Cementation studies focus almost exclusively on the movement of carbon, described through the diffusion equations, often with constant coefficients and without regard to temperature. This approach does not allow, to take into account the further diffusion of carbon into the workpiece in a lower temperature range at the stage preceding quenching. The paper describes the modeling of the diffusion saturation of steel by carbon in the cementation process, taking into account the influence of temperature on the example of a numerical solution of the gear cementation problem using the COMSOL Multiphysics program. It was shown that the finite element mathematical calculation of the process of saturation of austenite with carbon during cementation gives good agreement with experimental data, and finite element analysis methods can be used for multivariate calculation of the carbon content in austenite after diffusion saturation
Keywords: carbon diffusion, carburization, COMSOL Multiphysics, numerical modeling, carbon distribution, carburization, Fick diffusion law, mass transfer, heat transfer, gear, finite element method
During the year, depending on the latitude and climatic zone, the number of thunderstorms and their intensity vary greatly, these parameters decrease to the Northern latitudes due to a decrease in humidity and temperature and, accordingly, a decrease in the probability of forming conditions for the formation of convective and thunderstorm clouds. The article deals with the mechanisms of dangerous effects of lightning discharges. The electric parameters of the discharges for thunderstorm processes in the atmosphere were studied using data from the geophysical monitoring center of the FGIBU "VGI", which includes a network of sensors of the automatic thunder-gauge finder - the range finder LS8000. The results of the analysis of the recording of ground-discharge currents and the time of their growth obtained during the period of its operation are presented. The authors determined the statistical distributions of the lightning current amplitude. It is established that the discharge parameters in different regions differ and can change with time. This means that for the effective operation of lightning protection systems and the implementation of measures to ensure life safety during thunderstorms, it is necessary to monitor the lightning situation in each individual region.
Keywords: atmospheric electricity, lightning discharges, lightning guides, lightning protection measures, life safety
The work is a continuation of the study of cable-stayed roofs of large-span sports buildings, it focuses on the technological aspect of the construction of stadiums and sports palaces. Due to the introduced criterion of the location of the assembly of structures, the systematization of technologies for the construction of facilities currently commissioned has been carried out. The result of the work is a comparative table that allows to rationalize the choice of methods of pre-assembly and installation.
Keywords: cable-stayed covering, large-span building, steel cable, cable, pylon, sports building, stadium, hanging roof, cable installation, pre-assembly, jack, disassembly of scaffolding
A method for the intellectualization of measurement procedures has been developed. It is based on the step-by-step optimization procedure, which provides a reduction of the stochastic estimation problem to a number of deterministic problems. The task of the first stage of optimization is the synthesis of an adaptive mathematical model of the measuring process based on the combined principle of maximum, which, unlike the known methods, will ensure the constructiveness of its use in the next stages of optimization. The task of the subsequent stages of optimization is to solve the estimation problem based on the regularization method A.N. Tikhonov. Equations of an iterative measurement procedure are obtained that differ from the state transition vector functions known in structure. It belongs to the category of intelligent measuring procedures, since it makes a targeted choice of the closest to the true value of the assessment of the measured parameter in the conditions of structural uncertainty of the model of the studied object and parametric uncertainty of the observation model.
Keywords: two-stage synthesis, intellectualization, the combined principle of maximum, regularization
Phantoms are an imitation of biological tissue. With the help of phantoms, it is possible to simulate the propagation of light in biological tissue. During any biophysical experiments there is a need for the constancy of the initial conditions of the experiment. The use of solid phantoms that do not degrade over time and under the influence of external factors is the Foundation for reliable results and repeatability of the experiment. The creation of phantoms of biological tissue containing fluorescent nanoparticles or nanoparticles with high absorption, and which correspond to specific mechanical or optical properties, is an urgent task. The paper describes the development, fabrication and characterization of solid tissue phantoms containing gold and upconversion nanoparticles. Optical and mechanical properties of phantoms are studied. The temperature range suitable for the use of samples as phantoms of biological tissue for laser thermolysis problems was revealed.
Keywords: phantom, gold nanorods, luminescence, quantum dots, thermogravimetric analysis
The paper presents an analytical description of the unfolding surface of one of the products of light industry – aerodynamic shape. All surface elements are designed in the Maple environment based on the 4GL package commands. A set of commands allowing to describe surfaces and spatial curves analytically is proposed for the construction of 3D graphical objects. Elements sweep aerodynamic shape are conical and cylindrical sweep with a special character of their boundaries. The proposed description of the surface of the air shape allows you to design a technical product of specified geometric dimensions according to the calculated geometry of the elements of the air shape.
Keywords: description of the spatial shape of aero figures, Maple 2015 package, 3D graphic objects of conical and cylindrical types, 2D scanning
This article discusses strategies for the introduction and development of BIM technologies in a number of leading countries in this area. Based on the analysis of literature and other sources, the main factors influencing the BIM implementation process are highlighted. As a result, it was concluded that the role of the state in the implementation of BIM is quite high. Countries in which BIM is implemented with government support will succeed more quickly and more likely.
Keywords: BIM, information modeling, implementation, implementation strategies
The paper presents an analysis of stadiums with cable-stayed roof, in the context of progressive solutions used in various construction cycles. On the basis of the systematization carried out, the directions of the rational use of the identified methods of reducing material consumption and deformability, increasing the rigidity, stability of structures, improving the efficiency of installation work have been highlighted.
Keywords: cable-stayed roof, long-span building, steel cable, aerodynamics, cable-stray, pylon, sports object, stadium, hanging roof, translucent roofing, light opening roof, monitoring system of the technical condition of the object, cable roof mounting
Restoration and strengthening of building structures damaged during operation in conditions of constant soaking and aggressive influence of liquids. On the example of the overhaul of the floor structures of the premises and tunnels of the champagne factory "Abrau-Durso" were shown the most effective and technological ways to strengthen the load-bearing structures.
Keywords: shotcrete, concrete, reinforcement, bearing structures, reinforcement, bearing capacity, shotcrete, reinforcement, corrosion, repair, finishing
The main features of the technology of continuous basalt fiber production at the «NPO Vulkan» (LLC, Perm, Russia) are given. As raw materials the study has been used CEM I 42,5 N (activity 45,1 MPa), natural sand with a fineness modulus of 2.3, gravel of dense gabbro-igneous rocks (size up to 20 mm), basalt fiber length of 6 mm and diameter 11 microns production "NPO Vulcan" (LLC, Perm, Russia). The results of determining the ultimate strength in compression and bending of fine-grained and heavy concrete without the addition of basalt fiber (control composition) and with the addition of fiber 0.1-0.9% by weight of cement are described. It is shown that the optimal limits of the introduction of fiber into the mixture of sand concrete can be considered 0.1-0.2% by weight of cement, which leads to an increase in compressive strength up to 70% and bending strength up to 35%. A further increase in the fiber content to 0.9% leads to a decrease in compressive strength to 27% compared to the control values.
Keywords: basalt fiber, sand concrete, heavy-weight concrete, fiber concrete, continuous fiber, optimization, disperse reinforcement
The paper reveals data on the development of simulation models of integrated circuit pulse voltage converters for applying in automated measuring equipment used in the tests of integrated circuits. The integrated circuit of switching voltage converter LM2676 was simulated taking into account heat generation and taking into account the mutual influence of crystal temperature on external electrical characteristics as part of a general behavioral model.The authors obtained results and dependences, coinciding with the experimental data and with the SPICE model at the transistor level, that reflects the influence of the crystal temperature on the the chip operation. In addition, the authors consider a possibility of using behavioral models as a source of reference information in the process of testing electronic components.
Keywords: ATE, integrated circuit (IC) testing, switching voltage converters, behavioral model, VHDL-AMS
Innovative organizations have begun to use fixed-wing Unmanned Aerial Vehicles (UAVs) for healthcare delivery since they can fly faster and provide a proper solution in locations with difficult access or unsafe to human life. Moreover, they assure greater utility and better cost effectiveness than manned aircraft. However, the wind affects both the longitudinal and the lateral variables of the fixed-wing UAV contributing to its nonlinear and due to such external disturbances the UAV can fail its mission. Therefore, this review paper discusses on effects of wind disturbances on navigation of fixed-wing UAV. Full nonlinear equations of motion by including the effects of the wind on the fixed-wing UAV performance are developed. Also an overview of different approaches is presented.
Keywords: Unmanned aerial vehicle, fixed-wing UAV, navigation control, wind disturbances
In article the situational centers operating in the territory of Russia in the educational sphere are considered, their classification is offered and need of expansion of functionality of their activity is revealed. The structural model of the innovative situational center within the certain region allowing to carry out processing of big data arrays that will increase efficiency of decision-making process in crisis situations is developed. This model is universal and applicable to any region.
Keywords: situational center, education, model, region, information systems, management, digitalization, information system
The composition of fine-grained fiber-reinforced concrete using Portland cement, stone crushing waste, volcanic ash and basalt fiber are considered. It was revealed that with an increase in the ash content in cement, the compressive and flexural strength of fine-grained concrete decreases, and the water absorption increases. Without a significant reduction in the properties of fine concrete, you can enter no more than 10% of volcanic ash.It has been established that with an increase in the content of large fractions of aggregate, the compressive and flexural strength of fine-grained concrete increases as a result of a more compact arrangement of sand grains. The increase in the content of fine sand fractions reduces the strength characteristics of concrete, and increases water absorption. The dependence of the properties of fine-grained fiber-reinforced concrete on the method of mixing the mixture and molding products
Keywords: portland cement, stone-breaking wastes, volcanic ash, basalt fiber, grain size distribution, fine-grained fiber-reinforced concrete, bending strength and compression, method of mixture preparation, method of molding products
The task of identifying the properties of concrete and the location of damage in the layout structures of the beam type based on the application of experimental vibration analysis is considered. As a simple analysis model, beam constructions are defect-free and with defects. Based on the experimental approach, the model oscillations with shock and vibration excitation are analyzed. Based on analytical modeling, the dynamic modulus of elasticity, the speed of sound in the beam, the location of the defect are calculated. A technique and an example of determining the location of a defect in beam-type structures is presented. The article was published as part of the implementation of the program of the International Forum "Victorious May 1945"
Keywords: vibration diagnostics, identification, beam type construction, defect, experimental approach, analytical modeling, vibration excitation