Role Of Particle Size Distribution Research Articles

Effect of interparticle correlation on magnetic hyperthermia in biological media: A numerical study

Numerical simulations of the temperature field of a circular tumour subjected to magnetic hyperthermia are presented. The calculation domain is composed by a 5 mm circular tumour surrounded by a 2 cm × 2 cm region of a healthy tissue. Realistic values of the biological media properties are considered. Simulations are carried by an in-house research code that solves the biological heat equation in the presence of a magnetic dissipation term through a finite differences scheme. The magnetic source term is expressed in terms of the out-of-phase response of the fluid’s complex susceptibility, when subjected to an oscillatory magnetic field. This quantity is obtained using asymptotic theories and numerical simulations in the scale of the magnetic nanoparticles through another in-house research code based on Langevin Dynamics. Dipolar particle interactions are computed through a robust scheme of Ewald summation. The microscopic formulation for the particles also considers Brownian effects in their translational and rotational motion. Realistic values of these parameters are considered in order to provide a dimensional evaluation of the temperature field in the biological tissue comparable to previous numerical and experimental studies. The role of particle size distribution on the temperature field is carefully investigated. Temperature fields are also linked with microscopic geometrical features of suspended magnetic particles in order to provide a clear multiscale understanding of the physics of magnetic heat induction using alternating fields. Our results indicate that the role of dipolar interactions seems to be relevant for particle radii in the range 5nm≤a≤7nm, specially for higher volume fraction of particles, where the classical Langevin model for the saturation susceptibility fails in the prediction of the steady-state tumour temperature. For a volume fraction of particles of 15% the differences on the final temperature of the tumour associated with dipolar interactions are in the order of 20% for particles with a nominal radius in the range 5nm≤a≤7nm. In dilute regimes the classical Langevin model succeeds in the prediction of the final temperature of the tumour as expected.

Experimental Investigation of the Non-Darcy Equivalent Permeability of Fractured Coal Bodies: The Role of Particle Size Distribution

The permeability of crushed coal bodies plays a bottom neck role in seepage processes, which significantly limits the coal resource utilisation. To study the permeability of crushed coal bodies under pressure, the particle size distribution of crushed coal body grains is quantitatively considered by fractal theory. In addition, the parameters of the percolation characteristics of crushed coal body grains are calculated. Moreover, the permeability of the crushed coal body during recrushing is determined by the fractal dimension and porosity. A lateral limit compression test with the crushed coal bodies was carried out to illustrate the effect of the porosity on the permeability, In addition, a compressive crushed coal body size fractal–permeability model was proposed by combination of the fractal dimension and the non-Darcy equivalent permeability. The results show (1) the migration and loss of fine particles lead to a rapid increase in the porosity of the crushed coal body. (2) Increases in the effective stress cause the porosity and permeability to decrease. When the porosity decreases to approximately 0.375, its effect is undermined. (3) The migration and loss of fine particles change the pore structure and enhance the permeability properties of the skeleton, causing sudden seepage changes. (4) At low porosity, the permeability k is slightly larger than the non-Darcy equivalent permeability ke. Thus, the experimental data show an acceptable agreement with the present model. A particle size fractal–percolation model for crushed coal bodies under pressure provides a solution for effectively determining the grain permeability of the crushed coal bodies. The research results can contribute to the formation of more fractal-seepage theoretical models in fractured lithosphere, karst column pillars and coal goaf, and provide theoretical guidance for mine water disaster prevention.

New Estimate of Organic Carbon Export From Optical Measurements Reveals the Role of Particle Size Distribution and Export Horizon

AbstractExport of sinking particles from the surface ocean is critical for carbon sequestration and to provide energy to the deep biosphere. The magnitude and spatial patterns of this export have been estimated in the past by in situ particle flux observations, satellite‐based algorithms, and ocean biogeochemical models; however, these estimates remain uncertain. Here, we use a recent machine learning reconstruction of global ocean particle size distributions (PSDs) from Underwater Vision Profiler 5 measurements to estimate carbon fluxes by sinking particles (35 μm–5 mm equivalent spherical diameter) from the surface ocean. We combine global maps of PSD properties with empirical relationships constrained against in situ flux observations to calculate particulate carbon export from the euphotic zone (5.8 ± 0.1 Pg C y−1) and annual maximum mixed layer depths (6.1 ± 0.1 Pg C y−1). The new flux reconstructions suggest a less variable seasonal cycle in the tropical ocean and a more persistent export in the Southern Ocean than previously recognized. Smaller particles (less than 418 μm) contribute most of the flux globally, while larger particles become more important at high latitudes and in tropical upwelling regions. Export from the annual maximum mixed layer exceeds that from the euphotic zone over most of the low‐latitude ocean, suggesting shallow particle recycling and net heterotrophy in the deep euphotic zone. These estimates open the way to fully three‐dimensional global reconstructions of particle fluxes in the ocean, supported by the growing database of in situ optical observations.

The Role of Particle Size Distribution for Fluid Loss Materials on Formation of Filter-Cakes and Avoiding Formation Damage

Abstract Numerous studies have shown that careful particle size selection is the main parameter for reducing fluid loss when drilling permeable or fractured formations. The methods are generally built around either the D50 or D90 values of the particles in the fluid as a relative size to the pore openings of the formation to minimize fluid loss. A series of studies were conducted with the aim of assessing if analysis of fluid loss could be used to separate the formation of internal and external filter-cakes, thereby enabling a more accurate estimate of the permeabilities of the internal and external filter-cakes. It was concluded that conventional particle size methods were found to be adequate for designing a fluid for wellbore stabilization purposes. This led to higher solids invasion and a more impermeable internal filter-cake. However, for optimization of reservoir drilling fluids, a different particle size selection method was found to be more useful to prevent reservoir formation damage. This method involves selecting particles that are resistant towards shear-degradation and with a D90 particle size ⪞3/2 the pore size of the formation. By analyzing fluid loss regression data and correlating these with indicators of formation damage, such as disc mass and permeability change, it was found that a ratio defined as the relative plugging factor could provide insight into the extent of solids invasion into the formation and potential formation damage.

Large-scale frictionless jamming with power-law particle size distributions.

Due to significant computational expense, discrete element method simulations of jammed packings of size-dispersed spheres with size ratios greater than 1:10 have remained elusive, limiting the correspondence between simulations and real-world granular materials with large size dispersity. Invoking a recently developed neighbor binning algorithm, we generate mechanically stable jammed packings of frictionless spheres with power-law size distributions containing up to nearly 4000000 particles with size ratios up to 1:100. By systematically varying the width and exponent of the underlying power laws, we analyze the role of particle size distributions on the structure of jammed packings. The densest packings are obtained for size distributions that balance the relative abundance of large-large and small-small particle contacts. Although the proportion of rattler particles and mean coordination number strongly depend on the size distribution, the mean coordination of nonrattler particles attains the frictionless isostatic value of six in all cases. The size distribution of nonrattler particles that participate in the load-bearing network exhibits no dependence on the width of the total particle size distribution beyond a critical particle size for low-magnitude exponent power laws. This signifies that only particles with sizes greater than the critical particle size contribute to the mechanical stability. However, for high-magnitude exponent power laws, all particle sizes participate in the mechanical stability of the packing.

CFD-DEM simulation of polydisperse gas-solid flow of Geldart A particles in bubbling micro-fluidized beds

Polydisperse particles are ubiquitous, yet their unique roles are inadequately understood. In this study, CFD-DEM study on the fluidization of polydisperse particles in bubbling micro-fluidized beds was performed. The method was firstly validated by the experimentally measured bed expansion characteristics and voidage of emulsion phase. Detailed analysis of bed hydrodynamics was then performed. It was shown that (i) gas back-mixing is minimized in micro-fluidized beds due to the near plug gas flow; (ii) bubble pattern in micro and large fluidized beds is similar; (iii) particle size distribution (PSD) enhances fluidization quality in terms of higher bed expansion and higher voidage of emulsion phase, where ”fines” is the root cause; and (iv) significant axial segregation is only observed in the case of wide PSD, and microscale segregation analysis indicates that coarse particles are preferentially following the motion of bubbles. Present study not only offers insights into the role of PSD in gas fluidization, but also sheds light on the similarity and difference between micro and large fluidized beds.

Cloud condensation nuclei characteristics at the Southern Great Plains site: role of particle size distribution and aerosol hygroscopicity

The activation ability of aerosols as cloud condensation nuclei (CCN) is crucial in climate and hydrological cycle studies, but their properties are not well known. We investigated the long-term measurements of atmospheric aerosol properties, CCN concentrations (NCCN) at supersaturation (SS = 0.1%–1.0%), and hygroscopicity at the Department of Energy’s Southern Great Plains (SGP) site to illustrate the dependence of NCCN on aerosol properties and transport pathways. Cluster analysis was applied to the back trajectories of air masses to investigate their respective source regions. The results showed that aged biomass burning aerosols from Central America were characterized by higher accumulation mode particles (Naccu; median value 805 cm−3) and relatively high aerosol hygroscopicity (κ; median value ∼0.25) values that result in the higher CCN activation and relatively high NCCN (median value 258–1578 cm−3 at a SS of 0.1%–1.0%). Aerosols from the Gulf of Mexico were characterized by higher Naccu (∼35%), and NCCN (230–1721 cm−3 at a SS of 0.1%–1.0%) with the lowest κ (∼0.17). In contrast, relatively high nucleation mode particles (Nnucl; ∼20%) and low NCCN (128–1553 cm−3 at a SS of 0.1%–1.0%) with higher κ (∼0.30) values were observed on the aerosols associated with a westerly wind. The results indicate particle size as the most critical factor influencing the ability of aerosols to activate, whereas the effect of chemical composition was secondary. Our CCN closure analysis suggests that chemical composition and mixing state information are more crucial at lower SS, whereas at higher SS, most particles become activated regardless of their chemical composition and size. This study affirms that soluble organic fraction information is required at higher SS for better NCCN prediction, but both the soluble organics fraction and mixing state are vital to reduce the NCCN prediction uncertainty at lower SS.

Breakdown strength and energy density enhancement in polymer-ceramic nanocomposites: Role of particle size distribution

Polymer-ceramic nanocomposites play a very promising role for energy-storage in high power electronics and advanced pulsed power systems, due to their extremely fast charge-discharge capability. The low energy density is the key factor hindering their application, for which large endeavors have been made in the modulation of the fraction, morphology, size, and dispersion of the particle fillers but small in that of the size distribution, which is critical for energy-storage performance. We first investigated the role of this based on simulated nanocomposites with controlled lognormal distributions via a generation algorithm devised in this work. Dielectric response, breakdown behavior and energy-storage performance were explored for distributions with different standard deviations (SD) and mean values (MV), which were solved with the energy equivalence basis and a phase-field dielectric breakdown model. With the decrease of SD and MV, the effective permittivity declines slightly with enhanced permittivity change, which was related with the enhanced local electric field with intensified fluctuation and should be originated from the major contribution of the polymer matrix from the local energy perspective; whereas improved nominal breakdown strength was achieved owing to the weakened local maximum electric field, which leads to distinctly increased nominal energy density despite the slight decline of the permittivity. Keeping the fillers within a narrow disperse outperforms employing super fine particles. This work demonstrates that enhancement in breakdown strength and energy density can be attained via particle size distribution modulation, paving a new way for the further improvement of the energy-storage performance of polymer-ceramic nanocomposites.

Role of particle size distribution of bridging agent for drilling mud on formation damage near wellbore

One of the most important aspects of drilling mud is the optimization of particle size of bridging agent. The bridging agent is deliberately sized to minimize the fluid loss into the reservoir and to control the permeability near the wellbore. The objective of this study is to visualize the invasion depth of drilling mud particles into the formation and to evaluate the effects of bridging agent particle size and distribution on permeability and porosity near wellbore. Calcium carbonate was used as a bridging agent. It is important to know the severity of formation damage caused by the drilling mud to attain maximum production over a long period of time. This paper describes an experimental approach to study the effects of bridging agent particles in drilling mud on formation damages. The work was performed by changing the size of bridging agent particles from fine to medium and medium to coarse. It was observed that the calcium carbonate size should be almost identical to the pore throat median size of the formation face. The minimum reduction in permeability was noticed when pore spaces were covered with bridging particles, which prevent the fluid loss into the formation.

Role of wide particle size distribution on magnetization

Role of particle size distribution on magnetization of two polydispersed samples of antiferromagnetic NiO particles is investigated. Zero field-cooled and field-cooled susceptibility as a function of temperature (10–350 K) data indicate that samples are superparamagnetic. This behavior is again confirmed from M–H loops (up to $${\pm }\,70$$ kG) at 10 and 350 K. The magnetization as a function of applied magnetic field data at 350 K is analyzed considering a lognormal distribution in particle size. The estimated particle size distributions are compared with those determined from transmission electron micrographs. We find that the particle size distribution is overestimated if magnetic anisotropy is ignored while analyzing the magnetization data.

Effect of particle size distribution of metakaolin on hydration kinetics of tricalcium silicate

AbstractThe focus of this study is to elucidate the role of particle size distribution (PSD) of metakaolin (MK) on hydration kinetics of tricalcium silicate (C3S–T1) pastes. Investigations were carried out utilizing both physical experiments and phase boundary nucleation and growth (pBNG) simulations. [C3S + MK] pastes, prepared using 8%mass or 30%mass MK, were investigated. Three different PSDs of MK were used: fine MK, with particulate sizes <20 µm; intermediate MK, with particulate sizes between 20 and 32 µm; and coarse MK, with particulate sizes >32 µm. Results show that the correlation between specific surface area (SSA) of MK's particulates and the consequent alteration in hydration behavior of C3S in first 72 hours is nonlinear and nonmonotonic. At low replacement of C3S (ie, at 8% mass), fine MK, and, to some extent, coarse MK act as fillers, and facilitate additional nucleation and growth of calcium silicate hydrate (C–S–H). When C3S replacement increases to 30% mass, the filler effects of both fine and coarse MK are reversed, leading to suppression of C–S–H nucleation and growth. Such reversal of filler effect is also observed in the case of intermediate MK; but unlike the other PSDs, the intermediate MK shows reversal at both low and high replacement levels. This is due to the ability of intermediate MK to dissolve rapidly—with faster kinetics compared to both coarse and fine MK—which results in faster release of aluminate [Al(OH)4−] ions in the solution. The aluminate ions adsorb onto C3S and MK particulates and suppress C3S hydration by blocking C3S dissolution sites and C–S–H nucleation sites on the substrates’ surfaces and suppressing the post‐nucleation growth of C–S–H. Overall, the results suggest that grinding‐based enhancement in SSA of MK particulates does not necessarily enhance early‐age hydration of C3S.

Sintering processes in direct ink write additive manufacturing: A mesoscopic modeling approach

Direct ink write (DIW) is an emerging additive manufacturing technique that allows for the fabrication of arbitrary complex geometries required in many technologies. DIW of metallic or ceramic materials involves a sintering step, which greatly influences many of the microstructural features of the printed object. Herein, we explore solid-state sintering in DIW through a mesoscopic modeling framework that is capable of capturing bulk and interface thermodynamics and accounting for various mass transport mechanisms. Simulation results of idealized geometries identify regimes in materials parameter space, where densification rates are enhanced. With the aid of several statistical and topological descriptors, the role of particle size distribution (PSD) on the microstructural evolution is explored and quantified. More specifically, it is found that a bi-dispersed PSD enhances pore shrinkage kinetics. However, bi-dispersity yields microstructures with pores that are highly eccentric, an effect that could be detrimental to the mechanical properties of the printed material. On the whole, our modeling approach provides a capability to explore the phase space of DIW process parameters and determine ones that lead to optimal microstructures.

Role of particle size distribution and magnetic anisotropy on magnetization of antiferromagnetic nanoparticles

Magnetization measurements on antiferromagnetic iron storage protein ferritin are reported. The magnetization as a function of applied magnetic field data in superparamagnetic region are analyzed considering a distribution in particle size. The estimated particle size distribution is compared with that determined from transmission electron micrograph. Effect of magnetic anisotropy on magnetization process of this nanoparticle system is also discussed.

Discussion of “Laboratory Assessment of the Role of Particle Size Distribution on the Deformation and Degradation of Ballast under Cyclic Loading” by Buddhima Indraratna, Yifei Sun, and Sanjay Nimbalkar

Discussion of “Laboratory Assessment of the Role of Particle Size Distribution on the Deformation and Degradation of Ballast under Cyclic Loading” by Buddhima Indraratna, Yifei Sun, and Sanjay Nimbalkar

Closure to “Laboratory Assessment of the Role of Particle Size Distribution on the Deformation and Degradation of Ballast under Cyclic Loading” by Buddhima Indraratna, Yifei Sun, and Sanjay Nimbalkar

Closure to “Laboratory Assessment of the Role of Particle Size Distribution on the Deformation and Degradation of Ballast under Cyclic Loading” by Buddhima Indraratna, Yifei Sun, and Sanjay Nimbalkar

Discussion of “Laboratory Assessment of the Role of Particle Size Distribution on the Deformation and Degradation of Ballast under Cyclic Loading” by Buddhima Indraratna, Yifei Sun, and Sanjay Nimbalkar

Discussion of “Laboratory Assessment of the Role of Particle Size Distribution on the Deformation and Degradation of Ballast under Cyclic Loading” by Buddhima Indraratna, Yifei Sun, and Sanjay Nimbalkar

Chalcopyrite and pyrite floatabilities in the presence of sodium sulfide and sodium metabisulfite in a high pyritic copper complex ore

ABSTRACTOne of the principal problems in flotation of copper complex ores is the presence of pyrite and copper-activated pyrite in moderately alkaline pHs. Misreported pyrite into copper concentrates dramatically declines copper grade and its recovery. In this study, the effect of sodium sulfide, sodium metabisulfite (SMBS), and their dosages (100, 200, 300, and 400 g/t) were investigated on chalcopyrite and pyrite floatabilities in a high pyritic copper sulfide ore. Furthermore, the role of particle size distribution (PSD) in three different levels (i.e., d70, d75, and d80 of passing 75 µm) was evaluated by a series of batch flotation experiments. It was revealed that using 200 g/t SMBS provides not only the highest and the lowest chalcopyrite and pyrite recoveries, but also the maximum and minimum copper and iron grades. Pyrite recovery was sharply increased by the addition of sodium sulfide in light of sodium sulfide-induced collectorless flotation; however, it showed a very weak effect on chalcopyrite floatability. In addition, the highest and lowest chalcopyrite and pyrite recoveries were, respectively, identified when d75 equaled to 70% 75 µm. In other words, for the high pyritic copper ore type, it is feasible to achieve the highest chalcopyrite recovery consuming the lowest grinding energy.

The kinetics modeling of chalcopyrite and pyrite, and the contribution of particle size and sodium metabisulfite to the flotation of copper complex ores

ABSTRACTIn this study, a series of batch flotation experiments was conducted to evaluate both the role of particle size distribution and the presence of sodium metabisulfite Na2S2O5 (SMBS) in chalcopyrite and pyrite flotation. Kinetic flotation tests were also carried out in order to evaluate the kinetics behavior of the above-mentioned minerals. Following this, different flotation kinetics models were compared to the data from the experiments. According to the obtained results, it can be stated that feed particle size distribution plays a greater role in chalcopyrite and pyrite grades rather than their recoveries. However, the contribution of SMBS is higher than that of particle size with respect to pyrite recovery. In this study, the maximum recoveries for chalcopyrite and pyrite were found to be 92.2% and 47.5%, respectively. The minimum pyrite recovery (13.47%) occurred in the presence of 40 g/t Xanthate-flomin (C-4132), 20 g/t methyl isobutyl carbonyl (MIBC), 20 g/t polypropylene glycol (F742), 200 g/t sodium metabisulfite (SMBS), and at a d70 of 70 µm. A comparison between several flotation kinetics models and the experimental data revealed that the perfect mixer and the Arbiter models showed completely similar results for both chalcopyrite and pyrite with respect to the use of different configuration of chemical reagents.

Laboratory Assessment of the Role of Particle Size Distribution on the Deformation and Degradation of Ballast under Cyclic Loading

AbstractThe deformation and degradation of ballast is influenced by the size of the aggregates. In this study, a series of cyclic drained triaxial tests was conducted on ballast with different sizes using the large-scale cylindrical triaxial apparatus designed and built at the University of Wollongong, and two different frequencies of cyclic loading were used to simulate low-speed and high-speed trains. From the laboratory results, coarse particles experience less vertical and lateral strains, whereas the volumetric strains decrease and then increase as the coefficient of uniformity increases, regardless of the loading frequency. Resistance to deformation and degradation is found to be improved by increasing ballast density. Different trends between the extent of breakage and particle size are observed for different breakage indices, and accordingly the extent of breakage is characterized into two distinct zones, depending on the coefficient of uniformity (Cu), where the significantly reduced breakage cor...

Chemical Soil Degradation n the Area of the Głogów Copper Smelter Protective Forest/ Degradacja Ziemi Na Terenach Byłej Strefy Ochronnej Huty Miedzi Głogów

Earth surface is under the continous influence of the environmental factors - both natural and anthropogenic. The significant impact on the environment can be noted in areas adjacent to the metal industry plants, in a consequence of pollutants emission, especially dusts containing the heavy metals, into the atmosphere,. In the surroundings of Głogów Copper Smelter (GCS) elevated amounts of copper and lead has been noted. In the soils of the test sites were found up to 5250 mg・kg<sup>-1</sup> Cu and 1290 mg・kg<sup>-1</sup> Pb. The forest litter contained 3.3-5.1 more Cu and 3.9-8.6 Pb than the humic horizon of the soil. Analyse of the different soils covering the GCS protective forest area let specify the stabilising role of particle size distribution, TOC content and the soil reaction to Cu and Pb migration in the environment.