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Iron is the primary constituent element of Earth's core, and its equation of state plays a pivotal role in understanding the thermodynamic properties of the core. However, uncertainties in experimental data have significant effects on the parameters within the iron equation of state. Using Bayesian statistical analysis coupled with Markov chain Monte Carlo simulation methods, we quantified the uncertainties in the equation of state parameters. During the simulation process, we proposed a simple yet efficient computational method for determining the probability of phase boundary data. The equation of state we obtained accurately reproduces various experimental data, including phase boundary experiments, static pressure data under different conditions, shock wave data, and sound velocity data at different states. With 100 posterior parameter samples, we predict that the density deficit of Earth's outer core falls within a range of approximately 9.5%–10.7%. [ABSTRACT FROM AUTHOR]

Cerium is regarded as one of the few metals that exhibit a first-order liquid–liquid phase transition (LLPT). However, despite the theoretical attribution of the LLPT to the localized-itinerant transition of f-electrons, there is still a lack of compelling experimental evidence to support this important scientific inquiry. In this study, we investigate the evolution of sound velocity in molten cerium along the isothermal and isobaric paths under static compression. Drawing parallels with the extensively studied γ–α isostructural phase transition, the V-shaped trend of temperature-dependent sound velocity in liquid suggests the existence of LLPT and identifies an associated mechanism predominating liquids' compressibility. [ABSTRACT FROM AUTHOR]

Despite the conventional view of liquid aluminum (l-Al) as a simple metal governed by the free-electron model, it exhibits unique bonding characteristics. This study uncovers a gradual transition from free electron to electride behavior in l-Al at high pressure and temperature, forming a type of two-component liquid where atomic and electride states coexist. The proportion of electride increases with pressure and temperature until reaching saturation, leading to notable changes in the pair-correlation function and coordination number of l-Al at saturation pressure. Furthermore, this electride transition was found to profoundly impact the thermodynamic and dynamic properties, as evidenced by anomalous crossovers in the isothermal bulk modulus, thermal expansivity, heat capacity, sound speed, and self-diffusion coefficient correlated with varying pressure and temperature. The finding of the anomalous behavior of l-Al described in this work will deepen our understanding of the electronic structure and also lay ground work for interpreting and predicting new physical and chemical behavior under extreme conditions. [ABSTRACT FROM AUTHOR]

In the experiments of measuring the strength of materials under ramp compression, accurately determining in situ particle velocity is crucial for calculating material sound speed during loading–unloading path and materials strength under high pressure. This paper proposes a machine learning approach that utilizes Long Short-Term Memory (LSTM) neural networks and Bayesian optimization algorithms to enhance the analysis of data from ramp compression strength measurement experiments. This method leverages LSTM neural networks to uncover the complex relationship between the rear interface velocity of the sample and the in situ particle velocity in numerical simulations. By using a well-trained network model, it enables direct interpretation of experimental data, leading to accurate predictions of key physical quantities along the loading and unloading paths in ramp compression experiments. A comparative analysis between theoretical curves from numerical simulations and LSTM neural network predictions shows a high degree of consistency. This approach is applied to ramp compression experiments on Ta and CuCrZr materials, demonstrating superior accuracy over the free-surface approximation and incremental impedance matching methods. Additionally, this method relies solely on the equation of state during numerical computations, eliminating the need for the complex constitutive equations required by the transfer function method, thus enhancing data processing efficiency and practicality. [ABSTRACT FROM AUTHOR]

We apply the methodology of Lustig, with which rigorous expressions for all thermodynamic properties can be derived in any statistical ensemble, to derive expressions for the calculation of thermodynamic properties in the path integral formulation of the quantum-mechanical isobaric–isothermal (NpT) ensemble. With the derived expressions, thermodynamic properties such as the density, speed of sound, or Joule–Thomson coefficient can be calculated in path integral Monte Carlo simulations, fully incorporating quantum effects without uncontrolled approximations within the well-known isomorphism between the quantum-mechanical partition function and a classical system of ring polymers. The derived expressions are verified by simulations of supercritical helium above the vapor–liquid critical point at selected state points using recent highly accurate ab initio potentials for pairwise and nonadditive three-body interactions. We observe excellent agreement of our results with the most accurate experimental data for the density and speed of sound and a reference virial equation of state for helium in the region where the virial equation of state is converged. Moreover, our results agree closer with the experimental data and virial equation of state than the results of semiclassical simulations using the Feynman–Hibbs correction for quantum effects, which demonstrates the necessity to fully include quantum effects by path integral simulations. Our results also show that nonadditive three-body interactions must be accounted for when accurately predicting thermodynamic properties of helium by solely theoretical means. [ABSTRACT FROM AUTHOR]

We study the elastic behavior of hexagonal close-packed (hcp) Fe at the high temperature and pressure conditions of the Earth Core, using an embedded-atom method interatomic potential adjusted to those conditions. We calculate diffusivity, elastic constants, density, bulk modulus, shear modulus, and sound velocities vs temperature. We obtain reasonable agreement with ab initio simulations and with other empirical potential simulations. Our densities and shear modulus are slightly higher than those in the preliminary reference earth model for the core. Phase stability is discussed in terms of the Born criteria and free energies, finding that hcp is mechanically stable and that the free energy difference between hcp and body-centered cubic (bcc) is very small compared to the thermal energy. We compare our simulated shear modulus G to several analytical models, obtaining excellent agreement with the Atom in Jelium model by Swift and co-workers. Assuming that the yield strength Y is equal to the shear modulus G , Y = G / 30 , we find reasonable agreement with a recent parametrization of the Steinberg–Guinan model. These results can lead to future large-scale, multi-million simulations of Fe under core conditions for samples with microstructure like grain boundaries and twins, which might be present under those conditions. [ABSTRACT FROM AUTHOR]

We present ab initio simulations of a large system of 2400 particles of molten NaCl to investigate the behavior of collective mode dispersion beyond the hydrodynamic regime. In particular, we aim to explain the unusually strong increase in the apparent speed of sound with wave number, which significantly exceeds the typical positive sound dispersion of 10%–25% observed in simple liquids. We compare dispersions of "bare" acoustic and optic modes in NaCl with ab initio simulations of other ionic melts such as CuCl and LiBr, metallic liquid alloys such as Pb44Bi56 and Li4Tl, and the regular Lennard-Jones KrAr liquid simulated by classical molecular dynamics. Analytical expressions for the "bare" acoustic and optic branches of collective excitations help us to identify the impact of the high-frequency optic branch on the emergence of "fast sound" in binary melts. Our findings show that in ionic melts, the high-frequency speed of sound is much larger than in the simple Lennard-Jones liquids and metallic melts, leading to an observed strong viscoelastic increase in the apparent speed of sound—more than double its adiabatic value. [ABSTRACT FROM AUTHOR]

As elastography, an emerging medical imaging strategy, advances, surface acoustic waves have been utilized to examine superficial tissues quantitatively. So far, most studies are experimental, and a numerical method is needed to cost-effectively investigate surface acoustic wave generation and propagation for technical development and optimization purposes. This study aims to develop a reliable numerical method for simulating impulse-induced surface acoustic waves using the k-wave simulation toolbox. According to the physical process of surface acoustic wave based elastography, the proposed simulation method consists of two stages: compressional wave simulation and elastic wave simulation, which aim to generate acoustic radiation force impulse and elastic waves, respectively. The technical procedures were demonstrated by a wave simulation on a water–tissue model. Meanwhile, three acoustic radiation force modeling methods were adopted. The compressional wave simulation showed that the three force modeling methods could produce similar force distribution in space but largely different amplitudes. The elastic wave simulation confirmed the feasibility of numerically generating surface acoustic waves. The reliability of the simulated waves was verified by a quantitative comparison between the numerically acquired sound speeds and their theoretical expectations and by a qualitative comparison between the numerically generated waves and the experimental observations under similar conditions. In summary, this study confirms k-wave as an effective numerical method for simulating surface acoustic waves for elastography purposes. This study provides an immediate simulation platform for investigating Scholte waves, the surface acoustic wave at a liquid–solid interface, and also, a potential numerical framework to investigate other surface acoustic waves. [ABSTRACT FROM AUTHOR]

Three third-order dielectric constants, 8 electrostrictive constants, 13 third-order piezoelectric constants, and 14 third-order elastic constants for lithium tantalate (LiTaO3) single crystals, which are mainly used in surface acoustic wave (SAW) devices, were determined as part of basic research to realize SAW devices with a low degree of nonlinearity. The third-order dielectric constants were determined by measuring the change in capacitance along selected directions when an alternating electric field was applied to the crystal. The electrostrictive constants were determined by measuring the change in capacitance when static stress was applied. Some of the piezoelectric constants were determined directly from the change in sound velocity due to the application of an alternating electric field, whereas others were obtained from the measured dielectric constants, electrostrictive constants, and the change in sound velocity due to an alternating electric field. In addition, the elastic constants (compliance) were determined using the three aforementioned determined nonlinear constants and the measured small-amplitude ultrasonic velocity change as a function of applied static stress. The measurements performed in the present study are more advanced than those reported for LiNbO3 single crystals in 1987 due to the adoption of the d-form nonlinear piezoelectric equation (instead of the e-form) and a higher degree of precision using dynamic measurement methods. The use of the d-form of the nonlinear piezoelectric equation allows many nonlinear constants to be determined independently from other nonlinear constants, eliminating measurement errors associated with these other constants. The d-form nonlinear constants obtained in the present study were converted to e-form constants to make them applicable to the analysis of nonlinear phenomena in piezoelectric devices. [ABSTRACT FROM AUTHOR]

Picosecond ultrasonics is a technique where coherent acoustic phonons are generated with frequencies in the GHz frequency range. When optical detection is operated in a transparent medium, the interaction of these phonons with the probe pulses yields oscillations in the time domain that reveal Brillouin scattering. Their frequency is at the Brillouin frequency shift, commensurate with the phonon velocity. As the pump–probe experiments are time-resolved, changes in the Brillouin frequency with time can be attributed to changes in sound velocity with depth. As sound velocity is temperature-dependent in liquids, we show that the picosecond ultrasonics technique can be used for temperature depth profiling in liquids. In this work, the concept is proved using the pump absorption itself as a heat source and confronting measured changes in Brillouin frequency with depth with data resulting from the derivation of a 3D modeling of the temperature rise in the liquid. We demonstrate the remote depth profiling of temperature, with measured data spaced at a distance less than the optical wavelength. [ABSTRACT FROM AUTHOR]

Experimental studies of the shock wave properties of two epoxy resins with the same composition but different curing temperatures (160 and 200 °C) at up to 330 GPa pressure have been carried out. Laser interferometry was used to record particle velocity profiles at up to 73 GPa pressure while measuring the shock wave velocity. The release sound velocity was experimentally determined in the 3–73 GPa pressure range. Cumulative explosive shock wave generators were used to study the shock Hugoniot of epoxy resins at pressures above 100 GPa. It was shown that the shock compressibility data of both samples are approximated by a single shock Hugoniot within the experimental error. A kink on Hugoniot recorded close to 25 GPa pressure indicates a chemical decomposition in epoxy resin. Above this kink, a change in the shock wave front structure was recorded. Hugoniots of epoxy resin and unidirectional carbon/epoxy composite were compared at up to 370 GPa pressure. [ABSTRACT FROM AUTHOR]

Within the low-frequency limit, this work analyzes the viscous absorbing properties of circular clusters and semi-infinite slabs made of rigid scatterers embedded in a fluid, such as air or water. These structures are made of rigid scatterers distributed in a hexagonal lattice, and they are proposed as useful absorbing devices in the core of acoustic black holes or acoustic metasurfaces. It is demonstrated that in both types of structures, an optimum value of the filling fraction produces the maximum absorption in a given frequency band. To avoid heavy numerical simulations, the broadband absorbing power has been obtained using a homogenization theory providing not only the effective acoustic parameters (effective mass and effective sound speed) but also the decay coefficient due to viscosity. An enhancement of the broadband sound absorption can be obtained by using a refractive index gradient allowing an increase of the acoustic energy into the semi-infinite slabs. The theoretical predictions are well supported by numerical simulations based on the finite-element and boundary-element methods, respectively, for the semi-infinite slabs and clusters. These predictions have potential applications in the design of structures and metasurfaces with enhanced absorbing power at low frequencies. The analytical model is further supported by experiments made with a 3D-printed sample. [ABSTRACT FROM AUTHOR]

We present the ab initio thermoelastic properties of body-centered cubic molybdenum under extreme conditions obtained within the quasi-harmonic approximation including both the vibrational and electronic thermal excitation contributions to the free energy. The quasi-harmonic temperature-dependent elastic constants are calculated and compared with existing experiments and with the quasi-static approximation. We find that the quasi-harmonic approximation allows for a much better interpretation of the experimental data, confirming the trend found previously in other metals. Using the Voigt–Reuss–Hill average, we predict the compressional and shear sound velocities of polycrystalline molybdenum as a function of pressure for several temperatures, which might be accessible in experiments. [ABSTRACT FROM AUTHOR]

We report a kind of coiled-up meta-liners with nonuniform cross sections (CMNC), which can efficiently attenuate low-frequency sound waves under grazing flow with a deep subwavelength thickness (e.g., ∼λ/17 at 500 Hz). At a grazing flow Mach number of 0.26, the average transmission loss of the meta-liner is 12.6 dB at 500–1000 Hz, which is twice as much as that of a double-degree-of-freedom acoustic liner of the same size. Physically, the nonuniform cross-sectional distribution and significant cross-sectional area ratio enhances vortex shedding, thus resulting in severe acoustic energy dissipation. The excellent low-frequency acoustic attenuation performance of CMNC is investigated thoroughly with experimental, theoretical, and numerical methods. This work provides an avenue for low-frequency noise reduction in grazing flow scenarios (e.g., in a high bypass ratio turbofan engine). [ABSTRACT FROM AUTHOR]

The thermophysical properties and elemental abundances of the noble gases in terrestrial materials can provide unique insights into the Earth's evolution and mantle dynamics. Here, we perform extensive ab initio molecular dynamics simulations to determine the melting temperature and sound velocity of neon up to 370 GPa and 7500 K to constrain its physical state and storage capacity, together with to reveal its implications for the deep interior of the Earth. It is found that solid neon can exist stably under the lower mantle and inner core conditions, and the abnormal melting of neon is not observed under the entire temperature (T) and pressure (P) region inside the Earth owing to its peculiar electronic structure, which is substantially distinct from other heavier noble gases. An inspection of the reduction for sound velocity along the Earth's geotherm evidences that neon can be used as a light element to account for the low-velocity anomaly and density deficit in the deep Earth. A comparison of the pair distribution functions and mean square displacements of MgSiO3–Ne and Fe–Ne alloys further reveals that MgSiO3 has a larger neon storage capacity than the liquid iron under the deep Earth condition, indicating that the lower mantle may be a natural deep noble gas storage reservoir. Our results provide valuable information for studying the fundamental behavior and phase transition of neon in a higher T–P regime, and further enhance our understanding for the interior structure and evolution processes inside the Earth. [ABSTRACT FROM AUTHOR]

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]

The motivation of the present study is to gain insights into the evolution of elastic properties of cemented tungsten carbides (WC) shock compressed to 100 GPa. Seven plate impact experiments—two front surface impact and five release wave overtake—are conducted to make simultaneous measurements of Hugoniot states and longitudinal sound speeds in shocked WC with 3.7wt.% cobalt binder. The sound speeds along with estimates for bulk sound speeds, obtained using the Birch–Murnaghan EoS, are analyzed to determine the elastic moduli—longitudinal, bulk, and shear—as a function of Hugoniot stress. The longitudinal and bulk sound speeds at Hugoniot states of interest are found to increase linearly with longitudinal stress. Consistent with the increase in sound speeds, the longitudinal and bulk moduli also increase with Hugoniot stress; however, the increase in longitudinal modulus is modest when compared to predictions of theoretical models that account for pressure and temperature dependence of elastic moduli, but with no damage. The shear moduli remain nearly constant at ∼ 318 GPa over the range of Hugoniot states investigated. These values are, however, much lower than those predicted by the Steinberg–Guinan model with no damage. Poisson's ratio decreases initially from its ambient value of 0.208 to ∼ 0.199 for Hugoniot stress ≤ 10 GPa indicating consolidation of the WC microstructure with low initial stress; however, with an increase in Hugoniot stress to ∼ 100 GPa, Poisson's ratio increases to ∼ 0.317, indicating degradation of shear moduli with increasing stress. The product of density and Grüneisen parameter (ρ Γ), after an initial spike, remains nearly constant for volumetric strains ≥ 0.07. The maximum average temperature rise is estimated to be ∼ 286 ° C at the highest Hugoniot stress employed in the study. [ABSTRACT FROM AUTHOR]

Water is one of the most abundant substances on earth, but it is still not entirely understood. It shows unusual behavior, and its properties present characteristic extrema unlike any other fluid. This unusual behavior has been linked to the two-state theory of water, which proposes that water forms different clusters, one with a high density and one with a low density, which may even form two distinct phases at low temperatures. Models incorporating the two-state theory manage to capture the unusual extrema of water, unlike traditional equations of state, which fail. In this work, we have derived the framework to incorporate the two-state theory of water into the Statistical-Associating-Fluid-Theory (SAFT). More specifically, we have assumed that water is an ideal solution of high density water molecules and low density water molecules that are in chemical equilibrium. Using this assumption, we have generalized the association term SAFT to allow for the simultaneous existence of the two water types, which have the same physical parameters but different association properties. We have incorporated the newly derived association term in the context of the Perturbed Chain-SAFT (PC-SAFT). The new model is referred to as PC-SAFT-Two-State (PC-SAFT-TS). Using PC-SAFT-TS, we have succeeded in predicting the characteristic extrema of water, such as its density and speed of sound maximum, etc., without loss of accuracy compared to the original PC-SAFT. This new framework is readily extended to mixtures, and PC-SAFT-TS manages to capture the solubility minimum of hydrocarbons in water in a straightforward manner. [ABSTRACT FROM AUTHOR]

Analysis methods for GNSS-A seafloor geodetic observations have become sophisticated in recent years. A Bayesian statistical approach with the Markov-Chain Monte Carlo (MCMC) method enables observers to flexibly estimate seafloor positions simultaneously with the perturbation of the sound speed in the ocean under several spatiotemporal patterns. To select the perturbation model appropriately and quantitatively, we implemented the widely applicable Bayesian Information Criterion (WBIC) in our software. The WBIC value is an approximation of the Bayes free energy that indicates the statistical appropriateness of the given model, which is available after running an MCMC sequence with a certain inverse temperature. Applying the WBIC-based model selection method to the actual data obtained at the seafloor GNSS-A sites along the Japanese archipelago by the Japan Coast Guard, we found that a simpler model, where the perturbation field is characterized by a uniformly inclined layer is more preferable than models with more degrees of freedom, especially in regions, where the Kuroshio current is strong. For the sites in the area where the cold and warm currents tend to cause multi-scale eddies, the model with more degrees of freedom was occasionally selected. [ABSTRACT FROM AUTHOR]

The Vlowk-renormalization group approach on the surface of Fermi liquid for nuclear matter to which Tom Kuo made a pioneering contribution at Stony Brook is found to inject the pivotal input in the formulation of the generalized nuclear effective field theory with acronym “GnEFT” applicable to superdense compact-star physics. A topology change in terms of skyrmions and half-skyrmions is shown to play the role of the “putative” hadron-quark continuity conjectured in QCD. Crucially involved are hidden local symmetry and hidden scale symmetry with the vacuum sliding with density in nuclear medium, with the nuclear tensor force emerging as a Landau Fermi-liquid fixed-point quantity. A possibly novel paradigm, a “Cheshire Catism,” in nuclear correlations is suggested. [ABSTRACT FROM AUTHOR]

This paper reports a novel sensor using integrated ultrasonic guided waveand bulk wave sensors to monitor fuel adulteration. The longitudinal-L(0,1), torsional-T(0,1) and flexural-F(1,1) modes were simultaneously generated in the helical-waveguide configuration using pulse-echo-(PE) and through-transmission(TT) techniques. A shear probe was connected at 45° orientation of the waveguide axis for transmitting and receiving all three modes in both techniques simultaneously. Also, the bulk wave (PE-approach) was integrated with the same ultrasonic setup for fuel density and sound velocity measurements using a longitudinal probe. We developed custom-made sensor holders to access guided wave-(GW) and bulk wave-(BW) sensors simultaneously to study fuel adulteration. In this measurement, we prepared different fluid samples by varying blend percentages (0% to 40%) in four cases: (a) ethanol with petrol, (b) kerosene with petrol, (c) ethanol with diesel and (d) kerosene with diesel. The novel sensor system detected fuel adulterations ≤2.5% w.r.to waveguide sensor’s F(1,1) mode attenuations and fuel mixture ultrasonic velocity measured using a bulk wave sensor. Multiple trials were performed (all cases) to ensure the sensors’ repeatability. Monitoring fuel quality is essential to reduce air pollution and prevent fuel adulterations (oil industries) to extend the life of internal combustion engine vehicles (ICEV). [ABSTRACT FROM AUTHOR]

Recently, the Rastall–Rainbow gravity emerged as an intriguing modified gravity theory. This theory is a combination of two theories, namely, the Rastall theory and the Rainbow description. This study aims to investigate the potential existence of static, spherically symmetric wormholes in this gravity theory. Specifically, we provide precise solutions to asymptotically flat wormhole geometries for the specific choice of the redshift and shape functions. With the specific examples, we investigate some issues concerning energy conditions and adiabatic sound velocity. We also consider the “volume integral quantifier” to assess the total amount of energy-condition violation matter. Finally, we conclude that reducing Rastall’s parameters and adjusting the Rainbow functions may alleviate the violation of energy conditions. [ABSTRACT FROM AUTHOR]

To elucidate the mechanism by which choline-based ionic liquids potentially can enhance the sugar conversion to bioethanol, this work was conducted to study the thermodynamic behavior of D(+)-glucose in aqueous solutions of choline-based ionic liquids, choline salicylate [Ch][Sal], choline formate [Ch][For], and choline acetate [Ch][Ace]. This study involved measuring density, speed of sound, viscosity, and electrical conductivity at various concentrations and temperatures. Analysis of the calculated parameters, including apparent molar volume, Vφ, apparent molar isentropic compressibility (κφ), viscosity B-coefficient, and molar conductivity (Λ) values provide deep insights into intermolecular interactions between the components of the solutions studied. The standard partial molar volume values ( V φ 0 ) of D(+)-glucose, show stronger interactions between D(+)-glucose and the [Ch][Sal]. The computed transfer volume values ( Δ tr V φ 0 ), with the help of co-sphere overlap model confirm intensified hydrophilic-hydrophilic interactions in [Ch][Sal] [(1.99 to 2.08) cm3·mol−1] solutions. Hepler's constants suggest that D(+)-glucose acts as a structure-maker in the presence of choline-based ILs, especially in [Ch][Sal] solutions. Also, the DFT-COSMO calculations result in [Ch][Sal] the most favorable interactions among the other choline based ILs. Apparent specific volume (ASV), and apparent specific isentropic compressibility, (ASIC), values revealed that D(+)-glucose exhibits the taste behavior with [Ch][Sal]. The hydration number of D(+)-glucose diminishes as the temperature rises due to weakened hydrogen bonds between D(+)-glucose and water molecules. These findings suggest that [Ch][Sal] could be a promising candidate for accelerating sugar conversion to bioethanol. [ABSTRACT FROM AUTHOR]

A breakthrough has been achieved in solving the Einstein field equations for a specific class of charged compact objects existing in higher dimensions with inhomogeneous matter distribution. The geometry of space-time is believed to be spheroid, encapsulated in (n + 2) dimensions of Euclidean space where n = D − 2, D be the space-time dimension. The internal physical (n + 1) space is elucidated by the Vaidya–Tikekar metric ansatz, which is defined by spheroidal and curvature parameters. The form of the equation of state in MIT bag model, p = 1 3(ρ − 4B), where the constant B is termed as bag constant, is implemented to investigate the relevant physical features of anisotropic strange quark stars containing a net amount of charge. The inclusion of higher dimensions effectively decreases the mass retained within a given radius of a compact object but increases its compactness. For a particular dimension, if one increases the value of B, the mass increases for a given value of radius. Determination of maximum radius and consequently, maximum mass have been obtained by equating the value of radial sound velocity as the extreme limit of causality (= 1) at the center of the star. Both the maximum mass and radius of a given compact object are found to increase when both charge and pressure anisotropy increase and decrease for an increment of surface density or bag constant B. The maximum mass attained in the model is 3.498M⊙. Prediction of the radius of some recently observed compact objects has also been done for different D, B, charge and pressure anisotropy parameters. Different energy conditions and stability criteria stand up throughout the compact object containing anisotropy in pressure and net charge. The tidal deformability of some compact objects has also been investigated using the present model. [ABSTRACT FROM AUTHOR]

Introduction: The accurate determination of the ocean sound speed profile (SSP) is essential for oceanographic research and marine engineering. Traditional methods for acquiring SSP data are often time-consuming and costly. Machine learning techniques provide a more efficient alternative for SSP inversion, effectively addressing the limitations of conventional approaches. Methods: This study proposes a novel SSP inversion model based on a grouped dilated convolution (GDC) Informer architecture. By replacing the standard one-dimensional convolution in the Informer model with GDC, the proposed model expands its receptive field and improves computational efficiency. The model was trained using Argo profile data from 2008 to 2017, incorporating empirical orthogonal function (EOF) decomposition data, geographic location, temporal information, and historical SSP data, enabling SSP inversion across diverse regions and time periods. Results: The model's performance was evaluated using mean absolute error (MAE), root mean square error (RMSE) and mean absolute percentage error (MAPE) metrics. Experimental results demonstrate that the Informer-GDC model achieves evaluation metrics of 0.355 m/s and 0.611 m/s for MAE, 0.241 m/s and 0.394 m/s for RMSE, and 0.018% and 0.025% for MAPE compared with measured data from 2018. Discussion: Compared to the LSTM and Informer models, the proposed model improves MAE, RMSE, and MAPE by 46.51% and 29.66%, 51.65% and 39.28%, and 51.25% and 37.08%, respectively. These findings highlight the superior accuracy, stability, and efficiency of the Informer-GDC model, marking a significant advancement in SSP inversion methodologies. [ABSTRACT FROM AUTHOR]

Some studies have developed different kinds of vibration-reducible construction materials. However, no existing study has applied these materials in a building to prove their effectiveness at a structural level. Besides, much of the related research has focused only on measuring sound pressure or vibration levels within buildings adjacent to railway systems. Although some studies have provided methods to predict the vibration of a building structure, they cannot determine the train-induced sound pressure level simultaneously. Therefore, this study used the finite element model to simulate an existing building structure to prove the effectiveness of this method. Based on the combination of the acoustic and solid interaction modules in the finite element analysis method, the vibration and sound levels of buildings based on different kinds of vibration-reducible cementitious materials were estimated using different models. The results show that vibration-reducible cementitious materials can reduce vibration velocity and sound pressure levels by up to 7.1 dB and 5.2 dB with an increased floor height, respectively. In addition, reduced vibration can decrease structure-borne noise by up to 2.9 dB. A further parametric study shows that cementitious materials with a relatively high elastic modulus, a high damping loss factor, and low density can be effective for vibration and sound reduction. [ABSTRACT FROM AUTHOR]

A new interior solution of Einstein’s equations is derived for a static and spherically symmetric space–time that contains fluid with anisotropic pressures, characterized by a parameter N. The model presented is a generalization to a proposal which contemplated a perfect fluid, which allows us to do an analysis of the impact of the anisotropy on the compactness, density and speed of sound. Taking the observational data of the mass M=1.7M⊙ and radius R=9 km as well as the mass M=1.4M⊙ and radius R=11km reported for the star EXO 1745-248, it is determined that the range of values of the density varies between 5.7651×1017 and 1.0937×1018 and these increase as the anisotropy parameter increases; it also shows an effect of the anisotropy on the speed of sound. The stability of the solution is shown through the Zeldovich criteria and through the adiabatic index, and from a graphic analysis it is verified that the behavior of the density, pressures and speed of sound are physically acceptable. [ABSTRACT FROM AUTHOR]

This research paper examines the feasibility and stability of compact stars in the context of f(풬) theory, where 풬 represents the non-metricity scalar. To achieve this objective, a static spherical line element is assumed in the interior region and the Schwarzschild spacetime is used in the exterior region of the star. The unknown constants are determined by using the Darmois junction conditions. We consider a specific model of this theory to investigate the viability of compact stars through various physical quantities such as matter contents, energy bounds, anisotropy and state parameters. The stability states for the stellar objects under consideration are determined by the speed of sound and adiabatic index, respectively. The resulting data indicate that the compact stars in this modified framework are physically viable and stable. [ABSTRACT FROM AUTHOR]

Variations in the underwater sound speed significantly influence sound propagation in the ocean, thereby impacting both underwater navigation systems and a substantial portion of marine organisms reliant on sound. This study utilizes cruise data from the Beibu Gulf during the summer and winter of 2023–2024 to explore the seasonal variations in temperature and salinity affecting the sound speed distribution and characteristics of sound propagation. Results indicate significant differences in the sound speed on either side of the 30-m isobath in the Beibu Gulf, with pronounced changes corresponding to seasonal temperature and salinity variations. In summer, the sound speed in the Beibu Gulf exhibits a north-high–south-low pattern. In areas shallower than 30 m, the sonocline is predominantly positive or absent, whereas, in deeper areas, it is mainly negative. During winter, there is a south-high–north-low pattern in sound speed across the Beibu Gulf, with pronounced sound speed extremes in areas shallower than 30 m. Sound propagation simulations based on the Beibu Gulf sound-speed field reveal that sounds at the 100-Hz frequency propagate significantly farther and cover larger areas in depths less than 30 m compared to deeper areas. In summer, this phenomenon is more pronounced than in winter due to the presence of positive sonoclines. The results have significant implications for target detection, underwater acoustic communication, and the protection of aquatic animals that rely on underwater sound for survival in the Beibu Gulf. [ABSTRACT FROM AUTHOR]

In the present communication, we have reported the experimental measurements on the ($\rho $ρ) speed of sound (u) and dynamic viscosity (η) for furfural (FA), butyl acetate (BA), isobutyl acetate (IBA) and tert-butyl acetate (TBA) and their binary mixtures taking furfural as common component at T = (298.15, 303.15, 308.15) K over the entire composition range. The experimental data for density, speed of sound and dynamic viscosity were further utilised to compute excess molar volume (V_m^E), excess molar isentropic compression (K_(S,m)^E), excess speed of sound (u^E), dynamic viscosity deviation (Δη), excess Gibb’s free energy of activation for viscous flow (ΔG^(*E)) and partial molar volume (${\bar V_{m,i}}$Vˉm,i). Furthermore, these calculated properties have been correlated using a Redlich–Kister type polynomial equation through the method of least squares to estimate the binary coefficients. [ABSTRACT FROM AUTHOR]

The dynamic and static elastic parameters of rocks exhibit differences. It is of great practical significance to carry out experiments on dynamic and static elastic parameters of rocks under reservoir conditions and determine the conversion relationship between dynamic and static elastic parameters. In this study, shale oil samples from the second member of Kongdong sag in Dagang Oilfield were analyzed by triaxial compression experiments at different bedding angles and longitudinal and shear wave velocity tests. Dynamic and static stiffness coefficient, elastic modulus and acoustic wave velocity change under different directions of pressure and pressure relief. The results indicate that the P-wave velocity, fast shear wave velocity, slow shear wave velocity, dynamic and static Young's modulus exhibit an increase as the confining pressure rises, and the parameters are greater during the unloading process than during loading process. At identical confining pressures, the dynamic Young's modulus measured by cores with parallel bedding plane is greater than that measured by cores with vertical bedding plane. The dynamic and static elastic mechanical parameters of different bedding angles can be transformed under varying pressures, and the dynamic elastic mechanical parameters measured under varying levels of confining pressure can be transformed into static elastic mechanical parameters under equivalent confining pressures, which offer fundamental parameters for examining rock mechanics properties and serving as a reference for developing fracturing construction plans for oil and gas reservoirs. [ABSTRACT FROM AUTHOR]

In the present work, we investigate anisotropic compact stars under the general relativistic platform. Following a novel technique, we found an exact self-bound analytical stellar solution. The obtained solution was matched on the spherical surface of the boundary to the Schwarzschild metric in order to find the expressions of the constants involved in the neutral system. We conducted various critical investigations such as on the variations in pressures, density, energy conditions, pressure–density ratios, the velocity of sounds, and gravitational potentials within stellar objects. We also conducted a stability analysis of the models using the cracking concepts and the adiabatic index. The values of the constant parameters were taken corresponding to the secondary components of GW190814 to validate the physical viability of our solution. This study provides fruitful results that are physically viable and, hence, satisfactory. [ABSTRACT FROM AUTHOR]

Cellulose is widely considered an outstanding biomaterial due to its remarkable ionic properties, exceptional biocompatibility, and low toxicity. Its abundant surface hydroxyl groups facilitate increased hydrogen bonding, improving gelation and swelling capabilities. Moreover, incorporating carboxymethyl groups enhances solubility and allows for diverse formulations, serving as multifunctional cross-linkers. Among the various sources of this compound, tunicate-derived cellulose is an animal-derived cellulose and food byproduct with low utility. However, recycling tunicate skin into a useful biomaterial would provide access to the unique characteristics of animal cellulose, distinct from those of plant-derived cellulose. Particularly, tunicate cellulose has a longer fiber length than plant cellulose, enhancing the sound propagation speed within the material and making it suitable for the production of ultrasound-responsive gels. This study examined the viscosity and conductivity of tunicate-derived carboxymethyl celluloseto assess its applicability as an ultrasound gel. Additionally, small molecule release after ultrasound stimulation was also evaluated. [ABSTRACT FROM AUTHOR]

For a new parameterization of the modified effective chiral model, developed primarily to regulate the density content of the symmetry energy and its higher order terms, equations of state (EoSs) for hyperon-rich matter (H) and delta baryon matter (Δ) were obtained. The models were used to investigate the emission of gravitational waves (GWs) through f-mode oscillations in the corresponding neutron stars. We obtained the stellar structure, f-mode frequency and tidal deformability Λ for our models. We report that the Δ EoS is stiffer compared to the H EoS. We also analyzed the velocity of sound in these media. The corresponding mass–radius relationships were obtained and compared with various observations. We studied the dependence of f-mode frequencies on the stellar mass, redshift and tidal deformability. We employed the well known Cowling approximation to obtain the f-mode frequencies for l = 2 , 3 and 4 modes of oscillation. We found that the f-mode frequencies of the H and Δ EoSs were almost the same in the lower mass region, while we observed a substantial difference between them in the high-mass region. We also obtained an empirical relation for the EoSs considered. The various attributes obtained for our models showed close agreement with various observational constraints from pulsars and GW events. [ABSTRACT FROM AUTHOR]

Experimental densities and sound speeds at temperatures (293.15, 298.15, 303.15, and 313.15) K and under ambient pressure conditions are reported for the first time for the ternary system {MTBE + benzene + n-hexane} covering the entire composition range. The corresponding binary subsystems have also been studied. The excess molar volume and excess isentropic compressibility, derived from experimental density and sound speed data, were correlated using Redlich-Kister and Cibulka equations for binary and ternary systems, respectively. The composition and temperature dependence of these properties provided insights into the nature of molecular interactions and structural effects within the mixtures. The Perturbed Chain Statistical Associating Fluid Theory Equation of State was used to model the densities of both binary and ternary mixtures using a predictive approach. Schaaff's Collision Factor Theory and Nomoto's relation modeled the sound speeds. Further, this work utilized the Jouyban–Acree model to represent the composition and temperature dependence of experimental densities and sound speeds of the studied binary and ternary mixtures. Finally, the ternary excess properties are compared with the predicted values from binary contribution symmetric (Kohler and Muggianu) and asymmetric (Hillert and Toop) geometric models. The accuracy of the theoretical and empirical models was assessed by computing various statistical indicators. [ABSTRACT FROM AUTHOR]