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Scattering by an assembly of particles
Published in Subodh Kumar Sharma, Elastic Scattering of Electromagnetic Radiation, 2018
The mathematical treatment of scattering for this class of models relies on the RGA. Recall, that this approximation is also known as the Born approximation. The validity domain of this approximation from (3.70b) is, Δm(r)kL≪1, $$ \Delta m({\text{r}})kL \ll 1, $$
Gapless Superconductivity
Published in R. D. Parks, Superconductivity, 2018
Here the first term is the ordinary impurity scattering potential while the second term is the so-called exchange interaction. S denotes the spin operator of the localized magnetic moment. It is important to note that from the criterion given in Section II, it follows that the spin exchange interaction is a time-reversal breaking perturbation. The significant differences in the energy shifts caused by U1ρ3 and U2S · α have been noticed previously by Suhl and Matthias and Baltensperger (20,21). The first satisfactory treatment based on the above model was given by Abrikosov and Gor’kov (1). They were able to obtain the Green’s function which describes the equilibrium as well as nonequilibrium properties of the system. In particular, they predicted the existence of the gapless region in which the excitation spectrum begins continuously from zero energy. This prediction was subsequently confirmed in a beautiful experiment by Woolf and Reif (22). In the case of rare earth impurities such as Gd which have unfilled f-shells, the agreement between theory and experiment was good, while in the case of transition metal impurities such as Fe and Mn, a density of states larger at low excitation energies than theoretically expected was observed. Although we shall not discuss critically the AG theory, here, there are several assumptions which have been made in the calculation and which we will mention here. The correlations among the impurity spins are neglected (23,6).The scattering amplitude due to the exchange interaction is treated in Born approximation.
Computational Biophotonics
Published in Vadim Backman, Adam Wax, Hao F. Zhang, A Laboratory Manual in Biophotonics, 2018
Vadim Backman, Adam Wax, Hao F. Zhang
Of course, the field inside the scattering potential is not a priori known. Thus, various approximations, analytical and numerical, can be constructed by substituting field E by a defined function. In the simplest case—and “simplest” is a relative term—the field inside the scattering potential is approximated as the incident field. This is the first-order or single-scattering Born approximation. It is valid for weakly scattering media, including most biological tissue.
Acoustic backscattering properties of manganese nodules: Numerical and laboratory experiments based on Sub-bottom acoustic profile surveys
Published in Marine Georesources & Geotechnology, 2022
Jun Matsushima, Hirohisa Kobayashi, Soichiro Tanaka
The numerical simulation study revealed that the scattering phenomenon due to nodules is significantly dependent on the sphere size with respect to the wavelength of the acoustic wave. Scattering is a phenomenon that is dependent on the relationship between the wavelength and heterogeneity magnitude (i.e., nodule size). Wu and Aki (1988) categorized scattering into the following four regimes: The product of wavenumber k and characteristic length a is used as an index to describe the effects of the heterogeneity size on seismic waves. When ka < 0.01 (quasi-homogeneous regime), the heterogeneous medium acts as an effective homogeneous medium wherein scattering effects may be neglected. When 0.01 < ka < 0.1 (Rayleigh scattering regime), scattering effects may be characterized by the Born approximation, which is based on the single scattering assumption. When 0.1 < ka < 10 (Mie scattering regime), the sizes of the heterogeneities are comparable to the wavelengths. Scattering effects were the most significant. When ka > 10 (forward scattering regime), a heterogeneous medium may be considered as a piecewise homogeneous medium, where the ray theory may be applicable. We used the classification by Wu and Aki (1988) to summarize the numerical experiments in Table 5.
Effects of the surrounding medium on terahertz wave scattering loss in intrabody communication
Published in Waves in Random and Complex Media, 2022
Therefore, as the main contribution of this work, we calculate and compare the air-enclosed and tissue-enclosed scattering losses at different frequencies due to the contrast of the cell's and tissue's refractive indices. These results are presented for blood and skin layers in the wrist of the human body. In this paper, by referring to both the scatterer and the medium's refractive indices which are frequency dependent, the scattering path loss for blood and skin layers (epidermis and dermis) are calculated in the terahertz region. We have applied the Born approximation in our simulation to examine the tissue-enclosed scattering coefficient and path loss for three biological layers of blood, epidermis, and dermis. We take into account the size and shape of the particles, the complex refractive index of the scattering particles and the host medium, and also the efficient scattering regimes. In each layer, the air-enclosed and tissue-enclosed scattering are compared and the reason for superiority is surveyed. The remainder of this paper is organized as follows. In Section 2, scattering path loss for spherical and disk-shaped particles with extension to born approximation is reviewed. In Section 3, the air-enclosed and tissue-enclosed scattering for blood, epidermis, dermis, and skin is computed and analyzed. At last, the conclusion is highlighted in Section 4.
Through-the-Wall Radar Imaging: A Review
Published in IETE Technical Review, 2018
P. K. M. Nkwari, S. Sinha, H. C. Ferreira
In TWRI, LISP is used to find the wall characteristics while detecting a target behind the wall. To address the issue in real situations where the parameters of the wall are either unknown or known with some level of uncertainty, several approaches have been reported in [16,17]. Though LISP can be used in TWRI with great accuracy, nonlinearity of the wall increases the data acquisition time [18,19]. Therefore, Soldovieri and Solimene [19] proposed a linear inverse scattering algorithm based on the Born approximation to mitigate the wall effect. In [18], to perform fast data acquisition, the authors proposed an efficient data acquisition and processing scheme based on three-dimensional (3D) TWRI.