WAVE PROPAGATION IN A TRANSVERSELY ISOTROPIC THERMOELASTIC SOLID CYLINDER OF ARBITRARY CROSS-SECTION

The wave propagation in an infinite, homogeneous, transversely isotropic solid cylinder of arbitrary cross-section is studied using Fourier expansion collocation method, within the frame work of linearized, three-dimensional theory of thermoelasticity. Three displacement potential functions are introduced, to uncouple the equations of motion and the heat conduction. The frequency equations are obtained for longitudinal and flexural (symmetric and antisymmetric) modes of vibration and are studied numerically for elliptic and parabolic cross-sectional zinc cylinders. The computed non-dimensional wave numbers are presented in the form of dispersion curves.     

分区均匀介质静电场的求解

1分区均匀介质静电场求解方法的回顾分区均匀介质静电场的求解是电磁学课程中比较有难度和有特色的内容.有两种情形的分区均匀介质静电场问题可以解析求解:一种是介质-介质界面与撤去电介质时的电场线平行;另一种是介质-介质界面与撤去电介质时的电场线垂直.它是唯一性定理应用的一个生动的实例,并且涉及到静     

新型内反射旋光光学滤波器研究

基于氯酸钠晶体的各向同性和旋光色散特性,利用线偏振光以Brewster角内反射时P分量反射率为零的特性,研制出一种新型内反射旋光光学滤波器,该光学滤波器仅需采用单个偏振片,即可达到良好的滤波效果.利用Mueller矩阵对该滤波器的滤波特性进行理论分析以及实验测试,结果表明对含有532 nm和632.8 nm谱线的线偏振光,改变起偏器角度即可连续调制出射红、绿光的光强,当起偏器较初始位置旋转过133.36°和173.06°时,绿光和红光分别消光,绿光和红光的隔离度可达10 dB. 关键词： 光学滤波器 各向同性 旋光色散 偏振     

Cloaking an object in a half space without reflection

A novel cloaking scheme to hide an object in a half space from electromagnetic (EM) detection without reflection is firstly presented. The proposed cloaking scheme contains a couple of matching strips, which consist of an isotropic material layer and an anisotropic UPML layer, located right under the bottom surface of a semi-cylindrical cloaking shell. Simple expressions for the material parameters of the cloaking scheme are derived. Numerical simulations are also performed, and a good cloaking effect is achieved. The cloaking scheme is effective to hide the local object with strong scattering characters placed on mobile carriers, such as the radar antenna system on an aircraft.1     

Hypersurfaces with isotropic para-Blaschke tensor

Let Mnbe an n-dimensional submanifold without umbilical points in the(n + 1)-dimensional unit sphere Sn+1.Four basic invariants of Mnunder the Moebius transformation group of Sn+1are a 1-form Φ called moebius form,a symmetric(0,2) tensor A called Blaschke tensor,a symmetric(0,2) tensor B called Moebius second fundamental form and a positive definite(0,2) tensor g called Moebius metric.A symmetric(0,2) tensor D = A + μB called para-Blaschke tensor,where μ is constant,is also an Moebius invariant.We call the para-Blaschke tensor is isotropic if there exists a function λ such that D = λg.One of the basic questions in Moebius geometry is to classify the hypersurfaces with isotropic para-Blaschke tensor.When λ is not constant,all hypersurfaces with isotropic para-Blaschke tensor are explicitly expressed in this paper.     

Scaling law of resolved-scale isotropic turbulence and its application in large-eddy simulation

Eddy-damping quasinormal Markovian （EDQNM） theory is employed to calculate the resolved-scale spectrum and transfer spectrum, based on which we investigate the resolved-scale scaling law. Results show that the scaling law of the resolved-scale turbulence, which is affected by several factors, is far from that of the full-scale turbulence and should be corrected. These results are then applied to an existing subgrid model to improve its performance. A series of simulations are performed to verify the necessity of a fixed scaling law in the subgrid modeling.     

层状横观各向同性地基上异性矩形薄板的弯曲解析解

选用更具广泛性的层状横观各向同性弹性地基模型,来分析四边自由各向异性矩形地基板的弯曲解析解。先基于直角坐标下横观各向同性体的静力胡海昌通解,借助双重傅里叶变换及矩阵传递法,获得层状横观各向同性地基的静力位移场和应力场;然后将异性薄板的弯曲控制方程,与基于层状横观各向同性弹性地基的位移解建立的板与地基变形协调方程相结合,先按对称性分解,再用三角级数法,得出层状横观各向同性弹性地基上四边自由各向异性矩形薄板的弯曲解析解,包括地基反力、板的挠度及板的内力的解析表达式。克服了数值法的弊端,取消了对地基反力的假设,且避免了矩阵指数函数的计算;同时考虑了地基的层状性及板和地基的各向异性,从而得到板的内力及地基反力更切实际的分布规律。算例结果与文献的有限元结果吻合良好,证明本文方法是切实可行的。     

Two-phase turbulence models for simulating dense gas-particle flows

The two-fluid model is widely adopted in simulations of dense gas-particle flows in engineering facili- ties. Present two-phase turbulence models for two-fluid modeling are isotropic. However, turbulence in actual gas-particle flows is not isotropic. Moreover, in these models the two-phase velocity correlation is closed using dimensional analysis, leading to discrepancies between the numerical results, theoretical analysis and experiments. To rectify this problem, some two-phase turbulence models were proposed by the authors and are applied to simulate dense gas-particle flows in downers, risers, and horizontal channels; Experimental results validate the simulation results. Among these models the USM-O and the two-scale USM models are shown to give a better account of both anisotropic particle turbulence and particle-particle collision using the transport equation model for the two-phase velocity correlation.     

纤维增强复合材料靶板抗钢球贯穿的工程分析方法研究

介绍了钢球贯穿纤维增强复合材料靶板的一维工程近似分析方法.钢球被假定为刚体,复合材料靶被近似为横观各向同性弹埋性材料.通过将球腔膨胀模型和柱腔贯穿相结合的方法,提出了一种改进的复合材料靶抗贯穿的工程近似分析方法.利用该方法,对三维芳纶纤维编织(3DKw)复合材料靶板开展了抗钢球贯穿的工程近似分析,计算结果与实验结果一致性较好;并进一步讨论了计算中材料主要参数对靶板抗贯穿规律的影响.     

On weak solutions for an image denoising-deblurring model

A new denoising-deblurring model in image restoration is proposed,in which the regularization term carries out anisotropic diffusion on the edges and isotropic diffusion on the regular regions.The existence and uniqueness of weak solutions for this model are proved,and the numerical model is also testified.Compared with the TV diffusion,this model preferably reduces the staircase appearing in the restored images.