激光测距新方法研究

传统相位式激光测距存在着后续信号处理复杂 ,器件性能要求高的缺陷 ,本文通过信号分析 ,提出一种新的非合作目标激光测距方法 ,消除了传统相位式激光测距的缺陷     

A generalized higher order finite-difference time-domain method and its application in guided-wave problems

In this paper, a (2M,4) scheme of the finite-difference time-domain (FDTD) method is proposed, in which the time differential is of the fourth order and the spatial differential using the discrete singular convolution is of order 2M. Compared with the standard FDTD and the scheme of (4, 4), the scheme of (2M, 4) has much higher accuracy. By choosing a suitable M/spl ges/2, the (2M, 4) scheme can arrive at the highest accuracy. In addition, an improved approximation of the symplectic integrator propagator is presented for the time differential. On the one hand, it can directly simulate unlimited conducting structures without the air layer between the perfectly matched layer and inner structure; on the other hand, it needs only a quarter of the memory space required by the Runge-Kutta time scheme and requires one third of the meshes in every direction of the standard FDTD method. By choosing suitable meshes and bandwidth M, our scheme not only retains higher accuracy but also saves memory space and CPU time. Numerical examples are provided to show the high accuracy and effectiveness of the proposed scheme.     

IPSEC技术的研究及实现

介绍了IPSec技术的结构框架并详细讨论各个组成部分(包括认证协议头，安全加载封装安全保护机制，互联网密钥交换协议，解释域，策略等)，讨论了IPSec的实现方式，重点指出了隧道实现方式，并提出了IPSec隧道模式的一个实现框架。     

A prediction-based link availability estimation for routing metrics in MANETs

A Mobile Ad hoc Network (MANET) is a collection of wireless mobile terminals that are able to dynamically form a temporary network without any aid from fixed infrastructure or centralized administration. One critical issue for routing in MANETs is how to select reliable paths that can last as long as possible since terminal mobility may cause radio links to be broken frequently. To solve this problem, a criterion that can judge path reliability is needed. The reliability of a path depends on the number of links and the reliability of each link constituting the path. Many routing metrics in terms of number of links have been proposed, such as the shortest path routing. However, how to measure link availability or reliability in order to find more reliable paths has not been addressed adequately in the literature. (By a link being available, we mean that the radio quality of the link satisfies the minimum requirement for successful communication. Link availability is used to measure probability or degree that a link is available. The terms availability and reliability are used interchangeable in this paper.) This paper first introduces a prediction-based link availability estimation to quantify the link reliability. This quantity makes use of some instantly available information and also considers the dynamic nature of link status in order to properly reflect the link reliability. Then, this quantity has been further used to develop routing metrics for path selection in terms of path reliability to improve routing performances. The proposed schemes have been investigated through computer simulation.     

基于Goldreich压缩函数的LMAC分析和Hash设计

O.Goldreich等人在Ajtai的研究基础之上提出了一种基于格上最近向量难题(CVP)的压缩函数,该函数具有可证明碰撞免疫特性。文献[3]在文献[2]的基础之上设计了消息认证码LMAC,本文分析了LMAC安全性证明中存在的问题,并对LMAC进行了改进,使之能够达到文献[3]所声称的安全性。在此基础之上,本文利用Goldreich压缩函数构造了一种碰撞免疫的GHash函数,并分析了其安全性,提出了GHash的安全参数集。     

Modeling the Effect of Human Body on TOA Based Indoor Human Tracking

In time-of-arrival (TOA) based indoor human tracking system, the human body mounted with the target sensor can cause non-line of sight (NLOS) scenario and result in significant ranging error. However, the previous studies on the behavior of indoor TOA ranging did not take the effects of human body into account. In this paper, measurement of TOA ranging error has been conducted in a typical indoor environment and sources of inaccuracy in TOA-based indoor localization have been analyzed. To quantitatively describe the TOA ranging error caused by human body, we introduce a statistical TOA ranging error model for body mounted sensors based on the measurement results. This model separates the ranging error into multipath error and NLOS error caused by the creeping wave phenomenon. Both multipath error and NLOS error are modeled as a Gaussian variable. The distribution of multipath error is only relative to the bandwidth of the system while the distribution of NLOS error is relative to the angle between human facing direction and the direction of transmitter–receiver, signal to noise ratio and bandwidth of the system, which clearly shows the effects of human body on TOA ranging.     

IP微移动性协议研究

IP微移动性协议弥补了移动IP的不足,在一定的范围内可以提供快速切换。介绍了三种主要的微移动性协议：层次型移动IP、蜂窝IP、HAWAII,并对三种协议的主要性能进行了比较。通过仿真得到了层次型移动IP、蜂窝IP、HAWAII协议在不同情况下的分组丢失率,进一步的比较了三种协议的性能差异并分析了原因。最后给出移动IP研究的建议。     

流水线综合调度算法

在ASIC设计中,时序行为是设计者考虑的主要目标.高层次综合领域中时序约束下的调度算法对ASIC设计的优化结果起着重要作用.对于通信接口芯片设计,数据帧依照时间顺序依次到达,因此,采用流水线数据通道对帧数据进行处理是有效的优化方法.下文提出的对于流水线结构综合的调度算法采用拉格朗日松弛对系统进行初步估计,在次梯度迭代过程中对底层优化问题进行分解,以减小拉格朗日松弛的震荡.在对系统初步估计满足设计要求的情况下,采用粒子群算法进行优化,以求得在时序约束下的最优化流水线调度解.     

Preparation,Infrared Emissivity,and Dielectric and Microwave Absorption Properties of Fe-Doped ZnO Powder

Fe-doped ZnO powders have been synthesized by the coprecipitation method using zinc nitrate [Zn(NO₃)₂·6H₂O] as starting material, urea [CO(NH₂)₂] as precipitator, and ferric nitrate [Fe(NO₃)₃·9H₂O] as doping source. The microstructure of the prepared powders has been characterized by x-ray diffraction and scanning electron microscopy. Results show that, when the molar ratio of Fe to (Zn + Fe) was less than 0.09, the prepared powder was ZnO(Fe) solid solution, and the ZnFe₂O₄ impurity phase appeared when the Fe doping content was further increased. The electric permittivity in the frequency range of 8.2 GHz to 12.4 GHz and the average infrared emissivity in the wavelength range of 8 μm to 14 μm have been determined for the prepared powders. The average infrared emissivity decreased with increasing Fe doping content. The real (ε′) and imaginary part (ε″) of the permittivity of the prepared powders showed opposite trends. When the molar ratio of Fe to (Zn + Fe) was 0.03, the prepared Fe-doped ZnO powder demonstrated the best microwave absorption in the frequency range of 8.2 GHz to 12.4 GHz.