Статьи журнала - Журнал Сибирского федерального университета. Серия: Техника и технологии
Все статьи: 1404
Electronic structure of SnO 2 when doped with Sb and V
Статья научная
There was carried out theoretical and experimental investigation of the influence of Sb and V dopes on the electrophysical properties of the SnO2-based ceramic materials. Modeling was done with the help of the program package VASP within the density functional formalism. The SnO2-based ceramics was synthesized according to the standard technology at the sintering temperature 1300 ºС with different Sb dope concentrations (1 to 5 %). The material made with V dopes had a low electrical conductivity. The structure investigation showed Sb being completely dissolved in the SnO2. The calculations showed that the activation energies are Egap(SbSn47O96)= 1.19 eV and Egap(VSn47O96)= 1.33 eV. The experimental investigation showed that the increase of the stibium oxide concentration leads to the decrease of the band-gap energy from 1.33 eV to 0.75 eV. The difference between the calculated activation energy value of the Sb-doped SnO2 and that obtained from the experiments is 19 %.
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Energy and ecological aspects of coal-water slurry utilization
Статья научная
The opportunity of technological and modified lignosulphonate wastes, process water, oxygenized brown coal with high content huminic acid (to 60 %) with alkali usage as plasticizer agent in the coal-water slurry (CWS) production technological process was checked. The CWS stability scheme in alkali additives interaction was suggested. The bituminous and brown coal mixture (10: 90) CWS was investigated. The anthracite and brown coal relation is from 5 to 95. The discovered regularities demonstrated the slurry properties optimization opportunity in industrial conditions by combined changing of additive quantity and coal physical-chemical composition. The suggested CWS production technology allows solving some questions of ecological safety and resource-saving at the expense of the sources of raw materials assortment expansion. The CWS production industrial scheme on production run equipment without its modernization is developed. The combustion parameters of this fuel are shown. It is established that CW fuel combustion allows reducing the harmful emissions in atmosphere several times.
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Energy efficient dynamic bid learning model for future wireless network
Статья научная
In this paper, an energy efficient learning model for spectrum auction based on dynamic spectrum auction process is proposed. The proposed learning model is based on artificial intelligence. This paper examines and establishes the need for the users to learn their bid price based on information about the previous bids of the other users in the system. The paper shows that using Q reinforcement learning to learn about the bids of the users during the auction process helps to reduce the amount of energy consumed per file sent for the learning users. The paper went further to modify the traditional Q reinforcement learning process and combined it with Bayesian learning because of the deficiencies associated with Q reinforcement learning. This helps the exploration process to converge faster thereby, further reducing the energy consumption by the system.
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Energy efficient modular block diagram of an air heat pump heat supply system
Статья научная
The use of air source heat pumps, together with other renewable energy devices and high efficiency heating equipment, together with digital control systems, is a promising European trend that continues to grow in the face of rising costs of traditional energy carriers. The article presents a number of technical energy-saving solutions, such as a mixing chamber for HHP, built into the heat supply system and the use of a supply and exhaust ventilation system, which is based on the principle of recuperation. A digital modular-functional-structural diagram of heat generation of a coolant from the environment is proposed. Based on the energy efficiency of the circuit solution with an electric boiler, a buffer tank and a patented mixing chamber, the authors achieve a rationally controlled heat and air exchange of a combined heat pump space heating system. Automation of the joint work of rationally selected elements of the heat pump air system is one of the Smart Home technologies that improve the efficiency of heat supply, create comfortable living conditions and security due to the digitalization of the control algorithm for this system.
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Статья научная
The research represents the method of initial alignment of attitude navigation receivers that allows ensuring the required accuracy of initial alignment of attitude navigation receivers (ANR) on the customer’s objects.
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Статья научная
The purpose of this study is analysis of relationship between chlorophyll content and chlorophyll photosynthetic potential of oats and barley cultivars. For this aim we used ground remote sensing and laboratory data. Ground data were obtained at the experimental fields, located in the Krasnoyarsk region. Experiments were carried out in different seasons, under various lighting conditions with the control of plants state. Spectral measurements were done by double-beam spectroradiometer. It is installed on the mobile work platform at heights of 5 to 18 m. The study showed good correlation between chlorophyll photosynthetic potential and chlorophyll content for different oats and barley cultivars. The value of chlorophyll photosynthetic potentials is different for barley and oats cultivars during the growing season.
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Статья научная
This paper covers the results of the composition and structure evolution of nanostructured materials produced by separate electrochemical oxidation of metals (copper and aluminum). The electrolysis products after short-term and long-term aging were characterized by XRD (X-ray diffraction) and DSC (differential scanning calorimetry) analysis. There is the difference in aging of nanostructures of copper- and aluminum-compounds. Short-term aging results in the phase transformation of copper(I) oxide and the stability of aluminum oxyhydroxide (boehmite). Copper (I) oxide is oxidized to copper (II) oxide and copper carbonate hydroxide. At long-term aging the oxidation of copper (I) oxide does not completed because the Pilling-Bedworth ratio for copper (II) oxide, copper carbonate hydroxide is greater than one. The structure of all copper-containing compounds (copper (I) oxide, copper (II) oxide, copper carbonate hydroxide) is changed. It results in the increases of both the interplanar spacing and the temperature of the phase transformations. Coherent scattering region (CSR) of boehmite and copper (I) oxide are 3-4 nm and 20-30 nm, respectively, and does not change at short-term and long-term aging.
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Статья научная
In this work, welding explosion of multiple sample with its further annealing to 300 degrees is used as the method of receiving layered materials. Using this technology allows heating in the air; herewith possibility of oxygen penetration into internal material layers is eliminated. Using this technology allows heating in the air. Furthermore, pressures developed in the process of welding exposure ensure quality contact between the surfaces of plates [1].
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Exotic grains in a core from Cornwall, NY - do they have an impact source?
Статья научная
We have found seven discrete layers in a bog core from Cornwall, NY about 80 km away from the Atlantic Ocean. All but two layers contain material that is unlikely to be locally derived. In most cases, the material in the layers has been transported thousands of kilometers from its source area. Six out of the seven layers are difficult to explain except through impact processes. If all of these layers are derived from impacts that produced craters, the data imply a very high impact rate during late Holocene time. In addition, we have been able to associate two of the impact ejecta layers with dated tsunami events that span the Atlantic Ocean. If this discovery is validated by further research, it implies a much larger tsunami hazard in the Atlantic Ocean than previously reported.
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Статья научная
Presented the experience of the application method of combined rolling-extruding of metals for obtaining semi-finished products from deformed and secondary aluminum alloys on combined treatment installations. Research the structure and properties, and the possibility of obtaining hot-extruded semi-fi nished products from recycled aluminum alloy AV93.
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Статья научная
The article presents the results of experimental research and numerical simulation of the amplitude-frequency characteristics (AFC) of the voltage transmission ratio (voltage gain) |Ku| and frequency characteristics of the voltage standing wave ratio from the input (input VSWR) to three bandpass filters on the waveguide-slot membranes (WSM) with L-shaped resonance slot: to the single stage, to the three stages and to the four stages. The filter designs are given in article. The results of numerical simulation and experimental study show that in the frequency range 5,0...8,5 GHz filters provide attenuation behind the pass band up to 30 dB at the level of the introduced losses in the pass-band from 0,2 to 1,0 dB. The values of the calculated and experimental input VSWR in the filter bandwidth of pass-band are from 1,1 to 1,74 relative units (r. u.) and in the stop bands from 2 to 300 r. u. The authors believe that using of waveguide-slot membranes will significantly reduce the overall dimensions of microwave bandpass and bandstop filters in the middle of the centimeter wavelength range.
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Experimental study of temperature distribution in a cyclone-vortex furnace
Статья научная
This article describes the experience and results of experimental study of the temperature distribution in the refractory lining of the gas and liquid fuel cyclone-vortex furnace (CVF). Temperatures were measured with type K thermocouples. Most of the thermocouples are located a depth of 25 mm from the surface combustion chamber. With increasing boiler load observed decrease in temperature and increase of plating unevenness of the temperature distribution in the combustion chamber. This is due to the redistribution of heat generated between the combustion chamber and the firebox as the load increases. The results of heat transfer studies in CVF will lead to a reduction in the thickness of the lining, modernization of the CVF structure. In the future, abandon the use of refractory lining in CVF.
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Experimental study of the effective insulation of building envelopes
Статья научная
The relevance of research is caused by the fact that at present, modern standards for saving thermal energy and thermal protection of buildings are focused on the use of a very limited set of solutions to reduce energy consumption, which do not always meet the specific conditions of construction and are often very expensive. A method for studying the effective insulation of building envelopes is proposed, taking into account the relationship between structural, heating, regime parameters and economic indicators. The goal is to determine the optimal value of the insulation thickness of the heat-insulating material, taking into account the thermal energy supplied to the object. The study used methods of mathematical modeling of heat transfer, optimization problem. An experimental study is presented, showing the possibility of applying the method of technical and economic optimization of thermal insulation of building envelopes. It was determined on the basis of the mathematical model of the thermal insulation of building envelopes developed by the authors, taking into account the regulation of the supplied thermal energy. The result of the study is to reduce the cost of heat losses through building envelopes and electrical energy for the regulation of the “heating, ventilation and air conditioning” system. The conducted studies testify to the expediency of using the proposed developments, which contribute to determining the optimal thickness of wall insulation with heat-insulating material, finding the minimum reduced costs, and an advantageous choice of a method for regulating the supplied thermal energy.
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Extended role access control model for web applications based on path hierarchy
Статья научная
Web applications security is a complex problem with several aspects. One aspect is access control according to specified security policy. Access control is accomplished by security model restrictions. This research is dedicated to developing security access control model for web applications. This work describes path-based RBAC model, which improves RBAC and allows flexible access control using request path (URI). Authors created guidelines to apply model’s elements for real-world web applications. Developing web applications with model described allows reducing security risks.
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Статья научная
The conversion of different brown coals from the Kansk-Achinsk and Lena Basins in an aqueous medium and in toluene containing mixtures with water and tetralin additives was studied under supercritical conditions over the temperature range of 375-550 °C and at pressures from 7 to 40 MPa. It was found that the liquefaction of brown coals in the medium of toluene solvent with small amount of hydrogen-donor tetralin co-solvent effectively occurred at low temperature 400 °C. On the other hand, coal methanation, hydrolysis, and oxidation reactions with the predominant generation of methane, carbon dioxide, and hydrogen prevailed in the water containing mediums. In a supercritical toluene at 440 °C, the addition of a small amount of water (15 %) stimulated destruction of coals with the predominant production of liquid products and moderate gas yields. The use of calcium oxide, sodium hydroxide and hematite as the catalysts increased the yields of liquid products.
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Extreme value theory and peaks over threshold model in the Russian stock market
Статья научная
Traditional research methods adopts normal distributions as a pattern of the stock market behavior. This paper utilized POT model of extreme value theory, and GPD distribution which can give more accurate description on tail distribution of financial returns/losses. EVT and POT techniques are applied to a series of daily losses of the RTS index (RTSI) over a 15-year period (1995-2009), RTSI is total index of 50 largest Russian stocks. The focus is on the use of proposed methods to asses tail related risk providing a modeling tool for modern risk management.
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Flow past various types of vane mechanisms by a two-phase compressible flow
Статья научная
The statement of boundary value problems for the flow around real wing-shaped profiles of supercavitation mechanisms near the separation boundary is stated. The problem under consideration is extremely important for the numerical study of the processes occurring in heating equipment, supercavitation devices, and heat and mass transfer technologies. The discussed algorithms have been implemented as computational programs for algebraic (ALFA) and integral (OMEGA) equations, ordinary (SIMP) and improper (SECOB) integrals, including the Cauchy integral (DSECOB) as well as summation programs for sequences and series (SHENKS, AYTKEN), including divergent ones (EULER).
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Fluid dynamic bearings: modelling of elastic deformations
Статья научная
This article deals with a new approach for calculation of self-consistent pressure distribution and surface deflection for a lubricated journal bearing. This approach is based on the numerical solution of the 2-D Reynolds’ equation for the lubrication layer, numerical calculation of the surface deformations by the 3-D ANSYS package and Fourier series expansion for the compliance matrix. A simple analytical approximation is found for the obtained compliance matrix, which can be used for heavy loaded journal bearings. The compliance matrix is implemented into the iterative procedure for calculation of self-consistent pressure distribution and surface deflection in the contact zone. Results of calculations are presented for the particular journal bearing.
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Foam metals high-temperature electrical characteristics investigation
Статья научная
In the work presented we have carried out experimental investigations of high- temperature electrophysical properties of foam metals. We have obtained data of foam nickel and foam copper resistivity and temperature coefficients of resistance (TCR) versus their plane deformation degree within the temperature range from 100 to 950 ºС.
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Forecasting properties of facing construction ceramics on the base of industrial wastes
Статья научная
The work contains the results of study on improving the grain distribution of high-silica technogenic products for obtaining facing ceramic materials with forecastable operating properties. The study presents a model of facing composite material on the base of quartz grain fill. The optimal grain distribution of high-silica wastes was detected with the purpose of adjusting the packing density of ceramic materials at the stage of feed preparation, moulding and baking.
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