Non-equilibrium Conditions Research Articles

Supersonic separation benefiting the decarbonization of natural gas and flue gas

Supersonic separation utilizes the cryogenics created by gas expansion to purify the mixture. This method is a novel carbon capture scheme. In this work, the models of N2-CO2 (flue gas) and CH4-CO2 (natural gas) are established to calculate the condensation flow. The condensation behavior of CO2 in natural gas and flue gas is clarified respectively, and the difference between the two is compared for the first time. Under the same conditions, CO2 in flue gas reaches the limit non-equilibrium state first, forming non-equilibrium condensation with limit nucleation rate of 7.78 × 1020 m−3s−1 and maximum droplet growth rate of 8.19 × 10−3 m s−1. However, the maximum droplet growth rate in natural gas is only 2.22 × 10−3 m s−1, which implies that the interphase mass transfer rate in flue gas is larger during the CO2 condensation. In addition, the condensation behavior of CO2 in natural gas is more sensitive to the changes of inlet parameters. This work provides an invaluable contribution to the development of supersonic carbon capture.

Small cluster formation in a free argon jet

A free argon jet flow accompanied by small clusters formation is studied with the direct simulation Monte Carlo method. Some near-continuum flow regimes characterized by Knudsen numbers in the 2×10−4−2×10−3 range are considered. A model for the argon clusters' growth/decay is proposed, taking into account the phase state of the clusters. The model consists of a chain of reactions leading to the clusters' formation, including the clusters' growth via triple/pair collisions of particles, and the clusters decay according to the collisional/unimolecular mechanism. The cluster size distributions in the jet far field are obtained. The results are compared with two experimental datasets. Good agreement is shown for most of the considered range of parameters. The triple particle collisions' influence on the argon clusters growth process is studied, and their important role in small cluster formation is demonstrated. It has been established that the cluster formation process is limited to an enough small spatial zone near the source outlet, of the order of several exit orifice diameters. The simulation shows a significant influence of cluster formation on the temperature and Mach number distributions, and a weak influence on the flow velocity. The formed clusters' translational temperatures and their velocities are close to the argon atoms' corresponding parameters. A non-equilibrium state, featured by a significant difference between the clusters' internal temperatures and the flow temperature, develops with distance from the source outlet.

In Situ High-Pressure Correlated Transportation of Heavy Rare-Earth Perovskite Nickelates as Batch Synthesized within Eutectic Molten Salts at MPa-pO2.

The multiple magneto-/electrical quantum transitions discovered with d-band correlated metastable perovskite oxides, such as rare-earth nickelate (ReNiO3), enable applications in artificial intelligence and multifunctional sensors. Nevertheless, to date such investigation merely focuses on ReNiO3 with light or middle rare-earth composition, while the analogous explorations toward heavy rare-earth (ReHNiO3, ReH after Gd) are impeded by their ineffective material synthesis relying on GPa pressure. Herein, for the first time we synthesized the powder of ReHNiO3 in grams/batch with ∼1000 times lower pressure and ∼300 °C lower temperature in comparison to the previous ∼101 milligram/batch results, assisted by their eutectic precipitation and heterogeneous growth within alkali-metal halide molten salt at MPa oxygen pressures. Further in situ characterizations under high pressures within a diamond anvil cell reveal a distinguishing pressure predominated bad metal transport within the nonequilibrium state of ReHNiO3 showing high-pressure sensitivity up to 10 GPa, and the temperature dependences in electrical transportations are effectively frozen.

Non-equilibrium transport in polymer mixed ionic-electronic conductors at ultrahigh charge densities.

Conducting polymers are mixed ionic-electronic conductors that are emerging candidates for neuromorphic computing, bioelectronics and thermoelectrics. However, fundamental aspects of their many-body correlated electron-ion transport physics remain poorly understood. Here we show that in p-type organic electrochemical transistors it is possible to remove all of the electrons from the valence band and even access deeper bands without degradation. By adding a second, field-effect gate electrode, additional electrons or holes can be injected at set doping states. Under conditions where the counterions are unable to equilibrate in response to field-induced changes in the electronic carrier density, we observe surprising, non-equilibrium transport signatures that provide unique insights into the interaction-driven formation of a frozen, soft Coulomb gap in the density of states. Our work identifies new strategies for substantially enhancing the transport properties of conducting polymers by exploiting non-equilibrium states in the coupled system of electronic charges and counterions.

Rotational state-to-state transition rate coefficients for H2O + H2O collisions at nonequilibrium conditions

The goal is to develop a database of rate coefficients for rotational state-to-state transitions in H$_ $O + H$_ $O collisions that is suitable for the modeling of energy transfer in nonequilibrium conditions, in which the distribution of rotational states of H$_ $O deviates from local thermodynamic equilibrium. A two-temperature model was employed that assumed that although there is no equilibrium between all possible degrees of freedom in the system, the translational and rotational degrees of freedom can be expected to achieve their own equilibria independently, and that they can be approximately characterized by Boltzmann distributions at two different temperatures, $T_ kin $ and $T_ rot Upon introducing our new parameterization of the collisional rates, taking into account their dependence on both $T_ kin $ and $T_ rot $, we find a change of up to 20<!PCT!> in the H$_ $O rotational level populations for both ortho and para-H$_ $O for the part of the cometary coma where the nonequilibrium regime occurs.

Programmable Crowding and Tunable Phases in a Binary Mixture of Colloidal Particles under Light-Driven Thermal Convection.

We employ photothermally driven self-assembly of colloidal particles to design microscopic structures with programmable size and tunable order. The experimental system is based on a binary mixture of "plasmonic heater" gold nanoparticles and "assembly building block" microparticles. Photothermal heating of the gold nanoparticles under visible light causes a natural convection flow that efficiently assembles the microscale building block particles (diameter 1-10 μm) into a monolayer. We identify the onset of active Brownian motion of colloidal particles under this convective flow by varying the conditions of light intensity, gold nanoparticle concentration, and sample height. We realize a crowded assembly of microparticles around the center of illumination and show that the size of the particle crowd can be programmed using patterned light illumination. In a binary mixture of gold nanoparticles and polystyrene microparticles, we demonstrate the formation of rapid and large-scale crystalline monolayers, covering an area of 0.88 mm2 within 10 min. We find that the structural order of the assembly can be tuned by varying the surface charge of the nanoparticles and the size of the microparticles, giving rise to the formation of different phases-colloidal crystals, crowds, and gels. Using Monte Carlo simulations, we explain how the phases emerge from the interplay between hydrodynamic and electrostatic interactions, as well as the assembly kinetics. Our study demonstrates the promise of self-assembly with programmable shapes and structural order under nonequilibrium conditions using an accessible setup comprising only binary mixtures and LED light.

Transport coefficient approach for characterizing nonequilibrium dynamics in soft matter

Nonequilibrium states in soft condensed matter require a systematic approach to characterize and model materials, enhancing predictability and applications. Among the tools, X-ray photon correlation spectroscopy (XPCS) provides exceptional temporal and spatial resolution to extract dynamic insight into the properties of the material. However, existing models might overlook intricate details. We introduce an approach for extracting the transport coefficient, denoted as [Formula: see text], from the XPCS studies. This coefficient is a fundamental parameter in nonequilibrium statistical mechanics and is crucial for characterizing transport processes within a system. Our method unifies the Green-Kubo formulas associated with various transport coefficients, including gradient flows, particle-particle interactions, friction matrices, and continuous noise. We achieve this by integrating the collective influence of random and systematic forces acting on the particles within the framework of a Markov chain. We initially validated this method using molecular dynamics simulations of a system subjected to changes in temperatures over time. Subsequently, we conducted further verification using experimental systems reported in the literature and known for their complex nonequilibrium characteristics. The results, including the derived [Formula: see text] and other relevant physical parameters, align with the previous observations and reveal detailed dynamical information in nonequilibrium states. This approach represents an advancement in XPCS analysis, addressing the growing demand to extract intricate nonequilibrium dynamics. Further, the methods presented are agnostic to the nature of the material system and can be potentially expanded to hard condensed matter systems.

Physics-informed Hermite neural networks for wetted porous fin under the local thermal non-equilibrium condition: application of clique polynomial method

Physics-informed Hermite neural networks for wetted porous fin under the local thermal non-equilibrium condition: application of clique polynomial method

Selective laser sintering and spark plasma sintering of (Zr,Nb,Ta,Ti,W)C compositionally complex carbide ceramics

AbstractTwo advanced manufacturing processes, spark plasma sintering (SPS) and selective laser sintering (SLS), have been developed for synthesis of (Zr,Nb,Ta,Ti,W)C compositionally complex carbide (CCC) via reactive sintering of a powder mixture of constitute monocarbides. X‐ray diffraction analysis confirmed that the single‐phase CCC can be formed by both SPS and SLS. While a homogenous microstructure with uniform metal element distributions was developed during SPS, three‐layer microstructures with a thin TiC‐rich layer and two TaC‐rich layers along with a TiO2‐rich surface layer containing W nanoparticles were formed during SLS. In addition, cellular structures with W, Zr, and Ti element segregation and dislocations on cell boundaries were observed in the SLS‐CCC sample, indicating the effect of nonequilibrium conditions on microstructure formation during laser melting followed by rapid cooling and solidification process. Compared to the SPS‐CCC sample, the SLS‐CCC showed enhanced hardness and reduced thermal conductivity, which may be related to their unique cellular structures.

Thermodynamic circuits: Association of devices in stationary nonequilibrium.

For a circuit made of thermodynamic devices in stationary nonequilibrium, we determine the mean currents (of energy, matter, charge, etc.) exchanged with external reservoirs driving the circuit out of equilibrium. Starting from the conductance matrix describing the nonlinear current-force characteristics of each device, we obtain the conductance matrix of the composite device. This generalizes the rule of resistance addition (serial association) or conductance addition (parallel association) in stationary out-of-equilibrium thermodynamics and for multiple coupled potentials and currents of different natures. Our work emphasizes the pivotal role of conservation laws when creating circuits of complex devices. Finally, two examples illustrate among others the determination of the conservation laws for the serial and parallel associations of thermodynamic devices.

Photoswitchable Imines Drive Dynamic Covalent Systems to Nonequilibrium Steady States.

Coupling a photochemical reaction to a thermal exchange process can drive the latter to a nonequilibrium steady state (NESS) under photoirradiation. Typically, systems use separate motifs for photoresponse and equilibrium-related processes. Here, we show that photoswitchable imines can fulfill both roles simultaneously, autonomously driving a dynamic covalent system into a NESS under continuous light irradiation. We demonstrate this using transimination reactions, where E-to-Z photoisomerism generates a more kinetically labile species. At the NESS, energy is stored both in the metastable Z-isomer of the imine and in the system's nonequilibrium constitution; when the light is switched off, this stored energy is released as the system reverts to its equilibrium state. The system operates autonomously under continuous light irradiation and exhibits characteristics of a light-driven information ratchet. This is enabled by the dual-role of the imine linkage as both the photochromic and dynamic covalent bond. This work highlights the ability and application of these imines to drive systems to NESSs, thus offering a novel approach in the field of systems chemistry.

CLT for NESS of a reaction-diffusion model

We study the scaling properties of the non-equilibrium stationary states (NESS) of a reaction-diffusion model. Under a suitable smallness condition, we show that the density of particles satisfies a law of large numbers with respect to the NESS, with an explicit rate of convergence, and we also show that at mesoscopic scales the NESS is well approximated by a local equilibrium (product) measure, in the total variation distance. In addition, in dimensions d≤3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d \\le 3$$\\end{document} we show a central limit theorem for the density of particles under the NESS. The corresponding Gaussian limit can be represented as an independent sum of a white noise and a massive Gaussian free field, and in particular it presents macroscopic correlations.

Unlocking the unfolded structure of ubiquitin: Combining time-resolved x-ray solution scattering and molecular dynamics to generate unfolded ensembles.

The unfolding dynamics of ubiquitin were studied using a combination of x-ray solution scattering (XSS) and molecular dynamics (MD) simulations. The kinetic analysis of the XSS ubiquitin signals showed that the protein unfolds through a two-state process, independent of the presence of destabilizing salts. In order to characterize the ensemble of unfolded states in atomic detail, the experimental XSS results were used as a constraint in the MD simulations through the incorporation of x-ray scattering derived potential to drive the folded ubiquitin structure toward sampling unfolded states consistent with the XSS signals. We detail how biased MD simulations provide insight into unfolded states that are otherwise difficult to resolve and underscore how experimental XSS data can be combined with MD to efficiently sample structures away from the native state. Our results indicate that ubiquitin samples unfolded in states with a high degree of loss in secondary structure yet without a collapse to a molten globule or fully solvated extended chain. Finally, we propose how using biased-MD can significantly decrease the computational time and resources required to sample experimentally relevant nonequilibrium states.

Influence of multiphase microstructure on the strength and ductility of Nb–Zr–Ti–V refractory high entropy alloys

In this investigation, we focused on the lightweight Nb–Zr–Ti–V alloys as representative model alloys to explore improving mechanical properties of refractory high entropy alloys (RHEAs) through phase engineering. The alloys were deliberately designed with different element concentrations and varied cooling rates after homogenization treatment, resulting in formation of multiple secondary phases. Microstructures of prepared alloys were reported, revealing the decomposition of the BCC matrix into dual-BCC phases with increasing V content. We attribute this phenomenon to the substantial atomic size misfit between V and Zr. Additionally, a metastable FCC phase and an intermetallic Laves phase emerged at intermediate temperatures in Nb0.75ZrTiV0.75, influenced by the nonequilibrium condition during cooling and the enthalpic effect. Compression tests were performed to access mechanical characteristics of different phases. The dual-BCC phases, featuring granular or multilayer morphology, enhanced ductility of the alloy by facilitating dislocation movement at BCC interfaces. In contrast, the FCC and Laves phases, characterized by a needle-like morphology, increased strength of the alloy owing to their intrinsic hardness. Based on the current discovery and understanding on secondary phases in the Nb–Zr–Ti–V alloys, our future objective is to obtain a modulated microstructure with an appropriate combination of different phases to optimize strength and ductility simultaneously.

A device for dynamic testing of the refractory ceramic resistance to biomass ash

The corrosive effects of biomass ash on refractory materials in combustion chambers pose challenges. Development of new castable refractory materials which are more resistant to corrosion requires tests that accurately reflect the conditions occurring in real devices. This article describes the Computational Fluid Dynamics (CFD) design and construction of a device for evaluating the corrosion of refractory materials in dynamic regime. The device allows to simulate combustion chamber conditions accurately, to regulate an injection of corrosive medium on the tested material surface under the specified conditions (temperature, time, and flow). In the present investigation the conventional refractory material was exposed to attack of biomass ash at the temperature of 1300 °C for 3 h to test the functionality of the device. A burner with technology oxygen–enriched combustion was used to heat the device. The corrosion tests were conducted in accordance with the standard P CEN/TS 15,418 and the standard STN EN ISO 21404. The operational state required for corrosion tests at 1300 °C was achieved within 1.12 h. The extent of refractory material degradation in the dynamic corrosion regime was evaluated using electron microscopy-energy dispersive spectroscopy (EM-EDS) and compared with the results of a static crucible test (3 h at 1300 °C). The dynamic test provided sufficient information on the interactions of corrosion medium with the refractories. Its main advantages are the maintenance of non-equilibrium conditions by controlled deposition of the corrosion medium in quantity from 1 to −100 g/h, fast heating rate to operating temperature (20 °C/min), and the possibility of conditions variability during tests (temperature, ox-red. atmosphere, fuel gas flow etc.).

Investigation of Magneto-convection in Viscoelastic Fluid Saturated Anisotropic Porous Layer Under Local Thermal Non-equilibrium Condition

The problem of magneto-convection in viscoelastic fluid saturated anisotropic porous layer under local thermal non-equilibrium (LTNE) effect is investigated. Extended Darcy model with time derivative term for viscoelastic fluid of the Oldroyd type with an externally imposed vertical magnetic field is used to model the momentum equation. The entire investigation has been split into two parts: (i) linear stability analysis (ii) weakly non-linear stability analysis. We perform normal mode technique to examine linear stability analysis while truncated representation of Fourier series method is used for weakly non-linear stability analysis. The onset of convection is set in through oscillatory rather than stationary mode due to competition between the processes of thermal, magnetic effect and viscoelasticity. A comparative study between anisotropic and isotropic porous medium is made as a function of Q (Chandrasekhar number), 𝛤 (non dimensional inter phase heat transfer coefficient), 𝜆1 (Relaxation time) and λ2 (Retardation time). Apart from this, Q, 𝛤 and λ2 stabilize the system in oscillatory case while 𝜆1 destabilize the system. Furthermore 𝜉 (mechanical anisotropic parameter), 𝜂s (thermal anisotropic parameter for solid phase), destabilizes the system and 𝜂f (thermal anisotropic parameter for fluid phase) stabilizes the system. The effect of Q, 𝜆1, λ2, 𝛤, 𝜉, 𝜂f and 𝜂s on heat transfer is also examined.

Kinetically Controlled and Nonequilibrium Assembly of Block Copolymers in Solution.

Covalent polymers are versatile macromolecules that have found widespread use in society. Contemporary methods of polymerization have made it possible to construct sequence polymers, including block copolymers, with high precision. Such copolymers assemble in solution when the blocks have differing solubilities. This produces nano- and microparticles of various shapes and sizes. While it is straightforward to draw an analogy between such amphiphilic block copolymers and phospholipids, these two classes of molecules show quite different assembly characteristics. In particular, block copolymers often assemble under kinetic control, thus producing nonequilibrium structures. This leads to a rich variety of behaviors being observed in block copolymer assembly, such as pathway dependence (e.g., thermal history), nonergodicity and responsiveness. The dynamics of polymer assemblies can be readily controlled using changes in environmental conditions and/or integrating functional groups situated on polymers with external chemical reactions. This perspective highlights that kinetic control is both pervasive and a useful attribute in the mechanics of block copolymer assembly. Recent examples are highlighted in order to show that toggling between static and dynamic behavior can be used to generate, manipulate and dismantle nonequilibrium states. New methods to control the kinetics of block copolymer assembly will provide endless unanticipated applications in materials science, biomimicry and medicine.

Duality for the multispecies stirring process with open boundaries

We study the stirring process with N − 1 species on a generic graph G=(V,E) with reservoirs. The multispecies stirring process generalizes the symmetric exclusion process, which is recovered in the case N = 2. We prove the existence of a dual process defined on an extended graph G~=(V~,E~) which includes additional sites in V~∖V where dual particles get absorbed in the long-time limit. We thus obtain a characterization of the non-equilibrium steady state of the boundary-driven system in terms of the absorption probabilities of dual particles. The process is integrable for the case of the one-dimensional chain with two reservoirs at the boundaries and with maximally one particle per site. We compute the absorption probabilities by relying on the underlying gl(N) symmetry and the matrix product ansatz. Thus one gets a closed-formula for (long-ranged) correlations and for the non-equilibrium stationary measure. Extensions beyond this integrable set-up are also discussed.

Signals of detailed balance violation in nonequilibrium stationary states: subtle, manifest, and extraordinary

The evolution of physical systems are often modeled by simple Markovian processes. When settled into stationary states, the probability distributions of such systems are time independent, by definition. However, they do not necessarily fall within the framework of equilibrium statistical mechanics. Instead, they may be non-equilibrium steady states (NESS). One distinguishing feature of NESS is the presence of time reversal asymmetry (TRA) and persistent probability current loops. These loops lead naturally to the notion of probability angular momenta, which play a role on the same footing as the noise covariance in stochastic processes. Illustrating with simulations of simple models and physical data, we present ways to detect these signals of TRA, from the subtle to the prominent.

Entropy Theory in the Context of Physics Education

Entropy, initially a concept in thermodynamics describing the degree of disorder in a system, has been extended to information theory and non-equilibrium thermodynamics. The article proposes that the physical classroom teaching system can be viewed as a dissipative structure, promoting the orderly development of students' cognition through openness, non-equilibrium states, and fluctuation mechanisms. Specific strategies include opening up teaching content and methods, creating non-equilibrium state experiments, introducing cognitive fluctuations, and utilizing non-linear effects. These approaches help to stimulate students' desire for knowledge, optimize the teaching process, and achieve efficient physical classroom teaching.