Nonequilibrium Thermodynamic State Research Articles

Bimodal plate structures induced by pulsed laser in duplex-phase Zr alloy

A duplex-phase Zr-2.5Nb alloy was treated by pulsed laser, followed by careful microstructural characterization using field emission gun scanning electron microscope and attached electron backscatter diffraction. Beneath the modification zones with common uniform α-plate structures (UPS), a layer of unreported bimodal α-plate structures (BPS) featured by coarse (submicron) plates forming multiple cores surrounded by dense fine (nanoscale) plates was found. Presence of such BPS is attributed to non-equilibrium thermodynamic conditions induced by the pulsed laser treatments. Limited diffusion of Nb due to the short pulse during laser heating allows β phases with distinctly different Nb contents to be presented: Nb-enriched prior β films and Nb-depleted β phases, transforming into the fine and the coarse plates during cooling, respectively. Orientation analyses show that both types of plates in the BPS are aroused essentially from a single β orientation, suggesting epitaxial growth of the Nb-depleted β phases from the preexisting β films.

Two-Temperature Nonequilibrium Model of a Marine Boundary Layer Laden with Evaporating Ocean Spray under High-Wind Conditions

AbstractA nonequilibrium two-temperature multiphase model of the atmospheric boundary layer above wave crests that is laden with evaporating ocean spray in high-wind condition is presented. The governing equations are derived from basic physical principles of conservation of momentum, mass, and thermal energy in multiphase flows. The model derivation uses an Eulerian multifluid approach that considers spray as a continuous medium interacting with the gas phase. The E − ε turbulence closure is used. The developed theoretical framework accounts for the nonuniform ocean spray distribution and the thermal energy exchange between air and spray droplets that, in general, have different temperatures above the wave crest level. Such thermodynamic nonequilibrium conditions are shown to exist when the spray concentration is relatively low and the air humidity is far from saturation. The mechanical and thermodynamic effects of the evaporating spray on airflow and heat transport characteristics are obtained and shown to depend sensitively on the spray concentration.

Electrocaloric Effect in Ba(Zr,Ti)O3–(Ba,Ca)TiO3 Ceramics Measured Directly

In this paper, we report on studies of the electrocaloric (EC) effect in lead‐free (1−x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 ceramics with compositions range between 0.32 ≤ x ≤ 0.45. The EC effect was measured directly using a modified differential scanning calorimeter. The maximum EC temperature change, ΔTdirect = 0.33 K under an electric field of 2 kV/mm, was observed for the composition with x = 0.32 at ~63°C. We found that the EC effect peaks not only around the Curie temperature but also at the transition between the ferroelectric phases with different symmetries. A strong discrepancy observed between the results of the direct measurements and indirect estimations points out that using Maxwell's equations is invalid for the thermodynamic nonequilibrium conditions that accompany only partial (incomplete) poling of ceramics. We also observe a nonlinearity of the EC effect above the Curie temperature and in the temperature range corresponding to the tetragonal ferroelectric phase.

Crystallization of glass-forming liquids: Specific surface energy

A generalization of the Stefan-Skapski-Turnbull relation for the melt-crystal specific interfacial energy is developed in terms of the generalized Gibbs approach extending its standard formulation to thermodynamic non-equilibrium states. With respect to crystal nucleation, this relation is required in order to determine the parameters of the critical crystal clusters being a prerequisite for the computation of the work of critical cluster formation. As one of its consequences, a relation for the dependence of the specific surface energy of critical clusters on temperature and pressure is derived applicable for small and moderate deviations from liquid-crystal macroscopic equilibrium states. Employing the Stefan-Skapski-Turnbull relation, general expressions for the size and the work of formation of critical crystal clusters are formulated. The resulting expressions are much more complex as compared to the respective relations obtained via the classical Gibbs theory. Latter relations are retained as limiting cases of these more general expressions for moderate undercoolings. By this reason, the formulated, here, general relations for the specification of the critical cluster size and the work of critical cluster formation give a key for an appropriate interpretation of a variety of crystallization phenomena occurring at large undercoolings which cannot be understood in terms of the Gibbs’ classical treatment.

Study of Current-Voltage Characteristics of Electroactive Polymers Placed in Non-Equilibrium Thermodynamic Conditions

The article proposes a method of studying the localized states (“traps”) in the band gap of dielectrics. The method combines both the method of current-voltage characteristics and the method of thermally stimulated currentIt is intended to use the method for analyzing the materials, in which trapping states are quasi-continuously distributed. The article gives an example of using the method for studying of the advanced polymer material - polydiphenylenephthalide. It presents calculation of values of the activation energies and the depth of the traps. The results are compared with the data obtained by traditional methods.

TOPOLOGY AND DISTINCT FEATURES OF FLASHING FLOW IN AN INJECTOR NOZZLE

The effect of thermodynamic non-equilibrium conditions (liquid superheat) on the two-phase flow field developing inside an axisymmetric, single-orifice nozzle is numerically investigated by means of different variations of a two-phase mixture model. A number of hybrid mass-transfer models that take into account both the effect of inertial forces (cavitation) and liquid superheat have been proposed and evaluated against widely used, pure-cavitation models, in order to pinpoint the flow conditions necessary for flash boiling to occur and to elucidate the distinct features of the phase and velocity fields that characterize flashing flows. The effect of the number of nucleation sites, required as an input by the models, on the developing two-phase flow has also been looked into. The numerical results have shown that incorporation of an additional term corresponding to liquid superheat into the mass-transfer rate leads to increased evaporation rate, compared to pure-cavitation models with liquid vaporization taking place within the entire nozzle cross section. The cavitation nucleation sites have been confirmed to act as the necessary flow perturbations required for flash boiling to occur. In addition, the developing velocity field has been found to be in close correlation to the mass-transfer rate imposed. It has been established that increased liquid evaporation leads to choked-flow conditions prevailing in a larger part of the nozzle and accompanied by a more significant expansion of the two-phase mixture downstream of the injector exit that results to increased jet cone angle. Finally, the results demonstrated that liquid cooling due to the increased mass-transfer rate is not significant within the nozzle and thus consider that a constant liquid temperature produces adequately accurate results with a decreased computational cost.

Experimental investigation on no-vent fill process using tetrafluoromethane (CF4)

This paper investigates the transfer of liquid cryogens using a no-vent fill (NVF) process experimentally to identify the dominant NVF parameters. The experimental apparatus has been fabricated with extensive instrumentations to precisely study the effects of each NVF parameter. Liquid tetrafluoromethane (CF4) is selected as the working fluid due to its similar molecular structures and similar normal boiling point and triple point with liquid methane which has been considered as an attractive future cryogenic propellant. The experimental results show that the initial receiver tank wall temperature and the incoming liquid temperature are the primary factors that characterize the (non-equilibrium) thermodynamic state at the start of a NVF transfer. The supply pressure is also critical as it indicates the ability to condense vapor in the receiver tank. A non-dimensional map based on energy balance is proposed to find acceptable initial conditions of the filling volume at the desired final tank pressure. The non-dimensional map shows good agreement with the NVF data not only in this paper but also in the previous research.

(Invited) The Effect of Molecular Dynamics on Charge Transport in Organic Semiconductors

Organic semiconductors are studied extensively for their incorporation in next generation large-area, low-weight flexible optoelectronic applications. Librational motion is ubiquitous in such materials; this motion, however, has been difficult to connect with experimental observations of a material’s electronic properties. Here we present the effect of libration on charge transport in monomolecular compounds and binary charge-transfer (CT) complexes through a combined experimental and theoretical approach. The case study of trans-stilbene (STB) and its CTs with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (STB:F4TCNQ) and 7,7,8,8-tetracyanoquinodimethane (STB:TCNQ) will be discussed. It will be shown that the change in amplitude of the torsional oscillation (libration) of the double bond connecting the C7 and C7a carbons in the stilbene molecule results in a crossover from thermally activated to a temperature-independent charge transport. This pedal-like (crankshaft) motion, is responsible for inter-conversion between the two possible conformers. At low temperature the libration amplitude is not sufficiently large to mediate this rotation, generating thermodynamic non-equilibrium states and resulting in freezing in of orientational disorder. The transport can take place only via tunneling, therefore being temperature-independent. At higher temperatures, when inter-conversion motion is fast, a transition to temperature-activated hopping transport occurs. The following people contributed to this work: K. P. Goetz, A. Fonari, D. Vermeulen, P. Hu, H. Jiang, P. J. Diemer, J. W. Ward, M. E. Payne, C. S. Day, C. Kloc, V. Coropceanu, L.E. McNeil, and O. D. Jurchescu.

Biological organisation as closure of constraints.

We propose a conceptual and formal characterisation of biological organisation as a closure of constraints. We first establish a distinction between two causal regimes at work in biological systems: processes, which refer to the whole set of changes occurring in non-equilibrium open thermodynamic conditions; and constraints, those entities which, while acting upon the processes, exhibit some form of conservation (symmetry) at the relevant time scales. We then argue that, in biological systems, constraints realise closure, i.e. mutual dependence such that they both depend on and contribute to maintaining each other. With this characterisation in hand, we discuss how organisational closure can provide an operational tool for marking the boundaries between interacting biological systems. We conclude by focusing on the original conception of the relationship between stability and variation which emerges from this framework.

Nonequilibrium Thermodynamic State Variables of Human Self-Paced Rhythmic Motions: Canonical-Dissipative Approach, Augmented Langevin Equation, and Entropy Maximization

Nonequilibrium thermodynamic state variables are derived for a stochastic limit-cycle oscillator model that has been used in motor control research to describe human rhythmic limb movements. The nonequilibrium thermodynamic state variables are regarded as counterparts to the thermodynamic state variables entropy, internal energy, and free energy of equilibrium systems. The derivation of the state variables is based on maximum entropy distributions of the Hamiltonian energy of the stochastic limit-cycle oscillators. The limit-cycle oscillator model belongs to the class of canonical-dissipative systems, on the one hand, and, on the other hand, can be cast into the form of an augmented Langevin equation. Both concepts are known as physical models for open systems. Experimental data from paced and self-paced pendulum swinging experiments are presented and estimates for the nonequilibrium thermodynamic state variables are given. Entropy and internal energy increased with increasing oscillation frequency both for the paced and self-paced conditions. Interestingly, the nonequilibrium free energy decayed when oscillation frequency was increased, which is akin to the decay of the Landau free energy when the control parameter is scaled further away from its critical value.

Air Collisional-Radiative Modeling with Heavy-Particle Impact Excitation Processes

This paper reviews the electron- and heavy-particle impact processes governing the population/depletion of the states of N, O, , and , which can be significantly affected by nonequilibrium conditions while strongly radiating in lunar-return shock layers. The collisional-radiative model developed in this work includes electron-impact excitation, ionization, heavy-particle impact excitation, vibration–electron, vibration–translation, dissociation and bound–bound radiative mechanisms. The available experimental and theoretical reaction rates governing these processes were critically reviewed to produce a reliable set of rate constants. The collisional-radiative model was then applied to typical nonequilibrium thermodynamic conditions encountered during lunar-return Earth reentry. The effect of heavy-particle impact processes is discussed.

From Where Did the Water Come That Filled the Earth’s Oceans? A Widely Overlooked Redox Reaction

Though two-thirds of Earth’s surface is covered by oceans, measurements of hydroxyl concentrations in upper mantle minerals, specifically in olivine, reportedly provide surprisingly low values. This has been interpreted to mean that there is little dissolved H2O in the Earth’s mantle. By inference, when Earth formed, there might not have been able enough water to fill the oceans through volcanic degassing. It has therefore been proposed that the missing water was delivered to Earth from space, through comets and other impacting bodies. However, the reported low hydroxyl concentrations in olivine and similar mineralsis probably based on a profound misunderstanding of a solid state reaction that converts hydroxyls into something more difficult to detect. There is indeed a redox reaction that converts, during cooling, solute hydroxyls in the matrix of minerals into peroxy plus H2. This widely overlooked redox conversion takes place under thermodynamic non-equilibrium conditions. Its significance is that any mineral and any rock available for collection at the Earth surface has gone through a process that causes hydroxyls, the telltale sign of dissolved H2O, to change into peroxyplusH2. The H2 molecules are diffusively mobile and may leave even structurally dense mineral grains. The remaining peroxy thus become the memory of the “true” solute H2O content, besides a few residual hydroxyls. Though first described over 30 years ago, this redox conversion has been largely ignored. As a result it is unknown how much H2O is contained in the Earth’s upper mantle but it is certainly much more than has been assumed until now on the basis of analysis of residual hydroxyls.

Grand Challenges in Glass Science

INTRODUCTION Glass science offers researchers an ample range of open questions, starting from one of the most difficult problems in science: the basic nature of the glassy state. Atomic-level descriptions of the glassy state are extremely complex due to the lack of long-range order found in crystalline materials. Our understanding of fundamental glass physics and chemistry is also hindered by the non-equilibrium thermodynamic state of glass. Recent theoretical and experimental advances are enabling the field to mature from an empirical discipline to one built upon rigorous scientific principles. These advancements not only offer a remarkable level of understanding but also contribute to the atomic-level design of novel functional glasses (Mauro et al., 2013a). Glass science combines the cutting edge of a multitude of technical subjects: physics, chemistry, geology, engineering, and mathematics. Glass transition and relaxation phenomena are at the frontiers of condensed matter and statistical physics. From a chemical perspective, a nearly infinite combination of compositions can lead to successful glass formation. To facilitate progress at a large scale and exploit all of the unique properties that glasses may offer, the boundaries of glass engineering technology must also be pushed forward. Recent advances of the domain have coincided with an unprecedented demand for glass as a high-tech material in consumer electronic devices. Working in the field of glass has never been more stimulating – glass plays a critical role in solving several of the global energy and healthcare challenges of today.

Theoretical and numerical predictions of hypervelocity impact-generated plasma

The hypervelocity impact generated plasmas (HVIGP) in thermodynamic non-equilibrium state were theoretically analyzed, and a physical model was presented to explore the relationship between plasma ionization degree and internal energy of the system by a group of equations including a chemical reaction equilibrium equation, a chemical reaction rate equation, and an energy conservation equation. A series of AUTODYN 3D (a widely used software in dynamic numerical simulations and developed by Century Dynamic Inc.) numerical simulations of the impacts of hypervelocity Al projectile on its targets at different incident angles were performed. The internal energy and the material density obtained from the numerical simulations were then used to calculate the ionization degree and the electron temperature. Based on a self-developed 2D smooth particle hydrodynamic (SPH) code and the theoretical model, the plasmas generated by 6 hypervelocity impacts were directly simulated and their total charges were calculated. The numerical results are in good agreements with the experimental results as well as the empirical formulas, demonstrating that the theoretical model is justified by the AUTODYN 3D and self-developed 2D SPH simulations and applicable to predict HVIGPs. The study is of significance for astrophysical and cosmonautic researches and safety.

Absorption of a single 500 fs laser pulse at the surface of fused silica: Energy balance and ablation efficiency

Ablation of fused silica by a single femtosecond laser pulse of 500 fs pulse duration is investigated from the perspective of efficiency of incident photons to remove matter. We measure the reflected and transmitted fractions of the incident pulse energy as a function of fluence, allowing us to recover the evolution of absorption at the material surface. At the ablation threshold fluence, 25% of incident energy is absorbed. At high fluences, this ratio saturates around 70% due to the appearance of a self-triggered plasma mirror (or shielding) effect. By using the energy balance retrieved experimentally and measurements of the ablated volume, we show that the amount of absorbed energy is far above the bonding energy of fused silica at rest and also above the energy barrier to ablate the material under non-equilibrium thermodynamic conditions. Our results emphasize the crucial role of transient plasma properties during the laser pulse and suggest that the major part of the absorbed energy has been used to heat the plasma formed at the surface of the material. A fluence range yielding an efficient and high quality ablation is also defined, which makes the results relevant for femtosecond micromachining processes.

H, D and HD adsorption upon the metal-organic framework [CuZn(btc)] studied by pulsed ENDOR and HYSCORE spectroscopy

The adsorption of hydrogen has become interesting in terms of gas separation as well as safe and reversible storage of hydrogen as an energy carrier. In this regard, metal-organic framework compounds are potential candidates. The metal-organic framework [CuZn(btc)] as a partially Zn-substituted analogue of the well known compound HKUST-1 is well suited for studying adsorption geometries at cupric ions by electron paramagnetic resonance (EPR) methods due to the formation of few mixed Cu/Zn paddle wheel units with isolated S = 1/2 electron spins. The adsorption of hydrogen (H2) as well as the deuterium (D2) and HD molecules were investigated by continuous wave EPR and pulsed ENDOR and HYSCORE spectroscopy. The principal values of the proton and deuterium hyperfine coupling tensors and were determined by spectral simulations as well as of the deuterium nuclear quadrupole tensor for adsorbed HD and D2. The results show a side-on coordination of HD and D2 with identical Cu–H and Cu–D distances rCuX = 2.8 Å with the tensors and aligned parallel to the C4 symmetry axis of the paddle wheel unit. A thermodynamic non-equilibrium state with J = 1, mJ = ±1 is indicated by the experimental data with and averaged by rotation around C4.

DELAYED EQUILIBRIUM MODEL (DEM) OF FLASHING CHOKED FLOWS RELEVANT TO LOCA

In the context of nuclear reactor safety, a pipe breach in the primary circuit is the initiator of a loss of coolant accident (LOCA). The calculation of leak rates involving the discharge of water and steam mixtures plays an important role in the modeling of LOCAs for both generation (GEN) II and GEN III reactors, and also for the supercritical water reactor of GEN IV. Indeed, the flow though the breach determines the depressurization rate of the system and the time to core uncover, which in turn are of major concern for when and how different mitigation auxiliary systems will be initiated and efficient. This paper deals with the delayed equilibrium model (DEM), which focuses on thermodynamic non-equilibrium conditions that prevail in the flashing flow process near the critical section. The DEM developed at the University of Louvain is a one-dimensional model for the choked or critical flow rate in steady-state or quasi-steady-state conditions, which deals with the effect of the metastable liquid phase during the flashing process. The DEM has been compared with 500 experimental data. The DEM was recently assessed against the Super-Mobydick and Bethsy experiments done at the Commissariat a L'Energie Atomique during the 1980s.

Non-equilibrium "thermal noise" of low loss oscillators

The RareNoise project aims at studying how ground-based gravitational wave detector are affected by the thermodynamic non-equilibrium states which are present in their experimental apparatus. We present the RareNoise experimental work which focuses on the study of the 'thermal noise' of low loss oscillators subject to steady-state thermal gradients. We also present the first results of the experimental campaign on steady-state non-equilibrium oscillators around room temperature.

A PROPER NONLOCAL FORMULATION OF QUANTUM MAXIMUM ENTROPY PRINCIPLE IN STATISTICAL MECHANICS

By considering Wigner formalism, the quantum maximum entropy principle (QMEP) is here asserted as the fundamental principle of quantum statistical mechanics when it becomes necessary to treat systems in partially specified quantum states. From one hand, the main difficulty in QMEP is to define an appropriate quantum entropy that explicitly incorporates quantum statistics. From another hand, the availability of rigorous quantum hydrodynamic (QHD) models is a demanding issue for a variety of quantum systems. Relevant results of the present approach are: (i) The development of a generalized three-dimensional Wigner equation. (ii) The construction of extended quantum hydrodynamic models evaluated exactly to all orders of the reduced Planck constant ℏ. (iii) The definition of a generalized quantum entropy as global functional of the reduced density matrix. (iv) The formulation of a proper nonlocal QMEP obtained by determining an explicit functional form of the reduced density operator, which requires the consistent introduction of nonlocal quantum Lagrange multipliers. (v) The development of a quantum-closure procedure that includes nonlocal statistical effects in the corresponding quantum hydrodynamic system. (vi) The development of a closure condition for a set of relevant quantum regimes of Fermi and Bose gases both in thermodynamic equilibrium and nonequilibrium conditions.

Delayed equilibrium model and validation experiments for two-phase choked flows relevant to LOCA

Abstract This paper deals with the 1-D Delayed Equilibrium Model (DEM) for choked or critical flow rate in steady state or quasi-steady state conditions and the selection of the relevant experimental data for assessing such models. In particular, the focus is made on thermodynamic non-equilibrium conditions, which prevail in the flashing process near the critical section. In this regard, relaxation models such as the DEM developed and tested in previous studies at UCL was revisited and improved in view of their implementation in the next CATHARE code generation during the EU NURISP (NUclear Reactor Integrated Software Platform) project. A methodology to implement the DEM into is developed. Some new results of the DEM are compared against experimental data such as Super Moby-Dick experiments done in CEA and the well-known Marviken experiments performed at quasi-real scale geometry of Nuclear Plant.