Solidification Of Binary Mixture Research Articles

Exsolution process in white dwarf stars

Context. White dwarf stars are considered to be suitable cosmic laboratories for studying the physics of dense plasma. Furthermore, the use of white dwarf stars as cosmic clocks to date stellar populations and main sequence companions demands an appropriate understanding of the physics of white dwarfs in order to provide precise ages for these stars. Aims. We aim to study exsolution in the interior of white dwarf stars, a process in which a crystallized ionic binary mixture separates into two solid solutions with different fractions of the constituents. Depending on the composition of the parent solid mixture, this process can release or absorb heat, thus leading to a delay or a speed-up of white dwarf cooling. Methods. Relying on accurate phase diagrams for exsolution, we modeled this process in hydrogen(H)-rich white dwarfs with both carbon–oxygen (CO) and oxygen–neon (ONe) core composition, with masses ranging from 0.53 to 1.29 M⊙ and from 1.10 to 1.29 M⊙, respectively. Results. Exsolution is a slow process that takes place at low luminosities (log(L/L⊙)≲ − 2.75) and effective temperatures (Teff ≲ 18 000 K) in white dwarfs. We find that exsolution begins at brighter luminosities in CO than in ONe white dwarfs of the same mass. Massive white dwarfs undergo exsolution at brighter luminosities than their lower-mass counterparts. The net effect of exsolution on white dwarf cooling times depends on the stellar mass and the exact chemical profile. For standard core chemical profiles and preferred assumptions regarding miscibility gap microphysics, the cooling delay can be as large as ∼0.35 Gyr at log(L/L⊙)∼ − 5. We neglect any chemical redistribution possibly associated with this process, which could lead to a further cooling delay. Although the chemical redistribution is known to accompany exsolution in binary solid mixtures on Earth, given the solid state of the matter, it is hard to model in a reliable way, and its effect may be postponed until very low luminosities. Conclusions. Exsolution has a marginal effect on white dwarf cooling times and, accordingly, we find no white dwarf branches associated with it on the Gaia color–magnitude diagram. However, exsolution in massive white dwarfs can alter the faint end of the white dwarf luminosity function, thus impacting white dwarf cosmochronology.

Development of a multi-stage model for freezing of a suspended binary solution droplet

The importance of developing spray freeze-drying technology for extending the shelf life of biological and pharmaceutical materials has never been greater, given the increasing food shortage and the strong demand for pharma processes. In particular, the optimal thermal design and application of spray freeze-drying technologies now depend on the estimation of nucleation behavior for droplet solidification (especially the droplets of binary mixtures). Although earlier nucleation models could estimate the nucleation rate and temperature of solidifying droplets, few considered extreme environmental factors, such as extremely low ambient temperatures below −60C∘. To ensure the preservation and storage of biological and pharmaceutical products, such as vaccines and protein drugs, these conditions are essential. Hence, developing an accurate and trustworthy mathematical framework for simulating nucleation is paramount. In this study, a multi-stage, hybrid analytical-numerical model for droplet solidification is developed while coupled with a gradient-based optimization algorithm. Specifically, the five-stage solidification of binary mixtures is simulated (including supercooling of liquid, nucleation, recalescence, equilibrium freezing, and subcooling of solid), which captures the dynamic behaviors of temperature and composition or solute concentration during phase change. The heterogeneous nucleation of a binary-mixture droplet in a frigid environment is predicted and validated against a series of experiments on single suspended droplets at a wide range of ambient temperatures between −20 and −160C∘. The freezing curves of different solute concentrations are also validated against experimental data. It is found that significant variations in interfacial tension lead to abrupt changes in nucleation temperature for extremely cold environments. Further, the effects of the concentration, contact angle, droplet size, and heat transfer coefficient are investigated.

Terminal settling velocity of the binary solid mixture in the non-Newtonian pseudoplastic liquid system

Particle settling in a non-Newtonian pseudoplastic liquid has gained interest in various industrial applications, including chemical, petroleum, food and pharmaceutical industries. Terminal settling velocities (TVS) of non-spherical particles of binary systems in non-Newtonian viscous pseudoplastic shear thinning solutions were investigated experimentally. An aqueous solution of the sodium salt of carboxymethyl cellulose (SCMC) differing in the concentration of (0.4–0.8) kg/m3 was used as the liquid phase in two different size fluidized bed columns. TSV of the binary solid mixture increases with particle size and decreases with SCMC concentration. The following empirical correlation has been developed which showed an average relative error is 11.41% against 64.98% (minimum) by the earlier correction. Bio-inspired ANNs integrated with GA (Genetic Algorithm) develop a generalized model for estimating settling velocity with an average relative error of 6.9%.

Singular limits of binary mixtures in solids theory

We investigate the long-term behavior, as a certain coupling parameter α becomes large, of a one-dimensional model of a binary mixture of solids with nonlinear damping and nonlinear feedback forces. We prove the existence of a smooth global attractor with finite fractal dimension and study its limiting properties when α tends to infinity. More precisely, we prove that this limit coincides with a one-dimensional single wave equation. Finally, we also prove convergence of the global attractor of the binary mixture model to the global attractor of the single wave equation as α→∞. To the best of our knowledge, this result is new for singularly perturbed systems of a binary mixture of solids.

Minimum elutriation velocity of the binary solid mixture — Empirical correlation and genetic algorithm (GA) modeling

Minimum elutriation velocity of the binary solid mixture — Empirical correlation and genetic algorithm (GA) modeling

Attractors for partially damped systems of binary mixtures of solids

This paper targets the long-time dynamics of a semilinear system modeling a binary mixture of solids with frictional dissipation mechanism acting only on the elastic equation and subjected to nonlinear source term. The coupling gives new contributions to the theory associated with nonlinear dynamics of partially damped semilinear systems of a binary mixture of solids. Using the quasi-stability methods, we prove the existence of a smooth finite-dimensional global attractor irrespective of the wave speeds of the system. Moreover, we establish the existence of exponential attractors.

Asymptotic analysis and upper semicontinuity with respect to delay term of attractors to binary mixtures of solids

We investigated the asymptotic dynamics of a nonlinear system modeling binary mixture of solids with delay term. Using the recent quasi-stability methods introduced by Chueshov and Lasiecka, we prove the existence, smoothness and finite dimensionality of a global attractor. We also prove the existence of exponential attractors. Moreover, we study the upper semicontinuity of global attractors with respect to small perturbations of the delay terms.

A CFD-DEM study of monocomponent and same size binary-solid beds at incipient fluidization

This work analyses in detail the transition process from the fixed to the fluidized state for homogenous and binary mixtures of particles differing in density, with different initial configurations. The phenomenon is studied in cylindrical columns fed with water, with the aid of CFD-DEM numerical simulations. With regard to the homogenous case, the well-established knowledge is substantially confirmed. The transition to the fluidized state strongly depends on the initial solid configuration in the case of same density binary-solid mixture. For the segregated case, the experimental behaviour reported by Di Felice and Scapinello in 2010 is closely reproduced, whereas for the initially perfectly mixed case, the contemporary presence of a fixed and a fluidized region is observed. A simple model that predicts the extent of these two regions as a function of the fluid velocity is proposed.

Minimum Fluidization Velocities of Binary Solid Mixtures: Empirical Correlation and Genetic Algorithm‐Artificial Neural Network Modeling

AbstractExperimental investigation of the fluidization behavior in single and binary solid‐liquid fluidized beds of nonspherical particles as solid phase and water as liquid phase was performed in a Perspex column. Different particle sizes were used to prepare single and binary mixtures with different weight ratios for fluidization. Minimum fluidization velocity increased with increasing average particle size and decreasing sphericity for the binary mixture. An empirical correlation was developed to predict the minimum fluidization velocity. Genetic algorithm‐artificial neural network (GA‐ANN) modeling was applied to predict the minimum fluidization velocity for single and binary solid‐liquid fluidized beds. The application of GA‐ANN analysis leads to designing binary solid‐liquid fluidization systems without experimentation.

Heat transfer during diffusion-controlled unidirectional solidification of binary mixtures: effect of material advection

Heat transfer during diffusion-controlled unidirectional solidification of binary mixtures: effect of material advection

Prediction of solids outlet moisture content in a continuous wall heated fluidised bed dryer for uniform and binary solid mixtures

Most of the industries perform drying of solids to enhance the durability of the product. The solid nature and available resources will play an important role in the selection of the dryer and there are more than a hundred types of dryers currently used in different industries. In the dryer, the heat to wet solids is supplied in different ways such as conduction, convection or in combination. The application of fluidisation phenomena to drying will have several advantages and disadvantages. The advantages are the drying rate is higher than most of the dryers, due to the high transfer rate of heat and mass and also applicable for various ranges of particle sizes. In the present study, ambient air is used instead of hot air and also the heat to wet solids is provided from the wall. The significance of conventional parameters and effect of the mixture of solids have been studied.

Prediction of solids outlet moisture content in a continuous wall heated fluidised bed dryer for uniform and binary solid mixtures

Prediction of solids outlet moisture content in a continuous wall heated fluidised bed dryer for uniform and binary solid mixtures

Solid State Stability and Preformulation Studies for Acetylcholinesterase Inhibitor Drug Tacrine

In this paper, the acetylcholinesterase inhibitor drug tacrine was investigated by two complementary instrumental techniques, namely infrared spectroscopy and thermal analysis, as pure drug and in solid binary mixtures with nine excipients frequently used in the pharmaceutical industry, namely starch, sodium carboxymethyl cellulose, polyvinylpyrrolidone K30, fumed silica (Aerosil), talc, anhydrous lactose, magnesium stearate, mannitol and calcium lactate pentahydrate. The corroboration of obtained data by the two complementary methods confirmed the incompatibility of this drug with anhydrous lactose, mannitol, magnesium stearate and calcium lactate under both ambient conditions and thermal stress, and thermally induced interactions between tacrine and silica. In the development of new generic solid formulations, four of the investigated excipients (i.e., starch, sodium carboxymethyl cellulose, polyvinylpyrrolidone K30 and talc) can be used, since they are compatible with tacrine under ambient conditions as well as under thermal stress.

Authentication of equine DNA from highly processed donkey-hide glue (Colla Corii Asini) using SINE element

In order to detect the DNA from highly processed medicinal donkey-hide glue Colla Corii Asini from adulterants blended or totally substituted with horse, cattle, and pig tissues, various species-specific PCR assays based on highly repetitive SINE elements were established. For horse and donkey tissues, a two-step PCR assay was adopted, including an initial detection of equine DNA based on the equine SINE ERE-1 and a further detection of horse DNA based on the horse specific satellite. The assay can detect the equine DNA and the horse DNA from binary solid glue mixtures spiked with 0.1% Colla Corii Asini and 1% horse-hide glue respectively. In addition, for bovine and porcine detection, the primer pairs were designed upon 1.711B bovine repeat and PRE-1 respectively. The developed methods can detect bovine and porcine DNA from binary solid glue mixtures spiked with 0.1% cattle-hide glue and 0.1% pig-hide glue respectively. The result shows that our developed PCR assays were useful, convenient and sensitive for Colla Corii Asini identification.

Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

Binary mixtures of the laterally substituted Schiff base/ester derivatives, namely 4-((2- or 3-) substituted phenyl imino methyl) phenyl-4”-alkoxy benzoates, Ia–d, were prepared and mesomorphically studied by differential scanning calorimetry (DSC) and their mesophases identified by polarized optical microscopy (POM). The lateral group (1-naphthyl, 2-F, 2-Br, 3-F in Ia–d, respectively) is attached to different positions of the phenyl Schiff moiety. The mixtures investigated were made from two differently shaped compounds that differ from each other in the polarity, size, orientation, and relative positions of the lateral group. The results revealed that the binary mixture Ia/Ib (bearing the naphthyl and 2-flouro substituents) exhibited the SmA phase, which covered the whole composition range. For the mixtures Ib/Id (2-F and 2-Br), the isomeric lateral F-group in compound Ib distributed the SmA arrangement of Id. In the Ic/Id mixture bearing two positionally and structurally different substituents, the addition of Ic to Id resulted in solid binary mixtures where its behavior may be attributed to the negligible steric effect of the small electronegative fluorine atom compared to the Br atom. Density functional theory (DFT) theoretical calculations were carried out to estimate the geometrical parameters of individual components and to show the effect of these parameters in the mesophase behavior of the binary system, where the higher dipole moment of Id (6 Debye) may be the reason for its high π–π molecular stacking, which influences its mesophase range and stability.

Effect of calcination/carbonation and oxidation/reduction on attrition of binary solid species in sorption-enhanced chemical looping reforming

The effects of chemical reactions on the attrition of oxygen carrier particles and CO2 sorbent based on a chemical looping reforming (CLR) process with intrinsic CO2 capture were analyzed. Iron/hematite as an oxygen carrier, and limestone/lime as a CO2 sorbent were tested in a jet attrition apparatus. Attrition tests were conducted with particles of a single species and with binary solid mixtures, for different temperatures, different gas species and ranges of gas concentrations, varied to the reactions. Material properties were measured to investigate how the chemical conversion of particle species affects the attrition in both single-species, and two-species environments. Iron oxidation decreased the particle crushing strength, forming a porous iron oxide layer on the surface. When hematite was reduced with CH4, the proportions of reduced iron oxides increased the intrinsic crushing strength on the surface. For limestone, calcination increased the attrition due to a decrease in the intrinsic particle crushing strength. Lime carbonation reduced attrition because of increasing ductility and sintering, as well as the formation of a limestone surface layer of carbonate. Particle attrition increased when two solid species were mixed together, due to the increasing frequency of inter-particle collisions.

Initial correlation dependence of aging in phase separating solid binary mixtures and ordering ferromagnets

Following quenches of initial configurations having long range spatial correlations, prepared at the demixing critical point, to points inside the miscibility gap, we study aging phenomena in solid binary mixtures. Results on the decay of the two-time order-parameter autocorrelation functions, obtained from Monte Carlo simulations of the two-dimensional Ising model, with Kawasaki exchange kinetics, are analyzed via state-of-the art methods. The outcome is compared with that obtained for the ordering in uniaxial ferromagnets. For the latter, we have performed Monte Carlo simulations of the same model using the Glauber mechanism. For both types of systems we provide comparative discussion of our results with reference to those concerning quenches with configurations having no spatial correlation. We also discuss the role of structure on the decay of these correlations.

Compatibility study of hydroxychloroquine sulfate with pharmaceutical excipients using thermal and nonthermal techniques for the development of hard capsules

Hydroxychloroquine is effectively used in the treatment for malaria, lupus erythematosus and rheumatoid arthritis. The study of drug–excipient compatibility is an important tool for the development of safe and effective pharmaceutical forms. The present study describes the use of thermal and nonthermal techniques for evaluating the physicochemical compatibility of hydroxychloroquine with excipients for the development of solid dosage forms, including microcrystalline cellulose, corn starch, mannitol, magnesium stearate and colloidal silicon dioxide. The analytical techniques employed to evaluate the drug and the drug–excipient interactions in solid binary mixtures (1:1 w:w) were differential scanning calorimetry (DSC), thermogravimetry, Fourier transform infrared spectroscopy (FTIR) and isothermal stress test. Four different formulations were prepared and drug dissolution test was determined by rotating-basket system method in water. Evidence of solid-state interactions of hydroxychloroquine and mannitol, magnesium stearate and colloidal silicon dioxide was observed in the DSC analysis and subsequently confirmed by FTIR; however, no degradation profile was observed by HPLC and no interference was seen in the drug dissolution rate and no change in physicochemical properties of hydroxychloroquine was observed. The combination of techniques is very important to correctly identify drug–excipients incompatibilities in the earliest stage of a formulation design in order to ensure the choice of suitable excipients for the development of stable and effective dosage forms of hydroxychloroquine.

Blow-up result and energy decay rates for binary mixtures of solids with nonlinear damping and source terms

In this paper we study the long-time behavior of binary mixture problem of solids, focusing on the interplay between nonlinear damping and source terms. By employing nonlinear semigroups and the theory of monotone operators, we obtain several results on the existence of local and global weak solutions, and uniqueness of weak solutions. Moreover, we prove that every weak solution to our system blows up in finite time, provided the initial energy is negative and the sources are more dominant than the damping in the system. Additional results are obtained via careful analysis involving the Nehari Manifold. Specifically, we prove the existence of a unique global weak solution with initial data coming from the “good” part of the potential well. For such a global solution, we prove that the total energy of the system decays exponentially or algebraically, depending on the behavior of the dissipation in the system near the origin.

CFD Simulation of Mixing and Segregation of Binary Solid Mixtures in a Dense Fluidized Bed

The mixing and segregation behaviour of binary solid mixtures has been extensively studied through various experiments, while accurate CFD simulations are difficult to achieve due to process complexity and a lack of reliable constitutive relations. In this study, CFD simulations of a dense fluidized bed with glass and polystyrene particles were performed in order to identify a universal set of simulation parameters and models for simulating binary mixtures with different mixed and segregation behaviour. Through a comparison to experimental data, it was found that the EMMS drag model coupled with the Ma‐Ahmadi solid pressure and radial distribution models predicted more a reasonable axial distribution of solid phases than the Syamlal O'Brien drag model coupled with the Lun et al. solid pressure and radial distribution models. The increase in the solid‐solid drag further improved the simulation results.