判断一类双系统同时精确可观测的充分条件

利用反自伴算子生成系统是精确可观测的Hautus条件,得到判断如下双系统同时精确可观测的充分条件.Z·1(t)=A1z1(t),z1(0)=z1,y1(t)=C1z1(t)Z·2(t)=A2z2(t),z2(0)=z2,y2(t)=C2z2(t)     

多自由度振动系统的同相振动性

采用反射函数法研究了多自由度振动系统x′=p(t)x, 当p(t)=diag(A(t),B(t))时,给出其等价系统y′=A(t)y, z′=B(t)z同相振动的充分必要条件,其中A(t)=(aij(t))2×2, B(t)=(bij(t))2×2, y=(y1,y2)T, z=(z1,z2)T, p(t+2ω)=p(t), ω>0, t∈R, x∈R4, p(t)为连续可微的矩阵函数.     

Banach空间非柱形域上微分系统解的存在性

考虑在Banach空间非柱形域Ω上,微分系统 (IVP;τ,z0) z′=x′ y′=f1(t,x,y) f2(t,x,y)=f(t,z), (t,z)∈Ω, z(τ)=x(τ) y(τ)=z0=x0 y0 解的局部存在性,其中f1,f2分别满足紧性条件与耗散性条件,得到的结果推广并完善了已有的相关结果。     

一类完全三阶常微分方程边值问题的正解

用锥上的不动点指数理论与导数估计技巧,研究完全三阶边值问题{-u′′′(t)=f(t,u(t),u′(t),u″(t)),t∈[0,1],u(0)=u′(0)=u″(1)=0正解的存在性,其中f:[0,1]×R_+~3→R_+连续.在f(t,x,y,z)满足|(x,y,z)|充分小或充分大时的一些不等式条件下,得到该方程正解的存在性结果,这些不等式条件允许f(t,x,y,z)关于x,y,z超线性或次线性增长.     

完全三阶边值问题解的存在性

本文讨论了如下完全三阶两点边值问题{-u(t)=f(t,u(t),u′(t),u″(t)),t∈[0,1],u(0)=u′(0)=u″(1)=0解的存在性,其中f:[0,1]×R3→R为连续函数.当f(t,x,y,z)满足关于x,y,z超线性增长的不等式条件及f(t,x,y,z)关于z满足Nagumo型增长条件时,本文应用Leray-Schauder不动点定理获得了该问题解的存在性.     

临界情况下一类拟线性方程组的初值问题

本文将讨论下列方程组 εdx/dz=A(y,x)z εf(y,x),dy/dx=z, (1) 具有无穷大初值 y(0,ε)=y0,z(0,ε)=z-1/ε, (2) 其中z=(z1,z2)T,y=(y1,y2)T,f=(f1,f2)T都是二维向量,记号T表示向量的转置,ε是小参数,A(y,x)是行列式为零的二阶矩阵.在文献[1]讨论过数量情况下具有无穷大初值的二阶方程.由于在向量情况下,临界情况比较复杂,本文仅讨论一类特殊的矩阵A:     

一类积分微分方程Robin边值问题的奇异摄动

本文研究奇摄动积分微分方程的Robin边值问题 εy″=f(t,Ty,y,y′,ε), α(ε)y(0)—b(ε)y′(0)=A(ε),c(ε)y(1)+d(ε)y′(1)=B(ε),其中T是定义在C[0,1]上的一个积分算子。文中用微分不等式方法证明了解的存在性,构造出解的渐近展式并给出了余项的一致有效估计.最后把所得结果用于研究奇摄动四阶边值问题. εx~((4))=f(t,x,x″,x,ε), x(0)=φ(ε),x(1)=φ(ε), α(ε)x″(0)—b(ε)x(0)= A(ε),c(ε)x″(1)+d(ε)x(1)=B(ε).     

二阶微分方程组边值问题2个正解的存在性

讨论了二阶微分方程组x″(t)+λa(t)f(x(t),y(t))=0,y″(t)+λb(t)g(x(t),y(t))=0,0≤t≤1,x(0)=y(0)=x′(1)=y′(1)=0,其中f,g连续,并赋予f,g一定的增长条件,证明了方程组至少存在2个正解。     

一类完全三阶两点边值问题解的存在性与唯一性

讨论如下完全三阶两点边值问题{-u(t)=f(t,u(t),u′(t),u″(t)),{t∈[0,1],u(0)=u′(0)=u′(1)=0解的存在性与唯一性.其中f(t,x,y,z):[0,1]×R3→R为连续函数.在f(t,x,y,z)关于z满足Nagumo型增长条件下,应用上下解方法与截断技巧,获得了该问题解的存在性和唯一性结果.     

关于丢番图方程Ax4+Bx2y2+Cy4=z2的解

证明了丢番图方程4x4-6x2y2 3y4=z2,(x,y)=1的全部正整数解为(x,y,z)=(x0／2,ab,(3a4 b4)／4), (Xn,2yn,2zn),认为仅有正整数解(x,y,z)=(1,1,1)是不妥的,它漏掉了(xn,2yn,2zn)及(x0／2,ab,(3a4 b4)／ 4);丢番图方程x4-6x2y2 12y4=z2,(x,y)=1的全部正整数解为(x,y,z)=(x0,ab,(3a4 b4)／2),(xn,yn, zn),认为仅有正整数解(xn,yn,zn),则漏掉了(x0,ab,(3a4 b4)／2)。     

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