Browsing by Author "Radchenko, Yurii M."

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    Patterns of Air Mixture Movement in the Operating Area for the Annular Ejector of Pneumatic Transportation System
    (НТУ «Дніпровська політехніка», Дніпро, 2023) Ponomarenko, Serhii M.; Potapchuk, Iryna Yu.; Kabakova, Liudmyla B.; Radchenko, Yurii M.
    ENG: Purpose. To establish the regularities of two-phase flow of “gas-solid particles” in the operating area of an annular ejector where the following processes take place: air mixture ejecting, compressed air outflow from the ejector nozzle, air mixture flows mixing in the transport pipeline. In the work, the velocity distribution is also examined for dispersed phase and air phase of air mixture during its loading and accelerating in the transport pipeline of the pneumatic transport system. Methodology. The research is based on the fundamental approaches of mass point dynamics, aerodynamics, the theory of jet flows and iteration methods of numerical solution of equations. Findings. The mechanics of the air mixture flow under the ejection and aerodynamic force in the operating area of an annular ejector and at the beginning of transport pipeline is analyzed using the method of iterations. The impact of air mixture flow in the operating area of an annular ejector on energy performance of the pneumatic transport system is evaluated. Originality. The originality is that, for the first time, the regularities describing two-phase “gas-solid particles” flow at the loading area of the pneumatic transport system with an annular ejector have been obtained. This made it possible to characterize the velocity distribution of the dispersed and air phases of the air mixture during their loading and aerodynamic acceleration in the transport pipeline. Also, an innovative approach to the effectiveness of the use of pipeline pneumatic transport is the assessment of the energy indicators of the use of ejector-type pneumatic transport equipment depending on the rate of compressed air outflow from the ejector. Practical value. The implementation of the results in the modernization of existing and in the creation of new pneumatic transport systems with an annular ejector makes it possible to increase the efficiency of their use in the technological processes of moving dispersed materials at mining and metallurgical enterprises and in other areas of technology.
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    The Phenomenon of a Mixed Colony: The Case of Lasius Brunneus and Lasius Umbratus (hymenoptera, Formicidae)
    (Publishing House “Akademperiodyka”, Kyiv, 2024) Stukalyuk, S.; Radchenko, Yurii M.; Akhmedov, A.; Stelia, V.
    ENG: The aim of this work is to study to find out why, in the case of temporary social parasitism, a mixed colony of Lasius brunneus (Latreille, 1798) and Lasius umbratus (Nylander, 1846) exists in this state for many years. In 2023, a mixed colony of L. brunneus (host species) / L. umbratus (temporary social parasite) was discovered in Moldova. This mixed colony is located at the same site where another mixed colony containing Lasius fuliginosus (Latreille, 1798), L. umbratus disappeared in 2017. Video recordings of the intensity of movement of workers of the two species along the trails were made to study the frequency of antennal contacts and to calculate the colony population. Based on the previously used algorithms, it was assumed that the queen oviposition rate of L. umbratus is 1.5 times higher than that of L. niger, while that of L. brunneus is comparable to that of Lasius niger (Linnaeus, 1758). Chi-square test and post-hoc Dunn's test were used for statistical analysis of the data. Mathematical modelling was used to analyse the rate of colony development. Results of the analysis of worker activity on the trail showed that L. brunneus had 11 times more foragers than L. umbratus. A high number of interspecific antennal contacts between workers was recorded. The population of the mixed colony was estimated to be 48.880 L. brunneus and 24.433 L. umbratus workers. Mathematical modelling confirmed the failure of L. brunneus monogyny in a mixed colony and suggested that high L. brunneus abundance is ensured by multiple queens (oligogyny). Probably in 2021, the L. brunneus colony moved to a new habitat, which was invaded by the L. umbratus queen. After the invasion, several L. brunneus queens survived, allowing a mixed colony to exist.