Constant Particle Research Articles

Investigation of iron oxide nanoparticle formation in a spray-flame synthesis process using laser-induced incandescence

In this work, iron-oxide nanoparticle formation in the spray-flame synthesis (SFS) process of the standardized SpraySyn 2.0 burner was investigated in situ using laser-induced incandescence (LII). For the evaluation of these measurements, prior LII-experiments within iron-oxide aerosols (Fe3O4 and α-Fe2O3) with known primary particle size distribution and morphological properties were performed to determine the thermal accommodation coefficient (TAC) α, which led to approx. α = 0.08. The applicability of the TAC results within the flame was validated using spectrally and temporally resolved measurements in the flame at 65 mm HAB employing a spectrograph. Data for a bimodal particle size distribution, obtained from Transmission Electron Microscopy (TEM), were used in the LII-evaluation. The validated TAC was then used to evaluate the primary particle size evolution from in situ Time-Resolved (TiRe) LII-measurements using PMTs along the centre axis of the burner, ranging from 10 mm to 50 mm HAB. These measurements reveal a relatively constant effective particle diameter along HAB with dp,eff ≈ 300 nm. To further investigate particle formation in SFS, 2-dimensional time-resolved LII-measurements in the SFS flame were performed, showing a clear particle formation region up to approx. 30 mm HAB, from where on a constant particle mass is observed.

Single cell-inductively coupled plasma-mass spectrometry (SC-ICP-MS) reveals metallic heterogeneity in a macrophage model of infectious diseases.

Single cell-inductively coupled plasma-mass spectrometry (SC-ICP-MS) offers an attractive option for rapidly measuring trace metal heterogeneity at the single cell level. Chemical fixation has been previously applied to mammalian cells prior to sample introduction so that they can be resuspended in a solution suitable for SC-ICP-MS. However, the effect of fixation on the elemental composition of suspended cells is unknown, and robust methodologies are urgently needed so that the community can measure the effects of intracellular pathogens on elemental composition of their host cells. We demonstrate that different fixatives impact measured cell elemental composition. We have compared suspensions treated using different fixatives (methanol 60-100% in H2O and 4% paraformaldehyde in phosphate-buffered saline solution), and the number of distinguishable single cell events, keeping a constant particle number concentration. Significantly more single cell events (n = 3, P ≤ 0.05) were observed for Ca and Mg when cells were fixed in 4% paraformaldehyde than for the methanol-based fixatives, confirming the hypothesis that methanol fixatives cause leaching of these elements from the cells. The impact of fixation on Mn and Zn was less pronounced. Microbial and viral infection of eukaryotic cells can have profound effects on their elemental composition, but chemical fixation is necessary to render infected cells safe before analysis. We have successfully applied our methodology to a macrophage model of tuberculosis demonstrating utility in understanding metal homeostasis during microbial infection of mammalian cells.

The “three-point shooting paradox”: An artifact or a real phenomenon? Replication with large-scale National Basketball Association (NBA) data

Psychological science is often being criticized for failing to reproduce some of its findings. Considering this critique, Iso-Ahola (2024) argues that it is important to establish a demarcation line between artifact and a real phenomenon, recognizing that psychological phenomena are not constant particles that can be definitively declared to exist or not exist upon discovery. In this brief paper, we utilize newly available large-scale data to replicate a finding by Lidor et al. (2022), who reported a psychological effect wherein professional basketball players shoot better under tight defensive pressure rather than free of it. The current analysis of 781,663 three-point shots over 11 seasons in NBA (as compared to 382 shots taken by 12 players during 12 games in the original study) failed to support the idea of the three-point shooting paradox but instead strongly supports the commonsense hypothesis that tight defense hinders shooting performance.

Preparation and characterization of smart hydrogels (magnetic field responsive)

Iron nanoparticles were prepared by using the co-precipitation process, and then used to fabricate magnetic field-responsive hydrogel films. The magnetic nanoparticles' structural, physical-chemical, morphological, and magnetic characteristics and the effect of hydrogel films' coating concentration were studied. The properties of the hydrogel film responsive to the magnetic field were investigated using Fourier analysis spectroscopy infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and a vibration sample magnetometer (VSM). The results indicated that all samples showed good inter-integration of the constituent materials and their functional groups. The hydrogel film samples which were polycrystalline, had broad diffraction peaks and showed constant particle size with nearly spherical particles with rounded edges. The SEM image of the magnetic nanoparticles with and without coating was established for the accumulation of numerous nanoparticles with a 17 nm mean diameter. In addition, the magnetic properties of the magnetic field-sensitive hydrogel films were evident and sufficient for drug delivery to the desired location.

Comprehensive design and performance validation of a wind tunnel for advanced respirable dust deposition investigations

This study presents the comprehensive design and performance validation of a wind tunnel specifically developed for advanced investigations into respirable dust deposition pertinent to coal mining environments. The design integrates a constant particle delivery system engineered to maintain uniform particle dispersion, which is critical for replicating real-world conditions in coal mines. Our methodology involved using ANSYS Fluent for the design and optimization of a blowing-type wind tunnel, with a focus on controlling turbulence levels and minimizing pressure drops, which are crucial for accurate dust behaviour simulation. The core of our research emphasizes the deployment of the Aerosol Lung Deposition Apparatus (ALDA) alongside a custom dust injection system to measure particle distributions within the test section. This setup enabled us to simulate the inhalation of coal dust particles, providing a realistic scenario for assessing potential hazards to miners. Validation of the tunnel’s performance was achieved through extensive testing with dust sensors and a hot-wire anemometer, which verified the airflow velocity and turbulence against the initial design specifications. The findings affirm the wind tunnel's capability to effectively model dust deposition and its impacts, thereby offering opportunities for enhancing miner safety and health standards.

Constant speed random particles spontaneously confined on the surface of an expanding sphere

The particles that we describe here can only move at the speed of light c in three-dimensional space. The velocity, which randomly but continuously changes direction, can be represented as a point on the surface of a sphere of constant radius c, and its trajectories may only connect points of this variety. The Wiener process that we use to describe the velocity dynamics on the surface of the sphere is anisotropic since the infinitesimal variation of the velocity is not only always orthogonal to the velocity itself (which guarantees a constant speed), but also to the position. This choice for the infinitesimal variation of the velocity is the one that best slows down the diffusion of particles in space by random motion at the speed of light. As a result of these dynamics, the position of the particles spontaneously remain confined on the surface of an expanding sphere whose radius increases, for large times, as the square root of time.

Experimental investigations with machine learning techniques for understanding of erosion wear in advanced aluminum nanocomposites

This article addresses the significant challenge of erosion wear in aluminum composites, particularly in industries such as automotive, aerospace and energy, where sustained material performance is crucial. The study focuses on the experimental investigation of erosive wear characteristics exhibited by advanced aluminum nanocomposites, utilizing an air jet erosion wear test apparatus. The erosion wear tests were conducted using diverse parameters, such as angles (30°, 45°, 60° and 90°), air pressures (1–4 bar) and a fixed 600-s duration, maintaining a constant sand particle feed rate of 2.0 (g/min) and utilizing stand-off distances of 10, 15 and 20 mm. Surface assessments were conducted using field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). The results revealed observable specimen wear, particularly at a 45° angle, with wear rates decreasing at higher impingement angles and reaching a minimum at 90°. Notably, the Al-4 wt.%TiC nanocomposites exhibited a 25% improvement in wear resistance compared to the base alloy. Further analysis of eroded surfaces through (FE-SEM) revealed a mechanism involving micro-cutting, plowing and grain pull-out, attributing wear primarily to plastic deformation and crack formation. Evaluating erosive wear results through six machine learning (ML) models demonstrated that gradient boosting regression emerged as the most accurate, achieving an R2 value of 0.97. This highlights the effectiveness of ML in predicting erosion wear rates and offers insights for improving aluminum composite materials in demanding industrial applications.

A comparative study on design standards of screw conveyors in China, Germany, and the USA – Part II: Discrete element method

This part of the study aims to evaluate the advantages and disadvantages of technical standards of screw conveyors in China, Germany, and the USA for industrial applications. The source or determination method of empirical coefficients as well as the theoretical foundation of dimensioning-relevant diagrams in these standards is not explicitly documented in the literature. Therefore, instead of less efficient on-site tests, the numerical simulation by discrete element method is conducted. Based on the geometrical and operational designs determined in three standards for horizontal, slightly inclined, and vertical conveyance of three representative bulk solids (barley, lignite, and sand), the potential influencing factors are discussed. With constant particle and contact parameters, the potential deviations caused by particle models are eliminated. Furthermore, the accuracy of power consumption calculation of each standard and the divergence between accessible and required mass flows is comprehensively assessed based on the analysis of simulated outcomes. Two main conclusions are drawn: (1) Particle fall back is barely considered by all three standards and leads to overestimated mass throughput; (2) The decrease in mass throughput caused by an increasing degree of filling can be compensated by slowing down the rotational speed.

A numerical analysis of multi-dimensional iron flame propagation using boundary-layer resolved simulations

Iron combustion is emerging as a topic of immediate interest, given the need for the decarbonization of heat and power generation. Opposite to other solid fuels, iron particles burn predominantly in a non-volatile, heterogeneous combustion mode. For iron dust flames, two modes of flame propagation have been observed i.e. the discrete mode, when the heat transfer time scale is larger than the particle burn-time, and the continuous mode, when the heat transfer timescale is smaller than the burn-time of a single particle. The flame speed of such a flame primarily depends on the heat and mass transfer which is characterized by the distance between the particles for a dispersed mixture. Depending on the variation in particle distance and local distribution, planar or curved flames can form and propagate. The characteristics of flame propagation motivate this study and for the first time, three-dimensional particle boundary layer resolved simulations are used to analyse the effect of curvature and variable particle distances on iron–air flame propagation. Simulations are carried out for (1) planar flame propagation with constant particle spacing in the direction of propagation, and (2) curved flame propagation with varying particle spacing in the direction of propagation. The analysis of the flame speed for the planar flame propagation later guides the analysis of curved flames propagating through 900 boundary-layer resolved particles distributed in a 30 by 30 grid. The curved flame propagates with a uniform but decreased flame speed compared to the planar flame propagation with equivalent particle spacing. It is shown that positive curvature decreases the heat transfer from the burnt to the unburnt side while a variable spatial arrangement of particles allows for a local re-distribution of oxygen which causes some regions to burn richer or leaner than the corresponding planar flames with similar particle spacing.

Optimization of Pb (II) Ion Removal from Synthetic Wastewater Using Dead (Chlorophyta) Macroalgae: Prediction by RSM Method

The Pb2+ ions biosorption removal onto dead biomass of Chlorophyta algae is optimized by employing response surface methodology (RSM). Central composite design (CCD)-based experiments were carried out, and RSM was used to evaluate the results. The effects of contact time (15-120min), with pH solution (2-7), initial lead concentration (25-100 mg/L), biomass dose (0.01-1 g/100 mL), agitation speed (100-300 rpm) on the biosorption process were investigated. The optimal conditions of the experimental, data were pH (5), metal concentration (50mg/L), dosage (0.2g/100mL), agitation speed (200 rpm), and contact time of 120 min with constant particle size (63 mm), which gave 98.88% removal efficiency. All the variables and reactions in the biosorption experiments were evaluated using the desirability function to determine the optimal point at which the desired parameters may be attained. The promising results obtained indicate the potential use of Chlorphyta green macroalgae to treat industrial wastewater polluted with toxic metals.

Evaluation of Mixing Effects and Particle Breakage on a Cross Flow Turbine with DEM

AbstractVarious effects during conveying and storage processes lead to size segregation of bulk material, but many applications require a mostly constant particle size distribution. Especially during bunker filling, segregation effects are noticed, which are further intensified by possible core flow effects. In order to reduce segregation effects during bunker filling, a cross flow turbine is installed at a bunker used for storage of blast furnace sinter. In this contribution, discrete element simulations were performed to analyze mixing effects and possible particle breakage due to the cross flow turbine. Significant mixing effects during bunker filling are noticed due to the cross flow turbine. The results show a more evenly distributed bunker outflow in terms of particle size.Particle breakage is analyzed by means of a newly developed breakage model for the Discrete Element Method (DEM). The model is based on a probabilistic particle replacement with voronoi-tessellated fragments. The validated breakage model allows high accuracy in prediction of fragment size distribution. Fragments are further breakable, which allows simulation of processes with several damaging effects. The breakage model was calibrated with a specially developed automated single particle impact tester for rapid analysis of breakage characteristics of bulk materials.

Evaluation of Stability and Enhancement of Nano Fluid Methods

Over the last ten years, there has been a substantial increase in research on nanofluids, and the findings indicate that these fluids are superior heat transfer fluids for application in engineering. The improved heat transfer is exclusively dependent on the thermal conductivity of the nanoparticles at constant particle volume concentrations and flow rates. By creating hybrid nanoparticles, one can change or vary the thermal conductivity of nanoparticles. Nanoscale particles with two or more separate components come together to form hybrid nanoparticles. Fluids made from hybrid nanoparticles are known as hybrid nanofluids. By utilizing more sophisticated materials, hybrid Nano fluids aim to significantly boost heat transmission. Results shows that the nanofluid stability is sensitive to environmental conditions including temperature, pH, and shear rate. It should be using surfactants, additives such as polymers and colloids, ultra-sonication, high shear mixing, applying magnetic field.

Layer-by-layer self-assembled liposomes prepared using sodium alginate and chitosan: Insights into vesicle characteristics and physicochemical stability

In this study, layer-by-layer self-assembled liposomes were prepared with different mixing ratios (3:7, 1:1, and 7:3) of sodium alginate (SA) and chitosan (CS), and the morphology, structure, and physicochemical properties of liposomes after layer-by-layer coating were investigated. After coating the liposomes with SA-CS layer-by-layer (S–C-L), the particle size of liposomes increased from 244.50 to 423.33 nm, the potential changed from negative to positive to 21.20 mV, and the PDI was only 0.393. In the S–C-L 7:3 formulation, the liposomes were uniformly distributed and spherical in size with a clear fingerprint structure. In addition, S–C-L reduced the number of hydrophobic regions within the molecule, allowing the phospholipid molecules to bind tightly into stacks, thus making the liposomes more stable. The S–C-L 7:3 formulation effectively improved the tolerance of liposomes to strong acids and bases, high-salt environments, and UV exposure, and maintained a constant particle size of 400 nm after 28 days of storage. The findings of this study might contribute to the development of polysaccharide layer-by-layer modification of liposomes for a more stable liposomal transport system.

Influence of particle parameters on micro-machining performance of CoCrFeNiAlX/Al composite materials

This study delves into the influence of particle size on the micro-machining performance of CoCrFeNiAlXp/Al composite materials. It employs a combination of experimental and simulation methods to investigate the effect of different particle sizes on the surface integrity of the composite material. The research also scrutinizes the impact of tool particle size on cutting forces, cutting temperatures, and chip morphology across a range of cutting parameters. Additionally, it establishes a clear link between the quality of the machined surface and the relative position of the tool particles. The findings reveal that an increase in particle diameter leads to a reduction in cutting forces. Furthermore, at a constant particle size, an initial rise in cutting speed results in an increased cutting force, which subsequently decreases. Specifically, the maximum cutting force is observed at a particle size of 10 μm, reaching its peak at a cutting speed of 60 m/min, approximately 1.6 times that of the 40 μm particle size. The primary cutting force displays a positive correlation with cutting depth but a negative correlation with particle diameter. For particles of uniform size, an increment in the Al element content initially reduces the cutting force, which subsequently increases, with the minimum force occurring at an Al element molar ratio of 13 %, roughly 60 % of the Al0 particle. Cutting temperature rises with higher cutting speed and depth but inversely correlates with particle diameter and Al content. A particle size of 10 μm generates the highest cutting temperature, approximately 1.4 times that of a 40 μm particle with identical Al content. The completeness of the chip positively correlates with cutting speed, but at a speed of 70 m/min, chip breakage experiences a significant upsurge. The bending radius of the chip increases with cutting depth, ultimately leading to fracture at a depth of 60 μm. A higher Al content in the particles results in more pronounced chip breakage. The optimal surface quality is achieved when the tool is positioned above the particles, while positioning it below or at a 1/2 distance from the particles is more likely to cause damage to the machined surface.

An improved model for predicting froth recovery

In froth flotation, froth recovery is a key factor as it quantifies the effect that the froth has on the overall cell recovery. Froth recovery is affected by a number of variables, including froth stability, particle size and density, and the operating conditions of the flotation cell. Despite its importance, modelling froth recovery is challenging due to the large number of competing effects involved. In this paper, we present a model for froth recovery that takes into account the effects of detachment and subsequent transport of particles. The model is phenomenological and is derived from a set of coupled partial differential equations used to describe both liquid and particle motion within a froth. An analytical algebraic solution is obtained for the froth recovery by making a number of assumptions, which are discussed and justified in the paper. This model is related to a previous model produced by the authors, in which froth recovery was described in terms of a constant particle detachment fraction. Conversely, this enhanced model includes an improved description for particle detachment behaviour during coalescence events, allowing for a variable particle detachment fraction. The key parameters in the model are two dimensionless groups. The first group combines the particle settling velocity, the air addition rate and froth stability parameters such as air recovery and the change in bubble size over the froth, while the second key dimensionless group is the ratio of the surface loading on the incoming bubbles to the maximum surface loading. This model is compared to experimental results and is shown to accurately describe the evolution of the froth recovery behaviour down a bank of cells in response to the decreasing froth stability.

Experimental validation of particle-in-cell/Monte Carlo collisions simulations in low-pressure neon capacitively coupled plasmas

Plasma simulations are powerful tools for understanding fundamental plasma science phenomena and for process optimisation in applications. To ensure their quantitative accuracy, they must be validated against experiments. In this work, such an experimental validation is performed for a one dimensional in space and three dimensional in velocity space particle-in-cell simulation complemented with the Monte Carlo treatment of collision processes of a capacitively coupled radio frequency plasma driven at 13.56 MHz and operated in neon gas. In a geometrically symmetric reactor the electron density in the discharge centre and the spatio-temporal distribution of the electron impact excitation rate from the ground into the Ne 2p1 level are measured by a microwave cutoff probe and phase resolved optical emission spectroscopy, respectively. The measurements are conducted for electrode gaps between 50 mm and 90 mm, neutral gas pressures between 20 mTorr and 50 mTorr, and peak-to-peak values of the driving voltage waveform between 250 V and 650 V. Simulations are performed under identical discharge conditions. In the simulations, various combinations of surface coefficients characterising the interactions of electrons and heavy particles with the anodised aluminium electrode surfaces are adopted. We find, that the simulations using a constant effective heavy particle induced secondary electron (SE) emission coefficient of 0.3 and a realistic electron–surface interaction model (which considers energy-dependent and material specific elastic and inelastic electron reflection, as well as the emission of true SEs from the surface) yield results which are in good quantitative agreement with the experimental data.

Experimental study on heat transfer characteristics between particle flow and wall

ABSTRACT This study experimentally and numerically investigated the characteristics of heat transfer between particle flow and a cylindrical wall. The theoretical model of the heat transfer coefficient calculation was verified and modified according to experimental data. In the experimental scheme, the temperature at the axis of the cylinder under different conditions was measured to determine the effects of temperature, relative motion velocity, and cylinder diameter on the heat transfer coefficient between the particle flow and the cylindrical wall. Results revealed the benefits of using high temperature for increasing the heat transfer coefficient. The relative motion velocity between the wall and particles had no significant effect on the heat transfer coefficient. Furthermore, the change in the heat transfer coefficient was less than 10% in the range of relative velocity v = 0.03 to 0.12 m·s−1 between the wall and particles. The heat transfer coefficient almost independents on cylinder diameter under constant particle diameter conditions.

Modifying reaction rates and stimulus-responsive behavior of polymer-coated catalysts using aprotic solvents

The impact of solvent composition on the reaction rates and apparent activation barriers for the reduction of nitrobenzene on Pd has been investigated by changing the solvent from pure water to mixtures with increasing concentrations of 1-methyl-2-pyrrolidone (NMP). When using pure NMP as the solvent, the activity was negligible and a high activation energy barrier was observed. Surprisingly, switching to water led to faster reaction rates and lower apparent barriers. Considering that previous research has demonstrated that water molecules near the catalyst surface facilitate the hydrogen insertion on R-NO* and R-HNO* surface species via proton-electron transfer, it is possible to link the herein observed trends in activity for the nitrobenzene hydrogenation to the ability of the reaction media to shuttle protons during the reaction. Furthermore, the polymer-induced solvation effects were investigated using thermo-responsive Pd/SiO2-p-NIPAM catalyst. Here, we observed that the utilization of NMP inhibits the thermo-responsive behaviour of poly N-isopropylacrylamide (p-NIPAM). This explains the constant particle size of Pd/SiO2-p-NIPAM catalyst observed at different temperatures during dynamic light scatting characterization (DLS). We speculate that this non-responsive behaviour of the p-NIPAM in the presence of NMP is the cause of the constant activation energy barrier at temperatures above and below the lower critical solution temperature (LCST) of the polymer (32 °C). When the reaction was conducted in pure water, the polymer-coated catalyst showed significant changes in both the apparent enthalpy and entropy of activation for temperatures below and above the LCST. This suggests that the microenvironment induced by the polymer can significantly influence the reaction rate.

Polarized microwave emission from space particles in the upper atmosphere of the Earth

ABSTRACT Tons of space particles enter the Earth atmosphere every year, being detected when they produce fireballs, meteor showers, or when they impact the Earth surface. Particle detection in the showers could also be attempted from space using satellites in low Earth orbit. Measuring the polarization would provide extra crucial information on the dominant alignment mechanisms and the properties of the meteor families. In this article, we evaluate the expected signal to aid in the design of space probes for this purpose. We have used the radmc-3d code to simulate the polarized microwave emission of aligned dust particles with different compositions: silicates, carbonates, and irons. We have assumed a constant spatial particle density distribution of 0.22 cm−3, based on particle density measurements carried during meteor showers. Four different grain size distributions with power indices ranging from −3.5 to −2.0 and dust particles with radius ranging from 0.01 $\mathrm{\mu }$m to 1 cm have been considered for the simulations. Silicates and carbonates align their minor axis with the direction of the solar radiation field; during the flight time into the Earth atmosphere, iron grains get oriented with the Earth’s magnetic field depending on their size. Alignment direction is reflected in the Q-Stokes parameter and in the polarization variation along the orbit. Polarization depends on the composition and on the size distribution of the particles. The simulations show that some specific particle populations might be detectable even with a small probe equipped with high-sensitivity, photon-counting microwave detectors operating in low Earth orbit.

Effects of soft and hard fillers on electromechanical properties and performance of polydimethylsiloxane elastomer for actuator applications

AbstractDesired ratio of relative permittivity and elastic modulus limits the application of silicone rubbers as flexible electromechanical actuators. The relative permittivity can be improved by incorporating varieties of high‐k (high dielectric constant) particles and polymer reagents as plasticizers and crosslinkers into elastomer matrix. The present work investigates the effect of polyethylene glycol (PEG) flakes, as a soft filler, and titanium diborides (TB) particles, as a hard filler, on electromechanical actuation performance of polydimethylsiloxane elastomer for soft actuator. Elastomer composites with various concentrations of fillers are prepared to compare the influences on optical, dielectric, and mechanical properties. Uniform dispersion of fillers is confirmed by field emission scanning electron microscopy, energy dispersive x‐ray spectrometer, and Fourier transform‐infrared spectroscopy analysis. Results show that the elastic modulus and relative permittivity are significantly influenced by filler contents. The elastic modulus increases with lower concentrations of PEG fillers, and at 8 wt%, it becomes comparable to the base material. Soft fillers aid in maintaining low elastic modulus, whereas hard fillers increase electrical breakdown strength as well as dielectric loss with almost equal changes in relative permittivity for both composites. The maximum actuation strain of 30.8% and 26.2% is attained for an in‐house fabricated linear actuator with 8 wt% of PEG and TB particles, respectively.