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Experimental data on the motion parameters of a steel spherical impactor whose diameter is 13.5 mm and which moves in a sandy medium at a velocity of 1470 m/s are presented. Induction sensors and the PIV (particle image velocimetry) method are used to record the impactor motion near a sandy obstacle and in a sandy medium, thereby allowing one to visualize a surface wave via high-speed video recording of the sand surface. The values of the parameters characterizing the impactor motion in the sandy medium and the surface wave propagation are obtained.

The theoretical analysis of hybrid surface wave propagation at chiral-plasma planar interface is presented in this manuscript. The dispersion relation is obtained for the proposed structure by appl...

In the present investigation, surface wave propagation in a semiconducting medium under photothermal theory has been discussed. A non-viscous fluid of uniform thickness is overlying the infinite se...

As an attempt to develop a reconfigurable surface architecture that can use liquid metal such as Galinstan to shape surface channels on demand, this paper considers a punctured surface where cavities are evenly distributed and can be filled with liquid metal potentially via digitally controlled pumps. In this paper, we look at the benefits of such architecture in terms of surface-wave signal enhancement and isolation, and examine how various system parameters impact the performance using full wave 3-dimensional electromagnetic simulations. It is shown that extraordinary signal shaping can be obtained.

A shallow water theory is developed which applies to surface wave propagation over structured bathymetry comprising rapid abrupt fluctuations in depth between two smoothly varying levels. Using a homogenization approach coupled to the depth-averaging process which underpins shallow water modelling, governing equations for the wave elevation are derived which explicitly relate local spatially varying anisotropy of wave speeds to properties of the microstructured bed. The model is applied to two water wave scattering problems both to demonstrate the complex wave propagation characteristics exhibited by structured beds and to provide examples of how to use structured beds to engineer bespoke wave propagation. This includes propagating waves with practically zero reflection and loss of form through circular bends in channels.

Due to the compact size planar design and economical aspects microstrip patch antenna are mostly been used for wireless communication. The major disadvantage in the method is that serious hindrances of polarization mismatch and surface wave propagation. The hindrance of the surface wave propagation can be reduced using electromagnetic band gap structure. The main technique involved in this method is the suppression of the surface wave propagation

International audience

International audience; Rockfalls generate seismic signals that can be used to detect and monitor rockfall activity. Event locations can be estimated on the basis of arrival times, amplitudes, or polarization of these seismic signals. However, surface topography variations can significantly influence seismic wave propagation and hence compromise results. Here, we specifically use the signature of topography on the seismic signal to better constrain the source location. Seismic impulse responses are predicted using Spectral Element based simulation of three dimensional wave propagation in realistic geological media. Subsequently, rockfalls are located by minimizing the misfit between simulated and observed inter station energy ratios. The method is tested on rockfalls at Dolomieu crater, Piton de la Fournaise volcano, Reunion Island. Both single boulder impacts and distributed granular flows are successfully located, tracking the complete rockfall trajectories by analyzing the signals in sliding time windows. Results from the highest frequency band (here 13-17 Hz) yield the best spatial resolution, making it possible to distinguish detachment positions less than 100 m apart. By taking into account surface topography, both vertical and horizontal signal components can be used. Limitations and the noise robustness of the location method are assessed using synthetic signals. Precise representation of the topography controls the location resolution, which is not significantly affected by the assumed impact direction. Tests on the network geometry reveal best resolution when the seismometers triangulate the source. We conclude that this method can improve the monitoring of rockfall activity in real time once a simulated database for the region of interest is created.

This work presents a metamaterial structure to improve the isolation between two linear slotted waveguide arrays. The proposed decoupling structure consists of two columns of metal pin arrays that can suppress surface wave propagation. Also, the resulting structure only takes up a small space between the radiating slots of the two arrays. Simulated results show a 5 dB improvement in the inter-element isolation without a significant impact on the antenna radiation performance. Moreover, the reflection coefficient bandwidth can be slightly increased.

International audience; This paper deals with a new definition of the Radar Cross Section suitable for surface wave propagation in the HF band. Indeed, it can be shown that the classical definition of the RCS cannot converge for this kind of propagation. This is an issue for the performance assessment of High Frequency Surface Wave Radars. Thanks to the analysis of different wave propagation models, the differences between the space wave propagation and surface wave propagation have been highlighted. The required modifications of the RCS should then be performed. The new definition is explained in the paper and it is shown that it is suitable for the surface wave propagation. Moreover, this new definition has been used for the computation of the RCS of 3D naval targets and the obtained results will be presented during the conference.

Electromechanical Impedance (EMI) approach is a widely used Structural Health Monitoring (SHM) method. The EMI of a piezoelectric disk is monitored with an impedance analyzer or impedance measurement chip. In addition to the cracks, EMI may monitor compressive forces and may be used for detection of loose bolts. Surface Response to Excitation (SuRE) method is a low-cost alternative to the EMI method. The SuRE method uses one piezoelectric disk for excitation and a sensor to monitor the surface wave propagation. Digitization and Fast Fourier Transformation (FFT) of the signal of the sensor, such as another piezoelectric disk, is satisfactory to monitor the characteristics of the system. The important weakness of both approaches is not being able to estimate the location of the defect at their minimal configuration. Recently, Additive Manufacturing (AM) has been used for the manufacturing of parts for various reasons. The layer by layer part building techniques of the AM methods allow for the hiding of geometric features behind the part’s exposed skin. Use of the hidden features of the additively manufactured parts is proposed in the paper to help the SuRE method for estimation of the location of defects. Experimental studies verified the validity of the proposed approach. In addition, the EMI methods may benefit from this same approach.

The present investigation is focused on studying the surface wave propagation in a generalized magneto-thermoelastic materials taking (Green Lindsay) model with voids. The general surface wave speed is derived to study the effects of magnetic field and rotation on surface wave in the presence of voids. In addition the present study can be comprehensively applied to the magneto-thermoelastic medium with voids. The possible non-dimensional frequency of surface wave propagation has been obtained as the solution of an algebraic equation involving a determinant whose elements contain the material parameters, the direction of applied magnetic field and rotation of surface wave propagation. The comparisons for the physical quantities are established numerically and represented graphically in different cases with respect to the used effects. Keywords: Green Lindsay theory, Thermoelasticity, Surface waves

Seven subsurface Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats measured the voltage induced by the motional induction of seawater under Typhoon Fanapi in 2010. Measurements were processed to estimate high-frequency oceanic velocity variance associated with surface waves. Surface wave peak frequency fp and significant wave height Hs are estimated by a nonlinear least squares fitting to , assuming a broadband JONSWAP surface wave spectrum. The Hs is further corrected for the effects of float rotation, Earth’s geomagnetic field inclination, and surface wave propagation direction. The fp is 0.08–0.10 Hz, with the maximum fp of 0.10 Hz in the rear-left quadrant of Fanapi, which is ~0.02 Hz higher than in the rear-right quadrant. The Hs is 6–12 m, with the maximum in the rear sector of Fanapi. Comparing the estimated fp and Hs with those assuming a single dominant surface wave yields differences of more than 0.02 Hz and 4 m, respectively. The surface waves under Fanapi simulated in the WAVEWATCH III (ww3) model are used to assess and compare to float estimates. Differences in the surface wave spectra of JONSWAP and ww3 yield uncertainties of 10% within the eyewall. The estimated fp is 10% less than the simulated before the passage of Fanapi’s eye and 20% less after eye passage. Most differences between Hs and simulated are

The present article is concerned with the Stroh analysis of Rayleigh surface wave propagation in anisotropic homogeneous thermoelastic medium. The problem is considered in the context of th...

Subsurface velocity structures must be estimated to predict long-period ground motions and seismic hazards. Subsurface velocity structures can be constructed via an inversion of the horizontal-to-vertical (H/V) spectral ratio of microtremor (MHV) curves; thus, a method of simulating the MHV curves is key. In this study, we use the H/V spectral ratio of the surface wave (SHV) based on the surface wave propagation theory in a layered half-space to simulate the MHV curves at sites A and B of the Yuxi basin. Then, we attempt to analyze the features of the SHV curves. We find the H/V ratio of the microtremor loading source to be independent of the peak frequency of the SHV curve, but it has some relation to the amplitude of the SHV curve. Moreover, to reduce the error in subsurface velocity structures obtained by the MHV curves, we suggest that the SHV curves at near-peak frequencies should not be considered in the inversion, because the amplitude deviation is higher at the peak frequency of the MHV curve. In addition, the best frequency ranges for the inversion of the microtremor H/V spectrum are between the peak and trough frequencies of the microtremor H/V spectrum.

We extend the conformal mapping technique for water waves over topography, from its natural two-dimensional (2D) setting to three dimensions (3D) where the Laplacian, from potential theory, is no l...

Wentzel–Kramers–Brillouin approximation technique serves as a powerful tool to find the particle displacements due to surface wave propagation in bedded structure with distinct material properties....

The present paper deals with the mathematical modeling of the propagation of torsional surface waves in a non-homogeneous transverse isotropic elastic half-space under a rigid layer. Both rigidities and density of the half-space are assumed to vary inversely linearly with depth. Separation of variable method has been used to get the analytical solutions for the dispersion equation of the torsional surface waves. Also, the effects of nonhomogeneities on the phase velocity of torsional surface waves have been shown graphically. Also, dispersion equations have been derived for some particular cases, which are in complete agreement with some classical results.

The mild-slope equations, devised to approximate surface wave propagation over water of slowly varying depth, have hitherto been based on either the velocity potential formulation or the streamfunction formulation. By using a more general version of the governing equations, a single framework is developed that relates the existing mild-slope equations and provides new examples and derivations.

The July 6 , 2019 M 7.1 Ridgecrest earthquake event originated north north-east of Los Angeles, at a distance of ~150 km as a result of shallow strike slip faulting in the crust of the North America plate. Using a very effective tool, referred to as the Normalized Inner Product (NIP), we detect, identify and extract surface wave energy propagating in the Los Angeles Basin induced by the abovementioned event. We identified both Love and Rayleigh waves, and assessed the spatial distribution of their amplitudes and durations. Love wave energy is propagating to the S, SW with an average azimuthal direction of 217˚, while Rayleigh wave energy propagates to the W, SW with an azimuthal direction 242˚. The dominant frequency of the most energetic Love waves is < 0.15 Hz. Stations that have recorded very strong Love waves are located in the vicinity of the deepest parts of the basin and in close proximity to regions where the basin displays the greatest gradients (south of downtown LA and reasonably close to the LA airport). Low frequency Love wave energy is observed also at the south-eastern part of the basin where its depth displays much smaller gradients, but it is not as strong. The duration of Love waves increases as one moves to the deepest parts of the basin. However, the increase in the duration never exceeds 10% of the duration of the remaining energy present in the signal. The dominant frequency of Rayleigh wave energy lies in the range 0.10 to 0.20 Hz, consistently throughout the basin. The Rayleigh waves are less energetic than Love waves and their peak amplitudes are observed more to the south. Rayleigh waves have been identified also outside the basin. The distributions of their duration is less clear as compared to those of Love waves. Nevertheless, the largest delay time is observed in the vicinity of the SW edge of the basin, and the duration does not exceed that of the remaining signal (i.e. after extraction of the Rayleigh wave energy).