混沌神经网络逆控制的同步及其在保密通信系统中的应用

利用神经网络的学习、逼近能力构造混沌神经网络，提出逆控制混沌同步方法来同步两个混沌神经网络，并基于逆控制和混沌神经网络的同步给出一种新的混沌保密通信系统.理论分析和数值实验结果表明，新系统能够有效地克服信道噪声对信息传输的不良影响，具有较强通用性和柔韧性，且有同步速度快，信号恢复精度高和密钥量大的优点. 关键词： 混沌同步 自适应逆控制 混沌神经网络 保密通信     

具有垂直各向异性(Pt/Co)n/FeMn多层膜的交换偏置

采用磁控溅射方法制备了以Pt为缓冲层和保护层的具有垂直各向异性(Pt/Co)n/FeMn多层膜.研究结果表明,多层膜的垂直交换偏置场Hex和反铁磁层厚度的关系与其具有平面各向异性的交换偏置场随反铁磁层厚度变化趋势相近.随着铁磁层调制周期数的增加,垂直交换偏置场Hex相应减小,并且与铁磁层的调制周期数近似成反比关系.(Pt/Co)3/FeMn的垂直交换偏置场Hex已经达到22.3kA/m.为了进一步提高Hex,在Co/FeMn的界面插入Pt层,当Pt层厚度为0.4nm时,Hex达到最大值39.8kA/m.     

大学物理实验教学改革的调查研究

近几年来，实验教学越来越受到重视．笔者向本学期开设大学物理实验课的3个院系972名学生发出调查问卷，访谈50多人次，加以分析研究后提出大学物理实验教学改革的几点意见．     

混合导电型陶瓷透氧膜材料的化学稳定性

考察了Sr-Co -Fe -O系列和Bi-Sr-Fe -O系列混合导电型无机透氧膜材料在氧分压小于 1.0 13Pa的气氛中 ,在 850℃和 950℃高温下加热 2 4～ 10 0h前后结构的变化。发现Bi -Sr -Fe-O系列透氧膜材料具有良好的化学稳定型 ,可以用于还原气氛下的催化反应。     

数学问题解答

2005年10月号问题解答(解答由问题提供人给出)1576求函数y=cscx-cotxarctan94≤x≤arctan23的值域.解如图,构造一组邻边分别为3、4,4、6的矩形ABCF,CDEF,P为线段BC上的任意一点,则∠EBD=arctan94,∠ECD=arctan32,∠EPD=x,BE=97,CE=213,PE=4cscx,PD=4cotx,PB=9-4cotx,PC=4cotx-6,由PE+PB≥BE,即4cscx+9-4cotx≥97,有cscx-cotx≥974-9①又PE-PC≤CE,即4cscx-4cotx+6≤213,有cscx-cotx≤132-3②由①、②,得974-9≤cscx-cotx≤13-32,即所求值域为974-9,132-3.1577D是△ABC的边AB的中点,E是BC边上的点,且AC=EB-EC,在边C…     

Double Jet Emission of Hot Electrons from a Micro-droplet Spray

Spatial distribution of hot electrons with energies above 50 keV are investigated by an ethanol micro-droplet spray irradiated by linearly and elliptically polarized 150 fs laser pulses at an intensity of 10^18 W/cm^2. Two symmetric hot electron jets with respect to the laser propagation direction are observed in the polarization plane for a     

Quantum spectra and classical periodic orbit in the cubic billiard

Quantum billiards have attracted much interest in many fields. People have made a lot of researches on the two-dimensional (2D) billiard systems. Contrary to the 2D billiard, due to the complication of its classical periodic orbits, no one has studied the correspondence between the quantum spectra and the classical orbits of the three-dimensional (3D) billiards. Taking the cubic billiard as an example, using the periodic orbit theory, we find the periodic orbit of the cubic billiard and study the correspondence between the quantum spectra and the length of the classical orbits in 3D system. The Fourier transformed spectrum of this system has allowed direct comparison between peaks in such plot and the length of the periodic orbits, which verifies the correctness of the periodic orbit theory. This is another example showing that semiclassical method provides a bridge between quantum and classical mechanics.     

Influence of Growth Temperature and Trimethylindium Flow of InGaN Wells on Optical Properties of InGaN Multiple Quantum-Well Violet Light-Emitting Diodes

An InGaN multiple-quantum-well (MQW) violet-light-emitting diode (LED) is grown by low-pressure metalorganic chemical vapour deposition. It is found that photoluminescence wavelength of the InGaN MQW violet LED is lengthened with increasing growth temperature and with the increasing trimethylindium flow of the InGaN wells. The electroluminescence peak wavelength of the violet LED are about 401 nm with full width at half maximum of 14nm, and the output power in injection current of 2OmA at room temperature is 4.1mW.     

评冯端、金国钧著《凝聚态物理学》（上卷）（高等教育出版社出版）

凝聚态物理是涉及面很广而又充满活力的学科．它描述自然界物质存在的最普遍形态，又是高新技术的基础．两次诺贝尔物理奖得主Bardeen曾不止一次将凝聚态物理比作一棵根深叶茂的大树，有些枝干会成熟、干枯，但会不断冒出新芽，长成新枝，开花结果．这是一幅很生动的写照．