Irregular-shaped Particles Research Articles

Discrete Element Modeling of Irregular-Shaped Particles Using an Automatic Generation Algorithm-Based Multi-Sphere Model

Within the Discrete Element Method (DEM) framework, the multi-sphere model capable of creating irregular-shaped particles by several sub-spheres attracts increasing attention. Traditionally, the creation of irregular-shaped particles using the multi-sphere model requires manual determination of the position and diameter of each sub-sphere, which extremely increases the difficulty and workload of DEM modeling of irregular-shaped particles. To tackle this issue, a new automatic generation algorithm that helps to create arbitrary-shaped multi-sphere particles automatically was developed in this study. The quality of created multi-sphere particles can be easily controlled by adjusting the number of sub-spheres and size factor referred to as the size ratio of the smallest sub-sphere to the largest sub-sphere. To verify the effectiveness of the newly developed automatic generation algorithm, two verification tests were conducted in this study: (i) The packing behavior of irregular-shaped particles in a rectangular container and (ii) the mechanical behavior of irregular-shaped particles under the uniaxial compression. The fill heights of the simulations were in line with those of the experiments with an error of less than 8%. The mechanical behavior of irregular-shaped particles under the uniaxial compression can also be well reproduced. Besides, the influence of important parameters on simulation accuracy was also investigated. The results demonstrated that the newly developed automatic generation algorithm can accurately create complex-shaped particles with a small number of sub-spheres. Increasing the number of sub-spheres will improve the simulation accuracy but at the expense of computational efficiency. A larger size factor leads to higher computational efficiency in DEM simulation but is accompanied by a significant loss of accuracy.

A novel mesh algorithm to improve the packing efficiency of irregular-shaped particles in simulating cement paste's microstructure

A novel mesh algorithm to improve the packing efficiency of irregular-shaped particles in simulating cement paste's microstructure

STRUCTURAL AND MAGNETIC PROPERTIES OF Gd1-xBixFeO3

This work presents the synthesis of the Gd1-xBixFeO3 system by the combustion method at a temperature of 650°C using citric acid, the doping with Bi3+ took values from x=0.0 to x=0.14 with an increase of 0.02 per sample. The structural characterization of the system was carried out with the application of X-Ray Diffraction (XRD), which by Rietveld refinement showed a perovskite-type compound with orthorhombic structure, Pbnm space group, preferential orientation in the (112) plane and no secondary phases. The micrographs SEM show the presence of particles with irregular shape and average particle size between 0.092 to 0.24 µm. Finally, the magnetic analysis showed that the materials obtained exhibit anti-ferromagnetic properties with ferromagnetic components.

Computed Tomography-Driven Analysis of Particle Breakage Using a Coupled FDM-DEM Approach

This study proposes a refined approach for simulating the mechanical behavior of soils under high stress by integrating the Finite Difference Method-Discrete Element Method (FDM-DEM) with in-situ experiment. This novel framework incorporates advanced technologies such as flexible membrane and X-ray computed tomography (CT) to enhance the predictive capabilities of the simulation with physical insight. The FDM-DEM model adeptly simulates irregular particle shapes, capturing their interactions and the dynamics of particle breakage. The use of flexible membrane within the model further enriches this approach by enabling the capture of deformation responses in granular materials during shearing. Moreover, the adoption of CT technology facilitates continuous optimization of the simulation process. Validation through in-situ experiments has confirmed the model's effectiveness. The ability of the model to predict areas of high stress concentration—and their correlation with observed particle breakage patterns—underscores the utility of the enhanced FDM-DEM framework as a robust predictive tool for understanding the behavior of granular materials under shearing.

Wear behavior of CoCrFeNi high-entropy alloy prepared by mechanical alloying

Equiatomic quaternary CoCrFeNi powder was prepared from the individual metals by mechanical alloying of the mixed powders at room temperature. The as-milled powder contained particles of irregular shape with an average particle size of 0.62 μm, and exhibited a dual-phase composition of the face-centered cubic and the body-centered cubic structures. The as-milled powder was consolidated by hydraulic pressing at room temperature and sintered at 950 °C in argon and vacuum. The compacted material exhibited a single-phase composition of the face-centered cubic structure alone and a chemical composition close to equiatomic with uniform distribution of all constituents, indicating that the desired CoCrFeNi high-entropy alloy (HEA) had been formed. The microhardness of the vacuum-sintered CoCrFeNi HEA was measured to be 118±7 HV, exceeding that calculated by the rule of mixture. The coefficient of friction was determined by pin-on-disk dry sliding studies at room temperature and found to be 0.65 and 0.44 for the applied loads of 25 for 35N, respectively, and the corresponding wear rates were 4.6×10-4 and 9.1×10-4 mm3/N·m. XPS studies on the worn alloy surfaces showed the formation of oxidized tribo-layers, composed of predominantly Cr2O3. Overall, this study has demonstrated that mechanical alloying followed by simple furnace sintering at a moderate temperature is able to yield an abrasion-resistant CoCrFeNi HEA suitable for structural applications.

Evaluation of dimensional stability, setting time, tensile strength, and rheological properties of kaolin clay incorporated alginate impression material

This study aims to determine and compare the dimensional stability, setting time, tensile strength, and rheological properties of kaolin clay powder-modified and unmodified alginate impression material. Commercially available alginate-based impression material was considered as a control (C) while experimental groups E-1, E-2, and E-3 were fabricated by adding 2%, 4%, and 8% of kaolin clay powder in the control, respectively. Analytical techniques were used for the characterization of the samples. A tensile strength, rheological property, dimensional stability, and setting time were recorded for control and experimental groups. FTIR analysis confirmed the presence of kaolin clay powder in all experimental groups. SEM showed a round solid structure and irregular shape particle appearance in all experimental groups as well as a control group. The dimensional stability was improved by the addition of kaolin clay powder to the alginate impression material. The percentage dimensional change at 5 min, 6, and 12 h was increased for E3 adding (8% kaolin clay powder) and decreased for the control group. The mean value of tensile strength was highest for E3 followed by E2, E1, and least in control groups. Higher Young’s Modulus and lower deformation values were measured for E3. The mean value of setting time was highest for E3 and the least was in the control group. The results for both setting time and tensile strength were very highly statistically significant (p < 0.001). The mean values of viscoelasticity, flow, and drip test were increased statistically by adding various concentrations of kaolin clay powder to the alginate impression material.

The angle of repose and base stress distribution of granular piles: An experimental investigation

The angle of repose and characteristics of the base stress distribution underneath granular piles serve as essential indicators in understanding the mechanical and packing properties of particle system. One counterintuitive phenomenon is that there is an evident dip of the base stress beneath the pile apex that might have implications in the design of granular pile facilities. The repose angle and stress dip are influenced by many categories of factors and exhibit different variations. Based on the localized source method, particle packing experiments were conducted to investigate the effects of funnel height, particle size, particle shape, and packing method on the repose angle and the vertical stress distribution of granular piles. The experimental results show that the repose angle of piles of irregular particle shape and higher funnel height is much larger, but there is a decreasing trend of repose angle with increasing particle sizes. The natural packing angles before and after the critical collapse of granular pile exhibits periodic variation. On the other hand, the stress dip phenomenon occurred in all granular piles constructed by localized procedure. An increase in funnel height and a middle particle size mitigate the stress dip to some extent, whereas irregular particle shape exacerbates it. Comparison of the results from different packing methods reveals that larger repose angle and more pronounced stress dip are observed in confined packing piles compared to that in free packing piles. Considering a growth rate of less than 5 %, the average vertical stress under the sand silo reaches saturation state. Moreover, the pressure on the silo wall increases with the height of silo pile but remains somewhat lower than predicted by the Ketchum equation and current design values.

Evaluation of sustainability of fabrication process and characterization studies of activated carbon nanocatalyst from waste chestnut peels

This study uses waste chestnut peels to synthesize low-cost activated carbon-based catalysts through pyrolysis and calcination, investing distinct structural and compositional variations for sustianble application in manufacturing innovation and allied industries. The X-ray diffraction (XRD) analysis indicated sharp crystalline peaks in the calcinated product, contrasting with the amorphous nature of carbon material with some partially crystalline and distorted graphitic phases of the pyrolyzed product. Fourier-transform Infrared spectroscopy (FT-IR) analysis shows the presence of various functional groups such as O–H, C–O, C–H, CO, and CC. The analysis made through the scanning electron microscope (SEM) and transmission electron microscope (TEM) depicted a packed and agglomerated structure with different irregular particle shapes in the calcined carbon, while the sample prepared through pyrolysis exhibited a network-like structure with some interconnected voids. Energy dispersive X-ray (EDX) analysis showed varying carbon content which is found to be 47.41 % in the case of the calcinated sample and 99.7 % in the product prepared through pyrolysis. The calcined carbon exhibited a band gap of 4 eV, while the pyrolyzed carbon showed a higher band gap of 4.8 eV. In addition, the catalyst prepared through the calcination process exhibited significantly higher luminance intensity than that produced through pyrolysis, while both samples showed an excitation-dependent emission property. This work presents two simple methods for synthesizing nanocarbon-based catalysts using waste lignocellulosic biomass. In addition, the optical properties of the resulting nanocarbons suggest that they can be further explored for their applications as catalysts or biosensing agents.

Pembuatan Arang Aktif Nanopartikel Kulit Nangka Menggunakan High Energy Milling dengan Aktivator H3PO4

Activated charcoal is a compound formed from the arrangement of C atoms with a porous internal structure so that it has adsorption properties. One of the materials that can be used to make activated charcoal is jackfruit peel which contains cellulose (52.739%), lignin (10.599%), and hemicellulose (16.913%). Grind it to size of 100 mesh and put it in milling nanoparticles using tools HEM at a speed of 1200 rpm for 2 hours. Next, the activation process was carried out with phosphoric acid compounds and variables of 1 hour, 6 hours, 12 hours, 18 hours, 24 hours and concentrations of 5%, 10%, 15%, 20%, 25%. Samples in powder form were characterized by size, SEM, ash content and water content. Size test results with method Particle Size Analyzer (PSA) was found to be 1.22 nm. SEM test results show that jackfruit peel activated charcoal is composed of particles of diverse size, irregular shape and porous. EDX results showed that the chemical components of activated charcoal were C (57.08%), O (33.30%), Mg (1.33%), Si 1.57%, K 5.73%. Analysis of water content and ash content is the smallest, namely 0.18% and 0.2%.

On the mechanical behaviour of a coral silt from the South China Sea

During land reclamation on the reef islands, large amounts of silt-sized coral soils were created by segregation and degradation. The accumulation of silt-sized coral soils is fairy uncommon while the research on the geotechnical properties of the coral silt is very limited. In this study, a systematic experimental investigation on the mechanical behaviour of a coral silt obtained from a reclaimed reef island in the South China Sea has been performed, with comparisons to the coral sand collected from the same area. Similar to the coral sand, the coral silt particles also exhibit irregular particle shape and intra-particle pore due to their nature origin. According to the limiting water contents, the coral silt is classified as a low-plasticity clayey silt. Under one-dimensional compression, the coral silt exhibits a much quicker convergence compared to coral sand. Prior to convergence, the compressibility of coral silt is higher. After yielding, the compressibility of coral sand becomes higher due to significant particle breakage. The loose coral silt subjected to undrained shearing at low confining pressures exhibits obvious strain softening behaviour, indicating static liquefaction or flow failure. The peak and critical state friction angles of coral silt are lower than those of coral sand but much higher than those of the other terrigenous clayey silts. A curved critical state line with well-defined horizontal asymptote in the deviatoric stress – mean effective stress plane is identified for coral silt, again indicating higher potential to static liquefaction.

Fuel reactor simulation for coal chemical looping process: Effects of ash on flow behavior

Chemical looping gasification (CLG) is an environmentally friendly strategy for using coal that has significant promise for application in reality. Nevertheless, the process of generating and accumulating ash from coal presents obstacles to the advancement of this technology. To fully comprehend the effects of ash from coal on the internal flow properties of a fuel reactor (FR). The Computational Particle Fluid Dynamics (CPFD) approach was applied to predict the CLG with coal at the FR, uncovering distinctive flow properties of gas-solid reactions. This study investigated the effects of ash particles content, polydispersity and sphericity on the flow behavior within the bed. The simulation accurately predicted the motion of the bubbles within the FR, and the gas phase composition distribution at the outlet is closer to the experimental data. Introducing coal ash creates a reduction in the concentration of ilmenite, resulting in a drop in the rates of the related reactions. The narrow particles diameter distribution among coal ash facilitates the particles arrangement in the bed and improves the overall reaction. The addition of moderately irregular-shaped coal ash particles has a certain positive effect on improving the gas-solid contact.

Influence of Rolling Resistance and Particle Size Distribution in the Simulation of Sand Infiltration into the Static Gravel Bed

Fine sediment infiltration and subsequent clogging in a gravel bed affect several fluvial, ecological, and biological processes, resulting in the degradation of the river ecosystem. Despite many experimental and a few numerical studies, the process is yet to be entirely understood. We employed a pure Lagrangian framework, called the Discrete Element Method (DEM), to numerically investigate the infiltration process. Special attention is given to tackling the issue of non-spherical and irregular particle shapes and particle size distributions (PSDs) in numerical simulations. Due to computational limitations, these aspects were either not considered or simplified in previous numerical studies. We implicitly included non-spherical and irregular shape effects through rolling resistance models, which do not cause excessive computational overhead. Our study shows that rolling resistance models greatly influence packing and fine sediment infiltration. However, they may also lead to unphysical particle behavior; thus, they should be carefully used in numerical simulations. Oversimplified PSDs do not mirror natural systems, and full PSDs pose computational challenges. Sufficient grain classes are needed to mimic the non-homogeneity and poly-dispersity found in natural fluvial sediments. The infiltrating characteristics of sand concerning PSD and shape effects are linked to size ratio D15,Gravel/D85,Sand, assuring physical and realistic modeling of the infiltration process.

Reconstruction Of The Shape Of Irregular Rough Particles From Their Interferometric Images Using A Convolutional Neural Network

We have developed a convolutional neural network (CNN) to reconstruct the shape of irregular rough particles from their interferometric images. The CNN is based on a UNET architecture with residual block modules. The database has been constructed using the experimental patterns generated by perfectly known pseudo-particles programmed on a Digital Micromirror Device (DMD) and under laser illumination. The CNN has been trained on a basis of 18000 experimental interferometric images using the AUSTRAL super computer (at CRIANN in Normandy). The CNN is tested in the case of centrosymmetric (stick, cross, dendrite) and non-centrosymmetric (like T, Y or L) particles. The size and the 3D orientation of the programmed particles are random. The different shapes are reconstructed by the CNN with good accuracy. Using three angles of view, the 3D reconstruction of particles from three reconstructed faces can be further done.

Analysis of Morphological and Elemental Composition in Rice, Beans, and Groundnut Husk

The morphological characteristics and elemental composition of these agricultural products provides insights into their nutritional value, chemical properties, and potential industrial applications, contributing to advancements in food science, agriculture, and environmental sustainability. The comprehensive analysis of the morphological and elemental composition of three widely consumed agricultural products: rice, beans, and groundnut husk as a partial substitute for sand due to its high content of calcium, silicon, aluminum, iron, and other elements when properly controlled. Transforming them into practical materials in order to reduce their detrimental impact on the environment. An equal weight of 50 g of Rice husk, 25 g of bean husk, and 25 g of groundnut shell were measured out of 100 g of untreated samples and oven dried at 1000C for 4 hours. The samples were the crushed to fine particle and sieve, which was burned at a temperature of 5500C in an electric furnace for 4 hours. The result obtained microscopic techniques such as Scanning Electron Microscope (SEM) with Energy Disperse X-ray fluorescence (EDXRF) and X-ray diffraction (XRD), were used to observe the surface and element presence in RBGH. The result among other things shows that untreated RBGH atomic concentration of Si is 65.79%, K is 16.01.53%, P is 5.14% Ca is 3.36% and Mg is 3.35% respectively, and the SEM shows that it has a porous cellular structure and consists of irregular-shape particles. The findings shed light on the potential industrial applications of these agricultural byproducts

Photocatalytic removal of some selected antibiotics in polluted water system by graphitic carbon nitride-enhanced vanadium ferrite (VFe2O4@g-C3N4)

Antibiotics such as sulfamethoxazole (SUF), ciprofloxacin (CIP) and erythromycin (ERY) are frequently detected in water systems without being efficiently removed during water treatment. This study synthesized a graphitic carbon nitride-enhanced vanadium ferrite (VFe2O4@g-C3N4) as a photocatalyst for degrading SUF, CIP and ERY in an aqueous solution. VFe2O4@g-C3N4 was characterized with X-ray diffractometry (XRD), thermogravimetry analysis (TGA), ultraviolet (UV)-visible spectrophotometry, scanning electron microscope (SEM) and transmission electron microscope (TEM). The XRD characterization of VFe2O4@g-C3N4 revealed diffraction patterns with a crystallite size of 22.45 nm and a bandgap energy of 1.94 eV. The SEM image revealed the surface to be rough with irregular particle shape and size. The TEM image showed an average particle size of 92.47 nm. VFe2O4@g-C3N4 exhibited a degradation efficiency, which showed complete removal of SUF (100 %) from solution while the efficiency towards CIP is 94 ± 0.60 % and 90 ± 0.8 % towards ERY. The best photocatalytic performance was achieved with 0.12 g L−1 of VFe2O4@g-C3N4 and pH = 7.0 as the optimal conditions for achieving complete removal of SUF, CIP and ERY at a concentration lower than 10.00 mg L−1 under visible-light irradiation. The photodegradation of SUF, CIP and ERY by VFe2O4@g-C3N4 was found to be promoted by ROS with ˙OH and SO4˙− radicals playing a significant role. VFe2O4@g-C3N4 demonstrated a regeneration capacity that is above 90 % at the 10th cycle of regeneration treatment, suggesting it to be stable and reusable with the X-ray diffraction pattern remaining unchanged and no leaching of VFe2O4@g-C3N4 into solution. The result from the study reveals VFe2O4@g-C3N4 as a promising photocatalyst for removing antibiotics from an aqueous solution.

Microstructure, XRD, and strength performance of ultra-high-performance lightweight concrete containing artificial lightweight fine aggregate and silica fume

Ultra-high-performance lightweight concrete (UHPLC), a sustainable and environmentally friendly concrete crafted with artificial lightweight aggregates to preserve non-renewable natural resources like river sand, has garnered significant attention due to its exceptional mechanical properties. This study explores the use of artificial lightweight fine aggregate (ALWFA) as a substitute for fine aggregate in UHPLC production, investigating both fresh properties and mechanical performance. Microstructure analysis, utilizing SEM, and crystalline phase evaluation, employing XRD, were also conducted. The study results indicated that due to the irregular shape of ALWA particles with sharp edges, increasing the content of ALWFA led to a reduction in the flowability of UHPLC. Additionally, it was found that increasing the amount of ALWFA as a replacement for fine aggregate negatively affected both the compressive and tensile strength of UHPLC. This reduction in strength can be attributed to the higher porosity and lower intrinsic strength of ALWFA particles, as well as the weaker cohesion between ALWFA particles and the matrix. SEM analysis revealed that elevating the ALWFA content as a replacement for fine aggregate resulted in an increase in both the number and dimensions of voids, which is responsible for the weaker performance of ALWFA concrete. Finally, XRD analysis showed no significant alteration in the crystalline phases as the ALWFA content increased.

Manipulation of large, irregular-shape particles using contour-tracking optical tweezers.

While the optical tweezers technique is a promising tool for manipulation of microparticles, its application to large (>50 µm) particles and irregular-shape ones is still a hard task. In this Letter, we propose what is to our knowledge a novel concept of contour-tracking optical tweezers (CTOTs), which extract the contour of the objective particle to form the illumination pattern of the trapping laser into the contour shape in real time. We demonstrated the trapping of polystyrene particles of irregular shape with the size of over 100 µm with CTOTs. Our approach has potential to open the way for expanding the applicability of optical tweezers by enabling manipulation of a variety of samples.

Settling velocity of atmospheric particles in seawater: Based on hydrostatic sedimentation method using video imaging techniques

When atmospheric particles deposit to the ocean, their settling velocities and residence times associated are critical for their effects on oceanic ecosystems. We developed a hydrostatic sedimentation method using video imaging techniques to track particles of 5–20 μm in diameter falling into seawater and determine the particle settling velocities in relation to their diameter, shape, organic matter contained, and seawater salinity. The measured settling velocities varied from 0.025 to 0.41 mm/s. Irregular particle shape and organic matter contained in particles also, however, reduced the values. The settling velocities were decelerated by the dissolution process of particle in seawater. Combined with the experimental results, a formula for calculating the settling velocity formulae for atmospheric particles was estimated. Using this equation, the residence time of particles is estimated to be less than one month in continental shelf sea and more than 100 days in the oceans.

Neural-network-based drag force model for polydisperse assemblies of irregular-shaped particles

In this study, a drag force model of irregular-shaped particles in gas-solid flows is investigated using neural network approaches. Pre-developed variational autoencoder, multi-layer perceptron model, and transpose convolutional neural-network model are utilized to obtain intermediate parameters of a pair-wise interaction point-particle (PIEP) model. These parameters are utilized to predict individual drag force coefficients of polydisperse, particulate flows. To apply the PIEP-based model to medium-concentration flows, the average drag force coefficients are obtained through an in-house particle-resolved direct numerical simulation, and a regressed model is developed to predict solid volume fraction factors. With the regression model, the PIEP-based model using the neural-network approaches shows good prediction in particulate systems from low to intermediate concentrations. This study provides computationally efficient models of practical, realistic particulate systems for large scale fluid dynamics simulation, in that it allows predicting the drag forces of polydisperse particles with a small amount of data.

Hydrophilic properties of the aluminum alloy induced by femtosecond laser structuring

This study explored the changes in wetting property and surface morphology in aluminum alloy plates due to femtosecond laser structuring. The laser scanning produced a hierarchical micro- and nano-scale structure consisting of microchannels decorated by irregular shape particles. The surface morphology was controlled by laser power and scanning line density. The surface wettability gradually changed from hydrophilic to hydrophobic one due to various chemical reactions for low laser power and scanning line density. However, femtosecond laser structuring with appropriate laser power and scanning line density was demonstrated to maintain strong and stable hydrophilic properties of aluminum alloy surfaces.