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A piecewise-homogeneous medium, consisting of anisotropic layers, is excited by a primary spherical sound wave due to a point source lying in the exterior of the medium or in one of its layers. The direct scattering problem is formulated by means of a modified scalar Helmholtz equation incorporating the anisotropic characteristics of the problem. The T-matrix of the problem is determined analytically by means of a suitable coordinate transformation. Then, the acoustic fields in all layers are obtained. Finally, specific reductions to special cases are presented. [ABSTRACT FROM AUTHOR]

The Young's modulus is an essential factor for improving turbine blade design. The present study aims to obtain the flexural frequencies (f1) and corresponding dynamic Young's modulus (Ed) of Ni‐based single‐crystal DD6 across a temperature range of 25–1200 °C using a nondestructive dynamic testing method. The relationship between the elastic constants and various crystal orientations is derived by employing the transformation of the elastic matrix. In addition, finite element (FE) simulation is conducted to calculate the flexural frequency (f1) of the [001] crystal orientation. The findings indicate that the dynamic Young's modulus (Ed) decreases as the temperature increases within the range of 25–1200 °C. Furthermore, the Ed values for different crystal orientations follow the trend: Ed[1] < Ed[11] < Ed[111]. This suggests significant anisotropy in the material. The normalized model, matrix transformation calculation method, and finite element method demonstrate high accuracy in predicting the elastic modulus of DD6, as evidenced by the good correspondence between the fitting curves obtained using the normalization method and the test results. These results have practical applications in engineering, particularly in turbine blade design and other applications, and serve as valuable references for mechanical property testing and finite element simulations. [ABSTRACT FROM AUTHOR]

In this work, we study the light scattering properties of dust aggregates (0.7 µm  ≲  R c  ≲ 2.0 µm) with a wide range of porosity ( P = 0.59 to 0.98). The simulations are executed using the Superposition T-matrix code with BCCA, BA, BAM1 and BAM2 clusters of varying porosity. We investigate the nature and dependencies of the different scattering parameters on porosity, size and composition of the aggregated particles for wavelengths 0.45 µm and 0.65 µm. We find that the scattering parameters are strongly correlated with the porosity of the aggregated structures. Our results indicate that, when the porosity of the aggregates decreases, keeping characteristic radius of the aggregates ( R c ) same for all structures, there is an enhancement in the negative polarization branch (NPB) which is accompanied by a substantial increase in the anisotropies present in the material. Also at the exact backscattering region, the anisotropies are found to be linearly correlated with the porosity of the aggregated structure. The computational study reveals that, for low absorbing materials ( k  ≤ 0.1), the negative polarization minimum ( P min ) is strongly correlated with the associated anisotropies. Finally, we put forward a qualitative comparison between our computationally obtained results and some selected data from the Amsterdam Light Scattering Database for both low and high absorbing materials. The experimental results also suggest that an increase in the NPB is always accompanied by an enhancement in the anisotropy at the backscattering region. [ABSTRACT FROM AUTHOR]

Using the conventional T-matrix approach, we discuss gapped phases in one-, two-, and three-dimensional (3D) spin systems (both with and without a long-range magnetic order) with bond disorder and with weakly interacting bosonic elementary excitations. This work is motivated by recent experimental and theoretical activity in spin-liquid-like systems with disorder and in the disordered interacting boson problem. In particular, we apply our theory to both paramagnetic low-field and fully polarized high-field phases in dimerized spin-½ systems and in integer-spin magnets with large single-ion easy-plane anisotropy V with disorder in exchange coupling constants (and/or V). The elementary excitation spectrum and the density of states are calculated in the first order in defects concentration c ⪡ 1. In 2D and 3D systems, the scattering on defects leads to a finite damping of all propagating excitations in the band except for states lying near its edges. We demonstrate that the analytical approach is inapplicable for states near the band edges and our numerical calculations reveal their localized nature. We find that the damping of propagating excitations can be much more pronounced in considered systems than in magnetically ordered gapless magnets with impurities. In ID systems, the disorder leads to localization of all states in the band, while those lying far from the band edges (short-wavelength excitations) can took like conventional wave packets. [ABSTRACT FROM AUTHOR]

Abstract: A T-matrix solution is developed for the aim of predicting the electromagnetic scattering behaviors from a nonspherical gyroelectric particle. The theoretical treatments is implemented within the framework of the extended boundary condition method (EBCM), where a system of quasi-spherical vector wave functions (qSVWFs) for expanding electromagnetic fields inside gyroelectric media is derived by using an inverse Fourier transform operation. As verification, comparisons are made between numerical results obtained using the presented method and those published data calculated using other methods. Very good agreements are achieved for the present cases, which partially indicate the correctness of the derived theoretical formulae and the home-made program. Influences of shape deformation as well as of anisotropy components in permittivity tensor upon the scattering properties are then analyzed. Numerical results show that a dramatic decrease in radar cross sections (RCSs) level occurs when the gyroelectric cross terms are included in the permittivity tensor, and a clear shift of peaks in RCSs to smaller angles is displayed as a prolate spheroid is deformed to an oblate spheroid. [Copyright &y& Elsevier]

• An optimized Discrete Dipole Approximation-Monte Carlo (DDA-MC) algorithm is developed to investigate the influence of structural anisotropy on polarized light transportation. • Experiment on the Mueller matrix of polystyrene fibers has been carried out to validate the DDA-MC model. • Fibrous materials-orientation angle and deviation of fibers can be obtained by othe Mueller matrix transformation method (MMT). Structural anisotropy exists prevalently in complex materials. Quantitatively extracting structural information is a long-standing challenge in optical imaging. In this paper, we propose an optimized Discrete Dipole Approximation-Monte Carlo (DDA-MC) algorithm to investigate the polarized light transportation in fibrous materials, which is validated by experiments on polystyrene fibers. Based on this model, the impact of structural anisotropy of fibrous scatterers on polarized light transportation has been analyzed quantitatively. In addition, simulation results show that structural anisotropy like the orientation angle of cylinders can be deduced from polarization signatures of backscattering light distribution with different polarized incidences. Furthermore, as a label-free and non-invasive tool, the Mueller matrix polarimetry has recently demonstrated promising potential in biomedical diagnosis. By combining with the Mueller Matrix Transformation (MMT), we present how the structural characteristics of fibrous materials, including the orientation angle and deviation of fibers, can be obtained by a Mueller matrix parameter. Therefore, this study not only provides an understanding of the role of structural anisotropy in polarized light transport but also showcases new insight into the nondestructive polarization imaging to characterize fibrous materials. [ABSTRACT FROM AUTHOR]

A new theoretical approach for calculating the extinction coefficient of magnetic fluid is proposed, which is based on molecular dynamics (MD) simulation and T-matrix method. By means of this approach, the influence of particle diameter, particle volume fraction, and external magnetic filed on the extinction coefficient of magnetic fluid is investigated. The results show that the extinction coefficient of the magnetic fluid linearly increases with increase in the particle volume fraction. For a given particle volume fraction, the extinction coefficient increases with increase in the particle diameter which varies from 5 to 20 nm. When a uniform external magnetic filed is applied to the magnetic fluid, the extinction coefficient of the magnetic fluid presents an anisotropic feature. These results agree well with the reported experimental results. The proposed approach is applicable to investigating the optical properties of magnetic fluids. [ABSTRACT FROM AUTHOR]

Solutions for characterizing both electromagnetic wave propagation in, and scattering by, a gyrotropic sphere are obtained based on some recently published literature. Both gyrotropic permittivity and permeability tensors are considered herein, and both transmitted internal fields and scattered external fields are derived theoretically. Compared with problems of a uniaxial sphere, a gyroelectric sphere, and a gyromagnetic sphere, the scattering problem considered here is found to be astonishingly complicated but more generalized in formulation and solution procedure. Numerical validations are made by reducing our results to a gyromagnetic sphere and comparing them with the results obtained using the Fourier transform method, where excellent agreements are observed. Then, radar cross sections (RCSs) versus electric and magnetic gyrotropy ratios are computed, while hybrid effects due to both electric and magnetic gyrotropies are studied extensively, where some special cases of uniaxial spheres are demonstrated. It is shown that characteristics of gyrotropy parameters in Cartesian coordinates may lead to considerably large variations in RCS values, elucidating physical significance of gyrotropy and anisotropy ratios in scattering control. The generalized formulation of the problem is expected to have wide practical applications, while some features of this gyrotropic sphere may help other researchers or engineers to understand more physical insight. In addition, some critical mistakes made in literature were corrected. [ABSTRACT FROM AUTHOR]

Abstract: In turbid media, the partial or global orientation of anisotropic particles induces anisotropic light transport. In this study, we discuss the anisotropic incoherent transport of light in media where prolate ellipsoids are oriented in the same direction. In these anisotropic media, incoherent light transport is investigated using Monte Carlo simulations where the influence of particle anisotropy, size and optical properties are explored in a systematic way, from the local scattering event up to the diffusion limit. The database allows inverting the anisotropy of the backscattered image to yield the form factor of the particles. We then illustrate the relevance of such an analysis to assess the deformability of human erythrocytes in blood samples under normal physiological conditions. [Copyright &y& Elsevier]

Abstract: Using the T-matrix approach electromagnetic scattering by a biaxial anisotropic non-axisymmetric particle is studied. Electromagnetic fields inside the scatterer are expressed by a system of quasi-spherical vector wave functions which are derived by use of inverse Fourier transform. Using this expansion a solution of the light scattering problem in the framework of the null-field method with discrete sources is obtained. Numerical scattering results for ellipsoids and cubes are presented. For validation the calculation results obtained are compared with results from other light scattering programs such as DDSCAT and ADDA. [Copyright &y& Elsevier]

For analysing the scattering problem in conductive medium with the new unconditionally stable associated Hermite (AH) finite-difference time-domain (FDTD) method, the formulation of uniaxial anisotropic perfectly matched layer absorbing boundary condition (UPML-ABC) and the total-field/scattered-field (TF/SF) implementation scheme are deduced. By virtue of AH differential transformation matrix and the eigenvalue transformation, frequency-dependent parameters of the lossy medium can be well treated in AH-UPML, without using any additional auxiliary variables. Numerical verification for the scattering of buried conductor in lossy half-space is performed. Compared with Mur's ABC, UPML increases the absorbing performance by more than 80 dB in AH-FDTD analysis. [ABSTRACT FROM AUTHOR]