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Добірка наукової літератури з теми "Propagative waves"

Автор: Grafiati
Опубліковано: 7 липня 2024
Оновлено: 7 липня 2024

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Статті в журналах з теми "Propagative waves":

1

Sheng, Xi, Huike Zeng, Sara Ying Zhang, and Ping Wang. "Numerical Study on Propagative Waves in a Periodically Supported Rail Using Periodic Structure Theory." Journal of Advanced Transportation 2021 (October 14, 2021): 1–12. http://dx.doi.org/10.1155/2021/6635198.

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This paper presents the numerical study on propagative waves in a periodically supported rail below 6000 Hz. A periodic rail model, which considers the effects of both the periodic supports and the rail cross section deformation, has been established based on the periodic structure theory and the finite element method. Two selection approaches are proposed to obtain the concerned dispersion curves from the original calculation results of dispersion relations. The differences between the dispersion curves of different support conditions are studied. The propagative waves corresponding to the dispersion curves are identified by the wave modes. The influences of periodic supports on wave modes in pass bands are revealed. Further, the stop band behaviors are investigated in terms of the bounding frequencies, the standing wave characteristics, and the cross-sectional modes. The results show that eight propagative waves with distinct modes exist in a periodically supported rail below 6000 Hz. The differences between the dispersion curves of periodically and continuously supported rails are not obvious, apart from the stop band behaviors. All the bounding-frequency modes of the stop bands are associated with the standing waves. Two bounding-frequency modes of the same stop band can be regarded as two identical standing waves with the longitudinal translation of the quarter-wavelength, one of which is the so-called pinned-pinned resonance.
2

Dupuy, Bastien, Louis De Barros, Stephane Garambois, and Jean Virieux. "Wave propagation in heterogeneous porous media formulated in the frequency-space domain using a discontinuous Galerkin method." GEOPHYSICS 76, no. 4 (July 2011): N13—N28. http://dx.doi.org/10.1190/1.3581361.

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Biphasic media with a dynamic interaction between fluid and solid phases must be taken into account to accurately describe seismic wave amplitudes in subsurface and reservoir geophysical applications. Consequently, the modeling of the wave propagation in heteregeneous porous media, which includes the frequency-dependent phenomena of the fluid-solid interaction, is considered for 2D geometries. From the Biot-Gassmann theory, we have deduced the discrete linear system in the frequency domain for a discontinuous finite-element method, known as the nodal discontinuous Galerkin method. Solving this system in the frequency domain allows accurate modeling of the Biot wave in the diffusive/propagative regimes, enhancing the importance of frequency effects. Because we had to consider finite numerical models, we implemented perfectly matched layer techniques. We found that waves are efficiently absorbed at the model boundaries, and that the discretization of the medium should follow the same rules as in the elastodynamic case, that is, 10 grids per minimum wavelength for a P0 interpolation order. The grid spreading of the sources, which could be stresses or forces applied on either the solid phase or the fluid phase, did not show any additional difficulties compared to the elastic problem. For a flat interface separating two media, we compared the numerical solution and a semianalytic solution obtained by a reflectivity method in the three regimes where the Biot wave is propagative, diffusive/propagative, and diffusive. In all cases, fluid-solid interactions were reconstructed accurately, proving that attenuation and dispersion of the waves were correctly accounted for. In addition to this validation in layered media, we have explored the capacities of modeling complex wave propagation in a laterally heterogeneous porous medium related to steam injection in a sand reservoir and the seismic response associated to a fluid substitution.
3

Smith, William V. "Wave motion in a conducting fluid with a layer adjacent to the boundary, II. Eigenfunction expansions." ANZIAM Journal 43, no. 2 (October 2001): 195–236. http://dx.doi.org/10.1017/s1446181100013031.

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AbstractThe wave motion of magnetohydrodynamic (MHD) systems can be quite complicated. In order to study the motion of waves in a perfectly conducting fluid under the influence of an external magnetic field in a stratified medium, we make the simplifying assumption that the pressure is constant (to first order). This is the simplest form of the equations with variable coefficients and is not strongly propagative. Alfven waves are still present. The system is further simplified by assuming that the external field is parallel to the boundary. The Green's function for the operator is constructed and then the spectral family is constructed in terms of generalized eigenfunctions, giving four families of propagating waves, including waves “trapped” in the boundary layer. These trapped waves are interesting, since they are not the relics of surface waves, which do not exist in this context when the boundary layer shrinks to zero thickness no matter what (maximal energy preserving) boundary condition is chosen. We conjecture a similar structure for the full MHD problem.
4

Gavaix, Anne-Marie, Jean Chandezon, and Gerard Granet. "PROPAGATIVE AND EVANESCENT WAVES DIFFRACTED BY PERIODIC SURFACES: PERTURBATION METHOD." Progress In Electromagnetics Research B 34 (2011): 283–311. http://dx.doi.org/10.2528/pierb11070504.

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5

Dupuy, Bastien, and Alexey Stovas. "Influence of frequency and saturation on AVO attributes for patchy saturated rocks." GEOPHYSICS 79, no. 1 (January 1, 2014): B19—B36. http://dx.doi.org/10.1190/geo2012-0518.1.

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Partially saturated rocks are considered to be major sources of seismic wave velocity dispersion and attenuation in recorded real data. From the physical description of partially saturated gas-water and oil-water reservoirs, we use upscaling theories to compute an equivalent frequency-dependent porous medium. These homogenization methods are associated with mesoscale description of attenuation and dispersion coming from wave-induced flow phenomena. To compute wave propagation, we use numerical codes in the frequency domain that allow us to take into account all the frequency-dependent parameters without approximation or local time steps. In this way, the Biot slow compressional wave is well modeled and its partially diffusive, partially propagative behavior is completely considered. The attenuation and dispersion of the waves in such media are coming partly from the wave mode conversion into diffusive slow waves, not visible on seismograms. But the amplitude of propagative P- and S-waves are mainly affected by these energy losses at interfaces. Using full waveform modeling, we investigate the amplitude versus offset (AVO) attributes with respect to saturation and frequency. For a simple three-layer case, we compute poroelastic wave propagation, extract maximum amplitude with respect to angle, and, through a least-square fitting method, we obtain the AVO attributes for PP- and PS-reflected events. Due to the influence of mesoscale induced-flow phenomena and relatively to the regime of the Biot slow wave, the main results show a strong variability of the AVO attributes with the frequency and a lower variability with the saturation for reflected PP or PS events. We show that gas-water and oil-water systems have similar behaviors. Strong differences between patchy saturation and effective fluid phase theories are highlighted, especially at high frequency, for PP events and for gas-water systems. Then, we conclude that these AVO attributes carry information about the saturation that can be used to estimate the saturation variations in time-lapse studies.
6

Babilotte, Philippe. "Simulation of multiwavelength conditions in laser picosecond ultrasonics." SIMULATION 97, no. 7 (March 25, 2021): 473–84. http://dx.doi.org/10.1177/0037549721996451.

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Complete numerical simulations are given under SciLab® and MATLAB® coding environments, concerning propagative acoustic wavefronts, for laser picosecond ultrasonics under multiwavelength conditions. Simulations of the deformation field and its propagation into bulk material are given under different wavelength configurations for optical pump and probe beams, which are used to generate and to detect the acoustic signal. Complete insights concerning the dynamics of the acoustic waves are given, considering the absence of carrier diffusions into the material. Several numerical approaches are proposed concerning both the functions introduced to simulate the wavefront ( Heaviside or error) and the coding approach (linear/vectorized/ Oriented Object Programming), under the pure thermo-elastic approach.
7

Intravaia, F., and A. Lambrecht. "The Role of Surface Plasmon Modes in the Casimir Effect." Open Systems & Information Dynamics 14, no. 02 (June 2007): 159–68. http://dx.doi.org/10.1007/s11080-007-9044-4.

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In this paper, we study the role of surface plasmon modes in the Casimir effect. First we write the Casimir energy as the sum over the modes of a real cavity. We may identify two sorts of modes, two evanescent surface plasmon modes and propagative modes. As one of the surface plasmon modes becomes propagative for some choice of parameters we adopt an adiabatic mode definition where we follow this mode into the propagative sector and count it together with the surface plasmon contribution, calling this contribution “plasmonic”. The remaining modes are propagative cavity modes, which we call “photonic”. The Casimir energy contains two main contributions, one coming from the plasmonic, the other from the photonic modes. Surprisingly we find that the plasmonic contribution to the Casimir energy becomes repulsive for intermediate and large mirror separations. Alternatively, we discuss the common surface plasmon defintion, which includes only evanescent waves, where this effect is not found. We show that, in contrast to an intuitive expectation, for both definitions the Casimir energy is the sum of two very large contributions which nearly cancel each other. The contribution of surface plasmons to the Casimir energy plays a fundamental role not only at short but also at large distances.
8

ERMANYUK, E. V., J. B. FLÓR, and B. VOISIN. "Spatial structure of first and higher harmonic internal waves from a horizontally oscillating sphere." Journal of Fluid Mechanics 671 (February 10, 2011): 364–83. http://dx.doi.org/10.1017/s0022112010005719.

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An experimental study is presented on the spatial structure of the internal wave field emitted by a horizontally oscillating sphere in a uniformly stratified fluid. The limits of linear theory and the nonlinear features of the waves are considered as functions of oscillation amplitude. Fourier decomposition is applied to separate first harmonic waves at the fundamental frequency and higher harmonic waves at multiples of this frequency. For low oscillation amplitude, of 10% of the sphere radius, only the first harmonic is significant and the agreement between linear theory and experiment is excellent. As the oscillation amplitude increases up to 30% of the radius, the first harmonic becomes slightly smaller than its linear theoretical prediction and the second and third harmonics become detectable. Two distinct cases emerge depending on the ratio Ω between the oscillation frequency and the buoyancy frequency. When Ω > 0.5, the second harmonic is evanescent and localized near the sphere in the plane through its centre perpendicular to the direction of oscillation, while the third harmonic is negligible. When Ω < 0.5, the second harmonic is propagative and appears to have an amplitude that exceeds the amplitude of the first harmonic, while the third harmonic is evanescent and localized near the sphere on either side of the plane through its centre perpendicular to the direction of oscillation. Moreover, the propagative first and second harmonics have radically different horizontal radiation patterns and are of dipole and quadrupole types, respectively.
9

Bristeau, Marie-Odile, Bernard Di Martino, Ange Mangeney, Jacques Sainte-Marie, and Fabien Souille. "Some quasi-analytical solutions for propagative waves in free surface Euler equations." Comptes Rendus. Mathématique 358, no. 11-12 (January 25, 2021): 1111–18. http://dx.doi.org/10.5802/crmath.63.

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10

Gavrić, L. "Computation of propagative waves in free rail using a finite element technique." Journal of Sound and Vibration 185, no. 3 (August 1995): 531–43. http://dx.doi.org/10.1006/jsvi.1995.0398.

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Також вас можуть зацікавити розширені добірки на тему "Propagative waves" для конкретних типів джерел:
Статті в журналах Дисертації Книги

Дисертації з теми "Propagative waves":

1

Lalloz, Samy. "De la diffusion à la propagation d'ondes en magnétohydrodynamique bas-Rm : études théorique et expérimentale." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALI020.

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L'objectif de cette thèse est de clarifier les conditions d'émergence en métaux liquides des ondes d'Alfvén dans un domaine géométriquement contraint. La première partie de ce travail de recherche est consacrée à une étude linéaire des ondes d'Alfvén dans l'approximation bas-Rm et en régime non inertiel. La seconde partie porte sur l'étude expérimentale d'un écoulement oscillant forcé électriquement, soumis à un champ magnétique axial, statique et uniforme, et confiné entre deux parois horizontales rigides, sans glissement et électriquement isolantes.Dans l'étude théorique menée, une première partie vise à discuter la relation de dispersion pour la dynamique des ondes d'Alfvén. Elle présente les conséquences liées à des gradients (mécaniques et magnétiques) perpendiculaires au champ magnétique imposé, plus particulièrement la manière dont la propagation de l'onde est ainsi modifiée. Dans la deuxième partie, un vortex axisymétrique confiné entre deux parois horizontales isolées électriquement et sans glissement est magnétiquement forcé à une fréquence donnée. Ce forçage prend en compte le rayon du vortex afin d'étudier l'impact des gradients transversaux sur la dynamique de l'écoulement. Une étude semi-analytique de la dynamique de l'écoulement est à nouveau réalisée dans un cadre bas-Rm et non inertiel. Cette étude, réalisée en faisant varier la fréquence de forçage et l'intensité du champ magnétique, met en évidence deux régimes très distincts, à savoir un premier régime oscillant-diffusif, régi par la compétition entre l'effet pseudo-diffusif de la force de Lorentz et le terme instationnaire de la quantité de mouvement, et un second régime, propagatif, régi par les ondes d'Alfvén et obtenu pour des fréquences de forçage plus élevées. L'étude met également en évidence l'impact des gradients transversaux sur ce régime propagatif. En plus de sur-amortir les ondes, les gradients transversaux modifient les fréquences naturelles des pics de résonance d'ondes, lesquels résultent de la superposition d'ondes incidentes et réfléchies entre les parois du domaine d'étude.Parallèlement à ce travail théorique, un dispositif a été conçu afin d'étudier expérimentalement la dynamique d'écoulements oscillants sous un champ magnétique (jusqu'à 10T). Un écoulement est forcé dans un récipient cubique de 15 cm x 15 cm x 10 cm au moyen d'un courant alternatif injecté à l'aide de quatre électrodes situées sur la plaque inférieure. En utilisant une instrumentation basée sur les différences locales de potentiel électrique aux niveau des plaques (d'Hartmann) supérieure et inférieure, nous validons les prédictions du modèle. Plus précisément, nous retrouvons un régime propagative modifié par les gradients transversaux ainsi que le régime oscillant-diffusif, obtenu pour des fréquences de forçage plus faibles.En plus des résultats obtenus à la fréquence de forçage, un premier aperçu des signaux obtenus à d'autres fréquences est présenté. Certains des pics de fréquence obtenus ne pouvant pas être expliqués par une approche linéaire, nous suggérons qu'ils sont générés par des interactions non linéaires d'ondes d'Alfvén. En outre, une étude préliminaire sur le pic à la première harmonique de la fréquence de forçage montre qu'il est très probablement associé à des ondes d'Alfvén
The thesis aims to clarify the conditions for Alfvén waves to propagate in a closed liquid metal domain. A first part of the research work presented is dedicated to a linear study of Alfvén waves in the low-Rm approximation and under the inertia-less limit. The second part is the experimental investigation of an electrically-induced oscillating flow subjected to an axial, static and uniform magnetic field and confined between two electrically insulating and no-slip horizontal walls.The theoretical study is itself split into two sub-parts. The first one aims to discuss the dispersion relation which contains the Alfvén wave dynamics. It presents the consequences of (mechanical and magnetic) gradients perpendicular to the imposed magnetic field. As such transverse gradients tend to impede the wave propagation. In the second sub-part an axisymmetric vortex confined between to electrically insulated and no-slip horizontal walls is magnetically forced at a given frequency. This forcing is radially dependent so as to study the impact of transverse gradients on the flow dynamics. A semi-analytical investigation of the flow dynamics is again carried out in the low-Rm approximation and under the inertia-less limit. This investigation is performed by varying the forcing frequency and the magnetic field intensity. This brings to emphasize two very distinct regimes for the oscillating vortex:- an oscillating-diffusive regime governed by the competition between pseudo-diffusive effects of the Lorentz force and the unsteady term of the momentum- a truly propagative regime, obtained for higher forcing frequencies, found definitelygoverned by Alfvén waves.The study also highlights how the propagative regime can be affected by transverse gradients. In addition to over-damping the waves, transverse gradients are found to modify the natural frequencies for which wave resonance peaks result from the superimposition of incident and reflected waves in the container.Beside this theoretical work, a setup has been designed in order to experimentally investigate the dynamics of oscillating flows under a strong magnetic field (up to 10T). A flow was forced in a cuboid vessel 15 cm x 15 cm x 10 cm by means of AC currents injected through a cartesian grid of four electrodes located at the bottom plate. Using instrumentation based on the measurement of local electric potential differences at the top and bottom horizontal (Hartmann) plates, we validate model's prediction. More precisely, a propagative dynamics in the presence of transverse gradients is recovered. The oscillating-diffusive regime is also recovered from experiments performed at small enough forcing frequency.In addition to results obtained at the forcing frequency, a first insight of signals obtained at other frequencies is shown. Frequency peaks obtained, eg the harmonics of the forcing frequency, are demonstrated not to be explained by a linear approach. We suggest that Alfvén wave non-linear interactions are a good candidate to explain these peaks. A preliminary study further shows that peaks at the first harmonic are likely to be Alfvén waves
2

Schlottmann, Robert Brian. "A path integral formulation of elastic wave propagation /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004372.

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3

Kil, Hyun-Gwon. "Propagation of elastic waves on thin-walled circular cylinders." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/15967.

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4

Fu, Y. "Propagation of weak shock waves in nonlinear solids." Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384589.

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5

Gandhi, Navneet. "Determination of dispersion curves for acoustoelastic lamb wave propagation." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37158.

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The effect of stress on Lamb wave propagation is relevant to both nondestructive evaluation and structural health monitoring because of changes in received signals due to both the associated strain and the acoustoelastic effect. A homogeneous plate that is initially isotropic becomes anisotropic under biaxial stress, and dispersion of propagating waves becomes directionally dependent. The problem is similar to Lamb wave propagation in an anisotropic plate, except the fourth order tensor in the resulting wave equation does not have the same symmetry as that for the unstressed anisotropic plate, and the constitutive equation relating incremental stress to incremental strain is more complicated. Here we review the theory of acoustoelastic and develop theory for acoustoelastic Lamb wave propagation and show how dispersion curves shift anisotropically for an aluminum plate under biaxial tension. We also develop an approximate method using the effective elastic constants (EECs) and show that existing commercial tools to generate dispersion curves can be used under restricted conditions to describe wave propagation in biaxially stressed plates. Predictions of changes in phase velocity as a function of propagation direction using theory and the EEC method are compared to experimental results for a single wave mode.
6

Pack, Jeong-Ki. "A wave-kinetic numerical method for the propagation of optical waves." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/104527.

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7

Zandi, Bahram. "Propagation of optical waves in tapered fibers and metallic wave guides." PDXScholar, 1986. https://pdxscholar.library.pdx.edu/open_access_etds/2693.

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The equations tor the propagation of Electromagnetic and Optical waves in tapered fibers and metallic waveguides are derived. Solutions are derived for the displacement of the beam from the waveguide axis as a function of distance along the axis, and also tor the beam width as a function of distance. These equations are solved numerically for a variety of tapered guides. Experiments are conducted which verify the theoretical results.
8

Reese, Owein. "Homogenization of acoustic wave propagation in a magnetorheological fluid." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0430104-101629.

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9

Lane, Ryan Jeffrey. "Study of Wave Propagation in Damaged Composite Material Laminates." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/86366.

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The characteristics of carbon fiber composites have enabled these materials to be accepted as replacements for metal parts in industry. However, due to their unsymmetrical material properties, carbon fiber composites are susceptible to damage, such as a delamination, which can cause premature failure in the structure. This has resulted in the need for nondestructive testing methods that can provide quick, reliable results so that these parts can be tested while in service. In this study, an approach was examined that involved a pencil lead break to excite multiple wave modes in a composite plate in an effort to identify key characteristics based on the wavespeed and frequency. These characteristics were then compared to models based on boundary conditions to generate dispersion curves using the transfer matrix method for whole composite plates that were either undamaged or damaged. To first test this approach, experiments were performed on multilayer isotropic plates and then on a composite plate. The results for all cases showed that modes could be excited by the pencil lead break in the undamaged region of the plates that were not theoretical possible in a delaminated region. Also modes that were specific to the delaminated region were excited and this allowed for a clear comparison between the two regions. This approach could be placed into practice to provide routine testing to detect delamination for in-service, carbon fiber composite parts.
Master of Science
The physical properties of high strength and low weight and the economic benefits of carbon fiber composites has resulted in these materials replacing metals in several industries. It is important, however, to be aware that the change in materials used impacts the different types of damage composites experience compared to conventional metals. One type of damage that could cause a composite part to fail is a delamination or a separation of layers. In order to identify if this damage has occurred, it is beneficial to have an inspection technique that will not damage the part. In this study, a technique was tested that involved breaking a piece of pencil lead on a plate in order to generate multiple wave modes that would propagate in the plate. Based on boundary conditions caused by the damage in the plate, the speed of the wave and frequency content could be compared to an undamaged plate to identify a delamination. A model was created to compare experimental results and demonstrated that using wavespeed and frequency could identify a delamination. The experimental results compared well with the model dispersion curves for a plate with and without a delamination suggesting this approach could be placed into practice to provide routine testing to detect delamination for in-service, carbon fiber composite parts.
10

Iskandarani, Saad S. "Electromagnetic wave propagation in anisotropic uniaxial slab waveguide." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182437230.

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Книги з теми "Propagative waves":

1

Barclay, Les, ed. Propagation of radiowaves. London: Institution of Engineering and Technology, 2013.

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2

Maclean, T. S. M. Radiowave propagation over ground. London: Chapman & Hall, 1993.

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3

1941-, DeSanto J. A., and International Conference on Mathematical and Numerical Aspects of Wave Propagation, eds. Mathematical and numerical aspects of wave propagation. Philadelphia: Society for Industrial and Applied Mathematics, 1998.

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4

International Conference on Mathematical and Numerical Aspects of Wave Propagation Phenomena (1st 1991 Strasbourg, France). Mathematical and numerical aspects of wave propagation phenomena. Philadelphia: Society for Industrial and Applied Mathematics, 1991.

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5

Shibuya, Shigekazu. A basic atlas of radio-wave propagation. New York: Wiley, 1987.

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6

Shugaev, F. V. Propagation and reflection of shock waves. Singapore: World Scientific, 1998.

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7

Andrzej, Hanyga, Lenartowicz E, and Pajchel J, eds. Seismic wave propagation in the Earth. Amsterdam: Elsevier, 1985.

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8

Mukherji, Uma. Electromagnetic field theory and wave propagation. Oxford, U.K: Alpha Science International, 2006.

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9

I, Tatarskiĭ V., Ishimaru Akira 1928-, and Zavorotny V. U, eds. Wave propagation in random media (scintillation). Bellingham, Wash., USA: SPIE, 1993.

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10

E, Kerr Donald, and Institution of Electrical Engineers, eds. Propagation of short radio waves. London, U.K: P. Peregrinus on behalf of the Institution of Electrical Engineers, 1987.

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Частини книг з теми "Propagative waves":

1

Resseguier, Valentin, Erwan Hascoët, and Bertrand Chapron. "Random Ocean Swell-Rays: A Stochastic Framework." In Mathematics of Planet Earth, 259–71. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-18988-3_16.

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AbstractOriginating from distant storms, swell systems radiate across all ocean basins. Far from their sources, emerging surface waves have low steepness characteristics, with very slow amplitude variations. Swell propagation then closely follows principles of geometrical optics, i.e. the eikonal approximation to the wave equation, with a constant wave period along geodesics, when following a wave packet at its group velocity. The phase averaged evolution of quasi-linear wave fields is then dominated by interactions with underlying current and/or topography changes. Comparable to the propagation of light in a slowly varying medium, over many wavelengths, cumulative effects can lead to refraction, i.e. change of the direction of propagation of a given wave packet, so that it departs from its initial ray-propagation direction. This opens the possibility of using surface swell systems as probes to estimate turbulence along their propagating path.
2

Garrett, Steven L. "Nonlinear Acoustics." In Understanding Acoustics, 701–53. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44787-8_15.

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Abstract A fundamental assumption of linear acoustics is that the presence of a wave does not have an influence on the properties of the medium through which it propagates. By extension, the assumption of linearity also means that a waveform is stable since any individual wave does not interact with itself. Small modifications in the sound speed due to wave-induced fluid convection (particle velocity) and to the wave’s effect on sound speed through the equation of state can lead to effects that could not be predicted within the limitations imposed by the assumption of linearity. Although a wave’s influence on the propagation speed may be small, those effects are cumulative and create distortion that can produce shocks. These are nonlinear effects because the magnitude of the nonlinearity’s influence is related to the square of an individual wave’s amplitude (self-interaction) or the product of the amplitudes of two interacting waves (intermodulation distortion). In addition, the time-average of an acoustically induced disturbance may not be zero. Sound waves can exert forces that are sufficient to levitate solid objects against gravity. The stability of such levitation forces will also be examined along with their relation to resonance frequency shifts created by the position of the levitated object.
3

Garrett, Steven L. "One-Dimensional Propagation." In Understanding Acoustics, 453–512. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44787-8_10.

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Abstract Having already invested in understanding both the equation of state and the hydrodynamic equations, only straightforward algebraic manipulations will be required to derive the wave equation, justify its solutions, calculate the speed of sound in fluids, and derive the expressions for acoustic intensity and the acoustic kinetic and potential energy densities of sound waves. The “machinery” developed to describe waves on strings will be sufficient to describe one-dimensional sound propagation in fluids, even though the waves on the string were transverse and the one-dimensional waves in fluids are longitudinal. These results are combined with the thermal and viscous penetration depths to calculate the frequencies and quality factors in standing wave resonators. The coupling of those resonators to loudspeakers will be examined. The introduction of reciprocal transducers that are linear, passive, and reversible will allow absolute calibration of transducers using only electrical measurements (i.e., currents and voltages) by the reciprocity method, if the acoustic impedance that couples the source and receiver is calculable. Reflection and transmission at junctions between multiple ducts and other networks will be calculated and applied to the design of filters. The behavior of waves propagating through horns will provide useful impedance matching but introduce a low-frequency cut-off.
4

Zuo, Jian Min, and John C. H. Spence. "Electron Waves and Wave Propagation." In Advanced Transmission Electron Microscopy, 19–47. New York, NY: Springer New York, 2016. http://dx.doi.org/10.1007/978-1-4939-6607-3_2.

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5

Li, Xueyi, Feidong Zheng, Duoyin Wang, and Ming Chen. "Propagation and Development of Nonlinear Long Waves in a Water Saving Basin." In Lecture Notes in Civil Engineering, 565–77. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-6138-0_49.

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AbstractThe water saving lock layout plays a key role in addressing the navigation hydraulic problems with high dams. However, the study of the propagation and development of nonlinear long waves induced by ship-lock operation in a water saving basin has received less attention so far. Specially, the mechanisms governing the formation of secondary waves and the impact of these waves on the impoundments of the basin are still not fully understood. In the present study the entire evolution of a nonlinear long wave in a water saving basin was numerically simulated. The wave shape, wave celerity and wave force were analyzed. It was found that the leading edge of a long wave propagated along the water saving basin with a celerity which varied with time and space. Two distinct stages could be recognized and defined: a rapid acceleration phase characterized by a sharp increase in the celerity with propagation distance and a gentle acceleration phase where the long wave propagated in a more gradual manner. Moreover, the water surface slop of a long wave front equal to 0.045 could be used as an estimate of the occurrence of secondary waves. Furthermore, the present results highlighted the wave force on the impoundments of a water saving basin was controlled by wave nonlinearity. These results may provide theoretical guidance and technical support for the hydraulic design and operation of water saving locks.
6

Aydan, Ömer. "Waves and theory of wave propagation." In Earthquake Science and Engineering, 33–54. London: CRC Press, 2022. http://dx.doi.org/10.1201/9781003164371-3.

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7

Khalil, Abdelgalil, Faeez Masurkar, and A. Abdul-Ameer. "Estimating the Reliability of the Inspection System Employed for Detecting Defects in Rail Track Using Ultrasonic Guided Waves." In BUiD Doctoral Research Conference 2023, 190–202. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-56121-4_19.

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AbstractThis work focuses on the implementation of a data-based method to determine the inspection system reliability in terms of detecting different types of damages in rail tracks using ultrasonic-guided Rayleigh waves and a probability of detection (POD) technique. In this study, the reliability is tested against a surface crack (SC) and sub-surface damage – a through-side thickness hole (TSTH). The guided Rayleigh waves are generated using a custom-designed sensor that excites Rayleigh surface waves in the specimen and the propagating waves are sensed on the rail track surface. The wedge shape design of the sensor helps to excite a specific ultrasonic mode in the sample thereby hindering the ultrasonic energy of other coupled guided waves that can propagate simultaneously and the wedge angle is determined according to Snell’s law relying on the wave velocity of Rayleigh wave and bulk longitudinal wave. The guided wave responses as a function of varying severity of defects are obtained through a simulation study after the verification of the obtained guided wave responses with the help of an experimental study. A damage index (DI) is defined depending on defect size that gives the trend of damage severity from the captured ultrasonic responses and for monitoring defects in the rail track. This DI is eventually fed into the POD model to determine the probability of defect detection which in turn helps determine the inspection system reliability. The POD method also helps to study the critical design parameters that could affect or improve crack detection results.Purpose – To determine the reliability of inspection system deployed for interrogating health status of rail track.Methodology – Employing the Probability of detection technique for determining how reliable the inspection system is in detecting the health status of the rail track specimen using the ultrasonic guided waves.Findings – It has been found that the proposed inspection system is >90% reliable in detecting defects.Implications – This methodology can help maintenance engineers to make an informed decision on their developed technique for investigating the health status of the rail track sample.Originality/ value – 13%.
8

Mikhailov, Alexander S., and Gerhard Ertl. "Propagating Waves." In Chemical Complexity, 69–87. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-57377-9_6.

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9

Carcangiu, Sara, Augusto Montisci, and Mariangela Usai. "Waves Propagation." In Ultrasonic Nondestructive Evaluation Systems, 3–15. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-10566-6_1.

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10

Needham, Charles E. "Blast Wave Propagation." In Blast Waves, 87–99. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-05288-0_7.

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Тези доповідей конференцій з теми "Propagative waves":

1

Malinowski, Owen M., Matthew S. Lindsey, and Jason K. Van Velsor. "Ultrasonic Guided Wave Testing of Finned Tubing." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45594.

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In the past few decades, ultrasonic guided waves have been utilized more frequently Non-Destructive Testing (NDT); most notably, in the qualitative screening of buried piping. However, only a fraction of their potential applications in NDT have been fully realized. This is due, in part, to their complex nature, as well as the high level of expertise required to understand and utilize their propagation characteristics. The mode/frequency combinations that can be generated in a particular structure depend on geometry and material properties and are represented by the so-called dispersion curves. Although extensive research has been done in ultrasonic guided wave propagation in various geometries and materials, the treatment of ultrasonic guided wave propagation in periodic structures has received little attention. In this paper, academic aspects of ultrasonic guided wave propagation in structures with periodicity in the wave vector direction are investigated, with the practical purpose of developing an ultrasonic guided wave based inspection technique for finned tubing. Theoretical, numerical, and experimental methods are employed. The results of this investigation show excellent agreement between theory, numerical modeling, and experimentation; all of which indicate that ultrasonic guided waves will propagate coherently in finned tube only if the proper wave modes and frequencies are selected. It is shown that the frequencies at which propagating wave modes exist can be predicted theoretically and numerically, and depend strongly on the fin geometry. Furthermore, the results show that these propagating wave modes are capable of screening for and identifying the axial location of damage in the tube wall, as well as separation of the fins from the tube wall. The conclusion drawn from these results is that Guided Wave Testing (GWT) is a viable inspection method for screening finned tubing.
2

Behbahani-Nejad, M., and N. C. Perkins. "Forced Wave Propagation in Elastic Cables With Small Curvature." In ASME 1995 Design Engineering Technical Conferences collocated with the ASME 1995 15th International Computers in Engineering Conference and the ASME 1995 9th Annual Engineering Database Symposium. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/detc1995-0548.

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Abstract This study presents an investigation of the coupled longitudinal-transverse waves that propagate along an elastic cable. The coupling considered derives from the equilibrium curvature (sag) of the cable. A mathematical model is presented that describes the three-dimensional nonlinear response of a long elastic cable. An asymptotic form of this model is derived for the linear response of cables having small equilibrium curvature. Linear in-plane response is described by coupled longitudinal-transverse partial differential equations of motion, which are comprehensively evaluated herein. The spectral relation governing propagating waves is derived using transform methods. In the spectral relation, three qualitatively distinct frequency regimes exist that are separated by two cut-off frequencies. This relation is employed in deriving a Green’s function which is then used to construct solutions for in-plane response under arbitrarily distributed harmonic excitation. Analysis of forced response reveals the existence of two types of periodic waves which propagate through the cable, one characterizing extension-compressive deformations (rod-type) and the other characterizing transverse deformations (string-type). These waves may propagate or attenuate depending on wave frequency. The propagation and attenuation of both wave types are highlighted through solutions for an infinite cable subjected to a concentrated harmonic excitation source.
3

Di Bartolomeo, Mariano, Francesco Massi, Anissa Meziane, Laurent Baillet, and Antonio Culla. "Dynamics of Rupture at Frictional Rough Interfaces During Sliding Initiation." In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-25247.

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The aim of this work is to present the results from a non linear finite element analysis in large transformations of the contact interface between two deformable bodies when sliding initiates and the roughness is introduced at the contact surfaces. The two-dimensional in-plane dynamic model consists of two different isotropic elastic media separated by an interface governed by Coulomb friction law, and subject to remotely applied normal and shear tractions (pre-stress phase). Once the ratio between the local values of tangential and normal stresses reaches the limit value, the sliding initiates and local ruptures are activated (nucleation phase). The propagation of the ruptures over the interface and the wave propagation inside the solids are analyzed. The interactions between the waves propagating into the two solids (P waves, shear waves, surface waves) give raise to different types of ruptures. They can be classified depending on their velocity front (sub-Rayleigh, sub-shear, super-shear) or on their interface states (pulse-like, crack-like). A sinusoidal roughness is introduced at the contact surfaces and the analysis is performed for different values of the roughness parameters. Depending on the relative dimension between the roughness wavelength and the width of the wave fronts, two different behaviour can be observed: i) a coupling between the wave propagating into the two bodies; ii) a decoupling of the wave propagation inside the two materials, characterized by an independent wave propagation. First the wave propagation is analyzed when a single rupture is originated in pre-sliding conditions; successively, the wave generation during sliding initiation is addressed.
4

Maldonado, Theresa A., and Thomas K. Gaylord. "Characteristics of hybrid modes in biaxial planar waveguides." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.tuz6.

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Light propagation in biaxially anisotropic dielectric crystals may be conveniently described by the two-sheeted wave vector surface. Each sheet represents the properties of one of the two allowed orthogonally polarized propagating waves. In general, the two allowed propagating waves are "extraordinary-like," and the Poynting (ray) vector direction for each wave differs from the wave vector direction. Dielectric planar waveguides may be biaxial, either naturally or through the electro-optic effect (as is frequently the case with modulators). The electromagnetic fields in a biaxial waveguide consist of a weighted sum of four "extraordinary-like" plane waves which are coupled. The directional properties of the hybrid guided modes are determined by using a complete and concise coordinate-free approach for isolating each sheet of the wave vector surface. The ranges of propagation constants for the hybrid modes are determined as a function of the orientation of the principal dielectric axes, and this leads to the classification scheme that uniquely identifies each guided mode.
5

Chi, Sien, and Tian-Tsorng Shi. "TE waves propagating in a nonlinear planar asymmetric converging waveguide Y junction." In Nonlinear Guided-Wave Phenomena. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/nlgwp.1991.me4.

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Recently nonlinear waveguide junctions have been investigated intensively for their interesting switching behaviors1,2. The waves propagating in a nonlinear converging waveguide Y junction in which the two branches and the stem are single mode waveguides are less reported. For a linear case, the field injected into the thinner branch at a distance from the junction will not evolve into the fundamental mode of the stem, and the field injected into the thicker branch will propagate without loss3. Here we simulate the waves propagating in the Y junction with a nonlinear cladding by using beam propagation method4, and we find that the field injected into the thinner branch is possible to transmit to the stem with a high efficiency.
6

Dai, Liming, and Guoqing Wang. "Wave Field of Porous Medium Saturated by Two Immiscible Fluids Under Excitation of Multiple Wave Sources." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-13326.

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Wave propagation in porous medium saturated by immiscible fluids has received significant interests from the researchers in searching for comprehensively understanding the behavior of underground motion such as seismic wave propagation and artificial vibration in oil or gas reservoirs. In this research, the wave field of a porous medium saturated by two immiscible fluids is investigated. The elastic domain considered is excited by multiple cylindrical energy sources. The wave field of the whole domain with the excitation of several fast compressible waves in low frequency range is considered. Polar coordinates are utilized for the need of describing the multi-energy sources, so that the propagating waves can be expressed with the utilization of Hankel function. A moving-coordinate method is employed to study the coupling of multiple waves. The combined effects from several sources on the wave propagation are investigated and comparison with that of a single phase fluid is also addressed. With the employment of the methodology established, the wave field at any desired domain considered can be quantitatively determined in terms of wave propagation, frequencies and amplitudes of the source waves. To demonstrate the implementation of the model developed in this research, a numerical simulation is provided. The results of this research contribute to the comprehension of liquids and solid interaction under the excitation of waves, such as seismic, electromagnetic and other artificial vibrations.
7

Tian, Zhenhua, Guoliang Huang, and Lingyu Yu. "Study of Guided Wave Propagation in Honeycomb Sandwich Structures." In ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7642.

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This paper studies the guided waves in honeycomb sandwich structures and explores the ability of guided waves for the debonding damage detection. Both the finite element (FE) simulations and laser vibrometry experiments are used. A three-dimensional (3D) FE model is built to simulate the guided waves in a honeycomb sandwich plate. The simulation results show the guided waves in the structure depend on the wave frequency. At low frequencies, the global guided waves propagate in the entire sandwich, while leaky guided waves dominate in the skin panel at high frequencies. To further understand the guided wave propagation fundamentals, laser vibrometry experiments are performed. The waveforms, time-space wavefields, and frequency-wavenumber spectra obtained from the experiments are used to unveil the wave propagation features. The experimental results confirm the leaky guided waves. Moreover, the experimental results show the complex wave interactions induced by the honeycomb core. When the debonding between the skin and honeycomb core presents, the guided wave amplitude increases, and the wave interaction with the honeycomb core reduces.
8

van Essen, Sanne. "Variability in Encountered Waves During Deterministically Repeated Seakeeping Tests at Forward Speed." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95065.

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Abstract Numerical seakeeping codes for ships at forward speed in waves are often validated or tuned based on experiments, which makes knowledge about the experimental variability essential. This variability was evaluated using repeat tests during a state-of-the-art seakeeping campaign. A steep wave condition over the longitudinal basin axis (waveA) and a less steep oblique wave condition (waveB) were studied. Overall similarity as well as individual crest height, steepnesses and timing variability are discussed, because ship response is not equally sensitive for every point in the wave time series. The variability of the measured incoming wave crests and their timing increases with distance from the wave generator for waveA. The crest height variability for waveB is lower and more constant over the basin length (because the propagation distance to the model is constant in oblique waves and wave breaking is less likely). It was shown that only a small part of the variability close to the wave generator is caused by ‘input’ uncertainties such as the accuracy of the wave generator flap motions, measurement carriage position, their synchronisation and measurement accuracy. The rest of the variability is caused by wave and basin effects, such as wave breaking instabilities and small residual wave-induced currents from previous tests. The latter depend on previous wave conditions, which requires further study. Further work on the influence of the wave variability on the variability of ship motions, relative wave elevation along a ship and impact loads on deck of a ship at forward speed will be presented in a next publication.
9

Miller, D. A. B. "A New Principle of Wave Propagation: Huygens’ Principle Corrected After 300 Years." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.pdp16.

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Huygens' principle that every point on a wavefront can be regarded as a source of spherical wavelets is very useful, but is known to be incomplete because it would also imply backward propagating waves. Huygens (and subsequently Fresnel) simply neglected such waves "ad hoc". Later, Helmholtz and Kirchhoff showed rigorously that the wave from sources inside an arbitrary surface S could be generated by an appropriate set of point and dipole sources on S. For the special case of wavefront (mathematically, a surface approximately normal to the wave propagation on which the wave amplitude changes only slowly), Kirchhoff dropped near-field terms to obtain his diffraction theory, but in so doing lost the intuitive simplicity of Huygens' wavefront sources. I show that we can quantitatively model wave propagation from a wavefront simply by replacing Huygens' point sources by "spatio-temporal dipoles" oriented perpendicular to the wavefront. The spatiotemporal dipole consists of "positive" and "negative" point sources of spherical waves separated (infinitesimally) in space and time; the negative source is delayed relative to the "positive" source by the wave propagation time between the sources. We therefore obtain a wave propagation principle that is both rigorous and intuitive.
10

Pushkarev, Andrei, and Vladimir Zakharov. "Nonlinear Laser-Like Ocean Waves Radiation Orthogonal to the Wind." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-19357.

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Abstract We study deep water ocean wind-driven waves in strait, with wind directed orthogonally to the shore, through exact Hassel-mann equation. The strait has “dissipative” shores, there is no any reflection from the coast lines. We show that the wave turbulence evolution can be split in time into two different regimes. During the first regime, the waves propagate along the wind, and the wind-driven sea can be described by the self-similar solutions of Hasselmann equation. The second regime starts later in time, after significant enough wave energy accumulation at the down-wind boundary. Since this moment the ensemble of waves propagating against the wind starts its formation. Also, orthogonal to the wind waves, propagating along the strait, start to appear. The wave system eventually reaches asymptotic stationary state in time, consisting of two co-existing states: the first, self-similar wave ensemble, propagating with the wind, and the second – quasi-monochromatic waves, propagating almost orthogonally to the wind direction, and tending to slant against the wind at the angle of 15° closer to the wave turbulence origination shore line. Those “secondary waves” appear only due to intensive nonlinear wave-wave interaction. The total wave energy exceeds its “expected value” approximately by the factor of two, with respect to estimated in the absence of the shores. It is expected that in the reflective shores presence this amplification will grow essentially. We propose to call this “secondary” laser-like Nonlinear Ocean Waves Amplification mechanism by the acronym NOWA.

Звіти організацій з теми "Propagative waves":

1

Muhlestein, Michael, and Carl Hart. Numerical analysis of weak acoustic shocks in aperiodic array of rigid scatterers. Engineer Research and Development Center (U.S.), October 2020. http://dx.doi.org/10.21079/11681/38579.

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Nonlinear propagation of shock waves through periodic structures have the potential to exhibit interesting phenomena. Frequency content of the shock that lies within a bandgap of the periodic structure is strongly attenuated, but nonlinear frequency-frequency interactions pumps energy back into those bands. To investigate the relative importance of these propagation phenomena, numerical experiments using the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation are carried out. Two-dimensional propagation through a periodic array of rectangular waveguides is per-formed by iteratively using the output of one waveguide as the input for the next waveguide. Comparison of the evolution of the initial shock wave for both the linear and nonlinear cases is presented.
2

Ostashev, Vladimir, Michael Muhlestein, and D. Wilson. Extra-wide-angle parabolic equations in motionless and moving media. Engineer Research and Development Center (U.S.), September 2021. http://dx.doi.org/10.21079/11681/42043.

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Wide-angle parabolic equations (WAPEs) play an important role in physics. They are derived by an expansion of a square-root pseudo-differential operator in one-way wave equations, and then solved by finite-difference techniques. In the present paper, a different approach is suggested. The starting point is an extra-wide-angle parabolic equation (EWAPE) valid for small variations of the refractive index of a medium. This equation is written in an integral form, solved by a perturbation technique, and transformed to the spectral domain. The resulting split-step spectral algorithm for the EWAPE accounts for the propagation angles up to 90° with respect to the nominal direction. This EWAPE is also generalized to large variations in the refractive index. It is shown that WAPEs known in the literature are particular cases of the two EWAPEs. This provides an alternative derivation of the WAPEs, enables a better understanding of the underlying physics and ranges of their applicability, and opens an opportunity for innovative algorithms. Sound propagation in both motionless and moving media is considered. The split-step spectral algorithm is particularly useful in the latter case since complicated partial derivatives of the sound pressure and medium velocity reduce to wave vectors (essentially, propagation angles) in the spectral domain.
3

Zandi, Bahram. Propagation of optical waves in tapered fibers and metallic wave guides. Portland State University Library, January 2000. http://dx.doi.org/10.15760/etd.2688.

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4

Keller, Joseph B. Mathematical Problems of Nonlinear Wave Propagation and of Waves in Heterogeneous Media. Fort Belvoir, VA: Defense Technical Information Center, October 1986. http://dx.doi.org/10.21236/ada177549.

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5

Keller, Joseph. Mathematical Problems of Nonlinear Wave Propagation and of Waves in Heterogeneous Media. Fort Belvoir, VA: Defense Technical Information Center, October 1993. http://dx.doi.org/10.21236/ada282217.

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6

Wang, Bingnan. Wave propagation in photonic crystals and metamaterials: Surface waves, nonlinearity and chirality. Office of Scientific and Technical Information (OSTI), January 2009. http://dx.doi.org/10.2172/972072.

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7

Arnold, Joshua. DTPH56-16-T-00004 EMAT Guided Wave Technology for Inline Inspections of Unpiggable Natural Gas Pipelines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), September 2018. http://dx.doi.org/10.55274/r0012048.

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This project developed compact, lightweight, prototype Electro-Magnetic Acoustic Transducers (EMATs) and studied guided waves for defect detection, classification, and characterization in cast iron and steel pipes. Through lab testing, design, and Finite Element Analysis (FEA), guided wave propagation and defect interactions were evaluated, and the results were employed to optimize the prototype EMATs through successive design and testing iterations. The goal of developing EMATs for robotic inspection of unpiggable pipe was successfully achieved and demonstrated not only through prototype fabrication and testing but also through conceptual design modifications to ULC's CIRRIS XITM robot that incorporated EMATs onto the robot.
8

Bain, Rachel, Richard Styles, and Jared Lopes. Ship-induced waves at Tybee Island, Georgia. Engineer Research and Development Center (U.S.), December 2022. http://dx.doi.org/10.21079/11681/46140.

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Commercial vessels transiting the Savannah entrance channel intermittently generate large wake events at Tybee Island, Georgia, creating a potential hazard for beachgoers. However, not all commercial vessels generate large wakes, and the relationship between vessel dimensions, operating conditions, wake height, and drawdown magnitude is unclear. This study evaluates bathymetric data, high-frequency wave and vessel wake measurements, and broadcast vessel identification over a 4-month period with the goal of providing a quantitative characterization of vessel wake conditions at Tybee Island. Data from 1,386 cargo vessel passages and 202 tanker passages indicate that vessel dimensions (length and beam) are positively correlated with drawdown magnitude and secondary wake height, although large vessels do not consistently generate large wakes. Container ships, which tended to travel faster than tankers, corresponded to the largest wakes in the dataset. A further hypothesis is that tidally modulated energy dissipation may favor smaller vessel wake uprush at low tide and larger uprush at high tide, but this idea cannot be confirmed without additional measurements to quantify nonlinear wave propagation on the beach face. Based on the collected data, the study concludes with four recommendations for reducing risk to beachgoers.
9

Alter, Ross, Michelle Swearingen, and Mihan McKenna. The influence of mesoscale atmospheric convection on local infrasound propagation. Engineer Research and Development Center (U.S.), February 2024. http://dx.doi.org/10.21079/11681/48157.

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Infrasound—that is, acoustic waves with frequencies below the threshold of human hearing—has historically been used to detect and locate distant explosive events over global ranges (≥1,000 km). Simulations over these ranges have traditionally relied on large-scale, synoptic meteorological information. However, infrasound propagation over shorter, local ranges (0–100 km) may be affected by smaller, mesoscale meteorological features. To identify the effects of these mesoscale meteorological features on local infrasound propagation, simulations were conducted using the Weather Research and Forecasting (WRF) meteorological model to approximate the meteorological conditions associated with a series of historical, small-scale explosive test events that occurred at the Big Black Test Site in Bovina, Mississippi. These meteorological conditions were then incorporated into a full-wave acoustic model to generate meteorology-informed predictions of infrasound propagation. A series of WRF simulations was conducted with varying degrees of horizontal resolution—1, 3, and 15 km—to investigate the spatial sensitivity of these infrasound predictions. The results illustrate that convective precipitation events demonstrate potentially observable effects on local infrasound propagation due to strong, heterogeneous gradients in temperature and wind associated with the convective events themselves. Therefore, to accurately predict infrasound propagation on local scales, it may be necessary to use convection-permitting meteorological models with a horizontal resolution ≤4 km at locations and times that support mesoscale convective activity.
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Hart, Carl R., and Gregory W. Lyons. A Measurement System for the Study of Nonlinear Propagation Through Arrays of Scatterers. Engineer Research and Development Center (U.S.), November 2020. http://dx.doi.org/10.21079/11681/38621.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
Анотація:
Various experimental challenges exist in measuring the spatial and temporal field of a nonlinear acoustic pulse propagating through an array of scatterers. Probe interference and undesirable high-frequency response plague typical approaches with acoustic microphones, which are also limited to resolving the pressure field at a single position. Measurements made with optical methods do not have such drawbacks, and schlieren measurements are particularly well suited to measuring both the spatial and temporal evolution of nonlinear pulse propagation in an array of scatterers. Herein, a measurement system is described based on a z-type schlieren setup, which is suitable for measuring axisymmetric phenomena and visualizing weak shock propagation. In order to reduce directivity and initiate nearly spherically-symmetric propagation, laser induced breakdown serves as the source for the nonlinear pulse. A key component of the schlieren system is a standard schliere, which allows quantitative schlieren measurements to be performed. Sizing of the standard schliere is aided by generating estimates of the expected light refraction from the nonlinear pulse, by way of the forward Abel transform. Finally, considerations for experimental sequencing, image capture, and a reconfigurable rod array designed to minimize spurious wave interactions are specified. 15.

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