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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]

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]

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]

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]

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]

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]

The study aimed to investigate the properties of thermodynamics, acoustics, and electromagnetism in order to understand the interactions between molecules both within and between different compounds. The study also examined how molecular shape and structure, as well as temperature and the presence of chlorine atoms in alkanes and alkenes, influenced these properties. Measurements were taken for densities (ρ), speeds of sound (u), and refractive indices ( n D ) in various mixtures containing acetophenone with 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, trichloroethene or tetrachloroethene at temperatures ranging from 298.15 K to 318.15 K. Additionally, excess molar volumes ( V m E ), isentropic compressibilities (K s ), excess isentropic compressibilities ( κ S E ), and excess refractive index (n D E) , were calculated. The quantities were correlated with the Werblan relation. The V m E values exhibited negative for all mixtures except for acetophenone + 1,2-dichloroethane which had positive values while the tetrachloroethene system showed both positive and negative values. The (κ S E) , values were showed negative for all binary mixtures. Lastly, the (n D E) values for acetophenone with 1,2-dichloroethane were negative and with tetrachloroethene an inversion in sign at low volume fraction of acetophenone was observed. For the three remaining binary mixtures the (n D E) values were exhibited positive. The PC-SAFT model accurately predicted mixture densities and matched well with experimental data. [ABSTRACT FROM AUTHOR]

We do a careful investigation of the prospects of dark energy (DE) interacting with cold dark matter in alleviating the |$S_8$| clustering tension. To this end, we consider various well-known parametrizations of the DE equation of state (EoS) and consider perturbations in both the dark sectors, along with an interaction term. Moreover, we perform a separate study for the phantom and non-phantom regimes. Using cosmic microwave background (CMB), baryon acoustic oscillations, and Type Ia supernovae data sets, constraints on the model parameters for each case have been obtained and a generic reduction in the |$H_0 \!\!-\!\! \sigma _{8,0}$| correlation has been observed, both for constant and dynamical DE EoS. This reduction, coupled with a significant negative correlation between the interaction term and |$\sigma _{8,0}$|⁠ , contributes to easing the clustering tension by lowering |$\sigma _{8,0}$| to somewhere in between the early CMB and late-time clustering measurements for the phantom regime, for almost all the models under consideration. Additionally, this is achieved without exacerbating the Hubble tension. In this regard, the interacting Chevallier–Polarski–Linder and Jassal–Bagla–Padmanabhan models perform the best in relaxing the |$S_8$| tension to |$<\!\! 1\sigma$|⁠. However, for the non-phantom regime the |$\sigma _{8,0}$| tension tends to have worsened, which reassures the merits of phantom DE from latest data. We further investigate the role of redshift space distortion data sets and find an overall reduction in tension, with a |$\sigma _{8,0}$| value relatively closer to the CMB value. We finally check whether further extensions of this scenario, such as the inclusion of the sound speed of DE and warm dark matter interacting with DE, can have some effects. [ABSTRACT FROM AUTHOR]

Introduction: The image formation process of conventional pulse-echo Ultrasound mainly uses the backscattered amplitude and assumes constant attenuation and speed of sound in the penetrated media. Thus, many commercially available ultrasound imaging phantoms use only a limited choice of materials with simple geometric shapes. Part of today's research in ultrasound is to gain more information on the acoustic properties of the object imaged. These advanced imaging and reconstruction procedures require more complicated phantom designs that contain different materials with precisely designable acoustic properties for validation and quality assurance (QA). Methods: To fabricate such phantoms, we produced molds for casting ultrasound phantoms using additive manufacturing. Phantom materials used were based on agar and polyvinyl alcohol. To adapt the speed of sound glycerol was added to the mixtures. As glycerol diffuses out of the phantom material, polluting the surrounding water, we designed a watertight sample holder. The effect of the freeze-thaw cycles (FTCs) on the acoustic properties of the polyvinyl alcohol (PVA)-based phantoms was also investigated. Speed of sound and attenuation were determined for both phantoms materials, and Shore hardness measured for the PVA-based phantoms. Results: Shore hardness of the PVA phantoms increased by up to 79% of the initial value with increasing number of freeze-thaw cycles, but showed a saturation after 5 FTCs. However, the number of FTCs had only a small effect on the speed of sound and attenuation, as the sound speed increased slightly from 1,530.14 m/s to 1,558.53 m/s, (1.86%) and the attenuation exhibited only an increase of 6.75%. In contrast, differences of around 100 m/s in the speed of sound in the PVA phantoms (from 1,558.53 to 1,662.27 m/s), as well as in the agar-based phantoms (from 1,501.74 to 1,609.36 m/s) could be achieved by adding glycerol, making these materials appropriate candidates for the design and fabrication of US phantoms with defined sections and details with different speed of sound and attenuation. The use of the sample holder showed only an influence of 0.63% on the measured speed of sound. Discussion: 3D printed molds led to an improved manufacturing process as well as a free choice of the shape of the phantoms. A sample holder could prevent contamination of the water with no significant differences in the measured speed of sound. [ABSTRACT FROM AUTHOR]

The successful prospecting of kimberlite pipes is dependent upon a comprehensive understanding of the deep structures of the pipes and the host geological formation. This is a challenging task, given the complex nature of diamond deposits, the small size of pipes in the plan, the absence of stable features in potential fields, etc. As a consequence, the allocation of control structures is practically not used in exploration work. In this regard, the Arkhangelsk diamond province (NW Russia) is distinguished by the considerable overburden thickness, which presents a significant challenge for the application of geophysical methods. It is thus imperative to devise novel methodologies for conducting investigations. In order to achieve this, a set of methods was employed, including microseismic sounding, passive seismic interferometry, and radon emanation mapping. This set of methods has previously been tested only on a few pipes and has not previously been employed in the Griba deposit. The Volchya pipe was selected as the test object due to its proximity to the Griba pipe. The findings revealed that the pipe displayed a more complex configuration than was previously postulated. The controlling faults were found to be oriented in a southwesterly to northwesterly direction and to exhibit a contrasting narrow vertical structure at depths greater than 400 m. Further identification of control structures by the proposed set of methods can increase the efficiency of diamond prospecting. [ABSTRACT FROM AUTHOR]

This review is devoted to summarizing recent developments of the linear sigma model (LSM) in cold and dense two-color QCD (QC2D), in which lattice simulations are straightforwardly applicable thanks to the disappearance of the sign problem. In QC2D, both theoretical and numerical studies derive the presence of the so-called baryon superfluid phase at a sufficiently large chemical potential ( μ q ), where diquark condensates govern the ground state. The hadron mass spectrum simulated in this phase shows that the mass of an iso-singlet ( I = 0 ) and 0 − state is remarkably reduced, but such a mode cannot be described by the chiral perturbation theory. Motivated by this fact, I have invented a LSM constructed upon the linear representation of chiral symmetry, more precisely Pauli–Gürsey symmetry. It is shown that my LSM successfully reproduces the low-lying hadron mass spectrum in a broad range of μ q simulated on the lattice. As applications of the LSM, topological susceptibility and sound velocity in cold and dense QC2D are evaluated to compare with the lattice results. Additionally, the generalized Gell–Mann–Oakes–Renner relation and hardon mass spectrum in the presence of a diquark source are analyzed. I also introduce an extended version of the LSM incorporating spin-1 hadrons. [ABSTRACT FROM AUTHOR]

Changes in pore pressure within geological reservoirs, due to, for example hydrocarbon production, CO2 and energy storage or wastewater disposal, may cause substantial stress changes in the overburden, altering propagation velocities of elastic waves. The corresponding time-shifts are detected and quantified using time-lapse (4-D) seismic analysis. To invert seismic time-shifts for changes in stress and strains, stress sensitivity of rocks is studied in laboratory experiments on core plugs. Such measurements are typically conducted at ultrasonic frequencies. However, previous studies indicate that the stress sensitivity of velocities at seismic frequencies could be higher than that at ultrasonic frequencies. Therefore, calibration based on laboratory ultrasonic data may lead to inaccurate prediction of stresses and strains when applied to 4-D seismic data. To study the influence of frequency on stress sensitivity of acoustic wave velocities, a series of laboratory experiments was performed on two overburden shales with different petrophysical properties. In a low-frequency apparatus—a triaxial pressure cell that combines measurements at low (seismic) and high (ultrasonic) frequencies—the shale samples underwent stress changes with different ratios of horizontal to vertical stress amplitudes to mimic stress variations across the overburden. High-frequency velocity changes were directly recorded, while low-frequency velocity changes were obtained indirectly from the elastic parameters measured at seismic frequency by applying a rock physics inversion using third-order elasticity model. The experiments were conducted at undrained conditions, a representative state for reservoir overburden composed of shales. The results suggest that the stress sensitivities and strain sensitivities (R-factor) of P -wave velocities could be two to four times greater at seismic frequencies than at ultrasonic frequencies. Furthermore, it was found that the previously reported linear relation between the stress sensitivity and stress-path parameter (horizontal/vertical stress change) at ultrasonic frequencies also holds for seismic frequencies. We discuss the theoretical background for frequency-dependent stress sensitivity of wave velocities that supports the experimental findings. The effect of frequency when using laboratory-based calibrations should be taken into account when inverting time-lapse seismic data for changes in stresses and strains. [ABSTRACT FROM AUTHOR]

The remote sensing-based inversion of sound speed profile (SSP) enables the acquisition of high-spatial-resolution SSP without in situ measurements. The spatial division of the inversion grid is crucial for the accuracy of results, determining both the number of samples and the consistency of inversion relationships. The result of our research is the introduction of a physics-inspired self-organizing map (PISOM) that facilitates SSP inversion by clustering samples according to the physical perturbation law. The linear physical relationship between sea surface parameters and the SSP drives dimensionality reduction for the SOM, resulting in the clustering of samples exhibiting similar disturbance laws. Subsequently, samples within each cluster are generalized to construct the topology of the solution space for SSP reconstruction. The PISOM method significantly improves accuracy compared with the SOM method without clustering. The PISOM has an SSP reconstruction error of less than 2 m/s in 25% of cases, while the SOM method has none. The transmission loss calculation also shows promising results, with an error of only 0.5 dB at 30 km, 5.5 dB smaller than that of the SOM method. A physical interpretation of the neural network processing confirms that physics-inspired clustering can bring better precision gains than the previous spatial grid. [ABSTRACT FROM AUTHOR]

The shear wave speed is often small compared to the compressional wave speed in the top part of the seabed, where acoustic normal modes penetrate. In sediments with weak but finite shear rigidity, the strongest conversion from compressional to shear waves occurs at interfaces within the sediment. Shear wave generation at such interfaces and interference within sediment layers lead to first-order perturbations in the normal mode phase speed and contributions to sound attenuation, which vary rapidly with frequency. Weak shear rigidity is shown to lead to unexpectedly strong mode group speed perturbations that retain finite magnitudes for very small shear speeds in range-independent waveguides. Variation of the waveguide parameters with range affects shear-induced attenuation and mode travel time perturbations in a different manner, depending on whether shear wave interference conditions vary appreciably along the propagation path. In horizontally inhomogeneous ocean, weak shear magnifies the horizontal refraction of adiabatic normal modes due to sloping intra-sediment interfaces. In contrast to normal modes, attenuation of lateral waves with range is insensitive to weak shear. Concurrent measurements of normal mode and lateral wave attenuation can be potentially used to identify and separate the contributions of dissipation and shear waves into observed sound attenuation. [ABSTRACT FROM AUTHOR]

A study is presented of a method for creating an acoustic flow sensor that is generally compatible with current silicon microfabrication processes. An aim of this effort is to obtain a design consisting of a minimal departure from the existing designs employed in mass-produced silicon microphones. Because the primary component in all of these microphones is the cavity behind the pressure-sensing diaphragm, we begin with a study of the acoustic particle velocity within a cavity in a planar surface. The sound within the cavity is caused by the external plane sound wave traveling parallel to the cavity's open surface. It is shown that with suitable dimensions of the cavity, the acoustic particle velocity simultaneously flows inward at one end and outward at the other end of the single open cavity surface. A simple analytical model is presented to estimate the required length and depth of the cavity such that the acoustic particle velocity into and out of the opening is a reasonable approximation to that of a plane traveling sound wave in the free field. Measurements of the acoustic particle velocity into and out of the cavity are in close agreement with both the simple model and a more detailed finite element model. Agreement between two dissimilar modeling approaches and experiments suggests that the dominant features of the system have been accounted for. By redirecting the acoustic particle velocity into and out of the cavity opening rather than the flow being parallel to the plane surface, this configuration greatly facilitates the design and fabrication of structures intended to sense the acoustic flow. [ABSTRACT FROM AUTHOR]

The thermophysical properties, as densities, speeds of sound, and refractive indices, for pure compounds: iso-propylbenzene (cumene), cyclopentanone, and diethylketone (3-pentanone), as well as for their two selected binary mixtures, have been measured over the entire range of composition, at few temperatures between (298.15 and 318.15) K and atmospheric pressure p = 0.1 MPa. From the experimental results, the thermodynamic properties, namely: the excess molar volumes, the partial or apparent molar volumes, the isentropic compressibilities, the excess isentropic compressibilities and the excess molar isentropic compressions, have been calculated. The values of experimental excess molar volumes have been used to test the applicability of the Prigogine–Flory–Patterson (PFP) theory and the results were analyzed in terms of molecular interactions and structural effects, occurred between the components of the mixtures. Moreover, from the measured densities data, the surface tensions and the surface tension deviations, for both mixtures have been predicted. Also, using the experimental density and speed of sound data, the acoustic impedance values were estimated. From the experimental refractive index data, the deviations in refractive indices, the molar refractions and the excess molar refractions, have been calculated. Furthermore, the refractive indices values have been used for the prediction of the space-filling factor and the specific refraction. All the excess thermodynamic properties calculated for both mixtures, have been correlated with composition by the Redlich–Kister polinomial equation. The values of the excess properties have been represented graphically. The parameters of correlation were estimated and their values have been reported at working temperatures. [ABSTRACT FROM AUTHOR]

Coaxial rotor helicopters have many advantages and have a wide range of civilian and military applications; however, there is a risk of blade collision between the upper and lower rotor blades, and the challenge still exists in balancing rotor parameters and flight control. In this paper, a blade tip distance measurement method based on coded ultrasonic ranging and phase triggering is proposed to tackle this measurement environment and expand the application of ultrasonic ranging in high-speed dynamic measurement. The time of flight (Tof) of coded ultrasonic ranging is calculated by the amplitude threshold improvement method and cross-correlation method, and the sound velocity is compensated by a proposed multi-factor compensation method. The static distance error of coded ranging with different codes are all within ±0.5 mm in the range of 10–1000 mm. The measurement error characteristics under different trigger phases and different rotational speeds are studied, and the error model is fitted by the back-propagation neural network method. After compensation, the vertical distance measurement errors are within ±2 mm in the range of 100–1000 mm under the condition that the rotational speed of the blade is up to 1020 RPM. It also provides a potential solution for other high-speed measurement problems. [ABSTRACT FROM AUTHOR]

The structural, elastic, and thermal characteristics within the 0–30 GPa pressure range of Al3Ni intermetallic compounds were extensively studied using first-principles computational techniques. Using structural optimization, lattice parameters and the variation in volume variation under diverse pressures were determined, and the trends in their structural alteration with pressure were identified. The computed elastic constants validate the mechanical stability of Al3Ni within the applied pressure range and show that its compressive stiffness and shear resistance increase rapidly with increasing pressure. The Cauchy pressure variation implies that the metallic nature of Al3Ni increases gradually with increasing pressure. Moreover, through analysis of Poisson's ratio, the anisotropy factor, and the sound velocity, we ascertained that pressure attenuates the anisotropic attributes of the material, and Al3Ni exhibits more pronounced isotropic characteristics and mechanical homogeneity under high-pressure conditions. The substantial increase in the Debye temperature further suggests that high pressure fortifies the lattice dynamic rigidity of the material. This current research systematically elucidated the stability of Al3Ni under high-pressure conditions and the law of the transformation of it mechanical behavior, providing a theoretical foundation for its application under extreme circumstances. [ABSTRACT FROM AUTHOR]

In the present work, the influence of the addition of graphene nanoplatelets presenting different dimensions on polyurethane–polyisocyanurate aerogel structure and properties has been studied. The obtained aerogels synthesized through a sol–gel method have been fully characterized in terms of density, porosity, specific surface area, mechanical stiffness, thermal conductivity, and speed of sound. Opacified aerogels showing high porosity (>92%) and low densities (78–98 kg/m3) have been produced, and the effect of the size and content of graphene nanoplatelets has been studied. It has been observed that formulations with less than 5 wt.% of graphene nanoplatelets larger than 2 microns can effectively reduce the total thermal conductivity by absorption and scattering of the infrared radiation, reducing the heat transfer by this mechanism. The resulting opacified samples are highly insulating materials, with thermal conductivities less than 18 mW/m·K. Moreover, it has been observed that smaller particles with ca. 200 nm of average length can promote an increase in the elastic modulus, therefore obtaining stiffer aerogels, combined with thermal conductivities lower than 20 mW/m·K. Results have been studied in detail, providing a further understanding of the mechanisms for improving the final properties of these materials, making them more suitable for industrial applications. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to investigate the performance of the Network Real-time Kinematic (NRTK) technique in hydrographic surveying and check whether it meets the International Hydrography Organization (IHO) minimum bathymetry standards for the safety of navigation hydrographic surveys. To this end, the KAU-Hydrography 2 vessel was used to conduct a hydrographic survey session at Sharm Obhur. NRTK corrections were streamed in real time from the KSA-CORS NTRIP server and GNSS data were collected at the same time at the base station using a Trimble SPS855 GNSS receiver. Multibeam records were collected using a Teledyne RESON SeaBat T50-P multibeam echosounder in addition to Valeport's sound velocity profiler records and Applanix POSMV data. Applanix POSPac MMS 8.3 software was used to process the GNSS data of the base station along with the POSMV data to obtain the Smoothed Best Estimate of Trajectory (SBET) file, which is used as a reference solution. The NRTK solution is then compared with the reference solution. It is shown that the Total Horizontal Uncertainty (THU) and the Total Vertical Uncertainty (TVU) of the NRTK solution are 6.38 cm and 3.10 cm, respectively. Statistical analysis of the differences between the seabed surface generated using the NRTK solution and the seabed surface generated using the Post-Processed Kinematic (PPK) technique showed an average of −0.19 cm and a standard deviation of 2.4 cm. From these results, we can conclude that the KSA-CORS NRTK solution successfully meets IHO minimum bathymetry standards for the safety of navigation hydrographic surveys at a 95% confidence level for all orders of hydrographic surveys. [ABSTRACT FROM AUTHOR]

Abstract Considerable efforts have been devoted in recent years to enhancing the efficacy medicinal substance, leading to the discovery of innovative drug formulations and delivery techniques. The successful design of these processes necessitates a profound understanding at the molecular level of how these substances interact with biological membranes. Thorough thermodynamic investigations provide invaluable insights into these interactions and aid in selecting suitable compounds for pharmaceutical production. This study aims to determine the density and speed of sound for D-calcium pantothenate in mixtures of water and deep eutectic solvents (DESs), specifically choline chloride/sucrose, choline chloride/ glucose, and choline chloride/ fructose (with 2:1 molar ratio) over a temperature range of 288.15 K to 318.15 K under atmospheric pressure. In order to predict the behavior of molecules, COSMO model (the Conductor-Like Screening Model) offer complementary strengths in quantum chemistry. This approach allows for calculating solvation free energies, making it ideal for predicting properties like solubility, where understanding solvent-solute interactions is crucial. By correlating the measured parameters using standard relationships, important partial molar parameters such as apparent molar volumes and apparent molar isentropic compressibility are calculated. Additionally, apparent molar isobaric expansion, and Hepler’s constant are derived from the density and speed of sound data. The experimental apparent molar volumes, and apparent molar isentropic compressibility data is fitted to the Redlich-Meyer equation to obtain significant quantities such as standard partial molar volume, and partial molar isentropic compression. The comprehensive thermodynamic analysis of this studied system holds immense significance for advancements in the pharmaceutical industry.

The strong-field gravity in general relativity (GR) realized in neutron stars (NSs) renders the equation of state (EOS) P (ε) of supradense neutron star matter to be essentially nonlinear and refines the upper bound for ϕ ≡ P / ε to be much smaller than the special relativity (SR) requirement with linear EOSs, where P and ε are respectively the pressure and energy density of the system considered. Specifically, a tight bound ϕ ≲ 0.374 is obtained by perturbatively anatomizing the intrinsic structures of the scaled Tolman–Oppenheimer–Volkoff (TOV) equations without using any input nuclear EOS. New insights gained from this novel analysis provide EOS-model-independent constraints on the properties (e.g., density profiles of the sound speed squared s 2 = d P / d ε and trace anomaly Δ = 1 / 3 − ϕ) of cold supradense matter in NS cores. Using the gravity-matter duality in theories describing NSs, we investigate the impact of gravity on supradense matter EOS in NSs. In particular, we show that the NS mass M NS , radius R , and compactness ξ ≡ M NS / R scale with certain combinations of its central pressure and energy density (encapsulating its central EOS). Thus, observational data on these properties of NSs can straightforwardly constrain NS central EOSs without relying on any specific nuclear EOS model. [ABSTRACT FROM AUTHOR]

Negative velocity discontinuities are often observed at the base of the D'' layer, yet their formation mechanisms remain elusive. Here, we present the first investigation of thermoelastic properties of SiO2‐seifertite under 30–200 GPa and 1,000–4,000 K using first‐principles molecular dynamics simulations. We find that the compressional and shear wave velocities of seifertite are 2.0%–4.3% and 7.4%–11.3% lower, respectively, than those of CaCl2‐type SiO2 in the D'' layer. The reductions in VS across the phase transition are significantly larger than previous estimates from density functional theory results. Incorporating the elastic properties of other minerals, we demonstrate that the presence of SiO2 in the accumulated subducted oceanic crust and the associated VS reductions can contribute to the negative velocity discontinuities observed in the D'' layer. The observed low seismic velocities at the base of the lower mantle can be matched if 19–27 vol.% SiO2 is present in the D'' region. Plain Language Summary: Geochemical and seismic observations suggest that subducted oceanic crust can accumulate at the core‐mantle boundary, but its effects on the seismic velocity of the D'' layer remain poorly constrained. In fact, the thermoelastic properties of seifertite, which is a major mineral in the deeply subducted oceanic crust at the lowermost mantle, have not been previously investigated at high pressure‐temperature conditions. Using first‐principles molecular dynamics simulations, we computed the thermoelastic properties of seifertite under high pressures and temperatures up to 200 GPa and 4000 K. Our findings shows that seifertite has lower compressional and shear wave velocities than the CaCl2‐type SiO2, but has slightly higher density and bulk sound velocity. Thus, the reductions in VS of SiO2‐bearing mantle assemblages, such as the subducted oceanic crust, upon transition from CaCl2‐type SiO2 to seifertite, could contribute to the negative velocity discontinuities observed in certain regions of the D'' layer. Key Points: Thermoelastic properties of seifertite were determined using first‐principles molecular dynamics simulationsSeifertite has lower compressional and shear wave velocities than the CaCl2‐type SiO2 in the D'' layerCombined effects of SiO2 phase transition and temperature increase may lead to large shear velocity reductions in the D'' layer [ABSTRACT FROM AUTHOR]

This paper considers the problem of flying a UAV along a given trajectory at speeds close to the speed of sound and above. A novel pitch channel control system is presented using the example of a trajectory with rapid and large changes in flight height. The control system uses a proportional–integral–differential (PID) controller, whose gains were first determined using the Ziegler-Nichols II method. The determined gains were then optimised to minimise height error using a recurrent back-propagation neural network (PIDNN), with which new controller gains were determined, which is also a novelty of this study. Simulations were carried out for flights at subsonic speeds close to the speed of sound and supersonic speeds, at low and high altitudes. The simulations showed that determining controller gains using a recurrent neural network significantly minimises height errors and increases the flexibility of the PID controller. [ABSTRACT FROM AUTHOR]

Acoustic tweezers can trap and manipulate a target along a desired path without physical contact. Potential applications of this technology may require the propagation of acoustic waves through non-homogeneous media. It is typically assumed that the acoustic impedance of media is the same. However, this assumption leads to reduced efficiency in both the trapping accuracy and strength of the acoustic tweezers. In this study, we propose a method to derive phases driving an 8x8 array of ultrasonic transducers using generalized Snell's law to account for the variation in the speed of sound between media layers of planar or non-planar interfaces. The results indicate that the tweezers formed with our approach maintain their patterns and trapping capability at selected trapping locations. In addition, our method significantly enhances the trapping accuracy and force, achieving up to ten times greater force and more accurate alignment with the selected trapping points compared to the previous method that assumes a uniform speed of sound. [ABSTRACT FROM AUTHOR]

Based on experimental data from the deep-sea sound channel axis in the Western Pacific, the statistical distribution law of cluster structure and channel delay spread characteristics are analyzed for three typical receiving depths near the sound channel axis in this paper. A ray theory-based underwater acoustic channel model is used to explain the variations in channel parameters over time and the receiving depth. The results indicate that the underwater acoustic communication channel at the channel axis depth over a 20-km range exhibits a clustered structure that depends on the emission angles of sound rays. For the amplitude characteristics, the amplitude of each cluster follows an inverse Gaussian distribution, with the maximum average amplitude observed when the receiver and transmitter depths are similar. The amplitude of each cluster fluctuation decreases as the receiving depth increases. Regarding delay spread characteristics, the delay spread of each cluster, as well as the maximum and root mean square delay spread of the channel, conform to a Gaussian mixture distribution. The mean and fluctuation of the delay spread parameters increase with the receiving depth. Variations in the cluster structure and channel delay spread characteristics above are primarily attributed to the time-varying sound speed along the propagation paths of sound rays emitted at small upward angles. [ABSTRACT FROM AUTHOR]

As representative compositions of the mold flux used in the continuous casting of steel, the temperature and composition dependence of the thermal conductivity of alkali silicate glasses and melts was investigated in the range of 300–1700 K using molecular dynamics (MD) simulations. MD simulations can exclude disturbances such as radiation, convection, and impurities, and extract only the effect of phonons on the thermal conduction. Thermal conductivity determined by the laser flash (LF) method was reported to be three times higher than that obtained by the unsteady hot wire (HW) method in the high‐temperature range of 1250–1550 K for 33.3Na2O–66.7SiO2 (mol%). This study shows that (1) the thermal conductivity estimated by MD simulations was closer to the experimental value of the LF method than those of the HW method above 1200 K, which suggests that the LF method is reliable and that the effect of radiation on the thermal conductivity is not significant. (2) The decrease in the thermal conductivity measured by the LF method in the range of 1250–1550 K was attributed to the decrease in the bulk modulus of the 33.3Na2O–66.7SiO2 melt. (3) In a series of Na2O–SiO2 melts, the sound velocity calculated by MD decreased with increasing Na2O content, which is consistent with Shiraishi's ultrasonic wave measurements. [ABSTRACT FROM AUTHOR]

Since Biot's first work on acoustic waves in non-dissipative solid media, it has been known that the group velocity of bulk acoustic waves coincides with the velocity of wave energy transport. The recent studies on these types of velocities for electromagnetic waves reveal that (i) these can differ, and (ii) the superluminal group velocities may exist. The current research demonstrates that in the case of Lamb waves propagating in sandwich clamped–clamped plates, the group velocity can exceed the largest longitudinal bulk wave velocity, and, moreover, the group velocity can be infinitely large, similarly to electromagnetic waves. [ABSTRACT FROM AUTHOR]

The present study provides an experimental method for measuring acoustic velocity components (amplitude and spatial phase shift) in the presence of turbulent flows using either low-frequency particle image velocimetry (PIV) or laser Doppler velocimetry (LDV). The approach leverages compressed sensing (CS) principles to overcome the limitations of classical PIV techniques, such as the need for a reference signal for synchronization, large data size and long measurement duration. Theoretical aspects of CS for extracting acoustic components from PIV and LDV measurements are discussed. The proposed method is applied to both PIV and LDV systems, and the results are compared with microphone measurements. The results show the ability of the proposed experimental method to accurately measure acoustic velocity components at different frequencies and sound pressure levels in the presence of turbulent flow. The presented experimental method offers several advantages, including reduced data size, no need for phase-locking measurements and reduced measurement duration. The actual limitation is the need for a low noise-to-signal ratio (NSR). The effects of high NSR can be mitigated by increasing acquisition time in some cases. The non-intrusive nature of the method makes it valuable for aeroacoustic research. Ongoing research focuses on applying the method to higher-order duct modes and investigating its potential for modal decomposition using optical techniques. [ABSTRACT FROM AUTHOR]

The sonar detection of salt cavern gas storage (SCGS) has a low accuracy due to sound wave attenuation. To solve the problem, this paper analyzes the attenuation features of sound waves in SCGS, based on the mechanical wave equation and Urick sound wave attenuation theory, as well as expression of sound velocity in dilute solution and the general empirical formula of solution density. Specifically, three attenuation forms of sound waves in dilute solutions with different concentrations were studied, and a theoretical model for the total attenuation of sound waves in SCGS was established. The model was adopted to explore the effect of solution temperature and concentration on sound wave attenuation. The results yield some interesting findings. It is shown that the temperature has a small overall effect on the attenuation of sound waves. Also, the total attenuation coefficient of sound waves in suspensions with different concentrations increases with the frequency of the sound waves. Furthermore, when the frequency of the sound waves remains unchanged, the total attenuation coefficient increases with the concentration of the suspension. Finally, when the solution concentration is less than 10%, the total attenuation coefficient of the sound waves depends on scattering attenuation, and the sound wave attenuation is not greatly affected by the viscous attenuation and thermal attenuation. Four salt solutions were tested to verify the correctness of the theoretical research. The experimental results show that, in the SCGS environment, the salt solutions are ranked in a descending order of the influence over sonar detection accuracy starting from potassium chloride solution, via magnesium sulfates solution and calcium chloride solution to sodium chloride solution. The research provides a strong theoretical guidance for sonar detection of SCGS, and a powerful engineering reference for sonar detection in brine. [ABSTRACT FROM AUTHOR]

Ultrasonic testing is utilized to ensure weld quality during the fabrication of steel bridges by identifying discontinuities that are classified as either acceptable or rejectable. The classification of a discontinuity can be affected by differences in the acoustic properties of the material under test and the reference standard used for calibration. Differences in wave velocity affect the refracted angle and amplitude of refracted shear waves. As a result, indications can be missed or incorrectly classified, or incorrectly located in the material. The objective of this research study was to characterize the acoustic wave velocities in a sample of contemporary steels to better understand the range over which velocities may vary for common steels. To address this objective, a series of velocity measurements have been conducted for shear waves propagating through different directions in steel plates of different strengths and reported manufacturing processes. The study also examines the loss of signal amplitude that results from changes in the refracted angle of shear waves used for the inspection of welds. Beam splitting that may occur in anisotropic materials and the potential impact on signal amplitudes is also presented. It was shown in the research that relatively small differences in velocity between the material under test and the reference standard cause a loss of sensitivity of the test. Data presented in the paper documents wave velocity and anisotropic ratios for a population of contemporary bridge steels used for the fabrication of steel bridges and an assessment of how velocity differences affect the amplitude of reflected shear waves. [ABSTRACT FROM AUTHOR]

The star matter composed of nucleons deep inside compact stars, such as neutron stars, is believed to be very dense, such that various types of new concepts and physical phenomena are naturally expected due to the nontrivial strong correlations between hadrons. The possibility of revealing the hidden scale symmetry in dense baryonic matter has been discussed recently, to uncover the pseudo-conformal phase in dense star matter. In the pseudo-conformal phase, the trace of the energy–momentum tensor becomes density-independent, and the speed of sound approaches the conformal velocity in scale symmetric matter. Interestingly, it is also observed that the effective nucleon mass becomes a density-independent finite quantity, which can be identified as the chiral invariant mass of the parity doublet model, indicating that the parity doubling is an emergent phenomenon. In this paper, we will discuss how parity-doubling symmetry emerges inside the core of a compact star as a consequence of the interplays between ω vector mesons and nucleons (or dilaton, χ , equivalently) and between the chiral symmetry and the scale symmetry. [ABSTRACT FROM AUTHOR]

This study examines the thermophysical, acoustical, and spectral properties of binary mixtures of a-terpineol with fluorobenzene, chlorobenzene, and bromobenzene under standard atmospheric pressure at 303.15 K, 308.15 K and 313.15 K. Molar volume (vm) excess molar volume (vme) partial molar volume (Vomi excess partial molar volume VoEm,i, apparent molar volume (Vm,Q,i) deviation in speed of sound (Δu), isentropic compressibility (ks) deviation in isentropic compressibility (Δks) acoustical impedance (z), deviation in acoustical impedances (Δz) intermolecular free length (lf), partial molar isentropic compression (KoEs,m,i) excess partial molar isentropic compression and apparent molar isentropic compression have been measured. Parameters such as infinite dilution apparent molar volume, infinite dilution apparent molar isentropic compression have also been determined. The Redlich-Rosenberg-Mayer equation for empirical coefficients and applied theoretical models to analyze speed of sound and deviation properties have been used. FT-IR spectral analysis has been performed on binary mixtures at 298.15 K, while computational investigations include gas phase optimization, Mulliken charges, vibrational frequencies, NCI, ELF, LOL, and NBO analyses using DFT. These studies elucidate intermolecular interactions, their strengths, and variations with temperature and halobenzene concentration. [ABSTRACT FROM AUTHOR]

Matter properties at the intermediate densities are still unknown to us. In this work, we use a neural network approach to study matter at intermediate densities to analyze the variation of the speed of sound and the measure of trace anomaly considering astrophysical constraints of mass–radius measurement of 18 neutron stars. Our numerical results show that there is a sharp rise in the speed of sound just beyond the saturation energy density. It attains a peak around 3–4 times the saturation energy density and, after that, decreases. This hints towards the appearance of new degrees of freedom and smooth transition from hadronic matter in massive stars. The trace anomaly is maximum at low density (surface of the stars) and decreases as we reach high density. It approaches zero and can even be slightly negative at the centre of massive stars. It has a negative trough beyond the maximal central densities of neutron stars. The change in sign of the trace anomaly hints towards a near-conformal matter at the centre of neutron stars, which may not necessarily be conformal quark matter. [ABSTRACT FROM AUTHOR]

The Tolman VII space-time is one of the few physically acceptable exact solutions in general relativity. In this paper, we derive a generalised Tolman VII solution which includes a charge and a cosmological constant. We analyse the spatial geometry of the solution and present conditions for zero and non-zero spatial curvature. We show that for a particular value of the boundary, the Tolman VII space-time can be matched to the charged Nariai space-time. This represents a new class of interior Nariai solutions. Matching with the Reissner–Nordström-de Sitter space-time, we derive analytic expressions for the metric functions and the pressure. Using this, we show that the solution allows for trapped null geodesics for a broad range of values for the total charge, central density, and the cosmological constant. We investigate the physical properties and derive an equation of state for the fluid. We show that the fluid can be considered a polytrope with, Γ ∼ 2.5 . Finally, we analyse the sound speed and energy conditions to conclude that only a subclass of the solution follows all the basic physical acceptability criteria. [ABSTRACT FROM AUTHOR]

The underwater environment introduces uncertainty into the acoustic velocity, which affects the performance of traditional direction of arrival (DOA) estimation methods. This research proposes a cascaded neural network based underwater DOA estimate approach to address this issue. In this method, the cascade neural network is composed of a velocity regressor and a velocity classifier. To determine the estimated value of acoustic velocity, the velocity classifier first breaks down the input data into distinct velocity domains. It then regulates the velocity regression process. Then, the array steering matrix predicted by the blind source separation algorithm is utilized to determine the angle, and the acoustic velocity is modiffed by the cascaded neural network. Eventually, it is possible to derive the DOA estimation value under the calculated acoustic velocity. The suggested method has a high estimation accuracy especially when the acousitc velocity is unknown, as shown by the simulation results. [ABSTRACT FROM AUTHOR]

This article presents a spatial environmental inversion scheme using broadband impulse signals with deep learning (DL) to model a single spatially-varying sediment layer over a fixed basement. The method is applied to data from the Seabed Characterization Experiment 2022 (SBCEX22) in the New England Mud-Patch (NEMP). Signal Underwater Sound (SUS) explosive charges generated impulsive signals recorded by a distributed array of bottom-moored hydrophones. The inversion scheme is first validated on a range-dependent synthetic test set simulating SBCEX22 conditions, then applied to experimental data to predict the lateral spatial structure of sediment sound speed and its ratio with the interfacial water sound speed. Traditional geoacoustic inversion requires significant computational resources. Here, a neural network enables rapid single-signal inversion, allowing the processing of 1836 signals along 722 tracks. The method is applied to both synthetic and experimental data. Results from experimental data suggest an increase in both absolute compressional sound speed and sound speed ratio from southwest to northeast in the NEMP, consistent with published coring surveys and geoacoustic inversion results. This approach demonstrates the potential of DL for efficient spatial geoacoustic inversion in shallow water environments. [ABSTRACT FROM AUTHOR]

An acoustic propagation experiment was conducted in the western continental shelf of India (off Kollam, Kerala) in water depth of ∼71 m with seafloor consisting of hard sandy sediments. The multipath arrival times are obtained from peaks in acoustic impulse response measurements made on a single hydrophone for two source-receiver ranges of 245 m and 320 m. The arrival times are used for inverting the water column sound speed profile (SSP) utilizing the empirical orthogonal functions (EOFs), which can completely describe large datasets. The EOFs are generated from a seasonal dataset consisting of 12 SSPs collected once every month of the year at the same location. Inversion is formulated as an optimization problem and solved by employing the method of Differential Evolution Algorithm. A ray-theory based forward propagation model is implemented to model multipath arrival times with candidate SSPs, reconstructed from the EOFs as input for the two source receiver ranges. The objective function measures mismatch between the observed and modeled travel time estimates. The SSP estimated from modeled arrival times with EOFs as search space is found to agree reasonably well with in situ SSP for the two ranges. [ABSTRACT FROM AUTHOR]