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AbstractThe paper explores the increasing concern over environmental vibrations resulting from machine operation and rail transit. Notably, low-frequency vibrations generate surface waves with characteristics like significant energy carrying capacity, long-distance propagation, and slow attenuation. The primary challenge in ground vibration attenuation lies in addressing low-frequency vibrations. The study employs the finite element method to investigate the vibration attenuation of a three-component local resonance pile in three-dimensional space. The analysis delves into the impact of the unit cell structure’s geometry size on bandgaps, and the influences of the period number on the Attenuation Zones (AZs) are also discussed. Furthermore, a comparison is made regarding the vibration attenuation performance of a two-component local resonance pile. The findings reveal that the appropriate design of a three-component local resonance pile can generate low-frequency complete bandgap. The concrete radius, rubber layer thickness, and buried depth of the pile significantly affect Rayleigh wave bandgap. Frequency domain analysis indicates that an increase in period number expands AZs into the bandgap range. Time domain analysis demonstrates a noticeable decrease in ground acceleration amplitude within the bandgap range. The research results presented in this paper offer a novel approach to address the low-frequency vibration attenuation. [ABSTRACT FROM AUTHOR]

The analytical and numerical treatments of horizontal and vertical forced time-harmonic vibrations of a rigid circular foundation in a transversely isotropic elastic half-space ground are presented. A complete discussion on the boundary conditions and elastic wave propagation due to horizontal and vertical vibrations of the foundation on the half-space is presented and a comparison is made with the full-space problem. With the aid of appropriate dynamic Green's functions reported in the literature, the horizontal and vertical vibrations of the foundation are treated analytically, and the results are expressed in terms of the solutions of several Fredholm integral equations. For these two vibration modes, the relations for the contact normal and shear stresses, the resultant forces acting on the foundation, and the dimensionless impedance and compliance functions are given. To validate the analytical formulations, the results obtained in this paper are reduced to static responses for transversely isotropic half-space, and to dynamic responses for isotropic half-space; and compared with the results reported in the literature. An efficient numerical procedure is presented to evaluate the semi-infinite integrals appeared in the analytical solutions utilizing some features of the Mathematica software. The Fredholm integral equations and impedance and compliance functions are solved and evaluated numerically using the Gaussian quadrature method. Some graphical results are provided to present the impedance and compliance functions for different transversely isotropic materials. The effects of material anisotropy, as well as the frequency of excitation on the responses are discussed. The differences between vibrations of rigid foundations in the half-space and full-space mediums are emphasized in view of the Rayleigh wave propagation. Moreover, the difficulties related to numerical procedures needed for handling the strong singularities due to propagation of Rayleigh waves in the half-space media are presented. [ABSTRACT FROM AUTHOR]

We report a home-built velocity-gradient-tensor-resolved particle image velocimetry (VGTR-PIV) system which spatio-temporally resolves all components of the velocity gradient tensor. This technique is applied to the paradigmatic turbulent Rayleigh–Bénard convection system in a cylindrical cell at three representative positions, i.e. centre, side and bottom regions. The VGTR-PIV system allows us to directly measure, for the first time, the spatio-temporally resolved energy dissipation rate and enstrophy in turbulent thermal convection. In the experiment, the Rayleigh number $Ra$ varied in the range $2 \times 10^8 \leqslant Ra \leqslant 8 \times 10^9$ and the Prandtl number $Pr$ was fixed at $Pr = 4.34$. Compared with the fully resolved energy dissipation rate $\varepsilon$ , the pseudo-dissipation provides the best estimate within $3\,\%$ , the planar (two-dimensional) surrogate has a larger relative error and the one-dimensional surrogate leads to the largest error. The power-law scalings of the time-averaged energy dissipation rate with the Rayleigh number follow $\langle \varepsilon _c \rangle _t / (\nu ^3 H^{-4}) = 9.86 \times 10^{-6} Ra^{1.54 \pm 0.02}$ , $\langle \varepsilon _s \rangle _t / (\nu ^3 H^{-4}) = 9.26 \times 10^{-3} Ra^{1.25 \pm 0.02}$ and $\langle \varepsilon _b \rangle _t / (\nu ^3 H^{-4}) = 2.70 \times 10^{-2} Ra^{1.23 \pm 0.02}$ in the centre, side and bottom regions, respectively where $\nu$ is dynamic viscosity and $H$ is cell height. These scaling relations, along with our earlier measured time-averaged energy dissipation rate at the bottom wall surface $\langle \varepsilon _w \rangle _t / (\nu ^3 H^{-4}) = 9.65 \times 10^{-2} Ra^{1.25 \pm 0.02}$ (J. Fluid Mech. , vol. 947, 2022, A15), provide important constraints against which theoretical models may be tested. For the centre and side locations in the convection cell, the probability density functions (p.d.f.s) of the energy dissipation rate and enstrophy both follow a stretched exponential distribution. For the bottom region, the p.d.f.s of dissipation and enstrophy exhibit a stretched exponential distribution outside the viscous boundary layer and an exponential distribution inside the viscous boundary layer. It is also found that extreme events with high dissipation are the most intermittent in the side region, whereas the bottom region is less intermittent than the cell centre. [ABSTRACT FROM AUTHOR]

In this paper, we propose and demonstrate a network analysis optical frequency domain reflectometer (NA-OFDR) for distributed temperature measurements at high spatial (down to ≈3 cm) and temperature resolution. The system makes use of a frequency-stepped, continuous-wave (cw) laser whose output light is modulated using a vector network analyzer. The latter is also used to demodulate the amplitude of the beat signal formed by coherently mixing the Rayleigh backscattered light with a local oscillator. The system is capable of attaining high measurand resolution (≈50 mK at 3-cm spatial resolution) thanks to the high sensitivity of coherent Rayleigh scattering to temperature. Furthermore, unlike the conventional optical-frequency domain reflectometry (OFDR), the proposed system does not rely on the use of a tunable laser and therefore is less prone to limitations related to the laser coherence or sweep nonlinearity. Two configurations are analyzed, both numerically and experimentally, based on either a double-sideband or single-sideband modulated probe light. The results confirm the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

Ice accumulation on infrastructure poses severe safety risks and economic losses, necessitating effective detection and monitoring solutions. This study introduces a novel approach employing surface acoustic wave (SAW) sensors, known for their small size, wireless operation, energy self-sufficiency, and retrofit capability. Utilizing a SAW dual-mode delay line device on a 64°-rotated Y-cut lithium niobate substrate, we demonstrate a solution for combined ice detection and temperature measurement. In addition to the shear-horizontal polarized leaky SAW, our findings reveal an electrically excitable Rayleigh-type wave in the X+90° direction on the same cut. Experimental results in a temperature chamber confirm capability for reliable differentiation between liquid water and ice loading and simultaneous temperature measurements. This research presents a promising advancement in addressing safety concerns and economic losses associated with ice accretion. [ABSTRACT FROM AUTHOR]

Background: Transthoracic echocardiography (TTE) is the gold standard modality for evaluating cardiac morphology, function, and hemodynamics in clinical practice. While artificial intelligence (AI) is expected to contribute to improved accuracy and is being applied clinically, its impact on daily clinical practice has not been fully evaluated. Methods: We retrospectively examined 30 consecutive patients who underwent AI-equipped TTE at a single institution. All patients underwent manual and automatic measurements of TTE parameters using the AI-equipped TTE. Measurements were performed by three sonographers with varying experience levels: beginner, intermediate, and expert. Results: A comparison between the manual and automatic measurements assessed by the experts showed extremely high agreement in the left ventricular (LV) filling velocities (E wave: r = 0.998, A wave: r = 0.996; both p < 0.001). The automated measurements of LV end-diastolic and end-systolic diameters were slightly smaller (−2.41 mm and −1.19 mm) than the manual measurements, although without significant differences, and both methods showing high agreement (r = 0.942 and 0.977, both p < 0.001). However, LV wall thickness showed low agreement between the automated and manual measurements (septum: r = 0.670, posterior: r = 0.561; both p < 0.01), with automated measurements tending to be larger. Regarding interobserver variabilities, statistically significant agreement was observed among the measurements of expert, intermediate, and beginner sonographers for all the measurements. In terms of measurement time, automatic measurement significantly reduced measurement time compared to manual measurement (p < 0.001). Conclusions: This preliminary study confirms the accuracy and efficacy of AI-equipped TTE in routine clinical practice. A multicenter study with a larger sample size is warranted. [ABSTRACT FROM AUTHOR]

The primary purpose of this study is to develop an asymptotic formulation for boundary value problems in a non-local elastic half-space. For the sake of simplicity, the non-locality is limited to the vertical direction, which is represented by a one-dimensional exponential kernel, and the problem is formulated within the framework of Eringen's theory. The proposed asymptotic approach is based on the assumption that the internal characteristic length is significantly smaller than a typical wavelength. This assumption allows for the development of an asymptotic formulation that expresses the considered boundary value problem in terms of local stresses. Additionally, the formulation includes explicit correction terms to the classical boundary conditions, which arise from the non-local effects. As an example application of the derived formulation, the Rayleigh surface waves in a plane strain problem are considered. Finally, numerical results are presented for certain specific values of elastic parameters to illustrate the effects of non-locality on the analyzed system. [ABSTRACT FROM AUTHOR]

We determined the velocity structure of the upper crust in the Jiaodong area using double difference seismic tomography, and found that the Jiaodong inland area near the surface (0–5 km) is mainly characterized by high-velocity anomaly, and there are several obvious low-velocity anomalies in the Bohai Sea. The Queshan metamorphic core complex shows obvious low-velocity anomaly at the depth of 5–15 km, and the southern part of the Linglong shows low-velocity anomaly at the depth of 10–20 km. It indicates the existence of significant mantle material upwelling and magmatic activity beneath metamorphic core complex. The Linglong and Queshan metamorphic core complex may be still in the process of uplift. The high-velocity anomaly of the Wulian-Yantai fault is likely closely related to the basic to ultrabasic rocks from the mantle. The basic to ultrabasic rocks upwelling along the Wulian-Yantai fault zone is segmented and mainly concentrated in the southern of the fault zone. [ABSTRACT FROM AUTHOR]

We investigate the self-modulation of Love waves propagating in a nonlinear half-space covered by a nonlinear layer. We assume that the constituent material of the layer is nonlinear, homogeneous, isotropic, compressible, and hyperelastic, whereas for the half-space, it is nonlinear, heterogeneous, compressible and a different hyperelastic material. By employing the nonlinear thin layer approximation, the problem of wave propagation in a layered half-space is reduced to the one for a nonlinear heterogeneous half-space with a modified nonlinear homogeneous boundary condition on the top surface. This new problem is analyzed by a relevant perturbation method, and a nonlinear Schrödinger (NLS) equation defining the self-modulation of waves asymptotically is obtained. The dispersion relation is derived for different heterogeneous properties of the half-space and the thin layer. Then the results of the thin layer approximation are compared with the ones for the finite layer obtained in Teymur et al. (Int J Eng Sci 85:150–162, 2014). The solitary solutions of the derived NLS equation are obtained for selected real material models. It has been discussed how these solutions are influenced by the heterogeneity of the semi-infinite space. [ABSTRACT FROM AUTHOR]

This paper deals with in situ characterization of the small-strain shear-wave velocity VS and damping ratio DS from an advanced interpretation of Multi-channel Analysis of Surface Waves (MASW) surveys. A new approach based on extracting Rayleigh wave data using the CFDBFa method has been discussed in the companion paper. This paper focuses on mapping the experimental Rayleigh wave phase velocity and attenuation into profiles of VS and DS versus depth, which is achieved through a joint inversion procedure. The joint inversion of phase velocity and attenuation data utilizes a newly developed Monte Carlo global search algorithm, which implements a smart sampling procedure. This scheme exploits the scaling properties of the solution of the Rayleigh eigenvalue problem to modify the trial earth models and improve the matching with the experimental data. Thus, a reliable result can be achieved with a limited number of trial ground models. The proposed algorithm is applied to the inversion of synthetic data and of experimental data collected at the Garner Valley Downhole Array site, as described in the companion paper. In general, inverted soil models exhibit well-defined VS profiles, whereas DS profiles are affected by larger uncertainties. Greater uncertainty in the inverted DS profiles is a direct result of higher variability in the experimental attenuation data, the limited wavelength range at which reliable values of attenuation parameters can be retrieved, and the sensitivity of attenuation data to both DS and VS. Nonetheless, the resulting inverted earth models agree well with alternative in situ estimates and geological data. The results stress the feasibility of retrieving both stiffness and attenuation parameters from active-source MASW testing and the effectiveness of extracting in situ damping ratio estimates from surface wave data. [ABSTRACT FROM AUTHOR]

A robust, in situ estimate of shear-wave velocity VS and the small-strain damping ratio DS (or equivalently, the quality factor QS) is crucial for the design of buildings and geotechnical systems subjected to vibrations or earthquake ground shaking. A promising technique for simultaneously obtaining both VS and DS relies on the Multichannel Analysis of Surface Waves (MASW) method. MASW can be used to extract the Rayleigh wave phase velocity and phase attenuation data from active-source seismic traces recorded along linear arrays. Then, these data can be inverted to obtain VS and DS profiles. This paper introduces two novel methodologies for extracting the phase velocity and attenuation data. These new approaches are based on an extension of the beamforming technique which can be combined with a modal filter to isolate different Rayleigh propagation modes. Thus, the techniques return reliable phase velocity and attenuation estimates even in the presence of a multimode wavefield, which is typical of complex stratigraphic conditions. The reliability and effectiveness of the proposed approaches are assessed on a suite of synthetic wavefields and on experimental data collected at the Garner Valley Downhole Array and Mirandola sites. The results reveal that, under proper modelling of wavefield conditions, accurate estimates of Rayleigh wave phase velocity and attenuation can be extracted from active-source MASW wavefields over a broad frequency range. Eventually, the estimation of soil mechanical parameters also requires a robust inversion procedure to map the experimental Rayleigh wave parameters into soil models describing VS and DS with depth. The simultaneous inversion of phase velocity and attenuation data is discussed in detail in the companion paper. [ABSTRACT FROM AUTHOR]

Dense array observation and seismic interferometry have revolutionized the imaging schemes of the earth structure. It is becoming possible to directly obtain the lateral variation of the earth's structure by applying array-based methods such as the cross-correlation beamforming (CBF) of the ambient noise to the subsets of the dense array, without tomography. CBF has been proven to extract the azimuth-averaged multimode surface wave dispersion curves. However, the resolution of the dispersion image generated by conventional CBF is low at high frequencies in the frequency–velocity (f - v) domain. Moreover, the irregular array geometry and uneven source distribution would bias the result of CBF, especially for the estimation of azimuth-dependent velocity. In this paper, two beamforming (BF) es are suggested to improve the resolution of multimode dispersion images in the f - v domain. First, the geometrical spreading of the wavefield is corrected to enhance the amplitude at high frequency (or large distance) and thereby improve the resolution of the dispersion image at high frequency. We call this scheme weighted correlation beamforming (WCBF). The azimuth-averaged velocity can be estimated with sufficient resolution using WCBF by stacking the BF output at each azimuth. We show that WCBF is the 2-D Fourier transform of the spatial wavefield from the viewpoint of the wavefield transform. Secondly, a modified beamforming scheme (MCBF) is suggested to reduce the effect of uneven source and/or irregular array geometry. The delay and summation in MCBF are performed only for plane waves incident from the stationary phase region. The azimuth-dependent velocity can therefore be estimated by MCBF with less dependence on the array geometry, as well as on the uneven source distribution. In terms of the estimation of azimuth-averaged phase velocity, we show the F-J method, another array-based method for extracting multimode surface waves from ambient noise using the Fourier–Bessel transform, is the azimuth-averaged version of WCBF. The reliability of WCBF and MCBF is verified based on the synthetic and field data using the array with different geometry. The dispersion image of multimode Rayleigh wave phase velocity at local and regional scales can be generated by WCBF or MCBF with high resolution. In particular, multimode dispersion curves at the local scale can be measured by MCBF with sufficient accuracy using quite short recordings from hours to days. This offers the possibility of a rapid assessment of the media properties. [ABSTRACT FROM AUTHOR]

The heart beats are due to the synchronized contraction of cardiomyocytes triggered by a periodic sequence of electrical signals called action potentials, which originate in the sinoatrial node and spread through the heart's electrical system. A large body of work is devoted to modeling the propagation of the action potential and to reproducing reliably its shape and duration. Connection of computational modeling of cells to macroscopic phenomenological curves such as the electrocardiogram has been also intense, due to its clinical importance in analyzing cardiovascular diseases. In this work, we simulate the dynamics of action potential propagation using the three-variable Fenton–Karma model that can account for both normal and damaged cells through a the spatially inhomogeneous voltage diffusion coefficient. We monitor the action potential propagation in the cardiac tissue and calculate the pseudo-electrocardiogram that reproduces the R and T waves. The R-wave amplitude varies according to a double exponential law as a function of the (spatially homogeneous, for an isotropic tissue) diffusion coefficient. The addition of spatial inhomogeneity in the diffusion coefficient by means of a defected region representing damaged cardiac cells may result in T-wave inversion in the calculated pseudo-electrocardiogram. The transition from positive to negative polarity of the T-wave is analyzed as a function of the length and the depth of the defected region. [ABSTRACT FROM AUTHOR]

In 1904, Prandtl introduced his famous boundary layer in order to describe the behavior of solutions of Navier Stokes equations near a boundary as the viscosity goes to 0. His Ansatz has later been justified for analytic data by R.E. Caflisch and M. Sammartino. In this paper, we prove that his expansion is false, up to O (ν 1 / 4) order terms in L ∞ norm, in the case of solutions with Sobolev regularity, even in cases where the Prandlt's equation is well posed in Sobolev spaces. In addition, we also prove that monotonic boundary layer profiles, which are stable when ν = 0 , are nonlinearly unstable when ν > 0 , provided ν is small enough, up to O (ν 1 / 4) terms in L ∞ norm. [ABSTRACT FROM AUTHOR]

We show the emergence of shock waves at the final stages of the complete collapse of a spherical cavity in a liquid with a smoothly decreasing density. The well-known Rayleigh assumption of fluid homogeneity is altered, while maintaining that of divergenceless flow. The fundamental difference between both infinite liquids is that his has an infinite mass, while ours, a finite one. Given the ease of deformation of non-homogeneous media in relation to homogeneous ones, as observed in several materials, all Rayleigh results are modified, including the cavity wall speed and acceleration, total time of complete collapse, and distribution of pressure in the infinite liquid. Rather than the homogeneous Rayleigh fluid, our non-homogeneous liquid can support a finite local sound speed. As a result, we succeed to show the emergence of shock patterns at the final stages of the cavity collapse. The analytical formulation is compared with underwater implosion and explosion experiments and simulations. Possible applications as a benchmark test for hydrocodes are briefly discussed. [ABSTRACT FROM AUTHOR]

We investigate the boundary layer characteristics within annular centrifugal Rayleigh–Bénard convection (ACRBC) considering a Rayleigh number R a ∈ [ 10 8 , 10 11 ] , a Prandtl number Pr = 10.7, and an inverse Rossby number R o − 1 = 16. Our study is based on the temperature and velocity data obtained from direct numerical simulations. Different from the flow over a flat plate, the ACRBC system bifurcates into three regions: the plume-impacting regions, plume-ejecting regions, and plume-sweeping regions, and all three regions are moving with the zonal flow. Our focus is primarily on the temperature dynamics within the plume-sweeping region, where the wind of large-scale circulation shears the boundary. We determine the transient thermal boundary layer thickness over time using the slope method, relying on the temperature curve's orientation relative to the wall. Notably, the probability density function distribution of the thermal boundary layer thickness is reminiscent of traditional RBC systems, albeit with a more extended exponential tail. Employing a dynamic frame based on time resampling, we discern that the temperature boundary layer traits align with the Prandtl–Blasius boundary layer theory. In conclusion, we show that the exponential decay index for the thermal boundary layer thickness harmonizes with the system's heat transfer scaling law. It is found that the ratio between the inner and outer boundary layer thickness remains stable, providing theoretical guidance for the design and control of the internal flow field of high-speed rotating machinery. [ABSTRACT FROM AUTHOR]

Numerous scientists have thoroughly researched cavitation bubble dynamics using experimental methods such as tube arrest, underwater discharge, ultrasound, and laser focusing. In this study, with the aid of high-speed photography, the formation mechanism of the electrode-contact spark-induced cavitation bubble is discovered, i.e., electrolysis results in non-condensable gases wrapping the small inter-electrode gaps, and the non-condensable gases are broken down by discharge to form plasma, which then induces the cavitation bubble. Since the cavitation bubbles already contain a certain amount of non-condensable gases during the discharge process, the differences in the spatiotemporal evolution and collapse characteristics of the cavitation bubbles with varying amounts of non-condensable gases are further analyzed. The results show that underwater electrode-contact discharge system has an optimal voltage if the capacitance and discharge electrode size remain constant, and the cavitation bubbles generated under the optimal voltage condition are not only morphologically closest to the laser-induced cavitation bubbles, but also the change in radius over time during collapse is quite consistent with the Rayleigh bubble. Furthermore, compared to cavitation bubbles generated under varying voltages, those induced by the optimal voltage have a lower amount of non-condensable gases. This leads to the minimum first contraction radius and the maximum rebound radius being close to the corresponding values of the laser-induced cavitation bubbles. These new findings are of great significance for the improvement of experimental technology in the study of cavitation bubble dynamics, obtaining precise and dependable experimental data, and validating numerical simulations. [ABSTRACT FROM AUTHOR]

The tomography results reveal not only distinct velocity structures in different tectonic zones but can also provide valuable insights into the geological features of the area. This study presents the results of 2D Rayleigh wave tomographic maps obtained in NE Iran. For this purpose, we used the recorded waveforms of more than 500 earthquakes with M > 4 that occurred between January 2000 and October 2020 at 165 stations. The calculated tomographic maps cover a period range of 3 to 36 s, providing the 3D VS model to analyze crustal structure at depths ranging from 2 to 30 km. At shorter periods, the tomographic maps are primarily influenced by sediment thickness, with the presence of thick sediment layers (~ 10 km) responsible for the observed low VS anomalies (< 3.1 km/s) in the study area. At longer periods, the tomographic maps highlight the structural characteristics of the middle-lower crustal layers and, somewhere, the depth variations of the Moho discontinuity. The VS model also confirms the correlation between tectonic fractures and known faults in the study area as boundaries of seismotectonic provinces. Moreover, a distinct area was observed beneath the Binalud foreland, which we interpreted as a suture zone, as suggested by previous studies. The reliability of the resolved anomalies was supported through a series of tests, including checkerboard and earthquake location uncertainties. These tests demonstrated the robustness of the results and provided confidence in the accuracy of the findings. [ABSTRACT FROM AUTHOR]

Nondestructive testing (NDT) for damage in thermal barrier coatings (TBCs) is significant for the safety guarantee of gas turbine blades. As a new NDT technology, electromagnetic acoustic transducer (EMAT) is widely applied for NDT of conductive structural components due to its advantages of coupling-free and high adaptability. In this paper, numerical simulations are conducted to study the wave propagation and interaction with delamination defects in TBCs inspected with a Rayleigh wave EMAT of the Lorentz force mechanism. Based on the numerical results, the wave structure in TBC, wave conversion at delamination defect, time domain EMAT signals, and its B-scan images are evaluated and the feasibility of Rayleigh wave EMAT to inspect delamination in TBCs was theoretically clarified. [ABSTRACT FROM AUTHOR]

A series of models based on the finite element method (FEM) for analyzing the parameters of surface acoustic waves (SAWs) and devices based on them are described. The computer method for generating models in the COMSOL Multiphysics program is described in a generalized form. The work in three main solvers in the COMSOL environment—the stationary mode, eigenfrequency domain, and frequency domain—is described and graphically illustrated. The properties of Rayleigh waves and leaky SAWs are analyzed. A visualization of a number of characteristics is presented. The analysis of parameters such as the phase velocity of the wave, electromechanical coupling coefficient, and static capacitance of the transducer is considered. The examples consider an equidistant transducer, a transducer with split electrodes, and a unidirectional transducer of the DART type. Methods for analyzing harmonics in SAWs and the waveguide effect are proposed. It is shown that the model is valid for both single-crystal substrates and layered structures. The analysis of the temperature coefficient of the frequency for structures as such TCSAW (temperature-compensated SAW) and I.H.P.SAW (incredible high-performance SAW) is considered. A model for calculating the amplitude-frequency responses of devices is presented. It is shown that the data obtained as a result of the numerical analysis correspond to the experimental data and known published sources. [ABSTRACT FROM AUTHOR]

This paper investigates the motion of Rayleigh wave fields produced by a seismic surface pulse in an isotropic micropolar elastic half-space and in a multilayered micropolar media. The method of potentials followed by the Hankel transformation technique is used to determine explicitly the displacement vector components and microrotation vector components. Two different cases of surface seismic pulses are taken into account and the behavior of Rayleigh waves displacement components are studied separately. A matrix approach has been implemented to obtain solutions for the wave equations to reflect the motion of Rayleigh wave fields produced in multilayered micropolar elastic media due to surface seismic loadings. The displacement solutions for the half-space are obtained in the form of integral equations, which are further numerically evaluated and a few 2D and surface plots are plotted to describe the characteristics of the solutions. [ABSTRACT FROM AUTHOR]

The polarization state of transionospheric high frequency (HF) radio waves can be determined using the crossed-dipole antennas of the Radio Receiver Instrument (RRI) onboard Enhanced Polar Outflow Probe (e-POP) on the CAScade, Smallsat, and IOnospheric Polar Explorer/Swarm-E satellite. Coordinated experiments between ground radars and RRI showed that the radio waves have high ellipticity angles (elliptical or circular polarization) for propagation direction 6°-25° from the perpendicular direction to the local geomagnetic field. However, from magnetoionic theory and a typical assumption of roughly equal power in the O- and X-modes, radio waves can have high ellipticity angles only when the propagation direction is within 10° of perpendicularity. This investigation uses coordinated experiments between the Saskatoon SuperDARN radar and RRI. Magnetoionic modeling reveals that the relative strengths of the O- and X-modes for the HF radio waves transmitted from the Saskatoon SuperDARN change significantly poleward of the radar. Differences in the relative power between the two wave modes were found to significantly modify the polarization state of radio waves, and govern the sense of rotation of the wave. Even a relatively modest 2-5 dB power difference in the X-mode over the O-mode was found to result in unexpected observations of circularly polarized radio waves at aspect angles 6°-10° from perpendicular, and unexpected elliptically polarized waves observed at aspect angles more than 10° from perpendicular. Therefore, a combination of RRI observations and modeling, which accounts for relative differences in the O- and X-mode powers, was used here to better understand the unexpected observations of polarization states of transionospheric radio waves. [ABSTRACT FROM AUTHOR]

In this paper, the ability of a metasurface made of resonant elliptical pillars to focus flexural Lamb waves in the sub-wavelength regime is investigated. We report on the influence of the ellipticity parameter on the local resonances of the pillars, in particular the monopolar compressional and dipolar bending modes that are responsible for the desired focusing effect. We also discuss how the transmission through a line of pillars reveals these modes when the orientation of the pillars is changed with respect to the incident wave. Both the resonances can be superimposed for a particular choice of the ellipticity parameter, allowing a phase shift of 2π in the transmission coefficient for an incident antisymmetric Lamb wave, which is a necessary condition for the design of the metasurface. Finally, a gradient design for the pillar ellipticity is investigated, and its capacity to choose the focusing directionality of the transmitted wave at different targeted points is demonstrated. [ABSTRACT FROM AUTHOR]

This work investigates the longitudinal vibration characteristics of the pipe pile in the liquid-saturated ground due to Rayleigh waves propagation with considering the influence of the nonisothermal condition on the wave motion. Firstly, the Rayleigh wavefield in the liquid-saturated thermoelastic ground is deduced theoretically with taking advantage of the Biot theory and the non-Fourier law of heat conduction. Secondly, the longitudinal frequency domain solution of the pipe pile under Rayleigh waves is derived analytically. Finally, the dependence of the pipe pile response on the physical parameter is illustrated by utilizing several numerical examples. The result reveals that increase in the thermal expansion coefficient of saturated soil significantly augments the longitudinal displacement and side friction of pile body. Increase in the permeability of saturated soil will reduce the pile head displacement. When the pile length is less than its effective length, the rise of the pile length will reduce the pile head displacement. Augment of both the outer radius and wall thickness of the pipe pile will help to reduce the pile head displacement. However, the lateral inertia effect of the pipe pile has slight influence on its longitudinal behavior under Rayleigh waves. [ABSTRACT FROM AUTHOR]

Adhesive joints are non-separable connections that are used in numerous ways in vehicle construction, particularly in buses. The widespread use of adhesive joints makes it necessary to assess their quality, especially under production conditions. The main goal of this study was to develop a mathematical model to estimate the width of the adhesive path in a plywood-adhesive-closed-profile joint based on selected parameters of the ultrasonic surface wave. A digital ultrasonic flaw detector and Rayleigh wave probes were applied. The test involved evaluating different widths of hybrid adhesive and two-component epoxy adhesive. The tests were conducted on a steel profile from a bus construction. The attenuation of the ultrasonic waves on the steel profile (0.026 db/mm) and the adhesive (0.264 dB/mm) was determined. A one-size-fits-all model for estimating adhesive path width for specific conditions is proposed. [ABSTRACT FROM AUTHOR]

Volcanic eruptions are potential sources for generating the Earth's free oscillations at spheroidal modes of 0 S 29 and 0 S 37 through acoustic resonant coupling between the Earth and its atmosphere. Then, does every volcano produce Earth's free oscillations? We answer this question by analyzing eight large volcanic eruption events, (i) 15 January 2022 Hunga Tonga-Hunga Ha apai (HTHH), (ii) 13–14 January 2022, HTHH, (iii) 13 August 2021 Fukutoku-Okanoba, (iv) 22 April 2015 Calbuco, (v) 13 February 2014 Kelud, (vi) 4 November 2010 Merapi, (vii) 15 June 1991 Mt Pinatubo, and (viii) 4 April 1982 El Chichon. Our analysis revealed that the 15 January HTHH, Mt. Pinatubo, and El Chichon eruptions excited the Earth's free oscillations globally at spheroidal modes of 0 S 29 and/or 0 S 37 but no such modes were excited during other eruptions. However, harmonic oscillations in the ionosphere were seen during all recent eruption events. We demonstrate that stronger eruptions excite stronger atmospheric modes as the plume arrives at higher atmospheric heights which enable efficient ground-atmosphere acoustic resonant coupling for the excitation of spheroidal modes. Further, we hypothesize that relatively weaker eruptions/lower plume height perhaps caused weakly confined atmospheric modes thus failure of excitation of the spheroidal modes. A quantitative analysis of source efficiency versus source heights provides more insights into our hypothesis. [ABSTRACT FROM AUTHOR]

This study investigates the transmission characteristics of natural forests with branches and introduces a bio-inspired branch structure seismic metamaterial (SM) designed to create bandgaps for low-frequency Rayleigh waves. Employing the finite element method, we reveal the mechanism behind the generation of these Rayleigh wave bandgaps and their transmission properties. A distinct 'collectivization mode' within the bio-inspired branch structure SM is identified, effectively attenuating Rayleigh waves. A collectivization coefficient is introduced for quantitative characterization, and we extend the analysis to multi-layered soil mediums, demonstrating an interface with the metamaterial's bandgaps. The frequency-domain analysis highlights the difference between using the collectivization mode and traditional methods for attenuating surface waves, offering a novel approach to low-frequency Rayleigh wave reduction with implications in seismology and related engineering fields. [ABSTRACT FROM AUTHOR]

An understanding of the development of strong very low frequency chorus elements is important in the study of the rapid MeV electron acceleration observed during radiation belt recovery events. During such events, chorus elements with long-duration (20-40 ms), strong (|Bw| 0.5-2.0 nT) subpackets with smoothly varying frequency and phase capable of producing nonlinear energy gain of 1%-2% for multi-MeV seed electrons. For such strong chorus elements, we examine the consequences of an upstream motion of the chorus wave generation region using Van Allen Probes observations and nonlinear theory. For a given upstream velocity, v[sub s], resonant electron energy (50-350 keV) and pitch angle (105-115 deg) are uniquely determined for each wave frequency. We examine the effect of an upstream v[sub s] on the inhomogeneity factor that controls wave growth. For steadily increasing upstream motion as the chorus element evolves, vs/c ranging over [-0.001, -0.065], nonlinear wave growth takes place at ≥ 50% of the theoretical maximal value during the development of the observed strong subpackets. For the cases examined, resonant electron energies and pitch angles closely match those of the observed injected electron flux enhancements responsible for chorus development and the nonlinear acceleration of MeV radiation belt electrons. [ABSTRACT FROM AUTHOR]

In practical applications, microtremor data often encounter contamination from various sources of noise, leading to suboptimal processing outcomes. This study aimed to provide a comprehensive analysis of the impact of noise on the microtremor method. The focus was on presenting explicit and quantitative evidence to demonstrate the extent to which these noises influence the accuracy and reliability of the method. Initially, a ten-station triangular array was employed to gather a sequence of high-precision microtremor data. Next, various influencing factors, such as high-amplitude random noise, were generated and incorporated into the meticulously collected real data in order to simulate the actual perturbation process. Based on both the raw and the artificially contaminated data, a series of dispersion curves of the fundamental-mode Rayleigh waves were obtained by applying the extended spatial autocorrelation method (ESAC). Based on the obtained results, several valuable conclusions have been derived that can effectively inform the procedures for acquiring and processing microtremor data. If the amplitude and duration of sudden onset vibrations are considerable, more data should be collected to reduce the Negative impact. If non-random noise exhibits similar frequency characteristics as microtremor data, and the duration and energy of the noise are relatively small, it can be ignored; otherwise, more data should be collected. The dispersion curve, determined by the principle of the ESAC method, remains unaffected by any changes in the amplitude of one or more traces. The likelihood of frequency dispersion curve distortion increases as the impact of entire data anomalies on the coherence curve becomes greater. In general, when the collection positions of abnormal data are more widely spaced, the impact on the frequency dispersion curve tends to decrease. It is important to note that, in a nested-triangular array configuration, the central geophone plays a crucial role in ensuring accurate and dependable outcomes. [ABSTRACT FROM AUTHOR]

The research on the attenuation law of blasting vibration has become the foundation and precondition of the effective control of blasting vibration damage. Aiming at the characteristics of low frequency, low velocity, and strong amplitude of the R wave, an improved wave component separation method based on R wave suppression is proposed. Combined with the measured vibration signals of a field test, the attenuation parameters of different types of waves in the propagation process of blasting seismic waves are studied. The analysis results show that, in the process of blasting seismic wave propagation, the attenuation parameters of different types of waves are significantly different. With an increase in propagation distance, the proportion of the different types of waves will also change. The study of attenuation law with only coupled particle peak vibration velocity often showed high discreteness. The fitting correlation coefficient and prediction accuracy of peak vibration velocity without distinguishing wave modes are lower than those induced by the P wave or R wave alone, which should be attributed to the conversion of dominant wave modes in blasting vibration at different distances. [ABSTRACT FROM AUTHOR]

We develop a 3‐D isotropic shear velocity model for the Alaska subduction zone using data from seafloor and land‐based seismographs to investigate along‐strike variations in structure. By applying ambient noise and teleseismic Helmholtz tomography, we derive Rayleigh wave group and phase velocity dispersion maps, then invert them for shear velocity structure using a Bayesian Monte Carlo algorithm. For land‐based stations, we perform a joint inversion of receiver functions and dispersion curves. The forearc crust is relatively thick (35–42 km) and has reduced lower crustal velocities beneath the Kodiak and Semidi segments, which may promote higher seismic coupling. Bristol Bay Basin crust is relatively thin and has a high‐velocity lower layer, suggesting a dense mafic lower crust emplaced by the rifting processes. The incoming plate shows low uppermost mantle velocities, indicating serpentinization. This hydration is more pronounced in the Shumagin segment, with greater velocity reduction extending to 18 ± 3 km depth, compared to the Semidi segment, showing smaller reductions extending to 14 ± 3 km depth. Our estimates of percent serpentinization from VS reduction and VP/VS are larger than those determined using VP reduction in prior studies, likely due to water in cracks affecting VS more than VP. Revised estimates of serpentinization show that more water subducts than previous studies, and that twice as much mantle water is subducted in the Shumagin segment compared to the Semidi segment. Together with estimates from other subduction zones, the results indicate a wide variation in subducted mantle water between different subduction segments. Plain Language Summary: This study uses seismic data from the 2018–2019 Alaska Amphibious Community Seismic Experiment and other land stations to image the 3‐D seismic velocity structure of the Alaska subduction zone. The analysis combines constraints from both Rayleigh waves and converted body waves. The results provide insight into the distinct lateral variations observed for many properties of the subduction zone. Thick, low‐velocity forearc crust is found beneath the Kodiak and Semidi segments, which may be related to the higher seismic coupling in these regions. The Bristol Bay Basin has a thin crust with a high velocity lower layer, suggesting a dense mafic lower crust emplaced by the extensional processes that formed the basin. Low velocities in the incoming plate near the trench in the Shumagin segment indicate pronounced mantle hydration, extending to about 18 km below the Moho. Together with estimates from other subduction zones, the results indicate a wide variation in subducted mantle water between different subduction segments. Key Points: Crustal thickness of the inner forearc (35–42 km) generally exceeds that of the volcanic arc, but becomes variable in the Shumagin segmentThe Shumagin segment has more incoming plate mantle hydration than the Semidi segment, aligning with abundant plate bending normal faultsHydration extends to depths of 18 km below the Moho, indicating more water subducts than most previous estimates [ABSTRACT FROM AUTHOR]

Ambient noise tomography has become a popular method in the past two decades to image the crust and uppermost mantle structure. To date, broadband Rayleigh wave signals can be obtained from ambient noise, which can be utilized to study the earth's interior structure from the surface down to ∼200–300 km depths. However, it is hard to extract intermediate‐ and long‐period (>50 s) Love wave signals from ambient noise using conventional data processing techniques for ambient noise. Array‐based data processing techniques can enhance weak signals. In this study, we adopt a modified algorithm of the double‐beamforming method to extract broadband Love wave signals from ambient noise. We validate the accuracy of the dispersion curves measured from our method by comparing them to those measured from the conventional method. Then, we use a finite frequency ambient noise tomography method to construct broadband Love wave phase velocity maps across the contiguous USA. These phase velocity maps are consistent with those obtained from conventional methods at short periods (<40 s). Finally, we analyze the resolution of our double‐beamforming method based on checkerboard tests and find that the resolution of phase velocity maps based on our method is close to the aperture of the subarrays used in our double‐beamforming method. Plain Language Summary: Ambient noise tomography can be used to study the Earth's structure and has advantages over traditional teleseismic surface wave tomography. Broadband Rayleigh waves can be extracted from ambient noise data, but it is still challenging to extract intermediate‐ and long‐period Love wave signals from ambient noise data. Array‐based data processing techniques have the capability to enhance weak seismic signals. In this study, we adopt an array‐based method of double‐beamforming to improve the extraction of high‐quality broadband Love wave signals and demonstrate that these data can be used to image broadband Love wave phase velocity maps. Key Points: We adopt a modified double‐beamforming method to improve the extraction of broadband Love waves from ambient noiseWe obtain broadband Love waves at 10–120 s periods from ambient noise dataWe construct broadband Love wave phase velocity maps of the USA based on finite frequency ambient noise tomography [ABSTRACT FROM AUTHOR]

To integrate structural subsurface models and smooth seismic velocity models, they need to share common features and resolutions. Here, we propose a new approach, Depth Assessment from Rayleigh Wave Ellipticities (DARE), for estimating the depth of sudden velocity changes from ambient‐noise multi‐mode Rayleigh waves applicable to a wide range of frequencies. At frequencies where multi‐mode Rayleigh waves have an extremum in ellipticity, the phase velocity can be used to estimate the depth of sudden velocity changes. We test our approach theoretically, numerically, and on real data from two geothermal sites by extracting Rayleigh wave ellipticities and phase velocities from three‐component beamforming of ambient noise using the python code package B3AMpy. For a small‐scale array, our approach validates the depth of quaternary sediments predicted by geological models. For deeper velocity changes, high uncertainties remain but the general trend of inclining boundaries can be recovered well. We demonstrate that, if impedance contrasts are larger than three, our approach is valid for multiple layers, laterally heterogeneous models, and a wide range of Poisson ratios. Plain Language Summary: To effectively combine structural models and seismic velocity models, we've developed a new method. It estimates the depth of sudden changes in seismic velocity using Rayleigh waves from ambient noise. By identifying minima and maxima in Rayleigh wave ellipticity, we determine the depth of sudden velocity changes from the observed phase velocity at that point. We tested the method and found it works well for various scenarios, including multiple layers, heterogeneous models, and different material properties. This new Rayleigh wave method could be useful in seismic hazard studies to determine the depth of sedimentary basins. Key Points: We estimate the depth of sudden velocity increases from phase velocity and ellipticity of ambient‐noise multi‐mode Rayleigh wavesThree‐component ambient‐noise beamforming is used to estimate phase velocity and ellipticityFeasibility is demonstrated with noise recordings from multiple sites and validated with results from other studies [ABSTRACT FROM AUTHOR]

We conduct an exploration-scale ambient noise tomography (ANT) survey over the Hillside Iron Oxide–Copper–Gold (IOCG) deposit in South Australia, leveraging Fleet's direct-to-satellite technology for real-time data analysis. The acquisition array consisted of 100 sensors spaced 260 m apart which recorded continuous vertical-component seismic ambient noise for 14 days. High quality Rayleigh wave signals, with a mean signal-to-noise ratio (SNR) of 40, were recovered in the frequency band 1–4 Hz after processing the recorded data between 0.1–9 Hz. Our modelling results capture aspects of the deposit's known geology, including depth of cover, structures linked to mineralisation, and the mineralised host rock, down to approximately 1 km depth. We compare our velocity model with existing magnetic, gravity, induced polarisation and drilling data, showing strong correlation with each. We identify several new features of the local geology, including the behaviour of key structures down to 1 km, and highlight the significance of a Cambrian-age dolomite that cuts across the main structural corridor that hosts the Hillside deposit. An analysis of model convergence rates with respect to Rayleigh wave SNRs shows that real-time data analysis can reduce recording duration at the site by 65% compared to traditional deployment durations, from ∼14 days to ∼5 days. Finally, we conclude by commenting on the efficacy of the ANT technique for the exploration of IOCG systems more broadly. [ABSTRACT FROM AUTHOR]

The present article focuses on the Rayleigh surface wave propagation in homogeneous isotropic thermoelastic medium. This works aims to develop a new nonlocal elasticity model based on three-phase-lag model of hyperbolic thermoelasticity under double porosity structure. New constitutive relations and equations are derived using nonlocal continuum mechanics. State space approach is employed to solve the problem. Frequency equation is derived using appropriate boundary conditions. Path of surface particles is found elliptical at the time of Rayleigh surface wave propagation. Different characteristics of Rayleigh waves are calculated numerically and presented graphically for different wave number. Various characteristics of wave for different thermoelastic models are also presented graphically. The effect of nonlocal parameters and void parameters on phase velocity, attenuation coefficient, penetration depth, and specific loss of Rayleigh waves are shown graphically. Some special cases are deduced from this study which agree with the existing literatures. [ABSTRACT FROM AUTHOR]

The article presents the discussion on list is compiled from publications, products and information received as a result of exchange agreements, goodwill, research and subscriptions.

The seismological data recorded at our four semi-permanent broadband seismographs installed by the CSIR-NGRI, Hyderabad, Telangana in the Aravalli mobile belt (AMB) and Rajasthan craton in the northwest Indian shield during the period 2014–2016 are used in the study. The 16 selected regional Indian earthquakes of Mw 5.5–7.8 that occurred in the North India region recorded at the four seismic stations are used to compute the surface wave (both Rayleigh and Love waves) group velocity dispersion characteristics and average 1-D regional shear wave velocity (Vs) structure beneath the North India which covers the northern part of India between the whole Himalayan region and Rajasthan craton including AMB. First, we compute Rayleigh waves (at 7–87 s) dispersion curves and Love waves (at 7–82 s) group velocity dispersion curves by utilizing the standard frequency time analysis (FTAN) of 3-component broadband data recorded at these four 3-component broadband seismic stations. After that, using the logarithmic stacking technique, we compute the final average stacked fundamental mode dispersion curves of surface waves (both Love and Rayleigh waves) for our study area. Then, we finally invert the final average dispersion curves of surface waves (both Love and Rayleigh waves) to compute the average one-dimensional regional shear velocity structure beneath North India. Our modelling result in North India suggests a two-layered crustal structure with a crustal thickness of 39 km. The thickness of the first crustal layer (upper crust) is 20 km with a shear wave velocity (Vs) of 3.30 km/s. On the other hand, the second crustal layer (lower crust) marks a 19-km thickness with a Vs of 3.70 km/s. Our modelling result suggests that the Vs of the upper mantle is found to be 4.35 km/s below the study region. Research highlights: Modelled average one-dimensional regional Vs structure below northern part of India. A 2-layered crustal velocity model below North India. Upper crust at 20 km thick with Vs of 3.30 km/s. And, lower crust at 19 km thick with Vs of 3.70 km/s. The Moho depth is 39 km and Vs below the Moho depth is found to be 4.35 km. [ABSTRACT FROM AUTHOR]

A transversely isotropic elastic medium with a vertical axis of symmetry is considered. We obtain dispersion equations in real terms for guided Love and Rayleigh waves in a such a medium consisting of horizontal layers sandwiched between two half‐spaces by brief modifications of the available literatures on dispersion equations in elastic layered media through transfer matrix. To illustrate the applicability, dispersion curves of guided waves are computed for three‐ and five‐layered symmetric models with transversely isotropic coal seam in the middle. The Airy phase is marked by a minimum or maximum of group velocity in a dispersion curve, and this phase is important to get seam structure for mining safety. For the first three modes, the effect of Thomsen anisotropy parameters γ, ε and δ of a coal seam on frequency (fA) and group velocity (UA) of the Airy phase is similar in three‐ and five‐layered models. For guided Love waves, fA and UA have nearly a uniform increase with the increase of γ. For guided Rayleigh waves, the increase of ε causes fA and UA to increase; however, the increase of δ causes fA and UA to decrease. [ABSTRACT FROM AUTHOR]

Understanding turbulent thermal convection is essential for modeling many natural phenomena. This study investigates the spatiotemporal dynamics of the vortical structures in the mid-plane of turbulent Rayleigh–Bénard convection in SF6 via experiments. For this, a Rayleigh–Bénard cell of aspect ratio 10 is placed inside a pressure vessel and pressurized up to 1, 1.5, and 2.5 bar in order to reach Rayleigh numbers of Ra = 9.4 × 10 5 , 2.0 × 10 6 , and 5.5 × 10 6 , respectively. For all three cases, the Prandtl number is Pr = 0.79 and Δ T ≈ 7 K. Then, stereoscopic particle image velocimetry is conducted to measure the three velocity components in the horizontal-mid-plane for 5.78 × 10 3 free fall times. For the given aspect ratio, the flow is no longer dominated by the side walls of the cell and turbulent superstructures that show a two-dimensional repetitive organization form. These superstructures show diverse shapes with faster dissipation rates as Ra increases. Out-of-plane vortices are the main feature of the flow. As Ra increases, the number of these vortices also increases, and their size shrinks. However, their total number is almost constant for each Ra through the measurement period. Furthermore, their occurrence is random and does not depend on whether the flow is upward-heated, downward-cooled, or horizontally directed. Vortex tracking was applied to measure lifetime, displacement, and traveled distance of these structures. The relation between lifetime and traveled distance is rather linear. Interestingly, in the vortex centers, the out-of-plane momentum transport is larger in comparison to the bulk flow. Therefore, these vortices will play a major role in the heat transport in such flows. [ABSTRACT FROM AUTHOR]

We present an experimental study on the large-scale circulation (LSC) and temperature oscillation in the flattened cylindrical turbulent Rayleigh–Bénard Convection cell with aspect ratio Γ = 2. The Prandtl number is maintained at Pr = 5.7, and the Rayleigh number Ra ranges from 8.0 × 10 7 to 6.5 × 10 8 . The strength and the orientation of the LSC are measured through the multi-point temperature signal at the mid-height of the convection cell. Our findings reveal that the single roll form of the LSC consistently dominates the flow, with its orientation confined to a narrower azimuthal range compared to the slender cell (e.g., Γ = 1 cell). Differing from the diffusion process observed in the Γ = 1 cell, the azimuthal motion of the LSC in the Γ = 2 cell exhibits a superdiffusion process. The mean square change of the strength of the LSC displays multiple regimes, with the scaling exponent of the first regime being 2, indicating ballistic motion within the short time interval. The scaling exponent of the second regime is 0.5 (0.2) for a leveled (tilted) cell, signifying a subdiffusion motion. Moreover, the temperature oscillations in the Γ = 2 cell differ significantly from those reported in a Γ = 1 cell, and it is found that the temperature oscillation exits everywhere at the mid-height of the cell. Furthermore, at the mid-height of the cell, the orientation and strength of the LSC exhibit prominent oscillations with characteristic frequencies of f0 and 2 f 0 , respectively, which are absent in Γ = 1 and 1/2 cells. These behaviors can be well-explained by the motion of the vortex center. [ABSTRACT FROM AUTHOR]

The article is focused on the analysis of a mathematical model known as the Nizhnik–Novikov–Veselov (SNNV) system, which incorporates a specialized mathematical tool called the truncated M-fractional derivative (TMD). This model has broad applications in various scientific fields and considered an isotropic Lax extension of the one-dimensional Kdv equation which has diverse applications in the areas of warm ions, shallow water waves, electromagnetic signals, and river irrigation flows. To extract the solutions of the SNNV system, a modified version of the extended tanh-function method which is known as amended extended tanh-function method (AETF) is brought into play to derive solitary wave solutions for the SNNV system. These formulated solutions are categorized as trigonometric, exponential, and hyperbolic functions. For physical exemplification and knowledge of the dynamic physical features of the governing model, some reported solutions have been deliberated graphically by selecting appropriate parametric values. The computed outcomes have implications in diverse areas of applied sciences such as quantum mechanics, magneto-electrodynamics, heavy ion collisions, optical fiber technology and also opens doors to practical applications in diverse domains. The application of the AETF approach in this study demonstrates its efficiency and competence in scrutinizing and extracting soliton solutions in nonlinear partial differential equation. [ABSTRACT FROM AUTHOR]

THIS PAPER DESCRIBES A THEORY for surface Rayleigh waves propagating in a viscoelastic medium. The Zener model to describe the viscoelastic behavior of the medium is used. This simple model captures both the relaxation and retardation. An analytical expression for the complex dispersion equation of Rayleigh waves is established. The influence of the normalized frequency and the ratio of shear moduli on the dispersion curves of the Rayleigh wave velocity and attenuation is analyzed numerically. The numerical solutions show the dependence of the phase velocity change and the wave attenuation in terms of the normalized frequency and the ratio of shear moduli. As an important result, the Zener model can be used at a normalized low frequency to predict creep phenomenon as well as at a normalized high frequency to predict relaxation. The obtained results are fundamental and can be applied to characterize the viscoelastic properties of soft biomaterials and tissue, in nondestructive testing of materials, in geophysics and seismology. Thus, the obtained complex dispersion equation can be very useful to interpret the experimental measurements of Rayleigh waves propertie in a viscoelastic medium. [ABSTRACT FROM AUTHOR]

The eastern Alpine crust has been shaped by the continental collision of the European and Adriatic plates beginning at 35 Ma and was affected by a major reorganization after 20 Ma. To better understand how the eastern Alpine surface structures link with deep seated processes, we analyze the depth‐dependent seismic anisotropy based on Rayleigh wave propagation. Ambient noise recordings are evaluated to extract Rayleigh wave phase dispersion measurements. These are inverted in a two step approach for the azimuthally anisotropic shear velocity structure. Both steps are performed with a reversible jump Markov chain Monte Carlo (rj‐McMC) approach that estimates data errors and propagates the modeled uncertainties from the phase velocity maps into the depth inversion. A two layer structure of azimuthal anisotropy is imaged in the Alpine crust, with an orogen‐parallel upper crust and approximately orogen‐perpendicular layer in the lower crust and the uppermost mantle. In the upper layer, the anisotropy tends to follow major fault lines and may thus be an apparent, structurally driven anisotropy. The main foliation and fold axis orientations might contribute to the anisotropy. In the lower crust, the N‐S orientation of the fast axis is mostly confined to regions north of the Periadriatic Fault and may be related to European subduction. Outside the orogen, no clearly layered structure is identified. The anisotropy pattern in the northern Alpine foreland is found to be similar compared to SKS studies which is an indication of very homogeneous fast axis directions throughout the crust and the upper mantle. Plain Language Summary: The formation of the European Alps is due to the continental collision of the Adriatic and the European plates which started approximately 35 million years ago and is still ongoing. To better understand how the plates behaved during this collision process, how the crust was deformed and how distinct features like the Tauern Window were formed, we image the upper 70 km under the Eastern Alps using seismic background noise. We focus on the anisotropic shear‐velocity structure of the underground, because it provides valuable additional information that can be related to the fault geometry or the main movement direction of the material. We present a probabilistic approach that attributes errors to the measured data and propagates this error through the two steps of the 3D imaging procedure, to be able to assess the uncertainty of the final model. The results show that there are two anisotropic layers in the crust, an upper crustal layer that is dominated by faster wave propagation parallel to the orientation of the mountain chain, and a lower crustal/uppermost mantle layer that has a dominantly perpendicular fast propagation direction. Key Points: A new, probabilistic method is presented to obtain an azimuthally anisotropic shear‐velocity model from Rayleigh wavesThe model shows a two‐layer anisotropic structure in the eastern Alpine crust [ABSTRACT FROM AUTHOR]

An isotropic elastic solid reinforced with a family of parallel fibres behaves anisotropic to any deformation. With orientation of all fibres along a coordinate axis in rectangular Cartesian system, this anisotropy reduces to transverse isotropy. Else with arbitrary orientation of fibre‐family, induced anisotropy lacks any symmetry. In this composite medium with arbitrary anisotropy, three‐dimensional wave motion decaying with depth propagates as a surface wave along all directions on plane boundary. Real phase velocity for this surface wave lies implicit in a system of three equations with complex coefficients. An appropriate transformation of this system yields a real characteristic equation, which is solved to get the anisotropic phase velocity of generalised surface wave. This phase velocity defines a complex slowness vector, which is used to calculate the particle motion at any point in the medium. Effects of fibre‐orientation are analysed, numerically, on the phase velocity and polarisation of surface wave. For example, in the reinforced fibres alters the contours of particle motion through increased ellipticity. However, in the presence of fibres, the decay of particle motion with depth slows down. [ABSTRACT FROM AUTHOR]

This paper investigates the propagation of in-plane surface waves in a coated thermoelastic half-space. First, it investigates a special case where the surface layer is described by the Maxwell–Cattaneo thermoelastic approach, while the half-space is filled by a thermoelastic material described by the classical Fourier law for the heat flux. The contact between the layer and the half-space is assumed to be welded, i.e., the displacements and the temperature, as well as the stresses and the heat flux are continuous through the interface of the layer and the half-space. The boundary and continuity conditions of the problem are formulated and then the exact dispersion relation of the surface waves is established. An illustrative numerical simulation is presented for the case of an aluminum thermoelastic layer coating a thermoelastic copper half-space, highlighting important aspects regarding the propagation of Rayleigh waves in such structures. The exact effective boundary conditions at the interface are also established replacing the entire effect of the layer on the half-space. The general case of the problem is also investigated when both the surface layer and the half-space are described by the Maxwell–Cattaneo thermoelasticity theory. This study helps to further understand the propagation characteristics of elastic waves in layered structures with thermal effects described by the Maxwell–Cattaneo approach.

Iron is an important metal, scientifically and technologically. It is a common metal on Earth, forming the main constituent of the planet's inner core, where it is believed to be in solid state at high pressure and high temperature. It is also the main component of many important structural materials used in quasistatic and dynamic conditions. Laser-driven Rayleigh–Taylor instability provides a means of probing material strength at high pressure and high temperature. The unavoidable phase transition in iron at relatively low pressure induces microstructural changes that ultimately affect its strength in this extreme regime. This inevitable progression can make it difficult to design experiments and understand their results. Here, we address this challenge with the introduction of a new approach: a direct-drive design for Rayleigh–Taylor strength experiments capable of reaching up to 400 GPa over a broad range of temperatures. We use 1D and 2D hydrodynamic simulations to optimize target components and laser pulse shape to induce the phase transition and compress the iron to high pressure and high temperature. At the simulated pressure–temperature state of 350 GPa and 4000 K, we predict a ripple growth factor of 3–10 depending on the strength with minimal sensitivity to the equation of state model used. The growth factor is the primary observable, and the measured value will be compared to simulations to enable the extraction of the strength under these conditions. These experiments conducted at high-energy laser facilities will provide a unique way to study an important metal. [ABSTRACT FROM AUTHOR]

Passive underwater acoustic markers are promising in terms of applications in underwater target recognition, positioning, and navigation. In this paper, a passive underwater acoustic marker composed of acrylic sphere combinations is designed for acoustic coding based on the subsonic Rayleigh wave resonance phenomenon, where strong backscattering resonance peaks appear when an acrylic sphere is excited by a broadband pulse. Due to the fact that the resonance frequencies are dependent on the Rayleigh wave velocity and the radius of the sphere, the backscattering response of markers can be regulated by changing the radius of a sphere or combining spheres with different radii. Each marker has a unique acoustic signature for a selected frequency band, akin to acoustic barcodes. The feasibility of this acoustic coding method has been evaluated by comparing the numerical results and experimental results. Compared with active acoustic markers, passive acoustic markers naturally operate in a wider frequency band, have a longer lifetime, and lower cost. [ABSTRACT FROM AUTHOR]