奇异摄动系统状态反馈 H∞控制

利用线性矩阵不等式方法研究了奇异摄动系统的H∞控制问题.结合奇异摄动系统和它所对应的广义系统的关系,给出奇异摄动系统可状态反馈 H∞控制的条件及控制器的求解.这种方法适用于标准和非标准的奇异摄动系统,仿真结果表明该方法是简单和有效的.     

一类不确定奇异摄动系统的稳定鲁棒控制

对于含有不确定量的一类奇异摄动系统,通过引入新的寄生变量,利用Lyapunov理论进行了鲁棒性研究.在一定条件下,得到了一个理想奇异摄动系统的稳定鲁棒控制,也是不确定奇异摄动系统的稳定控制,并给出了鲁棒界.     

奇异摄动系统正实性能分析

利用广义系统模型,通过改进已有的广义系统正实引理,讨论了奇异摄动系统的正实性判断问题.利用隐函数存在定理,基于代数Riccati等式讨论了当小参数趋于零时奇异摄动系统正实性与极限系统正实性之间的关系.进一步提出了根据极限系统对奇异摄动系统的正实性进行判断的判据.算例验证了结果的有效性,为在一定条件下对奇异摄动系统的正实性进行有效判断提供了一种新的方法.     

含摄动二次指标的线性奇异摄动最优控制问题的广义系统途径

通过讨论降阶慢子系统的奇异二次指标最优控制问题 ,研究了指标含摄动的线性奇异摄动系统的最优控制问题 .在一些假定下 ,奇异摄动系统的最优性能指标逼近于降阶控制所得到的最优性能指标     

离散时滞不确定奇异摄动系统的稳定性分析

针对一类时滞不确定离散奇异摄动系统稳定性的相关问题,运用构造Lyapunov-Krasovskii函数的方法,再结合线性矩阵不等式,对离散奇异摄动系统的稳定性进行研究,得出了使奇异摄动系统稳定的条件,并证明了该方法的可行性.     

求解一类高阶奇摄动线性边值问题

文章研究了一类高阶奇异摄动线性系统的近似解,通过降阶将高阶奇异摄动系统转化成一般的低阶变系数奇异摄动系统,再根据不同的边界层引入伸长变量构造渐近解,并对其进行分析,得出了相应的结果.     

奇异奇摄动系统的几何方法(英文)

研究了一类奇异奇摄动系统边值问题.通过几何奇摄动理论构造了系统的奇异轨道,并用交换引理证明了解的存在性.最后用该方法研究了一个经典半导体模型.     

奇异摄动小参数上界的求法

研究了在线性连续奇异摄动系统中奇异摄动小参数的选取方法.提出了一种求该系统稳定性界的新方法,由实例可知这种方法比起原有的方法简便可行.     

时滞独立状态下离散控制系统的稳定性分析

针对一类系统矩阵中含有不确定性、系统状态中含有时变时滞的时滞奇异摄动不确定性综合控制系统,进行了时滞独立的稳定性分析.通过构造一种含有奇异摄动的双二次型Lyapunov泛函,推出系统渐近稳定性判据,给出鲁棒稳定区间以及奇异摄动的最小上界,继而给出相应推论.最后用数值样例说明所得方法的有效性和可行性,并展示了时滞独立情形...     

时变时滞奇异摄动系统的稳定性研究

针对时变时滞奇异摄动系统,该文用线性矩阵不等式方法给出了判定该系统稳定的充分条件.首先将此系统转化为一个与之等价的广义系统,然后基于线性矩阵不等式(LMI)方法,得到了该系统稳定且依赖于摄动参数的充分条件,为了消除由此带来的数值病态问题,该文将上述条件转化为与摄动参数无关的LMI条件.在此基础上,给出变时滞奇异摄动系统状态反馈控制器存在的充分条件,并由此得到了控制器增益.最后通过数值算例表明了上述方法的有效性.     

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