Reconstruction of Piecewise Smooth Functions from Non-uniform Grid Point Data

Spectral series expansions of piecewise smooth functions are known to yield poor results, with spurious oscillations forming near the jump discontinuities and reduced convergence throughout the interval of approximation. The spectral reprojection method, most notably the Gegenbauer reconstruction method, can restore exponential convergence to piecewise smooth function approximations from their (pseudo-)spectral coefficients. Difficulties may arise due to numerical robustness and ill-conditioning of the reprojection basis polynomials, however. This paper considers non-classical orthogonal polynomials as reprojection bases for a general order (finite or spectral) reconstruction of piecewise smooth functions. Furthermore, when the given data are discrete grid point values, the reprojection polynomials are constructed to be orthogonal in the discrete sense, rather than by the usual continuous inner product. No calculation of optimal quadrature points is therefore needed. This adaptation suggests a method to approximate piecewise smooth functions from discrete non-uniform data, and results in a one-dimensional approximation that is accurate and numerically robust.      

基于MNF和SVM的高光谱遥感影像分类研究

通过分析高光谱遥感影像分类的现状及遇到的困难,以OMIS1高光谱数据为实验数据,提出了基于最小噪声分离(Minimum Noise Fraction-MNF)变换和支持向量机(Support Vector Machine-SVM)的高光谱遥感影像分类方法。分类实验结果表明:与传统的最大似然分类法(Maxi mum Likelihood Classification-MLC)比较,该方法克服了Hughes现象,分类速度得以提高,总体分类精度达到94.85%,从而表明了该方法用于高光谱遥感影像分类的实用性和优越性。     

Generalized likelihood ratio test for varying-coefficient models with different smoothing variables

Varying-coefficient models are popular multivariate nonparametric fitting techniques. When all coefficient functions in a varying-coefficient model share the same smoothing variable, inference tools available include the F-test, the sieve empirical likelihood ratio test and the generalized likelihood ratio (GLR) test. However, when the coefficient functions have different smoothing variables, these tools cannot be used directly to make inferences on the model because of the differences in the process of estimating the functions. In this paper, the GLR test is extended to models of the latter case by the efficient estimators of these coefficient functions. Under the null hypothesis the new proposed GLR test follows the χ²-distribution asymptotically with scale constant and degree of freedom independent of the nuisance parameters, known as Wilks phenomenon. Further, we have derived its asymptotic power which is shown to achieve the optimal rate of convergence for nonparametric hypothesis testing. A simulation study is conducted to evaluate the test procedure empirically.     

聚羟基丁酸酯球晶的微观结构及其对力学性能的影响

本文采用基于数字图像相关计算技术的显微数字分析系统,结合原子力显微镜等,实验研究了晶态高聚物聚羟基丁酸酯(PHB)的细观结构及对其力学性能的影响规律.结果发现:实验用的PHB球晶是台阶式生长或螺旋式生长,其生长台阶高度差在200nm～500nm之间;PHB球晶同心圆环随着结晶温度的提高,同心圆环的环间距增大.球晶结晶度、球晶尺寸对冲击强度、拉伸强度以及断裂伸长率的影响呈线性关系.     

粒子群优化算法的改进及其实现

基本粒子群优化算法存在着"早熟"现象。究其主要原因是由于全局最优粒子的运动形式滞留在局部最优。为此,根据基本PSO算法的特点,在粒子运动过程中加入了个体小概率随机变异,增强了粒子运动形式改变能力,减小了陷入局部最优的可能性。通过数值计算结果表明,该方法能有效地解决粒子群优化"早熟"问题。     

Words, music, and other measures: Predicting the repertoire popularity of 597 Schubert lieder.

To address the venerable aesthetic question of the relative importance of music and words, musical and textual characteristics were used to predict recording counts of 597 Franz Schubert lieder. Predictors included career variables (age and concurrent productivity), "whole song" variables (e.g., performance duration, structural complexity, major vs. minor key), thematic measures of the first six notes of the vocal incipit (e.g., melodic and rhythmic originality), poet variables (Goethe, Schiller, etc.), and text variables (computer content analysis measures of primordial and conceptual thought and positive and negative emotions). Many correlations between predictors were small but reliable; career variables accounted for most strong correlations. A 45-predictor regression model was highly significant (R2 = .63), with 13 reliable (p     

力标准机独立加码与逆程交换研究

静重式力标准机在施加递增或递减负荷过程中，当砝码进行逆程交换时会出现逆负荷现象。为此，提出了力标准机独立加码的概念与方法，建立并讨论了独立加码方法的驱动方式、砝码加卸过程的运动规律、加卸过程中吊挂受力变化、加载稳定性和工作效率问题。研究了通过少量砝码的合理组合与交换，实现多力级等力值间隔加载的技术方法。当砝码进行逆程交换时，为减小以至消除逆负荷现象进行了理论分析和实验验证。结果表明，提出的方法是可行的和有效的。为力基、标准机的技术发展和提高提供了一种新的理论方法和试验依据，对力值计量检测技术的进步具有重要意义。     

Pattern synthesis of antennas based on a modified particle swarm optimization algorithm

In order to overcome the drawbacks of standard particle swarm optimization (PSO) algorithm, such as prematurity and easily trapping in local optimum, a modified PSO algorithm is proposed, in which special techniques, as global best perturbation and inertia weight jump threshold are adopted. The convergence speed and accuracy of the algorithm are improved. The test by some benchmark problems shows that the proposed algorithm achieves relatively higher performance. Thereafter, the applications of the modified PSO in the radiation pattern synthesis of antenna arrays are presented. __________ Translated from Chinese Journal of Radio Science, 2006, 21(6): 873–878 [译自: 电波科学学报]     

梁板壳有限单元中的各种闭锁现象及解决方法

对梁元和板壳单元中存在的各种闭锁现象进行详细的分析，对现有的一些解决方法的优劣性进行比较，以使人们对闭锁现象有更深入的认识，并能有效地消除或减轻它们的不利影响.分别在二维、三维梁元与板壳单元有限元公式中引入Hellinger-Reissner混合函数或降阶积分，以减轻或消除闭锁现象对单元计算精度的不利影响.通过4个算例来阐明闭锁现象随单元受力情况、单元厚度、单元网格划分的不同而对结构非线性分析结果所带来的不同程度的影响. 结果表明，闭锁现象对结构的数值分析结果影响显著，对以受弯为主而膜应力很小甚至为零的单元，膜闭锁现象非常严重，而对薄壁单元，剪切闭锁的影响特别严重；采用单元的混合公式或在协调元中采用降阶积分，可有效地消除单元的各种闭锁现象和插值函数的误差对单元计算精度带来的不利影响，能使单元计算精度和计算效率得到显著改善.     

GSM系统中TCH自适应均衡解调算法的研究

针对移动信道多径效应造成的严重的符号间干扰（ISI）问题，研究了基于最大似然序列估计（MLSE）的GSM系统中TCH自适应均衡解调算法，并对这种自适应均衡解调算法在Jake移动信道模型环境下的性能进行了分析和计算机仿真，仿真结果表明，该自适应均衡解调算法能够很好地克服符号间干扰（ISI）问题，性能良好。