二维声子晶体带隙计算中的时域有限差分方法

通过将各向同性介质动态弹性方程转化为一阶双曲型波动方程，采用交错网格法改进了O(2,4)的时域有限差分算法. 进而将其应用于二维声子晶体带隙特性计算，理论计算结果和实验结果符合较好，证明该方法适用于声子晶体带隙特性的计算. 关键词： 声子晶体 声子带隙 时域有限差分 交错网格PACC：     

基于不分裂算法的Euler网格细分方法

 对考虑多物质相互作用的爆炸冲击数值模拟,Euler型流体动力学方法是最有效的方法之一。采用维数不分裂算法处理Euler坐标下的纯物质网格,混合网格在Youngs界面重构技术的基础上进行细分,消除混合网格复杂的输运计算。对纯物质网格和细分后网格,都具体给出了往相邻八个网格输运的所有可能分配量的表达式。最后将该方法加入到自行开发的MMIC-2D通用多物质二维爆炸与冲击问题数值仿真程序中,数值算例显示本文采用方法不仅能有效地提高计算精度,同时能降低问题的计算工作量,节省计算时间。     

三维电子回旋脉塞的数值模拟研究

为了打破二维模拟回旋脉塞的一些局限性,研究了电子回旋受激辐射的基本原理,使用唯象的描述方法,以统计物理学为基础,在电子回旋中心坐标系中完成了三维Yee网格模型中对电子注平衡态物理模型的数值建模,并结合PIC方法和FDTD算法进行电子回旋脉塞的数值模拟.为了减少计算时间,在模拟中加入了MPI并行算法,加速比能提高到2.7以上.最后以一个94 GHz的回旋振荡管为例,对它的整体结构进行了模拟,并通过对频谱,功率,工作模式等方面验证了模拟的正确性. 关键词： 电子回旋脉塞 Yee网格模型 PIC方法 FDTD算法     

An efficient finite difference technique for computing incompressible viscous flows

An improved Navier–Stokes solver is presented to compute two-dimensional incompressible flows in the stream–vorticity formulation at high Reynolds number. The technique is based on both the IMM for the non-orthogonal co-ordinate system and a specialized TVD scheme to cope with non-linear transport terms. Numerical results are shown to demonstrate the accuracy and efficiency of the technique. The method is robust and holds promise to handle complex geometries economically. © 1997 John Wiley & Sons, Ltd.     

Micro-experimental study of large plastic deformation for high-purity polycrystalline aluminum

This paper aims at revealing various micro- deformation characteristics, such as crystalline slip and grain boundary slide, which are recorded under scanning electronic microscope for high-purity aluminum tensile specimen at room temperature. These experimental data provide us direct evidence for shear localization near the grain boundary network via multi- directional grain boundary slide. The nonuniform deformation induced in the grain interiors would have decisive effect on the plastic flow and failure of polycrystalline materials. Sponsored by the National Natural Science Foundation of China and the Fok Ying- Tung Education Foundation.     

一种非结构化同位网格算法

本文介绍了任意网格系统中的SIMPLE算法的推导过程，并将此算法应用于二维非结构化网格（三角形网格）之中，网格由DELAUNAY三角化方法生成．对顶盖驱动空腔流的计算表明该算法是令人满意的．     

基于IEEE-754标准和现场可编程门阵列技术的混沌产生器设计与实现

提出了基于IEEE-754标准的现场可编程门阵列(FPGA)通用混沌与超混沌信号产生器设计与硬件实现的一种新方法. 首先,根据Euler算法,对连续混沌系统作离散化处理,便于FPGA等一类数字信号处理器件的实现. 其次,基于IEEE-754标准和模块化设计理念,用硬件描述语言构建出浮点数的乘法运算、加法运算、符号函数运算、正负绝对值运算、初始值与迭代值选择等5个基本模块,并以此为基础,进一步在FPGA平台上产生包括网格状多涡卷蔡氏系统在内的多种不同类型的混沌与超混沌信号. 最后,通过对语音芯片的配置,利用 关键词： 网格状多涡卷混沌系统 IEEE-754标准 现场可编程门阵列 浮点数算法     

四芯光纤弯曲传感器

提出了一种新颖的基于四芯光纤的弯曲传感器,可用于弯曲测量。该传感器采用一段四芯光纤作为敏感单元,四芯光纤的四个纤芯作为一个四光束干涉仪,在光纤出射端远场形成周期分布的干涉格子。该四光束干涉仪的干涉相位差是光纤弯曲曲率半径的函数,因而,弯曲曲率半径的变化可导致格子光场的移动。波长为650 nm的低相干半导体激光二级管被用来做为光源,所形成的干涉格子光场由CCD探测器记录。理论上,建立了远场格子图案强度分布函数与曲率半径的关系,并得到了实验的验证。     

基于自适应格网数字水深模型的水下地形匹配定位算法

为了解决当前的水下地形匹配定位算法未考虑格网大小随海底地形变化而自动调整的问题,提出了一种基于自适应格网数字水深模型的水下地形匹配定位算法。首先,引入基于四叉树的自适应格网模型,改进其局部格网的相似性评估指标与构网约束方法;然后,设计匹配区的确定及待匹配航迹的选取策略,给出待匹配航迹的水深值的计算方法,构建出目标匹配定位的地形相关组合算子。实验结果表明:提出的算法相比于基于等距离的规则格网模型的算法有以下优势:1)在地形特征丰富区域的定位精度明显提高;2)可以避免出现地形特征越明显匹配定位精度越低的情况;3)能一定程度地克服水深系统误差对定位精度的影响。     

A multi-moment finite volume formulation for shallow water equations on unstructured mesh

A novel and accurate finite volume method has been presented to solve the shallow water equations on unstructured grid in plane geometry. In addition to the volume integrated average (VIA moment) for each mesh cell, the point values (PV moment) defined on cell boundary are also treated as the model variables. The volume integrated average is updated via a finite volume formulation, and thus is numerically conserved, while the point value is computed by a point-wise Riemann solver. The cell-wise local interpolation reconstruction is built based on both the VIA and the PV moments, which results in a scheme of almost third order accuracy. Efforts have also been made to formulate the source term of the bottom topography in a way to balance the numerical flux function to satisfy the so-called C-property. The proposed numerical model is validated by numerical tests in comparison with other methods reported in the literature.