Median Particle Diameter Research Articles

Analysis of Local Scour around Double Piers in Tandem Arrangement in an S-Shaped Channel under Ice-Jammed Flow Conditions

The stability of bridge foundations is affected by local scour, and the formation of ice jams exacerbates local scour around bridge piers. These processes, particularly the evolution of ice jams and local scour around piers, are more complex in curved sections than in straight sections. This study, based on experiments in an S-shaped channel, investigates how various factors—the flow Froude number, ice–water discharge rate, median particle diameter, pier spacing, and pier diameter—affect the maximum local scour depth around double piers in tandem and the distribution of ice jam thickness. The results indicate that under ice-jammed flow conditions, the maximum local scour depth around double piers in tandem is positively correlated with the ice–water discharge rate, pier spacing, and pier diameter and negatively correlated with median particle diameter. The maximum local scour depth is positively correlated with the flow Froude number when it ranges from 0.1 to 0.114, peaking at 0.114. Above this value, the correlation becomes negative. In curved channels, the arrangement of double piers in tandem substantially influences ice jam thickness distribution, with increases in pier diameter and spacing directly correlating with greater ice jam thickness at each cross-section. Furthermore, ice jam thickness is responsive to flow conditions, escalating with higher ice–water discharge rates and decreasing flow Froude numbers.

First insights into the new particle formation and growth at a north-eastern Romanian urban site, Iasi. Potential health risks from ultrafine particles

New particle formation (NPF) process brings significant contribution to the global atmospheric particle number concentrations. Evidence on the formation and growth of NPF is reported for the first time at a Romanian urban site, i.e., Iasi, north-eastern Romania. Size-dependent aerosol number concentrations were obtained during two short-term campaigns undertaken in 2017 by using a scanning mobility particle sizer. The existence of two categories of events can be highlighted by investigating the net maximum increase in the nucleation mode particle number concentration and the maximum size of the geometric median diameter of new particles. The variability of meteorological parameters showed that the solar radiation peak was usually associated with NPF events, while relative humidity was anti-correlated with those events. Calculated nucleation rate values for events in May, median of 4.5 cm−3 s−1, was lower than the corresponding median values of 8.6 cm−3 s−1 for December. The particle growth rates showed a similar trend with a median of 4.0 nm h−1 and 7.7 nm h−1, in May and December, respectively. The obtained results suggest that regional emission sources might bring some contributions on the particle nucleation and growth processes, particularly over the cold season. Regarding the deposition of particles in the respiratory system, it appears that ultrafine particles are among the most significant contributors to the alveolar deposits. Moreover, evidences were obtained that the impact on the particle deposition at the alveolar region is not mandatory in direct relation to the intensity of the NPF event, the pollution burden of the particles most probably playing an important role.

Probing Iceland's dust-emitting sediments: particle size distribution, mineralogy, cohesion, Fe mode of occurrence, and reflectance spectra signatures

Abstract. Characterising the physico-chemical properties of dust-emitting sediments in arid regions is fundamental to understanding the effects of dust on climate and ecosystems. However, knowledge regarding high-latitude dust (HLD) remains limited. This study focuses on analysing the particle size distribution (PSD), mineralogy, cohesion, iron (Fe) mode of occurrence, and visible–near infrared (VNIR) reflectance spectra of dust-emitting sediments from dust hotspots in Iceland (HLD region). Extensive analysis was conducted on samples of top sediments, sediments, and aeolian ripples collected from seven dust sources, with particular emphasis on the Jökulsá basin, encompassing the desert of Dyngjunsandur. Both fully and minimally dispersed PSDs and their respective mass median particle diameters revealed remarkable similarities (56 ± 69 and 55 ± 62 µm, respectively). Mineralogical analyses indicated the prevalence of amorphous phases (68 ± 26 %), feldspars (17 ± 13 %), and pyroxenes (9.3 ± 7.2 %), consistent with thorough analyses of VNIR reflectance spectra. The Fe content reached 9.5 ± 0.40 wt %, predominantly within silicate structures (80 ± 6.3 %), complemented by magnetite (16 ± 5.5 %), hematite/goethite (4.5 ± 2.7 %), and readily exchangeable Fe ions or Fe nano-oxides (1.6 ± 0.63 %). Icelandic top sediments exhibited coarser PSDs compared to the high dust-emitting crusts from mid-latitude arid regions, distinctive mineralogy, and a 3-fold bulk Fe content, with a significant presence of magnetite. The congruence between fully and minimally dispersed PSDs underscores reduced particle aggregation and cohesion of Icelandic top sediments, suggesting that aerodynamic entrainment of dust could also play a role upon emission in this region, alongside saltation bombardment. The extensive analysis in Dyngjusandur enabled the development of a conceptual model to encapsulate Iceland's rapidly evolving high dust-emitting environments.

Production of ultrafine particles with nanometer size distribution via a bubble film bursting method

Producing particles smaller than 50 nm continues to be a challenge for commonly used atomization techniques. In the present study, an atomization method based on bubble film bursting was proposed to generate ultrafine nanoparticles. The atomization solution added with surfactant was converted to big bubble with thin film, and three needles were employed to puncture the bubbles to produce small droplets. Droplets formed ultrafine nanoparticles after being dried by a diffusion dryer. The results showed that the median diameter of particles generated by bubble film bursting could be as low as 30 nm. The thinness of the bubble film played a significant role in producing small droplets. Additionally, the size distribution of particles was influenced by the NaCl concentration and the distance of the needle to orifice, as they altered the thickness of the bubbles. The bubble film bursting atomization method offers the advantage of producing ultrafine particles and holds potential for application in various fields.

How particle size reduction improves pectin extraction efficiency in carrot pomace

Particle size reduction of raw materials is suggested to improve the extraction efficiency of pectin. However, conflicting reports have been published in literature, questioning to what extent particle size reduction is beneficial. This study investigated the role of reduced particle size and altered microstructure on the extraction efficiency and structure of pectin obtained from carrot pomace. High shear mixing and high pressure homogenization at different pressure levels (5–100 MPa) resulted in samples with a median particle diameter between 563 μm and 68 μm. Particle size reduction was shown to increase the pectin extraction yield. High shear mixing followed by high pressure homogenization, more specifically, resulted in a 50% increase of the pectin yield, resulting in the extraction of 62% of the pectin content. Interestingly, the extent to which the extraction yield was improved was more related to changes in the microstructure than to the particle size as such, with tissue disruption leading to more outspoken changes in pectin extractability than further disintegration of cell fragments. The additional fraction of extracted pectin is thought to originate from the middle lamella rather than the primary cell wall. Overall, particle size reduction did not alter the molecular structure of the extracted pectin.

Phase-sensitive optical coherence tomography reveals droplet penetration into a powder bed

Understanding the mixing behavior that unfolds when liquid droplets impact on powder beds requires a sub-surface dynamic imaging method that provides high spatial and temporal resolution. In this study, a high-resolution phase-sensitive optical coherence tomography (PhS-OCT) technique was introduced to provide in-depth insights into the interaction of droplets and powder beds. A theoretical model correlating changes in the optical path differences (OPD) of the OCT signal with physical properties of the powder bed was presented. Experiments were conducted on three powders with median particle diameters, i.e., the size corresponding to the 50th percentile of the cumulative volume distribution, of 3 µm (mannitol), 4 µm (mannitol) and 109 µm (SV010). Water and ethanol droplets were used to illustrate the technique. The results demonstrated that OPD maps can qualitatively resolve the liquid-powder mixture region, both temporally and spatially, as the droplet diffuses into the powder bed, allowing for a quantitative description of diffusion behavior. A comparison of lactose and mannitol powder samples revealed varying diffusion rates, potentially attributed to differences in porosity, particle size, and agglomeration. Additionally, water and ethanol droplets exhibited significantly different (p = 0.005) diffusion profiles for the same powder properties. In general, the findings indicate the potential of the proposed PhS-OCT technique for evaluating the mixing behavior of multi-phase mixtures, holding promise in applications such as pharmaceutical drug formulations and additive manufacturing.

Gas atomization of AA2017 aluminum alloy: Effect of process parameters in the physical properties of powders for additive manufacturing

Close-coupled gas atomization (CCGA) uses pressurized gas jets to atomize molten metals, producing powders suitable for additive manufacturing (AM). Optimization of processing parameters is crucial to achieve powders with good fluidity and high apparent density for laser powder bed fusion (L-PBF) and increase production yield. This study evaluated the influence of melt feed nozzle diameter, superheating temperature, and atomization pressure on AA2017 aluminum alloy powders' physical properties. Parameters variation poorly affected the median particle diameter (d50), while significantly altering the particle size distribution curves width (IDR = d90-d10). Suitable powders for AM/L-PBF were produced using a specific set of parameters (d0= 1.5 mm; ΔT= 150 °C; PG= 20 Bar), presenting appropriate fluidity and apparent density due to an optimal granulometric distribution and morphological characteristics. Mathematical analysis showed a good correlation between experimental and calculated mean particle size, suggesting an equation to predict percentile d90 based on previous correlations.

New optically stimulated luminescence dosimetry film optimized for energy dependence guided by Monte Carlo simulations

Optically stimulated luminescence (OSL) film dosimeters, based on BaFBr:Eu2+ phosphor material, have major dosimetric advantages such as dose linearity, high spatial resolution, film re-usability, and immediate film readout. However, they exhibit an energy-dependent over-response at low photon energies because they are not made of tissue-equivalent materials. In this work, the OSL energy-dependent response was optimized by lowering the phosphor grain size and seeking an optimal choice of phosphor concentration and film thickness to achieve sufficient signal sensitivity. This optimization process combines measurement-based assessments of energy response in narrow x-ray beams with various energy response calculation methods applied to different film metrics. Theoretical approaches and MC dose simulations were used for homogeneous phosphor distributions and for isolated phosphor grains of different dimensions, where the dose in the phosphor grain was calculated. In total 8 OSL films were manufactured with different BaFBr:Eu2+ median particle diameters (D50): 3.2 μm, 1.5 μm and 230 nm and different phosphor concentrations (1.6%, 5.3% and 21.3 %) and thicknesses (from 5.2 to 49 μm). Films were irradiated in narrow x-ray spectra (N60, N80, N-150 and N-300) and the signal intensity relative to the nominal dose-to-water value was normalized to Co-60. Finally, we experimentally tested the response of several films in Varian 6MV TrueBeam STx linear accelerator using the following settings: 10 × 10 cm2 field, 0deggantry angle, 90 cm SSD, 10 cm depth. The x-ray irradiation experiment reported a reduced energy response for the smallest grain size with an inverse correlation between response and grain size. The N-60 irradiation showed a 43% reduction in the energy over-response when going from 3 μm to 230 nm grain size for the 5% phosphor concentration. Energy response calculation using a homogeneous dispersion of the phosphor underestimated the experimental response and was not able to obtain the experimental correlation between grain size and energy response. Isolated grain size modeling combined with MC dose simulations allowed to establish a good agreement with experimental data, and enabled steering the production of optimized OSL-films. The clinical 6 MV beam test confirmed a reduction in energy dependence, which is visible in small-grain films where a decrease in out-of-field over-response was observed.

A new automatic analysis tool for the determination of primary particle size from electron microscopy images: Application of the Cellpose software

To assess if an aggregated or an agglomerated material has to be considered as a nano-material, the size distribution of its constituent primary particles needs to be measured and the median diameter determined. To this end, the reference method uses either transmission or scanning electron microscopy to obtain images of the sample. The size of a significant number, usually a few hundreds, of primary particles are then measured manually. This task is highly time-consuming and subjected to operator bias. Some attempts have been made to automatize the size measurements. The algorithms and software available are generally successful at segmenting images of spherical objects with no or partial overlap but fail to properly segment irregular objects with strong overlap.The advances made with deep learning algorithms are promising to solve the segmentation issues encountered so far on complicated samples. In this paper, we tested the open source deep learning Cellpose software on transmission and scanning electron microscope images of different samples to retrieve the median diameter of the primary particles and compare the results with both the manual and theoretical values. This software was chosen for its ease of use, its free availability and the fact that it is pre-trained, allowing the use of a limited set of training images.For the samples used in this study, the quality of the segmentation was highly dependent on the number of objects on which the software model was trained, but a number of 500 to 1000 objects was enough to obtain good performances. The diameters measured using Cellpose segmentation are most of the time in agreement within 10% with the manual values. Interestingly, for scanning electron microscopy data, the results obtained with Cellpose are closer to the theoretical values when compared to the measurements obtained by hand, implying a smaller operator bias. If an uncertainty assessment still needs to be investigated for the diameters determined using Cellpose, this first attempt to use this software to segment electron microscope images of diverse samples is very promising and opens the possibility to fully automatize the identification of nano-structured materials.

Metal(loid) Partitioning and Transport in the Jinsha River, China: From Upper Natural Reaches to Lower Cascade Reservoirs-Regulated Reaches

Riverine contamination of metals and metalloids is a growing global concern. However, our understanding of how cascade reservoirs influence the fate of these pollutants remains limited. In this study, we focused on the Jinsha River, a typical large river polluted with metal(loid)s in Southwest China, to investigate the partitioning and transport of these substances from the upper natural reaches to the lower cascade reservoirs-regulated reaches during both flood and dry seasons. Results revealed that the rapid urbanization and industrial development following the construction of reservoirs led to significant copper (Cu), nickel (Ni), lead (Pb), chromium (Cr), and cadmium (Cd) pollution. Through various analytical techniques such as correlation analysis, principal component analysis, redundancy analysis, and structural equation modeling, we determined that reservoirs had a profound impact on solid-associated parameters, including particulate organic matter (POM), suspended solid concentration (SSC), and median particle diameter (D50). These parameters, in turn, affected the fate of metal(loid)s through processes like sorption-desorption and dissolution-precipitation. High POM concentrations and low SSC and D50 values resulted in the precipitation of most particulate metal(loid)s, thereby reducing their transport across reservoirs. As river water moved downstream across the reservoirs, the percentage of particulate metal(loid)s decreased by 6.1% for arsenic (As), 38.3% for Cu, 74.9% for Ni, 36.8% for Cr, 17.8% for Cd, and 41.9% for Pb, respectively. Furthermore, the cascade reservoirs had cumulative effects on the deposition of particulate metal(loid)s, particularly concerning Cr, Cd, and Pb in the final reservoirs. Human health risk assessments indicated that dissolved As and Pb posed potential non-carcinogenic threats to residents. Despite the fact that reservoirs captured most particulate metal(loid)s, the transport of dissolved As and Pb across the reservoirs still impacted the safety of downstream drinking water. Therefore, in cascade reservoir systems, the concern regarding dissolved metal(loid) pollution remains a priority for future reservoir management.

Size-tunable silicon nanoparticles synthesized in solution via a redox reaction.

A current challenge in silicon chemistry is to perform liquid-phase synthesis of silicon nanoparticles, which would permit the use of colloidal synthesis techniques to control size and shape. Herein we show how silicon nanoparticles were synthesized at ambient temperature and pressure in organic solvents through a redox reaction. Specifically, a hexacoordinated silicon complex, bis(N,N'-diisopropylbutylamidinato)dichlorosilane, was reduced by a silicon Zintl phase, sodium silicide (Na4Si4). The resulting silicon nanoparticles were crystalline with sizes tuned from a median particle diameter of 15 nm to 45 nm depending on the solvent. Photoluminescence measurements performed on colloidal suspensions of the 45 nm diameter silicon nanoparticles indicated a blue emission signal, attributed to the partial oxidation of the Si nanocrystals or to the presence of nitrogen impurities.

On the Total Load Calculation in Combined Urban Sewer Conduits

Background: Particle size of sediment is necessary to design and operation of sewer systems. In this regard, calculation of the equivalent particle diameter (EPD) is of important to determine the particle Reynolds number (Ret ) as well as total load calculation. Methods: In this research work, 5 different particle diameters (i.e. d35, d50, d65, dm and deff) have been used in three famous total load calculation methods for calculating the best EPD. For this goal, a field experimental data has been collected at the entrance grit chamber of wastewater treatment plant (WWTP) of Khomein city, Iran. The total load of the sediments has been measured and the results compared with the total loads calculated by the three famous total load computation methods (i.e. Graf & Acaroglu method, Laursen method and Yang & Lim method) by using the particle diameters. Results: The results show that the methods estimate the total load of sediments with the relative errors of 4.25, 10.80 and 1.26 by using dm, d35 and d65 as the EPDs, respectively. Also, a simplified and improved correction factor has been developed and the results show that by applying the correction factor the relative errors of the methods decrease and they are equal to 10.34, 3.45 and 496.5, respectively. The improvement of the mentioned total load methods is equal to are 82.70%, 93.10% and 34.80%, respectively. Conclusion: The proposed correction factor can be applied for the standard deviation between 2.5-4.7 and the median particle diameter between 0.84-2.90 mm.

Research and modeling of the ecological efficiency of drying refractory and building materials in vertical shaft furnaces

Based on the hypothesis of the dominant effect on the environmental efficiency of drying materials in shaft furnaces of the concentration, median diameter, dispersion, temperature and humidity of dust particles at the outlet of the dryer, a device for thermal aeration separation of dust is proposed. The analysis of mathematical modeling of aerothermodynamic processes in a two-phase medium asbestos dust ‒ gas flow confirmed the conclusions of industrial studies on the influence of aerothermodynamic parameters of direct flow on the temperature and humidity of asbestos dust in the pneumatic dryer. Based on the principle of additive classification, a mathematical model of aeration separation of dust particles directly in the dryer of the shaft furnace is constructed, depending on the parameters of the heat carrier and the proposed device.

Influences of Sediment Particles on Air Vessel Water Hammer Protection Effect in the Long-Distance Water Supply Systems

Abstract Long-distance water supply systems are important measures to improve the water resources distribution, and the water hammer protection devices such as air vessels are usually added in the project to ensure the safety and stable operation. However, the sediment particles are always ignored in the design. Hence, a numerical model and program were established for sediment laden water hammer based on the method of characteristics (MOC). Using the proposed model, the water hammer protection influences of sediment particles parameters are simulated for the same pipeline system of a water supply project. The result shows that the resistance loss of sediment-laden water in pipelines is larger than that of water, and the initial head of pump needed to be increased to ensure the water levels of downstream reservoirs are consistent. After power failure and pump stopping, the negative pressure wave of sediment-laden water is 2.97 m higher than that of water, and the theoretical minimum internal pressure along pipelines is 7.8 m lower. With the same air vessel protection, the lowest minimum internal pressure heads along pipelines decrease with the increase of quantities of sediment, while the results show no obvious influence by changes of median particle diameters. The lowest absolute pressure of pipeline could reach −0.69 m under the condition of 50 kg/m3 quantity of sediment and 0.05 mm median particle diameter. The relevant research results are of great significance sediment-laden water hammer numerical simulation and water hammer protection design.

Enhancing Biochar Impact on the Mechanical Properties of Cement-Based Mortar: An Optimization Study Using Response Surface Methodology for Particle Size and Content

The utilization of agricultural waste, specifically biochar (BC), as an alternative material to conventional Portland cement offers substantial potential for enhancing sustainability within the construction industry. This study investigates how variations in BC particle size and content affect the properties of cement mortar using Response Surface Methodology (RSM). By manipulating BC’s content and particle size in the mortar mixture and analyzing the data with RSM, this study establishes response surface models to predict the relationship between BC characteristics and cement mortar strength. The results demonstrate that the optimal combination for enhancing the mechanical performance of the mortar is achieved when BC particles have a median particle diameter of 51.08 μm and a content of 2.69% of the mixture. Additionally, utilizing scanning electron microscopy (SEM), it is revealed that BC serves as a nucleation site for cement hydration, thereby inducing a more compact and dense microstructure within the cement mortar. Furthermore, BC particles contribute to enhancing the interfacial transition zone between the cement paste and aggregate, leading to increased compressive strength and fracture toughness of the mortar while simultaneously curbing crack propagation.

TSUNAMI RUN-UP CONSIDERING TIME VARIATION OF DENSITY OF INUNDATION WATER

Aiming for the advancement of tsunami load, historical and/or prospective tsunami scale evaluations, practical empirical formulas for evaluating friction factor K of inundation flow and density ρ of inundation water over a movable bed, which can be applied to a tsunami run-up theory, are proposed using experimental data whose amount (range) is increased (expanded) by carrying out additional experiments on ρ and run-up of inundation flow with sediment, and verification data of the above theory under a uniformly sloping movable bed condition are provided. Series solutions with a higher universality to the run-up of tsunami inundation flow with sediment over a uniformly sloping movable bed, in which both K and ρ depend on time, are derived under the conditions depending on an incident bore height h1 at shoreline (or an initial stored water depth), bed slope i, median particle diameter d50 of initial bed material, and examples of the solutions are shown. The solutions are applicable to the case that ρ is independent on time, i.e., the case of inundation flow without sediment over a movable bed or fixed bed. Including the case of inundation flow without sediment, validity of one of the solutions is also verified through a comparison with the verification data on run-up distance.

Predicting propeller jet scour in silty and sandy marine environments

The propeller jet generated by a ship's propeller during berthing and unberthing from quays initiates sediment transport and causes scouring around the quay structures. Investigating the flow area caused by ship propeller jets at quays and piers is important in terms of determining the local scour at the seabed. In this study, the water jet formed by ship's propellers and sediment movements on the seabed were investigated. While medium sand is typically used as the sediment type in literature, fine-grained sand and silt were used as base materials in this study. As a result of the experiments conducted with a three-dimensional flow velocity measuring device (ADV), the measured three-dimensional velocity components and the propeller efflux velocity coefficients were redefined. By examining the time dependent scour graphs of silt and sand, their scour rates were compared, and time scales were obtained from graphs. Silt was observed to have a significantly slower scour rate compared to sand. Contrary to the findings in the literature, despite silt having a smaller median particle diameter than sand, the maximum scour depths of silt were found to be less than those of sand under the same experimental conditions. Based on the results of this study and previous studies, two equations were proposed to quantify the scour depth for sand material, and silt and sand-clay mixtures.

Effect of micronisation on colour and optical properties of ceramic colourants for inkjet printing

The advent of inkjet printing (IJP) as the main used decoration technique for ceramic products has changed the technological requirements for pigments and the way they are obtained. To meet IJP and durability requirements, it is necessary to micronise the colourants to achieve particles smaller than 1 μm (median particle diameter d50 ∼300 nm). The high-energy milling process induces microstructural changes that affect the colour properties. In order to understand the effect of particle size reduction on chromatic properties, an in-depth study was carried out by simulating the industrial milling process on a pilot scale. The effect of micronisation was investigated for four ceramic pigments (yellow zircon, brown spinel, pink malayaite, and green eskolaite) and one dye (blue olivine) by UV–vis–NIR optical spectroscopy (DRS), chromatic coordinates and XRPD analyses (Rietveld method). This study was carried out on the colourants both as they were and mixed with glass, reproducing the industrial firing process. The results obtained led to the definition of the main aspects responsible for the colour evolution derived from the milling process.

Abstracts from The Aerosol Society Drug Delivery to the Lungs 33.

Abstracts from The Aerosol Society Drug Delivery to the Lungs 33.

Physiologically Based Pharmacokinetic Model Development and Verification for Bioequivalence Testing of Bempedoic Acid Oral Suspension and Reference Tablet Formulation.

The bioequivalence of bempedoic acid oral suspension and commercial immediate release (IR) tablet formulations were assessed using a physiologically based pharmacokinetic (PBPK) model. The mechanistic model, developed from clinical mass balance results and in vitro intrinsic solubility, permeability, and dissolution data, was verified against observed clinical pharmacokinetics (PK) results. Model inputs included a fraction of a dose in solution (0.01%), viscosity (118.8 cps), and median particle diameter (50 µm) for the suspension and particle diameter (36.4 µm) for IR tablets. Dissolution was determined in the relevant media (pH 1.2-6.8) in vitro. Model simulations of bioequivalence predicted oral suspension (test) to IR tablet (reference) geometric mean ratio estimates of 96.9% (90% confidence interval [CI]: 92.6-101) for maximum concentration and 98.2% (90% CI: 87.3-111) for the area under the concentration-time curve. Sensitivity analyses showed gastric transit time had a minor impact on model predictions. Oral suspension biopharmaceutical safe space was defined by extremes of particle size and the percent of bempedoic acid in solution. PBPK model simulations predicted that the rate and extent of bempedoic acid absorption are unlikely to exhibit clinically meaningful differences when dosed as an oral suspension compared with an IR tablet without requiring a clinical bioequivalence study in adults.