Graded Witt ring and unramified cohomology

It is proved that for a smooth affine curveX over a local ring or global field, the graded Witt ring ofX is isomorphic to the graded unramified cohomology ring ofX. IfX is projective and has a rational point, the same result holds if and only if every quadratic space defined on the complement of a rational point extends toX. Such an extension is possible, for instance, if the canonical line bundle onX is a square in PicX.     

Shell Partition and Metric Semispaces: Minkowski Norms, Root Scalar Products, Distances and Cosines of Arbitrary Order

Vector semispaces are studied from a realistic way with the intention to define a natural metric, adapted to their peculiar structure, which reside on the essential positive definiteness of their elements. From this point of view, Minkowski norms allow classifying semispaces in shells, that is: subsets where all the vector elements possess the same norm values. Shell structure appears to be a possible disjoint partition of any semispace and so shells become equivalence classes Then, the unit shell appears to be the core of the semispace homothetic construction as well as the origin of the semispace metrics. Minkowski or root scalar products permit to connect two or more semispace elements and conduct towards generalized definitions of Pth order root distances and cosines. Finally, the unit shell of a given semispace, in company of both Boolean tagged sets, inward matrix products and with the aid of the matrix signatures as well, it is seen as the seed to construct any arbitrary element of the semispace connected vector space. Finite and infinite dimensional vector spaces application examples are provided along the work discussion.     

高斯切趾型光纤布拉格光栅外腔半导体激光器的混沌输出特性

基于光反馈半导体激光器(SL)速率方程模型,理论仿真研究了高斯切趾型光纤布拉格光栅(GAFBG)反馈SL(GAFBGF-SL)混沌输出的延时特征(TDS)以及混沌带宽特性.结果表明:随着反馈强度的增加,GAFBGF-SL表现出由准周期进入混沌的动力学演化路径;通过合理选择GAFBG布拉格频率与SL中心频率之间的频率失谐及反馈强度,GAFBGF-SL混沌输出的TDS能得到有效抑制(低于0.02);通过进一步绘制混沌信号TDS及带宽在GAFBG布拉格频率与SL中心频率之间的频率失谐和反馈强度构成的参量空间中的分布图,确定了获取弱TDS、宽带宽光混沌信号的参数范围.     

Suboptimal control of systems with multiple delays

The application of Pontryagin's maximum principle to the optimization of linear systems with time delays results in a system of coupled two-point boundary-value problems involving both delay and advance terms. The exact solution of this system of TPBV problems is extremely difficult, if not impossible. In this paper, a fast-converging iterative approach is developed for obtaining the suboptimal control for nonstationary linear systems with multiple state and control delays and with quadratic cost. At each step of the proposed method, a linear nondelay system with an extra perturbing input must be optimized. The procedure can be extended for the optimization of nonlinear systems with multiple time-varying delays, provided that some of the nonlinearities satisfy the Lipschitz condition.     

Delay-independent absolute stability for time-delay Lur''e systems with sector and slope restricted nonlinearities

This Letter presents an analysis method for a delay-independent absolute stability of time-delay Lur'e systems with sector and slope restrictions. The proposed method is based on the Lyapunov functions with quadratic form of states and nonlinear functions of the systems. Several criteria are derived in terms of linear matrix inequalities (LMIs). A numerical example is illustrated to show the effectiveness of the proposed method.     

一类二阶时滞微分方程在控制系统中的应用

基于时滞微分方程稳定性理论,针对一类状态向量中含有时滞的控制系统,研究其时滞相关稳定性问题.通过构造Lyapunov函数,获得了系统稳定、分岔的时滞相关充分条件,所得结论推广和改进了某些已有文献的相应结果.且借助实例及仿真结果解释所得结果的有效性.     

基于观测器的模糊时滞系统指数稳定的一种设计方法

研究了一类模糊时滞系统的指数稳定问题.首先利用T-S模型对非线性不确定性时滞系统进行建模,在此基础上设计了基于观测器的模糊状态反馈控制器,通过巧妙选取Lyapunov函数给出了模糊闭环时滞系统的条件及稳定裕度且模糊反馈增益和模糊观测器增益可通过求解线性矩阵不等式获得.     

LMI Optimization Approach to Observer-Based Controller Design of Uncertain Time-Delay Systems via Delayed Feedback

In this paper, we propose a design method of an observer-based controller for uncertain time-delay systems by delayed feedback. Based on the Lyapunov method, an LMI (linear matrix inequality) criterion is derived to design an observer-based controller which makes the system stable. A numerical example is included to illustrate the design procedure.     

电力系统中的非同期合闸产生过电压控制模型研究

本文首先建立了电力系统中非同期合闸过电压的时延控制系统的数学西模型,得到了相应闭环系统的稳定性以及振动性,同时利用时延控制次优控制的灵敏度系数研究者到了该系统的次优控制设计方法及相应的次优控制设计过程,最后我们结合采样数据,利用泛函微分方程的分布迭代方法进行数值计算,得到了均优于已有文献的结果。     

考虑控制延时影响的相邻建筑结构的离散变结构振动控制方法

研究了基于离散变结构控制算法的考虑控制延时影响的相邻建筑结构体系地震反应半主动控制的基本设计和计算方法。首先,建立了相邻结构体系的力学模型及连续运动状态方程,并将其离散化成标准离散状态方程形式。其次,简要地讨论了离散变结构控制器的设计方法,包括切换平面的选择及离散趋近率的构成．最后,应用本文方法对主楼12层,裙房5层的实例结构进行了数值仿真分析,结果表明,该控制方法不仅能有效抑制相邻结构地震反应的鞭梢效应,而且在控制延时存在的情况下,仍能保证系统的减震性能和稳定性。