Particle Transfer Research Articles

Radiative property model for non-gray particle based on dependent scattering

The radiative heat transfer of the particles has been investigated based on the gray body and the independent scattering. However, the radiative properties of the particles are strongly wavelength dependent and interact with each other with the increase of particle concentration. In order to indicate the radiative heat transfer under the high particle volume fraction, the radiation heat transfer model of non-gray particle is developed in this paper, which is based on the ideology of the weighted sum of gray gases (WSGG) model and the full-spectrum correlated k-distribution (FSCK) model, and the dependent scattering of particles is considered. For a one-dimensional plane-parallel slab system, the WSCK (the Weighted Sum of Gray Particles based on the full-Spectrum Correlated k-distribution) model is verified. Compared with the modified LBL model based on Mie theory and dependent scattering theory, the maximum errors of the dependent scattering WSCK (WSCKD) model are about 3.3% for the radiative heat flux and 11.5% for the radiative source term under non-isothermal and inhomogeneous conditions. The radiative heat flux and radiative source term by the WSCKD model and the independent scattering WSCK (WSCKI) model are almost identical for the low particle volume fraction and the calculation accuracy is higher by the WSCKD model on the industrial scale. For the high particle volume fraction, the WSCKD model is more accurate, especially for particle systems with a large percentage of small particles or a relatively high-volume fraction. In addition, the radiative heat transfers of gases, particles and gas-particle mixtures at different one-dimensional scales are examined, highlighting the crucial role of particle radiative property model in large furnaces.

Potential of NRF2 Pathway in Preventing Developmental and Reproductive Toxicity of Fine Particles.

Air pollution is associated with significant adverse health effects. Recent studies support the idea that inhalation of fine particles can instigate extrapulmonary effects on the cardiovascular system through several pathways. The systemic transfer of ultrafine particles (UFPs) or soluble particle components (organic compounds and metals) is of particular concern. An integral role of reactive oxygen species (ROS)-dependent pathways has been suggested in systemic inflammatory responses and vascular dysfunction at the molecular level. Accumulating lines of evidence suggest that fine particles affect fetal development, giving rise to low birth weight and a reduction in fetal growth, and also affect the immune, cardiovascular, and central nervous systems. Oxidative stress plays an important role in fine particles toxicity; pre-treatment with antioxidants partially suppresses the developmental toxicity of fine particles. On the other hand, Nuclear factor erythroid-derived 2-like 2 (Nfe2l2), also known as NRF2, is a transcription factor essential for inducible and/or constitutive expression of phase II and antioxidant enzymes. Studies using Nrf2-knockout mice revealed that NRF2 dysfunction is intimately involved in the pathogenesis of various human diseases. Multiple single nucleotide polymorphisms (SNPs) have been detected in human NRF2 locus. An NRF2 gene SNP (−617C > A; rs6721961), located in the upstream promoter region, affects the transcriptional level of NRF2 and thereby the protein level and downstream gene expression. It has been reported that the SNP-617 is associated with various diseases. The onset and exacerbation of the diseases are regulated by genetic predisposition and environmental factors; some people live in the air-polluted environment but are not affected and remain healthy, suggesting the presence of individual differences in the susceptibility to air pollutants. NRF2 polymorphisms may also be associated with the fetal effects of fine particles exposure. Screening high-risk pregnant women genetically susceptible to oxidative stress and prevention by antioxidant interventions to protect fetal development in air-polluted areas should be considered. This article reviews the recent advances in our understanding of the fetal health effects of fine particles and describes potential chemoprevention via the NRF2 pathway to prevent the developmental and reproductive toxicity of fine particles.

Fabrication of Ring-Shaped Deposits of Polystyrene Microparticles Driven by Thermocapillary Mechanism.

Fabrication of ring-shaped deposits of microparticles on solid surfaces with the desired length scales and morphology of particle arrangements is of great importance when developing modern optical and electronic resonators, chemical sensors, touch screens, field-emission displays, porous materials, and coatings with various functional properties. However, the controlled formation of ring-shaped patterns scaling from a few millimeters up to centimeters with simultaneous control of particle arrangement at the microscale is one of the most challenging problems in advanced materials science and technology. Here, we report a fabrication approach for ring-shaped structures of microparticles on a glass surface that relied on a local thermal impact produced by the subsurface heater and heat sink. Thermocapillary convection in the liquid covering microparticles in combination with evaporative lithography is responsible for the particle transport and the assembling into the ring-shaped patterns. An advantageous feature of this approach is based on the control of thermocapillary flow direction, achieved by changing the sign of the temperature gradient in the liquid, switching between heating and cooling modes. That allows for changing the particle transfer direction to create the ring-shaped deposits and dynamically tune their size and density distribution. We have studied the influence of the power applied to the heat source/sink and the duration of the applied thermal field on the rate of the ring fabrication, the sizes of the ring and the profile of the particle distribution in the ring. The proposed method is flexible to control simultaneously the centimeter scale and microscale processes of transfer and arrangements of particles and can be applied to the fabrication of ring structures of particles of different nature and shape.

Positioning, transfer, and rotation movements of particles manipulated by a novel piezoelectric acoustofluidic device with multiple vibration modes

Acoustic-based manipulation platforms are the preferred device to manipulate particles in analytical chemistry and biomedicine due to their label-free and high biocompatibility. As a significant wave mode of the acoustic manipulation method, bulk acoustic waves (BAWs) have been wildly concerned by academia and industry. To realize the high-precise multi-mode manipulation of particles with a simple structure, a BAWs-based piezoelectric acoustofluidic device is proposed. It is composed of a Langevin transducer and a disk with a circular groove. Two vibration modes of the disk with three and five node circles, respectively, are used to manipulate particles to position, transfer, and rotate. A non-nodal acoustic trap is induced in the disk center by producing its first out-of-plane bending vibration mode. In this acoustic trap, the spherical particles and irregularly shaped particles can be fixed entirely and rotated, respectively. Simultaneously, the disk center is an antinode of the acoustic field induced by the second disk out-of-plane bending vibration mode, leading to that the trapped particles can be equidistantly transferred from the disk center to the nearest node. The effectiveness of the proposed device is verified by simulations and experiments. With appropriate control parameters, the minimum position fluctuation of the submillimeter-hollow-glass sphere (SHGS) after being positioned is 0.32% of its diameter. Moreover, the maximum transfer speed of the SHGS and maximum rotation speed of the cylindrical metal wire are 130.8 mm s−1 and 23.51 rad s−1, respectively. This proposed device is capable of multiple manipulation modes for particles with simple control strategy, providing a novel method for designing a BAWs-based device to achieve the manipulation of particles.

Peptide Derivatives of Platelet-Derived Growth Factor Receptor Alpha Inhibit Cell-Associated Spread of Human Cytomegalovirus.

Cell-free human cytomegalovirus (HCMV) can be inhibited by a soluble form of the cellular HCMV-receptor PDGFRα, resembling neutralization by antibodies. The cell-associated growth of recent HCMV isolates, however, is resistant against antibodies. We investigated whether PDGFRα-derivatives can inhibit this transmission mode. A protein containing the extracellular PDGFRα-domain and 40-mer peptides derived therefrom were tested regarding the inhibition of the cell-associated HCMV strain Merlin-pAL1502, hits were validated with recent isolates, and the most effective peptide was modified to increase its potency. The modified peptide was further analyzed regarding its mode of action on the virion level. While full-length PDGFRα failed to inhibit HCMV isolates, three peptides significantly reduced virus growth. A 30-mer version of the lead peptide (GD30) proved even more effective against the cell-free virus, and this effect was HCMV-specific and depended on the viral glycoprotein O. In cell-associated spread, GD30 reduced both the number of transferred particles and their penetration. This effect was reversible after peptide removal, which allowed the synchronized analysis of particle transfer, showing that two virions per hour were transferred to neighboring cells and one virion was sufficient for infection. In conclusion, PDGFRα-derived peptides are novel inhibitors of the cell-associated spread of HCMV and facilitate the investigation of this transmission mode.

Micro- and Nanowear of Self-Mated Steel Generated and Studied With an AFM at the Single Asperity Level

Single asperity nanowear phenomena are fundamental for understanding basic tribological mechanisms. Yet, they are studied mostly through theoretical and simulation works. Few experiments were conducted in the past decades, usually with materials which are commonly used in micro- and nanotechnology, but not for macroscopic components with relevance in tribology. In the present work, we show for the first time tribotests performed with self-mated 100Cr6 steel, a very widespread material at the macroscale, taking advantage of an AFM, employed as a tribometer for the tribotests as well as for the inspection of wear of both tribopartners. Emphasis is put on the morphology of the scars, on wear particles, and on wear of the “colloidal” particles glued on the AFM cantilever. Measurements demonstrate the possibility of characterizing single asperity events leading to very small wear (scars with isolated, down to 1-nm-deep scratches). We highlight several phenomena, for example, transfer of wear particles and their negative contribution to wear volume, which are elementary key constituents of tribological processes. Such phenomena, probably occurring also at the macroscale, can be detected, identified, and characterized with high spatial and time resolution only at the nanoscale, thus giving insight into conditions and causes of their emergence.

Simulation of heat transfer characteristics of tire particles in rotary kiln reactor

Abstract In this study, we examined and strengthened the motion and heat transfer characteristics of tire particles in a rotary kiln. To overcome the difficulty of controlling the residence time of tire pellets and poor heat transfer, a study was conducted on heat transfer enhancement owing to lifting flight in a rotary kiln with spiral grooves. We developed a particle mechanics model using the discrete element method, and then simulated tire particle motion and obtained results using the EDEM software platform. The obtained motion results were programmed on a MATLAB platform for performing a heat transfer simulation study on the improvement in heat transfer. The coupling model of motion and heat transfer of waste tire particles was established. Through the analysis of particle movement and heat transfer, the following conclusions are obtained: with the increase of the lifting flight, the particle swarm heats up faster and more uniformly; with the increase of the rotation speed, the temperature of the particles rises faster and more uniformly, which has only the same effect as the lifting flight; to a certain extent, the smaller particle size can also improve the heat transfer effect. The maximum error of the relatively accurate coupling model of tire particle motion and heat transfer in a rotary kiln was only 12%, which provides a certain guiding significance for the improved design of the reactor.

Passenger exposure to respiratory aerosols in a train cabin: Effects of window, injection source, output flow location.

Nowadays the use of public transportation (PT) has been identified as high risk as due to the transfer of particles carrying the coronavirus from an infected passenger to others. This study puts forward a new computational framework for predicting the spread of droplets produced while the infected passenger talking inside the cabin of a train during various scenarios, including the changes in the outflows' location and the infected passenger's position. CFD was used to conduct the study, using the Euler-Lagrange approach to capture the transmission of particles, and Reynolds-averaged Navier–Stokes equations (RANS) to compute the airflow field. The results revealed that opening the window reduces the duration of particles inside the domain. So that when the window is open, the particle's shelf time can decrease to 25 percent comparing with closed mode. It was found that the passenger sitting next to the infected passenger encountered the highest infection risk. The conclusions made in this work show that the most desirable situation is obtained when the infected passenger is sitting next to the exits, whether the window is closed or open. The results of this paper offer comprehensive insights into how to keep indoor environments safe against infection aerosols.

Microstructured Surfaces for Reducing Chances of Fomite Transmission via Virus-Containing Respiratory Droplets.

Evaporation-induced particle aggregation in drying droplets is of significant importance in the prevention of pathogen transfer due to the possibility of indirect fomite transmission of the infectious virus particles. In this study, particle aggregation was directionally controlled using contact line dynamics (pinned or slipping) and geometrical gradients on microstructured surfaces by the systematic investigation of the evaporation process on sessile droplets and sprayed microdroplets laden with virus-simulant nanoparticles. Using this mechanism, we designed robust particle capture surfaces by significantly inhibiting the contact transfer of particles from fomite surfaces. For the proof-of-concept, interconnected hexagonal and inverted pyramidal microwall were fabricated using ultraviolet-based nanoimprint lithography, which is considered to be a promising scalable manufacturing process. We demonstrated the potentials of an engineered microcavity surface to limit the contact transfer of particle aggregates deposited with the evaporation of microdroplets by 93% for hexagonal microwall and by 96% for inverted pyramidal microwall. The particle capture potential of the interconnected microstructures was also investigated using biological particles, including adenoviruses and lung-derived extracellular vesicles. The findings indicate that the proposed microstructured surfaces can reduce the indirect fomite transmission of highly infectious agents, including norovirus, rotavirus, or SARS-CoV-2, via respiratory droplets.

Acoustic drug delivery to the maxillary sinus

Acoustic drug delivery (ADD) is an innovative method for drug delivery to the nose and paranasal sinuses and can be used to treat chronic rhinosinusitis (CRS). The underlying mechanism of ADD is based on the oscillatory exchange of air between the nasal cavity (NC) and the maxillary sinus (MS) through the ostium, which assists with the transfer of the drug particles from the NC to the sinuses. This study aims to examine the efficacy of ADD for drug delivery to the MS using an acoustic wave applied to nebulised aerosols entering the nostril. Here, the effect of acoustic frequency, amplitude, and nebulisation flowrate on the efficiency of ADD to the MS is investigated experimentally. A computational fluid dynamics model was also developed to understand the deposition and transport patterns of the aerosols. The results showed that superimposing an acoustic frequency of 328 Hz, which is the resonance frequency of the selected 3D printed model of the NC-MS combination, on the nebulised aerosols could improve the efficiency of the drug delivery to the MS by 75-fold compared with non-acoustic drug delivery case (p < 0.0001). The experimental data also shows that an increase in the amplitude of excitation, increases the concentration of aerosol deposition in the MS significantly; however, it reaches to a plateau at a sound pressure level of 120 dB re 20 µPa.

The General Particle Transfer Potential in a Range of Physical Systems and its Long Range Component

The General Particle Transfer Potential in a Range of Physical Systems and its Long Range Component

Characteristics of Moisture Transfer and Surface Crack Development of a Single Lignite Particle Driven by Humidity Difference.

The research on moisture transfer characteristics and surface crack development of a single lignite particle (SLP) driven by humidity difference is helpful to achieve a better understanding of the fragmentation characteristics of lignite during the moisture transfer process. This is of great significance to the safe operation of a drying system. The characteristics of moisture transfer within SLP driven by humidity difference were studied in different stages. Six drying equations commonly used in the literature were selected to describe the moisture transfer behavior. The apparent diffusion coefficient (Deff) of moisture in each stage was calculated to compare the driving forces of moisture transfer in different stages. The surface crack rate (CR) was used to quantitatively analyze the fragmentation characteristics of SLP caused by moisture transfer. The results showed that the moisture transfer process of SLP driven by humidity difference can be divided into three stages, and stage I is the main moisture removal stage. The larger the particle size, the longer the stage I, while less moisture is removed in this stage. A logarithmic drying equation best simulates the moisture transfer process of SLP. The larger the particle size, the larger the Deff value in each stage. The driving force of moisture transfer in stage I is the largest, which is the opposite of a thermal drying process. CR for SLP has experienced a rapid increase – stable at the highest value – rapid decrease – stable during the moisture transfer process driven by the humidity difference.

An improved method for determination of isotope ratios in individual uranium particles by thermal ionization mass spectrometry

The determination of isotope ratios of individual uranium particles in environmental swipe samples is very important for nuclear safeguards. A new technique to measure isotope ratios for individual uranium particle was developed in this work, which was a combination of particle transfer by scanning electron microscope (SEM) and isotope ratios analysis by thermal ionization mass spectrometry (TIMS). The technique was verified by measuring isotope ratios in individual micrometer-size uranium particles of known isotopic abundance. The particles were identified by SEM combined with energy dispersive X-ray spectrometer (EDX) and transferred by micromanipulator, which could improve the efficiency of sample preparation and simplify the procedure. The experimental condition was optimized by using a new kind of thermal ion emitter to enhance the ionization efficiency of uranium. Several individual uranium particles from certified reference materials were successfully measured by SEM-TIMS. The results show that the measured isotope ratios were in good agreement with the reference values. The relative errors of 13 particles were within 2.7% for 234U/238U, 1.1% for 235U/238U and 4.5% for 236U/238U isotope ratios, respectively, and the relative standard deviation (RSD) were within 1.6% for 234U/238U, 0.5% for 235U/238U and 3.3% for 236U/238U, respectively. It is expected that this method will become a promising alternative technique for determining uranium isotope ratios in particle analysis. The particles used in this study had sizes between 1.3 and 4.7 μm.

Use of pulsed spray airflow for electric arc spraying of different types of wires

The object of research is the control of the process of formation of a spraying air flow and the transfer of particles of liquid metal from electrodes during arc spraying. One of the problem areas of the arc spraying process is the oxidation of the sprayed metal particles by the oxygen of the air flow during their transportation to the sprayed surface. This leads to the formation of a sufficiently large amount of oxides of chemical elements, which significantly deteriorate the adhesion strength and burn out alloying elements that are necessary to obtain a wear-resistant and corrosion-resistant coating. The suitability and durability of coatings during use depends on the strength of adhesion to the substrate. In the course of the study, methods were used to determine the adhesion strength of the coating to the base – the Steffens method and methods for studying the microstructure of coatings were taken as the basis. The data was processed and dependencies were plotted. The proposed method makes it possible to improve the quality of the resulting coating in terms of such an indicator as improvements in chemical composition. And also to influence the chemical composition by controlling the process of transfer of molten metal using a pulsating air flow. The obtained results of approbation of the method allow us to consider it effective, as evidenced by the quality of the obtained coatings. This is due to the fact that the correctness of the formulation and solution of the problem provided adequate results. In contrast to the existing methods, the proposed one makes it possible to significantly influence the amount of harmful oxygen involved in the formation of a sprayed coating, which makes it possible to obtain a sprayed layer with the required performance characteristics. And also allows to improve its quality without significant capital costs. In addition, the issues of resource and energy saving are being addressed, since the burnout of chemical elements decreases and the air consumption during arc metallization decreases. To solve this problem, a simple design of the pulsator is proposed, which provides the ability to control the spray flow by adjusting the level of overlapping of the holes.

Coarse-grained discrete element method of particle behavior and heat transfer in a rotary kiln

Recent improvements in computational capabilities have made numerical simulation of the particle behavior and heat transfer in a rotary kiln reactor possible via the discrete element method (DEM). However, even with current computational capabilities, it is still difficult to simulate particle behavior and heat transfer in a rotary kiln reactor on the manufacturing scale because an enormous number of particles would be required. To address this issue, here, we propose for the first time a coarse-graining method for the Hertz–Mindlin contact force, the rolling friction, and conductive heat transfer between particles called the modified coarse-grained method for granular shear flow (M-CGSF). In M-CGSF, the scaling laws and governing equations for motion and conductive heat transfer of coarse-grained particles were derived according to matching centroid motions, elastic and rotational energy, and the overall heat transfer rate between the cluster of original particles and coarse-grained particles. Verification tests showed that coarse-graining of the particle dynamics, particle mixing, and particle heating behaviors in a rotary kiln were successfully performed by applying M-CGSF, demonstrating the effectiveness of M-CGSF for coarse-grained DEM simulations with conductive heat transfer in a rotary kiln reactor.

Using the activity of naturally occurring radionuclides to identify the contribution of the Al industry to the atmosphere and plants

Alumina production from bauxite ore gives rise to a large amount of liquid and solid waste since the production of 1 kg of alumina involves the same weight of solid residue, the well-known red muds enriched in iron and heavy metals. Up to now, without any valorization of by-products, the red muds have been stored in artificial ponds which are a potential source of pollutants for the surroundings due to the uplift of red dust under strong wind conditions. The goal of the current work is to perform an in situ study of the transfer of red mud micro particles in the atmosphere and in the terrestrial environment around the red mud disposition basins. To this end, the activity concentration of NORM (Naturally Occurring Radioactive Materials such as 238U, decay products and 232Th) determined in plant leaves (Quercus robur and leaf vegetables) and in grains (wheat) is compared with the activity of the atmospheric micro particles, both taken in the environment of the red mud disposition basins (100–1,500 m). The activity ratios of NORM in vegetation and atmospheric micro particles are also compared to the ratios of potential sources of dust, such as soil and, above all, the red mud and bauxite emitted from the basins and from the piles, respectively.The increase in 232Th and 238U activity concentration in a few tree leaves (by a factor of 9 and 4, respectively) and in some aerosol samples is accompanied by a decrease in 238U/232Th activity ratio for these matrices. Low 238U/232Th is also observed in bauxite and red mud. This suggests that the airborne particles emitted by bauxite piles and red mud basins first contaminate the atmosphere and then the leafs surfaces, after deposition. Locally-produced foodstuffs at a distance greater than 1,000 m from the ponds do not show any excess radionuclides, suggesting the low influence of airborne particles from the alumina production. Further variations in the 210Po/210Pb ratio in the plants and the atmospheric micro particles are consistent with the variation over time of these radionuclides coming in all likelihood from the atmosphere rather than from the aluminum industry.

ASYMPTOTICS OF THE FILTRATION PROBLEM WITH ALMOST CONSTANT COEFFICIENTS

During the construction of hydraulic and underground structures, a grout solution is pumped into the ground to create waterproof partitions. The liquid grout is filtered in the porous rock and clogs the pores when hardened. The mathematical model of deep bed filtration describes the transfer of suspension particles and colloids by a fluid flow through the pores of a rock. For a one-dimensional filtration problem in a homogeneous porous medium with almost constant coefficients, an asymptotic solution is constructed. The asymptotics is compared with the numerical solution.

Black Carbon Emissions from the Siberian Fires 2019: Modelling of the Atmospheric Transport and Possible Impact on the Radiation Balance in the Arctic Region

The work is devoted to the study of the climatic effects of black carbon (BC) transferred from forest fires to the Arctic zone. The HYSPLIT (The Hybrid Single-Particle Lagrangian Integrated Trajectory model) trajectory model was used to initially assess the potential for particle transport from fires. The results of the trajectory analysis of the 2019 fires showed that the probability of the transfer of particles to the Arctic ranges from 1% to 10%, and in some cases increases to 20%. Detailed studies of the possible influence of BC ejected as a result of fires became possible by using the climate model of the INMCM5 (Institute of Numerical Mathematics Climate Model). The results of the numerical experiments have shown that the maximum concentration of BC in the Arctic atmosphere is observed in July and August and is associated with emissions from fires. The deposition of BC in the Arctic increases by about 1.5–2 times in the same months, in comparison with simulation without forest fire emissions. This caused an average decrease in solar radiation forcing of 0.3–0.4 Wt/m2 and an increase in atmospheric radiation heating of up to 5–6 Wt/m2. To assess the radiation forcing from BC contaminated snow, we used the dependences of the change in the snow albedo on the snow depth, and the albedo of the underlying surface for a given amount of BC fallen on the snow. These dependences were constructed on the basis of the SNICAR (Snow, Ice, and Aerosol Radiative) model. According to our calculations, the direct radiative forcing from BC in the atmosphere with a clear sky is a maximum of 4–5 W/m2 in July and August.

Model reduction for Smoluchowski equations with particle transfer

Abstract In this paper we consider the problem of modelling a system of aggregating particles, that are being transported with stationary velocities dependent on masses of the particles in one-dimensional case. A numerical method based on the ideas of POD (Proper Orthogonal Decomposition) is constructed, and its capacity to speed up the solution up to 40 times is demonstrated.

ANALYSIS OF THE QUALITY OF MOISTENING OF THE SINTER MIX IN THE DRUM PELLETIZER

The analysis of changes in moisture, equivalent diameter of the granules, layer porosity and size variation under the abrupt perturbing effect on the input humidity of the charge was made. The change in other parameters from the charge moisture lags about 30 seconds. This is due to different mass transfer rates for moisture and fine fractions. PI-controller settings for control of all measured parameters were calculated. The best indicators of the transition process comply with the control of moisture content of the charge. However, the most representative is the simultaneous control of these parameters. A new indicator of the effectiveness of the shower unit of the pelletizer drum is developed, based on the difference in the rates of mass transfer of moisture and solid particles. The value of this indicator should be kept to a minimum.