Search

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

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

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

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

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]

This paper investigates the acoustic streaming effects (ASEs) and mechanisms behind the transmittance of sound in a metallic micro-cavity acoustic black hole (ABH) structure with an abrupt cross-section and examines the sound field flow characteristics inside the micro-cavity ABH under the sound excitation, such as the velocity, acceleration and pressure fields. And the sound transmission mechanisms are characterized by the ASEs which can be obtained by solving Navier–Stokes equations. The numerical results show that the sharp increase in the velocity and acceleration at the ABH tip position is the main reason for the focusing of the sound energy. And the dramatic increase in the tip cross-section reduces the acoustic streaming velocity, which is the main reason for the attenuation of the sound energy. Additionally, the thermoviscous effect of the acoustic boundary layer can also dissipate the low-frequency sound energy. The sound insulation experiment shows that the proposed micro-cavity ABH structure has a sound transmission loss (STL) of over 15 dB in the low-frequency regime. This research reveals the mechanisms of the ASE's work on the sound transmission properties of the micro-cavity ABH and provides new insight into low-frequency sound wave suppression. The ABH structure proposed in this paper has excellent strength, bearing capacity and long lifecycle, so it can be applied in the construction industry through its integrated design of structure and performance. [ABSTRACT FROM AUTHOR]

The fascinating characteristics, such as straightforward and stable crystal structure, and double perovskites are currently popular materials for applications in renewable energy. In our study, we applied CASTEP and DFT, called density functional theory, to theoretically investigate the mechanical, optical, and thermoelectric characteristics of cubic Rb 2 TlCoF 6. Calculations of the compound Rb 2 TlCoF 6 's structural, electrical, optical, mechanical, and thermodynamic properties are made using the GGA-PBE exchange correlational functional and the Fm3m with space group no.225 vol and compound lattice constant are 9.08 Å and 748.613 Å3, respectively. For Rb 2 TlCoF 6 , the measured energy band gaps are 1.45 eV. The mechanical and elastic constants are calculated to confirm the ductile properties of Rb 2 TlCoF 6. The brittle characteristics have been verified using Passion and Pugh's ratios, which are 1.67 and 0.25, according to elastic constants. Vickers compound hardness H v and anisotropy factor "A" are 4.19 and 0.77, respectively. The compounds' optical characteristics reveal significant conductivity and absorption. The compound exhibits high-efficiency photocatalytic activity based on its optical characteristics. Based on mechanical stability, such as Debye temperature, melting temperature, minimum thermal conductivity, average sound velocity, free energy, and other variables, the thermodynamic and structural stabilities are calculated. These materials controlled electrical and other properties make them potentially useful in photocatalytic applications. According to the outcomes, Rb 2 TlCoF 6 is appropriate for photocatalytic water-splitting applications and water deterioration. • To utilize Density Functional Theory (DFT) with mBJ and GGA-PBE methods. • The elastic constants values show that Rb 2 TlCoF 6 is mechanically stable. • The density of state calculations indicates semiconductor. • Studied materials are most suitable for photocatalytic for water splitting applications. [ABSTRACT FROM AUTHOR]

Densities (ρ), speeds of sound (u), and viscosities (η) were derived for three distinct binary mixtures comprising allyl alcohol in conjunction with chlorinated methanes. The Exploration ranged from 303.15 K to 313.15 K, at atmospheric pressure across all composition. The empirical data from the measurements formed the foundational basis for the determination of excess molar volume, excess isentropic compressibility, viscosity deviation and excess Gibbs free energy with the activation of viscous flow. We computed partial molar and infinite dilution properties for each binary system. The results are interpreted in the forming complexes, chemical forces and specific interactions with binary mixtures. The implication drawn from the application of the Jouyban-Acree model are expounded, taking into account the mean relative deviation (MRDs) and individual relative deviation (IRD) between the calculated and experimental densities, speed of sound, and viscosities as a criterion for accuracy criterion. FTIR studies validate experimental findings in investigated mixtures. [ABSTRACT FROM AUTHOR]

Densities (ρ), speeds of sound (u), and viscosities (η) for three binary mixtures of 4-Hydroxy-4-methyl-pentan-2-one with 3-amino-propan-1-ol, 2-amino-2-methyl-propan-1-ol, and 1-amino propan-2-ol were calculated at temperatures ranging from 303.15 to 313.15 K and atmospheric pressure over the entire composition range. Experimental measurements were used to calculate the excess molar volume, excess isentropic compressibility, deviation in viscosity, and excess Gibbs free energy of the activation of viscous flow. Partial molar properties and infinite dilution molar partial properties are also calculated for each binary system. Heteroassociates molecules forming complexes and chemical forces with specific interactions can be discussed from the results. The Prigogine–Flory–Patterson theory is used to identify the most important interaction. The results of the Jouyban–Acree model are discussed in terms of the mean relative deviation and individual relative between the calculated and experimental densities, speed of sound, and viscosities as an accuracy criterion. FTIR studies confirm the experimental findings of the investigated mixtures. [ABSTRACT FROM AUTHOR]

Excess molar volume, excess isentropic compressibility, deviation in viscosity and excess Gibbs free energy for activation of viscous flow for binary mixtures of propargyl alcohol (J) with benzyl aldehyde (J1), benzylamine (J2) and benzyl alcohol (J3) components with selected compositions were determined from the measured values of densities (ρ), viscosities (η), and speeds of sound (u) of pure components and their mixtures from 303.15 K to 313.15 K. The effect of various functional groups on the excess properties has been discussed in terms of attractive forces between the components. The results of the Jouyban-Acree model are discussed in terms of the mean relative deviation and individual relative between the calculated and experimental densities, speed of sound, and viscosities as an accuracy criterion.FTIR studies have also been added to confirm the experimental findings of the investigated mixtures [ABSTRACT FROM AUTHOR]

The thermodynamic and transport properties of binary mixtures of N-methyl benzyl amine (NMBA) with halo methane compounds at temperatures from 303.15 K to 313.15 K were investigated. The study analysed the excess molar volume, excess isentropic compressibility, deviation in viscosity, and excess Gibbs free energy for activation of viscous flow using measured densities (ρ), viscosities (η), and speeds of sound (u). The research also examined the impact of the inductive effect on excess properties concerning intermolecular attractive forces between the respective constituents. Furthermore, the Jouyban–Acree model was employed to correlate density, speed of sound, and viscosity with composition and obtained good agreement. [ABSTRACT FROM AUTHOR]

Excess molar volume, excess isentropic compressibility, deviation in viscosity, and excess Gibbs free energy of activation of viscous flow for binary mixtures of Hexylene glycol (2-methyl-pentanediol-2,4 or MPD) with aliphatic ketones (4-hydroxy-4-methyl-pentan-2-one (J1), 4-methyl-pentan-2-one (J2), and pentan-2-one (J3)) components selected compositions were determined from the measured values of densities (ρ), viscosities (η), and speeds of sound (u) of pure components and their mixtures from 303.15 K to 313.15 K. The results were analysed in terms of intermolecular interactions or hydrogen bonding or hetero-association interactions in the binary mixtures. Finally, the Prigogine-Flory-Patterson (PFP) theory is applied to identify the most predominant molecular interaction. The results of the Jouyban-Acree model are discussed in terms of mean relative deviation (MRDs) and individual relative deviation (IRD) between calculated and experimental densities, speeds of sound, and viscosities as an accuracy criterion. [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]

This paper examines the viable characteristics of anisotropic compact stars in f (ℜ , T 2) theory (ℜ is the Ricci scalar and T 2 = T α β T α β ). In this perspective, we use Tolman–Kuchowicz solutions (μ = w r 2 + 2 ln z and ν = ln (1 + x r 2 + y r 4)) to examine the configurations of static spherically symmetric structures. The unknown constants are found by the first fundamental form of Darmois junction conditions. We analyze the behavior of fluid parameters in the interior of 4U 1538-52, PSRJ 1614-220, EXO 1785-248 and SAXJ 1808.4-3658 compact stars correspond to different models of this theory. Furthermore, the stability of the proposed compact stellar objects is examined through sound speed and adiabatic index methods. The satisfaction of requisite conditions ensures that stable compact objects exist in this framework. [ABSTRACT FROM AUTHOR]

This paper considers the only sectors to constitute the present universe as the dark matter and dark energy. The proposed new agegraphic dark energy model studies the gradual transition from matter to dark energy in sequential order, including the current dominance of the matter sector by dark energy. The model utilizes concepts of Tsallis entropy and the Karolyhazy relation with conformal time η as the time scale. Various evolutionary aspects of the universe are characterized by Tsallis parameter δ and the model constant c. Expressions for dynamic behavior of dark energy, as a differential equation, equation of state and deceleration parameters are obtained to describe the thermal history of universe evolution. Also, the stability of the model is analyzed through squared sound speed parameter. The analysis is made by considering an interaction as well as independence among the constituent sectors of the universe. [ABSTRACT FROM AUTHOR]

The propagation of sound in a uniform flow with rigid body swirl has been considered in the approximation of low swirl Mach number M 2 ≪ 1 ,where the swirl Mach number M = Ω r / c 00 is specified by the angular velocity Ω , stagnation sound speed c 00 and radial distance r; in this case the mass density and sound speed in the mean flow are constant, and the convected wave equation is solved in terms of Bessel functions. In this paper the restriction on swirl Mach number is relaxed from M 2 ≪ 1 to M 4 ≪ 1 , thus keeping O ( M 2 ) terms in the mean flow, mass density and sound speed, that become non-uniform; the acoustic vortical wave equation is no longer the convected wave equation, and is extended to this case and solved in terms of generalized Bessel functions. The radial dependence to second order in the swirl Mach number is specified by a generalized Bessel differential equation for decoupled acoustic or vortical modes and for acoustic-vortical waves to first order in the swirl Mach number. The solutions are obtained: (i) for finite radius in terms of generalized Bessel and Neumann functions, that determine the radial wavenumbers, natural frequencies and normal eigenfunctions for cylindrical or annular ducts with rigid or impedance wall boundary conditions; (ii) asymptotically for large radius in terms of generalized Hankel functions, specifying the growth of amplitude with radius either as a power law or as an exponential of one-half of the square of the swirl Mach number. Thus the compressible uniform mean flow with rigid body rotation is spatially unstable in the radial direction; it is also unstable in time for cut-on modes with real axial wavenumbers and cut-off modes with imaginary axial wavenumbers. Compared with acoustic waves the acoustic-vortical waves have more modes, some with complex rather than real eigenvalues leading to instabilities. [ABSTRACT FROM AUTHOR]

This study reports the density (ρ), speed of sound (u), and viscosity (η) of N,N-dimethyl benzyl amine (DMBA) binary mixtures with propiophenone, p-methylacetophenone, and p-chloroacetophenone in a temperature range of 303.15–313.15 K for various compositions. Excess thermodynamic properties (excess molar volume, VE; excess isentropic compressibility, κsE; viscosity deviation, Δη; and excess Gibbs free energy of activation of viscous flow, ΔG*E) were derived from the experimental data. The analysis focused on understanding intermolecular interactions, particularly the influence of the inductive effect on hydrogen bonding and dipole–dipole interactions within the mixtures. The Jouyban-Acree model was employed to predict the densities, speeds of sound, and viscosities. The model’s accuracy was assessed using the mean relative deviations (MRDs) and individual relative deviations (IRDs) between the calculated and experimental values. To further support these findings, Fourier Transform Infrared (FT-IR) spectroscopy was conducted to provide complementary insights into the intermolecular interactions within the mixtures. [ABSTRACT FROM AUTHOR]

This paper introduces a new sensing approach utilizing a solid-solid phononic crystal (PnC) channel drop filter structure for the detection of varying molar fractions of Ethyl lactate within a mixture of Ethyl lactate and 2-butoxy ethanol. The sensor features a two-dimensional PnC constructed from poly methyl methacrylate as the background material, incorporating a regular arrangement of circular Tungsten columns. The design integrates a bus waveguide linked to two interconnected ring resonators, which are coupled to a drop waveguide. Each ring resonator is equipped with three strategically positioned pillars near the coupling region, allowing for the accommodation of varying concentrations of Ethyl lactate. The sensor's performance is significantly influenced by the ring resonators and the integrated pillars. It identifies specific resonance frequencies that shift in response to changes in Ethyl lactate concentrations within the resonators. The transmission resonance frequency exhibits valuable sensitivity to these concentration variations, reflecting the unique sound velocities and mass densities associated with each level of Ethyl lactate. The effectiveness of the proposed sensor is validated through coupled mode theory, demonstrating a close match with the device's observed behavior. The measured frequency range spans from 1.972 MHz to 1.979 MHz with a step size of 1 Hz. Notably, the sensor displays considerable characteristics, including an average quality factor of 90,613, an average sensitivity of 3816 Hz, an average figure of merit of 172, an average signal-to-noise ratio of 137, an average resolution of 22 Hz, an average damping ratio of 0.56 × 10− 5, and an average limit of detection of 34 × 10− 5. These results underscore the potential of the channel drop filter for the accurate detection of Ethyl lactate concentrations with high quality factor and sensitivity. The sensor can effectively identify variations in Ethyl lactate levels, which are prevalent in various applications, including pharmaceuticals and food additives. [ABSTRACT FROM AUTHOR]

On 13–15 January 2022, the Hunga Tonga–Hunga Ha'apai underwater volcano erupted. This powerful eruption generated infrasonic waves with amplitudes of thousands of Pascals in the near field. The ground infrasonic stations in China, located approximately 10 000 km from the Hunga volcano, also received waves with frequencies from 0.01 to 0.05 Hz. However, the amplitude reached 17 Pa, which is higher than the predicted amplitude using the absorption model without considering the dispersion effect in the thin thermosphere. At high altitudes, dispersion exists and the sound speed depends on the ratio of the molecular mean collision ratio to sound frequency, which is proportional to the ratio (frequency/pressure). And attenuation coefficients are complex to model. We simulate dispersive sound speeds and attenuation coefficients at different frequencies according to theory and our experimental data. In the thermosphere, the dispersion effect causes noticeable changes of sound speed and then affects wave propagation paths in the far field. The abnormal attenuation coefficient has a smaller impact on thermospheric returns than that of the dispersive sound speed, but it is also not negligible. It explains the large amplitude of thermospheric signals received in our infrasound stations. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'. [ABSTRACT FROM AUTHOR]

The study of the ultrasonic acoustic response of materials is of increasing interest for the characterisation of high-frequency applications. In this work, some elastic properties (acoustic velocity and acoustic attenuation) and some physical properties (thickness and density), together with the phase shift of the transducer, are estimated via one method. Scanning acoustic microscopy was performed via an innovative and different method using a high-frequency (50 MHz) planar wave transducer. In addition, the Debye series model (DSM) was used to model the acoustic response of the bilayer structure of the glass substrate and the resin‒epoxy sample. The inverse problem of estimating the acoustic parameters that results in a DSM reflected echo that matches the experimental signal is solved by proposing an innovative step-by-step curve fitting algorithm. The algorithm for solving the inverse problem is then optimised via relative mean square error (RMSE) curves, resulting in a robust method for assessing the uniqueness of the multiparameter solution. [ABSTRACT FROM AUTHOR]

The elucidation of chemical bonding, coupled with an exploration of the correlated dynamics of constituent atoms, is essential for unravelling the underlying mechanism responsible for low lattice thermal conductivity (κL) exhibited by a crystalline solid, which is essential for thermoelectrics and thermal barrier coatings. In this regard, Pauling's third empirical rule, which deals with the cationic repulsion due to proximity in the face or edge shared polyhedra in a crystal structure, can bring about the lattice instability required to suppress the κL. Here, we demonstrate the presence of such instability in a ternary selenide, TlAgSe, leading to a ultra‐low κL of 0.17 W/m.K at 573 K. Our study reveals the instability arising from Ag−Ag repulsion within edge‐shared AgSe4 tetrahedra through investigation of the local structure using synchrotron X‐ray pair distribution function (PDF) analysis and supported by first‐principles density functional theory calculations. We observe correlation between weakening in the Ag and the Tl‐sublattice, providing direct experimental evidence of Pauling's third empirical rule. The correlated rattling of Ag and Tl induces a highly anharmonic lattice and low energy optical phonons, resulting in suppressed sound velocity and ultralow κL in TlAgSe. The electronic origin of soft and anharmonic lattice is the presence of filled antibonding states in the valence band near the Fermi level constructed by Ag(4d)−Se(4p) and Tl(6s)−Se(4p) interactions. This work demonstrates that the evidence of dynamic distortion in a crystal lattice is governed by the third empirical rule given by Pauling, which can act as a potential new strategy for diminishing κL in crystalline solids. [ABSTRACT FROM AUTHOR]

The elucidation of chemical bonding, coupled with an exploration of the correlated dynamics of constituent atoms, is essential for unravelling the underlying mechanism responsible for low lattice thermal conductivity (κL) exhibited by a crystalline solid, which is essential for thermoelectrics and thermal barrier coatings. In this regard, Pauling's third empirical rule, which deals with the cationic repulsion due to proximity in the face or edge shared polyhedra in a crystal structure, can bring about the lattice instability required to suppress the κL. Here, we demonstrate the presence of such instability in a ternary selenide, TlAgSe, leading to a ultra‐low κL of 0.17 W/m.K at 573 K. Our study reveals the instability arising from Ag−Ag repulsion within edge‐shared AgSe4 tetrahedra through investigation of the local structure using synchrotron X‐ray pair distribution function (PDF) analysis and supported by first‐principles density functional theory calculations. We observe correlation between weakening in the Ag and the Tl‐sublattice, providing direct experimental evidence of Pauling's third empirical rule. The correlated rattling of Ag and Tl induces a highly anharmonic lattice and low energy optical phonons, resulting in suppressed sound velocity and ultralow κL in TlAgSe. The electronic origin of soft and anharmonic lattice is the presence of filled antibonding states in the valence band near the Fermi level constructed by Ag(4d)−Se(4p) and Tl(6s)−Se(4p) interactions. This work demonstrates that the evidence of dynamic distortion in a crystal lattice is governed by the third empirical rule given by Pauling, which can act as a potential new strategy for diminishing κL in crystalline solids. [ABSTRACT FROM AUTHOR]

Pressure dependences of the highest and lowest possible longitudinal sound velocities in single crystals of the B1 and B2 phases of NaCl were extracted from examination of their polycrystalline samples using the technique of time-domain Brillouin scattering. Based on the data collected up to 41 GPa, we largely extended the pressure range where single-crystal elastic moduli, Cij(P), and elastic anisotropy of the two cubic phases are measured, especially the experimental data for the B2 phase formed upon the reconstructive phase transition. The B1 phase of NaCl exhibits strong and growing anisotropy with increasing pressure, while that of the B2 phase is much weaker. Comparing with the previous experimental Cij(P) of other compounds exhibiting or expected to exhibit the B1–B2 phase transition, such as CaO, MgO, and (Mg1−x, Fex)O, we concluded that the transition is initiated by the shear instability due to violation of the Born stability criterion [C44(P)–P] > 0 and predicted the presently-not-verified transition pressures for MgO and (Mg1−x, Fex)O. [ABSTRACT FROM AUTHOR]

The properties and relative stability of different structures of iron at the extreme conditions of pressure and temperature of relevance for the Earth's core were determined with ab‐initio atomistic simulations aided by a machine‐learning force‐field. We find that the body‐centered cubic (bcc) structure is mechanically stable at core temperatures, but its free energy is marginally higher than those of the hexagonal close‐packed and face‐centered cubic structures. The bcc structure is the only structure whose shear sound velocity matches seismic data. The small free‐energy difference between competing structures suggests that the role of impurities could be crucial in stabilizing the bcc structure in the inner core. Plain Language Summary: Determining the crystal structure and the elastic properties of the compound that forms the Earth's solid inner core is crucial to interpret seismic data. We know that the inner core is predominantly composed of iron, but laboratory‐based experiments and theoretical modeling haven't yet been able to constrain the crystal structure and the properties of pure Fe at the conditions of pressure and temperature found in the inner core. We have recently developed a deep‐learning‐aided atomistic simulation method that is able to determine Gibbs free energies of solids with quantum‐chemical accuracy (a few meV/atom). We find that although body‐centered cubic Fe is energetically slightly less favored than the hexagonal close‐packed form, the shear wave velocity of bcc Fe matches seismic data much better than all other crystal structures, suggesting that bcc is a strong candidate for the crystal structure of Fe in the Earth's inner core and could be stabilized by the presence of light elements in the core. Key Points: The body‐centered cubic structure of iron is mechanically stable at inner core conditionsThe hexagonal close‐packed structure is more stable, but small free energy differences could allow impurities to reverse this stabilityThe observed low shear velocity in the Earth's inner core is likely to be caused by the presence of the body‐centered cubic phase [ABSTRACT FROM AUTHOR]

Measurements of densities (ρ), speeds of sound (u), and viscosities (η) for binary mixtures of N,N-dimethyl benzyl amine (DMBA) with 1-octanol (D1), 1-nonanol (D2), and 1-decanol (D3) were performed across temperatures from 303.15 K to 313.15 K under atmospheric pressure, covering all composition ranges. These experimental results were utilised to calculate the excess molar volume, excess isentropic compressibility, viscosity deviation, and the excess Gibbs free energy of activation for viscous flow. Calculations for partial molar properties and infinite dilution partial molar properties were also carried out for each binary mixture. The dominant intermolecular interactions within these mixtures were analysed using the PFP theory. Additionally, the Jouyban−Acree model was applied to predict the thermo physical properties such as density, speed of sound, and viscosity. The model’s accuracy was evaluated by comparing predicted values with experimental data through mean relative deviations (MRDs) and individual relative deviations (IRDs). [ABSTRACT FROM AUTHOR]

Excess molar volume, excess isentropic compressibility, deviation in viscosity, and excess Gibbs free energy of activation for viscous flow for binary mixtures of N-Methyl benzyl amine (NMBA) with 2-Methyl-2-butanol (2M2B), 2-Methyl-1-butanol (2M1B), and 3-Methyl-1-butanol (3M1B) were determined from measured densities (ρ), viscosities (η) and speeds of sound (u) at 303.15 K to 313.15 K. Influence Structural disparities on excess properties is discussed concerning intermolecular forces. The Prigogine – Flory – Patterson (PFP) theory identifies predominant molecular interactions, and the Jouyban – Acree model correlates density, speed of sound, and viscosity with composition. Thermodynamic activation parameters were calculated using the Eyring equation to study viscous flow thermodynamics. FT-IR and 1H NMR spectra of equimolar binary mixtures were analysed to confirm experimental findings through absorption bands (cm−1) and chemical shifts. [ABSTRACT FROM AUTHOR]

Speed of sound data, measured using a dual-path pulse-echo instrument, are reported for three binary mixtures of 1,1-difluoroethylene (R-1132a) with propane at temperatures ranging from 230 to 345 K and pressures ranging from slightly above the bubble curve to a maximum pressure of 50 MPa. Significant attenuation of the pulse-echo signals was observed for measurements on pure R-1132a. Therefore, the R-1132a sample was doped with propane at mole fractions ranging from 0.0274 to 0.0887 and the propane + R-1132a mixture data was used to derive sound speeds for pure R-1132a. The data were compared to a preliminary equation of state for R-1132a, and deviations ranged from 2 % to 8 %. This demonstrates that the preliminary R-1132a EoS needs to be refit to better represent the speed of sound. [ABSTRACT FROM AUTHOR]

Sound speed data measured using a dual-path pulse-echo instrument are reported for pure trans-1,2-dichloroethene (R-1130(E)) and an azeotropic blend of cis-1,1,1,4,4,4-hexafluorobutene (R-1336mzz(Z)) and R-1130(E) with a composition of 74.8 mass % R-1336mzz(Z) with the balance being R-1130(E). The azeotropic blend of R-1336mzz(Z)/1130(E) is classified as R-514A in ANSI/ASHRAE standard 34. Liquid phase speed of sound data are reported from just above the saturation pressure of pure R-1130(E) or the bubble point pressure of R-514A to a maximum pressure of 26.7 MPa. The relative combined expanded uncertainty in the speed of sound varies from 0.032 % to 0.148 % with the greatest deviations occurring at the lowest sound speeds. At present, no reference Helmholtz-energy-explicit equation of state (EOS) is available for R-1130(E). Therefore, the reported data for pure R-1130(E) are compared to an extended corresponding states (ECS) model. Deviations between the pure R-1130(E) sound speed data and the ECS model were found to be consistently negative ranging between − 4.1 % and − 3.5 %. The R-514A data are compared to a multifluid model inclusive of the established reference Helmholtz-energy-explicit EOS for R-1336mzz(Z) and ECS model for R-1130(E) with estimated binary interaction parameters. Deviations between the experimental speed of sound data and the multifluid model were also found to be consistently negative. However, deviations from the multifluid model were found to be as great as − 17.1 %. The large deviations from the ECS model and multifluid model underscore the need for a robust Helmholtz-energy-explicit EOS for R-1130(E). [ABSTRACT FROM AUTHOR]

The deceleration of a monoenergetic rarefied ion beam in nonisothermal plasma in a constant magnetic field has been studied. It is shown how ion-acoustic turbulence generated by a current along the magnetic field leads to an effective decrease in the velocity of ions moving with a speed higher than the speed of ion sound. When an ion beam is injected into plasma across the magnetic field, the trajectory of the ions has the form of a contracting spiral elongated along the magnetic field. The deceleration occurs due to the Cherenkov interaction of ions with ion-acoustic waves and stops when the ion velocity decreases to the speed of ion sound. The braking lengths and the beam velocity components, which are set at the moment of stopping braking, are found. After the end of deceleration, the ions move with constant velocity in a spiral along the magnetic field. [ABSTRACT FROM AUTHOR]

The damage ability of hypervelocity kinetic energy projectile penetrating ground has become a hotspot in modern military research. In this study, a hypervelocity impact test on a granite target subjected to projectiles using a two-stage light gas gun is conducted to study the stress wave evolution in granite under hypervelocity penetrations. The parameters of the *MAT_JOHNSON_HOLMQUIST_CERAMICS(JH-2) constitutive equation are calibrated using the results of the splinter impact test and the static test, and numerical simulations are performed using the smoothed particle hydrodynamics method coupled with finite element method (SPH-FEM coupled method) to extend the resulting data. A formula for calculating the stress wave peak attenuation is established, indicating that the maximum impact pressure produced by the hypervelocity impact decreases exponentially with scaling distance, and the attenuation coefficient is related to the degree of rock damage. Additionally, the attenuation of the speed of sound is used to characterize rock damage, and the damage deterioration law of granite under hypervelocity impact is analyzed based on the damage factor. [ABSTRACT FROM AUTHOR]

The measurement of high-pressure sound velocity in solid materials is crucial for developing constitutive equations and equations of state for materials in extreme stress–strain rate conditions. In this study, we propose a novel method for high-pressure sound velocity measurement using laser-induced micro-flyer technology. By optimizing laser driving conditions and target structure design, we measure high-pressure sound velocity using the "reverse-impact geometry" approach. The well-established Photon Doppler Velocimetry system allows for high-precision, single-shot measurements of both flyer velocity and particle velocity histories. A systematic error analysis shows that the longitudinal sound velocity of aluminum obtained in this experiment is consistent with data from traditional devices, such as gas guns, within the error margin. Finally, we analyze the potential application value of this method in laser technology as well as high-pressure dynamic responses of materials, and conclude the current shortcomings and possible improvements of this method. [ABSTRACT FROM AUTHOR]

Sandwich structures with functionally graded (FG) cores have gained interest in vibroacoustic applications. This article considers the vibroacoustic properties of double-walled sandwich magneto-electro-elastic (MEE) plates with a functionally graded carbon nanotube-reinforced composite (FG-CNTRC) core layer in a thermal environment. A coupled multiphysics model is developed based on third-order shear deformation theory (TSDT) and acoustic-structure interaction. Special attention is paid to the transmission loss of this arrangement for simply supported and clamped boundaries for four different kinds of CNT distributions, namely, UD, FG-V, FG-O, and FG-X. Sound velocity potential, normal velocity continuity conditions, and Hamilton's principle are used to generate the coupled vibroacoustic equations, which are then solved using the Galerkin method. The effects of boundary conditions, CNT distributions, cavity depth, multiphysics coupling fields, and temperature on the STL are comprehensively studied. The results provide guidelines for tailoring the dynamic response of these materials to achieve enhanced acoustic insulation performance. It enhances fundamental understanding and enables the engineering design of multilayered composite panels with optimized vibration and noise control capabilities. [ABSTRACT FROM AUTHOR]

Cadmium zinc telluride (CdxZn1-xTe) is frequently used material for the production of nuclear radiation detectors and solar cells. Therefore, the characterization of its quality by different methods is very important. This work is devoted to the development of a technique for mapping the poly-crystalline structure of CdxZn1-xTe, alternative to the X-ray technique usually used for this goal. In comparison with X-ray, the non-destructive and contactless picosecond laser ultrasonic technique provides numerous advantages, including simplicity of the analysis of the results and possibility to work with very compact laser spots (about 1 µm) probing the sample. As a step to achieve this goal, picosecond laser ultrasonics is applied in this work to study the samples in the form of 8 mm-diameter discs of 1 mm thickness including several connected disoriented crystals of CdxZn1-xTe. The experimental study is performed using classical pump-probe experimental set-up based on Tsunami femtosecond laser and delay line with moving retro-reflector. The sound velocities of the samples have been evaluated from frequency spectra of obtained signals, using the literature data on the index of refraction. Then, the value of the longitudinal sound velocity in the direction perpendicular to the sample surface is traced as a function of Zn concentration. Finally, measured sound velocities are compared with their available theoretical evaluation, using statistical analysis. [ABSTRACT FROM AUTHOR]

l‐Isoleucine is subjected to density and sound velocity measurements in aqueous solutions of potassium (KCl) and sodium chlorides (NaCl) as well as water, from 288.15 to 298.15 K. Through the use of these experimental data, a variety of volumetric and acoustical parameters are calculated, including values for molar volume (Vm), available volume (Va), adiabatic compressibility (β), nonlinear parameters (B/A), Wada constant (W), Rao's constant (R), and van der Wall's constant (a). The findings shed light on many electrostatic and hydrophobic interactions within the binary system involving electrolytes, water, and amino acids. The interactions between the electrolytes and l‐isoleucine are thoroughly examined under varying electrolyte concentrations and temperatures, revealing many interactions. Positive transfer quantities demonstrate the ion‐hydrophilic and solute–solvent interaction in the aqueous medium, particularly between l‐isoleucine and NaCl and KCl. The influence of electrolyte type and temperature on these interactions is discernible. The culmination of the study's outcomes is elaborated through analyzing solute–solvent and solute–solute interactions. In particular, the interaction hierarchy is identified as l‐isoleucine + water + KCl > l‐isoleucine + water + NaCl > l‐isoleucine + swater. [ABSTRACT FROM AUTHOR]

In fermentation processes, changes in yeast cell count and substrate concentration are indicators of yeast performance. Therefore, monitoring the composition of the biological suspension, particularly the dispersed solid phase (i.e., yeast cells) and the continuous liquid phase (i.e., medium), is a prerequisite to ensure favorable process conditions. However, the available monitoring methods are often invasive or restricted by detection limits, sampling requirements, or susceptibility to masking effects from interfering signals. In contrast, ultrasound measurements are non-invasive and provide real-time data. In this study, the suitability to characterize the dispersed and the liquid phase of yeast suspensions with ultrasound was investigated. The ultrasound signals collected from three commercially available Saccharomyces yeast were evaluated and compared. For all three yeasts, the attenuation coefficient and speed of sound increased linearly with increasing yeast concentrations (0.0–1.0 wt%) and cell counts (R2 > 0.95). Further characterization of the dispersed phase revealed that cell diameter and volume density influence the attenuation of the ultrasound signal, whereas changes in the speed of sound were partially attributed to compositional variations in the liquid phase. This demonstrates the ability of ultrasound to monitor industrial fermentations and the feasibility of developing targeted control strategies. [ABSTRACT FROM AUTHOR]

The aerogel performance for industrial uses can be tailored using several chemical and physical strategies. The effects of a controlled densification on polyurethane aerogels are herein studied by analyzing their textural, mechanical, sound, optical, and thermal insulating properties. The produced aerogels are uniaxially compressed to different strains (30%–80%) analyzing the consequent changes in the structures and, therefore, final properties. As expected, their mechanical stiffness can be significantly increased by compression (until 55‐fold higher elastic modulus for 80%‐strain), while the light transmittance does not noticeably worsen until it is compressed more than 60%. Additionally, the modifications produced in the heat transfer contributions are analyzed, obtaining the optimum balance between density increase and pore size reduction. The minimum thermal conductivity (14.5%‐reduction) is obtained by compressing the aerogel to 50%‐strain, where the increment in the solid conduction is surpassed by the reduction of the radiative and gas contributions. This strategy avoids tedious chemical modifications in the synthesis procedure to control the final structure of the aerogels, leading to the possibility of carefully adapting their structure and properties through a simple method such as densification. Thus, it allows to obtain aerogels for current and on‐demand applications, which is one of the main challenges in the field. [ABSTRACT FROM AUTHOR]

This article provides an analysis of the physics behind the shattering of glass and ceramic objects when they are dropped or impacted. The study utilizes video analysis to examine the process of fracture propagation and the phenomenon of bouncing before breaking into pieces. The article emphasizes the significance of understanding the resilience of ceramic and glass materials to impacts, particularly in applications such as vehicle and aircraft armor and orthopedic surgery. The experimental setup and results are presented, highlighting the necessity of high-speed cameras to capture crack propagation on a precise timescale. The article also discusses an experiment involving the impact and breakage of ceramic mugs and a wine glass, focusing on the physics of breakage and the conservation of energy. The experiment demonstrates that the speed of crack propagation is limited and that each individual piece of the broken object possesses less kinetic energy than the original object. The article suggests that this experiment can serve as an educational tool for students to comprehend materials and load bearing. Further investigations can be conducted to examine the properties of the materials and the exact failure mechanism during load bearing. [Extracted from the article]

The paper briefly discusses hypotheses about the nature of a centuries-old mysterious phenomenon, for which there is still no clear explanation. Its essence is that an observer, usually located at a distance of 50–100 km from a flying meteor body, sometimes hears sound simultaneously with its radiation. It seems that sound travels at the speed of light. Historically, the situation was such that it was only no more than sixty years ago that attempts to instrumentally study this unusual phenomenon began. The difficulty of these searches is also due to the fact that only a few percent of the total number of observed meteoroids have this property. About forty years ago it was discovered that meteoroids can emit electromagnetic pulses of varying duration and frequency composition. However, it turned out that this fact does not always have an unambiguous relationship to electrophonic phenomena. This paper provides a brief overview of the most meaningful hypotheses and experiments of past years. It is possible that this phenomenon is of a fundamental nature and its study can introduce previously unknown information into science. [ABSTRACT FROM AUTHOR]

Observational evidence revealed that in the composition of the Universe, the dark energy is in heap proportion which is mainly responsible for the accelerated expansion of the Universe. The astrophysicists hypothesized that every astrophysical object is likely interact with the dark energy Sakti and Sulaksono [Phys. Rev. D 103 (2021) 084042]. Therefore, researchers are intended to study the astrophysical objects with dark energy interaction. In this paper, we proposed a dark energy stars (composed of with dark matter and ordinary matter) model in the Rastall theory of gravity. The Rastall field equations are obtained in the Tolman–Kuchowicz-type metric. To solve the field equations, the arbitrary constants involved in the field equations (due to Tolman–Kuchowicz ansatz) are obtained by matching the interior geometry with the exterior Schwarzschild geometry. The obtained solution is tested physically by computing some analytical results and plotting graphs of different physical parameters like pressure, density for ordinary matter, density for dark matter, mass function, compactness and surface redshift. Stability of the model is also analyzed by different tests like velocity of sound, adiabatic index and TOV equations. The influence of the Rastall parameter on the model has been studied by plotting graphs and computing numerical values of model's physical parameters for different values of the Rastall parameter. We infer that our propounded model fulfills all the necessary requirements for a physically plausible model. [ABSTRACT FROM AUTHOR]

Sub-photospheric acoustic resonators allow for the formation of standing p-mode oscillations by reflecting acoustic waves with frequencies below the acoustic cut-off frequency. We employ the Klein–Gordon equation with a piecewise acoustic potential to study the characteristic frequencies of intermediate-degree p modes, modified by the cut-off effect. For a perfectly reflective photosphere, provided by the infinite value of the acoustic cut-off frequency, characteristic discrete frequencies of the trapped p modes are fully prescribed by the width of the acoustic potential barrier. Finite values of the acoustic cut-off frequency result in the reduction of p-mode frequencies, associated with the decrease in the sound speed by the cut-off effect. For example, for a spherical degree of |$\ell = 100$|⁠ , characteristic p-mode frequencies are found to decrease by up to 200 µHz and the effect is more pronounced for higher radial harmonics. The frequency separation between two consecutive radial harmonics is shown to behave non-asymptotically with non-uniform spacing in the radial harmonic number due to the cut-off effect. We also show how the 11-yr variability of the Sun's photospheric magnetic field can result in the p-mode frequency shifts through the link between the acoustic cut-off frequency and the plasma parameter |$\beta$|⁠. Using this model, we readily reproduce the observed typical amplitudes of the p-mode frequency shift and its phase behaviour relative to other 11-yr solar cycle proxies. The use of the developed model for comparison with observations requires its generalization for 2D effects, more realistic profiles of the acoustic potential, and broad-band stochastic drivers. [ABSTRACT FROM AUTHOR]

Context. Merging compact objects such as binary black holes provide a promising probe for the physics of dark matter (DM). The gravitational waves emitted during inspiral potentially allow one to detect DM spikes around black holes. This is because the dynamical friction force experienced by the inspiralling black hole alters the orbital period and thus the gravitational wave signal. Aims. The dynamical friction arising from DM can potentially differ from the collisionless case when DM is subject to self-interactions. This paper aims to understand how self-interactions impact dynamical friction. Methods. To study the dynamical friction force, we use idealised N-body simulations, where we include self-interacting dark matter. Results. We find that the dynamical friction force for inspiralling black holes would be typically enhanced by DM self-interactions compared to a collisionless medium (ignoring differences in the DM density). At lower velocities below the sound speed, we find that the dynamical friction force can be reduced by the presence of self-interactions. Conclusions. DM self-interactions have a significant effect on the dynamical friction for black hole mergers. Assuming the Chandrasekhar formula may underpredict the deceleration due to dynamical friction. [ABSTRACT FROM AUTHOR]

The properties of the first kilometers of the Martian atmospheric Planetary Boundary Layer have until now been measured by only a few instruments and probes. InSight offers an opportunity to investigate this region through seismoacoustics. On six occasions, its seismometers recorded short low‐frequency waveforms, with clear dispersion between 0.4 and 4 Hz. These signals are the air‐to‐ground coupling of impact‐generated infrasound, which propagated in an low‐altitude atmospheric waveguide. Their group velocity depends on the structure of effective sound speed in the boundary layer. Here, we conduct a Bayesian inversion of effective sound speed up to 2,000 m altitude using the group velocity measured for events S0981c, S0986c and S1034a. The inverted effective sound speed profiles are in good agreement with estimates provided by the Mars Climate Database. Differences between inverted and modeled profiles can be attributed to a local wind variation in the impact→station direction, of amplitude smaller than 2 m/s. Plain Language Summary: The Martian Planetary Boundary Layer corresponds to the first few kilometers of the atmosphere. The InSight lander offers the opportunity to investigate its properties via the coupling of seismic and acoustic waves. Impact‐generated infrasound waves were recorded for the first time on Mars by the seismometers of the InSight mission. These infrasound waves propagated in an atmospheric waveguide in the first kilometers above the Martian surface, and thus present a frequency‐dependent group velocity. This frequency‐dependence, also known as a dispersion relation, is influenced by the structure of the speed of sound in the waveguide. Here, we use group velocity measured for events S0981c, S0986c and S1034a to invert the variations of effective sound speed between 0 and 2,000 m altitude. For the three events, the inverted profiles are in good agreement with estimates provided by the Mars Climate Database using global climate modeling. The differences between inverted and modeled profiles can be attributed to a local variation in wind in the impact→station direction, with magnitude smaller than 2 m/s. Key Points: InSight recorded impact‐generated infrasound on Mars. Their group velocity is sensitive to the structure of the atmospheric boundary layerWe conduct a Bayesian inversion of effective sound speed profiles with altitude based on group velocities measured for three impact eventsThe inverted profiles provide an indirect measurement of the Martian boundary layer, and validate models of the Mars Climate Database [ABSTRACT FROM AUTHOR]

This paper explores cosmic evolution in f(R,T) gravity considering two distinct models with minimal coupling that are linear and quadratic in T; f(R,T) = R + αT and f(R,T) = R + αT2. The flat FRW space-time under the matter and radiation distribution has been considered to complete the analysis. In this background, the dynamical equations for dust in terms of dimensionless variables are developed. Via solutions of these dynamical equations, we develop significant cosmological parameters to compare the obtained results with the ΛCDM model and analyze them graphically. It is found that these parameters efficiently explain the expanding phenomenon of the universe for constrained values of the involved model parameters using some recent observational data. Moreover, the results are found to be stable via the square speed of sound. The matter and radiation fixed points are calculated by an autonomous set of dynamical equations, which are the stable and unstable saddle points. Also, the growth of matter perturbation in the f(R,T) theory has been discussed. Under this scenario, it is also checked that exact solutions of the dynamical equations are not possible for non-minimal coupling between geometry and matter. [ABSTRACT FROM AUTHOR]

A comprehensive study on the thermodynamic and transport properties of binary mixtures composed of active amyl alcohol (AAA) and haloalkane’s was conducted within a temperature range of 303.15 K to 313.15 K. Experimental data on densities (ρ), viscosities (η), and speeds of sound (u) were employed to calculate excess molar volume (VE), isentropic compressibility (KsE), viscosity deviation (Δη), and excess Gibbs free energy for viscous flow (∆G*E). The impact of dipole moment on these excess properties was investigated to gain insights into the prevailing intermolecular interactions within the mixtures. The Prigogine – Flory – Patterson (PFP) theory is applied to identify the predominant molecular interaction. The accuracy of the Jouyban–Acree model in correlating densities (ρ), viscosities (η), and speeds of sound (u) with composition were evaluated, demonstrating satisfactory agreement with experimental data. [ABSTRACT FROM AUTHOR]