Numerical modeling of open pit ventilation when varying the location of the dust and gas cloud

Research objective is to estimate the effect of bulk explosion location and the initial height of the dust and gas cloud on open-pit natural ventilation time and the level of air contamination of the upper edge of the open pit down the wind. Methods of research. Computer modeling of aerodynamics and gaseous component transfer in the 2D geometry is carried out with the COMSOL software. To calculate the aerodynamic characteristics, the approximation of the incompressible fluid with the standard k–ε turbulence model was carried out. Gaseous component distribution was modeled using the numerical solution to the convection-diffusion equation of contaminant transfer. Numerical experiments under the fixed initial concentration of the gaseous component and the speed of the incoming wind flow have been carried out for three locations of bulk explosions and six values of the initial height (from 70 to 420 m with a step of 70 m) of the dust and gas cloud. Research results and analysis. Spatial distributions of the model’s aerodynamic characteristics and contaminants gaseous component when reaching the maximum permissible concentration in the modeled area have been obtained. The estimated time of the open-pit natural ventilation and the dynamics of the open-pit upper edge air contamination dynamics down the wind have been analyzed. The complex and diversified nature of open pit ventilation for various locations of bulk explosions has been recorded. The undulating character of contaminant loss has been predicted (with different heights of peaks) conditioned by the presence of vortex formation in the open pit. Conclusion and scope of results. For the recirculation scheme of ventilation, the situations with the bulk explosion locations shifted to the windward edge of the open pit are the longest. It has been shown that the reduction in the dust and gas cloud lift does not always ensure the reduction in the contamination level at the upper edge of the open pit down the wind.

A study of the influence produced by the dynamics of the working bodies of cotton-processing machines on the cotton fibre quality

Cotton mass is considered as a compressible porous two-component medium, consisting of a mixture of cotton fibres and air included in the porous medium, which is essential in dynamic treatment processes and requires consideration when planning technological modes. It was found that the speed of sound in multicomponent media significantly decreases with an increase in the content of the gaseous component. With a certain content of components, it can become less than in each of the components separately. This is due to the fact that with an increase in the content of the gaseous component, the density of the medium increases insignificantly, and the compressibility of air sharply decreases in the pores. As a result of the research, it was found that the value of the dynamic change in the density of cotton raw materials can significantly exceed its density during static compression. This kind of influence can have both adverse and desirable effects on the primary stage of cotton processing. The dynamic characteristics of raw cotton as an object of mechanical technology were studied. The values of the speed of sound as a function of the density of cotton raw materials were determined on the basis of the theory of a two-component porous medium. The types of the dynamic compression curve of raw cotton have been established. Experimental studies on the compressibility of raw cotton are generalized. From the analysis of the cleaning processing of fibres and seeds on cleaning machines, it follows that when assigning a technological processing mode, it is necessary to comply it with the value of the sound speed for a given density of raw materials. It is necessary to avoid such rates of penetration of the working bodies into raw materials that are commensurate with the speed of sound at a given raw material density. This local dramatic increase in cotton media characteristics is a significant cause of fibre damage

Circularization of tidal debris around white dwarfs: implications for gas production and dust variability

White dwarf (WD) pollution is thought to arise from the tidal disruption of planetary bodies. The initial fragment stream is extremely eccentric, while observational evidence suggest that discs are circular or nearly so. Here we propose a novel mechanism to bridge this gap and show that the fragments can rapidly circularise through dust or gas drag when they interact with a pre-existing compact disc. We assume that the tidal stream mainly consists of small cohesive fragments in the size range 10-1000 m, capable of resisting the WD tidal forces, whereas the compact discs span a wide mass range. We provide an analytical model, accompanied by N-body simulations, and find a large parameter space in fragment sizes and orbital separation that leads to full circularization. Partial circularization is possible for compact discs that are several orders of magnitudes less massive. We show that dust-induced circularization inherently produces gas as tidal fragments collisionally vaporize the pre-existing dust along their path. We show that ongoing gas production has a higher probability to occur during the early stages of tidal disruption events, resulting from the fact that smaller fragments are the first to circularize. Intermittent gas production however becomes more likely as the tidal stream matures. This could explain why only a small subset of systems with dusty compact discs also have an observed gaseous component. Additionally, the interaction yields fragment erosion by collisional shattering, sputtering, sublimation and possibly ram-pressure. Material scattered by the collisions might form a thin dusty halo that evolves through PR drag, in compatibility with observed infrared variability.

Silicon ISM X-ray absorption: the gaseous component

ABSTRACT We present a detailed analysis of the gaseous component of the Si K edge using high-resolution Chandra spectra of low-mass X-ray binaries. We fit the spectra with a modified version of the ISMabs model, including new photoabsorption cross-sections computed for all Si ionic species. We estimate column densities for Si i, Si ii, Si iii, Si xii, and Si xiii, which trace the warm, intermediate temperature, and hot phases of the Galactic interstellar medium. We find that the ionic fractions of the first two phases are similar. This may be due to the physical state of the plasma determined by the temperature or due to the presence of absorber material in the close vicinity of the sources. Our findings highlight the need for accurate modelling of the gaseous component before attempting to address the solid component.

Effect of the gas percentage on the thickness of the galactic discs during minor mergers using hydrodynamical simulations

We study the minor mergers of galaxies using simulations. For this we use GADGET2 code. We present results of simulations of minor mergers of disc galaxies of mass ratio 1:10. These simulations consist of collisionless as well as hydrodynamical runs including a gaseous component in the galactic disc of primary galaxy. Our goal is to establish the characteristics of discs obtained after the merger.We observe that the primary galaxy discs are not destroyed after the merger. We take different initial conditions for the primary galaxy varying the gas percentage in disc from 0–40 percentage and study the thickness of the disc after the merger. We generally observe that the thickness of the disc increases after the merger for any gas percentage. We also observe that as the gas percentage increases in the disc of initial primary galaxy, the increase in the thickness keeps decreasing.

A chemiresistive thin-film translating biological recognition into electrical signals: an innovative signaling mode for contactless biosensing

An innovative signaling mode in which a chemiresistive thin-film electrode monitors the specific gaseous component that results from a biological recognition event to indirectly detect targets in the liquid phase is developed for highly-efficient contactless biosensing. This signaling mode may open a new horizon in designing robust biosensing devices for bioanalysis.

3D-Modeling of the Distribution of Welding Aerosol Nano- and Microparticles in the Working Area

The first results of the research of the distribution of welding aerosol nano- and microparticles in the working area based on substance and morphological analysis are presented in the paper. A 3D-model of the welding aerosol cloud demonstrating the distribution of nano- and microparticles in the working area of the welder was created using the granulometric data of the samples. The most dangerous area with maximum density of nano- and microparticles of welding fumes was singled out: 1.3 m in height and 5 meters in all directions.Welding aerosol is a disperse system in which the solid component of the welding aerosol (SCWA) acts as the phase, and the mixture of gases (gaseous component of welding aerosol, or GCWA) – as the medium. SCWA stays suspended in the air for a long time spreading far beyond the working area of a welder [1].The aim of this work was to create a 3D-model of a welding aerosol cloud, demonstrating the spread of nano- and microparticles of welding aerosol in the working area of a welder. The 3D model was created using granulometric data of samples collected by the author’s method.

Role of Gaseous Disk in the Formation of the Spiral Structure of the Milky Way Galaxy

We use observational gaseous and stellar density distributions in the disk of the Milky Way (MW) galaxy together with the disk rotation curve and measured disk velocity dispersion to build collisionless and combined collisionless-gaseous equilibrium models of the Milky Way disk. A purely collisionless MW disk is unstable towards the development of a central bar, so that during the nonlinear stage of instability the stellar bar is a dominant non-axisymmetric structure developing the disk. A ten percent admixture of a gaseous component leads to the development of a three-armed spiral structure in the stellar disk, decoupled spatially from the central bar-like structure. In our simulations, the spiral structure lasts for about 3 Gyr.

Portable flow board for storage of fruits and vegetables in mini-chambers with controlled atmosphere

ABSTRACT A portable flow board system was developed in the present study with the aim to facilitate lab-scale experiments of controlled atmosphere (CA) with fruits and vegetables. This sturdy flow board combines ease fabrication, low cost and gas economy. Its functionality is provided by manifolds and gas mixers. Each gaseous component is supplied by a gas cylinder through a differential valve of adjusted pressure control, generally at 6 kPa, and forced through 13 standardized restrictors coupled to each manifold output. Controlled atmospheres are then formed with one, two or three gases in 13 gas mixers affixed to the flow board base, which are further conducted through flexible tubes to storage mini-chambers that can also be used to study metabolic consumption and production of gaseous components. The restrictors used in the flow gaseous components were manufactured from microhematocrit test-type capillary glass tubes following the hot forming method under continuous air flow. The portable flow board showed to be low cost and simple post-harvest equipment that allows preparing controlled atmospheres in open systems with stable composition and flow, in a manner similar to traditional flow boards with control of gas escape by barostats.