Статті в журналах: "Multimodal acoustic propagation"

1

Félix, S., and V. Pagneux. "Multimodal analysis of acoustic propagation in three-dimensional bends." Wave Motion 36, no. 2 (August 2002): 157–68. http://dx.doi.org/10.1016/s0165-2125(02)00009-4.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

2

Troian, R., D. Dragna, C. Bailly, and M. A. Galland. "Broadband liner impedance eduction for multimodal acoustic propagation in the presence of a mean flow." Proceedings of the Mavlyutov Institute of Mechanics 11, no. 2 (2016): 150–55. http://dx.doi.org/10.21662/uim2016.2.022.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Modeling of acoustic propagation in a duct with absorbing treatment is considered. The surface impedance of the treatment is sought in the form of a rational fraction. The numerical model is based on a resolution of the linearized Euler equations by finite difference time domain for the calculation of the acoustic propagation under a grazing flow. Sensitivity analysis of the considered numerical model is performed. The uncertainty of the physical parameters is taken into account to determine the most influential input parameters. The robustness of the solution vis-a-vis changes of the flow characteristics and the propagation medium is studied.

3

Liu, Juan, and Qi Li. "Coupled Mode Sound Propagation in Inhomogeneous Stratified Waveguides." Applied Sciences 11, no. 9 (April 27, 2021): 3957. http://dx.doi.org/10.3390/app11093957.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

An efficient coupled mode method for modeling sound propagation in horizontally stratified inhomogeneous waveguides, in which the seabed is modeled as a (layered) acoustic medium, is presented. The method is based on Fawcett’s coupled mode method and the multimodal admittance method. The acoustic field is expanded onto the unusual local eigenfunctions composed by normal modes in the corresponding one-layer homogeneous waveguides with constant depth equal to the local total depth of the multilayered waveguide. A set of energy-conserving first-order differential equations governing the modal amplitudes of acoustic fields is derived. The admittance method is employed to solve the differential equations in a numerically stable manna. The coupled mode method considers the backscattering effect of inhomogeneities and full coupling between local modes, and offers improvement from the viewpoint of efficiency and computational cost. The acoustic fields predicted by the method agree well with those computed by the commercial finite element software COMSOL Multiphysics. The method can be extended to further establish fast and accurate 3D sound propagation models in complex shallow water environments.

4

McTavish, James P., and Edward J. Brambley. "Nonlinear sound propagation in two-dimensional curved ducts: a multimodal approach." Journal of Fluid Mechanics 875 (July 19, 2019): 411–47. http://dx.doi.org/10.1017/jfm.2019.497.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

A method for studying weakly nonlinear acoustic propagation in two-dimensional ducts of general shape – including curvature and variable width – is presented. The method is based on a local modal decomposition of the pressure and velocity in the duct. A pair of nonlinear ordinary differential equations for the modal amplitudes of the pressure and velocity modes is derived. To overcome the inherent instability of these equations, a nonlinear admittance relation between the pressure and velocity modes is presented, introducing a novel ‘nonlinear admittance’ term. Appropriate equations for the admittance are derived which are to be solved through the duct, with a radiation condition applied at the duct exit. The pressure and velocity are subsequently found by integrating an equation involving the admittance through the duct. The method is compared, both analytically and numerically, against published results and the importance of nonlinearity is demonstrated in ducts of complex geometry. Comparisons between ducts of differing geometry are also performed to illustrate the effect of geometry on nonlinear sound propagation. A new ‘nonlinear reflectance’ term is introduced, providing a more complete description of acoustic reflection that also takes into account the amplitude of the incident wave.

5

Félix, Simon, Agnès Maurel, and Jean-François Mercier. "Improved multimodal methods for the acoustic propagation in waveguides with finite wall impedance." Wave Motion 54 (April 2015): 1–10. http://dx.doi.org/10.1016/j.wavemoti.2014.11.007.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Baccouche, Ryan, Soléne Moreau, and Mabrouk Ben Tahar. "Test of single degree of freedom acoustic treatment impedance models for multimodal acoustic propagation in duct with flow." Journal of the Acoustical Society of America 141, no. 6 (June 2017): 4168–78. http://dx.doi.org/10.1121/1.4983653.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

7

Boucheron, R., H. Bailliet, and J. C. Valiere. "Analytical solution of multimodal acoustic propagation in circular ducts with laminar mean flow profile." Journal of Sound and Vibration 292, no. 3-5 (May 2006): 504–18. http://dx.doi.org/10.1016/j.jsv.2005.08.017.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

8

Mercier, Jean-François, and Agnès Maurel. "Acoustic propagation in non-uniform waveguides: revisiting Webster equation using evanescent boundary modes." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 469, no. 2156 (August 8, 2013): 20130186. http://dx.doi.org/10.1098/rspa.2013.0186.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

The scattering of an acoustic wave propagating in a non-uniform waveguide is inspected by revisiting improved multimodal methods in which the introduction of additional modes, so-called boundary modes, allows to better satisfy the Neumann boundary conditions at the varying walls. In this paper, we show that the additional modes can be identified as evanescent modes. Although non-physical, these modes are able to tackle the evanescent part of the field omitted by the truncation and are able to restore the right boundary condition at the walls. In the low-frequency regime, the system can be solved analytically, and the solution for an incident plane wave including one or two boundary modes is shown to be an improvement of the usual Webster equation.

9

Odo, Wataru, Daisuke Kimoto, Makoto Kumon, and Tomonari Furukawa. "Active Sound Source Localization by Pinnae with Recursive Bayesian Estimation." Journal of Robotics and Mechatronics 29, no. 1 (February 20, 2017): 49–58. http://dx.doi.org/10.20965/jrm.2017.p0049.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

[abstFig src='/00290001/05.jpg' width='300' text='Schematic of the proposed system for actively localizing the sound source' ] Animals use two ears to localize the source of a sound, and this paper considers a robot system that localizes a sound source by using two microphones with active external reflectors that mimic movable pinnae. The body of the robot and the environment both affect the propagation of sound waves, which complicates mapping the acoustic cues to the source. The mapping may be multimodal, and the observed acoustic cues may lead to the incorrect estimation of the locations. In order to achieve sound source localization with such multimodal likelihoods, this paper presents a method for determining a configuration of active pinnae, which uses prior knowledge to optimize their location and orientation, and thus attenuates the effects of pseudo-peaks in the observations. The observations are also adversely affected by noise in the sensor signals, and thus Bayesian inference approach to process them is further introduced. Results of experiments that validate the proposed method are also presented.

10

Troian, Renata, Didier Dragna, Christophe Bailly, and Marie-Annick Galland. "Broadband liner impedance eduction for multimodal acoustic propagation in the presence of a mean flow." Journal of Sound and Vibration 392 (March 2017): 200–216. http://dx.doi.org/10.1016/j.jsv.2016.10.014.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Mercier, Jean-François, and Agnès Maurel. "Improved multimodal method for the acoustic propagation in waveguides with a wall impedance and a uniform flow." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, no. 2190 (June 2016): 20160094. http://dx.doi.org/10.1098/rspa.2016.0094.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

We present an efficient multimodal method to describe the acoustic propagation in the presence of a uniform flow in a waveguide with locally a wall impedance treatment. The method relies on a variational formulation of the problem, which allows to derive a multimodal formulation within a rigorous mathematical framework, notably to properly account for the boundary conditions on the walls (being locally the Myers condition and the Neumann condition otherwise). Also, the method uses an enriched basis with respect to the usual cosine basis, able to absorb the less converging part of the modal series and thus, to improve the convergence of the method. Using the cosine basis, the modal method has a low convergence, 1/ N , with N the order of truncation. Using the enriched basis, the improvement in the convergence is shown to depend on the Mach number, from 1/ N 5 to roughly 1/ N 1.5 for M =0 to M close to unity. The case of a continuously varying wall impedance is considered, and we discuss the limiting case of piecewise constant impedance, which defines pressure edge conditions at the impedance discontinuities.

12

Bailliet, H., R. Boucheron, J. P. Dalmont, Ph Herzog, S. Moreau, and J. C. Valière. "Setting up an experimental apparatus for the study of multimodal acoustic propagation with turbulent mean flow." Applied Acoustics 73, no. 3 (March 2012): 191–97. http://dx.doi.org/10.1016/j.apacoust.2011.07.008.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Fadden, Christopher, and Sri-Rajasekhar Kothapalli. "A Single Simulation Platform for Hybrid Photoacoustic and RF-Acoustic Computed Tomography." Applied Sciences 8, no. 9 (September 6, 2018): 1568. http://dx.doi.org/10.3390/app8091568.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

In recent years, multimodal thermoacoustic imaging has demonstrated superior imaging quality compared to other emerging modalities. It provides functional and molecular information, arising due to electromagnetic absorption contrast, at ultrasonic resolution using inexpensive and non-ionizing imaging methods. The development of optical- as well as radio frequency (RF)-induced thermoacoustic imaging systems would benefit from reliable numerical simulations. To date, most numerical models use a combination of different software in order to model the hybrid thermoacoustic phenomenon. Here, we demonstrate the use of a single open source finite element software platform (ONELAB) for photo- and RF-acoustic computed tomography. The solutions of the optical diffusion equation, frequency domain Maxwell’s equations, and time-domain wave equation are used to solve the optical, electromagnetic, and acoustic propagation problems, respectively, in ONELAB. The results on a test homogeneous phantom and an approximate breast phantom confirm that ONELAB is a very effective software for both photo- and RF-acoustic simulations, and invaluable for developing new reconstruction algorithms and hardware systems.

14

Kantartzis, Nikolaos V., Theodoros K. Katsibas, Christos S. Antonopoulos, and Theodoros D. Tsiboukis. "A 3D multimodal FDTD algorithm for electromagnetic and acoustic propagation in curved waveguides and bent ducts of varying cross‐section." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 23, no. 3 (September 2004): 613–24. http://dx.doi.org/10.1108/03321640410540520.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Zaccherini, R., A. Palermo, A. Marzani, A. Colombi, V. K. Dertimanis, and E. N. Chatzi. "Geometric and material attenuation of surface acoustic modes in granular media." Geophysical Journal International 230, no. 1 (February 24, 2022): 288–97. http://dx.doi.org/10.1093/gji/ggac076.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

SUMMARY Granular materials can be used in laboratory-scale physical models to simulate and study seismic wave propagation in various unconsolidated, porous heterogeneous media. This is due to the diverse available grain configurations, in terms of their shape, size and mechanical parameters, which enable the physical and geological modelling of various complex substrates. In this work, an unconsolidated granular medium, made of silica microbeads, featuring a gravity-induced power-law stiffness profile is experimentally tested in a laboratory setting. The objective is to investigate the attenuation mechanisms of vertically polarized seismic waves traveling at the surface of unconsolidated substrates that are characterized by power-law rigidity profiles. Both geometric spreading and material damping due to skeletal dissipation are considered. The understanding of these two attenuation mechanisms is crucial in seismology for properly determining the seismic site response. An electromagnetic shaker is employed to excite the granular medium between 300 and 550 Hz, generating linear modes that are localized near the surface. A densely sampled section is recorded at the surface using a laser vibrometer. The explicit solution of the geometric attenuation law of Rayleigh-like waves in layered media is employed to calculate the geometric spreading function of the vertically polarized surface modes within the granular material. In accordance with recent studies, the dynamics of these small-amplitude multimodal linear waves can be analysed by considering the granular medium as perfectly continuous and elastic. By performing a nonlinear regression analysis on particle displacements, extracted from experimental velocity data, we determine the frequency-dependent attenuation coefficients, which account for the material damping. The findings of this work show that laboratory-scale physical models can be used to study the geometric spreading of vertically polarized seismic waves induced by the soil inhomogeneity and characterize the material damping of the medium.

16

Ustinova, Elena S., Vladimir I. Volovach, Tatyana A. Antipova, and Kaira A. Adishirin-Zade. "Reflection of waves from a mobile elastic layer in a multimode waveguide." Physics of Wave Processes and Radio Systems 24, no. 2 (September 6, 2021): 73–78. http://dx.doi.org/10.18469/1810-3189.2021.24.2.73-78.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Waveguide structures are used to transmit energy and information signals in a wide range of wavelengths and, in terms of wave-guiding physical properties, usually have mutual (identical) properties in forward and backward directions. The asymmetry of the structure and external influences can often cause non-reciprocity of structures for waves, propagating in mutually opposite directions (this property, although limited, is already used in the so-called nonreciprocal devices of microwave, EHF and optical ranges such as ferrite valves, circulators, phase shifters). At the same time, the nonreciprocal properties of wave-guiding structures, independent of their physical nature, were not considered. It is found, that the motion of the medium filling the acoustic waveguide leads to nonreciprocity of its parameters in the forward and backward directions. The degree of nonreciprocity is proportional to the velocity of the medium. The velocity of the medium also affects the propagation velocity of acoustic waves and leads to a change in the critical frequencies or critical wavelengths of the waveguide modes. As the velocity of the medium increases, the number of modes for which the propagation condition is satisfied increases as well.

17

Ouédraogo, B., R. Maréchal, J. M. Ville, and E. Perrey-Debain. "Broadband noise reduction by circular multi-cavity mufflers operating in multimodal propagation conditions." Applied Acoustics 107 (June 2016): 19–26. http://dx.doi.org/10.1016/j.apacoust.2016.02.001.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

18

Bi, WenPing, Vincent Pagneux, Denis Lafarge, and Yves Aurégan. "An improved multimodal method for sound propagation in nonuniform lined ducts." Journal of the Acoustical Society of America 122, no. 1 (July 2007): 280–90. http://dx.doi.org/10.1121/1.2736785.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

19

Li, Jing. "Tunable Multimode Filtering of Solid Acoustic Waves in a Three-Component Phononic Crystal Slab." Advanced Materials Research 150-151 (October 2010): 1625–39. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.1625.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Using of the multiple scattering methods, we characterize the positive and negative multi-refraction and transmission properties of a solid-based phononic crystal composed of coated solid inclusions in view of its applications in tunable multimode filtering. The geometrical parameters are chosen so that a left-handed longitudinal wave mode and a right-handed transverse wave mode, are simultaneously obtained in this three-component phononic crystal. When multimode Gaussian beams are placed transmitting through the phononic crystal slab, both positive and negative refractions are observed. We then study the individual propagation behavior of different modes. The angle dependent transmission beams with different energy distributions are found at the other side of the slab. Transmitted transverse waves coming from different directions incidence finally walk together into four oriented beams. Meanwhile, longitudinal wave incidence with different directions behaves simply as negative refraction in the slab. A far-field longitudinal wave image can be achieved being excited by a longitudinal wave point source. The three-component phononic crystal slab thus can be served as an alternate in tunable multimode filtering devices.

20

Gentili, G. G., M. Khosronejad, G. Bernasconi, S. Perotto, and S. Micheletti. "Efficient modeling of multimode guided acoustic wave propagation in deformed pipelines by hierarchical model reduction." Applied Numerical Mathematics 173 (March 2022): 329–44. http://dx.doi.org/10.1016/j.apnum.2021.12.008.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

21

Núñez, Ismael, and Carlos Negreira. "Efficiency parameters in time reversal acoustics: Applications to dispersive media and multimode wave propagation." Journal of the Acoustical Society of America 117, no. 3 (March 2005): 1202–9. http://dx.doi.org/10.1121/1.1856272.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

22

Guennoc, Thomas, Jean-Baptiste Doc, and Simon Félix. "Improved multimodal formulation of the wave propagation in a 3D waveguide with varying cross-section and curvature." Journal of the Acoustical Society of America 149, no. 1 (January 2021): 476–86. http://dx.doi.org/10.1121/10.0003336.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Merklein, Moritz, Birgit Stiller, Khu Vu, Pan Ma, Stephen J. Madden, and Benjamin J. Eggleton. "On-chip broadband nonreciprocal light storage." Nanophotonics 10, no. 1 (October 2, 2020): 75–82. http://dx.doi.org/10.1515/nanoph-2020-0371.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

AbstractBreaking the symmetry between forward- and backward-propagating optical modes is of fundamental scientific interest and enables crucial functionalities, such as isolators, circulators, and duplex communication systems. Although there has been progress in achieving optical isolation on-chip, integrated broadband nonreciprocal signal processing functionalities that enable transmitting and receiving via the same low-loss planar waveguide, without altering the frequency or mode of the signal, remain elusive. Here, we demonstrate a nonreciprocal delay scheme based on the unidirectional transfer of optical data pulses to acoustic waves in a chip-based integration platform. We experimentally demonstrate that this scheme is not impacted by simultaneously counterpropagating optical signals. Furthermore, we achieve a bandwidth more than an order of magnitude broader than the intrinsic optoacoustic linewidth, linear operation for a wide range of signal powers, and importantly, show that this scheme is wavelength preserving and avoids complicated multimode structures.

24

Sugimoto, Rie, R. Jeremy Astley, Claire R. McAleer, and Iansteel Achunche. "A numerical study on multimode sound propagation in lined ducts and radiation to the far field." Journal of the Acoustical Society of America 123, no. 5 (May 2008): 3128. http://dx.doi.org/10.1121/1.2933070.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Bauer, Adam Q., Christian C. Anderson, Karen R. Marutyan, G. Larry Bretthorst, Keith A. Wear, Mark R. Holland, and James G. Miller. "Experimental confirmation of negative dispersion and Bayesian inversion of multimode propagation in a bone‐mimicking phantom." Journal of the Acoustical Society of America 123, no. 5 (May 2008): 3512. http://dx.doi.org/10.1121/1.2934415.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Alleyne, D., and P. Cawley. "A two-dimensional Fourier transform method for the measurement of propagating multimode signals." Journal of the Acoustical Society of America 89, no. 3 (March 1991): 1159–68. http://dx.doi.org/10.1121/1.400530.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Yang, Minye, Zhilu Ye, Mohamed Farhat, and Pai-Yen Chen. "Cascaded PT-symmetric artificial sheets: multimodal manipulation of self-dual emitter-absorber singularities, and unidirectional and bidirectional reflectionless transparencies." Journal of Physics D: Applied Physics 55, no. 8 (November 15, 2021): 085301. http://dx.doi.org/10.1088/1361-6463/ac3300.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Abstract We introduce cascaded parity-time (PT)-symmetric artificial sheets (e.g. metasurfaces or frequency selective surfaces) that may exhibit multiple higher-order laser-absorber modes and bidirectional reflectionless transmission resonances within the PT-broken phase, as well as a unidirectional reflectionless transmission resonance associated with the exceptional point (EP). We derive the explicit expressions of the gain–loss parameter required for obtaining these modes and their intriguing physical properties. By exploiting the cascaded PT structures, the gain–loss threshold for the self-dual laser-absorber operation can be remarkably lowered, while the EP remains unaltered. We further study interferometric sensing based on such a multimodal laser-absorber and demonstrate that its sensitivity may be exceptionally high and proportional to the number of metasurfaces along the light propagation direction.

28

Zhu, Wujun, Yanxun Xiang, Chang-jun Liu, Mingxi Deng, Congyun Ma, and Fu-zhen Xuan. "Fatigue Damage Evaluation Using Nonlinear Lamb Waves with Quasi Phase-Velocity Matching at Low Frequency." Materials 11, no. 10 (October 9, 2018): 1920. http://dx.doi.org/10.3390/ma11101920.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Due to the dispersive and multimode natures, only nonlinear Lamb waves with exact phase-velocity matching were generally used in previous studies to evaluate the evenly distributed microstructural evolution in the incipient stage of material degradation, because of the cumulative generation of second harmonics, which was also found within a significant propagation distance for mode pair S0-s0 with quasi phase-velocity matching at low frequency. To explore the feasibility of fatigue damage evaluation by using this mode pair and fully utilize its unique merits, the cumulative second harmonic analysis was performed on aluminum alloy specimens with various material damage produced by the continuous low cycle fatigue tests. Similar to mode pair S1-s2 with exact phase-velocity matching, a mountain shape curve between the normalized acoustic nonlinearity parameter and the fatigue life was also achieved with the peak point at about 0.65 fatigue life for mode pair S0-s0, even though a relatively higher sensitivity to fatigue damage was observed for mode pair S1-s2. The excited frequency selection was further analyzed in a certain frequency range, where the quasi phase-velocity matching condition was satisfied for mode pair S0-s0 owing to the less dispersive property. Results show that the fatigue damage can be effectively detected using the mode pair S0-s0, and a relatively lower excited frequency was preferred due to its higher sensitivity to microstructural evolution.

29

Raghavan, Ajay, and Carlos E. S. Cesnik. "3-D Elasticity-Based Modeling of Anisotropic Piezocomposite Transducers for Guided Wave Structural Health Monitoring." Journal of Vibration and Acoustics 129, no. 6 (February 8, 2007): 739–51. http://dx.doi.org/10.1115/1.2748776.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Anisotropic piezocomposite transducers (APTs), such as macro fiber composites and active fiber composites, have great potential to be used as structurally integrated transducers for guided-wave (GW) structural health monitoring. Their main advantages over conventional monolithic piezoceramic wafer transducers are mechanical flexibility, curved surface conformability, power efficiency, their ability to excite focused GW fields, and their unidirectional sensing capability as a GW sensor. In this paper, models are developed to describe excitation of GW fields by APTs in isotropic structures. The configurations explored are plane Lamb-wave fields in beams with rectangular cross-section, axisymmetric GW fields in cylinders, and 3-D GW fields in plates. The dynamics of the substrate and transducer are assumed uncoupled. The actuator is modeled as causing shear traction at the edges of the actuator’s active area along the fiber direction. The sensor is modeled as sensing the average extensional strain over the active area along the fiber direction. The work is unique in that the formulation is based on 3-D elasticity, and no reduced-order structural assumptions are used. This is crucial to model multimodal GW propagation, especially at high frequencies. A formulation is also proposed to model the behavior of APTs as GW sensors. Finally, results from experimental tests to examine the validity of the models are discussed and the possible sources of error are examined in detail.

30

Kauffmann, Pierre, Marie-Aude Ploix, Jean-François Chaix, Cécile Gueudre, Gilles Corneloup, and François Baque. "Interferences in the re-emission field of multimodal leaky lamb waves propagating in an immersed plate: Analytical modelling, simulation and experimentation." Journal of Sound and Vibration 465 (January 2020): 115015. http://dx.doi.org/10.1016/j.jsv.2019.115015.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

31

Prasad, Rajan, and Abhijit Sarkar. "Broadband Seismic Isolation of Periodic Ladder Frame Structure." Journal of Vibration and Acoustics 143, no. 1 (July 28, 2020). http://dx.doi.org/10.1115/1.4047704.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Abstract Ladder frame structures are used as models for multistorey buildings. These periodic structures exhibit alternating propagating and attenuating frequency bands. Of the six different wave modes of propagation, two modes strongly attenuate at all frequencies. The other four modes have nonoverlapping stop band characteristics. Thus, it is challenging to isolate such structures when subjected to broadband, multimodal base excitation. In this study, we seek to synthesize a periodic ladder frame structure that has attenuation characteristics over the maximal range of frequencies for all the modes of wave propagation. We synthesize a unit cell of the periodic structure, which comprises two distinct regions having different inertial, stiffness, and geometric properties. The eigenvalues of the transfer matrix of the unit cell determines the attenuating or the nonattenuating characteristics of the structure. A novel pictorial presentation in the form of eigenvalue map is developed. This is used to synthesize the optimal unit cell. Also, design guidelines for suitable selection of the design parameters are presented. It is shown that a large finite periodic structure comprising a unit cell synthesized using the present approach has significantly better isolation characteristics in comparison to the homogeneous or any other arbitrarily chosen periodic structure.

32

Dawidowski, David, Richard Nauber, Lars Büttner, and Jürgen Czarske. "Time reversal ultrasound focusing through multimode waveguides." tm - Technisches Messen 84, no. 9 (January 1, 2017). http://dx.doi.org/10.1515/teme-2016-0062.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

AbstractUltrasound imaging in harsh environments, such as the continuous steel casting process, benefits from a spatial separation of sensors and measuring volume to avoid damaging e.g. because of high temperatures. This can be achieved through acoustical multimode waveguides. To focus ultrasound in the measuring volume despite the complex sound propagation, we propose using the time reversal technique. We present numerical simulations and experiments using the phased array ultrasound Doppler velocimeter to focus through a water filled waveguide with a 64 element array. A resolution in the millimetre range is achieved for a 68 mm long waveguide.

Статті в журналах з теми "Multimodal acoustic propagation"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями