Temat: scattering matrix - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Numerical characterization of an axisymmetric lined duct with flow using the multimodal scattering matrix
Numeryczna charakteryzacja wyściełanego przewodu osiowo-symetrycznego z przepływem za pomocą wielomodalnej macierzy rozpraszania
Autorzy:: Taktak, M.
Majdoub, M. A.
Haddar, M.
Bentahar, M.
Tematy:: lined duct
scattering matrix
mean flow; Pokaż więcej
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/281218.pdf Link otwiera się w nowym oknie
Opis:: In this paper, the development of a numerical method to compute the multimodal scattering matrix of a lined duct in the presence of flow is presented. This method is based on the use of the convected Helmholtz equation and the addition of modal pressures at duct boundaries as additional degrees of freedom of the system. The boundary effects at the inlet and outlet of the finite waveguide are neglected. The choice of this matrix is justified by the fact that it represents an intrinsic characterization of a duct system. The validation of the proposed finite element is done by a comparison with the analytical formulation for simple cases of ducts. Then, the numerical coefficients of the scattering matrix of a lined duct and its acoustic power attenuation are computed for several flow velocities to evaluate the flow effect.
W pracy zaprezentowano numeryczną metodę wyznaczania macierzy rozpraszania dla wyściełanego przewodu z uwzględnieniem wewnętrznego przepływu czynnika. Metodę oparto na zastosowaniu równania konwekcji Helmholtza z wprowadzeniem ciśnień modalnych na brzegach jako dodatkowych stopni swobody układu. Efekty brzegowe na wlocie i wylocie przewodu falowego o skończonej długości pominięto. Wybór macierzy rozpraszania uzasadniono faktem, że reprezentuje ona wewnętrzną charakterystykę analizowanego modelu. Zaproponowany element skończony zweryfikowano poprzez porównanie z istniejącymi rozwiązaniami analitycznymi dla prostych przypadków konfiguracji przewodu. Następnie numerycznie obliczono wartości elementów macierzy rozpraszania oraz współczynniki tłumienia akustycznego dla kilku prędkości przepływu w celu określenia, jak dalece wpływa on na badany układ.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: On the imaginary part of coupling resonance points
Autorzy:: Azamov, Nurulla
Daniels, Tom
Tematy:: scattering matrix
scattering phase
resonance point
Breit-Wigner formula; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/255376.pdf Link otwiera się w nowym oknie
Opis:: We prove for rank one perturbations that the imaginary part of a coupling resonance point is inversely proportional by a factor of —2 to the rate of change of the scattering phase, as a function of the coupling variable, evaluated at the real part of the resonance point. This equality is analogous to the Breit-Wigner formula from quantum scattering theory. For more general relatively trace class perturbations, we also give a formula for the spectral shift function in terms of coupling resonance points, non-real and real.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: On reflectionless equi-transmitting matrices
Autorzy:: Kurasov, P.
Ogik, R.
Rauf, A.
Tematy:: quantum graphs
vertex scattering matrix
equi-transmitting matrices; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/255075.pdf Link otwiera się w nowym oknie
Opis:: Reflectionless equi-transmitting unitary matrices are studied in connection to matching conditions in quantum graphs. All possible such matrices of size 6 are described explicitly. It is shown that such matrices form 30 six-parameter families intersected along 12 five-parameter families closely connected to conference matrices.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: On the $S$-matrix of Schrödinger operator with nonlocal $\delta$-interaction
Autorzy:: Główczyk, Anna
Kużel, Sergiusz
Tematy:: Lax-Phillips scattering scheme
scattering matrix
S-matrix
nonlocal -interaction
non-cyclic function; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/2051910.pdf Link otwiera się w nowym oknie
Opis:: Schrodinger operators with nonlocal δ-interaction are studied with the use of the Lax-Phillips scattering theory methods. The condition of applicability of the Lax-Phillips approach in terms of non-cyclic functions is established. Two formulas for the S-matrix are obtained. The first one deals with the Krein-Naimark resolvent formula and the Weyl-Titchmarsh function, whereas the second one is based on modified reflection and transmission coefficients. The S-matrix S(z) is analytical in the lower half-plane $\mathbb{C}$_ when the Schrodinger operator with nonlocal δ-interaction is positive self-adjoint. Otherwise, S(z) is a meromorphic matrix-valued function in $\mathbb{C}$_ and its properties are closely related to the properties of the corresponding Schrodinger operator. Examples of S-matrices are given.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Identification of Physical Parameters of a Porous Material Located in a Duct by Inverse Methods
Autorzy:: Kani, Marwa
Makni, Amine
Taktak, Mohamed
Chaabane, Mabrouk
Haddar, Mohamed
Tematy:: porous materials
inverse methods
scattering matrix
acoustic power attenuation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/2141708.pdf Link otwiera się w nowym oknie
Opis:: Lined ducts with porous materials are found in many industrial applications. To understand and simulate the acoustic behaviour of these kinds of materials, their intrinsic physical parameters must be identified. Recent studies have shown the reliability of the inverse approach for the determination of these parameters. Therefore, in the present paper, two inverse techniques are proposed: the first is the multilevel identification method based on the simplex optimisation algorithm and the second one is based on the genetic algorithm. These methods are used of the physical parameters of a simulated case of a porous material located in a duct by the computation of its acoustic transfer, scattering, and power attenuation. The results obtained by these methods are compared and discussed to choose the more efficient one.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Effect of Liner Characteristics on the Acoustic Performance of Duct Systems
Autorzy:: Othmani, C.
Hentati, T.
Taktak, M.
Elnady, T.
Fakhfakh, T.
Haddar, M.
Tematy:: porous material
perforated plate
duct system
scattering matrix
acoustic attenuation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/176887.pdf Link otwiera się w nowym oknie
Opis:: Porous materials are used in many vibro-acoustic applications. Different models describe their performance according to material’s intrinsic characteristics. In this paper, an evaluation of the effect of the porous and geometrical parameters of a liner on the acoustic power attenuation of an axisymmetric lined duct was performed using multimodal scattering matrix. The studied liner is composed by a porous material covered by a perforated plate. Empirical and phenomenal models are used to calculate the acoustic impedance of the studied liner. The later is used as an input to evaluate the duct attenuation. By varying the values of each parameter, its influence is observed, discussed and deduced.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 7.

Tytuł:: Constant co-polarized echo curves on the Poincare sphere
Autorzy:: Czyż, Z.H.
Tematy:: radar polarimetry
Poincare sphere module of scattering matrix
Kennaugh matrix
Cassini ovals; Pokaż więcej
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Powiązania:: https://bibliotekanauki.pl/articles/309100.pdf Link otwiera się w nowym oknie
Opis:: A set of useful formulae has been presented allowing for computation of the equipower curves on the Poincare sphere of the co-polarized radar returns for both mono- and bi-static scatterings.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Investigation on the Effects of Acoustic Liner Variation and Geometry Discontinuities on the Acoustic Performance of Lined Ducts
Autorzy:: Dhief, Raja
Makni, Amine
Taktak, Mohamed
Chaabane, Mabrouk
Haddar, Mohamed
Tematy:: absorbent systems effect
discontinuities effect
scattering matrix
acoustic power attenuation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/177513.pdf Link otwiera się w nowym oknie
Opis:: Noise reduction inside waveguide systems has gained momentum owing to a great interest in it. To attenuate the sound in a broad frequency range, this study aims to compare the effects of two acoustic liners, a perforated plate backed by an air cavity (PP-Air cavity), or by a porous material (PP-PM), on the acoustic behaviour of lined ducts using a numerical model to compute the multimodal scattering matrix. From this matrix, the reflection and the transmission coefficients are computed and therefore the acoustic power attenuation is deduced. Moreover, the effects of geometry of ducts with and without changes in the section are investigated. The numerical results are obtained for five configurations, including cases of narrowing and widening of a duct portion with sudden or progressive discontinuities. Accordingly, numerical coefficients of reflection and transmission as well as the acoustic power attenuation show the relative influence of acoustic liners in each type of configuration.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Experimental Determination of a Reflective Muffler Scattering Matrix for Single-Mode Excitation
Autorzy:: Gorazd, Łukasz
Tematy:: cylindrical duct
reflective muffler
single mode generation
multi-port method
scattering matrix; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/2141712.pdf Link otwiera się w nowym oknie
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.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Evaluation of the transmission and the scattering matrix applicability to the mufflers analysis
Autorzy:: Snakowska, Anna
Gorazd, Łukasz
Jurkiewicz, Jerzy
Tematy:: transmission matrix
scattering matrix
multimode wave
silencer
muffler
macierz transmisji
macierz S
fala wielomodowa
tłumik; Pokaż więcej
Wydawca:: Politechnika Poznańska. Instytut Mechaniki Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/127786.pdf Link otwiera się w nowym oknie
Opis:: The analysis of the acoustical systems can be carried out based on a number of different formalisms, of which applied frequently are the transfer matrix formalism, in which the chosen state variables are the sound pressure p and the sound velocity v, and the scattering matrix formalism adopting the sound pressures p⁺ and p⁻ and the sound velocities v⁺ and v⁻ of waves propagating through an element in both directions. Even though, they are mathematically equivalent, i.e. there exists the unequivocal transformation from one to another there are some advantages and disadvantages in applying one or the other to analyse mufflers or other acoustic system, especially when the propagation of a multimode wave is assumed and numerical calculations are indispensable. In the paper the transformation between the formalisms has been derived and applied to analyse the phenomena at a junction between the tail pipe and the chamber and also in mufflers composed of one or two chambers. The more flexible for numerical calculations seems the scattering matrix formalism, especially when the number of propagating modes differs on both sides of a junction. On the other hand the transmission matrix formalism is suitable for analysing systems constituting a cascade. The sources of the advantages and disadvantages of both formalisms are explained. The results obtained can be helpful in the effective design of silencers with specific properties.
Dostawca treści:: Biblioteka Nauki

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