Rayleigh Propagation Research Articles

Novel techniques for in situ estimation of shear-wave velocity and damping ratio through MASW testing – I: a beamforming procedure for extracting Rayleigh-wave phase velocity and phase attenuation

SUMMARY 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.

Discovering asymptotic expansions for problems in mechanics using symbolic regression

Recently, symbolic regression (SR) has demonstrated its efficiency for discovering basic governing relations in physical systems. A major impact can be potentially achieved by coupling symbolic regression with asymptotic methodology. The main advantage of asymptotic approach involves the robust approximation to the sought for solution bringing a clear idea of the effect of problem parameters. However, the analytic derivation of the asymptotic series is often highly nontrivial especially, when the exact solution is not available.In this paper, we adapt SR methodology to discover asymptotic series. As an illustration we consider three problem in mechanics, including two-mass collision, viscoelastic behavior of a Kelvin–Voigt solid and propagation of Rayleigh–Lamb waves. The training data is generated from the explicit exact solutions of these problems. The obtained SR results are compared to the benchmark asymptotic expansions of the above mentioned exact solutions. Both convergent and divergent asymptotic series are considered. A good agreement between SR expansions and exact analytical results is observed. It is demonstrated that the proposed approach can be used to identify material parameters, e.g. Poisson’s ratio, and has high prospects for utilizing experimental and numerical data.

Acoustoelectric Effect of Rayleigh and Sezawa Waves in ZnO/Fused Silica Produced by an Inhomogeneous In-Depth Electrical Conductivity Profile

The acousto-electric (AE) effect associated with the propagation of Rayleigh and Sezawa surface acoustic waves (SAWs) in ZnO/fused silica was theoretically investigated under the hypothesis that the electrical conductivity of the piezoelectric layer has an exponentially decaying profile akin to the photoconductivity effect induced by ultra-violet illumination in wide-band-gap photoconducting ZnO. The calculated waves' velocity and attenuation shift vs. ZnO conductivity curves have the form of a double-relaxation response, as opposed to a single-relaxation response which characterizes the AE effect due to surface conductivity changes. Two configurations were studied which reproduced the effect of UV light illumination from the top or from the bottom side of the ZnO/fused silica substrate: 1. the ZnO conductivity inhomogeneity starts from the free surface of the layer and decreases exponentially in depth; 2. the conductivity inhomogeneity starts from the lower surface of the ZnO layer contacting the fused silica substrate. To the author's knowledge, this is the first time the double-relaxation AE effect has been theoretically studied in bi-layered structures.

Removal of Non-Specifically Bound Proteins Using Rayleigh Waves Generated on ST-Quartz Substrates.

Label-free biosensors are plagued by the issue of non-specific protein binding which negatively affects sensing parameters such as sensitivity, selectivity, and limit-of-detection. In the current work, we explore the possibility of using the Rayleigh waves in ST-Quartz devices to efficiently remove non-specifically bound proteins via acoustic streaming. A coupled-field finite element (FE) fluid structure interaction (FSI) model of a surface acoustic wave (SAW) device based on ST-Quartz substrate in contact with a liquid loading was first used to predict trends in forces related to SAW-induced acoustic streaming. Based on model predictions, it is found that the computed SAW body force is sufficient to overcome adhesive forces between particles and a surface while lift and drag forces prevent reattachment for a range of SAW frequencies. We further performed experiments to validate the model predictions and observe that the excitation of Rayleigh SAWs removed non-specifically bound (NSB) antigens and antibodies from sensing and non-sensing regions, while rinsing and blocking agents were ineffective. An amplified RF signal applied to the device input disrupted the specific interactions between antigens and their capture antibody as well. ST-quartz allows propagation of Rayleigh and leaky SH-SAW waves in orthogonal directions. Thus, the results reported here could allow integration of three important biosensor functions on a single chip, i.e., removal of non-specific binding, mixing, and sensing in the liquid phase.

An Efficient Plane-Waves Superposition Method for Improved Spatial Correlation in Simulated Reverberation Chambers

Accurate Rayleigh propagation environments within an ideal reverberation chamber (RC) are synthesized computationally using a superposition of plane-waves (PWs). Randomness in the electro-magnetic (EM) field distribution is achieved by synthesizing many field realizations featuring slant-polarized PWs with randomly defined transverse field components. These PWs propagate along a large number of predefined and uniformly distributed directions determined only once via an efficient spiraling sampling scheme over the unit sphere. Comparisons with theoretical Rayleigh field statistics indicate that the proposed method yields random EM field distributions that in several cases follow more closely the field spatial correlation properties, for comparable numerical burden, than other available numerical techniques. Finally, a formula relating the number of PWs to the size of a desired RC analysis volume was provided.

Surface Rayleigh-Lamb waves in stratified substrate

Propagation of Rayleigh - Lamb waves has shortage of theoretical studies and demands in deeper analyses. Understanding the process of propagation of Rayleigh-Lamb waves depending on the geometrical and acoustical properties of the individual layers within the Earth’s crust is of great importance for the NDT of Earth exploration and development of seismic protection of buildings and structures. Propagation of these waves in the Earth’s crust upper layers is studied by analytical methods. A mathematical model for analyzing Rayleigh -Lamb waves propagating in stratified media is worked out. The analytical solution is constructed using Cauchy complex formalism and the method called Modified Transfer Matrix (MTM). As an example a multilayer system modeling the Earth’s crust, consisting of sedimentary rocks, a layer of granite, basalt and mantle, is considered. Equation for dispersion relations is derived. Fundamental modes of the dispersion curves for a stratified media are obtained.

Experimental and Theoretical Study of Multifrequency Surface Acoustic Wave Devices in a Single Si/SiO2/ZnO Piezoelectric Structure.

The propagation of surface acoustic waves (SAWs) along a ZnO/SiO2/Si piezoelectric structure is experimentally and theoretically studied. Six surface acoustic modes were experimentally detected in the 134 to 570 MHz frequency range, for acoustic wavelength λ = 30 μm, and for SiO2 and ZnO layers with a thickness of 1 and 2.4 μm. The numerical and three-dimensional (3D) finite element method analysis revealed that the multilayered substrate supports the propagation of Rayleigh and Sezawa modes (Rm and Sm), their third and fifth harmonics at λ/3 and λ/5. The velocity of all the modes was found in good agreement with the theoretically predicted values. Eigenfrequency, frequency domain, and time domain studies were performed to calculate the velocity, the electroacoustic coupling coefficient, the shape of the modes, the propagation loss, and the scattering parameter S21 of the SAW delay lines based on the propagation of these modes. The sensitivity to five different gases (dichloromethane, trichloromethane, carbontetrachloride, tetrachloroethylene, and trichloroethylene) was calculated under the hypothesis that the ZnO surface is covered by a polyisobutylene (PIB) layer 0.8 µm thick. The results show that the modes resonating at different frequencies exhibit different sensitivities toward the same gas. The multi-frequency ZnO/SiO2/Si single device structure is a promising solution for the development of a multiparameters sensing platform; multiple excitation frequencies with different sensing properties can allow the parallel analysis of the same gas with improved accuracy.

Fabrication and characterization of one-port surface acoustic wave resonators on semi-insulating GaN substrates**Project supported by the National Key Research and Development Program of China (Grant No. 2017 YFB0403002), the National Science Fund for Distinguished Young Scholars, China (Grant No. Y3CHC11001), and the National Natural Science Foundation of China (Grant No. 11604368).

One-port surface acoustic wave resonators (SAWRs) are fabricated on semi-insulating high-quality bulk GaN and GaN film substrates, respectively. The semi-insulating GaN substrates are grown by hydride vapor phase epitaxy (HVPE) and doped with Fe. The anisotropy of Rayleigh propagation and the electromechanical coupling coefficient in Fe-doped GaN are investigated. The difference in resonance frequency between the SAWs between [11 0] GaN and [1 00] GaN is about 0.25% for the Rayleigh propagation mode, which is smaller than that of non-intentionally doped GaN film (̃1%) reported in the literature. The electromechanical coupling coefficient of Fe-doped GaN is about 3.03%, which is higher than that of non-intentionally doped GaN film. The one-port SAWR fabricated on an 8- Fe-doped GaN/sapphire substrate has a quality factor of 2050, and that fabricated on Fe-doped bulk GaN has a quality factor as high as 3650. All of our results indicate that high-quality bulk GaN is a very promising material for application in SAW devices.

Model parameter extraction of lateral propagating surface acoustic waves with coupling on SiO2/grating/LiNbO3 structure

This paper investigates how lateral propagation of Rayleigh and shear horizontal (SH) surface acoustic waves (SAWs) changes with rotation angle θ and SiO2 and electrode thicknesses, hSiO2 and hCu, respectively. The extended thin plate model is used for purpose. First, the extraction method is presented for determining parameters appearing in the extended thin plate model. Then, the model parameters are expressed in polynomials in terms of hSiO2, hCu, and θ. Finally, a piston mode structure without phase shifters is designed using the extracted parameters. The possible piston mode structures can be searched automatically by use of the polynomial expression. The resonance characteristics are analyzed by both the extended thin plate model and three-dimensional (3D) finite element method (FEM). Agreement between the results of both methods confirms validity and effectiveness of the parameter extraction process and the design technique.

Study of the influence of semiconductor material parameters on acoustic wave propagation modes in GaSb/AlSb bi-layered structures by Legendre polynomial method

The propagation of Rayleigh–Lamb waves in bi-layered structures is studied. For this purpose, an extension of the Legendre polynomial (LP) method is proposed to formulate the acoustic wave equation in the bi-layered structures induced by thin film Gallium Antimonide (GaSb) and with Aluminum Antimonide (AlSb) substrate in moderate thickness. Acoustic modes propagating along a bi-layer plate are shown to be quite different than classical Lamb modes, contrary to most of the multilayered structures. The validation of the LP method is illustrated by a comparison between the associated numerical results and those obtained using the ordinary differential equation (ODE) method. The convergency of the LP method is discussed through a numerical example. Moreover, the influences of thin film GaSb parameters on the characteristics Rayleigh–Lamb waves propagation has been studied in detail. Finally, the advantages of the Legendre polynomial (LP) method to analyze the multilayered structures are described. All the developments performed in this work were implemented in Matlab software.

Melt-rock interactions, deformation, hydration and seismic properties in the sub-arc lithospheric mantle inferred from xenoliths from seamounts near Lihir, Papua New Guinea

Abstract This study analyses the interactions between deformation and reactive fluid and melt percolation, and their effects on sub-arc mantle seismic properties based on microstructural observations on mantle xenoliths extracted by the Tubaf and Edison seamounts close to the Lihir Island, in the Papua New Guinea archipelago. These xenoliths sample an oceanic lithosphere, which has experienced high-temperature deformation in the presence of fluids or melts. This was followed by metasomatism under static conditions. Syn-kinematic percolation of reactive Si-rich melts or fluids in peridotites has produced pyroxene-enrichment, grain size reduction, and dispersion of olivine crystal preferred orientation (CPO). Fourier transform infrared spectroscopy analyses show that olivine has very low water contents (1–4 wt. ppm H 2 O), similar to spinel peridotites from other subduction zones. These low values may record both low water solubility in olivine at low pressure and dehydration during transport and exhumation. Water contents in pyroxenes are highly variable and likely result from spatially heterogeneous melt or fluid percolation. Analysis of olivine CPO indicates dominant activation of both (010)[100] and (001)[100] slip systems, which are characteristic of deformation under high temperature, low stress, low pressure and low to moderate hydrous conditions. Fast S-wave polarization and P- and Rayleigh propagation directions are thus parallel to the mantle flow direction. The pyroxene enrichment by melt-rock reactions is accompanied by dispersion of olivine CPO and induces a significant decrease of the maximum S-wave and P-wave anisotropy in the peridotites. The calculated seismic properties also show that the lowest Vp/Vs ratios (

Performance Evaluation of Digital Modulation Techniques on DS-WCDMA

The objectives of this paper are to study, analyze and evaluate the performance of Direct Sequence – Wide Code Division Multiple Access (DS-WCDMA) systems in Mobile Rayleigh fading propagation channel. The Parameters which are considered for the evaluation performance are Additive white Gaussian noise (AWGN),Rayleigh propagation fading channel and the Code sequence .length. The evaluation of DSWCDMA was derived for different type of digital modulation using Mat lab simulation link. The results were obtained in terms of bit error rates(BER)in graphical form.

The Love's problem for hyperbolic thermoelasticity

AbstractIn our paper we investigated the initial‐boundary value problem for elastic layer situated on half space of another elastic medium. In this medium the thermomechanical interactions were taken into consideration. The system of equations with initial‐boundary conditions describes the phenomenon of wave propagation with finite speed. In our problem there are two surfaces ie. free surface and contact surface between layer and half space. On the free surface are setting boundary conditions for normal and tangent surface force. We consider two types of contact between layer and half‐space: rigid contact and slip contact. The initial‐boundary value problem was solved by using integral transformations and Cagniard‐de Hoope methods. From the solution of this problem follows that in layer and half space exist some kind of thermoelastic waves. We investigated moreover the conditions which should be fullfiled for propagation of Rayleigh and Love's type waves on the contact surface between layers and half space. The results obtained in our investigation were used in technical applications especially engineering design and diagnostics of roads and airfields. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Exact bit error probabilities and packet error statistics for SVD transmission over time-varying dual-branch MIMO systems obtained by a Markov model

Using a finite state Markov channel model, we develop an analytical method for evaluation of the packet error structure in multiple-input multiple-output (MIMO) systems based on singular value decomposition (SVD). We consider dual-branch MIMO systems, with either two transmit and arbitrary number of receive antennas, or arbitrary number of transmit and two receive antennas. The corresponding Markov model parameters are obtained using a novel closed-form expressions for probability density function and level crossing rate of the signal-to-noise ratio at the output of eigenchannels in a MIMO system, derived for a case of Rayleigh propagation, imperfect channel state information and any fixed power allocation. The exact bit error rate for the transmission of quadrature amplitude modulated (QAM) symbols through the eigenchannels is derived in polynomial closed form. Furthermore, by using the developed Markov model, the packet error statistics in the corresponding eigenchannels are determined, and the closed-form analytical expression for the system throughput is derived when ‘go-back-N’ automatic repeat request procedure is applied in time-varying eigenchannels. The analytical results are validated by using Monte Carlo simulations.

Activation of Nanoflows for Fuel Cells

Propagation of Rayleigh traveling waves from a gas on a nanotube surface activates a macroscopic flow of the gas (or gases) that depends critically on the atomic mass of the gas. Our molecular dynamics simulations show that the surface waves are capable of actuating significant macroscopic flows of atomic and molecular hydrogen, helium, and a mixture of both gases both inside and outside carbon nanotubes (CNT). In addition, our simulations predict a new “nanoseparation” effect when a nanotube is filled with a mixture of two gases with different masses or placed inside a volume filled with a mixture of several gases with different masses. The mass selectivity of the nanopumping can be used to develop a highly selective filter for various gases. Gas flow rates, pumping, and separation efficiencies were calculated at various wave frequencies and phase velocities of the surface waves. The nanopumping effect was analyzed for its applicability to actuate nanofluids into fuel cells through carbon nanotubes.

Influence of Initial Stress and Gravity Field on Propagation of Rayleigh and Stoneley Waves in a Thermoelastic Orthotropic Granular Medium

The propagation of Rayleigh and Stoneley waves in a thermoelastic orthotropic granular half‐space supporting a different layer under the influence of initial stress and gravity field is studied. The frequency equation of Rayleigh waves in the form of twelfth‐order determinantal expression and the frequency equation of Stoneley waves in the form of eighth‐order determinantal expression are obtained. The standard equation of dispersion is discussed to obtain Rayleigh and Stoneley waves that have complex roots; the real part gives the velocity of Rayleigh or Stoneley waves but the imaginary part gives the attenuation coefficient. Finally, the numerical results have been given and illustrated graphically, and their physical meaning has been explained.

A numerical study on the propagation of Rayleigh and guided waves in cortical bone according to Mindlin’s Form II gradient elastic theory

Cortical bone is a multiscale heterogeneous natural material characterized by microstructural effects. Thus guided waves propagating in cortical bone undergo dispersion due to both material microstructure and bone geometry. However, above 0.8 MHz, ultrasound propagates rather as a dispersive surface Rayleigh wave than a dispersive guided wave because at those frequencies, the corresponding wavelengths are smaller than the thickness of cortical bone. Classical elasticity, although it has been largely used for wave propagation modeling in bones, is not able to support dispersion in bulk and Rayleigh waves. This is possible with the use of Mindlin's Form-II gradient elastic theory, which introduces in its equation of motion intrinsic parameters that correlate microstructure with the macrostructure. In this work, the boundary element method in conjunction with the reassigned smoothed pseudo Wigner-Ville transform are employed for the numerical determination of time-frequency diagrams corresponding to the dispersion curves of Rayleigh and guided waves propagating in a cortical bone. A composite material model for the determination of the internal length scale parameters imposed by Mindlin's elastic theory is exploited. The obtained results demonstrate the dispersive nature of Rayleigh wave propagating along the complex structure of bone as well as how microstructure affects guided waves.

Effect of Rotation on Rayleigh—Lamb Waves in an Isotropic Generalized Thermoelastic Diffusive Plate

The present investigation is aimed at studying the effect of rotation on propagation of Rayleigh—Lamb waves in a homogeneous isotropic thermoelastic diffusive plate of finite width in the framework of different theories of thermoelasticity, including the Coriolis and centrifugal forces. The medium is subjected to stress-free, thermally insulated, isothermal, and chemical potential boundary conditions and is rotating about an axis perpendicular to its plane. Secular equations corresponding to the symmetric and skew-symmetric modes of the plate are derived. Phase velocities and attenuation coefficients of various possible modes of wave propagation are computed from the secular equations. Amplitudes of displacements, temperature, and concentration for symmetric and skew-symmetric modes of plate vibrations are computed numerically. The computed results are presented graphically.

The Second Order Statistics of Maximal Ratio Combining with Unbalanced Branches

In this letter, exact closed form expressions for the level crossing rate and the autocorrelation function are derived for maximum-ratio-combining with independent but unbalanced diversity branches. The novel expressions are given for Rayleigh propagation and an arbitrary number of diversity branches. The derived identities can be applied to isotropic as well as to nonisotropic scattering environment. The analytical results are validated by simulation.

Level Crossing Rates in Transmit Beamforming Systems

In this paper, the second-order statistics of the signal to noise ratio (SNR) at the output of a multiple-input-multiple-output (MIMO) system employing maximal ratio combining (MRC) are analyzed. Exact expressions for the level crossing rate (LCR) and the average fade duration (AFD) are derived for the Rayleigh propagation and arbitrary channel matrix dimensions. The analytical results are validated by simulation