Non-equilibrium Model Research Articles

In-situ activation of persulfate by emplaced magnetite nanoparticles for degradation of 1,2-dichloroethane in porous media

In this study, column experiments were conducted to explore on the method of emplacement of magnetite nanoparticles (MNPs) for in situ activation of persulfate (PS) in sand porous media to degrade 1,2-dichloroethane (DCA), a typical recalcitrant chlorinated compound. Different molar ratios between PS and DCA (0:1, 2:1, 5:1 and 20:1) and mass contents of MNPs in the sand (0%, 1.9% and 5.4%) were tested. In the absence of MNPs, degradation of DCA was negligible for a hydraulic retention time of 7 h. Presence of MNPs at the content of 1.9% enhanced degradation of DCA and the highest removal efficiency (34.2%) was observed at the PS-to-DCA molar ratio of 5:1. At the MNPs content of 5.4%, increase of the PS-to-DCA molar ratio from 2:1 to 20:1 lead to not only increase in DCA removal efficiency but also substantial enhancement in chloride production, indicating that high PS concentration could cause significant degradation of the Cl-containing intermediates. In contrast to MNPs, Fe3O4 solids with much larger size (∼1 μm) were much less effective in activating PS for DCA removal even at a significantly higher content in the medium. The transport data could be well fitted by the one-site chemical nonequilibrium model, which showed kinetic DCA sorption to the MNPs as a key process for the transport. In the long-term injection experiment, a stable and significant removal of DCA (∼50%) was observed for 254 days at the MNP content of 1.9 %. The results of this study show the potential of MNPs as a sustainable PS activator in injection-based in situ chemical oxidation for groundwater remediation.

Spectral eigenfunction decomposition of a Fokker–Planck operator for relativistic heavy-ion collisions

A spectral solution method is proposed to solve a previously developed non-equilibrium statistical model describing partial thermalization of produced charged hadrons in relativistic heavy-ion collisions, thus improving the accuracy of the numerical solution. The particle’s phase-space trajectories are treated as a drift-diffusion stochastic process, leading to a Fokker–Planck equation (FPE) for the single-particle probability distribution function. The drift and diffusion coefficients are derived from the expected asymptotic states via appropriate fluctuation–dissipation relations, and the resulting FPE is then solved numerically using a spectral eigenfunction decomposition. The calculated time-dependent particle distributions are compared to Pb–Pb data from the ATLAS and ALICE collaborations at the Large Hadron Collider.

Two-temperature thermochemical nonequilibrium model based on the coarse-grained treatment of molecular vibrational states.

Although the high-fidelity state-to-state (StS) model accurately describes high-temperature thermochemical nonequilibrium flows, its practical application is hindered by the prohibitively high computational cost. In this paper, we develop a reduced-order model that leverages the widelyused two-temperature (2T) framework and a coarse-grained treatment of molecular vibrational states to achieve accuracy comparable to the StS model while ensuring computational efficiency. We observe that the multigroup coarse-grained model (CGM), lumping vibrational energy levels into several groups, yields results close to the StS model for the high-temperature postshock oxygen flows, even using only two groups. However, theone-group CGM (CGM-1G), equivalent to the 2T model but using the StS kinetics, fails to approximate the StS results. Analysis of microscopic group properties reveals that the failure of the CGM-1G stems from the inability to capture the non-Boltzmann effects of mid-to-high vibrational levels, overestimating apparent dissociation rates and vibrational energy loss in the dissociation-dominated region. We then propose an analytical distribution function of vibrational groups by incorporating Treanor-like terms and an additional linear term (addressing the dissociation depletion of high-lying levels). Building upon this algebraic group distribution function and reconstructing vibrational levels within each group using the vibrational temperature, we develop a new 2T model called CG2T, which demonstrates accuracy much closer (than the CGM-1G) to the StS results for the postshock oxygen flows with varying degrees of thermochemical nonequilibrium. Moreover, a fullyconnected neural network is pretrained to substitute the module for the mass and vibrational energy source terms to enhance computational efficiency, achieving about 30-fold speedup in the CG2T model without sacrificing accuracy.

Numerical Simulation of Spectral Radiation for Hypersonic Vehicles

The spectral radiation of hypersonic vehicles and surrounding flow fields is crucial for optical target detection. A novel approach combines Low-Discrepancy Sequences with the Reverse Monte Carlo Method to simulate the spectral radiation of hypersonic missiles. The effects of chemical non-equilibrium reactions and high-emissivity coating failures on the spectral radiation of a typical biconical hypersonic missile were investigated. Significant differences were found among chemical equilibrium, non-equilibrium, non-reactive, and catalytic wall models. High-emissivity coating failures occur mainly in the high-temperature regions of the nose cone and fins. The non-equilibrium model shows a transition peak distribution of NO in the head shock layer within the ultraviolet gamma band, with integrated ultraviolet radiation (200–300 nm) three times higher than the equilibrium model. In the 1–3 μm band, the non-equilibrium model’s radiation intensity at a 120° horizontal detection angle is about 1.46 times that of the equilibrium model. Using real coating emissivity, the 3–5 μm band radiation intensity is about 5% higher, and the 8–14 μm band is about 8.51% lower than the uniform emissivity model. When high-emissivity coating emissivity fails by 40%, the 3–5 μm band intensity decreases by about 15.38%, and the 8–14 μm band intensity decreases by about 12.67%.

Numerical Simulation and Neural Network Model for Hydromagnetic Nanofluid Convection in a Porous Wavy Channel with Thermal Non-Equilibrium Model

Abstract The present study aims to analyze the nonfluid MHD convective heat transfer in a porous wavy channel with a local thermal non-equilibrium (LTNE) model. Such a model finds applications related to enhancement in thermal performance, increasing the heat transfer coefficient in the compact design of heat exchangers for the aerospace and automotive industries and elevation in the efficiency of the solar collector. A sinusoidal porous wavy LTNE channel containing nanofluid and subjected to the induced and applied magnetic fields is considered. A uniform magnetic field is applied orthogonal to the channel and the induced magnetic field effects are considered due to the large magnetic Reynolds number. The momentum, continuity, energy, and nanoparticle volume fraction equations constitute the coupled nonlinear system of differential equations and are solved using the Galerkin finite element method. The reliability of the technique is assessed by comparing the proposed procedure with the results from earlier sources. A detailed analysis is presented to determine the effects of different physical parameters arising in the system on temperature, nanoparticle concentration, and velocity profiles. As an illustration, the findings exhibit that increasing the modified diffusivity ratio increases the values of the nanoparticle volume fraction whereas, reducing the modified diffusivity ratio enhances the temperature distribution. A higher value of thermal Rayleigh number presents a significant involvement of buoyancy forces, potentially resulting in the development of convective currents. A higher Nield number indicates more effective heat transport from the solid surface to the nanofluid. Consequently, there is a minimal thermal difference between the solid surface and the bulk nanofluid. Effective heat transmission enhances the nanofluid ability to absorb heat and generates a more consistent dispersion of temperature inside the fluid. The performance of the designed algorithms of the artificial neural network, namely, the Levenberg – Marquardt algorithm, in the problem under consideration is evaluated and the methodology is found reasonably precise with the matching of order around 6 to 7 decimal places of accuracy.

General properties of the response function in a class of solvable non-equilibrium models

Abstract We study the non-equilibrium response function $R_{ij}(t,t')$, namely the variation of the local magnetization $\langle S_i(t)\rangle$ on site $i$ at time $t$ as an effect of a perturbation applied at the earlier time $t'$ on site $j$, in a class of solvable spin models characterized by the vanishing of the so-called {\it asymmetry}.
This class encompasses both systems brought out of equilibrium by the variation of a thermodynamic control parameter, as after a temperature quench, or intrinsically out of equilibrium models with violation of detailed balance. The one-dimensional Ising model and the voter model (on an arbitrary graph) are prototypical examples of these two situations which are used here as guiding examples. Defining the fluctuation-dissipation ratio $X_{ij}(t,t')=\beta R_{ij}/(\partial G_{ij}/\partial t')$, where $G_{ij}(t,t')=\langle S_i(t)S_j(t')\rangle$ is the spin-spin correlation function and $\beta$ is a parameter regulating the strength of the perturbation (corresponding to the inverse temperature when detailed balance holds), we show that, in the quite general case of a kinetics obeying dynamical scaling, on equal sites this quantity has a universal form
$X_{ii}(t,t') = (t+t')/(2t)$, whereas $
\lim _{t\to \infty}X_{ij}(t,t')=1/2$ for any $ij$ couple. The specific case of voter models with long-range interactions is thoroughly discussed.

Energy Aware Technology Mapping of Genetic Logic Circuits.

Energy and its dissipation are fundamental to all living systems, including cells. Insufficient abundance of energy carriers -as caused by the additional burden of artificial genetic circuits- shifts a cell's priority to survival, also impairing the functionality of the genetic circuit. Moreover, recent works have shown the importance of energy expenditure in information transmission. Despite living organisms being non-equilibrium systems, non-equilibrium models capable of accounting for energy dissipation and non-equilibrium response curves are not yet employed in genetic design automation (GDA) software. To this end, we introduce Energy Aware Technology Mapping, the automated design of genetic logic circuits with respect to energy efficiency and functionality. The basis for this is an energy aware non-equilibrium steady state (NESS) model of gene expression, capturing characteristics like energy dissipation -which we link to the entropy production rate- and transcriptional bursting, relevant to eukaryotes as well as prokaryotes. Our evaluation shows that a genetic logic circuit's functional performance and energy efficiency are disjoint optimization goals. For our benchmark, energy efficiency improves by 37.2% on average when comparing to functionally optimized variants. We discover a linear increase in energy expenditure and overall protein expression with the circuit size, where Energy Aware Technology Mapping allows for designing genetic logic circuits with the energy efficiency of circuits that are one to two gates smaller. Structural variants improve this further, while results show the Pareto dominance among structures of a single Boolean function. By incorporating energy demand into the design, Energy Aware Technology Mapping enables energy efficiency by design. This extends current GDA tools and complements approaches coping with burden in vivo.

Regulation of the co-transport of toluene and dichloromethane by adsorbed phase humic acid under different hydro-chemical conditions

The transport behavior of combined organic pollutants in soil and groundwater has attracted significant attention in recent years. Research on the influence of humic acid (HA) on organic pollutant transport behavior mainly focuses on the study of the mobile phase HA, with less research on the adsorbed phase HA, especially regarding its interaction with combined pollutants. To enhance understanding of the regulation of co-transport and retention of combined pollutants by adsorbed phase HA, in this study, tests were conducted to investigate how toluene (TOL) and dichloromethane (DCM) are transported in the presence of adsorbed phase HA at different pH levels and ionic strengths. As the proportions of HA-coated sand increased, so did its adsorption capacity for TOL and DCM, which can be attributed to adsorbed phase HA providing more adsorption sites compared to plain sand, thereby reducing the transport potential of the pollutants. The presence of both TOL and DCM facilitated their mutual transportation due to competitive adsorption controlled by the adsorbed phase HA content in the porous medium. Furthermore, it was observed that pH levels influenced the transport behavior of TOL and DCM when adsorbed phase HA was present since adsorbed phase HA transformation into mobile phase was regulated by pH levels. The transport patterns can be effectively simulated using the chemical nonequilibrium two-site sorption model in HYDRUS-1D, accurately reflecting the retardation coefficients and transport distances based on model parameters. This work sheds new light on the regulatory role of adsorbed phase HA in TOL and DCM transport under diverse hydrochemical conditions, with implications for accurately depicting the behavior of combined pollutants, optimizing the remediation strategies and improving remediation efficiency in contaminated sites.

On the Energy Cost for Nitrogen Fixation in DC Glow Discharges in Atmospheric‐Pressure Air

ABSTRACTModeling of the production of nitrogen oxide molecules in DC discharges in laminar longitudinal flows of atmospheric‐pressure air is performed. Two‐dimensional nonequilibrium discharge model includes the system of gas dynamic equations and balance equations for various plasma components. Simulations are performed for the discharge currents 50–600 mA and gas flow velocities 1–10 m/s. In considered conditions, the gas temperature in the discharge core varies in the range of 3000–6000 K. Spatial profiles of the densities and fluxes of produced species are obtained, both inside the discharge and in the afterglow region. The energy cost for the production of nitrogen oxides is calculated, depending on the discharge current, gap length, and gas flow velocity. The results of the simulation are compared with available experimental data.

Non-equilibrium thermal models of lithium batteries

Temperature fluctuations impact battery performance, safety, and health. Industry-standard cell-level models of these phenomena ignore thermal gradients within the electrodes’ active material, i.e., assume the latter to be in “thermal equilibrium”. We present a “non-equilibrium” thermal model that explicitly accounts for spatial variability of temperature with the active material (and the carbon-binder domain). We investigate the conditions, expressed in terms of the heat-generation rate and the thermal properties of a cell’s liquid (electrolyte) and solid (active material and CBD) phases, under which the thermal equilibrium assumption breaks down and our model should be used instead. The differences between these two thermal models are investigated further by coupling them with an industry-standard electrochemical model. The resulting thermal–electrochemical model demonstrates the importance of thermal gradients within the active material at high C-rates (discharge current densities) and for large grain sizes. Under these conditions, the equilibrium assumption underestimates internal temperature by as much as 50%. These two thermal models are then applied to a commercial NMC battery with multiple units. Our non-equilibrium model predicts the battery surface temperature that is in good agreement with measurements, while the equilibrium model underestimates the observed temperature.

Convective heat transfer in porous channel with multi-layer fractures under Local thermal non-equilibrium condition

Based on Brinkman-extended-Darcy model and Local thermal non-equilibrium (LTNE) model, analytical solutions of velocity and temperature fields, pressure drop and Nusselt number of porous channels containing different number of fracture layers are obtained. The characteristics of fluid flow and heat transfer in multi-layer parallel fractured channels are further studied. Results show that for a single-layer or multi-layer fractured channel, the pressure drop changes sensitively at small hollow ratio and increases as the number of fracture layers increases with decreasing increase degree, but the pressure drop tends to be consistent regardless of the number of fracture layers when Darcy number is high. For small ratio of effective thermal conductivity, LTE model is valid regardless of Biot number, and the heat transfer intensity in multi-layer fractured channels is always higher than that in single-layer fractured channel at any hollow ratio, but the heat transfer intensity is still low. For large ratio of effective thermal conductivity, increasing Biot number or fracture layer number makes the Nusselt number increase under very small hollow ratio for both single and multiple fracture cases, and when both the ratio of effective thermal conductivity and Biot number are high, there is an intersection point occurs at hollow ratio near 0.1, which makes same heat transfer effect under different fracture numbers.

The Red Snapper Fishery in the Eastern Java Sea and Its Fishery Management Recommendation

Abstract For decades, the red snapper fishery has been considered a potential demersal fishery in the east part of Java Sea. The fluctuating fishing effort caused the biomass of red snapper has a fluctuate every year. The study’s goal is to analyze the changing conditions of the red snapper fishery in the east part of Java Sea as a basis for developing management recommendations. The production and efforts data were collected from Brondong Nusantara Fishing Port from 2008 to 2021. The data was analyzed using a non-equilibrium surplus production model and depicted using Kobe Plot to know the change direction of red snapper fishery. The result shows that red snapper fishery in the east part of Java Sea has been overfishing with the abundance of biomass has been overfished. This study’s recommendations for fisheries management are to limit fishing efforts and allowable catch in order to improve the red snapper fishery in the east part of Java Sea.

Study of X-ray emission from the S147 nebula with SRG/eROSITA: X-ray imaging, spectral characterization, and a multiwavelength picture

Simeis 147 (S147, G180.0-01.7, “Spaghetti nebula”) is a supernova remnant (SNR) extensively studied across the entire electromagnetic spectrum, from radio to giga-electronvolt γ-rays, except in X-rays. Here, we report the first detection of significant X-ray emission from the entire SNR using data of the extended ROentgen Survey Imaging Telescope Array (eROSITA) onboard the Russian-German Spektrum Roentgen Gamma (SRG). The object is located at the Galactic anticenter, and its 3° size classifies it among the largest SNRs ever detected in X-rays. By employing ∼15 years of Fermi-LAT data, our study confirms the association of the remnant with a spatially coincident diffuse giga-electronvolt excess, namely 4FGL J0540.3+2756e or FGES J0537.6+2751. The X-ray emission is purely thermal, exhibiting strong O, Ne, and Mg lines; whereas it lacks heavier-Z elements. The emission is mainly confined to the 0.5–1.0 keV band; no significant emission is detected above 2.0 keV. Both a collisional plasma model in equilibrium and a model of nonequilibrium collisional plasma can fit the total spectrum. While the equilibrium model – though statistically disfavored – cannot be excluded by X-ray fitting, only the absorption column of the nonequilibrium model is consistent with expectations derived from optical extinction data. Adopting an expansion in a homogeneous medium of typical interstellar medium (ISM) density, the general SNR properties are broadly consistent with an expansion model that yields an estimated age of ∼0.66 − 2 × 105 yr, that is a rather old age. The preference for an X-ray-emitting plasma in nonequilibrium, however, adds to the observational evidence that favors a substantially younger age. In a companion paper, we explore an SNR-in-cavity scenario, resulting in a much younger age that alleviates some of the inconsistencies of the old-age scenario.

Thermodynamic evaluation of metal foams with partial filling in a pipe

This study presents numerical findings on the flow and heat transfer irreversibility when metal foams are partially filled in a horizontal pipe. A heater is embedded in the pipe's circumference with a known heat input. Aluminum metal foam, characterized by a pore density of 10 and porosity of 0.95, is placed next to the inner wall of the pipe to enhance heat transfer. To determine the optimal thickness of the metal foam for thermodynamic performance enhancement, metal foams of five different thicknesses (10–80 mm) are examined under forced convection heat transfer conditions. The study integrates the Darcy Extended Forchheimer and local thermal nonequilibrium models to predict flow and heat transfer characteristics through the metal foams. Validation of the numerical methodology is conducted by comparing the results with experimental data available in the literature. A novel aspect of this investigation is the application of the second law of thermodynamics to analyze the thermodynamic performance of metal foams. Exergy and irreversibility analyses are used to evaluate the thermodynamic performance, revealing that a pipe filled with metal foams up to a thickness of 40 mm exhibits superior thermodynamic performance compared to other cases examined in the study.

A shell-tube latent heat thermal energy storage: Influence of metal foam inserts in both shell and tube sides

Enhancing heat transfer in latent heat thermal energy storage systems is of utmost importance to facilitate the efficient absorption and release of thermal energy. The primary objective of the current study is to investigate the influence of a metal foam layer on heat transfer enhancement in both the heat transfer fluid side and the shell side. The research explores the incorporation of a fixed 30 % foam layer, which can either extend along the tube wall or penetrate deeper into the shell, moving away from the heat transfer fluid tube. A local thermal non-equilibrium two-temperature heat equation model is utilized to mathematically model the interactions within the metal foam embedded in the heat transfer fluid tube and the phase change material domain. The governing equations are solved using the finite element method. The results indicate that adjustments to the inlet pressure and the metal foam shape parameter (FL) can significantly reduce the melting time, with a variation of approximately 40 %. Specifically, at a constant inlet pressure of 750 Pa, the energy storage power at a 90 % charging increases from 32.2 W (FL = 0.75) to 48.7 W (FL = 1.37). A modification of FL shape parameter increased the power output by 34 %.

Hidden collective oscillations in a disordered mean-field spin model with non-reciprocal interactions

Abstract We study the effect of introducing separable quenched disorder on a non-equilibrium mean-field spin model exhibiting a phase transition to an oscillating state in the absence of disorder, due to non-reciprocal interactions. In the disordered model, the magnetisation and its time derivative no longer carry the signature of the phase transition to an oscillating state. However, thanks to the separable (Mattis-type) form of the disorder, the presence of oscillations can be revealed by introducing a specific, disorder-dependent observable. We also introduce generalised linear and non-linear susceptibilities associated either with the magnetisation or with its time derivative. While linear susceptibilities show no sign of a phase transition, the third-order susceptibilities present a clear signature of the onset of an oscillating phase. In addition, we show that the overlap distribution also provides evidence for the presence of oscillations, without explicit knowledge of the disorder.

Condensation mechanism and pressure fluctuation of a steam centrifugal compressor based on a non-equilibrium condensation model

In this paper, the condensation mechanism and pressure fluctuation of a steam centrifugal compressor are deeply studied based on a non-equilibrium condensation model. The wet steam model is generated to predict the flow characteristics and the condensation of the steam centrifugal compressor. The effect of different inlet temperatures on the steam condensation characteristics is deeply explored. Numerical results show that the steam condensation phenomenon on the high span surface is increasingly obvious, and the mass fraction of liquid steam first increases and then decreases with the increase in temperature. The droplet particle diameter and the droplet number gradually increase with the increase in temperature. It is also found that the blade loading on the impeller blade also becomes more unstable with the increase in inlet temperature. The amplitude spectrum of pressure fluctuation on the both sides of impeller blade and diffuser blade is analyzed through the fast Fourier transform. The pressure fluctuation in the flow channel becomes severe first and then becomes stable with the increase in temperature, which is well consistent with the variation trend of liquid mass fraction. The quantitative relationship between condensation strength and operating temperature is established to explore the variation trend essence of surface-average wetness fraction of different span surfaces at different inlet temperatures, which further reveals the condensation sensitivity to temperature at different blade heights. It is further found that the condensation strength on the low span surface and the average wetness fraction of steam condensation in the flow field increasingly decrease with the increase in inlet temperature.

A thermochemical nonequilibrium model of CO2 plasma for studying flow-field properties of the spacecraft Mars Pathfinder

A thermochemical nonequilibrium model of CO2 plasma for studying flow-field properties of the spacecraft Mars Pathfinder

A three-dimensional thermochemical nonequilibrium model for simulating air plasma flows around an inflatable membrane reentry vehicle

A three-dimensional thermochemical nonequilibrium model for simulating air plasma flows around an inflatable membrane reentry vehicle

Unusual nanoscale amorphization of metallic chromium interfacing with SiC under high energy irradiation

Layered metal/silicon carbide (SiC) materials systems are becoming increasingly relevant to solve materials challenges in advanced fission and fusion nuclear energy systems, necessitating a deeper understanding of how interfaces between dissimilar materials behave under high energy irradiation. In this work, we use a Cr-SiC bilayer system as a model to study the behavior of such interfaces under high energy ion irradiation (80 MeV Xe26+ ions) at elevated temperatures (∼350 °C). Through high resolution characterization of the interface, we observed the formation of a nanoscale Cr-rich amorphous layer adjacent to crystalline SiC. We explain this phenomenon through a multi-scale computational approach incorporating ballistic mixing simulations, density functional theory calculations, and CALPHAD-based non-equilibrium modeling that shows the localized amorphization of Cr to be driven by the synergistic action of irradiation-induced point defects within Cr and transport of Si and C atoms across the interface. In particular, the accumulation of radiation damage results in the thermodynamic destabilization of the point-defect containing, metastable Cr-Si-C solid solution with respect to an amorphous phase of identical composition. This study advances the understanding of how metal/SiC interfaces behave under irradiation and establishes a modeling framework that can be applied to interfacial systems to understand irradiation-induced amorphization.