问题变分不等式的一类各向异性Crouzeix-Raviart型有限元逼近

本文研究了Signorini变分不等式问题的一类各向异性Crouzeix-Raviart型非协调有限元逼近。通过一些新的技巧,得到了相应的最优误差估计。     

各向异性表面张力对定向凝固中共晶生长形态稳定性的影响

研究各向异性表面张力对定向凝固中共晶生长形态稳定性的影响.应用多重变量展开法导出了共晶界面表达式和扰动振幅的变化率满足的色散关系.结果表明,共晶生长系统有两种整体不稳定性机理:由非震荡导致的"交换稳定性"机理和由震荡导致的"整体波动不稳定性"机理.震荡有四种典型模式,即:反对称-反对称(AA-),对称-反对称(SA-)、反对称-对称(AS-)和对称-对称(SS-)模式.稳定性分析表明:共晶界面形态稳定性取决于Peclet数ε的某一个临界值ε_*,当ε大于临界值ε_*时,共晶界面形态不稳定;当ε小于临界值ε_*时,共晶界面形态稳定.随着各向异性表面张力增大,对应于AA-,SA-和SS-模式的临界值ε_(aa*),ε_(sa*)和ε_(ss*)随之减小,表明各向异性表面张力减小这三种模式的稳定性区域;然而,随着各向异性表面张力增大,对应于AS-模式的临界值ε_(as*)随之增大,表明各向异性表面张力增大AS-模式的稳定性区域.     

3D FDTD Implementation for Scattering of Electric Anisotropic Dispersive Medium Using Recursive Convolution Method

The finite-difference time-domain method based on recursive convoltion method (RC-FDTD) for the electric anisotropic dispersive medium is discussed in detail. To exemplify the availability of the three-dimensional RC-FDTD algorithm, the backscattering Radar-Cross-Section(RCS) of a non-magnetized plasma sphere is computed, and the numerical results are the same as the one of the Shift Operater-FDTD method, and show that the RC-FDTD method is correct and efficient. In addition, the co-polarized and cross-polarized backscattering time-domain of a magnetized plasma sphere are obtained by the RC-FDTD algorithm. The results show that when the external magnetic field is implemented, the cross-polarized component appear, evidently.     

Mechanical,elastic, anisotropy,and electronic properties of monoclinic phase of m-Si_xGe_(3-x)N_4

The structural,mechanical,elastic anisotropic,and electronic properties of the monoclinic phase of m-Si_3N_4,mSi_2GeN_4,m-SiGe_2N_4,and m-Ge_3N_4are systematically investigated in this work.The calculated results of lattice parameters,elastic constants and elastic moduli of m-Si_3N_4and m-Ge_3N_4are in good agreement with previous theoretical results.Using the Voigt–Reuss–Hill method,elastic properties such as bulk modulus B and shear modulus G are investigated.The calculated ratio of B/G and Poisson’s ratio v show that only m-SiGe_2N_4should belong to a ductile material in nature.In addition,m-SiGe_2N_4possesses the largest anisotropic shear modulus,Young’s modulus,Poisson’s ratio,and percentage of elastic anisotropies for bulk modulus ABand shear modulus AG,and universal anisotropic index AUamong m-Si_xGe_(3-x)N_4(x=0,1,2,3.)The results of electronic band gap reveal that m-Si_3N_4,m-Si_2GeN_4,m-SiGe_2N_4,and m-Ge_3N_4 are all direct and wide band gap semiconducting materials.     

电化学刻蚀法制备LaB6场发射微尖锥阵列

采用电化学刻蚀方法,成功制备出单尖的六硼化镧、钼、钨及钨铼合金场发射冷阴极尖锥,并对这几种场发射单尖锥阴极的电子发射性能进行了测试比较.结果表明,LaB₆作为场发射阴极,具有良好的发射性能和稳定性.在〈111〉面单晶LaB₆基片上,用PECVD法沉积非晶硅作掩膜,制备出具有一定高度的LaB₆微尖锥场发射阵列,结果发现,LaB₆基底较为平整,尖锥阵列呈现出各向异性.该结论对LaB₆材料在场发射阴极方面的进一步研究具有重要的指导意义.     

基于自适应侧抑制网络的红外弱小目标检测

 为了提高远距离红外弱小目标的检测效率,提出了一种基于自适应侧抑制网络的复杂背景下的红外弱小目标检测方法。该方法建立了改进的侧抑制网络数学模型,利用各向异性滤波来自适应地确定侧抑制网络的抑制系数,不需要人为干预,实现了侧抑制网络与各向异性高斯滤波的有机结合。同时,在各向异性高斯滤波器两轴确定方面进行了改进,两轴分别采用对比度尺度模型和强度尺度传播模型来独立确定。通过与传统弱小目标检测方法的对比实验,验证了方法的有效性。     

三维各向异性耦合谐振子哈密顿量的对角化

根据物理量的可测实在性,应用二次型理论,一般地解决了3个质量与3个频率均不相同、坐标和动量各自具有全耦合谐振子系统的哈密顿量的可对角化问题,并具体给出了哈密顿量对角化的标准形.     

Viscosity Effects on Anisotropic Universe in Curvature-Matter Coupling Gravity

In this paper, we study evolution of the universe in the background of f(R, T) gravity using LRS Bianchi type-Ⅰ model. We discuss scale factors as well as deceleration parameter in dark energy dominated era for different bulk viscosity models. The occurrence of big-rip singularity is also examined. It is concluded that expansion is faster when bulk viscosity is proportional to Hubble parameter as compared to other models.     

各向异性超导体电阻转变的修正Kosterlitz-Thouless相变模型

从二维系统的Kosterlitz-Thouless (KT) 相变理论出发，在关联长度中引入热激活能和平均钉扎高度，提出了修正的KT相变模型.该模型与库伦气体标度理论和Halperin-Nelson关系具有一致性.应用修正的KT相变模型研究磁场下Tl₂Ba₂CaCu₂O_x(Tl-2212)薄膜电阻转变的标度行为，发现由电阻转变计算得到的平均钉扎高度与温度具有线性依赖关系，实验结果支持修正的KT相变模型. 关键词： 标度行为 各向异性超导体 电阻转变