Nonideal Systems Research Articles

Joint Training and Reflection Pattern Optimization for Non-Ideal RIS-Aided Multiuser Systems

Joint Training and Reflection Pattern Optimization for Non-Ideal RIS-Aided Multiuser Systems

A new activity coefficient model for describing adsorbed phase nonidealities

The following study introduces a new adsorbed phase activity coefficient model, the SPLINT model, for describing nonideal multicomponent systems. The derivation is presented and simplification to the thermodynamically robust ABC model in the low‑coverage limit is shown. Both the SPLINT and ABC models are fit to 25 binary systems. Thermodynamic consistency of the data is established through multiple consistency tests including the intersection rule, closed‑loop reduced spreading pressure integration, the Gibbs‑Duhem integral equality, and alignment of pure and binary data. Regressed parameters are used in Real Adsorbed Solution Theory to predict both binary and ternary adsorption. The ABC and SPLINT models accurately describe systems with considerable nonideality when the activity coefficients are symmetric; however, the SPLINT model is required for accurate description of systems with complex, asymmetric activity coefficient behavior. The new model includes one more fitting parameter than the ABC model for a single binary system, but less across multiple data sets and higher‑order systems due to the theoretical basis. The importance of capturing activity coefficient asymmetry is demonstrated with a highly nonideal system across various pressures and temperatures measured by the present authors using the Integral Mass Balance method with HFC‑125 (pentafluoroethane), HFC‑32 (difluoromethane), and zeolite H‑ZSM‑5. The theoretical basis of the SPLINT model is further enforced by presenting two methods for predicting activity coefficients with the SPLINT model: correlating the fitting parameters individually and simultaneously regressing pure isosteric heat data to extract SPLINT fitting parameters. The study concludes with a discussion of pure and binary HFC‑125/HFC‑32 data with zeolite H‑ZSM‑5. A possible binary adsorption mechanism is proposed based on isosteric heat and excess enthalpy predictions and observed system irreversibility.

Thermal Hazard Analysis of Two Non-Ideal Explosives Based on Ammonium Perchlorate/Ammonium Nitrate and Aluminium Powder.

In recent years, various kinds of civil explosive detonation accidents have occurred frequently around the world, resulting in substantial human casualties and significant property losses. It is generally believed that thermal stimulation plays a critical role in triggering the detonation of explosives; consequently, the study of the thermal hazards of explosives is of great significance to many aspects of safety emergency management practices in the production, transportation, storage, and use of explosives. It is known that the thermal stability of the ammonium perchlorate-aluminium system and the ammonium nitrate-aluminium system has been extensively investigated previously in the literature. However, there is a paucity of research on the thermal hazard characteristics of non-ideal explosives under varying oxygen balance conditions within the academic sphere. Therefore, this research focused on the study of the thermal hazards of non-ideal explosives based on thermokinetic analysis. The thermal hazards of non-ideal explosive mixtures of ammonium perchlorate and aluminium and of ammonium nitrate and aluminium were studied by thermal analysis kinetics. The thermokinetic parameters were meticulously studied through differential scanning calorimetry (DSC) analysis. The results showed that the peak reaction temperature and activation energy of the ammonium perchlorate-aluminium system were significantly higher than those of the ammonium nitrate-aluminium system. Under the condition of zero oxygen balance, the peak reaction temperature of the ammonium nitrate-aluminium system was 259 °C (heating rate 5 °C/min), and the activation energy was 84.7 kJ/mol. Under the same conditions, the peak reaction temperature and activation energy of the ammonium perchlorate-aluminium system were 292 °C (heating rate 5 °C/min) and 94.9 kJ/mol, respectively. These results indicate that the ammonium perchlorate-aluminium system has higher safety under the same thermal stimulation conditions. Furthermore, research on both non-ideal explosive systems reveals that the activation energy is at its peak under negative oxygen balance conditions, recorded at 104.2 kJ/mol (ammonium perchlorate-aluminium) and 86.2 kJ/mol (ammonium nitrate-aluminium), which indicates a higher degree of safety. Therefore, the investigation into the thermal hazards of non-ideal explosive systems under different oxygen balance conditions is of utmost importance for the enhancement and improvement of safety emergency management practices.

Computer Simulation of Three-Phase Equilibria for Some Water/n-Alkane Binary Systems.

In this work, the vapor-liquid-liquid equilibrium (VLLE) of the water/n-pentane, water/n-hexane, water/n-octane, and water/n-decane binary systems is calculated by computer simulation using the NVT-Gibbs ensemble (in the version of three simulation boxes) combined with the configurational bias Monte Carlo method. The combination of both methods, the molecular potential models used, and the simulation details allowed us to calculate the triphasic equilibrium properties of the systems studied: the densities of the three phases in equilibrium, their compositions, and potential energies. In previous works, these simulations were not carried out at a temperature range nor water/n-alkanes systems simulated in this work, probably because they are highly nonideal systems; so, to the best of our knowledge, this is the first time that this phenomenon is studied in detail. The results from VLLE simulations of the water/n-pentane system for temperatures from 343.2 to 435 K, the water/n-hexane system for temperatures from 373.11 to 473.15 K, the water/n-octane system for temperatures from 310.9 to 500 K, and for the water/n-decane system for temperatures from 374.15 to 525 K are reported here. The temperature range was selected in concordance with the experimental data available for an adequate study of the VLLE simulation results. The subcritical densities (vapor and liquid rich in n-alkane phases) at various temperatures fit well with the scaling law and the law of rectilinear diameters, allowing the estimation of upper critical end point temperature and density of the VLLE. The simulation results show a good prediction with experimental data reports in the literature.

Ab Initio Path Integral Monte Carlo Simulations of the Uniform Electron Gas on Large Length Scales.

The accurate description of non-ideal quantum many-body systems is of prime importance for a host of applications within physics, quantum chemistry, materials science, and related disciplines. At finite temperatures, the gold standard is given by ab initio path integral Monte Carlo (PIMC) simulations, which do not require any empirical input but exhibit an exponential increase in the required computation time for Fermionic systems with an increase in system size N. Very recently, computing Fermionic properties without this bottleneck based on PIMC simulations of fictitious identical particles has been suggested. In our work, we use this technique to perform very large (N ≤ 1000) PIMC simulations of the warm dense electron gas and demonstrate that it is capable of providing a highly accurate description of the investigated properties, i.e., the static structure factor, the static density response function, and the local field correction, over the entire range of length scales.

Mutual aid instead of mutual restraint: interactive probing for topological charge and phase of a vortex beam of large aberrations

An imperfect propagation environment or optical system would introduce wavefront aberrations to vortex beams. The phase aberrations and orbital angular momentum in a vortex beam are proved to be mutually restrictive in parameter measurement. Aberrations make traditional topological charge (TC) probing methods ineffective while the phase singularity makes phase retrieval difficult due to the aliasing between the wrapped phase jump and the vortex phase jump. An interactive probing method is proposed to make measurements of the aberrated phase and orbital angular momentum in a vortex beam assist rather than hinder each other. The phase unwrapping is liberated from the phase singularity by an annular shearing interference technique while the TC value is determined by a Moiré technique immune to aberrations. Simulation and experimental results proving the method effective are presented. It is of great significance to judge the characteristics of vortex beams passing through non-ideal environments and optical systems.

Simulation Methods to Model Chemical Processes at Elevated Pressures and the Theory of Non-Ideal Reaction Systems

Simulation Methods to Model Chemical Processes at Elevated Pressures and the Theory of Non-Ideal Reaction Systems

Simulation Methods to Model Chemical Processes at Elevated Pressures and the Theory of Non-ideal Reaction Systems

Literature analysis shows that the main method to model the equilibrium characteristics of reaction systems at elevated pressures, including processes under supercritical conditions, are equations of state describing the non-ideality of the vapor and liquid phases, while the law of mass action is applied to describe the kinetics of the elementary and chemical stages. The mentioned difference in the types of models used to describe the equilibrium and kinetic characteristics of the same experimental system under study violates thesecond law of thermodynamics formulated by Clausius. The only theoretical method consistent with the second law of thermodynamics is the molecular theory based on the lattice gas model. In order to satisfy the second law of thermodynamics, molecular models must provide the self-consistent description of the rates of the chemical process at the equilibrium and elementary stages. This means that the molecular models must providea single mathematical apparatus to calculate the states of the system both outside and inside the equilibrium point. The molecular models can differ in both the effective parameters of the interparticle interaction and the methods of refining these models due to taking into account distinctions in sizes, contributions of the vibrational motions of the components, as well as the accuracy of description of the correlation effects. To ensure the self-consistent description of the equilibrium and kinetics, the models must at least reflect the effects of direct correlations. One-particle approximations (mean field, chaotic, density functional) do not correspond to the self-consistency condition and violate the second law of thermodynamics.

Nonideal Reaction-Diffusion Systems: Multiple Routes to Instability.

We develop a general classification of the nature of the instabilities yielding spatial organization in open nonideal reaction-diffusion systems, based on linear stability analysis. This encompasses dynamics where chemical species diffuse, interact with each other, and undergo chemical reactions driven out of equilibrium by external chemostats. We find analytically that these instabilities can be of two types: instabilities caused by intermolecular energetic interactions (E type), and instabilities caused by multimolecular out-of-equilibrium chemical reactions (R type). Furthermore, we identify a class of chemical reaction networks, containing unimolecular networks but also extending beyond them, that can only undergo E-type instabilities. We illustrate our analytical findings with numerical simulations on two reaction-diffusion models, each displaying one of the two types of instability and generating stable patterns.

(Invited) a Dynamically Reprogrammable Surface with Self-Evolving Shape Morphing

Shape-morphing soft materials are ubiquitous in living systems. They are of increasing relevance to emerging technologies in soft machines, flexible electronics, and smart medicine. The past decade has witnessed phenomenal investment in developing active materials that can shift their shapes, and henceforth their performing functions. However, creating schemes to swiftly reprogram target shapes after fabrication remains challenging. Complexities associated with the operating physics and disturbances from the environment can stop the use of deterministic theoretical models to guide inverse design and control strategies. In this work, we describe a dynamically reprogrammable metasurface with embedded actuation, sensing, and feedback control. The voltage-controlled electromagnetic force drives a flexible, conductive 2D mesh into a diverse set of complex 3D surfaces in the presence of a static magnetic field. The unusual construction of the metasurface from a matrix of filamentary metal traces enables the system to adopt an approximately linear model for inverse design. Implementing an in-situ stereo-imaging feedback strategy with a digitally controlled actuation scheme guided by an optimization algorithm yields surfaces that can morph into target shapes without any presuming models. The closed-loop self-evolving inverse design approach opens opportunities for physical simulations for non-linear or non-ideal systems.

Molecular Modeling of Supercritical Processes and the Lattice—Gas Model

The existing possibilities for modeling the kinetics of supercritical processes at the molecular level are considered from the point of view that the Second Law of thermodynamics must be fulfilled. The only approach that ensures the fulfillment of the Second Law of thermodynamics is the molecular theory based on the discrete–continuous lattice gas model. Expressions for the rates of the elementary stage on its basis give a self-consistent description of the equilibrium states of the mixtures under consideration. The common usage today of ideal kinetic models in SC processes in modeling industrial chemistry contradicts the non-ideal equation of states. The used molecular theory is the theory of absolute reaction rates for non-ideal reaction systems, which takes into account intermolecular interactions that change the effective activation energies of elementary stages. This allows the theory to describe the rates of elementary stages of chemical transformations and molecular transport at arbitrary temperatures and reagent densities in different phases. The application of this theory in a wide range of state parameters (pressure and temperature) is considered when calculating the rates of elementary bimolecular reactions and dissipative coefficients under supercritical conditions. Generalized dependencies are calculated within the framework of the law of the corresponding states for the coefficients of compressibility, shear viscosity, and thermal conductivity of pure substances, and for the coefficients of compressibility, self- and mutual diffusion, and shear viscosity of binary mixtures. The effect of density and temperature on the rates of elementary stages under supercritical conditions has been demonstrated for a reaction’s effective energies of activation, diffusion and share viscosity coefficients, and equilibrium constants of adsorption. Differences between models with effective parameters and the prospects for developing them by allowing for differences in size and contributions from the vibrational motions of components are described.

Modeling and simulation of pervaporation (PV) separation for alcohol dehydration

The separation performance of commercial crosslinked poly (vinyl alcohol) (PVA) membranes (i.e., the new commercial membrane PERVAP™ 4100 H F and standard membrane PERVAP™ 4100) used for the dehydration of two alcohol-water systems (i.e., ethanol-water and isopropanol-water mixtures, with an azeotropic point) were studied based on pervaporation process (PV) experimental data and mathematical modeling. Pervaporation process experiments proved that these two membranes have excellent applicability for the dehydration of alcohol. A semi-empirical solution-diffusion transport model was developed to describe the mass transport in the PVA membranes, which showed a good agreement with the experimental values. The universal quasi-chemical (UNIQUAC) model was utilized to predict the activity coefficient of nonideal alcohol-water systems in PVA membranes. In addition to the UNIQUAC model, the transport of alcohol-water across the commercial polymeric membrane was modeled using the conventional driving force model. The PV process experimental data with the mathematical model were used to develop the diffusivity correlations for water and alcohol (i.e., ethanol and isopropanol) through the PVA membranes. It was found that for swollen membranes (PVA), the developed correlations of water and alcohol diffusivity were strongly influenced by the feed water activity and feed temperature. Based on the mass transport model and developed diffusivity correlations, the permeation flux of water and alcohol through the PVA membranes was predicted, and the results showed a good agreement between the experimental data and the predictive model. The mean relative errors estimated for the permeate mass fluxes of water were 8.4%, and 3.8%, and for the permeate mass fluxes of ethanol were 18%, and 13.6% for the PERVAP™ 4100 and 4100 H F, respectively, as well as for the IPA-water-PVA system are as follows: 5% and 2.8% for the permeate mass fluxes of water and 14.4%, and 12.6% for the permeate mass fluxes of IPA for the PERVAP™ 4100 and 4100 H F, respectively.

Kinetic Relevance of Surface Reactions and Lattice Diffusion in the Dynamics of Ce–Zr Oxides Reduction–Oxidation Cycles

Reduction–oxidation cycles in oxides are ubiquitous in oxygen storage and transport, chemical looping processes, and fuel cells. O-atom addition and removal are mediated by coupling reactions of oxidants and reductants at surfaces with diffusion of O-atoms within oxide crystals, with either or both processes as limiting steps. CeO2–ZrO2 solid solutions (CZO) are ubiquitous in practice. They are used here to illustrate general experimental strategies and reaction–diffusion formalisms for nonideal systems that enable assessments of the kinetic relevance of the steps that mediate O-atom addition and removal in these materials; these experiments are described within the context of models that describe the driving forces for reaction and diffusion rigorously in terms of oxygen chemical potentials (μO). These strategies assess the rate consequences of varying the fluid phase redox potential, through changes in the identity and pressures of the reactants and products used in redox cycles (O2; CO/CO2; H2/H2O; N2O/N2), of introducing dispersed metal nanoparticles that capture and react lattice O-atoms in CZO using CO or H2, and of imposing intervening dwells without reaction within redox cycles. O-removal rates depend on reductant pressures, even when CO/CO2 and H2/H2O ratios are chosen to maintain the same surface μO if surface reactions were quasi-equilibrated. These data, taken together with significant rate enhancements in O-removal when Pt nanoparticles are present at CZO crystal surfaces and with similar rates before and after inert dwells, demonstrate that reduction rates by both CO and H2 are limited by surface reactions without the presence of consequential spatial gradients in μO within CZO crystals. In contrast, O-addition rates to partially reduced CZO crystals are similar for N2O and O2 reactants and are not affected by the presence of Pt nanoparticles; O-addition rates are significantly higher after intervening inert dwells during CZO oxidation, indicative of spatial gradients in μO, which relax during nonreactive periods. These methods and models, illustrated here for CZO redox cycles at conditions relevant to oxygen storage practice, allow systematic assessments of the kinetic relevance of lattice diffusion and surface reactions for systems that use solids for the reversible storage and release of atoms, irrespective of the identity of the solids or the atoms (e.g., O, H, N, and S).

Equivalence Analysis of Cascade Control for a Class of Cascade Integral Systems

A class of generalized proportional-integral-derivative (PID) control with feedforward compensation (FFC) is obtained for a class of cascade integral systems by equivalence analysis of the cascade control and such the analysis is obtained by using the information of the model and outermost loop feedback. Firstly, a new type of error related to the traditional error such as proportional (P) or proportional integral (PI) is given. Secondly, by analyzing cascade control for a class of ideal cascade integral systems, the generalized PID control with FFC is presented based on the proposed new type of error. Then, the generalized PID control with FFC is extended to a class of non-ideal cascade integral systems to reduce the number of feedback loop and sensors. Finally, the simulation results of the speed/position servo system of direct current motor are given to verify the theoretical analysis results.

Fuel Cell Module Control Based on Switched/Time-Based Adaptive Super-Twisting Algorithm: Design and Experimental Validation

Fuel cells (FCs) have emerged as a sound promising technology for their application in emissions-free generation systems. Their high efficiency, reliability, and clean energy make these electrochemical devices especially suitable for manifold applications such as transportation, stationary generation, and portable devices. In view of the inherent complexity of this technology, the FC control plays a fundamental role to guarantee stability and high performance against system uncertainties and disturbances. Regarding this, sliding mode control has proved to be a powerful technique for the design of robust controllers for generation systems involving FCs. However, its discontinuous control action gives rise to some undesired effects when applied to real nonideal systems, being control chattering is usually the main drawback. In this framework, the brief presents the design and experimental implementation of an FC module control via a switched/time-based adaptive super-twisting algorithm (STA). The designed algorithm is evaluated in an experimental platform of a hybrid generation system based on a commercial 1.2-kW FC. The proposed controller exhibits a low value of chattering and similar robustness features compared to traditional STA.

Typical and generalized transitions to deterministic chaos for atypical attractors of non-ideal dynamic systems

Some applied nonlinear, non-ideal dynamic systems of the fifth order, which are used to describe the oscillations of spherical pendulums and in hydrodynamics, are considered. Maximal attractors, both regular and chaotic, of such systems are constructed. Various bifurcations of maximal attractors are discussed. The transition to deterministic chaos is established for maximal attractors in typical Feigenbaum and Manneville–Pomeau scenarios. The implementation of the generalized alternation scenario for chaotic maximum attractors of such systems is investigated. A sign of the implementation of the scenario of generalized alternation has been revealed.

Information-geometric structure for chemical thermodynamics: An explicit construction of dual affine coordinates.

We construct an information-geometric structure for chemical thermodynamics, applicable to a wide range of chemical reaction systems including nonideal and open systems. For this purpose, we explicitly construct dual affine coordinate systems, which completely designate an information-geometric structure, using the extent of reactions and the affinities of reactions as coordinates on a linearly constrained space of amounts of substances. The resulting structure induces a metric and a divergence (a function of two distributions of amounts), both expressed with chemical potentials. These quantities have been partially known for ideal-dilute solutions, but their extensions for nonideal solutions and the complete underlying structure are novel. The constructed geometry is a generalization of dual affine coordinates for stochastic thermodynamics. For example, the metric and the divergence are generalizations of the Fisher information and the Kullback-Leibler divergence. As an application, we identify the chemical-thermodynamic analog of the Hatano-Sasa excess entropy production using our divergence.

Design of Deep Eutectic Systems: Plastic Crystalline Materials as Constituents.

Deep eutectic solvents (DESs) are a class of green and tunable solvents that can be formed by mixing constituents having very low melting entropies and enthalpies. As types of materials that meet these requirements, plastic crystalline materials (PCs) with highly symmetrical and disordered crystal structures can be envisaged as promising DES constituents. In this work, three PCs, namely, neopentyl alcohol, pivalic acid, and neopentyl glycol, were studied as DES constituents. The solid–plastic transitions and melting properties of the pure PCs were studied using differential scanning calorimetry. The solid–liquid equilibrium phase diagrams of four eutectic systems containing the three PCs, i.e., L-menthol/neopentyl alcohol, L-menthol/pivalic acid, L-menthol/neopentyl glycol, and choline chloride/neopentyl glycol, were measured. Despite showing near-ideal behavior, the four studied eutectic systems exhibited depressions at the eutectic points, relative to the melting temperatures of the pure constituents, that were similar to or even larger than those of strongly nonideal eutectic systems. These findings highlight that a DES can be formed when PCs are used as constituents, even if the eutectic system is ideal.

Molecular correlation function integrals for condensed systems with solid-liquid-liquid equilibria

Fluctuation Solution Theory (FST) is an exact statistical mechanical formulation for solution thermodynamic properties and their derivatives via integrals of direct correlation functions (DCFI) and total correlation functions (TCFI). This work tabulates DCFIs and TCFIs for a series of strongly nonideal systems involving condensed-phase equilibria (LLE, SLE and SLLE) over wide ranges of temperature, pressure, and composition. The values obtained can be used for FST modeling of such systems as well as to test the accuracy of other models such as equations of state.

Revealing the invariance of vectorial structured light in complex media

Optical aberrations have been studied for centuries, placing fundamental limits on the achievable resolution in focusing and imaging. In the context of structured light, the spatial pattern is distorted in amplitude and phase, often arising from optical imperfections, element misalignment, or even from dynamic processes due to propagation through perturbing media such as living tissue, free-space, underwater and optical fibre. Here we show that the polarisation inhomogeneity that defines vectorial structured light is immune to all such perturbations, provided they are unitary. By way of example, we study the robustness of vector vortex beams to tilted lenses and atmospheric turbulence, both highly asymmetric aberrations, demonstrating that the inhomogeneous nature of the polarisation remains unaltered from the near-field to far-field, even as the structure itself changes. The unitary nature of the channel allows us to undo this change through a simple lossless operation, tailoring light that appears robust in all its spatial structure regardless of the medium. Our insight highlights the overlooked role of measurement in describing classical vectorial light fields, in doing so resolving prior contradictory reports on the robustness of vector beams in complex media. This paves the way to the versatile application of vectorial structured light, even through non-ideal optical systems, crucial in applications such as imaging deep into tissue and optical communication across noisy channels.