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A quasi-steady-state model for accurately predicting the detailed diffusion-dominated dissolution process of polydisperse spheroidal (prolate, oblate and spherical) particle systems was presented in Part I of this study. In the present paper, the dissolution characteristics of typical polydisperse spheroidal particle systems have been extensively investigated. The effects of the distributions of particle size and shape have been studied by examining the detailed dissolution processes, such as the size reduction rates of individual particles, the increase in bulk concentration and the dissolution time of the polydisperse systems. Some important factors controlling the dissolution process, including initial particle concentration, smallest and largest particle sizes, and the smallest and largest Taylor shape parameters, have been identified. [ABSTRACT FROM AUTHOR]

A quasi steady-state model (QSM) for accurately predicting the detailed diffusion-dominated dissolution process of polydisperse spheroidal (prolate, oblate and spherical) particle systems with a broad range of distributions of particle size and aspect ratio has been developed. A rigorous, mathematics-based QSM of the dissolution of single spheroidal particles has been incorporated into the well-established framework of polydisperse dissolution models based on the assumption of uniform bulk concentration. Validation against experimental results shows that this model can accurately predict the increase in bulk concentration of polydisperse systems with various particle sizes and shape parameters. A series of representative instances involving the dissolution of polydisperse felodipine particles at various concentration ratios is used to demonstrate the model's effectiveness, rendering it a valuable tool for understanding and managing complex systems with diverse particle characteristics. [ABSTRACT FROM AUTHOR]

Extracting information about the shape or size of non-spherical aerosol particles from limited optical radar data is a well-known inverse ill-posed problem. The purpose of the study is to figure out a robust and stable regularization method including an appropriate parameter choice rule to address the latter problem. First, we briefly review common regularization methods and investigate a new iterative family of generalized Runge–Kutta filter regularizers. Next, we model a spheroidal particle ensemble and test with it different regularization methods experimenting with artificial data pertaining to several atmospheric scenarios. We found that one method of the newly introduced generalized family combined with the L-curve method performs better compared to traditional methods. [ABSTRACT FROM AUTHOR]

In this mini‐review, the main differences between spherical and spheroidal particles in terms of their size, surface area, morphology, and ability to penetrate biological membranes are described. The main routes of manufacturing of prolate spheroidal particles with controlled aspect ratio are reported. There are also shown exemplary results of computational and experimental studies of spheroids useful in biomedical applications, such as controlled drug delivery and numerical studies of the passage of spheroids through biological membranes. The relations of shape, size, aspect ratio of spheroidal particles and particle–biological membrane interactions, bioavailability, and flow in blood vessels are presented. The perspectives for future studies leading to resolve crucial problems and to explain basic issues related to acting of ellipsoidal particles in biological environment are also discussed. [ABSTRACT FROM AUTHOR]

A mathematical model describing the propagation of monochromatic electromagnetic waves in a medium with spatial dispersion containing spheroidal particles of the along prescribed direction has been developed. The initial classical integro-differential model for electromagnetic fields in a medium with spatial dispersion is transformed, within the third-order infinitesimal, to the differential model, where the integro-differential Maxwell equations are represented as a system of second-order differential equations. In this case electrical and magnetic polarizations of the medium are given in the Laplace operators. This system of equations is analytically solved; a complete system of four forward and four backward counter-propagating electromagnetic waves is formed. The analytical representation of the fields includes a vector determining the propagation direction of plane waves. Wave numbers of the fields also depend on their propagation directions pointing to anisotropic character of the developed mathematical model.

• Enhancement of settling velocity is observed for both oblate and prolate tracer spheroids in downward and upward flow. • Slip velocity originating from preferential orientation accounts for the major enhancement of settling velocity. • Particles' preferential sampling of high or low speed flow regions is the result of clustering and influences settling velocity. • Wall-normal distribution of particle is dominated by wall-normal slip velocity. Transport of particles in the wall-normal direction reaches a stable state when the velocity due to sampling and the slip velocity balance each other. The motion of particles settling in turbulence is an intriguing problem, which is relevant to an in-depth understanding of planktons in marine flows or the design of photobioreactors. This work studies the motion, orientation and distribution of inertia-less spheroidal particles settling in vertical channel flows by direct numerical simulations. We show that, compared to spherical tracers, the settling velocity of spheroidal tracers is enhanced due to preferential orientation and local clustering (not due to particle inertia, in the present case). Prolate spheroids tend to align their symmetry axes in the direction of gravity while oblate ones align perpendicular to it. Both kinds of particles attain a larger slip velocity in the direction of gravity and, therefore, settle faster. We also show that particles sample preferentially regions of high fluid velocity in downward flow and regions of low fluid velocity in upward flow. Such preferential sampling, which also contributes to the enhancement of settling, is the result of clustering. Besides, tracer particles are observed to accumulate in the channel center in downward flow and near the wall in upward flow: We show that tracer transport in the wall-normal direction is controlled by the particle-to-fluid slip velocity and by clustering. The slip velocity dominates the transport initially, but tracers increasingly cluster in regions with opposite flow direction as they accumulate either in the channel center or near the wall. Clustering appears to be associate with the coherent structures that characterize wall turbulence, and tracer distribution in the wall-normal direction is found to reach a steady state when the two qualitatively different mechanisms balance each other. [ABSTRACT FROM AUTHOR]

A method for the preparation of stripe‐like monolayers of microspheroids is described. The particles were obtained from polystyrene core/polyglycidol‐rich shell microspheres by stretching poly (vinyl alcohol) films that contain embedded particles. The stretching was performed under controlled conditions at temperatures above the Tg of the films and particles. The elongated films were dissolved in water, and the microspheroids were subsequently removed and purified from the poly (vinyl alcohol). The aspect ratio (AR) of the particles, which denotes the ratio of the lengths of the longer to shorter particle axes, was determined by the film elongation. The AR values were in the range of 2.9‐7.7. Spheroidal particles with various ARs were deposited onto silicon wafers from an ethanol (EtOH) suspension. The particle concentration and volume of the suspension were the same in each experiment. Evaporation of the EtOH yielded stripes of spherical particles packed into nematic‐type colloidal crystals and assembled into monolayers. The orientation of the stripes after ethanol evaporation was perpendicular to the triphasic (silicon‐ethanol‐air) interface along the silicon substrate. The adsorbed stripes on the wafers were characterized in terms of their interstripe distance (ID), stripe width, and crystal domain size. Nematic‐type spheroid arrangements in the stripes were the dominant structure, which enabled denser packing of the particles into colloidal crystals than that allowed by the smectic‐type arrangements. Furthermore, the number of spheroids adsorbed per surface unit of the silicon wafers was similar for all ARs, but the width and frequency of the spheroid stripes adsorbed on the wafers were different. [ABSTRACT FROM AUTHOR]

A novel method, powder thixoforming, for net-shape forming of the particle-reinforced Aluminum matrix composites in semi-solid state has been proposed based on powder metallurgy combining with thixoforming technology. The microstructural evolution and phase transformations have been investigated during partial remelting of the 2024 bulk alloy, prepared by cold pressing of atomized alloy powders to clarify the mechanisms of how the consolidated powders evolve into small and spheroidal primary particles available for thixoforming. The effect of heating temperature on the resulting semisolid microstructure has also been discussed. The results indicate that the microstructural evolution includes three stages—the initial rapid coarsening of the fine grains within the powders, the formation of continuous liquid layer on the primary particle surface (the original powder), and the final coarsening—that result from the phase transformations of θ→α, α→L, and α→L and L→α, respectively. The coarsening rate of the primary particles is low, and one original powder always evolves into one spheroidal particle with a continuous liquid layer surface. Properly raising the heating temperature is beneficial for obtaining an ideal semisolid microstructure.

Thermophoresis of spheroidal colloids in aqueous media under the thermal conductivity effect is analyzed. The thermophoretic velocity and the thermodiffusion coefficient of spheroidal colloids have been formulated for extremely thin electric double layer (EDL) cases. Furthermore, a numerical thermophoretic model is built for arbitrary EDL thickness cases. The parametric studies show that the thermal conductivity mismatch of particle and liquid gives rise to a nonlinear temperature region around the spheroid, with the thickness close to the minor semiaxis. When the EDL region is thin relative to such nonlinear temperature region, the thermal conductivity effect on the thermophoresis of spheroidal colloids is significant, which strongly depends on the ratio of the minor semiaxis to the EDL thickness, the thermal conductivity ratio of particle to liquid, and the particle aspect ratio. Finally, to estimate the thermodiffusion coefficient of spheroidal colloids with arbitrary thermal conductivity, electrolyte concentration, and particle shape, the average dimensionless axial temperature gradient on the spheroidal equator plane in the EDL region is proposed., (© 2023 Wiley-VCH GmbH.)

Highlights • The viscosity of suspensions of rigid spheroids in a Carreau fluid is computed. • The rheological coefficients in the TIF equation are determined. • The rheological coefficients depend strongly on the thinning index. • In the non-linear regime some of the coefficients show an orientation dependence. • A model is proposed to describe the TIF coefficients in the non-linear regime. Abstract When non-spherical particles, like rods or discs, are added to a liquid the increase in viscosity of the mixture is often described by the Lipscomb model. One important result of Lipscomb's model is that it predicts a strong increase in the viscosity of the suspension with increasing aspect ratio of the filler particles. Despite the fact that this model was originally proposed for a Newtonian matrix fluid it is also applied to polymer melts filled with non-spherical particles. Such an approach completely decouples the influence of the particle shape from the nonlinear properties of the suspending fluid. Yet, since polymer melts often exhibit strong non-Newtonian behavior, e.g. shear thinning, it is to be expected that such a superposition will give a wrong prediction of the suspension viscosity. To investigate this problem we performed a numerical study of a suspension based on a non-Newtonian matrix fluid and rigid spheroidal particles. In particular, we simulated different flows of a Carreau fluid around spheroidal particles and used numerical homogenization to obtain the intrinsic viscosity of the suspension as function of applied rate of deformation, thinning exponent and aspect ratio. In the Newtonian regime we also compare with results from literature. In the transition region from Newtonian to non-Newtonian behavior we obtained lower values of the intrinsic viscosity. In the power-law regime of the Carreau model, i.e. at high deformation rates, we found that the intrinsic viscosity of the suspension is independent of the applied rate of deformation. Further we obtained from the simulations that the intrinsic viscosity at high deformation rates strongly depends not only on the aspect ratio of the particles but also one the thinning exponent in the Carreau model, implying that the superposition approach in fact leads to a wrong prediction of the suspension viscosity at high deformation rates. [ABSTRACT FROM AUTHOR]

Abstract The aim of this paper is to study the design of isotropic composites reinforced by aligned spheroidal particles made of a transversely isotropic material. The problem is investigated analytically using the framework of mean-field homogenization. Conditions of macroscopic isotropy of particle-reinforced composites are derived for the dilute and Mori–Tanaka's schemes. This leads to a system of three nonlinear equations linking seven material constants and two geometrical constants. A design tool is finally proposed, which permits to determine admissible particles achieving macroscopic isotropy for a given isotropic matrix behavior and a given particle aspect ratio. Correlations between transverse and longitudinal moduli of admissible particles are studied for various particle shapes. Finally, the design of particles is investigated for aluminum and steel matrix composites. [ABSTRACT FROM AUTHOR]

Computation of a dilute suspension of prolate spheroidal particles in a turbulent channel flow is undertaken to study the influence of inertia and shape on acceleration statistics. A pseudo-spectral direct numerical simulation is coupled with Lagrangian tracking under the one-way coupling assumption. Simulations are carried out at friction Reynolds number , for three aspect ratios , 3 and 10, and two Stokes numbers St=5 and 30. Results indicate that, as a consequence of the filtering effect of inertia, particle acceleration RMS decreases with increasing inertia. In addition, the normalised streamwise acceleration PDFs depart from that of the conditional fluid and their tails become narrower as inertia is increased. Furthermore, acceleration statistics show that particle elongation has a significant effect on the mean drag and on the particle selective sampling. Moreover, the classification of elongated particle behaviour in turbulent channel flow based on a global Stokes number is questioned. The zero-crossing acceleration autocorrelation timescales presented points out the need for a local dimensionless number estimation adapted to the case of prolate spheroids. [ABSTRACT FROM AUTHOR]

This paper describes the preparation of spheroidal polystyrene core and polyglycidol-rich microparticles by stretching the relevant core-shell microspheres embedded into the poly(vinyl alcohol) film. The requirements for the preparation of the defect-free core-shell spheroids were determined. The rearrangement of the microparticle interfacial layer accompanying the conversion of the microspheres into microspheroids is described. [ABSTRACT FROM AUTHOR]

• The polarization properties of spheroidal particles are studied using the T -matrix code. • An attempt has been made to check whether a correlation between polarization maximum to polarization minimum ratio (Pz) exists or not with various scattering parameters (e.g. size, shape of the particles, refractive indices etc.). • A strong correlation between Pz and various scattering parameters is obtained which is fitted by a second-degree polynomial equation. • A qualitative comparison of simulated results is made with the experimental data. This paper investigates the correlation between the ratio of polarization maximum to polarization minimum (P z) and different scattering parameters such as complex refractive indices (m = n + i k), effective radius (r e f f), effective variance (v e f f), and axial ratio (E) for spheroidal particles. The simulations are executed using the double-precision T -matrix code for randomly oriented spheroidal particles, considering different sets of scattering parameters. For a specific range of n , k , E , r e f f , and v e f f , a strong correlation between P z and other scattering parameters is observed in all cases, which can be fitted by a second-degree polynomial equation. The simulations are conducted at two wavelengths (λ = 0.50 µm and 0.65 µm). Additionally, we compare our results obtained from numerical simulation with the experimental data for a few forsterite samples conducted by Muñoz et al. (2021). A set of conclusions is presented based on our work. [ABSTRACT FROM AUTHOR]

Light scattering by optically soft particles is being theoretically investigated in many radiative studies. An interest is growing up to develop approximate methods when the resolution of Maxwell's equations is impractical due to time and/or memory size problems with objects of complex geometries. The participation of experimental studies is important to assess novel approximations when no reference solution is available. The microwave analogy represents an efficient solution to perform such electromagnetic measurements in controlled conditions. In this paper, we take advantage of the particular features of our microwave device to present an extensive experimental study on the electromagnetic scattering by spheroidal particles analogs with low refractive indices, as a first step toward the assessment of micro-organisms with low refractive index and heterogeneities. The spheroidal analogs are machined from a low density material and they mimic soft particles of interest to the light scattering community. The measurements are confronted to simulations obtained with Finite Element Method and T-Matrix method. A good agreement is obtained even with refractive index as low as 1.13. Scattered signals of low intensities are correctly measured and the position of the targets is precisely controlled. The forward scattering measurements show high sensitivity to noise and require careful extraction. The configuration of the measurement device reveals different technical requirements between forward and backward scattering directions. The results open interesting perspectives about novel measurement procedures as well as about the use of high prototyping technologies to manufacture analogs of precise refractive indices and shapes. [ABSTRACT FROM AUTHOR]

Polysiloxane macroporous microspheres and macroporous spheroidal particles were generated from a linear siloxane polymer using a simple emulsion procedure. Osmotic pressure produced by nano-dispersed ionic salt solution in polysiloxane droplets formed in aqueous emulsion is proposed as a mechanism of macropore formation. The competition between cross-linking of the polymer and osmotic swelling of the microspheres governs the shape and porosity of the particles which were characterized by SEM, Si MAS NMR, mercury intrusion porosimetry, and X-ray computed tomography. [ABSTRACT FROM AUTHOR]

In the stereological unfolding problem for spheroidal particles the extremal shape factor is predicted. The theory of extreme values has been used to show that extremes of the planar shape factor of particle sections tend to the same limit distribution as extremes of the original shape factor for both the conditional and marginal distribution. Attention is then paid to the extreme shape factor conditioned by the particle size. Normalizing constants are evaluated for a parametric model and the numerical procedure is tested on real data from metallography.

A study has been carried out to assess the discrepancies between computed and observed aerosol scattering and backscattering properties in the atmosphere. The goals were: (i) to analyse the uncertainty associated with computed optical properties when spherical and spheroidal approximations are used, and (ii) to estimate nephelometry errors due to angular truncation and non-Lambertian illumination of the light source in terms of size range, particle shape and aerosol chemical compounds. Mie and T-matrix theories were used for computing light optical properties for spherical and spheroidal particles, respectively, from observed particle size distributions. The scattering coefficient of the fine mode was not much influenced by the particle shape. However, computed backscattering values underestimated the observed values by ∼15%. For the coarse mode, the spheroidal approximation yielded better results than that for spherical particles, especially for backscattering properties. Even after applying the spheroidal approximation, computed scattering and backscattering values within the coarse mode underestimated the observed values by ∼49% and ∼11%, respectively. The angular correction most widely used to correct the nephelometer data was discussed to explore its uncertainty. In the case of the scattering properties within the coarse mode, the change of the computed optical parameter is ∼+8% and for the scattering and backscattering values within the fine mode it is lower than ∼±4% for spherical and spheroidal particles. Additionally, if the spheroidal particles are used to evaluate the aerosol optical properties, the correction must be reconsidered with the aim of reducing the uncertainty found for scattering within the coarse mode. This is recommended for sites with desert dust influence; then the deviation of the computed scattering can be up to 13%. [ABSTRACT FROM AUTHOR]

Monosize spheroidal porous particles of copper oxide were produced by controlled calcination of the copper basic carbonate particles, synthesized by the urea-based homogeneous precipitation process. After characterization by various physical methods, such as SEM, XRD, and FTIR, the copper oxide particles were employed for the fabrication of the gas sensor. The latter was made up of a thick film of copper oxide on alumina plate, having printed interdigitated gold electrodes. Electrical properties of the sensor material were evaluated as a function of the temperature, which indicated its semiconductor behavior. On exposing to ammonia gas, the sensor responded in the form of a decrease in electrical resistance in a reproducible manner. Reproducibility in performance was attributed to the use of monodispersed particles of copper oxide in the fabrication of sensor. [ABSTRACT FROM AUTHOR]

A possible means of optical sensing, based on a porous hyperbolic material that is infiltrated by a fluid containing an analyte to be sensed, was theoretically investigated. The sensing mechanism relies on the observation that extraordinary plane waves propagate in the infiltrated hyperbolic material only in directions enclosed by a cone aligned with the optic axis of the infiltrated hyperbolic material. The angle this cone subtends to the plane perpendicular to the optic axis is θc. The sensitivity of θc to changes in the refractive index of the infiltrating fluid, namely nb, was explored; also considered were the permittivity parameters and porosity of the hyperbolic material, as well as the shape and size of its pores. Sensitivity was gauged by the derivative dθc/dnb. In parametric numerical studies, values of dθc/dnb in excess of 500 deg per refractive index unit were computed, depending upon the constitutive parameters of the porous hyperbolic material and infiltrating fluid and the nature of the porosity. In particular, it was observed that exceeding large values of dθc/dnb could be attained as the negative-valued eigenvalue of the infiltrated hyperbolic material approached zero. [ABSTRACT FROM AUTHOR]

This study aims to investigate turbulent plasma flow over spheroidal particles using the lattice Boltzmann (LB) method. A double population model D2Q9-D2Q4 is employed to calculate the plasma velocity and temperature fields. Along with the calculation process a conversion procedure is made between the LB and the physical unit systems, so that thermo-physical properties variation is fully accounted for and the convergence is checked in physical space. The configuration domain and the boundary condition treatment are selected based on the most cited studies in order to illustrate a realistic situation. The jet morphology analysis gives credible results by comparison with commonly published works. A second Lagrangian model has been developed to investigate the plasma-particles exchange during its in-flight. The tracking of the µ-sized particles allows concluding that our results are in sufficient agreement with those of the Jets&Poudres code and that the LB method account well for plasma jet physics which affects directly the particles in-flights. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes an investigation on the electric permittivity of concentrated suspensions of non-spherical particles, specifically prolate spheroids. It is first discussed how the determination of the frequency (ω) dependence of the electric permittivity (a phenomenon traditionally known as LFDD or low-frequency dielectric dispersion) can provide ample information on the properties of the dispersed material (shape, size, state of aggregation, conductivity) and of its interface with the (typically aqueous) medium. The basic quantities are the strength and frequency dependence of the dipole moment induced by the applied field, and its dimensionless counterpart, the dipole coefficient, C ∗(ω). It is explicitly shown how the (complex) relative permittivity of the suspension, , can be calculated from it. Two theoretical models on the polarizability of spheroidal colloidal particles will be used as theoretical starting point; one of them (Model I) explicitly considers two relaxations of the permittivity, each associated to one of the particle axes. The other (Model II) is a semi-analytical theory that yields an LFDD practically independent of the axial ratio of the particles. Both models are aimed to be used if the suspensions are dilute (low volume fraction of solids, ), and here they are generalized to concentrated systems by means of a previously published approximate evaluation of the permittivity of concentrated suspensions. Experiments are performed in the 1kHz–1MHz frequency range on suspensions of elongated goethite particles; the effects of ionic strength, pH, and volume fraction are investigated, and the two models are fitted to the data. In reality, taking into account that the particles are non-uniformly charged (a fact that contributes to their instability), two zeta potentials (roughly representing the lateral surface and the tip of the spheroid) are used as parameters. The results indicate that, when experimental conditions are optimal (high ionic strength and low zeta potential), the suspensions do indeed display two relaxations, that we ascribe to the long axis (and to flocs likely present in suspension) and to the short one. The permittivity increases with ionic strength, a result found with other systems, and compatible with a zeta potential that, on the average, decreases with ionic strength, an equally well known result, consequence of electric double layer compression. Another reasonable finding is the increase of estimated average dimensions and the decrease of electrokinetic potentials when the pH is close to the isoelectric point of goethite (around pH 9). The increase in volume fraction, finally, produces an overall increase in the permittivity, and the approximate model used for the evaluation of volume fraction variations can describe properly these effects, with basically constant zeta potentials and dimensions. [Copyright &y& Elsevier]

Abstract: Methodology of calculation of coherent and non-coherent light scattering by arbitrarily oriented optically soft spheroidal particles in geometric optics approximation is presented. The aim of this work is to develop an instrument for quick calculation of scattering patterns from particles modeling red blood cells and their aggregates. Results of calculation describing the dependences of scattering patterns on refractive index, eccentricity and orientation of an ellipsoidal particle with size parameter about 40 are presented. [Copyright &y& Elsevier]

Abstract: When one sphere adheres to a second sphere, the location or orientation of the adhesion on the second sphere is seldom considered. However, when a sphere adheres to a prolate spheroid, the orientation of the adhesion is sometimes critical. We have performed Brownian dynamics simulations to predict the orientation of adhesion of a sphere on a prolate spheroid. When the spheroid has a high rotational diffusion coefficient, simulations show that the spherical particle adheres near the end of the spheroid. We tested our model experimentally for two systems: (1) oppositely-charged spherical and spheroidal colloids and (2) like-charged colloidal spheres and E. coli K-12 D21 bacteria. For the latter case, the spheres have previously been shown to adhere only to one end of the bacterium. Experiments in case (1) support the results of the simulations, while data from case (2) do not agree with predictions. Case (2) data reveal that the end-on adhesion of the spheres on the bacteria is not a purely Brownian phenomenon. [Copyright &y& Elsevier]

Asymptotic expressions for the electrostatic interaction energy between two weakly charged spheroidal particles (prolate and oblate) with uniform surface potential or surface charge density at large separations in an electrolyte solution are derived on the basis of the linear superposition approximation. The electrostatic interaction between two spheroids is found to be the screened Coulomb interaction between two hypothetical point particles with orientation-dependent charges. Explicit interaction energy equations, which are expressed in terms of spheroidal wave functions, are given for four particular configurations of two similar spheroids, that is, side-to-side prolates, end-to-end prolates, side-to-side oblates, and end-to-end oblates. Comparison is also made with results obtained using Derjaguin's approximation. Electrostatic interaction between two spheroids [Display omitted] • Asymptotic expressions for the electrostatic interaction energy between two spheroidal particles are derived. • Constant surface potential and charge density cases are considered. • Side-to-side prolates, end-to-end prolates, side-to-side oblates, and end-to-end oblates are considered. [ABSTRACT FROM AUTHOR]