Changes In Particle Concentration Research Articles

Assistance of analytical ferrography in the interpretation of wear test results carried out with biolubricants

Analytical ferrography plays a crucial role in predictive maintenance, which is a proactive approach to asset and equipment management. This technique provides valuable information about the internal condition of machines and components, allowing early identification of potential problems and the scheduling of maintenance interventions before catastrophic failures occur. Ferrography allows you to identify worn particles, non-metallic inclusions and other indicators of wear on components. By analyzing samples of lubricating oil or hydraulic fluid, analytical ferrography can offer insights into the health of internal components such as gears, bearings and other critical elements. Changes in particle concentration and composition may indicate abnormal wear. This work involves the use of analytical ferrography to interpret wear results carried out with two vegetable lubricants with additives, compared to a mineral lubricant, also with additives. To assist in the interpretation of the results, the open source software Image J and a small program developed in Python were used. It was found that it is possible to use these two tools to aid the interpretation of ferrograms.

Aerodynamic breakup of gel suspension droplets loaded with aluminum particles

The persistent and frequent space explorations are affected by the performance of propellants, among which the closely related gel propellants have been widely used due to their unique characteristics. Currently, research efforts primarily concentrate on the metallization and atomized combustion of gel propellants, emphasizing the combustion performance of metallized gel propellants. However, little attention has been given to the secondary breakup process that occurs just before combustion. By utilizing high-speed flow visualization technology, this study examines the key aerodynamic breakup process of gel suspension droplets loaded with micro aluminum particles, experimentally and theoretically investigating the droplet dynamics induced by particle volume fraction. The experimental confirmation of the three breakup behaviors exhibited by gel suspension droplets, namely oscillation mode, bag-stamen breakup, and hemline breakup, is presented along with the construction of a phase diagram. The impact of heterogeneous effects resulting from an increase in particle volume fraction on the critical breakup Weber number is revealed, with a concentration of 9 % as the turning point. Within the range of moderate Weber numbers, the tail flick deformation of suspension droplets in airflow is observed and reported for the first time. At different particle concentrations, there keeps a linear correlation between the dimensionless tail length and Weber number. Spherical suspension droplets will deform into thin disks in the airflow, with a nearly constant deformation rate regardless of changes in particle concentration. Additionally, the relationships between characteristic times and droplet parameters are discussed through statistical analysis of the results. As Ohnesorge number and particle volume fraction increase, the characteristic times both show a monotonically increasing trend. Moreover, a model of unstable growth rate associated with the particle volume fraction is established through linear instability analysis, accurately predicting the variation in critical Weber number for gel suspension droplet breakup. The congruence between our theoretical framework and experimental findings not only enhances comprehension of the impact of micro aluminum particles on the secondary breakup of gel suspension droplets but also provides valuable guidance for the aerospace applications of metallized gel propellants.

Evaluating viral filtration efficiency in non-centralized air-conditioning systems: a novel approach grounded in medical experimental data

This study enhances the understanding of virus removal efficiency by filters, crucial for predicting respiratory disease transmission risk and guiding outbreak prevention. Current research often neglects the survival behaviour of pathogens. Addressing this, our research develops a novel approach anchored in medical experimental data. A mathematical model was established to depict the dynamic changes in particulate concentration within non-centralized air-conditioned rooms, considering indoor and outdoor concentrations, natural ventilation, and filter dynamics. The model’s reliability was affirmed through particle and aerosolized pathogen filtration experiments, showing an R 2 value over 0.99, indicating strong agreement with empirical data. Analysis of filter operation, both with and without infection sources during epidemics, reveals that the use of split air conditioners and filters significantly reduces pathogen concentration. Pathogens trapped in filters undergo natural decay, considerably lowering transmission risk compared to airborne states. This research offers a scientifically grounded, precise methodology for evaluating respiratory disease transmission risks, contributing substantially to public health management.

Rheological characteristics and thermal studies of EG based Cu:ZnO hybrid nanofluids for enhanced heat transfer efficiency

The present work describes an experimental investigation of Cu-doped ZnO–EG hybrid nanofluids for better viscous nature and thermal efficiency in cooling systems. The initial phase involves synthesizing copper (Cu) doped zinc oxide (ZnO) nanoparticles using chemical precipitation method. The structural and morphological properties of these nanoparticles are determined using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thermo-physical measurements are conducted to analyze the viscosity and thermal conductivity of Cu-doped ZnO nanofluids based on ethylene glycol (EG) at varying particle concentrations (ranging from 0.01 wt% to 0.08 wt%) with various temperature ranges of 298 K to 328 K. The observed rheological properties showed that the viscosity of tested Cu-doped ZnO-EG nanofluids exhibited non-Newtonian shear-thinning behavior due to the alignment of nanoparticle agglomerates with increasing shear rate. Similarly, the thermal properties of the prepared Cu:ZnO-EG nanofluids are examined, demonstrating a smooth increase in thermal conductivity with changes in particle concentration and temperature. The thermal conductivity ratio of the nanofluids suggests that the newly developed hybrid nanofluids exhibit superior heat transfer characteristics.

Capture of colloidal fine suspended particle by aquatic vegetation under rainfall

The capture of colloidal fine suspended particles by vegetation plays an important role in water quality of the shallow aquatic system under rainfall. Quantifying impact of rainfall intensity and vegetation condition on this process remains poorly characterized. In this study, the colloidal particle capture rates under three rainfall intensities, four vegetation densities and with submerged or emergent vegetation were investigated in different travel distance in a laboratory flume. Considering vegetation as porous media, non-Darcy's law with rainfall as a source term, was coupled with colloid first-order deposition model, to simulate the particle concentration changes with time, determining the particle deposition rate coefficient (kd), representing capture rate. We found that the kd increased linearly with rainfall intensity; but increased and then decreased with vegetation density, suggesting the existence of optimum vegetation density. The kd of submerged vegetation is slightly higher than emergent vegetation. The single collector efficiency (η) showed the same trend as kd, suggesting colloid filtration theory well explained the impact of rainfall intensity and vegetation condition. Flow hydrodynamic enhanced the kd trend, e.g., the theoretical strongest flow eddy structure represented in the optimum vegetation density. This study is helpful for the design of wetland under rainfall, to remove colloidal suspended particles and the hazardous material, for the protection of the downstream water quality.

Coagulation contributing to electrostatic precipitation of ultrafine fly ash from small-scale biomass combustions

An electrostatic precipitator (ESP) is an efficient device for removing fly ash from small-scale solid-fuel combustion. Under corona discharge, a gaseous medium becomes ionised, and particles become charged by colliding with ions. An electric field forces the movement of charged particles to remove gases and induces the movement of generated ions, causing secondary electrohydrodynamic flow. Thus, particle charge, the presence of neighbouring particles, an ESP electric field, and gas flow turbulence can enhance particle coagulation. Therefore, the ultrafine particle concentration in an ESP is expected to evolve under electrostatic removal and enhanced coagulation. In the present study, the contribution of coagulation is explored and confirmed using experimental measurements performed on an ESP used to control emissions from a 160-kW boiler with biomass combustion. The ESP was operated under several modes to obtain different coagulation conditions. Changes in particle concentrations were measured simultaneously using two techniques. It was found that coagulation could be responsible for up to 5% of the total removal efficiency, depending on the ESP operation parameters. The present study can promote a deeper understanding of the processes involved in electrostatic precipitation, and the obtained results can be useful for practical ESP engineering.

Reviewing the links and feedbacks between climate change and air pollution in Europe

Feedbacks between air pollutants and meteorology play a crucial role in the direction of the response of future climate and air pollution. These feedbacks are important to understand and quantify the potential impact of adaptation and mitigation policies setup for protecting the population against air pollution and heat stress. We review the interactions between climate and air pollution, with special focus on the projections of air pollution under different future climate scenarios and time horizons, based on a literature review of research articles and reports from the last decade. The assessment focuses on 1) the specific impacts of climate change on air pollution and natural particle and precursor emissions in Europe in the near future (2030), by mid-century (2050) and by end of the century (2100), 2) impacts on air pollution due to changes in emissions vs. changes in climate, 3) feedbacks from air pollution on climate, 4) impacts of climate change on wildland fires and air pollutant levels, and 5) the role of adaptation and mitigation policies on climate change and air pollution. Available literature to a large extent suggests that ozone concentrations will likely increase in the second half of the century by up to 9 ppb [−4 + 9.3], while in the first half of the century, changes are much smaller and are up to ±1.5 ppb. These changes are mainly attributed to increased temperatures and emissions of biogenic volatile organic compounds, but also depends on the models and scenarios used in these studies. On the other hand, the predicted changes in particle concentrations and chemical composition are uncertain and much smaller. Similar to ozone, larger changes in the particle concentrations are projected in the second half of the century. The main conclusion from this review is that the estimated changes in pollutant levels in the future vary significantly depending on the applied model systems, as well as the different emission or meteorological scenarios used in the different studies. Nevertheless, studies generally agree on the overall trend of the changes in pollutant levels due to climate change, in particular in the second half of the century.

Sub-lethal effects of nanoplastics upon chronic exposure to Daphnia magna

Studies of microplastic and nanoplastic toxicity on aquatic invertebrates predominantly focus on short-term effects such as mortality and immobility. This study investigated sublethal effects on Daphnia magna when exposed to dialyzed 20 nm and 200 nm carboxylated polystyrene nanoplastics for 21 days. The study tested the effects of 50 mg/L of both particle sizes and 0.1 mg/L of the 20 nm particles. Data results between the 50 mg/L for both particle sizes, which maintains the particle mass concentration constant, and between the 50 mg/L 200 nm and 0.1 mg/L 20 nm treatments, which maintains particle number concentration constant, allowed comparison of dose metrics. Exposures of Daphnia magna to 0.1 mg/L and 50 mg/L of 20 nm particles enabled the evaluation of the effects of particle mass concentration on the toxicity of the smaller particles. Chronic exposure to polystyrene nanoplastics impacted growth, molting and reproduction of Daphnia magna at both tested sizes, and at particle concentrations as low as 0.1 mg/L. Overall, the results of this study showed similar trends in several measured endpoints whether using the mass concentration or particle counts as dose metrics and change in particle concentration did not result in a significant difference in the observed endpoints for 20 nm particles.

Impact of the Speed of Airflow in a Cleanroom on the Degree of Air Pollution

The high-energy requirements of cleanrooms are the main motivation for optimizing their operational conditions. The ventilation system consumes the most energy in order to ensure the precise air conditioning of the room (filtration, temperature, and humidity adjustment). The main function of the ventilation system is to keep particle concentration to a minimum. This work deals with the optimization of an experimental operating room via the optimization of air supply through the distribution element (laminar airflow ceiling) in the range of 0.15–0.25 m·s−1. The laminar airflow between the distribution element and the patient is influenced by the operating light and different airflow velocities. These factors affect changes in particle concentration. Ansys Fluent software was used to investigate the nature of the flow, velocity profiles, and particle trajectories. The results of our numerical simulation demonstrate that a suitable flow rate setting increases the efficiency of particle reduction in the operating table area by up to 54%, which can, in turn, reduce operating costs. The simulated air velocity profile was subsequently verified using the particle image velocimetry (PIV) method. The typical size of particles monitored for in cleanrooms is 0.5 μm according to ISO EN 7. Therefore, the results of this study should be helpful in correctly designing distribution elements for clean rooms.

Reconstruction of the Long-Term Dynamics of Particulate Concentrations and Solid–Liquid Distribution of Radiocesium in Three Severely Contaminated Water Bodies of the Chernobyl Exclusion Zone Based on Current Depth Distribution in Bottom Sediments

Given the importance of understanding long-term dynamics of radionuclides in the environment in general, and major gaps in the knowledge of 137Cs particulate forms in Chernobyl exclusion zone water bodies, three heavily contaminated water bodies (Lakes Glubokoe, Azbuchin, and Chernobyl NPP Cooling Pond) were studied to reconstruct time changes in particulate concentrations of 137Cs and its apparent distribution coefficient Kd, based on 137Cs depth distributions in bottom sediments. Bottom sediment cores collected from deep-water sites of the above water bodies were sliced into 2 cm layers to obtain 137Cs vertical profile. Assuming negligible sediment mixing and allowing for 137Cs strong binding to sediment, each layer of the core was attributed to a specific year of profile formation. Using this method, temporal trends for particulate 137Cs concentrations in the studied water bodies were derived for the first time and they were generally consistent with the semiempirical diffusional model. Based on the back-calculated particulate 137Cs concentrations, and the available long-term monitoring data for dissolved 137Cs, the dynamics of 137Cs solid–liquid distribution were reconstructed. Importantly, just a single sediment core collected from a lake or pond many years after a nuclear accident seems to be sufficient to retrieve long-term dynamics of contamination.

Small-Angle Particle Counting Coupled Photometry for Real-Time Detection of Respirable Particle Size Segmentation Mass Concentration.

Respirable particulate matter air pollution is positively associated with SARS-CoV-2 mortality. Real-time and accurate monitoring of particle concentration changes is the first step to prevent and control air pollution from inhalable particles. In this research, a new light scattering instrument has been developed to detect the mass concentration of inhalable particles. This instrument couples the forward small-angle single particle counting method with the lateral group particle photometry method in a single device. The mass concentration of four sizes of inhalable particles in the environment can be detected simultaneously in a large area in real-time without using a particle impactor. Different from the traditional light scattering instrument, this new optical instrument can detect darker particles with strong light absorption, and the measurement results mainly depend on the particle size and ignore the properties of the particles. Comparative experiments have shown that the instrument can detect particles with different properties by simply calibrating the environmental density parameters, and the measurement results have good stability and accuracy.

Contributions of Coagulation, Deposition, and Ventilation to the Removal of Airborne Nanoparticles in Indoor Environments.

Airborne nanoparticles are frequently released in occupied spaces due to episodic indoor source activities. Once generated, nanoparticles undergo aerosol transformation processes such as coagulation and deposition. These aerosol processes lead to changes in particle concentration and size distribution over time and accordingly affect human exposure to nanoparticles. The present study establishes a framework for an indoor particle dynamic model that can predict time- and size-dependent particle concentrations after episodic indoor emission events. The model was evaluated with six experimental data sets obtained from previous measurement studies in the literature. The indoor particle dynamic model quantified the relative contributions of three particle loss mechanisms (i.e., coagulation, deposition, and ventilation) to the total reduction in number concentration. The results show that particle coagulation and indoor surface deposition are two dominant processes responsible for temporal changes in particle size and concentration following indoor emission events. The first-order equivalent coagulation loss rate notably varies with indoor emission source and accounts for up to 59% of the total particle loss for burning a candle, 42% for broiling a fish, and 10% for burning incense. The results reveal that while the coagulation loss rate changes markedly with the particle concentration and source type, the deposition loss rate is more dependent on particle size. Compared to coagulation and deposition, the effect of ventilation is marginal for most of the nanoparticle emission events indoors; however, ventilation loss becomes pronounced with the decrease of particle concentration below 5 × 104 cm-3, especially for particles larger than 100 nm in aerodynamic diameter.

Research on the transportation and flow characteristics of deep-sea ore transportation equipment

This paper takes the valve-controlled clean water pump ore transportation equipment as the research object, and establishes the mathematical model and finite element model of the ore separator. Based on the calculation method provided by Computational Fluid Dynamics, the numerical simulation and experimental study of the solid-liquid two-phase flow process inside the ore separator is carried out. Furthermore, a single factor analysis method is used to analyze its working performance, separation and conveying efficiency. The change in particle concentration changes the flow characteristics of the internal flow field of the storage tank, increases the number of ore flowing into the separator per unit time, and ultimately affects the separation performance of the ore separator. With the increase of particle concentration, the ore separation efficiency η increases first and then decreases. When the particle concentration is 10%, the slurry separation efficiency is the highest, about 98.93%. With the increase of the particle size, the efficiency of ore particles flowing into the storage tank increases first and then decreases. When the particle size is 20 mm, the value of ξ is higher, reaching more than 92%.

Simulation study on the relationship between catalyst particle concentration and flow field of a gas turbine

In this paper, the characteristics of the flow field in the gas turbine under different catalyst particle concentrations are simulated and analyzed by FLUENT software. The influences of catalyst particle concentration on the high-temperature smoke flow field, the movement track of catalyst particles and the erosion of the moving blade are studied in detail. The results show that the change of particle concentration has no obvious influence on the high temperature smoke flow field. The erosion wear of moving blade mainly occurs near the leading edge and trailing edge of the blade. The possibility of erosion wear at the leading edge is obviously greater than that at the trailing edge. The concentration of catalyst particles has a great influence on the erosion wear of moving blade. The erosion wear will be aggravated with the increase of catalyst particle concentration.

Open waste burning causes fast and sharp changes in particulate concentrations in peripheral neighborhoods

The open burning of municipal solid waste (MSW) –frequently observed in developing countries– emits harmful pollutants, including fine particulate matter (PM2.5) and black carbon (BC), and deteriorates the air quality in urban areas. This work reports on PM2.5 and BC measurements (fixed and mobile) conducted in a residential neighborhood on the outskirts of a Brazilian city (Londrina), complemented by a public opinion survey to understand the open burning in the context of waste management. Mean (± standard deviation) BC concentration (1.48 ± 1.40 μg m−3) at the fixed sites of the neighborhood was lower than downtown, while PM2.5 (9.68 ± 8.40 μg m−3) concentration was higher. The mobile monitoring showed higher mean PM2.5 concentrations but lower BC/PM2.5 ratios than downtown, with sharp and fast spikes (up to 317.87 and 565.21 μg m−3 for BC and PM2.5, respectively). The large spatial heterogeneity of particulate concentrations was associated with the occurrence of MSW burning events. Our observations were verified by the survey respondents who identified poor waste management practices: garbage in streets, waste burning, and illegal dump sites. Even though the area has a municipal waste collection service, the majority of the respondents (87%) had seen waste burning close to their homes on a weekly basis, and think that people burn waste out of habit (54%) and because they are not patient to wait for the collection services (67%). To combat this illegal practice, we suggest raising the public awareness through campaigns at local level, adopting education initiatives and economic incentives for correct waste segregation, and enforcing regular inspection of burning events by the authorities. Our research method proved to be a time- and cost-effective approach for mapping particulate concentrations and for identifying undesirable waste practices, and could be effectively applied to other global cities.

Direct numerical simulations of nanoparticle formation in premixed and non-premixed flame–vortex interactions

Direct numerical simulations (DNSs) of nanoparticle formation in reactive flows are challenging, and only greatly simplified DNS test-cases are possible, which help clarify the turbulence–particle–dynamics interaction and guide the necessary modeling efforts. As a basis for such studies, a new DNS database is introduced, which resolves the smallest relevant scales of the nanoparticle concentration field to obtain insights into the statistics of nanoparticle formation in reactive flows. Formation and evolution of iron oxide nanoparticles in premixed and non-premixed flames wrapped-up by a vortex have been investigated using the sectional model and direct chemistry. The DNSs capture the “engulfing” and local dilution of the particle fields. Different zones of high particle number concentration have been found in every flame, and it was shown that the thickness of these zones decreases with increasing Schmidt number, which confirms that in simulations of nanoparticle-forming turbulent reacting flows, the grid resolution has to be very fine to resolve the characteristic scale for high sections. The contributions to the change in particle concentration due to diffusion, coagulation, and nucleation have been analyzed in detail, and dominant contributions across the particle number concentration layers and across the flames have been identified. This analysis has also been carried out in terms of flat, concave, and convex iso-surface geometries, induced by the flame–vortex interaction and characterized by the curvature of the particle number concentration fields and also by the flame curvature. The results demonstrate that the flame curvature effects cannot be ignored in modeling strategies. The probability density functions for the particle number concentrations have been analyzed and quantified in terms of Shannon information entropy, which illustrates the effect of fast diffusion (and entropy production) of the smaller particles and slow diffusion (and entropy production) of the largest particles with high Schmidt numbers. In addition, the unclosed filtered or averaged agglomeration term was evaluated as a basis for future modeling efforts, showing that agglomeration rates will be underestimated by orders of magnitude unless suitable models are developed.

Impacts of microplastic vs. natural abiotic particles on the clearance rate of a marine mussel

AbstractIn coastal habitats, mussels are exposed to microplastics (MP; plastic 0.1 μm–5 mm) and silt, two abiotic particles that are similarly sized and lack nutrition. The addition of MP or silt may change the functional response of mussels. We measured clearance rate (CR) of Mytilus trossulus in three particle treatments (algae, MP + algae, and silt + algae) across four concentrations to (1) determine if the effects of MP and silt are similar and (2) disentangle the effects of particle type, particle concentration, and proportion of abiotic particles. CR decreased by 62% at high MP concentrations (> 1250 particles mL−1) but was not affected at equivalent silt concentrations. These findings suggest high MP concentrations inhibit mussel CR, more than expected by changes in particle concentration or the proportion of abiotic particles. As plastic production increases, mussel exposure to MP will increase, potentially reducing energy transfer, benthic‐pelagic coupling, and water clarity.

Clustering and energy spectra in two-dimensional dusty gas turbulence.

We present direct numerical simulation of heavy inertial particles (dust) immersed in two-dimensional turbulent flow (gas). The dust particles are modeled as monodispersed heavy particles capable of modifying the flow through two-way coupling. By varying the Stokes number (St) and the mass-loading parameter (ϕ_{m}), we study the clustering phenomenon and the gas phase kinetic energy spectra. We find that the dust-dust correlation dimension (d_{2}) also depends on ϕ_{m}. In particular, clustering decreases as mass loading (ϕ_{m}) is increased. In the kinetic energy spectra of gas we show (i) the emergence of a different scaling regime and that (ii) the scaling exponent in this regime is not universal but a function of both St and ϕ_{m}. Using a scale-by-scale enstrophy budget analysis we show that in this emerged scaling regime, which we call the dust-dissipative range, viscous dissipation due to the gas balances the back-reaction from the dust.

Two-Hour Postprandial Lipoprotein Particle Concentration Differs Between Lean and Obese Individuals.

The concentrations of lipoprotein particles [high-density lipoproteins (HDLs), low-density lipoproteins (LDLs), very-low-density lipoproteins (VLDLs), and chylomicrons] are associated with the risk of cardiovascular diseases. Most studies have examined these associations in the fasting state. Previous studies have shown lipoprotein particle concentration change following meal, and these changes are different in individuals with obesity. In this study, we aimed to assess whether various meal compositions lead to adverse short-term (2-h) postprandial lipoproteinemia in obese insulin resistant (obese-IR) subjects as compared to lean insulin sensitive (lean-IS) subjects. In a randomized crossover trial, nine lean-IS and nine obese-IR Chinese men aged 22–35 years were challenged with isoenergetic and isovolumic meals rich in protein (HP), fat (HF), or carbohydrate (HC). Plasma samples were collected after a 10-h fast, as well as 1-h and 2-h post-meal and analyzed using nuclear magnetic resonance. Plasma concentration of large VLDLs and chylomicron particles was higher and increased more after all meals in obese-IR compared to lean-IS subjects. The HP meal decreased small LDL particle concentration in obese-IR subjects, and increased small HDL particle concentration in all subjects. The HF meal led to a decrease in small HDL concentration in all subjects. In conclusion, obese-IR subjects revealed a detrimental response to meal challenges even as early as 2-h after meal intake.

Effect of Small‐Scale Gravity Waves on Polar Mesospheric Clouds Observed From CIPS/AIM

AbstractData from the Cloud Imaging and Particle Size experiment on the Aeronomy of Ice in the Mesosphere (AIM) satellite are employed to study the impact of small‐scale gravity wave (GW) on albedo, ice water content (IWC), and particle radius (PR) of polar mesospheric clouds. Overall, 23,987 eligible GW events, with a horizontal wavelength of 20–150 km are eventually extracted from Cloud Imaging and Particle Size level 2 orbit albedo maps during 2007–2011. The overall statistical results show that when small‐scale GWs travel horizontally in polar mesospheric clouds, they can amplify the albedo and IWC by a rate of 10.0–22.6%, while reducing the PR by as much as −7.01%. Owing to the strong temporal and spatial dependences, the albedo and IWC variations are larger on an average during the core of the season, while they decrease during the initial and final periods of the season. The obvious zonal asymmetries are also found. The albedo variations show a positive linear relation with the GW amplitudes in albedo, as opposed to a negative linear relation with GW horizontal wavelengths. In most of the GW events, the periodic variation in the trend of albedo exhibits an anticorrelation with that of PR. Combining previous research studies with our results, we deduce that the rapid change in particle concentration and the upward movement of water vapor by GWs may be very important aspects for explaining the influence mechanism.