防范IP地址欺骗的机制和基于拥塞控制的方法，指出了进一步的研究方向。     

分布式拒绝服务攻击追踪方法的分析

分布式拒绝服务攻击（DDoS）给政府部门和商业机构的网络安全造成严重威胁。IP追踪技术能够反向追踪IP数据包到它们的源头,所以是识别和阻止DDoS攻击的重要一步。本文针对DDoS攻击,对比分析了各个IP反向追踪方法的基本原理和优缺点。     

基于流量强度的DDoS攻击源追踪快速算法

DDoS攻击以其破坏力大、易实施、难检测、难追踪等特点,而成为网络攻击中难处理的问题之一。攻击源追踪技术是阻断攻击源、追踪相关责任、提供法律证据的必要手段。基于网络拓扑理论和路由器流量特性原理以及可编程式路由器的体系结构,提出了一种追踪DDoS攻击源的分布式快速算法,该算法可以准确、协调、高效地判断路由器的数据流量值,受害者可以根据流量强度推断出恶意攻击数据流的来源,从而快速追溯和定位DDoS攻击源。     

基于流记录的非对称路由检测

针对同时使用多个ISP接入服务的校园网,网络边界路由的错误配置导致非对称路由现象发生,提出了一种基于流记录的非对称路由检测(FARD, flow-based asymmetry routing detection)方法。该方法利用TCP面向连接的传输特性结合IP地址的归属,基于边界路由器提供的流记录数据定位网络中可能存在非对称路由的IP地址。算法基于CERNET 2个主节点的接入路由器流记录进行了验证。     

基于代数方法的概率报文标注算法研究

网络攻击的追踪是对网络攻击做出正确响应的重要前提,采用代数方法,利用IP报文中的选项字段,以概率将流经路由器的地址标注报文,使得受攻击主机端能够利用被标注报文内的地址信息重构攻击路径,从而追踪到攻击源点.重点讨论了如何运用代数方法记录报文流经路由器的地址,以及利用报文中记录的信息重构路径使ISP部署相关策略对这些范围的主机加以防范.可以预见,网络攻击的追踪和路径重构技术仍将是目前网络安全一个重要的研究热点,而且随着IPv6的应用,攻击源追踪问题将取得实质性突破.同时指出了该方法存在的问题,并进行了进一步展望.     

焦作广电局内部办公网的外网访问

一、绪论 随着网络技术的发展和单位办公自动化（OA）技术的应用，焦作市广播电视局在内部办公局域网上建设了自己的办公自动化系统，运行近一年来，在方便内部办公方面发挥了较大的作用。焦作广播电视局的内部办公网通过路由器接入互联网，路由器具有一个固定IP地址。整个办公网通过路由器的DHCP动态IP功能连接外网。     

动态概率包标记算法分析及改进

IP追踪技术是防御拒绝服务攻击的一个研究热点。本文对IP追踪中的动态概率包标记算法进行了介绍和分析,在总结其优点的同时也发现其存在不足。针对动态概率包标记算法使得距离攻击者最近的边界路由器的标记负载太大的不足提出了一个可行性改进方案,经对比分析效果明显。     

并行网络模拟中远程路由策略的研究

首先对并行网络模拟所采用的远程路由策略进行了分析研究,之后提出了基于优化边界的远程路由策略.该策略用边界路由器ID取代目的IP地址作为路由转发方式,有效地提高了路由查询速度.同时,通过树区域收缩、后连节点去重和边界路由器去重3种方法降低了内存的占用量.基于PDNS的实验结果表明,相对于基于边界路由器的远程路由策略,该方法降低了85％的内存使用量,并减少了75％的模拟时间.     

针对DoS攻击的IP跟踪技术研究

IP追踪技术是检测和防御分布式拒绝服务攻击的重要手段,它的主要目的是想办法追踪到攻击数据包的源地址,弥补IP协议的不足。成熟的IP追踪技术可以有效抑制DDoS攻击的发生,对网络故障的诊断和减少数据包欺骗将有很大的帮助。文中对当前现有的IP追踪和攻击源定位技术作了系统的分类,分别对它们作了全面的分析并比较了相互之间的异同及优缺点。同时,针对当前的IP追踪和攻击源定位技术现状,讨论了其未来的发展趋势。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.