构造IFS吸引子的新算法

迭代函数系统（IFS）是定义和描绘分形的有效方法，每个IFS确定了唯一一个称为吸引子的分形，随机迭代算法虽然能够简单快捷地在计算机上构造IFS的吸引子，但是不能保证在有限步内计算出组成吸引子的所有点，针对这一不足，利用IFS吸引子局部间具有的相似性，提出了由IFS中可逆仿射变换的不动点来逐步生成吸引子的原理和方法，实验证明，该算法是可行的，它不仅能在有限步内生成整个吸引子，并且不必引进概率。     

基于IFS理论的数字水印算法

为了使数字水印算法具有更好的鲁棒性,首先阐述了迭代函数系(iterated function system,IFS)理论,并给出了构造IFS吸引子的随机迭代算法;然后从理论分析了IFS吸引子抗几何失真的特性,并提出了一种非对称数字水印算法;接着利用三点法将数字水印信息转化为IFS码,并由重构的分形水印图像与原始图像进行相关性处理得到索引集;最后版权者和第3信任方用私钥将索引集进行数字签名和加盖时间戳。水印检测时,只需利用第3信任方和版权者的公钥,而不需要原始图像参与。实验结果表明,该算法对噪声、滤波、压缩、旋转等图像处理方法具有较好的鲁棒性。     

迭代函数系IFS吸引子的通用参数控制系统

讨论一个通用的参数控制方法，通过改变参数控制IFS吸引子的形状，最终生成不同的计算机图像。该方法首先给出两个原始三角图形，通过对两者位置和形状的改变得到IFS码，并通过不断引入新的三角形并改变其位置和形状来影响IFS吸引子的外观。最后，给出了利用此参数控制方法进行仿真试验所得到的几个经典IFS吸引子的图形。     

IFS吸引子范围的估算及应用

文章通过对IFS吸引子的分析,给出了IFS吸引子范围的估算公式和两种算法,这为IFS吸引子的计算机生成的通用算法提供了可能。     

Julia集的反函数迭代算法

在研究二次函数等简单幂函数的Julia（朱利亚）集过程中，发现传统的逃逸时间算法耗费机时，并且得到的是Julia集的填充集而不是Julia集的吸引子。该文介绍了Julia集的反函数迭代基本算法和基于IFS（函数迭代系）反函数迭代算法。并且在反函数迭代的基本算法的基础上，提出了通过对迭代顺序的改变，以减少在迭代过程中对内存空间的需求。文中将反函数迭代算法与传统的Julia集的逃逸时间算法进行了仿真对比，表明利用反函数迭代算法可以极大的减少机时，并且利用该算法可以得到Julia集的吸引子。     

二维迭代函数系统分形吸引子自适应对应变形算法

构造迭代函数系统（iterated function system,IFS）仿射变换的相似函数,并在所建立的IFS模糊相似图中搜索带约束条件的最佳路径最大化IFS模糊集隶属函数,从而确定2个IFS特征对应关系.通过插值实现二维IFS分形吸引子变形.实验结果表明：所给出的自适应模糊对应算法简单有效,为分形变形技术提供了一种新的处理方法.     

一种抗几何形变的数字水印方法的研究

基于迭代函数系统IFS的数字水印算法首先将数字水印信息转化成自相似分形集的IFS参数，然后给出由该IFS参数生成的自相似分形图对给定图像的嵌入和提取数字水印算法，最后，对该算法抗几何形变和JPEG压缩的顽健性进行了测试，结果表明基于IFS的数字水印算法具有很好的顽健性。     

基于凝聚IFS的三维树木风中模拟

针对目前模拟动态自然景物的方法存在的缺点和不足,提出一种风场凝聚迭代函数系统IFS(Iterated Function System)变形算法。首先根据风的自然规律建立风场数学模型,并利用物理原理计算推导出风力参数;然后从一个已模拟的三维树木IFS吸引子出发,将风力参数与凝聚IFS相结合来控制不同层次树木枝条的变形,使模拟的三维动态树木既符合自然规律又符合分形的一系列特征。最后,通过实验结果表明用这种算法可以有效地模拟出三维树木在风中的动态摇曳。     

基于离散余弦变换基函数迭代的人脸图像识别

使用非线性混沌方法处理与识别图像的研究工作逐渐增多,已有文献给出了一种 将正弦函数作为辅助函数与图像构造动力系统,迭代生成混沌吸引子作为图像特征。为进一步 探究图像吸引子作为图像的特性,改进识别效果,使用离散余弦变换(DCT)基函数矩阵代替正 弦函数,迭代生成近似混沌吸引子,用于人脸识别。首先,研究分析了DCT 基函数矩阵的多样 性与振荡特性;然后利用DCT 基函数矩阵与图像矩阵构造迭代表达式,通过给出的迭代算法使 其产生吸引子,再对吸引子进行快速傅里叶变换,计算相关系数,识别人脸图像。对于Yalefaces 图像库,每幅图像都参加训练,识别率可以达到100%,当使用每组前5 幅图像训练提取特征, 识别率可以超过85%;对于CMU PIE 数据库,每幅图像都参加训练,识别率可以超过99%。 该吸引子方法可以作为一种图像底层特征提取方法,有待于进一步深入研究。     

基于遗传算法的异构分布式并行分形图像压缩算法

阐述了一种有效的基于遗传算法和迭代函数系统(IFS)的二值图像压缩的基本思想和实现算法。同时，根据现有的并行遗传算法的框架，实现了一种基于遗传算法的异构分布式并行分形图像压缩基本模型算法，并在此基础上提出了复杂模型的设计方案。理论分析及实验结果表明，该分布式并行算法有较强的搜索能力，算法效率、可移植性较高，能找到近似最优的IFS解，其解码图像十分相似于原图像，并有很高的图像质量及压缩比。     

On the versatility of the combination of the weighted log-rank statistics

In many applied situations, it is difficult to specify in advance the types of survival differences that may exist between two groups. Therefore, it is tempting to use some tests that emphasize these differences, but are sensitive to a wide range of the survival differences. In this paper such versatile tests are considered, whose procedures are based on the simultaneous use of the weighted log-rank statistics that are asymptotically normal under the null hypothesis of no difference between two groups. Simulations are performed to examine power of the tests in small and moderate sample sizes when the data are uncensored to heavily censored. Implementation of the procedures are discussed in a real data example for illustration.     

On the versatility of the combination of the weighted log-rank statistics

In many applied situations, it is difficult to specify in advance the types of survival differences that may exist between two groups. Therefore, it is tempting to use some tests that emphasize these differences, but are sensitive to a wide range of the survival differences. In this paper such versatile tests are considered, whose procedures are based on the simultaneous use of the weighted log-rank statistics that are asymptotically normal under the null hypothesis of no difference between two groups. Simulations are performed to examine power of the tests in small and moderate sample sizes when the data are uncensored to heavily censored. Implementation of the procedures are discussed in a real data example for illustration.     

Modelling the dynamics of the tilt-casting process and the effect of the mould design on the casting quality

All titanium alloys are highly reactive in the molten condition and so are usually melted in a water-cooled copper crucible to avoid contamination using processes such as Induction Skull Melting (ISM). These provide only limited superheat which, coupled with the surface turbulence inherent in most conventional mould filling processes, results in entrainment defects such as bubbles in the castings. To overcome these problems, a novel tilt-casting process has been developed in which the mould is attached directly to the ISM crucible holding the melt and the two are then rotated together to achieve a tranquil transfer of the metal into the mould. From the modelling point of view, this process involves complex three-phase flow, heat transfer and solidification. In this paper, the development of a numerical model of the tilt-casting process is presented featuring several novel algorithm developments introduced into a general CFD package (PHYSICA) to model the complex dynamic interaction of the liquid metal and melting atmosphere. These developments relate to the front tracking and heat transfer representations and to a casting-specific adaptation of the turbulence model to account for an advancing solid front. Calculations have been performed for a 0.4 m long turbine blade cast in a titanium aluminide alloy using different mould designs. It is shown that the feeder/basin configuration has a crucial influence on the casting quality. The computational results are validated against actual castings and are used to support an experimental programme. Although fluid flow and heat transfer are inseparable in a casting, the emphasis in this paper will be on the fluid dynamics of mould filling and its influence on cast quality rather than heat transfer and solidification which has been reported elsewhere.     

XML模式到关系模式的转换研究

本文研究了XML模式，分析了已有的XML模式到关系模式的转换算法及其存在的问题，提出了新的转换算法XTR，并探讨了保留语义约束的方法。新算法更符合范式的要求，并且能处理多对多关系。     

新型智能材料在力/触觉反馈中的应用

新型智能材料电/磁流变液在电/磁场作用下,能够在几毫秒时间内由牛顿流体状态变为半固体状态.在简单介绍电/磁流变效应产生机理、特点的基础上,阐述了国内外几种典型的基于电/磁流变液体的力/触觉反馈设备的原理、结构和应用,比较了电/磁流变液的优缺点,总结了基于电/磁流变液设备的优势和存在的问题,展望了应用前景.     

标准标签报表系统分析与实现

随着质量监督系统要求的提高，开发一些对商品标签进行规范化的软件的需要越来越迫切。本文以某标准标签报表系统的项目需求为基础，详细介绍了对这一标准标签报丧系统的分析和设计。然后对各个功能的实现提出了几种实现方法，并对这些实现方法作了分析和比较。重点比较了顺序窗口的实现方法，选定了一种应用在了系统实现中，并详细介绍了这种方法的实现思路和具体程序。实践证明，这一系统在标准化商品标签的应用中是合理并行之有效的。     

复合模糊命题运算中的弱范数研究

在模糊诊断和分析问题中,一个复合命题往往由多个子命题组成,子命题之间除有合取、析取及加权平均运算关系外,还存在一种非常重要的弱逻辑关系。对基于单一数值表达的模糊命题间的合取、析取关系的最一般运算形式是三角范数和三角余范数。该文给出基于单一数值表示模糊命题的弱逻辑关系的最一般运算形式f范数和基于区间值表示的模糊命题弱逻辑关系最一般运算形式f-范数,具体给出相关算子,讨论了它们的性质及与传统的一些算子之间的联系,通过引入强f范的概念,给出了构造f－范数算子的一般方法,对具有弱逻辑关系复合模糊命题的真值运算可采用本文介绍的概念和方法。     

Remote sensing of the atmosphere and the small angle approximation to the solution of the radiative transfer equation

Modern methods of remote sensing of the atmosphere and the surface are based on minimizing the difference between simulated and measured reflectances. An iterative process to specify the model of the atmosphere is used, and the direct problems to the radiative transfer equation (RTE) are solved on each iteration loop. These direct problems have to be solved quickly for realistic models of the atmosphere under peaked-forward scattering by aerosol particles, water droplets, and ice crystals. Accurate and fast algorithms to solve the RTE under these conditions are in great demand. A method based upon the new version of small angle approximation to the singular component of the solution is presented. Numerical results in the problem on reflection of the visible light by aerosol and cloud layers are presented. Calculation time reduction due to the small angular technique is shown.     

应用马尔可夫链优化配置WiMax基站的带宽资源

本文对WiMax与WiFi融合组网结构中的WiMax基站带宽进行分配,应用马尔可夫链算法对分配过程进行优化,进行了大量的模拟实验,总结了一些关于如何配置WiMax基站带宽资源以提高网络性能的结论。     

Testing the link when the index is semiparametric—a comparative study

Generalized structured models are popular in applied statistics. They can circumvent the curse of dimensionality and provide results that are easy to interpret. However, there are two major concerns that need to be addressed before they are applied. Firstly, the credibility of the specified structure, such as additivity, and secondly, the specification of the link function need to be assessed. The focus is on the latter issue. In many cases it is feasible to estimate a nonparametric link, but the effort is often not justified. In contrast parametric links enable the use of likelihood-based estimates, which are asymptotically efficient, and which perform excellently in practice, particularly for small samples. Several statistics for testing the credibility of parametric link specifications are introduced. Estimation and implementation are discussed, and the performance of the statistics is compared in an intensive simulation study. Applications to real data are also described.