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    Wyświetlanie 1-7 z 7
    Tytuł:
    The influence of wave-noise on wave speeds and amplitudes of surface-gravity waves
    Autorzy:
    Murawski, K.
    Zawada, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1954094.pdf
    Data publikacji:
    2004
    Wydawca:
    Politechnika Gdańska
    Tematy:
    random waves
    dispersion relation
    wave-noise
    Opis:
    We have analytically examined surface-gravity waves which propagate in space- and time-dependent random velocity fields. Using a perturbative method, we have derived a dispersion relation which is solved for the case of wave-noise whose spectrum E(k,omega) ~ E(k)delta(omega-crk), where delta is Dirac's delta-function and cr is the random phase speed. We have found that for a dispersionless noise resonance occurs when cr is equal to the group velocity cg of the surface-gravity wave. In this resonance the real part of the wave frequency is finite, but its imaginary part exhibits the characteristic 1/x singularity. The wave-noise interacts with a packet of the surface-gravity waves in such a way that the waves are attenuated for cr < cg and are amplified for cr > cg. As the real part is positive for high values of k, the surface-gravity waves are accelerated by the wave-noise.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2004, 8, 3; 321-326
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The properties of coupled waves propagating in long suspended cables
    Własności sprzężonych fal rozprzestrzeniających się w linach o znacznej długości
    Autorzy:
    Snamina, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/280708.pdf
    Data publikacji:
    2008
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    long cables
    coupled waves
    dispersion relation
    cut-off frequencies
    Opis:
    In this paper, the properties of coupled waves travelling along a long cable are analysed. Since the tension and curvature in the equilibrium position of the cable are slowly varying functions of the arc co-ordinate, the problems concerning the travelling waves can be solved using the Wentzel-Kramers-Brillouin (WKB) method. The waves propagating in the plane of the equilibrium curve are coupled. The wave associated with displacements perpendicular to the plane is uncoupled from the remaining waves. Applying the WKB method, the dispersion relation and equations describing the amplitudes of waves are determined. For a longitudinal-dominated pair of waves, there exist two cut-off frequencies depending on the arc co-ordinate. The results of calculations of wavelengths and amplitudes are presented in the form of plots.
    W pracy przedstawiono analizę własności fal mechanicznych rozprzestrzeniających się w linach o znacznej długości. W liniowej teorii fale rozchodzące się w płaszczyźnie zwisu są ze sobą sprzężone, a fala wywołująca przemieszczenia punktów liny w kierunku prostopadłym do płaszczyzny zwisu rozprzestrzenia się niezależnie od pozostałych fal. W rozważaniach uwzględniono wolno-zmienną zależność siły osiowej i krzywizny od współrzędnej łukowej, w położeniu równowagi statycznej liny. Zagadnienia dotyczące przemieszczających się wzdłuż przewodu fal rozwiązano metodą WKB (Wentzel-Kramers-Brillouin).Wyznaczono związki dyspersyjne charakteryzujące ruch falowy w linach, wyprowadzono prędkości fazowe i grupowe z uwzględnieniem sprzężenia fal rozchodzących się w płaszczyźnie zwisu. Analizie poddano zależność liczb falowych oraz amplitud od współrzędnej łukowej. W rozważaniach wykorzystano symetrię ruchu fal. Wyniki obliczeń zostały zobrazowane na szeregu wykresach.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2008, 46, 4; 973-992
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Estimation of acoustically induced refractive index perturbation in silicon and germanium slab for optical applications
    Autorzy:
    Sharma, G.
    Kumar, S.
    Kumar, D.
    Singh, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/173371.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    dispersion relation
    Lamb wave mode in silicon and germanium
    displacement field
    refractive index modulation
    Opis:
    In-plane displacement field and refractive index variation for silicon and germanium in the presence of Lamb wave is estimated for optical applications. The required dispersion equation in a thin silicon and germanium plates is obtained using the method of potentials with boundary conditions involving the bulk and surface stress of the materials considered. The eigen-values thus obtained are used to compute the Lamb wave modes for the slab of silicon and germanium at same thickness. The fundamental anti-symmetric and symmetric plate modes and their overtones are observed due to confinement of acoustic energy within the slab thickness. In addition, the excited symmetric modes in silicon have longer wavelengths than those of germanium at a fixed frequency. Therefore, the refractive index modulation through the Lamb wave in silicon is always larger as compared to that of germanium. This refractive index modulation can be treated as periodic sinusoidal refractive index variation and may be considered as a tunable one-dimensional photonics crystal.
    Źródło:
    Optica Applicata; 2015, 45, 4; 491-500
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Properties of low frequency TE-electromagnetic wave in ternary plasma photonic crystal
    Autorzy:
    Dehnavi, Z. N.
    Askari, H. R.
    Malekshahi, M.
    Dorranian, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/174815.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    plasma photonic crystal
    effective plasma frequency
    photonic band gap
    dispersion relation
    group velocity
    reflectivity
    Opis:
    In this study, the oblique incident of the electromagnetic waves with frequencies lower than plasma frequency in one dimensional ternary plasma photonic crystal has been investigated. The unit cell of crystal contains a plasma layer that is embedded in two different dielectric layers. Using the wave equation, Bloch theory, and boundary condition, the dispersion relation, the group velocity and the reflection relation of the structure have been obtained. Numerical results are presented in the form of dispersion curves. The dependence of photonic band gap characteristics on plasma frequency is discussed. One attempt has been made to show how the photonic band gap characteristic of a particular structure changes when the dielectric material of the unit cell is replaced by other dielectric materials or when the incident angle of the electromagnetic wave is changed. Results show that plasma layer characteristics has a significant effect on band gaps and wave propagation characteristics; also the results show that the proposed multi-layered structure can act as a tunable photonic crystal which can be controlled by the external parameters.
    Źródło:
    Optica Applicata; 2017, 47, 3; 457-470
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Instability and the formation of bubbles and the plugs in fluidized beds
    Autorzy:
    Schulz, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/2050193.pdf
    Data publikacji:
    2004
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    multiphase flow
    bubbling
    linear and non linear instability
    dispersion relation
    periodic plugs (or slugs)
    Opis:
    This is an review paper, particulary concentrate on results not many researches by reason that are explain in the text. We consider stability of disperse, two-phase flow (gas-solid particles or liquid-solid particles) linear and non-linear. In particular we discuss the result of Anderson, Sundareson and Jackson (1995) [3] that for vertical dispersion flow one- and two-dimensional, they attack problem growing disturbances directly by numerical integration of equations of motion from given initial conditions (using computer Cray C-90). In principle, this would allow authors to explore all aspects of dynamical behaviour of fluidized beds. It is interesting mechanism of periodic plug describing by Anderson et al. and attest by other researchers. Second part of paper is more general, dedicate the problem of linear stability of uniformly fluidized state ("fluidized bed"). We make the most important stages of calculations (after to Jackson (2000) [23]) and demonstrate that the majority (but not all) of fluidized beds with parameters having technical importance is unstable, or stable in narrow interval of wave numbers k.
    Źródło:
    Opuscula Mathematica; 2004, 24, 1; 133-159
    1232-9274
    2300-6919
    Pojawia się w:
    Opuscula Mathematica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Extended elliptic mild slope equation incorporating the nonlinear shoaling effect
    Autorzy:
    Xiao, Q. L.
    Li, Ch. H.
    Fu, X. Y.
    Wang, M. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/258718.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    nonlinear dispersion relation
    nonlinear shoaling coefficient
    extended elliptic mild slope equation
    surf zone
    wave transformation
    Opis:
    The transformation during wave propagation is significantly important for the calculations of hydraulic and coastal engineering, as well as the sediment transport. The exact wave height deformation calculation on the coasts is essential to near-shore hydrodynamics research and the structure design of coastal engineering. According to the wave shoaling results gained from the elliptical cosine wave theory, the nonlinear wave dispersion relation is adopted to develop the expression of the corresponding nonlinear wave shoaling coefficient. Based on the extended elliptic mild slope equation, an efficient wave numerical model is presented in this paper for predicting wave deformation across the complex topography and the surf zone, incorporating the nonlinear wave dispersion relation, the nonlinear wave shoaling coefficient and other energy dissipation factors. Especially, the phenomenon of wave recovery and second breaking could be shown by the present model. The classical Berkhoff single elliptic topography wave tests, the sinusoidal varying topography experiment, and complex composite slopes wave flume experiments are applied to verify the accuracy of the calculation of wave heights. Compared with experimental data, good agreements are found upon single elliptical topography and one-dimensional beach profiles, including uniform slope and step-type profiles. The results indicate that the newly-developed nonlinear wave shoaling coefficient improves the calculated accuracy of wave transformation in the surf zone efficiently, and the wave breaking is the key factor affecting the wave characteristics and need to be considered in the nearshore wave simulations.
    Źródło:
    Polish Maritime Research; 2016, S 1; 44-51
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Edge waves over a shelf
    Autorzy:
    Dolai, P.
    Dolai, D. P.
    Powiązania:
    https://bibliotekanauki.pl/articles/264611.pdf
    Data publikacji:
    2019
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    fala brzegowa
    wielomian Gegenbauera
    relacja dyspersji
    shelf
    edge wave
    Havelock expansion
    Galerkin approximation
    Gegenbauer polynomial
    dispersion relation
    Opis:
    The problem considered in this paper is the derivation of properties of edge waves travelling along a submerged horizontal shelf. The problem is formulated within the framework of the linearized theory of water waves and Havelock expansions of water wave potentials are used in the mathematical analysis to obtain the dispersion relation for edge waves in terms of an integral. Appropriate multi-term Galerkin approximations involving ultra spherical Gegenbauer polynomials are utilized to obtain a very accurate numerical estimate for the integral and hence to derive the properties of edge waves over a shelf. The numerical results are illustrated in a table and curves are presented showing the variation of frequency of the edge waves with the width of the shelf.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2019, 24, 2; 453-460
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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