Asymptotic stabilization of a class of continuous-time linear periodic systems

In this paper, the problem of the asymptotic stabilization of a class of continuous-time linear periodic systems is considered. First, under a simplifying assumption, necessary conditions, involving the concept of left eigenvector, are derived for the asymptotic stabilization of continuous-time linear periodic systems belonging to such a class. Then, under the same simplifying assumption, conditions are given under which a static state feedback control law can be designed, in an iterative manner, so that the closed-loop system is π-stable.     

Computational p-element method on the effects of thickness and length on self-weight buckling of thin cylindrical shells via various shell theories

This paper is concerned with the development of a global p-element method for the analysis of self-weight buckling of thin cylindrical shells. Such buckling problems occur when cylindrical shells are subject to high-g acceleration, for instance the launching of rockets and missiles under high propulsive power. The cylindrical shells may have any combination of free, simply supported and clamped ends. A p-element computational method has been developed based on various thin shell theories including Donnell, Sanders and Goldenveizer-Novozhilov models. The strain energy for the global element during buckling is formulated and an eigenvalue equation is derived. Unlike the conventional buckling problem where the eigenvalue is directly solved, a pre-determined buckling parameter is fixed at the outset for a geometric-dependent stiffness and a recursive numerical procedure is developed to compute the effect of critical buckling length. The critical buckling length is found to be proportional to thickness to a power of approximately 0.9. The effects of shell thickness and length on buckling parameter are also investigated. Comparison of results from various shell theories indicates solutions of the Sanders and Goldenveizer-Novozhilov shell theories are in excellent agreement while the Donnel shell theory is good for buckling of short cylindrical shells.The work described in this paper was fully supported by grants from City University of Hong Kong [Project Nos. 7001186 (BC) and 7100256 (BC)].     

Generic eigenvalue assignment by memoryless real output feedback

By extensive use of methods from algebraic geometry, X. Wang proved that arbitrary pole placement by static output feedback is generically possible for strictly proper plants with n states, m inputs, and p outputs, if n < mp. Here we show the same result using no more of algebraic geometry than the definition of genericity.     

基于分离度的图象特征提取与识别方法

对于图象中不同类别（以其统计分布函数一表征）的可识别性，分离度的统计定义可做出定量的描述。根据分离度在一一对应映射变换下的不变性，应用Ｋａｒｈｕｎｅｎ－Ｌｏｅｖｅ变换对两类分布撮识别特征，发现分离度只依赖于特征值最大和最小的两个特征向量。而且，分离度的大小依赖于特征值怀某个定定值的偏差。由此我们提出一个识别模型，使每次分类后的样本集的特征值都趋近于两上定值，从而得到最佳的识别效果。由该模型设计的     

Impact of wind generation uncertainty on power system small disturbance voltage stability: A PCM-based approach

The connection of wind generators with electric power system influences the system stability and nodal voltages. This paper performs uncertainty analysis to investigate the impact of wind generation variation on the small disturbance voltage stability. The probabilistic collocation method (PCM) is presented as a computationally efficient method to conduct the uncertainty analysis. It has been implemented in a simple system to demonstrate its applicability in analyzing wind generation uncertainty. More case studies on a larger system are conducted to obtain a deeper understanding of how the system voltage stability is affected by the integration of DFIG-based wind farms. As compared with the traditional Monte Carlo simulation method, the collocation method could provide a quite accurate approximation for the eigenvalue probabilistic distribution with fewer simulation runs.     

线性回归中粗差的特征值判别法及其应用

随着仪器仪表智能化程度的提高，在线性回归中寻求较好的粗差剔除算法变得越来越重要。通常的方法是在所有观测值的基础上作一初始的线性回归，然后将离差最大的点作为可能的粗差点。该方法常由于粗差值参与初始回归造成的不准确而发生判别错误。本文提出一种在线性回归中用特征值方法判别粗差点的方法，它不依赖于初始的回归离差，从而提高了判别的准确性。该方法应用于智能离子计中有关线性回归校正法及Ｇｒａｎ法数据处理软件中，取得满意的效果。     

齿轮耦合对转子-轴承系统固有特性的影响

计算了齿轮耦合的转子 -轴承系统及其非耦合子系统的特征值及其振型 ,并对特征值和振型进行了比较。在耦合系统中 ,子系统的某些特征值及其振型没有产生变化 ,而另一些却发生了变化。新产生的振型多为弯扭耦合振型。在大多数振型中 ,每一个子系统都有位移产生 ,因此 ,一个子系统中的不平衡质量将引起整个系统产生振动。     

基于新极化特征参数的SAR海洋溢油检测

为了提升海上油膜与其他目标的可分离程度,提出基于特征值分解的一种新的极化特征G,该特征不仅能够反映集合中不同目标之间的极化状态,还能够描述不同散射类型在统计意义上的不纯度。若某个区域中去极化状态越弱,不纯度越低,则该区域中新极化特征G的值越低。利用两景Radarsat-2全极化SAR (Synthetic Aperture Radar)影像对新特征的有效性进行实验验证。结果表明：海水具有较小的特征值,油膜具有较大的特征值,生物膜的特征值介于两者之间。且与span、\bar{\mathrm{\alpha }}、P、A、CPD等5种经典的极化特征相比,新特征在图像对比度、局部标准偏差及概率密度曲线等三个指标上均有更好的表现,不仅能区分生物膜（植物油模拟）与原油,且具有更好的抑噪性。     

半刚性连接钢管混凝土框剪结构的计算探讨

通过引入梁的等效惯性矩,导出半刚性连接框架剪力墙结构中的重要参数-结构刚度特征值的计算公式;探讨了半刚性连接对框剪结构中剪力墙位移系数、弯矩系数、剪力系数和框架剪力系数等的影响;使用ANSYS建立了半刚性连接钢管混凝土框剪结构的有限元模型.算例分析表明:ANSYS分析结果和本文公式计算结果吻合较好.据此,提出了考虑半刚性连接的设计建议,可供工程设计人员参考.