干涉测量波面重构DCT算法研究

采用一种空间移相干涉仪测量凹形非球面反射镜光学表面,使用偏振元件和多幅图像同步采集实现移相,并对测量得到的干涉条纹采用基于离散余弦变换的相位解包裹算法,对不连续相位分布采用非加权的最小二乘法进行优化目标函数,最终重构出被测光学表面的面形.这种结构形式的干涉仪具有一定的抗振能力,同时在数字图像处理上优化了算法,能够快速稳定地得到被测面形,而且对硬件要求不高.结果表明:这种算法能够适用于非实验室条件下的光学测量,在一定干扰条件下可以达到较高的测量精度.     

Dimensionality reduction via variables selection – Linear and nonlinear approaches with application to vibration-based condition monitoring of planetary gearbox

Feature extraction and variable selection are two important issues in monitoring and diagnosing a planetary gearbox. The preparation of data sets for final classification and decision making is usually a multi-stage process. We consider data from two gearboxes, one in a healthy and the other in a faulty state. First, the gathered raw vibration data in time domain have been segmented and transformed to frequency domain using power spectral density. Next, 15 variables denoting amplitudes of calculated power spectra were extracted; these variables were further examined with respect to their diagnostic ability. We have applied here a novel hybrid approach: all subset search by using multivariate linear regression (MLR) and variables shrinkage by the least absolute selection and shrinkage operator (Lasso) performing a non-linear approach. Both methods gave consistent results and yielded subsets with healthy or faulty diagnostic properties.     

遗传算法在LED光源光谱匹配技术中的应用

为利用单色LED实现CIE-D65标准光源、AM1.5标准太阳光目标光谱的匹配,提出简单遗传算法作为光谱匹配算法,通过求解超定方程组的非负最小二乘解,优化不同峰值波长、峰值波长间隔、半高宽的单色LED匹配光源组合,达到光源光谱匹配的目的.仿真实验表明:该算法拟合的相关指数达0.99以上,模拟光谱与目标光谱基本吻合;匹配光源的峰值波长间隔越小,光谱拟合性越好,但结合工程应用需要,峰值波长要选取适中;所提遗传算法运行速度快、效率高、拟合误差小,可广泛应用于植物照明、医疗照明等特殊照明领域的光谱匹配仿真试验和工程实践.     

综合诊断光路快速自动准直系统设计与实现

为了实现综合诊断光路全程快速准直,从并行处理、快速收敛电机运动模型和最小外切圆特征点提取三个方面对自动准直系统进行了总体设计.首先,对全部准直步骤采取并行、串并结合的方式执行,并将关键准直任务归纳成单元准直模型;其次,使用准直数学模型,实现单元准直模型中电机的快速收敛;最后,针对小孔图像灰度对比低、分布极不均匀、光斑很不完整的特点,提出在最小外切圆的圆环上,取两两距离最大的100个点为特征点,使用最小二乘法进行圆拟合法计算小孔图像圆心.研究表明优化后系统的准直时间从优化前40min减少到8min,小孔图像圆心误差在2个像素之内,满足打靶实验的要求.     

一类四元数矩阵方程的循环解及其最佳逼近

本文研究了四元数体上矩阵方程XB = C 的循环解及其最佳逼近问题. 利用循环矩阵的结构表示式, 以及四元数矩阵的复分解, 得到了方程XB = C 的循环解存在条件及其通解形式; 在循环矩阵约束条件下, 给出了该方程的最小二乘解集合; 与此同时, 在最小二乘解集合中, 获得与给定四元数循环矩阵的最佳逼近解. 推广了约束矩阵方程的数值求解范围. 数值算例验证了本文算法的可行性.     

线性随机微分方程多步法的稳定性

研究了多步法用于求解线性随机微分方程的稳定性,利用维纳过程的增量服从正态分布的性质,得到了在乘性噪声情况下,多步法用于线性随机微分方程的均方稳定性的条件,并用MATLAB对实际算例进行了数值模拟.     

功率放大器失真问题研究及预失真建模

电子器件中的功率放大器常常伴随着非线性失真效应.为解决此类非线性失真问题,通过研究无记忆和有记忆功放的失真特性,运用最小二乘法来构建多种形式的特性拟合函数,在选择了效果较好的特性拟合函数基础上,根据实际约束条件进行预失真模型的建立,使失真处理后的输出信号趋于线性,最后从信号的功率谱密度的角度出发检验预失真模型的补偿效果,证明模型具有较好的可行性和准确性.     

Gaussian approximation of exponential type orbitals based on B functions

This work gives new, highly accurate optimized gaussian series expansions for the B functions used in molecular quantum mechanics. These functions are generally chosen because of their compact Fourier transform, following Shavitt. The inverse Laplace transform in the square root of the variable is used for Gauss quadrature in this work. Two procedures for obtaining accurate gaussian expansions have been compared for the required extended precision arithmetic. The first is based on Gaussian quadratures and the second on direct optimization. Both use the Maple computer algebra system. Numerical results are tabulated and compared with previous work. Special cases are found to agree before pushing the optimization technique further. The optimal gaussian expansions of B functions obtained in this work are available for reference. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Optical coefficient‐based multivariate calibration on near‐infrared spectroscopy

The time and expense of calibration development limit the feasibility of NIR spectroscopy for many industrial applications, with a major portion of the costs being related to creation of a sufficient set of calibration samples. Net analyte signal (NAS) and generalized least squares (GLS) pre‐processing have been proposed in the literature as methods to simplify multivariate calibration by reducing the quantity of calibration samples by orthogonalizing or shrinking interference signals. Synthetic calibration has also been reported as a method to combine interference signals with pure component spectra to generate virtual calibration models, thereby reducing the number of real calibration samples required. The goals of this paper were to (1) compare theoretical and practical differences between NAS and GLS pre‐processing and (2) explore the potential of simplified NIR calibrations, both empirical and synthetic, constructed using optical coefficient‐based signal processing on predicting chemical compositions of pharmaceutical powder mixtures. A reduced calibration dataset including only one pharmaceutical powder mixture composition and pure component spectra was used for both empirical and synthetic calibrations. Absorption and reduced scattering coefficients, obtained from spatially‐resolved spectroscopy, were used herein as interference signals in NAS/GLS pre‐processing for both calibrations. As a result, NAS and GLS were shown to be equivalent in both theoretical and practical senses. After optical coefficient‐based signal processing, simplified calibrations, both empirical and synthetic, were demonstrated to have similar model performance as generic pre‐processing methods such as SNV and derivative, while requiring fewer principal components and achieving a lower prediction error. Copyright © 2010 John Wiley & Sons, Ltd.