Distinct Particle Research Articles

Decomposition mechanism of a mixed rare earth concentrate with sodium hydroxide in the microwave heating process

In this paper, a novel process is proposed for extracting rare earth elements through intensifying the decomposition of mixed rare earth concentrates by microwave heating. The objective of the present study was to investigate the phase transition mechanism of a mixed rare earth concentrate with sodium hydroxide in a microwave field. To this end, the decomposition and separation efficiencies of the rare earth elements and fluorine were analyzed. The results showed that the decomposition reaction of the tested mixed rare earth concentrate in the microwave irradiation field occurred in three stages. The rare earth elements initially presented in bastnaesite and monazite were gradually converted to rare earth hydroxides (RE(OH)3), rare earth oxides (RE2O3), and composite oxides (Ce0.5Nd0.5O1.75), with fluorine eventually forming sodium fluoride. The decomposition ratio of the mixed concentrate and conversion ratio of the fluoride reached 88.73% and 89.32%, respectively. Furthermore, the decomposition temperature of the mixed concentrate with microwave heating was lower than that required with conventional heating, which indicated that microwave heating could decrease the thermodynamic reaction temperature. The results of the microscopic morphology analysis showed that after microwave heating, the samples exhibited two distinct particle morphologies, which was different from that of a mixed concentrate in any case. The decompositions of bastnaesite, monazite, and fluorite were somewhat non-interfering in nature, and sodium fluoride and calcium phosphate were separated from the rare earth oxides in the decomposition products. These results indicated that the proposed process was conducive to the separation of rare earth elements and fluoride and helpful for improving the efficiency of rare earth leaching.

Numerical study of shear thickening fluid with distinct particles dispersed in carrier fluid

The Shear Thickening Fluid (STF) is a non- Newtonian fluid which comes under dilatant material, STF undergoes phase transition from a low to high viscosity when shear stress is applied on it. In this paper modelling and simulation tools are used to study the STF fluid interaction when subjected to applied shear stress. The Eulerian description used for the fluid flow and the model considered the Lagrangian description of the rigid particles. The numerical analysis inspects important guideline such as acceleration of the flow, particle dispersion and the base of Non-Newtonian fluid. The fluid particles interrelation of STF showed that the shape, arrangement, volume concentration, and size of the particles had a vital effect on the behavior of STF. By adding sand particles in non-Newtonian fluids and applying high shear strain rates showed improvement in the shear thickening effects.

Evaluation of Three Morphologically Distinct Virus-Like Particles as Nanocarriers for Convection-Enhanced Drug Delivery to Glioblastoma.

Glioblastoma is a particularly challenging cancer, as there are currently limited options for treatment. New delivery routes are being explored, including direct intratumoral injection via convection-enhanced delivery (CED). While promising, convection-enhanced delivery of traditional chemotherapeutics such as doxorubicin (DOX) has seen limited success. Several studies have demonstrated that attaching a drug to polymeric nanoscale materials can improve drug delivery efficacy via CED. We therefore set out to evaluate a panel of morphologically distinct protein nanoparticles for their potential as CED drug delivery vehicles for glioblastoma treatment. The panel consisted of three different virus-like particles (VLPs), MS2 spheres, tobacco mosaic virus (TMV) disks and nanophage filamentous rods modified with DOX. While all three VLPs displayed adequate drug delivery and cell uptake in vitro, increased survival rates were only observed for glioma-bearing mice that were treated via CED with TMV disks and MS2 spheres conjugated to doxorubicin, with TMV-treated mice showing the best response. Importantly, these improved survival rates were observed after only a single VLP–DOX CED injection several orders of magnitude smaller than traditional IV doses. Overall, this study underscores the potential of nanoscale chemotherapeutic CED using virus-like particles and illustrates the need for further studies into how the overall morphology of VLPs influences their drug delivery properties.

The nonhomogeneous frog model on ℤ

Abstract We examine a system of interacting random walks with leftward drift on ℤ, which begins with a single active particle at the origin and some distribution of inactive particles on the positive integers. Inactive particles become activated when landed on by other particles, and all particles beginning at the same point possess equal leftward drift. Once activated, the trajectories of distinct particles are independent. This system belongs to a broader class of problems involving interacting random walks on rooted graphs, referred to collectively as the frog model. Additional conditions that we impose on our model include that the number of frogs (i.e. particles) at positive integer points is a sequence of independent random variables which is increasing in terms of the standard stochastic order, and that the sequence of leftward drifts associated with frogs originating at these points is decreasing. Our results include sharp conditions with respect to the sequence of random variables and the sequence of drifts that determine whether the model is transient (meaning the probability infinitely many frogs return to the origin is 0) or nontransient. We consider several, more specific, versions of the model described, and a cleaner, more simplified set of sharp conditions will be established for each case.

Dynamic optimization of a two-stage emulsion polymerization to obtain desired particle morphologies

Particle morphology is a key property of hybrid waterborne polymer dispersions that are used in high-end applications. However, evolving these product-by-process material properties is still mainly achieved by trial-and-error guided semi-empirical knowledge. In this work, a recently published mathematical model for the development of the particle morphology and a dynamic optimization method based on the direct single shooting approach are used to demonstrate in silico the feasibility of process optimization aimed at controlling particle morphology of waterborne polymer dispersions. This knowledge-based approach is assessed for existing and new materials with distinct particle morphologies. The batch times can be reduced by up to 13%.

Soot Modeling of Ethylene Counterflow Diffusion Flames

ABSTRACTCombustion-generated nanoparticles cause detrimental effects to not only health and environment but also combustion efficiency. A detailed kinetic mechanism employing a discrete sectional model is validated using experimental data obtained in laminar counterflow diffusion flames of ethylene/oxygen/nitrogen. Two configurations, named Soot formation (SF) and soot formation/oxidation (SFO) flames, are modeled using one-dimensional simulations. Radiative heat losses reduce the maximum flame temperature in the range of 20–60 K and therefore reduce soot volume fraction by ~ 10%. The model predictions accounting for the radiation effects are quite satisfactory. The model can reproduce the qualitative trends of soot volume fraction peaks that are slightly shifted toward the oxidizer zone with the increased oxygen content. In SF flames, the model predicts the maximum soot volume fraction quite well with the largest discrepancy of two folds. The particle stagnation locations can be reproduced by the model, although they are slightly shifted toward the oxidizer nozzle by ~ 0.4 mm. In SFO flames, the most considerable discrepancy is observed at the least sooting flame (xF,o = 0.23) in which the model over-predicts the maximum soot volume fraction by a factor of two. The effect of soot oxidation is important. The model shows that neglecting oxidation of soot significantly increases soot volume fraction in SFO flames by two folds while SF flames are only marginally affected. Also, ignoring soot oxidation leads to the presence of soot particles in the oxidizer zone where they are not observed experimentally. OH is the most effective oxidizer because the sooting zone is located inside the flame region. The effect of thermophoresis is also investigated. It strongly influences SFO flames due to the high temperature gradient. The model accounting particle diffusivities from Stokes–Cunningham correlation can better characterize the distinct particle stagnation plane of SF flames due to their low diffusion coefficients.

Impenetrable SU(N) fermions in one-dimensional lattices

We study SU(N) fermions in the limit of infinite on-site repulsion between all species. We focus on states in which every pair of consecutive fermions carries a different spin flavor. Since the particle order cannot be changed (because of the infinite on-site repulsion) and contiguous fermions have a different spin flavor, we refer to the corresponding constrained model as the model of distinguishable quantum particles. We introduce an exact numerical method to calculate equilibrium one-body correlations of distinguishable quantum particles based on a mapping onto noninteracting spinless fermions. In contrast to most many-body systems in one dimension, which usually exhibit either power-law or exponential decay of off-diagonal one-body correlations with distance, distinguishable quantum particles exhibit a Gaussian decay of one-body correlations in the ground state, while finite-temperature correlations are well described by stretched exponential decay.

Ultrafast Myoglobin Adsorption into Double‐Shelled Hollow Mesoporous Silica Nanospheres

AbstractThe fabrication of hollow mesoporous materials with hierarchical pore structures, regular shape, and uniform particle size via a simple and efficient approach is a major challenge. In this study, a facile preparation approach of hierarchically structured double‐shelled hollow mesoporous silica nanospheres (HS‐DS‐HMSN) is developed. Treatment of monodisperse nonporous silica spheres with CTAB and F127 as well as N,N‐dimethylhexadecylamine as a cosurfactant under basic conditions gives access to HS‐DS‐HMSNs of uniform particle size. Such HS‐DS‐HMSN‐type materials show a high monodispersibility in aqueous solution, a double‐shelled structure with hierarchically adjustable pore sizes, perpendicularly aligned mesochannels, and high surface areas as well as large pore volumes. On the basis of structure and morphology evolutions as well as unambiguous and reproducible experimental data, a micelle‐assisted self‐assembly process is proposed as a mechanism of formation, further involving cosurfactant‐expanded micelles and a heterogeneous nucleation deposition. The syntheses of a series of HS‐DS‐HMSNs with distinct particle sizes (162–364 nm) as well as distinct inner (range of thickness/pore size: 18–41 nm/3.1–3.7 nm) and outer shells (18–41 nm/3.7–8.0 nm) verify the feasibility and effectiveness of this approach. Such HS‐DS‐HMSNs show an ultrahigh adsorption rate (≈1.7 mg mg−1 min−1) and loading (≈300 mg g−1) for myoglobin.

Effect of elevated temperatures and applied pressure on the tribological properties of LM30/sillimanite aluminium alloy composites

The present study focuses on the development of low-cost, lightweight and highly wear resistant composites for brake rotor applications. Sillimanite mineral reinforced aluminum matrix composites were stir cast using three distinct reinforcement particle sizes. Reinforcement level was varied in the range of 3–15 wt%. The influence of operating temperature (50℃–300℃) and applied pressure (0.2–1.0 MPa) on the wear/friction behaviour of composites was observed. Optical micrographs showed homogenous particle distribution throughout the matrix. The high nanohardness obtained for interface regions signifies good particle–matrix bonding of processed composites. Dilatometry studies showed that the increase in sillimanite content decreased the coefficient of thermal expansion of the composites. Maximum improvement of 33% in coefficient of thermal expansion (over base alloy) was observed for 15 wt% fine composites. Wear analysis revealed that the developed composites provided adequate wear resistance till an operating temperature of 200℃, beyond which wear rate increased significantly. For the high operating temperature of 200℃, the steady-state wear of composites was comparable (only 6.62% higher) to the commercial cast iron alloy used in brake rotor applications. The aluminium-based composites developed in the present research are low cost (sillimanite is a naturally occurring mineral sand) and lightweight (60% lighter than cast iron) and can be used as an alternate material for brake rotors in light vehicles. Finally, SEM of worn out surfaces divulged the dominance of adhesive wear for material removal.

Tribological behaviour and wear fashion of processed AA6061/ZrO2 composite

PurposeThis study aims to develop a less weight high wear resistant material to fabricate brake components especially in automotive sector.Design/methodology/approachEffort was initiated to design and develop aluminium metal matrix composite by combining aluminium alloy AA6061 and zirconium oxide (ZrO2) with the help of stir casting coupled with squeeze casting unit. Morphology analysis of advanced composite has been carried out by optical microscopy and scanning electron microscopy (SEM). The hardness of composites having different compositions was tested using Vickers micro hardness tester. The tribological property of the developed three specimens having different composition has been tested using pin-on-disc wear test equipment under dry sliding conditions. To obtain better understanding of wear mechanism, SEM image of worn-out surface was captured and analysed. SEM images and the corresponding Energy-dispersive X-ray spectroscopy (EDX) on the wear surface were carried out.FindingsThe optical and SEM images evidenced the existence of ZrO2 particles along the metal matrix composite. Porosity values shows that the porosity level is acceptable as it falls below 7 per cent. Also, the finding proves that increase in the percentage of reinforcement particle instigates agglomeration on the AA6061 composites. Hardness test demonstrated that the inclusion of hard ZrO2 particles leads to substantial improvement in hardness and the hardness value started deteriorating when the composition reaches 15 per cent. The wear test results substantiated the enhancement of tribological property due to the inclusion of distinct ZrO2 particles. Also, despite of addition of reinforcements, the wear rate increased when the load increases. SEM images proved that AA6061/ZrO2-5 per cent composite fashioned steady-state mild and smooth wear. EDX spectrum analysis revealed the existence of ZrO2 particles along with wear debris, which caused wear of 685 µm in AA6061/ZrO2-15 per cent composite.Originality/valueThe developed material possesses low wear rate which is the unique property of composite and frictional force which is directly proportional to load but the coefficient of friction remains apparently constant. As a whole, investigations on developed composites introduce a new material which is suitable for manufacturing of brake components for automobile industry.

Effect of Foliation and Fluid Viscosity on Hydraulic Fracturing Tests in Mica Schists Investigated Using Distinct Element Modeling and Field Data

Several hydraulic fracturing tests were performed in boreholes located in central Hungary in order to determine the in-situ stress for a geological site investigation. At a depth of about 540 m, the observed pressure versus time curves in mica schist with low dip angle foliation shows atypical pressure versus time results. After each pressurization cycle, the fracture breakdown pressure in the first fracturing cycle is lower than the refracturing or reopening pressure in the subsequent pressurizations. It is assumed that the viscosity of the drilling mud and observed foliation of the mica schist have a significant influence on the pressure values. In order to study this problem, numerical modeling was performed using the distinct element code particle flow code, which has been proven to be a valuable tool to investigate rock engineering problems such as hydraulic fracturing. The two-dimensional version of the code applied in this study can simulate hydro-mechanically coupled fluid flow in crystalline rock with low porosity and pre-existing fractures. In this study, the effect of foliation angle and fluid viscosity on the peak pressure is tested. The atypical characteristics of the pressure behaviour are interpreted so that mud with higher viscosity penetrates the sub-horizontal foliation plane, blocks the plane of weakness and makes the partly opened fracture tight and increase the pore pressure which decreases slowly with time. We see this viscous blocking effect as one explanation for the observed increase in fracture reopening pressure in subsequent pressurization cycles.

A stochastic airplane boarding model in a framework of ASEP with distinguishable particles

The asymmetric simple exclusion process (ASEP) is a paradigmatic model for nonequilibrium systems and has been used in many applications. Airplane boarding provides another interesting example where this framework can be applied. We propose a simple model for boarding process, in which a particle moves along a one-dimensional aisle after being injected, and finally is removed at a reserved site. Different from the typical ASEP model, particles are removed in a disorderly or a parallel way. Detailed calculations and discussions of some related characteristics, such as mean boarding time and parallelism indicator, are provided based on Monte-Carlo simulations. Results show that three phases exist in the boarding process: free-flow, jamming and maximum current. Transitions between these phases are governed by the difference between the injection and removal rate. Further analysis shows how the scaling behavior depends on the system size and the boarding conditions. Those results emphasize the importance of utilizing the whole length of the aisle to reduce the boarding time when designing an efficient boarding strategy.

A non-Markovian approach for two dissipative quantum walks

We study the non-Markovian evolution of two free spinless distinguishable particles in a 1D lattice using a completely positive map. The Renewal theory is used to introduce, in a phenomenological way, the concept of disorder in the random time-interventions of the environment. If the waiting-time of the Renewal approach is exponential, we recover a semigroup description for the density matrix. Introducing a non-Poissonian random-time bath-interventions a non-Markovian evolution for the density matrix has been worked out. Under this scenario, we have studied the time evolution of the Quantum Coherence and Negativity measures for local and non-local initial conditions. We show the relevance of the (weak) non-Markovian evolution in calculating short-time correlations, while in the long-time regime a renormalized Markovian evolution appears.

Initial growth of Moringa oleifera Lam. as a function of poultry litter doses and granulometry

ABSTRACT There is an increasing use of poultry litter in seedling production. However, studies regarding the effect of different particle-size litter on plant growth are still scarce. This study aimed to evaluate the growth of Moringa oleifera Lam. fertilized with poultry litter doses (0 g dm-3, 40 g dm-3, 80 g dm-3 and 120 g dm-3) with distinct particle sizes (1 mm and 4 mm), with four replications. The following variables were evaluated: plant height; root and stem diameter; leaf, stem, shoot and root dry matter mass; shoot/root dry matter mass ratio; and the Dickson quality index. There was no influence of the particle size on the studied variables, except for plant height. The root diameter decreased with the increase of the poultry litter doses. The accumulation of dry matter mass from the shoot and root increased with the increase of poultry litter doses up to 120 g dm-3. A linear increase of the Dickson quality index, relatively to days and poultry litter doses, was observed. It is recommended to apply 80 g dm-3 of poultry litter to fertilize M. oleifera plants, independently of the granulometry used.

Effects of random pinning on the potential energy landscape of a supercooled liquid.

We use energy landscape methods to investigate the response of a supercooled liquid to random pinning. We classify the structural similarity of different energy minima using a measure of overlap. This analysis reveals a correspondence between distinct particle packings (which are characterised via the overlap) and funnels on the energy landscape (which are characterised via disconnectivity graphs). As the number of pinned particles is increased, we find a crossover from glassy behavior at low pinning to a structure-seeking landscape at high pinning, in which all thermally accessible minima are structurally similar. We discuss the consequences of these results for theories of randomly pinned liquids. We also investigate how the energy landscape depends on the fraction of pinned particles, including the degree of frustration and the evolution of distinct packings as the number of pinned particles is reduced.

Correlation of nanoparticle size distribution features to spatiotemporal flame luminosity in gasoline direct injection engines

Particle size distribution measured by mobility instruments is a common diagnostic used to characterize ultrafine and nanoparticle emissions in engine exhaust; however, some features of particle size distribution data are poorly correlated to in-cylinder combustion phenomena. In this work, in-cylinder spatiotemporal flame luminosity is quantitatively correlated to features in the solid particle size distribution measured in the exhaust of a gasoline direct injection engine operating in lean and stoichiometric combustion modes. A multi-channel optical sensor was used to measure diffusion flame light intensity in different areas of the combustion chamber. Total solid particle number and particle size distribution in the exhaust were measured using a scanning mobility particle sizer after a catalytic stripper that removed semi-volatile compounds. Results of the experiments showed that different flame phenomenon resulted in distinct particle size distribution characteristics. A large accumulation mode (particles with diameter of 50–100 nm) in the particle size distribution from stoichiometric engine operation with early injection resulted from anomalous diffusion flames like piston-top pool fires. In lean operation incorporating a secondary fuel injection, particle emissions were dominated by flame propagation through fuel-rich regions of the combustion chamber resulting in a comparatively broad particle size distribution. More generally, this work illustrates how particle size distribution data can be more accurately used to diagnose soot formation in gasoline direct injection engines.

Effect of amorphization method on the physicochemical properties of amorphous sucrose

Our objective was to characterize the physicochemical properties of amorphous sucrose prepared by freeze-drying (FreD), spray-drying (SprayD), ball milling (BallM), melt-quenching (MeltQ), and spin-melt-quenching (SpinMeltQ). Scanning electron microscopy indicated that FreD, SprayD, BallM, and SpinMeltQ formed distinct particles, while MeltQ formed a single mass. Powder X-ray diffraction confirmed that BallM was semi-crystalline, while FreD, SprayD, MeltQ, and SpinMeltQ were amorphous. However, total scattering pair distribution function analysis of synchrotron X-ray diffraction data suggested that local molecular-level ordering differences existed between MeltQ and FreD, SprayD, and SpinMeltQ. Chromatographic analyses revealed that thermal decomposition indicator compounds were present in BallM, MeltQ, and SpinMeltQ, but not in FreD and SprayD. All samples exhibited a glass transition. Additionally, FreD, SprayD, BallM, and SpinMeltQ exhibited an exothermic cold crystallization peak, but MeltQ did not. Overall, this research provides evidence that sucrose is a material whose physicochemical properties are strongly influenced by amorphization method.

Combinatorial representations for the scheme of allocations of distinguishable particles into indistinguishable cells

Abstract For a scheme of allocation of distinguishable particles into indistinguishable cells we describe types of representation, numbering and enumerating of its outcomes in terms of the transition graph; this graph allows, in particular, to find the distribution on the set of outcomes. Several methods of statistical simulation of scheme outcomes are described.

Classification of particle height in a hopper bin from limited discharge data using convolutional neural network models

Hopper bin discharge processes are ubiquitous in many industrial applications. The preponderance of previous studies of this system has been focused on the forward discharge process given an initial particle packing configuration. Motivated by the needs in reaction design and optimization, we develop here an inverse reconstruction procedure that enables one to obtain the particle height information in the initial packing configuration in the hopper bin from limited discharge dynamics data and particle characteristics. Our procedure is based on convolutional neural network (CNN) models, which take experimentally measurable particle residence time, diameter and density as input, and provide a classification of particle height in the initial packing as output. Using MFIX-DEM simulations with enhanced physical modeling capabilities, we generate extensive discharge data for hoppers containing two distinct solid phase particles with four distinct classes of initial packing geometries. The CNN reconstruction models are subsequently trained and tested using the discharge data. We find that the reconstruction (i.e., particle height classification) accuracy strongly depends on the initial packing geometry. For hopper-specific CNN models exclusively trained using discharge data from a single hopper, the classification can attain an accuracy up to almost 90%. The accuracy decreases for generic reconstruction models trained using a collection of discharge data for multiple hoppers. Finally, we apply the CNN model to accurately reconstruct a hopper containing four distinct solid phases with a layered configuration to further demonstrate its utility.

Particle Shape Control via Etching of Core@Shell Nanocrystals

The application of nanocrystals as heterogeneous catalysts and plasmonic nanoparticles requires fine control of their shape and chemical composition. A promising idea to achieve synergistic effects is to combine two distinct chemical and/or physical functionalities in bimetallic core@shell nanocrystals. Although techniques for the synthesis of single-component nanocrystals with spherical or anisotropic shape are well-established, new methods are sought to tailor multicomponent nanocrystals. Here, we probe etching in a controlled redox environment as a synthesis technique for multicomponent nanocrystals. Our Monte Carlo computer simulations demonstrate the appearance of characteristic non-equilibrium intermediate microstructures that are further thermodynamically tested and analyzed with molecular dynamics. Convex platelet, concave polyhedron, pod, cage, and strutted-cage shapes are obtained at room temperature with fully coherent structure exposing crystallographic facets and chemical elements along distinct particle crystallographic directions. We observe that structural and dynamic properties are markedly modified compared to the untreated compact nanocrystal.