Dust Velocity Research Articles

Evaluation of air quality in intensive care units and its relationship with sick building syndrome in nurses

Introduction: Indoor air quality can lead to health problems such as Sick Building Syndrome among nurses who spend many hours in intensive care units.The aim of this study was to determine the relationship between Sick Building Syndrome in nurses and indoor air quality of intensive care units in educational hospitals in Rasht.
 Materials and Methods: This cross-sectional analytical study was performed on 144 nurses in intensive care units who were randomly selected by quota random sampling. Some of the physical and chemical factors affecting indoor air quality including volatile organic compounds (Ethyl benzene, Xylene, Toluene), carbon monoxide, dust, temperature, humidity, brightness, noise,and airflow velocity were measured by calibrated equipment and symptoms of building syndrome were assessed by the MM040EA questionnaire.
 Results: The chemical factors were lower; temperature, humidity and noise were higher and brightness was lower than the recommended minimum. However, no statistically significant relationship was observed between indoor air quality and Sick Building Syndrome.
 Conclusion: Although the measured physical and chemical factors in intensive care units were often at the occupational limits. The studied nurses reported poor physical conditions in their workplaces. Identifying and controlling occupational hazards in intensive care units can improve nursing performance by increasing job satisfaction.

New coal-charging method: analysis of force characteristics and velocity distribution of coal particles with dense phase continuous flow in cylinder

ABSTRACT Low-moisture coal used in coking has the advantages of increasing production capacity and reducing power consumption but produce a lot of dust during coal charging. A new method of coking coal charged into top-charge coke oven was built, in which the cylinder with telescopic and high-temperature resistant was used to realize the coal flow as dense phase continuous. Based on the 400 kg top-charged coke oven, theoretical analysis, calculation, and numerical simulation were used to study the forces and motion of coal particles under the conditions of temperature gradient. The temperature distribution and particle motion characteristics were simulated by FLUENT when the distance between the coal outlet and the bottom of the coking chamber is 0 mm, 0.5 m, 0.7 m, and 0.9 m. The results show that the dust formed by coal particles was mainly affected by thermophoretic force and air resistance. In the non-uniform temperature field, the radiative heat transfer drop reduces the deposition rate of coal particles. The initial thermal migration velocity of particles in the lower part of the coking chamber is 0.4 m/s, and that of particles in the upper is only 0.1 m/s. As the temperature gradient of coking chamber tends to be uniform, the thermal velocity of particles gradually stabilizes. After the time of particles in the furnace exceeds 0.5 ~1s, the thermophoretic velocity of each part tends to be the same. There was no dust escapes from the coal charging hole during the cylinder lifting process, the escape velocity of dust was controlled below 0.4 m/s by new method. Through simulation and experiment, the simulation results were similar to the experimental when the distance between coal outlet and the bottom of coking chamber is 0 m and 0.7 m, and the maximum error is less than 0.1.

Gas temperature meter

Purpose: of the article is to develop a digital portable gas temperature meter in the range of -50…+600°C. To measure the temperature of dusty gas flows in the air pollution sources with the least significant digit of the digital device 1°C. Design/methodology/approach: The microprocessor measuring unit, probe and software is proposed. It leads to build a high-precision temperature meter based on a thin film sensor HM220 type "pt100". Findings: The calculation of the electrical schematic diagram parameters for signal conditioning of the sensor relative to the input range of the analog-to-digital converter. The experimental measuring unit and the probe of the gas temperature meter are assembled. The principle of the gas temperature meter calibration with the help of a precision resistance box MSR-60M is considered. The experimental gas temperature meter has a total standard uncertainty determined by type B for a maximum value of the measurement range of 1.94°C. The error of the sensor "pt100" makes the largest contribution to the total standard uncertainty, so the error increases in proportion to the value of the measured temperature. Research limitations/implications: On the basis of the proposed design of gas temperature meter it is possible to construct devices with various lengths of probes. Practical implications: The proposed meter is designed for environmental laboratories that measure the velocity, flow and sampling of dust and gas emissions from sources of air pollution. Originality/value: The device design differs due to the use of thermostable wire made of constantan as extending conductors of the temperature sensor, which is included in the unbalanced Wheatstone bridge. This solution allows the use of unipolar power supply 3.3 V for both analog and digital part of the meter. Temperature meter based on a thin film resistance thermometer is characterized by relative ease of manufacture, low material consumption, cost and high reliability.

Investigating and Simulating the Electrostatic Field of Four Types of Collectors in Electrostatic Dust Filters

Electrostatic dust purifiers are widely used in many industries such as thermal power plants, cement plants, waste incineration and glass production. Optimization of the electrode and collector is important for higher efficiency (to achieve high efficiency) in electrostatic dust filtration. This study examines the electrostatic properties of four types of collector plates: flat, curved, spike, and spike with groove. The electric field strength, the charge density, the velocity of movement, and the collection efficiency are analysed for each type of collector. The inflow of air is perpendicular to the collector plate instead of parallel in traditional models, which improves the efficiency. The velocity of dust towards the collector plate depends on the electrostatic force and the velocity field around the collector. The Deutsch model is used to determine the performance among receiver plate types. The results show that the spike plate achieves the best collection efficiency because of the optimal static electric field and velocity field around it.

Sensor-Based Machine Learning Approach for Indoor Air Quality Monitoring in an Automobile Manufacturing

The alternative control concept using emission from the machine has the potential to reduce energy consumption in HVAC systems. This paper reports on a study of alternative inputs for a control system of HVAC using machine learning algorithms, based on data that are gathered in a welding area of an automotive factory. A data set of CO2, fine dust, temperatures and air velocity was logged using continuous and gravimetric measurements during two typical production weeks. The HVAC system was reduced gradually each day to trigger fluctuations of emission. The data were used to train and test various machine learning models using different statistical indices, consequently to choose a best fit model. Different models were tested and the Long Short-Term Memory model showed the best result, with 0.821 discrepancy on R2. The gravimetric samples proved that the reduction of air exchange rate does not correlate to escalation of fine dust linearly, which means one cannot rely on just gravimetric samples for HVAC system optimization. Furthermore, by using machine learning algorithms, this study shows that by using commonly available low cost sensors in a production hall, it is possible to correlate fine dust data cost effectively and reduce electricity consumption of the HVAC.

Particle flow velocity detection technology based on electrostatic induction method and urban block distance method

Aiming at the problem of difficulty in detecting the velocity of coal dust particles in pneumatic conveying coal dust pipelines, this study is based on electrostatic induction method and urban block distance algorithm to achieve accurate detection of coal dust velocity in dust conveying pipelines. Firstly, the principle of electrostatic induction is introduced in this paper. The dust particles with static electricity can sense fluctuation signals on the surface of the metal detector electrode. Then two electrostatic sensors are designed and installed on the upstream and downstream of the dust conveying pipeline. The actual flow velocity of coal dust is obtained by using the urban block distance method to analyze the electrostatic induction signals generated with the two sensors. Compared with the current cross-correlation algorithm, the urban block distance method has the advantage of better real-time performance and less computation. Finally, the experimental results show that the detection error of the coal dust velocity detection technology based on the electrostatic method and the urban block distance method is small, and the maximum absolute error does not exceed 0.16m/s compared with the velocity of the airflow. The results are reliable and effective.

Dust observations from Parker Solar Probe: dust ejection from the inner Solar System

Context. The FIELDS instrument onboard Parker Solar Probe (PSP) observes dust impacts on the spacecraft. The derived dust flux rates suggest that the particles originate from the vicinities of the Sun and are ejected by radiation pressure. Radiation pressure typically ejects particles of several 100 nm and smaller, which are also affected by the electromagnetic force. Aims. We aim to understand the influence of the electromagnetic force on the dust trajectories and to predict the dust fluxes along the orbit of PSP, within 1 AU and near Earth. Methods. We study the trajectories of dust particles influenced by gravity, radiation pressure, and the electromagnetic force assuming that pitch-angle scattering can be neglected (scatter-free approximation). We estimate the dust fluxes along the second orbit of PSP and in the vicinity of the Earth based on average dust velocities derived from the trajectory calculations and dust production rates derived from a fragmentation model. Results. The calculated cumulative flux of dust particles larger than 100 nm is of the same order (within a factor of ~2) as implied by PSP observations. In this size interval, the dynamics of most particles is dominated by the radiation pressure force. The Lorentz force becomes more important for smaller particles and fluxes can vary with magnetic field conditions. The calculated flux of the 30 to 75 nm particles at the PSP is negligible for most of the second orbit, except for an isolated peak at the perihelion. The 30–75 nm particles that were created inwards from 0.16 AU from the Sun are in trapped orbits if the radiation pressure force is weaker than gravity, which is the case for dust from asteroids and for cometary dust that was altered in space. Conclusions. The inner Solar System is the most likely source of dust smaller than 100 nm that enters Earth’s atmosphere and our results suggest the flux is time-variable.

Characteristics of Magnetized Dusty Plasma Sheath With Two Ion Species and q-Nonextensive Electrons

The effect of q-nonextensive electrons, nature, and magnitude of dust charge on magnetized dusty plasma sheath with two ion species has been numerically investigated via fluid model. The initial common speed of ion species at the sheath entrance has been extended, which increases from subsonic to supersonic with the decrease in nonextensive parameter q and ion-neutral drag force as well. The presence of super extensive primary electrons ( q <; 1) has significantly affected the sheath parameters characterizing the dusty plasma sheath: dust charging, potential profile, ion and electron densities profile, ion velocity profile, and dust dynamics. It is found that the negatively charged dust grains accelerate in the region of weak electric field, whereas the fluctuation decreases in the region of strong electric field. A significant change has been observed in dust dynamics with the presence of two different natures of dust charges and its magnitudes. The velocity fluctuations of negatively and positively charged grains are in opposite phase. Furthermore, the comparative study of dust velocity in the presence and absence of dust-neutral collisions has been presented.

Cometary Activity Begins at Kuiper Belt Distances: Evidence from C/2017 K2

Abstract We study the development of activity in the incoming long-period comet C/2017 K2 over the heliocentric distance range 9 ≲ r H ≲ 16 au. The comet continues to be characterized by a coma of submillimeter-sized and larger particles ejected at low velocity. In a fixed co-moving volume around the nucleus we find that the scattering cross section of the coma, C, is related to the heliocentric distance by a power law, , with heliocentric index s = 1.14 ± 0.05. This dependence is significantly weaker than the r H −2 variation of the insolation as a result of two effects. These are, first, the heliocentric dependence of the dust velocity and, second, a lag effect due to very slow-moving particles ejected long before the observations were taken. A Monte Carlo model of the photometry shows that dust production beginning at r H ∼ 35 au is needed to match the measured heliocentric index, with only a slight dependence on the particle size distribution. Mass-loss rates in dust at 10 au are of order 103 kg s−1, while loss rates in gas may be much smaller, depending on the unknown dust to gas ratio. Consequently, the ratio of the nongravitational acceleration to the local solar gravity, α′, may, depending on the nucleus size, attain values of ∼10−7 ≲ α′ ≲ 10−5, comparable to values found in short-period comets at much smaller distances. Nongravitational acceleration in C/2017 K2 and similarly distant comets, while presently unmeasured, may limit the accuracy with which we can infer the properties of the Oort cloud from the orbits of long-period comets.

Two-phase flow of dusty fluid with suspended hybrid nanoparticles over a stretching cylinder with modified Fourier heat flux

The current paper explores the influence of hybrid nanoparticles on the dusty liquid flow through a stretching cylinder by employing the modified Fourier heat flux law. Two phase model is implemented in the present research to characterise the fluid flow. Molybdenum disulphide and silver are used as nanoparticles suspended in base fluid water. The equations which represent the described flow are changed into a set of ordinary differential equations by opting appropriate similarity variables. The reduced dimensionless nonlinear ODEs are numerically solved out by using Runge–Kutta–Fehlberg fourth fifth order inclusive of shooting approach. The impact of several dimensionless parameters over velocity and thermal gradients are deliberated by using graphs. Graphical illustrations for skin friction are also executed. Result outcome reveals that, rise in values of mass concentration of particle declines the velocity and thermal gradient of both dust and fluid phases and cumulative in curvature parameter upsurges the velocity and thermal gradient within the boundary. Further, the heightening of thermal relaxation parameter enhances the thermal profile of both fluid and dust phases.

Investigation of particle density on dust cloud dynamics in a minimum ignition energy apparatus using digital in-line holography

Solids industries have inherent dust explosion hazards. Process risk assessment parameters include overpressure, deflagration index, and minimum ignition energy. These parameters are influenced by dust dynamics, such as turbulence and concentration. Cloud dynamics are affected by particle morphology, density, size, and polydispersity, which affect explosion parameters. Influence of properties such as density during explosion parameter measurement is often overlooked. This study examines particle density influence on dust clouds in the Kühner MIKE3. Two clouds of particles with different density, but similar particle size and morphology were examined with high-speed digital in-line holography, providing velocity and concentration measurements prior to ignition. Results show velocity and concentration of denser dust is lower compared to lighter dust after ignition delay. The results highlight the density effect on cloud dynamics and make a case for particle density to be considered in setting ignition delay in order to get consistent cloud dynamics and test results.

Impact of dust events on the optimization of photovoltaic-wind hybrid system in desert

Reliable optimization of renewable energy systems has to be adapted to the installation site and its environmental factors. In dust event sources, the impact of dust on solar irradiance or on system’s production is not usually taken into consideration during optimization of photovoltaic (PV) or PV-wind hybrid systems. The first objective of this paper was to make observatory studies on wind velocity and lifting of Saharan dust that characterize Algerian desert which allowed us to extract a wind threshold for each event in our desert site. The second objective was to quantify this dust suspension and its negative impact, up to 47.46% on global solar irradiance (GSI) and 48.95% on photovoltaic yield effects were observed. The third and main objective of this paper was evaluating changes in optimized system when the dust impact was taken into account. To achieve that we adjusted GSI satellite data on HOMER software to dust presence, and then we run an optimization on HOMER with its GSI database and the new data, this data adjustment leads to a significant expansion of 13.70% on the size of PV generator, also 7.66% and 7.68% increase on the investment expenses and cost of energy respectively. Results obtained on this paper can be used to make PV-hybrid system’s technical and financial optimization in the main Algerian dust source trustworthy.

Effects of Dispersion of the Dust Velocity in the LISM on the Interstellar Dust Distribution inside the Heliosphere

Interstellar dust (ISD) penetrates into the heliosphere due to the relative motion of the Sun and the local interstellar medium (LISM). Inside the heliosphere and at the boundaries, where solar wind interacts with the LISM, distribution of ISD is modified due to the action of the electromagnetic forces, the solar gravitation and the radiation pressure. These forces make the distribution of the ISD particles in the heliosphere inhomogeneous. In previous work we demonstrated the existence of singularities in the ISD density distribution at 0.03 - 10 a.u. north and south with respect to the heliospheric current sheet. In this paper we show that dispersion in the ISD velocity distribution strongly affects the singularities. Even small values of dispersion have the drastic impact on the density distribution and smooth the high density layers discovered previously.

Three-component modelling of C-rich AGB star winds – V. Effects of frequency-dependent radiative transfer including drift★

ABSTRACT Stellar winds of cool carbon stars enrich the interstellar medium with significant amounts of carbon and dust. We present a study of the influence of two-fluid flow on winds where we add descriptions of frequency-dependent radiative transfer (RT). Our radiation hydrodynamic models in addition include stellar pulsations, grain growth and ablation, gas-to-dust drift using one mean grain size, dust extinction based on both the small particle limit (SPL) and Mie scattering, and an accurate numerical scheme. We calculate models at high spatial resolution using 1024 gridpoints and solar metallicities at 319 frequencies, and we discern effects of drift by comparing drift models to non-drift models. Our results show differences of up to 1000 per cent in comparison to extant results. Mass-loss rates and wind velocities of drift models are typically, but not always, lower than in non-drift models. Differences are larger when Mie scattering is used instead of the SPL. Amongst other properties, the mass-loss rates of the gas and dust, dust-to-gas density ratio, and wind velocity show an exponential dependence on the dust-to-gas speed ratio. Yields of dust in the least massive winds increase by a factor 4 when drift is used. We find drift velocities in the range $10\!-\!67\, \mbox{km}\, \mbox{s}^{-1}$, which is drastically higher than in our earlier works that use grey RT. It is necessary to include an estimate of drift velocities to reproduce high yields of dust and low wind velocities.

Multiwavelength modelling of the circumstellar environment of the massive protostar AFGL 2591 VLA 3

ABSTRACT We have studied the dust density, temperature, and velocity distributions of the archetypal massive young stellar object (MYSO) AFGL 2591. Given its high luminosity ($L=2\times 10^5\, \mbox{L$_{\odot}$}$) and distance (d = 3.3 kpc), AFGL 2591 has one of the highest $\sqrt{L}/d$ ratio, giving better resolved dust emission than any other MYSO. As such, this paper provides a template on how to use resolved multiwavelength data and radiative transfer to obtain a well-constrained 2D axisymmetric analytic rotating infall model. We show for the first time that the resolved dust continuum emission from Herschel 70- μm observations is extended along the outflow direction, whose origin is explained in part from warm dust in the outflow cavity walls. However, the model can only explain the kinematic features from CH3CN observations with unrealistically low stellar masses (&amp;lt;15 M⊙), indicating that additional physical processes may be playing a role in slowing down the envelope rotation. As part of our three-step continuum and line fitting, we have identified model parameters that can be further constrained by specific observations. High-resolution mm visibilities were fitted to obtain the disc mass (6 M⊙) and radius (2200 au). A combination of SED and near-infrared observations were used to estimate the luminosity and envelope mass together with the outflow cavity inclination and opening angles.

Laboratory Investigation of Particle‐Scale Factors Affecting the Settling Velocity of Volcaniclastic Dust

AbstractIceland contains some of the largest and most active dust sources in the Arctic, with the frequency of major emission events increasing in the wake of catastrophic volcanic eruptions, such as the 2010 Eyjafjallajökull eruption. Relatively juvenile Icelandic volcaniclastic dust particles are porous and highly angular, and they frequently bear ultrafine nanoscale dustcoats. Their low density is speculated to affect deposition rates in the atmosphere, while substantial amounts of water adsorbed onto their expansive surface area may affect nucleation, aggregation, and settling. Using a 2‐D laser Doppler anemometer, the present paper reports on a set of highly controlled fall column experiments designed to evaluate the dependency of the settling velocity upon particle morphology (e.g., size, shape, density, and surface area) and relative humidity (RH). Measurements for samples obtained from four Icelandic field sites are compared to those for solid glass spheres of similar diameter. The results confirm that the amount of adsorbed water increases with RH and the particle specific surface area. Higher dust concentrations are found to favor particle interaction and the formation of aggregates, especially at higher RH. Under dry conditions (20 % &lt; RH &lt; 30 % ), the horizontal drift velocity measured for the angular, porous Icelandic particles exceeds that observed for solid glass spheres, although these measurements are an order of magnitude smaller than the vertical velocity. As compared to particle diameter, shape does not appear to influence either the settling rate or drag coefficient at Reynolds numbers ≤10−2, owing to the dominance of viscous effects over form drag.

Experimental Determination of the Terminal Velocity and the Drag Coefficient of Peat Dust Particles

The results of experimental studies of the terminal velocity of peat dust in an air flow with different size distributions of dust particles are presented, and the particle sizes and shapes were examined by microscopic methods. The aerodynamic drag of peat particles of various sizes in an air flow was studied, and a criterion relationship between the drag coefficient CD and the Reynolds number (Re) was determined. The experimental results on the terminal velocity of peat dust were compared with data calculated using well-known methods, and recommendations for their application in the design of pneumatic fuel supply systems were given.

The Axisymmetric Streaming Instability in Protoplanetary Disks

Abstract We reexamine the streaming instability in protoplanetary disks under the axisymmetric geometry. We identify the roles of all the relevant physical processes and clarify the clustering mechanism of dust, offering a new physical interpretation. Through back-reaction, the dust density fluctuations in combination with the mean relative drift velocity provide a source for the gas velocity, which in turn drives the velocity and divergence of the dust flow. In the limit where the dust-to-gas ratio , the action of the Coriolis force on the radial gradient of the azimuthal dust velocity generates the divergence of the dust. In the opposite limit , the vertical gradient of the vertical dust velocity makes the main contribution to the dust divergence. The different dust clustering mechanisms at and are referred to as Mode I and Mode II, respectively. In both cases, the dust divergence further enhances the dust density fluctuations, resulting in a positive feedback loop. In Mode I (or Mode II), the growth rate is contributed by the mean azimuthal (or radial) drag force in the gas equation of motion, while the mean radial (or azimuthal) drag tends to reduce it. The instability makes a transition from Mode I to Mode II when the coupling between the perturbed gas and dust velocities is stronger than the Coriolis force in the gas equations, which occurs at and for Stokes numbers St &lt; 1 and St &gt; 1, respectively.

Theoretical Analysis of Peristaltic Viscous Fluid with Inhomogeneous Dust Particles

Variation in the density of the solid particles suspended in the fluid must have an impact on its flow and behavior. This study deals with the inhomogeneous behavior of the solid grains suspended in the fluid. The number density of the dust grains is taken as a variable. The coupled equations for solid granules and the fluid under long wavelength have been modeled. Streamline transformations have been invoked and results are discussed through graphs. Results show decay in the velocity of dust and fluid is observed as the slip parameter enhances. The trapped bolus enlarges in the lower part of the passage, with the increase in number density of dust particles.

Simulating diverse instabilities of dust in magnetized gas

ABSTRACT Recently, Squire &amp; Hopkins showed that charged dust grains moving through magnetized gas under the influence of a uniform external force (such as radiation pressure or gravity) are subject to a spectrum of instabilities. Qualitatively distinct instability families are associated with different Alfvén or magnetosonic waves and drift or gyro motion. We present a suite of simulations exploring these instabilities, for grains in a homogeneous medium subject to an external acceleration. We vary parameters such as the ratio of Lorentz-to-drag forces on dust, plasma β, size scale, and acceleration. All regimes studied drive turbulent motions and dust-to-gas fluctuations in the saturated state, rapidly amplify magnetic fields into equipartition with velocity fluctuations, and produce instabilities that persist indefinitely (despite random grain motions). Different parameters produce diverse morphologies and qualitatively different features in dust, but the saturated gas state can be broadly characterized as anisotropic magnetosonic or Alfvénic turbulence. Quasi-linear theory can qualitatively predict the gas turbulent properties. Turbulence grows from small to large scales, and larger scale modes usually drive more vigorous gas turbulence, but dust velocity and density fluctuations are more complicated. In many regimes, dust forms structures (clumps, filaments, sheets) that reach extreme overdensities (up to ≫109 times mean), and exhibit substantial substructure even in nearly incompressible gas. These can be even more prominent at lower dust-to-gas ratios. In other regimes, dust self-excites scattering via magnetic fluctuations that isotropize and amplify dust velocities, producing fast, diffusive dust motions.