具两个非线性机的控制系统绝对稳定性的频率准则

对具有两个非线性机构的控制系统。本文得到绝对稳定性的新的频率准则，它是存在“二次型加积分项”型Liapunov函数的充要条件。它包了含了已有的一些稳定性准则。例如Popov准则等。     

关于时滞Volteraa型离散系统的稳定性

讨论Volterra型离散系统的稳定性.对于带有无限时滞的Volterra型离散系统,建立了某些有关稳定性的判定准则.     

中立型延时微分代数方程的稳定性准则

研究了中立型延时微分代数方程的渐进稳定性.给出了判断其稳定性的两种稳定性准则,并利用在一个环形区域边界上对一种相应的调和函数的估计来描述这两种准则.     

线性中立型时滞系统稳定性的代数准则

研究线性时滞中立型微分系统的渐近稳定性.基于系统的特征方程,利用恰当的模矩阵的谱半径导出了新的时滞无关稳定性准则,给出了用以阐明所得稳定性准则的数值算例以及相应的仿真结果.     

区间时变时滞奇异系统稳定性准则改进

为解决区间时变时滞奇异系统的稳定性问题,基于Lyapunov稳定性理论,通过采用新构造的Lyapunov泛函和线性矩阵不等式方法,以线性矩阵不等式形式给出了使得系统满足正则、无脉冲且稳定的时滞相关型准则的改进结果.研究结果表明:所给准则可有效判定区间时变时滞奇异系统的稳定性,它比已有一些结果包含更少的矩阵变量,且具有较小的保守性,同时通过数值实例进行了验证.     

无界滞后中立型泛函微分方程的稳定性

本文应用Liapunov泛函方法,研究了一类无界滞后中立型泛函微分方程的稳定性,给出了零解一致渐近稳定性,一致L~P—稳定性的判别准则.     

一类控制系统的Ляпунов函数的构造方法

本文给出了一类非定常非线性控制系统的绝对稳定性准则,证明了它是无亏损性准则,同时还给出了Ляпунов函数的数值构造方法。     

参数与时滞相关延迟振子的稳定性及Hopf分岔分析

首先, 采用特征根法分析参数与时滞相关延迟振子的稳定性, 并给出稳定性切换准则; 其次, 应用中心流形和规范型理论分析系统分岔周期解的稳定性和周期性.     

直接调节系统的一个绝对稳定准则

本文应用直接方法研究直接调节系统的绝对稳定性问题.提出一种处理“二次型加非线性函数的积分”形式的函数的方法,并得到一个新的绝对稳定准则.这个准则表明,有名的Popoy准则当其中的参数取无穷值时,只要加上适当的条件,也可以保证系统的绝对稳定性.     

线性离散大系统的稳定性

本文直接利用线性范数型 Liapunov 函数处理线性定常和时变离散大系统的稳定性,得到了渐近稳定性若干显式判别准则.     

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