Статьи журнала - Журнал Сибирского федерального университета. Серия: Техника и технологии

Все статьи: 1355

Evolution of phase composition of composite materials at contact of titanium-aluminium obtained by welding explosion

Evolution of phase composition of composite materials at contact of titanium-aluminium obtained by welding explosion

Zakharova Yelena V., Alekseeva Ksenya V., Zhmak Yelena G.

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].

Бесплатно

Exotic grains in a core from Cornwall, NY - do they have an impact source?

Exotic grains in a core from Cornwall, NY - do they have an impact source?

Abbott Dallas H., Gerard-Little Perri, Coste Sarah, Coste Stephanie, Breger Dee, Haslett Simon K.

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.

Бесплатно

Experience of using and application prospects of rolling-extruding process for obtaining semi-finished products from aluminum alloys

Experience of using and application prospects of rolling-extruding process for obtaining semi-finished products from aluminum alloys

Sidelnikov Sergey B., Dovzhenko Nikolai N., Konstantinov Igor L., Galiev Roman I., Kiselev Andrey L., Samchuk Anton P.

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.

Бесплатно

Experimental and numerical simulation frequency characteristics of L-shaped waveguide-slot membranes bandpass filters

Experimental and numerical simulation frequency characteristics of L-shaped waveguide-slot membranes bandpass filters

Kopylova Natalia A., Kopylov Alexei F., Ogorodnikov Dmitri K., Nesterov Denis A.

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.

Бесплатно

Experimental study of temperature distribution in a cyclone-vortex furnace

Experimental study of temperature distribution in a cyclone-vortex furnace

Kulik Aleksandr V., Dorogov Evgenij Iu., Soloveva Tatyana A., Shtym Konstantin A.

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.

Бесплатно

Experimental study of the effective insulation of building envelopes

Experimental study of the effective insulation of building envelopes

Petrov Pavel V., Vedruchenko Viktor R., Rezanov Evgeny V., Kadtsin Ivan I., Kulagin Vladimir A.

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.

Бесплатно

Extended role access control model for web applications based on path hierarchy

Extended role access control model for web applications based on path hierarchy

Kononov Dmitry D., Isaev Sergey V.

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.

Бесплатно

Extraction of brown coals from Kansk-Achinsk and Lena basins with toluene and water containing fluids

Extraction of brown coals from Kansk-Achinsk and Lena basins with toluene and water containing fluids

Kuznetsov Peter N., Kolesnikova Svetlana M., Kuznetsova Ludmila I., Kamensky Evgeny S., Kashirtsev Vladimir A.

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.

Бесплатно

Extreme value theory and peaks over threshold model in the Russian stock market

Extreme value theory and peaks over threshold model in the Russian stock market

Andreev Vladimir O., Tinykov Sergey E., Ovchinnikova Oksana P., Parahin Gennady P.

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.

Бесплатно

Flow past various types of vane mechanisms by a two-phase compressible flow

Flow past various types of vane mechanisms by a two-phase compressible flow

Kulagina Ludmila V., Shtym Konstantin A.

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).

Бесплатно

Fluid dynamic bearings: modelling of elastic deformations

Fluid dynamic bearings: modelling of elastic deformations

Ivanov Viktor A., Erkaev Nikolai V., Langmayr Daniel

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.

Бесплатно

Foam metals high-temperature electrical characteristics investigation

Foam metals high-temperature electrical characteristics investigation

Kirko Vladimir I., Dobrosmislov Sergey S., Gusev Alexander O., Simakov Dmitry A., Stepanov Egor I.

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.

Бесплатно

Forecasting properties of facing construction ceramics on the base of industrial wastes

Forecasting properties of facing construction ceramics on the base of industrial wastes

Eromasov Roman G., Nikiforova Eleonora M.

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.

Бесплатно

Formation of nanomaterials based on non-ferrous and noble metals in autoclaves

Formation of nanomaterials based on non-ferrous and noble metals in autoclaves

Belousov Oleg V., Sirotina Anastasia V., Belousova Nataliya V., Fesik Elena V., Borisov Roman V., Malchikov Gennadiy D.

Статья научная

The physicochemical laws of formation of multicomponent phases containing noble metals in hydrothermal conditions were investigated. Approaches to a purposeful variation of structure and composition of mono-, bi- and polymetallic phases based on non-ferrous and noble metals were realized. Structural, phase and chemical stability of polymetallic nanostructures in some carrier materials was investigated.

Бесплатно

Full analysis of Sierra Leone bauxite and possibilities of bauxite residue filtration

Full analysis of Sierra Leone bauxite and possibilities of bauxite residue filtration

Dobra Gheorghe, Kiselev Anatoly, Filipescu Laurentiu, Alistarh Vicol, Anghelovici Nicolae, Iliev Sorin

Статья научная

Chemical analysis, classical or instrumental using ICP and the XRF spectrometry, offers complete information on elemental composition and major chemical constituents of bauxite and bauxite residues resulted from the Bayer process. The XRD diffractometric analysis provides information on quantitative mineralogical composition of these materials and it enables the real identifi cation of main chemical combinations, whose reactivity is essential in driving the process of obtaining alumina through the Bayer process. Mineralogical components identified in the bauxite samples were Gibbsite (30-40 %), Al - goethite (20-30 %) and hematite (less than 5 %). About 40 % of the Sierra Leone bauxite mineralogical phases were found in amorphous state, but all these amorphous phases are also originating from the above crystalline components, under the excessive wearing during bauxite deposit formation and its metamorphic transformations. The minor crystalline components from bauxite are: kaolin, quartz, zircon, ilmenite and anatase, but their concentration is below 2 % (close to the detection limit of the XRD analysis). The main mineralogical components identified in red mud are the Al-goethite (35 %) and the hematite (12 %). The minor crystalline components from red mud are: gibbsite, katoite, sodalite, calcite, rutile and anatase. Experimental data of this type of bauxite have shown that a compact mass of approximately 50-55 % of bauxite passes fully untransformed through all important stages of the Bayer process. This material of uniform size and composition can form a structure with low hydraulic resistance, easy filterable both on conventional or hyperbaric steam fi lters.

Бесплатно

Further developments and advantages utilizing slotted anodes

Further developments and advantages utilizing slotted anodes

Campice Giovanni

Статья научная

Slotted anodes have been used by smelters that require large size anodes. Being inter-anode separations, slots can be considered acting as expansion gaps to safely absorb the heat-induced expansions. The slots are helping to reduce the thermal stresses in the anodes and thus reducing the risk of cracking. Approach to slots cut in the bottom surface of the anodes has nowadays changed and become extremely important, since they represent effective ways to escape gas continuously formed during Aluminium reduction process, thus reducing the accumulation of gas bubbles underneath the anodes. For this reason the use of slots in the anodes allows to reduce electrical cell resistance as well as to improve cell stability. Slots in the anodes therefore result in reduced electrical power consumption for the Aluminium production. The depth of the slots is important to ensure that these benefits last throughout the entire life of the anodes (“ full-life slots”), while slot shape, which determines the gas escape direction and related areas of influence, is also important to achieve further benefits in pot management. Cutting slots with reduced width reduces the amount of carbon removed from anodes when slots are cut. Narrow slots are improving specific Aluminum production per anode as well as prolonging anodes cycle time.

Бесплатно

Harald Oye - 80th years full of energy birthday

Harald Oye - 80th years full of energy birthday

Другой

Бесплатно

Harmonics and neutral line current compensation in three-phase four-wire power systems

Harmonics and neutral line current compensation in three-phase four-wire power systems

Chernyshov Maxim O., Dovgun Valery P., Vazhenina Irina G., Temerbaev Sergei A., Novikov Victor V.

Статья научная

Load unbalance and modern office equipment result in a significant neutral current in three-phase four-wire low-voltage power systems. This paper considers a new configuration of hybrid power filter for power quality management in three-phase four-wire low voltage power systems. The proposed hybrid filter is composed of a single-phase power converter and a three-phase passive filter connected in series. The hybrid filter can be operated in both passive and hybrid mode. The compensating performance of the filter is confirmed with computer simulation using MATLAB software. Analysis and simulation proved that the hybrid filter is an effective solution for neutral current mitigation.

Бесплатно

Heavy metals as impurities in the bayer production cycle of the aluminum hydroxide from sierra leone bauxite. Preliminary study

Heavy metals as impurities in the bayer production cycle of the aluminum hydroxide from sierra leone bauxite. Preliminary study

Dobra Gheorghe, Iliev Sorin, Cotet Lucian, Boiangiu Alina, Hulka Iosif, Kim Lidia, Catrina Gina Alina, Filipescu Laurentiu

Статья научная

This paper is reporting the data of a preliminary study on heavy metals distribution in the fluid and solid phases involved in dry and classified aluminium hydroxide production through Bayer process. For heavy metals released in the fluid phases, the main source of contamination is the bauxite through its mineralogical phases soluble or insoluble in alkaline solution. It was shown that predominant way to transfer contaminating elements in aluminium hydroxide particles is the occlusion of very fine particles coming from mineralogical phases of bauxite residue. New born mineralogical phases from bauxite residue, like poor crystallized sodalite and cancrinite, are the most active occlusion contaminants.

Бесплатно

High gain Ku-band substrate integrated waveguide slot antenna array

High gain Ku-band substrate integrated waveguide slot antenna array

Lemberg Konstantin V., Nazarov Oleg A., Panko Vasiliy S., Salomatov Yury P.

Статья научная

16 x 16 element waveguide-slot antenna array at 14.4 GHz is described. Antenna is built using substrate integrated waveguide (SIW) technology. Simulated and measured characteristic of fabricated antenna are presented.

Бесплатно

Журнал