Статьи журнала - Журнал Сибирского федерального университета. Серия: Техника и технологии
Все статьи: 1404
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.
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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.
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Calculation features of trapezoidal combined ribbed slabs on wooden frame
Статья научная
The article describes the features of design and calculation of ribbed slabs on wooden frame with trapezoidal plan, where the cover is included in the general work of the structure on operational loads. The field of possible application of the investigated elements is shown. The features of trapezoidal slab design are described. The main provisions of the proposed method of the considered structures class calculation are reflected. The formula dependencies of trapezoidal slabs calculation on deformations have been determined due to the use of the calculation method of structures that consist of different module materials; the outcomes of previous numerical studies carried out by the authors of the paper as well as the algorithms of a numerical functions determination based on a particular integral method. The location of a weak slab section when calculating on a normal stress has been defined with the regard to a part of an operating cover, which varies along the span length. It is shown that the proposed method allows to assess adequately the stress-deformed state of trapezoidal slabs and to calculate them on strength and rigidity according to the suggested algorithm.
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Can the toxicity of asbestos be reduced?
Статья научная
Asbestos, an extremely useful natural resource, has been studied extensively mineralogically and for industrial application. Its extraction from ores has been greatly improved with respect to safety in the work place. In spite of that, there is a decisive effort in many countries to ban its use on the grounds that it is a toxic substance. This action resulted in drastic decrease in production and the possibility of destroying the industry. The chelation of asbestos with organic dyes seems to be a promising way to abate its toxicity. Dyeing can be done when the fi bers are slurred in water at ambient conditions in the same way as textile fi bers.
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Carrying out of effective recovery algorithms of distorted images
Статья научная
Methods of distorted images reconstructing are considered and there are developed algorithms to recover images distorted by noise arising in the environment and movement of objects relative to each other. Distortion of the «blurring» type is considered to be the most difficult to restore, so the purpose of this work is to develop algorithms to recover images after this type of interference exposure.
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Changes in operating practice for increasing the life of pots in Alro Slatina
Статья научная
Changes in operating practice has made ALRO one of the most efficient smelters of its generation in the world. Aiming to design a high performance pot technology, with high productivity and low capital expenditures, ALRO has redesigned its low-amperage pots in order to create an advanced pot, by integrating the latest technology in lining design and anode rodding, in such a way as to maximize pot production by amperage increase, without decreasing the technical performance and potlife; we were thus able to obtain increase of the potlife from 1,440 days in 2004 to 2,860 days in 2016 and decrease of the DC reactive power consumption, from 14.18 MWh/Mt to 13.28 MWh/Mt.
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Статья научная
Ceramic semiconductor SnO2-based materials with MnO2 and CuO additives were synthesized at 1300 ºС and 1400 ºС. There has been carried out an investigation of the physical–mechanical and high–temperature electric properties. As a result, sintering of the material with MnO2 additive is shown to be improved at increasing firing temperature. The composition 96 % SnO2-2 % Sb2O3-2 % CuO made at the temperature 1300 ºС has the best electrophysical properties (its resistivity is 0.09 mOhm m). The resistivity of the 94 % SnO2-2 % Sb2O3-2 % CuO-2 % MnO2 composition in the high-temperature region is more by a factor of 3. The 96 % SnO2-2 % Sb2O3-2 % MnO2 composition has nonlinear voltage-currant characteristic, and hysteresis is present.
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Статья научная
Agricultural applications of the Gaussian process (GP) based techniques is considered. A method of classifying crops from multi-temporal Landsat 8 satellite imagery is proposed. The method uses the model of spectral features based on GP regression with constant expectation and square exponential covariance functions. Main steps of the classification procedure and examples of recognition of culture species are represented. The ground based data are used for quantitative validation of the proposed classification method. The highest overall classification accuracy in three classes of crops is 77.78%.
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Cleaning of industrial emissions from gas and dispersive particles
Статья научная
This article presents the results of experimental and theoretical studies of the effective purification of dispersed-ring two-flow industrial gases from gaseous and dispersed particles, hydrodynamics and mass transfer. The devices are designed to reduce the harmful emissions of the established threshold permissible (ChRET) at relatively low energy costs.
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Cleaning of natural gases from sour components
Статья научная
The article presents absorption, adsorption, catalytic and membrane methods of purification of hydrocarbon gases from acidic components, as well as the technology of membrane purification methods.
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Cognitive analysis of intrusion detection system
Статья научная
Usability evaluation methods have gained a substantial attention in networks particularly in Intrusion Detection System (IDS) as these evaluation methods are envisioned to achieve usability and define usability defects for a large number of practical software’s. Despite a good number of available survey and methods on usability evaluation, we feel that there is a gap in existing literature in terms of usability evaluation methods, IDS interfaces and following usability guidelines in IDS development. This paper reviews the state of the art for improving usability of networks that illustrates the issues and challenges in the context of design matters. Further, we propose the taxonomy of key issues in evaluation methods and usability problems. We also define design heuristics for IDS users and interfaces that improves detection of usability defects and interface usability compared to conventional evaluation heuristics. The similarities and differences of usability evaluation methods and usability problems are summarized on the basis of usability factors, current evaluation methods and interfaces loopholes.
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Combined energy supply for sixty-two heliostats of the big solar furnace
Статья научная
The article discusses the issues of increasing the reliability of regular, systematic, continuous operation during the day of 62 heliostats in the sun tracking mode by connecting to the centralized power network an additional autonomous power supply system with a power of 15 kW, consisting of a standard gasoline engine with an inverter and а solar Fresnel mirror-concentrating system with a steam turbine generator that produces electric power.
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Compact radar system safe helicopter landing
Статья научная
Practical realization the radar device is capable safe landing an aircraft of the helicopter type on unprepared sites in any time the day, in VFR and IFR weather conditions, in the presence natural and artificial interference. The calculation range based on measuring the transit time of the signal to the earth’s surface and back. The results in each time on the LCD display, applied to it the scale range elevations of objects with a height exceeding the permissible limits, which are in dangerous proximity to the aircraft under.
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Comparative analysis of phase-lock control system algorithms for spread-spectrum signal receiver
Статья научная
This paper investigates noise-immunity of phase-lock control system for spread-spectrum minimum shift keying signal receiver in case of adjacent channel interference influence. Four algorithms of phase-lock control system are suggested and described. Statistic simulations of signal processing in involved system are given.
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Статья научная
This paper reviews three methods of spectral-spatial classification for hyperspectral images of high spatial resolution: 1) pixelwise classification with post-filtering of resulting class map; 2) spectral-spatial classification based on geometric moments; 3) spectral-spatial classification based on segmentation. The paper provides the results of experimental comparison of these methods. The experiments are based on classification of images obtained by airborne hyperspectral sensor.
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Compensation of thermal deformations of heat supply network with radial expansion bends
Статья научная
A methodology for structural analysis of compensation of thermal expansions used for channel or aboveground sections of heat network pipelines with radial expansion bends has been proposed. The methodology is based on the methods of structural mechanics and allows to find technically based dimensions of radial expansion bends. Increased flexibility of the heat pipe angles and stress-raisers of additional bending stresses have been taken into account, the functional and graphical dependencies of the stress caused by thermal deformations of the heat pipe section with the U-shaped radial expansion bends on the temperature of the coolant have been presented. The authors developed and presented the computer program used for calculating radial expansion bends. Due to the program analyzing the model of a heat pipe section with a radial U-shaped expansion bend has been calculated. Comparison of the calculation results with the results obtained by means of the well-known software system “Start” developed by the scientific-and-technological enterprise “Pipeline” has shown a sufficient convergence of results, which confirms the efficiency of the presented methodology and computer program.
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Статья научная
In this study, the data obtained by satellite remote sensing and by studying a mathematical model are combined to investigate seasonal dynamics of wheat and oat agroecosystems with different levels of weed infestation. The study was performed in the south of the Krasnoyarskii Krai. NDVI was used to show the possibility of identifying weed-free and weed-infested crop fields. The model study was based on variations in the initial percentages of the crop and weed biomasses, with plant growth limited by mineral element deficiency. Model prediction of productivity of agroecosystems with different levels of weed infestation showed that the initial weed biomass higher than 30% is critical for crop productivity and may result in considerable crop yield loss.
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Complex approach to the evaluation of the reactivity of solid organic fuels
Статья научная
A universal experiment-calculation approach for the evaluation of the kinetic characteristics of thermochemical transformation of solid organic fuels based on the application of the methods of complex thermal analysis and mathematical simulation has been proposed. The technique of the thermogravimetric experiment data processing and mathematical model description bases itself on a unifi ed calculation scheme of material balances and kinetic processes of natural coal burnout. Satisfactory qualitative and quantitative convergence of experimental and numerical results has been obtained.
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Статья научная
The article deals with the complex computer applications and techniques for solving problems with the fatal errors and synthesis of optimal characteristics of materials and design parameters. A number of examples of typical problems solved these programs and methods.
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Composite multicomponent of gallium pastes-solders
Статья научная
Contact interaction of copper-zinc and copper-silver alloys is investigated with eutectics melts of the system Ga-Zn as composite components of gallium pastes - solders have been revealed. Interaction products have been determined depending on the structure and temperature of contacting components. Structures of developed new low temperature solders have been approved on the basis of gallium.
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