Radial Segregation Research Articles

Effect of combined ferrous burden composition and ore-coke interaction on blast furnace burden distribution

The distribution of burden materials at the blast furnace throat is highly correlated with the combined ferrous burden with different mass percentages of sinter, pellet, and lump ore. In this work, the motion behavior of the burden particles was studied under different combined ferrous burden composition, and an analysis was conducted on the cooperative influence of the combined ferrous burden composition and ore-coke interaction on the burden distribution characteristics. The results indicate that the particle flow trajectory is stable when the total mass fraction of pellet and lump ore is less than 32 %. Central coke charging can minimize the radial segregation of the combined ferrous burden. At the ore-coke layer interface, the accumulation and percolation behaviors of ore particles are observed. When the pellet ratio is high, the ore particles can easily penetrate into the void structure of the coke layer.

Hubble Space Telescope proper motions of Large Magellanic Cloud star clusters

We present proper motion (PM) measurements for a sample of 23 massive star clusters within the Large Magellanic Cloud using multi-epoch data from the Hubble Space Telescope (HST). We combined archival data from the ACS/WFC and WFC3/UVIS instruments with observations from a dedicated HST programme, resulting in time baselines between 4.7 and 18.2 yr available for PM determinations. For bright well-measured stars, we achieved nominal PM precisions of 55 μas yr−1 down to 11 μas yr−1. To demonstrate the potential and limitations of our PM data set, we analysed the cluster NGC 1850 and showcase a selection of different science applications. The precision of the PM measurements allows us to disentangle the kinematics of the various stellar populations that are present in the HST field. The cluster has a centre-of-mass motion that is different from the surrounding old field stars and also differs from the mean motion of a close-by group of very young stars. We determined the velocity dispersion of field stars to be 0.128 ± 0.003 mas yr−1 (corresponding to 30.3 ± 0.7 km s−1). The velocity dispersion of the cluster inferred from the PM data set most probably overestimates the true value, suggesting that the precision of the measurements at this stage is not sufficient for a reliable analysis of the internal kinematics of extra-galactic star clusters. Finally, we exploit the PM-cleaned catalogue of likely cluster members to determine any radial segregation between fast and slowly-rotating stars, finding that the former are more centrally concentrated. With this paper, we also release the astro-photometric catalogues for each cluster.

Experimental and Numerical Study of Computer Vision-Based Real-Time Monitoring of Polymeric Particle Mixing Process in Rotary Drum.

In the drum mixing of particulate polymers, segregation may occur. By measuring the mixing status in real time, it is possible to implement corrective measures to prevent separation and improve the efficiency of the process. This study aims to develop and validate a real-time vision system designed to monitor the mixing process of polymeric particles in a rotary drum mixer, employing a novel centroid-based model for determining the mixing index. The proposed centroid-based model is capable of addressing the radial particle segregation issue without the need for extra image-processing procedures like image subdivision or pixel randomization. This innovative approach greatly improves computational efficiency by processing over 68 image frames per second. The new processing method is 2.8 times faster than the gray-level co-occurrence matrix method and 21.6 times faster than the Lacey index approach. This significantly improves real-time monitoring capabilities and enables real-time image processing using only affordable single-board computers and webcams. The proposed vision-based system for monitoring rotary drum mixing has undergone validation via cross-validation using discrete element method simulations, ensuring its accuracy and reliability.

Experimental investigation on shape segregation of 3D printed particles using an Freeman FT4 rheometer

This study examines how granular mixtures of differently shaped particles segregate in a Freeman (FT4) rheometer apparatus. The mixtures contained two sets of particles with varying shapes and relative sizes. While our focus was on the effect of particle shape on segregation, we recognized that even slight differences in size could lead to segregation. We specifically investigated when particles of different shapes have the same effective size, exploring three cases: 1) the largest sphere within a cubic particle (inscribed sphere), 2) the smallest sphere enclosing a cubic particle (circumscribed sphere), and 3) a sphere and cube with equal volume. Our key finding indicates that binary mixtures of cubical and spherical particles can significantly segregate either axially or radially in the particle bed with a circumscribed sphere configuration. We propose that the primary mechanism for this is percolation and additionally, in the case of radial segregation, ordering of cubes adjacent to the cylinder wall.

PDS 70 unveiled by star-hopping: Total intensity, polarimetry, and millimeter imaging modeled in concert

Most ground-based direct-imaging planet search campaigns use angular differential imaging that distorts the signal from extended sources, such as protoplanetary disks. In the case of the young system PDS 70, for which two planets were detected within the cavity of a protoplanetary disk, obtaining a reliable image of both planets and the disk is essential to understanding planet-disk interactions. Our goals are to reveal the true intensity of the planets and disk without self-subtraction effects for the first time, search for new giant planets beyond separations of 0.1$''$, and to study the morphology of the disk shaped by two massive planets. We present $YJHK$-band imaging, polarimetry, and spatially resolved spectroscopy of PDS 70 using near-simultaneous reference star differential imaging, also known as star-hopping. We created a radiative transfer model of the system to try to match the near-infrared imaging and polarimetric data within measurement errors. Sub-millimeter imaging data from ALMA were also modeled. Furthermore, we extracted the spectra of the planets and the disk and compared them. With strong constraints, we find that the disk is quite flared, with a scale height of sim 15<!PCT!> at the outer edge of the disk at sim 90 au, similar to some disks in the literature. The gap inside sim 50 au is estimated to have sim 1<!PCT!> of the dust density of the outer disk. The northeast outer disk arc seen in previous observations is likely the outer lip of the flared disk. Abundance ratios of sub-micron, micron, and grains estimated by the modeling indicate a shallow grain-size index greater than $-2.7$, instead of the canonical -3.5. There is both vertical and radial segregation of grains. Planet $c$ is well separated from the disk and has a spectrum similar to planet $b$, and it is clearly redder than the disk spectra. Planet $c$ is possibly associated with the sudden flaring of the disk starting at sim 50 au. We found no new planets in the system. If we assume DUSTY models and an age of 5 Myrs, this indicates no new planets more massive than 5 outside a 12 au separation.

Kinetic cooperativity resolves bidirectional clogging within the nuclear pore complex

As the main gatekeeper of the nucleocytoplasmic transport in eukaryotic cells, the nuclear pore complex (NPC) faces the daunting task of facilitating the bidirectional transport of a high volume of macromolecular cargoes while ensuring the selectivity, speed, and efficiency of this process. The competition between opposing nuclear import and export fluxes passing through the same channel is expected to pose a major challenge to transport efficiency. It has been suggested that phase separation-like radial segregation of import and export fluxes within the assembly of intrinsically disordered proteins that line the NPC pore could be a mechanism for ensuring efficient bidirectional transport. We examine the impact of radial segregation on the efficiency of bidirectional transport through the NPC using a coarse-grained computational model of the NPC. We find little evidence that radial segregation improves transport efficiency. By contrast, surprisingly, we find that NTR crowding may enhance rather than impair the efficiency of bidirectional transport although it decreases the available space in the pore. We identify mechanisms of this novel crowding-induced transport cooperativity through the self-regulation of cargo density and flux in the pore. These findings explain how the functional architecture of the NPC resolves the problem of efficient bidirectional transport, and provide inspiration for the alleviation of clogging in artificial selective nanopores.

Discrete element method study of the mixing and heat transfer behaviour of a binary‐size granular system in a rotating drum

AbstractUnderstanding the internal solid motion and heat transfer behaviour within rotating drums is paramount for their design and operation across various industries. The discrete element method (DEM) is utilized to elucidate the general flow, mixing, and heat transfer characteristics of particles within rotating drums. Following model validation, this study delves into the mixing behaviour and heat transfer patterns of binary‐size particles in the rotating drum, while also assessing the impact of size ratio and rotating speed. The findings reveal that variations in particle size result in noticeable radial segregation, consequently affecting the heat transfer dynamics of solid phase within the system. Higher rotating speeds enhance mixing and dispersion of solid phase but lead to a decrease in the averaged particle temperature. Furthermore, the heat flux exhibits a negative correlation with particle size. Distinct heat transfer behaviours are observed among particles of different sizes in both active and passive areas, with larger particle size ratios exacerbating segregation, potentially impacting final product quality. In summary, these findings offer crucial insights into heat transfer phenomena in rotating drums, aiding in the design and operation of apparatus.

Constrain the Dark-matter Distribution of Ultra-diffuse Galaxies with Globular-cluster Mass Segregation: A Case Study with NGC5846-UDG1

The properties of globular clusters (GCs) contain valuable information of their host galaxies and dark-matter halos. In the remarkable example of ultra-diffuse galaxy, NGC5846-UDG1, the GC population exhibits strong radial mass segregation, indicative of dynamical-friction-driven orbital decay, which opens the possibility of using imaging data alone to constrain the dark-matter content of the galaxy. To explore this possibility, we develop a semianalytical model of GC evolution, which starts from the initial mass, structural, and spatial distributions of the GC progenitors, and follows the effects of dynamical friction, tidal evolution, and two-body relaxation. Using Markov Chain Monte Carlo, we forward-model the GCs in a UDG1-like potential to match the observed GC statistics, and to constrain the profile of the host halo and the origin of the GCs. We find that, with the assumptions of zero mass segregation when the star clusters were born, UDG1 is relatively dark-matter-poor compared to what is expected from stellar-to-halo–mass relations, and its halo concentration is lower than the cosmological average, irrespective of having a cuspy or a cored profile. Its GC population has an initial spatial distribution more extended than the smooth stellar distribution. We discuss the results in the context of scaling laws of galaxy–halo connections, and warn against naively using the GC-abundance–halo–mass relation to infer the halo mass of ultra-diffuse galaxies. Our model is generally applicable to GC-rich dwarf galaxies, and is publicly available.

Improving the quality and properties of GaInSb crystal with Al doping

GaInSb crystal is a promising substrate material that can be used to prepare various high-performance devices. Ga0.86In0.14Sb and Al-doped Ga0.86In0.14Sb (Ga0.86In0.14Sb:Al) crystals were grown with the vertical Bridgman method (VB). The doping concentration of aluminum (Al) is 0.005–0.015 molar ratio. The effect of Al doping on the structure and properties of Ga0.86In0.14Sb crystal was studied. The results indicated that Al doping significantly reduced the segregation of indium (In) component in the crystal, with the radial segregation reaching a minimum of 0.051 mol% mm−1 and the axial segregation reaching a minimum of 0.067 mol% mm−1. The doping of Al also improved the crystal quality (lattice structure integrity) of Ga0.86In0.14Sb. The passivation and compensation of Al on the intrinsic defects of Ga0.86In0.14Sb crystal significantly inhibited the generation of dislocation, of which density decreased to 2.461 × 103 cm−2. The doping of Al as the equivalent electron element of gallium (Ga) and In not only made the carrier concentration increase to 1.848 × 1018 cm−3 but also made the carrier mobility increase to 1.982 × 103 cm2/(V·s), resulting in the resistivity decreasing to 1.261 × 10−3 Ω·cm.

The frequency and mass-ratio distribution of binaries in clusters II: radial segregation in the nearby dissolving open clusters Hyades and Praesepe

ABSTRACT We have determined the mass functions, mass-ratio distribution functions, and fractions of binary stars with mass ratios above particular thresholds for radially separated populations of stars in the nearby open clusters Hyades and Praesepe. Radial mass segregation is detected, with the populations of stars within the tidal radii having much flatter mass functions than those outside the tidal radii. Within the tidal radii, the frequency of binary stars with mass ratio q > 0.5 is 50–75 per cent higher for Hyades and 5–30 per cent higher for Praesepe. We also, for the first time, detect mass-ratio radial segregation. Of the binaries for which q > 0.5, ∼80 per cent of the inner Hyades population also have q > 0.75, while for the extra-tidal population, the ratio is ∼50 per cent. For Praesepe, ∼67 per cent of the inner sample have q > 0.75, and 35–45 per cent of the outer sample.

Effect of granular shape on radial segregation in a two-dimensional drum

Granular segregation is widely observed in nature and industry. Most research has focused on segregation caused by differences in the size and density of spherical grains. However, due to the fact that grains typically have different shapes, the focus is shifting towards shape segregation. In this study, experiments are conducted by mixing cubic and spherical grains. The results indicate that spherical grains gather at the center and cubic grains are distributed around them, and the degree of segregation is low. Through experiments, a structured analysis of local regions is conducted to explain the inability to form stable segregation patterns with obviously different geometric shapes. Further, through simulations, the reasons for the central and peripheral distributions are explained by comparing velocities and the number of collisions of the grains in the flow layer.

Shape-dependent radial segregation in rotating drum: Insights from DEM simulations

This study evaluates how particle shape affects the segregation behavior of binary mixtures in a rotating drum. The Discrete Element Method (DEM) is used to investigate radial segregation and its dependence on particle shape by varying the particle’s aspect ratio. Two scenarios are examined: one when the shape of fine particles held constant and varying shape for coarse particles, and another when the shape of coarse particles held constant and varying shape for fine particles. These scenarios help quantify the relative mixing observed in the system for the considered shapes. The SI trend in terms of aspect ratio (AR) for coarse particles is as follows: AR (5.0) > AR (2.5) > AR (1). In contrast, for fine particles, the trend is AR (5.0) > AR (1) > AR (2.5). The results indicate that coarse particles with lower packing density exhibit higher segregation. Conversely, fine particles with pronounced elongation facilitate mixing.

Recognition and reconstruction of cell differentiation patterns with deep learning.

Cell lineage decisions occur in three-dimensional spatial patterns that are difficult to identify by eye. There is an ongoing effort to replicate such patterns using mathematical modeling. One approach uses long ranging cell-cell communication to replicate common spatial arrangements like checkerboard and engulfing patterns. In this model, the cell-cell communication has been implemented as a signal that disperses throughout the tissue. On the other hand, machine learning models have been developed for pattern recognition and pattern reconstruction tasks. We combined synthetic data generated by the mathematical model with spatial summary statistics and deep learning algorithms to recognize and reconstruct cell fate patterns in organoids of mouse embryonic stem cells. Application of Moran's index and pair correlation functions for in vitro and synthetic data from the model showed local clustering and radial segregation. To assess the patterns as a whole, a graph neural network was developed and trained on synthetic data from the model. Application to in vitro data predicted a low signal dispersion value. To test this result, we implemented a multilayer perceptron for the prediction of a given cell fate based on the fates of the neighboring cells. The results show a 70% accuracy of cell fate imputation based on the nine nearest neighbors of a cell. Overall, our approach combines deep learning with mathematical modeling to link cell fate patterns with potential underlying mechanisms.

A deep dive into the Type II Globular Cluster NGC 1851

Abstract About one-fifth of the Galactic globular clusters (GCs), dubbed Type II GCs, host distinct stellar populations with different heavy elements abundances. NGC 1851 is one of the most studied Type II GCs, surrounded by several controversies regarding the spatial distribution of its populations and the presence of star-to-star [Fe/H], C+N+O, and age differences. This paper provides a detailed characterization of its stellar populations through Hubble Space Telescope (HST), ground-based, and Gaia photometry. We identified two distinct populations with different abundances of s-process elements along the red-giant branch (RGB) and the sub-giant branch (SGB) and detected two sub-populations among both s-poor (canonical) and s-rich (anomalous) stars. To constrain the chemical composition of these stellar populations, we compared observed and simulated colors of stars with different abundances of He, C, N, and O. It results that the anomalous population has a higher CNO overall abundance compared to the canonical population and that both host stars with different light-element abundances. No significant differences in radial segregation between canonical and anomalous stars are detected, while we find that among their sub-populations, the two most chemical extremes are more centrally concentrated. Anomalous and canonical stars show different 2D spatial distributions outside ∼3 arcmin, with the latter developing an elliptical shape and a stellar overdensity in the northeast direction. We confirm the presence of a stellar halo up to ∼80 arcmin with Gaia photometry, tagging 14 and five of its stars as canonical and anomalous, respectively, finding a lack of the latter in the south/southeast field.

Radial mixing and segregation of binary density ellipsoids in a rotating drum

In this paper, the Discrete Element Method (DEM) is applied to investigate the radial mixing and segregation of a binary mixture of ellipsoids with different densities in a rotating drum. The ellipsoidal particles are constructed with multi-sphere model, and the periodic boundary condition is adopted. The influences of aspect ratio and density ratio on the mixing quality and final segregation extent are examined. Simulation results show that, light particles are inclined to occupy at the periphery of the granular bed, whereas heavy ones concentrate in the center area. As particle aspect ratio deviates from unity, i.e. oblate or prolate shape, the mixing index is increased and final segregation degree is decreased. It is discovered that convective mixing is predominant over diffusion for any given particle shape (oblate, spherical, prolate). The prolate particles (AR=4.0) reveal the highest compactness of a binary mixture system in the rotating drum. Particle translation is the main movement mode and ellipsoids are more easily to rotate. Particle shape affects collision probability and strength, and ellipsoidal particles need more energy to be driven. The reduction of density ratio of light to heavy particles does inevitably contribute to a greater segregation degree. The results also indicate that the initial states of binary mixtures do not affect the final segregation patterns.

Effect of aspect ratio of ellipsoidal particles on segregation of a binary mixture in a rotating drum

In this work, the Discrete Element Method (DEM) is used to investigate the evolution of radial segregation and its dependence on the shape by varying the particle’s aspect ratio. A total of 37 different types of binary mixtures are created, where the aspect ratio of particles varies from 0.25 to 4.0. The results shows that in binary mixture the aspect ratio of both coarse and fine particles influence mixing. The initial well-mixed binary mixture of coarse and fine particles evolves into a radial segregated state where the fine particles occupy a central core of the drum surrounded by coarse particles. Spherical shape particles, whether acting as coarse or fine in binary mixture, promote segregation. Two characteristics of particles i.e., Monodisperse random packing density and sphericity are used to explain the segregation trend and its relationship to aspect ratio.

Study on radial segregation of whole and broken rice in an indented cylinder separator

Indented cylinder separators are often used to complete the grading of rice, but there is radial segregation which affects the screening performance. To clarify the cause of its radial segregation, the rice data required for simulation were first obtained through experiments, and then discrete element method (DEM) was used to analyze the segregation process of whole and broken rice at low filling levels. The results showed that with the intensification of segregation, the screening efficiency decreased gradually. Increasing the filling level will increase segregation. Segregation core to form in the center of the left half of the bed. The radial segregation mechanism of whole and broken rice is “percolation”, which is the result of a combination of particle size and shape driving forces. This study is helpful to improve the screening efficiency of rice and provides some reference for exploring segregation of multi-component mixture with multi-attribute differences.

Size-induced axial segregation of ellipsoids in a rotating drum

Granular materials of different sizes and shapes in a rotating drum tend to segregate in the axial direction. In the past, extensive numerical studies have been conducted for spherical particles, showing the phenomenon of band formation. However, the axial size-induced segregation of non-spherical particles receives limited attention. In this work, we report an interesting finding of band formation for ellipsoidal particles with aspect ratio varying from 0.5 to 2.0. The results show that for ellipsoids, two weak bands appear in the vicinity of endwalls, indicating that low flowability of ellipsoids reduces the tendency of band formation. Moreover, for different shaped particles, small particles in the bands come from different regions. The results also illustrate that the radial size-induced segregation pattern develops quickly, with small particles located at the centre and then the small particles tend to migrate along the drum to form bands.

Effect of rotating magnetic field intensity on structure and electrical and optical properties of GaInSb crystal grown with travelling heater method

Ga1−x In x Sb(0 < x < 1) crystal is a very promising substrate material, which can be used to fabricate a variety of high-performance infrared detectors and lasers by epitaxial growth. Herein, we prepared high quality Ga0.86In0.14Sb crystal (25 mm diameter, 100 mm length) with travelling heater method applied rotating magnetic field (RMF), and revealed the effects of RMF intensity on structure and electrical and optical properties of the crystal. As the RMF intensity increased the crystal quality significantly improved, and the radial segregation of indium decreased from 0.258 to 0.031 mol% mm−1, in the center of the crystal. Similarly, the segregation of indium along the ingot between 20 to 80 mm, toward the traveling zone, decreased from 0.114 to 0.038 mol% mm−1. The dislocation density of GaInSb crystal ingot also decreased from 5.361 × 105 cm−2 to 5.295 × 103 cm−2. The electric properties of the crystal also improved, the carrier mobility increased to 1.902 × 103 from 1.358 × 103cm2 (V·s)−1, the resistivity decreased to 1.047 × 10−3 from 1.822 × 10−3 Ω·cm. Moreover, the infrared transmittance increased from 36% to 39%.

Segregation behavior of particles with Gaussian distributions in the rotating drum with rolling regime

The mixing and segregation of granular materials are essential to provide valuable insights and references for practical industrial production. In this paper, the segregation behaviors of particles with Gaussian distributions and 40% filling level in the rotating drum with rolling regime were numerically studied by the discrete element method. The effects of rotation speed and particle size parameter λ (size ratio of the largest versus smallest particles) on the segregation behavior (mixing index, segregation rate), flow characteristics (particle velocity and trajectory, gyration degree and radius, particle size distributions) and the microscopic properties (collision, contact force, axial diffusion, and kinetic energy) of granular systems were systematically investigated. The results show that the segregation rate and degree of particles with Gaussian distributions gradually increase with the increase of the rotation speed and particle size parameter λ. The radial and axial segregation patterns become more obvious with the increase of λ. And the variation of the flow characteristics of particles with different sizes in the same system is also inconsistent. The microscopic properties of Gaussian-dispersed particles change with the rotation speed and λ. The rapid radial segregation depends on the larger pores existed in the granular system, which leads to a gradual increase of the axial dispersion coefficient of large particles and a gradual decrease of the axial dispersion coefficient of small particles.