Wave Dispersion Research Articles

Inversion of shear wave slowness and attenuation from dipole acoustic logging data based on an equivalent tool theory

The presence of a sonic logging tool affects the propagation characteristics of dipole-flexural waves in a fluid-filled borehole. As a result, the tool effect should be considered during the processing and inversion of the dipole-flexural waves for the acoustic properties of a shear wave (S wave). We show that the presence of the tool not only changes the slowness dispersion of the flexural wave but also results in a shift of its frequency-dependent attenuation toward lower frequencies. The equivalent tool theory (ETT) can realistically model the effect of an acoustic tool on guided wave propagation. With the ETT framework, we develop a unified workflow for estimating the S-wave slowness and attenuation from dipole array acoustic waveforms. The workflow is an extension of the model-based dispersive processing of dipole logging data. Our workflow involves two inversion procedures. By matching the actual dispersion data with the theoretical dispersion predicted by the ETT, we can invert the S-wave slowness and tool parameters. With the estimated S-wave slowness and other borehole parameters, we further calculate the partition coefficients of flexural waves using the ETT. Based on the concept of energy partitioning, we formulate a linear optimization problem and invert for the S-wave attenuation from the frequency-dependent dipole attenuation. We use synthetic and field data to demonstrate the effectiveness and applicability of the developed method. The results show that it is important to incorporate the tool effect when processing dipole acoustic logging data for S-wave slowness and attenuation, especially in a fast formation.

Multiple user-defined dispersive waves generation in silicon nitride waveguide

Multiple user-defined dispersive waves generation in silicon nitride waveguide

Research and application of Rayleigh wave imaging based on the Born–Jordan time‐frequency distribution

AbstractCurrently, the horizontal resolution of Rayleigh wave exploration is low. In this study, we propose the Born–Jordan time‐frequency distribution to analyse Rayleigh waves. The seismic signal was filtered with a wavelet transform for denoising, and the Rayleigh wave was separated in the time domain. Using the Born–Jordan time‐frequency distribution, the time waveform of each frequency comprising the Rayleigh wave from every seismic channel was obtained, and the time difference of the Rayleigh wave with the same frequency was calculated, based on which the dispersion curve between the two channels was obtained. Combined with the multichannel Rayleigh wave dispersion curve, phase velocity and frequency imaging under the seismic arrangement were obtained. Applying this method to detect abnormal geological bodies in engineering investigations showed that hard geologic bodies, such as comcrete rocks, have high velocity and frequency, whereas weak ones have low velocity and frequency. This strategy facilitated the detection of fractured zones, underground goafs and obstacles during pipe‐jacking construction near the surface.

Adjoint Synthesis for Trans‐Oceanic Tsunami Waveforms and Simultaneous Inversion of Fault Geometry and Slip Distribution

AbstractTsunamis propagate over long distances and can cause widespread damage even after crossing ocean basins. Prediction of tsunamis in distant areas based on observations near their sources is critical to mitigating damage. In recent years, the accuracy of numerical models of trans‐oceanic tsunami propagation has improved significantly due to the incorporation of effects such as the solid earth response to tsunami loading and wave dispersion. However, these models are computationally expensive and have not been fully utilized for real‐time prediction. Here, we derive the adjoint operator for the linear set of equations describing deep‐ocean tsunami propagation and show how a pre‐computed database of adjoint states can achieve rapid synthesis of tsunami waveforms at target sites from nonpoint arbitrary tsunami sources. The adjoint synthesis method allows for an exhaustive parameter search for tsunami source estimation. A method for simultaneous inversion of fault geometry and slip distribution using adjoint synthesis with Sequential Monte Carlo method was proposed and applied to the 2012 Haida Gwaii earthquake tsunami. The influence of model accuracy and the amount of observed data on the estimation of tsunami sources and waveforms was examined. It was found that with a highly accurate propagation model, using only a limited amount of observed data produced source and waveform estimates very similar to the final models obtained with much larger data sets. The final inferred fault model involved megathrust slip distributed between the Haida Gwaii trench and the Queen Charlotte fault. The proposed method can also quantify the uncertainty of the waveform forecasts.

Numerical Investigation of Evaluating the Degree of Damage in Concrete Plate Cold Joints through Surface Wave Dispersion Velocity Profiles

This study aims to develop a technology for assessing the interfacial condition of cold joints in concrete plates, focusing on the dispersion velocity profile of surface waves. The methodology employs a small impact hammer embedded with a piezoelectric element and a displacement receiver strategically positioned on either side of the seam. In this initial investigation, numerical models were constructed using ANSYS LS-DYNA. The cold joint zone was simulated by randomly removing elements with a predetermined void ratio. Displacement waveforms at the sensor node underwent analysis using a short-time Fourier Transform and the reassigned method to derive the dispersive velocity profile of surface waves. The study delves into the impacts of varying test-line lengths, impact durations, and void distributions. Numerical findings indicate that cold joints are detectable with a void ratio of 40% or greater. For the 60% and 80% void ratios, surface wave velocities register notably lower for wavelengths below 0.1 m and 0.2 m, respectively. Under the same porosity ratio for surface-observable cold joints, if their extension depth is smaller, the wave velocity on the dispersion curve will be lower than that of a fully penetrated cold joint. The current study reveals that a contact duration of 60 μs and an impactor-receiver distance of 0.82 m yield the most distinguishable results for detecting the extension and porosity ratio of a cold joint. Accompanied by tests with a hammer with a contact duration of 20 μs, additional information about the joint can be unveiled. Finally, various void distributions in the cold joint predominantly influence the wave velocity at shorter wavelengths.

Mechanical normal dispersive 𝒩ℒℋ𝒮 shock waves of microfluidics in shallow model

Mechanical normal dispersive 𝒩ℒℋ𝒮 shock waves of microfluidics in shallow model

Twist-Induced Hyperbolic Shear Metasurfaces

Following the discovery of moiré-driven superconductivity and density waves in twisted-graphene multilayers, twistronics has spurred a surge of interest in tailored broken symmetries through angular rotations enabling new properties, from electronics to photonics and phononics. Analogously, in monoclinic polar crystals a nontrivial angle between nondegenerate dipolar phonon resonances can naturally emerge due to asymmetries in their crystal lattice, and its variations are associated with intriguing polaritonic phenomena, including axial dispersion, i.e., the rotation of the optical axis with frequency, and microscopic shear effects that result in an asymmetric distribution of material loss. So far, these phenomena have been restricted to specific midinfrared frequencies difficult to access with conventional laser sources and fundamentally limited by the degree of asymmetry and by the strength of light-matter interactions available in natural crystals. Here, we leverage the twistronics concept to demonstrate maximal axial dispersion and loss redistribution of hyperbolic waves in elastic metasurfaces, achieved by tailoring the angle between coupled metasurface pairs featuring tailored anisotropy. We show extreme control over elastic wave dispersion and absorption via the twist angle and leverage the resulting phenomena to demonstrate enhanced propagation distance, in-plane reflection-free negative refraction and diffraction-free defect detection. Our work welds the concepts of twistronics, non-Hermiticity, and extreme anisotropy, demonstrating the powerful opportunities enabled by metasurfaces for tunable, highly directional surface-acoustic-wave propagation of great interest for a wide range of applications spanning from seismic mitigation to on-chip phononics and wireless communication systems, hence paving the way toward their translation into emerging photonic and polaritonic metasurface technologies. Published by the American Physical Society 2024

Increased risk of supraventricular tachycardia with polycystic ovarian syndrome

Abstract Background Many arrhythmias are known to be triggered by hormonal imbalances. Polycystic ovarian syndrome (PCOS) is a common hormonal imbalance seen in reproductive aged women. There is sparse literature linking PCOS to increased risk of atrial fibrillation (1). We hypothesise that PCOS could also be associated with Supraventricular tachycardia (SVT) Purpose To determine if PCOS is a risk factor for SVT and Atrial fibrillation/flutter (AF/AFL). Methods Utilising the National Inpatient Sample (NIS) of the years 2015-2020, We performed a multivariable logistic regression analysis to determine if PCOS was independently associated with SVT and AF/AFL. The NIS is the largest publicly available database of United States containing data on upto 7 million hospital visits per year. Results From the years 2015 to 2020, PCOS was present in 367,375 adult patients and SVT was observed in 965, 799 patients. After adjusting for relevant risk factors, PCOS was associated with increased odds of SVT (OR 1.23, 95% CI 1.12-1.36, P<0.001) (Table 1). However, PCOS was not associated with increased odds of atrial fibrillation and atrial flutter (OR 0.72, 95% CI 0.66-0.77, P<0.001) Conclusion SVTs have been clinically observed to be more frequent in the luteal phase of the menstrual cycle due to low estrogen. The high androgen/estrogen ratio seen in PCOS may result in a similar increased risk of SVT in PCOS patients. PCOS is known to increase P wave maximum duration and dispersion, indicating abnormal atrial conduction (2). The negative association between AF/AFL is likely because PCOS is seen more commonly in younger patients, and AF/AFL is a disease of older adults. We recommend further studies in PCOS women to confirm our findings and characterise the mechanisms of SVT.

SH-wave based defect imaging method for CFRP plates with variable thickness

ABSTRACT Classical guided wave imaging methods find applicability in uniform-thickness plates or quasi-isotropic plates. To be compared with, the method presented in this paper advances damage imaging accuracy for both uniform-thickness and variable-thickness anisotropic plates by incorporating new compensation terms grounded in the theoretical excitation directivity of the quasi-SH0 mode in anisotropic material. Specifically, the nondispersive nature of the wave speed and skew angle of the quasi-SH0 mode in the low- fd states (frequency-thickness-product lower than the cut-off value of SH1 mode) is established through dispersion curves and wave structure calculations. Additionally, employing the elastic dynamics reciprocity theorem reveals that the directivity of this mode is also nondispersive in the low- fd states. Therefore, the quasi-SH0 mode is theoretically insensitive to thickness variation. Experiment validated these theoretical calculations. On this basis, this paper proposed an integrated imaging method that utilises transmitted and reflected wave information by incorporating matching pursuit algorithm, cross-correlation analysis, probabilistic reconstruction and delay-and-sum method that incorporates new compensation terms based on the quasi-SH0 mode theory. Experimental validation of uniform-thickness carbon fibre-reinforced polymer (CFRP) plates and variable-thickness CFRP plates shows the insensitivity of this method to structural thickness variation, enabling effective imaging of damage in such anisotropic structures.

Long Propagating Polaritonic Heat Transfer: Shaping Radiation to Conduction.

Surface phonon polaritons (SPhPs) originate from the coupling of mid-IR photons and optical phonons, generating evanescent waves along the polar dielectric surface. The emergence of SPhPs gives rise to a phase of quantum matter that facilitates long-range energy transfer (100s μm-scale). Albeit of the recent experimental progress to observe the enhanced thermal conductivity of polar dielectric nanostructures mediated by SPhPs, the potential mechanism to present the high thermal conductivity beyond the Landauer limit has not been addressed. Here, we revisit the comprehensive theoretical framework to unify the distinct pictures of two heat transfer mechanisms by conduction and radiation. We first designed our experimental platform to distinguish contributions of two distinct fundamental modes of SPhPs, resulting in far-field radiation and long propagating conduction, respectively, by tuning the configuration of a nanostructured heat channel integrated into the thermometer. We could effectively control the transmission of long-propagating SPhPs to influence the apparent thermal conductivity of the nanostructure. This study reveals the high thermal conductance of 1.63 nW/K by a fast SPhP mode comparable to that by classical phonons, with measurements showing apparent conductivity values of up to 2 W/m·K at 515 K. The origin of the enhanced thermal conductivity was exploited by observing the interference of dispersive evanescent waves by double heat channels. Furthermore, our experimental observations of length-dependent thermal conductance by SPhPs are in good agreement with the revisited Landauer formula to illustrate a polaritonic mode of heat conduction, considering the dispersive nature of radiation not limited to the physical boundaries of a solid object yet directionally guided along the surface.

Understanding the structure of crust and shallow upper mantle beneath western Tibet through the joint inversion of Rayleigh wave group velocity dispersion with interpolated receiver functions

We present the 3-D shear wave velocity variationin the crust and upper mantle structure of western Tibet using a joint inversion of Rayleigh wave group velocity dispersion and interpolated receiver function. The lateral sampling of the receiver function and the surface wave dispersion is equalized by the interpolation scheme. This new method of spatial interpolation eliminates difficulties caused by back azimuthal variation in the receiver function. We have jointly inverted these interpolated receiver functions with the Rayleigh wave group velocity dispersions obtained from the earthquake and ambient noise tomography to map the tectonic structure of western Tibet. The study reveals remarkable variation of the seismic characteristics in the crust and shallow upper mantle of western Tibet. The mapped Moho depth is ~74 km in the northern part of the plateau, whereas it is ~69 km in the southern part. A thick mid-crustal slow-velocity zone from ~10km up to ~40 km depth has been observed, which could be attributed to partial melt. A noteworthy finding is the variation in slower crustal velocity between the south and north of the Lhasa Block (LB). We interpret this as the Indian crust that has been underthrusted beneath the Tibetan plateau, and the northern limit of the Indian lithosphere extends to the southern part of the LB.

Existence of Electrostatic Ion Cyclotron Waves in a Laboratory Created E Region Ionospheric‐Like Plasma

AbstractMolecular ions are relatively cold in the E region ionosphere; however, they can upwell to the magnetosphere during geomagnetically active times. Resonance between electrostatic ion cyclotron (EIC) waves is a potential pathway to energize molecular ions. In this work, the E region ionospheric plasma was modeled in the laboratory, and EIC waves were excited by a nonuniform field‐aligned current. The EIC wave was excited even when the ion neutral collision frequency is much higher than the ion cyclotron frequency, and the fundamental frequency was observed to be below the ion cyclotron frequency. In addition, the wave dispersion of the collisional EIC wave was calculated, which shows a consistent trend with experimental results as the collisions increasing. Therefore, this work suggests that EIC waves can be excited in the E region ionospheric‐like plasma, which can support the explanation of the energization of molecular ions in the E region ionosphere.

Deep Structure of the Baikal Rift Zone and Central Mongolia

The upper mantle and the transition zone of the Baikal rift zone (BRZ) are studied. The observations are analyzed using P-wave receiver functions. It is found that in the BRZ central and northeastern part, the P410s converted seismic phase is preceded by a precursory wave with negative polarity which is formed in the low S-wave velocity layer at a depth of 350–410 km. A similar precursory wave with low S-wave velocity and negative polarity is formed at a depth of 600–660 km. The low-velocity layers are interpreted as resulting from the hydration of wadsleyite and ringwoodite during the subduction of the Pacific lithosphere. A similar study of the mantle in Central Mongolia found no expected signs of hydration. Modeling of the lithosphere–asthenosphere system in Central Mongolia by joint inversion of the body wave receiver functions and surface wave dispersion curves reveals a very thin lithospheric lid beneath Khangai and a thick layered asthenosphere to a depth of 200 km with a lithospheric inclusion between low-velocity layers.

Mechanisms of Fundamental Electromagnetic Wave Radiation in the Solar Wind

Large-scale and long-term two-dimensional particle-in-cell simulations performed for parameters relevant to type III solar radio bursts have provided new results on the generation mechanisms of fundamental electromagnetic waves radiated at the plasma frequency ω p . The paper first considers the nonlinear wave interaction process of electromagnetic decay (EMD) in a homogeneous solar wind plasma with an electron-to-ion temperature ratio T e /T i > 1. The dynamics of ion-acoustic waves (dispersion, spectra, growth/damping) is studied, and signatures confirming the three-wave interactions (cross-bicoherence, correlations between waves’ phases and between waves' growths, resonance conditions) are provided. The decisive role played in EMD by the backscattered Langmuir waves coming from the electrostatic decay (ESD) is demonstrated. EMD can be triggered by ion acoustic waves coming from the two cascades of the faster and more intense ESD. The same study is then performed in a solar wind plasma with random density fluctuations. In this case, EMD is not suppressed but develops only within plasma regions of reduced or quasi-uniform density. It coexists with linear mode conversion (LMC) of Langmuir waves into electromagnetic radiation, which is the fastest and most prominent process, as well as with ESD. LMC can lead to enhanced occurrence of EMD in the early stage. Moreover, the impact of T e /T i on electromagnetic energy growth and saturation is shown to be rather weak. Ion-acoustic waves are heavily damped at T e ∼ T i , so that EMD is overcome by nonlinear induced scattering on thermal ions. In actual solar wind plasmas, EMD should be more easily observed in plasma regions weakly perturbed by the background density turbulence and where ion temperature is decreased.

Near-Surface Rayleigh Wave Dispersion Curve Inversion Algorithms: A Comprehensive Comparison

Near-Surface Rayleigh Wave Dispersion Curve Inversion Algorithms: A Comprehensive Comparison

Flexural wave propagation characteristics of advanced nanocomposites reinforced sandwich structure via 3D-flexibility-deep neural networks approaches

The propagation of flexural waves in advanced nanocomposites reinforced sandwich structures is a topic of paramount importance in the field of structural engineering and materials science. This study investigates the dynamic behavior of such structures, focusing on the wave propagation characteristics along with longitude and lateral directions and their influence on structural performance. Advanced nanocomposites, with their unique material properties and enhanced mechanical properties, offer promising opportunities for the development of lightweight and high-strength sandwich structures. For this important aim, first, a mathematical modeling using three-dimensional flexibility theory and an analytical solution procedure, the results are collected. After that using the datasets of the mathematical modeling section, the hybrid deep neural networks are trained, tested, and validated. Through comprehensive analytical simulations and machine network validations, this research elucidates the complex interplay between material composition, structural geometry, and wave propagation phenomena. Key parameters, such as wave velocity, dispersion, and geometry conditions are analyzed to gain insights into the dynamic response of the sandwich structure. The findings contribute to a deeper understanding of the underlying physics governing flexural wave propagation in nanocomposite-reinforced sandwich structures, thereby facilitating the design and optimization of lightweight and resilient structural systems for diverse engineering applications.

Exact solution of the propagation of ON-OFF signals by dispersive waves

The propagation of ON-OFF signals with dispersive waves is examined in this study. An integral-form exact solution for a simple ON-OFF switching event is derived, which holds for any dispersion relation. The integral can be exactly calculated for two types of dispersion relations. Further, the analysis of these solutions shows that the ON-OFF signal propagates with the group velocity and that the boundary thickness of the signal increases with time, typically at a rate proportional to the square root of time, owing to dispersion. Additionally, an approximate solution for a general dispersion relation is derived, and for a higher-complexity ON-OFF switching pattern is constructed.

Peregrine soliton emits dispersive waves within graded-index multimode fibers without higher-order dispersion

We investigate the propagation dynamics of the Peregrine soliton, a significant prototype of rogue waves, within the graded-index multimode fibers, in the absence of higher-order dispersion. The Peregrine soliton keeps the approximate evolution trend when propagating within the graded-index multimode fibers to replace the single-mode fibers when preserving the equivalent nonlinear effect. In addition, a series of dispersive waves (also called resonant radiation) can be emitted by the Peregrine soliton, perturbated by the periodic beam oscillation caused by the spatial self-imaging effect within the graded-index multimode fibers. To be more exact, the location of the multiple resonant frequencies can be predicted using the modified quasi-phase-matching conditions, which are verified by the numerically calculated results. We can also manipulate the locations of spectral sidebands and the peak power of dispersive waves by changing the self-imaging parameter of the graded-index multimode fibers. Our findings can provide a deeper comprehension of the propagation characteristic of the Peregrine soliton within the graded-index multimode fibers and provide valuable instruction for further rich nonlinear experiments.

Effect of bathymetry data on tsunami wave ray tracing in the western Banten sea

The lack of tsunami wave warning during the Anak Krakatau collapse in 2018 resulted in devastating damage to coastal areas. The tsunami wave arrived in the coastal areas approximately half an hour after the collapse. As a tsunami wave can travel abruptly, an early warning system should warn faster. However, a warning system based on a sophisticated hydrodynamic model in real-time would take time to conduct the numerical tsunami wave simulation. Hence, this study proposes a fast and reliable estimation of tsunami wave propagation through a classic ray tracing analysis. We use two ray-tracing methods to investigate the tsunami wave propagation from Anak Krakatau to the western Banten Sea. The first method follows Snell’s law, considering dispersive waves, and the second assumes non-dispersive waves based on the ray tracing equations, considering the Earth’s sphericity. Both methods are quantitatively evaluated by comparing the travel time measured at Anyer and Marina Jambu. This study finds that non-dispersive wave tracing performs a shorter computational time and slightly better prediction of tsunami wave propagation than dispersive-based wave tracing, with a relative absolute difference of the travel time of 17.9–26.7% in Anyer and 3.6–5.2% in Marina Jambu. This study also confirms the importance of bathymetry validity in wave ray tracing. Two regional bathymetry datasets with a mean difference of less than 5 m result in different wave ray tracing, in which one dataset does not produce the wave ray path towards the Panaitan Island. Based on bathymetric surveys in Anyer and Marina Jambu, the national bathymetry data (BATNAS) has shown its superiority to being used as a bathymetry in the ray-tracing process, with correlations of 81% and 93% in both areas compared to other available bathymetry datasets. We summarize that reliable bathymetry data and the non-dispersive ray tracing method can be used as an initial estimation of tsunami wave propagation efficiently.

Supercontinuum generation optimization in a dispersion-varying chalcogenide fiber

We experimentally demonstrate that a variable longitudinal dispersion profile can enhance supercontinuum generation in a chalcogenide tapered fiber, compared to tapered fibers with a standard, constant dispersion profile. For this purpose, nonlinear As2S3 tapered fibers are compared experimentally and numerically based on their dispersion profile. The optimal taper with non-uniform dispersion profile simultaneously enhances the energy transfer to both dispersive waves and Raman solitons towards shorter and longer wavelengths, respectively. The generated supercontinuum spans within the spectral range of 1.20–2.98 μm with an out-of-pump power enhancement of 4.3 dB at shorter wavelengths, 2.5 dB at longer wavelengths, and a bandwidth extension of 262 nm, compared to the supercontinuum generated with an optimal but constant dispersion profile.