Particles Of Different Diameters Research Articles

4D Printed Soft Microactuator for Particle Manipulation via Surrounding Medium Variation.

Soft actuators have assumed vital roles in a diverse number of research and application fields, driving innovation and transformative advancements. Using 3D molding of smart materials and combining these materials through structural design strategies, a single soft actuator can achieve multiple functions. However, it is still challenging to realize soft actuators that possess high environmental adaptability while capable of different tasks. Here, the response threshold of a soft actuator is modulated by precisely tuning the ratio of stimulus-responsive groups in hydrogels. By combining a heterogeneous bilayer membrane structure and in situ multimaterial printing, the obtained soft actuator deformed in response to changes in the surrounding medium. The response medium is suitable for both biotic and abiotic environments, and the response rate is fast. By changing the surrounding medium, the precise capture, manipulation, and release of micron-sized particles of different diameters in 3D are realized. In addition, static capture of a single red blood cell is realized using biologically responsive medium changes. Finally, the experimental results are well predicted using finite element analysis. It is believed that with further optimization of the structure size and autonomous navigation platform, the proposed soft microactuator has significant potential to function as an easy-to-manipulate multifunctional robot.

Antimicrobial effects of chlorine dioxide in a hospital setting

Chlorine dioxide is a powerful disinfectant with strong antibacterial properties. We conducted a study at different sites of the Lebanese American University Medical Center-Rizk Hospital to determine the efficacy of the ECOM air mask in decreasing the particle load. Air cultures were obtained from three different locations, namely the patients’ elevator, visitors’ elevator and mobile clinic and the number of colonies grown on each type of agar was determined. We also measured particle counts at the three sites both at baseline and after placement of the ECOM air mask. After 7 days of ECOM air mask use, the numbers of colonies grown on all types of media was decreased by 20–100% versus the baseline values. The counts of particles of different diameters (0.3, 0.5 and 5 µm) were decreased at all three sampled sites. This study highlighted the efficacy of the ECOM air mask. The utility of the gaseous form of ClO2 as an antiseptic in the hospital setting appears promising.

Simulation of fluid flow and heat-moisture transfer mechanism in packed bed based on double-diffusion model

Based on the discrete element method (DEM), four packed beds composed of soybean kernels with diameters of 6.4, 6.8, 7.4 mm, and the mixture of three kinds of particles were established. Then, a double-diffusion heat and mass transfer model between the grain pile and the interstitial air was established based on the local mass and thermal non-equilibrium (LMTNE) mechanism. Finally, employing particle-resolved computational fluid dynamics (PRCFD), the heat and mass transfer between the grain kernels and air during the drying process in the four packed beds were numerically resolved. It was found that the packed bed formed by stacking particles of different diameters had a minimum porosity of 0.4547. The radial porosity of the packed bed oscillates and decreases toward the central axis, while the tortuosity of the airflow path oscillates and decays toward the periphery. The mass transfer Biot number for soybean kernels with diameters of 6.4, 6.8, and 7.4 mm were 2.38 × 106, 2.44 × 106, and 2.53 × 106, respectively. This indicates that the mass transfer rate in the grain pile primarily depends on the magnitude of the moisture diffusion coefficient within the grain kernels. Compared with mass diffusion, thermal diffusion occurs much faster, which results in temperature gradients in packed beds only existing in the first 5 min of drying, and the drying rate in the early stage is higher than that in the later stage. Most importantly, the airflow characteristics, heat and moisture content are not in local equilibrium in the packed bed, and should be considered when designing drying systems.

A preliminary investigation of gyroids made of W-Cu composite materials produced by investment casting into SiO2-based molds 3D-printed by stereolithography

In this work, a new indirect additive manufacturing technique to produce tungsten-copper composites (W-Cu) triply periodic minimal surface (TPMS) geometries by investment casting is proposed. The process consists in the combination of stereolithography (SLA) and molten copper casting to realize complex architectures (i.e., gyroids) and to control the volume fractions of W and Cu, tailoring the composite properties.SiO2-based tubular molds were produced by SLA to reproduce the negative of the object to be casted. The positive shape of the final object was obtained by filling the cavity of the SiO2 mold with a mixture of tungsten and corn starch (CS), which was used as space holder. After a pyrolysis stage at high temperature, the W porous structure was infiltrated by melted copper under vacuum. The leaching of the SiO2 mold using a basic solution allowed obtaining the final geometry. W-based particles of different diameter (i.e., d50 = 10, 22, and 150 µm) were used, and CS content was changed between 5 and 30 %vol. (with respect to W) to adjust the copper content in the composite. In all cases, produced samples retained the geometric properties of the CAD design.

Numerical study on coupled flow characteristics of a gas-solid two-phase jet in a supersonic crossflow

In this study, the Eulerian-Lagrangian scheme coupled with the gas-solid two-phase Reynolds-average Navier-Stokes (RANS) method was used to study the airflow and particles flow characteristics of particles of different diameters injected into a supersonic flow field by a sonic jet. The results show that introducing small particles has little effect on the flow field. When the particle diameter is 1e-6 m, most particles are mainly distributed in the shear layer, and some parts of the particles are sucked into the surface trailing counter-rotating vortex pairs (TCVP) and the wall boundary layers by the airflow. The introduction of large diameter particles hinders the jet's development, reduces the Mach disk's height, and makes the counter-rotating vortex pair (CVP) closer to the wall. This leads to a decrease in the streamwise velocity and an increase in the wall-normal velocity near the wall downstream of the jet. The streamwise velocity increases and the wall-normal velocity decreases at the far wall downstream of the jet. At the same time, it exacerbates the Kelvin-Helmholtz (K-H) instability in the shear layer on the windward side of the jet, forming a large-scale coherent structure between the shear layer and crossflow. The penetration depth and diffusion range of particles increase with particle diameter and density, and the velocity decreases with particle diameter increase by comparing the trajectories of particles with different diameters and densities.

Particles of Different Sizes Affect the Retention Pattern of the Fat Grafts in a Mouse Model.

Autologous fat grafting is an effective form of soft tissue regeneration. However, the optimal fat particle size and graft retention pattern need more research. The mouse inguinal fat pad was harvested and cut into fat particles of different diameters: ≥ 5 mm, 3-4 mm, 2-3 mm, 1-2 mm and 1 mm (micro-fat). A volume of0.2 ml fat was transplanted into another mouse dorsum. Volume and retention rate were measured at 1, 4, 8 and 12 weeks. Histology analysis was performed. Immunofluorescence staining was used to evaluate M1 and M2 macrophage infiltration and graft angiogenesis. Fat retention was highest in the "> 5 mm" group and lowest in the "micro-fat" group. Large vacuoles were more common in larger-diametered fat particles. There was less collagen accumulation in the well-vascularized connective tissue in the "1-2 mm" group. The infiltrated nucleated cells peak at week 4 in groups of fat particles under 3 mm and at week 8 in in groups with fat particles above 3 mm. The number of M1 macrophages peaked at week 1 and then declined in all groups except for the "5 mm" group. The number of M2 macrophages peaked at week 4 and gradually decreased through 12 weeks in the groups below 3 mm, but increased through 12 weeks in the groups above 3 mm. Vascular intensity was similar to M2 macrophage prevalence. Fat particles of different sizes may posses different retention patterns. Larger grafts have higher retention rate but worse quality. Meanwhile, smaller grafts have better quality with lower retention rate. This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

AQAFI: a bioanalytical method for automated KPIs quantification of fluorescent images of human leukocytes and micro-nano particles.

Micro-nanoparticle and leukocyte imaging find significant applications in the areas of infectious disease diagnostics, cellular therapeutics, and biomanufacturing. Portable fluorescence microscopes have been developed for these measurements, however, quantitative assessment of the quality of images (micro-nanoparticles, and leukocytes) captured using these devices remains a challenge. Here, we present a novel method for automated quality assessment of fluorescent images (AQAFI) captured using smartphone fluorescence microscopes (SFM). AQAFI utilizes novel feature extraction methods to identify and measure multiple features of interest in leukocyte and micro-nanoparticle images. For validation of AQAFI, fluorescent particles of different diameters (8.3, 2, 1, 0.8 μm) were imaged using custom-designed SFM at a range of excitation voltages (3.8-4.5 V). Particle intensity, particle vicinity intensity, and image background noise were chosen as analytical parameters of interest and measured by the AQAFI algorithm. A control method was developed by manual calculation of these parameters using ImageJ which was subsequently used to validate the performance of the AQAFI method. For micro-nanoparticle images, correlation coefficients with R2 > 0.95 were obtained for each parameter of interest while comparing AQAFI vs. control (ImageJ). Subsequently, key performance indicators (KPIs) i.e., signal difference to noise ratio (SDNR) and contrast to noise ratio (CNR) were defined and calculated for these micro-nano particle images using both AQAFI and control methods. Finally, we tested the performance of the AQAFI method on the fluorescent images of human peripheral blood leukocytes captured using our custom SFM. Correlation coefficients of R2 = 0.99 were obtained for each parameter of interest (leukocyte intensity, vicinity intensity, background noise) calculated using AQAFI and control (ImageJ). A high correlation was also found between the CNR and SDNR values calculated using both methods. The developed AQAFI method thus presents an automated and precise way to quantify and assess the quality of fluorescent images (micro-nano particles and leukocytes) captured using portable SFMs. Similarly, this study finds broader applicability and can also be employed with benchtop microscopes for the quantitative assessment of their imaging performance.

EVALUATION OF THE EFFICIENCY OF A MULTI-CHANNEL DUST COLLECTOR USING NUMERICAL SIMULATION

Multi-channel dust collectors are based on previously known designs of vortex dryers for bulk products. However, their use for air dust removal is promising. In earlier studies of these devices using numerical simulations, the dust capture coefficient was not evaluated, although it is the most important indicator of their efficiency. In this article, the numerical simulation of MCDC is carried out. The first stage of modeling is the calculation of the gas flow velocity and pressure fields in the device under study. At the second stage, a large number of trajectories of dust particles of different diameters were calculated with subsequent statistical processing. Dust capture coefficients and hydraulic loss coefficients were calculated. It is shown that for the reliability of the results of the numerical experiment, the number of dust particles should be at least 2000. To determine the effect of the outer half-shells on the efficiency of the device, these half-shells were discarded, as a result of which the multi-channel dust collector turned into a cyclone. The comparison of characteristics showed that, other things being equal, the devices being investigated have some advantages over cyclones in capturing of small fractions of dust. The hypothesis that the capture of particles in curved channels occurs mainly due to particle collisions with the front edges of metal half-shells was put forward and refuted. The results of numerical modeling do not support the hypothesis that some dust particles rotate along closed trajectories and form a filter for other particles. The formulas of other authors, which do not take into account the parameters of dust particles, are recognized as unworkable. The speculations of some authors about the influence of the Ranque-Hilsch vortex effect on the process of dust capture cannot be taken into account due to the low subsonic air velocities under the operating conditions of the apparatus.

A numerical study on the relationship between particle dispersion, accumulation, and indoor airflow in different ventilated rooms

AbstractThis study serves as a basic study of the indoor dispersion of pollen particles, simulating the flow field and discussing the behavior of particles of different diameters in different rooms. By comparing the vertical velocity components of particles () and the mean flow velocity of z‐direction component () plus the terminal settling velocity in a gravitational field (), the differences between values and plus values are found to occur mainly at locations close to the opposite wall of the inlet. The location of the differences between values and plus values is important findings of this study, which facilitates the improvement of the simulation method at a later stage and the rational design of indoor ventilation patterns to easily remove particles from the room.

Investigation of effects of sand particles on aerodynamic performance of NACA 0012 airfoil

The purpose of this paper is to study the effects of turbulence kinetic energy structures formed during flow and particles of different diameters and different flow velocities in the air in different regional areas on aerodynamic performance characteristics in NACA 0012. Single and two phase fluid flows were worked out by using Ansys Fluent Computational Fluid Dynamics (CFD) code. Computational results obtained from Ansys Fluent CFD code for pure air and the air containing sand particles were compared with numerical values gained in the literature for validation. Results obtained from the numerical tests demonstrate good agreement with the value in the literature. These results indicate the turbulence kinetic energy value occurred in the tail region of the airfoil increases with the increase in the angle of attack and shifts towards the upper region of the airfoil at high attack angle. Moreover, the upper region of the airfoil at high attack angle becomes larger at low Reynolds numbers due to viscous effects. The drag and lift coefficients obtained in the numerical tests of the airfoils and in the experimental tests in the wind tunnel will differ from the values in the application area. Because, in the operation of airfoils in different regional environments, there are always particles of various concentrations and diameters in the air. In this case, the drag coefficient increases and the lift coefficient decreases.

Effect of particle packing structure on the elastic modulus of wet powder compacts analyzed by persistent homology

This study applies persistent homology (PH) to the structural analysis of wet powder compacts to clarify the effect of packing structure on the elastic modulus, and proposes an equation for the relationship between saturation and elastic modulus based on the index of structural homogeneity. The relationship between the saturation and the elastic modulus was experimentally obtained by compression tests of wet powder compacts. The elastic modulus decreased linearly with increasing saturation, but the slope was different depending on the packing structure of compacts which were made from high purity alumina with different particle size distributions. PH was applied to the packing structure of particles of different diameters calculated by DEM simulation to evaluate the packing structure. The features of each packing structure were extracted by PH, and the index of structural homogeneity was obtained. A new empirical equation is proposed which can predict the relationship between the elastic modulus and the saturation considering structural homogeneity, specific surface area, surface tension, and porosity as the main factors affecting the elastic modulus in the partially saturated state. These results indicate that PH analysis is effective to evaluate the packing structure and that this method may predict the mechanical properties of wet powder compacts.

Asymmetric Three‐Phase Surface Tension Forces in Agglomerating Particulate Systems

AbstractIn accurate simulation of surface tension dominating systems, such as particulate systems in the nano‐ and mesoscale, the computation of interface curvature is essential. In a previous work a formulation using discrete differential geometry was demonstrated that could be used to find exact equilibrium solutions of surfaces. However, it was also shown that this formulation, as well all other tested formulations from those found in literature, fail to find accurate point‐wise estimates for curvatures for particle‐particle capillary liquid bridges. In this communication we elaborate on how total curvatures can be used for computing forces of parameterized models as well as in direct numerical simulations and demonstrate the infeasibility of using point‐wise estimates on any asymmetric discretization. Near‐exact numerical solutions are demonstrated for asymmetrically triangulated Catenoids and a minimal surface suitable for modeling liquid bridges between particles of different diameters.

Hydrodynamic characteristics of a rectangular gas-driven inverse liquid-solid fluidized bed

The hydrodynamic characteristics of a rectangular gas-driven inverse liquid-solid fluidized bed (GDFB) using particles of different diameters and densities were investigated in detail. Rising gas bubbles cause a liquid upflow in the riser portion, enabling a liquid downflow that causes an inverse fluidization in the downer portion. Four flow regimes (fixed bed regime, initial fluidization regime, complete fluidization regime, and circulating fluidization regime) and three transition gas velocities (initial fluidization gas velocity, minimum fluidization gas velocity, and circulating fluidization gas velocity) were identified via visual observation and by monitoring the variations in the pressure drop. The axial local bed voidage (ε) of the downer first decreases and then increases with the increase of the gas velocity. Both the liquid circulation velocity and the average particle velocity inside the downer increase with the increase of the gas velocity in the riser, but decrease with the particle loading. An empirical formula was proposed to successfully predict the Richardson-Zaki index “n”, and the predicted ε obtained from this formula has a ±5% relative error when compared with the experimental ε.

Investigation of the applicability of silica-graphene hybrid materials as stationary phases for capillary liquid chromatography

Graphene and graphene-derived substances are cutting-edge materials receiving increasing attention in the analytical chemistry field. Graphene oxide sheets bonded to amino silica particles functionalized with octadecyl (C18) groups and endcapped, also known as SiGO-C18ec, have been successfully employed as extraction phases and in analytical columns associated with conventional liquid chromatography (LC). In this work, SiGO-C18ec particles of 3, 5, and 10 µm nominal id were employed to pack capillary LC columns (100 mm long x 0.3 mm id), and their performance in the gradient mode was evaluated and compared. A 3 µm C18 capillary LC column (50 x 0.3 mm) was used as a reference column. Eight analytes having different polarities and topological surface areas were selected as a probe in this study: carbofuran clomazone, hexazinone, carbamazepine, citalopram, clomipramine, desipramine, and ochratoxin A. Studies about orthogonality were performed to investigate the orthogonality between the SiGO-C18ec and C18 phases. Among the SiGO-C18ec phases investigated, the column packed with 5 µm SiGO-C18ec particles presented the best peak capacity (29) in 15 min.Additionally, the performance of the columns packed with 5 µm SiGO-C18ec particles overcame the performance of the C18 columns used. Significant orthogonality was found between C18 and SiGO-C18ec packed columns; however, no significant differences were found between columns packed with SiGO-C18ec particles of different diameters.

Nanoparticle manipulation using plasmonic optical tweezers based on particle sizes and refractive indices.

As an effective tool for micro/nano-scale particle manipulation, plasmonic optical tweezers can be used to manipulate cells, DNA, and macromolecules. Related research is of great significance to the development of nanoscience. In this work, we investigated a sub-wavelength particle manipulation technique based on plasmonic optical tweezers. When the local plasmonic resonance is excited on the gold nanostructure arrays, the local electromagnetic field will be enhanced to generate a strong gradient force acting on nanoparticles, which could achieve particle sorting in sub-wavelength scale. On this basis, we explored the plasmonic enhancement effect of the sorting device and the corresponding optical force and optical potential well distributions. Additionally, the sorting effect of the sorting device was investigated in statistical methods, which showed that the sorting device could effectively sort particles of different diameters and refractive indices.

Simulation research on the force and motion of solid particles in transformer oil under DC voltage

As the essential equipment in ultra-high voltage direct current transmission systems, converter transformers provide an important role in the stable operation of the power grid. During the long-term operation of converter transformers, the aging and decomposition of the oil-paper insulation cause a great quantity of metal and non-metal solid particles in the transformer oil, which is one of the important reasons for the equipment failure. The solid particles are affected by various forces in transformer oil, among which the Coulomb force dominates their motion characteristics. The charging process of solid particles contacting the electrode is very important. There are many discussions on the charge carried by metal particles after colliding with the electrode, but less research on the Coulomb force of non-metallic particles in the oil. A simulation model is established to calculate the Coulomb force of metal and non-metal particles in the oil, and the moving process of spherical solid particles of different diameters under different voltages is observed. The research shows that for spherical solid particles with the same material, the Coulomb force increases non-linearly with the increase of particle size. For particles with different materials of the same particle size, the Coulomb force experienced by metal particles is relatively large. Therefore, the charge carried by non-metal particles after colliding with the electrode cannot be calculated by the charge calculation method of metal particles. The research is helpful to analyze the force and movement process of particles in oil and provides support for transformer fault diagnosis and insulation structure design.

Turbulence modulation by finite-size particles of different diameters and particle–fluid density ratios in homogeneous isotropic turbulence

In this paper, the influence of particle-fluid density ratio and particle diameter on the turbulence modulation by finite-size particles in forced homogeneous isotropic turbulence is investigated. Results show that the presence of finite-size particles always attenuate the turbulence, and the attenuation is larger for particles with larger density when the particle diameter is fixed. But the attenuation is smaller for particles with larger diameter if the density is fixed, and the weaker attenuation is due to the wake fluctuation when the particle Reynolds number is large enough. The turbulence kinetic energy is attenuated at the large scales and augmented at the small scales. The radial dissipation profiles show that the region affected by the particles with same diameter is identical, but the dissipation near the particle surface is larger if the density is larger due to larger slip velocity and particle Reynolds number. For particles with same density, smaller particles have smaller dissipation near the particle surface but the influence region is larger, and the combined effect leads to the result that the contribution of dissipation in the influence region of smaller particles to the total dissipation is larger. The influence region mainly depends on the particle diameter.

A New Method for Calculating the Relative Permeability Curve of Polymer Flooding Based on the Viscosity Variation Law of Polymer Transporting in Porous Media.

Relative permeability of polymer flooding plays a very important role in oil field development. This paper aimed to measure and calculate the relative permeability curves of polymer flooding more accurately. First, viscosity variation law of polymer in porous media was studied. Rock particles of different diameters and cementing agent were used to make artificial cores and hydrophobically associating polymer solutions were prepared for experiments. Polymer solutions were injected into the cores filled with crude oil and irreducible water. In the process of polymer flooding, produced fluid was collected at different water saturations and locations of the core. Polymer solutions were separated and their viscosities were measured. With the experimental data, the viscosity variation rule of polymer transporting in porous media was explored. The result indicates that the viscosity retention rate of polymer solutions transporting in porous media has power function relationship with the water saturation and the dimensionless distance from the core inlet. Finally, the relative permeability curves of polymer flooding were measured by unsteady state method and the viscosity variation rule was applied to the calculation of the relative permeability curves.

Hydrodynamic characteristics of a pilot-scale gas-driven inverse liquid-solid fluidized bed with a central draft tube

A new pilot-scale gas-driven inverse liquid-solid fluidized bed with a central draft tube (GDFB-II) was studied. With gas bubbles rising through the draft tube and enabling an upflow liquid, the associated liquid downflow fluidizes light particles downwards in the main column, forming a GDFB. Hydrodynamic characteristics of the GDFB-II were carefully studied using particles of different diameters and densities. Three flow regimes including packed bed, fluidized bed, and circulating bed regimes were identified and these regimes were demarcated by the initial fluidization gas velocity (Ug,if) and the minimum circulating gas velocity (Ug,mc). Ug,if and Ug,mc increase with the increase of particle diameter or the decrease of particle density. The effects of the draft tube diameter and the gas injection tube diameter on Ug,if and Ug,mc were also investigated. As the superficial gas velocity increases, the particle bed height increases first and then plateaus, while the average solids holdup decreases rapidly first and then remains constant.

Comparison between one- and two-way coupling approaches for estimating effective transport properties of suspended particles undergoing Brownian sieving hydrodynamic chromatography

Simplified one-way coupling approaches are often used to model transport properties of diluted particle suspensions for predicting the performance of microcapillary hydrodynamic chromatography (MHDC). Recently, a one-way coupling approach was exploited to optimize the geometry and operating conditions of an unconventional double-channel geometry with a square cross section, where a Brownian sieving mechanism acting alongside the MHDC separation drive (BS-MHDC) is enforced to boost separation resolution. In this article, a cylindrical geometry enforcing the same BS-MHDC separation drive is thoroughly investigated by following a two-way coupling, fully three-dimensional approach, and results are compared with those obtained enforcing the one-way coupling analysis. Device geometry and operating conditions are optimized by maximizing the separation resolution. The effective velocity and dispersion coefficient of spherical, finite-sized particles of different diameters are computed, and two-phase effects are discussed in detail. Similar to the square channel device, the cylindrical double-channel geometry allows for a sizable reduction in the column length and in the analysis time (a factor above 12 for the length and a factor larger than 3 for the processing time) when compared to the standard MHDC configuration ensuring the same separation resolution. As expected, the one-way coupling approach overestimates the separation performance of both the BS-MHDC and the standard MHDC devices with respect to the two-way coupling analysis. But, surprisingly, the enhancement factor of the BS-MHDC over the standard MHDC is underestimated by the single-phase approximation as it doubles when wall/particle interactions are properly accounted for with a two-phase description.