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数值求解三维时域Maxwell方程的过程中,保持方程的内在结构显得尤为重要.利用Hamilton函数的变分形式,将Maxwell方程表述为Hamilton正则方程形式.在时域方向,利用辛传播子技术对方程进行离散以保持方程的内在结构;在空域方向,采用时域多分辨率方法对三维旋度算符进行差分离散,建立了求解Maxwell方程的辛时域多分辨率(S-MRTD)方法.对S-MRTD方法的稳定性及数值色散性进行了系统的探讨,数值结果表明该方法的正确性及高精度性. 相似文献
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通过理论分析和数值计算,比较了时域相位共轭技术和频域相位共轭技术对光纤中由于色散和非线性引起的超短光脉冲传输失真的补偿效果。结果表明,在仅考虑群速度色散和自相位调制效应时,时域相位共轭技术与频域相位共轭技术的补偿效果一致;当需要考虑三阶色散时,频域相位共轭技术的补偿效果优于时域相位共轭技术;当需要考虑脉冲内拉曼散射时,时域相位共轭技术的补偿效果优于频域相位共轭技术;当上述四种效应同时考虑时,频域相位共轭技术的补偿效果略优于时域相位共轭技术。同时还对上述两种补偿技术的应用进行了讨论。 相似文献
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本文利用统一的简化二维时域有限差分法分析了几种没的各向异性波导,通过所得的数值结果与其它解析技术和数值技术获得的数值结果作比较,证实了我们所用的方法的精度和有效性。 相似文献
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针对电磁波多尺度问题的高效仿真需求,提出了基于亚网格技术的时域有限差分(FDTD)方法与时域精细积分(PITD)方法的混合数值算法。该混合算法的基本思想是采用局部亚网格技术分别对精细结构区域以及其他区域进行剖分,并应用FDTD方法和PITD方法分别对粗网格区域与细网格区域进行求解,同时构建信息交互策略交换细网格区域与粗网格区域的计算信息。一方面该方法减少了电磁波多尺度问题的网格剖分数目,显著降低了内存需求;另一方面由于应用于细网格区域的PITD方法不受Courant-Friedrich-Levy(CFL)数值稳定性条件的限制,该混合方法能够采用较大的时间步长进行仿真,减少了迭代步数以及CPU执行时间。数值计算结果验证了混合算法的稳定性、可行性以及高效性。 相似文献
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图像增强技术在指纹中的应用 总被引:2,自引:0,他引:2
描述了在空间域、频率域以及数学形态学上的图像增强技术,分析和讨论了空间域和频率域以及形态学三种方法在指纹上的应用。由于采用单一的图像增强技术不能达到令人满意的效果,有必要将多种方法结合使用。经过实验处理后得到的结果图像,表现出指纹中的突出特征,实验结果中有些特征是单一图像增强技术不能提取出来的。 相似文献
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Electromagnetic scattering by an electromagnetic wave is more and more considered in the time domain. So numerical methods of resolution such as the finite difference time domain method have been particularly studied since some years, this is due to their versatility and their numerous possibilities. Two finite difference methods are presented in this paper first a scattered field, then a total field method. Because of the impossibility of the classical method to take dielectric structures into account, a total field method has been developed. These numerical methods are then applied in the domain of microstrip patch antennas, first in emission, then in reception to analyse the susceptibility of antennas boarded on satellites. 相似文献
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Motion estimation methods can be broadly classified as being spatiotemporal or frequency domain in nature. The Gabor representation is an analysis framework providing localized frequency information. When applied to image sequences, the 3-D Gabor representation displays spatiotemporal/spatiotemporal-frequency (st/stf) information, enabling the application of robust frequency domain methods with adjustable spatiotemporal resolution. In this work, the 3-D Gabor representation is applied to motion analysis. We demonstrate that piecewise uniform translational motion can be estimated by using a uniform translation motion model in the st/stf domain. The resulting motion estimation method exhibits both good spatiotemporal resolution and substantial noise resistance compared to existing spatiotemporal methods. To form the basis of this model, we derive the signature of the translational motion in the 3-D Gabor domain. Finally, to obtain higher spatiotemporal resolution for more complex motions, a dense motion field estimation method is developed to find a motion estimate for every pixel in the sequence. 相似文献
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The Method of the Weighted Residuals (MWR), sometimes known as the Method of Moments (MoM), has traditionally been applied in the frequency domain and has been shown to be effective and efficient, especially in computing open electromagnetic structure problems. Although it has been extended to the time domain in various forms, it is generally employed to solve integral formulations derived from Maxwell's equations. Therefore, it is often considered to be one type of numerical method that is different from other numerical methods, such as finite-difference methods. However, in this paper we will show that the MWR, or MoM, is not just a method per se: it can in fact be a general framework for or approach to unifying or deriving most of the numerical methods developed so far, either in the frequency domain or in the time domain. As a result, all numerical methods can be quite easily understood and can be categorized in one general method, although their conventional derivations may still have their respective advantages. One potential application is that the hybridization of different numerical methods can now be done within a uniform framework. The paper is intended for both beginners and experienced practitioners in the area of numerical electromagnetic modeling. 相似文献
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通过分析网络流量数据在FrFT域的统计特性发现,实际网络流量在FrFT域满足自相似性,进一步地,针对网络流量在FrFT域的“时域”和“频域”展开,分别给出了基于改进的整体经验模态分解—去趋势波动分析(MEEMD-DFA)的Hurst指数估计法以及基于加权最小二乘回归(WLSR)的Hurst指数自适应估计法。实验结果表明,相比于现有估值算法,MEEMD-DFA法具有较高的估计精度,但计算复杂度高;而FrFT自适应估计法则具有更优的估计顽健性,且计算复杂度较低,可作为一种实时在线估计真实网络数据Hurst指数的方法。 相似文献