方程的同解性

在中学数学里,方程这个课题的内容,总起来说,主要包括三个方面: (一)方程(方程组)的概念:包括什么叫做等式;什么叫做方程(方程组);什么叫做方程(方程组)的解(根)和解方程。 (二)各类方程(方程组)的解法。 (三)方程(方程组)的应用:包括“列方程(方程组)解应用问题”;求两条曲线交点的坐     

一元初等方程的等价问题

在将方程变形时,所得方程与原方程有时等价有时不等价。究竟哪些变形使方程等价,哪些变形使方程不等价呢?这个问题在现有的参考书上已有所论述,但还不够系统和完善。这里我们将在实数范围内进一步讨论这个问题。先介绍几个概念。若方程f(x)=g(x)中f(x)、g(x) 都是一元初等函数,则称该方程为一元初等方程。若方程f(x)=g(x) (1) 的任一解都是方程F(x)=G(x) (2) 的解,反之,方程 (2) 的解也都是方程 (1) 的解,也就是说两方程的解集相同,则称它们为等价方程。若两方程不仅解集相同且每个重根的重数也都相同时,则称它们为严格等价方程。本文只讨论等价方程而不讨论严格等价方程。为叙述方便再作如下约定:下面所说方程是指一元初等方程;所说的函数是指一元初等     

Kolmogorov-Petrovskii-Piskunov方程和Zhiber-Shabat方程的行波解

利用常微分方程定性理论分析了Kolmogorov-Petrovskii-Piskunov方程(KPP方程)和Zhiber-Shabat方程(ZS方程)的行波解.证明了KPP方程在一定的条件下存在扭波解,给出了ZS方程存在扭波解或反扭波解的充分条件.     

ZSM方程和CDGSK方程的无穷Lie-Bācklund对称序列之间的联系

本文证明,Caudrey-Dodd-Gibbon-Sawada-Kotera方程和Ziber-Shabat-Mikhailov方程的无穷Lie-Bācklund对称序列之列之间存在着一个简单的联系.这一联系是由这样的观察事实所提供的:Ziber-Shabat-Mikhailov 方程和被积修正Caudery-Dodd-Gibbon-Sawada-Kotera 方程的无穷Lie-Bācklund 对称序列是全同的.此外,我们还证明,这一联系是与如下的事实相关的:所有这些方程(包括Cau-drey-Dodd-Gibbon-Sawada-Kotera(cDGSK)方程,修正Caudrey-Dodd-Gibbon-Sawada-Kotera(MCDGSK)方程,被积修正Caudrey-Dodd-Gibbon-Sawada-Kotera(IMCDGSK)方程和Ziber-Shabat-Mikhailov(ZSM)方程)的无穷多守恒律可以变换成同一组具有零Poisson 括号的Virasoro 生成元的多项式函数的无穷集.     

具连续变量非线性差分方程的振动性

文章通过时滞微分方程和离散型差分方程的振动性,研究了一类具有连续变量非线性差分方程Δ[y(t)-p(t)y(t-τ)]+sum from i=1 to m qi(t)fi(y(t-σi))=0的振动性,得出了方程依赖于时滞差分方程和离散型差分方程振动的几个充分条件。     

(2+1)维ZK方程的多孤立波解

通过引入一个简单的线性变换,将(2+1)维Zakharov-Kuznetsor(ZK)方程化为一维Korteweg-de Vries(KdV)方程,然后利用KdV方程的多孤立波解得到了ZK方程的多孤立波解.结果表明,此时ZK方程的多孤立波为彼此平行的线孤子.     

关于高维与低维的Sine-Gordon方程的Backlund变换之间的关系

近几年来,物理学家沟非线性色散型波动方程的研究表示了极大的兴趣。Sine-Gordon方程(简称SG方程)其中,是一个典型的研究得较为透彻的非线性色散型方程。 最近,人们的兴趣已从低维的,如(1+1)一维(1维空间和1维时间),(2+0)一维(2维空间,与时间无关)的SG方程扩展到高维的,如(2+1)一维,(3+0)一维,(3+1)维的 SG方程[2,3],文[3]直接利用了三维和四维SG方程的Backlund变换求出了方程的解。本文则指出;文[3]所用的高维SG方程的Backlund变换实质上不过是几个常见的二维SG方程的Backlund 变换的组合。 我们以(3+1)一维SG方程为例来加以论证,…     

(1+1)维修正Broer-Kaup-Kupershmidt方程的Painlevé分析与精确解

利用Painlevé分析的方法,对(1+1)维修正Broer-Kaup-Kupershmidt方程进行奇异流形展开,利用调谐因子项将展开方程有限项"截断",证明(1+1)维修正方程具有Painlevé可积性。在Painlevé分析的基础上,导出(1+1)维修正方程B■cklund变换和奇异流形满足的Schwarz导数方程,通过Schwarz导数方程的性质,求出方程的精确解。     

关于Euler-Poisson-Darboux方程的推广

简称EPD方程,是偏微分方程中的一个重要方程。我们在[1]中曾作过系统地介绍。近年来不少作者对(1)作了不同程度的推广(例如见文集[2]),也有的作者是从研究奇性方程出发,讨论了一些方程,虽然没有提及方程(1),但其结果似乎和(1)很类似。 本文准备初步探讨一下,方程(1)的结果能推广到那些情形?哪些方程可以变换为(1)?     

Boussinesq方程的经典李群分析及群不变解和行波解

研究了Boussinesq方程的经典李群分析、群不变解及行波解.采用经典李群分析法获得了Boussinesq方程的李群分析、群不变解及约化方程.应用Burgers方程的约化变换方程及其精确解构造了φ(ξ)展式法,利用φ(ξ)展式法找到了Boussinesq方程的多种类型行波解.φ(ξ)展式法还可用于求解其他非线性偏微分方程.     

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     

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     

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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