一类三次Kolmogorov系统的定性分析

研究一类三次Kolmogorov系统:{=x(A0+A1x-A3x2+A2y+A4xy)=y(-1+x2-y)(*)其中:A0>0,A3>0,A1,A2,A4不定号.对A1>0,A2<0,A4<0的情形,利用环域定理、Dulac函数法和张芷芬唯一性定理等手法得到系统(*)在第一象限内极限环存在、不存在及极限环的唯一性的充分条件.     

关于一般Liénard系统解的唯一性问题的注记

研究dxdt=h(y)-F(x),dydt=-g(x)关于初值问题解的唯一性问题,给出了如下定理:定理A,设系统(2)仅有有限奇点,若F(x)和g(x)在R上连续,h(y)在R上具有连续导数且h′(y)>0,则系统(2)满足初始条件x(t0)=x0,y(t0)=y0的解唯一.其中M0(x0,y0)不为奇点.同时,当h(y)为严格下凸函数时,给出了类似的定理B.     

Lienard系统x=φ（y）—F（x）,y=—g（x）极限环的一个存在唯一性定理

讨论了系统x=φ(y)-F(x),y=-g(x)的极限环的存在唯一性问题,借助连续函数的零点定理,得到了一个判断系统极限环存在唯一的较实用的方法。     

一类三次系统含单奇点的极限环

证明三次系统x.=y-εy3,y.=x(1-x2)+(α-x2)y,ε>0,当0<1-α<<1时,在区域y<1ε内含单奇点的极限环的存在性与唯一性.根据Hopf分支定理,证明了当0<1-α<<1时,存在含单奇点的极限环,再由唯一性定理证明了当0<1-α<<1时,含单奇点的极限环的唯一性.     

一类高阶非线性微分方程解的稳定性

本文对高阶非线性微分方程组x=f_1(x,y,x,y,x,y)…y=f_2(x,y,x,y,x,y)的某些特殊类型,研究了平凡解的全局渐近稳定性[1],用类比法[2]构造李雅普诺夫函数,得到了全局渐近稳定性的一些充分条件。主要结果为定理2、定理3和定理4。文中具体研究了如下三种类型的方程:和x a_1x a_2y a_3x a_4y f(x)=0…y b_1x b_2y b_3x b_4y g(y)=0x a_1x a_2y f(x) a_4y a_3x=0…y b_1x b_2y b_3x g(y) b_6y=0x f(x) a_2y a_3x a_4y a_5x=0…y b_1x g(y) b_3x b_4y b_6y=0其中ai,bi(i=1.2.…,6)均为常数,f和g具有保证解对初值唯一性的条件。     

一类被开发的食饵-捕食者两种群模型的定性分析

讨论被开发的食饵-捕食者两种群系统模型:dx/dt=x(r1-ax-by/(1 ωx)) G,dy/dt=y(-r2 kbx/(1 ωx))的平衡点性态和全局稳定性,用Bendixson环域定理证明极限环的存在性,用张芷芬唯一性定理证明极限环的唯一性.     

Liénard系统=φ(y)-F(x), =-g(x)极限环的一个存在唯一性定理

讨论了系统=φ(y)-F(x), =-g(x)的极限环的存在唯一性问题,借助连续函数的零点定理,得到了一个判断系统极限环存在唯一的较实用的方法.     

一类Kolmogorov捕食系统的定性分析

研究一类Kolmogorov捕食系统:ddxt=x(a0-a1x+a2xn-1-a3xn+a4xφ(y)),ddyt=y(b1xn-b2),其中φ(0)=0,φ′(y)ε0,(y0).首先运用等式gf((uu))′=Δlui→m0f(u+Δu)g(u+Δu)-gf((uu))Δu将张芷芬唯一性定理和微分不等式定理中需要的两个不等式联系起来,再配合运用环域定理、ΦИЛИППОВ变换及Dulac函数法得到了该系统存在唯一极限环和不存在极限环的充要条件,从而对其参数范围就其极限环存在性与不存在性讨论完全,推广了前人相关的结果.     

Liénard系统=φ(y)-F(x),

讨论了系统=φ(y)-F(x),=-g(x)的极限环的存在唯一性问题,借助连续函数的零点定理,得到了一个判断系统极限环存在唯一的较实用的方法.     

减弱定理条件拓宽应用范围

<正> 在微积分中,为解决含参量积分的求导与积分顺序可交换的问题,教科书上多采用下述定理1与定理2。 定理1 若函数f(x,y)与f_y(x,y)在R[a,b;c,d]上连续,则函数φ(y)=integral from n=a to b(f(x,y)dx)在[c,d]上可导,且 φ′(y)=integral from n=a to b(f_y(x,y)dx) (1)     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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