关于非线性时滞微分系统的R-K方法的稳定性

具有时滞微分系统的稳定性问题是近年来讨论的热门话题。迄今，有关时滞微分系统稳定性的概念和结论都仅限于常时滞问题且都只考虑定步变的情况。本文在此基础上对变时滞变步长的情况进行了研究，并证明了在变时滞状态下，具有代数稳定的非线性微分系统的Runge-Kutta方法（简称R-K方法）仍然是零稳定的结论。     

单自由度时滞系统振动主动控制

对单自由度时滞系统主动控制的最优控制方法和变结构控制方法进行了研究,给出了反馈增益的稳定性条件和最大时滞量的解析确定方法,并采用移相技术进行时滞补偿．算例结果显示,移相技术能够较好地对系统中的时滞进行补偿,时滞补偿变结构控制方法的控制效果优于时滞补偿最优控制方法．     

时标上的变时滞二维动力系统的振动性

利用广义Riccati变换和不等式技巧,讨论一类时标上具有两个变时滞的二维动力系统的解的振动性质,得到的振动定理既适用于变时滞二维动力系统,也适用于变时滞二维微分系统和差分系统及某些二阶时滞动力系统。     

基于LTR观测器的输入时滞系统的滑模控制

针对一类线性时滞系统且存在外部噪声干扰和参数不确定性问题,提出一种基于回路传输恢复(LTR)观测器的滑模变结构控制方法.为了简化时滞变结构控制器的设计,采用非奇异线性变换将输入时滞的线性系统转化为无时滞系统,并进行滑模变结构控制器的设计、理论分析及稳定性证明.仿真结果表明,该方法对时滞系统在噪声干扰和过程参数不确定性时系统状态快速达到稳态,得到的控制效果仍具有较好的稳定性.     

具变系数变时滞非线性中立型方程的振动性

建立了具变系数变时滞非线性中立型方程解振动的充分条件．当此类方程的所有系数和时滞变元都是常数时，所给条件是ｓｈａｒｐ条件．所得结论推广并改进了已知的一些结果     

模糊细胞神经网络系统鲁棒稳定性分析

采用Lyapunov稳定理论,通过构造Lyapunov函数方法研究具有变时滞模糊神经网络系统鲁棒稳定性,给出了具有变时滞模糊神经网络系统鲁棒渐近稳定性的充分条件.     

变时滞反馈控制的混合中立型随机延迟微分方程的指数稳定性

研究了变时滞反馈控制的混合中立型随机延迟微分方程(HNSDDEs)的指数稳定性。采用函数方法设置合适的变时滞反馈控制函数,得到了该系统的指数稳定性。对比已有的研究成果,本文的主要贡献是在变时滞反馈控制下对HNSDDEs的指数稳定性作了进一步研究。最后,给出一个例子证明了结论的有效性。     

一类时变时滞静态神经网络的指数稳定性

基于线性矩阵不等式方法建立了时变时滞静态神经网络的指数稳定判据.考虑到时滞变化率对稳定性能的影响,分别建立了仅依赖时滞上界的稳定判据和完全依赖时滞信息的稳定判据.所得到的稳定判据能够适应慢变时滞和快变时滞两种情况,具有适用范围宽、保守性小和易于验证等特点,并通过几个注释说明与现有的文献结果进行了比较.仿真示例验证了所得结果的有效性.     

变时滞反馈控制的混合中立型随机延迟微分方程的稳定性

研究了变时滞反馈控制的具有时变延迟的高度非线性混合中立型随机微分方程(NSDDE)的稳定性.通过Lyapunov函数方法研究了该随机系统LP的渐近稳定性和H∞稳定性.对比已有的科研成果,该研究的主要贡献是将反馈控制函数和系统本身的时滞从常时滞推广到变时滞.最后,用一个例子来证明结论的有效性.     

一类具有分段常数变元的时滞微分方程解的收敛性

本文利用推广的Ｇｒｏｎｗａｌｌ－Ｂｅｌｌｍａｎ不等式给出具有多个分段常数变元的时滞微分方程解与具有连续变元的中立型时滞微分方程解之间的极限关系。     

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