一种高安全性的级联型混沌扩频序列

针对传统一维混沌映射产生序列复杂度低、保密性不理想等问题,提出了一种基于Logistic改进型映射和Cubic映射的级联型混沌序列。新序列的混沌映射表达式由原来的低次一阶差分方程扩展为高次二阶差分方程,映射迭代过程由单级迭代变为二级交叉迭代,从而提高了混沌系统的复杂性。对新序列的非线性动力学混沌特性和扩频通信性能进行了仿真对比,结果表明新序列具有混沌吸引子结构更加复杂、初值敏感性更强、序列复杂度更高、安全性更好的特点,最后验证了新混沌序列具有和传统一维混沌序列相当的扩频特性。     

基于双重混沌映射的数码防伪技术研究

提出了一种基于双重混沌映射系统对商品的生产号进行数字加密的加密算法.在加密的过程中用二维lo-gistic映射和Henon映射联合对商品的生产号进行加密,得到商品的防伪码,并对双重混沌映射的性能进行了分析,利用双重混沌系统的伪随机性、初值敏感性、遍历性等所特有的性质,得出双重混沌映射具有良好的密码学特性,提高了算法的复杂度,增大了算法的密钥空间,增加了破译的难度,使商品在流通的过程中具有更强的防伪性能.     

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。     

基于混沌映射的数码防伪技术研究

提出了一种基于混沌映射的数码防伪的加密算法.在加密的过程中,选用结构相对简单且生成序列相对复杂的正弦混沌映射和Chebyshev映射.对两个混沌映射进行敏感性和随机性测试,得出两个混沌映射具有良好的密码学特性,并验证得出该加密系统具有良好的加密性能.应用该混沌系统进行加密,提高了算法的复杂度,增大了密钥空间,提高了破译难度,使商品在市场流通的过程中具有更强的防伪性能.     

一类混沌映射扩频序列的有限精度实现及其相关性能分析

低维混沌映射序列具有类似白噪声的统计特性，可有效地用作扩频地址码，但有限精度问题影响了它在实际中的应用。本文提出了一种基于素数的拟混沌序列的产生方法能够很好地逼近理想的混沌映射，从而可产生大量具有良好相关性能的序列，对序列统计特性的分析验证了这一点。     

改进分段Skew Tent 映射及其在扩频通信中应用

混沌序列用作扩频系统扩频码,具有码元丰富、保密性好等优点。针对传统Skew Tent 映射所产生随机序列的混沌特性较弱,特别是其随机性、相关性等指标较差等不足,将Skew Tent 映射进行分段对偶扩展获得一种改进分段Skew Tent 映射构造方法,并将其所产生的随机序列用于构造扩频通信系统的扩频码。通过扩频通信系统仿真测试验证了改进分段Skew Tent 映射相比Skew Tent 映射具有更加良好的混沌特性,以及所产生随机序列作为扩频系统地址码在降低系统的误码率方面有了较大的改善。改进分段Skew Tent 映射作为加密算法用于图像通信系统中,有效提高了图像信息的传输质量和安全性。混沌映射进行分段对偶扩展是一种行之有效的改进方法,混沌特性更好的迭代映射更利于扩频通信在军民领域的广泛应用。     

一种新型离散指数混沌映射的实现及其研究

针对Logistic映射参数简单、混沌区间范围小的缺点,提出一种新型的离散指数混沌映射。通过引入指数项和增加参数个数,进而扩大映射的混沌区间。利用常规的动力学分析方法,对指数混沌映射进行了动力学特性分析,包括Lyapunov指数图、分岔图等。在此基础上,对Logistic映射和离散指数混沌映射进行了特性比较。最后对由该离散混沌映射产生的序列进行NIST测试,测试结果表明序列性能更良好。     

基于Cat映射和Lu混沌映射的图像加密方案

由于混沌系统对初始条件和混沌参数非常敏感,以及生成的混沌序列具有伪随机性的特性,近年来在图像加密领域得到了广泛的应用.经典的Arnold cat映射通过迭代虽然可以改变图象各像素点的位置,但是多次迭代之后会还原出原始图像,给系统带来一定的安全隐患.使用Arnold cat映射和Lu混沌映射可以有效地避免这一缺点,从而实现混淆和扩散的目的.通过仿真实验,结果分析表明该种方法能够得到令人满意的加密效果.     

一种基于混沌猫映射的图像加密算法

在传统混沌猫映射基础上提出了一种改进的三维混沌猫映射算法。该算法将图像的像素坐标和灰度值作为广义猫映射的初始值,映射参数和迭代次数作为密钥,应用到图像加密中。理论证明所提出的三维混沌猫映射改进算法具有可逆惟一性,且具有像素位置置换和替代作用。同时试验结果表明该算法对二维图像混沌加密是有效的。     

Logistic混沌映射性能分析与改进

混沌系统是基于混沌的数据加密领域的一个重要研究对象,Logistic混沌映射是最简单和有效的混沌系统,被广泛应用在大多数混沌加密算法中,Logistic映射的安全性成为研究的热点。针对Logistic序列存在的吸引子与空白区问题,该文提出一种基于初始值和分形控制参数之间关系的Logistic映射改进方法。利用两者之间关系对映射自变量区间进行合理分段,扩大了混沌控制参数区域,将满射范围扩大到整个控制参数区间,使产生的序列分布更均匀,解决了稳定窗与空白区等问题。通过将改进Logistic与其它分段Logistic映射进行仿真对比,实验结果表明改进后的映射产生的序列混沌特性得到显著加强,分布更均匀,具有更好的随机性能测试指标。另外,改进Logistic映射计算复杂度低,实现简单,在扩频通信与混沌密码等领域有广阔的应用前景。     

基于混沌的双组合图像置乱算法研究

为了解决图像置乱算法在加密强度和算法泛化性方面存在局限性的问题,提出了双组合置乱算法,该算法充分利用了混沌映射无序、随机、对初值敏感的特性,将Logistic混沌映射巧妙地应用于序列交叉原则上。解决了直接序列交叉算法只适用于偶数元素图像的局限性,并且将单个密钥的敏感精度提高到10-9数量级。此外,实验结果表明应用该方法置乱后的图像,其像素相关性比直接应用序列交叉原则置乱后的图像像素相关性更小。     

Pulse broadening factor as a criterion to assess nonlinear penalty of 40-Gbit/s RZ-DQPSK signals in dynamic transparent optical networks

The real-time scheduling and routing in dynamic transparent optical networks requires fast and accurate evaluation of transmission penalty caused by nonlinear kerr effects with different dispersion maps. However, the conventional method using nonlinear phase shift can only be applied to assess the nonlinear penalty with optimized dispersion maps. In this paper, we introduce pulse broadening factor into the approach and propose a novel method to accurately evaluate nonlinear penalty and numerically investigate the feasibility of our novel method in 40-Gb/s Return-to-Zero Differential Quadrature Phase-Shift Keying (RZ-DQPSK) systems. Simulation results show that our approach can achieve good evaluation performance even with non-optimized dispersion maps.     

Tactile maps provide location-based services for individuals with visual impairments

People with visual impairments are unable to collect the external visual stimuli from the environment or to use conventional maps. Hence, the importance of tactile maps as informational and orientation means is undoubted. The blind user perceives the information graphed on the tactile map by feeling the elements of the map with the fingertips. There has been considerable research into the design of these maps over recent decades, providing answers to most of the questions which have arisen concerning their intelligibility–the use of symbols, for example, and the implementation of uniform standards to make the maps generally accessible. For the production of tactile maps a number of methods have been developed worldwide. The introduction of new technologies has contributed to the design and production of tactile maps, following procedures appropriate to the special needs of tactile mapping, with automatic cartography. During the procedure of implementing a tactile map with the use of a personal computer, a basic stage is the construction of a digital map. In this article, the design of tactile maps of Thessaloniki (the second largest city in Greece) is discussed, with special emphasis on a number of relevant issues influencing the whole process.     

A Method for Auto-Inputting Color Maps

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矢量地图图形的多功能显示

本文着重研讨了一种根据计算机图形学中空间分布的型值点来构造插值样条曲线的造型方法。用此方法对矢量地图进行分层（分类）显示，并且能够对恢复后的矢显地图进行放大与缩小变换和特写显示。     

Separation Conditions,Myopic Maps,and Criteria for Uniform Approximation of Input-Output Maps

This paper considerably extends recent discrete-time (and discrete-space) results concerning the problem of obtaining criteria under which input-output maps can be uniformly approximated arbitrarily well using a certain structure consisting of a not-necessarily linear dynamic part followed by a nonlinear memoryless section that may contain sigmoids or radial basis functions, etc. In those results certain separation conditions of the kind associated with the Stone-Weierstrass theorem play a prominent role and emerge as criteria for approximation—not just sufficient conditions under which an approximation exists. Here we give corresponding results for a much larger set of maps of interest. More specifically, corresponding results are given for an important family of continuous-time and continuous space systems. As an example, it is shown that a large class of continuous-space myopic systems with continuous inputs can be uniformly approximated arbitrarily well using just a bank of shift operators followed by a nonlinear memoryless section. This directs attention to approximants for such systems of a very different type than those discussed earlier in the literature. In another example, a new result is given concerning the uniform approximation of a large class of myopic continuous-time systems with inputs that may have discontinuities.     

Monitoring the Formation of Kernel-Based Topographic Maps with Application to Hierarchical Clustering of Music Signals

When using topographic maps for clustering purposes, which is now being considered in the data mining community, it is crucial that the maps are free of topological defects. Otherwise, a contiguous cluster could become split into separate clusters. We introduce a new algorithm for monitoring the degree of topology preservation of kernel-based maps during learning. The algorithm is applied to a real-world example concerned with the identification of 3 musical instruments and the notes played by them, in an unsupervised manner, by means of a hierarchical clustering analysis, starting from the music signal's spectrogram.     

基于共形对应的球面图像的计算全息图

研究了基于共形对应的球面图像的计算全息图(CGH)的生成和重现.通常,当用平面波照射全息图时,所重现的图像一般显示在平面上.共形对应在计算机图形学中被广泛应用,它可以将平面图像和任意曲面对应.相对于简单的坐标变换,共形对应关系具有很多优点,如它可以保持变换前后图像之间的几何形状不变性等.将共形对应引入计算机全息图的生成过程中,利用平面与球面的共形对应关系,生成显示于球面的二维图像的计算全息图,并由所生成全息图得到原始图像,从而实现整个全息记录和重现过程的计算机模拟.二维图像重现于球面实际上了产生三维显示,因此上述方法在从计算全息图重现三维图像方面起到重要的作用.     

结合深度信息的多视点视频编码快速模式选择算法

多视点视频加深度(MVD,multi-view video plus depth)的编码格式包含多个纹理视频序列及其对应的深度图,深度图与对应的纹理视频具有相似的边缘信息。传统的编码模式不考虑两者的联系,单独编码导致复杂度高、编码时间过长。因此,合理利用深度图与纹理图的相似性进行编码,可以有效降低编码复杂度,同时应该确保编码质量不受影响。本文利用深度图的这一特点辅助纹理视频的编码,提出一种帧间快速模式选择算法,充分利用深度图与纹理图之间的相似性,建立一种联合复杂度模型,根据模型得到每个宏块的复杂度。对于复杂度低的宏块,在计算率失真代价之前跳过编码中一些不必要的模式,从而降低编码复杂度。实验表明,本文提出的快速模式选择算法,在保证率失真性能基本不变的情况下,能减少60.57%的编码复杂度,并最高能减少80.64%的编码时间。     

Approximation of Myopic Systems Whose Inputs Need Not Be Continuous

Our main result is a theorem that gives, in a certain setting, a necessary and sufficient condition under which multidimensional shift-invariant 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. The inputs considered need not be continuous, and noncausal as well as causal maps are addressed. 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.