The paper is based on a review of the scientific publications released from May through October 2019, the greater part of which, namely 14 papers, is included in the Web of Science scientometric database. The authors of the papers analyzed explore the construction industry problems over the past 5 years. The foreign studies listed in the reference section were based on the analysis of reviews falling in the above-mentioned timeline. The purpose of this paper is to identify the problems hindering the implementation of BIM technologies in the construction sector, not only in the foreign countries, but also in Russia.
Keywords: building information modeling, construction organizations, critical problems, external factors, absence of organizational support
The emergence of digital X-ray machines and the development of cloud storage technology has led to the accumulation of a huge number of medical X-rays, in particular, chest x-rays - fluorography. The accumulated image bases after high-quality preprocessing can be used to train the deep convolutional neural networks that have received the most development in recent years, the trained network performs preliminary binary classification of the incoming flow of images and can be used as a radiologist assistant. For this purpose, it is necessary to adequately train the neural net-work to minimize errors of the first and second kind. A possible approach to improving the efficiency of neural networks, reducing the computational complexity and quality of image classification by the criteria is the use of auxiliary approaches of image preprocessing and preliminary entropy calculation. The article presents an algorithm for the X-ray image preprocessing, its division into fragments and the calculation of the entropy of individual fragments. During the preprocessing, the region of interest with lungs and the spine is selected from the entire image, constituting about 30-40% of the entire image, then the image is divided into a fragment matrix and the entropy of individual fragments is calculated using the Shannon formula, by analyzing individual pixels. By determining the frequency of each of the 255 colors, the total entropy is calculated. The use of entropy for detecting pathologies is based on the assumption of dif-ferences in its values for individual fragments and the overall picture of its distribution between images with the norm and pathologies. Statistical indicators are analyzed: standard deviation of error, variance.
Keywords: image entropy, fragments, deep convolutional neural network, machine learning, x-rays images, computational experiment, matrix of elements, image preprocessing, statistical analysis, binary classification
The reliability of the solar heating system with solar collectors was studied using the logical-probabilistic method by building a fault tree. The fault tree was obtained by sequentially detailing the events associated with failures of the solar heating system, as well as its elements. Events were taken into account: conducting test diagnostics of elements of the power supply system, repairing failed elements, failure of elements, reducing the power of solar collectors due to a decrease in the intensity of the solar radiation. The events were divided into two groups: events in which there is sufficient intensity of solar radiation for the hot water supply from the solar collectors, as well as events when the heating supply cannot be provided only due to the solar collectors. The last group of events was divided into two subgroups, within events caused short-term downtimes (at the time of switching) and long-term downtimes (at the time of replacing or repairing a failed system element). Long shutdowns are associated with the coincidence of failures, repair or diagnosis of one or more elements of the solar heating system. Expressions are compiled to calculate the probability of long downtimes, the probability of short downtimes, the probability of failure due to a decrease in the intensity of the solar radiation, and the total probability of failures. As a result of substituting the values of the reliability indicators of the elements of the solar heating system, the value of the total probability of failure during the year is 4.03∙10-5.
Keywords: solar hot water supply, reliability, solar collector, failure cause, reliability modeling
Various methods are used to scatter warm fogs: direct combustion of fuel in the fog; electric heating of the fog; introduction of streams or jets of warm and dry air into the fog; use of radiant energy for direct evaporation of hydrometeors; using explosions of highly heat-forming substances, etc. . In this paper, artificially sprayed water droplets are used to scatter warm fogs. Refined calculations were made to investigate the possibility of fog scattering by artificial droplets. The model describes the fall of drops of radius r2 through the fog, consisting of drops of radius r1, the concentration of which is equal to n1. Detailed equations of gravitational coagulation are used taking into account the hydrodynamic interaction of droplets. The temporal characteristics of fog scattering (increase in visibility range) depending on the size of artificial droplets and their concentration are investigated. The size of artificial drops and their concentration, at which the maximum effect on fog scattering is achieved, are determined.
Keywords: scattering of warm fogs, meteorological visibility range, concentration of fog drops, fog water content, artificial influence on fog
The article is considered the wall stability of a steel cylindrical pre-stressed granary, compressed by the friction forces of grain and shell, taking into consideration the influence of the grain internal pressure, its elastic resistance from the inside and the elastic resistance of the pre-stressed shell outside. In this case, the initial and subcritical deflection of the shell is assumed to be axisymmetric, and the loss of the shell stability occurs with the formation of asymmetric deflection. The given solution of the problem allows to determine the magnitude of the critical efforts taking into consideration the influence of the grain internal pressure, its elastic repulsion, the magnitude of the initial deflections and the ratio of shell dimensions.
Keywords: stability calculation, wall stability, prestressing, internal lateral pressure, elastic rebound
metamaterials, microwave, antennas, diffraction, Maxwell equations, electromagnetic waves, the dielectric constant
Keywords: metamaterials, microwave, antennas, diffraction, Maxwell equations, electromagnetic waves, the dielectric constant
The article is devoted to the possibility of applying the methods of successive approximations in the analysis of the instantaneous scheme of the traction network. The described approach allows to improve the accuracy of modeling dynamic modes of traction power supply sections, and also allows to significantly improve the process of modeling diagnostic systems and control of electric rolling stock at the design stage based on a more accurate model of dynamically changing input parameters of the traction network depending on their required level.
Keywords: traction network, instantaneous circuit, diagnostics, simulation, iteration
During the harvesting of crops, a significant amount of straw residues is formed, which can be used as raw material for subsequent processing. To assess the volume of straw suitable for processing for various needs of the agro-industrial complex, it is proposed to apply the Lotka-Volterra method. Using this method, it is possible to predict the formation of straw residues depending on the initial indicators during harvesting.
Keywords: straw residues, processing of straw raw materials, modeling, Lotka-Volterra method
This article is devoted to the study of the problem of power supply of low-power consumers distributed along the path of electric Railways AC, which can act as a system of sensors diagnostics of automated control systems of various objects located along the contact network. The main part of the article is devoted to the description of the primary model necessary for further consideration of such a method of electric power supply and experimental modeling.
Keywords: contactless power transmission, capacitive communication, power supply, contact network, electric Railways
Automation of agriculture is currently a promising and actively developing branch of robotics. At the moment, there are many foreign analogues offering ready-made solutions for automatic control of sowing crops. However, in Russia, most of the sowing is carried out on mechanized plants under the mandatory supervision of a highly qualified specialist in the maintenance of the plant.
Keywords: seeding control, microprocessor system, selection, seeding algorithm, system architecture, hardware, system structure, layout base, management methodology, import substitution
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
A method for the quasi-optimal synthesis of a multi-mode synchronization system based on the maximum condition of the generalized power function has been developed. The effectiveness of its operation in capture mode is demonstrated on the basis of mathematical modeling. The results showed high resistance to disturbances and a decrease in the synchronization error of the multimode system in the steady state.
Keywords: phase locked loop, combined maximum principle, multi-mode control
The article discusses the methodology and concept of situation rooms. The methodology and concept of situation rooms has a long history. As a first step, one can recall the methodology of a classic board in Cretaceous technology. Smart boards have now emerged, where hardware and software are present alongside the light pencil, to display various kinds of information. The second level in cognitive modeling systems is the collective panel display of various information products. Finally, the third level of situation rooms implies a significant development of the software and hardware of the decision-maker support complex. The high level of complexity of the third stage in the creation of the situation room is the creation of developed mathematical support in brainstorming tasks, as well as in the provision of analysis of weakly structured systems. However, while our work deals with the creation of a theoretical model of semantic identification of various scenes, situations of the person making the decision.
Keywords: Information collection and display system, decision maker, electronic counteraction
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
This article may be of interest to researchers who are designing new machine systems for felling-area works with autonomous energy supply. A methodology based on the decomposition method for creating an simulation functional model of a system consisting of a mobile wood chipper for felling-area works and a mobile energy module is proposed. The machine system of interest is an original technical solution. It consists of an autonomous energy supply module with powered by wood fuel external combustion engine and a logging machine for the production of wood chips. The functioning equipment units of the system is simulated using the MATLAB Simulink dynamic simulation environment. For the convenience of experiments, the use of LabVIEW virtual instruments is proposed for setting input and control parameters, as well as displaying output parameters. The input, control, disturbing and output parameters of each functional block of the system are described: gas generator, external combustion engine, electric generator, uninterruptible power supply, electric motor, propulsion device, wood chipper unit, hydraulic manipulator. It is supposed to use this simulation model to justify the main parameters of the autonomous system for the production of wood chips, as well as the further development of an automated control system.
Keywords: fuel chips, wood fuel, unmerchantable tree, simulation model, LabVIEW, Simulink, mobile chipper, autonomous power supply, logging