Pb(Zr0.52Ti0.48)O3 nanotubes synthesis and infrared absorption properties

Herein a useful methodology to synthesize the lead zirconate titanate (PZT) nanotubes via a dip-coating deposition process with anodic aluminum oxide (AAO) template is proposed. The nano-porous AAO templates were produced using a controlled two-step electrochemical anodization technique. The PZT/AAO composite was formed using the dip-coating wetting technique. The prepared PZT precursor solution was driven into the nanopore channels of AAO template under the driving force of capillary action, subsequently the sintering process of the as-filled templates was carefully tuned to obtain Pb(Zr_0.52Ti_0.48)O₃ nanotubes of crystalline tetragonal phase with uniform pore size and ordered arrange. Fourier transform infrared spectroscopy (FTIR) results show that in the 1200–1900 cm⁻¹ band, the composite structure of PZT/AAO has obvious absorption peaks at 1471.56 cm⁻¹ and 1556.09 cm⁻¹, the absorption intensity of the composite structure is about six times of pure AAO template. The unusual optical properties found in PZT/AAO composite will stimulate further theoretical and experimental interests in ferroelectric nanostructures.     

一种AVS亚像素运动估计快速算法

为提高图像的质量和压缩率,AVS视频标准中的运动补偿精确到了1/4像素,但采用亚像素全搜索算法的计算量太大,导致整个编码器的编码速率很低。针对该问题,提出一种新的亚像素运动估计快速算法,在保证图像质量的同时,使亚像素搜索点数减少53.0%~ 76.5%,视频序列总编码时间节省了23%~33%。     

基于AD9789的DVB-C调制系统的实现

设计了一个基于AD9789和低功耗FPGA Spartan-6的DVB-C调制系统。介绍了AD9789的基本结构、参数配置以及系统实现方式,给出了系统射频输出信号的实测结果,其性能指标符合国家标准。     

有意义的MD4碰撞攻击(英文)

2005年的欧密会,Wang等提出了一种构造MD4碰撞的有效方法,该方法不仅对寻找随机碰撞有效,还可以用于构造有意义的碰撞。以Wang的技术为基础,进一步分析和探讨了对构造纯文本文件有意义的MD4碰撞,给出了一种构造纯文本文件的有意义MD4碰撞的方法,概率为2-33.77。在1996年的FSE会议上,Dobbertin的"Crypt analysis of MD4"给出了一个有意义的碰撞,而其在开头包含了16个随机字符。这里给出了一个基于Latin-1字符集的有意义的碰撞。     

基于SVM和小波分析的脑电信号分类方法

根据癫痫脑电信号与正常脑电信号波形和能量特征的不同,研究了两种的脑电信号分类方法,一种采用支持向量机SVM(Support Vector Machines)分类器对正常脑电和癫痫脑电进行分类;另一种使用小波分析和支持向量机相结合的方法对脑电进行分类,并比较了这两种方法对正常脑电和癫痫脑电分类的正确率。实验结果表明,小波分析和SVM结合的方法对脑电信号分类可以取得更好的效果,能有效区分癫痫脑电和正常脑电。     

A split least-squares characteristic mixed finite element method for Sobolev equations with convection term

In this paper, a split least-squares characteristic mixed finite element method for a kind of Sobolev equation with convection term is proposed, in which the characteristic method is based on the approximation of the material derivative term, that is, the time derivative term plus the convection term. The resulting least-squares procedure can be split into two independent symmetric positive definite sub-schemes and does not need to solve a coupled system of equations. Theory analysis shows that the method yields the approximate solutions with optimal accuracy in L²(Ω) norm for the primal unknown and in H(div;Ω) norm for the unknown flux, respectively. Numerical examples in one dimension, which are consistent with the theoretical results, are provided to demonstrate the characteristic behavior of this approach.