不确定输入时滞系统的滞后相关型鲁棒H∞控制

针对带有输入时滞的不确定线性时滞系统,基于适当形式的Lyapunov泛函,利用线性矩阵不等式方法讨论了时滞相关型鲁棒H∞状态反馈控制器设计问题,其中不确定性是时变未知的,满足范数有界条件,且控制器存在的充分条件由线性矩阵不等式的形式给出.给出了一个应用实例,并与已有结果进行了比较.与通常所采用的导出时滞相关型鲁棒H∞状态反馈控制器的设计方法相比,只需进行两次矩阵不等式的放大,就可得到相应的控制器设计方案.仿真结果表明控制器设计方案具有较小的保守性.     

多时滞不确定系统的鲁棒指数镇定

基于新型稳定性分析技术及线性矩阵不等式方法,研究了含有参数不确定性的线性多时滞系统的鲁棒指数镇定问题.首先,对不含参数的不确定性时滞系统设计无记忆状态反馈控制器,给出了在该控制器作用下,闭环系统指数稳定的线性矩阵不等式形式的充分条件;然后,将其推广到含有范数有界参数不确定性的时滞及多时滞线性不确定系统,得到了保证系统鲁棒指数稳定的充分条件,并提供了指数衰减度及衰减因子的估计方法.所给出的判据避免了现有文献中对时变时滞导数小于1的要求,比已有的结果具有更少的保守性,数值例子验证了本方法的有效性.     

一类混合时滞系统对时滞参数的自适应控制

研究了一类较为复杂的混合时滞系统——被控状态为连续形式且状态时滞参数未知,而控制输入为离散序列.在分别建立了连续与离散的模型基础上,根据已有的混合系统的稳定性定理及一种Lyapunov-Krasovskii泛函方法,提出了一种镇定系统的方法,并得到了离散形式的可用于控制输入的对未知时滞参数的自适应律.在该自适应律作用下,未知时滞参数能始终反映在带记忆状态反馈控制器中,依赖于时滞的反馈控制器存在的充分条件可通过一组线性矩阵不等式(LMIs)表示.     

不确定广义时变时滞系统的鲁棒H_∞控制

针对具有时变时滞和线性分式参数不确定性广义系统,研究基于状态反馈的鲁棒H∞控制问题.利用增广Lyapunov泛函并结合自由权矩阵方法,保留了Lyapunov泛函导数中的时滞上界信息,得到时变时滞广义系统的一个新的有界实引理(BRL).在此基础上,给出不确定广义时变时滞系统H∞状态反馈控制律的一个直接设计方法.所给结果均以严格线性矩阵不等式(LMI)表示.数值实例表明了结果的有效性和较小保守性.     

具头胞型不确定性时滞系统的鲁棒控制

探讨了一类带有头胞型不确定性非线性时滞系统的鲁棒镇定问题,利用参数相关的Lyapunov泛函,设计了状态反馈控制律使闭环系统鲁棒稳定.以线性矩阵不等式形式给出主要结果,所期望的状态反馈控制律可通过求解给定的线性矩阵不等式得到.所得结论是时滞相关的,保守性相对较小.     

具有状态和控制时滞的不确定线性系统的鲁棒镇定

针对仿射参数不确定性和范数有界不确定性,研究具有状态和控制时滞的不确定线性系统的鲁棒镇定问题·基于Lyapunov泛函,利用线性矩阵不等式给出了系统可由状态反馈鲁棒镇定的充分条件,并且利用线性矩阵不等式的解构造了状态反馈控制律·所得线性矩阵不等式直接保证Lyapunov泛函对时间的导数为负,降低了控制器设计的保守性·最后,给出两个算例说明本文方法的有效性·     

变时滞不确定性神经网络的鲁棒稳定性标准

研究了一类带变时滞和参数不确定的神经网络鲁棒稳定性问题。其中考虑的不确定性为范数有界不确定性,系统参数具有的这种不确定性是与时间相关的,但它的参数被限制在一定范围内,时间滞后函数是随时间变化而改变的,但它的导数是小于1的。并且通过一个线性矩阵不等式的方法得到一个充要条件,这个充要条件可以使带时滞的神经且有一个平衡点,并且在这个平衡点上具有鲁棒稳定性。这种基于线性矩阵不等式的充分条件可以通过近年发展的解线性矩阵不等式的算法得到数值结果,并通过数值例子说明了这个技术的有效性。     

网络环境下混合时滞系统对时滞参数的自适应控制

在网络环境下,建立了一类复杂的混合时滞系统模型,该模型被控对象为连续系统,控制输入为离散序列且状态时滞参数未知.在分别建立了连续与离散的模型基础上,根据已有的混合系统的稳定性定理,提出了一种镇定系统的方法,并得到了离散形式的可用于控制输入的对未知时滞参数的自适应律.控制方法基于一种Lyapunov-Krasovskii泛函,且在得到的自适应律作用下,对未知时滞参数的估计值能始终被反映在带记忆状态反馈控制器中,且依赖于时滞的反馈控制器,存在的充分条件均可通过一组线性矩阵不等式LMIs表示.     

时滞依赖不确定状态时滞系统鲁棒故障诊断

针对一类具有未知输入和模型不确定性的动态时滞系统,基于H∞滤波器技术,提出了一种鲁棒故障诊断方法.首先引入一个参考模型,形成广义残差系统,然后引入一个新的具有时滞依赖的有界实引理;利用对偶原理,针对对偶系统,借助线性矩阵不等式(LMI)技术,给出了基于状态观测器的时滞依赖鲁棒故障诊断滤波器(RFDF)设计方案,推导出具有时滞依赖解存在的条件以及观测器增益矩阵的求解算法.仿真算例验证了该方法的有效性.     

具有时变时滞的广义系统的稳定性判别方法

针对时滞是时变的且属于一个区间的情况,研究时滞广义系统的稳定性问题.利用4个线性矩阵不等式给出了系统正则、无脉冲且渐近稳定的判别方法.把时滞区间分成两个相等的子区间,对应于每个子区间,利用适当的不等式对积分的系数进行放大,把Lyapunov-Krasovskii泛函导数的上界表示成某个参数的仿射函数.用两个线性矩阵不等式保证该导数的负定性,进而推广了文献中的凸组合方法.理论分析和数值算例表明,所得结果比现有结果具有更小的保守性.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

<正>~~     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme     

WIMAX与WI-FI技术分析及联合组网

介绍了WiMAX与Wi-Fi两种无线宽带接入技术,并对两者之间的关系及相互之间的影响做了对比及分析,并对WiMAX的关键技术进行了详细说明,最后对两者的联合组网方式做了简单的探讨。