基于微分几何的非线性汽车悬架主动控制

汽车悬架是复杂的非线性系统,采用传统的近似线性化方法得到的模型不够精确,文章建立了1/4车悬架系统非线性振动模型,应用基于微分几何理论的精确线性化方法,通过恰当的坐标变换和非线性状态反馈将系统简化为一线性系统,实施线性最优控制策略解得控制器。作为比较,建立了传统的近似线性化1/4车悬架系统的模型,应用线性最优控制策略获得控制器。最后将这2个控制器的控制效果进行仿真比较,结果表明前者效果较好。     

一级直线型倒立摆的控制及实现

研究一级直线型倒立摆的起摆、镇定与跟踪问题.采用基于Lyapunov能量反馈方法和基于精确线性化与LQR(linear quadratic regulator)算法结合的方法设计控制器,提出分阶段起摆的控制思想,并将这两种控制器有效地联系起来,最后对控制器的跟踪性能作了讨论.仿真结果与上机实验表明了方法的有效性和优越性.     

基于精确线性化理论的倒立摆系统最优控制

倒立摆是自动控制理论研究的典型实验设备,由于其具有强非线性与强耦合性,一直是先进控制算法研究的热点.文章采用了一种微分几何方法--李理论,对倒立摆系统进行精确反馈线性化,此种线性化方法使模型更多地保留了原系统主要的非线性部分,更能逼近实际系统.在此线性化模型的基础上,对倒立摆系统进行最优稳定控制设计.仿真结果表明,所提出的精确反馈线性化方法对于倒立摆系统的控制器设计是有效的.     

基于T-S模糊模型的Nadolschi混沌系统同步控制

为了实现一类新型混沌系统的同步控制,提出一种基于T-S模型的模糊控制方法。利用T-S模糊模型对Nadolschi混沌系统进行精确描述;采用并行分布补偿技术设计状态反馈控制器;进而将Nadolschi系统的同步控制问题转化为误差模糊系统零平衡点的镇定问题。然后,利用精确线性化的方法将误差模糊系统转换成定常系统,最后,根据线性系统理论,得出使Nadolschi混沌系统达到渐近同步的充分条件。仿真结果验证了所提方法的有效性,所设计的模糊控制器具用结构简单,规则少,控制响应速度快等优点。     

带有执行器的船舶航向控制反馈线性化设计

针对带有执行机构的船舶航向保持控制系统，采用输入．状态反馈线性化方法设计控制器．由于船舶航向保持控制系统数学模型满足“三角形系统”的形式，可以直接得到反馈线性化的充分必要条件，可以避免反馈线性化理论中复杂对合条件的验证．基于该控制器，可以使得偏航船舶以指数渐进镇定于设定航向．并以大连海事大学远洋实习船“育龙”号为例，利用Matlab的Simulink工具箱进行了仿真研究，对所提出的控制器进行了验证．     

基于神经模糊系统的自适应前馈-反馈控制系统设计

在前馈控制器设计思想的启发下,提出了一种基于神经模糊系统的自适应前馈-反馈控制系统。该控制系统首先把非线性过程近似为一个线性的ARX模型和一个基于神经模糊系统的线性化误差模型(FNNM)组成的合成模型,把线性化误差模型的输出看作可测量的"扰动",然后再引入前馈控制器,利用被控制过程的输入、误差模型的输出、线性ARX模型输出和系统输出值之间的误差以及被控制过程的合成模型的梯度信息对控制器参数进行在线调节,从而获得较好的控制结果。将提出的基于线性化误差模型的自适应控制系统用于简单不可逆放热反应的连续搅拌型化学反应器CSTR中,并与传统的PID控制器进行比较。仿真结果表明:这种基于神经模糊系统的自适应前馈-反馈控制器和PID控制器相比,能得到更快、更好的控制效果。     

基于反馈精确线性化的电力系统混沌振荡控制

借助于三母线电力系统模型,说明了无功功率变化会引起电力系统出现混沌振荡现象,并导致负载电压骤降。为了抑制混沌振荡,提高电力系统运行的稳定性,应用基于微分几何的反馈精确线性化方法,通过严格的状态变换和反馈方法,将非线性电力系统反馈线性化,并得到非线性反馈控制律来控制电力系统中的混沌。仿真结果表明,加入设计好的控制器后,消除了电力系统中的混沌,负载电压很快趋于稳定,受控后的电力系统是渐进稳定的,收敛速度快,没有出现电压崩溃现象。     

基于反馈线性化的气压伺服系统非线性H∞控制

该文将基于直接反馈线性化的非线性H∞控制策略应用于气压伺服系统。一方面，引入反馈线性化把具有强非线性的气压伺服系统转化为伪线性系统，从而可利用线性系统理论进行控制器设计；另一方面，引入H∞控制，处理由于模型不准确，运行参数的摄动等引起的鲁棒性问题。这使得对于气压伺服系统能够按照一定的性能指标来设计控制器，并且该控制器对于系统运行参数摄动和建模不准确具有鲁棒性。     

用精确线性化方法设计的SVC非线性控制器

用非线性控制系统几何理论中状态反馈精确线性化方法设计了 ＳＶＣ非线性控制器，解决了电力系统强非线性给设计带来的困难。在此基础上，针对单机无穷大系统进行了数字仿真。分析和仿真结果表明：ＳＶＣ的非线性控制方式与ＳＶＣ的常规控制相比，可以显著地改善电力系统的稳定性。     

反馈线性化方法在锅炉-汽轮机系统控制中的应用

为提高锅炉 -汽轮机系统的信号跟踪和抗干扰能力 ,利用输入 -状态反馈线性化和输入 -输出反馈线性化方法分别设计了锅炉 -汽轮机系统的控制律。对于输入 -状态线性化方法由于输入状态为线性关系 ,因此系统可以在较大的范围内正常的工作。对于输入 -输出线性化方法可以验证系统在平衡点邻域零动态稳定 ,然而计算机仿真表明利用输入 -输出反馈线性化设计的控制器由于零动态的稳定范围较小 ,系统只能工作在工作点的邻域。基于以上结果对输入 -状态和输入 -输出反馈线性化方法进行了比较分析。计算机仿真表明利用输入 -状态线性化方法所设计的控制器具有良好的信号跟踪和抗干扰能力     

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