Quasi-equilibrium Regime Research Articles

Study of High-Temperature Oxygen Release from Strontium Cobaltite in Quasi-Equilibrium Regime

Study of High-Temperature Oxygen Release from Strontium Cobaltite in Quasi-Equilibrium Regime

Features of ion exchange between the electrodes in metal-ion batteries during discharge

The importance and relevance of the storage of electrical energy is confirmed by events in the world and trends in the development and use of various electrical energy systems, household appliances, computer equipment, communication devices, etc. In addition to the growth of the metal-ion battery markets, there are trends towards a search for metals that in the future will be inexpensive and will have characteristics required for storage systems. This paper considers ion exchange between the electrodes of metal-ion batteries whose charge carriers are metal ions, which diffuse in the process of discharge from the negative electrode to the positive one. A mathematical model was developed and tested. The model is based on a system of diffusion transport equations with the Nernst–Planck–Poisson potential equation replaced by an equivalent conductivity potential equation. Quasi-equilibrium regimes are considered. The entire working area consists of a pore electrode space and a neutral separator. The mathematical model employed consists of potential distribution equations and an electrolyte concentration distribution equation supplemented by the dependence of the electrode surface current on the overvoltage and equations that determine the electrode pore structure depending on the masses transferred inside the electrode. The electric potential and diffuse component mass transfer equations are written within the framework of the modern theory of effective electrical conductivity in batteries with account for current exchange between the solid electrodes and the liquid electrolyte. The research results showed the following. A change in the resistance of the separator (a change in porosity) has little effect, if any, on the electrode current densities, but it causes some change in the potentials themselves. A change in the resistance of the electrolyte affects both the electrode potentials and the internal current distribution between the electrodes and the electrolyte.

Dynamics of intermetallics formation in the Al/Ni reactive wetting system

Due to the complexity of interfacial reactions during reactive wetting process at high temperatures, the intrinsic mechanism behind the formation and growth of intermetallic compounds (IMCs) is still unclear. This study presents insight into the possible formation of Al/Ni IMCs in the Al (l)/Ni (s) wetting system at 1023.15 K using molecular dynamics (MD) simulation. The reactive wetting process has been broadly classified into three regimes based on the Al/Ni interphase condition: fast spreading (mostly non-reactive), crossover (dissolutive), and slow-spreading (reactive). It is found that the intermetallic phases are nucleated during the dissolutive phase; however, the stable IMCs are formed during the reactive stage and are mostly composed of AlNi and Al3Ni5. The growth of IMCs in the radial direction shows the same behavior as the contact radius of the droplet, which is a significant increase of both the droplet radius and IMCs growth in the radial direction before the droplet reaches its quasi-equilibrium base radius. Quasi-equilibrium droplet radius occurs when changes in droplet radius are negligible. In a quasi-equilibrium regime, no significant change in droplet radius and IMCs growth is observed. In contrast, the IMCs growth in the normal direction shows the opposite behavior: the thickness of IMCs increases significantly during the quasi-equilibrium regime.

Step-scan differential calorimetry of protein denaturation: Modeling and experiment

Calorimetric step-scan curves of the reversible protein denaturation were modeled numerically. The quasi-equilibrium denaturation regime can be realized if the duration of isothermal steps is long enough so that the system is able to settle to equilibrium. We show the changes in the real and imaginary parts of the complex heat capacity during the denaturation process depending on the kinetic regime of denaturation. The practical application of the step-scan method for denaturation of lysozyme in water has revealed the negative temperature coefficient of the excess heat capacity of lysozyme. In the case of denaturation of lysozyme in glycerol studied by fast scanning calorimetry, the step-scan technique can be used to improve the quality of the baseline and reveal a heat capacity step after during denaturation.

New insights into modeling disjoining pressure and wettability alteration by engineered water: Surface complexation based rock composition study

Several laboratory studies observed wettability alteration of carbonate rocks towards a more water-wet state through modifying the composition of injected water. The change in carbonate surface charge was reported as the underlying reason behind this wettability alteration and the corresponding incremental oil recovery by engineered water injection (EWI). Although the reported results of carbonate rock sensitivity to injected water ionic strength, pH, salinity, and concentration of potential determining ions (Ca 2+ , Mg 2+ , and SO 4 2− ), there is still an ambiguity on the way carbonates interact with injected water/ions. This is due to the different mineralogical compositions and electrokinetic properties of carbonates. Therefore, this paper provides more insight into the role of major rock-forming carbonate minerals (calcite and dolomite) in engineered water injection at different water compositions by utilizing surface complexation modeling (SCM). The study utilizes a geochemical simulator to highlight the effect of dolomite surface complexation reactions. After determining the total rock surface charge and surface potential, the disjoining pressure was calculated to estimate the water film thickness and consequently, infer about wettability alteration. The results showed that a successful EWI operation creates three regimes: displacement regime, surface reaction regime, and quasi-equilibrium regime. These regimes can be characterized by the proposed surface complexation technique to calculate/optimize the injection pore volumes needed for each regime, determine the location of EWI effect in the reservoir, and predict the time ranges when EWI will reach to the surface in the form of additional oil recovery. Also, it was found that the surface reaction regime is the most important one where main surface reactions and oil recovery occur. Furthermore, the study utilizes SCM for both calcite and dolomite minerals for the first time highlighting their importance in geochemical reactions of EWI when the rock has dolomite in its composition. Existing SCM considers oil-brine and rock-brine interfaces where only calcite mineral is captured in the rock-brine interface. The latter is based on assuming that the rock composition is pure calcite, which is not necessary the case. The findings of this study confirm that seawater is capable of inducing wettability alteration in carbonates under certain favorable conditions due to adsorption/desorption of the potentially determining ions. • This paper provides novel insight into the role of major rock-forming carbonate minerals (calcite and dolomite) in EWI/LSWI at different water compositions by utilizing the surface complexation reactions. • It is found that in a successful EWI operation, three regimes would be created, i.e. displacement regime, surface reaction regime, and equilibrium regime. • These regimes can be characterized by the proposed technique to calculate/optimize the injection pore volumes needed for each zone. • The developed approach can determine the location of EWI effect in the reservoir, and predict the time ranges when EWI would reach to the surface in the form of additional oil recovery. • This study utilizes SCM for both calcite and dolomite minerals for the first time highlighting their importance in geochemical reactions during EWI when the rock has dolomite as a constituent.

Channel morphologic processes of a highly sinuous bend approaching neck cutoff by bank erosion in the middle Yangtze River

The distal reach of the Lower Jingjiang River (LJR) in the middle of the Yangtze River consists of five adjacent bends, among which the Qigongling Bend is a Ω-shaped meander with a mean sinuosity of 2.2 and the narrowest neck 525 m in width. This bend is slowly approaching neck cutoff owing to progressive bank erosion. An abnormal phenomenon has occurred in this bend since the Three Gorges Reservoir (TGR) began to operate in 2003 which is erosion in the inner bank zone and deposition in the outer bank zone. This problem has not been fully understood because of the interplay of changes in water-sediment, bank erosion, and artificial bank revetment. In this study, aerial and remote sensing images, hydrological data, channel topography, and an existing bank erosion model are used to reveal channel morphodynamics of this bend and the trend of the potential neck cutoff induced by bank erosion. The study results show that the clear water released from the TGR has provided by forcefully eroded the point bar of inner bank but failed to scour the outer bank due to the protection of bank revetment since the 1990s. Thus far, the outer bank zone near the bend apex has increasingly widened in conjunction with the formation of 2 emerging sand bars. Consequently, the thalweg of the main channel has laterally shifted toward the inner bank by roughly 800 m. More severely, the rate of bank retreat on the upstream side of the bend neck was about 4.5 m/yr in 2010–2019, but the downstream side of this neck was experienced slight deposition. Bank erosion could be accelerated by progressively increasing erosion and eventually trigger the occurrence of neck cutoff in the next few decades, thereby significantly altering the quasi-equilibrium regime of channel morphodynamics in the LJR.

Near- and far-field structure of shallow mixing layers between parallel streams

Abstract

A simple theory of the quasi-equilibrium regime of atmospheric circulation, using the concept of a modified potential vorticity

The application of the general Ertel’s vorticity theorem to the diagnosis of general atmospheric circulation processes is discussed. The concepts of a modified potential vorticity (PV) and the “PV of the second generation” are used; the latter quantity is obtained by substituting a PV into Ertel’s vorticity theorem. The requirement that the “second-generation PV” vanishes when the PV is properly modified leads to the condition for local compensation of the action of heat sources and frictional stresses on the Earth’s surface: namely, to the condition of surface air heating / cooling under anticyclonic / cyclonic circulation conditions. The situation with locally uncompensated anomalous wintertime near-surface air heating over the Barents Sea is discussed in the context of the current reduction in the ice cover over the Arctic, which at the global level should be compensated by the intensification of anticyclonic circulation systems over the continents and the corresponding surface air cooling.

THE KINETIC BOLTZMANN EQUATION IN GENERALIZED MODEL OF ELECTRON TRANSPORT FOR MICRO- AND NANOELECTRONICS

In a tutorial article directed to serve researchers, university teachers and students, we study Boltzmann kinetic equation (BKE), which in its application to nanoelectronics serves to solve the same problems as the generalized Landauer-Datta-Lundstrom (LDL) transport model does. For some problems BKE formalism is preferable, for the other – LDL model is. Under correct performance of calculations the two approaches leads to similar results. In this article we answer the following questions: how to compose the equation for distribution function f (r, k, t) as a solution of BKE beyond equilibrium, how to solve this equation for the linear response regime, how to compare the obtained results with those, which can be obtained within LDL model for diffusive transport regime, how to take into consideration the external magnetic field and its effect on electron transport.We formulate BKE in the approximation of relaxation time (RT) and search for its solution in the dynamic equilibrium regime. Than we calculate the transport coefficients. We consider the calculation of the surface concentration of electrons in 2D resistor as an example. The solution for BKE in quasi-equilibrium regime within RT approximation is the expression, well known for LDL model. We also demonstrate that BKE within RT approximation leads to the same expressions for Seebeck coefficient and electron thermo-conductivity, as LDL transport model does. The LDL model advantage is its physical transparency and the fact that it enables to consider quasi-ballistic and ballistic transport regimes as simply, as the diffusive one. On the other hand, BKE formalism should be used for studies of the anisotropic transport.

Influx and Production Rates in Peak-Mode Isotachophoresis.

We present an analytical model useful in the design of peak-mode isotachophoresis (ITP) experiments. The model quantifies sample influx and production rates, the latter in applications where ITP is used to accelerate chemical reactions. We include analysis of the effect of initial sample placement location. We derive and identify key nondimensional parameters for the general case of weak electrolyte buffer ions in terms of sample placement (injection mode), initial concentrations, fully ionized mobilities, and reaction kinetic constants. We then discuss how to use these parameters in the optimal design of peak-mode ITP assays and highlight regimes of particular interest. We clearly identify a quasi-equilibrium regime wherein production rates increase until they equal the influx rate of the low abundance sample species. The model and analysis are generally applicable to both cationic and anionic ITP assays and likely to a wide range of sample species.

Recovery of SINIS turnstile accuracy in a strongly nonequilibrium regime

We perform a theoretical study of nonequilibrium effects in charge transport through a hybrid single-electron transistor based on a small normal metal (N) island with the gate-controlled number of electrons, tunnel-coupled to voltage-biased superconducting (S) electrodes (SINIS). Focusing on the turnstile mode of the transistor operation with the gate voltage driven periodically, and electrons on the island being out of equilibrium, we find that the current quantization accuracy is a nonmonotonic function of the relaxation rate ${\mathrm{\ensuremath{\Gamma}}}_{\mathcal{F}}$ of the distribution function $\mathcal{F}(\ensuremath{\epsilon})$ on the island due to tunneling, as compared to the drive frequency $f$, electron-electron $1/{\ensuremath{\tau}}_{ee}$, and electron-phonon $1/{\ensuremath{\tau}}_{eph}$ relaxation rates. Surprisingly, in the strongly nonequilibrium regime, $f\ensuremath{\gg}{\mathrm{\ensuremath{\Gamma}}}_{\mathcal{F}}\ensuremath{\gg}{\ensuremath{\tau}}_{ee}^{\ensuremath{-}1},{\ensuremath{\tau}}_{eph}^{\ensuremath{-}1}$, the turnstile current plateau is recovered, similarly to the ideal equilibrium regime, ${\ensuremath{\tau}}_{eph}^{\ensuremath{-}1}\ensuremath{\gg}{\mathrm{\ensuremath{\Gamma}}}_{\mathcal{F}}$. The plateau is destroyed in the quasiequilibrium regime when the electron-electron relaxation is faster than tunneling.

Asymptotically stable states of nonlinear age-structured monocyclic population model I. Travelling wave solution

This paper is devoted to the study of evolutionary dynamics of monocyclic age-structured population including effect of nonlinear mortality (population growth feedback) and proliferation. The total population is considered as partitioned by fixing age into two subpopulations. Individuals of first population are born, mature, die and can at the final fixed age give birth for some new individuals (with null age). Individuals of the second subpopulation are older than those of the first one. They can mature, die and do not have possibility to proliferate. This model was considered as a system of two initial–boundary value problems for nonlinear transport equations with non-local boundary conditions. We obtained explicit travelling wave solution provided the model parameters (coefficients of equations and initial values) satisfy the restrictions that guarantee continuity and smoothness of solution. Explicit form of solution allowed us to perform numerical experiments with high accuracy using the set of parameterized algebraic functions which do not depend from the time. In all performed experiments solutions are attracted to some stationary functions for a long time period (asymptotically stable states of system). We indicated and studied three different regimes of population dynamics. The first is quasi-equilibrium regime, when the maximum value of population density by age, as a function of time, is attracted to the point from the neighbourhood of initial value. This is a result of balance between effects of proliferation and nonlinear mortality (like behaviour of microorganism population in the cases of asymptomatic or healthy carriers). The second and third regimes are characterized by increasing (decreasing) maximum by age values of population density with following attracting to values higher (lower) than initial one. We studied also the impact of parameters of nonlinear death rate on the tremendous growth of population density followed by transition to asymptotically stable states (like infection generalization process in living organisms).

Predictive DFT-based approaches to charge and spin transport in single-molecule junctions and two-dimensional materials: successes and challenges.

CONSPECTUS: The emerging field of flexible electronics based on organics and two-dimensional (2D) materials relies on a fundamental understanding of charge and spin transport at the molecular and nanoscale. It is desirable to make predictions and shine light on unexplained experimental phenomena independently of experimentally derived parameters. Indeed, density functional theory (DFT), the workhorse of first-principles approaches, has been used extensively to model charge/spin transport at the nanoscale. However, DFT is essentially a ground state theory that simply guarantees correct total energies given the correct charge density, while charge/spin transport is a nonequilibrium phenomenon involving the scattering of quasiparticles. In this Account, we critically assess the validity and applicability of DFT to predict charge/spin transport at the nanoscale. We also describe a DFT-based approach, DFT+Σ, which incorporates corrections to Kohn-Sham energy levels based on many-electron calculations. We focus on single-molecule junctions and then discuss how the important considerations for DFT descriptions of transport can differ in 2D materials. We conclude that when used appropriately, DFT and DFT-based approaches can play an important role in making predictions and gaining insight into transport in these materials. Specifically, we shall focus on the low-bias quasi-equilibrium regime, which is also experimentally most relevant for single-molecule junctions. The next question is how well can the scattering of DFT Kohn-Sham particles approximate the scattering of true quasiparticles in the junction? Quasiparticles are electrons (holes) that are surrounded by a constantly changing cloud of holes (electrons), but Kohn-Sham particles have no physical significance. However, Kohn-Sham particles can often be used as a qualitative approximation to quasiparticles. The errors in standard DFT descriptions of transport arise primarily from errors in the Kohn-Sham energy levels (self-energy errors). These errors are small in the strong-coupling regime where the molecular levels are significantly broadened at the Fermi level but are large in the coherent off-resonant tunneling regime where DFT overestimates conductance by orders of magnitude. The DFT+Σ approach uses a physically motivated, parameter free estimate of the self-energy corrections to correct the energy levels in DFT, giving conductance in quantitative agreement with experiment for a large but nonexhaustive class of single-molecule junctions. In 2D materials, the self-energy error is relatively small, and critical issues stem instead from the large length scales in experiments, which make it necessary to consider band-bending within the 2D material, as well as scattering due to electron-phonon interactions, spin-flip interactions, defects, etc.

Low temperature thermally stimulated current characterization of nanoporous TiO2 films

Nanoporous films of TiO2 have been obtained by deposition on an alumina substrate of a commercial colloid and Au contacts have been put on surface for in-plane conductivity measurements. Samples have been characterized by means of a series of sequential thermally stimulated currents scans, from nearly liquid He temperature up to 200 K, in order to get information on: conduction mechanisms, distribution of intragap density of states and recombination times of free an localized carriers. A model for hopping conductivity has been considered to properly take into account of localized states filling; it has been used to fit the experimental data, without a-priori assumptions on the nature of the conduction mechanisms. It is found that hopping conductivity prevails over free-carrier, in quasi-equilibrium regime, in the investigated temperature range.

Self-Assembly of Multicomponent Structures In and Out of Equilibrium

Theories of phase change and self-assembly often invoke the idea of a "quasiequilibrium," a regime in which the nonequilibrium association of building blocks results nonetheless in a structure whose properties are determined solely by an underlying free energy landscape. Here we study a prototypical example of multicomponent self-assembly, a one-dimensional fiber grown from red and blue blocks. We find that if the equilibrium structure possesses compositional correlations different from those characteristic of random mixing, then it cannot be generated without error at any finite growth rate: there is no quasiequilibrium regime. However, by exploiting dynamic scaling, structures characteristic of equilibrium at one point in phase space can be generated, without error, arbitrarily far from equilibrium. Our results, supported by mean-field theory in higher dimensions, thus suggest a "nonperturbative" strategy for multicomponent self-assembly in which the target structure is, by design, not the equilibrium one.

The role played by a polymer matrix in the transfer of charge carriers in molecularly doped polumers

Transient current curves were recorded for polystyrene and polycarbonate doped with 15 wt % tritolylamine using both surface and volume charge carrier generation. The multiple trapping model was used to perform numerical calculations of time-of-flight curves for the published Gaussian disorder model parameters. The calculation results were compared with the experimental data. It was shown that the experimental and calculated curves satisfactorily coincided. The flat plateau observed in time-of-flight curves should not be associated with the establishment of a quasi-equilibrium transport regime.

Quasiequilibrium directed hopping in a time-dependent two-well periodic potential

We consider the directed motion of a Brownian particle in a two-well periodic potential with time-varying barriers and wells described by arbitrary periodic functions of time, v(t) and u(t), alternating with the period τ. In the framework of the low-temperature kinetic approach, we obtain explicit formulas for the probabilities of finding the particle in potential wells, average velocity of directed motion, input energy P(in) and useful work P(out) against additionally introduced stationary load force f. These formulas are considerably simplified by the assumption of the quasiequilibrium regime of motion corresponding to small values of u(t) and f. It is shown that depending on the same or opposite parity of the functions v(t) and u(t) with respect to time reversal, the motion direction of a Brownian particle is retained or reversed under the reversal of the direction of movement along the (v-u) loop in the phase space of the functions v(t) and u(t), and the nondiagonal kinetic coefficients are mutually symmetric or antisymmetric. In the adiabatic limit τ→∞, the average velocity is proportional to τ(-1) in two cases: (i) the above loop has a nonzero area, (ii) the functions v(t) and u(t) are proportional to each other (zero loop area) and include intervals of fast changes with small durations τ(0) on the period τ of their variations. In both of these cases, the efficiency of energy conversion, η=P(out)/P(in), tends to unity at large variations of the barriers v(t). In the second case, the deviation of η from unity can be split into two contributions: The former decreases exponentially with increasing amplitude v(0) of v(t), while the latter is a small nonadiabatic correction proportional to v(0)(-3/2). It is the nonadiabatic correction that limits high efficiencies at large variations of barriers.

Imaginary Magnetic Tweezers for Massively Parallel Surface Adhesion Spectroscopy

A massively parallel magnetic tweezer system has been constructed that utilizes the self-repulsion of colloidal beads from a planar interface via a magnetic dipole image force. Self-repulsion enables the application of a uniform magnetic force to thousands of beads simultaneously, which permits the measurement of unbinding histograms at the lowest loading rates ever tested. The adhesion of 9.8 μm polystyrene beads to a fluorocarbon, PEG, and UV-irradiated PEG surfaces were measured between 10(-3)-10(0) pN/s force loading rates, revealing the presence of both kinetic and quasi-equilibrium unbinding regimes.

Modelling of fluidized bed biomass gasification in the quasi-equilibrium regime for preliminary performance studies of energy conversion plants

Thermodynamic equilibrium-based models of gasification process are relatively simple and widely used to predict producer gas characteristics in performance studies of energy conversion plants. However, if an unconstrained calculation of equilibrium is performed, the estimations of product gas yield and heating value are too optimistic. Therefore, reasonable assumptions have to be made in order to correct the results. This paper proposes a model of the process that can be used in case of deficiency of information and unavailability of experimental data. The model is based on free energy minimization, material and energy balances of a single zone reactor. The constraint quasiequilibrium calculations are made using approximated amounts of non-equilibrium products, i.e. solid char, tar, CH4 and C2H4. The yields of these products are attributed to fuel characteristics and estimated using experimental results published in the literature. A genetic algorithm optimization technique is applied to find unknown parameters of the model that lead to the best match between modelled and experimental characteristics of the product gas. Finally, generic correlations are proposed and quality of modelling results is assessed in the aspect of its usefulness for performance studies of power generation plants.

Modeling the global circulation response and the regional response of the Arctic Ocean to the external forcing anomalies

The problem of numerical modeling and analysis of the large-scale World Ocean circulation variability under variations of the external forcing is considered. A numerical model was developed in the INM RAS and is based on the primitive equations of the ocean circulation written in a spherical generalized σ-coordinate system. The model’s equations are approximated on a grid with resolution of 2.5° × 2° × 33, and the North Pole is displaced to the continental point (60°E, 60.5°N). There are two stages for the numerical experiments. The quasi-equilibrium circulation of the World Ocean under the climatological atmospheric forcing is simulated at the first stage. The run is carried out over a period of 3000 years during which a quasi-equilibrium model regime is formed. At the second stage, the sensitivity of the model ocean circulation to the atmospheric forcing perturbations in the Southern Hemisphere is studied. According to the results, the strongest regional changes in the hydrography take place in the Arctic Ocean. Substantial changes of sea’s surface height and local anomalies of the temperature and salinity are formed there.