改进粒子群优化 BP 神经网络的洪水智能预①测模型研究

该文提出改进的PSO-BP算法在洪水预测应用中建立预测模型.以BP神经网络为基础,提取观测站往年平均径流量作为洪水属性.采用改进的PSO-BP算法对神经网络的各个参数进行优化,最后建立模型应用于流域观测站的洪水预报模型,叙述了PSO粒子群算法和BP神经网络算法,详细阐述粒子群算法优化BP神经网络的权值和阈值,得出最优的BP神经网络预测适应度值.通过实验仿真对比,结果表明此方法预测结果比BP神经网络算法和混沌径向基神经网络模型算法精度更高,提高了预测的效率.     

基于BP神经网络的股票价格预测

影响股票价格变动的因素有很多,且股票数据具有高度的非线性和时变性等特征,因而采用经典线性时间序列模型可能无法完全提取非线性部分的信息.针对这一问题,建立了BP神经网络模型、PCA-BP神经网络模型、GA-BP神经网络模型和ARIMA(6,1,6)模型对上证综合指数的收盘价格进行预测.计算各预测模型下的统计指标RMSE和MAE,并对4个模型进行对比分析.结果表明,GA-BP神经网络预测模型与其它三种模型相比具有更小的误差,也就是说GA-BP神经网络预测模型对上证综合指数的收盘价格预测效果更好.     

基于动量自适应学习率PSO-BP神经网络的钻速预测模型研究

机械钻速(rate of penetration, ROP)是钻井作业优化和减少成本的关键因素,钻井时有效地预测ROP是提升钻进效率的关键。由于井下钻进时复杂多变的情况和地层的非均质性,通过传统的ROP方程和回归分析方法来预测钻速受到了一定的限制。为了实现对钻速的高精度预测,对现有BP (back propagation)神经网络进行优化,提出了一种新的神经网络模型,即动态自适应学习率的粒子群优化BP神经网络,利用录井数据建立目标井预测模型来对钻速进行预测。在训练过程中对BP神经网络进行优化,利用启发式算法,即附加动量法和自适应学习率,将两种方法结合起来形成动态自适应学习率的BP改进算法,提高了BP神经网络的训练速度和拟合精度,获得了更好的泛化性能。将BP神经网络与遗传优化算法(genetic algorithm, GA)和粒子群优化算法(particle swarm optimization, PSO)结合,得到优化后的动态自适应学习率BP神经网络。研究利用XX8-1-2井的录井数据进行实验,对比BP神经网络、PSO-BP神经网络、GA-BP神经网络3种不同的改进后神经网络的预测结果...     

改进型BP神经网络的港口吞吐量预测

为了提高港口吞吐量预测模型的适用性,满足港口决策的需求,对传统时间序列BP神经网络预测模型进行改进,将未来三年的吞吐量作为输出层参数,以tansig函数和logsig函数为传递函数,建立了改进型时间序列BP神经网络预测模型,利用trainlm函数训练神经网络,预测未来三年的港口吞吐量。对深圳港集装箱吞吐量进行了预测,结果表明,改进型时间序列BP神经网络模型泛化能力更强,拟合精度更高,且避免了传统预测模型循环预测产生的误差叠加,具有较好的适用性。     

基于改进RBF神经网络的混沌时间序列预测

基于RBF神经网络与相空间重构理论,对网络预测模型进行改进,并以Lorenz动力系统产生的混沌时间序列作为研究对象,建立预测模型并对其进行数值仿真.实验结果表明,基于改进RBF神经网络与相空间重构理论的混沌时间序列预测方法比BP、RBF神经网络模型的预测精度高、误差小、性能优越,改进方法可行、有效.     

分布式系统主机负载预测方法的评估

动态负载均衡是网络计算的关键技术,如何提高动态负载均衡的性能,一直是网络计算人员研究的一个热点.通过实验评估比较了线性时间序列模型、特殊的自我平衡及趋势预测时间序列模型、神经网络BP模型的预测性能,获得了各预测模型的优劣,从中选择了具有较佳预测性能的时间序列AR、混合趋势预测MT两种预测模型构建了预测模型模板库。     

基于GA-BP模型的船舶柴油机排气温度趋势预测

建立基于BP神经网络的时间序列预测模型,并用遗传算法(GA)对模型的权值和阈值进行优化.通过对某船舶主机排气温度实际案例的预测对该模型进行验证.结果表明:两组GA-BP模型预测结果的平均偏差分别为0.39℃和0.74℃,模型比较可靠、准确,可适用于船舶主机排气温度的趋势预测.     

基于云计算和GA-BP神经网络的西江水质评价研究

为提高水质评价精度,针对BP神经网络的预测结果易受初始连接权值和阈值的影响以及易陷入局部极值的问题,提出一种遗传算法优化BP神经网络的水质评价模型.针对水质评价数据特性,引入Multi-Agent和分布式思想,利用云计算的MapReduce框架对GA-BP模型进行并行化改进,提高其处理海量高维水质评价数据的能力.为证明所提算法的效果,选择西江2011-2015年的水质监测数据为研究对象,研究结果表明,与PSO-BP,GA-BP,DE-BP和BP相比,所提算法MR-GA-BP不但可以提高水质评价的精度,而且能够降低计算资源的消耗,缩短训练时间,具有很好的并行性能.     

熵在空气质量指数(AQI)预测中的应用

为了更准确地找出影响空气质量指数的气象因子与提高其预测精度,提出了基于熵、BP神经网络和时间序列模型的组合预测模型。该方法利用增加了特征变量的转移熵方法,得到影响AQI的气象因子及其影响度,将得到的气象因子与AQI实测值作为BP神经网络的输入因子和时间序列分析模型的特征因子,影响度作为BP神经网络输入因子的初始权重,构建BP神经网络预测模型和时间序列分析预测模型,最后用熵值法组合各个预测模型的预测结果。实验表明利用该方法对空气质量指数进行预测可提高其预测精度。     

基于GA-BP神经网络的柴油喷雾贯穿距预测

为解决柴油喷雾贯穿距测量的问题,提出一种基于GA-BP神经网络的预测方法。首先通过实验得到30组柴油在定容弹中不同环境背压、喷油压力和喷油脉宽等条件下的喷雾贯穿距,然后将前20组数据作为训练样本,后10组数据作为测试样本,最后分别通过BP神经网络和GA-BP神经网络建立喷雾贯穿距的预测模型。研究结果表明:GA-BP神经网络预测模型的平均相对误差和相对误差方差均比BP神经网络预测模型的低,并且其达到收敛时所需的迭代次数比BP神经网络预测模型的少。基于GA-BP神经网络的柴油喷雾贯穿距预测模型具有较高精度和适用性,为喷雾贯穿距的测量提供了一种低成本、高效率的方法。     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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     

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