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提出了一种新的算法—高阶辛时域有限差分法(SFDTD(3,4):symplectic finite-difference time-domain)求解含时薛定谔方程.在时间上采用三阶辛积分格式离散,空间上采用四阶精度的同位差分格式离散,建立了求解含时薛定谔方程的高阶离散辛框架;探讨了高阶辛算法的稳定性及数值色散性.通过理论上的分析及数值算例表明:当空间采用高阶同位差分格式时,辛积分可提高算法的稳定度;SFDTD(3,4)法和FDTD(2,4)法较传统的FDTD(2,2)法数值色散性明显改善.对二维量子阱和谐振子的仿真结果表明:SFDTD(3,4)法较传统的FDTD(2,2)法及高阶FDTD(2,4)法有着更好的计算精度和收敛性,且SFDTD(3,4)法能够保持量子系统的能量守恒,适用于长时间仿真. 相似文献
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提出了一种新的算法——高阶辛时域有限差分法(SFDTD(3, 4): symplectic finite-difference time-domain)求解含时薛定谔方程.在时间上采用三阶辛积分格式离散, 空间上采用四阶精度的同位差分格式离散, 建立了求解含时薛定谔方程的高阶离散辛框架;探讨了高阶辛算法的稳定性及数值色散性.通过理论上的分析及数值算例表明:当空间采用高阶同位差分格式时, 辛积分可提高算法的稳定度;SFDTD(3, 4)法和FDTD(2, 4)法较传统的FDTD(2, 2)法数值色散性明显改善.对二维量子阱和谐振子的仿真结果表明: SFDTD(3, 4)法较传统的FDTD(2, 2)法及高阶FDTD(2, 4)法有着更好的计算精度和收敛性, 且SFDTD(3, 4)法能够保持量子系统的能量守恒, 适用于长时间仿真. 相似文献
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收发分置目标强度的计算及前向散射信号的分离 总被引:3,自引:0,他引:3
研究时域有限差分(FDTD)法计算收发分置弹性目标散射声场的有效性,和实验测量中从直达与散射干涉信号中分离目标前向散射信号的方法。将FDTD法应用于三维声场计算,分别计算了平顶圆柱、球顶圆柱、球锥顶圆柱和扁长回转椭球等几种不同形状的弹性体散射近场空间分布,再用近远场变换方法获取远场目标强度空间分布。模拟结果表明:目标强度的空间指向性是受声波入射方向、无量纲波数kL(k-波数,L-目标特征尺度)、目标形状、材料等影响;在本文所计算的几种不同形状目标的尺度和kL取值范围内,计算得到的收发分置目标强度空间分布均有显著的前向散射与镜反射特征。计算结果得到解析解和实验结果的印证,从而表明了FDTD法计算收发分置目标散射场的有效性。对接收信号采用相关处理方法,能有效地分离出目标前向散射信号,表明对于收发分置目标散射声强的测量,这是一种简单有效的分离目标前向散射信号的方法。 相似文献
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提出了一种新的算法一高阶辛时域有限差分法(SFDTD(3,4):symplectic finite—difference time-domain)求解含时薛定谔方程.在时间上采用三阶辛积分格式离散,空间上采用四阶精度的同位差分格式离散,建立了求解含时薛定谔方程的高阶离散辛框架;探讨了高阶辛算法的稳定性及数值色散性.通过理论上的分析及数值算例表明:当空间采用高阶同位差分格式时,辛积分可提高算法的稳定度;SFDTD(3,4)法和FDTD(2,4)法较传统的FDTD(2,2)法数值色散性明显改善.对二维量子阱和谐振子的仿真结果表明:SFDTD(3,4)法较传统的FDTD(2,2)法及高阶FDTD(2,4)法有着更好的计算精度和收敛性,且SFDTD(3,4)法能够保持量子系统的能量守恒,适用于长时间仿真. 相似文献
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应用Compton散射模型和非线性Schrdinger方程,研究了Compton散射对等离子体零色散附近调制不稳定性的影响,提出了将Compton散射作为形成调制不稳定性的新机制,给出了等离子体修正色散方程,并进行了数值计算.结果表明:二阶色散较大时,远离零色散附近调制不稳定性增益谱由入射和散射光产生的二阶色散决定,随二阶色散增大,四阶色散作用迅速减小,这是因散射效应有效削弱了四阶效应的缘故.零色散附近调制不稳定性增益谱由入射和散射光产生的四阶色散决定,二阶色散被湮灭,微扰频率最大值向临界微扰频率较快靠近,这是因散射效应有效增强了四阶效应的缘故.增益谱宽随等离子体损耗增大而迅速增大,这是因功率增大使散射效应增强,导致带电粒子辐射阻尼增强的缘故. 相似文献
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基于数字信号处理中的半解析递归卷积(SARC)算法,提出了一种用于色散介质电磁特性分析的半解析递归卷积时域有限差分方法(SARC FDTD). 该方法既保持了FDTD方法处理复杂目标的灵活性,又吸取了线性系统SARC算法的绝对稳定性和高精度、低内存、高效率等优点,只需给出色散介质模型的极点和对应系数,即可运用SARC FDTD递推公式和通用程序进行计算,具有较好的通用性. 通过Debye,Drude和Lorentz三种常用色散介质模型对算法进行了验证.
关键词:
时域有限差分
色散介质
半解析递归卷积 相似文献
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A parallel dispersive finite-difference time-domain (FDTD) method for the modeling of three-dimensional (3-D) electromagnetic cloaking structures is presented in this paper. The permittivity and permeability of the cloak are mapped to the Drude dispersion model and taken into account in FDTD simulations using an auxiliary differential equation (ADE) method. It is shown that the correction of numerical material parameters and the slow switching-on of source are necessary to ensure stable and convergent single-frequency simulations. Numerical results from wideband simulations demonstrate that waves passing through a three-dimensional cloak experience considerable delay comparing with the free space propagations, as well as pulse broadening and blue-shift effects. 相似文献
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采用移位算子方法把时域有限差分法推广应用于二维磁各向异性色散介质—磁化铁氧体中.证明了电磁波横向入射二维轴向磁化铁氧体目标情形下,电磁波可按目标的轴向分解为横电波(TE波)和横磁波(TM波),且TE波的散射特性与铁氧体介质无关,而TM波的散射特性与介质电磁参量密切相关,同时对其物理原因进行了分析.通过采用移位算子方法处理磁化铁氧体频域本构关系,得到该情形下目标电磁散射的移位算子时域有限差的迭代计算公式,同时解决了电磁波在各向异性和频率色散介质中传播的问题.计算了轴向磁化铁氧体涂敷VonKarman型导体柱的TM波双站雷达散射截面,分析了铁氧体参量对目标双站雷达散射截面的影响.结果表明:恰当地选择铁氧体参量能有效地减少目标的雷达散射截面,本文时谐因子取exp〔jωt〕. 相似文献
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Archana Rajput Kumar Vaibhav Srivastava 《Applied Physics A: Materials Science & Processing》2015,120(2):663-668
In this paper, dispersive cloak design with broad bandwidth and minimal scattering cross section is proposed by appropriately selecting a radial permeability for each shell in a discretized reduced cloak. The dispersive medium is constructed by artificially varying the inner radius of the cloak with frequency, and this variation results into unique material properties at every frequency. The variation of inner radius of the cloak with frequency is artificial since the actual physical dimension of inner radius remains invariant. The relation between bandwidth and geometrical parameters of cloak is obtained by ensuring that transformation media must satisfy the condition that group velocity must remain less than the speed of light along every direction for a finite frequency range. The proposed cloak provides \(8.9\,\%\) bandwidth with respect to the center frequency for \(50\,\%\) reduction in total scattering cross section, and at the design frequency, the minimum scattering cross section obtained is \(0.266\). The proposed dispersive cloak design is verified by numerical full-wave simulations results which also confirm good cloaking performance. 相似文献
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Zhao S 《Optics letters》2011,36(16):3245-3247
This Letter introduces a novel finite-difference time-domain (FDTD) formulation for solving transverse electromagnetic systems in dispersive media. Based on the auxiliary differential equation approach, the Debye dispersion model is coupled with Maxwell's equations to derive a supplementary ordinary differential equation for describing the regularity changes in electromagnetic fields at the dispersive interface. The resulting time-dependent jump conditions are rigorously enforced in the FDTD discretization by means of the matched interface and boundary scheme. High-order convergences are numerically achieved for the first time in the literature in the FDTD simulations of dispersive inhomogeneous media. 相似文献
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Fan-Yi Meng Ying Liang Qun Wu Le-Wei Li 《Applied Physics A: Materials Science & Processing》2009,95(3):881-888
In this paper, the invisibility of a metamaterial cloak illuminated by spherical electromagnetic wave is analytically investigated
based on the full wave Mie scattering model. It is shown that for a cloak with ideal parameters the scattered field intensity
is zero, but for a cloak with a loss, only the backscattering is exactly zero. Moreover, in the loss case, the scattered field
intensity increases as the loss increases, which is very different from that in the conventional stealth case, where the scattered
field intensity decreases as the loss of coated material increases. In addition, it is shown that scattering cross-section
of the cloak with perturbed parameters decreases as the thickness of the cloak decreases, which means that thinner cloak can
exhibit more stable invisibility. 相似文献
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We establish analytically the interactions of electromagnetic wave with a general class of spherical cloaks based on a full wave Mie scattering model. We show that for an ideal cloak the total scattering cross section is absolutely zero, but for a cloak with a specific type of loss, only the backscattering is exactly zero, which indicates the cloak can still be rendered invisible with a monostatic (transmitter and receiver in the same location) detection. Furthermore, we show that for a cloak with imperfect parameters the bistatic (transmitter and receiver in different locations) scattering performance is more sensitive to eta(t)=square root micro(t)/epsilon(t) than n(t)=square root micro(t)epsilon(t). 相似文献
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J. J. Yang M. Huang C. F. Yang J. Yu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(3):731-736
The first invisibility cloak was proposed by Pendry et al. [Science 312, 1780 (2006)]. But the object enclosed in this original cloak is “blind", that is, it cannot see the outside world, since
no electromagnetic waves can reach within the cloaked space. Based on the concept of complementary media, we propose a reciprocal
invisibility cloak, in which the hidden object can see the outside world, but its presence cannot be detected by electromagnetic
wave. The performance of the cloak has been verified by full-wave simulations. 相似文献
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XIANG Zhi Hai 《中国科学:物理学 力学 天文学(英文版)》2014,57(12):2285-2296
According to the principle of relativity,the equations describing the laws of physics should have the same forms in all admissible frames of reference,i.e.,form-invariance is an intrinsic property of correct wave equations.However,so far in the design of metamaterials by transformation methods,the form-invariance is always proved by using certain relations between field variables before and after coordinate transformation.The main contribution of this paper is to give general proofs of form-invariance of electromagnetic,sound and elastic wave equations in the global Cartesian coordinate system without using any assumption of the relation between field variables.The results show that electromagnetic wave equations and sound wave equations are intrinsically form-invariant,but traditional elastodynamic equations are not.As a by-product,one can naturally obtain new elastodynamic equations in the time domain that are locally accurate to describe the elastic wave propagation in inhomogeneous media.The validity of these new equations is demonstrated by some numerical simulations of a perfect elastic wave rotator and an approximate elastic wave cloak.These findings are important for solving inverse scattering problems in many fields such as seismology,nondestructive evaluation and metamaterials. 相似文献
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Based on the effective medium theory, the triangular ground plane cloak can be realized by thin layered systems. Two solutions of parameter setting of the layered cloak are suggested to demonstrate the invisibility performance of a hybrid incoming wave. The hybrid parameters are derived from the equivalent of both anisotropies of permittivity and permeability to the alternating layers. The performance of the designed layered cloak is validated by both TM and TE wave simulations with near-field distributions and average scattering power outflows on an observation semicircle. From the simulation results, the layered cloak with both hybrid parameters and improved hybrid parameters can reflect the incoming TM/TE waves in a specular direction, and the latter behaves with a better overall invisibility performance. 相似文献