Issues in nonlinear stochastic grey box identification

Grey box identification refers to the practice of identifying dynamical systems in model structures exploiting partial prior information. This contribution reviews a method for stochastic grey box identification and surveys experiences and lessons of applying it to a number of industrial processes. Issues to be addressed include advantages and costs of introducing stochastics into the model, the question of what contribution must be expected from the model designer as opposed to what can be formalized in computer algorithms, and an outlook on future plans to resolve present shortcomings.     

泥沙起动条件及机理的非线性研究

 分析了单颗粒、均匀沙及非均匀沙的起动现象及其机理，认为泥沙的起动属于突变论研究的范畴。从泥沙起动所遵循起动条件的力学规律出发，导出泥沙起动条件方程。在此基础上，利用尖点突变性质对各种泥沙起动现象及机理进行了描述和说明。     

混凝土结构非线性全过程分析中的迭代控制法研究

在深入研究各类迭代控制法的基础上，针对混凝土结构的非线性全过程分析，在常规的位移和弧长控制法中引入了简单适用的考虑路径搜寻和单因加速的方法，明显改善了收敛情况。     

广义频率响应函数的鲁棒建模新方法

针对基于非线性谱分析的故障诊断技术的需要,研究了非线性系统的广义频率响应函数的鲁棒在线建模方 法。首先将次元分析算法应用于Volterra级数模型的辨识,并通过对此算法的修正,得到了一种改进的Volterra系统的鲁 棒辨识算法。对其鲁棒性能进行的分析表明,改进算法的鲁棒抗噪性能被明显提高。在此基础上,提出了一种广义频率响 应函数的两步鲁棒建模新方法。仿真实验表明,该方法具有良好的鲁棒收敛性能,能够有效解决GFRF的在线建模问题。     

Iterative finite element model of nonlinear viscoplastic analyses for blended granular porous media

The iterative finite element model, in which an element is used to represent a single particle, is generated to analyze the global behavior of multiple-material aggregates of materially nonlinear viscoplastic particles. The generalized Maxwell model is used to define four types of specific nonlinear viscoplastic materials, which are the elasto visco-plastic matter with linear viscosity, the plasto visco-plastic material with linear viscosity, the elasto visco-plastic media with nonlinear viscosity, and the plasto visco-plastic media with nonlinear viscosity. The theory and relevant penalty iterative algorithm are developed to analyze the four representative mixed granular systems consisting of materially nonlinear viscous particles. To verify precision of stress calculation, solutions of an axis-symmetric radial flow problem are compared with results of the literature and they are in a great agreement. The results present here provide significant insight into the fundamental behavior of granular media under compaction conditions, including prediction of the overall aggregates stress-strain response.     

SPECTRAL DENSITY ESTIMATION FROM NONLINEARLY OBSERVED DATA

Abstract. The estimation of the spectral density function of a stationary Gaussian process at the input of an instantaneous nonlinearity is considered when the nonlinearity is known and a finite set of observations of the output process is given. A class of spectral estimates is considered and their quadratic-mean consistency is established; precise asymptotic expressions for their bias and covariance are derived and their asymptotic normality is obtained.     

承压水漏斗地区地下水位时空分布预报的BP网络模型

依据水均衡原理，导出承压水漏斗区任意一点水位与其影响因素之间的复杂的非线性关系，在此基础上提出承压水漏斗水位时空分布预报的BP神经网络模型。该模型具有 分布参数模型的特征，且不需用到区域的水文地质参数。最后针对某实例进行了模型设计及预报分析，通过对部分观测井后期实测数据的训练，优选出双隐层的网络结构及其网络参数。随后用这些观测井的前3年数据进行了检验，并对其他观测井数据进行预报。计算表明，该模型对地下水位拟合与预报的合格率较高，可以获得研究区域某一时刻水位在空间上的分布。     

住宅电气设计中应注意的细节问题

就住宅电气设计中，常常被忽略的细节问题进行阐述，提出了在住宅室内几个功能区内，如何使灯具和插座的布置更合理，以最大限度地满足居住者的需求。     

压电陶瓷微位移器件迟滞模型的研究

在通过统计物理学角度分析压电陶瓷迟滞规律的基础上，结合数学建模方法，提出了一种简单实用的压电陶瓷迟滞数学模型。并设计了压电陶瓷实验控制系统，对迟滞数学模型进行了验证，实验结果表明，此模型可以有效减小压电陶瓷的迟滞非线性误差，提高压电陶瓷微位移的控制精度，本研究有助于实现基于压电陶瓷的高精度开环微位移控制。     

特低渗透油藏驱替及开采特征的影响因素

应用非达西渗流理论和非线性弹性渗流理论，分析了影响特低渗透油藏驱替及开采特征的主要因素。研究结果表明，启动压力梯度和毛细管压力是影响特低渗透油藏驱替特征的主要因素；而影响特低渗透油藏开采特征的主要因素是储层的弹塑性，即储层的压力敏感性。在特低渗透油藏的开发中应适当缩小注采井距提高驱替压力梯度，采取整体压裂措施减小启动压力梯度，通过气驱或活性水驱油减小毛细管压力，及时补充地层能量以减少压力敏感性对储层的伤害。