元胞自动机仿真技术

元胞自动机仿真技术（CAST）开创了探索复杂性的新途径,在材料、生物、物理等领域有广泛的应用前景,是发达国家激烈竞争的重大前沿学科领域．本文综述了CAST的产生与发展过程,概括了仿真模型的构成要素,评述了CAST的典型应用实例,着重指出了CAST是对材料进行原子级微观辅助设计的强有力工具．最后,探讨了CAST的特点：它抓住了简单性与复杂性这一对主要矛盾,从而触及并体现了其它有关矛盾,诸如局部与整体,宏观与微观,线性与非线性,决定性与随机性,数学模型与物理实质．     

Using ROC curves to assess the efficacy of several detectors of damage-induced nonlinearities in a bolted composite structure

We offer a comparison of several different detectors of damage-induced nonlinearities in assessing the connectivity of a composite-to-metal bolted joint. Each detector compares the structure's measured vibrational response to surrogate data, conforming to a general model for the healthy structure. The strength of this approach to detection is that it works in the presence of certain types of varying ambient conditions and is valid for structures excited with any stationary process. Here we employ several such detectors using dynamic strain response data collected near the joint as the structure was driven using simulated wave forcing (taken from the Pierson–Moskowitz frequency distribution for wave height). In an effort to simulate in situ monitoring conditions the experiments were carried out in the presence of strongly varying temperatures. The performance of the detectors was assessed using receiver operating characteristic (ROC) curves, a well known method for displaying detection characteristics. The ROC curve is well suited to the problem of vibration-based structural health monitoring applications where quantifying false positive and false negative errors is essential. The results of this work indicate that using the estimated auto-bicoherence of the systems response produced the best overall detection performance when compared to features based on a nonlinear prediction scheme and another based on information theory. For roughly 10% false alarms, the bicoherence detector gives nearly 90% probability of detection (POD). Conversely, for several of the other detectors 5–10% false alarms leads to 70% POD. While the bicoherence (and bispectrum) have been used previously in the context of damage detection, this work represents the first attempt at using them in a surrogate-based detection scheme.     

A comparison of Carlet's second-order nonlinearity bounds

Carlet provides two bounds on the second-order nonlinearity of Boolean functions. We construct a family of Boolean functions where the first bound (the presumed weaker bound) is tight and the second bound is strictly worse than the first bound. We show that the difference between the two bounds can be made arbitrarily large.     

基于切换模型的无人直升机偏航通道系统辨识方法?

针对直升机偏航通道中舵机控制量的饱和非线性问题,提出基于切换模型的无人直升机偏航通道系统辨识方法。首先分析无人机偏航通道的特征,建立包含饱和单元的切换模型。其次通过扫频实验采集辨识所需的数据,并在频域下采用遗传算法辨识得到切换模型的所有参数。再根据实验数据分析辨识模型的残差序列,得到系统的残差模型,并利用该残差模型修正辨识得到的无人机偏航通道模型,进一步提高模型的准确度。最后通过实验数据分析文中模型的准确性,并利用该模型设计无人机飞行控制器。实验结果也证明模型的有效性。     

高阶模糊控制器在网络控制系统中的应用

当网络控制系统存在非线性随机延迟时，不能直接使用传统的控制方法。针对这种随机延迟该文提出了高阶模糊控制方法。该方法在经典PID控制器的理论基础上进行改进，增加了系统输出的高阶信息，同时利用模糊控制理论对控制器参数进行在线自适应调节。为此该文首先简要地介绍了网络控制系统中存在的随机延迟，然后分析了延迟引起的非线性特征。结合该文的算法思想和模糊控制器的设计原理给出模糊控制器的设计过程。最后给出了应用此方法的一个仿真实例。     

简化的330MW机组非线性动态模型

该文采用机理分析和数据拟合的方法，建立330MW机组滑压运行下大负荷变化范围内的模型。该模型的主要特点是：将水冷壁换热过程归入制粉动态，将锅炉汽包蓄热及过热器蓄热做为一体考虑，在能够反映机组主要动态的前提下降低了模型的阶次；指出机组制粉动态惯性时间和锅炉蓄热系数是随机组负荷和压力变化的，并根据现场数据和机理分析分别给出其变化趋势；考虑到蒸汽在过热器管道内是吸热膨胀的过程并且有减温水的喷入，对过热器差压模型进行了修正，以锅炉吸热量代替主蒸汽流量建立模型。模型使用机组55％～100％负荷时的静态工作点数据确定静态参数，通过汽轮机调门扰动和燃料扰动实验确定动态参数，经过机组运行数据验证，该模型具有较好的复现性，可用于控制系统的设计和控制算法的性能评价。     

pH过程的模糊控制仿真研究

pH过程广泛存在于化工、生物工艺、污水处理、发电等工业过程中，对这一过程进行良好的控制有着十分重要的意义。由于pH过程是一个具有严重非线性及滞后性的被控对象，传统的PID控制难以达到理想的控制效果。本文使用模糊控制技术，设计采用了带有自调整因子的模糊控制器，不仅能较好地处理pH过程的严重非线性和滞后性，而且具有较强的鲁棒性和抗干扰能力。     

Toward a unified description of nonlinearity and frequency dispersion of piezoelectric and dielectric responses in Pb(Zr,Ti)O3

A phenomenological approach is proposed describing both nonlinearity and frequency dispersion in dielectric and piezoelectric properties of lead zirconate titanate, Pb(Zr,Ti)O₃ (PZT), thin films and ceramics. The approach couples the frequency dependent response in form of the power law, 1/ω^β, with the rate-independent nonlinear response described by the Rayleigh law. The main experimental trends are well described by the model.     

静态测量系统线性度与温度的模型化补偿方法

本介绍了一种对静态线性测量系统的线性度和温度效应进行补偿的模型化方法。使用多变量多项式回归模型表述静态测量系统的传递特性,以求获得对“线性测量系统”的精确描述,达到对其线性度和温度特性进行补偿,从而实现精确测量的目的。选用一个压力测量系统作为实验例证,验证了本所述方法的实用性和可行性。