Particle Size Ratio Research Articles

DYNAMICS OF VIBRATION GRINDING WITH REGARD TO THE INFLUENCE OF SORTING MATERIAL ON ITS WORKING PARAMETERS

The general calculation model of the screen system was determined - the material is based on the study of the interaction processes between the sieve and the crushed stone that was on the screen. The selected model of vibration movement of loose material made it possible to determine the qual-itative and quantitative characteristics of the dynamic impact on the working body. The sorting process is presented as some orderly process of movement of a large number of different particles in a layer on a sieve. The main provisions for the calculation of the main parameters of the screen are formulated, which ensure the specified modes of the process of sorting the material and obtaining the appropriate fractional composi-tion of crushed stone. The prerequisite for choosing the calculation scheme "screen-sieving material" is the determination of the vibrational movement of a material particle along a vibrating hard surface inclined to the horizon at an angle that carries out rectilinear oscillations at an angle to the plane of the screen. At the same time, weight, friction force and normal reaction act on the particle. The proposed model made it possible to determine the speed of transportation in the case when the screening screen performs a circular motion, which is the addition of two independent oscillations with different amplitudes and frequencies. The sorting process is significantly affected by the probability of grains passing through the holes of the sieve. This prob-ability depends on the size of passing particles, the dynamic parameters of screen vibrations, the design of the sieve, the shape of the sieve openings, the coefficient of the live section (the ratio of the area of the openings in the light to the total area of the sieve. The average speed of passage of particles through the sieve is determined by the frequency of contact of particles with the surface and the ratio of particle sizes and the hole. The frequency of particle contact with the sieve is affected by the amplitude and frequency of vibrations of the sieve surface. The probability of a particle passing through the sieve hole during one collision can be estimated based on the calculation charts.

Mechanical properties and soluble phosphorus solidification mechanism of a novel high amount phosphogypsum-based mortar

Phosphogypsum (PG) has great potential for recovery and utilization, but its effective utilization is greatly limited by the harmful impurities mainly composed of soluble phosphorus (SP). Based on excess-sulfate phosphogypsum slag cement (PPSC), a novel type of high amount phosphogypsum-based mortar (HAPBM) is proposed, which is an ideal solidification material. HAPBM has good compressive strength with the high amount PG. The mechanical properties of HAPBM and the solidification mechanism of phosphorus are studied and analyzed. With the changes in PG particle size and sand-cement (s/c) ratio, the influence of SP on the system is further explored. The solidification ability of HAPBM to phosphorus is further studied by adding different forms of SP. XRD analysis shows that in addition to the Brushite, there are also differences in the existences of insoluble phosphorus (ISP) formed by different forms of SP in HAPBM. The leaching results of SP indicate that through the solidification of HAPBM, all groups of leaching solution can meet the Class I (cI = 0.02 mg/L) or II (cII = 0.1 mg/L) limitation of national standard (GB 3838-2002). The microstructure is characterized in detail using SEM images, and the distribution of hydration products and ISP is elucidated through EDS and Mapping results. This study provides possibilities and references for the large-scale recovery and utilization of PG and the solidification of harmful impurities SP.

Variables that contribute to tabia's high mechanical strength — A study using traditional residential flooring tabia from Zhejiang, China

Tabia has a long history of application in China, particularly as traditional residential flooring. In this work, we analyzed traditional residential flooring tabia samples from six residential flats in Zhejiang Province, China, to determine its composition and physical properties. We performed surface Leeb hardness test, compressive strength test, specific density and total porosity test, component composition test, sand and clay grain size distribution test, organic additives test, SEM, and XRD tests, capillary water absorption rate test, freeze-thaw damage test for the tabia samples. Results showed that these residential flooring tabia samples exhibit high compressive strength that can reach as high as 10 MPa. Furthermore, additional analysis determined that the high compressive strength is a function of the following criteria: 1) high density; 2) suitable mass ratio of sand, lime, and clay; 3) the appropriate sand particle size ratio; and 4) formation of hydrated calcium silicate (C-S-H). Moreover, sticky rice and egg white were also detected in the residential flooring tabia samples. The tabia's water absorption coefficient rate decreases with their density. The freeze-thaw resistance of tabia is related to many factors such as calcite content, density and porosity, microstructure. The data obtained from this study will provide guidance for conservators in the protection and restoration of tabia relics.

Optimization of Soxhlet Extraction Papaya Seed Oil (Carica papaya L.) with Petroleum Ether

Papaya seed oil is a high source of fatty acids, especially oleic acid, and palmitic acid. It has 71.60% oleic acid, 15.13% palmitic acid, and has a low cholesterol content so it can be useful as a food oil. This study aims to determine the effect of the ratio of ingredients, time, and particle size on the maximum extraction of papaya seed oil. Extraction of papaya seed oil was carried out by the soxhletation extraction method using petroleum ether solvent. The factorial experimental design of 23 was used to determine the significant parameters for the resulting papaya seed oil: yield, density, fatty acid content, viscosity, and water content. The most influential process variable is particle size. The most optimal papaya seed oil extraction results were obtained at a particle size of 20 mesh, an extraction time of 180 minutes, and a ratio of ingredients to the dissolution of 1:9 (35 gram500 mL). That value obtains a yield of 57.029%.

Microwave heating of silicon carbide and polypropylene particles in a fluidized bed reactor

Microwave-assisted recycling of plastics has become an increasingly attractive technology. In this study, the effects of microwave power, fluidization velocity, particle size and mass ratio on heating performances of polypropylene (PP), silicon carbide (SiC), and the binary mixed (PP/SiC) particles in a microwave fluidized bed reactor were experimentally investigated. The maximum temperature of SiC particles was increased when the microwave power, particle size increased and fluidization velocity decreased. The maximum temperature of SiC particles was 965.7 °C in this study, whereas the maximum temperature of PP particles was only 113.5 °C, and the heating rate of SiC particles was about 7.8–77.2 times that of PP particles. For SiC/PP mixture particles, when the microwave power was 400 W, fluidizing velocity was 3.54 × 10−3 m/s, and the mass ratio of SiC-to-PP was 40:5, the temperature of the mixture particles increased to 600 °C rapidly and then fixed at 600 °C. However, when the fluidizing velocity was slow (1.18 × 10−3 m/s) or the mass ratio was changed (40:1 and 40:10), the temperature decreasing phenomenon appears during the microwave heating process of mixture particles.

Aggregate size characterisation and porosity analysis of granular mixtures

ABSTRACT This paper aims to explore the correlate relationship between particle size composition and porosity of particles and reveal its influence mechanism. First, aggregate particles were divided into coarse aggregate, medium aggregate and fine aggregate. Combination of the particle size ratio and mixing proportion of each grade aggregate were used to characterize the particle size distribution. Second, a mixture proportion triangular coordinate system was proposed; and a series of void ratio contour maps of granular mixtures were plotted in the coordinates based on results of the discrete element numerical simulation test. Finally, correlation between mixture composition and porosity has been analysed. It was found that (1) The void ratio of mixtures with different particle size ratio combinations is mainly different from the size and distribution. (2) Both proportion and particle size composition of coarse aggregate are main factors affecting the change of porosity. (3) For mixtures with the maximum particle size of 16 mm, various particle size ratios within that definition of coarse aggregate are possible. Suitable combination schemes of particle size ratio for each grade of aggregate are recommended for the gradation evaluation and design. (4) The relationship between gradations and voids for the granular mixtures has been established and quantitatively characterised..

Effect of particle size ratio and fines content on drained/undrained behavior of binary granular soil according to confining pressure and packing density: a DEM simulation

Effect of particle size ratio and fines content on drained/undrained behavior of binary granular soil according to confining pressure and packing density: a DEM simulation

DEM modeling direct shearing behavior of sand considering anti-rotation of particle

Considering anti-rotation of sand particles, two-dimensional Discrete Element Method (DEM) has been employed to reproduce direct shear behaviors of sand with different particle distribution sizes, so as to explore effects of anti-rotation of particle on responses of stress-displacement and dilatancy, the evolution law of shear stress, coordination number and vertical displacement of sand samples, and analyze the contact force chain, contact fabric and porosity of the samples after shearing.The results show that the anti-rotation ability of sand is enhanced, the torque of overcoming the relative rotation between particles is increased, and the peak shear stress, dilatancy and porosity in the middle of the sample are increased; with the increase of the anti-rotation coefficient, the coordination number decreases more obviously. The proportion of the contact number in the direction of 100°–160° to the total contact number decreases with the increase of the anti-rotation coefficient. The elliptical shape of the contact configuration becomes more flat, and the anisotropy of the contact force chain is more obvious; compared with fine sand, the coarse sand has greater shear capacity, more obvious dilatancy and larger porosity in the middle of the sample.The maximum minimum particle size ratio of the sample becomes larger, so that the shear strength of the sample is reduced, and the dilatancy is also weak.

Augmented flow and reduced clogging of particles passing through small apertures by addition of fine grains

The effect on the flow and clogging of a sample of particles passing through an orifice due to the addition of a second fine-graded species is investigated. The flow rate of the main species is measured for various parameters: the mass ratio of the big species, the particle size ratio and the orifice diameter. We show that when the fine grains are added into the system the flow rate of the larger species can be increased and its clogging significantly reduced. In particular, we were able to flow (without clogging) the big species through an orifice only 1.5 times its particle diameter. This allows for applications such as the alignment of particles in a narrow tube without clogging. A simple state diagram is presented to describe the clogging transition for these binary mixtures. The experimental results are compared with various existing models for the flow rate of binary mixtures.

A Methodology to Investigate the Design Requirements of Plant Root-Inspired Robots for Soil Exploration

This paper proposes a methodology to investigate soil penetration requirements to extract specifications for designing robotic soil excavators and explorers. To this purpose, a three-dimensional (3-D) numerical model based on the Discrete Element Method (DEM) is proposed to simulate an intruder penetration and its interaction with the environment. In this study, the penetration process was analyzed as a function of the intruder diameter to median particle size ratio (Droot/D50), highlighting important differences for small and big ratios conditions (i.e., Droot/D50<<1 and Droot/D50>>1). In particular, the soil resistance force that autonomous penetration systems must overcome when moving into cohesionless granular soil was estimated based on the intruder size (diameter) and the median granularity (D50). This study estimates how the penetration requirements vary according to different penetration strategies. Specifically, a plant root-inspired axial movement emulating the growth from the tip adopted by plants is compared with a penetration obtained by pushing a system from the top. Our findings provide important guidelines about the design requirements (system size, penetration strategy, and actuation power) for artificial penetrating systems, like autonomous explorative robots, to improve their performances during underground exploration.

Wet-ground calcium aluminate cement as a binder for directly-foamed high-temperature macroporous ceramics

Calcium aluminate cement (CAC) is broadly used as a binder for ceramic materials as it can provide suitable setting times, green mechanical strength and refractoriness. When applied to directly-foamed macroporous refractories, this binder can set the fresh foam before bubble coalescence, favouring higher porosity. Nevertheless, its large particles tend to thermodynamically stabilize bigger bubbles, resulting in samples with larger pores and broader cell size distribution, which is undesirable for high-temperature thermal insulation applications. An alternative to overcome this issue is CAC milling, which can be carried out in water by using sodium gluconate (SG) to produce a stable suspension of this binder. By using 1 wt% of SG, it was possible to grind the CAC in water for 6 h without hydration. When applied to macroporous samples, milled CAC provided faster setting kinetics and in situ formation of hibonite after firing. Additionally, smaller average pore size and higher cold crushing strength were attained when used for the production of ultrastable foam-derived refractories, whereas less significant changes were observed for samples based on surfactant-stabilized foams. The study also showed that the CaO/Al2O3 particle size ratio was an important feature to control the shrinkage/expansion effects after sintering, based on the morphological aspect of the resulting hibonite (CA6) phase.

Modeling stratified segregation in periodically driven granular heap flow

We present a continuum approach to model segregation of size-bidisperse granular materials in unsteady bounded heap flow as a prototype for modeling segregation in other time varying flows. In experiments, a periodically modulated feed rate produces stratified segregation like that which occurs due to intermittent avalanching, except with greater layer-uniformity and higher average feed rates. Using an advection-diffusion-segregation equation and characterizing transient changes in deposition and erosion after a feed rate change, we model stratification for varying feed rates and periods. Feed rate modulation in heap flows can create well-segregated layers, which effectively mix the deposited material normal to the free surface at lengths greater than the combined layer-thickness. This mitigates the strong streamwise segregation that would otherwise occur at larger particle-size ratios and equivalent steady feed rates and can significantly reduce concentration variation during hopper discharge. Coupling segregation, deposition and erosion is challenging but has many potential applications.

Numerical investigations on evolution mechanism of contact erosion in layered soils considering particle-scale parameters

Internal erosion is one of the leading causes of failures in transportation infrastructures including bridges and road embankments. For layered subsoil conditions, contact erosion may occur if the gradation of soil in different layers is not properly selected, and is controlled by the speed of inflowing water and the particle sizes. This phenomenon is difficult to observe on-site or in the laboratory and the underlying mechanism still needs to be clarified as it occurs inside the subsoil layer. This paper presents a particle-scale study that utilizes physical tests and representative volume CFD-DEM simulations to explore the contact erosion process at the interface between soil layers consisting of coarse-grained and fine-grained particles. It is first calibrated and validated by comparing the simulation results with experimental observations. Then the influences of contributing factors on contact erosion initiation and progression from the view of particle scales are analyzed. The results show that particle size ratio is a significant factor that determines the occurrence and development of contact erosion. The specific gravity of particles affects their erosion resistance, while the effect of particle friction is not obvious since the transport of fine non-cohesive particles does not involve significant particle sliding. Particle shape has a major influence on the contact erosion process. Meanwhile, the critical inflow velocity and particle size ratio for contact erosion occurrence can be determined via the coupled model presented in this study.

Pore network modeling of capillary barrier effects: impact of pore sizes

Although the working principles of capillary barrier effects (CBEs) have been well explained based on unsaturated soil mechanics, the selection of materials for engineering structures with CBEs mostly relies on designers’ experience or previously reported data, largely due to the lack of understanding of the microscale behavior of CBEs. This study explores the impact of pore sizes on CBEs based on pore network modeling. The results indicate that the pore size variability in either the fine or coarse layer has a remarkable influence on CBEs, with the latter having a dominating influence. A larger coarse-to-fine mean pore size ratio results in more effective CBEs. In addition to selecting materials with more uniform pore sizes, the coarse-to-fine mean pore size ratio is recommended to be &gt;6 (median particle size ratio of 30) to ensure the performance of CBEs.

Numerical simulation of the dynamic wetting of coal dust by spray droplets

The dust particles generated during coal mining and processing are generally removed by spray dust reduction. The dynamic process via which spray droplets wet and wrap coal dust can directly affect the spray dust reduction efficiency. Here, we analyzed the contact wetting and wrapping process of dust particles by droplets under different particle size ratios and different initial droplet velocities. The results show that the larger the particle size ratio θ of the droplets and dust particles, the greater the variation in the dimensionless spreading coefficient. When the particle size ratio is more than 2, the droplets can completely wrap the coal dust particles. If the initial velocity is too small, the droplets will shrink and return to form a single sheet after coming into contact with the coal dust. With increasing velocity, the dimensionless spreading coefficient increases rapidly, and the coal dust is moistened and rapidly wrapped. By experimenting with various spray atomization characteristics, when the spray pressure is 6 MPa，the droplet size distribution in the spray field accounting for the highest proportion is 10 μm. Under the optimized parameters, the settling efficiency of respirable dust at each measuring point of mine return air duct reaches 86.2% on average.

High-Performance Refractive Index-Based Sensor Using Ellipsoid Ag–Au Nanoparticles

The nanoparticles’ localized surface plasmon resonance (LSPR) is sensitive to the surrounding medium refractive index change. Therefore, biosensing devices commonly use it as a refractive index-based sensor. In this work, an improvement strategy for the sensing performance of gold (Au) and silver (Ag) ellipsoid nanoparticles (NP-ELs) through controlling the size, aspect ratio, and core@shell structure was proposed. The investigation was started by constructing a multiple oscillator model to derive the optical permittivity function and compute the absorption of nanoparticles via discrete dipole approximation (DDA). The change in position and width of the LSPR peak concerning the refractive index of the medium was calculated to determine the sensing performance. Sensitivity and figure of merit (FOM) were used to describe sensing performance. As a result, the aspect ratio parameter of nanoparticles was found to be more dominant in increasing sensitivity and figure of merit (FOM) compared to particle size. In the core@shell structure, the absorption spectrum is also affected by the shell thickness, particle size, and aspect ratio. Therefore, those parameters can tune the sensing performance of the Ag@Au NP-ELs. The maximum sensitivity obtained for Ag@Au NP-ELs was 597.7 nm/RIU with a FOM of 34 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . Therefore, the high performance refractive index-based sensor proposed in this study opens a new gate for developing biosensors in future.

Influence of Physico-Chemical and Bioactivators for Composting of Traditional Market Vegetable Waste

Reprocessing organic vegetable waste from conventional markets can have beneficial effects, such as producing bioenergy, reducing the need for inorganic fertilizers, and minimizing the volume of contaminants in the environment. Organic material composting can help lower greenhouse gas emissions and generate income. Physical-chemical factors like temperature, pH, particle size, moisture content, aeration, and CN ratio were used to regulate the breakdown process. Trichoderma harzianum, an effective microorganism, and Trichoderma harzianum helped the degradation process function. High-quality compost is produced by converting organic matter in a bioreactor system, where the solid substrate replenishes nutrients. Based on the optimum point of the decomposition procedure, the analytical findings were achieved. After that the material had been homogenized and aerated, this process took place (oxygen). When the temperature is increased, the active and ripening stages take place, which triggers the breakdown process. The ideal temperature for composting, between 30-45 °C, was reached. The temperature steadily drops when the majority of the material has broken down, and the composting process is complete.

3D-printed concrete permanent formwork: Effect of postcast concrete proportion on interface bonding

Using 3D concrete printing technology to produce permanent formwork for building components is a promising method that maximizes design freedom and material savings. In this study, 3D-printed permanent formwork made of concrete with coarse aggregate is manufactured and post cast with concrete containing different coarse aggregate particle size ratios. The results indicate that the splitting tensile strength of the concrete interface reaches 2.3 ∼ 4.4 MPa, of which the reduction rate range from 12.8%∼35.7% with higher bonding positions. Mesoscopic observation reveals the voids concentration and a lack of coarse aggregate phenomenon in the interface area. Increasing the proportion of small-sized coarse aggregates in the pouring concrete can better fill and improve the splitting strength of the interface area.

Size effect of iron oxide nanorods with controlled aspect ratio on magneto-responsive behavior

Iron oxide (Fe3O4) has been widely used as a magnetic material for magnetorheological (MR) fluids due to its facile geometric control, magnetic properties, and surface functionalization. However, studies on controlling the aspect ratio of iron oxide nanoparticles applied to MR fluids have rarely been reported due to difficulties in preparing anisotropic magnetic particles. To gain insight into the application of anisotropic nanoparticle in MR fluids, in this work iron oxide nanorods are prepared by using β-FeOOH nanorods as a template. The size of the β-FeOOH nanorods is controlled by adding polyethyleneimine (PEI) as the size controlling agent, and further reduction results in iron oxide nanorods. The resulting iron oxide nanorods are uniform in size and shape and exhibit superparamagnetic properties and high magnetic saturation, which is suitable for MR applications. The influence of particle size of the iron oxide nanorods on MR properties is evaluated, and the result shows the MR fluids prepared with larger size nanorods exhibit higher shear stress due to the higher magnetic saturation ascribed to larger crystalline domain. Consequently, gaining control over the size and aspect ratio of the magnetic particles can lead to high performance MR fluids.

Study of Microstructure and Wear Resistance of AA5052/B4C Nanocomposites as a Function of Volume Fraction Reinforcement to Particle Size Ratio by ANN

The effects of the percentage volume of reinforcement, the ratio of reinforcement, and the matrix size of particles on the wear behavior of AA5052/B4C metal matrix composites (MMCs) examine. This research examines a model function developed from an artificial neural network (ANN). AA5052/B4C composites bent using a powder metallurgy technique to hardness and ball-on-disc wear testing. There are two exemptions such as (1) when the percentage volume of reinforcement is less than 8% and (2) when the ratio of reinforcement particle size (Rs) and matrix particle size (Ms) increases before decreasing. The results show that wear loss decreases with increasing percentage volume of reinforcement and ratio of Rs and Ms. In the second case, wear loss is increased at high levels of percentage volume (14%) since the proportion of reinforcement and matrix size of the particle is close to 1. When the volume percentage of reinforcement is high (14%) and the matrix and reinforcement particle sizes are substantial (120 m), the reinforcement particles become dislodged and break. Because these broken-up particles are easily removed from the surface, the material’s wear resistance is reduced. In this case, raising the volume fraction yields a uniformly higher hardness for all Rs/Ms values; hence, composites with lower reinforcement volume percentages show better wear resistance. Hardness and wear resistance have no relationship with one another.