共查询到20条相似文献,搜索用时 15 毫秒
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The electromagnetic potentials of a finite crystalline slab of oscillating point charges are separated into parts with distinct properties. One part is the Ewald potential. 相似文献
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V. G. Burdukovskaya I. P. Smirnov A. I. Khil’ko 《Radiophysics and Quantum Electronics》1999,42(12):1032-1039
We propose, and prove mathematically, an algorithm for calculation of the acoustic field intensity of a point monochromatic
source in an inhomogeneous medium. This algorithm is based on the notion of ray-beam concentration introduced here. Comparative
calculations using the proposed and previously known algorithms are performed.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 12, pp. 1172–1180, December, 1999. 相似文献
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有限长导管声场预报的一种边界元方法 总被引:1,自引:0,他引:1
为了研究介质流动情况下有限长导管中点声源产生的声场,提出了一种以源势密度作为未知数的间接边界元方法。首先将整个求解空间划分为管内和管外两个相互独立的封闭域,然后利用压力和速度在开口处的连续条件和壁面边界条件将内外域的声场方程联立为一个矩阵方程,求解出源势密度后由源势密度计算出任意位置的声场。与Myers的基准数据比较表明本文所得计算结果与之相符。该方法简化了过去声场边界积分方程的形式和数值积分奇性的解决过程,稍加变换便可应用于任意形状导管和复杂声源。 相似文献
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Heterogeneous anisotropic diffusion problems arise in the various areas of science and engineering including plasma physics, petroleum engineering, and image processing. Standard numerical methods can produce spurious oscillations when they are used to solve those problems. A common approach to avoid this difficulty is to design a proper numerical scheme and/or a proper mesh so that the numerical solution validates the discrete counterpart (DMP) of the maximum principle satisfied by the continuous solution. A well known mesh condition for the DMP satisfaction by the linear finite element solution of isotropic diffusion problems is the non-obtuse angle condition that requires the dihedral angles of mesh elements to be non-obtuse. In this paper, a generalization of the condition, the so-called anisotropic non-obtuse angle condition, is developed for the finite element solution of heterogeneous anisotropic diffusion problems. The new condition is essentially the same as the existing one except that the dihedral angles are now measured in a metric depending on the diffusion matrix of the underlying problem. Several variants of the new condition are obtained. Based on one of them, two metric tensors for use in anisotropic mesh generation are developed to account for DMP satisfaction and the combination of DMP satisfaction and mesh adaptivity. Numerical examples are given to demonstrate the features of the linear finite element method for anisotropic meshes generated with the metric tensors. 相似文献
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A finite element algorithm on eigenvalue problem of the dielectric waveguide with chiral material is presented. The chiral
material is defined by the constitution relations which make the electromagnetic coupling between the electric and magnetic
fields by means of the chirality admittance. The chiral material has potential applications in the areas of infrared and mm-wave
band. For different chirality admittance, the computation is developed for different structure of waveguides which are difficult
for analytical calculation. From the eigenvalues and the eigenvectors, the dispersion curves, the modes and the field patterns
are obtained. The maximum value of dispersion curves is obvious greater than that without chiral material. The main points
of the results of finite element calculation are consistent with those of analytical approach. 相似文献
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A general method to design a 2D dissimilar cloak for irregular regions is presented by operating a nonlinear transformation in polar coordinates. The material parameters avoid discontinuities while the thickness of the cloak shell is effectively limited in elongated directions. Full-wave simulations of an elliptic cloak, a rectangular cloak, and an arbitrary-shape cloak are performed to verify the validity of the design. Both the material parameters and the scattering widths of different models are calculated and illustrated for comparison. This method provides a possible approach for designing complex shaped cloaks. 相似文献
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V. V. Skobelev 《Russian Physics Journal》1987,30(3):188-190
Generation of photons in a curved space-time due to polarization of the electron-positron vacuum is considered: R 2. A general expression for the number of photon pairs is obtained, and the limits of its applicability are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 9–12, March, 1987. 相似文献
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A coordinate transformation technique between straight magnetic field line coordinate system (Ψ, θ) and Cartesian coordinate system (R, Z) is presented employing a Solov'ev solution of the Grad-Shafranov equation. Employing the equilibrium solution, the poloidal magnetic flux Ψ(R, Z) of a diverted tokamak, magnetic field line equation is solved computationally to find curves of constant poloidal angle θ, which provides us with explicit relations R = R(Ψ, θ) and Z = Z(Ψ, θ). Correspondingly, conversion from one coordinate to the other along particle trajectories in the vicinity of separatrix is demonstrated. Based on the magnetic structure, a finite element mesh is generated in a diverted tokamak geometry to solve Poisson's equation. 相似文献
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Peijun Li 《Journal of computational physics》2010,229(2):481-497
Consider a time-harmonic electromagnetic plane wave incident on an inhomogeneity embedded in a two-layered medium. In this paper, a method of coupling of finite element and boundary integral equation methods is presented for the solutions of electromagnetic scattering in both transverse electric and magnetic polarization cases. The well-posedness of the continuous and discrete problems, as well as optimal error estimates for the coupled variational approximations, are obtained. Numerical results are included to illustrate the accuracy with the optimal convergence property of the proposed method and to show the wave features in a two-layered medium. 相似文献
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Circuit-field coupled finite element analysis method for an electromagnetic acoustic transducer under pulsed voltage excitation 下载免费PDF全文
This paper presents an analytical method for electromagnetic acoustic transducers (EMATs) under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs including the non-uniform biased magnetic field, a pulsed eddy current field and the acoustic field is built up. The pulsed voltage excitation is transformed to the frequency domain by fast Fourier transformation (FFT). In terms of the time harmonic field equations of the EMAT system, the impedances of the coils under different frequencies are calculated according to the circuit-field coupling method and Poynting’s theorem. Then the currents under different frequencies are calculated according to Ohm’s law and the pulsed current excitation is obtained by inverse fast Fourier transformation (IFFT). Lastly, the sequentially coupled finite element method (FEM) is used to calculate the Lorentz force in the EMATs under the current excitation. An actual EMAT with a two-layer two-bundle printed circuit board (PCB) coil, a rectangular permanent magnet and an aluminium specimen is analysed. The coil impedances and the pulsed current are calculated and compared with the experimental results. Their agreement verified the validity of the proposed method. Further- more, the influences of lift-off distances and the non-uniform static magnetic field on the Lorentz force under pulsed voltage excitation are studied. 相似文献
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Analysis and finite element simulation of electromagnetic heating in the nitride MOCVD reactor 下载免费PDF全文
Electromagnetic field distribution in the vertical metal
organic chemical vapour deposition (MOCVD) reactor is simulated by
using the finite element method (FEM). The effects of alternating
current frequency, intensity, coil turn number and the distance
between the coil turns on the distribution of the Joule heat are
analysed separately, and their relations to the value of Joule heat
are also investigated. The temperature distribution on the
susceptor is also obtained. It is observed that the results of the
simulation are in good agreement with previous measurements. 相似文献
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The spatial correlator of vector potentials is calculated for a dispersing absorbing medium. Quantum electrodynamics calculations
performed without resorting to the fluctuation_dissipation theorem show that this correlator is determined solely by the refractive
index of the medium at low temperatures. In thermally excited media, the correlator is determined by a characteristic which
differs from the refractive index entering into the Maxwell equations for classical fields.
Moscow Energy Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 17–21, June, 2000. 相似文献
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《声学学报:英文版》2012,(1):18-28
A method was presented to extend the Convolution Perfectly Matched Layer(CPML), which bases on the complex coordinates transformation and complex frequency shifted stretched-coordinate metrics,to the 2D acoustic equation calculated with the method of Finite Element Method(FEM).This non-physical layer is used at the computational edge of a FEM as an Absorbing Boundary Condition(ABC) to truncate unbounded media.In this paper,the CPML equations have been presented in frequency domain and in time domain,respectively,and the calculations have been realized in the FEM software of COMSOL.The main advantage of CPML over the classical PML layer is that it is based on the unsplit components of the wave field leading to a more stable,highly effective absorption and a more facility to realize.The results of numerical simulation demonstrate that CPML has better absorbability than PML and it absorbs the outgoing energy more effectively. 相似文献