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    Wyświetlanie 1-6 z 6
    Tytuł:
    Effect of Rotation on the Piezoelectric Wave Impedance Characteristics
    Autorzy:
    Yuan, Xiaoguang
    Hao, Chaoyu
    Jiang, Quan
    Powiązania:
    https://bibliotekanauki.pl/articles/31339852.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    wave impedance
    Coriolis acceleration
    piezoelectric crystal
    wave velocity
    Opis:
    The dependence of piezoelectric wave impedance on the rotation speed is investigated theoretically and numerically. The Coriolis force due to rotation is introduced into the piezoelectric motion equations, which is solved by the harmonic plane wave solution. It is shown that the wave impedance variations of longitudinal and transverse waves due to rotation are clearly different. The longitudinal wave impedance continuously increases with a small rotation ratio and one transverse wave impedance is almost irrespective of a rotation ratio. In contrast, the rotation applies a big impact on the other transversal wave impedances in the piezoelectric crystal which decreases monotonically with the rotation speed. Such characteristics are significant in piezoelectric transducers and sensors.
    Źródło:
    Archives of Acoustics; 2023, 48, 3; 231-234
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of diffusion and impedence parameters on wave propagation in thermoelastic medium
    Autorzy:
    Kaushal, Sachin
    Kumar, Rajneesh
    Parmar, Kulwinder
    Powiązania:
    https://bibliotekanauki.pl/articles/2174177.pdf
    Data publikacji:
    2021
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    fala płaska
    dyfuzja
    impedancja
    plane wave
    amplitude ratios
    diffusion
    impedance parameters
    Opis:
    The aim of the present paper is to study the impact of diffusion and impedance parameters on the propagation of plane waves in a thermoelastic medium for Green and Lindsay theory (G-L) and the Coupled theory (C-T) of thermoelasticity. Results are demonstrated for impedance boundary conditions and the amplitude ratios of various reflected waves against the angle of incidence are calculated numerically. The characteristics of diffusion, relaxation time and impedence parameter on amplitude ratios have been depicted graphically. Some cases of interest are also derived from the present investigation.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2021, 26, 4; 99--112
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Trombone Transfer Functions: Comparison Between Frequency-Swept Sine Wave and Human Performer Input
    Autorzy:
    Beauchamp, J. W.
    Powiązania:
    https://bibliotekanauki.pl/articles/176612.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    brass acoustics
    trombone
    transfer function
    nonlinear propagation
    input impedance
    Opis:
    Source/filter models have frequently been used to model sound production of the vocal apparatus and musical instruments. Beginning in 1968, in an effort to measure the transfer function (i.e., transmission response or filter characteristic) of a trombone while being played by expert musicians, sound pressure signals from the mouthpiece and the trombone bell output were recorded in an anechoic room and then subjected to harmonic spectrum analysis. Output/input ratios of the signals’ harmonic amplitudes plotted vs. harmonic frequency then became points on the trombone’s transfer function. The first such recordings were made on analog 1/4 inch stereo magnetic tape. In 2000 digital recordings of trombone mouthpiece and anechoic output signals were made that provide a more accurate measurement of the trombone filter characteristic. Results show that the filter is a high-pass type with a cutoff frequency around 1000 Hz. Whereas the characteristic below cutoff is quite stable, above cutoff it is extremely variable, depending on level. In addition, measurements made using a swept-sine-wave system in 1972 verified the high-pass behavior, but they also showed a series of resonances whose minima correspond to the harmonic frequencies which occur under performance conditions. For frequencies below cutoff the two types of measurements corresponded well, but above cutoff there was a considerable difference. The general effect is that output harmonics above cutoff are greater than would be expected from linear filter theory, and this effect becomes stronger as input pressure increases. In the 1990s and early 2000s this nonlinear effect was verified by theory and measurements which showed that nonlinear propagation takes place in the trombone, causing a wave steepening effect at high amplitudes, thus increasing the relative strengths of the upper harmonics.
    Źródło:
    Archives of Acoustics; 2012, 37, 4; 447-454
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Acoustic Impedance of Outlet of a Hard-Walled Unbaffled Cylindrical Duct for Multimode Incident Wave
    Autorzy:
    Jurkiewicz, J.
    Snakowska, A.
    Smolik, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/1504427.pdf
    Data publikacji:
    2011-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    43.20.Mv
    43.20.Rz
    Opis:
    In the paper, the specific acoustic impedance of outlet of an unbaffled duct for incident wave composed of one or many circumferential cut-on duct modes has been derived and presented on graphs. When considering the multimode excitation the equal energy per mode principle and random phases have been assumed. Experimentally verified assumption on equal energy per mode allows for quantitative analysis of the sound field and thus provides more physical insight into the in-duct and out-duct phenomena. The assumption of random phase was implemented by means of the Monte Carlo method and so the expected value, the standard deviation and the percentile curves of the impedance were presented. Numerical data obtained according to the derived theoretical formulae for single and multimode incident wave manifest strong modal character and dependence on the modes phases. The assumption of multimode incident wave has brought the theoretical model closer to what is being observed in practice, especially when ducts of large radius, such as heating and air conditioning systems or turbojet engines, are considered.
    Źródło:
    Acta Physica Polonica A; 2011, 119, 6A; 1061-1067
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Propagation in dielectric rectangular waveguides
    Autorzy:
    Yeap, K. H.
    Teh, K. H.
    Yeong, K. C.
    Lai, K. C.
    Loh, M. C.
    Powiązania:
    https://bibliotekanauki.pl/articles/173566.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    dielectric rectangular waveguide
    transverse wave numbers
    attenuation coefficient
    surface impedance
    propagation constant
    fundamental mode
    Opis:
    We present a fundamental and accurate approach to compute the attenuation of electromagnetic waves propagating in dielectric rectangular waveguides. The transverse wave numbers are first obtained as roots of a set of transcendental equations developed by matching the fields with the surface impedance of the wall. The propagation constant is found by substituting the values of transverse wave numbers into the dispersion relation. We have examined the validity of our model by comparing the computed results with those obtained from Marcatili’s equations and the finite element method. In our results, it is shown that the fundamental mode is identical with that found in a perfectly conducting waveguide. Our analysis also shows that a hollow waveguide is found to have much lower attenuation than its dielectric counterparts. Since the cutoff frequency is usually affected by the constitutive properties of the dielectric medium, for a waveguide designed for wave with the same cutoff frequency, hollow waveguides turn out to be relatively larger in size.
    Źródło:
    Optica Applicata; 2016, 46, 2; 317-330
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Impedance and Scattering Variance Ratios of Complicated Wave Scattering Systems in the Low Loss Regime
    Autorzy:
    Yeh, J.
    Drikas, Z.
    Gil Gil, J.
    Hong, S.
    Taddese, B.
    Ott, E.
    Antonsen, T.
    Andreadis, T.
    Anlage, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399042.pdf
    Data publikacji:
    2013-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    05.45.Mt
    24.60.-k
    42.25.Dd
    78.20.Bh
    Opis:
    Random matrix theory successfully predicts universal statistical properties of complicated wave scattering systems in the semiclassical limit, while the random coupling model offers a complete statistical model with a simple additive formula in terms of impedance to combine the predictions of random matrix theory and nonuniversal system-specific features. The statistics of measured wave properties generally have nonuniversal features. However, ratios of the variances of elements of the impedance matrix are predicted to be independent of such nonuniversal features and thus should be universal functions of the overall system loss. In contrast with impedance variance ratios, scattering variance ratios depend on nonuniversal features unless the system is in the high loss regime. In this paper, we present numerical tests of the predicted universal impedance variance ratios and show that an insufficient sample size can lead to apparent deviation from the theory, particularly in the low loss regime. Experimental tests are carried out in three two-port microwave cavities with varied loss parameters, including a novel experimental system with a superconducting microwave billiard, to test the variance-ratio predictions in the low loss time-reversal-invariant regime. It is found that the experimental results agree with the theoretical predictions to the extent permitted by the finite sample size.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 6; 1045-1052
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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