具有转向点的奇摄动特征值问题

具有转向点的奇摄动方程的求解是一个较难处理的问题. 利用Liourille-Green变换将二阶线性奇摄动方程转化为Airy方程, 并用Bessel函数表示Airy方程的通解.得到了一类具有转向点的奇摄动特征值问题的特征函数及特征值.     

一个带边界摄动的非线性特征值问题

本文考虑一类带有临界指数的Emden-Fowler方程特征值和特征函数的摄动,给出有关的估计,并应用于一个带边界摄动的半线性椭圆型方程的特征值问题,得到摄动问题特征值和特征函数的适当的估计式。     

带输入饱和的奇异摄动双线性系统的无源控制

针对具有输入约束和变时滞的奇异摄动双线性系统,提出一种状态反馈无源控制器的设计方法,以消除时滞因素和输入饱和对闭环系统的影响.首先,在Lyapunov稳定性理论和无源性理论的框架下,应用线性矩阵不等式技术和凸组合技术,将系统状态反馈控制器的设计归结为求解一组与时滞上界无关的线性矩阵不等式问题.所得控制器使闭环系统渐近稳定且无源,同时构造了与奇异摄动参数相关的椭圆吸引域估计,并将上述方法推广到不含时滞和外部输入的系统.然后,提出凸优化问题,得到闭环系统吸引域的极大估计,其中奇异摄动参数稳定界也是设计的目标之一.最后,通过数值仿真算例说明了所提理论方法的有效性.     

边界与算子摄动相结合的高阶拟线性常微分方程边值问题的奇摄动

文[1]-[4]的作者曾研究过高阶线性常微分方程边值问题的正则摄动和奇异摄动以及特征值和特征函数的摄动。在前文的基础上,本文应用和的渐近方法和泛函分析的不动点原理进一步研究了边界与算子摄动相结合的高阶拟线性常微分方程边值问题的奇摄动,证明了摄动问题解的存在且唯一,给出其解的渐近展开式和余项估计。     

阻尼系统特征值问题的高阶摄动

提出了求解阻尼系统特征值问题的高阶摄动法。当结构参数发生变化时，不必重新求解特征值问题，只需以原结构的特征值问题为基础，应用摄动法即可求得改变后结构的特征值及特征向量。高阶摄动法能解决阻尼系统参数变化较大时的特征值问题，具有较强的实用性。     

无穷维线性系统的可控可观性算子与Hankel算子的奇异数

本文定义了无穷维线性控制系统的可控性与可观性算子，用这两个算子给出了指数稳定的线性无穷维系统的近似可控性与近似可观性的充要条件，文中还讨论可控性算子、可观性算子以及所论系统的Ｈａｎｋｅｌ算子的性质及其关系。     

有界参数结构特征值的区间分析方法

针对具有不确定但有界参数的结构系统的固有振动频率问题,提出一种近似求解结构固有频率上、下界值的区间特征值摄动法.该方法基本上是两步法,首先,将结构系统的振动描述为区间数学中的广义区间特征值问题,形成矩阵方程.其次,把特征值看作是摄动矩阵的函数,利用区间分析和摄动理论计算特征值的上下界值,从而根据其值来估计结构固有振动频率的范围.通过两个数值例子表明,该方法在结构参数的不确定量较小时可得到满意的结果.     

耦合动力学方程的非线性特征值渐近求解

介绍由约束场和受重力影响的对流扰动耦合而成的衰减平衡向量场动力学方程的特征值渐近求解.通过引进新的参数,将一个复杂的三维约束耦合动力学特征方程转化成复空间里一维的边界层问题.通过进一步分析计算非线性特征值问题并做了渐近摄动分析,最后给出多场耦合中扰动问题的特征值边界层解法.     

具有转向点的奇摄动方程

利用L iouville-G reen变换构造新的变量,使二阶线性奇摄动方程转化为A iry方程和W eber方程,得出了一类在大特征值的情形下具有两阶转向点的奇摄动方程在不同范围内一致有效的展开式.     

一类Lipschitz奇异摄动系统的观测器设计

考虑了一类Lipschitz奇异摄动系统的观测器设计问题,系统中的非线性函数满足Lipschitz条件.基于Lyapunov稳定性理论,给出了带有奇异摄动参数的Luenberger状态观测器的设计方法,证明了系统状态与观测器状态的误差指数稳定,并用线性矩阵不等式表示了观测器存在的条件.仿真例子说明了设计方法的有效性.     

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