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Optimization of the water flow distribution is an important problem in the field of the operative control over technological processes in water supply systems. In this article we describe the comparative analysis results showing the efficiency of various methods used to optimize flow distribution in water supply systems with a large number of active sources. The research has shown that the Hooke and Jeeves method of the direct search is the most efficient in terms of the cost of computer time and the amount of used memory.

The study aims to develop a method of effectiveness evaluation for geothermal heat recovery in closed mines of Donbas using relations of heat transfer theory in rocks and fluids. Geothermal heat is proposed to recover using coaxial geothermal probes to be installed in flooded closed mines. As a result of evaluation and ranking, five top promising sites with the highest expected performance indicators among 27 closed mines located in Donbas have been identified. The evaluation method takes into account geological settings, mine condition, and heat exchange parameters of the probe with mine water. The locations of the most promising sites were found to correlate with the areas of higher geothermal flux and the deeper mines. The results obtained can be used in feasibility studies on installation and operation of geothermal probes in closed mines.

There has been established in the article the correlation and regression relationship between the factors of the country’s development and the level of environmental safety on the basis of identifying the patterns of certain factors sets influencing the volume of harmful emissions into the atmosphere. On the basis of modeling, there has been carried out the analysis of individual groups of factors influencing the volumes of harmful emissions in the countries selected for the study. The nature and degree of influence of the selected factors on the resulting indicators (volumes of harmful emissions) have been determined. It has been found that the number of these factors is significantly higher in France than in Ukraine. This is due to both the political and economic situation in the country. The level of energy efficient technologies implementation and environmental restructuring of business entities are no less significant. The ranking of factors has been carried out based on the value of the correlation coefficient within a separate group and each country. There are also highlighted differences in the research results and their reasons.

Increase of operating efficiency of mine energy complexes is an actual scientific and technical problem. Systems that utilize energy of low-potential sources and have freon-steam turbines are suggested to be included in mine energy complexes. Principles of selection of freons as working fluids in energy systems are suggested in the paper. Usage of some thermal equations of state for defining thermal and physical properties of freons is analyzed. Equation of isentropic process for the thermal Redlich–Kwong equation of state is obtained. Calculation of energy efficiency of a system with a freon-steam turbine for selected variants of usage of working fluids is performed. A calculation method of thermodynamic parameters that are necessary for energy conversion efficiency estimation of specific freons in a system of useful utilization of energy is developed. Analysis of results indicates that usage of ozone-safe and fire-safe freons in energy utilization systems of low-potential sources with a possibility of utilization of additional waste heat, which was not used in the past, allows increasing the operating efficiency of mine energy complexes.

The article discusses the effect of fluids on the properties of rocks. It is known that surface active environments, including gas, can significantly change the mechanical characteristics of solids. To establish the dependence of the effect of methane on the strength characteristics of rocks, the results of full-scale and laboratory studies are considered. The experiments were carried out on samples of outburst sandstone formation m3, taken at a depth of 915 m. Analysis of research results allowed to establish the effect of changes in gas saturation of rocks on their mechanical properties before and after degassing and partial discharge of experimental areas after they have been worked by lavas along m3 formation. It has been established that the reason for the increase in drillability and strength of sandstones was their degassing, and not a change in the stress state of the environment. This led to a change in the deformation properties of rocks in gas-saturated and degassed states.

Topical problem concerning the improvement of intermediate rail fastening of a railway track of railroad transport as well as industrial and underground rail one has been considered taking into account peculiarities of operation in terms of curved sections of a route with small-radius curvature. Objective of the paper is to improve operational parameters of a railway track with extra small curvature radii in terms of railroad gauge adjustment. Operation of the components of intermediate rail fastening, being subject to intense wear and destruction due to the effect of great transverse and horizontal loading within the curved route sections with small-radius curvature, has been and analysed. Innovative engineering solutions to improve intermediate rail fastening have been proposed. Such peculiarity of the device of intermediate rail fastening provides increased durability and working capacity of rail fastening components in terms of considerable transverse loading within the route sections with small-radius curvature. The obtained results may be applied for underground and industrial rail transport as well as for railroad one.

This paper aimed at studying the current state of development of liquid biofuels’ world market. The authors considered the theoretical bases of liquid biofuels production, their types, disadvantages and advantages. The world experience of introducing stimulation mechanisms of development and their influence on the sectors’ growth is analyzed. In this study’s frame, there is outlined the world leaders in the production of liquid biofuels. The findings represent the peculiarities of state regulation in implementing mandates for creating transport fuels with bioliquids. The current state of investment in the production of liquid biofuels was investigated. The obtained results contribute to the prospects for promoting world production of liquid biofuels to achieve the Paris Agreement’s goals by 2030 under the sustainable development scenario.

The scientific and technical task for determining the stress-strain state of mine workings is complicated by the presence of a layered massif. This task assumes particular importance in the case of circular tunneling. During its operation, it is important to predict the change of the stressstrain state for the massif or to carry out the prompt determination in the change of stresses and displacements for the unsupported working. The solution of this geomechanical task allows performing geometrical matching of the working, ensuring its strength and stability in the layered massif. A numerical finite element method based on StructureCAD (SCAD) software package was used to solve it. Four geomechanical systems were calculated: “unsupported working – layered massif”. Owing to the obtained results, graphs of stresses and displacements were constructed, which allow to determine these parameters for workings with different geometric parameters and X-parameter characterizing the ratio of the elasticity modulus of the matrix and the layer. Obtained regularities of change of stresses and displacements for the unsupported working when zooming made it possible to introduce scaling-parameters, which are a dimensionless ratio of the radii for a real system and a system with a unit diameter.