非线性网络广义频率响应函数统一递推分析法

假设非线性动态网络解为Volterra级数响应,利用一般的网络分析法,对任一定常非线性动态网络列出其时域的标准动态方程.将该非线性微分方程分解成一个线性动态系统与一组非线性电源,利用线性微分方程求解方法求出线性系统的解,即一阶Volterra级数响应,再考虑系统非线性电源的作用和幂级数递推关系式,导出N 阶(N≥2)Volterra响应的递推算式,即可得到非线性网络响应的Volterra级数形式.在此基础上,讨论了Volterra级数时域响应的频域变换,推导出对应的广义频率响应函数,即Volterra级数的频域核的递推算式,并给出了计算实例.     

基于Volterra级数的RFPA特征模型及其仿真实验

主要运用Volterra级数理论分析射频功放(RFPA)器件工作在弱非线性条件下信号失真特性介绍了Volterra级数在非线性建模中的应用,推导了非线性传递函数的公式。在Advanced Design System 2006A软件的仿真环境下对射频功率放大器进行仿真,利用计算机仿真实现了在弱非线性条件下对任意频率输入时功率放大器的输出频谱估计。     

基于Volterra级数的RFPA特征模型及其仿真实验

主要运用Volterra级数理论分析射频功放(RFPA)器件工作在弱非线性条件下信号失真特性.介绍了Vol-terra级数在非线性建模中的应用,推导了非线性传递函数的公式.在Advanced Design System 2006A软件的仿真环境下对射频功率放大器进行仿真,利用计算机仿真实现了在弱非线性条件下对任意频率输入时功率放大器的输出频谱估计.     

基于Volterra模型的一类通信系统的参数辨识

分析了Volterra级数理论对于非线性系统的模型建造的意义，提出了一类通信系统的适用于系统辨识的新模型──Volterra离散频域模型．应用此模型对一个具体的通信系统有效地进行了非线性故障诊断和参数辨识．     

Volterra级数与摄动法的内在关系研究

摄动法是求解弱非线性方程的经典定量方法之一,而Volterra级数是一种可表征弱非线性系统的经典数学模型．研究表明,对于受迫多项式非线性系统,只有当其线性派生系统是阻尼耗散系统,由对系统输入进行小参数摄动求得的稳态输出响应才和由Volterra级数给出的解完全一致．结论意味着：Volterra级数并不能表示任意的多项式非线性系统,而仅适合表征线性派生系统是阻尼耗散系统的多项式非线性系统．     

一种简化Volterra级数的记忆功放行为模型

考虑强非线性和长记忆效应的功放行为模型,需要降低Volterra级数模型的辨识参数,提出了一种基于简化Volterra级数的功率放大器行为模型。通过对广义记忆多项式模型(GMP)中的交叉相乘项的记忆时间距离l进行有效控制,可以在满足系统误差要求的同时减少辨识参数的数量。仿真结果表明,简化的Volterra级数模型性能优于记忆多项式模型(MP),略低于GMP模型,模型辨识参数大大减少。     

基于非线性输出频率响应函数的转子系统碰摩故障的定位方法研究

提出采用一种新的基于非线性输出频率响应函数(NOFRFs)的方法,进行转子系统碰摩故障的定位识别.NOFRFs由非线性系统的Volterra级数理论发展起来.对多自由度振动系统中的非线性环节具有定量的检测能力.对不同碰摩位置的转轴横向振动进行有限元仿真,进而计算NOFRF函数的值,用于对碰摩所处的区间位置进行判定.     

一种基于功率谱分析的非线性系统故障诊断方法

首先分析了Volterra级数的各级输出之间存在相互耦合的原因,然后,利用Gram-Schmidt正交化方法在频域内对Volterra级数的各级输入向量进行正交化,以消除各级输出之间的相互耦合.并依此提出了一种基于Volterra级数各阶核输出功率谱分析的非线性系统故障诊断方法.文中给出了对Volterra级数各阶输入向量正交化的具体步骤,并利用一个工程实例验证了该故障诊断方法的有效性.     

一种非线性系统自适应辨识的新方法

研究了Volterra级数模型的非线性系统的自适应辨识问题．并提出了基于Volterra滤波器的自适应算法，讨论了步长因子的确定问题以及对算法收敛性的影响．最后给出了一个用Volterra自适应滤波器对非线性系统建模的实例，证明了这种方法的有效性．     

一种分析锁相环非线性的新方法─Volterra─wiener分析法

在双输入端口系统的Volterra级数理论基础上，建立一种新的分析方法．对非线性反馈系统一锁相环进行了分析，求出了Volterra核，得到了锁相环的解析解．     

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.     

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     

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

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Brief Introduction to “Journal of Jilin University( Science Edition) ”

<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has