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We conducted ultrasonic (1-MHz) laboratory measurements on 210 samples from the Vaca Muerta Formation (Neuquén Basin, Argentina) to determine the factors influencing acoustic velocities in siliciclastic–carbonate mudstone. We quantitatively assessed the calcium carbonate and total organic carbon (TOC) content and qualitatively identified the quartz and clay mineralogy. For brine-saturated samples, P-wave velocities ranged from 2826 to 6816 m/s, S-wave velocities ranged from 1474 to 3643 m/s, and porosity values ranged from 0.01 to 19.4%. Carbonate content percentages, found to be critically important, vary widely from 0.08 to 98.0%, while TOC ranged from 0 to 5.3%. Velocity was primarily controlled by carbonate content and, to a lesser extent, by the non-carbonate mineralogy of the rock (e.g., quartz, clay minerals). TOC content had little effect on the acoustic properties. Due to the low porosity of most samples, mineral composition had a stronger influence on velocity than porosity or pore geometry. The Vp/Vs ratio of dry samples ranged from 1.38 to 1.97 and decreased as porosity increased. In saturated samples, the Vp/Vs ratio ranged from 1.46 to 2.06 and appeared independent of porosity. A clear distinction between carbonate and mixed lithofacies under both saturated and dry conditions was observed in all samples.

Flow-induced noise issues are widely present in practical engineering fields. Accurate prediction of noise signals is fundamental to studying the mechanism of noise generation and seeking effective noise suppression methods. Complete acoustic field information often includes both acoustic pressure and velocity vectors. However, the classic acoustic analogy theory can only consider the feature distribution of acoustic pressure. This study starts from the dimensionless Navier-Stokes equations followed by fluid motion and, with the concept of electromagnetic analogy, introduces a vector form of the fluctuation equation that includes density perturbations and velocities in three directions. By choosing the permeable integral surface surrounding the object as the sound source surface, this study further analyzes the composition of the volume source term and extract the complete load source term, proposing the time-domain integral analytical formula T4DC and the frequencydomain integral formula F4DC. Numerical predictions for stationary dipoles and rotating monopoles are carried out in the time domain, frequency domain, and spatial domain. The numerical results show that the time-domain and frequency-domain noise obtained by this method can be consistent with the analytical solution, while the method of Dunn has a significant difference from the analytical solution, especially for dipole noise distribution. Compared with the accurate solution, the acoustic velocity amplitude error obtained by Dunns method reached more than 35% at m=l frequency, fully demonstrating that our method can accurately predict far-field acoustic pressure and velocity vectors.

Comparison between geophysical observations and laboratory measurements yields contradicting estimations of the melt fraction for the partially molten regions of the Earth, highlighting potential disagreements between laboratory-based electrical conductivity and seismic wave velocity measurement techniques. In this study, we performed simultaneous acoustic wave velocity and electrical conductivity measurements on a simplified partial melt analogue (olivine + mid oceanic ridge basalt, MORB) at 2.5 GPa and up to 1650 K. We aim to investigate the effect of ongoing textural modification of partially molten peridotite analog on both electrical conductivity and sound wave velocity. Acoustic wave velocity ( V p and V s ) and EC are measured on an identical sample presenting the same melt texture, temperature gradient, stress field and chemical impurities. We observe a sharp decrease of acoustic wave velocities and increase of electrical conductivity in response to melting of MORB component. At constant temperature of 1650 K, electrical conductivity gradually increases, whereas acoustic velocities remain relatively constant. While the total MORB components melt instantaneously above the melting temperature, the melt interconnectivity and the melt distribution should evolve with time, affecting the electrical conduction. Consequently, our experimental observations suggest that acoustic velocities respond spontaneously to the melt volume fraction for melt with high wetting properties, whereas electrical conduction is significantly affected by subsequent melt texture modifications. We find that acoustic velocity measurements are thus better suited to the determination of the melt fraction of a partially molten sample at the laboratory time scale (~ h). Based on our estimations, the reduced V s velocity in the major part of the low velocity zone away from spreading ridges can be explained by 0.3–0.8 vol% volatile-bearing melt and the high V p / V s ratio obtained for these melt fractions (1.82–1.87) are compatible with geophysical observations.

This study performed a pilot evaluation of the wood quality—defined by a single parameter: dynamic modulus of elasticity (MOEdyn, N mm−2)—of small-leaved lime (Tilia cordata Mill.) trees in urban areas. A search of the literature revealed few studies which examined the specifics of tree wood development in urban areas. Little is known about the potential of wood from urban trees wood of their suitability for the timber industry. In this study, an acoustic velocity measuring system was used for wood quality assessment of small-leaved lime trees. The MOEdyn parameter was evaluated for small-leaved lime trees growing in two urban locations (along the streets, and in an urban park), with an additional sample of forest sites taken as the control. MOEdyn was also assessed for small-leaved lime trees visually assigned to different health classes. The obtained mean values of MOEdyn of 90–120-year old small-leaved lime trees in urban areas ranged between 2492.2 and 2715.8 N mm−2. For younger trees, the values of MOEdyn were lower in the urban areas than in the forest site. Otherwise, the results of the study showed that the small-leaved lime wood samples were of relatively good quality, even if the tree was classified as moderately damaged (which could cause a potential risk to the community). Two alternatives for urban tree management can be envisaged: (1) old trees could be left to grow to maintain the sustainability of an urban area until their natural death, or (2) the wood from selected moderately damaged trees could be used to create wood products, ensuring long-term carbon retention.

In this paper, an automatic liquid level monitoring device is designed, its working principle and technological process are described, and a workover dynamic liquid level testing scheme is established. In view of the factors affecting the sound velocity in the annular space of the oil jacket, the calculation formula and mathematical model of the sound velocity and the depth pressure temperature density are established. The sound velocity changes caused by the changes in temperature, pressure and the composition of the well gas are accurately corrected. It is confirmed that the modified model provides a method that can not only ensure accuracy but also greatly reduce the calculation amount, greatly simplifying the real-time calculation amount of the system. The obtained liquid level depth is approximate, but it is sufficiently accurate to meet the requirements of the technical indicators of the project.

Sound waves are significantly influenced by boundaries during their propagation in certain environmental conditions. The extent of this impact is related to the complexity of the boundary, such as in the case of slopes and seamounts. In these areas, sound waves may deviate from their original paths, resulting in three-dimensional effects. Recent experiments and simulations have demonstrated that three-dimensional effects occur when sound waves propagate over seamounts in the South China Sea, leading to larger acoustic shadow regions. However, there are limited studies on 3D acoustic propagation based on measured slope topography or database topography. In this study, the topography of the South China Sea area database is selected, and the measured sound velocity profile and seabed acoustic parameters in the South China Sea are taken into considered. The FOR3D sound field calculation model is used to calculate the N×2D and 3D results. The simulation results show that in the southern continental slope region of the South China Sea, when the sound source frequency is 50 Hz, the acoustic wave exhibits significant horizontal refraction with a refraction angle of approximately 13°.

In this current study, our main focus is on modeling the specific charged compact star SAX J 1808.4-3658 (M = 0.88 M⊙, R = 8.9 km) within the framework of f(R,T) modified gravity theory using the metric potentials proposed by Tolman–Kuchowicz (Tolman in Phys Rev 55:364, 1939; Kuchowicz in Acta Phys Pol 33:541, 1968) and the interior spacetime is matched to the exterior Reissner–Nordström line element at the surface of the star. Tolman–Kuchowicz metric potentials provide a singularity-free solution which satisfies the stability criteria. Here we have used the simplified phenomenological MIT bag model equation of state (EoS) to solve the Einstein–Maxwell field equations where the density profile (ρ) is related to the radial pressure (pr) as pr(r)=(ρ-4Bg)/3. Furthermore, to derive the values of the unknown constants a,b,B,C and the bag constant Bg, we match our interior spacetime to the exterior Reissner–Nordström line element at the surface of stellar system. In addition, to check the physical validity and stability of our suggested model we evaluate some important properties, such as effective energy density, effective pressures, radial and transverse sound velocities, relativistic adiabatic index, all energy conditions, compactness factor and surface redshift. It is depicted from our current study that all our derived results lie within the physically accepted regime which shows the viability of our present model in the context of f(R,T) modified gravity.

This article uses the distance and sound spread time of each monitoring base station in the underwater positioning system, calculates the effective sound speed of the sound wave to the base station, and proposes a TOA underwater positioning method based on the average speed. The influence of small underwater sound changes the system positioning accuracy, reducing system positioning errors. Simulation experiments show that compared with the traditional fixed sound velocity method, this method has higher positioning accuracy and lower error. The positioning effect in a long baseline underwater positioning system is less dependent on the number of monitoring base stations. The cumulative probability of positioning error within 5 m can reach 70%, and the cumulative probability of error within 10 m can reach over 95%.

This paper suggests a full-waveform ultrasonic imaging strategy for bone. A novel forward wavefield propagation is performed in the frequency-domain. To improve the efficiency of full-waveform inversion bone imaging, all relative computations are also conducted in the frequency-domain. Additionally, a conjugate gradient algorithm is employed in the inversion procedure to accelerate the reconstruction of the bone acoustic velocity. Eventually, numerical experiments on different bone models are carried out to demonstrate the effectiveness of explored imaging strategy.

Acoustic emission technology is an effective nondestructive testing method for fiber-reinforced composites, which can monitor the damage process in real time. The main purpose of this paper is to review the information from the various literature articles published on mechanical property and acoustic emission technology of fiber-reinforced composites. It presents a comprehensive review of acoustic emission source location, damage mechanism analysis and life prediction. Initially, several localization methods were introduced in detail under known and unknown sound velocities. More importantly, cluster analysis (unsupervised learning and supervised learning) and waveform processing based on acoustic emission detection technology were discussed. Furthermore, features regarding the prediction of the remaining strength or service life of the composites were listed and explained. Finally, the future development of acoustic emission precise location and intelligent damage pattern recognition were prospected. Starting from the achievable functions, it provides theoretical support for the wider application and further development of the technology. Graphical abstract