百度百科合作网络的分形生长机制研究*

基于复杂网络理论,引入和研究百度百科贡献者的合作网络的网络特性和生长机制。根据网页抓取的百度百科数据建立贡献者的百度百科合作网络,并对网络的相应拓扑指标进行分析,揭示网络的特点。用网络分形的思想对百度百科合作网络的网络谱的结构进行分析,结果发现百度百科合作网络的网络谱具有单分形的结构特性并且Hurst指数小于0.5。从分形的角度探讨网络的生长机制,百度百科合作网络的生长方式具有倾向于hub节点与非hub节点相连的特性。     

网络流量模型的非线性特征量的提取及分析

本文基于相空间重构理论,在高维相空间中对网络流量的宏观和微观特性进行研究分析.首先,提取网络流量的宏观非线性特征量,如关联维数、Kolmogorov熵和最大Lyapunov指数,实现了网络流量时序非线性动力学特性的定量分析.然后,通过对四种典型突发性流量模型的多重分形谱的计算,揭示了流量模型不同层次的行为特征,并给出了刻画突发性流量的有效微观参数.为进一步利用混沌动力学理论对网络行为的控制和建模奠定了基础.     

MPEG-4视频业务的多重分形分析与建模

基于对象编码的MPEG-4视频业务将是网络业务中的主流业务，因而研究MPEG-4视频业务的特性对网络设计，容量规划，性能评估，接入控制与性能分析有重要的意义。通过应用多重分形分析方法对MPEG-4视频业务的分形行为进行分析，结果表明MPEG-4视频业务多重分形特性的存在，因而采用多重分形小波模型对MPEG-4视频业务进行建模分析，通过仿真试验结果的比较和分析，表明该模型能够真实反映MPEG-4视频业务的突发特性。     

基于多重分形的雷达目标的模糊检测

利用多重分形的概念对海杂波和舰船雷达目标回波进行了分析,并提取出其多重分形特征用于舰船目标检测.实验表明,广义维数谱具有良好的可分性和稳定性.在检测中,将待查信号分为两类:海杂波目标和舰船目标,将广义维数谱作为特征矢量,计算其相对于两类目标的隶属度并作出判断.多组检测实验证明了该方法的有效性和实用性.     

粗糙薄膜表面的原子力显微镜研究和多重分形分析

用一系列生成元模拟了具有不同特征的、与原子力显微镜图像相似的规则粗糙表面。详细讨论了规则粗糙表面多重分形谱参数的意义。并通过与方均根粗糙度（rms）和简单分形维数D0的比较，描述了多重分形分析的优点。最后用多重分形的方法分析了由AFM测量的ZnO薄膜和高聚物PtBuA薄膜的表面形貌。     

Domain Wall Dynamics Near the Phase Transition in PZN-9%PT

To investigate the paraelectric–ferroelectric phase transition in relaxor Pb(Zn_1/3Nb_2/3)O₃-9% PbTiO₃, correlations and scaling relations were measured from the domain structure of single crystals near the Curie temperature using a multifractal analysis. The dynamics of the domain walls were observed in (100) platelets using polarized light microscopy. The complexity of the domain wall distribution was evaluated by means of its fractal dimension and singularity spectrum. The changes in the energy state of the samples are assessed by measuring changes of the spatial distribution of the walls as a function of temperature; this can be used to estimate the specific heat.     

Multifractal analysis of inclined oil-water countercurrent flow

Characterizing countercurrent flow structures in an inclined oil-water two-phase flow from one-dimensional measurement is of great importance for model building and sensor design.Firstly,we conducted oil-water two-phase flow experiments in an inclined pipe to measure the conductance signals of three typical water-dominated oil-water flow patterns in inclined flow,i.e.,dispersion oil-in-water pseudo-slug flow （PS）,dispersion oil-in-water countercurrent flow （CT）,and transitional flow （TF）.In pseudo-slug flow,countercurrent flow and transitional flow,oil is completely dispersed in water.Then we used magnitude and sign decomposition analysis and multifractal analysis to reveal levels of complexity in different flow patterns.We found that the PS and CT flow patterns both exhibited high complexity and obvious multifractal dynamic behavior,but the magnitude scaling exponent and singularity of the CT flow pattern were less than those of the PS flow pattern; and the TF flow pattern exhibited low complexity and almost monofractal behavior,and its magnitude scaling was close to random behavior.Meanwhile,at short time scales,all sign series of two-phase flow patterns exhibited very similar strong positive correlation; at high time scales,the scaling analysis of sign series showed different anti-correlated behavior.Furthermore,with an increase in oil flow rate,the flow structure became regular,which could be reflected by the decrease in the width of spectrum and the difference in dimensions.The results suggested that different oil-water flow patterns exhibited different nonlinear features,and the varying levels of complexity could well characterize the fluid dynamics underlying different oil-water flow patterns.     

基于多重分形理论的心电诊断系统设计与应用

设计实现了一种利用差分阈值法进行心电数据自动分段算法,该算法可识别连续心电数据的各个心电周期;基于多重分形理论,获取心电数据的多重分形半谱特征和广义 Hurst 指数特征,用于神经网络模型的训练,以实现心电数据分类,其分类的准确率为97%。实现了心电诊断系统并用于实际应用,该系统能自动识别包含多个周期的心电序列,忽略该心电序列中首尾不完整心电周期数据,并可对心电数据各个周期进行分类标注。     

快速路交通流时间序列的多重分形分析

采用多重分形消除趋势波动分析法研究城市快速路交通流的多重分形特征。首先,计算和比较了实测的流量和速度序列的广义hurst指数,结果表明：流量序列和速度序列均呈现多重分形,且流量序列的波动程度强于速度序列。然后,对两种序列的重排序列的计算结果显示,重排序列的广义hurst指数远小于原序列且不为0.5,说明交通流的多重分形特征主要由序列的长程相关性决定,同时与概率分布有关。