Experimental investigation of vapor pvT properties and PC-SAFT equations of state for renewable methanol and ethanol at elevated temperatures

Forecast of segregation in jet fuel under gravitational field using the VTPR equation of state

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Inference of Neutron Star Mass Distributions and the Dense Matter Equation of State from Multimessenger Observations

Evidence of a gravitational wave (GW) signal has emerged in pulsar timing array (PTA) data, opening a new window into the nanohertz GW Universe. We explore the physics of GW signals that may explain the data, with a focus on GW backgrounds (GWBs) considering both astrophysical and cosmological origins. We describe how: ▪ An astrophysical nanohertz GWB emerges as the superposition of individual signals from inspiraling massive black hole binaries. ▪ Environment coupling, eccentricity, and sparse sampling cause great uncertainty in the theoretical prediction of the supermassive black hole signal but also offer a way to determine the origin of the signal. ▪ PTA data offer unprecedented opportunities to constrain high-energy physics beyond the Standard Model by probing early Universe GWBs that originated during or after inflation. ▪ Different early Universe GWBs, typically created by nonlinear and out-of-equilibrium dynamics, can explain the PTA data (e.g., those from inflation scenarios, first-order phase transitions, or topological defects). ▪ The PTA detection of GWs opens a new window to explore the Universe, with profound implications for astrophysics and particle physics (probing, e.g., the equation of state of the early Universe, the origin of cosmological perturbations, the nature of dark matter, or whether exotic objects like primordial black holes or cosmic strings exist).

Valorization of glycerol via continuous etherification with ethanol: Thermodynamic modeling and process optimization.

This study presents a multi-scale finite-discrete element modeling approach for blasting-induced fracture in polycrystalline granite, with explicit consideration of grain boundary effects, to accurately reproduce the mesoscopic heterogeneity and dynamic fracture responses of granite under ultra-small diameter borehole blasting. A Voronoi-based polycrystalline geometric model is established via Neper software to characterize mineral distribution and microstructural anisotropy. Cohesive elements are simultaneously inserted into intragranular and grain boundary regions in Abaqus with differentiated mechanical parameters, and the Jones-Wilkins-Lee (JWL) equation of state is used to apply the dynamic blasting load of PETN explosive. Numerical results agree well with laboratory blasting tests, showing typical failure zones including a crushing zone, a radial fracture zone, and a circumferential tensile fracture zone. The polycrystalline model exhibits prominent non-uniformity and dynamic anisotropy in crack propagation, which is strongly governed by grain morphology and grain boundary properties. Grain boundary strength is identified as a key factor controlling the dynamic fracture mode: with decreasing grain boundary strength, the failure pattern gradually shifts from transgranular fracture to mixed fracture and then to intergranular fracture. Under moderate grain boundary strength, blasting energy is first transmitted inside grains and then released and dissipated at weak grain boundaries, forming a chain-type dynamic failure mechanism: intragranular energy transfer to grain boundary fracture. The proposed method reveals the micro-dynamic evolution mechanism of granite damage under ultra-small diameter blasting and provides a reliable theoretical basis for blasting parameter optimization, rock fragmentation control, and blast-induced vibration prediction in precision rock blasting engineering.

To address the critical challenge where the excessively high Minimum Miscibility Pressure (MMP) restricts the effectiveness of CO2 flooding, this study proposes a novel strategy utilizing SiO2-ethanol nanofluids (SiO2-C2H6O NFs) as additives to reduce the MMP. By systematically optimizing particle size, concentration, and dispersant types, a 5 nm/5 wt% SiO2 nanofluid with polyvinylpyrrolidone (PVP) as the dispersant was successfully prepared, demonstrating excellent long-term dispersion stability. Phase equilibrium experiments indicate that after adding 20 vol% of the optimized nanofluid into crude oil model components (n-alkanes and cycloalkanes), the solubility of CO2 in the oil phase is significantly enhanced. The maximum average equilibrium pressure reduction (PAVG) reached 2.24 MPa, effectively lowering the MMP of the system. Furthermore, a modified PR-vdW1 equation of state considering nano-confinement effects was developed and validated to systematically reveal the phase equilibrium behavior of CO2-alkane systems within nanopores. This research not only enriches the fundamental thermodynamic data for CO2-hydrocarbon systems but also provides a novel and efficient technical pathway for improving CO2 flooding efficiency and achieving synergistic carbon emission reduction.

Compared with water-flooding reservoirs, gas-flooding reservoirs exhibit more complex characteristics, primarily attributed to the significant viscosity difference between the displacing phase and the displaced phase. Under the influence of the equation of state, gas viscosity and deviation factor are binary functions of temperature and pressure. As the reservoir recovery degree increases, regardless of the injection strategy employed, the reservoir pressure will present a complex heterogeneous spatial distribution. When analyzing the variation of gas saturation at different positions during the production process, it is necessary to consider the effects of reservoir pressure at the corresponding location on gas viscosity and compressibility. An extensive literature review reveals that most publicly published studies on fluid saturation in gas-flooding reservoirs are based on numerical reservoir simulation methods, where the gas state equation is introduced for quantitative description. Based on the Buckley-Leverett water-flooding equation, this study proceeds as follows: ① Firstly, a one-dimensional homogeneous radial flow tube model is established. Considering that the fractional flow curve is an S-shaped nonlinear function, a novel fully implicit method is adopted to automatically search and calculate the optimal water saturation value at each spatial step and time step. ② Secondly, considering the heterogeneity of the actual model, a multi-flow tube model accounting for permeability variation is further constructed; the fingering phenomenon of the displacing phase considering heterogeneity can be obtained by averaging the saturation distribution changes of different flow tubes. ③ Thirdly, considering the compressibility and viscosity variation of gas, the volume conservation in the water-flooding mode is converted into the mass conservation in the gas-flooding mode. Subsequently, combined with the Buckley-Leverett equation and the fully implicit solution applied to the multi-flow tube model, the fluid saturation distribution of immiscible gas flooding can be derived. The proposed method in this paper is applied to interpret and analyze the field data of an actual restricted channel gas-flooding case, and the theoretically calculated gas breakthrough time of the oil well is in high agreement with the actual data. This research method features rigorous theoretical derivation and has been verified to be feasible through practical application, thereby providing certain practical guidance and reference significance for reservoir engineering researchers.

Impact on inferred neutron star equation of state due to nonlinear hydrodynamics, background spin, and relativity

Abstract In this article, we present a theoretical and phenomenological study of the gravastar in the presence of a global monopole in teleparallel gravity, specifically $$f(\mathbb {T})$$ f ( T ) gravity. We have constructed the interior based on both the global monopole and the dark energy, and on the shell, we have taken the stiff matter equation of state. We studied the thin shell surrounding the gravastar using the Israel junction conditions and derived a sufficient condition for its stability. We determined the deflection angle around the gravastar using both Gauss-Bonnet topological methods and analytical Hamilton–Jacobi methods. We checked the shadow around the gravastar at the equator using the ray-tracing method. We have presented the null-geodesic equation as an initial-value problem and applied numerical methods to trace the rays around the gravastar, also illustrating the photon sphere that surrounds it. We further present the complete 3D shadow, incorporating observer inclination and relativistic effects to provide a direct link to high-resolution interferometric imaging. In addition, we have determined the scalar field perturbation in the interior and computed its quasinormal modes using the third-order WKB approximation. The potential is plotted against the tortoise coordinate and shows a single peak with an asymptotic decay, as expected for a stable configuration. Our stability analysis, evidenced by imaginary negative quasinormal modes for various values of $$\eta $$ η , predicts detectable ring-down overtones for the LISA and the Einstein Telescope, thereby establishing a direct phenomenological link between our model and upcoming gravitational-wave observations.

The thermodynamic properties and the microscopic structure of Lennard-Jones fluids residing in two to five spatial dimensions are discussed. Complementing literature data for one to three dimensions, molecular dynamics simulations are conducted in four and five dimensions. Thermodynamic properties are sampled over wide temperature and density ranges and used to develop accurate Helmholtz energy equations of state that are also adequate near the critical point. The influence of the number of dimensions n on the critical point, vapor-liquid equilibrium, bulk properties, microscopic structure, and second virial coefficient is analyzed. The results show that with an increasing number of dimensions, there is a remarkable loss of structure and a strong expansion of the state region with a gas-like behavior. This is a consequence of the rise of the critical density (for n ≥ 3) that is accompanied by an almost exponential increase of the critical temperature. In addition, a clear reduction of criticality is observed with a rising number of dimensions. Moreover, the second virial coefficient is shifted to higher temperature values as the number of dimensions increases. Based on the power-law scaling behavior of the critical exponent β, a simple estimate of an upper critical dimension nc of Lennard-Jones fluids is given for the first time, roughly confirming the prediction of the Ising model, being nc = 4.

Dependence on the Equation of State in SPH Simulations of Proto-Uranian Disk Formation from a Giant Impact

Reliable estimation of self-diffusion coefficient is fundamental for characterizing mass transport within fluids; however, an accurate prediction remains difficult due to the strong influence of thermodynamic conditions (temperature and pressure) and molecular characteristics (such as size, shape, and intermolecular forces). In this study, a hybrid predictive model is introduced, combining the PCP-SAFT equation of state with an artificial neural network (ANN) to estimate self-diffusion coefficients over a broad range of conditions. The model is developed using a dataset comprising 2263 experimental measurements for 67 compounds, spanning temperatures between 93.0 and 973.2 K, pressures up to 3036 bar, corresponding to self-diffusion coefficients spanning nearly five orders of magnitude from 10-12 to 10-7 m2 s-1. To regorously assess the predictive performance, the dataset was partitioned into 30% reserved for independent validation and 70% for training. The proposed model incorporates thermodynamic inputs, namely density and dimensionless form of residual entropy obtained from PCP-SAFT, together with molecular descriptors derived from COSMO-SAC sigma profiles. The selected ANN architecture, comprising two hidden layers with 14 and 7 neurons, respectively, provides high predictive performance, achieving R2 values of 0.9937 and 0.9763 and AARD values of 8.89% and 15.89% for the training and testing datasets, respectively. Overall, the proposed framework offers a unified, reliable model for predicting diffusion behavior under diverse thermodynamic conditions.

We present a thermodynamically consistent framework to model adsorption in flexible nanoporous materials by coupling three-dimensional classical density functional theory (cDFT) based on the SAFT-VR-Mie equation of state with the osmotic ensemble formalism. This approach enables the treatment of fluid adsorption in deformable frameworks, overcoming the rigid-host limitation of conventional cDFT descriptions. The methodology is first validated on a simplified MIL-53-type model, where adsorption isotherms and grand potential trends are shown to be in good agreement with molecular simulation data. The analysis highlights how breathing transitions and hysteresis emerge from the interplay between the fluid grand potential and the host free-energy landscape, emphasizing the critical role of the relative stability of narrow- and large-pore states and of the associated energy barriers. The framework is then applied to methane adsorption in the flexible metal-organic framework MIL-53. After minimal calibration of the fluid-framework cross-interactions, the model reproduces experimental adsorption isotherms at 300 and 213 K and captures adsorption-induced structural transitions within the osmotic description. While quantitative prediction of hysteresis remains sensitive to the assumed host free-energy profile, the present osmotic SAFT-cDFT approach provides a computationally efficient and predictive tool for investigating adsorption-deformation coupling in responsive porous materials, opening perspectives for the screening and thermodynamic analysis of flexible metal-organic frameworks.

The influence of three-body interactions on thermodynamic response functions in the extended critical region is investigated by using molecular simulations. Results obtained with a high-level ab initio two- and three-body potential for krypton are compared to those from the Lennard-Jones potential and a reference equation of state. While the former model shows excellent agreement with the equation of state, the Lennard-Jones potential exhibits significant deviations that cannot be corrected by parameter adjustment, emphasizing the importance of many-body effects for quantitative predictions.

Adsorption of surfactants to fluid interfaces occurs in numerous daily life and technological contexts. The surfactant surface coverage Γ governs interface characteristics like tension γ, viscoelastic properties, and the stability of thin foam films. Directly measuring Γ as a function of the bulk concentration c is highly desirable but challenging, particularly for nonionic surfactants that lack easily detectable labels. Neutron reflectometry is currently the only generally applicable method, but it is not available for routine experiments. Here, we propose a simulation-assisted approach to deduce the adsorption isotherm Γ(c) from X-ray reflectivity data: as a first step, we use atomistic molecular dynamics simulations of surfactant-loaded air/water interfaces with prespecified Γ to obtain interfacial electron density profiles. From these profiles, we compute theoretical X-ray reflectivity curves and compare them with experimental measurements to determine the matching bulk concentration. We focus on two nonionic surfactants (C12EO6 and β-C12G2) with previously established force fields to illustrate how this combined approach of experiments and simulations can determine the adsorption isotherm. Additional insights are gained through comparison with the measured surface tension isotherms γ(c), based on the equation of state γ(Γ) from simulations.

We elucidate the stress in a system of active Brownian particles augmented with translational and rotational inertia (ABP+TRI). Stress tensors are derived for periodic systems as well as systems confined between walls by employing Lagrange's equations of motion of the first kind for the rotational motion. Using Langevin simulations of an ideal active gas in two dimensions, we confirm the existence of an equation of state for periodic systems that depends on translational and rotational inertia in general. Confinement implies a strong polarization of the propulsion direction near a wall and an enhanced density, both of which increase with increasing rotational inertia. This affects the local stress tensor normal to the confining walls, leading to a breakdown of the equation of state. Yet the local stress in the bulk part of the confined systems is identical with that of the periodic system. Importantly, for both kinds of boundary conditions, the so-called swim stress is not included in the local stress tensor; therefore, in general, the swim stress is not representative of the stress in systems of ABP+TRIs.

ABSTRACT Self-consistent thermodynamic description of a mixture (a compound, an alloy, etc.) including both its equation of state (EOS) and solidus and liquidus boundaries is a challenging problem. We review several standard approaches with the associated mixing rules and discuss their shortcomings. We propose a new thermodynamics-based analytic model for the EOS of a N-component mixture, N ≥ 2 . The model uses N−1 free parameters the values of which can be easily determined from the available experimental data. The calculation of the liquidus surface of a N-component mixture, which the model also suggests, requires the knowledge of the melting curves of each of the constituents of the mixture, but no other information such as their EOSs is really needed. We apply the new model to a ternary mixture in general, and to the ThO 2 -UO 2 -PuO 2 mixed-oxide (MOX) system as an example in particular.

The study of dense matter has been greatly advanced by progress in theoretical high-energy simulations and modern observational astronomy. Neutron stars serve as natural laboratories for probing matter under extreme density and strong gravitational fields. While polytropic equations of state are widely employed, conventional models based on a single polytropic index cannot adequately represent the stratified, layered nature of realistic compact-star interiors. To address this limitation, we develop a composite relativistic polytropic model in which the polytropic index varies smoothly with radius. By coupling the Einstein field equations with a generalized composite polytropic equation of state, we derive the composite Tolman–Oppenheimer–Volkoff (CTOV) system. The resulting nonlinear equations are solved using a Monte Carlo-based numerical integration method, which efficiently handles stiffness while enabling probabilistic exploration of the parameter space and natural uncertainty quantification. Our results demonstrate that increasing the relativistic parameter σ significantly reduces both the Emden function and the enclosed mass function, producing more compact stellar configurations. Sharper core–envelope transitions (ε = 0.01) yield systematically higher compactness than smoother transitions (ε = 0.03). The derived mass–radius relations reproduce the observed diversity of neutron stars, successfully matching both low-mass, large-radius systems such as PSR J0030 + 0451 and high-mass compact pulsars such as PSR J1614–2230. Importantly, the maximum-mass analysis shows that stiff composite configurations (nc = 1, ne = 2, xc = 0.7) can support gravitational masses up to Mmax ≈ 3.47 M_{ odot } for ε = 0.01 and Mmax ≈ 2.71 M_{ odot } for ε = 0.03, with corresponding minimum radii in the range Rmin ≈ 10.6–13.2 km, consistent with current observational constraints. These findings confirm that composite polytropes provide a flexible, physically motivated framework for modeling stratified compact stars and for constraining the dense-matter equation of state.