A two scale method for modulated vibration modes of large,nearly repetitive,structuresUne méthode asymptotique à deux échelles pour les modes de vibrations modulés des longues structures presque répétitives

Nearly repetitive structures can present at least two kinds of vibration modes: localized modes and modulated ones. In this Note, the multiple scale method is applied to characterize a packet of modulated modes. In this respect, only small size problems are to be solved: periodic problems posed on a few basic cells and amplitude equations, which define a sort of homogenized model for this type of modes. It is established that the influence of the non-repetitive part of the structure is accounted by a boundary condition. To cite this article: E.M. Daya et al., C. R. Mecanique 331 (2003).     

高应变率大变形下的聚丙烯/尼龙共混高聚物损伤型本构特性

对两种采用不同相容剂的聚丙烯（PP）和尼龙（PA）共混高聚物材料在大变形下的粘弹性力学行为进行研究,着重考察应变率效应和损伤的演化,从而分析不同的界面分子设计对共混体系材料宏观性能的作用。在准静态及冲击实验研究的基础上,基于ZWT非线性粘弹性模型,并结合了遗传算法,分别得到了能有效描述两种共混高聚物大变形阶段计及损伤的非线性粘弹性本构关系。两种材料在不同加载条件下表现出明显不一致的性能,原因在于其损伤演化的率相关性,且两种材料的大变形机制存在一定的差别,能用ZWT方程进行描述的范围也不一样。     

微型燃料电池制备及其微通道摩擦性能的研究

阐述了微型燃料电池的制备过程,结合传统燃料电池数学理论和微流体力学,建立了微型质子交换膜燃料电池(μPEMFC)的数学模型,分析了微通道特性(如摩擦系数和水力直径等)对微型燃料电池性能的影响.结果表明:运用Fluent软件对模型进行计算的仿真结果与公开实验数据基本符合,验证了模型正确性;而传统模型的仿真结果小于真实值;当气道的水力直径Dh从348降至100时,电池性能有所上升;而当Dh值降至61.1时,其性能有所下降.     

Dispersion de Taylor généralisée à un fluide à propriétés physiques variablesGeneralized Taylor dispersion for heterogeneous fluid

The investigation of non-reactive miscible solute dispersion in a vertical Hele–Shaw cell is considered. An asymptotic method is used to extend Taylor model to the case of the fluid density, the dynamic viscosity and the molecular diffusion coefficient are solute concentration-dependent. It is demonstrated that the averaged variables over the gap are governed by a convection–dispersion equation in which the dispersion tensor is concentration-dependent. To cite this article: C. Felder et al., C. R. Mecanique 332 (2004).     

Complexification phenomenon in an example of sensitive singular perturbationPhénomène de complexification dans un exemple de perturbation singulière sensitive

We consider singular perturbation problems depending on a parameter ε?0 such that for ε>0 the solution u^ε belongs to a Sobolev space on a domain $\text{Ω}$, but the limit u⁰ is not a distribution on $\text{Ω}$. A very simple model problem, solvable by Fourier transform allows us to study the complexification process of u^ε as $\text{ε↘0}$. The limit holds in the topology of a space of analytical functionals. To cite this article: C.A. De Souza, É. Sanchez-Palencia, C. R. Mecanique 332 (2004).     

SOLVING THE FREE BOUNDARY PROBLEM IN CONTINUOUS CASTING BY USING BOUNDARY ELEMENT METHOD

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Fourier transform mechanical spectroscopy of the sol-gel transition in zirconium alkoxide ceramic gels

The gelation of a ceramic precursor, zirconium alkoxide, has been studied using dynamic oscillatory measurements. The gelation time is controlled by varying the concentrations of zirconium propoxide, hydrolysis with water, and acetylacetone concentration which acts as a chelating ligand. Gelation times were varied from minutes to months. The gelation time varied with zirconium concentration to the –10 power, hydrolysis to the –7 power, and ligand concentration of the –17 power. The sol-gel transition was monitored using the criteria of Winter in which GG ⁿ and tan () = tan . It is shown that the use of multiple superimposed sinusoidal waves to simultaneously measure the moduli at several frequencies is faster than using individual frequency sweep experiments. The selection of rate and strain criteria for brittle network gels is discussed in detail.     

断层活动性评价中关于测年资料的引用

断层活动性评价是研究区域构造稳定性的基础,它直接影响到水工建筑物本身的抗震安全。目前,对于断层活动性评价较常用的方法就是有关断层样品的年龄测试,这是比较直观的定量方法之一。但由于测年方法有多种,同一样品用不同的测年方法测得的结果有时偏差很大,哪种结果更为可靠始终是众多学者所关心的问题。本文对在水利水电工程断层活动性评价中关于断层年龄引用方面存在的一些问题进行探讨,并结合溪洛渡工程对研究区的马边—盐津断裂、莲峰断裂和金阳断裂进行了断裂活动性分析与评价。     

岩爆与围岩分类

岩爆是高地应力条件下完整脆性硬质围岩失稳的一种表现型式,岩爆烈度如何影响围岩类别尚不清楚,探索岩爆与围岩分类的关系,对准确判别高地应力条件下的围岩类别有着重要意义。本文以某深埋隧洞围岩分类为依据,对我国水利水电地下洞室围岩分类中岩爆烈度与围岩类别的关系、岩爆判别指标的选取等问题进行了探讨。     

连铸结晶器内部流场及熔渣卷入的数值模拟

针对连铸结晶器内部流场及熔渣卷入过程 ,提出了两方程k -ε湍流模型和充填法数值计算模型 ,并采用硅油 /水模拟体系代替熔渣 /钢液体系 ,进行了模拟试验和数值计算。对充气造成的浸入式水口水流脉动的影响进行分析。计算结果与试验结果符合良好 ,表明本文所采用的数值模拟方法是适用的