Abstract. Objectives The problem of physically modelling stresses in a compound solid body of revolution having a complex shape and with a complex load distribution is considered. According to the similarity criteria of stress, deformations and displacements from the volume forces decrease proportionally to the scale of similarity of geometric dimensions, which complicates their direct modelling by the photoelasticity method typically using models made from epoxy materials. Methods Based on the principle of the independent action of the forces, the initial problem is represented as the sum of two problems. In the first uniform problem, the stresses in the body of revolution from the centrifugal forces are simulated by the conventional “freezing” method. In order to solve the second nonuniform problem, the stresses in the region of the model, corresponding to the acting centrifugal forces, are “frozen”. The models are glued in a natural state at room temperature, and the compound model is annealed. Results The band patterns in sections as well as components of radial, tangential and axial stresses on contours and in sections of models are obtained by the methods of normal transmission and numerical integration of the equilibrium equation. According to the modelling criteria, the formula for the transition from stresses in models to stresses in the natural structure is established. The results of the analysis of the effect of a body's material density ratio on the stress state of the entire structure are obtained. Conclusion  Axial stresses have insignificant value as compared to radial and tangential stresses; in addition, the ratio of the densities of the compound body has both a quantitative and qualitative influence on the stress state of the structure.

Abstract. Objectives Based on a critical analysis of the results of complex studies, we set out to demonstrate the advantages, as compared with existing technologies, of a developed technology that uses a new cutting scheme with a combined countersink-tap tool. Methods One way to improve the processing capacity, tool life and quality of a cut thread is to reduce the torque and strain hardening of the processed material by employing a new cutting approach to completely eliminate the friction of the lateral sides of the tooth on the surface of the cut thread. It was necessary for this technology to be checked in real production conditions. Results The conducted production tests of a combined countersink-tap tool with the new cutting scheme developed by the inventors have shown that, as a result of a significant reduction in the torque and a decrease in the strain hardening of the processed material, it is possible to increase the cutting speed and increase labour productivity by more than 2 times as compared with the thread cutting processes using taps with staggered teeth, 1.2 times as compared to taps with a corrected structure, and more than 6 times as compared to standard taps. At the same time, the stability of the tool is increased 3-5 times and the number of breakages is also sharply reduced. Conclusion It has been established that the accuracy of the geometric parameters as well as the strength and quality of the thread surface cut by the combined countersink-tap tool with the new cutting scheme in hard-to-work materials is much higher than the same thread parameters obtained by processing with standard and other known taps. The studies also indicated its high reliability, operability and expediency of application for processing the above-mentioned materials. The advantages of the combined tool also include a reduction in thread cutting time as compared to a separate machining of the threaded hole (countersinking with a standard countersink followed by subsequent tapping).

Abstract. Objectives The aim of the research is to study the features of the propagation of mechanical oscillation waves of ultrasonic frequency through composite materials, including those exposed to a microwave electromagnetic field. Methods The propagation of mechanical waves generated by a source of ultrasonic vibrations is investigated in samples of composite materials reinforced by carbon fibres as used in aircraft construction. Results It is established that, when passing through a composite material, the frequency of the waves decreases by almost two orders of magnitude in comparison with the frequency of the driving dynamic force, while the method of laying reinforcing fibres has a significant effect: the greatest decrease in frequency is observed in composites with a quasiisotropic structure. When the oscillations pass directly through the metal surface, the frequency decreases by not more than an order of magnitude. The amplitude values of vibration acceleration increase with decreasing thickness of the samples and exceed by 2-3 times the waves obtained during the control passage through the steel surface of the gear. The sound pressure level changes from 4.1 Pa for samples with a quasi-isotropic structure to 8.4 Pa for samples reinforced with a metal grid. The processing of the investigated materials in a microwave electromagnetic field leads to a change in the character of the passage of the oscillation waves. The average for a specified period of time vibration acceleration value increases slightly (7-9%), while its unevenness decreases significantly (by between 0.2 and 6 times), i.e. vibrations become stable. For some materials (reinforced with a quasi-isotropic and laminated pressed metal mesh), the vibration acceleration values  do not change at all during a cycle. Conclusion  The obtained result can form the basis for developing technologies for creating structures from composite materials with stable vibroacoustic characteristics.

Abstract. Objectives In general, the reliability of dredgers is highly dependent on the performance of the scoop chain, a working body that is subject to high dynamic loads, a significant part of which falls on the swivel. The wear of the scoop chain swivel is complicated by the ingress of abrasive particles into the gap. Aims and tasks: increasing the wear resistance of the scoop chain swivel having an abrasive component of the general destruction process; determination of the abrasive wear durability of test materials; analysis of test results and recommendations for improving the reliability and efficiency of the swivel. Methods Comparative tests for the abrasive wear of samples manufactured according to proprietary technologies for the assembly of parts from 38HN3MA and 110G13L steels; samples manufactured from 38HN3MA and 110G13L steels using a modified manufacturing technology; surfacing using E-50-UONI 13/55 electrodes followed by subsequent hardening and without it; surfacing using E-190H5S7-LEZ-Т-590-NG electrodes without hardening and with surface-plastic deformation. The samples were tested for abrasion against fixed abrasive particles at pressures of 27.3 kPa and 47.4 kPa. Results The abrasion resistance characteristics are obtained for samples: (1) made of 38HN3MA, 110Г13Л steels, manufactured by the factory technology and adopted as the standard; (2) made of 38HN3МА steel after quenching and low tempering; (3) made of 110G13L steel after quenching and surface-plastic deformation; (4) after surfacing using E-50-UONI 13/55 electrodes without hardening, hardened by surface-plastic deformation and hardened by carburising, quenching and low tempering; (5) after surfacing using E-190H5S7-LEZ-Т-590-NG electrodes without hardening and with hardening by surface-plastic deformation. The dependences of the mass Δm and the linear Δl abrasions, as well as the relative wear resistance Im, Il on the hardness, are plotted. Conclusions Changing and supplementing the factory technologies of the swivel details manufactured from 38HN3MA and 110G13L steels will increase the wear resistance of the friction pair. Restoration of worn fingers by surfacing using E-50-UONI 13/55 electrodes with subsequent carburising, quenching and low tempering can be recommended for use in operation. Surfacing using E-190H5S7-LEZ-Т-590NG electrodes with subsequent surface-plastic deformation will significantly increase the wear resistance of the restored fingers.

Abstract. Objectives The aim of the research was the development of an ultrasonic generator of technological design with a wide frequency range of output voltage. Methods The prototype works were performed and the functional scheme of the multifrequency ultrasonic generator realised in the experimental sample was developed, as well as the design of an ultrasonic piezoceramic system capable of operating at two resonant frequencies of 22 and 44 kHz. Results Based on the feature analysis of the modern composite material structure and technologies for moulding products, it was found to be expedient to introduce ultrasonic impregnation into the technological process, which can ensure increased uniformity in filling the structure with a binder as well as greater homogeneity of physicomechanical characteristics. A schema for the ultrasonic generator built into the technological equipment is developed, providing the formation of harmonic signals with a frequency alternating from 20 to 60 kHz, and power adjustable from 100 to 500 W, which will allow the implementation of highperformance ultrasonic technologies for processing materials with a heterogeneous structure formed during the manufacturing process. The studies were carried out according to parametric optimisation of the converter taking into account the specific load types. A special feature of the generator's power supply is its versatility in terms of frequency and voltage ranges, as well as the required quality indicators of the energy generated. The generator allows the reference frequency to be programmed using a laptop and then fine-tuned from the control panel in resonance with the radiator with a resolution of 10 Hz directly. The built-in microprocessor allows the reference frequency entered from the laptop to be stored in the memory. Conclusion The use of multifrequency ultrasonic sources allows the acting parameters to be optimised for ultrasonic impregnation of fibre-reinforced composite materials as well as their finishing dimensional processing, depending on the density of the structure and the reinforcement scheme used.

Abstract. Objectives The aim of the present work is to carry out mathematical modelling of heat exchange in rough flat channels and round pipes with rough walls during one-sided heating. Methods The calculation was based on the superposition principle of turbulent viscosity. The solution of the problem of intensified heat transfer in a flat channel and in a round tube with rough walls was obtained using the Lyon's integral. Results A methodology for the theoretical computational heat exchange determination for flat rough channels and round pipes with rough walls during one-sided heating is developed, in contrast to existing theoretical approaches, on the basis of the principle of full viscosity superposition in a turbulent boundary layer. The analysis of the calculated heat exchange and hydraulic resistance values for flat rough channels and round rough pipes under one-sided heating shows that the increase in heat exchange is always less than the corresponding increase in hydraulic resistance, which is a disadvantage as compared to the channels with turbulators, all else being equal. The results of calculating the heat exchange for channels with rough walls at one-sided heating in an extended range of determinant parameters differ significantly from the corresponding data for channels with turbulators and are used to determine the level of heat exchange intensification. Conclusion An increase in the calculated values of the relative average heat exchange Nu / NuGLduring one-sided heating for flat rough channels and rough pipes having very high relative roughness values is significantly affected by both an increase in the relative roughness height h/R0 and an increase in the Re Reynolds number. The main advantage of solutions for averaged heat transfer for rough flat channels and round pipes under symmetrical thermal load, obtained according to the developed theory, is that they allow the calculation of heat exchange in rough pipes to be made in the case of large and very large relative heights of roughness protrusions, including large Reynolds numbers, which is typical for pipes of small diameters and narrow flat channels. An increase in the relative heat exchange in air due to an increase in the relative height of the roughness or the Reynolds number is accompanied by an even more significant increase in the hydraulic resistance. Calculated data on averaged heat transfer obtained in the work indicated that in the range of determinant parameters for flat rough channels with one-sided heating, the average heat exchange is lower by (4  10)% as compared to round rough pipes, all other things being equal.

Abstract. Objectives The main aim is to develop a mathematical model of a centrifugal compressor and carry out a parametric diagnostics of a centrifugal supercharger's technical condition during operation. Methods  A model is proposed for calculating the thermodynamic properties of natural gas, reducing the parameters of a centrifugal compressor to the initial conditions and to the rotation frequency, as well as the integral indicators of the supercharger's technical state. The technical state of the gas path of the centrifugal supercharger of the compressor unit is determined by the parametric diagnostic method. Results  The software implementation of the mathematical model of centrifugal compressor is carried out using a DVIGwT PC. The analysis of calculations indicates that the model is appropriate, with the error being due to taking into account the properties of iso-butane and i-hexane, in contrast with the VNIIGAZ technique. The evaluation studies of a centrifugal compressor's state are indicative of the presence or absence of its defects. Conclusion  Among a number of the diagnostic methods for evaluating a centrifugal supercharger, the most effective is vibrodiagnostics. However, the search for malfunctions and nascent defects in the flowing part of the centrifugal compressor cannot be limited only to vibrodiagnostic data, which provides about 60% of the reliable information about the state of the gas-air tract. About 20% of the compressor's malfunctions and approximately half of the dangerous modes of the supercharger's flow-through part is detected using thermogasdynamic parametric analysis (parametric diagnostics). The main difficulty of the control over the technical state of the flow-through part of the centrifugal supercharger is in the complication of the quantitative evaluation of the processes taking place in the supercharger, which leads to problems in providing reliable diagnosis during a reasonable period of time.

Abstract. Objectives This work is a continuation of a series of articles devoted to an analysis of the effect of the utilised second-order surface types on the accuracy of determining earthquake epicentre and hypocentre coordinates. Methods  In order to find the density of error probability distribution during the determination of earthquake hypocentres, approaches using spheres, hyperboloids, as well as combined spheres and hyperboloids, are used.The hyperboloid-based methods used for determining hypocentre coordinates have fewer errors as compared to the sphere-based method. This is explained by the fact that when determining the travel times of seismic waves, it is assumed that the error increase is the same for the difference in the seismic wave arrival times to two seismic sensors (for methods using hyperboloid), and for the difference in the arrival times of the two seismic waves to the one seismic sensor (for methods using spheres). Results  The expression for determining the earthquake focus coordinates by the hyperboloid method, as well as the density of error probability distribution during the earthquake hypocentre determination, is obtained for calculations using the sphere method, the hyperboloid method, as well as the combined sphere and hyperboloid method. A graph for the error distribution when determining the earthquake hypocentre is obtained for different locations of seismic sensors and for various error values concerning differences in the travel times of seismic waves. Conclusion  The obtained dependencies have the form of an error distribution close to the Cauchy distribution. A wavelet in the zero regions for all distributions was obtained as a result of calculations of the earthquake focus coordinates in the absence of errors in the determination of the time difference. The combined method of the hyperboloid and the sphere has a distribution form close to the hyperboloid method, while the distribution curve in the region close to zero is similar to the sphere method.

Abstract. Objectives An analysis of open access literature sources and normative documents on the problem of information protection in automated systems was carried out. This showed the absence in these documents of quantitative parameters of the probability-time characteristics of network attacks carried out on information resource of automated systems. To such parameters one can attribute the average time of a network attack in one of its states, realising destructive impacts, in order to develop an effective model for countering threats implemented in systems and information security products. Methods One of the methods for solving this problem is a full-scale experiment; however, in practice many difficulties arise during its implementation, namely the determination of the probabilitytime characteristics of network attacks (if the time is much less than a second). To solve this complex problem, it is necessary to use new information technologies, which include the CPNTools simulation modelling software environment. Results The methodology for determining the probability-time characteristics of network attacks carried out on the information resource of automated systems (the quantitative values of the times of the network attack at all states of the formal model of their operation) is developed. A classification of network threats comprising unauthorised access in automated systems based on the data bank of the Federal Service for Technical and Export Control of Russian Federation is proposed. Conclusion  The output data of the methodology developed in the article are the probability-time characteristics of network attacks carried out on the information resource of automated systems. This data was obtained during the simulation using CPNTools software environment in the form of the residence time (realisation) in one of the realisation states of these destructive effects in automated systems. The main aspects of the obtained results are analysed and prospects for their future use, connected with the increase of real security of existing, as well as developed, automated systems, are outlined.

Abstract. Objectives The study of geomechanical phenomena and processes in rock massifs, manifested during the extraction of minerals, results in the need for research methods for solving the problem of zonal disintegration of rocks around deep underground excavations. In conditions of extremely small sample sizes, due to external circumstances, and the absence of a large number of deposits, the question of the quality of obtained results is very relevant. Methods  As a solution to the problem, it is proposed to refine the results obtained by using numerical resampling methods, which include randomisation, bootstrap and Monte Carlo methods. Due to the specifics of the methods, special attention is paid to the number of bootstrapping implementations, which are inversely proportional to the size of the bootstrap sample. Results  A solution to the problem of zonal disintegration of rocks around deep underground excavations is derived in which refined estimates of the significance of the analytic dependency of the defect function periodicity parameter on the position of the fracture zones are obtained using bootstrapping methods. The determination coefficient is chosen as the primary indicator in the work, allowing the most suitable form of the studied analytic dependency to be determined. The deviation of the determination coefficient in the nonlinear model reliably does not exceed 0.5% for any bootstrap sample size, while in the case of the linear model the deviation is less than 1% only for n≥122. Conclusion  The interval estimates of the determination coefficients obtained by bootstrapping methods have a significant advantage in comparison with traditional approaches. Their quality is directly dependant on the number of bootstrap implementations and the volume of the bootstrapped sample. The latter is especially important in the context of considering extremely small data samples, since it becomes possible to reduce the dimension of confidence intervals to a given level at the initial significance level of the result.

Abstract. Objectives The process of managing complex dynamic objects and systems is inevitably connected with the problem of the effectiveness of providing qualitative support information for making managerial decisions. The creation and application of an information system (IS) makes it results in a need to evaluate its effectiveness. Methods The article presents a methodology for evaluating the effectiveness of information systems in solving problems related to the management of complex dynamic objects. The content of the functional information system quality criteria is specified. Results  Efficiency and quality indicators of an information system oriented towardsthe analysis of data related to information processing problems are substantiated. It is suggested that the necessary and sufficient condition for evaluating the effectiveness of an information system is the dimensionality of its indicator. A comparative analysis of variants of the solution is presented on the basis of their direct ranking, taking into account the significance of the scalar integral quality indicator. The transition to a vector indicator, whose elements are partially derived from the system’s own quality indicators, each of which can have an independent value for the subsequent level of the hierarchy, is indicated. Conclusion  The need to take into account the partial indicators leads to specific methods for analysing and synthesising systems on the basis of a multi-criteria approach based on the state space concept. The content of the quality criteria for the information systems is specified in the article. A developed methodology for evaluating the effectiveness of information systems in solving problems relating to the management of complex dynamic objects, based on multi-criteria optimisation, is presented. Thedeveloped generalised information system quality indicator is justified. On the basis of the state space concept, it is possible to move away from the generally unsuitable scalar integral quality criterion of information systems to the vector of eigenvalues.

Abstract. Objectives The article is devoted to an analysis of the systems of supply and exhaust ventilation in mass-constructed residential buildings with the purpose of justifying the need for separation of gravitational exhaust ventilation systems into zones on the example of a nineteen-storey residential building. Methods  The need for zoning of the ventilation system is determined by the traditional aerodynamic calculation, which in this article is carried out using universal programmes compiled in computational systems such as Excel and Mathcad. Results An aerodynamic calculation of the natural ventilation system of the selected object is carried out for several options: the ventilation scheme actually designed in this building (separation of the exhaust gravitational ventilation system into two prefabricated vertical channels with individual satellites connected to it) and the traditional scheme of natural ventilation (identical scheme, but with a single prefabricated vertical channel). Analysis of the results does not give an unambiguous answer concerning the need for zoning of exhaust systems. For an accurate determination of the necessity of zoning the ventilation system, aerodynamic calculations were carried out for 40 and 60-storey buildingshaving the same layout. In the aerodynamic calculation, pressure losses of the system sections were determined as the sum of pressure losses due to friction and in local resistances. The obtained values had to correspond to the required discrepancy. The difficulty is in the determination of the coefficients of local resistances (CLR) of triple junctions due to the wide variety of calculation formulas and tabulated values. Conclusion The analysis of the results of the aerodynamic calculation of the selected natural ventilation systems determines the need for zoning the exhaust systems along the building's vertical aspect.

Abstract. Objectives Concretes for injection with a two-stage expansion are a kind of selfstressing concrete obtained with the use of self-stressing cement.The aim of the work is to study the influence of the duration of aging on the porosity, strength and self-stress of concrete hardening in water, depending on the expansion value at the first stage. At the first stage, the compacted concrete mixture is expanded to ensure complete filling of the formwork space. At the second stage, the hardening concrete expands due to the formation of an increased amount of ettringite. This process is prolonged in time, with the amount of self-stress and strength dependant on the conditions of hardening. Methods  Experimental evaluation of self-stress, strength and porosity of concretes that are permanently hardened in water, under air-moist and air-dry conditions after different expansion at the first stage. The self-stress of cement stone is the result of superposition of two processes: the hardening of the structure due to hydration of silicates and its expansion as a result of hydration of calcium aluminates with the subsequent formation of ettringite. The magnitude of self-stress is determined by the ratio of these two processes. The self-stress of the cement stone changes in a manner similar to the change in its expansion. The stabilisation of expansion is accompanied by stabilisation of self-stress of cement stone. Results  The relationship of self-stress, strength and porosity of concrete for injection with a two-stage expansion on the duration and humidity conditions of hardening, taking into account the conditions of deformation limitation at the first stage, is revealed. Conclusion During prolonged hardening in an aqueous medium, self-stresses are reduced up to 25% with the exception of expansion at the first stage and up to 20% with an increase in volume up to 5% at the first stage. The increase in compressive strength is up to 28% relative to the 28-day period.

Abstract. Objectives  It is known that the moisture content of wood has a significant effect on the joint strength of elements of wooden structures. However, there has been little research in establishing a specific relationship between the moisture content of wood and the nailed joint strength of wooden elements. The aim of the study is to determine the influence of capillary (free) and bound (hygroscopic) wood moisture on the strength of nailed connections during pull-out. Methods  Conducting experimental studies. Results Three series of samples were tested. For each sample the maximum nail pulling force was determined, with the ultimate pulling resistance calculated according to the formula supplied by the appropriate Rules and Regulations. The samples of the first series were tested with wood having low moisture content. The samples of the second series were moistened prior to the test by being immersed in water for 24 hours to gain capillary moisture. The samples of the third series were moistened prior to the test hygroscopic moisture absorption by being placed in a desiccator above water for a long time without direct contact. Conclusion  In the course of the study, it was found that both capillary and hygroscopic moisture significantly affects the strength of nailed connections, and that the effect on the maximum pulling force is not determined by the type of moisture, but by its value. The samples of the first series indicated the greatest nail pulling resistance. The samples of the second series had nail pulling resistance less by 48%. In the third series, the strength of the nailed connection was reduced by 31% as compared to the dry wood. The results of the study confirm the necessity of taking into account the humidity during the design and operation of nailed connections.

Abstract. Objectives To consider the possibility of applying the principle of reversing air flows for a centralised ventilation system; to develop a specific scheme for air exchange reversible ventilation, which will take into account the peculiarities of the microclimate of administrative buildings; to select the type of filling of the air-permeable element and justify this choice; to determine the conditions for changing the direction of air movement in the ventilation system and the area of its application; to form a list of equipment necessary for the operation of such a system; to consider the influence of supply and exhaust devices on the heat and humidity regime of claddings. Methods  To achieve this goal, the published thematic material was reviewed and a patent search carried out using Russian and European databases. Data on mathematical modelling of filtration in porous media and experimental results were used. A method for ventilating rooms in administrative building using the reversal of movement of supply and exhaust air streams along the same channels was applied. Results  Schemas for reversible ventilation systems are presented and their modes of operation considered. It is established that the idea of reversing ventilation flows has not yet been applied in the development of centralised ventilation systems. Based on these published materials, it was concluded that the proposed design of supply and exhaust devices can be used in practice. An original air exchange scheme for the ventilation of administrative buildings and design of supply and exhaust devices for this system are proposed. The conditions for changing the operating modes of the system and the scope of its application are determined. Conclusion The use of the proposed ventilation system allows normative air exchange to be provided without using a supply unit during the cold season. This application of airflow reversal allows the potential of natural forces to be used to the fullest extent to ensure the air exchange of the rooms.

Abstract. Objectives The statistical analysis of real accelerograms is considered. For this purpose, graphs of real accelerograms are enlarged in abscissa and ordinate, allowing the appropriate measurements to be made and the accelerograph records to be presented in the form of numerical tables. To process these tables, a mathematical model is constructed that allows statistical studies of actual accelerograms to be carried out. Methods The acceleration of the Earth's surface during an earthquake is represented as a non-stationary random Gaussian process. The non-stationary process describing the acceleration of the Earth's surface is modelled as a function of three random parameters. In this case, the real accelerogram, which is presented in a single copy, is modelled by a random ergodic function. Results  Accelerograms of strong real earthquakes and corresponding fragments of tables are given. An algorithm that allows all parameters of correlation functions and spectral densities to be determined corresponding to real earthquakes is described in detail. A constructed algorithm that allows the statistical parameters of an earthquake to be calculated, including the dominant frequency, the standard deviation, the correlation coefficient and a coefficient that takes into account the non-stationary nature of the earthquake process, is discussed. The parameters of the correlation functions of accelerograms of strong earthquakes that occurred in the cities of Taft (USA) and Gazli (Uzbekistan) are calculated. The results of the study are presented in the form of graphs and tables. Conclusion The algorithm constructed by the authors allows the statistical study of strong earthquakes, whose accelerograms are presented in a single copy, to be carried out and the corresponding correlation function parameters to be calculated. The proposed algorithm can be used for the statistical analysis of accelerograms of strong earthquakes.The parameters of correlation functions can find application in the investigation of seismic resistance of buildings, both with passive and active seismic protection.

Abstract. Objectives  The purpose of this work is to study the dependency of the fluidity of foam concrete mixtures on the water-cement ratio when using various local aggregates and wastes from the Republic of Dagestan and comparing the fluidity characteristics of mixtures for the same watercement ratios. During the experimental work, the following materials were used: M500 cement, siliceous filler (quartz sand from the deposit in the Kumtorkalinsky district of the Republic of Dagestan with a low modulus of grain size, various synthetic foaming agents), perlite sand, ground expanded clay sand (Kizilyurt, Republic of Dagestan), stone crushing screenings (Kizilyurt, Republic of Dagestan). Methods  During the production of foam concrete, a method was used in which foam was prepared in the foam generator, then a solution was prepared from the cement, siliceous component (filler), and water. Then the foam was mixed with the solution in the foam concrete mixer up to the set of the appropriate multiplicity. (The multiplicity in this case was defined as ratio of the volume of the solution of the foam concrete mixture after mixing to the volume of the solution before mixing. During the studies, the water-cement mixture ratio for all three kinds of filler (expanded clay sand, quartz sand from the deposit of the Kumtorkalinsky region, and perlite) was determined. The fluidity index of the foam concrete mixture was determined using a Suttard's viscometer. Results  The results of the research indicated that with an increase in the water-cement ratio for all three types of filler (expanded clay sand, quartz sand from the Kumtorkalinsky region and perlite), the foam concrete mixture fluidity index will increase. Conclusion  With the same fluidity index values, the mixture with perlite filler has the lowest fluidity, which in turn affects the further structure formation of the foam concrete, allowing the optimal composition with the specified properties to be selected.

Abstract. Objectives Leasing, which is an alternative to traditional forms of investment for Russia, is currently among the most effective methods of financing construction organisations. Under conditions of shortage of available financial resources, leasing allows the modernisation of production to be carried out, modern equipment to be used or new production facilities to be opened in the shortest possible time. The purpose of the study is to comprehensively substantiate the specifics of leasing operations in construction and demonstrate its advantages as a tool for financing construction organisations. Methods The theoretical basis of the study was the fundamental provisions of economic, financial and management theory. During the process of research, logical, statistical and comparative analysis methods were used alongside expert evaluation and factor analysis approaches. Results For a leasing company whose purpose is to identify potential risk areas associated with the possibility of exceeding planned costs, it is recommended that a feasibility analysis be carried out prior to forming a loan portfolio. It is established that the transactions of a leasing company with a construction organisation can be presented as a separate investment project with a complex financial structure and a combination of interrelated long-term contracts. It is shown that the standardisation of principles of corporate governance and risk management is capable not only of reducing the susceptibility of a construction organisation to risk, but also of increasing the degree of trust on the part of customers and counterparties. Conclusion The expediency of using leasing in construction is due to the insufficient volume of private funds for the acquisition of equipment, which becomes particularly relevant against the background of rapidly aging facilities of construction organisations. Under conditions of largescale technical re-equipment, in which advanced construction equipment and technologies are being introduced, leasing-based financing approaches can be considered as one of the most effective ways to solve existing problems.

Abstract. Objectives The aim of the study is to develop a methodology for networking between small towns and regional centres on the basis of developing areas of mutual benefit. It is important to assess the possibility of cooperation between small towns and regional centres and local selfgovernment bodies on the example of individual territorial entities of Russia in the context of the formation and strengthening of networks and support for territorial development. Methods Systemic and functional methodical approaches were taken. The modelling of socio-economic processes provides a visual representation of the direction of positive changes for small towns and regional centres of selected Subjects of the Russian Federation. Results Specific examples of cooperation between small towns and district centres are revealed in some areas; these include education, trade and public catering, tourist and recreational activities. The supporting role of subsystems, including management, regulatory activity, transport and logistics, is described. Schemes, by to which mutually beneficial network interaction is formed, are characterised in terms of the specific advantages accruing to each network subject. Economic benefits of realising interaction between small cities and regional centres are discussed. The methodology is based on assessing the access of cities to commutation, on which basis contemporary regional and city networks are formed. Conclusion On the basis of the conducted study, a list of areas for mutually beneficial networking between small towns and district centres has been identified, allowing the appropriate changes in regional economic policies to be effected in terms of programmes aimed at the development of regions and small towns, including those suffering from economic depression.

Abstract. Objectives The purpose of the study is to identify the specifics of the organisation of import substitution of building materials in the sectoral market and the development on this basis of programme actions that ensure the competitiveness of domestic producers in the sectoral market. Methods  During the research process, logical, statistical and comparative analysis approaches were used alongside expert evaluation. Results  It is demonstrated that the transition to import substitution is promoted by price rises of building materials due to changes in foreign currency exchange rates and the unstable situation in foreign trade relations. It is shown that, in addition to the present state of the building materials market,demand for modern technologies constitutes an additional factor determining the strategic priorities of the industry. It is proposed to create a register of innovative products in the field of building materials in the construction product market. The implementation of this programme will allow all the standardisation and technical regulation elements of the construction product market to be linked into a single system matrix.The necessity of implementing the planned policy of import substitution of construction materials in the construction product market is substantiated. Conclusion  In the context of the import substitution policy, the increase in the competitiveness of building materials provides for the expansion of the range of construction materials and an increase in the proportion of innovative goods. Adaptation of the regulatory and legal framework and norms of technical regulation for the production and use of domestic building materials and technologies will favour the promotion of innovative products in the construction product market. In view of the implementation of the strategy for the introduction of innovative technologies in the construction industry, a positive implementation of the import substitution programme in construction is expected, which will create additional jobs and lead to the emergence of new companies and enterprises under increasingly favourable conditions for domestic producers.