基于改进的粒子群算法的移动互联网扩散预测

为了准确预测移动互联网扩散趋势,采用一种改进的Bass创新扩散模型,将三个参数都表示为随时间变化的函数。为了得到精确参数值,提出一种新的粒子群优化算法,该算法在初始化阶段和运行过程中使用反向学习策略。引入种群密集度指标来判断种群收敛状态。当算法陷入局部最优时,对全局最优粒子进行柯西和高斯混合变异。实验结果表明改进后的粒子群优化算法能有效提高最优解精度和收敛速度,改进之后的Bass模型能够更准确的预测移动互联网扩散趋势。     

有害生物侵扰在多样化生境中的一种随机扩散过程及网络计算软件

生境多样性是自然界延缓有害生物扩散和毁灭性群体形成的重要机制。根据有害生物侵扰扩散的基本特征建立了有害生物侵扰在多样化生境中的一种随机扩散算法，研制了相应的网络计算软件PercoModel^(c)。该软件由8个Java类和一个HTML文件组成，可运行于多种操作系统和网络浏览器上，可读取多种类型的ODBC数据库文件，如MSAccess,Excel,FoxPro,dBASE等，该算法及软件可用于：（1）分析生境多样性，如不同生境的镶嵌格局和植物分布对有害生物扩散过程及其结局的影响；（2）分析生境和植物镶嵌格局对植物和昆虫疾病流行的影响；（3）研究生境和植物镶嵌格局对火灾蔓延的影响；（4）确定有害生物造成的损失及分布，以及探明最佳的生境和植物镶嵌格局等等。     

基于信息素扩散机制的双种群蚁群优化算法

针对基本双种群蚁群算法在进化中容易出现早熟、停滞的现象,对算法进行了改进.在双种群蚁群分别独立进化、定期进行信息交换的基础上,提出一种新的蚁群优化算法,通过建立信息素扩散模型,并在每种蚁群的局部信息素更新上采用扩散模型,使蚂蚁更好的发挥了协作能力.以旅行商(Travel Salesman Problem,TSP)问题为例的仿真实验表明,该算法比基本双种群蚁群算法具有更好的收敛速度和寻优能力.     

模拟煤层气泄露扩散的高斯改进模型

为准确预测煤层气泄露污染的扩散路径及范围,结合了我国煤层气低压、管网密集和地处山区的特点,以高斯扩散模型为基础,提出适合煤层气泄露扩散模拟的高架点源模型和山谷模型,根据第二代大气扩散模型对地形产生影响的处理方法,研究了适合山区的扩散模型。以山西省沁水盆地南部潘河区块煤层气集输工程为例,模拟了煤层气泄露扩散,并与野外实验数据进行比较,发现提出的煤层气泄漏扩散模式能够较好地模拟煤层气在空气中的扩散分布状况。     

求解动态优化问题的自组织进化算法

为在环境发生变化后跟踪最优解的变化,提出一种自组织单变量边缘分布算法(SOUMDA)来求解动态优化问题.自组织策略包含扩散和惯性速度模型,扩散模型利用当前环境的局部信息使群体向外扩散,惯性速度模型利用最优解的历史信息进行预测.将自组织策略与单变量边缘分布算法(UMDA)结合,使得算法在环境变化后自适应地增加种群多样性,提高算法适应能力,快速跟踪最优解.利用动态sphere函数对所提出的算法进行测试,并与UMDA和MUMDA算法进行比较,结果表明所设计的算法能快速适应环境的变化,跟踪最优解.     

一类分数阶种群扩散模型解的研究

从推广的Fick扩散定律出发研究了一类时间分数阶Fisher单种群扩散模型。利用变分迭代法求解了三种不同情况下的近似解,对结果进行了讨论和数值模拟。     

牺牲层腐蚀改进模型与模拟研究

牺牲层腐蚀主要受腐蚀液的扩散过程制约,由扩散方程决定.扩散系数在腐蚀过程中随温度和腐蚀液浓度变化而改变.文中对改进的腐蚀模型给出有限差分算法,由每一时刻溶液在具体位置的浓度值得出扩散系数,再由Topography模型计算前端面的腐蚀情况得到腐蚀前端行进的轮廓线.并编程对一些MEMS结构的释放过程进行仿真,最后给出实验验证.     

应用遗传算法仿真墨扩散轮廓

墨扩散效果的模拟是水墨画仿真的重要工作之一,在分析绘画材料特性和扩散形成机制的基础上,提出一个全新的基于遗传算法的墨扩散仿真模型系统.首先将笔迹和纸张离散化为笔元和纸元;其次借用遗传算法基本概念和原理,对给定的输入笔迹进行轮廓提取作为初始种群,通过种群个体间的选择、重组和变异等遗传活动模拟笔元的扩散过程;最后为了更好地模拟墨扩散方向,使用Ashikhmin算法合成各种宣纸的自然纹理,增强了真实感.实验结果表明,方法可以生成丰富的扩散效果,并且接近真实水墨画.     

基于扩散机制的双种群粒子群优化算法*

为了避免标准粒子群优化算法（PSO）过早收敛的缺点,把热力学中的扩散现象引入到PSO算法的改进当中,提出了基于扩散机制的双种群粒子群优化算法(DPSO)。DPSO算法中定义了粒子的扩散能、种群的温度和粒子的扩散概率三个概念,两个群体中的粒子在进化过程中根据粒子的扩散概率被选入到各自种群的扩散池中,从而实现两个种群之间信息的交换和共享。通过解决典型的多峰、高维函数优化问题来证实DPSO算法的有效性,实验结果表明DPSO比标准PSO具有更高的性能。     

电子邮件病毒传播仿真模型及影响因素模拟

通过对传统sEIR模型进行扩展和修正,建立了一个适合模拟电子邮件（E-mail）病毒在网络系统内扩散的E-sEIR模型,并以此为基础研究了E-mail用户的邮件信息处理行为和反病毒技术支持等关键因素对E-mail病毒扩散的影响.从实验结果看,E-SEIR模型能够很好模拟E-mail病毒在网络系统中的扩散过程,同时也可用于E-mail信息网络中环境参数和某些病毒控制策略的模拟和评价.     

New results on the Gaussian projection filter with small observation noise

In this paper we define a one dimensional Gaussian projection filter (GPF) for a one dimensional diffusion and show that it behaves as nicely as the previously studied two dimensional GPF w.r.t. the true state. We extend part of the results on its nice behaviour to systems with bounded but not necessarily Lipschitz drift, and observe that in this case the resulting efficient filter does not depend on the drift itself.     

基于高维超混沌系统和矩阵张量积的图像分组加密新算法

目前混沌加密算法主要存在三方面的不足:1)采用低维混沌序列造成混沌退化;2)采用的混沌系统结构过于简单;3)算法只依赖于混沌系统的结构和密钥。针对这些不足,提出一种新的图像分组加密算法。为了克服混沌退化,算法借助矩阵张量积将高维超混沌系统所产生混沌序列和一维混沌序列充分耦合,产生像素扩散矩阵。在此过程中,用明文信息控制扩散矩阵生成,使算法与明文相关,提高了算法的安全强度。     

Development of new encryption system using Brownian motion based diffusion

Multimedia Tools and Applications - A new cryptographic model is proposed incorporating intertwining logistic map based confusion process and two dimensional Brownian Motion based diffusion...     

A CCD–ADI method for unsteady convection–diffusion equations

With a combined compact difference scheme for the spatial discretization and the Crank–Nicolson scheme for the temporal discretization, respectively, a high-order alternating direction implicit method (ADI) is proposed for solving unsteady two dimensional convection–diffusion equations. The method is sixth-order accurate in space and second-order accurate in time. The resulting matrix at each ADI computation step corresponds to a triple-tridiagonal system which can be effectively solved with a considerable saving in computing time. In practice, Richardson extrapolation is exploited to increase the temporal accuracy. The unconditional stability is proved by means of Fourier analysis for two dimensional convection–diffusion problems with periodic boundary conditions. Numerical experiments are conducted to demonstrate the efficiency of the proposed method. Moreover, the present method preserves the higher order accuracy for convection-dominated problems.     

On Rényi information for ergodic diffusion processes

In this paper, we derive explicit formulas of the Rényi information, Shannon entropy and Song measure for the invariant density of one dimensional ergodic diffusion processes. In particular, the diffusion models considered include the hyperbolic, the generalized inverse Gaussian, the Pearson, the exponential family and a new class of skew-t diffusions.     

Regional output feedback stabilization of semilinear time‐fractional diffusion systems in a parallelepipedon with control constraints

This article is concerned with the regional output feedback stabilization problems for semilinear time‐fractional diffusion systems in a 1≤n?dimensional parallelepipedon with control inequality constraints. For this, the spectrum decomposition method is used to derive a finite‐dimensional fractional ordinary differential equation (ODE) system that captures the dominant dynamics of the considered system. With this ODE system, we propose a finite‐dimensional fractional compensator to guarantee that the constrained closed‐loop semilinear systems are Mittag‐Leffler stable in some subregions of their evolution domains. An example is finally included to illustrate our results.     

基于三维亚仿射变换的数字图像置乱技术

为了提高数字图像信息隐藏的安全性和灵活性,利用亚仿射变换的原理设计了一种新的基于三维亚仿射变换的图像加密算法。该算法通过分析三维亚仿射变换的约束条件,根据变量之间的联系和随机性,给出了一种三维亚仿射变换的快速构造方法。在色彩空间中对每个像素点的三个色彩分量选择不同的方式进行变换,达到图像置乱的效果;对其周期性进行了研究,并提出了奇异点与伪周期的概念。经实验验证,该算法置乱效果良好,具有密钥空间较大、加密灵活、扩散性和扰乱性比较理想、安全性较高的优点。     

Orthogonal spline collocation scheme for the multi-term time-fractional diffusion equation

A novel numerical technique is considered for the solution of a multi-term time-fractional diffusion equation. The orthogonal spline collocation method is used for in space, and a finite difference method in time. The stability and convergence are provided. The numerical experiments for one and two dimensional problems support our theoretical analysis.     

Anisotropy Preserving DTI Processing

Statistical analysis of diffusion tensor imaging (DTI) data requires a computational framework that is both numerically tractable (to account for the high dimensional nature of the data) and geometric (to account for the nonlinear nature of diffusion tensors). Building upon earlier studies exploiting a Riemannian framework to address these challenges, the present paper proposes a novel metric and an accompanying computational framework for DTI data processing. The proposed approach grounds the signal processing operations in interpolating curves. Well-chosen interpolating curves are shown to provide a computational framework that is at the same time tractable and information relevant for DTI processing. In addition, and in contrast to earlier methods, it provides an interpolation method which preserves anisotropy, a central information carried by diffusion tensor data.     

Stochastic differential equations with variable structure driven by multiplicative Gaussian noise and sliding mode dynamic

This work is concerned with existence of weak solutions to discontinuous stochastic differential equations driven by multiplicative Gaussian noise and sliding mode control dynamics generated by stochastic differential equations with variable structure, that is with jump nonlinearity. The treatment covers the finite dimensional stochastic systems and the stochastic diffusion equation with multiplicative noise.