交通流的混沌特性分析及其预测

实时准确的短时交通流预测是智能交通系统中实现交通控制和诱导的关键技术之一.首先,采用饱和关联维数法和互信息量法对交通流时间序列的嵌入维数和延迟时间进行计算,并根据计算结果对交通流时间序列进行相空间重构;然后,采用wolf方法计算其最大Lyapunov指数,并对其进行功率谱分析,结果表明,交通流时间序列具有噪声;最后,分别采用基于BP神经网络和RBF神经网络的预测模型对交通流时间序列进行预测,结果表明,2种模型对短时交通流均能较好预测,但后者的预测精度较高,预测速度较快.嵌入维数;延迟时间;相空间重构;BP神经网络;RBF神经网络     

基于相空间重构和RELM的短时交通流量预测

为了提高短时交通流量预测的精度,构建了基于相空间重构和正则化极端学习机的短时交通流量预测模型.首先采用C-C算法求解交通流量时间序列的最佳时间延迟和嵌入维数,进行相空间重构;然后选用G-P算法计算序列关联维数,判断出短时交通流量序列具有混沌特性.在此基础上,将重构数据作为正则化极端学习机的输入和输出来训练模型,并采用网格搜索法优化模型参数.最后以实测数据为基础,对模型的预测效果进行对比分析.结果表明,新构建模型的预测效果良好,能够有效提高短时交通流量预测精度.     

基于改进黑洞算法优化ESN的网络流量短期预测

网络流量数据序列具有混沌特性.相空间重构后,采用一种改进黑洞算法优化回声状态网络的非线性模型对网络流量进行预测.改进黑洞算法是在现有工作的基础上提出一种新的新解生成机制,可以提高算法的收敛速度和精度;相比于遗传算法、和声搜索算法等其他优化算法,所提出的改进黑洞算法不依赖自身相关参数的准确设定;将其应用于回声状态网络4个重要参数的优化选取,使得预测模型具有较好的预测稳定性.通过Mackey-Glass混沌时间序列和网络流量公共数据集的仿真实验,结果表明所提出的方法具有较好的预测性能.     

基于混沌理论和MEA-BPNN模型的快速路短时交通流预测

为提高短时交通流预测的精度,在分析北京市二环路实测交通流数据时空特性和混沌性的基础上,利用混沌理论方法对交通流量时间序列进行相空间重构,并基于思维进化算法提出一种改进的BP神经网络模型,将重构的时间序列数据作为模型输入进行交通流预测。结果表明,基于该模型的预测结果与基于传统BPNN模型的预测结果相比,均方根误差、平均绝对误差和平均绝对百分误差分别下降31.11%、20.71%和37.28%,证明了模型具有更精确的预测能力。     

基于回声状态网络模型的短时交通流混沌预测

为了提高短时交通流预测的准确度,提出基于回声状态网络模型的短时交通流混沌预测方法;利用C-C法计算相空间重构的延迟时间和嵌入维数;利用遗传算法对回声状态网络模型进行参数寻优,进而构建基于遗传算法的回声状态网络模型;采用城市快速路实测数据进行实验验证和对比分析.结果表明,所提出方法的预测效果明显优于支持向量机模型、小波神...     

基于特性和影响因素分析的短时交通流预测

可靠的短时交通流预测是智能交通系统的重要基础。为了提高短时交通流预测的预测精度和对于不同交通状态的适应性,在分析了交通流特性以及时空二维影响因素的基础上,提出了一种组合预测模型,使其能够综合反映这些特性和影响因素。该组合预测模型包括时间序列模块、空间相关模块和组合预测模块三个子模块。单项预测模型包括自适应单指数平滑模型和RBF神经网络模型,组合系数是以两个单项预测子模块的平滑百分比相对误差作为输入,以神经网络作为学习算法自适应地得到。最后通过平峰和高峰时段实测的交通流量数据来验证模型的有效性和可靠性,结果表明:该组合预测模型的预测精度高于单项预测模型各自单独使用时的精度,且对于不同的交通流状况具有较好的适应性。     

基于IFA优化RBF神经网络的短时交通流预测模型

针对短时交通流不确定性极强引起的预测结果精度低的问题,提出一种改进萤火虫算法(IFA)优化RBF神经网络的短时交通流预测模型(IFA-RBF).该模型通过引入线性递减惯性权重和混沌机制,来改进FA后期存在的易陷入局部极值和种群多样性匮乏的不足,利用IFA优化RBF神经网络的连接权重和基函数宽度,以提升RBF神经网络的短时交通流预测精度.实验结果表明,与Elman、BP、RBF和FA-RBF模型相比,构建的短时交通流预测模型(IFA-RBF)具有更高的预测精度,预测值与实际值拟合度较高.     

基于复杂网络的交通序列数据特性

为了进一步研究交通流特性,采用复杂网络方法对交通序列数据进行分析。提出了箱型图-聚类算法模型用于识别和填充初始数据中的缺失值和异常值;通过相空间重构方法将一维数据重构为网络节点,选取连接阈值确定网络节点的连接关系,将交通序列数据构建为复杂网络,对复杂网络的结构和定量指标进行分析。研究结果表明交通序列数据复杂网络的结构一定程度上可以反映路段的交通流状态。该结果有助于优化数据预处理方法,拓展复杂网络在交通序列数据研究中的应用。     

考虑时空相关性的网络交通流短期预测

实时、准确的交通流短期预测是交通诱导、管理的前提.为了提高预测精度,结合交通流数据中的历史时间相关性与网络空间断面相关性,构建了一种基于皮尔森相关系数法(Pearson Cor-relation Coefficient,PCC)与双向长短时记忆(Bidirectional Long Short Term Memory,BLSTM)架构的交通流短时预测模型.该模型可以通过PCC筛选路网中与目标路段空间相关的路段,并将其重构为新数据集,作为BLSTM预测模型的输入,以实现交通流短期预测.通过美国加州交通流数据对模型预测性能进行评价,实验结果表明:该模型可以融合交通流数据中的时空相关性,相对于其他主流预测模型精度平均可提高4.83％.     

基于改进萤火虫算法优化BP神经网络的路网速度分布预测

浮动车数据的挖掘是目前交通领域广泛使用的研究手段之一,基本的BP神经网络也多被用于交通流的预测研究。本文引入小波变换将低频信号和高频信号进行分解和重构,结合改进萤火虫算法寻优速度快、收敛率高的特点对基本的BP神经网络进行优化,构建了路网交通流速度的预测模型。利用城市路网浮动车真实数据对模型进行训练并通过测试数据对模型预测结果进行实证分析,证明模型对特定时刻路网交通流速度预测的准确性相比于基本BP神经网络算法有46.56%的提升,对路网24h内交通流速度预测的稳定性有39.08%的提升。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

正~~