Today there is not enough scientific data on the energy level and the velocity of an explosion in actual mine workings, which have a cross-sectional area larger than experimental mine workings. The ...objective of the paper is to justify the energy parameters of an explosion in actual mine workings based on the disclosure of the fire front development mechanism when coal dust explodes in an experimental mine working with a limited cross-sectional area. These studies can be the basis for choosing the speed of action and the strength of the means of the localization of dust explosions. The main research method is an experimental and analytical method, based on the analysis of the results of experimental explosions of coal dust in experimental mine workings and theoretical substantiation of the regularities of the development of the velocity and additional energy of the fire front with further extrapolation to the conditions of actual mine workings. It is proposed to supplement the mechanism of explosion development with an idea about the sections of development of explosion dynamics, i.e. initiation, dust explosion, crater, which determine the characteristic parameters of the explosive front velocity: maximum initiating velocity, average velocity, and maximum velocity in a crater. It was established that during methane initiation in the experimental mine working at the boundary between the initiation and dusting zones, there is a situation of a hybrid explosion of a mixture of methane and dust with air, which has its own velocity and energy indicators. A linear dependence of the energy generated during the coal aerosol explosion on the cross-sectional plane of the mine working was established. This makes it possible to use the results of testing the coal from certain deposits in small-scale experimental set-ups to justify the parameters of protective means for the actual mine workings.
The article is devoted to the improvement of the design of a desalination solar plant for more efficient and economical production of desalinated water due to intensive evaporation of the boiling ...solution, reduction of energy losses to the external environment and the absence of the need for continuous adjustment of the direction of the light-receiving part of the solar plant. The expedient parameters of the angles of inclination of the optical axis of the lens relative to the azimuth and the incidence vector of solar radiation, which ensure high performance of the solar plant, were experimentally substantiated. The use of a solar collector equipped with an additional heat accumulator will allow water to be supplied for desalination at a temperature of more than 50 °C in sunny weather, and at a temperature of 33–36 °C in variable cloudiness, which will help to increase the efficiency of the desalination solar plant. The presence of a heat accumulator and a layer of thermal insulation under cloudy conditions allows maintaining the operating water temperature at 33–36 °C 4.4 times longer than without them.
The object of this paper is to study the specificity of the dynamics of carbon monoxide in mining to determine the location of the source of coal self-heating or spontaneous combustion. The Fire ...Dynamics Simulator software package was used to model the gas hazard of coal mine workings. Given the typical details for the western coal basin of Donbas geo metric dimensions of workings, properties of coal, etc., a model of a fragment of emergency mining of a coal mine was created, which allows for the display of geometric and physical similarity to processes in actual mine workings. The results of the simulation for the studied scenarios with different air supply systems related to the detection and location of sources of self-heating or spontaneous combustion in the coal mine workings were obtained and analysed. It was established that low-density fire gases are concentrated in the vault of the workings, where they slowly dissolve in the air, with the dissolution process being linear. It was revealed that air velocity up to 0.67 to 0.7 m/s contributes to the formation of fire gas flows, which move towards the ventilation flow, almost without mixing, which is referred to as bifurcation. Numerical parameters of fire gas dynamics in near-real conditions were established, which can become a basis for the detection and location of sources of endogenous thermodynamic processes in mine workings.
The article is devoted to the disclosure of the effect on the vital activity of cyanobacteria by changes in the nutrients in the chemical composition of artificial aquatic biotopes. The research ...results allowed us to establish that the dissolution of complex mineral fertilizer (nitrogen, phosphorus and potassium) in the range of up to 10 g/L contributes to the active development of cyanobacteria, which is accompanied by complete binding of mineral additives and absorption of oxygen. The addition of fertilizers in the amount of more than 1 g/L contributes to a sharp increase in the growth rate of the cyanobacteria population, which provokes the conditions for the blooming of the solutions. Enrichment of the nutritive base of biotopes ensures rapid growth of biocenosis and accelerated consumption of dissolved substances. The recorded average absorption rate of phosphorus reached more than 17 g/(L*day), and nitrogen – 30 g/(L*day). The formation of sediment and foam in the test vessels was associated with the depletion of nutrients and the death of hydrobionts. This phenomenon can serve as an indicator of oxygen decrease in the water. The results of the experiment confirmed the ability of cyanobacteria to transform nitrogen and phosphorus dissolved in water into bound organic forms with high intensity. This opens up the prospect of creating biological methods and means of wastewater demineralization.
The objective of this paper is to substantiate the method of construction and design parameters of explosion-proof stoppings for the quick and safe remote sealing-off of the sources of complex fires ...and explosions in coal mines. A new method was designed for the remote erection of explosion-proof stoppings in mine workings and a mathematical model of mass transfer through the body of a stopping made of discrete material. Tactics were improved for the containment of underground fires and explosions due to rapid remote erection of explosion-proof stoppings. The technology of the quick erection of stoppings made of rocks crushed by an explosion for sealing-off of the emergency sections of the mine has been proposed. A computational model and a method for calculating the parameters of explosion-proof stoppings erected by the method of directed explosion have been created. The results of the calculations open the possibility to prepare the means of containment of dust explosions in advance and to improve the tactics of safe containment of explosions and fires.
The article is devoted to solving the issue of ensuring the efficient operation of aeration equipment in the conditions of shallow water bodies with an average depth of only a few meters. The article ...offers a technical solution for reducing the size of airlift aerators and increasing their performance by creating a recirculation movement of water inside the unit. With the help of a laboratory model, it was established that the dynamics of oxygenation of water in the pool with the help of a recirculating airlift is subject to a logarithmic dependence on the size of the flow regulator. It was possible to increase the oxygen concentration in the pool by 2.6 times within three hours as part of the simulation. The rate of water oxygenation was much higher than for a conventional airlift of the same size. The offered cost-efficient aeration unit, which uses wind flow as an energy source, can be used for fish farms and other applications.
Aim: To study the peculiarities of the mental health of children with special educational needs after 1.5 years of full-scale war in Ukraine.
Materials and Methods: The mental health of children with ...special educational needs (SEN) as well as the peculiarities of the impact of hostilities on their emotional and volitional sphere was assessed through the anonymous survey of their parents using the questionnaire developed by the authors (25 questions). The research, which was conducted in 2023 using a Google form, involved 466 parents having children with SEN aged 6 to 10.
Results: It was found that among the surveyed families raising children with SEN, 30.7 % of children were in the combat zone or zone of temporary occupation for a week to a month, 19.1 % - for more than a month; 36.9 % of children experienced relocation, 23.4 % were separated from their parents, 19.7 % witnessed hostilities; 49.4 % of children experienced an unstable psycho-emotional state ("emotional swings") during 1.5 years of war in Ukraine, 40.1 % - restlessness, 38.6 % - anxiety; 23.2 % of parents noted that their children were "hooked" on computer games and social networks, 11.2 % - had problems with sleep, 10.5 % - demonstrated the emergence or increase in cognitive problems.
Conclusions: The negative impact of prolonged stress during the war on the mental health of children with SEN has been revealed, which requires psychological support for such children from parents and psychologists.
The article is devoted to substantiation of parameters of water body aeration technology at high, as well as low, air temperatures. As a result of studies, the design of the water aerator based on a ...two-stage airlift has been improved. A study of its physical model has been conducted. The cost indicators of the set-up and its components have been obtained. It has been established that at various design parameters, the proposed scheme of operation allows to oxygenate water more effectively when compared to conventional design. A new type of water aerator based on two-stage airlift has been proposed. The linear dependence of the dynamics of the aerator flow rate on the supply of compressed air by the compressor, as well as the logarithmic dependence regarding the water oxygenation have been established. The indicator of effective rate, which allows for evaluating efficiency of water body oxygenation has been substantiated. The study results open the possibility of using an aerator with improved design to prevent eutrophication of water in open water and industrial reservoirs, e.g. in construction.
In this work, it is substantiated that it is possible to create a fire installation with parameters that will ensure higher environmental friendliness of the tests compared to large-sized furnaces. ...At the same time, its configuration will be universal, compact and capable of high reproducibility of experimental results. A full factorial experiment was conducted. According to its results, the parameters of the furnace chamber, which most significantly affect the reproducibility of the results, were determined. This are the volume of the chamber, the distance from the burners to the surface of the examined fragment of the load-bearing reinforced concrete building structure, and the height at which the opening for the exit of combustion products is located. Adequacy of operation of the designed installation was verified by the computer simulation method. Natural gas was used as fuel. On the basis of the received data, a sketch of the installation was created for conducting the experimental part of evaluating the fire resistance of load-bearing reinforced concrete building structures under the influence of the standard fire temperature regime. It can ensure a high degree of reproducibility of the test results.
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