Uniform Approximation of Discrete-Space Multidimensional Myopic Maps

Our main result is a theorem that gives, in a certain setting, a necessary and sufficient condition under which discrete-space multidimensional shift-invariant input-output maps with vector-valued inputs drawn from a certain large set can be uniformly approximated arbitrarily well using a structure consisting of a linear preprocessing stage followed by a memoryless nonlinear network. Noncausal as well as causal maps are considered. Approximations for noncausal maps for which inputs and outputs are functions of more than one variable are of current interest in connection with, for example, image processing.     

一类混沌映射扩频序列的研究

Logistic混沌映射可产生用于扩频系统的跳频序列。该文用Logistic映射构造了一个二维混沌映射,证明了该二维混沌映射轨道点的概率密度分布,提出了一种混沌跳频序列的产生方法,并通过数值仿真分析了此类扩频序列的奇、偶相关特性和序列码的平衡特性.结果表明:该混沌跳频序列具有良好的性能。     

基于混沌迭代映射的加密算法研究

论文提出了一种新的基于混沌迭代映射的加密算法。文中采用了直接对明文ASCⅡ编码后的0,1序列进行加密的方式,使得混沌迭代输出序列进入任意类型子区域的概率大为上升,从而大大减少了对任意明文字符进行加密时混沌迭代映射所需要进行的迭代次数。同时,文中在混沌系统中引入一个动态变化的参数来代表当前的加密进程,使得即使相同的明文,在不同的加密进程中也被加密成不同的密文。仿真表明,无论在安全性还是效率方面和已有的算法相比都有显著的提高。     

单周期控制开关电容DC-DC变换器

传统的开关电容DC-DC变换器通常采用PWM控制方法，以输出电压或者开关管的电流作为反馈信号来调节占空比，然而占空比信号的变化不能即时跟随输入电压或负载的变化，因而PWM控制方法的动态调节响应较慢。单周期控制方法是一种非线性控制技术，该技术利用开关变换器的非线性特点，对开关变量平均值实现即时的动态控制，只需在一个开关周期之内就能使开关变量平均值达到稳态，因而具有较快的响应速度。本文介绍了单周期控制方法的基本原理，并将该方法应用于一个恒定频率的升压(5V／12V)开关电容DC-DC变换器的控制．仿真结果轰明该方法是可行的。     

一类混沌映射产生跳频序列的方法

 本文基于两个拓扑共轭的混沌映射具有相同的动力学行为.对一类与分段线性满映射拓扑共轭的混沌映射,提出了产生独立、均匀分布的混沌跳频序列的方法.并从理论上分析估计了该序列的平衡性和汉明相关性.最后,用切比雪夫映射进行了实验研究.结果表明:理论分析与实验结果是一致的,该序列具有良好的性能.     

用于CDMA的四相混沌扩频序列

本文由混沌映射产生用于直扩码分多址（ＤＳ／ＣＤＭＡ）系统的四相扩频序列，证明了周期为Ｎ的此类扩频序列的四种广义奇相关均服从均方值为Ｎ的瑞利分布。混沌四相序列的相关峰值较混沌二相序列有显著的下降，多址性能与传统四相扩频序列相同。     

基于混沌映射的图像保密通信系统及软件实现

提出了一种基于混沌映射的图像保密通信系统的软件实现。算法程序首次采用了图像数据的混沌掩盖加密和图像象素位置的置乱加密相结合的方法，对图像进行了两次复合的混沌加密。它具有恢复精度高、保密度高、破译难度大、执行速度快的特点。文中给出示例显示了算法程序的有效性。     

一种改进的变结构混沌序列性能分析

自提出了基于广义混沌映射切换的混沌同步保密通信方法以来,这种通过混沌映射切换来改变混沌系统结构,以此产生伪随机序列的方法被频繁引用.但这种方法产生的序列的综合性能却一直未能得到有力的证明,而且尚存在不能充分保证序列周期足够长的致命弱点.本文对这种变结构混沌序列产生方法作了动力学分析,并通过数值仿真对该方法产生的序列做了统计性能分析和抗预测性能研究.为了解决周期问题,本文在变结构混沌序列基础上引入了m序列扰动.结果表明这种改进的变结构混沌序列具有典型的混沌特性,而且产生序列的周期,相空间分布,线性复杂度,相关性以及抗预测性等方面的性能明显优于基于单一混沌系统的序列.     

一种带扰动的高维混沌图像加密算法

针对已有的部分混沌加密算法存在的问题,设计了一个带有扰动的高维混沌图像加密算法。通过对三维Lorenz系统添加扰动改善了序列的随机性,引入了三维猫映射对扩散后的图像进行置乱,并通过二次置乱来提高算法的安全性。分析与仿真结果表明,该算法具有较大的密钥空间,加密后图像像素值分布较均匀,相关系数接近于零,可以有效抵抗已知明文攻击。     

基于混沌映射的偏振移位键控光通信系统

提出了一种基于数字混沌与偏振移位键控(PolSK)技术的光保密通信系统.该系统选取几种偏振态部分或完全相同的PolSK方式,在系统不同时钟周期,发送端根据实时产生的数字混沌序列选用不同的PolSK方式调制信息,接收端利用同步的混沌序列与相应的PolSK方式解调信息.数字混沌序列的伪随机特性使得该系统的PolSK调制方式呈现无规则变化.当星座点个数不少于6且选用的PolSK方式不少于4种时,可选的PolSK组合超过1060种,系统的密钥空间庞大.用OptiSystem和Matlab软件相结合的方法进行了系统仿真,并做了一定的数值分析.仿真与分析结果表明,该光通信系统通信正常,具有较强的保密性.     

用于跳频码分多址通信的混沌跳频序列

最近提出的混沌跳频序列具有均匀性、保密性好的优点,但存在较大的汉明相关值,本文给出了一种减小混沌跳频序列汉明相关值的方法,该方法的构造的跳频序列是帆努利随机序列,汉明相关函数服从Ｐｏｉｓｓｏｎ分布,在跳频码分多址（ＦＨ／ＣＤＭＡ）系统中,,这种混沌跞频序列的系统容量与常规跳频序列基本相同。     

基于一维分段非线性Markov映射的混沌滚动密钥产生器

用拓扑共轭映射对一维分段线性映射进行非线性化处理,所构成的复合迭代混沌系统及其不变分布具有偶对称特性,最终生成的二值混沌序列具有理想的密码学特性。     

A Secure and Efficient Chaotic Maps Based Authenticated Key-Exchange Protocol for Smart Grid

Nicanfar and Leung proposed a multilayer consensus elliptic curve based password authenticated key-exchange (MCEPAK) protocol for smart grid. They claimed that their protocol is secure against possible attacks. In this paper, we show that the MCEPAK protocol is vulnerable to the dictionary attack and an adversary can obtain the passwords of the appliances by eavesdropping the communicated messages in the protocol. Moreover, we state that the passwords can be discovered by curious operators of the building area networks and the neighbor area networks. Theses weaknesses motivated us to introduce a chaotic maps based authenticated key exchange protocol for smart grid. To the best of our knowledge, the chaotic maps based key exchange protocol has not yet been devised for smart grid and the same objective has been fulfilled in this paper. In addition, we prove the security of the proposed protocol by a formal analysis.

     

基于荷控忆阻器的四阶混沌电路

近年来,基于亿阻器的混沌电路受到国内外学者的广泛关注.然而现阶段的研究,大都采用通过磁控忆阻器和负电导并联构成的有源忆阻器替代蔡氏电路中蔡氏二极管的方法.而采用荷控忆阻器的混沌电路大都同时使用荷控忆阻器与磁控忆阻器构成的五阶双忆阻器混沌电路.该文在蔡氏电路的基础上,采用荷控忆阻器与电感串联的形式构造了一个新的四阶忆阻混沌电路,并提出改进的忆阻器非线性特性曲线,通过数值仿真的方法进行了验证.最后,对这个新的四阶忆阻混沌电路进行动力学特性分析,主要通过李雅普诺夫指数和吸引子在相平面的投影.     

用PID控制非线性混沌振动的主动隔振研究

应用主动隔振的控制策略,设计了参数自调节的PID控制算法,对Duffing振子混沌振动进行了主动隔振仿真实验,取得了良好的隔振效果。研究结果表明了在混沌振中应用主动隔振技术的有效性。     

一种空频域结合的多维混沌系统图像加密方案

研究了一种基于二维Logistic映射和三维混沌的图像加密系统.首先利用二维Logistic映射产生加密模板对小波分解的低频系数进行调整,接着由Chen系统对小波重构之后的图像进行异或操作,进一步使加密性能得到了很大的提高.通过试验比较分析,该方案不但密钥空间大,而且对密钥和明文相当敏感,具有更优良的扩散性和扰乱性能,并能抵抗各种攻击.     

基于混沌密钥控制的联合信源信道与安全算术码编译码算法

该文针对深空通信、移动通信等资源受限网络中的信息有效性、可靠性和安全性传输,提出一种基于混沌密钥控制的联合信源信道与安全算术码编译码算法。该算法在编码端通过混沌映射1控制在算术码内嵌入多个禁用符号,将信道编码检错与密码流的扰乱相结合;同时,通过混沌映射2控制信源符号的算术编码,将信源编码与信息安全相结合,实现了联合信源信道与信息安全编译码。实验结果表明,该算法与现有的同类算法相比,当误包率为10-3时,改善编译码性能0.4 dB,同时增强了可靠性和安全性。     

Modulations and fading points

This document relates to NRZ and QPSK modulation codes or formats that have varying degrees of success in optical links. Indeed, these modulation formats undergo, during their path through the optical media, encounter the following limitations: (1) linear effects (attenuation, chromatic dispersion, polarization mode dispersion), (2) non-linear effects (Kerr, Raman and Brillouin effects). In addition to these limiting factors, the NRZ code in its propagation on the optical links encounters phenomena of fading of the signal as a function of the flow and the range. To reduce these fading phenomena, the QPSK code can be a solution. QPSK code makes it possible to reduce the number of fading points to the third on an optical link using a bit rate ranging from 10 to 30 Gbit s^?1.

     

Optical Chaotic Communication Using Generalized and Complete Synchronization

We propose a secure optical communication system based on the principles of generalized and complete chaotic synchronization. A transmitter and a receiver both composed by two chaotic external-cavity semiconductor lasers are coupled in a master-slave configuration to provide generalized synchronization, while the master lasers in the transmitter and in the receiver are completely synchronized through the synchronization channel via an optical fiber. A message is added to the transmitter slave laser and sent to the receiver through the information channel to be compared with the output of the receiver slave laser. The system is robust to a small mismatch of the laser parameters or of the coupling between the master and slave lasers, unavoidable in a real system, and can even enable a good communication up to a 5 Gb/s transmission rate using the chaos masking encryption method, when the master laseres are coupled bidirectionally.      

A Clustering Method Using Hierarchical Self-Organizing Maps

We describe a method of clustering that uses self-organizing maps (SOMs) in a method of image classification. To ensure that this clustering method is fast, we defined a hierarchical SOM and used it to construct the clustering method (M. Endo, M. Ueno, T. Tanabe, and M. Yamamoto, in Proc. of the IEEE Int. Workshop on Neural Networks for Signal Processing X, 2000, pp. 261–270). We define the clustering method in detail and outline its behavior as determined on the basis of both theory and experiment. We also propose a cooperative learning algorithm for the hierarchical SOM. Experiments on artificial image data confirmed the basic performance and adaptability of the SOM in clustering images. We also confirmed, both experimentally and theoretically, that our method is faster SOM, for the objects used in these experiments, than a method based on a non-hierarchical SOM.