小波变换思想及其在信号处理中的应用

从傅里叶变换、短时傅里叶变换到小波变换的思想发展过程中分析了小波变换发展的必然性和重要性,并通过MATLAB仿真工具比较了三种变换在信号处理中的应用。实验结果表明,小波变换无论是对信号的时间定位还是对信号的频率定位都优于傅里叶变换和短时傅里叶变换。     

MEMS器件平板运动空气阻尼研究

针对微电子机械系统中平行板间的气膜阻尼问题,通过将平板沿垂直方向的位移运动方程展开为傅里叶级数,得到了微平面机构所受的空气阻尼力和阻尼系数的解析公式。结果表明,空气阻尼系数近似与两平板间气隙厚度的三次方成反比。通过对微加速度开关质量块工作时所受的空气阻尼进行仿真分析,得出该开关的阻尼系数在工作过程中为变阻尼的结论,并分析了空气阻尼系数对于开关性能的影响。     

Modified weighted squared error estimation procedures with special emphasis on the stable laws

Two families of parameter estimation procedures for the stable laws based on a variant of the characteristic function are provided. The methodology which produces viable computational procedures for the stable laws is generally applicable to other families of distributions across a variety of settings. Both families of procedures may be described as a modified weighted chi-squared minimization procedure, and both explicitly take account of constraints on the parameter space. Influence func-tions for and efficiencies of the estimators are given. If x₁, x₂, …x_n random sample from an unknown distribution F , a method for determining the stable law to which F is attracted is developed. Procedures for regression and autoregres-sion with stable error structure are provided. A number of examples are given.     

基于傅立叶和小波变换的非稳态谐波分析

电力系统信号中既含有稳态谐波分量又含有非稳态态谐波分量.本文结合傅立叶变换和小波变换的优点,提出了傅立叶—小波综合谐波分析方案.通过对具体模拟信号的仿真,验证了该方法具有可行性.     

MUSIC法的有限域单向快速频率搜索

快速傅里叶变换(FFT)算法在应用中速度快,精度较低,而MUSIC法精度高,实时性差。该文通过分析两者联合谐波频率估计的可能性,提出利用FFT算法对谐波频率进行预估计,用二分法将频域划分为有限个细小的频率区间,根据可能的有效频率选取有效区间,再通过MUSIC方法在有限的搜索区间进行频率细化,并在细化的过程中采用趋向谱幅值增大的单向搜索。通过仿真研究,该方法能有效提高信号的处理速度,加强MUSIC算法的应用。     

波前滤波小波函数的理论分析和构造方法

从惠更斯-菲涅耳的衍射理论出发．分析了受限孔径衍射相当于波前滤波．以夫琅和费单缝、圆孔为例．得到了小波在波前滤波时应满足的条件．并给出了满足波前滤波条件的小波的构造方法．     

机载SAR斜侧视成像的高效空变算法

针对机载合成孔径雷达ＳＡＲ斜侧视成像的二维处理特性，采用一种全聚焦的处理方法，它能方便地处理斜侧视ＳＡＲ参考函数的空间变化的特性，并提高计算效率。     

分层双各向异性媒质中基本振子源的电磁场(英文)

对于观察点不在任意方向放置的,位于分层双各向异性媒质中的基本电磁振子源附近的电磁场,本文给出了明显表达式。利用傅立叶变换谱域中的横向场矢量的矩阵分析,该问题得到了较为方筻的解决。     

A genetic algorithm for determining optimal replenishment cycles to minimize maximum warehouse space requirements

In a supply chain, it is an important issue for logistic managers to offset the replenishment cycles of multiple products sharing a warehouse so as to minimize the maximum warehouse space requirement (MWSR). Most of the studies in the literature assume that warehouses replenish at the beginning of some basic planning period. In this paper, we relax this assumption by allowing the warehouse to replenish at any time. In order to solve this problem, we conduct theoretical analysis based on Fourier series and Fourier transforms and propose a procedure that is used to calculate MWSR efficiently for any given replenishment schedule. Then, we employ this procedure in a genetic algorithm (GA) to search for the optimal replenishment schedule. Using randomly generated instances, we show that the proposed GA significantly outperforms a previously published heuristic.