Small Dust Particles Research Articles

Glass Substrate Dust Removal Using 233 fs Laser-Generated Shockwave.

Eliminating dust is gaining importance as a critical requirement in the display panel manufacturing process. The pixel resolution of display panels is increasing rapidly, which means that even small dust particles on the order of a few micrometers can affect them. Conventional surface cleaning methods such as ultrasonic cleaning (USC), CO2 cleaning, and wet cleaning may not be sufficiently efficient, economical, or environment friendly. In this study, a laser shockwave cleaning (LSC) method with a 233 fs pulsed laser was developed, which is different from the laser ablation cleaning method. To minimize thermal damage to the glass substrate, the effect of the number of pulses and the gap distance between the focused laser beam and the glass substrate were studied. The optimum number of pulses and gap distance to prevent damage to the glass substrate was inferred as 500 and 20 μm, respectively. With the optimal pulse number and gap distance, cleaning efficiency was tested at a 95% removal ratio regardless of the density of the particles. The effective cleaning area was measured using the removal ratio map and compared with the theoretical value.

Distribution of charged lunar dust in the south polar region of the moon

Lunar dust is one of the most threatening problems confronting the return of human beings to the moon. In this work we studied the spatial distribution behavior of charged lunar dust in the solar wind plasma environment in the south polar region of the moon and considered the influence of a mini-crater using Spacecraft Plasma Interactions Software. The distribution of dust and plasma at low solar altitude angles of 20° and 0° was studied, and the spatial density of lunar dust was ∼ 1010.4 m−3 and ∼ 1011.5 m−3, respectively. This is because a higher surface potential will result in transportation of small dust particles and photoelectrons can also neutralize positively charged lunar dust. The dust density in the plasma void region created by a mini-crater with a 5 m high wall was studied. We obtained a quasi-neutral electric environment in the plasma void region of the mini-crater, and the dust density was about a magnitude lower than that in other regions. The dust risk to a spacesuit is much lower on the nightside than on the dayside, but there is severe charged lunar dust transport in the region between light and shade, which is dominated by the difference in surface and plasma potential caused by photoelectrons.

Physical aspects of dust–plasma interactions

AbstractLow‐pressure gas discharge plasmas are known to be strongly affected by the presence of small dust particles. This issue plays a role in the investigations of dust particle‐forming plasmas, where the dust‐induced instabilities may affect the properties of synthesized dust particles. Also, gas discharges with large amounts of microparticles are used in microgravity experiments, where strongly coupled subsystems of charged microparticles represent particle‐resolved models of liquids and solids. In this field, deep understanding of dust–plasma interactions is required to construct the discharge configurations which would be able to model the desired generic condensed matter physics as well as, in the interpretation of experiments, to distinguish the plasma phenomena from the generic condensed matter physics phenomena. In this review, we address only physical aspects of dust–plasma interactions, that is, we always imply constant chemical composition of the plasma as well as constant size of the dust particles. We also restrict the review to two discharge types: dc discharge and capacitively coupled rf discharge. We describe the experimental methods used in the investigations of dust–plasma interactions and show the approaches to numerical modelling of the gas discharge plasmas with large amounts of dust. Starting from the basic physical principles governing the dust–plasma interactions, we discuss the state‐of‐the‐art understanding of such complicated, discharge‐type‐specific phenomena as dust‐induced stratification and transverse instability in a dc discharge or void formation and heartbeat instability in an rf discharge.

Thermal radiation pressure as a possible mechanism for losing small particles on asteroids

Context.Recent observations of dust ejections from active asteroids, including (3200) Phaethon, have drawn considerable interest from planetary astronomers studying the generation and removal of small dust particles on asteroids.Aims.In this work, we aim to investigate the importance of thermal radiation pressure from asteroid regolith (AR) acting on small dust particles over the surface of the AR. In particular, we aim to understand the role of thermal radiation in the near-Sun environment.Methods.We describe the acceleration of particles over the AR within the radiation fields (direct solar, reflected (scattered) solar, and thermal radiation) in addition to the asteroid’s rotation and gravitational field. Mie theory is used because the particles of interest have sizes comparable to thermal wavelengths (~1–100 μm), and thus the geometric approximation is not applicable. A new set of formalisms is developed for the purpose.Results.We find that the acceleration of particles with spherical radius ≲1 μm to ~10 μm is dominated by the thermal radiation from the AR when the asteroid is in the near-Sun environment (heliocentric distancerh≲ 0.8 au). Under thermal radiation dominance, the net acceleration is towards space, that is, outwards from the AR. This outward acceleration is the strongest for particles of ~1 μm in radius, regardless of other parameters. A preliminary trajectory integration using the Phaethon-like model shows that such particles escape from the gravitational field within about 10 min. Our results are consistent with the previous observational studies on Phaethon in that the ejected dust particles have a spherical radius of ~1 μm.

Effect of dust particle size on the climate of Mars

Dust particle size is one important property in evaluating the radiative effect of airborne dust. However, its effect on the climate of Mars is not clearly understood. In the present study, some numerical experiments with the Mars climate model MarsWRF have been performed to investigate this issue. In these simulations, the ratio of two sizes (small and large) of dust particles is changed gradually to investigate the corresponding effects on the distribution of dust mixing ratio, thermal field, and the dynamic field. Based on the results of this study, the following effects on the Martian climate have been identified. (1) The effect of small dust particles is significant in the dust season and mainly in the lower atmosphere. (2) Increasing the ratio of small dust particles may increase the heating rate, temperature, westerly wind, and the meridional wind associated with the Hadley circulation during the dust season, as well as a decrease in the easterly wind over the equatorial region. (3) The effect of increasing the ratio of small dust particles is generally more significant in the second episodic dust period during the dust season. This may be due to the longer time of sedimentation for small dust particles.

Study of shocks in a nonideal dusty gas using Maslov, Guderley, and CCW methods for shock exponents

Abstract In this work, we consider the system of partial differential equations describing one-dimensional (1D) radially symmetric (i.e., cylindrical or spherical) flow of a nonideal gas with small solid dust particles. We analyze the implosion of cylindrical and spherical symmetric strong shock waves in a mixture of a nonideal gas with small solid dust particles. An evolution equation for the strong cylindrical and spherical shock waves is derived by using the Maslov technique based on the kinematics of 1D motion. The approximate value of the similarity exponent describing the behavior of strong shocks is calculated by applying a first-order truncation approximation. The obtained approximate values of similarity exponent are compared with the values of the similarity exponent obtained from Whitham’s rule and Guderley’s method. All the above computations are performed for the different values of mass fraction of dust particles, relative specific heat, and the ratio of the density of dust particle to the density of the mixture and van der Waals excluded volume.

Properties of Bonding Sealants in the Sealing of Cement-Based Materials

This paper describes the issue of sealing cement-based materials. These materials can also include concrete elements or cement fiber boards. For the purposes of this work, a cement fiber material is selected, namely glass. This material has good effects in terms of small dust particles on the surface, which damage the bonding sealant and the substrate. Focus on its suitability for sealing cement-based substrates. The method for determining the properties of the sealant and the properties of the stylistic joint between the sealant and the base material is the tensile test. For the purpose of this test, one representative of neutral silicones, one representative of acetate silicones and one representative for acrylic sealants shall be selected. From the results of the tensile test, it is clear that with a suitable choice of the combination of bonding sealant and primer, it is possible to seal such a problematic substrate with good results.

Impact of dust diffusion on the rim shape of protoplanetary disks

Context. Multiple mechanisms are known to give rise to turbulence in protoplanetary disks, which facilitates the accretion onto the central star. Small dust particles that are well coupled to the gas undergo diffusion due to this turbulent motion. Aims. This paper investigates the influence of turbulence-induced dust diffusion on the equilibrium of protoplanetary disks. Methods. The model accounts for dust sublimation, radiative transfer with the flux-limited diffusion approximation, and dust diffusion. It predicts the density and temperature profiles as well as the dust-to-gas ratio of the disk. Results. It is shown that dust diffusion can have a large impact: Assuming the dust survives for 104 s or longer before it can be evaporated, this leads the dust diffusion to widen the inner disk considerably. This effect is generated through a feedback mechanism as the diffusion length is much shorter than the disk width. With increasing dust diffusion, the inclination of the inner rim toward the stellar radiation becomes steeper until it is almost vertical. The temperature range of evaporation and condensation, which is linked to the dust composition, has no influence on this effect. Conclusions. For realistic parameters, dust diffusion cannot be neglected when determining the equilibrium of the disk. Stronger turbulence inside the disk induces more dust diffusion. Therefore, the dust density grows more gradually over a greater distance and less radiation reaches the disk surface. The new equilibrium shape of the disk is more inclined toward the star. This effect is universal and independent of the specific dust composition.

An Analysis of Decay of Blast Waves in Dusty Gases

In this paper, the effect of the dust particles on the decay of blast waves is studied in a two-phase, unsteady flow of an inviscid gas with small dust particles. Asymptotic analysis is used to der...

A Layered Debris Disk around M Star TWA 7 in Scattered Light

Abstract We have obtained Hubble Space Telescope (HST) coronagraphic observations of the circumstellar disk around M star TWA 7 using the Space Telescope Imaging Spectrograph (STIS) instrument in visible light. Together with archival observations, including HST/NICMOS using the F160W filter and Very Large Telescope/SPHERE at the H-band in polarized light, we investigate the system in scattered light. By studying this nearly face-on system using geometric disk models and Henyey–Greenstein phase functions, we report a new discovery of a tertiary ring and a clump. We identify a layered architecture: three rings, a spiral, and an ≈150 au2 elliptical clump. The most extended ring peaks at 28 au, and the other components are on its outskirts. Our point-source detection-limit calculations demonstrate the necessity of disk modeling in imaging fainter planets. Morphologically, we witness a clockwise spiral motion, and the motion pattern is consistent with both solid body motion and local Keplerian motion; we also observe underdensity regions for the secondary ring that might result from mean-motion resonance or moving shadows: both call for re-observations to determine their nature. Comparing multi-instrument observations, we obtain blue STIS-NICMOS color, a STIS-SPHERE radial distribution peak difference for the tertiary ring, and a high SPHERE-NICMOS polarization fraction; these aspects indicate that TWA 7 could retain small dust particles. By viewing the debris disk around M star TWA 7 at a nearly face-on vantage point, our study allows for the understanding of such disks in scattered light in both system architecture and dust property.

Microstructural analysis of the PV module cementation process at the Solar Platform of the Atacama Desert

The understanding of soiling processes on photovoltaic modules is a necessary step for the development of cost-effective mitigation methods for the solar industry. This paper analyzes the soiling process for photovoltaic modules installed at the Atacama Desert. For this purpose, the dust deposited on photovoltaic modules and glasses (for one year) was characterized and the location's atmospheric parameters were monitored continuously. The dust samples were separated according to difference in solubility, obtaining three samples: soluble (recrystallized), insoluble (filtered), and original. Through x-ray diffraction measurements it was detected that the soluble part corresponds to gypsum and the other dust components are insoluble or low-solubility salts such as albite, anhydrite, calcite, quartz, and orthoclase. Scanning electron microscopy and energy dispersive x-ray spectroscopy of the dust on photovoltaic glasses show the presence of gypsum with a monoclinic prismatic structure covered with smaller dust particles. These prismatic crystals are also observed after recrystallization of the soluble sample suggesting that gypsum, as a soluble hygroscopic material, has a key role in the cementation process. Atmospheric parameters of each season were characterized through wind velocity, temperature, and relative humidity. All these parameters show large daily oscillation, which trigger a cementation process in which gypsum crystallization, after being completely or partially solubilized, causes the encapsulation of insoluble material.

A Critical Review on the Effect of Particulate Matter (PM) in Air on Public Health

According to the World Health Organization (WHO), particulate matter (PM) contamination causesaround 800,000 premature deaths per year, ranking 13th in the world in terms of mortality.However, several findings revealed that the correlation is much stronger and more complicated thanpreviously believed. PM is an element of emissions comprised of very small, acidic, organiccompounds, metals, and particulate soil or dust particles or fluid droplets. The most consistent airquality component linked to human illness is PM, which is categorized by size. PM is likely to developcardiovascular and cerebrovascular disorders due to the mechanisms of inflammation, overt andindirect coagulation activation, and direct translocation to the systemic circulation. The evidence onthe cardiovascular system that shows a PM effect is strong. Coronary incidence and mortality ratesin populations prone to long-term PM toxicity were significantly higher. Short-term acute emissionsincrease coronary incidence rates subtly within days of the pollution peak.

Identification of polluted clouds and composition analysis based on GF-5 DPC data

Large amounts of fine polluted particles due to anthropogenic activities can enter into the lower atmosphere and may pollute the lower water clouds, especially continental cumulus. Continental polluted cumulus (CPCU) plays an important role in the process of atmospheric radiative transfer and the Earth's environmental change. Based on the sensitivity of polarization to small particles, GF-5 DPC data were used to identify polluted clouds. In addition, dynamic transport and composition of polluted clouds were further analyzed. Firstly, a novel method based on two tests was used to identify polluted clouds in China. The source and transport characteristics of the polluted clouds were analyzed by using wind field and backward trajectory pattern. Secondly, based on the monitoring data from the Sun‐sky radiometer Observation NETwork (SONET), the types of atmospheric aerosol composition in China were classified into ten types by considering influences of the climate types, Digital Elevation Model and social economy, etc. Finally, the composition of polluted clouds in different regions was further identified according to regional aerosol composition, and the results were verified by the Optical Properties of Aerosols and Clouds (OPAC) software.The identifying results of polluted clouds showed that there were four polluted clouds over China on May 27, 2018 and high concentration of small dust particles. The changes in the component ratios of different polluted clouds respond well to the results of airflow sources and transport. Compared with the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Vertical Feature Mask (VFM) data, the proposed method is effective and robust. The proposed method of identification and composition analysis based on GF-5 DPC data for polluted clouds can enrich the application of DPC data in the field of atmospheric and environmental detection.

Similar effects as shade tolerance induced by dust accumulation and size penetration of particulates on cotton leaves

BackgroundDust accumulation covers the leaf’s surface and influences foliar physiological activity. Two independent experiments were carried out to instigate the foliar responses to dust accumulation and the penetration limitation of small dust particles (< 1 μm) on the foliar surface, respectively. In experiment I, three dust accumulation intensities were achieved by a dust spraying treatment. Photosynthesis CO2 exchange and fast chlorophyll fluorescence transient were measured, as well as chlorophyll contents and leaf thickness. In experiment II, the penetration limits of small particulates on the leaf surface were examined by feeding nano-fluorescent microspheres.ResultsDust accumulation alleviated the photoinhibition of Photosystem II and decreased photosynthesis, as represented by net photosynthetic rates (PN) and stomatal conductance to water vapor (gs). Photosynthetic response curves between net photosynthetic rate (PN) and photosynthetically active radiation (PAR) showed that heavy dust accumulation (34.98 ± 2.6 mg cm− 2) increased the light compensation point (LCP) and light saturation point (LSP) and decreased photosynthesis rates under saturating light (PNmax). Leaves became thin due to the lack of a palisade layer while chlorophyll content increased under dust accumulation. Confocal laser scanning microscopy (CLSM) images showed that the larger particles (1 μm) distributed in the regions below the stomata and the smaller ones (0.1 μm) were detected in the wider areas below stomata.ConclusionsThese results suggested that dust accumulation induced similar effects as shade tolerance in cotton leaves but did not trigger more photochemical acclimation to low light. Dust particles (< 1 μm) penetrated leaf surface through stomata.

Particle size distribution in a granular bed filter

The effects of the filtering granule particle size and filtration superficial velocity on the dust particle size distribution in different layers of a granular bed system are discussed herein. A multilayer drawer granular bed filtration system was designed for these experiments based on filtering fly ash from a power plant. After a 1-h experiment, 47.8% of dust particles smaller than 2.5μm, 63.7% of dust particles smaller than 10μm, and 39.1% of dust particles larger than 10μm were captured by the granular bed (corresponding to initial volume fractions of 6%, 19.3%, and 80.7%, respectively). Large dust particles were more easily trapped by the granular bed than small dust particles. Increasing the size of the filter granules and increasing the superficial velocity of the inlet flue gas were both effective ways to enhance the dust-holding capacity of the granular media throughout the granular bed.

Properties of Selected Polyurethane Sealants in the Sealing of Cement-based Materials

Since the rise of cement-based building elements, there has been a need to seal these materials. Therefore, this article deals with the sealing of cement-based materials, specifically glass cement. The aim of this work is to find a sealant for sealing this problematic substrate, to verify its suitability and to show that polyurethane sealants are also important in the construction market. The problem of a cement-based substrate lies mainly in the dustiness of its surface, where there are always small dust particles on its surface. The main method for testing these sealants is the tensile test, which checks both the properties of the sealant itself and the contact joint between the sealant and the base material. Tensile test specimens are made of glass-cement plates and three representatives of one-component flexible polyurethane sealants are selected as the sealing material. From the results of the tensile test, it can be concluded that, with the appropriate choice of sealant and primer, problematic cement-based materials with good results can be sealed, provided that the grinding is carried out correctly.

Planetesimal formation around the snow line

Context.The formation of rocky planetesimals is a long-standing problem in planet formation theory. One of the possibilities is that it results from gravitational instability as a result of the pile-up of small silicate dust particles released from sublimating icy pebbles that pass the snow line.Aims.We want to understand and quantify the role of the water snow line for the formation of rock-rich and ice-rich planetesimals. In this paper, we focus on the formation of rock-rich planetesimals. A companion paper examines the combined formation of both rock-rich and ice-rich planetesimals.Methods.We developed a new Monte Carlo code to calculate the radial evolution of silicate particles in a turbulent accretion disk, accounting for the back reaction (i.e., inertia) of the particles on their radial drift velocity and diffusion. Results depend in particular on the particle injection width (determined from the radial sublimation width of icy pebbles), the pebble scale height, and the pebble mass flux through the disk. The scale height evolution of the silicate particles, which is the most important factor for the runaway pile-up, is calculated automatically in this Lagrange method.Results.From the numerical results, we derive semi-analytical relations for the scale height of the silicate dust particles and the particle-to-gas density ratio at the midplane, as functions of a pebble-to-gas mass flux ratio and theαparameters for disk gas accretion and vertical/radial diffusion We find that the runaway pile-up of the silicate particles (formation of rocky planetesimals) occurs if the pebble-to-gas mass flux ratio is ≳ [(αDz/αacc)/3 × 10−2]1/2, whereαDzandαaccare theαparameters for vertical turbulent diffusion and disk gas accretion.

Amalgamation of diverse hydrodynamic effects with novel triple-sided membrane valves for developing a microfluidic device for filterless and continuous water purification.

The requirement for clean water has been increasing for several reasons, for instance, the fast industrialization of developing countries, climate change, environmental pollution, growth of biofuel use and the resulting growth in irrigation. To meet the requirements for contamination-free water, a cost-effective water treatment can substantially improve the developing world’s health, largely for children, and there is predicted to be a huge market for this. Existing water treatment processes consist of various phases that are time-consuming as well as pricey. There is an essential demand for cost-effective point of use methods to purify drinking water to reduce the impact of diseases induced by numerous waterborne pathogens. The development of micro-devices, with different outcomes, can be a helpful solution to various problems. To make this reality, a novel microfluidic device for the purification of water, with multiple hydrodynamic effects, has been shown in this paper. In the proposed novel device, the network of interconnected microfluidic channels was created in such a way that an amalgamation of multiple effects, such as the Fåhræus effect, centrifugal force, the Zweifach–Fung effect and constriction followed by expansion, act together in the microchannel to separate suspended impurities (i.e. bacteria and similar length scale particles present in water in the suspension form) from water. Furthermore, to improve the bacterial separation efficiency of the device, the pure water channel of the microdevice was designed with an encircled triple-sided film valve arrangement at a few points, which aided the modulation of the cross-sectional area of the pure water channel. Consecutively, the reduction of the cross-sectional area of the pure water channel caused a highly effective Zweifach–Fung effect, which aided the better separation of the suspended particles (i.e. bacteria, dust particles etc.). The device was observed to have an average of 99.6% efficiency in the separation of suspended microparticles/microbes with dimensions in the range of 1–10 micrometres. The device performance indicated its potential for the separation of other similar suspended impurities, i.e. small dust particles, bacteria, fungi, viruses and similar particles present in water in the suspension form.

Dynamics of charged dust in the orbit of Venus

We study the dynamics of co-orbital dust in the inner Solar System, that is, the role of the solar radiation pressure, the Poynting-Robertson effect, the solar wind, and the interplanetary magnetic field, on the location, width, and stability of resonant motion of charged and micron-sized dust grains situated in the 1:1 mean motion resonance with Venus. We find deviations and asymmetry between L4 and L5 in the locations of the libration centers and libration width caused by nongravitational effects with analytical and numerical methods. The triangular Lagrangian points become unstable when solar radiation pressure, the Poynting-Robertson effect, and solar wind drag are considered. The Lorentz force could further destabilize the orbits, especially for small dust particles. We also compare the circular and/or elliptic restricted three-body model and a more complete model that includes all planets.

Pozitivna i negativna uloga negativnih jona u svemirskim istraživanjima

Introduction/purpose: At altitudes of 80 to 40 km, while the spacecraft made of duralumin without a thermal-protective coating was descending from the flight orbit at the first and second cosmic velocities, data were obtained on the increase in density, pressure, and temperature behind the shock front, as well as on the backout of the shock wave from the surface of the descending spacecraft. Methods: Calculations were made of the energy fluxes on the surface of the spacecraft for every 10 km, for convective and radiative heat transfer, as well as for the impact of electrons produced due to ionization of negative ions. Results: At the first cosmic velocity, the greatest energy flux is realized under the influence of an electron flux, and at the second cosmic velocity, radiative heat transfer occurs. In the shock-compressed gas at all the considered altitudes, pressure increases instantly to a value of 109 ÷ 1011 Pa, which leads to a sequential explosion with increasing power resulting in shock waves in the surrounding atmosphere and compression waves in the entire aircraft structure. The last most powerful explosion occurs at an altitude of approx. 40 km. Conclusion: The descending aircraft is destroyed into separate small parts to the size of small dust particles.