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Atmospheric Lamb waveforms are useful for reconstructing large air events, but the propagation of Lamb waves is significantly affected by varying atmospheric conditions. The detailed dispersion of Lamb waves remains vague due to lack of data, but also to simplifications inherent in existing models. Here, we investigate the pressure perturbations induced by the 2022 Hunga‐Tonga eruption at both global and regional barometric arrays. After correction of the influence of wind and temperature, the group velocity dispersion curves, measured by tracking energy arrival times across different frequencies, show a decreasing trend with frequency which is superimposed by two low‐velocity bands. Regarding the synthetic results, we interpret these low‐velocity bands as the coupling effect between Lamb waves in the lower atmosphere and gravity or acoustic waves in the upper atmosphere, offering profound understandings of surface‐to‐space observations for hazard management and mitigation after extreme atmospheric events.

The so-called site effects caused by superficial geological layers may be responsible for strong ground motion amplification in certain configurations. We focus here on the industrialized Tricastin area, in the French Rhône valley, where a nuclear site is located. This area lies above an ancient Rhône Canyon whose lithology and geometry make it prone to site effects. This study presents preliminary measurements to investigate the local seismic amplification. We deployed three seismic stations in the area for several months: two stations were located above the canyon, the third one was located on a nearby reference rock site. The recorded seismicity was analysed using the Standard Spectral Ratio technique (SSR). The estimated amplification from weak motions reaches a value of 6 for some frequencies. These first results confirm the possibility of estimating seismic amplification using earthquakes recorded for less than one year, in this highly anthropogenic and industrialized environment, despite the local low-to-moderate level of seismicity. Noise-based SSR, that presents an obvious interest in such seismic context, shows also promising results in the area. To complement this empirical approach, we estimated the amplification using 1D wave propagation modelling. This numerical estimate is based on shear wave velocity profiles resulting from geophysical characterization campaigns. Comparison of the two approaches at low frequency, where numerical estimate is considered as the most representative, tends to suggest that edge-generated surface waves may have a strong influence in the local seismic response. This interpretation will be further investigated in the future.

Ambient noise surface wave exploration is one of the fields of interest in geophysical research. Extracting dispersion curves and inverting the S-wave velocity structure from the dispersion characteristics is also of primary importance. The accuracy of dispersion curves has great significance for the subsequent inversion result and its interpretation. The phase-shift method is widely used in dispersion imaging of surface waves. This method possesses advantages on stability but also suffers a lot from low resolution and low noise resistance. Therefore, we propose an improved phase-shift method based on semblance coefficients. This method replaces linear stacking in the traditional phase-shift method by calculating semblance coefficients and, therefore, can effectively improve the resolution and noise resistance of surface wave dispersion spectrum imaging. Tests are implemented on both synthetic ambient noise data and field data recorded by a short-period dense seismic array located in the ChangbaiShan region to evaluate the proposed method. The dispersion spectrum imaging results of the model and field data show that the semblance phase-shift (SPS) method has better noise resistance and computational accuracy than the traditional phase-shift method. The inversion results indicate that it is possible to obtain a reasonable S-wave velocity structure by inverting the dispersion curves resulting from the semblance phase-shift method. By constructing a 3 km deep and 4.8 km long S-wave velocity image, the velocity structure and abnormal conditions beneath the array in the ChangbaiShan region are presented. The results indicate a significant low-velocity anomaly at a depth of 1 km. It is inferred that it may be a fluid-rich structure.

This study aims to evaluate the effectiveness of five analytical and semi-analytical methods for estimating Lamb wave dispersion in viscoelastic plates—the Rayleigh–Lamb solution, the Global Matrix Method (GMM), the Semi-Analytical Finite Element (SAFE) method, the Scaled Boundary Finite Element Method (SBFEM), and the Legendre Polynomial Method (LPM). The Rayleigh–Lamb equations are solved using an optimized Newton–Raphson algorithm, enhancing computational efficiency while maintaining comparable accuracy. The SAFE method exhibited a remarkable balance between computational efficiency and physical accuracy, outperforming SBFEM at high frequencies. For epoxy and high-performance polyethylene (HPPE) plates, the SAFE method and the LPM significantly outperform the GMM in relation to computational efficiency, with errors below 1% for fundamental symmetric and antisymmetric modes across the tested frequency range of 0 to 100 kHz. In addition, the ability of the SAFE method to accurately predict both phase velocity and attenuation in viscous media supports their use in guided-wave-based structural health monitoring applications. Among the investigated approaches, the SAFE method emerges as the most robust and accurate for viscoelastic plates, while the SBFEM and LPM show limitations at higher frequencies. This study provides a quantitative and methodological foundation for selecting and implementing numerical methods for guided wave analysis, emphasizing the dual necessity of physical fidelity and numerical stability.

Crossed-dipole acoustic logging technology is mainly used to measure shear wave and determine the anisotropy or fractures of formation in the field of acoustic logging. Based on the propagation characteristics of dipole flexural waves in cased holes, and the wavefield of fundamental flexural mode at three bonding conditions: good cement bonding, poorly bonded interface I, and poorly bonded interface II. The dispersion curves of flexural waves are calculated, and the effects of cement parameters (elastic parameters and geometric dimensions) on dispersion curves are investigated. The RAI method is used to calculate the dipole full waveforms in a cased hole with conventional or ultralight cement surrounded by a soft formation. Then, the weighted spectral semblance is used to conduct the dispersion analysis of the full waves. The numerical results show that the cutoff frequency of flexural waves exceeds the frequency band of the current dipole logging tools in the well-bonded cased hole with conventional cement in soft formations. However, when ultralight cement is used, the cutoff frequency shifts toward low values, and the ultralight cement bonding is conducive to measuring flexural waves in soft formations. When interface I is poorly bonded, the cutoff frequency shifts toward low values, and the change is evident in soft formations. The cutoff frequency in the case of ultralight cement bonding is more evident than that of conventional cement bonding. If only interface II is poorly bonded, regardless of the cement used, the cutoff frequencies are all below 2 kHz. The dipole full-wave analysis of different bonding conditions further illustrates that the dispersion characteristics of flexural waves are sensitive to the cement bonding quality of cased holes.

The emergence of nanotechnology as a key enabling technology over the past years has opened avenues for new and innovative applications in nanomedicine. From the business aspect, the nanomedicine market was estimated to worth USD 293.1 billion by 2022 with a perception of market growth to USD 350.8 billion in 2025. Despite these opportunities, the underlying challenges for the future of engineered nanomaterials (ENMs) in nanomedicine research became a significant obstacle in bringing ENMs into clinical stages. These challenges include the capability to design bias-free methods in evaluating ENMs' toxicity due to the lack of suitable detection and inconsistent characterization techniques. Therefore, in this literature review, the state-of-the-art of engineered nanomaterials in nanomedicine, their toxicology issues, the working framework in developing a toxicology benchmark and technical characterization techniques in determining the toxicity of ENMs from the reported literature are explored.

In this paper, the dispersion parameters of Molybdenum Oxide thin films viz: oscillator energy, dispersion energy, transition moments, static refractive index, oscillator strength, and oscillator wavelength are estimated via Wemple–DiDomenico (WDD) single oscillator model. The crystal structural, surface morphological, and optical transmission properties of Molybdenum Oxide thin films are also investigated so as to extract vital in-put parameters for WDD model. The X-ray Diffraction and Fourier Transform of Infrared analysis confirm that the film fabricated at substrate temperature ~ 300 °C under goes a successful dual phase transformation from amorphous to α- and β-MoO 3 crystalline phase. Static refractive indices of the films are found to be vary from ~ 1.84 to 2.04 with the increase of substrate temperature during the thin film growth process via thermal evaporation technique. Moreover, the optical constants viz: film density, porosity, absorption coefficient, optical band gap, Urbach energy, steepness parameter, and strength of electron–phonon interaction are also studied as a function of substrate temperature. This is to establish a correlation between optical constants and dispersion parameters in the present paper.

In this work we study various continuous finite element discretization for two dimensional hyperbolic partial differential equations, varying the polynomial space (Lagrangian on equispaced, Lagrangian on quadrature points ( Cubature ) and Bernstein), the stabilization techniques (streamline-upwind Petrov–Galerkin, continuous interior penalty, orthogonal subscale stabilization) and the time discretization (Runge–Kutta (RK), strong stability preserving RK and deferred correction). This is an extension of the one dimensional study by Michel et al. (J Sci Comput 89(2):31, 2021. https://doi.org/10.1007/s10915-021-01632-7 ), whose results do not hold in multi-dimensional frameworks. The study ranks these schemes based on efficiency (most of them are mass-matrix free), stability and dispersion error, providing the best CFL and stabilization coefficients. The challenges in two-dimensions are related to the Fourier analysis. Here, we perform it on two types of periodic triangular meshes varying the angle of the advection, and we combine all the results for a general stability analysis. Furthermore, we introduce additional high order viscosity to stabilize the discontinuities, in order to show how to use these methods for tests of practical interest. All the theoretical results are thoroughly validated numerically both on linear and non-linear problems, and error-CPU time curves are provided. Our final conclusions suggest that Cubature elements combined with SSPRK and OSS stabilization is the most promising combination.

In the field of seismic exploration, scholars have been working to conduct wave propagation models that are close to physical reality. Researches for high-speed rail seismology show that the microstructural interactions by different scales will trigger the heterogeneous response of the medium, which in turn has an impact on the mechanical behavior of macro-scales. The generalized wave equations enhance the ability to reflect the heterogeneity of the medium by introducing the higher derivative of displacement and the characteristic scale parameters related to the microstructural properties of the medium. In this paper, we introduce the generalized wave equations under the single-parameter second-order strain gradient theory by considering the nonlocal effects, give the decoupled generalized wave equations using the Helmholtz decomposition theorem, and derive the expression of the phase-velocity of the P- and S-wave. Then, we investigate the dispersion characteristics of seismic wave propagation by considering the microstructural interactions in the medium utilizing theoretical dispersion analysis and numerical experiments which can provide a new approach for the establishment and interpretation of wave propagation models under actual medium.