一类有理Bézier曲线的等距线算法及MATLAB实现

构造一类正则有理Bézier曲线,利用改进的有理de casteljau算法求得这类正则有理n次Bézier曲线各点处的切矢,由此得出各点的单位法矢量,应用于原始曲线等距线的计算.该方法几何意义明显,算法简洁,实践效果比较好.同时给出了用Matlab绘制有理Bézier曲线及其等距线的程序,准确快捷,实践效果较好.     

基于Dyson同心光学系统的消色差Féry棱镜高光谱成像仪的设计

为实现高光谱成像系统小型化、轻量化和高成像质量的要求,并使全工作波段具有更高的光学效率,提出以Féry棱镜组合作为分光元件的Dyson高光谱成像仪系统,系统中引入消色差棱镜组合以减小光谱的非线性色散,使棱镜系统色散的线性度达到较高。结果表明,可见近红外（VNIR）光谱通道的光学调制传递函数（MTF）达到0.9以上,光谱分辨率为4.2～6.8 nm。短波红外（SWIR）光谱通道的MTF达到0.73～0.87,光谱分辨率为6.4～12.5 nm。通过消色差Féry棱镜组合的设计,该光学成像系统两个光谱通道内的相对谱线弯曲均小于0.05%,色畸变小于0.13%。     

基于伪Wigner-Ville分布和Rnyi熵的显著图目标检测

在复杂背景中,往往难以实现目标的自动检测,依据Wigner-Ville分布能够对图像在空间域/空间频率域上联合表示的特性.研究了图像经伪Wigner-Ville分布后Rnyi熵的统计特性,分析了人造目标的出现会引起自然场景中Rnyi熵统计特性的变化,并在此基础上提出了一种新的基于伪Wigner-Ville分布和Rnyi熵的显著图生成方法.之后对显著图进行简便的阈值分割,完成目标检测.实验结果表明,所提出的方法能够有效地检测复杂地面背景中的军用车辆.     

对称随机变量序列的Hájek-Rényi型不等式和强大数律

得到了对称随机变量序列的Hájek-Rényi型不等式,并利用它研究了对称随机变量序列的强大数律.     

某种局部凸空间上的Bishop-Phelps定理

本文通过在局部凸空间上引入新拓扑的方法,给出某种特殊局部凸空间上的另一种形式的Bishop-Phelps定理.     

AN IMPROVED NONLINEAR CLOSED GRAPH THEOREM

In this paper, a new nonlinear closed graph theorem is established, whose result improves substantially a recent-known important conclusion.     

A model for gas–liquid slug flow in downwardly inclined ductsUn modèle pour les écoulements gaz–liquide à bouchons en conduite inclinée

A simple theoretical model is proposed in order to represent gas–liquid slug flows in inclined ducts of arbitrary shape. To cite this article: A. Dyment, A. Boudlal, C. R. Mecanique 332 (2004).     

Solutions multiples pour les écoulements tridimensionnels en rotationMultiple solutions for three-dimensional swirling flows

The symmetry-breaking in a swirling flow generated inside a cylindrical tank of aspect ratio h=1 by the rotation of one lid is studied numerically. Beyond a critical Reynolds number, the flow undergoes a bifurcation to three-dimensional solutions. The spatial and temporal behaviour on these branches are examined. To cite this article: E. Barbosa, O. Daube, C. R. Mecanique 330 (2002) 791–796.     

Effets de la surface libre et du rapport d'aspect sur la transition de l'écoulement de Taylor–CouetteEffects of free surface and aspect ratio on the transition of the Taylor–Couette flow

This work deals with the study of free surface and aspect ratio effects on the instability of the Taylor–Couette flow. The experimental results have been obtained using the polarographic technique. The time-averaged values of the wall velocity gradient have been determined and the spectral analysis of its fluctuations has been done. These first results show the existence of a critical height Hc of the liquid column. For an aspect ratio Γ=H/d<10, the laminar turbulent transition occurs without azimuthal wave mode. To cite this article: A. Madamdia et al., C. R. Mecanique 331 (2003).