Scientific Horizons

9-18

Authors: Sergiy Kulman, Liudmyla Boiko, Ján Sedliačik

The existing behaviour models of the structures under constant load (creep) have a fairly wide forecast horizon and low accuracy. As a rule, they consider the transition from an undestroyed state of an element to a destroyed one, in one stage. The purpose of this study is to substantiate and develop a new approach to predicting long-term strength based on kinetic equations, which, in turn, should consider the multistage nature of the process of gradual destruction of structure elements. To achieve this purpose, the study solves the tasks of creating a multistage kinetic transition of individual structure elements from an initially elastic state to a viscoelastic state, and then to a fractured state. When describing this process, the authors employed the methods of formal kinetics and the theory of continuum damage mechanics, including the method of basic diagrams. Wood-based composites were used as the materials under study. Based on the results of the conducted full-scale and computational experiments, the study discovers that a mathematical model based on kinetic equations adequately describes the behaviour of the materials under study for long-term strength; the proposed two-stage model determines the forecast horizon much more accurately than the available one-stage models. The kinetic parameters that determine the rate of transition of a structural element from an elastic state to a viscoelastic state, and then to a destroyed state, were determined based on experimental base chart. The time to fracture was determined at three-point bending at a load equal to 70% of the flexural strength at temperatures of 20°C and 60°C, constant humidity RH 65% and moisture content MC 8%. When building control charts, the load increased by another 15%. The method allows narrowing the forecast horizon and determining the moment of transition of a structure from a stationary state to a blow-up regime with a higher accuracy

28-37

Authors: Oleksii Tkachenko, Kira Alifonova, Olena Gavrylina, Amelia Knight

This article presents materials on the role of the rice weevil (lat. Sitophilus oryzae) in the process of transmission of Mycobacterium of tuberculosis. The relevance of the study is conditioned by the rapid spread of tuberculosis around the world and the need to develop more advanced methods for diagnosing this disease, which, for its part, is impossible without expanding knowledge on all possible reservoirs of the causative agent of infection. Long-term research around the world has proven that insects are carriers of various microflora, including pathogenic ones. Therefore the purpose of study was to establish the epizootological role of the rice weevil as a reservoir for Mycobacterium bovis in the process of occurrence and spread of tuberculosis. The study determined the duration of transfer and isolation of Mycobacterium of tuberculosis in the external environment by infected beetles. The museum dissociative strain of Mycobacterium bovis (118 passage) was used for the study, the subject of the study was rice weevils. For the furtherance of this goal, the culture, microscopic, and statistical studies were conducted, and the viability of mycobacteria was determined after passages through the beetle body by evaluating colony-forming units. The epizootological role of the rice weevil in the development and spread of tuberculosis has been established. It is proved that the beetle can keep mycobacteria in its body for 50 days with a gradual decrease in their number and is then able to secrete the pathogen for another 30 days, contaminating environmental objects. When evaluating colony-forming units of mycobacteria in the dynamics of the experiment, a decrease in their viability after persistence through the body of beetles was revealed from 5.3*108 in 1 g of the original crop up to 1.4*108 in 1 g of crop that grew from beetle homogenisate for 30 days. These study results will allow developing and improving existing measures for the prevention of tuberculosis and prevent the introduction of this infection into safe territory

45-51

Authors: Roman Yakovenko

The water content in tissues is an important indicator of the physiological state of the plant and is of great importance in the comparative assessment of their cultivation measures that increase productivity. One of such measures is rational fertilisation of plantings, which determines the relevance of the study. The purpose of the study was to establish the effect of optimised fertiliser on the water content in pear tree leaves and the fractional composition of water during stressful growing periods. One of the critical problems is drought, which negatively affects the growth and productivity of plantings. Under such conditions, the turgor of plant cells decreases and the passage of biochemical and physiological processes in the plant slows down. The paper considers the results of studying the water regime of leaves (the content of total, available, and inaccessible moisture) of pear varieties Konferentsia and Osnovianska on vegetative rootstock Quince A grown using optimised fertiliser in nonirrigated plantations. The study was conducted in 2011 and 2018 in a certified educational and research laboratory of the Uman National University of Horticulture. It was found that during the age periods of growth and fruiting, there was a change in the total water content in the pear leaves of the studied varieties. Leaves from pear trees of the Konferentsia variety had a higher water content compared to the Osnovianska variety. Fertiliser options increased the total water content in the leaves, which had a positive effect on the condition of the trees. It was found that at the beginning of the growing season, the free water content in the leaves of pear varieties Konferentsia and Osnovianska was higher, while it significantly decreased in the middle of the season. The bound water content was higher in all studied options. Under stressful situations (drought, temperature increase), fertiliser application had a positive effect on the water content in the leaves of both studied pear varieties. The practical significance of the study is to recommend the production of a rational fertiliser system for nonirrigated pear plantations in different age periods of growth and fruiting, which positively affected the water content in leaves and the fractional composition of water during stressful periods of cultivation

58-67

Authors: Siarhei Rabko, Ivan Kimeichuk, Siarhei Surauyou, Vasyl Khryk, Svitlana Levandovska

The use of various types of neutralising materials in the cultivation of standard planting material of high-quality forest wood species has a significant effect on substrate acidity. Therefore, the study sets a goal to select peat substrates with different dosages of the neutralising component and determine their effect on the reaction of the peat substrate medium. The paper presents the results of the influence of neutralising materials of dolomitic meal and chalk of various doses with the use of mineral fertilisers. Dolomitic meal was used as a neutralising component, the pH of the peat substrate was 6.6 and chalk was 7.5. It was found that when neutralising a peat substrate created based on high-moor milled peat (pH 2.5) with the introduction of dolomitic meal in doses of 2-4 kg/m3 (European spruce), 3-4. 5 kg/m3 (Scots pine), optimal acidity can be achieved in a month. An increase in the concentration of lime material was recorded, which leads to an increase in the neutralisation of the substrate at a dose of 2.5 g and 3.0 g per 125 g of peat. The best indicators were demonstrated by options of doses of 1.5-2.5 g per 125 g of peat for 7-8 days of use and a dose of 3.0 g per 125 g of peat for 5-6 days compared with the control. An increase in the concentration of chalk in the neutralising material from 30% to 70% leads to a faster deoxidation of the substrate (pH 3.2), and an increase in the dosage of chalk increases substrate neutralisation. The electrical conductivity of the substrate at a dosage of 6-8 kg/m3 when applying chalk and dolomitic meal increases by 1.6-2.0 and 1.2-1.4 times, respectively. At the rate of application of 6-10 kg/m3, it has a lesser effect on the change in the electrical conductivity of the high-moor peat, and the introduction of dolomitic meal 2-4.5 kg/m3 into the milled peat during neutralisation does not lead to a change in the electrical conductivity of the peat. This data allows choosing neutralising materials of a certain concentration that will enable the cultivation of standard planting material of European quality and thereby ensure the proper quality of future stands

75-86

Authors: Elchyn Aliiev, Krystyna Lupko

Nowadays, an important aspect for achieving a high level of seed production is the expansion of the range of high-quality seed material, which disrupts the technological process of separation and increases its costs. The purpose of the study is to analyse indented separator cylinders for cleaning small-seed crops and develop an appropriate mechatronic system for their control, the use of which would allow performing the technological process of separation with lower specific operating costs and higher productivity. The presented analysis of the technical support of the process of separation of seed material of small-seeded crops indicates the need to improve indented separator cylinders based on automated control of their parameters using photo or video recording of the seed separation with subsequent processing. It has been established that the determination of formal performance indicators of an indented separator cylinder is not trivial. Based on the results of the analysis, a design and technological scheme of the mechatronic system of an indented separator cylinder has been developed. The difference between the proposed system and the conventional one is that the camera captures the trajectory of seeds. This information is processed in the control unit, which in turn changes the speed of rotation of the gear motor and, as a result, the drum with cells, the angle of inclination of the tray, the angle of rotation of the flap with the stepper motor of the hopper dispenser. These manipulations with the operating parameters of the indented separator allow adjusting it to changes in the seed mixture composition, thereby improving the quality and productivity of separation. In addition, due to the automatic adjustment of the operating parameters of the indented separator, the participation of the operator in the separation process is practically not required, which reduces labour costs