共查询到20条相似文献,搜索用时 109 毫秒
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解二维辐射输运问题时,对于矩形网格,用Sn菱形(diamond)格式处理十分简单有效,但该格式不能直接用于非矩形网格,而辐射流体力学计算往往要求在非矩形网格上进行.本文讨论任意四边形网格的辐射输运数值方法,给出一种全正的子网格平衡计算格式,并进行数值计算,与矩形网格Sn菱形格式结果比较,得出本方法可行性结论. 相似文献
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建立了电荷非平衡情况下super junction(SJ)耐压结构的二维电场分布理论模型. 获得了浓度和宽度非平衡、梯形n-/p- 区和横向线性缓变掺杂三种非平衡SJ结构的电场分布. 理论分析结果与二维器件数值仿真软件MEDICI的仿真结果符合良好. 虽然给出的电场分布为三角级数形式, 但仍能从中获得很多重要信息. 特别地, 由此可求出非平衡SJ结构的峰值电场和耐压. 该结果有助于对SJ结构的深入分析.
关键词:
super junction
电场分布
电荷非平衡 相似文献
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三维电磁粒子模拟基于时域有限差分算法(FDTD)和PIC(particle-in-cell)方法.根据FDTD和PIC方法的特点,可以将整个模拟区域分割为多个子区域,每个计算进程模拟计算一个子区域,通过消息传递交换子区域的边界数据从而实现并行计算这一基本思路,完成了并行算法的设计,并分析了并行加速比的影响因素.在三维电磁粒子模拟软件CHIPIC3D上实现了该并行算法并验证了算法的正确性,最后应用CHIPIC3D并行版本对磁绝缘线振荡器和相对论速调管两种典型的高功率微波源器件进行了模拟,证明了该并行算法能取
关键词:
电磁粒子模拟
时域有限差分
并行计算
高功率微波源 相似文献
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用非结构网格与欧拉方程计算复杂区域的二维流动 总被引:5,自引:1,他引:4
提出用Delaunay三角化方法生成非结构网格的一种过程。所生成的网格可用于复杂多连通域内的可压流计算。采用Euler方程和格心有限体积法,研制出程序,给出了算例。 相似文献
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为评定光斑环围参量(包括环围功率和环围尺寸)阵列测试法的测量不确定度,给出了环围参量一般形式的定义和连续形式的计算表达式,归纳并比较了阵列测试法下光斑环围参量的3种常用计算方法,即近似环围功率法、准确环围功率法和等效环围尺寸法,给出了零阶近似下环围参量离散形式的计算表达式。根据不确定度传递律,推导了基于等效环围尺寸法的环围参量测量不确定度的一般表达式,讨论了常见简化条件下的环围参量测量不确定度表达式。建立了光斑环围参量计算及其不确定度评定的一套较完整的方法。以强度为高斯分布的光斑为例,得到了简化条件下的环围参量测量不确定度的解析表达式,并用数值模拟法验证了其正确性。 相似文献
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As a subsequent work of previous studies of authors, a new parallel computation approach is proposed to simulate the coupled dynamics of a rigid-flexible multibody system and compressible fluid. In this approach, the smoothed particle hydrodynamics (SPH) method is used to model the compressible fluid, the natural coordinate formulation (NCF) and absolute nodal coordinate formulation (ANCF) are used to model the rigid and flexible bodies, respectively. In order to model the compressible fluid properly and efficiently via SPH method, three measures are taken as follows. The first is to use the Riemann solver to cope with the fluid compressibility, the second is to define virtual particles of SPH to model the dynamic interaction between the fluid and the multibody system, and the third is to impose the boundary conditions of periodical inflow and outflow to reduce the number of SPH particles involved in the computation process. Afterwards, a parallel computation strategy is proposed based on the graphics processing unit (GPU) to detect the neighboring SPH particles and to solve the dynamic equations of SPH particles in order to improve the computation efficiency. Meanwhile, the generalized-alpha algorithm is used to solve the dynamic equations of the multibody system. Finally, four case studies are given to validate the proposed parallel computation approach. 相似文献
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Liang D Lam EY Fung GS 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,188(1):141-150
The direct Fourier transform method is a straightforward solution with high accuracy for reconstructing magnetic resonance (MR) images from nonuniformly sampled k-space data, given that the optimal density compensation function is selected and the underlying magnetic field is sufficiently uniform. The computation however is very time-consuming, making it impractical especially for large-size images. In this paper, the least squares quantization table (LSQT) method is proposed to accelerate the direct Fourier transform computation, similar to the recently proposed methods such as using look-up table (LUT) or equal-phase-line (EPL). With LSQT, all the image pixels are first classified into several groups where the Lloyd-Max quantization scheme is used to ensure the minimal classification error. The representative value of each group is stored in a small-size LSQT in advance to reduce the computational load. The pixels in the same group receive the same contribution, which is calculated only once for each group instead of for each pixel, resulting in the reduction of computation because the number of groups is far smaller than the number of pixels. Finally, each image pixel is mapped into the nearest group and its representative value is used to reconstruct the image. The experimental results show that the LSQT method requires far smaller memory size than the LUT method and fewer multiplication operations than the LUT and EPL methods. Moreover, the LSQT method can perform large-size reconstructions that achieve comparable or higher accuracy as compared to the EPL and gridding methods when the appropriate parameters are given. The inherent parallel structure also makes the LSQT method easily adaptable to a multiprocessor system. 相似文献
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克尔型非线性薄膜波导的TE模 总被引:4,自引:1,他引:3
对于芯区为克尔型非线性介质,覆盖层和衬底为线性介质的平板波导,用Krylov-Bogoliubov-Mitropolsky的渐近法导出了色散方程及场分布的二阶近似数学表达式,计算量大为减少且结果精确。给出了对称和非对称情况的典型实例。 相似文献
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Algorithms for using the Galerkin projection method and the projection least squares method to analyze the three-dimensional model of the diffusion of minority charge carriers generated by an electron probe in a semiconductor material are presented. The results obtained using these methods are compared with the analytical solution. An estimate of the error is given, and the condition for the computation stability of the projection least squares method in the form of the limiting relation is obtained. 相似文献
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研究从运动微分方程构造加速度相关Lagrange函数的问题,给出一种由方程的自伴随形式计算加速度相关Lagrange函数的方法.举例说明结果的应用.
关键词:
分析力学
加速度相关Lagrange函数
自伴随性
Lagrange力学逆问题 相似文献
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The Fourier modal method for crossed gratings is reformulated by use of a group-theoretic approach when the grating structures have the equilateral triangular symmetry. In the new formulation, a grating problem is first decomposed into four symmetrical basis problems whose field distributions are the symmetry modes (two are nondegenerate and the other two are doubly degenerate) of the grating. Then the symmetry relations of fields in the symmetry modes are used to reduce the number of unknowns in numerical computation. After the symmetrical basis problems are solved, their solutions are superposed to get the solution of the original problem. It is shown that when the grating is at some incident mountings, the memory occupation can be saved by 2/3 and the computation time can be reduced to 1/12 to 1/13.5 of the original one for different incident cases. Numerical examples are given to illustrate the effectiveness of the new formulation and verify the improved computation efficiency. 相似文献