Effect Of Particle Distribution Research Articles

A new perspective of sediment layering scour and migration under the coupled effects of particle distribution and bio-viscosity–cavitation erosion

The scouring and migration of sediments in sewer systems are the key contributors to overflow pollution. Both physical and biological factors affect the erosion and migration of layered sediments. However, the functional characteristics of these factors and their quantification process still need to be further explored. In this study, the physical form and biological metabolism of the sediment are coupled, and the suspension mechanism under the dual action is proposed systematically and deeply. The influence coefficient of scour initiation was redefined as A^/prime, where the physical factors were particle size and mass, and the biological factors were bio-viscosity and internal cavitation. The bio-viscosity of layered sediment particles is provided by Extracellular Polymeric Substances (EPS). The slope value of |ΔD/−Δf| (ΔD: Dissipation; Δf: frequency) of surface EPS decreased from 0.489 to 0.315 when Quartz Crystal Microbalance with Dissipation (QCM-D) was used to analyse EPS viscosity, indicating that biological activities formed a dense biofilm on the sediment surface and enhanced the bond between particles. Meanwhile, by monitoring the accumulation density of sediments at different depths, it was found that the packing density of the bottom layer decreased from 1.50 to 1.45 g/cm3, which was mainly due to the internal cavitation caused by microorganism consuming organic matrix and releasing H2S and CH4. The delamination difference of EPS results in the uneven change of adhesion between different layers. This, combined with the internal erosion characteristics triggered by microbial stratified metabolism, collectively constitutes the biological effects on the sediment structure. Finally, the coupling mechanism of particle distribution and bio-viscous-cavitation erosion was formed, and the correctness of the formula was verified by repeated experiments, which proved the agreement between the theory and the practice and provided a scientific method for systematically analysing the erosion and migration law of sediment in the sewer system.

Achieving Superior Corrosion Resistance of TiB2 Reinforced Al-Zn-Mg-Cu Composites via Optimizing Particle Distribution and Anodic Oxidation Time

In this study, the effects of particle distribution and anodizing time on the microstructure and corrosion resistance of the TiB2 particle-reinforced Al-Zn-Mg-Cu composite were investigated. Relationships between TiB2 particle distribution, anodizing time, coating growth rule, and corrosion resistance were characterized and discussed using an optical microscope, a scanning electron microscope, an electrochemical test, and a salt spray test. Dispersion of TiB2 particles by powder metallurgy improved the corrosion resistance of the anodized coating on composites. Compared with the matrix, the corrosion potential (Ecorr) of the anodized coating shifted to the positive direction, and the corrosion current density (icorr) decreased. Meanwhile, the icorr of the coating decreased initially and then increased with the extension of the anodization time. The corrosion resistance of the coating was optimal at an anodization time of 20 min. The corrosion resistance of the composite was determined by both the porosity and thickness of the coating. Additionally, all samples treated by potassium dichromate sealing had no corrosion points after a 336-h salt spray test, demonstrating an excellent corrosion resistance suitable for harsh environmental applications in industry.

Chitosan particle-emulsion complex adjuvants: The effect of particle distribution on the immune intensity and response type

Particle-emulsion complex adjuvants as a new trend in the research of vaccine formulation, can improve the immune strength and balance the immune type. However, the location of the particle in the formulation is a key factor that has not been investigated extensively and its type of immunity. In order to investigate the effect of different combining modes of emulsion and particle on the immune response, three types of particle-emulsion complex adjuvant formulations were designed with the combination of chitosan nanoparticles (CNP) and an o/w emulsion with squalene as the oil phase. The complex adjuvants included the CNP-I group (particle inside the emulsion droplet), CNP-S group (particle on the surface of emulsion droplet) and CNP-O group (particle outside the emulsion droplet), respectively. The formulations with different particle locations behaved with different immunoprotective effects and immune-enhancing mechanisms. Compared with CNP-O, CNP-I and CNP-S significantly improve humoral and cellular immunity. CNP-O was more like two independent systems for immune enhancement. As a result, CNP-S triggered a Th1-type immune bias and CNP-I had more of a Th2-type of the immune response. These data highlight the key influence of the subtle difference of particle location in the droplets for immune response.

Effect of particle distribution on the shear behavior of recycled concrete aggregate

Effect of particle distribution on the shear behavior of recycled concrete aggregate

The effect of light scattering in stereolithography ceramic manufacturing

This research simulated the light scattering caused by ceramic particles' presence during stereolithography ceramic manufacturing and revealed the phenomena in the process. The theoretical derivation and calculation of a classic single-particle scattering model were used to verify the reliability of the simulation model. The light scattering simulation confirmed the effects of particle distribution, input energy, and relative refractive index, which were all supported by experiments. The simulation also showed the different scattering edge and the surface roughness at the micron level with verified experiment. Besides, as the particle size of Al2O3 particles increased, the curing thickness increased, the degree of side scattering increased slightly, and the regularity of the curing edge decreased. It was found through simulation that adding an appropriate amount of carbon powder can solve SiO2 inability to print. This study provides valuable guidance to the control of the light-cured 3D printing process for ceramics.

Effects of particle distribution and calculation method on results of nano-indentation technique in heterogeneous nanocomposites-experimental and numerical approaches

This study aims to investigate the effects of two testing parameters on the results of the nano-indentation experiment in the heterogeneous particle reinforced composites: (1) the particle distribution pattern, and (2) the methods for calculating the residual projected contact area of the sample under the indenter. For this purpose, several nano-indentation experiments were performed by using Berkovich indenter on the specimens prepared from Filtek Z350 XT dental nanocomposite as a particle reinforced composite with a volume fraction of 63.3 percent. Then, the nano-indentation procedure on the dental nanocomposite was simulated using the finite element (FE) method. In the FE simulation, several representative volume elements (RVEs) of the nanocomposite were modeled by modifying the Lubachevsky-Stillinger algorithm to distribute particles randomly with a volume fraction of more than 50 percent in a cubic volume. The hardness and elastic modulus of the nanocomposite were calculated from the results of the nano-indentation experiment and the simulation. In these calculations, the projected contact area of the indenter on the specimen was obtained using two different approaches of the Oliver-Pharr method and direct measurement of the area. The results indicated that the distribution of particles around the indenter has significant effects on the nano-indentation results. According to the simulation results, the heterogeneity of the material causes the projected contact area of the indenter on the sample to distort from its equilateral triangle shape, which is assumed in the Oliver-Pharr method. Therefore, the method of direct measurement of the indenter projected contact area on the specimen is proposed to obtain more precise results from the nano-indentation test on heterogeneous materials.

Computational analysis of a 3D mucociliary clearance model predicting nasal drug uptake

Accurate and realistic predictions of the fate of nasally inhaled drugs help to understand the complex fluid-particle dynamics in the nasal cavity. Key elements of such a comprehensive numerical analysis include: (i) inhaled drug-aerosol transport and deposition with air-particle-mucus interactions; and (ii) mucociliary clearance (MCC) dynamics, including drug transport, dissolution and absorption for different nasal inlet conditions.The open-source computational fluid dynamics (CFD) toolbox, OpenFOAM, has been employed for the development of the computer simulation model. As part of the design, a novel 3D meshing technique allows for the smooth capture of both the relatively large flow domain as well as the micron-size mucus layer. This efficient meshing strategy drastically reduces the overall meshing time from hours to a matter of minutes. The effect of pharmacokinetic characteristics of drugs on dissolution, subsequent uptake and clearance were analyzed. A method to impose a boundary-driven flow velocity was introduced in order to mimic the beating of the cilia. Several drug specific parameters, such as solubility, partition coefficient and particle size, were considered. The effects of particle distribution on MCC and uptake were simulated as well. The CFD predictions show that drugs with a high partition coefficient are absorbed rapidly. Similarly, drugs with higher solubility show an appreciable increase in cumulative uptake in the epithelium. Particle size, however, plays a more nuanced role in drug uptake. Specifically, smaller particles with their relatively large surface areas, tend to dissolve quicker and are absorbed more rapidly when compared to larger particles. However, after the initial steeper increase in cumulative uptake of the smaller particles, the difference in the uptake values for the two cases is negligible. Furthermore, the initial deposition locations in the nasal cavity play an important role in overall drug uptake. Particles deposited closer to the ciliated portion of the nasal cavity (i.e. the posterior region) were more readily absorbed when compared to particles deposited closer to the unciliated nasal vestibule.

Chain formation mechanism of magnetic particles in magnetorheological elastomers during pre-structure

Current research on magnetic particles in magnetorheological elastomers (MRE) mainly focuses on the effect of particle distribution and arrangement on the mechanical properties. However, there are few studies on the chain formation mechanism of magnetic particles in MRE. In order to solve the above problems, we proposed a numerical simulation method to study the movement of magnetic particles in MRE. First, the force of the magnetic particles under the magnetic field was analyzed, and the magnetic particle movement model was established. Further, the change of the movement parameters of the particles during the contact process was obtained, including the changes of magnetic force, viscous force, displacement, and velocity. According to the analysis results, the critical angle of attraction and repulsion was determined, and the simulation results were verified by experiments. Finally, the effect of magnetic field strength, volume fraction and particle size on the chain formation of magnetic particles was simulated, it was found that the strength of the external magnetic field affected the efficiency of particle chain formation, and the volume fraction and particle size affected the morphology of the particle chain formation.

Particle distribution-dependent micromechanical simulation on mechanical properties and damage behaviors of particle reinforced metal matrix composites

A micromechanical simulation has been performed to study the effect of particle distribution on the mechanical properties and damage behaviors of particle reinforced metal matrix composites (PRMMCs). Two-dimensional (2D) representative volume elements with variable particle size, volume fraction and particle distribution were generated and subjected to finite element simulation. An enhanced continuum model, which incorporates dislocation punching effect at particle-matrix interfaces and Taylor-based nonlocal theory of plasticity in matrix, was used to simulate the mismatch in coefficients of thermal expansion strengthening and particle size-dependent strengthening. Additionally, constitutive damage behaviors were involved in simulating the crack initiation and evolution, considering the ductile damage in matrix and dislocation punching zone, as well as the particle cracking. Simulation results indicate that refining the particle size is helpful to improve the tensile strength and fracture resistance of PRMMCs, whereas the increase of particle clustering volume fraction or severity facilitates damage evolution and deteriorates the mechanical properties. Statistical analysis indicates a negative linear dependence between particle distribution homogeneity and the ductility, given a constant particle size and volume fraction.

Quantification of Segregation in Portland Cement Concrete Based on Spatial Distribution of Aggregate Size Fractions

Segregation is one of the quality standards that must be monitored during the fabrication and placement of Portland cement concrete. Segregation refers to separation of coarse aggregate from the cement paste, resulting in inhomogeneous mixture. This study introduces a digital imaging based technique to quantify the segregation of Portland cement concrete from 2D digital images of cut sections. In the previous studies, segregation was evaluated based on the existence of coarse aggregate fraction at different geometrical regions of a sample cross section without considering its distribution characteristics. However, it is shown that almost all particle fractions can form clusters and increase the degree of segregation, thus deteriorating the structural performance of concrete. In the proposed methodology, a segregation index is developed by based on the spatial distribution of different size fractions of coarse aggregate within a sample cross section. It is shown that degradation in mixture’s homogeneity is controlled by the combined effect of particle distribution and their relative proportions in the mixture. Hence, a segregation index characterizing the mixture inhomogeneity is developed by considering not only spatial distribution of aggregate particles, but also their size fractions in the mixture. The proposed methodology can be successfully used as a quality control tool for monitoring the segregation level in hardened concrete samples.

Liquefaction Characteristics of Sands Based on Cyclic Direct Simple Shear Test

In this study, a series of cyclic direct simple shear tests were conducted on Pohang sand, Jumunjin sand, and Ottawa sand. The cyclic resistance ratio (CRR) was derived on the basis of the test results obtained. For verification of the effect of particle distribution on liquefaction resistance, the simplified method for evaluation of the possibility of liquefaction was used to assess these sands. The test results showed that the cyclic resistance ratio of Pohang sand was the lowest, which was consistent with the result of the simplified evaluation method for determining the possibility of liquefaction. In addition, the results showed that the liquefaction resistance increased for particle shapes being more angular than round. Normalization was subsequently applied to minimize the effects of the different factors, and the correlation between the CRR<sub>N=10</sub> normalization curve and the CRR<sub>N=15</sub> normalization curve was confirmed.

Effects of Alloying with Sn and Mg on the Microstructure and Electrochemical Behavior of Cast Aluminum Sacrificial Anodes

The influence of alloying with Sn and Mg instead of In during casting of Al–5 wt% Zn sacrificial anodes on their microstructure and electrochemical properties was investigated. The addition levels were 0.1–1.0 wt% Sn and 0.5–2.0 wt% Mg. The different microstructures were studied, and the effect of particles distribution on the performance of the alloys as sacrificial anodes was discussed. It was observed that increasing amount of Sn distributes its particles locally on the grain boundaries which remarkably affected the electrochemical behavior of the alloys. Adding Sn up to 1.0% gradually shifted the potential of the Al–5 wt% Zn alloy toward more negative values (~ − 0.92 to − 1.1 V) and enhanced the breakdown of the oxide layer. Accordingly, the alloys containing Sn in amounts that range between 0.3 and 1.0 wt% exhibited electrochemical properties close to that of the In-containing alloy. Magnesium addition of 0.5 wt% showed remarkable grain refinement where the grain size range of the base alloy was reduced from (150–200 μm) down to (70–100 μm) due to Mg distribution on the grain boundary area. With increasing Mg wt%, grain coarsening occurred due to the segregation of Mg in the matrix which encouraged the breakdown of the passive film and hence increased the corrosion rate. However, the potential levels of the investigated Mg alloys showed more positive values compared to that of the In-containing alloy, which may hinder using this group of alloys for sacrificial anodes applications.

Research on the Effect of Particle Distribution on the Crack Propagation in Shaped Energy Blasting Based on the Smoothed Particle Hydrodynamics

Conventional smoothed particle hydrodynamics (SPH) methods suffer from disadvantages, such as difficult initial particle configuration, uneven distribution of generated particles, and low computational efficiency when applied to numerical simulation of shaped charge blasting. In this research, to overcome these problems, a modified SPH method that generates the particle configuration through self-adaptive optimization is developed by the combined application of MATLAB and LS-DYNA. The results presented in this paper demonstrate that the modified configuration method solves the problem of uneven distribution of particles in complex geometry domains by providing a more uniform smoothed particle distribution than the conventional SPH method. Furthermore, the results from the application of these two methods to the bidirectional-shaped charge blasting problem reveal that the defects in the particle configuration in the conventional SPH method lead to the development of main cracks in both the shaped and the unshaped directions. However, with the self-adaptive optimization method, the main cracks develop only in the shaped direction. In addition, the equivalent stress difference between the shaped and unshaped directions, 0.7 ms after detonation, is 120 MPa with the modified method. This is 85 MPa more than that with the conventional method.

The Effect of Fineness on the Hydration Activity Index of Ground Granulated Blast Furnace Slag.

To improve the properties of ground granulated blast furnace slag (GGBS) and utilize ground granulated blast furnace slag efficiently, this study investigates the effect of fineness on the hydration activity index (HAI) of ground granulated blast furnace slag. The hydration activity index of GGBS with six specific surface areas (SSAs) was characterized by the ratio of compressive strength of the prismatic mortar test block. The particle size distribution of GGBS with different grinding times was tested by laser particle size analyzer. The paste of different specific surface area GGBSs in different curing ages was investigated at the micro level by X-ray diffraction, scanning electron microscope, energy dispersive spectrometer, thermogravimetric scanning calorimeter, and differential scanning calorimeter. The effect of particle distribution of GGBS on the hydration activity index of different curing ages was studied by gray correlation analysis. The results indicated that the compressive strength and hydration activity index increases with the increase of a specific surface area of GGBS at different curing ages. The hydration activity index at different curing ages is almost a linear role for specific surface areas. With the increase in the specific surface area of GGBS, the content of Ca(OH)2 in paste decreases gradually. When GGBS was added into a mortar test block, the hydrate calcium silicate gel in paste changed from a high Ca/Si ratio to a low Ca/Si ratio. The 0–10 micron particles of GGBS particle distribution were highly correlated with the hydration activity index at different curing ages.

Numerical analysis for the effects of particle distribution and particle size on effective thermal conductivity of hybrid-filler polymer composites

This study describes the thermal conductivity (TC) enhancement of polymer composites with randomly distributed hybrid fillers using both numerical and theoretical approaches. The effective thermal conductivity (ETC) of such composites is examined as a function of the TC ratios, volume fraction (VF), and particularly particle distribution and particle size. Effects of particle distribution were first explained comprehensively with combination of both numerical and theoretical analyses. Analyzed results show that particle distribution and particle size become important and affect significantly to the maximum ETC at high VF, high TC, and large size of hybrid fillers. However, the optimal TC ratio between two fillers is shown to be unaffected by both particle distribution and particle size. Particularly, the TC is generally enhanced when more particles are stacked and concentrated along the thermal flow direction. These results are very good in practical optimization process to achieve the maximum ETC of composites, thus total cost of composite synthesis can be reduced significantly.

Nebulized Mannitol, Particle Distribution, and Cough in Idiopathic Pulmonary Fibrosis.

Inhaled interferon, a potential treatment for idiopathic pulmonary fibrosis, must be formulated with mannitol, which can cause bronchospasm and cough. Coughing during drug inhalation can be affected by many factors, but some factors are fixed by the needs of the formulation and inflammatory disease in the airways. A component of the cough response may be related to sites of deposition, particularly upper and central airways. If deposition sites are important, then manipulating the particle distribution of the aerosol may mitigate coughing. To design a therapeutic formulation and delivery system for formulations that contain mannitol, we tested the effect of particle distribution on cough during mannitol inhalation in volunteers with idiopathic pulmonary fibrosis. A solution of mannitol was formulated to match requirements for future interferon formulations (40 mg/mL, 220 mOsm/L). Mannitol aerosols were generated by using different nebulizers providing particle distributions that were expected to vary upper airway deposition. The nebulizer fill volume was adjusted to correct for differences in nebulizer efficiency with a target inhaled mass of 20 mg. Particle distributions were measured by cascade impaction (mass median aerodynamic diameters, 1.2 and 6.5 μm). Seven subjects with idiopathic pulmonary fibrosis participated in the study. To maximize deposition, the subjects were trained to inhale slowly and deeply (6 s inspiration). Spirometry was measured before and after inhalation. The study was carried out on separate days (day 1: 1.2 μm; day 2: 6.5 μm), and the pattern of coughing was observed. Coughing was often spontaneous and provoked by spirometry. When inhaling the 1.2-μm distribution, no subject coughed during inhalation. Six of the seven subjects coughed when inhaling the 6.5-μm particles. Spirometry was unaffected. In subjects with idiopathic pulmonary fibrosis, nebulized mannitol can cause coughing. Modifying the aerosol distribution prevents coughing during mannitol inhalation. Mannitol aerosols can be inhaled safely without bronchospasm. These data serve to inform future formulation and/or device combinations for planned interferon therapy.

Computational Study of Shock-Driven Multiphase Mixing in Scramjet Conditions

Using a multiphase 3D large-eddy simulation approach, simulations were conducted to study the fundamentals of multiphase turbulent mixing in a scramjet combustor. These simulations studied the effects of particle distribution, acceleration history, and particle lag. Heterogeneous, clumped, particle distributions, as produced by fuel injector nozzles, were explored to determine the effect of particle distribution on multiphase mixing in a scramjet engine environment. The heterogeneity of the particle distributions is varied by examining different clump densities and distributions while maintaining a constant particle size distribution and mass ratio. Evaporation rates, particle lag distances, vapor mixing, and enstrophy are reported from these simulations. Overall, new-vapor production rates were found to be low, with vapor mixing being largely driven by the heterogeneity of the particle distribution. The primary finding of this work is that more heterogeneous distributions of particles produce greater mixing of the particle vapor. This enhanced mixing results from particle lag and a greater deposition of enstrophy by gradients in particle mass fraction.

Aggrandize efficiency of ultra-thin silicon solar cell via topical clustering of silver nanoparticles

A highly efficient photovoltaic nanocomposite device is demonstrated by fabrication of structural clusters of silver nanoparticles (Ag NPs) on silicon solar cells via a boil deposition method. The efficiency of silicon solar cell was augmented by coating Ag NPs ultra-thin-film deposition on silicon solar cell. Chemically synthesized silver NP’s, their consumption on a silicon thin layer and the operation of photovoltaic nanocomposite device were characterized by using several electron probe microscopic pectroscopic and spectrometric techniques viz. x-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), Photoluminescence, UV–visible absorption, dielectric, current vs. voltage (I∼V) and capacitance vs. voltage (C∼V) characteristics. Poly-dispersed nature of ‘Ag’ nanoparticles established the anisotropy of these NPs when coated on silicon solar cells. Their efficiency enhancement was confirmed from HR-TEM image via time-domain finite-difference technique to deliberate the particle distribution effect on an ultra-thin film of silicon solar cell, indicating the sufficient enrichment in the efficiency of solar cell. Furthermore, the current work explores the developement of novel glass frits for utilization in next generation of high efficiency smart solar cells.

Analytical study on thermal conductivity enhancement of hybrid-filler polymer composites under high thermal contact resistance

This paper presents an investigation on the thermal conductivity (TC) enhancement for polymer composites reinforced with randomly distributed hybrid filler using both numerical and theoretical approaches. Effects of thermal contact resistances (TCR) at the interfaces between fillers and the matrix material are considered comprehensively. Consequently, the deviation of ETC under the particle distribution effect generally increases as the filler volume fraction (VF) increases. Modified Hashin-Shtrikman model proposed in previous study can be used to predict accurately the TC of composites only if two fillers have the same TCR and TCR is less than prescribed value. The ETC depends significantly on the TCR ratio between two fillers, obviously at high sum of TCRs. Particularly, the TC can be enhanced significantly and effectively even at very high TCR by increasing VF ratio while keeping other appropriate conditions. Furthermore, the optimal TC ratio between two fillers at which the ETC is maximized, was shown to be independent on the TCR only if two fillers have the same TCR. These results provide a very good guideline for synthesizing hybrid-filler polymer composites and enhancing its TC under the effects of TCR.

Study of TiC particle distribution in Al-MMCs using finite element modeling

In order to enhance the efficiency of cutting process before resorting to costly and time consuming experimental trials, it is necessary to model and simulate the machining process by using Finite Element (FE) analysis. However, modeling of composite machining is difficult owing to its distinctive structure and composition which is anisotropic and heterogeneous. Limited studies have been done using microscopic model without considering the effect of particle distribution on chip morphology and coupled temperature displacement analysis during machining simulation of MMCs. Therefore, in the current research work an FE model of machining MMCs is built for analyzing the effect of particle distribution in matrix, tool and geometry cutting parameters on machining process. In FE analysis, the main phases of an Al-TiC MMC workpiece, namely the particle phase and the matrix phase are modeled. Parameters such as morphology of chip, cutting force, and temperature and stress distribution have significant influence on cutting performance and are successfully analyzed by 2D FE models developed. Two different strategies (model A and B) are utilized to arrange the particles in the matrix. Model B with angular distribution of particles shows better performance than the linear distribution of particles in model A. The Performance of model B at different machining conditions is successfully performed and achieves closer to experimental results. Further, heat transfer properties are incorporated in the FE code to perform the cryogenic machining simulation. The authenticity of the developed model is ensured as the simulation results closely agree with the experimental results. The developed FE model affords an insight on effect of particle distribution, cutting parameters and cryogenic technology on machining of MMC. The details presented in the current work are likely to form a scientific basis to simulate machining of MMCs to address the present-day requirements of manufacturing industries.