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二维多导电柱体电磁散射的快速算法 总被引:2,自引:1,他引:1
本文用积分方程的迭代求解方法处理二维多导电柱体的电磁散射问题。同时用双共轭梯度法代替共轭梯度法来加速迭代过程。数值结果显示了本文方法的高效性。 相似文献
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单层校正自适应光学系统只能在较小视场范围内对大气湍流进行有效校正,多层共轭自适应光学技术可以突破这种限制。介绍了层向多层共轭自适应光学系统基本结构及工作原理,研究了层向多层共轭自适应光学系统的模拟,内容包括:如何产生动态大气湍流波前数据、基于四棱锥波前传感器的波前复原算法、基于模式法的变形镜闭环校正控制过程等。对单层和两层的层向共轭自适应光学系统进行了模拟仿真,仿真结果表明:层向多层共轭自适应光学系统采用了更多的导星来校正两层大气湍流,比单层校正自适应光学系统具有更大的校正视场和更好的校正效果。 相似文献
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基于自适应同步的混沌系统参数辨识方法的研究 总被引:1,自引:1,他引:0
利用混沌系统的动力学特性对参数极其敏感的特点,以驱动响应同步结构为框架,设计了与同步误差有关的二次型指标函数,采用优化方法对参数进行自适应调节,直到同步误差最小,即实现混沌同步.该方法实现了参数未知混沌系统的参数辨识和自适应同步.为了研究参数收敛速度,对准高斯牛顿法、Hook-Jeeves方法(又名模式搜索法)和共轭梯度法等三种优化方法进行了对比研究.对具有两个未知参数的离散Hénon系统和连续Lorenz系统的仿真研究表明,基于共轭梯度的参数调节方法参数收敛速度最快,可以应用于混沌保密通信的解密. 相似文献
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开发了一种基于积分方程的模拟均匀介质中二维电磁成像的反演算法。在反演中采用了Born 迭代方法,该算法具有抗噪声能力强、迭代稳定的优点。在正演计算中采用了计算积分方程的稳定型双共轭梯度快速Fourier 变换(BCGS-FFT)算法,将插值函数作为基函数和试探函数对积分方程进行弱化离散,离散后的积分方程采用稳定型双共轭梯度迭代方法进行求解,从而得到异常体内电场的分布,迭代过程中采用快速傅里叶变换(FFT)技术进行加速。反演算例说明了所开发算法的精确性和有效性。 相似文献
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建立多层人工神经网络的最优化求解方法,以多层神经网络总体平均误差为目标函数,以权值和阈值作为设计变量,采用共轭梯度法对网络的权值和阈值进行优化计算,完成神经网络训练的方法.将优化原理应用到多层神经网络权值和阈值的计算问题,实现网络权值和阈值的快速计算,为分析神经网络的合理结构提供了必要条件. 相似文献
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目前太阳活动观测存在视场小和分辨率低的问题。单共轭自适应光学系统可校正的视场范围较小,多层共轭自适应光学系统使用三维重构的方法,耗时长且过程繁琐;而太阳地表层自适应光学系统只校正地表层湍流,效率高,能快速获得大视场、高分辨率图像。利用YAO软件,在四导星阵列分布情况下,应用平均算法对太阳,地表层自适应光学系统在40″和60″优化视场、J和H波段的性能进行数值仿真,并与相同条件下仿真得到的单共轭自适应光学系统性能结果进行比较。结果表明,在60″~120″成像视场内,地表层自适应光学系统的斯特列尔比值比单共轭自适应光学系统提高了130%~210%,该结果与太阳自适应光学领域其他软件得到的仿真结果一致。 相似文献
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多层共轭自适应光学系统被广泛应用于地基大型天文望远镜,其可以改善大气非等晕的影响,并有效扩大校正视场。基于MAOS软件,在仅考虑大气非等晕影响的情况下,研究了在可见光波段(0.6 m)和红外光波段(2 m)下两种自适应光学系统的对比,多层共轭自适应光学系统相比传统自适应光学系统在可见光波段性能提升显著;以及双层共轭系统中,当第一个变形镜共轭于入瞳处时,第二个变形镜共轭高度变化对系统性能的影响,在可见光波段确定最佳共轭高度对提升性能十分重要,并初步探讨了在单层自适应光学系统中,变形镜致动器个数对系统性能的影响。 相似文献
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In this paper the algebraic multi-grid principle is applied to the multilevel moment method, which makes the new multilevel method easier to implement and more adaptive to structure. Moreover, the error spectrum is analyzed, and the reason why conjugate gradient iteration is not a good relaxation scheme for multi-grid algorithm is explored. The numerical results show that our algebraic block Gauss Seidel multi-grid algorithm is very effective. 相似文献
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Wasfy B. Mikhael Raghuram Ranganathan Thomas Yang 《Circuits, Systems, and Signal Processing》2010,29(3):469-480
The conjugate gradient method is a prominent technique for solving systems of linear equations and unconstrained optimization
problems, including adaptive filtering. Since it is an iterative method, it can be particularly applied to solve sparse systems
which are too large to be handled by direct methods. The main advantage of the conjugate gradient method is that it employs
orthogonal search directions with optimal steps along each direction to arrive at the solution. As a result, it has a much
faster convergence speed than the steepest descent method, which often takes steps in the same direction as earlier steps.
Furthermore, it has lower computational complexity than Newton’s iteration approach. This unique tradeoff between convergence
speed and computational complexity gives the conjugate gradient method desirable properties for application in numerous mathematical
optimization problems. In this paper, the conjugate gradient principle is applied to complex adaptive independent component
analysis (ICA) for maximization of the kurtosis function, to achieve separation of complex-valued signals. The proposed technique
is called the complex block conjugate independent component analysis (CBC-ICA) algorithm. The CBC-ICA derives independent
conjugate gradient search directions for the real and imaginary components of the complex coefficients of the adaptive system
employed for signal separation. In addition, along each conjugate direction an optimal update is generated separately for
the real and imaginary components using the Taylor series approximation. Simulation results confirm that in dynamic flat fading
channel conditions, the CBC-ICA demonstrates excellent convergence speed and accuracy, even for large processing block sizes. 相似文献
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本文讨论了共轭梯度算法在自适应波束形成中的应用,指出在时域和空域同时处理,与仅在时域或空域处理的方法相比,不仅在性能上得到了改进,而且放宽了对阵元数目的要求。同时提出了一种前后向平均和多层前后向处理的结构和方法,使算法在性能上得到了进一步的改善。 相似文献
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ZHAO Xiao-hui ZHAO YueLaboratory of Information Science College of Communication Engineering Jilin University Changchun China 《中国邮电高校学报(英文版)》2005,12(3)
1 Introduction In speech communication applications ,the presence ofcoupling fromloudspeaker to the microphone often re-sults in undesired acoustic echo that seriously degradesspeech quality.Current solutions for removingthis echoare based on the real ti me identification of the acoustici mpulse response by using adaptive filtering or AdaptiveEcho Cancellation (AEC) filter techniques . Several AEC algorithms have been proposed for thisproblem. An acoustic echo canceller based upon inputort… 相似文献
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A new two-dimensional (2D) sample-based conjugate gradient (SCG) algorithm is developed for adaptive filtering. This algorithm is based on the conjugate gradient method of optimization and therefore has a fast convergence characteristic. The SCG is computationally simpler than the recursive least squares (RLS) algorithm. The SCG algorithm with the equation-error and output-error methods is investigated for application in image restoration. Simulation results show that the new algorithm significantly outperforms existing algorithms in the restoration of noisy images.This work was supported in part by a grant from the Colorado Advanced Software Institute. 相似文献
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高阶矩量法在计算电磁学中的应用越来越广泛, 为了进一步提高其计算规模, 引入并行的自适应交叉近似压缩算法(Adaptive Cross Approximation algorithm, ACA).该算法首先采用非均匀有理B样条建模(Non-Uniform Rational B-Splines, NURBS)的方法进行面片分组; 然后利用矩量法中远区阻抗矩阵的低秩特性进行ACA压缩; 最后采用稀疏近似逆预条件(Sparse Pattern Approximate Inverse preconditioning, SPAI)的共轭梯度法(Conjugate Gradient method, CG)快速求解矩阵方程.该算法中的ACA压缩过程和迭代求解过程都特别适合并行计算.数值实验表明, 对于电大尺寸问题, ACA压缩后的矩阵占用的内存远远低于原矩阵, 而预条件的共轭梯度法可以很快收敛.此外该算法在大规模并行时的效率较高. 相似文献
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This paper presents an efficient time-domain method for computing the propagation of electromagnetic waves in microwave structures. The procedure uses high-order vector bases to achieve high-order accuracy in space, Newmark's method to provide unconditional stability in time, and the transfinite-element method to truncate the waveguide ports. The resulting system matrix is real, symmetric, positive-definite, and can be solved by using the highly efficient multilevel preconditioned conjugate gradient algorithm. Since the method allows large time steps and nonuniform grids, the computational complexity for problems with irregular geometries is superior to that of the finite-difference time-domain method. 相似文献