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51.
Location information should be verifiable in order to support new computing and information services. In this paper, we adapt the classical challenge-response method for authentication to the task of verifying an entity's location. Our scheme utilizes a collection of transmitters, and adapts the power allocations across these transmitters to verify a user's claimed location. This strategy, which we call a power-modulated challenge response, is able to be used with existing. wireless sensor networks. First, we propose a direct method, where some transmitters are selected to send ldquochallengesrdquo that the claimant node should be able to witness based on its claimed location, and for which the claimant node must correctly respond to in order to prove its location. Second, we reverse the strategy by presenting an indirect method, where some transmitters send challenges that the claimant node should not be able to witness. Then, we present a signal-strength-based method, where the node responds with its received signal strength and thereby provides improved location verification. To evaluate our schemes, we examine different adversarial models for the claimant, and characterize the performance of our power-modulated challenge response schemes under these adversarial models. Further, we propose a new localization attack, where a set of nodes collaborates to pretend that there is a node at the claimed location. This collusion attack can do tremendous harm to localization and the performance of the aforementined methods under collusion attack are explained. Finally, we propose the use of a rotational directional power-modulated challenge response, where directional antennas are used to defend against collusion attacks.  相似文献   
52.
Pointer analysis is a technique to identify at copile-time the potential values of the pointer expressions in a program,which promises significant benefits for optimzing and parallelizing complilers.In this paper,a new approach to pointer analysis for assignments is presented.In this approach,assignments are classified into three categories:pointer assignments,structure(union)assignents and normal assignments which don‘t affect the point-to information.Pointer analyses for these three kinds of assignments respectively make up the integrated algorithm.When analyzing a pointer assigemtn.a new method called expression expansion is used to calculate both the left targets and the right targets.The integration of recursive data structure analysis into pointer analysis is a significant originality of this paper,which uniforms the pointer analysis for heap variables and the pointer analysis for stack variables.This algorithm is implemented in Agassiz,an analyzing tool for C programs developed by Institute of Parallel Processing,Fudan University,Its accuracy and effectiveness are illustrated by experimental data.  相似文献   
53.
系统地介绍了28000kN压铸机计算机控制系统的设计。在硬件方面,输入输出板均采用了光隔,抗干扰能力强。在软件设计上,采用定时中断,即实现了高速采样,又可周期性地扫描输入输出端口的状态,循环发出动作指令,这种模拟可编程控制器的程序设计方法,大大提高了整个系统的性能。  相似文献   
54.
Though principle component analysis (PCA) and locality preserving projections (LPPs) are two of the most popular linear methods for face recognition, PCA can only see the Euclidean structure of the training set and LPP preserves the nonlinear submanifold structure hidden in the training set. In this paper, we propose the elastic preserving projections (EPPs) which by incorporating the merits of the local geometry and the global information of the training set. EPP outputs a sample subspace which simultaneously preserves the local geometrical structure and exploits the global information of the training set. Different from some other linear dimensionality reduction methods, EPP can be deemed as learning both the coordinates and the affinities between sample points. Furthermore, the effectiveness of our proposed algorithm is analyzed theoretically and confirmed by some experiments on several well-known face databases. The obtained results indicate that EPP significantly outperforms its other rival algorithms.  相似文献   
55.
The dispersion of nanosilica that was modified and original in organic solvents could be judged directly by using methyl red as the indicator, and the principle of color development was also discussed. A method has been developed for the determination of the acidity of solid surfaces, which consists of titration of the solid suspended in benzene with n-butyl amine, using neutral red as the indicator. Basic indicator forms a red color on acidic solids, and the end-point of the titration is the disappearance of the red color. The text was submitted by the authors in English.  相似文献   
56.
Silane coupling agent was used to introduce polymeric groups that was C=C onto the surface of nano-SiO2 particles by self-assembling technique. Then, in situ grafted polymerization was carried out between the functionalized particles and butyl methacrylate monomers under the action of an initiating agent to accomplish the surface modification of nano-SiO2. The effect of different reaction conditions on grafting percentage was studied, and analyses of FTIR, TEM, and TG-DTA results show that new organic chains were introduced onto the surface of nano-SiO2, and the dispersion stability of nano-SiO2 in THF was obviously improved. The text was submitted by the authors in English.  相似文献   
57.
基于QuickServer设计并实现了支持IPv4和IPv6协议的Ftp服务器。对IPv4环境中的应用程序向IPv6迁移进行了实质性的探索和研究。  相似文献   
58.
CSP热连轧机振动性质的确定   总被引:1,自引:0,他引:1  
杨俊  吴迪平  秦勤  臧勇 《冶金设备》2006,(1):33-35,75
针对某钢厂CSP热连轧机出现的振动问题,综合运用现场实测和计算机仿真的方法对轧机振动的性质进行了系统的分析,并得到了如下初步结论:工作辊水平方向的振动是由主传动系统的扭转振动引起的强迫振动。  相似文献   
59.
深脱硫钢在LF炉中的脱硫处理   总被引:1,自引:0,他引:1  
讨论了LF炉添加脱硫剂对深脱硫钢进行脱硫的机理、脱硫剂的渣系选择及组成,并结合生产情况,着重介绍了LF炉添加脱硫剂的应用技术和效果.  相似文献   
60.
本文提出了由数字温度传感器组成的组态测温系统。它可使用手持设备调试器进行现场调试,并采用OPC和组态技术进行集成。文中详细阐述了系统组成原理,组件对象模型接口技术及组态软件。在本文基础上设计的测温单元已能在实际中应用。  相似文献   
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