Increasing Particle Concentration Research Articles

Measuring the effect of fireworks on air quality in Minneapolis, Minnesota

Air quality was measured before, during, and after a 4th of July fireworks display in downtown Minneapolis, Minnesota using a mix of low-cost sensors (CO, CO2, and NO) for gases and portable moderate cost instruments for particle measurements (PM2.5, lung deposited surface area, and number weighted particle size distributions). Meteorological conditions—temperature, humidity, and vertical temperature profile were also monitored. Concentrations of particles and most gaseous species peak between 10 pm and midnight on July 4th, decrease in the middle of the night but increase again and by between 6 and 7 am reach concentrations as high or higher than during fireworks. This overnight increase is likely due to a temperature inversion trapping emissions. Between 10 pm and midnight on July 4th the measures of particle concentration increase by 180–600% compared to the same period on July 3rd. Particle size distributions are strongly influenced by fireworks, shifting from traffic-like bimodal distributions before to a nearly unimodal distribution dominated by a large accumulation mode during and after. The shape of the size distribution measured during the early morning peak is nearly identical to that observed during fireworks, suggesting that the early morning peak is mainly due to trapped fireworks emissions not early morning traffic. Gaseous species are less strongly influenced by fireworks than particles. Comparing measurements made between 10 pm and midnight on July 4th and the same period on July 3rd, the concentration of CO increases 32% while the CO2 increases only 2% but increases by another 15% overnight. The NO concentration behaves oddly, decreasing during fireworks, but then recovering the next morning, more than doubling overnight. Our measurements of CO, NO, and PM2.5 are compared with those made at the nearest (~ 2 km away) Minnesota Pollution Control Agency Air Monitoring Station. Their NO results are quite different from ours with much lower concentrations before fireworks, a distinct peak during, followed by a strong overnight increase and an early morning peak somewhat similar in shape and concentration to ours. These differences are likely due mainly to malfunction of our low-cost NO sensor. Concentrations of CO and PM2.5 track ours within 25% but peak shapes are somewhat different, which is not unexpected given the spatial separation of the measurements.Article highlightsLow-cost and moderate-cost sensors are used to monitor the impact of a 4th of July fireworks display on local air quality.Particle concentrations and size are more strongly influenced by fireworks than are concentrations gaseous pollutants.Particle size distributions produced by fireworks are distinctly different from those associated with urban traffic sources.

The analysis of nickel-obsidian composite formation on mild steel surface through electrocodeposition process.

Composite, the engineering material consisting of two different macroscopic phases, can be synthesized through electro co-deposition reaction by adding particles into the solution of the electroplating process. The obsidian powder as dispersed particles and the nickel-metal as the matrix are the materials that can be synthesized using that technique. The hardness of obsidian is in the range of 650-900 HV, whereas nickel is 380 HV. We have investigated the formation mechanism of the coated composite layer made via electrocodeposition reaction. The electrocodeposition of the obsidian particle was controlled by kinetic, electrophoretic, and gravity forces that act on the particles. The resultant of these forces determines the direction of particles. The experimental result shows that increasing particle concentration from 0 to 25g/L increased the hardness of the coated layer from 380 to 504 HV. The kinetic force can keep the particles suspended in solution at this concentration range. However, a further increase in particle concentration to 50g/L decreases the kinetic energy of particles significantly, causing the particles to fall without depositing at the cathode and reducing the hardness down to 430 HV. Meanwhile, increasing current density increase the rapidness of the electro co-deposition reaction. At the increasing current density at a range of 3.3-10 Ampere/dm2, the hardness of the coated layer is at the range of 420-540 HV. Coated layer thickness decreases slightly as particle concentration increases but increases significantly as current density increases. The highest hardness of the coated layer, 540 HV, was obtained at a particle concentration of 25g/L and a current density of 10 A/dm2.

Numerical study on flow and wear characteristics of dense fine particle solid–liquid two-phase flow in centrifugal pump

The solid–liquid two-phase centrifugal pump is one of the core power equipment of solid phase material hydraulic transportation, widely used in hydraulic engineering, petrochemical industry, marine metal mineral exploitation, urban sewage treatment, and other sectors of the national economy. There is a significant increase in the need to transport dense fine particle slurry in industrial production. Under this condition, the influence of particle parameters on the performance of the centrifugal pump is still not clear. In order to study the flow and wear characteristics of dense fine particle solid–liquid two-phase transported by an open impeller centrifugal pump, the Re-Normalization Group k − ε and dense discrete phase models in Fluent were used to describe the characteristics of the solid–liquid two-phase flow. The numerical model is validated with the experimental data of the pump’s performance. The study indicates that the particle size and concentration have great influence on the wear of the impeller. The wear of the blade pressure surface is the most serious. With the increase of particle concentration and size, the wear area expands to the leading edge and the upper surface of the blade. These results can provide supporting theories for the design of a dense fine particle solid–liquid two-phase medium conveying pump.

Rendering discrete participating media using geometrical optics approximation

We consider the scattering of light in participating media composed of sparsely and randomly distributed discrete particles. The particle size is expected to range from the scale of the wavelength to several orders of magnitude greater, resulting in an appearance with distinct graininess as opposed to the smooth appearance of continuous media. One fundamental issue in the physically-based synthesis of such appearance is to determine the necessary optical properties in every local region. Since these properties vary spatially, we resort to geometrical optics approximation (GOA), a highly efficient alternative to rigorous Lorenz—Mie theory, to quantitatively represent the scattering of a single particle. This enables us to quickly compute bulk optical properties for any particle size distribution. We then use a practical Monte Carlo rendering solution to solve energy transfer in the discrete participating media. Our proposed framework is the first to simulate a wide range of discrete participating media with different levels of graininess, converging to the continuous media case as the particle concentration increases.

Effects of sediment diameter and concentration on cavitation characteristics and mechanism

The synergistic erosion caused by cavitation and abrasion is a common and severe problem for hydraulic machinery. In order to explore the mechanism of particles size and concentration effect on cavitation, taking the rotating disk as the research object. The solid-liquid-gas three-phase flow was calculated based on the non-homogeneous multiphase flow model, modified RNG k−εturbulence model, and ZGB model. The increase of particles size firstly inhibited the bubbles (0.02 mm ≤ d ≤ 0.1 mm) and then promoted the bubbles (0.1 mm <d ≤ 0.4 mm); When 0.27 mm < d ≤ 0.4 mm, both cavitation area and cavitation damage intensity are more significant than those of cavitation alone. When d = 0.1 mm, 1% ≤ Cv ≤ 10%, the increase of particles concentration promotes bubbles. However, that only enhances the cavitation area, but has little effect on the cavitation damage intensity. When particles severely inhibit the bubbles, the vortex rotation effect is the strongest, and the mainstream promotion and re-entrant jet inhibition effect are the strongest. The purpose of this paper is to provide some theoretical basis for exploring the mechanism of synergistic erosion.

Mechanical response and damage evolution of bio-inspired B4C-reinforced 2024Al composites subjected to quasi-static and dynamic loadings

Inspired by nacreous architecture, the 2024Al/20–50 vol% B4C composites with a lamellar-interpenetrated structure were successfully manufactured via freeze casting and pressure infiltration, and the quasi-static and dynamic characteristics were conducted at strain rates ranging from 0.001 to 3000 s−1. The strength of the composites enhanced as the strain rate increased up to 2000 s−1 since the strain rate hardening effect facilitated the accumulation of dislocations. At the strain rate of 3000 s−1, the adiabatic shear banding and its induced cracking were formed as the strengthening mechanisms were overcome by the thermal softening, which converted the dislocation structure from dislocation clusters to recrystallized grains, accompanied by a decrease in dislocation density, thereby degrading the compressive strength. A rigid network structure was formed in the composites with high particle content, and each particle had more inter-particle contact points, which made the strength of the composites increase with the increase of particle reinforcement content. This was also the reason why the strain rate sensitivity of the composites was considerably raised by introducing more particle reinforcement. However, increasing particle content heightened the composite susceptibility to strain localization and adiabatic shear damage, resulting in more brittleness of the 2024Al/50 vol% B4C composite at high strain rates. These findings could deepen the comprehension of the mechanical response and damage evolution of nacre-like composites exposed to extreme conditions and promote their applications.

Experimental Analysis of Double Pipe Heat Exchanger with V-cut Twisted Tape Inserts using PCM Dispersed Nanofluids

The performance of a double tube heat exchanger with V-cut twisted tape inserts (VCTT) and phase change material (PCM) dispersed nanofluid is investigated experimentally. The three water-based Al2O3, PCM, and Al2O3+PCM nanofluid with different concentrations (0.01-0.1% vol.) are used. The impacts of different geometric parameters, i.e., twist ratio (TR), depth ratio (DR) and width ratio (WR) of VCTT inserts on Nusselt number (Nu), friction factor (f) and entropy generation are examined. The outcomes expose that Nu and f increase as particle concentration increases and twisting ratio decreases. A higher Nu and f are generated by a higher DR or a lower WR. In all cases, the entropy generation of nanofluid is found to be lower than that of water. For all working fluids, a rise in TR, a fall in DR, and a rise in WR increases overall entropy generation.

Laser backscattering of multi-scaled large particles based on superimposed scattering

The scale, scattering and other optical properties of water droplets and ice crystals in clouds are the key factors affecting aircraft icing. Based on the superimposed scattering intensity distribution, the optical scattering model for cloud droplets and ice particles was established, the effects of different cloud types on laser backscattering were analyzed, and the backscattering coefficient and the echo power with different cloud particle concentrations were simulated and experimental measured. It was concluded that the particle backscattering of different cloud types varied greatly, especially with the increase of cloud particle concentration and the decrease of temperature. With the multi-scaled particle backscattering model for droplets and ice crystals presented here, the particle concentration of different types of clouds can be derived through mathematical inversion.

On the stratospheric chemistry of midlatitude wildfire smoke

SignificanceLarge wildfires have been observed to inject smoke into the stratosphere, raising questions about their potential to affect the stratospheric ozone layer that protects life on Earth from biologically damaging ultraviolet radiation. Multiple observations of aerosol and NO2 concentrations from three independent satellite instruments are used here together with model calculations to identify decreases in stratospheric NO2 concentrations following major Australian 2019 through 2020 wildfires. The data confirm that important chemistry did occur on the smoke particle surfaces. The observed behavior in NO2 with increasing particle concentrations is a marker for surface chemistry that contributes to midlatitude ozone depletion. The results indicate that increasing wildfire activity in a warming world may slow the recovery of the ozone layer.

Change the state of 2D nanofilms under the substrate influence

2D films deformations under action of ferroelectric substrate by computer modeling method are performed in article. The film has a square lattice. We use harmonic law for the energy of interatomic interaction. The substrate effect on the film is simulated by the 2D Frenkel-Kontorova potential. The orientation of the film and the substrate do not match. Different cases for periods of film and substrate are considered. The Monte Carlo method is used for computer modeling. If the period of the film and the substrate coincide, the film atoms are placed at the minimum points of the substrate. The film on the substrate has a square crystal lattice. If the period of the substrate is less than the period of the film, the continuous film is converted into a film 2D nanoparticles. The substrate potential amplitude affects the filling of the space between particles. If the period of the substrate is longer than the period of the film, a superstructure in the form of a periodic lattice with an increased particle concentration is formed in the film. The distribution of atoms in the superstructure is determined by the substrate potential amplitude of the substrate potential.

Mechanical, fracture toughness, and fatigue behavior of spinifex littoreus fiber on echinoidea‐spike toughened epoxy composite

AbstractNovel spinifex littores fiber‐reinforced echinoidea spike particle dispersed epoxy resin hybrid composite has been prepared and characterized. The main objective of this research work was to prepare a new system of epoxy hybrid composite comprises of surface‐treated novel spinifex littores fiber (SLF) and echinoidea spike powder (ESP) for sustainable material development. The fiber was treated with alkali and silane for effective adhesion with matrix. The composites were prepared using hand layup method and post cured at 120°C. The mechanical properties were improved with increasing particle content. The wear result shows a lowest coefficient of friction and sp. wear rate of 0.43 and 0.004 mm3/Nm for SP5 composite designation. Fracture toughness of 32.1 ± 0.69 MPa √m and energy release rate of 1.257 ± 0.071 mJ/m2 was observed for composite designation SP4. A highest fatigue life count of 26,832 was observed for composite contains 1 vol% of silane‐treated ESP and 8 h alkali cum silane‐treated SPF. The fractographs reveals toughness improved matrix phase via shear cup formation. These marine based eco‐friendly reinforcement based epoxy composites could be used in various applications in the cadre of automobile, mini‐aircrafts, structural, sports, and domestic.

Simulation study of natural gas hydrate slurry flow characteristics in a high-pressure flow loop

In this paper, Euler models suitable for hydrate slurry flow were established based on the particle dynamics theory. The results showed that the distribution of the velocity, particle concentration and turbulent kinetic energy in the curved pipe was more asymmetrical than that in the straight pipe due to the continuously changing flow field direction. The velocity, turbulent kinetic energy and particle concentration all increased with the increase of inlet velocity. The particle concentration gradient increased with the increase of the inlet particle volume fraction. The increase of particle size led to the increase of velocity heterogeneity and concentration gradient. The pressure drop factor along the pipeline increased with the increase of velocity, particle concentration and particle size, the pressure drop factor across the pipeline of 1.2 m/s was 78.08% higher than 0.5 m/s. It was found that the change of flow direction or the connection of different pipeline structure was the danger point of pipeline aggregation. Finally, based on the grey correlation analysis, the fluctuation of pressure drop factor was most affected by particle size, followed by particle concentration and velocity. The study provided reasonable suggestions and measures for practical pipeline transportation technology to avoid operational risks.

A solution for mixed elastohydrodynamic lubrication modeling considering effects of solid particles and surface roughness

To investigate the effects of solid particles on the point contact mixed lubrication, this paper aims to introduce solid particles into rough interfaces under mixed hydrodynamic lubrication. Statistical three-body micro-contact is utilized in modeling mixed EHL. The model is verified by comparing results without considering particles and roughness with those from classical EHL formula. Factors, such as particle physical parameters, surface roughness and operating condition acting on the system are discussed. The results show that the distribution of hydrodynamic pressure and oil film thickness on the point contact with particles still show typical characteristics of elastohydrodynamic lubrication. The physical parameters of particles and operating condition change the proportion of each part to the load carrying capacity, where an increase in particle size, concentration and surface orientation parameters increases the load ratio of particle and conversely an increase in surface roughness and sliding velocity decreases it. Both an increase in particle size and surface roughness result in an increase in the minimum oil film thickness, with the effect of surface roughness being more significant. In addition, the shear strength, size and concentration of the particles play an important role in the friction characteristics.

Wear particles recognition through teachable machine

PurposeThe purpose of this paper is to adapt teachable machine as a web-based tool for recognition of wear pattern and type of wear by training a convolutional neural network (CNN) model. This helps to monitor the health of the lubricated system as a part of condition monitoring.Design/methodology/approachFerrography technique is used for analysis of wear particles. It helps monitor the condition of lubricated mechanical system. In present paper, CNN model is developed for identifying the type of wear particles coming out of Gearbox system using teachable machine.FindingsFrom the experimentation, it has been observed that the wear severity index has been increased due to increase in wear particle concentration. CNN model has achieved an accuracy of 95.4% to recognize five categories of wear particles.Originality/valueTeachable machine is generally used for the prediction of images, gestures and sound features. An attempt is made to apply this model for micro and nano wear particles to classify them based on their characteristics.

Effects of Transportation of IV Bags Containing Protein Formulations Via Hospital Pneumatic Tube System: Particle Characterization by Multiple Methods

In hospitals, often drug products in intravenous (IV) bags are transported via pneumatic tube systems (PTS). The goal of this study was to evaluate the effects of such transportation of protein products on particle formation in polyvinyl chloride (PVC) and polyolefin (PO) IV bags, containing either IV saline or dextrose. We studied intravenous immunoglobulin (IVIG) and a monoclonal antibody (mAb). Particles were quantified with flow imaging, light obscuration and nanoparticle tracking analysis. PTS transportation of IVIG caused large increases in protein particle concentrations, with much greater increases observed in saline than in dextrose. The increases were greater in IV solutions in PO than those in PVC bags. With the mAb, PTS transportation in saline caused increases in protein particle levels in PO bags, but not in PVC bags. Transportation in dextrose did not result in significant increases in mAb particle concentrations in IV bags made of either material. Overall, the results document that the PTS transportation can result in large increases in protein particles and that magnitude of these increases depends the protein itself, the bag material and the IV solution. The main conclusion is that protein products in IV solutions should not be transported in hospital PTS.

Crude oil-water interface partitioning of polyvinylpyrrolidone-coated silica nanoparticles in low-salinity brine

Nanoparticles are of interest in recent oil production process due to their potential to wettability alteration, but not interfacially active at the crude oil-water interface. Stability loss in brine environment, where nanoparticles tend to aggregate, is another issue for field implementation. Hence, recent challenge is to functionalize nanoparticles that are interfacially active and still stabilized in brine. The current study fabricated and characterized the polyvinylpyrrolidone-coated silica composite nanoparticles for their interfacial activity at the crude oil-water interface. Reduction in oil-water interfacial tension was observed and more dramatic with increasing particle concentration, confirming particle adsorption performance. In low-salinity brine (2000 ppm NaCl), the composite particles remained stabilized with weakened electrostatic force between particle and crude oil surfaces, while their size was smaller due to polymer shell dehydration. These led to faster diffusion rate than in Milli-Q water, which affected the rate of change in oil-water/brine interfacial tension, with the early-stage adsorption being a diffusion-controlled in both fluids. At equivalent particle concentration, the oil-water interfacial tensions in brine were lower than those of Milli-Q water (by ∼2 mN/m), with interfacial coverage of the particles at the interface was found to be higher in the brine. Such difference is attributed to a weaker repulsive force between particle and the interface, induced by surface charge screening that is only present in brine. The study has demonstrated the potential use of polymer-coated nanoparticles as suitable additives for use in oil recovery, which can be used concurrently with low-salinity brine as a combined fluid. While both chemicals are known to construct disjoining pressure for wettability alteration, advantage of using interfacially active nanoparticles is additional mechanism to enhance oil recovery, i.e. reducing the oil-water interfacial tension, which unfunctionalized particles could not contribute.

Effect of Particle Concentration and Pipe Materials on the Formation of Biofilms in Drinking Water Distribution Systems

Microorganism rebreeding and biofilm shedding enter the water body in the process of a drinking water distribution system (DWDS), which poses a threat to public health. Particles in water can gather pollutants as well as providing favorable growth conditions for bacteria. To date, there are a few studies which focus on the relationship between particles and biofilm formation. Therefore, the microbial diversity of biofilms in the different pipe materials and the effect on particle concentration on biofilm formation were investigated in this study. Experiments were carried out under a simulative DWDS (including iron (DI) and polyvinyl chloride (PVC) pipe). The results showed that the microbial diversity in biofilms followed this order: DI pipe &gt; PVC pipe &gt; DI pipe (upper). Moreover, the microbial biomass of biofilm and the fluorescence intensity of extracellular polymeric substances (EPS, produced by microorganisms) were the largest in the absence of particles. The amount of biofilm bacterial and the fluorescence intensity of EPS both showed first an increasing and then decreasing trend with particle concentration increasing. When particle concentration was relatively low, the absorption of particles and bacteria played a major role, however, with the increasing particle concentration, more stable particle–particle were formed and thus, EPS was easily extracted, resulting in the increase of fluorescence intensity of EPS.

Modeling of nursing care-associated airborne transmission of SARS-CoV-2 in a real-world hospital setting

Respiratory transmission of SARS-CoV-2 from one older patient to another by airborne mechanisms in hospital and nursing home settings represents an important health challenge during the COVID-19 pandemic. However, the factors that influence the concentration of respiratory droplets and aerosols that potentially contribute to hospital- and nursing care-associated transmission of SARS-CoV-2 are not well understood. To assess the effect of health care professional (HCP) and patient activity on size and concentration of airborne particles, an optical particle counter was placed (for 24 h) in the head position of an empty bed in the hospital room of a patient admitted from the nursing home with confirmed COVID-19. The type and duration of the activity, as well as the number of HCPs providing patient care, were recorded. Concentration changes associated with specific activities were determined, and airway deposition modeling was performed using these data. Thirty-one activities were recorded, and six representative ones were selected for deposition modeling, including patient’s activities (coughing, movements, etc.), diagnostic and therapeutic interventions (e.g., diagnostic tests and drug administration), as well as nursing patient care (e.g., bedding and hygiene). The increase in particle concentration of all sizes was sensitive to the type of activity. Increases in supermicron particle concentration were associated with the number of HCPs (r = 0.66; p < 0.05) and the duration of activity (r = 0.82; p < 0.05), while submicron particles increased with all activities, mainly during the daytime. Based on simulations, the number of particles deposited in unit time was the highest in the acinar region, while deposition density rate (number/cm2/min) was the highest in the upper airways. In conclusion, even short periods of HCP-patient interaction and minimal patient activity in a hospital room or nursing home bedroom may significantly increase the concentration of submicron particles mainly depositing in the acinar regions, while mainly nursing activities increase the concentration of supermicron particles depositing in larger airways of the adjacent bed patient. Our data emphasize the need for effective interventions to limit hospital- and nursing care-associated transmission of SARS-CoV-2 and other respiratory pathogens (including viral pathogens, such as rhinoviruses, respiratory syncytial virus, influenza virus, parainfluenza virus and adenoviruses, and bacterial and fungal pathogens).

Синтез и свойства полиакриламидных феррогелей, наполненных магнитными наночастицами гексаферрита стронция

Ferrogels based on polyacrylamide with embedded magnetic particles of strontium hexaferrite SrFe12O19 with their content up to 17.9 wt. % have been synthesized and studied. The enthalpy of adhesion of polyacrylamide to the surface of particles was determined by the calorimetric method using a thermochemical cycle. Its negative values indicate good adhesion. This leads to a significant decrease in the degree of swelling of ferrogels with increasing particle content. The modulus of elasticity of ferrogels was measured under uniaxial compression with and without an external uniform magnetic field of 27.5 mT. The effect of a uniform magnetic field of 420 mT on the magnetostriction of ferrogels has been studied. It has been shown that ferrogels based on polyacrylamide filled with strontium hexaferrite underwent universal stretching in a magnetic field, leading to an increase in their volume and additional swelling.

Emission spectra of molecular gases CHF-=SUB=-3-=/SUB=-, CCl-=SUB=-2-=/SUB=-F-=SUB=-2-=/SUB=-, SF-=SUB=-6-=/SUB=- in the range 3-20 nm under pulsed laser excitation using various gas jets as targets

The article considers the results of studies of the emission spectra of CHF3, CCl2F2, SF6 upon excitation by pulsed laser radiation. We used Nd : YAG laser, λ = 1064 nm, tau = 5 ns, and Epulse = 0.8 J. The spectral range of 3-20 nm was studied. We used capillary and supersonic conical nozzles with dcrit = 145 μm, 2α = 12o, L = 5 mm, and dcrit = 450 μm, 2α = 11o, L = 5 mm to form an atomic cluster beam. The emission spectra for various gas targets were obtained, the obtained spectra were deciphered, and the ions emitting in this spectral range were determined. We observed that with increasing particle concentration in the zone of laser spark, the radiation intensity increases. In this case, the intensity of ion lines with high degrees of ionization increases faster. Keywords: cluster beams, extreme ultraviolet radiation, emission spectra, laser spark, x-ray spectrometer-monochromator.