数据处理常用数表的替代公式

数据处理与统计中查各种系数的数表很不方便,建立了一系列简化公式以替代这些数表.     

基于数学解析法的油纸绝缘参数辨识研究

现阶段变压器油纸绝缘等效弛豫机构参数辨识多采用拓扑支路数任意假定、粒子群等智能算法对 N组非线性方程组寻优迭代计算。其计算往往具有收敛性差、结果不唯一等问题,且难以从介质响应函数特性分析真实的油纸绝缘弛豫过程,影响后续弛豫参数对老化评估的准确性。基于此,提出一种应用数学解析法的变压器油纸绝缘弛豫机构参数辨识新方法。首先,从介质响应函数特性出发,深入挖掘弛豫项数信息,辨识油纸绝缘等效弛豫机构的拓扑结构;其次,公式推演得到参数辨识的数学计算公式,避免了智能算法对非线性方程组的寻优误差与不唯一性;最后,通过实例验证该方法的有效性与可行性,提出的数学解析法可为变压器油纸绝缘介质内部弛豫响应特性提供可靠的数学分析模型。     

改进的对称分布期望估计量的性质

本文证明了改进后的对称分布期望估计量W_p在一定条件下具有无偏性和强相合性,并给出了方差的上界,其中:W_p.=1/n-2[np] sum from a-[ap] to i=[ap]+1 X_(j),0≤p<1/2     

Use of Sobol's Quasirandom Sequence Generator for Integration of Modified Uncertainty Importance Measure

Sensitivity analysis of model output is relevant to a number of practices, including verification of models and computer code quality assurance. It deals with the identification of influential model parameters, especially in complex models implemented in computer programs with many uncertain input variables. In a recent article a new method for sensitivity analysis, named HIM* based on a rank transformation of the uncertainty importance measure suggested by Hora and Iman was proved very powerful for performing automated sensitivity analysis of model output, even in presence of model non-monotonicity. The same was not true of other widely used non-parametric techniques such as standardized rank regression coefficients. A drawback of the HIM* method was the large dimension of the stochastic sample needed for its estimation, which made HIM* impracticable for systems with large number of uncertain parameters. In the present note a more effective sampling algorithm, based on Sobol's quasirandom generator is coupled with HIM*, thereby greatly reducing the sample size needed for an effective identification of influential variables. The performances of the new technique are investigated for two different benchmarks.     

循环荷载作用下钢结构滞回性能的数值模型

提出了“塑性铰有限分布”的数值模型用以分析钢结构在循环荷载作用下的滞回性能。经与试验结果比较表明模型简单、易于实施，待进一步完善后，可直接用于对梁及压弯构件的模拟。     

用于自磨(半自磨)流程设计的现代试验方法(续)

介绍目前国际上主要的用于自磨(半自磨)流程设计之现代试验方法。这些试验方法以试验规模小型化为特点,以数学模型、计算机模拟技术和现代试验手段为背景,从不同角度反映自磨(半自磨)的过程特点,从而为自磨(半自磨)流程设计提供依据,代表了自磨(半自磨)试验技术的当代水平和发展潮流。     

炮塔加热过程数学模型与计算机仿真研究

通过对炮塔热处理加热过程的分析研究,取局部最大壁厚处作为二维非稳定态传热问题进行离散化处理,建立了工件加热过程显式有限差分仿真模型。并对计算机仿真结果与实测数据进行了比较验证。     

基础振动下直动式减压阀动态特性分析

针对基础振动对TBM液压元件性能的影响,为TBM液压元件优化设计提供理论依据,选择直动式减压阀为研究对象,分析其工作原理,建立减压阀的动态响应数学模型,仿真研究基础振动幅值和频率对减压阀波动特性的影响规律,分析减压阀不同结构参数对压力波动的影响.结果表明：基础振动会引起减压阀出口压力波动,波动幅值随振动幅值增加而增大;当基础振动频率大于50 Hz时,压力波动幅值随频率的增加明显增大;减小背压腔初始容积和回流通道直径能提高减压阀的动态稳定性.     

Constructing Facial Identity Surfaces for Recognition

We present a novel approach to face recognition by constructing facial identity structures across views and over time, referred to as identity surfaces, in a Kernel Discriminant Analysis (KDA) feature space. This approach is aimed at addressing three challenging problems in face recognition: modelling faces across multiple views, extracting non-linear discriminatory features, and recognising faces over time. First, a multi-view face model is designed which can be automatically fitted to face images and sequences to extract the normalised facial texture patterns. This model is capable of dealing with faces with large pose variation. Second, KDA is developed to compute the most significant non-linear basis vectors with the intention of maximising the between-class variance and minimising the within-class variance. We applied KDA to the problem of multi-view face recognition, and a significant improvement has been achieved in reliability and accuracy. Third, identity surfaces are constructed in a pose-parameterised discriminatory feature space. Dynamic face recognition is then performed by matching the object trajectory computed from a video input and model trajectories constructed on the identity surfaces. These two types of trajectories encode the spatio-temporal dynamics of moving faces.     

混合式步进电动机的矢量控制分析

混合式步进电动机与传统的异步、同步电动机相比,由于定子磁势、转子磁钢的非线性分布以及磁饱和等因素的存在而没有简单的线性化数学模型.根据已有数学模型,利用电动机矢量控制原理,在d-q坐标系下推导出混合式步进电动机电磁转矩与电流关系、静态控制与动态控制的数学模型,以及电动机定子电流细分算法,最后通过搭建实验样机验证其控制方法的有效性.