改进非平稳信号的分析方法

研究了WVD和短时傅里叶变换两种时频分析方法的优势和局限性,从两种方法的定义出发,分析了两者间存在的联系,通过构造窗函数,提出一种改进的非平稳信号分析方法,并进行了相应的计算机仿真,结果表明信号的时频特性得到了改善,该方法还适用于多分量非平稳信号的分析。     

自组织理论对技术发展极限问题的启示

技术的发展从内史和外史的角度来说都会遇到发展极限的问题,自组织理论对技术发展极限问题的认识有重要的启示:技术系统的涨落对技术发展的极限实现维持与突破;技术系统的开放性对技术发展的极限实现促进与制约;技术系统的序参量对技术发展的极限实现役使和规导。正确认识技术发展的极限问题,对于促进技术的完善与革新,对于更好地规范技术的社会价值取向有重要的意义。     

Ultrastructural elliptical models

Dolby's (1976) ultrastructural model with no replications is investigated within the class of the elliptical distributions. General asymptotic results are given for the sample covariance matrix S in the presence of incidental parameters. These results are used to study the asymptotic behaviour of some estimators of the slope parameter, unifying and extending existing results in the literature. In particular, under some regularity conditions they are shown to be consistent and asymptotically normal. For the special case of the structural model, some asymptotic relative efficiencies are also reported which show that generalized least squares and the method of moment estimators can be highly inefficient under nonnormality.     

A robust approach to longitudinal data analysis

The author introduces robust techniques for estimation, inference and variable selection in the analysis of longitudinal data. She first addresses the problem of the robust estimation of the regression and nuisance parameters, for which she derives the asymptotic distribution. She uses weighted estimating equations to build robust quasi‐likelihood functions. These functions are then used to construct a class of test statistics for variable selection. She derives the limiting distribution of these tests and shows its robustness properties in terms of stability of the asymptotic level and power under contamination. An application to a real data set allows her to illustrate the benefits of a robust analysis.     

Graphical models for skew-normal variates

This paper explores the usefulness of the multivariate skew-normal distribution in the context of graphical models. A slight extension of the family recently discussed by Azzalini & Dalla Valle (1996 ) and Azzalini & Capitanio (1999 ) is described, the main motivation being the additional property of closure under conditioning. After considerations of the main probabilistic features, the focus of the paper is on the construction of conditional independence graphs for skew-normal variables. Necessary and sufficient conditions for conditional independence are stated, and the admissible structures of a graph under restriction on univariate marginal distribution are studied. Finally, parameter estimation is considered. It is shown how the factorization of the likelihood function according to a graph can be rearranged in order to obtain a parameter based factorization.     

Saddlepoint approximations for some models of circular data

In this article we provide saddlepoint approximations for some important models of circular data. The particularity of these saddlepoint approximations is that they do not require solving the saddlepoint equation iteratively, so their evaluation is immediate. We first give very accurate approximations to P-values, critical values and power functions for some optimal tests regarding the concentration parameter under wrapped symmetric α-stable and circular normal models. Then, we consider an approximation to the distribution of a projection of the two-dimensional Pearson random walk with exponential step sizes.     

基于振动分析的工程结构损伤识别技术综述

综述了基于振动分析的工程结构损伤识别方法,并对各种方法进行了评述。根据国内外文献,对基于振动分析的工程结构损伤识别技术的发展趋势进行了展望。     

铝合金材料LY12CZ临界空穴扩张比的适用性探讨

对光滑试样和 3种不同曲率半径的切口试样 ,采用拉伸试验和电镜观测相结合的方法 ,研究了铝合金材料LY12CZ的VGC 参数的适用性。证实VGC 参数对材料的断裂形式较为敏感 ,适用于以拉伸型断裂为主的切口试样 ,对以剪切断裂为主的光滑拉伸试样不适用。     

SINUMERIK数控系统在车床改造中的应用

SINUMERIK80 2S数控系统用于C0 630车床电控系统改造。本文介绍CNC系统结构、电控系统改造方案及数控系统内部参数整定方法。     

论日本动画资讯杂志与动画产业的互动关系

日本在世界动画业处于举足轻重的领先位置,目前全球六成左右的动画节目皆是日本制作。动画资讯杂志见证了动画产业完成商业化蜕变的全过程。加深对动画资讯杂志的认识,本质上亦是加深对动画和动画产业的认识。通过横向比对与国外同行业的差异与差距。可以借他山之石,为我所用。从中获取成功经验,发展出适合自己的动画产业商业化道路。