Planar near-field scanning in the time domain .2. Sampling theorems and computation schemes

AbstractThis article presents results of near-field scanning optical microscope measurement of local luminescence of rhodamine 3B intercalated in montmorillonite samples. We focus on how local topography affects both the excitation and luminescence signals and resulting optical artifacts. The Finite Difference in Time Domain method (FDTD) is used to model the electromagnetic field distribution of the full tip-sample geometry including far-field radiation. Even complex problems like localized luminescence can be simulated computationally using FDTD and these simulations can be used to separate the luminescence signal from topographic artifacts.

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Scattering of an Impact Wave by a Crack in a Composite Plate

Journal of Applied Mechanics ◽

10.1115/1.2893765 ◽

1992 ◽

Vol 59 (3) ◽

pp. 596-603 ◽

Cited By ~ 31

Author(s):

S. K. Datta ◽

T. H. Ju ◽

A. H. Shah

Keyword(s):

Frequency Domain ◽

Time Domain ◽

Impact Load ◽

Near Field ◽

Boundary Integral ◽

Transition Elements ◽

Element Discretization ◽

Crack Tips ◽

Time Domain Response ◽

The Time Domain

The surface responses due to impact load on an infinite uniaxial graphite/epoxy plate containing a horizontal crack is investigated both in time and frequency domain by using a hybrid method combining the finite element discretization of the near-field with boundary integral representation of the field outside a contour completely enclosing the crack. This combined method leads to a set of linear unsymmetric complex matrix equations, which are solved to obtain the response in the frequency domain by biconjugate gradient method. The time-domain response is then obtained by using an FFT. In order to capture the time-domain characteristics accurately, high-order finite elements have been used. Also, both the six-node singular elements and eight-node transition elements are used around the crack tips to model the crack-tip singularity. From the numerical results for surface responses it seems possible to clearly identify both the depth and length of this crack.

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Calculations of near-field emissions in frequency-domain into time-dependent data with arbitrary wave form transient perturbations

Advanced Electromagnetics ◽

10.7716/aem.v1i2.9 ◽

2012 ◽

Vol 1 (2) ◽

pp. 26

Author(s):

Y. Liu ◽

B. Ravelo ◽

J. Ben Hadj Slama

Keyword(s):

Time Domain ◽

Near Field ◽

Wave Spectrum ◽

Computational Method ◽

Time Dependent ◽

Dependent Data ◽

Wave Form ◽

Frequency Dependent ◽

Transient Electromagnetic ◽

The Time Domain

This paper is devoted on the application of the computational method for calculating the transient electromagnetic (EM) near-field (NF) radiated by electronic structures from the frequency-dependent data for the arbitrary wave form perturbations i(t). The method proposed is based on the fast Fourier transform (FFT). The different steps illustrating the principle of the method is described. It is composed of three successive steps: the synchronization of the input excitation spectrum I(f) and the given frequency data H0(f), the convolution of the two inputs data and then, the determination of the time-domain emissions H(t). The feasibility of the method is verified with standard EM 3D simulations. In addition to this method, an extraction technique of the time-dependent z-transversal EM NF component Xz(t) from the frequency-dependent x- and y- longitudinal components Hx(f) and Hy(f) is also presented. This technique is based on the conjugation of the plane wave spectrum (PWS) transform and FFT. The feasibility of the method is verified with a set of dipole radiations. The method introduced in this paper is particularly useful for the investigation of time-domain emissions for EMC applications by considering transient EM interferences (EMIs).

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