Статьи журнала - Журнал Сибирского федерального университета. Серия: Техника и технологии
Все статьи: 1367
Статья научная
The article is devoted to the determination of the fractal dimension of the porous surface and further finding the relationship of the fractal dimension with the porosity of cellular concrete. A numerical experiment was carried out aimed at determining the fractal dimension of the structure of cellular concrete in order to clarify the relationship of the latter with its porous structure. An approach has been developed to assess the properties of cellular concrete based on the analysis of its image.
Бесплатно
Anodic behavior of Zn22Al alloy, doped with erbium
Статья научная
The article presents the results of a potentiodynamic study of the anodic behavior of the Zn22Al alloy with erbium dopants in various corrosive media of HCl, NaCl and NaOH electrolytes. Erbium alloying additions corrosion rate in various corrosive environments. In this case, there is a shift in the potentials in amounts of 0.01÷1.0 wt.% somewhat increase the anode resistance of the Zn22Al alloy by reducing the of corrosion, pitting formation and repassivation of alloys to the region of positive values. The dynamics of changes in electrochemical potentials favorably affects the parameters of the corrosion resistance of alloys. Erbium additions monotonically reduce the corrosion rate of the anode Zn22Al alloy in various media.
Бесплатно
Antenna arrays on surfaces of revolution
Статья научная
In this paper explicit analytical expressions are derived which describe radiation pattern of multi ring antenna array and multi ring continuous radiator allocated on an arbitrary surface of revolution. Radiation patterns of semi-spherical, conical and hyperbolical antenna arrays are shown.
Бесплатно
Application of error - correcting coding in hydroacoustic communication channels
Статья научная
The paper considers the possibility of using error-correcting coding in hydroacoustic communication channels (HACC).Comparison of test results shows that errors substantially packaged, resulting in increase of error probabilities with the large multiplicity and the likelihood of receiving a code word without error. Results of comparative statistical studies of these codes on a channel model with impulse hindranceare listed. As a result of theoretical and practical studies of various structures of error protection device (EPD) to improve the noise immunity of equipment sonar communication systems (HACC) was selected the algorithm of error correction, which is based on convolutional code R = 1/2 with block, the threshold, the iterative decoding. To ensure the independence of errors at the decoder input (decorrelation of error stream), the matrix interleaver are encouraged to use in the EPD.
Бесплатно
Application of methods combined treatment for obtaining welding wire from silumins
Статья научная
Developed technology of obtaining rods and wires from silumins using casting in electromagnetic crystallizer and follow combined rolling-extruding and drawing. Were carried studies of properties of deformed semi-finished products and obtained experimental batches of welding wire from alloys AlSi5 and AlSi12.
Бесплатно
Application of modified sorption material for efficient wastewater treatment of galvanic production
Статья научная
The galvanic production is one of the source of environmental contamination by harmful substances and especially heavy metals. The questions of water pollution prevention by wastewater containing heavy metal ions, are closely linked to the development of event to reduce fresh water consumption for technological needs of production and to reduce the amount of wastewater. One solution to this problem is the creation of low-waste and waste-free environmentally safe production processes of sewage treatment with the use of treated wastewater in the working cycle, which leads to a reduction of negative impacts on the environment.
Бесплатно
Статья научная
Entropy criteria of traction substations of 110-220 kV schemes’ unreliability are considered in this article in the conditions of indeterminacy of schemes’ conditions. It is shown how the application of entropy estimates during scheduling reconstruction of traction substations allows to estimate effectiveness of measuring to increase non-failure operation and substations’ schemes electrical connections availability.
Бесплатно
Статья научная
The article considers the application of two approaches to optimizing the direct-flow burners and nozzles location using numerical simulation. The study objects are two furnaces of the traditional and invert type with solid slag removal for boilers for supercritical and ultra- supercritical steam parameters, respectively. The lean hard Kuznetsk coal was used for both cases, somewhat different in characteristics in the cases under consideration. This coal type is currently burned mainly in furnaces with liquid slag removal. The use of the zone-by-zone optimization method implies a sequential each pre-selected zones optimization of the furnace in the direction of flue gas movement with modeling of the solid fuel combustion process with different burner and nozzle layouts. A dimensionless scheme for burning coal dust in a traditional furnace with an upward flue gases movement has been developed. The use of a simplified numerical model (SNM) due to certain settings made it possible to approximate the results of furnace aerodynamics modeling without taking into account the chemical reactions to the results with combustion simulation, which significantly reduced the conducting research time. As a result of modeling the invert furnace aerodynamics, the optimal arrangement of direct-flow burners and nozzles was selected. The article discusses the main features of each research method use, optimization criteria, research objects, initial combustion schemes, design parameters of combustion schemes that are changed during optimization, as well as the main results of the optimization. The solid fuel combustion schemes obtained using two approaches to conducting research using direct-flow burners and nozzles ensure the operation of the considered furnaces with better values of efficiency and environmental indicators than traditional combustion of similar fuel in furnaces with liquid slag removal. The obtained values are at a level acceptable for the Russian Federation.
Бесплатно
Application of «gradient» algorithm to modeling thermal pipeline networks with pumping stations
Статья научная
The paper deals with the analysis of flow distribution in regulated pipeline systems. Proposed inclusion of nodal elevations and piezometric heads into «global gradient» system of equations allows estimation of hydraulic regimes of thermal networks with pump stations, flow- and pressure-control valves during the process of iterative approach. Application of proposed modification of the Todini’s GGA method to calculation of flow distribution is shown on example of a small thermal network with pumps.
Бесплатно
Approaches to nordifikation of high-latitude construction engineering
Статья научная
The simple mechanical transfer of structural technologies to high-latitude construction engineering is not efficient. But construction engineering nordifikation seems to be effective and expedient, for example working camps. Severe, extreme conditions in the Arctic are similar to extraterrestrial, for example, Martian therefore use of space technologies is required here. From this point of view, it is expedient to build space frame constructions such as: domes, lenses, spheres, Rello’s cones united by the covered transitions of ribbed type or the common covering, having good aerodynamics. In this article is emphasized the rationality of designs made of timber itself and wood materials that defines need of creation of the glued elements industry, that is possible only in presence of government support.
Бесплатно
Approaches to simulation of interaction of concentrated solar radiation with materials
Статья научная
The paper analyzes approaches to modeling the processes of interaction of concentrated solar radiation with materials. The experimental results obtained on the synthesis of materials from a melt in a solar furnace are presented. It is shown that when melting in a solar furnace under the influence of concentrated solar radiation of high density due to the acceleration of the recovery process, it is possible to obtain a fine-grained microstructure that gives the material enhanced mechanical and dielectric properties. It is shown that the relationship between the structure and properties of the materials obtained with the technological parameters of melting and cooling in a solar furnace can be used as an approach to modeling the interaction of concentrated solar radiation with materials.
Бесплатно
Статья научная
The architecture and the main characteristics of an information system are presented in article, they allow to solve a complex of the problems connected with estimation of a condition of agricultural lands on the basis of processing of spatial data. The system is based on the ontology of estimation of agroeconomic capacity of lands developed by authors.
Бесплатно
Статья научная
For crystals grown from the liquid melt using the Czochralski method, the mathematical model of the current control chip area by controlling the conditions of the contact sensor circuit level of the melt in the crucible, which allows to calculate the control signal, as the difference between the current and the target area grown crystals.
Бесплатно
Assessment of agroecosystem productivity based on satellite data and a mathematical model
Статья научная
The possibility of determining seasonal dynamics of agroecosystem productivity was estimated based on the combined use of satellite data and results of a mathematical model study. The study showed a qualitative agreement between normalized difference vegetation index (NDVI) and the total aboveground phytomass of the wheat and oat agroecosystem. Analysis of the mathematical model proved the possibility of prediction and improvement of the crop yield estimate. A distinction has been made between the vegetative and reproductive biomass of the agroecosystem. Results of mathematical modeling were in good agreement with ground-truth data in the case of nutrient (nitrogen) limitation.
Бесплатно
Статья научная
Dynamic behaviour of isotropic rectangular plate resting on two-parameter foundation is investigated. The governing partial differential equation is transformed to ordinary differential equation due to Galerkin method of separation. The hybrid method of Laplace transform and variation parameters method is used to analyze the ordinary differential equation. Introduction of exact method helps in fast convergence of the results. Obtained analytical solutions are compared with existing literature and confirmed as accurate. They are used to examine the effect of controlling parameters on the plate natural frequencies. Due to obtained results it is obvious that, the increase of both elastic foundation parameter and aspect ratio results in increasing the natural frequency. The solution is found immediately by means of a few iterations.
Бесплатно
Bench mark prebaked anode production with Russian raw materials
Статья научная
Expansion of the Russian aluminium smelting is foreseen by using high amperage Rusal prebaked pot technology. For a high productivity of such modern smelters - thanks high amperage but also high current efficiency, but also for low energy consumption - the performance of the prebaked anodes is decisive. Bench mark anode quality is therefore critical for low metal production cost. The intrinsic quality of anodes depends on the raw materials, mainly on the coke properties, and on the production equipment and their operating parameter conditions. Based on a review of the domestic available green cokes, a prediction of the corresponding calcined coke blend and of the prebaked anode properties has been performed. Provided that a state of the art carbon plant installation is available, including the rodding shop for the butts quality, the bench mark quality of the prebaked anodes made with a representative coke blend has been defined. This forecast of the best achievable anode quality will be the basis for technical assessments of the performance of existing and future Russian carbon plants.
Бесплатно
Bit error ratio, caused by Doppler effect, for systems of space diversity reception
Статья научная
Today digital data transmission plays a leading role for satellite systems. However, digital data transmission is possible with errors at demodulation, which cause distortion of transmitting information. Errors of digital data transmission are due to three causes. First cause is a low level of signal to noise ratio. Second cause is Doppler Effect. Third cause is symbol-to-symbol interference conditional multipath propagation. Space diversity reception is effective method of bit error resistance. Doppler Effect is the most significant for bit error probability at satellite communication. Because satellite move very fast in cosmic space. This article show effective of space diversity reception for decrease of bit error probability, which caused by Doppler Effect.
Бесплатно
CFD of stationary supercavitating evaporator with steam extraction in constrained stream
Статья научная
Water flow with various temperature and velocity applied to the stationary cone cavitator with fixed dimensions in constrained flow combined with changing specific rate of steam extraction from the supercavity capture influence on cavitation number and the cross-sectional variation in threedimensional supercavity size. Total of eight numerical experiments resolve multifactor response. Three-dimensional simulation using ANSYS CFX v12.1 involving turbulent water-steam flow and heat-mass transfer shows that supercavity length is directly proportional to inlet temperature, and decreases with growth of specific rate of steam extraction. Reduction of the cavity dimensions during the steam extraction leads to the thinner supercavity. Therefore, results of CFD approach for stationary supercavitating evaporator with steam extraction qualitatively confirm with recent experimental results. Moreover, information about geometry, meshing, and setup of the problem, reveals the ways to improve the model and their difficulties.
Бесплатно
Статья обзорная
This article compares the performance of two modulation techniques - quadrature phase shift keying (QPSK) and M-ary quadrature amplitude modulation (M-QAM) with M=8, 16, 32, and 64-in a coded orthogonal frequency division multiplexing system. As an error-correcting code, convolutional technology is employed. A vehicular channel with additive white gaussian noise (AWGN) is utilized for communication. According to simulation data, for QPSK and M-QAM, a coded orthogonal frequency division multiplexing system performs better than an uncoded one. Additionally, the system performs better with QPSK than it does with M-QAM. Additionally, when M rises, the performance declines.
Бесплатно
Статья научная
A three-dimensional mathematical model of the solidification process of a liquid metal is considered, taking into account the mobility of the boundaries at which the phase transition is carried out (Stefan boundary value problem). The algorithm of calculation is improved, allowing due to the use of the Dirac δ-function in determining the effective heat capacity to take into account the nonlinearity of the equation of unsteady thermal conductivity and the heat of the phase transition. A numerical study of heat transfer during solidification of lead-containing aluminum melt droplets in air and water is carried out. The influence of droplet size and melt overheating on the solidification dynamics of granules has been studied. An approximate ratio based on the square root law is proposed, taking into account the amount of overheating of the liquid phase and linking the thickness of the formed solid phase with the duration of the granulation process.
Бесплатно
