Structuration de la convection mixte en milieu poreux confiné latéralement et chauffé par le bas : effets d''inertiePattern formation of mixed convection in a porous medium confined laterally and heated from below: effect of inertia

We consider the onset of convection in a porous medium heated from below and subjected to a horizontal mean flow. The effect of porous inertia is studied, and the transverse aspect ratio a of the medium is taken into accout. We find that the dominant modes are longitudinal rolls (L.R) if a is an integer or transverse traveling rolls (T.R) if a is below a_c with a_c<1. When a is not an integer with a>a_c, the setting on patterns are oscillatory three-dimensional structures (3D) for a>1 or T.R for a_c<a<1 provided that the Reynolds number remains below a critical value Re_K^*. We show that these structures are replaced by L.R if Re_K>Re_K^*. To cite this article: A. Delache et al., C. R. Mecanique 330 (2002) 885–891.     

从具体例子看惯性流形概念的推广

惯性流形的概念要求所有轨道指数收敛于唯一吸引子[5],这对于很多物理问题,例如sine-Gordon方程是很难满足的[4],本文中给出的人工例子建议了惯性流形的推广形式,这个推广形式去掉了整体吸引子是唯一的预先要求,该推广概念使用于sine-Gordon方程。     

扭摆法测物体转动惯量的不确定度分析

扭摆法是测量物体转动惯量的有效方法,其不确定度分析是关键.本文推导了扭摆法测物体转动惯量准确的不确定度传递公式,得到各直接测量量及其不确定度对转动惯量不确定度的影响.并进行了算例分析.结果表明,扭摆法比三线摆测得物体的转动惯量的误差以及不确定度要小很多.这对实验方法的选择和仪器的研制具有重要的实际意义.     

分形物体转动惯量的计算

由分形物体的自相似性、转动惯量的量纲和平行轴定理,分别计算并得到分形三角形、分形正方体、分形四面体和科赫雪花的转动惯量.     

基于电力线载波与TCP/IP协议的刚体转动惯量实验系统的设计

介绍了一种新的测量刚体转动惯量的实验方法与实验装置,在实验中,通过增加标准刚体试件,把细线拉力对转轴摩擦力矩的影响考虑进去,大幅度地提高了实验测试精度,另外,利用电力线载波通讯网络,将转动惯量测量仪采集的时间数据传输到PC机中,再经过PC机端数据处理软件,快速准确地将待测刚体的转动惯量以及其它与刚体有关的物理量计算、显...     

Selection of a staggered grid for inertia‐gravity waves in shallow water

The problem of accuracy in propagating inertia‐gravity waves on Arakawa grids is investigated. It is shown that the sole analysis of spatial discretization and the recommendation of the B‐grid for coarse resolution models and C‐grid for high resolution models must be re‐analysed when time discretization is taken into account as well. For a chosen time discretization, a coarse C‐grid is shown for example, to increase precision when using larger time‐steps (up to the stability limit) whereas the precision of the B‐grid decreases. Here, an analysis of error for different grids in function of the space–time resolutions and computational costs is presented and some recommendations on the choice of the particular staggered grid for a given application are outlined. Copyright © 2002 John Wiley & Sons, Ltd.     

端头带有质量块的悬臂梁在冲击载荷下的两种剪切失效模型

剪切失效是强动载荷作用下结构失效的重要模式。本文给出了计及梁的转动惯量时端头带有质量块的悬臂梁结构受到冲击载荷作用后发生剪切失效的无量纲判据。分析表明，在初始速度间断面上是否发生剪切失效取决于质量块初始动能和质量块尺寸与梁厚之比，而与梁的长度无关。梁的转动惯量对于剪切失效具有不可忽略的影响。     

两类惯量惟一的对称符号模式

§ 1　 IntroductionA sign pattern(matrix) A is a matrix whose entries are from the set{ +,-,0 } .De-note the setofall n× n sign patterns by Qn.Associated with each A=(aij)∈ Qnis a class ofreal matrices,called the qualitative class of A,defined byQ(A) ={ B =(bij)∈ Mn(R) |sign(bij) =aijfor all i and j} .　　 For a symmetric sign pattern A∈ Qn,by G(A) we mean the undirected graph of A,with vertex set { 1 ,...,n} and (i,j) is an edge if and only if aij≠ 0 .A sign pattern A∈ Qnis a do…     

用光电法测量刚体的转动惯量──对波纹法测量刚体转动惯量的改进

用Ｊ─ＬＤ２转动惯量测试仪的波纹法测试转动惯量的实验方法，测量精度差，操作不方便．利用实验室现有的仪器改进成光电法测试转动惯量的方法，简单易行，测量精度高，操作方使，实践效果良好．     

关于刚体转动惯量测定的计时方法研究

本文给出了在刚体转动惯量的测定中测定时间的计时装置，减小了计量时间所带来的误差。