Temat: multi-scattering - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Example of Structure Modeling and Analysis of Ultrasound Scattering for Trabecular Bone
Autorzy:: Wójcik, J.
Litniewski, J.
Nowicki, A.
Powiązania:: https://bibliotekanauki.pl/articles/177853.pdf
Data publikacji:: 2010
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:: multi-scattering
random complex structures
trabecular bone model
Opis:: A trabecular bone consists of trabeculae whose mechanical properties differ significantly from the surrounding marrow, therefore an ultrasonic wave propagating within the bone structure is strongly scattered. The aim of this paper was to evaluate the contribution of the first, second and higher order scattering (multiple scattering) into the total scattering of ultrasound in a trabecular bone. The scattering due to the interconnections between thick trabeculae, usually neglected in trabecular bone models, has been also studied. The basic element in our model of the trabecular bone was an elastic cylinder with a various finite-length and diameter as well as orientation. The applied model was taking into account variation of both, elements size and their spatial configuration. The field scattered on the bone model was evaluated by solving numerically the integral form of the generalized Sturm-Liouville equation describing a scalar wave in inhomogeneous and lossy media. For the scattered fields calculated numerically the effective cross-sections were determined. The influence of absorption on the scattering coefficients was demonstrated. The results allowed to conclude that within the frequency range from 0.5 to 1.5 MHz contribution of the second order scattering to the effective backscattering cross-section is at least 500 times lower than that due to the first order scattering. It was noticed that for a frequency higher than 1.5 MHz fast growth of the backscattering (reflection) coefficients, calculated for the second order scattering, occurs.
Źródło:: Archives of Acoustics; 2010, 35, 4; 701-713
0137-5075
Pojawia się w:: Archives of Acoustics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Electromagnetic Scattering of Inhomogeneous Plane Wave by Ensemble of Cylinders
Autorzy:: Dinia, Lorenzo
Mangini, Fabio
Frezza, Fabrizio
Powiązania:: https://bibliotekanauki.pl/articles/309062.pdf
Data publikacji:: 2020
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: electromagnetic scattering
inhomogeneous wave dispersion
lossy media
multi-cylinders scattering
vectorial cylindrical-harmonics
Opis:: The interaction between an ensemble of cylinders and an inhomogeneous plane wave is introduced and is determined, in the present paper, through a rigorous theoretical approach. Scattered electromagnetic ﬁeld generated by an indeﬁnite number of inﬁnite circular cylinders is analyzed by the application of the generalized vector cylinder harmonics (VCH) expansion. The exact mathematical model relied upon to represent this scenario considers the so-called complex-angle formalism reaching a superposition of vectorial cylindrical-harmonics and Foldy-Lax Multiple scattering equations (FLMSE) to account for the multiscattering process between the cylinders. The method was validated by comparing the numerical results obtained with the use of the ﬁnite element method and a homemade Matlab code.
Źródło:: Journal of Telecommunications and Information Technology; 2020, 3; 86-92
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Modeling spatial aspects of mobile channel for low antenna height environments
Autorzy:: Simsim, M. T.
Khan, N. M.
Rapajic, P. B.
Powiązania:: https://bibliotekanauki.pl/articles/309429.pdf
Data publikacji:: 2006
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: Gaussian distributions
geometric modeling
multi-path channels
scattering
Opis:: It is essential to have deep understanding of the mobile radio channel in particular for radio communication modeling and advanced technology system design. Models for the mobile radio channel are vital for the study of smart antenna systems, both for the design of algorithms, system-testing purposes, and for network planning. This paper provides an intensive study of the spatial characteristics of the mobile channel for low antenna height cellular environments, i.e., picocells and microcells, assuming Gaussian distributed scatterers. We investigate previous work on the angle of arrival (AoA) statistics for Gaussian distributed scatterers and make appropriate comments. Further, we employ the recently proposed eccentro-scattering physical channel model, as a generalized model, to derive the probability density function (pdf) of AoA of the multipaths at base station (BS) assuming Gaussian distributed scatterers around both BS and mobile station (MS). We found that the pdf of AoA at BS is directly affected by the standard deviation of the scatterers' density and the size of the scattering disc. The derived formulas, in closed form, can be used further for performance assessment of smart antennas and beamwidth design purposes.
Źródło:: Journal of Telecommunications and Information Technology; 2006, 2; 97-105
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Experimental Determination of a Reflective Muffler Scattering Matrix for Single-Mode Excitation
Autorzy:: Gorazd, Łukasz
Powiązania:: https://bibliotekanauki.pl/articles/2141712.pdf
Data publikacji:: 2021
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:: cylindrical duct
reflective muffler
single mode generation
multi-port method
scattering matrix
Opis:: The aim of the paper is to experimentally determine the scattering matrix S of an example reflective muffler of cylindrical geometry for Helmholtz number exceeding the plane wave propagation. Determining the scattering matrix of an acoustic systems is a new and increasingly used approach in the assessment of reduction of noise propagating inside duct-like elements of heating, ventilation and air conditioning systems (HVAC). The scattering matrix of an acoustic system provides all necessary information on the propagation of wave through it. In case of the analysed reflective silencer, considered as a two-port system, the noise reduction was determined by calculating the transmission loss parameter (TL) based on the scattering matrix (S). Measurements were carried out in two planes of the cross-section of pipes connected to the muffler. The paper presents results of the scattering matrix evaluation for the wave composed of the plane wave (mode (0,0)) and the first radial mode (0,1), each of which was generated separately using the self-designed and constructed single-mode generator. The gain of proceeding measurements for single modes stems from the fact that theoretically, calculation of the S-matrix does not require, as will be presented in the paper, calculation of the measurement data inverse matrix. Moreover, if single mode sound fields are well determined, it ensures error minimization. The presented measurement results refer to an example of a duct like system with a reflective muffler for which the scattering matrix S was determined. The acoustic phenomena inside such a system can be scaled by the parameter ka.
Źródło:: Archives of Acoustics; 2021, 46, 4; 667-675
0137-5075
Pojawia się w:: Archives of Acoustics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Application of the scattering matrix method to evaluate acoustic mufflers properties
Autorzy:: Gorazd, Łukasz
Powiązania:: https://bibliotekanauki.pl/articles/2202431.pdf
Data publikacji:: 2022
Wydawca:: Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:: cylindrical duct
reflective muffler
scattering matrix
multi-port method
kanał cylindryczny
tłumik refleksyjny
macierz rozproszenia
metoda wieloportowa
Opis:: The aim of the paper is to analyse acoustic reflective muffler applying the scattering matrix method. In general, the method is based on dividing the muffler/system into separate subsystems and apply the acoustic multi-ports theory to calculate the scattering matrix of each element to finally combine the results and obtain the scattering matrix of the entire system/muffler. The multi-port procedure is derived from the theory of electric networks and allows to analyse acoustic devises of complex geometry with prescribed accuracy. Based on the scattering matrix, the transmission loss was determined.
Źródło:: Vibrations in Physical Systems; 2022, 33, 2; art. no. 2022204
0860-6897
Pojawia się w:: Vibrations in Physical Systems
Dostawca treści:: Biblioteka Nauki

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