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Isotropic materials are required to adhere to various mechanical principles due to their limited thermal stability. For instance, it is essential for Poisson's ratio to be within the range of −1 to 0.5, and the longitudinal wave velocity must exceed the transverse wave velocity. Nevertheless, perfect crystals, as anisotropic materials, have the ability to defy conventional rules. Through the integration of high-throughput processes and first-principles calculations, a comprehensive exploration of known materials was conducted, resulting in the establishment of a database featuring an extreme anisotropic mechanism. This included the identification of abnormal Poisson's ratios (with the directional Poisson's ratio ranging from −3.00 to 3.67), the discovery of extreme negative linear compressibility, the determination of the upper and lower limits of the sound velocity, and other associated properties. Several materials with abnormal Poisson's ratios (<−1 or >0.5) were listed, and their peculiar mechanical behavior, wherein the volume decreased counterintuitively with uniaxial tension, was discussed. Finally, this study focused on the velocities of longitudinal and transverse waves, with specific emphasis on materials exhibiting transverse wave velocities that exceeded the longitudinal wave velocities. [ABSTRACT FROM AUTHOR]

This paper presents the design of a single-phase solid phononic crystal (PnC) structure featuring a regular hexagonal perforation pattern. The structure manifests three negative refraction bands, encompassing one for transverse waves and two for longitudinal waves, thereby enabling simultaneous control of shear and longitudinal waves. Due to the high symmetry of the triangular lattice, the equal frequency curves corresponding to the negative refraction band approach circular shapes, suggesting a nearly isotropic negative refraction effect. This negative refraction effect is achieved through specific mass resonance modes closely related to the porous structure designed in this paper. Initially, we analyze the band structure of the PnC, followed by designing the PnC plate structure to achieve negative refraction control for transverse waves at a frequency of 32.4 kHz, with a negative refraction index of −1. Additionally, negative refraction control for longitudinal waves is attained at frequencies of 44 and 64.54 kHz. Subsequently, we scrutinize the influence of various conditions on negative refraction, including different structural parameters, incident angles, and operating frequencies, while verifying the robustness of the designed phonon crystal structure. Leveraging the negative refraction characteristics of the structure, we construct an elastic wave lens to achieve perfect imaging of shear and longitudinal waves. Finally, employing finite element simulation and analyzing focusing imaging characteristics with different source positions, we validate that the results closely align with theoretical expectations. The solid PnC structure designed in this study holds significant potential for applications in the fields of elastic wave imaging. [ABSTRACT FROM AUTHOR]

Mode coupling and conversion between longitudinal and transverse modes are ubiquitous and universal in elastic waves, presenting a challenge in realistic applications such as nondestructive evaluation and geological exploration, where independent and separate manipulation of each mode is demanded. In this article, we propose a design of elastic metalens that can realize a high-efficiency focusing for the longitudinal wave and a V-shaped converging pattern for the transverse wave at the same time. The metalens is constructed from a metagrating, where each meta-atom has a simple configuration and renders high diffraction efficiency even for large steering angles, enabled by concurrent utilization of grating diffraction theory and advanced optimization algorithms. Interestingly, an arbitrary energy splitting ratio between the reflected longitudinal and transverse waves can be obtained by precisely controlling the coupling strength and conversion efficiency between them, providing improved flexibility and adaptability to various application environments. Two illustrative examples with a sharp focusing effect and tailored conversion efficiency are explicitly demonstrated, with a 50/50 energy splitting ratio between the longitudinal and transverse waves in the first case, and a 70/30 ratio in the second one. [ABSTRACT FROM AUTHOR]

We propose a Markovian quantum model for the time dependence of the pressure-induced decoherence of rotational wave packets of gas-phase molecules beyond the secular approximation. It is based on a collisional relaxation matrix constructed using the energy-corrected sudden approximation, which improves the previously proposed infinite order sudden one by taking the molecule rotation during collisions into account. The model is tested by comparisons with time-domain measurements of the pressure-induced decays of molecular-axis alignment features (revivals and echoes) for HCl and CO2 gases, pure and diluted in He. For the Markovian systems HCl–He and CO2–He, the comparisons between computed and measured data demonstrate the robustness of our approach, even when the secular approximation largely breaks down. In contrast, significant differences are obtained in the cases of pure HCl and CO2, for which the model underestimates the decay rate of the alignment at short times. This result is attributed to the non-Markovianity of HCl–HCl and CO2–CO2 interactions and the important contribution of those collisions that are ongoing at the time when the system is excited by the aligning laser pulse. [ABSTRACT FROM AUTHOR]

Anti-plane shear wave propagation in a functionally graded piezoelectric substrate and a piezoelectric substrate guided by a slit is analyzed theoretically. The equations of motion are taken from the linear theory of piezoelectricity for polarized ceramics. The dispersion relation is obtained by applying appropriate boundary conditions on the derived solutions. PZT-5 and ZnO are taken as numerical examples to manifest the effect of different material parameters (gradient factor, slit width etc.) graphically on the phase and group velocity of the considered wave. $ \textrm{LiI}{\textrm{O}_\textrm{3}} $ LiI O 3 and $ \textrm{BaTi}{\textrm{O}_\textrm{3}} $ BaTi O 3 materials are taken separately to compare the results. Also, graphs are plotted for different modes of the wave as well as for different frequency ranges and for the case when slit is absent. As a special case, it is remarked that the present study has resemblance with one of the existing works. The highlights of the study are to characterize the anti-plane wave propagation within a functionally graded piezoelectric substrate/gap/piezoelectric substrate coupled structure, to show the effect of different parameters, modes, frequency, etc. on the velocity profile of the considered wave and to show the effect of gap layer. The outcomes of this study may be used to enhance the sensitivity of acoustic wave devices and sensors. [ABSTRACT FROM AUTHOR]

The reliability of Vs30 and the performance of alternative time averaged shear wave velocities (Vsz) and shear wave travel times (Ttz) at various depths, z, were investigated for the estimation of site amplification and fundamental frequency (f0) characterization by considering the linear and nonlinear soil behavior. The study revealed that alternative parameters performed better than Vs30 and the best performing z parameters changed by switching from convex to concave theoretical profiles and by increasing ground motions. For a practical usage in site investigations, guidelines to estimate nonlinear soil amplification factor and fundamental frequency from the linear ones were presented. [ABSTRACT FROM AUTHOR]

Some soil characteristics, such as the shear wave velocity, the shear modulus, the Poisson ratio, and the porosity, affect how clay soils behave. The soil design parameters under loading, such as soil liquefaction induced by dynamic earthquake loading, employ the shear wave velocity and shear module with modest stress. In order to understand the pore saturation, the Poisson ratio and seismic velocity ratio are also utilized. Additionally, one of the most crucial physical characteristics for assessing permeability at the base of any engineering structure, resolving consolidation issues that may arise at the foundation of an engineering structure, and influencing the deformation behavior of soils is soil porosity. Predicting the porosity of clay soils is a crucial first step in tackling engineering and environmental issues that may arise in the soil after an earthquake or not. With the use of dynamic soil metrics such as seismic velocities, shear modules, bulk modules, seismic velocity ratios, and Poisson ratios, the current work aims to estimate soil porosity. Seismic refraction was used by various studies in the past to conduct in-situ geophysical research. The lithological characteristics of the soil (such as the grain size, shape, type, compaction, consolidation, and cementation of the grains) and the physical characteristics of the soil (such as porosity, permeability, density, anisotropy, saturation level, liquid–solid transition, pressure, and temperature), as well as the elasticity characteristics of the soil (such as shear modulus (G), bulk modulus (K), Young modulus (E), Poisson ratio (μ) and Lamé constants (λ )) all have an impact on seismic waves passing through a medium. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess cardiac shear wave imaging implemented in a new MACH 30 ultrasound machine (SuperSonic Imaging, Aix-en-Provence, France) and interfaced with a linear probe and a phased array probe, in comparison with a previously validated Aixplorer system connected to a linear probe (SuperSonic Imaging) using Elasticity QA phantoms (Models 039 and 049, CIRS Inc., Norfolk, VA, USA). Quantile–quantile plots were used for distribution agreement. The accuracy of stiffness measurement was assessed by the percentage error and the mean percentage error (MPE), and its homogeneity, by the standard deviation of the MPE. A p value <0.01 was considered to indicate statistical significance. The accuracy of dedicated cardiac sequences for linear probes was similar for the two systems with an MPE of 8 ± 14% versus 20 ± 21% (p = not significant) with the SuperSonic MACH 30 and Aixplorer, respectively, and was influenced by target stiffness and location of the measurement in the field of view, but without drift over time. The optimal transthoracic cardiac probe workspace was located between 4 and 10 cm, with an MPE of 29.5 ± 25% compared with 93.3 ± 130% outside this area (p < 0.0001). In this area, stiffness below 20 kPa was significantly different from the reference (p < 0.0001). The sectorial probe revealed no MPE difference in any of the measurement areas, with no significant lateral or axial gradient. The new Supersonic MACH 30 system upgraded with a sectorial probe and specific cardiac settings provided homogenous stiffness measurements, especially when operating at depths between 4 and 10 cm. These phantom results may be useful in designing future in vivo studies. [ABSTRACT FROM AUTHOR]

Objective: To investigate and quantify age-related changes in lower limb muscle stiffness in typically developing children and adolescents using acoustic radiation force impulse shear wave elastography. Materials and methods: Shear wave velocities of bilateral rectus femoris, tibialis anterior, and medial gastrocnemius muscles at rest were obtained in typically developing children and adolescents aged 3 to 18 years. The participants were classified into three age groups: Group 1 (children), 3 to 7 years old; Group 2, 8 to 12 (pre-adolescent); and Group 3 (adolescent), 13 to 18. The shear wave velocities of muscle were compared across the three age groups, as well as compared between right- and left-side limbs. The correlation between shear wave velocities and body weight or body mass index was assessed. Results: Of the 47 participants, 21 were in Group 1, 17 in Group 2, and 9 in Group 3. There were no significant differences among the three age groups' shear wave velocities of bilateral lower limb muscles, and no significant differences between right and left sides. There was no correlation between muscle stiffness and body weight or body mass index. Conclusion: The present pilot study applied acoustic radiation force impulse shear wave elastography to quantify lower limb muscle stiffness in typically developing children and adolescents aged 3 to 18 years, suggesting no marked change in muscle stiffness occurs as they develop. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a vibration pad suitable for renal MR elastography (MRE). Chronic kidney disease (CKD) is a progressive condition affecting >800 million people worldwide. Renal fibrosis is a common pathological feature of CKD that causes fibrotic regions to be much stiffer than those in normal renal tissues. Therefore, MRE can be used to diagnose CKD because it can image organ stiffness. In MRE, the shear modulus is obtained from the wavelength of the shear waves. Therefore, it is highly important to propagate shear waves with sufficient vibration strength in the tissue. By using a three-dimensional (3D) printer, we created a "Flexible Pad" suitable for renal MRE. The Flexible Pad was placed under the back of the participant in the supine position and deformed in response to the participant's weight, adhering closely to the body surface. Six healthy volunteers participated in this study. Our Flexible Pad allowed for coherent shear waves (clear waves with little scattering and interference) to be efficiently transmitted to the kidney deep-lying tissues in the abdomen. The shear moduli of the kidney (n = 6) were 8.95 ± 0.84 kPa in the right kidney and 9.70 ± 0.99 kPa in the left kidney. Our results indicate that using our Flexible Pad for renal MRE can provide a more reliable measurement of renal shear modulus. [ABSTRACT FROM AUTHOR]

Understanding how the Miocene N–S‐trending rifts on the southern Tibetan Plateau formed is crucial for understanding the evolution of the plateau. Most competing models suggest that all the rifts developed uniformly, but there are differences in magmatism among them. We conducted ambient noise tomography based on a broadband seismic array deployed across the rifts. A mid‐crustal low‐Vs layer extends laterally beneath the Tangra Yum Co Rift and the Pumqu‐Xianza Rift, implying that E‒W stretching of the ductile middle crust segmented the brittle upper crust, causing rifting and subsequent magmatism. In contrast, the Yadong‐Gulu Rift, which experienced prerifting magmatism, is characterized by an isolated low‐Vs anomaly extending subvertically from the surface to the middle crust, indicating that the crust experienced magmatic intrusion and local disruption, which promoted the later formation of a large rift. The results suggest that the various rifts might have distinct formation modes. Plain Language Summary: The rifts in the southern Tibetan Plateau are closely related to the growth and evolution of the plateau. These rifts are often considered as a whole in studies on their developmental modes. However, different rifts exhibit variations in terms of the timing of magmatism (before or after rifting). This implies that the developmental modes of different rifts are likely to involve different crustal deformation processes. To further investigate the formation modes of different rifts, we used the ambient noise method to obtain the crustal shear wave velocity structure. The presence of a low‐velocity layer in the mid‐crust indicates a vertical layering of crustal strength, which reveals that the upper crustal segmentation together with ductile deformation of the weak mid‐crust contributed to the formation of some rifts. In contrast, the presence of an isolated low‐velocity anomaly extending to the mid‐crust implies that a disruption of the lateral crustal strength caused the formation of another rift. Our findings will change the traditional understanding of the formation of N–S‐trending rifts and the evolution of the Tibetan Plateau. Key Points: The crustal structure beneath the rifts in southern Tibet is revealed by ambient noise tomographyRifts with post‐ or pre‐rifting magmatism lie above a mid‐crustal low‐velocity layer or a subvertical low‐velocity anomaly, respectivelyThe intrinsic differences in crustal structure indicate that the rifts in southern Tibet formed via different modes [ABSTRACT FROM AUTHOR]

Seismic tomography has shown that the shear wave velocities (Vs) under continents, especially under cratons, are extremely fast at 100–200 km depth, which is difficult to explain by low temperatures or high Mg#. Alternatively, delaminated eclogitic lower continental crust has been proposed to account for these fast seismic anomalies. However, the thermoelastic properties of jadeite which constitutes up to 60–80 mol% of clinopyroxene in the potentially delaminated lower continental crust are not well constrained. In this study, we measured the single‐crystal elasticity of jadeite by Brillouin spectroscopy under simultaneous high pressure and temperature conditions for the first time. We found that the temperature dependence of Vs of jadeite is extremely small if not negligible. The seismic velocities of the potentially delaminated lower continental crusts were subsequently modeled and found to match the widely observed fast seismic anomalies under cratons between 100 and 200 km depth. Plain Language Summary: The seismic wave velocity variation images show the potential composition and temperature heterogeneities inside the Earth. Fast shear wave velocities (∼7% higher than the global average) have been observed under continents at 100–200 km depths. A candidate explanation of this fast shear wave velocity anomaly is the existence of delaminated eclogitic lower continental crust. However, due to the lack of knowledge of the thermoelastic properties of clinopyroxene, which is the dominant mineral phase (up to 60 vol%) in delaminated eclogitic lower continental crust, evaluation of this hypothesis is difficult. Clinopyroxene in the potentially delaminated lower continental crust is jadeite‐rich (up to 60–80 mol%) due to its high Na content (2.5–3.5 wt%). In this study, we report single‐crystal elasticity of jadeite at high pressure‐temperature conditions. We found the Vs of jadeite is much higher than all the other major upper mantle minerals under upper mantle conditions. The calculated seismic velocities of the potentially delaminated lower continental crusts could easily account for the fast shear wave anomalies observed under cratons. Key Points: High pressure‐temperature single‐crystal elasticity measurements of jadeite are conducted by Brillouin spectroscopyJadeite is among the seismically fastest phases in the Earth's upper mantleDelaminated lower crust can help explain the fast seismic anomalies under cratons [ABSTRACT FROM AUTHOR]

The nondestructive spectral analysis of surface waves (SASW) technique determines the shear wave velocities along the wide wavelength range using Rayleigh-type surface waves that propagate along pairs of receivers on the surface. The typical configuration of source-receivers consists of a vertical source and three vertical receivers arranged in a linear array. While this approach allows for effective site characterization, laterally variable sites are often challenging to characterize. In addition, in a traditional SASW test configuration system, where sources are placed in one direction, the data are collected more on one side, which can cause an imbalance in the interpretation of the data. Data interpretation issues can be resolved by moving the source to opposite ends of the original array and relocating receivers to perform a second complete set of tests. Consequently, two different Vs profiles can be provided with only a small amount of additional time at sites where lateral variability exists. Furthermore, the testing procedure can be modified to enhance the site characterization during data collection. The advantages of performing SASW testing in both directions are discussed using a real case study. [ABSTRACT FROM AUTHOR]

A 3D vertical seismic profiling (VSP) survey was acquired using a distributed acoustic sensing (DAS) system in the Permian Basin, West Texas. In total, 682 shot points from a pair of vibroseis units were recorded using optical fibers installed in a 9000 ft (2743 m) vertical part and 5000 ft (1524 m) horizontal reach of a well. Transmitted and reflected P, S, and converted waves were evident in the DAS data. From first-break P and S arrivals, we found average P-wave velocities of approximately 14,000 ft/s (4570 m/s) and S-wave velocities of 8800 ft/s (3000 m/s) in the deep section. We modified the conventional geophone VSP processing workflow and produced P–P reflection and P–S volumes derived from the well's vertical section. The Wolfcamp formation can be seen in two 3D volumes (P–P and P–S) from the vertical section of the well. They cover an area of 3000 ft (914 m) in the north–south direction and 1500 ft (460 m) in the west–east direction. Time slices showed coherent reflections, especially at 1.7 s (~11,000 ft), which was interpreted as the bottom of the Wolfcamp formation. Vp/Vs values from 2300 ft (701 m) –8800 ft (2682 m) interval range were between 1.7 and 2.0. These first data provide baseline images to compare to follow-up surveys after hydraulic fracturing as well as potential usefulness in extracting elastic properties and providing further indications of fractured volumes. [ABSTRACT FROM AUTHOR]

Lateral-excited bulk acoustic wave resonators (XBARs) have a large electromechanical coupling coefficient and low mechanical loss. However, XBARs have not yet been commercialized in 5G communications due to spurious modes, high TCF, and low-power handling. This paper presents a lateral-excited bulk acoustic wave resonator with piston mode electrodes named PLBAR. Compared to the conventional interdigital transducer structure, the PLBAR suppresses the transverse waves due to the irregular boundary caused by piston mode electrodes. Higher order modes are also to some extent suppressed by increasing in metallization rate. The fabricated PLBAR achieves a high K eff 2 of 26.43% at 5.2 GHz using a 350 nm Z-cut lithium niobate on insulator substrate, effectively suppressing the transversal mode. Additionally, the power durability exceeds +14 dBm due to the increased metallization of the piston mode electrodes. The measured temperature coefficient of PLBAR is −42.55 ppm/°C. The PLBAR addresses some of the limitations of the XBARs and demonstrates significant improvements in performance without requiring additional fabrication steps, making it a promising solution for RF resonators in 5G communication systems. [ABSTRACT FROM AUTHOR]

Background: Assessment of dynamic parameters to guide fluid administration is one of the mainstays of current resuscitation strategies. Each test has its own limitations, but passive leg raising (PLR) has emerged as one of the most versatile preload responsiveness tests. However, it requires real-time cardiac output (CO) measurement either through advanced monitoring devices, which are not routinely available, or echocardiography, which is not always feasible. Analysis of the hepatic vein Doppler waveform change, a simpler ultrasound-based assessment, during a dynamic test such as PLR could be useful in predicting preload responsiveness. The objective of this study was to assess the diagnostic accuracy of hepatic vein Doppler S and D-wave velocities during PLR as a predictor of preload responsiveness. Methods: Prospective observational study conducted in two medical–surgical ICUs in Chile. Patients in circulatory failure and connected to controlled mechanical ventilation were included from August to December 2023. A baseline ultrasound assessment of cardiac function was performed. Then, simultaneously, ultrasound measurements of hepatic vein Doppler S and D waves and cardiac output by continuous pulse contour analysis device were performed during a PLR maneuver. Results: Thirty-seven patients were analyzed. 63% of the patients were preload responsive defined by a 10% increase in CO after passive leg raising. A 20% increase in the maximum S wave velocity after PLR showed the best diagnostic accuracy with a sensitivity of 69.6% (49.1–84.4) and specificity of 92.8 (68.5–99.6) to detect preload responsiveness, with an area under curve of receiving operator characteristic (AUC–ROC) of 0.82 ± 0.07 (p = 0.001 vs. AUC–ROC of 0.5). D-wave velocities showed worse diagnostic accuracy. Conclusions: Hepatic vein Doppler assessment emerges as a novel complementary technique with adequate predictive capacity to identify preload responsiveness in patients in mechanical ventilation and circulatory failure. This technique could become valuable in scenarios of basic hemodynamic monitoring and when echocardiography is not feasible. Future studies should confirm these results. [ABSTRACT FROM AUTHOR]

Ultrasound shear wave elastography (SWE) is an emerging non-invasive imaging technique for peripheral nerve evaluation. Shear wave velocity (SWV), a surrogate measure of stiffness, holds promise as a biomarker for various peripheral nerve disorders. However, to maximize its clinical and biomechanical value, it is important to fully understand the factors that influence nerve SWV measurements. This systematic review aimed to identify the normal range of SWV for healthy sciatic and tibial nerves and to reveal the factors potentially affecting nerve SWV. An electronic search yielded 17 studies eligible for inclusion, involving 548 healthy individuals (age range, 17 to 72 years). Despite very good reliability metrics, the reported SWV values differed considerably across studies for the sciatic (1.9-9.9 m/s) and tibial (2.3-9.1 m/s) nerves. Factors such as measurement proximity to joint regions, limb postures inducing nerve axial stretching, and transducer alignment with nerve fiber orientation were associated with increased SWV. These findings suggest regional-specific nerve mechanical properties, non-linear elastic behaviour, and marked mechanical anisotropy. The impact of age and sex remains unclear and warrants further investigation. These results emphasize the importance of considering these factors when assessing and interpreting nerve SWE. While increased SWV has been linked to pathological changes affecting nerve tissue mechanics, the significant variability observed in healthy nerves highlights the need for standardized SWE assessment protocols. Developing guidelines for enhanced clinical utility and achieving a comprehensive understanding of the factors that influence nerve SWE assessments are critical in advancing the field. [ABSTRACT FROM AUTHOR]

This paper introduces a novel approach to measure deformations in geomaterials using the recently developed 'Smart Pebble' sensors. Smart Pebbles were included in triaxial test specimens of unbound aggregates stabilized with geogrids. The sensors are equipped with an aggregate particle/position tracking algorithm that can manage uncertainty arising due to signal noise and random walk effects. Two Smart Pebbles were placed in each test specimen, one at specimen's mid-height, where a geogrid was installed in the mechanically stabilized specimen, and one towards the top of the specimen. Even with simple raw data processing, the trends on linear vertical acceleration indicated the ability of Smart Pebbles to assess the geomaterial configuration and applied stress states. Employing a Kalman filter-based algorithm, the Smart Pebble position coordinates were tracked during testing. The specimen's resilient deformations were simultaneously recorded. bender element shear wave transducer pairs were also installed on the specimens to further validate the Smart Pebble small-strain responses. The results indicate a close agreement between the BE sensors and Smart Pebbles estimates towards local stiffness enhancement quantification in the geogrid specimen. The study findings confirm the viability of using the Smart Pebbles in describing the resilient behavior of an aggregate material under repeated loading. [ABSTRACT FROM AUTHOR]

Background: Although premature ejaculation (PE) is the most common male sexual dysfunction, the underlying mechanisms are not fully understood. Aim: The study sought to evaluate the possible associations among glans penis volume and tissue stiffness measured using penile ultrasonography and penile shear wave elastography (SWE) with PE. Methods: Men 18 to 65 years of age with normal International Index of Erectile Function scores (>25) and who were diagnosed with PE between June 2021 and June 2022 were enrolled. The Premature Ejaculation Diagnostic Tool score and intravaginal ejaculation latency times were recorded. Healthy volunteers constituted the control group. The study group was divided into lifelong PE (LLPE) and acquired PE (AqPE) subgroups. In all groups, the glans penis volume was measured via penile ultrasonography and tissue stiffness of the glans penis, penile frenulum, postcircumcision mucosal cuff, and penile shaft were measured via SWE. The findings of the groups were compared using appropriate statistical methods. Outcomes: The outcomes included ultrasonographic and elastographic measurements of the glans penis. Results: Data on 140 men, including 70 PE patients and 70 healthy volunteers, were evaluated. Of the patients, 20 had LLPE and 50 had AqPE. The median glans penis volume was significantly greater in the LLPE group (14.1 [range, 6.6-19] mm3) compared with the AqPE group (11.7 [range, 5.1-27] mm3) and control group (11.4 [range, 6.1-32] mm3) (P =.03). According to the Youden index, the best cutoff value for glans penis volume in LLPE compared with non-LLPE (AqPE + control) was 12.65 mm3 (area under the curve, 0.684; 95% confidence interval, 0.556-0.812; P =.009). The risk of having LLPE in those with a glans penis volume ≥12.65 mm3 was 3.326 (95% confidence interval, 1.234-8.965) times higher than the non-LLPE group (P =.014). There were no significant differences between the groups in the SWE evaluation of glans penis, penile frenulum, mucosal cuff, and penile shaft tissue stiffness. Clinical Implications: The high incidence of PE in those with high glans penis volume may make glans penis volume a predictor for the development of LLPE. Strengths and Limitations: This was the first study to show that PE is more common in individuals with a high glans penis volume. It was also the first to perform a penile elastographic evaluation in patients with PE. The most important limitation was that we did not evaluate glans penile nerve function with a test, but rather we made an indirect inference about the density of free nerve endings based on increased glans penile volume. Conclusion: Glans penis volume was a significant predictor for LLPE. However, there are no associations between PE and the glans penis, postcircumcision mucosal cuff, penile frenulum, or penile shaft tissue stiffness and development. [ABSTRACT FROM AUTHOR]

Magnetoelastic (ME) effect-based sensors have been innovatively engineered for diverse applications, ranging from ensuring food safety to facilitating immunoassays and structural health monitoring. These cutting-edge devices leverage piezomagnetic/flexomagnetic plates to propagate waves, with the top surface of the plate frequently encountering contact with liquids. This article delves into the intricacies of analytically modeling the flexomagnetic effect, focusing on strain gradients within a finite-thickness plate. Additionally, it investigates the dispersion of shear horizontal (SH) waves within the same flexomagnetic plate when immersed in a Newtonian liquid region. The study meticulously considers the influences of plate thickness, flexomagnetic coefficient, and the viscosity of the liquid, particularly for a Cobalt-ferrite plate. The obtained dispersion equations are used to plot phase velocity spectra and frequency spectra. The implications of this research extend to optimizing surface acoustic wave sensors (SAW) designed for underwater applications, bio-sensing, and chemo-sensing. The comprehensive understanding of the dispersion characteristics of SH waves in piezomagnetic plates with flexomagnetic effect equips researchers and engineers to enhance the performance and efficiency of SAW devices across a spectrum of under-liquid scenarios. [ABSTRACT FROM AUTHOR]

The calculation of the spatial distribution of ground motion is one of the most important steps in earthquake scenarios. The advancements in machine learning algorithms and the release of new ground motion data can enable improvements in the reliability and accuracy of this component. We developed an artificial neural network (ANN) ground motion model using a compiled database from two subsets with measured Vs30 from the Pan-European strong motion database and the NGA-West2 database. The ANN model employs five input parameters: moment magnitude (Mw), hypocentral depth, Joyner–Boore distance (Rjb), shear wave velocity in the top 30 m (Vs30), and faulting type. The outputs of the ANN are the RotD50 horizontal components of common intensity measures used in seismic risk assessment: PGA, PGD, PGV, Arias Intensity, and 5% damped spectral acceleration at 27 periods from 0.01 to 4.0 s. A mixed-effects modelling approach was followed to train the ANN and partition the ground motion variability into between-event and between-site terms. The input parameter scaling relationships were studied and demonstrated physically sound trends of the ground motion with respect to Mw scaling, distance attenuation, and site amplification. The predicted median response spectra for several combinations of Mw and Rjb were compared to common ground motion models for Europe, and the results are discussed. The developed ANN is used in a companion study to calculate the hazard footprints for several historical earthquakes in the Balkan region. [ABSTRACT FROM AUTHOR]

High‐precision P‐wave and S‐wave velocity models are very important for seabed exploration. Elastic full‐waveform inversion is an effective way to obtain the velocity models. Full‐waveform inversion is strongly dependent on source wavelet, and inaccurate wavelet estimation will severely affect the inversion results. Furthermore, elastic full‐waveform inversion is a highly non‐linear problem and has larger calculation and memory cost. Based on the deconvolution method, we develop a multi‐scale source‐independent elastic full‐waveform inversion method in a hybrid domain to alleviate the non‐linearity, to improve computation efficiency and decrease memory cost and to reduce the influence of source wavelet. We reconstruct the deconvoluted objective function and further derive the adjoint source and gradient formulas for elastic full‐waveform inversion with the adjoint‐state method. We can obtain good inversion results by using this objective function, adjoint source and gradient even if the source wavelet is unknown. In order to illustrate the influence of different reference traces on the objective function, we provide the theoretical formula of the objective function changing with the variation of reference traces. Experiments show that the deconvolution objective function cannot completely eliminate the influence of inaccurate source wavelet on the inversion, and the inversion effect depends on the selection of reference trace. Different inversion results of the Marmousi2 model indicate that the minimum offset trace is the best reference trace. Comparison of the inverted Marmousi2 model by the proposed method and the conventional elastic full‐waveform inversion method using correct wavelet shows that the two inversion results are very close, which proves the effectiveness of the proposed method and indicates a potential application of the method in seabed exploration. [ABSTRACT FROM AUTHOR]

Seismic waves propagating in anisotropic earth media suffer from waveform distortion, which leads to degraded resolution in seismic data imaging if this adverse effect is not corrected. Additionally, the wavefields simulated by the traditional coupled pseudo‐acoustic wave equations contain undesired shear wave artefacts and are unstable when Thomsen's anisotropy parameter ε is less than δ. To address these issues, many pure qP‐wave equations are proposed to describe wave propagation in anisotropic media. However, these equations are either low precision or high accuracy but computationally expensive. Considering the trade‐off between the computation efficiency and simulation accuracy, we derive a pure qP‐wave equation from the exact dispersion formula in tilted transverse isotropic media. The newly derived equation has only two higher order partial derivatives, which can better balance the accuracy and efficiency than the previous pure qP‐wave equations. The least‐squares reverse time migration method can balance amplitudes, suppress migration artefacts and improve imaging resolution. Then, based on the newly derived pure qP‐wave equation, we derive the Born modelling operator and adjoint migration operator and develop an anisotropic least‐squares reverse time migration method. To achieve the accelerated convergence, we introduce a generalized minimum residual algorithm to implement the anisotropic least‐squares reverse time migration method. Numerical simulation results show that the proposed pure qP‐wave equation outperforms the previous equations in balancing the trade‐off between accuracy and efficiency. In addition, synthetic examples demonstrate the effectiveness and robustness of our proposed anisotropic least‐squares reverse time migration method in correcting the deviations due to anisotropic effects. [ABSTRACT FROM AUTHOR]

As one of wavefield separation methods in elastic reverse time migration, the decoupled wave equation succeeds to separate the particle velocity of P‐ and S‐wave without mode crosstalk. However, it fails to decouple the stress of P‐ and S‐wave which encounters with the problem of crosstalk. To overcome the crosstalk, the paper has proposed the quasi‐stress equations to decouple the stress tensor wavefields of P‐ and S‐wave based on the decoupled stress–strain relationship. Because P‐ and S‐wave stress wavefields are second‐order tensors, different from the imaging method of vector decoupled particle velocity wavefields, a double dot product imaging condition is proposed to obtain scalar images. Based on the total source‐stress tensor wavefields and separated receiver‐stress tensor wavefields, we obtain the scalar images of quasi‐PP and quasi‐PS from the stress information by the double dot product imaging condition. Several numerical examples are evaluated to demonstrate the effectiveness of the separation of P‐ and S‐wave stress and advantage of the proposed imaging condition from the second‐order stress tensor wavefields. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this prospective study was to investigate the diagnostic performance of shear wave elastography (SWE) in differentiating benign and malignant thyroid nodules and their correlation with the American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS). Methods: This prospective study included 370 thyroid nodules in 308 patients aged 18–70 years. All the patients underwent B-mode ultrasound (US), Doppler examination, and SWE and were given an ACR TI-RADS risk score before fine needle aspiration biopsy (FNAB) and/or surgery. The correlation between SWE parameters and ACR TI-RADS categories was investigated statistically and compared with histopathologic results. Additionally, the diagnostic performance of SWE was evaluated to distinguish malignant and benign thyroid nodules. Results: One hundred and thirty-five of the 370 thyroid nodules were malignant, and 235 nodules were benign. The mean shear wave velocity (SWV) value of the malignant nodules (3.70 ± 0.98 m/s) was statistically higher than that of the benign nodules (2.70 ± 0.37 m/s). The best cutoff value of the mean SWV for differentiating benign and malignant nodules was found to be 2.94 m/s (sensitivity 90.4%, specificity 89.9%, positive predictive value 81.3%, negative predictive value 94.1%, p < 0.001). The average score of the nodules according to the ACR TI-RADS was 3.57 ± 1.83 in benign nodules and 7.38 ± 2.69 in malignant nodules (p ≤ 0.001). Conclusion: This study showed that combining SWE and TI-RADS improves the specificity of TI-RADS alone in differentiating benign and malignant nodules. [ABSTRACT FROM AUTHOR]

We propose a new method to obtain 3-D shear wave velocity structures for regions with undulating topography based on surface wave dispersion data. In our method, we assume that surface waves propagate along a curved free surface, and the dispersion effects of these waves can be modelled as a frequency-dependent ray tracing problem. We use the shortest-path method to address off-great-circle propagation arising from inhomogeneous elastic parameters and topographic variations. We then apply our method to both synthetic and real-data inversions and demonstrate that ignoring topographic effects may significantly distort the inverted images. Finally, we analysed the accuracy of our method and provided a rule-of-thumb principle to quantitatively assess the need to account for topographic effects in surface wave tomography for a region. [ABSTRACT FROM AUTHOR]

We computed a 3-D shear wave velocity model of the Marmara Sea region from ambient noise tomography. The correlations of up to 8 yr of vertical-component seismic recordings from 80 broad-band stations provided Rayleigh wave group velocity measurements in the period band 6–21 s at more than 1400 selected virtual source–receiver pairs. Rayleigh wave group velocity maps were used to derive a shear wave velocity model through simulated annealing inversion. The resulting crustal model provides coverage of the Marmara Sea along with its surrounding regional tectonic features. This allows for an investigation of the spatial extents of the Marmara Sea on a scale larger than that of basins. The low-velocity structures of the Marmara Sea and the Thrace Basins are coeval to a depth of approximately 9 km. The crustal velocities beneath the Marmara Sea basins exhibit a low vertical gradient and smooth horizontal variations. The regional tectonic structures, such as Istranca Massif, Istanbul and Sakarya Zones, display sharp velocity contrasts with the lower velocity crust beneath the Marmara Sea. The observed low crustal velocities, along with depth variations of the velocity isosurfaces (i.e. 3.4 km s−1) indicate that the Marmara region is a structural depression much deeper and larger than the three basins of the North Marmara Trough. The North Anatolian Fault Zone is unlikely to be the primary factor contributing to the origin of this significant depression, as the basin's development appears to have occurred before the fault propagated into the region. [ABSTRACT FROM AUTHOR]

This work presents a model to characterize the behaviour of waves propagating in non-isothermal poroelastic solids saturated by two-phase fluids. The dynamic differential equations include the poroelasticity and heat equations with the solid, fluid and thermal fields combined using coupling terms. A plane wave analysis shows that five waves can propagate, three compressional, one fast (P 1) and two slow (P 2, P 3), a shear fast (S) and a thermal slow (T). P 2, P 3 and T are diffusive waves at low frequencies, while P 1 and S behave as propagating waves. The T wave is coupled with the compressional waves and uncoupled with the S wave. The plane wave analysis applied to a real sandstone saturated with gas–water mixtures compares phase velocities and attenuation factors for two-phase and effective single-phase fluids, considering or neglecting the coupling terms. It is observed that P 1 and P 2 waves have higher velocities for coupled cases, while P 3 and T waves exhibit the opposite behaviour. Furthermore the plane wave analysis is performed in the coupled case for oil–water and gas–water two-phase fluids, with compressional waves exhibiting higher velocities for gas–water than for oil–water mixtures. The propagation of waves in a 1-D thermo-poroelastic medium saturated by a gas–water mixture is presented and analysed using a finite element procedure. Considering temperature may become important in high-pressure high-temperature hydrocarbon and geothermal reservoirs. [ABSTRACT FROM AUTHOR]

Borneo and Sulawesi are two large islands separated by the Makassar Strait that lie within the complex tectonic setting of central Indonesia. The seismic structure beneath this region is poorly understood due to the limited data availability. In this study, we present Rayleigh wave tomography results that illuminate the underlying crustal structure. Group velocity is retrieved from dispersion analysis of Rayleigh waves extracted from the ambient noise field by cross-correlating long-term recordings from 108 seismic stations over a period of 8 months. We then produce a 3-D shear wave velocity model via a two-stage process in which group velocity maps are computed across a range of periods and then sampled over a dense grid of points to produce pseudo-dispersion curves; these dispersion curves are then separately inverted for 1-D shear wave velocity (Vs), with the resultant models combined and interpolated to form a 3-D model. In this model, we observed up to ± 1.2 km s−1 lateral Vs heterogeneities as a function of depth. Our models illuminate a strong low shear wave velocity (Vs) anomaly at shallow depth (≤ 14 km) and a strong high Vs anomaly at depths of 20–30 km beneath the North Makassar Strait. We inferred the sediment basement and Moho depth from our 3-D Vs model based on iso-velocity constrained by the positive vertical gradient of the Vs models. The broad and deep sedimentary basement at ∼14 ± 2 km depth beneath the North Makassar Strait is floored by a shallow Moho at ∼22 ± 2 km depth, which is the thinnest crust in the study area. To the east of this region, our model reveals a Moho depth of ∼45 ± 2 km beneath Central Sulawesi, the thickest crust in our study area, which suggests crustal thickening since the late Oligocene. Moreover, the presence of high near-surface Vs anomalies with only slight changes of velocity with increasing depth in southwest Borneo close to Schwaner Mountain confirm the existence of a crustal root beneath this region. [ABSTRACT FROM AUTHOR]

The recent rapid improvement of machine learning techniques had a large impact on the way seismological data can be processed. During the last years several machine learning algorithms determining seismic onset times have been published facilitating the automatic picking of large data sets. Here we apply the deep neural network PhaseNet to a network of over 900 permanent and temporal broad-band stations that were deployed as part of the AlpArray research initiative in the Greater Alpine Region (GAR) during 2016–2020. We selected 384 well distributed earthquakes with M L ≥ 2.5 for our study and developed a purely data-driven pre-inversion pick selection method to consistently remove outliers from the automatic pick catalogue. This allows us to include observations throughout the crustal triplication zone resulting in 39 599 P and 13 188 S observations. Using the established VELEST and the recently developed McMC codes we invert for the 1-D P - and S -wave velocity structure including station correction terms while simultaneously relocating the events. As a result we present two separate models differing in the maximum included observation distance and therefore their suggested usage. The model AlpsLocPS is based on arrivals from ≤130 km and therefore should be used to consistently (re)locate seismicity based on P and S observations. The model GAR1D_PS includes the entire observable distance range of up to 1000 km and for the first time provides consistent P - and S -phase synthetic traveltimes for the entire Alpine orogen. Comparing our relocated seismicity with hypocentral parameters from other studies in the area we quantify the absolute horizontal and vertical accuracy of event locations as ≈2.0 and ≈6.0 km, respectively. [ABSTRACT FROM AUTHOR]

Around the world the Earth's crust is blanketed to various extents by sediment. For continental regions, knowledge of the distribution and thickness of sediments is crucial for a wide range of applications including seismic hazard, resource potential and our ability to constrain the deeper crustal geology. Excellent constraints on the sediment thickness can be obtained from borehole drilling or active seismic surveys. However, these approaches are expensive and impractical in remote continental interiors such as central Australia. Recently, a method for estimating the sediment thickness using passive seismic data, the collection of which is relatively simple and low cost, was developed and applied to seismic stations in South Australia. This method uses receiver functions, specifically the time delay of the P -to- S converted phase generated at the sediment-basement interface, relative to the direct- P arrival, to generate a first-order estimate of the thickness of sediments. In this work, we expand the analysis to the vast array of over 1500 seismic stations across Australia, covering an entire continent and numerous sedimentary basins that span the entire range from Precambrian to present day. We compare with an established yet separate method to estimate the sediment thickness, which utilizes the autocorrelation of the radial receiver functions to ascertain the two-way traveltime of shear waves reverberating in a sedimentary layer. Across the Australian continent the new results match the broad pattern of expected sedimentary features based on the various geological provinces. We are able to delineate the boundaries of many sedimentary basins, such as the Eucla and Murray Basins, which are Cenozoic, and the boundary between the Karumba Basin and the mineral rich Mount Isa Province. Contrasts in seismic delay time across these boundaries are upwards of 0.4  |$\, \mathrm{s}$|⁠. The delay signal is found to diminish to <0.1  |$\, \mathrm{s}$| for older Proterozoic basins, likely due to compaction and metamorphism of the sediments over time. As an application of the method, a comparison with measurements of sediment thickness from local boreholes allows for a straightforward predictive relationship between the delay time and the cover thickness to be defined. This offers future widespread potential, providing a simple and cheap way to characterize the sediment thickness in underexplored areas from passive seismic data. [ABSTRACT FROM AUTHOR]

Irazú and Turrialba are a twin volcanic complex that marks a distinct stop in volcanism along the Central America volcanic arc. We present a new traveltime velocity model of the crust beneath Irazú and Turrialba volcanoes, Costa Rica, and interpret it considering the results of previous ambient noise tomographic inversions. Data were acquired by a temporary seismic network during a period of low activity of the Irazú–Turrialba volcanic complex in 2018–2019. Beneath the Irazú volcano, we observe low P -wave velocities (V P = 5 km s−1) and low velocity ratios (V P/ V S = 1.6). In contrast, below the Turrialba volcano, we observe low S -wave velocities (V S = 3 km s−1) and a high V P/ V S (= 1.85) anomaly. We found that locations of low V P and V S anomalies (−15 %) correspond well with shear wave velocity anomalies retrieved from ambient noise tomography. At shallower depths, we observe high V P and V S anomalies (+15 %) located between the summits of the volcanoes. Subvertical velocity anomalies are also observed at greater depths, with high V P and V S anomalies appearing at the lower limits of our models. We propose a complex structure of an intermediate magmatic reservoir, presenting multiphase fluid states of a liquid-to-gas transition beneath Irazú and a juvenile store of magmatic fluid beneath Turrialba, while shallow fluid transport provides evidence of magmatic–hydrothermal interactions. [ABSTRACT FROM AUTHOR]

Elastography can be used as a diagnostic method for quantitative characterization of tissue hardness information and thus, differential changes in pathophysiological states of tissues. In this study, we propose a new method for shear wave elastography (SWE) based on laser-excited shear wave, called photoacoustic shear wave elastography (PASWE), which combines photoacoustic (PA) technology with ultrafast ultrasound imaging. By using a focused laser to excite shear waves and ultrafast ultrasonic imaging for detection, high-frequency excitation of shear waves and noncontact elastic imaging can be realized. The laser can stimulate the tissue with the light absorption characteristic to produce the thermal expansion, thus producing the shear wave. The frequency of shear wave induced by laser is higher and the frequency band is wider. By tracking the propagation of shear wave, Young's modulus of tissue is reconstructed in the whole shear wave propagation region to further evaluate the elastic information of tissue. The feasibility of the method is verified by experiments. Compared with the experimental results of supersonic shear imaging (SSI), it is proved that the method can be used for quantitative elastic imaging of the phantoms. In addition, compared with the SSI method, this method can realize the noncontact excitation of the shear wave, and the frequency of the shear wave excited by the laser is higher than that of the acoustic radiation force (ARF), so the spatial resolution is higher. Compared to the traditional PA elastic imaging method, this method can obtain a larger imaging depth under the premise of ensuring the imaging resolution, and it has potential application value in the clinical diagnosis of diseases requiring noncontact quantitative elasticity. [ABSTRACT FROM AUTHOR]

Introduction and Aims: Approximately 21% of the world's population suffers from musculoskeletal conditions, often associated with sensations of stiff muscles. Targeted therapy requires knowing whether typically involved muscles are objectively stiffer compared to asymptomatic individuals. Muscle stiffness is quantified using ultrasound shear wave elastography (SWE). Publications on SWE‐based comparisons of muscle stiffness between individuals with and without musculoskeletal pain are increasing rapidly. This work reviewed and mapped the existing evidence regarding objectively measured muscle stiffness in musculoskeletal pain conditions and surveyed current methods of applying SWE to measure muscle stiffness. Methods: A systematic search was conducted in PubMed and CINAHL using the keywords "muscle stiffness", "shear wave elastography", "pain", "asymptomatic controls" and synonyms. The search was supplemented by a hand search using Google Scholar. Included articles were critically appraised with the AXIS tool, supplemented by items related to SWE methods. Results were visually mapped and narratively described. Results: Thirty of 137 identified articles were included. High‐quality evidence was missing. The results comprise studies reporting lower stiffness in symptomatic participants, no differences between groups and higher stiffness in symptomatic individuals. Results differed between pain conditions and muscles, and also between studies that examined the same muscle(s) and pathology. The methods of the application of SWE were inconsistent and the reporting was often incomplete. Conclusions: Existing evidence regarding the objective stiffness of muscles in musculoskeletal pain conditions is conflicting. Methodological differences may explain most of the inconsistencies between findings. Methodological standards for SWE measurements of muscles are urgently required. [ABSTRACT FROM AUTHOR]

The influence of anisotropic consolidation on the cyclic liquefaction resistance of granular materials is explored using 3D discrete element method simulations. In this study, the term anisotropic consolidation was defined as the ratio of initial horizontal and vertical normal stresses, and the hypothesis was that the conflicting results from previous laboratory experiments could be attributed to differences in inherent fabric. To test this hypothesis, three unique sample preparation protocols were employed to construct polydisperse spherical particle samples with varying inherent fabrics, as quantified by coordination number and contact-normal fabric anisotropy, under consistent initial mean stress and density conditions. The results were intriguing, as they revealed that anisotropic consolidation had a consistent impact on the cyclic liquefaction resistance of loose and medium-dense samples, regardless of preparation protocol. However, this relationship was not as straightforward in dense samples. In addition, the study assessed the correlations between various parameters, including initial shear wave velocity, state parameters associated with both void ratio and coordination number, fabric anisotropy, and their impact on the cyclic liquefaction resistance of the samples. The findings enhance the understanding of the intricate interplay between anisotropic consolidation and the resistance of granular materials to cyclic liquefaction, providing valuable insights that can inform the development of accurate models for predicting and mitigating cyclic liquefaction in various applications. [ABSTRACT FROM AUTHOR]

This study aims to investigate the mechanical properties of paretic and healthy plantar flexor muscles and assesses the spatial distribution of stiffness between the gastrocnemius medialis (GM) and lateralis (GL) during active force generation. Shear wave elastography measurements were conducted on a control group (CNT, n=14; age=59.9±10.6 years; BMI=24.5±2.5 kg/m2) and a stroke survivor group (SSG, n=14; age=63.2±9.6 years; BMI=23.2±2.8 kg/m2). Shear modulus within the GM and GL was obtained during passive ankle mobilization at various angles of dorsiflexion (P0 =0°; P1=10°; P2=20°; P3=-20° and P4=-30°) and during different levels (30%, 50%, 70%, 100%) of maximal voluntary contraction (MVC). Muscle activations of GM, GL, soleus and tibialis anterior were also evaluated. The results revealed a significant increase in passive stiffness within the paretic plantar flexor muscles under high tension during passive mobilization (p <0.05). Yet, during submaximal and maximal MVC, the paretic plantar flexors exhibited decreased active stiffness levels (p <0.05). A notable discrepancy was found between the stiffness of the GM and GL, with the GM demonstrating greater stiffness from 0° of dorsiflexion in the SSG (p <0.05), and from 10° of dorsiflexion in the CNT (p <0.05). No significant difference in stiffness was observed between the GM and GL muscles during active condition. Stroke affects the mechanical properties differently depending on the state of muscle activation. Notably, the distribution of stiffness among synergistic plantar flexor muscles varied in passive condition, while remaining consistent in active condition. [ABSTRACT FROM AUTHOR]

Low-velocity laminar flames gradually accelerates under the joint action of various mechanisms, and develops from deflagration to detonation, and the mechanism in this process is the focus of explosion dynamics research. This article presents experimental results of the propagation of premixed hydrogen/methane flames in square-section channels with flexible and rigid obstacles at a blockage ratio (BR) of 0.3. Theory and experiment show that the acceleration effect of flexible obstacles on flame is weaker than that of rigid obstacles. The results show that there are many differences in the physical mechanism of flame acceleration. It is mainly reflected in the difference between the two obstacles on turbulence guidance, and the difference in the peak pressure of flame propagation. The flexible obstacles create smaller turbulence and absorbs the transverse waves within the pipe that continuously accelerate the flame. At the same time, compared with rigid obstacles, flexible obstacles can effectively reduce the peak flame tip speed V max , and the peak flame tip speed reduction rate is the highest by 22.86%. In addition, unburned pockets formed by obstacles play a key role in the acceleration of the flames. The expansion of gas in the flexible obstacle pocket expands the obstacle spacing, accelerates the fuel combustion in the pocket, and avoids the concentrated release of fuel energy. The intensity of the turbulence and the velocity of the flame are lower after passing through the obstacle area, showing a lower explosion risk than rigid obstacles. • Rigid and flexible obstacles have different effects on turbulence guidance and peak flame propagation pressure. • Flexible obstacles generate smaller turbulence and dampen the transverse waves of the accelerating flame in the pipe. • The addition of hydrogen not only raises the upstream and downstream pressure peaks, but also makes the peaks appear earlier. • Flexible obstacles have a smoother change in peak flame velocity and a smaller change with hydrogen percentage. [ABSTRACT FROM AUTHOR]

Current osteoarthritis (OA) diagnosis relies on radiographic abnormalities found in later stages of the disease, posing a challenge to the treatment efficacy. Therefore, earlier detection of OA is essential for improving therapeutic outcomes. The aim of this study was to investigate the feasibility of shear wave ultrasound elastography (SWUE) to detect changes in cartilage mechanical properties under OA conditions ex-vivo. Bovine osteochondral units were harvested from femoral condyles and subjected to either trypsin degradation, cartilage surface roughness defect using varying degrees of sandpaper, or subchondral bone degeneration using formic acid (FA) injection. Shear waves were generated using a mechanical shaker, while a high-frequency ultrasound system operating at 18 MHz was employed to detect wave propagation along the samples. The elasticity of cartilage was estimated by the shear wave speed (SWS) through the auto-correlation method. Our results show that the estimated SWS of cartilage after 24, 48, and 72 hours of trypsin incubation significantly decreased by 37%, 43%, and 59%, respectively, compared to the control group. Surface roughness treatment using 150-grit sandpaper significantly decreased the SWS by 35% compared to the control. Samples treated with 7% FA showed a significant increase in SWS by 62%, 89%, and 53% compared to control, 1% FA, and 3% FA, respectively. Our findings demonstrate the feasibility of SWUE to differentiate the elastic properties of cartilage under different OA conditions. This study presents the potential of a noninvasive, nonionizing tool for early detection of OA, representing a significant step toward its clinical implementation. Highlights: • Shear wave ultrasound elastography noninvasively measure the elastic properties of soft tissue. • Increasing cartilage surface roughness and enzyme degradation results in slower shear wave speeds. • Subchondral bone degradation increases shear wave speed in cartilage. • Shear wave ultrasound elastography is a novel method for early osteoarthritis diagnosis. [ABSTRACT FROM AUTHOR]

Objective. An elevated interstitial fluid pressure (IFP) can lead to strain-induced stiffening of poroelastic biological tissues. As shear wave elastography (SWE) measures functional tissue stiffness based on the propagation speed of acoustically induced shear waves, the shear wave velocity (SWV) can be used as an indirect measurement of the IFP. The underlying biomechanical principle for this stiffening behavior with pressurization is however not well understood, and we therefore studied how IFP affects SWV through SWE experiments and numerical modeling. Approach. For model set-up and verification, SWE experiments were performed while dynamically modulating IFP in a chicken breast. To identify the confounding factors of the SWV-IFP relationship, we manipulated the material model (linear poroelastic versus porohyperelastic), deformation assumptions (geometric linearity versus nonlinearity), and boundary conditions (constrained versus unconstrained) in a finite element model mimicking the SWE experiments. Main results. The experiments demonstrated a statistically significant positive correlation between the SWV and IFP. The model was able to reproduce a similar SWV-IFP relationship by considering an unconstrained porohyperelastic tissue. Material nonlinearity was identified as the primary factor contributing to this relationship, whereas geometric nonlinearity played a smaller role. The experiments also highlighted the importance of the dynamic nature of the pressurization procedure, as indicated by a different observed SWV-IFP for pressure buildup and relaxation, but its clinical relevance needs to be further investigated. Significance. The developed model provides an adaptable framework for SWE of poroelastic tissues and paves the way towards non-invasive measurements of IFP. [ABSTRACT FROM AUTHOR]

Though previous studies have shown that the presence of water strongly influences wave responses of rock fractures, water effects on wave behaviours across clay-rich rock fractures have been ambiguous until now. In the present study, we conducted considerable ultrasonic measurements on single rock fractures filled with kaolinite-dominant gouges at varying water saturation degrees to investigate the water effects on elastic S-wave propagation and attenuation across clay-rich rock fractures. The experimental results reveal that the S-wave velocity across single clay-rich rock fractures slightly increases and decreases with the progressively increasing water saturation degree. An increase in water saturation leads to a concave trend of the spectral amplitudes, while it moderately affects the central frequency of transmitted S-waves. In addition, the seismic quality factor across single clay-rich rock fractures follows an exponential growth trend with the water saturation, suggesting the exponentially negative relation between S-wave attenuation and the water saturation. We attribute the water saturation-dependent S-wave attributes across single clay-rich rock fractures to the combined effects of the local flow and the degradation of grain contacts. Compared to P-wave, S-wave exhibits less sensitivity to varying water saturation of clay-rich rock fracture. Upon increasing water saturation, S-waves display similar velocity and central frequency trends with P-waves. The tendencies of spectral amplitude and seismic quality factor for S-waves are approximately opposite to those for P-waves as the water saturation degree increases. We interpret these discrepancies by the fact that S-wave attributes across single water-saturated clay-rich rock fractures mainly depend on the properties of the skeletal frame, while the characteristics of the particles, pore fluid, and skeleton frame dominate P-wave behaviours. The outcomes of the current work facilitate our understanding of the fluid effects on the interaction of waves with clay-rich rock discontinuities. Highlights: S-wave velocity and peak spectral amplitude across single clay-rich rock fractures exhibit concave trends upon rising water saturation. The increased water saturation modestly affects the central frequency of S-wave propagating across single clay-rich rock fractures. The seismic quality factor for S-waves exponentially grows with the water saturation degree of clay-rich rock fractures. The higher the S-wave frequency, the higher the wave velocity, the less the wave energy transmission, and the more the wave dissipation. The water-induced evolution of peak spectral amplitude and seismic quality factor for S-waves is roughly opposite to that for P-waves. [ABSTRACT FROM AUTHOR]

We cure the perturbative instability of the total-inclusive-photoproduction cross sections of vector S-wave quarkonia observed at high photon-proton-collision energies ( s γ p ) in Next-to-Leading Order (NLO) Collinear-Factorisation (CF) computations. This is achieved using High-Energy Factorisation (HEF) in the Doubly-Logarithmic Approximation (DLA), which is a subset of the Leading-Logarithmic Approximation (LLA) of HEF which resums higher-order QCD corrections proportional to α s n ln n - 1 (s ^ / M 2) in the Regge limit s ^ ≫ M 2 with M 2 being the quarkonium mass and s ^ is the squared partonic-center-of-mass energy. Such a DLA is strictly consistent with the NLO and NNLO DGLAP evolutions of the parton distribution functions. By improving the treatment of the large- s ^ asymptotics of the CF coefficient function, the resummation cures the unphysical results of the NLO CF calculation. The matching is directly performed in s ^ space using the Inverse-Error Weighting matching procedure which avoids any possible double counting. The obtained cross sections are in good agreement with data. In addition, the scale-variation uncertainty of the matched result is significantly reduced compared to the LO results. Our calculations also yield closed-form analytic limits for s ^ ≫ M 2 of the NLO partonic CF and numerical limits for contributions to those at NNLO scaling like α s 2 ln (s ^ / M 2) . [ABSTRACT FROM AUTHOR]

We study the effects of dipole–dipole interactions on the diffusion of an expanding atomic Bose–Einstein condensate with tunable s-wave interactions in three-dimensional disorder potentials. First-order correction due to local and nonlocal nonlinearities to the average atomic density is analytically calculated in the long expanding time limit using a perturbative theory. It is found that the diffusion coefficient exhibits a stronger anisotropy dependence due to the dipolar interactions. We show that the intriguing interplay of dipolar and nondipolar interactions and disorder potential may affect the diffusive expansion. Profiles of the dynamics of the average atomic density of attractive DDI from Eq.(19) for different values of ϵ dd and p = 0.08 . Black lines: ϵ dd = 0 . Red lines: ϵ dd = 0.16 . Blue lines: ϵ dd = 0.4 . Green lines: ϵ dd = 0.8 [ABSTRACT FROM AUTHOR]

Application of the reciprocity principle to evaluate the acoustic radiation from arbitrary multilayered fluid and solid materials is described. To include the effect of shear motion in surrounding media, including viscosity in a fluid, equations for the acoustic radiation from such materials under point force excitation are developed in terms of reflection and transmission coefficients for longitudinal and shear waves. Calculations for forcing on either side of the layered material and in arbitrary directions, and for any asymmetric layer arrangements, are conducted. The frequency range of the calculations is not restricted by thin-plate or thick-plate theory. The test case for the radiation from plates embedded in a viscous and attenuating fluid has been investigated in detail. The effect of viscosity and attenuation has been quantified and shown to be significant at high frequencies. Application to the problem of flow noise is also briefly discussed. [ABSTRACT FROM AUTHOR]

The mechanical properties of soft biological tissues can be characterized non-invasively by magnetic resonance elastography (MRE). In MRE, shear wave fields are induced by vibration, imaged by magnetic resonance imaging, and inverted to estimate tissue properties in terms of the parameters of an underlying material model. Most MRE studies assume an isotropic material model; however, biological tissue is often anisotropic with a fibrous structure, and some tissues contain two or more families of fibers—each with different orientations and properties. Motivated by the prospect of using MRE to characterize such tissues, this paper describes the propagation of shear waves in soft fibrous material with two unequal fiber families. Shear wave speeds are expressed in terms of material parameters, and the effect of each parameter on the shear wave speeds is investigated. Analytical expressions of wave speeds are confirmed by finite element simulations of shear wave transmission with various polarization directions. This study supports the feasibility of estimating parameters of soft fibrous tissues with two unequal fiber families in vivo from local shear wave speeds and advances the prospects for the mechanical characterization of such biological tissues by MRE. [ABSTRACT FROM AUTHOR]

Offshore assembly and disassembly operations represent a multi-billion-dollar market potential. Collaborative lifting by multiple vessels has emerged as a new operating paradigm for integrated offshore facilities assembly and disassembly. Hence, this paper investigates the hydro-dynamic interaction of dual lifting vessels in collaborative lifting operations. The coupled motions during multi-body operations are simulated using the commercial software SESAM. The feasibility of the numerical model for coupled motions in collaborative lifting is verified by comparing the numerical results of topside motions, vessel motions, and vertical lifting arm loads against experimental measurements. The effects of wave heading and period on the hydrodynamic responses of the topside module, dual lifting vessels, and lifting arms during collaborative operations are studied. Their influence patterns and mechanisms are analysed in detail. The results show that transverse waves and head wave induce significant heave and pitch motions of the topside module and vessels, but the maximum vertical loads on the lifting arms occur in oblique waves. The motion responses of the topside module and vessels increase with longer wave periods under the oblique sea condition, and roll motions are more sensitive to large periods compared to the gradual rise in heave and pitch. [ABSTRACT FROM AUTHOR]

Most common parameterization of anisotropic media is by twenty one independent elements aijkl of the density-normalized stiffness tensor or by twenty one independent elements Aαβ of the density-normalized matrix of elastic parameters in the Voigt notation. These parameters are commonly of significantly different sizes, are dimensional, in (km/s)2, often appear in combinations. We are offering an alternative parameterization by twenty one A-parameters (anisotropic parameters), which removes the mentioned disadvantages and possesses some additional useful properties. For example, axes or planes of coordinate systems, in which A-parameters are defined, need not be related to symmetry axes or planes of the considered anisotropy symmetry as required in other similar parameterizations. In combination with the first-order weak-anisotropy approximation, in which anisotropy is considered as the first-order perturbation of reference isotropy, parameterization by A-parameters yields insight into the role of individual A-parameters in the wave propagation problems. For example, it turns out that in the first-order weak-anisotropy approximation, P- and S-wave velocities are each controlled by fifteen A-parameters. A set of six of them appears only in the expression for P-wave velocity, a set of other six A-parameters appears only in S-waves velocity expressions. Remaining set of nine A-parameters is common for both waves. We present transformation of A-parameters, analogue to Bond transformation, and useful formulae for the weak-anisotropy approximation for anisotropy of any symmetry and arbitrary tilt. [ABSTRACT FROM AUTHOR]

Local soil effect plays an essential role in estimating of earthquake damage that occurs on the existing structures and in the planning and design of the new structures. One of the most critical steps in determining the earthquake design characteristics of a region is related with determining the behavior of the layers that form the soil in that region under cyclic stresses that develop because of earthquakes. Kütahya Dumlupınar University central campus needs constant new construction as the student potential increases each year in addition to the existing building stock. For this reason, data have been collected by using microtremor at 36 points and Multichannel Analysis of Surface Waves (MASW) at 4 points to determine the mechanical and physical characteristics of soil. Data being collected by the single station microtremor method were evaluated by means of horizontal-vertical spectral ratio technique, and the dominant vibration frequency values were evaluated, and the shear wave velocities (Vs30) up to a depth of 30 m were obtained by evaluating the data collected with MASW method. By establishing the relationship of the parameters obtained from both methods with the geological units, the results about the soil characteristics of the study zone were revealed. In accordance, the middle and northwest parts of the study area were composed of rock units when compared to the southeast part, and this boundary was controlled by an antithetic fault. [ABSTRACT FROM AUTHOR]

Real-time microseismic observations are extensively used in underground hard rock mines. However, microseismic monitoring in coal mines is not common. In this study, the features of microseismic (MS) event waveforms were discussed under conditions of thin-layered sedimentary media. The possibility of source mechanism evaluation was considered for the MS event recorded in coal mine. Moment tensor (MT) inversion of the waveforms can be challenging due to influence of thin-layered medium structure. Splitting of shear SH- and SV-waves is one of the characteristic features that affect MS records in coal mines. The effect of splitting was demonstrated using real microseismic data collected by an underground seismic array installed in the Polosukhinskaya coal mine, Russia. Velocities of shear SH- and SV-waves were estimated from travel times. The results reveal significant variations in shear wave velocities composed of a radial anisotropy of 75%, thus confirming the importance of a thin-layered model for moment tensor inversion. The thin-layered model was built for geological conditions at the Polosukhinskaya coal mine and synthetic seismograms were generated using QSEIS (Pyrocko OS). A full moment tensor of a single typical event was found employing the layered 1D velocity model. [ABSTRACT FROM AUTHOR]

Large Low Velocity Provinces (LLVPs) are situated oppositely in the lowermost mantle beneath the Pacific Ocean and Africa. Deciphering the detailed seismic structures at the edge of LLVPs can provide key information on the composition and dynamics in the deep Earth. Here, we provide a detailed seismic image at the western edge of the Pacific LLVP by dense recordings. Differential travel time residuals and amplitude ratios between ScS and S outline the S‐wave western boundary of the Pacific LLVP, suggesting the complex structures including low/high‐velocity patches in the lowermost mantle in our study region. We determine the 3D low‐velocity structure by modeling the delayed ScS and high‐velocity D″ layer structure by modeling the anomalous Scd, with tight constraints from multiple events data. The drastically varied waveforms in azimuth suggests a sharp transitional boundary among the complex structures. After comparing the velocity structures in adjacent regions, we propose that the 3D structures of the western edge of the Pacific LLVP are strongly influenced by the vigorous mantle flow associated with the actively subducted slab. Plain Language Summary: Seismic studies reveal two large‐scale low‐velocity anomalies in the lowermost mantle beneath the Pacific Ocean and Africa, respectively. Resolving the detailed structures at their edges is crucial for understanding the geodynamic evolution in the deep Earth. In this study, we determine the location of the western boundary of the Pacific anomaly by the measured travel time and amplitude of seismic waves that across through our study region. Dense recordings show that there are complex structures at the western edge of the Pacific anomaly, and we determine the 3D structures by modeling the seismic recordings. We conclude that the 3D structures of the western edge of the Pacific anomaly are majorly influenced by the actively subducted materials after comparing the greatly different structures in adjacent regions. Key Points: Complex structures are present at the western edge of the Pacific Large Low Velocity Province (LLVP)Drastically varied waveforms in azimuth suggest a sharp transitional boundary among the complex structuresThe 3D structures of the western edge of the Pacific LLVP are strongly influenced by the subducted slab [ABSTRACT FROM AUTHOR]

We present new observations of core‐diffracted shear waves which contain anomalous waveforms sampling the lowermost mantle beneath the southern Pacific region. Data in two distinct geometries, one from New Zealand to North America and the other from the Fiji and Solomon Islands to South America, show evidence of postcursor phases. The postcursor delays and move‐outs imply that they are caused by an ultra‐low velocity zone (ULVZ). Beamforming analyses of the observed diffracted postcursors show a strong backazimuthal deviation, suggesting this new ULVZ is likely to have a cylindrical shape similar to broad ULVZs sampled by shear diffracted waves elsewhere. Full‐waveform modeling suggests that the postcursors seen in North America might be due to the previously modeled ULVZ located to the west of the Galápagos, while those seen in South America are due to a previously unknown ULVZ beneath the Southern Pacific. We cannot fit observations in both geometries by a single ULVZ. For the new location, we propose one cylindrical ULVZ model with a radius of 400 km and a shear wave velocity decrease of 20% centered at geographical coordinates (−33.6, 130) close to the Pitcairn hotspot. Despite some uncertainty in the west‐east direction, this new ULVZ observation likely provides another example to support the hypothesis that ULVZs exist at the base of mantle plumes where primordial signatures are observed in the ocean island basalts. Plain Language Summary: We analyze shear waves that diffract along the core‐mantle boundary, called Sdiff, beneath the southern part of the Pacific Ocean. Sdiff waves are very sensitive to the seismic velocity structure of the lowermost mantle just above the boundary. For diffracted phases from several earthquakes and across a range of seismic stations, we observe anomalous waveform signals, which we refer to as Sdiff postcursors, and which arrive up to tens of seconds after the main Sdiff phase. We use the seismic data from many seismic stations to find from what direction the postcursor energy is coming from. We infer the cause of the anomalous postcursors are ultra‐low velocity zones (ULVZs) on the core‐mantle boundary, which are the strongest heterogeneities observed in the lower mantle. Additionally, we compute synthetic data for a range of potential ULVZ models. We find that some of the data can be explained by a previously modeled ULVZ near the Galápagos, but that other data point to a previously unknown ULVZ, beneath the southern Pacific region, although its exact location is somewhat uncertain, particularly in the west‐east direction. ULVZs, like this one, might represent the bases of upwelling mantle plumes that feed the hotspots at the surface. This particular one is in a location roughly beneath several southern Pacific hotspots, where geochemists find primordial isotope anomalies. Key Points: Detection of anomalous Sdiff postcursors sampling the core‐mantle boundary beneath the Southern PacificBeamforming and forward waveform modeling analyses find a new ultra‐low velocity zone (ULVZ) with an uncertain location beneath the southern PacificThis provides a potential new seismic example to support the correlation between surface ocean island basalts and ULVZs [ABSTRACT FROM AUTHOR]