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Wyświetlanie 1-5 z 5
Tytuł:
On the Nonlinear Effects of Magnetoacoustic Perturbations in Optically Thin Quasi-Isentropic Plasmas
Autorzy:
Perelomova, A.
Ratkowski, F.
Powiązania:
https://bibliotekanauki.pl/articles/1030551.pdf
Data publikacji:
2018-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.25.-x
43.25.Nm
Opis:
Nonlinear effects of planar magnetosound perturbations in a plasma are discussed. Plasma is non-adiabatic due to optically thin radiation and external heating. For these reasons, thermal instability of a plasma may appear which makes it acoustically active. The plasma is assumed to be initially homogeneous ideal gas with infinite electrical conductivity permeated by a straight magnetic field which is orthogonal to the trajectories of gas particles. The instantaneous dynamic equations which describe nonlinear effects of intense sound in quasi-isentropic plasma, are derived. Nonlinear interaction of periodic and aperiodic magnetoacoustic perturbations with the non-wave modes, are discussed. The conclusions concern dissipative or active behavior of magnetoacoustic perturbations which is determined by the kind of the heating-cooling function.
Źródło:
Acta Physica Polonica A; 2018, 133, 1; 194-200
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of material non-homogeneity and two parameter elastic foundation on fundamental frequency parameters of Timoshenko beams
Autorzy:
Avcar, M.
Powiązania:
https://bibliotekanauki.pl/articles/1070359.pdf
Data publikacji:
2016-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.43.Bn
62.20.-x
62.25.Jk
89.20.Kk
Opis:
In the present study, effects of material non-homogeneity and two-parameter elastic foundation on the fundamental frequency parameters of the simply supported beams are examined. Material non-homogeneity is characterized taking into account the parabolic variations of Young's modulus and density along the thickness direction of the beam while the value of Poisson's ratio is assumed to remain constant. The foundation medium is assumed to be linear, homogeneous and isotropic, and it is modeled by the Pasternak model with two parameters for describing the reaction of the elastic foundation on the beam. At first, the equation of the motion including the effects of the material non-homogeneity and two-parameter elastic foundation is provided. Then, the solutions including fundamental frequency parameters versus various non-homogeneity, density and foundation parameters, and length to depth ratio adopting the Timoshenko beam theory as well as the Euler-Bernoulli beam theory are presented. To show the accuracy of the present results, a comparison is carried out and a good agreement is found.
Źródło:
Acta Physica Polonica A; 2016, 130, 1; 375-378
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase-Locked Particle Image Velocimetry Visualization of the Sound Field at the Outlet of a Circular Tube
Autorzy:
Weyna, S.
Mickiewicz, W.
Powiązania:
https://bibliotekanauki.pl/articles/1196700.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.58.+z
43.28.Js
43.25.-x
47.35.Rs
Opis:
The shedding process and acoustic flow formation in the region of outlet of a cylinder duct has been investigated by means of the particle image velocimetry (PIV) technique. The research work on the behavior of the sound field at outlets of waveguides addresses issues of importance to industrial applications. The obtained results can be used in a number of industrial applications involving pipes, ducts and tubing. In our investigation the acoustics flow fields are measured with a phase-locked PIV system with high sampling rate and large internal memory block using DAVIS v. 8.11 software. A cross-correlation method, in conjunction with the FFT analysis, is used as a vector processing algorithm. A series of PIV vector maps was used to evaluate the acoustic velocity field at the open end of circular tube throughout the acoustic cycle for frequencies of 700 Hz and 1400 Hz. Six phase steps were assumed for one frequency cycle and the characteristic signal was extracted from the velocity data step and shown graphically.
Źródło:
Acta Physica Polonica A; 2014, 125, 4A; A-108-A-112
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non-Wave Variations in Temperature Caused by Sound in a Chemically Reacting Gas
Autorzy:
Perelomova, A.
Pelc-Garska, W.
Powiązania:
https://bibliotekanauki.pl/articles/1493610.pdf
Data publikacji:
2011-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.25.-x
43.20.Bi
Opis:
A weakly nonlinear generation of non-acoustic modes in the field of sound in a gas is considered. An exoteric chemical reaction of A → B type, which takes place in a gas, may be reversible or not. Two types of sound are considered, low-frequency and high-frequency as compared with the characteristic time of a chemical reaction. For both these cases, the governing equations of non-acoustic modes are derived and conclusions of the efficiency of their nonlinear generation by sound are made. The character of nonlinear generation of non-acoustic modes by sound depends essentially on reversibility of a chemical reaction.
Źródło:
Acta Physica Polonica A; 2011, 120, 3; 455-461
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Strong Acoustic Anisotropy on Reflection of Bulk Acoustic Waves in Crystals
Autorzy:
Polikarpova, N.
Powiązania:
https://bibliotekanauki.pl/articles/1811547.pdf
Data publikacji:
2008-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.35.Sx
78.20.Hp
43.25.-x
61.72.-y
Opis:
Propagation and reflection of plane elastic waves in the acousto-optic crystals tellurium dioxide and calomel as well as in the ferroelectric material barium titanate is examined in the paper. The reflection of the waves from a free and flat boundary separating the crystal and the vacuum is investigated in the (001) planes of $TeO_2$, $Hg_2Cl_2$, and $BaTiO_3$ in the case of glancing acoustic incidence on the boundary. The analysis shows that as much as two elastic waves may be reflected from the crystal surface. Energy flow of one of the reflected waves in paratellurite and calomel propagates in a quasi-back direction with respect to the incident energy flow, so that both energy flows are separated by an angle as narrow as a few degrees. It is found that a relative intensity of the unusually reflected wave in the acousto-optic crystals may be close to a unit in a wide variety of crystal cuts. Possible applications of the examined phenomena in acousto-optic devices are discussed in the presentation.
Źródło:
Acta Physica Polonica A; 2008, 114, 6A; A-175-A-182
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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