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Wyświetlanie 1-15 z 16
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.
Powiązania:
https://bibliotekanauki.pl/articles/281218.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
lined duct
scattering matrix
mean flow
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.
Źródło:
Journal of Theoretical and Applied Mechanics; 2013, 51, 2; 313-325
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the imaginary part of coupling resonance points
Autorzy:
Azamov, Nurulla
Daniels, Tom
Powiązania:
https://bibliotekanauki.pl/articles/255376.pdf
Data publikacji:
2019
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
scattering matrix
scattering phase
resonance point
Breit-Wigner formula
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.
Źródło:
Opuscula Mathematica; 2019, 39, 5; 611-621
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On reflectionless equi-transmitting matrices
Autorzy:
Kurasov, P.
Ogik, R.
Rauf, A.
Powiązania:
https://bibliotekanauki.pl/articles/255075.pdf
Data publikacji:
2014
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
quantum graphs
vertex scattering matrix
equi-transmitting matrices
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.
Źródło:
Opuscula Mathematica; 2014, 34, 3; 483-501
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the $S$-matrix of Schrödinger operator with nonlocal $\delta$-interaction
Autorzy:
Główczyk, Anna
Kużel, Sergiusz
Powiązania:
https://bibliotekanauki.pl/articles/2051910.pdf
Data publikacji:
2021
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
Lax-Phillips scattering scheme
scattering matrix
S-matrix
nonlocal -interaction
non-cyclic function
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.
Źródło:
Opuscula Mathematica; 2021, 41, 3; 413-435
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Powiązania:
https://bibliotekanauki.pl/articles/2141708.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
porous materials
inverse methods
scattering matrix
acoustic power attenuation
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.
Źródło:
Archives of Acoustics; 2021, 46, 4; 657-665
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Constant co-polarized echo curves on the Poincare sphere
Autorzy:
Czyż, Z.H.
Powiązania:
https://bibliotekanauki.pl/articles/309100.pdf
Data publikacji:
2001
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
radar polarimetry
Poincare sphere module of scattering matrix
Kennaugh matrix
Cassini ovals
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.
Źródło:
Journal of Telecommunications and Information Technology; 2001, 4; 7-10
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
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.
Powiązania:
https://bibliotekanauki.pl/articles/176887.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
porous material
perforated plate
duct system
scattering matrix
acoustic attenuation
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.
Źródło:
Archives of Acoustics; 2015, 40, 1; 117-127
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Powiązania:
https://bibliotekanauki.pl/articles/177513.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
absorbent systems effect
discontinuities effect
scattering matrix
acoustic power attenuation
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.
Źródło:
Archives of Acoustics; 2020, 45, 1; 49-66
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Artykuł
Tytuł:
Evaluation of the transmission and the scattering matrix applicability to the mufflers analysis
Autorzy:
Snakowska, Anna
Gorazd, Łukasz
Jurkiewicz, Jerzy
Powiązania:
https://bibliotekanauki.pl/articles/127786.pdf
Data publikacji:
2019
Wydawca:
Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:
transmission matrix
scattering matrix
multimode wave
silencer
muffler
macierz transmisji
macierz S
fala wielomodowa
tłumik
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.
Źródło:
Vibrations in Physical Systems; 2019, 30, 1; 1-8
0860-6897
Pojawia się w:
Vibrations in Physical Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Polarization method for navigation object selection in ship radar systems
Autorzy:
Korban, Dmytro
Powiązania:
https://bibliotekanauki.pl/articles/29521088.pdf
Data publikacji:
2023
Wydawca:
Akademia Morska w Szczecinie. Wydawnictwo AMSz
Tematy:
radar recognition
navigation object
Stokes polarization parameters
scattering matrix
fully polarized wave
degree of polarization
Opis:
This paper substantiates the method of polarization selection of navigation objects located in the zone of atmospheric formations (i.e., precipitation of different intensity and phase state), based on polarization differences in the parameters of their echo signals in a partially polarized electromagnetic wave arriving at the input of the all-polarized antenna of the ship radar polarization complex (SRPC). The partially polarized wave is represented as consisting of two polarized streams with polarization degrees m1 and m2 corresponding to the echo signals of the navigation object and atmospheric formation. The property of the partially polarized electromagnetic wave reflected from a complex object (i.e., navigation object located in the zone of atmospheric formation) is represented by real energy polarization Stokes parameters having intensity dimension. The scattering ability of the complex object is represented by the Mueller scattering matrix, the elements of which are measured by SRPC when it is sequentially irradiated with electromagnetic waves of four fixed polarizations. Polarization selection of navigation objects located in the zone of atmospheric formations uses the difference of polarization degrees of echo signals of the navigation object and atmospheric formation. The process of selection of the navigation object echo signal from the echo signal of the complex object and its observation on the screen of the SRPC indicator or computer display is based on the relationship between the degree of polarization of the electromagnetic wave and the polarization parameters of the navigation object echo signal and the atmospheric formation. The aim of this research is to develop polarization criteria of optimality of radar parameters of echo signals of partially polarized electromagnetic waves, represented by polarization degrees m1 and m2 corresponding to the navigational object and atmospheric formation observed by SRPC. As a result of the performed research, the problem of polarization selection of navigation objects located in the zone of atmospheric formations along the ship’s trajectory according to the values of the polarization degree of the navigation object echo signal is solved.
Źródło:
Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2023, 76 (148); 17-22
1733-8670
2392-0378
Pojawia się w:
Zeszyty Naukowe Akademii Morskiej w Szczecinie
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Artykuł
Tytuł:
Scattering of internal waves by vertical barrier in a channel of stratified fluid
Autorzy:
Dolai, P.
Powiązania:
https://bibliotekanauki.pl/articles/264794.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
stratified fluid
internal wave
vertical barrier
stream function
scattering matrix
Boussinesq approximation
eigen function expansion
rozwarstwienie
hydromechanika
fala wewnętrzna
Opis:
The problem of two dimensional internal wave scattering by a vertical barrier in the form of a submerged plate, or a thin wall with a gap in an exponentially stratified fluid of uniform finite depth bounded by a rigid plane at the top, is considered in this paper. Assuming linear theory and the Boussinesq approximation, the problem is formulated in terms of the stream function. In the regions of the two sides of the vertical barrier, the scattered stream function is represented by appropriate eigen function expansions. By the use of appropriate conditions on the barrier and the gap, a dual series relation involving the unknown elements of the scattering matrix is produced. By defining a function with these unknown elements as its Fourier sine expansion series, it is found that this function satisfies a Carleman type integral equation on the barrier whose solution is immediate. The elements of the scattering matrix are then obtained analytically as well as numerically corresponding to any mode of the incident internal wave train for each barrier configuration. A comparison with earlier results available in the literature shows good agreement. To visualize the effect of the barrier on the fluid motion, the stream lines for an incident internal wave train at the lowest mode are plotted.
Źródło:
International Journal of Applied Mechanics and Engineering; 2015, 20, 3; 471-485
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The J-matrix method: numerical computations
Autorzy:
Syty, P.
Powiązania:
https://bibliotekanauki.pl/articles/1954523.pdf
Data publikacji:
1999
Wydawca:
Politechnika Gdańska
Tematy:
atomic physics
scattering theory
J-matrix method
numerical computations
Opis:
Numerical calculations of scattering phase shifts have been done using J-matrix method (both non-relativistic and relativistic versions). Results of computations for some simple potentials are described and discussed in this paper. In particularly, it has been shown, that successive numerical approximations converge to results obtained using an analytical formula.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 1999, 3, 3; 269-276
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Calculation methods of interaction of electromagnetic waves with objects of complex geometries
Autorzy:
Shopa, M.
Powiązania:
https://bibliotekanauki.pl/articles/1938589.pdf
Data publikacji:
2016
Wydawca:
Politechnika Gdańska
Tematy:
light scattering
Mie theory
Direct dipole approximation
finite difference time domain method
T-matrix
Opis:
Modeling of the electromagnetic interaction with different homogeneous or inhomogeneous objects is a fundamental and important problem. It is relatively easy to solve Maxwell equations analytically when the scattering object is spherical or cylindrical, for example. However, when it loses these properties all that is left for us is to use approximation models, to acquire the solution we need. Modeling of complex, non-spherical, asymmetric particles is used to study cosmic, cometary dust, aerosols, atmospheric pollution etc. Few analytical, surface-based and volume-based methods of light scattering modeling, most commonly used by scientists, are reviewed here.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2016, 20, 2; 231-240
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
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