Optically Tunable Nonlinearities in Polymers Based on Photoisomerizable Metal‐Based Coordination Complexes

The bottom‐up design of polymer films exhibiting quadratic nonlinear optical properties that can be tuned optically and chemically is described. The polymer matrices are doped with metal‐containing chromophores built around a Zn^II core and photoisomerizable ligands with two different geometries. These molecules possess specifically designed photophysical and nonlinear optical properties to be used towards all‐optical poling, an interference process between one‐ and two‐photon excitations that locally induces macroscopic second‐order effects in polymer films. It is shown that grafting the molecules onto the polymer chains improves the stability of the macroscopic photoinduced nonlinearity in the films.     

反复荷载下钢筋混凝土剪力墙的非线性有限元分析

本文介绍了反复荷载下非线性有限元分析程序,该程序针对钢筋混凝土剪力墙类结构的特点,采用了钢筋与混凝土复合单元计算模型,考虑混凝土裂面接触效应的反复加载混凝土应力-应变关系。在钢筋应力-应变关系中,还同时考虑了混凝土开裂后钢筋的拉伸强化效应及反复荷载下钢筋的Bausinger效应。本文还介绍了作者利用该程序对反复荷载试验的试件及Ger-venka的剪力墙板进行的计算分析。结果表明,本文所采用的分析模型是合理、准确的;和国内外以往的分析比较,本文的方法成功地消去了力-位移滞回曲线中的拐点现象,而且计算的混凝土裂缝开闭也能和实测较好地吻合。表明本文方法能为分析反复荷载下钢筋混凝土剪力墙类结构性能提供一个准确、有力的工具。     

Parameter identification for nonlinear systems: Guaranteed confidence regions through LSCR

In this paper we consider the problem of constructing confidence regions for the parameters of nonlinear dynamical systems. The proposed method uses higher order statistics and extends the LSCR (leave-out sign-dominant correlation regions) algorithm for linear systems introduced in Campi and Weyer [2005, Guaranteed non-asymptotic confidence regions in system identification. Automatica 41(10), 1751-1764. Extended version available at 〈http://www.ing.unibs.it/∼campi〉]. The confidence regions contain the true parameter value with a guaranteed probability for any finite number of data points. Moreover, the confidence regions shrink around the true parameter value as the number of data points increases. The usefulness of the proposed approach is illustrated on some simple examples.     

Author's reply to “Comments on ‘Performance evaluation of UKF-based nonlinear filtering”’

It is stated in the above-mentioned comment that the main result of the paper Xiong, Zhang, et al. [(2006). Performance evaluation of UKF-based nonlinear filtering. Automatica 42(2), 261-270] can be extended to a class of filters, such as the extended Kalman filter (EKF). As we show here, this belief can be justified in a rigorous way, even for the nonlinear stochastic system with a nonlinear measurement equation.     

热能表中计算器非线性修正方法探讨

本文针对目前热能表中大量存在的计算器准确度较低的问题,提出了使用高次曲线拟合的非线性修正方法,提高了准确度.     

转子--轴承系统油膜失稳故障预测准则的探索

采用稳态非线性轴承理论，以多自由度转子系统为对象，运用模态降阶和变步长的Newmark积分方法，对非线性油膜力作用下轴颈振动的涡动轨迹、频谱及失稳前后的特征进行详细的计算分析，同时分析转子不平衡量的大小和转速对系统振动行为及其稳定性的影响。通过分析给出处于临界稳定状态的转子系统的轴心轨迹及其频谱图特征，这些结果有望对油膜失稳故障的预测和防范提供有应用价值的理论依据。     

Nonlinear black-box modeling in system identification: a unified overview

A nonlinear black-box structure for a dynamical system is a model structure that is prepared to describe virtually any nonlinear dynamics. There has been considerable recent interest in this area, with structures based on neural networks, radial basis networks, wavelet networks and hinging hyperplanes, as well as wavelet-transform-based methods and models based on fuzzy sets and fuzzy rules. This paper describes all these approaches in a common framework, from a user's perspective. It focuses on what are the common features in the different approaches, the choices that have to be made and what considerations are relevant for a successful system-identification application of these techniques. It is pointed out that the nonlinear structures can be seen as a concatenation of a mapping form observed data to a regression vector and a nonlinear mapping from the regressor space to the output space. These mappings are discussed separately. The latter mapping is usually formed as a basis function expansion. The basis functions are typically formed from one simple scalar function, which is modified in terms of scale and location. The expansion from the scalar argument to the regressor space is achieved by a radial- or a ridge-type approach. Basic techniques for estimating the parameters in the structures are criterion minimization, as well as two-step procedures, where first the relevant basis functions are determined, using data, and then a linear least-squares step to determine the coordinates of the function approximation. A particular problem is to deal with the large number of potentially necessary parameters. This is handled by making the number of ‘used’ parameters considerably less than the number of ‘offered’ parameters, by regularization, shrinking, pruning or regressor selection.     

非线性动态系统“黑箱”建模方法的研究

本文研究弱非线性动态系统“黑箱”建模的理论和方法，并简要给出根据此方法建模的结果。     

On uniform observation of nonuniformly observable systems

In [4,7,9,12], classes of nonlinear systems are considered for which observers can be designed. Although observability of nonlinear systems is known to be dependent on the input, the proposed observers have the property that the estimation error decays to zero irrespective of the input. In the first part of this paper, it is shown that this phenomenon follows from a common property of these systems: for all of them, the “unobservable states” with respect to some input, are in some sense “stable” (in the linear case, these systems are called detectable), and for this reason, a reduced order observer can be designed. In the second part is given a more general class of nonlinear systems for which such an observer can be designed.     

A globally stable discrete-time controller for current-fed induction motors

In this short paper we present a discrete-time field oriented controller (FOC) for current-fed induction motors which insures global asymptotic speed regulation as well as rotor flux norm tracking. To the best of our knowledge, this is the first time such a result is rigorously established for a controller implemented in discrete-time. To insure global stability a condition on the reference for the rotor flux norm, which is time-varying, is imposed. This condition disappears as the sampling period goes to zero, hence allowing for independent speed regulation and rotor flux norm tracking. One important feature of our scheme is that, compared with the first-difference approximation of the classical indirect FOC, the additional computational burden is negligible. It is also shown that the result can easily be extended to the case of tracking time-varying references in speed or position.