Karhunen–Loeve representations of turbulent channel flows using the method of snapshots

For three‐dimensional flows with one inhomogeneous spatial coordinate and two periodic directions, the Karhunen–Loeve procedure is typically formulated as a spatial eigenvalue problem. This is normally referred to as the direct method (DM). Here we derive an equivalent formulation in which the eigenvalue problem is formulated in the temporal coordinate. It is shown that this so‐called method of snapshots (MOS) has some numerical advantages when compared to the DM. In particular, the MOS can be formulated purely as a matrix composed of scalars, thus avoiding the need to construct a matrix of matrices as in the DM. In addition, the MOS avoids the need for so‐called weight functions, which emerge in the DM as a result of the non‐uniform grid typically employed in the inhomogeneous direction. The avoidance of such weight functions, which may exhibit singular behaviour, guarantees satisfaction of the boundary conditions. The MOS is applied to data sets recently obtained from the direct simulation of turbulence in a channel in which viscoelasticity is imparted to the fluid using a Giesekus model. The analysis reveals a steep drop in the dimensionality of the turbulence as viscoelasticity is increased. This is consistent with the results that have been obtained with other viscoelastic models, thus revealing an essential generic feature of polymer‐induced drag reduced turbulent flows. Published in 2006 by John Wiley & Sons, Ltd.     

边界拟合坐标系中的流动方程

本文提出了流体力学解析边界拟合坐标系方法，及建立在这种坐标系基础上对流动方程进行摄动处理的方法，并列举几种流动建立了解析边界拟合坐标系中的方程。     

SrFCl:Eu~(2+)晶体的电子自旋共振谱研究

用程序降温法生长了SrFCl:Eu~(2+)晶体,并测量了它的电子自旋共振谱。应用最小二乘法拟合技术对g因子及自旋哈密顿参数进行了精确拟合。报道了各向异性的g因子及有关自旋哈密顿参量。发现并归属了Eu~(2+)的高阶禁阻跃迁。     

Ba（n，x）~（134）Cs，~（134）Ba（n，2n）~（133）Ba，

用中子活化法相对于５４Ｆｅ（ｎ，Ｐ）５４Ｍｎ反应，在１３．５０—１４．８０ＭｅＶ中子能区测量了Ｂａ（ｎ，ｘ）１３４Ｃｓ，１３４Ｂａ（ｎ，２ｎ）１３３Ｂａ，１４０Ｃｅ（ｎ，２ｎ）１３９Ｃｅ，１４２Ｃｅ（ｎ，２ｎ）１４１Ｃｅ和２３Ｎａ（ｎ，２ｎ）２２Ｎａ的反应截面．并将所测的结果和其他作者的结果进行了比较，中子能量是用９０Ｚｒ（ｎ，２ｎ）８９ｍ＋ｇＺｒ反应和９３Ｎｂ（ｎ，２ｎ）９２ｍＮｂ反应截面比法测定的。     

Vibrational control of crystal growth from liquid phase

Modeling and numerical simulations of the convective flows induced by the vibration of the monocrystal during crystal growth have been performed for two configurations simulating the Cz and FZ methods. This permitted to emphasize the role of different vibrational mechanisms in the formation of the average flows. It is shown that an appropriate combination of these mechanisms can be used to counteract the usual convective flows (buoyancy- and/or thermocapillary-driven) inherent to crystal growth processes from the liquid phase. While vibrational convection is rather complex due to these identified mechanisms, the new modeling used in the present paper opens up very promising perspectives to efficiently control heat and mass transfer during real industrial applications of crystal growth from the liquid phase.     

中药材中孳生粉螨的初步调查

本文采用清水漂浮法和塔氏电热集螨器分离法,共分离中药材样本124种,1240份,从中分离出粉螨45种,隶属7科23属.得出结论:中药材粉螨的污染严重,应加强对中药螨类的防治,以保护中药材及预防人体螨病.     

关于一个非线性椭圆特征问题的某些注记

讨论一个非线性椭圆特征问题，减弱了原有结果中的一个条件而得到同样的结果，并讨论了参数小于λ１的情形。     

基于标记的分词算法

目前，自动分词的算法很多，但都有不能满足实用的要求。文中介绍一种在最大匹配法基础上，根据大量的真实语料中出现的语言现象，把汉语中的词按其在分词意义下的特性进行分类，并用不同的标记标识，对每一类词确定一组规则进行处理，使分词算法更接近于实用的目的。     

新的基团法估算沸点下蒸发焓

提出了估算沸点下蒸发焓的含基团重量分率的基团法和估算式，拟合团贡献值，对３８５种有机物的计算平均偏差约为１．５％。所提出的新方法明显优于３种对应状态和用蒸发熵的基团法。