Dust Size Research Articles

Dynamics of dusty vortices – II. Stability of 2D dust-laden vortices

ABSTRACT Vortices have long been speculated to play a role in planet formation, via the collection of dust in the pressure maxima that arise at the cores of vortices in protoplanetary discs (PPDs). The question remains, however: as dust collects in the core of a vortex, when does that vortex remain stable and able to collect further dust, and when and why does it break up? We study this question by running high-resolution 2D simulations of dust-laden vortices. By using the terminal velocity approximation in a local shearing box, it was possible to efficiently run simulations of back-reacting dust in a gas at high resolution. Our results show how the stability of 2D dust-laden vortices in PPDs depends on their size relative to the disc scale height, as well as the dust coupling. We find small vortices with semiminor axis much smaller than the scale height to be stable for the duration of the simulations (t > 2000 orbits). Larger vortices, with semiminor axis smaller than but of the order of scale height, exhibit a drag instability after undergoing a long period of contraction where the core becomes progressively more dust rich. The lifetime of these vortices depends on the dust size, with larger dust grains causing the instability to occur sooner. For the size ranges tested in this paper, micrometre- to millimetre-sized grains, vortices survived for several hundreds of orbits. The result implies that the stability of vortices formed by vertical shear instability and zombie vortex instability, or the breakup of larger vortices through hydrodynamic instabilities, is affected by the presence of dust in the disc. The lifetimes observed in this paper, while shortened by the presence of dust for larger vortices, were still long enough to lead to considerable dust enrichment in the vortex cores.

Abrasive wear of PEEK and ATSP-based polymer composite coatings under lunar regolith conditions

Abrasive wear of polyether ether ketone (PEEK) and aromatic thermosetting co-polyester (ATSP) based polymer composite coatings were examined with lunar regolith simulant environment by conducting pin-on-disk experiments under dry sliding conditions, contact pressure of 17.5 MPa, and sliding speed of 0.25 m/s. Three different tribo-interfaces, namely metal-on-metal, metal-on-polymer, and polymer-on-polymer were designed to evaluate the efficacy of each polymer coating on the friction and wear improvement, as well as the extent of sand-dust mitigation at the interface. The polymer-on-polymer system resulted in significant reduction in friction up to 70%. The wear mechanism was a mixed mode of two-body and three-body abrasion for metal-on-metal and metal-on-polymer tribopairs, while the polymer-on-polymer tribopair significantly mitigated the sand and dust accumulation at the interface with three-body abrasion as the dominant wear. Both polymer composites showed similar frictional behavior, while ATSP composite showed superior abrasive wear resistance, particularly under small size dust (<38 μm size) environment.

Relationship Between Exposure Levels of Dust Polymethyl Methacrylate And Characteristics of Workers With Subjective Respiratory Complaints in Dental Engineering Laboratory, Dki Jakarta Region in 2021

The manufacture of dentures, especially from polymethyl methacrylate affects the health of workers, especially those related to breathing. The manufacture produces dust of various sizes. The effects of exposure to dust cause discomfort at work and have a negative impact on health. This research objective was to determine the relationship between exposure to polymethyl methacrylate and subjective respiratory complaints. The method used was analytical quantitative research with a cross-sectional with a sample of 5 objects and a sample of 30 workers.dust content polymethyl methacrylate with a Portable High Volume Air Sampler and measurement of subjective respiratory Complaints with a questionnaire. There is a relationship between exposure to dust levels of polymethyl methacrylate on subjective respiratory complaints with p value = 0.006. The dust content of polymethyl methacrylate exceeds the threshold value at 2 sites (40% of the samples). There is a relationship between exposure to dust levels of polymethyl methacrylate on subjective respiratory complaints, p value 0.006 (p &lt;0.05).

Potential Heavy Metals Pollution Contribution from Wash-Off of Urban Road-Dust.

Based on the different particle sizes of street dust, the potential pollution load of heavy metals from dry and wet atmospheric deposition to surface runoff in different functional areas of Zhengzhou city was estimated by using the rain-scour heavy metal index model. Compared to the EA, IA, and CA areas, RA and PA have a higher potential contribution to heavy metal runoff pollution from Road deposited sediments (RDS) than the other watersheds. Zhengzhou utilized the RDS index model to calculate pollution loads in various areas around Zhengzhou (EA, IA, CA, PA, and RA). In the different land-use areas, the RDS indices for pollutant load (RDSindex,load) and pollutant strength (RDSindex,strength) varied greatly, and the RDS index strength values increased. RDSindex,load fell in the following order: IA > RA > PA > EA. Because the RDS index incorporates RDS characteristics such as the amount of RDS, grain sizes present, RDS mobility, and associated metals, the RDSindex,load and RDSindex,strength results did not merely match variability in the amounts of RDS found or metal concentrations in the RDS in various land-use areas. Metal’s presence in the dust is a direct health risk for humans and warrants immediate and effective pollution control and prevention measures in the city.

Impact of Dust Size Distribution Including Large Dust Grains on Magnetic Resistivity: An Analytical Approach

This paper investigates the impact of dust size distribution on magnetic resistivity. In particular, we focus on its impact when the maximum dust size significantly increases from a submicron level. The first half of the paper describes our calculation method for magnetic resistivity based on the model of Draine & Sutin and shows that the method reproduces the results of more realistic chemical reaction network calculations reasonably well. Then, we describe the results of the resistivity calculations for dust distributions with large maximum dust grains. Our results show that resistivity tends to decrease with dust growth, which is particularly true when the dust size power exponent q is q = 2.5. On the other hand, the decrease is less pronounced when the dust size power exponent q is q = 3.5, i.e., when the small dust is also responsible for the dust cross section. Our results suggest that detailed dust coagulation and fragmentation processes play a vital role in the magnetic resistivities in protostar formation.

Grain Size and Sedimentary Sorting Characteristics of Atmospheric Dust in the Cele Oasis, Southern Margin of Taklimakan Desert

Grain size is a proxy indicator of airflow intensity and also provides a scientific basis for the prevention of dust hazards. However, the variations in grain size characteristics that occur during transport and deposition processes are seldom discussed. Here, atmospheric dust samples were collected before and after deposition in a sand–dust storm for grain size analysis. The results showed that the grain size distributions of the atmospheric dust were unimodal during transportation but always became bimodal after deposition. This indicates that the bimodal grain size distribution of the aeolian deposits was caused by sedimentary sorting. The coarse-grained component, which was between 20 and 200 μm, was mainly deposited during the sand–dust storm. Grain size may indicate the strength of the airflow field. The fine-grained component, which ranged in size from 0.4 to 20 μm, was mainly deposited after the sand–dust storm. This component can remain suspended in the atmosphere for a long period of time. Oasis shelterbelts can be used to reduce the fine-grained component of the dust aerosol through the interception of particles by foliage. The grain size variation found in this study from before to after sand–dust storm deposition deepens our understanding of the sediment sorting process.

Global Dust Cycle and Direct Radiative Effect in E3SM Version 1: Impact of Increasing Model Resolution

AbstractQuantification of dust aerosols in Earth System Models (ESMs) has important implications for water cycle and biogeochemistry studies. This study examines the global life cycle and direct radiative effects (DREs) of dust in the U.S. Department of Energy's Energy Exascale Earth System Model version 1 (E3SMv1), and the impact of increasing model resolution both horizontally and vertically. The default 1° E3SMv1 captures the spatial and temporal variability in the observed dust aerosol optical depth (DAOD) reasonably well, but overpredicts dust absorption in the shortwave (SW). Simulations underestimate the dust vertical and long‐range transport, compared with the satellite dust extinction profiles. After updating dust refractive indices and correcting for a bias in partitioning size‐segregated emissions, both SW cooling and longwave (LW) warming of dust simulated by E3SMv1 are increased and agree better with other recent studies. The estimated net dust DRE of −0.42 Wm−2 represents a stronger cooling effect than the observationally based estimate −0.2 Wm−2 (−0.48 to +0.2), due to a smaller LW warming. Constrained by a global mean DAOD, model sensitivity studies of increasing horizontal and vertical resolution show strong influences on the simulated global dust burden and lifetime primarily through the change of dust dry deposition rate; there are also remarkable differences in simulated spatial distributions of DAOD, DRE, and deposition fluxes. Thus, constraining the global DAOD is insufficient for accurate representation of dust climate effects, especially in transitioning to higher‐ or variable‐resolution ESMs. Better observational constraints of dust vertical profiles, dry deposition, size, and LW properties are needed.

3D CFD modelling of dust deposition characteristics and influences on building-mounted photovoltaic system

Airborne dust deposition on the solar photovoltaic panels can significantly decrease the photovoltaic efficiency performance. Dust deposition characteristics and influences on building-integrated photovoltaic panels were studied by shear stress transfer k-ω turbulence model with inlet profiles and discrete particle model. The influences of dust size, wind velocity, and building roof inclination on the dust deposition behaviors were studied carefully. The air flow fields, the dust particle trajectories, the deposition rate on solar photovoltaic panels and the photovoltaic efficiency decrease by dust deposition were obtained and analyzed in the study. The three-dimensional simulation has great difference on the wind flow structures compared with two-dimensional simulation. The size of the separation vortex in the three-dimensional simulation is significantly smaller than that in two-dimensional simulation. The secondary flow structures become more significant in the rear of the building. The dust deposition rate is firstly increased and then decreased with the increasing of dust diameter. The maximum deposition rate is 2.54% for 150 μm particles. The minimum deposition rate is just 0.03% for 500 μm particles. The maximum deposition rate is 1.39%, 2.54% or 3.74% for the roof inclination angle of 16.7°, 22.6°or 36.9°, respectively. When particle size is 150 μm, the dust motions are determined by the air flow fields, mass inertia and gravitational settling. The photovoltaic efficiency reduction is significantly higher with increasing of dust size. The present model can conveniently estimate the photovoltaic efficiency decrease by dust deposition in realistic engineering application.

Spinning nano-carbon grains: Viable origin for anomalous microwave emission

Context. Excess microwave emission, commonly known as anomalous microwave emission (AME), is now routinely detected in the Milky Way. Although its link with the rotation of interstellar (carbonaceous) nano-grains seems to be relatively well established at cloud scales, large-scale observations show a lack of correlation between the different tracers of nano-carbons and AME, which has led the community to question the viability of this link. Aims. Using ancillary data and spinning dust models for nano-carbons and nano-silicates, we explore the extent to which the AME that come out of the Galactic Plane might originate with one or another carrier. Methods. In contrast to previous large-scale studies, our method is not built on comparing the correlations of the different dust tracers with each other, but rather on comparing the poor correlations predicted by the models with observed correlations. This is based on estimates that are as realistic as possible of the gas ionisation state and grain charge as a function of the local radiation field and gas density. Results. First, nano-carbon dust can explain all the observations for medium properties, in agreement with the latest findings about the separation of cold and warm neutral medium in the diffuse interstellar medium. The dispersion in the observations can be accounted for with little variations in the dust size distribution, abundance, or electric dipole moment. Second, regardless of the properties and abundance of the nano-silicate dust we considered, spinning nano-silicates are excluded as the sole source of the AME. Third, the best agreement with the observations is obtained when the emission of spinning nano-carbons alone is taken into account. However, a marginal participation of nano-silicates in AME production cannot be excluded as long as their abundance does not exceed YSi ∼ 1%.

Silicose

Introduction/framework/objectives Pneumoconiosis are the most frequent occupational diseases. Silicosis is caused by inhaling breathable crystalline Silica. It is a diffuse interstitial fibronodular lung disease. Initially it is asymptomatic, however, it is usually progressive and without cure. The diagnosis is partially based on a history of professional exposure. It is more prevalent in countries with considerable unemployment and/or little or no Health and Safety Surveillance at Work. Methodology This is a Bibliographic Review, initiated through a search carried out in January 2022, in the databases “CINALH plus with full text, Medline with full text, Database of Abstracts of Reviews of Effects, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Cochrane Methodology Register, Nursing and Allied Health Collection: comprehensive, MedicLatina and RCAAP”. Contents Silica or silicon dioxide (SiO2) is made up of oxygen and silicon. In nature it exists in amorphous and crystalline forms. The International Agency for Research on Cancer (IARC) considered inhaled crystalline Silica as a human carcinogen (group 1), probably due to cellular damage, inflammation, oxidative stress and inhibition of clearance. Amorphous silica is not considered carcinogenic to humans (group 3). Silicosis exists in all countries, but is more prevalent in the ones less developed, even realizing that the real incidence should be higher than the official one, due to the situation being underreported. In more developed countries, the incidence/prevalence has decreased, due to the improvement of working conditions. Exposure is relevant via inhalation; cutaneous and digestive tracts generally do not have important consequences in the work context. The health risk varies with concentration, particle size– diameter, surface and shape (more dangerous if smaller), exposure time, type of silica (crystalline, tridymite and cristobalite are the most harmful, although more rare), density, water and lipid solubility, chemical reactivity, hygroscopic and electrostatic character, temperature, air speed and employee physical activity. Also important are gender, body area, age, general health status, previous pathologies and smoking- that is, individual susceptibility. The particles can be inhaled, thoracic or respirable (the latter are able to settle in the lungs). The shape, size and density of dust will affect the behavior and penetration into the respiratory system. The respirable fraction consists of particles smaller than 10 micrometers, that is, they can reach the area where gas exchange takes place; larger than that, they are usually deposited in the nasal and thoracic region. Silica nanoparticles smaller than 100 nanometers can reach the bloodstream. After inhalation, Silica particles are mainly deposited in the bronchioles and alveoli; if mucociliary clearance is not sufficient, inflammation (alveolitis) develops, which can lead to fibrosis and cancer. Macrophage activation generates free radicals/reactive oxygen species, which are not always attenuated by anti-oxidant defenses. Continued exposure enhances the release of cytokines which, in turn, activate more macrophages, neutrophils and lymphocytes; the increased production of collagen will then lead to said fibrosis, decreasing lung profitability and efficiency; that is, decreasing gas exchange; being that it can also reach the pleura. Discussion and Conclusions Despite the advances provided by an increasingly effective Health and Safety system, Silicosis is still a problem in some contexts, so it is necessary that the professionals working in these teams have reasonable knowledge regarding the sectors/tasks where it can occur, auxiliary diagnostic tests and other surveillance parameters, collective and individual protection measures, as well as possible implications for the classification of aptitude to work. It would be relevant to better understand the national scenario, through the dissemination of investigations carried out in this context. KEYWORDS: silica, silicosis, safety at work, occupational health and occupational medicine.

Flame inhibition of coal dust with different particle sizes by Al(H2PO2)3 and Al2O3

To effectively mitigate coal dust/syngas deflagration accidents caused by leakage in a coal gasification scenario, inhibition experiments of flame propagation were conducted in a vertical combustion tube equipped with a high speed camera. And the inhibition performance of Al2O3 and Al(H2PO2)3 on deflagration of coal dust with different particle sizes was further investigated. The results showed that as the particle size of coal dust decreased, the flame intensity was enhanced first and then weakened. The flame propagation velocity and average degree of pulsation were the largest for 300 mesh coal dust, which were 23.90 and 7.32 m/s, respectively. After adding 80% Al(H2PO2)3 and Al2O3 to 200 mesh coal dust, the flame peak velocity decreased by 50% and 25%. And the flame was quenched and cannot propagate continuously under the inhibition of Al(H2PO2)3. The product analysis indicated that Al(H2PO2)3 generated PH3 and PO2 to dilute combustible substances in the reaction center and released heat-resistant phosphates to form an inorganic coating layer. Furthermore, the excellent inhibition performance of Al(H2PO2)3 was attributed to the scavenging of highly reactive radicals needed for combustion by P-containing radicals.

Influence of inclination angle on dust migration and settlement characteristics of excavation roadway.

The migration law of dust in the roadway is the basis of dust control, but most of the relevant studies are based on the horizontal roadway, ignoring the roadway inclination. Therefore, numerical simulation and similar experiments are used to systematically study the settlement and diffusion law of dust in roadways with different inclination angles. The results show that the roadway inclination has little effect on the structure of the convection field, but the roadway inclination will change the law of dust transport in the roadway. In the elevation roadway, with the increase of elevation, the settling particle size and distance of dust will increase, which is conducive to dust discharge, but it will also cause secondary dust in the roadway. In the depression angle roadway, with the increase of depression angle, the particle size and distance of dust settlement decrease, which is conducive to dust settlement, but will cause dust accumulation in front of the roadway. Based on this, it is proposed to reduce the wind speed in elevation roadway and increase the wind speed in depression roadway, which provides a basis for improving the dust transport theory and prevention and control work in heading roadway.

Nonlinear self-adjointness, conserved quantities and Lie symmetry of dust size distribution on a shock wave in quantum dusty plasma

The current exploration explains new traveling wave profiles by the Lie symmetry approach Here, we derive the (3+1)-dimensional Zakharov–Kuznetsov burgers equation for the shock wave phenomena in plasma with dust-charged particles having quantum effects. The structures of this model are made by Abelian algebra. The considered equation is reduced to an ordinary differential equation by the use of this Abelian algebra. The complete derivation of the classical symmetries of the considered model and reduction corresponding to the first four symmetries has been added. The new auxiliary equation method is implemented for the formation of the new traveling wave structures. The graphical explanation of some obtained results are elaborated in detail. The nonlinear self-adjointness of the considered model is also part of this work. By this concept, we have evaluated the conservation laws of the model. This work is new and does not exist in literature.

Opposite Effects of Mineral Dust Nonsphericity and Size on Dust‐Induced Snow Albedo Reduction

AbstractWe quantified the combined effects of mineral dust nonsphericity and size on snow albedo reduction using the MOPSMAP (Modeled optical properties of ensembles of aerosol particles) package and SAMDS (Spectral Albedo Model for Dirty Snow) with the consideration of dust from Sahara, Greenland, San Juan Mountains, and Tibetan Plateau. Results indicate that the dust‐induced albedo reduction decreases by up to 30% as the effective radii of dust particles increase in 1–5 μm. Nonspherical dust enhances snow albedo reduction relative to spherical dust by up to 20%. Stronger enhancements are obtained for higher dust concentration and larger dust size. Furthermore, the dust nonsphericity‐induced enhancement of snow albedo reduction is more pronounced for more‐absorptive dust. Finally, we develop a new parameterization for quantifying the dependence of snow albedo reduction on dust nonsphericity and size, and provide a convenient way for assessing the climate impacts of dust in snow.

Study on the Ablation of the Glacier Covered by Mineral Dust in Alpine Regions

Glaciers, known as solid reservoirs, are important water supply sources in northwest China. In this paper, mineral dust collected from a Chinese alpine mining area (Beizhan iron mine) and an ice cube (with a 225 cm2 section and a volume of 1000 mL) were employed via a delicate physical experiment to study the ablation of glaciers covered by mineral dust in alpine regions. After that, the ablation mechanism was revealed using the energy conservation theory. The main findings are as follows: (1) When the solar radiation intensity is 993 W/m2, the glacier ablation rate increases by 13.9% (from 282 to 321.2 mL/h) as the mineral dust coverage rate increases from 0% to 42.7%. (2) When the mineral dust coverage rate remains at 30%, the glacier ablation rate increases by 11.6% (from 291.8 to 325.78 mL/h) as the solar radiation intensity increases from 1007 to 1153 W/m2. (3) When the solar radiation intensity and mineral dust coverage rate remain unchanged, the ablation rate of the glacier covered by the mineral dust inversely increases with the dust particle size. The ablation rates of the particle size gradings C, B, and A (the dust particle sizes of gradings A, B, and C in 0.0375–0.075 mm, 0.075–0.125 mm, and 0.125–0.25 mm accounted for 5%:50%:45%, 30%:40%:30%, and 70%:30%:0%, respectively) were 293.4, 301.2, and 305.6 mL /h, respectively, and the corresponding ablation rates increased by 2.7% and 1.5%. (4) The smaller the average particle size of the mineral dust, the greater the contribution to the ablation rate; a 1 °C temperature increase to the glacier ablation rate is equivalent to 29.1%, 33.6%, and 40.6% increases in dust coverage for particle size classes C, B, and A. (5) The mineral dust covering the glacier surface could not only reduce the reflectivity of the glacier surface to solar radiation but could also continuously transfer the absorbed radiant energy and its own chemical energy to the glacier body, accelerating the glacier’s meltwater speed. The findings of this paper can provide the necessary theoretical basis for mineral dust control and glacier water conservation in alpine mining areas.

On the flammable behavior of non-traditional dusts: Dimensionless numbers evaluation for nylon 6,6 short fibers

Safety parameters assessment is not sufficient to fully understand the flammable and explosive behaviour of a combustible dust and correctly manage potential risk. A correct evaluation requires the identification of flame propagation path as well as the limiting step controlling fire propagation, through evaluation of dimensionless numbers (Biot, Damköhler, Thiele, Sherwood, Thiele modulus numbers). Herein, these aspects were investigated for non-traditional dusts, made of nylon 6,6 short fibers. To this purpose, flammability parameters including minimum ignition energy (MIE), the maximum pressure of explosion and the deflagration index were assessed and combined with results of extensive physical-chemical characterization, by means of several techniques (TGA/DSC, FTIR, XRD). In particular, thermogravimetric analysis highlighted the presence of homogeneous and heterogeneous phase phenomena activated at different temperatures and heating rates. The homogeneous phase processes are controlled by the pyrolysis process strictly dependent on the dust size and its decomposition kinetics. The most flammable sample is characterized by smaller dimensions and a fast decomposition kinetics at low temperature. Heterogeneous flame propagation is controlled by the intrinsic heterogeneous reaction. The most reactive sample is characterized by the highest value of specific surface area and by intense exothermic phenomena at low temperature, as evidenced by the analysis of the solid residue. As a main conclusion, the processes involving nylon fibres that may modify the key parameters influencing the flammable/explosive behaviour are also discussed.

A numerical study on the effect of dust particles on tritium deposition on plasma-facing materials

Tritium deposition is a key issue for fusion devices. The existence of dust leads to increase of tritium deposition rates due to the large specific surface area (SSA) of dust grains. Experiments in JET-ILW have indicated that the deposition and retention behavior of hydrogen on dust grains is complicated. In present work, the deposition behavior of tritium on the dust is studied by a hybrid particle simulation method. Our results indicate that the large SSA of dust is not the only mechanism that increases tritium deposition. Dust size and the electrostatic sheath induced by the dust are also important factors that influence the tritium deposition. The retention rate enhanced by dust grains is also predicted based on our study.

Dust Extinction Law in Nearby Star-resolved Galaxies. II. M33 Traced by Supergiants

The dust extinction curves toward individual sight lines in M33 are derived for the first time with a sample of reddened O-type and B-type supergiants obtained from the Local Group Galaxies Survey (LGGS). The observed photometric data are obtained from the LGGS, PS1 Survey, UKIRT, PHATTER Survey, Galaxy Evolution Explorer, Swift/UVOT, and XMM-SUSS. We combine the intrinsic spectral energy distributions (SEDs) obtained from the ATLAS9 and Tlusty stellar model atmosphere extinguished by the model extinction curves from the silicate-graphite dust model to construct model SEDs. The extinction traces are distributed along the arms in M33, and the derived extinction curves cover a wide range of shapes (R V ≈ 2–6), indicating the complexity of the interstellar environment and the inhomogeneous distribution of interstellar dust in M33. The average extinction curve with R V ≈ 3.39 and dust size distribution is similar to that of the Milky Way but with a weaker 2175 Å bump and a slightly steeper rise in the far-UV band. The extinction in the V band of M33 is up to 2 mag, with a median value of A V ≈ 0.43 mag. The multiband extinction values from the UV to IR bands are also predicted for M33, which will provide extinction corrections for future works. The method adopted in this work is also applied to other star-resolved galaxies (NGC 6822 and WLM), but only a few extinction curves can be derived because of the limited observations.

Modelling the secular evolution of protoplanetary disc dust sizes – a comparison between the viscous and magnetic wind case

ABSTRACT For many years, protoplanetary discs have been thought to evolve viscously: angular momentum redistribution leads to accretion and outward disc spreading. Recently, the hypothesis that accretion is due, instead, to angular momentum removal by magnetic winds gained new popularity: no disc spreading is expected in this case. In this paper, we run several 1D gas and dust simulations to make predictions on the time evolution of disc sizes in the dust and to assess whether they can be used to understand how discs evolve. We show that viscous and magnetic wind models have very different dust disc radii. In particular, magnetohydrodynamic wind models are compact and their sizes either remain constant or decrease with time. On the contrary, discs become larger with time in the viscous case (when α ≳ 10−3). Although current observations lack enough sensitivity to discriminate between these two scenarios, higher sensitivity surveys could be fruitful to this goal on a $1\!-\!10\, {\rm Myr}$ age range. When compared with the available ALMA (Atacama Large Millimeter/submillimeter Array) Band 7 data, both viscous and magnetic wind models are compatible with the observationally inferred dust radii in Lupus, Chamaeleon I, and Upper Sco. Furthermore, in the drift-dominated regime, the size–luminosity correlation is reproduced in Lupus, both in Band 7 and 3, while in Upper Sco a different slope than in the data is predicted. Sub-structures (potentially undetected) can explain several outliers with large observed sizes. Higher angular-resolution observations will be helpful to test our predictions in the case of more compact discs, expected in both frameworks, particularly at the age of Upper Sco.

Study on the distribution characteristics of dust with different particle sizes under forced ventilation in a heading face

Coal mines face a significant situation with regard to dust control. Numerical simulation was used in this paper to study the distribution of dust of different particle sizes in a specific case, as well as the influence of changing the supply airflow velocity on the dust distribution. The findings demonstrate that the airflow primarily migrates from the return air side to the air inlet side and the exit, with the intensity of the airflow decreasing as the distance increases. The amount of dust is high in the area with a strong airflow and low in other areas, and dust of different particle sizes is separated gradually. Increasing the supply air velocity has a greater effect on large dust particles than on small dust particles under the conditions and air speed range studied in this paper. Reasonable reduction of the supply air velocity can effectively reduce the amount of suspended dust.