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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]

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]

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]

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]

The exponential-6 (exp-6) potential is commonly used to model fluids at high densities. In this paper, I propose a new equation of state (EOS) in the form of an analytical expression for the excess Helmholtz free energy of an exp-6 fluid. The EOS is based on extensive Monte Carlo simulations and therefore combines the excellent accuracy of the simulations with the numerical efficiency of a polynomial expression. The mean relative error in compressibility factor and internal energy is 0.14% and 0.25% respectively, which is a significant improvement over statistical mechanical theories. The EOS was implemented into a thermochemical code in order to optimize gas parameters and evaluate its performance on pure gas data, shock compression and detonation properties. Predicted gas densities, heat capacities and speed of sound for pure gases were generally within experimental uncertainties at pressures up to 1 GPa and temperatures above 300 K. For polar molecules, a simple free energy correction was introduced which greatly improved accuracy at low temperature. Calculated shock Hugoniots showed excellent agreement with experimental values up to 150 GPa and 10 000 K, and the detonation performance was accurately predicted for a number of different types of explosives. [ABSTRACT FROM AUTHOR]

We employed high-pressure Brillouin scattering to study the pressure dependencies of acoustic modes of glycerol up to 14 GPa at 300 K. We observed longitudinal acoustic velocities and transverse acoustic velocities for the first time from 5 to 14 GPa. The results allow the determination of a complete set of elastic properties and an accurate determination of the pressure–volume (P–V) equation of state (EOS). EOS parameters, K0 = 14.9 ± 1.8 GPa and K′0 = 5.6 ± 0.5, were determined from fits to the data from ambient pressure to 14 GPa. Direct volume measurements of the P–V EOS are consistent with those determined by Brillouin scattering. A deviation from a Cauchy-like relationship for elastic properties was observed, and the pressure dependencies of the photoelastic constants and relaxation times were documented from 5 to 14 GPa. These results have broad implications for glass-forming liquids, viscoelastic theory, and mode coupling theory. [ABSTRACT FROM AUTHOR]

Optical phonons serve as the fast and efficient carriers of energy across periodic polymers due to their delocalization, large group velocity because of covalent bonding, and large energy quantum compared to that for acoustic phonons as it was observed in a number of recent measurements in different oligomers. However, this transport is dramatically sensitive to anharmonic interactions, including the unavoidable interaction with acoustic phonons responsible for transport decoherence, suppressing ballistic transport at long distances. Here, we show that this decoherence is substantially suppressed if the group velocity of optical phonons is less than the sound velocity of acoustic phonons; otherwise, ballistic transport is substantially suppressed by a Cherenkov-like emission of acoustic phonons. This conclusion is justified considering energy and momentum conservation during phonon absorption or emission and supported by the numerical evaluation of the lifetimes of the optical phonons. It is also consistent with the recent experimental investigations of ballistic optical phonon transport in oligomers with the minor exception of relatively short oligophenylenes. [ABSTRACT FROM AUTHOR]

This paper investigated the anisotropic quintessence stars in the f (R , ϕ) theory of gravity, where R is the Ricci scalar and ϕ is the scalar potential. We investigated the field equations of the f (R , ϕ) theory of gravity by using the Krori–Barua technique. We have determined that all the obtained solutions are free from central singularity and potentially stable. The observed values of mass and radius of the different strange stars Her X1, SAXJ1808.4-3658, and 4U1820-30 have been used to calculate the values of unknown constants in the Krori and Barua metric. The physical phenomena of stars, such as energy density, pressure components, anisotropy, sound speeds, equation of state parameters, energy conditions and redshift have been investigated in detail. [ABSTRACT FROM AUTHOR]

We present novel experimental measurements of acoustic velocity and attenuation in unconsolidated sand with water saturation within the sonic (well‐log analogue) frequency range of 1–20 kHz. The measurements were conducted on jacketed sand packs with 0.5‐m length and 0.069‐m diameter using a bespoke acoustic pulse tube (a water‐filled, stainless steel, thick‐walled tube) under 10 MPa of hydrostatic confining pressure and 0.1 MPa of atmospheric pore pressure. We assess the fluid distribution effect on our measurements through an effective medium rock physics model, using uniform and patchy saturation approaches. Our velocity and attenuation (Q−1) are accurate to ±2.4% and ±5.8%, respectively, based on comparisons with a theoretical transmission coefficient model. Velocity decreases with increasing water saturation up to ∼75% and then increases up to the maximum saturation. The velocity profiles across all four samples show similar values with small differences observed around 70%–90% water saturation, then converging again at maximum saturation. In contrast, the attenuation increases at low saturation, followed by a slight decrease towards maximum saturation. Velocity increases with frequency across all samples, which contrasts with the complex frequency‐dependent pattern of attenuation. These results provide valuable insights into understanding elastic wave measurements over a broad frequency spectrum, particularly in the sonic range. [ABSTRACT FROM AUTHOR]

The multi-layered media composed of layers with different sound velocities exhibit anisotropy, strong attenuation, and interface reflection in terms of sound propagation, posing challenges for conventional ultrasound imaging methods, especially in detecting deep-seated and near-interface defects. In this study, an improved far-focused pixel-based (FPB) imaging method for detecting internal defects in multi-layered media is proposed. First, the time delay calculation in the FPB method is corrected using the shortest path searching method to determine the acoustic time-of-flight. Then, phase information is extracted from the echo signal to construct a circular coherence factor (CCF) that dynamically weights the time-corrected FPB images, addressing the issue of ineffective detection of near-interface defects caused by interface reflection. Finally, considering the sound attenuation in multi-layered media, the directivity coefficient, transmission coefficient, and divergence coefficient are determined through theoretical derivation to compensate for the echo amplitude. Experimental results demonstrate that the improved FPB method significantly enhances the reflection echo from deep-seated defects, reduces the maximum relative localisation error to 0.9%, and the quantisation error to 6.4%. The proposed method also greatly improves the lateral resolution and signal-to-noise ratio (SNR) of internal defect imaging compared to the total focusing method (TFM) and traditional FPB method. [ABSTRACT FROM AUTHOR]

Hydrophilic and hydrophobic phenomena occur in aqueous solutions. Despite the complex nature of the molecular interactions, the propensity of molecules and ions to hydration is sometimes characterized by a single "hydration number". Passynski's method for determining the hydration numbers in dilute aqueous solutions belongs to the group of methods based on the analysis of the isentropic compressibility of a mixture. Isentropic compressibility is a thermodynamic material constant; thus, the paper deals with Passynski's approach discussed in terms of thermodynamics. First, Passynski's assumptions were applied to the volume of the mixture. Subsequent strict thermodynamic derivation led to a formula for the hydration number which resembled that of Onori rather than the original one. Passynski's number turned out to be inconsistent with the thermodynamics and mechanics of fluids. This is a rather purely empirical measure of the slope of the dependence of isentropic compressibility on the solute mole fraction in a dilute aqueous solution. Being the quotient of the slope and the isentropic compressibility of pure water, Pasynski's numbers are more convenient to analyze and discuss than the slopes themselves. Conclusions about molecular interactions based on these numbers must be treated with considerable caution. [ABSTRACT FROM AUTHOR]

In this work, the considered model is contained in higher dimensional compactified space in the form of M4 × M6, where M6 is compact inner space. Since, for a higher dimensional cosmological model, Tachyon matter is an automatic and fantastic choice, we have supposed that the scalar field is driven by Tachyon together with the higher dimensional cosmological constant Λ ¯ . Our observation is that the theory provides a good solution for the cosmological scale factor of the present universe. Here, it is important that the forms of the tachyonic field ϕ and potential V are simple trigonometric hyperbolic functions. We study the cosmographical parameters like equation of state parameter, statefinder parameters, jerk, snap, and lerk parameters. The graphical representations of cosmological parameters show the overall evolution of the universe under a tachyonic field in a higher dimensional model. The classical stability of the model due to small perturbations both for dark energy and metric are examined by the study of the square speed of sound and by the linear perturbation method. We also analyzed the model in ω−ω′ and r−s cosmological plane. [ABSTRACT FROM AUTHOR]

A systematic experimental density and sound velocity measurement was carried out for imidazolium-based ionic liquids (ILs) in pure water and in aqueous solutions of 0.03 w/w of water-miscible polymers with different structures and molar masses at T= (288.15, 293.15, 298.15, 303.15 and 308.15) K and p = 84.5 kPa. The ILs under investigation are 1-butyl-3-methylimidazolium hydrogen sulphate ([C4mim][HSO4]) and 1-butyl-3-methylimidazolium bromide ([C4mim]Br). The effects of temperature, polymer type, and IL anion type on the various volumetric and compressibility properties, such as apparent molar volume, isentropic compressibility, apparent molar isentropic compressibility, and infinite dilution apparent molar properties for transfer of ILs from water to aqueous polymer solution were scrutinised. From the gathered results, ion-water interactions, ion-ion interactions at finite concentration, and water-structure breaking character for aqueous solutions of [C4mim][HSO4] are more considerable than aqueous solutions of [C4mim]Br. However, [C4mim]Br-polymer interactions are more favourable than interactions between [C4mim][HSO4] and the studied polymers. [ABSTRACT FROM AUTHOR]

This work aims to explore the interactions between a wide-spectrum bactericidal drug, gemifloxacin (GMF), and micelles of cationic (dodecyltrimethylammonium bromide, DTAB) and anionic (sodium dodecyl sulfate, SDS) surfactants at the molecular level under physiological conditions (using a phosphate buffer, pH 7.4). Various physical parameters are calculated from volumetric and acoustic data. These include apparent molar volume ( ɸ V ), apparent molar isentropic compressibility ( ɸ K ), isentropic compressibility ( K s ), specific acoustic impedance (Z), relative association (RA), intermolecular free length (Lf) and sound velocity number (U). The obtained quantities are interpreted regarding of solute-solute and solute-solvent interactions employing the cosphere overlap model and electrostriction effect. Further, normal and differential UV-visible spectroscopy is employed to predict GMF locus in ionic micelles and to find the binding constant (Kb) and partition coefficient (Kc) along with the corresponding free energy changes of GMF-ionic micelle systems. The results demonstrate that the binding and partitioning of GMF with SDS is more significant than DTAB. [ABSTRACT FROM AUTHOR]

This research begins with the initial assessment of key physical properties—density (ρ), speed of sound (u), and refractive index (nD) in binary aqueous solutions of dorzolamide hydrochloride. These properties were measured in solutions with varying molalities, ranging from 0.0 to 0.0276, under standard atmospheric conditions and at temperatures between 300.15 and 320.15 K. From these measurements, we were able to calculate a range of important parameters, including the apparent molar volume (Vϕ), its limiting values ( V ϕ 0 ), limiting apparent molar expansivity ( E ϕ 0 ), Helper's constant ( ∂ 2 V ϕ 0 ∂ T 2 ), apparent molar isentropic compression (κϕ), and its limiting values ( κ ϕ 0 ), specific refraction (RD), molar refraction (RM), and hydration number (nh). These calculated values provided insights into the strong interactions between the solute and solvent in the liquid system. They also shed light on the presence of various molecular interactions, such as inter- and intramolecular hydrogen bonds, dipole–dipole, and dipole-induced-dipole interactions, as well as the ability of the solute to influence the structure of the surrounding water molecules. Additionally, we derived the densities of dorzolamide hydrochloride solutions from molecular dynamics (MD) simulations, which showed a strong correlation with our experimental findings, underscoring the reliability of MD simulations in such studies. In the end, our combined study on dorzolamide hydrochloride in water demonstrates that it shapes structures because it has lower volumetric properties and stronger hydrogen bonds in MD simulations. More alchemical free energy calculations show that there are big changes in solvation energies. This is important for understanding how dorzolamide hydrochloride works in water. [ABSTRACT FROM AUTHOR]

This article presents a study on the temperature-dependent sound speed in a beaker using a smartphone. The researchers conducted experiments with a tall beaker and a smartphone to measure the frequency and harmonics of the sound produced as the beaker was filled with water. They also investigated how the speed of sound changed as the air inside the beaker became warmer. The results showed that the frequency of the sound increased over time and that the speed of sound aligned with theoretical values at room temperature. The researchers also conducted experiments with hot air to observe any differences in the frequency response. Overall, this experiment provides a simple and replicable way to determine the speed of sound in air, making it a valuable teaching tool for acoustics. [Extracted from the article]

We construct a fundamental piece of the boundary of the maximal globally hyperbolic development (MGHD) of Cauchy data for the multi-dimensional compressible Euler equations, which is necessary for the local shock development problem. For an open set of compressive and generic H 7 initial data, we construct unique H 7 solutions to the Euler equations in the maximal spacetime region below a given time-slice, beyond the time of the first singularity; at any point in this spacetime, the solution can be smoothly and uniquely computed by tracing both the fast and slow acoustic characteristic surfaces backward-in-time, until reaching the Cauchy data prescribed along the initial time-slice. The future temporal boundary of this spacetime region is a singular hypersurface, containing the union of three sets: first, a co-dimension-2 surface of "first singularities" called the pre-shock; second, a downstream hypersurface called the singular set emanating from the pre-shock, on which the Euler solution experiences a continuum of gradient catastrophes; third, an upstream hypersurface consisting of a Cauchy horizon emanating from the pre-shock, which the Euler solution cannot reach. We develop a new geometric framework for the description of the acoustic characteristic surfaces which is based on the Arbitrary Lagrangian Eulerian (ALE) framework, and combine this with a new type of differentiated Riemann variables which are linear combinations of gradients of velocity, sound speed, and the curvature of the fast acoustic characteristic surfaces. With these new variables, we establish uniform H 7 Sobolev bounds for solutions to the Euler equations without derivative loss and with optimal regularity. [ABSTRACT FROM AUTHOR]

Objectives: To develop a robust algorithm for estimating ultrasonic axial transmission velocity from neonatal tibial bone, and to investigate the relationships between ultrasound velocity and neonatal anthropometric measurements as well as clinical biochemical markers of skeletal health. Methods: This study presents an unsupervised learning approach for the automatic detection of first arrival time and estimation of ultrasonic velocity from axial transmission waveforms, which potentially indicates bone quality. The proposed method combines the ReliefF algorithm and fuzzy C‐means clustering. It was first validated using an in vitro dataset measured from a Sawbones phantom. It was subsequently applied on in vivo signals collected from 40 infants, comprising 21 males and 19 females. The extracted neonatal ultrasonic velocity was subjected to statistical analysis to explore correlations with the infants' anthropometric features and biochemical indicators. Results: The results of in vivo data analysis revealed significant correlations between the extracted ultrasonic velocity and the neonatal anthropometric measurements and biochemical markers. The velocity of first arrival signals showed good associations with body weight (ρ = 0.583, P value <.001), body length (ρ = 0.583, P value <.001), and gestational age (ρ = 0.557, P value <.001). Conclusion: These findings suggest that fuzzy C‐means clustering is highly effective in extracting ultrasonic propagating velocity in bone and reliably applicable in in vivo measurement. This work is a preliminary study that holds promise in advancing the development of a standardized ultrasonic tool for assessing neonatal bone health. Such advancements are crucial in the accurate diagnosis of bone growth disorders. [ABSTRACT FROM AUTHOR]

On 18 November 2023, SpaceX launched the Starship, the tallest and the most powerful rocket ever built. The Super Heavy engine separated from the Starship spacecraft and exploded at 90 km of altitude, while the main core Starship continued to rise up to 149 km and exploded after ∼8 min of flight. In this work, we used data from ground‐based GNSS receivers and we analyzed total electron content (TEC) response to the Starship flight and the two explosions. For the first time, we observed large‐distance northward propagation of intensive 2,000 km V‐shaped ionospheric disturbances from the rocket trajectory. The observed perturbations, most likely, represent shock waves propagating with the cone angle of ∼14° on the North and ∼7° on the South against the flight track that corresponds to the Mach angle of the shock waves in the lower atmosphere. The Starship explosion also produced a non‐chemical depletion in the ionospheric TEC. Plain Language Summary: On 18 November 2023, SpaceX launched the Starship, the tallest and the most powerful rocket ever built. About 2 min and 40 s after the liftoff, the Super Heavy engine separated from the Starship spacecraft and exploded at an altitude of 90 km. The main core Starship continued to rise to 149 km and exploded as well. The rocket launch and explosion produced an unexpected response in the ionosphere—the ionized part of the Earth's atmosphere. The Starship flew at a velocity, exceeding the local sound speed, and generated cone‐like atmospheric shock‐acoustic waves. Most unexpectedly, the observed disturbances represented long and intensive multi‐oscillation wave structures that propagated northward, which is unusual for disturbances driven by a rocket launch. The Starship explosion also generated a large‐amplitude total electron content depletion that could have been reinforced by the impact of the spacecraft's fuel exhaust in the lower atmosphere. This study appears to be the first‐time detection of a non‐chemical ionospheric hole produced by a man‐made explosion. Key Points: The 18 November 2023 Starship flight and explosions generated large‐scale multi‐oscillation supersonic conic waves in the ionosphereThe cone angle of the V‐shaped ionospheric disturbances corresponds to the Mach angle of shock waves propagating in the lower ionosphereThe shock waves from the Starship explosion caused a depletion in total electron content (TEC) [ABSTRACT FROM AUTHOR]

The current investigation theoretically presents a one-dimensional phononic crystal (PnC) as a fluidic sensor. The sensor under consideration aims to distinguish the concentration of acetic acid. The primary configuration of the proposed sensor is constructed with lead, epoxy, and a defect layer in the middle of the structure, that is filled with acetic acid (vinegar). As a result of the rise in density and decline in the speed of sound at a 100% concentration of acetic acid in comparison to pure water, the peak frequency of the output has shifted towards lower frequencies. Given that the maximum permissible concentration of acetic acid in water for vinegar is above 30%, sensor simulations were conducted within the concentration range of 25–35% with a step size of 1%. Interestingly, the sensitivity of the sensor exhibits a polynomial change in response to the concentration of acetic acid. Consequently, the highest level of sensitivity, which corresponds to the lowest concentration of vinegar, is recorded as 48.44 × 106 (Hz). The proposed system exhibits a remarkable value of the quality factor of 2802.91. Furthermore, the optimal figure of merit (FOM) is achieved when the concentration is at its lowest, with a value of 94.00. Furthermore, the temperature effects are taken into account for a wide range between 10 and 60 °C. A pronouncing sensitivity is obtained for all temperatures changes and the highest one reached the value of 1.57 × 106 (Hz/°C) at a temperature of 25 °C. Considering the present circumstances, the suggested sensor configuration has the potential to cater to a diverse array of other fluids, specifically their concentration and temperature, thereby offering a broad scope of applications. [ABSTRACT FROM AUTHOR]

Summary Bone toxicities are common among paediatric patients treated for acute lymphoblastic leukaemia (ALL) with potentially major negative impact on patients' quality of life. To identify the underlying genetic contributors, we conducted a genome‐wide association study (GWAS) and a transcriptome‐wide association study (TWAS) in 260 patients of European‐descent from the DFCI 05–001 ALL trial, with validation in 101 patients of European‐descent from the DFCI 11–001 ALL trial. We identified a significant association between rs844882 on chromosome 20 and bone toxicities in the DFCI 05–001 trial (p = 1.7 × 10−8). In DFCI 11–001 trial, we observed a consistent trend of this variant with fracture. The variant was an eQTL for two nearby genes, CD93 and THBD. In TWAS, genetically predicted ACAD9 expression was associated with an increased risk of bone toxicities, which was confirmed by meta‐analysis of the two cohorts (meta‐p = 2.4 × 10−6). In addition, a polygenic risk score of heel quantitative ultrasound speed of sound was associated with fracture risk in both cohorts (meta‐p = 2.3 × 10−3). Our findings highlight the genetic influence on treatment‐related bone toxicities in this patient population. The genes we identified in our study provide new biological insights into the development of bone adverse events related to ALL treatment. [ABSTRACT FROM AUTHOR]

Background: This study aimed to investigate the association between body composition (BC) specific parameters such as fat mass (FM) and lean body mass (LBM) and bone quality in obese and non-obese young Slovak adults (18–30 years) using bioelectrical impedance analysis and quantitative ultrasound while considering the factors of sex and obesity status; Methods: BC was evaluated using bioelectrical impedance analysis (InBody 770) and bone quality by the speed of sound (SOS) in radius using QUS (Sunlight MiniOmni) in 774 young Slovak young adults aged 18–30 years, categorized by sex and obesity status (body fat %, PBF, ≥28% for men and ≥20% for women); Results: In non-obese individuals, radial SOS correlated positively with FM parameters. Significant positive correlations with LBM, including skeletal muscle mass (SMM), were observed in non-obese men but not in women. Conversely, SOS correlated negatively with FM parameters in obese individuals, significantly only in women. The correlation of SOS with LBM in obese individuals was insignificant in both sexes. Age, visceral FM, FM in the arm, and vitamin D intake were identified as the main predictors of radial SOS in young adults, except in obese men. Conclusions: Findings indicate FM benefits bone tissue in non-obese individuals, while excessive adiposity deteriorates bone quality in obese individuals, necessitating tailored evaluations and interventions based on sex, obesity status, and specific predictors. [ABSTRACT FROM AUTHOR]

Kuiyang-ST2000 is a deep-towed multichannel seismic system that provides high-resolution exploration of sub-seabed geological formations. Due to the uncertainty of the sound speed at full ocean depth, the travel-time positioning of sea surface reflected waves still has flaws in positioning arrays. This research reveals that the average sound speed of seawater selected for computing the array position only affects the vertical displacement of the arrays. thus, a polynomial fitting method is proposed to position the arrays. Because the nonuniform mass distribution complicates the array shape, first, the weight of the digital transmission unit is balanced by one designed floater so that the array shape becomes a simple convex curve during towing conditions. Afterward, one general sound speed is used to calculate the initial array position; then, the polynomial fitting method is used to tune the sound speed so that the seismic source and hydrophones are on the same convex curve. Finally, an accurate array position is calculated by the proposed positioning method, and the submarine shallow strata are imaged at a high resolution. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the anisotropic and spatially homogeneous Bianchi type-I universe with Kaniadakis holographic dark energy in Saez–Ballester [Phys. Lett. A 113, 467 (1986)] theory of gravitation. We determine Kaniadakis holographic dark energy model by assuming a correlation between the metric potentials to solve the field equations of the model. This results in a dynamical deceleration parameter which demonstrates an accelerating expansion of the universe. Our model's equation of state parameter ω khde close to − 1 (Λ CDM model) at late-times and is in agreement with the most recent observations. Next, we obtained the squared sound speed ( v s 2 ) and found that it is positive, implying stability against perturbations. The ω khde − ω khde ′ plane is constructed to investigate the evolution of the models' EoS parameter turned out to be in a freezing zone. As should be the case in an expanding universe, the strong energy conditions of the model are violated. Statefinders (r , s) , and r − q planes were also examined. Our model includes the Chaplygin gas, Λ CDM limit, and is inclined towards the steady-state model. [ABSTRACT FROM AUTHOR]

The anisotropic dependence of the velocity of surface acoustic waves (SAW) on silicon is explored using surface Brillouin light scattering. Measurements of the SAW velocity are compared to a numerical model that takes into account the native thin amorphous oxide layer formed at the top surface of the silicon wafer. The model accounts for material loss and provides a relative estimate for the backscattered intensity resulting from the ripple effect. For the (100) sample considered, a thickness of 4 nm fits well with experimental data, considering material constants of amorphous silica for the oxide. A global phase velocity decrease of −11 m/s per nanometer of silica thickness is predicted for surface phonons at frequencies around 16 GHz. [ABSTRACT FROM AUTHOR]

Compositional tuning of refractory high-entropy alloys (HEAs) is a powerful strategy to modulate their structural stability and mechanical properties. In this study, we investigate the sound velocities, elasticity, and mechanical properties of NbxTiZrHf (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) HEAs using ultrasonic interferometry combined with Vickers hardness measurements. Notably, the metastable bcc Nb0.2TiZrHf HEAs exhibits exceptional fracture toughness, reaching up to 12.2 MPa·m1/2, which is 1.7–3.3 times higher than that of other bcc NbxTiZrHf counterparts. The mechanism for the abnormal strengthening in fracture toughness of Nb0.2TiZrHf HEAs is primarily attributed to the stress-induced bcc-to-hcp phase transition, which promotes plasticity/ductility strengthening and crack deflection. These findings provide deep insights into "metastability engineering" for designing refractory HEAs with superior fracture toughness and high strength. [ABSTRACT FROM AUTHOR]

In this paper we derived an expression that allows the determination of the thermo-optic coefficient of weakly-guiding germanium-doped silica fibers, based on the thermal behavior of optical fiber devices, such as, fiber Bragg gratings (FBGs). The calculations rely on the full knowledge of the fiber parameters and on the temperature sensitivity of FBGs. In order to validate the results, we estimated the thermo-optic coefficient of bulk GeO2 glass at 293 K and 1.55 μm to be 18.3 × 10−6 K−1. The determination of this value required to calculate a correction factor which is based on the knowledge of the thermal expansion coefficient of the fiber core, the Pockels' coefficients (p11 = 0.125, p12 = 0.258 and p44 = −0.0662) and the Poisson ratio (ν = 0.161) of the SMF-28 fiber. To achieve that goal, we estimated the temperature dependence of the thermal expansion coefficient of GeO2 and we discussed the dispersion and temperature dependence of Pockels' coefficients. We have presented expressions for the dependence of the longitudinal and transverse acoustic velocities on the GeO2 concentration used to calculate the Poisson ratio. We have also discussed the dispersion of the photoelastic constant. An estimate for the temperature dependence of the thermo-optic coefficient of bulk GeO2 glass is presented for the 200–300 K temperature range. [ABSTRACT FROM AUTHOR]

Sonic layer depth (SLD) is crucial in ocean acoustics research and profoundly influences sound propagation and Sonar detection. Carrying 90% of oceanic kinetic energy, mesoscale eddies significantly impact the propagation of acoustic energy in the ocean. Recent studies classified mesoscale eddies into normal eddies (warm anticyclonic and cold cyclonic eddies) and abnormal eddies (cold anticyclonic and warm cyclonic eddies). However, the influence of mesoscale eddies, especially abnormal eddies, on SLD remains unclear. Based on satellite altimeter and reanalysis data, we explored the influence of mesoscale eddies on seasonal variations in SLD in the South China Sea. We found that the vertical structures of temperature anomalies within the eddies had a significant impact on the sound speed field. A positive correlation between sonic layer depth anomaly (SLDA) and eddy intensity (absolute value of relative vorticity) was investigated. The SLDA showed significant seasonal variations: during summer (winter), the proportion of negative (positive) SLDA increased. Normal eddies (abnormal eddies) had a more pronounced effect during summer and autumn (spring and winter). Based on mixed-layer heat budget analysis, it was found that the seasonal variation in SLD was primarily induced by air–sea heat fluxes. However, for abnormal eddies, the horizontal advection and vertical convective terms modulated the variations in the SLDA. This study provides additional theoretical support for mesoscale eddy–acoustic coupling models and advances our understanding of the impact of mesoscale eddies on sound propagation. [ABSTRACT FROM AUTHOR]

This work examines the thermodynamics and hydrodynamics behaviors of a five‐dimensional black hole under the influence of an external magnetic field. The solution is the gravity dual to the Anti‐de Sitter/Boundary Conformal Field Theory correspondence, enabling the study of properties within an anisotropic fluid framework. Utilizing holographic renormalization, the free energy and the holographic stress tensor residing on the boundary denoted as Q$Q$ are computed. Within the fluid/gravity correspondence framework, authors have a class of boundary extensions in Q$Q$, where the stress‐energy tensor describes a magnetizing conformal fluid. The characteristics of this special solution as well as its thermodynamic properties, including the bulk and shear viscosity, the square of the speed of sound, as well as the anisotropic effects induced by the magnetic field in the magnetized conformal plasma are discussed. [ABSTRACT FROM AUTHOR]

A sonic anemometer targeted at wind speed measurements on the surface of Mars is described. This environment requires transducer operation in 4–10 mbar CO2 at temperatures between 143 and 293 K (–130 °C and 20 °C, respectively). Over these ranges, transducer pressure and temperature sensitivity could be a source of measurement error. To investigate this, four candidate transducers were tested using transmission mode ultrasonic testing and impedance measurements: two narrowband piezoelectric transducers, a broadband capacitive transducer, and a micromachined capacitive ultrasound transducer. A system model was used for comparison and interpretation, and implications for a sonic anemometer were examined. Variation of transducer characteristics, including diffraction effects, across 2–10 mbar in CO2 and 190–293 K (–83 °C–20 °C) result in ±2.3% error in wind speed measurement and ±1.1% error in speed of sound measurement for the worst case but only ±0.14% error in wind and ±0.07% error in speed of sound for the best transducer operated off resonance. The acoustic conditions on Mars are similar to those in Earth's stratosphere at 30–42 km of altitude. Hence, testing was also conducted in dry air over the same range of pressures and temperatures with relevance to a secondary application of the instrument as a stratospheric anemometer for high altitude balloon missions on Earth. [ABSTRACT FROM AUTHOR]

Room impulse responses (RIRs) vary over time due to fluctuations in atmospheric temperature, humidity, and pressure. This can introduce uncertainties in room transfer-function measurements, which are challenging to account for. Previous methods of identification and compensation of time variance focus on systematic atmospheric changes and do not apply to subtle discrepancies in RIRs. In this work, we address this problem by proposing a model of short-time coherence between repeated RIR measurements as an indicator of time-frequency similarity and as a measure of time-variance-induced changes in RIRs. Atmospheric changes cause fluctuation in sound speed, which, in turn, results in variation in the time-of-arrival of sound reflections following a Generalized Wiener process. We show that the short-time coherence decreases exponentially with the reflection-path length and propose volatility as a single model parameter determining the coherence decay rate. The proposed model is validated on simulations and measurements, showing applicability in indoor scenarios. The method reliably estimates volatility of 10 − 6 s / s as measured under laboratory conditions. We exemplify the utility of short-time coherence loss by predicting the high-frequency energy loss stemming from RIR averaging. The proposed method is useful in assessing the uncertainty of RIR measurements, especially when repeated measurements are compared or averaged. [ABSTRACT FROM AUTHOR]

The deep-ultra deep carbonate reservoir in China, commonly subjected to modification of multi-stage diagenesis, has extremely high heterogeneity. Conventional rock physics analysis cannot accurately identify the elastic responses of reservoir. Here, the rock physics properties of the dolomite from the 4th Member of the Sinian Dengying Formation are experimentally measured, and the change law of rock physics characteristics is investigated within the framework of the diagenetic processes by the analysis of the elastic and petrologic characteristics, pore structure, and sedimentary environments. The results show that the differentiated diagenesis results in different pore structure characteristics and microtexture characteristics of the rock. The microbial dolomite of the algal mound-grain beach facies is subjected to the contemporaneous microbial dolomitization and seepage-reflux dolomitization, penecontemporaneous selective dissolution, burial dolomitization, and hydrothermal dolomitization. The resultant crystalline dolomite is found with one main type of the dolomite crystal contact boundaries, and the dissolution pore is extensive development. The siliceous, muddy, and limy dolomite of the interbeach sea environment mainly experiences the weak capillary concentration dolomitization, intensive mechanical compaction-induced densification, and burial dolomitization. Such crystalline dolomite is observed with four types of contact boundaries, namely the dolomite contact, clay contact, quartz contact, and calcite contact boundaries, and porosity mostly attributed to residual primary inter-granular or crystalline pores. The samples with the same crystal boundary condition have consistent correlations between the compressional- and shear-wave velocities, and between the compressional-wave velocity and the velocity ratio. Additionally, the variation of the acoustic velocity with effective pressure and the intensity of pore-scale fluid-related dispersion are controlled by the differentiation of pore structure types of the samples. The varied effects of soft pores like micro-cracks on the compressional- and shearwave velocity causes considerable changes in the relationships between the compressional- and shearwave velocities, compressional-wave velocity and velocity ratio, and porosity and acoustic velocity. This research is an attempt to demonstrate a novel method for investigating the rock physics variation of rock during the geological process, and the obtained findings can provide the rock physics basis for seismic prediction of the characteristics of deep carbonate reservoirs. [ABSTRACT FROM AUTHOR]

The World Federation for Ultrasound in Medicine and Biology (WFUMB) has promoted the development of this document on multiparametric ultrasound. Part 2 is a guidance on the use of the available tools for the quantification of liver fat content with ultrasound. These are attenuation coefficient, backscatter coefficient, and speed of sound. All of them use the raw data of the ultrasound beam to estimate liver fat content. This guidance has the aim of helping the reader in understanding how they work and interpret the results. Confounding factors are discussed and a standardized protocol for measurement acquisition is suggested to mitigate them. The recommendations were based on published studies and experts' opinion but were not formally graded because the body of evidence remained low at the time of drafting this document. [ABSTRACT FROM AUTHOR]

Because of the inhomogeneity and anisotropy of glass fibre reinforced plastics (GFRP), it is always a challenge to detect the real-time dynamic quality during manufacturing and service. In this paper, a virtual loading focusing enhancement technology (VLFET) based on time reversal (TR) theory is proposed to accurately locate the acoustic emission (AE) source in the GFRP. First, the focusing enhancement theoretical model with virtual reverse loading is deduced according to the TR theory. Then, after measuring the optimal detection range and the average acoustic velocity, the sensor array is positioned on the GFRP specimen. The excitation signals applied to simulate the AE source at some positions are produced by using lead breaking, and the detection signals are received by the sensor array. Finally, the signals received by the sensor array are processed according to the theoretical model, and the fluctuation image in the monitoring area is reconstructed with fluctuation amplitude of each pixel to evaluate the AE source position. The experimental results demonstrate that the excitation sources can be accurately evaluated with the VLFET. The location error with the proposed method is less than 3.1%, higher than that from the current AE instrument. The proposed technology can also be applied to the AE evaluation of other anisotropic materials. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (cBN) has been used as a tool material for several decades due to its high hardness and thermal stability. Various binders are commonly added to cBN to synthesise cBN composites for better cutting performance. However, most studies have only investigated properties such as hardness and bulk modulus, without comprehensively studying elastic properties through experiments. In this study, the sound velocities and elastic properties of cBN with AlN binder were determined by using the ultrasonic interferometry technique. The bulk and shear moduli with their pressure dependence were determined as B 0 = 351 (3) GPa, G 0 = 344 (3) GPa, B 0 ′ = 4.32 (4) and G 0 ′ = 1.74 (2) using the finite strain equation-of-state approaches. Elasticity-related thermal properties, such as Debye temperature, Grüneisen parameter, thermal conductivity and coefficient of thermal expansion were also estimated. The results show that the elastic properties of the cBN composite with vol. 8.8% AlN-binder are comparable to the pure cBN compact. Additionally, the thermal conductivity and coefficient of thermal expansion have little effect on cBN composite with AlN binder compared to pure cBN. [ABSTRACT FROM AUTHOR]

This study starts by evaluating essential physical characteristics—density (ρ), sound velocity (u), and refractive index (nD)—in binary mixtures of Moxifloxacin Hydrochloride with water. We measured these properties in solutions with different concentrations, from 0.0 to 0.05 molalities, under normal atmospheric pressure and at temperatures from 305.15 to 320.15 K. From these measurements, we were able to calculate a range of important parameters, including the apparent molar volume V ϕ , its limiting values V ϕ 0 , limiting apparent molar expansibility E ϕ 0 , Hepler's constant ∂ 2 V ϕ 0 ∂ T 2 , apparent molar adiabatic compressibility k ϕ and its limiting values k ϕ 0 , specific refraction R D , molar refraction R M and hydration number n h . The calculated values demonstrated dominant solute–solvent interactions in the liquid mixture in this study. These findings indicated that molecules interact through hydrogen bonds, dipole–dipole interactions, and dipole-induced dipole interactions. They also showed how the solute influences the structure of water molecules. Moxifloxacin Hydrochloride (MOX) solution densities have been determined by MD simulations. These simulations matched our experimental data, proving MD simulation's effectiveness in such investigations. Finally, our in-depth research of MOX in water shows that it changes the way structures are made because it has lower volumetric properties and stronger hydrogen bonds, as seen in MD simulations. Solvation energies changed a lot when we did more calculations of alchemical free energy. These changes are very important for understanding how MOX behaves in water. [ABSTRACT FROM AUTHOR]

This paper presents a localization method for an underwater multitonal source by using a vertically distributed system in deep water. The system is composed of two kinds of nodes. One is a node at large depth, and the other is a node covering most of the water column. The former and latter are utilized to estimate the source range and depth, respectively. Specifically, the proposed method estimates the source range by matching the spatial arrival angle measured by the first kind of node with the replicas calculated by the acoustic model. Based on the estimation value of the source range, the second kind of node is utilized to estimate the source depth by using an incoherent time reversal method. The effectiveness of the proposed method is demonstrated through numerical simulations. The effects of the measurement error and the sound speed profile mismatch on the performance of the proposed method are also analyzed. [ABSTRACT FROM AUTHOR]

Due to the influence of the complex underwater environment, the sound speed constantly changes, resulting in the acoustic signal propagation trajectory being curved, which greatly affects the positioning accuracy of the underwater long baseline (LBL) system. In this paper, an improved LBL positioning method based on a B-spline surface for fitting the effective sound speed table (ESST) is proposed. Firstly, according to the underwater sound speed profile, the discrete ESST of each measurement station is constructed before the positioning test, and then, the node position of the B-spline surface is optimized by particle swarm optimization (PSO) to accurately fit the discrete ESST. Based on this, the improved LBL positioning method is constructed. In the underwater positioning test, the effective sound speed can be quickly found by measuring the time of arrival (TOA) of the acoustic signal and the target depth, and moreover, the target position parameters can be quickly and accurately estimated. The numerical simulation results show that the improved positioning method proposed in this paper can effectively improve the LBL positioning accuracy and provide the theoretical basis and the technical support for the underwater navigation and positioning. [ABSTRACT FROM AUTHOR]

Background and Aim: This is a cross‐sectional observational study conducted on living liver donors focusing on "long‐term remnant liver health" specifically looking at steatosis, inflammation, and fibrosis using multiparametric ultra sonological evaluation and noninvasive blood tests. Methods: Multiparametric ultrasound evaluation included assessment of shear wave elastography (fibrosis), sound speed plane wave ultrasound, attenuation plane wave ultrasound (steatosis), and viscosity plane wave ultrasound (inflammation). Blood test based APRI and FIB‐4 were calculated. Liver biopsy was performed if noninvasive evaluation pointed toward clinically relevant fibro progression (F4). Results: Out of 36 donors, significant fibrosis (>F2) was found in 11 donors (30.5%), seven donors (19.4%) had severe fibrosis (>F3), and two donors had shear wave elastography values suggestive of cirrhosis(F4). Of these two, one donor was extensively evaluated and was found to have biopsy proven cirrhosis with endoscopic evidence of portal hypertension. The prevalence of fatty liver disease in our study group was 50%. Conclusion: We report the first liver donor cohort with fibroprogression and cirrhosis occurring in the remnant liver. Our donor cohort with a significant proportion having steatosis and fibroprogression underscores the importance of regular follow‐up of liver donors and evaluation of remnant liver. [ABSTRACT FROM AUTHOR]

In the current investigation, effect of triazolium-based ionic liquid 1, 4-Dimethyl- 4 H-1,2,4-triazolium iodide (DMTI) on volumetric and ultrasonic properties of binary aqueous solutions of benzamide/benzylamine is analysed at four equidistant temperatures and atmospheric pressure. Molecular interactions of DMTI in binary aqueous solutions of benzylamine/benzamide are also interpreted using density (ρ) and speed of sound (u) data along with FT-IR measurements. Different volumetric and ultrasonic parameters were also computed by employing the experimental values of density (ρ) and speed of sound (u), and are further used to elucidate various kinds of interactions in the ternary system. Volumetric and acoustic transfer parameters were further used for the computation of interaction coefficients (pair and triplet). To analyse the outcomes of the estimated parameters, spectroscopic and density-functional theory (DFT) investigations have also been carried out. [ABSTRACT FROM AUTHOR]

Bidirectional controllable propagation of waterborne sound holds significant importance in developing multifunctional underwater acoustic and mechanical devices. However, the existing waterborne acoustic metasurfaces have rarely explored the bidirectional sound modulations. Here, a class of Janus waterborne acoustic metasurface, enabling two‐faced arbitrarily asymmetric wavefront manipulations is reported. A three‐degree‐of‐freedom mechanical system facilitated by acoustic‐structure interaction underwater is proposed to introduce bianisotropic responses of unit cells. Monolayer ultrathin Janus metasurface is inversely designed by utilizing a function‐structure integrated topology optimization framework. Distinct underwater acoustic functionalities, including axial and oblique focusing, beam splitting, and sound diffusion, are successfully demonstrated. Underwater experiments are further conducted to validate the concept of Janus metasurface. The good consistency between experimental and simulated results confirms the excellent two‐faced asymmetric acoustic focusing performance. The proposed Janus metasurface opens up a new dimension for designing advanced waterborne acoustic devices with two‐faced multifunctional wavefront manipulations. [ABSTRACT FROM AUTHOR]

Merons, as a member of quasiparticle family characterized by half-integer of the skyrmion topological charge with nontrivial topological textures, are of great interest in various branches of physics. Here, we report the first experimental observation of a meron texture configuration in acoustic waves. A squared metastructure is designed to support the spoof acoustic surface wave, forming meron lattice patterns in the acoustic velocity field vectors. The experimental results indicate that the meron textures can be moved and shaped by tuning the phase and amplitude differences between the excited sound sources, respectively. To demonstrate the topologically protected character of meron against structure defects, we further measure the acoustic pressure and velocity field distributions on a defective surface. The acoustic meron texture not only provides potential applications toward topologically robust ways to manipulate vectorial characteristics of the acoustic waves but also instills confidence for exploring other members of the quasiparticle family, such as the acoustic hopfion in acoustic waves. [ABSTRACT FROM AUTHOR]

Mesoscale eddies are phenomena that widely exist in the ocean and have a significant impact on the ocean's temperature and salt structure, as well as on acoustic propagation effects. Currently, utilizing the limited data on mesoscale eddy environments for refined acoustic field reconstruction in offshore conditions at mid-to-far-ocean distances is an urgent problem that needs to be addressed. In this paper, we propose a mesoscale eddy reconstruction method (EddyGAN) based on the generative adversarial network (GAN) model which is inspired by the concept of global localization. We adopt a hybrid algorithm for eddy identification using JCOPE2M high-resolution reanalysis data and Archiving, Validation, and Interpretation of Satellite Oceanographic (AVISO) satellite altimeter data to extract mesoscale eddy sound speed profile (SSP) sample data, and then apply the EddyGAN model to train this dataset and perform mesoscale eddy acoustic field reconstruction. We also propose an evaluation method for mesoscale eddy acoustic field reconstruction that uses RMSE, SSIM, and convergence zone (CZ) accuracy based on World Ocean Atlas (WOA) climate state data completion as indicators. The reconstruction result of this model achieves an RMSE of 1.7 m/s, an SSIM of 0.77, and an average CZ accuracy of over 70%. This method better characterizes the mesoscale eddy sound field than the native GAN and other reconstruction methods, improves the accuracy of mesoscale eddy acoustic field reconstruction, and provides superior performance, offering significant reference value for mesoscale eddy reconstruction technology and subsequent ocean acoustic research. [ABSTRACT FROM AUTHOR]

Experiments were conducted in a stoichiometric hydrogen-oxygen mixture at initial pressure of 1 atm to study the flame acceleration and deflagration-to-detonation transition (DDT) in a 20 mm high channel equipped with continuous triangular obstacles. Effect of blockage ratio (br) was explored by considering different obstacle heights of 0, 1 mm, 3 mm, 5 mm, and 7 mm, corresponding to br = 0, 0.1, 0.3, 0.5, and 0.7, respectively. High-speed schlieren photography and OH* chemiluminescence recording were used to visualize the processes. Results show that blockage ratio has a significant effect on the scales and velocities of the vortices generated in the gaps between neighboring obstacles and consequently on the subsequent flame-vortex interactions. Higher br leads to faster flame acceleration via stronger flame-vortex interactions. The intricate shock-flame interactions cause successive local explosions in the br = 0.3, 0.5, and 0.7 cases, creating conditions for DDT. An eventual choking regime occurs in the br = 0.7 case due to energy losses by continuous diffractions at the obstacle vertices. It was found that the onset of DDT is triggered when the critical height of the unobstructed passage is approximately greater than three detonation cell sizes. The mechanism of DDT changes as the br decreases. One important feature observed is that the br = 0.1 case has the shortest DDT distance. In addition, the final flame speed (~740 m/s, 1.4 times unburned sound speed) before DDT for br = 0.1 is significantly smaller than those (~1300 m/s, 2.4 times unburned sound speed) for br ≥ 0.3. The reason is that the low obstacles retain the characteristics of the obstacle, while mimicking the wall roughness, resulting in both shock compression of unburned gas and viscous heating in the boundary layer ahead of the flame front. The combined effects promote the occurrence of DDT for the case with br = 0.1. [ABSTRACT FROM AUTHOR]