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This report reviews recent progress in computing Kubo formulas for general interacting Hamiltonians. The aim is to calculate electric and thermal magneto-conductivities in strong scattering regimes where Boltzmann equation and Hall conductivity proxies exceed their validity. Three primary approaches are explained. 1. Degeneracy-projected polarization formulas for Hall-type conductivities, which substantially reduce the number of calculated current matrix elements. These expressions generalize the Berry curvature integral formulas to imperfect lattices. 2. Continued fraction representation of dynamical longitudinal conductivities. The calculations produce a set of thermodynamic averages, which can be controllably extrapolated using their mathematical relations to low and high frequency conductivity asymptotics. 3. Hall-type coefficients summation formulas, which are constructed from thermodynamic averages. The thermodynamic formulas are derived in the operator Hilbert space formalism, which avoids the opacity and high computational cost of the Hamiltonian eigenspectrum. The coefficients can be obtained by well established imaginary-time Monte Carlo sampling, high temperature expansion, traces of operator products, and variational wavefunctions at low temperatures. We demonstrate the power of approaches 1–3 by their application to well known models of lattice electrons and bosons. The calculations clarify the far-reaching influence of strong local interactions on the metallic transport near Mott insulators. Future directions for these approaches are discussed. [ABSTRACT FROM AUTHOR]

We explore properties of matter and characteristics of Rayleigh–Taylor mixing by analyzing data gathered in the state-of-the-art fine-resolution experiments in high-energy density plasmas. The eminent quality data represent fluctuations spectra of the X-ray imagery intensity versus spatial frequency. We find, by using the rigorous statistical method, that the fluctuations spectra are accurately captured by a compound function, being a product of a power law and an exponential and describing, respectively, self-similar and scale-dependent spectral parts. From the self-similar part, we find that Rayleigh–Taylor mixing has steep spectra and strong correlations. From the scale-dependent part, we derive the first data-based value of the kinematic viscosity in high-energy density plasmas. Our results explain the experiments, agree with the group theory and other experiments, and carve the path for better understanding Rayleigh–Taylor mixing in nature and technology. [ABSTRACT FROM AUTHOR]

This paper examines the holographic computation of bulk and shear vis- cosity ratios in strongly coupled thermal plasmas using the AdS/BCFT correspon- dence within Horndeski gravity. We demonstrate that this framework leads to non-zero viscosity-to-entropy ratios (ζ/S and η/S) at low temperatures, indicating a break in conformal symmetry. At high temperatures, these ratios approach zero, recovering the expected conformal behavior of quark-gluon plasma. Our findings provide new insights into the hydrodynamic properties of strongly coupled plasmas and offer a more nuanced understanding of QCD-like theories in holographic models. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) is one of the most important staple food crops, and its sustained production and nutritional security have attracted much attention. Cadmium, a heavy metal toxic to plants and humans, can enter wheat in various ways. Foliar fertilization can reduce the cadmium content in plants, but how different fertilizers reduce the cadmium toxicity of plants is still unclear. In this study, the effects of foliar application of fertilizers on spring wheat yield, cadmium accumulation, and trace element contents were studied by applying three kinds of fertilizers (multi-element compound fertilizer, manganese-zinc micro fertilizer, and foliar silicon fertilizer) to spring wheat planted in mildly and moderately cadmium polluted areas. The results showed that the yield of wheat when fertilized with multi-element compound fertilizer, manganese-zinc micro fertilizer, and silicon fertilizer increased by 17.1%, 15.7%, and 16.9%, respectively, compared with the control. In addition, all three foliar fertilizers reduced the cadmium content in wheat grains to below the standard value of food pollutants (≤0.1mg/kg), and significantly reduced the transport of cadmium from glume to grain, among which manganesezinc micro fertilizer had the best effect, with a cadmium reduction rate of 41.7%. At the same time, manganese-zinc micro fertilizer significantly increased the absorption of trace elements in wheat organs. These results indicated that the foliar application of manganese-zinc micro fertilizer could be an effective way to increase wheat yield, inhibit cadmium accumulation, and increase nutrient absorption in mildly to moderately cadmium-polluted areas. [ABSTRACT FROM AUTHOR]

We highlight the recent progress in the calculation of transport coefficients pertinent to binary neutron star mergers. Specifically, we analyze the bulk viscosity coefficient driven by both the DURCA and MURCA processes and electron transport coefficients in dense and hot plasma relevant to the merger scenario. The study considers high temperatures ( T > 6 × 10 10 K) and dense environments ( n B ∼ n 0 − 3 n 0 ). Bulk viscosity exhibits resonant behavior, with peak values and peak positions dependent on particle interaction rates and thermodynamic susceptibilities. Susceptibilities are calculated by modeling the nuclear matter in the density functional approach. The bulk viscosity coefficient peaks at T ∼ 10 11 K, with a compression–rarefaction oscillation dissipation time scale of 20–50 ms. Electrical transports incorporate frequency-dependent dynamical screening in quantized electron–ion scattering rates. Consequently, dynamical screening reduces the maxima of electrical and thermal conductivities, shortening corresponding dissipation time scales. These results highlight the crucial role of dissipation coefficients in understanding binary neutron star mergers. [ABSTRACT FROM AUTHOR]

Matter prevailing during the early stages of the Universe or under extreme conditions in high-energy heavy-ion experiments supposedly possesses a rich phase structure. During the evolution of such a system, the complicated pictures of transitions among various phases are studied as part of hydrodynamics. This system, on most occasions, is considered to be non-viscous. However, various theoretical studies reveal the importance of incorporating viscous effects into the analysis. Here, the paper discusses the behavioral patterns of transport coefficients with varying temperatures and chemical potentials to obtain a qualitative, if not quantitative, picture of the same. Discussions are also shared regarding their impacts on such an exotic system for different energies, as explored in the experimental domain. This theoretical analysis, made using the structure of the Polyakov–Nambu–Jona-Lasinio (PNJL) model with a 2+1-flavor quark–antiquark system reveals important aspects of the inclusion of viscous effects in the hydrodynamic studies of QGP. [ABSTRACT FROM AUTHOR]

Recently new methods have been introduced to investigate the non‐renormalization properties of the anomalies at a non perturbative level and in presence of a lattice. The issue is relevant in a number of problems ranging from the anomaly‐free construction of chiral lattice gauge theory with large cut‐off to the universality properties observed in transport coefficients in condensed matter systems. A review of main results and future perspectives is presented. [ABSTRACT FROM AUTHOR]

The present review article has attempted a compact formalism description of transport coefficient calculations for relativistic fluid, which is expected in heavy ion collision experiments. Here, we first address the macroscopic description of relativistic fluid dynamics and then its microscopic description based on the kinetic theory framework. We also address different relaxation time approximation-based models in Boltzmann transport equations, which make a sandwich between Macro and Micro frameworks of relativistic fluid dynamics and finally provide different microscopic expressions of transport coefficients like the fluid's shear viscosity and bulk viscosity. In the numeric part of this review article, we put stress on the two gross components of transport coefficient expressions: relaxation time and thermodynamic phase-space part. Then, we try to tune the relaxation time component to cover earlier theoretical estimations and experimental data-driven estimations for RHIC and LHC matter. By this way of numerical understanding, we provide the final comments on the values of transport coefficients and relaxation time in the context of the (nearly) perfect fluid nature of the RHIC or LHC matter. [ABSTRACT FROM AUTHOR]

We explore properties of matter and characteristics of Rayleigh–Taylor mixing by analyzing data gathered in the state-of-the-art fine-resolution experiments in high-energy density plasmas. The eminent quality data represent fluctuations spectra of the X-ray imagery intensity versus spatial frequency. We find, by using the rigorous statistical method, that the fluctuations spectra are accurately captured by a compound function, being a product of a power law and an exponential and describing, respectively, self-similar and scale-dependent spectral parts. From the self-similar part, we find that Rayleigh–Taylor mixing has steep spectra and strong correlations. From the scale-dependent part, we derive the first data-based value of the kinematic viscosity in high-energy density plasmas. Our results explain the experiments, agree with the group theory and other experiments, and carve the path for better understanding Rayleigh–Taylor mixing in nature and technology.

We consider a family of models having an arbitrary positive amount of mass on each site and randomly exchanging an arbitrary amount of mass with nearest neighbor sites. We restrict to the case of diffusive models. We identify a class of reversible models for which the product invariant measure is known and the gradient condition is satisfied so that we can explicitly compute the transport coefficients associated to the diffusive hydrodynamic rescaling. Based on the Macroscopic Fluctuation Theory (Bertini et al. in Rev Mod Phys 87:593–636, 2015) we have that the large deviations rate functional for a stationary non equilibrium state can be computed solving a Hamilton–Jacobi equation depending only on the transport coefficients and the details of the boundary sources. Thus, we are able to identify a class of models having transport coefficients for which the Hamilton–Jacobi equation can indeed be solved. We give a complete characterization in the case of generalized zero range models and discuss several other cases. For the generalized zero range models we identify a class of discrete models that, modulo trivial extensions, coincides with the class discussed in Frassek and Giardinà (J Math Phys 63(10):103301–103335, 2022) and a class of continuous dynamics that coincides with the class in Franceschini et al. (J Math Phys 64(4): 043304–043321, 2023). Along the discussion we obtain a complete characterization of reversible misanthrope processes solving the discrete equations in Cocozza-Thivent (Z Wahrsch Verw Gebiete 70(4):509–523, 1985). [ABSTRACT FROM AUTHOR]

We present a method to compute transport coefficients in molecular dynamics. Transport coefficients quantify the linear dependencies of fluxes in non-equilibrium systems subject to small external forcings. Whereas standard non-equilibrium approaches fix the forcing and measure the average flux induced in the system driven out of equilibrium, a dual philosophy consists in fixing the value of the flux, and measuring the average magnitude of the forcing needed to induce it. A deterministic version of this approach, named Norton dynamics, was studied in the 1980s by Evans and Morriss. In this work, we introduce a stochastic version of this method, first developing a general formal theory for a broad class of diffusion processes, and then specializing it to underdamped Langevin dynamics, which are commonly used for molecular dynamics simulations. We provide numerical evidence that the stochastic Norton method provides an equivalent measure of the linear response, and in fact demonstrate that this equivalence extends well beyond the linear response regime. This work raises many intriguing questions, both from the theoretical and the numerical perspectives. [ABSTRACT FROM AUTHOR]

The structural, dynamical, electrical, magnetic, and thermoelectric properties of CoMRhSi (M = Cr, Mn) quaternary Heusler alloys (QHAs) were investigated using density functional theory (DFT). The Y-type-II crystal structure was found to be the most stable configuration for these QHAs. Both CoCrRhSi and CoMnRhSi alloys possess a half-metallic behavior with a 100% spin-polarization as the majority spin channel is metallic. On the other hand, the minority spin channel is semiconducting with narrow indirect band gaps of 0.54 eV and 0.57 eV, respectively, along the Γ − X high symmetry line. In addition, both CoCrRhSi and CoMnRhSi alloys possess a ferromagnetic structure with total magnetic moments of 4 μB, and 5 μB, respectively, which are prominent for spintronics applications. The thermoelectric properties of the subject QHAs were calculated by using Boltzmann transport theory within the constant relaxation time approximation. The lattice thermal conductivities were also evaluated by Slack's equation. The predicted values of the figure-of-merit (ZT) for CoCrRhSi and CoMnRhSi were found to be 0.84 and 2.04 at 800 K, respectively, making them ideal candidates for thermoelectric applications. [ABSTRACT FROM AUTHOR]

The present study is focused on the investigation of the possibility of implementing different machine learning methods for hypersonic flow modelling. The strongly nonequilibrium five-component reacting air mixture (N , N, O , O, NO) flow around a sphere is considered. The application of machine learning methods leading to a simultaneous increase in calculation speed and model accuracy is discussed. Various machine learning techniques, including linear regression, k-nearest neighbours, support vector machines, and neural network (multilayer perceptron) for the regression problem are investigated. The regression training proceeds on the basis of the accurate data of transport coefficients, given by the one-temperature approach of the kinetic theory. The dataset is constructed using the calculated transport coefficients. Using different machine learning methods for the regression problem, the transport coefficients of shear viscosity and thermal conductivity are modeled. Comparison between approximate formulae (Blottner–Eucken–Wilke model) and trained regressor's outcome is given. The computational speed and level of accuracy, obtained by applying different machine learning methods, are analyzed. The recommendation on the choice of the neural network regressor for the mixture transport coefficients calculation is stated. [ABSTRACT FROM AUTHOR]

Heat and mass transfer processes and the rate of fuel oxidation are the determining parameters of combustion of non-premixed gaseous fuel–oxidizer flows and solid-fuel combustion in a gaseous oxidizer. A correct description of these processes is of both scientific and practical interest. The influence of the kinetics of chemical reactions and diffusion of fuel molecules on the thermal and chemical structure of the flame forming around a polymethyl methacrylate (PMMA) sphere in air under natural convection has been studied by numerical simulation. The three-dimensional gas flow around the solid body has been calculated using the full Navier–Stokes equations for a multicomponent mixture taking into account diffusion and heat transfer between the surface and gas, convection, and radiative heat transfer. The kinetic model represents the conjugate reactions both on the condensed material surface and in the gas phase. The formation of the gaseous fuel methyl methacrylate (MMA) on the surface is described by an effective one-step pyrolysis reaction of PMMA. The oxidation of MMA in the gas phase is described by the global reaction C5H8O2 + 6O2 5CO2 + 4H2O. It has been found that the temperature and species concentration profiles in the flame practically do not depend on the rate constant of this reaction provided that the characteristic reaction time is much less than the characteristic time of MMA diffusion. It has been shown that varying the MMA diffusion coefficient has a significant effect on the thermal and chemical structure of the flame. Increasing the MMA diffusion coefficient increases the maximum flame temperature. The results of the study show that the transport properties of compounds required to calculate their transport coefficients are among the most important parameters for accurate CFD simulation. [ABSTRACT FROM AUTHOR]

We highlight the recent progress in the calculation of transport coefficients pertinent to binary neutron star mergers. Specifically, we analyze the bulk viscosity coefficient driven by both the DURCA and MURCA processes and electron transport coefficients in dense and hot plasma relevant to the merger scenario. The study considers high temperatures (T>6×1010 K) and dense environments (nB∼n0−3n0). Bulk viscosity exhibits resonant behavior, with peak values and peak positions dependent on particle interaction rates and thermodynamic susceptibilities. Susceptibilities are calculated by modeling the nuclear matter in the density functional approach. The bulk viscosity coefficient peaks at T∼1011 K, with a compression–rarefaction oscillation dissipation time scale of 20–50 ms. Electrical transports incorporate frequency-dependent dynamical screening in quantized electron–ion scattering rates. Consequently, dynamical screening reduces the maxima of electrical and thermal conductivities, shortening corresponding dissipation time scales. These results highlight the crucial role of dissipation coefficients in understanding binary neutron star mergers.

Matter prevailing during the early stages of the Universe or under extreme conditions in high-energy heavy-ion experiments supposedly possesses a rich phase structure. During the evolution of such a system, the complicated pictures of transitions among various phases are studied as part of hydrodynamics. This system, on most occasions, is considered to be non-viscous. However, various theoretical studies reveal the importance of incorporating viscous effects into the analysis. Here, the paper discusses the behavioral patterns of transport coefficients with varying temperatures and chemical potentials to obtain a qualitative, if not quantitative, picture of the same. Discussions are also shared regarding their impacts on such an exotic system for different energies, as explored in the experimental domain. This theoretical analysis, made using the structure of the Polyakov–Nambu–Jona-Lasinio (PNJL) model with a 2+1-flavor quark–antiquark system reveals important aspects of the inclusion of viscous effects in the hydrodynamic studies of QGP.

The paper presents a method of molecular modeling of fluid transport coefficients, which is an alternative to the method of molecular dynamics. The transport coefficients are determined using fluctuation-dissipation theorems. The dynamics of molecules is calculated stochastically, with intermolecular forces being set using the appropriate created database. A distribution function of intermolecular forces is constructed and a formula is obtained for its analytical approximation. The method effectiveness is demonstrated by the example of calculating the viscosity and thermal conductivity coefficients of liquid argon and benzene. The obtained data are compared with the data of experimental and molecular dynamic modeling and their good agreement is established. With the same modeling accuracy, the developed method is shown to be significantly more time-efficient compared to the molecular dynamics method. [ABSTRACT FROM AUTHOR]

The paper discusses the construction of non-extensive relativistic dissipative hydrodynamics of an anomalous hadronic fluid on the basis of relativistic kinetic equation, obtained earlier in the context of the Tsallis statistics, characterized by the nonextensivity parameter q, and taking into account correlation effects (by rejecting the standard hypothesis of molecular chaos) in the collision term for heavy ions. It is shown that some specific form of local thermal equilibrium quark-gluon matter is described by a generalized version of the relativistic Yüttner distribution. With the help of this distribution all thermodynamic parameters of state are defined in explicit form. Linear constitutive relations and transport coefficients such as shear viscosity, bulk viscosity and heat conductivity are derived from the linearized collision integral written in the Anderson-Witting form and evaluated using a relaxation time approximation. The designed non-extensive relativistic fluid dynamics is designed to simulate a wide range of phenomena in astrophysics, cosmology and high-energy physics. [ABSTRACT FROM AUTHOR]

The present review article has attempted a compact formalism description of transport coefficient calculations for relativistic fluid, which is expected in heavy ion collision experiments. Here, we first address the macroscopic description of relativistic fluid dynamics and then its microscopic description based on the kinetic theory framework. We also address different relaxation time approximation-based models in Boltzmann transport equations, which make a sandwich between Macro and Micro frameworks of relativistic fluid dynamics and finally provide different microscopic expressions of transport coefficients like the fluid’s shear viscosity and bulk viscosity. In the numeric part of this review article, we put stress on the two gross components of transport coefficient expressions: relaxation time and thermodynamic phase-space part. Then, we try to tune the relaxation time component to cover earlier theoretical estimations and experimental data-driven estimations for RHIC and LHC matter. By this way of numerical understanding, we provide the final comments on the values of transport coefficients and relaxation time in the context of the (nearly) perfect fluid nature of the RHIC or LHC matter.

A method of stochastic molecular modeling (SMM) of liquid transport coefficients has been developed. They are calculated using fluctuation-dissipation theorems, but, in contrast to the molecular dynamics (MD) method, the phase trajectories of the system are simulated stochastically. The force acting on a molecule is determined stochastically using a created database of intermolecular forces. The effectiveness of the method is demonstrated by an example of calculating transport coefficients. It is shown that the SMM method requires much less computational resources than the MD method. [ABSTRACT FROM AUTHOR]

The structural, dynamical, electrical, magnetic, and thermoelectric properties of CoMRhSi (M = Cr, Mn) quaternary Heusler alloys (QHAs) were investigated using density functional theory (DFT). The Y-type-II crystal structure was found to be the most stable configuration for these QHAs. Both CoCrRhSi and CoMnRhSi alloys possess a half-metallic behavior with a 100% spin-polarization as the majority spin channel is metallic. On the other hand, the minority spin channel is semiconducting with narrow indirect band gaps of 0.54 eV and 0.57 eV, respectively, along the Γ−X high symmetry line. In addition, both CoCrRhSi and CoMnRhSi alloys possess a ferromagnetic structure with total magnetic moments of 4 μB, and 5 μB, respectively, which are prominent for spintronics applications. The thermoelectric properties of the subject QHAs were calculated by using Boltzmann transport theory within the constant relaxation time approximation. The lattice thermal conductivities were also evaluated by Slack’s equation. The predicted values of the figure-of-merit (ZT) for CoCrRhSi and CoMnRhSi were found to be 0.84 and 2.04 at 800 K, respectively, making them ideal candidates for thermoelectric applications.

In this work, we perform a phenomenological derivation of the first- and second-order relativistic hydrodynamics of dissipative fluids. To set the stage, we start with a review of the ideal relativistic hydrodynamics from energy–momentum and particle number conservation equations. We then go on to discuss the matching conditions to local thermodynamical equilibrium, symmetries of the energy–momentum tensor, decomposition of dissipative processes according to their Lorentz structure, and, finally, the definition of the fluid velocity in the Landau and Eckart frames. With this preparatory work, we first formulate the first-order (Navier–Stokes) relativistic hydrodynamics from the entropy flow equation, keeping only the first-order gradients of thermodynamical forces. A generalized form of diffusion terms is found with a matrix of diffusion coefficients describing the relative diffusion between various flavors. The procedure of finding the dissipative terms is then extended to the second order to obtain the most general form of dissipative function for multiflavor systems up to the second order in dissipative fluxes. The dissipative function now includes in addition to the usual second-order transport coefficients of Israel–Stewart theory also second-order diffusion between different flavors. The relaxation-type equations of second-order hydrodynamics are found from the requirement of positivity of the dissipation function, which features the finite relaxation times of various dissipative processes that guarantee the causality and stability of the fluid dynamics. These equations contain a complete set of nonlinear terms in the thermodynamic gradients and dissipative fluxes arising from the entropy current, which are not present in the conventional Israel–Stewart theory. [ABSTRACT FROM AUTHOR]

This paper is concerned with the Boltzmann equation based on a continuous internal energy variable to model polyatomic gases with constant specific heats. We propose a family of models for the collision kernel and evaluate the nonlinear Boltzmann collision operator to get explicit expressions for transport coefficients like shear and bulk viscosities, thermal conductivity, depending on the collision kernel parameters. This model is shown to contain as a special case the collision kernel used in the direct simulation Monte Carlo method with the variable hard sphere cross section. Then, we show that it is possible to choose parameters in such a way that we recover various physical phenomena, in particular, experimental data for the shear viscosity, Prandtl number and the ratio of bulk and shear viscosities at the same time. [ABSTRACT FROM AUTHOR]

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The transport coefficients of model monatomic fluids are explored within the context of isomorph theory. An extension of our previous study in this field to the thermal conductivity of Lennard-Jones (LJ) fluids is reported here. The relationship to and comparisons with the behavior of the LJ system and those of hard spheres (HS), which form perfect isomorphs at all densities are made. The HS and LJ transport coefficients obtained by MD simulations when scaled by socalled macroscopic ('isomorph') units, and the density is scaled by the freezing density, form curves which are extremely similar, and in near quantitative agreement apart from close to freezing in most cases. It is shown that to a large extent the excellent 'isomorph' scaling of the transport coefficients exhibited by the LJ system, even at low densities, can be traced back to the dominance of the repulsive part of this potential for these dynamical quantities, which can reasonably accurately be accounted for by the scaling behavior of hard spheres. Numerical support for this conclusion using molecular dynamics data for the HS and LJ model fluids is presented. [ABSTRACT FROM AUTHOR]

In this paper we discuss the ultrafast transfer of charge and energy in a metal in the kinetic approximation. An exact solution of the Boltzmann transport equation for the electron distribution function in the relaxation time approximation is obtained, which is used to calculate transport coefficients for charge and heat fluxes. Different regimes of energy transfer under conditions of significant spatial dispersion and non-equilibrity of the electron distribution function are discussed. • Ultrafast transfer of charge and energy in a metal is considered. • Boltzmann transport equation solved for electrons on small time scales. • Analytical solution for the energy flux density in metals is obtained. • Energy transport is suppressed by the nonlocality. [ABSTRACT FROM AUTHOR]

• We explore data on fluctuations spectra in Rayleigh-Taylor mixing plasma experiments. • We accurately capture the fluctuations' self-similar and scale-dependent dynamics. • The self-similar dynamics have steep spectra, strong correlations, weak fluctuations. • The scale-dependent dynamics encapsulates information on plasma kinematic viscosity. • We find the first data based kinematic viscosity value in high energy density plasma. We report the first data based value of the kinematic viscosity in high energy density plasmas by using a rigorous statistical analysis of experimental data of fluctuations spectra in Rayleigh-Taylor mixing. The fluctuations spectra are found to be accurately described by compound functions capturing both self-similar and scale-dependent spectral parts. The self-similar dynamics have steep spectra, strong correlations and weak fluctuations. Characteristics of the scale-dependent dynamics directly determine the value of the kinematic viscosity. Our results explain the experimental observations, elucidate their consistency with group theory and other experiments, and chart research perspectives. [ABSTRACT FROM AUTHOR]

Thermoelectric effects play an important role in the programming operations of phase‐change memories. The electrothermal modeling of the device thus requires the knowledge of transport coefficients such as the electrical and thermal conductivities and the Seebeck coefficient at different temperatures. Herein, these transport coefficients of liquid Ge2Sb2Te5 at a few temperatures above melting are calculated by means of density functional molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

Thermoelectric effects play an important role in the programming operations of phase‐change memories. The electrothermal modeling of the device thus requires the knowledge of transport coefficients such as the electrical and thermal conductivities and the Seebeck coefficient at different temperatures. Herein, these transport coefficients of liquid Ge2Sb2Te5 at a few temperatures above melting are calculated by means of density functional molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

Blends of polynorbornene rubber and natural rubber with varying compositions were made and their swelling behavior in kerosene at 35, 45 and 55 °C were examined by conventional weight-gain method. Transport parameters such as diffusion, permeation and sorption coefficients were estimated for each blend systems, and the data obtained were utilized in the determination of activation energies of diffusion (ED) & permeation (EP) and enthalpy of sorption (ΔHs). Moreover, the kinetics of sorption was also studies and it was found that the transport behavior of blends systems changed from anomalous to Fickian to quasi Fickian diffusion for the penetrating molecules. PB-03 at 35 °C showed perfect Fickian diffusion behavior. Besides this, theoretical modeling of diffusion was carried out which revealed that the experimental data were best satisfied with Peppas-Sahlin model. SEM analysis was also carried out to identify the morphology of the blends. Furthermore, mechanical testing was also performed for unswollen, swollen and deswollen blends samples to evaluate the stability of rubber blends. [ABSTRACT FROM AUTHOR]

General analytic expressions for the thermal and viscous transport coefficients for a d-dimensional dilute gas are established from microscopic grounds. Both the kinetic theory formalism employed as well as the system considered are general enough in order to yield results for classical and degenerate systems with non-vanishing rest mass, for the whole range of temperatures, from newtonian to relativistic scenarios in the individual particles’ dynamics. The constitutive equations for the heat flux and the viscous tensor are established through the first order in the gradients Chapman-Enskog procedure, generalized to the relativistic scenario and considering the so-called fluid frame for the space-time decomposition. The expressions obtained for the transport coefficients are given in terms of collisional brackets and are thus valid for any interaction in a dilute situation. Moreover, such expressions could be able to shed light on the general behaviour of these coefficients. In particular, the positiveness of the bulk viscosity here obtained may be used in order to argue in favour of the Anderson-Witting model for a relaxation approximation, from this point of view. [ABSTRACT FROM AUTHOR]

Bedeaux, Albano, and Mazur (BAM) have developed a convenient method to derive the boundary conditions for non‐equilibrium thermodynamic systems made of two bulk phases separated by a free interface. In their description, the interface is considered as a thermodynamic system characterized by its intensive and extensive variables. The boundary conditions describing the free interface are expressed in terms of fluxes, thermodynamic forces, and interface transport coefficients. Previous works have focused on the derivation of the generalized boundary conditions for different systems using the BAM method, but the corresponding solutions and dynamics have not been widely studied. We consider a theoretical two dimensional system made of two incompressible fluids separated by a deformable interface for which the boundary conditions are obtained using the BAM method. Ignoring the effects of external forces, the dynamics of the system is investigated using the method of multiple scales. The hierarchy of equations is solved up to the second order and we obtain conditions that must be fulfilled by the transport coefficients modeling the cross‐effects of the velocity slips and temperature jumps so that non‐trivial asymptotic solutions for the temperature and velocity profiles can be constructed. [ABSTRACT FROM AUTHOR]

This letter is dedicated to providing proof of two statements concerning the gradient expansion of relativistic hydrodynamics. The first statement is that the ordering of transverse derivatives is irrelevant in the gradient expansion of a non-conformal fluid. The second statement is that the longitudinal projection of the Weyl covariant derivative can be eliminated in the gradient expansion of a conformal fluid. This second statement does not apply to curvature tensors. In the conformal case, we know that the ordering of Weyl covariant derivatives is irrelevant in the gradient expansion.

In this work, we perform a phenomenological derivation of the first- and second-order relativistic hydrodynamics of dissipative fluids. To set the stage, we start with a review of the ideal relativistic hydrodynamics from energy–momentum and particle number conservation equations. We then go on to discuss the matching conditions to local thermodynamical equilibrium, symmetries of the energy–momentum tensor, decomposition of dissipative processes according to their Lorentz structure, and, finally, the definition of the fluid velocity in the Landau and Eckart frames. With this preparatory work, we first formulate the first-order (Navier–Stokes) relativistic hydrodynamics from the entropy flow equation, keeping only the first-order gradients of thermodynamical forces. A generalized form of diffusion terms is found with a matrix of diffusion coefficients describing the relative diffusion between various flavors. The procedure of finding the dissipative terms is then extended to the second order to obtain the most general form of dissipative function for multiflavor systems up to the second order in dissipative fluxes. The dissipative function now includes in addition to the usual second-order transport coefficients of Israel–Stewart theory also second-order diffusion between different flavors. The relaxation-type equations of second-order hydrodynamics are found from the requirement of positivity of the dissipation function, which features the finite relaxation times of various dissipative processes that guarantee the causality and stability of the fluid dynamics. These equations contain a complete set of nonlinear terms in the thermodynamic gradients and dissipative fluxes arising from the entropy current, which are not present in the conventional Israel–Stewart theory.

The density functional theory and post density functional theory techniques are used to investigate the properties of BaLiP for potential applications in photovoltaic and thermoelectric (TE) applications. Density functional calculations of the cohesive energy, phonon‐dispersion, and elastic constant studies establish structural, dynamical, and mechanical stability of the compound. Density functional calculations show that BaLiP is a direct bandgap semiconductor while optical properties at the Bethe–Salpeter equation level of approximation suggest that BaLiP is anisotropic with the optical bandgaps of 2.22 and 1.59 eV for in‐plane and out‐of‐plane absorption, respectively. A maximum absorption coefficient of 4.35×105 cm−1 for in‐plane and 5.02×105 cm−1 for out‐of‐plane absorption in the visible range at 2.69 and 2.63 eV is found, respectively. Lattice thermal conductivity is computed using a Boltzmann transport equation approach. The calculations reveal that the average lattice thermal conductivity is 2.495 Wm−1K−1 at room temperature. The figure of merit, which is the main criterion for estimating the TE potential of a material, is estimated to have a maximum of 0.6 at 1000 K at a hole carrier concentration of 1019 cm−3. This study shows that BaLiP has some promise as a candidate for applications in electronics, optoelectronics, and TE applications. [ABSTRACT FROM AUTHOR]

In solving applied tasks of determining the characteristics of parameters changes in gaseous continuous media during convective heat and mass transfer, friction resistance in devices and equipment ensuring the operation of technological processes in the oil and gas industry, the understanding of mechanisms and intensity of heat, mass and momentum transfer processes is valuable. Such tasks are nontrivial because of the pronounced nonlinearity of effects, instability and diversity of the composition of mixtures, as the working medium of the apparatus, and require large a priori information in modeling, the obtaining of which is limited by specifics of the processes and their experimental analysis. The studies aimed at clarifying and predicting the patterns of changes in the local and integral properties of homogeneous and heterogeneous hydrocarbon systems in the apparatuses of fuel and energy complex are relevant and valuable for practice. The main aim of the study is to identify features and establish patterns of local parameters evolution of convective heat and mass transfer in oil and gas devices (such as the coefficients of dynamic and kinematic viscosity, heat and thermal diffusivity, diffusion, and their dimensionless analogs – Prandtl, Schmidt and Lewis numbers), focused on the use as working fluid of multicomponent hydrocarbon gas media in the range of temperature and pressure conditions typical for operation of oil preparation equipment at separation – T ≅ 0–70 °C and P ≅ 0,1–3,5 MPa. The methods: thermodynamic model in HYSYS software – Peng-–Robinson equation of state, statistical mechanics, the principle of corresponding states, the Chapman–-Enskog, Golubev methods, similarity theory and dimension analysis. Results. Within the framework of equilibrium thermodynamics the authors have carried out the detailed study of the evolution of local and integral parameters of momentum, heat and mass transfer in hydrocarbon gas mixtures under separation conditions at given temperatures and pressures in the working media. The limits of applicability of the practical use of the similarity method in quantitative estimates and qualitative predictions of the mechanisms and configurations of convective heat and mass transfer in oil preparation devices are established. The results of using the method of analogies in modeling separation in general issues of the momentum, heat and mass transfer in the problems of the oil and gas industry are discussed. The authors recommend in practice of designing equipment the conclusions on the peculiarities of properties changes in mixtures that are complex in structure and intensity of heat and mass transfer mechanisms during separation, violating the triple analogy in non-isothermal homogeneous and heterogeneous media.

Bak, Tang, and Wiesenfeld (BTW) proposed the theory of self-organized criticality (SOC), and sandpile models, to connect “1/f” noise, observed in systems in a diverse natural setting, to the fractal spatial structure. We review some of the existing works on the problem of characterizing time-dependent properties of sandpiles and try to explore if the BTW's original ambition has really been fulfilled. We discuss the exact hydrodynamic structure in a class of conserved stochastic sandpiles, undergoing a non-equilibrium absorbing phase transition. We illustrate how the hydrodynamic framework can be used to capture long-ranged spatio-temporal correlations in terms of large-scale transport and relaxation properties of the systems. We particularly emphasize certain interesting aspects of sandpiles—the transport instabilities, which emerge through the threshold-activated nature of the dynamics in the systems. We also point out some open issues at the end.