The paper presents analytical estimates of the proximity of solutions to boundary value problems for elastic-creeping layered composite materials widely used in technology under long-term loading, and also gives the corresponding averaged model for such materials. The estimates show the possibility of using the averaged model over a long time interval for the problem of loading by a constantly acting force. Previously, this statement was confirmed by numerical experiments comparing solutions of boundary value problems for an effective (averaged) model and direct numerical calculation using the original model for a highly inhomogeneous layered material. Analytical estimates are based on previously obtained estimates of the proximity of solutions to stationary problems of elasticity theory. For the one-dimensional model considered in this work, the following property is established: if the constitutive relations for various phases of the composite material are written as dependences of deformations on stresses, then the coefficients for the same form of writing the constitutive relations of the averaged model are obtained as simple weighted average values ​​of similar coefficients for individual phases.

Keywords: layered composite materials, creep theory, averaging method, evaluating the efficiency of the averaging method, asymptotically long time interval

This article is devoted to the study of indoor air quality in a higher education institution: assessment of the distribution patterns of suspended solids by equivalent diameters (RM0.5, RM1, RM2.5, RM5 and RM10).

Keywords: indoor air, indoor air quality, air pollution, dust, solid suspended particles, PM2.5, PM10

Modern trends of the concretes studies have been considered. Properties of the materials and additives used have been cited. There has been undertaken designing an experiment on a complex modifying additive application for a fine fibre-reinforced fine-sand cocrete. The results of the studies undertaken have been analyzed with regard to their statistical significance. On the bases of the reseach results there have been acquired regression equations for objective functions responses, namely ultimate strength on both compression and bending, and average density of fine fibre-reinforced concrete. There have been produced contour plots and those of response function surface - ultimate strength under compression for all combinations of the both factors. There have been determined the composition of the modifying additive, which ensures maximal strength properties for fine fibre-reinforced fine-sand concrete.

Keywords: fine concrete, complex additive, designing an experiment, strength, regression equation, plots of response function surface

In order for a person with an amputated limb to regain motor activity, should be created fitting lower limb prosthesis and able to movement. The goal of this research is to improve a passive prosthesis depending on microcontroller-unit, transfemoral prosthesis that can reach to the desired of rotational speed for functional use while remaining low-cost. The improvement of this design focuses on creating a new knee joint mechanism using a DC motor pre-existing, the foot, and the socket can get from the previous model. This entails simulating normal limb function while also enhancing the knee prosthesis range motion. the specific requirements that must be realize in this design, such as the knee joint new model ability to flex up to 90 degrees and be strong enough to support the weight of the amputee's body.

Keywords: knee joint, prosthetics, Solid works, ANSYS software, aluminum 6061-T6, stainless Steel 4130

The results of the automated evaluation of the dynamic quality of grinding machines in the process monitoring system are presented. The transfer function of the dynamic system is analytically obtained, a formula for the frequency function is derived from it, on the basis of which models of vibration spectra are constructed, in which frequencies are present that are adequate to the real vibro-acoustic vibrations of the dynamic system of the machine when processing rings. For experimental evaluation of the dynamic quality of machine tools, integral estimates of the low-frequency components of the vibration spectrum are used, characterizing the relationship between the quality of processing bearing rings and the dynamic quality of machine tools.

Keywords: dynamic quality of the grinding machine, vibroacoustic vibrations, bearing rings, processing quality, monitoring system

The study examines the manufacturing process of two types of ankle-foot orthoses (AFO): an adjustable joint and a modified static joint. Polypropylene and steel are used in manufacturing. Vacuum forming is used in the manufacturing process. The ankle orthosis test is performed on a patient with an ankle fracture as a result of a sports injury. The treadmill and F-Socket are used in the second step of the study for gait analysis. In addition, walking cycle results including: ground reaction force (GRF), center of pressure, pressure distribution, stride length, and footprint analysis were used to demonstrate a significant difference between healthy subjects and subjects with pathology who wore AFO. Interference, force, and pressure between feet with AFO contact areas were measured for all subjects.

Keywords: orthosis, ankle-foot orthosis, prosthetics, lower extremities, manufacturing procedure, subject with pathology, subject without pathology

The article describes the simulation in the Simulink environment of the operation of a stepper motor used as an electric drive of the scanning mechanism for the Earth orientation device. The purpose of the study is to determine the minimum power consumption in each range of values for inductance and resistance. If the model is found to be inoperable above certain values of the specified parameters, the measurement range narrows to an area where there is enough energy to properly work out a given angle. The simulation is based on the parameters of NEMA17 engines, in particular, NEMA 17HS3410. Voltage control in the system is carried out by means of a PI controller, the influence of the regulator on the energy consumption of the system is shown. The regularities of the formation of angular velocity of various amplitudes when working out a turn in open and closed control systems are noted. The range of electrical parameters at which the engine operates with almost the same power consumption is determined. The lowest power values at which the engine is operable are found. The results of the work are visualized in the form of three-dimensional surfaces, recommendations for the continuation of research are developed.

Keywords: stepper motor, simulation, Earth orientation device, power consumption

The development of technical devices in almost all industries is aimed at creating universal devices that allow performing several operations. The forest industry is no exception. The creation of a taxation tool that provides the ability to perform several measuring operations, which is the goal of the work, will increase the efficiency of the taxator while reducing the physical load on him due to the need to have fewer measuring instruments with him. All this indicates the relevance of this work. To achieve this goal, a number of tasks were solved in the course of the work, the main of which were: analysis of known designs of taxation instruments, synthesis of new technical solutions for their unification, patenting of a new technical solution. The use of system analysis made it possible to achieve the set goal, to propose a new patentable solution for a taxation device that combines the functions of an altimeter and a full gauge. The approach described in the paper to the creation of new designs of universal taxation devices can be used in teaching engineering creativity to students.

Keywords: full gauge, altimeter, taxation, forestry

Refrigerating machines are designed to cover peak heat generation in public buildings. At the same time, peak loads are often short-term and most of the time the refrigerating machines operate at 40-60% of their maximum capacity. The article deals with the issues of uneven cold consumption on the example of a sports complex located in Volgograd. When designing the air conditioning system of the games hall, a cooling system with the use of "chiller-fan coils"is used. An effective solution to reduce costs is to include a cold storage battery in the cooling station circuit. The use of a cold storage battery allows you to reduce operating costs.

Keywords: cooling system, air conditioning system, refrigeration machine, cold storage, energy consumption, peak loads, variable energy consumption

The paper presents the results of a study aimed at selecting a safe depth of an underground collector. In the scientific and normative literature there are no specific recommendations for the depth of tunneling through the existing highways. There are only recommendations for tunneling through railway embankments. Purpose of this study: scientifically substantiated recommendations for the use of reinforced concrete pipes as collector cases. The decision of problems for achievement of the objective will be carried out by means of numerical experiment - a method of finite elements.

Keywords: reinforced concrete case, underground collector, safe depth, mathematical modeling, case structures, highway, closed method of work, trenchless laying, finite element method, subsidence trough

The issues of optimization of ribbed reinforced concrete slabs with prestressing of reinforcement, taking into account geometric, strength and cost indicators, are considered. The study was car-ried out on the basis of an analysis of the sales market for building materials, the basics of rein-forced concrete resistance and the provisions of regulatory documents, design activities in the Russian Federation, as well as the works of domestic and foreign scientists. The research method is structural-analytical analysis taking into account the relationships of the factors under study. Analytical and graphic materials are presented, revealing the regularities between the geometric dimensions and the cost of components. The proposed method for determining the efficiency of a structure, taking into account the cost indicators of materials, indicates the feasibility of its ap-plication in design practice. Recommendations for design are given to ensure that structures of the minimum cost are obtained and that meet the requirements of strength and durability.

Keywords: reinforced concrete, strength, structure, reinforcement, diameter, price, cost, efficiency, dimen-sions, analysis, element

The article proposes a method for assessing the risk of a possible stay of an automated special-purpose information system in a critical state, based on the synthesis of two heterogeneous mathematical models, one of which allows taking into account the intensity of DDOS attacks and the intensity of application processing, based on Markov processes, and the second is one of the forms of a formal description of protection systems, with complete overlap, in which the interaction of the "threat area", "protected area" is considered – areas of resources of an automated information system for special purposes, and "protection systems" – security mechanisms of an automated information system. The developed method makes it possible to simulate the information security tools included in the automated information system for special purposes, under the influence of DDOS attacks, taking into account both the empirical values obtained as a result of measurements or modeling, and the theoretical base of parameters specified by input data. In the synthesis of the two models, the lack of uncertainty of some of the input parameters, taking into account the values based on expert estimates, was eliminated.

Keywords: automated information system, security assessment, queuing system, risk

This article discusses the importance of timely defect detecting of automated electronic car control systems for prevention of serious failures. Also the first stage of mathematic modeling mechanism is presented, it includes construction models of the dependence of the number of failures by time with various methods of diagnosting the technical condition of the car.

Keywords: diagnosting, modeling, technical service of the car, failure, automated system, electronic control unit, engine

The use of metal structures as load-bearing elements of building frames is incredibly extensive. They are used in all areas, from the construction of bridges to the construction of airports and other equally important facilities. Based on this, it is necessary to design such structures extremely accurately, take into account all possible effects on the elements of the building and lay the necessary safety margins. In turn, fire, as one of the extraordinary loads, must be investigated in all its aspects. From the study of the development of a fire, to the structural analysis of elements exposed to fire. This article is devoted to determining the fire resistance of steel beams by two approaches - analytical and numerical, as well as comparing the results. After testing the beam with two methods, it was concluded that the maximum value of the deflection rate in the analysis is 32.6 mm/min, which exceeds the limit value. Since only one limit condition is exceeded, the beam is considered to meet the R30 fire resistance requirement. To increase the fire resistance of the structure, it is necessary to apply various methods of protecting the beam section.

Keywords: metal structures, load-bearing element, extreme load, structural analysis, fire impact, fire resistance

In this article, the object of study is a research drying chamber of a convective type, in the design of which a condensing heat exchanger based on a vapor-compression heat pump is introduced. The drying process of lumber refers to energy-intensive technologies, since the share of drying in the cost of finished materials reaches 50% [1]. In the presented experimental study, comparative results of two operating modes of the experimental installation are presented: standard (soft mode) and recirculation mode with a condensate dryer. The obtained experimental drying curves show that the cost of electrical energy, taking into account the option with a condensing heat exchanger, decreased by 7.75% compared to the standard.

Keywords: drying modes, drying, heat pump unit, heat recovery unit, material balance, heat balance, moisture content, heat consumption, experimental setup