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1.
The study focuses on residential mobility propensities of Vietnamese immigrants in the city of Brisbane, Australia, as a principal force contributing to the persistence or change of ethnic residential segregation over time. Using 1990 survey data, discrete-time logit models are estimated to assess the effects of locational, contextual, and personal characteristics on the likelihood of changing residence within the city. The results indicate that locational variables operate in such a way that the most dominant Vietnamese neighborhood in Brisbane increases its prominence even further, while secondary Vietnamese clusters are likely to weaken. The results also indicate that initial settlement conditions are important for the first move only, whereas personal attributes contribute to variations in mobility propensities primarily in the second move. This implies that the composition of the immigrant population potentially influences the speed at which changes in ethnic residential patterns will occur in urban areas. 相似文献
2.
讨论了一类离散非线性系统降维观测器的存在性。对给定的Lyapunov函数,在保证观测误差渐近稳定的条件下,给出了该离散非线性系统降维观测器的设计方法。用数值例子说明了该设计方法的有效性。 相似文献
3.
本文概述了随机镇定与反镇定理论的研究现状.主要回顾了一个微分方程的随机镇定与反镇定普遍理论及其发展,并围绕该理论的应用和扩展从四个方面阐述连续时间系统噪声镇定理论的当前发展概况.此外,本文还概述了离散时间系统随机镇定方面的最新进展. 相似文献
4.
主要研究一类具有不确定项和外部扰动的离散时滞系统的鲁棒自适应控制,假设扰动和不确定项是有界的,而扰动和关于状态的不确定项的边界是不必知道的.设计了自适应控制器以保证系统能在有限时间内到达切换面,并且收敛到包含原点的一定的有界区域内.仿真的结果说明了该方法的有效性. 相似文献
5.
An array of 24 strong-motion accelerometers produced records for the New-Lian River Bridge, a five-span continuous bridge, during 25 February 1995 earthquake (weak motion) and 25 June 1995 earthquake (strong motion). This paper describes the application of linear discrete-time system identification methodology to the array of strong-motion measurements, in order to assess seismic response characteristics of the bridge. The structural system identification will concentrate not only on the global identification but also on the local structural system identification. Results of this application show that: (1) weak and strong ground excitation will induce significant differences on the dynamic response of the bridge; (2) linear models provide an excellent fit to the measured motions of the bridge from the records of these two seismic events; (3) the rigid-body rocking of the bridge pier during strong shaking is significant and cannot be ignored during identification; (4) the transverse motion at mid-span of the bridge is controlled by the quasi-static response from the boundary system and this phenomenon is quite significant during strong ground excitation. Also, systematic estimates of modal damping ratio and equivalent assessments of pier stiffness developed in the bridge during earthquake are discussed. © 1997 by John Wiley & Sons, Ltd. 相似文献
6.
针对一类具有配外部扰动的多输入多输出(MIMO)离散时间系统(DTS),提出了改进的状态观测器的设计方案,使得该观测器不受外部扰动的影响。对外部扰动满足匹配条件的MIMO-DTS,提出了基于状态观测器和扰动估计器的滑模控制器设计方案,该设计方案不要求知道系统的状态和外部扰动的上界。提出的仿真例子说明了本文方法的可行性和有效性。 相似文献
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《The Professional geographer》2013,65(3):344-357
The study focuses on residential mobility propensities of Vietnamese immigrants in the city of Brisbane, Australia, as a principal force contributing to the persistence or change of ethnic residential segregation over time. Using 1990 survey data, discrete-time logit models are estimated to assess the effects of locational, contextual, and personal characteristics on the likelihood of changing residence within the city. The results indicate that locational variables operate in such a way that the most dominant Vietnamese neighborhood in Brisbane increases its prominence even further, while secondary Vietnamese clusters are likely to weaken. The results also indicate that initial settlement conditions are important for the first move only, whereas personal attributes contribute to variations in mobility propensities primarily in the second move. This implies that the composition of the immigrant population potentially influences the speed at which changes in ethnic residential patterns will occur in urban areas. 相似文献
8.
灌溉输配水是水联网链路的重要环节,其自动控制水平直接影响着水联网效率和风险控制能力,对实现水资源高效管理与利用有重要意义。通过变化输水渠道线性积分时滞控制模型,建立了多级联渠道离散时间状态空间方程,基于线性二次型理论设计最优状态反馈控制器,利用MATLAB求解和SOBEK模拟进行了验证。在甘肃省昌马南灌区多级联渠道运行过程优化控制的模拟结果显示,线性二次型算法能够使控制点水位较快恢复并稳定在设定值,控制过程动作与水位波动次数少、幅度小,效果远优于常规分布式PI反馈控制。线性二次型算法能够应对多级联渠道时滞、耦合特性和一般未知取水扰动,实现可靠供水服务和有效运行控制。目前算法仅采用反馈控制,尚无法应对过大未知取水扰动,还有进一步改进空间。 相似文献
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MEMS加速度计的噪声和线性指标是地震监测应用领域的关键问题,采用闭环力反馈是提高这些性能的有效途径。然而,由于对质量块不需要额外的电极来施加电静力,并且其残余位移会给闭环传递函数带来显著的非线性,从而影响该方法的有效性。因此,本文提出一种基于离散时间反馈的闭环MEMS加速度计,分时完成电容变化检测及静电力反馈,最大程度的减小了反馈信号对检测信号的馈通及耦合。利用开关电容电路中的相关双采样电路噪声消除技术,及电路参数噪声优化,可实现噪声谱密度小于0.5μg/Hz1/2的微加速度计。 相似文献
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针对控制器存在随机不确定性的多智能体系统,研究了所有智能体状态达到一致的控制问题.首先,假设智能体连接网络拓扑是无向、固定和连通的,而且每个个体的控制器存在相同的随机不确定性,最终得到了融合随机控制器增益不确定的闭环控制系统模型.应用基于李雅普诺夫稳定性理论、线性矩阵不等式技术和鲁棒控制方法,得到了一种保证误差状态系统渐近稳定的充分条件.进一步通过一系列矩阵变换处理技巧,将状态反馈控制器的存在条件转化为一组线性矩阵不等式的可行解问题.最后应用计算机仿真验证了该控制器设计结果的有效性. 相似文献