Статьи журнала - Журнал Сибирского федерального университета. Серия: Техника и технологии
Все статьи: 1367
Methods for assessing the state of snow-ice cover
Статья научная
The development new methods for measuring the electrophysical and geometric parameters multilayer dielectric medium in order to identify their layers, as well as to detect inhomogeneities in them, is an urgent scientific task. Methods for assessing the state the snow-ice cover are proposed, based on the identification layers of the snow-ice cover by the dielectric permittivity obtained indirectly as a result inclined sounding of the underlying surface by an electromagnetic wave with vertical and horizontal polarization. Under normal sensing the underlying surface, in the form snow-ice cover, by radio waves with vertical and horizontal polarization, the obtained values the reflection coefficient from the boundary layers the received signals are identical. Oblique sensing by a vertically polarized wave in the range from 25 to 90 degrees leads to a sharp dip in the values the reflection coefficient from the boundary layers at certain angles, so for dry snow - 47…55°, dry firn - 55 … 58° and dry ice - 58…61°. These angles characterize the dielectric properties the layers (permittivity), which are explained by the complete polarization the reflected wave in a plane perpendicular to the plane incidence, since at this moment the vibrations the layer's electrons along the direction their movement do not lead to the emission electromagnetic waves in the direction the reflected wave (absent). The given estimated values the complex relative permittivity snow-ice cover as two component medium air and ice at a temperature from minus one to minus forty degrees, or three component medium air, ice and water at zero temperature are a sample for establishing the identity the characteristic properties layers. The purpose this article is to develop methods for assessing the state snow-ice cover used in determining the possibility performing a safe landing a helicopter - type aircraft on an unprepared site with snow-ice cover based on the identification the obtained characteristics snow-ice cover layers based on the results radar sensing with calculated data.
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Micro-LIF and numerical investigation of mixing in microchannel
Статья научная
Flow regimes and mixing pattern in a T-type micromixer at high Reynolds numbers were studied by numerical solution of the Navier–Stokes equations and by particle image velocimetry (micro-PIV) and laser induced fluorescence (micro-LIF) experimental measurements. The Reynolds number was varied from 1 to 1000. The cross section of the mixing channel was 200 μm×400 μm, and its length was 3000 μm. Five different flow regimes were identified: (I) steady vortex-free flow; (II) steady symmetric vortex flow with two horseshoe vortices; (III) steady asymmetric vortex flow; (IV) unsteady periodic flow; (V) stochastic flow. Maximum mixing efficiency was obtained for stationary asymmetric vortex flow. In this case, an S-shaped vortex structure formed in the flow field. Good agreement between calculation and experiment was obtained.
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Micrometeorite impacts in beringian mammoth tusks and a bison skull
Статья научная
We have discovered what appear to be micrometeorites imbedded in seven late Pleistocene Alaskan mammoth tusks and a Siberian bison skull. The micrometeorites apparently shattered on impact leaving 2 to 5 mm hemispherical debris patterns surrounded by carbonized rings. Multiple impacts are observed on only one side of the tusks and skull consistent with the micrometeorites having come from a single direction. The impact sites are strongly magnetic indicating significant iron content. We analyzed several imbedded micrometeorite fragments from both tusks and skull with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and X-ray fluorescence (XRF). These analyses confirm the high iron content and indicate compositions highly enriched in nickel and depleted in titanium, unlike any natural terrestrial sources. In addition, electron microprobe (EMP) analyses of a Fe-Ni sulfide grain (tusk 2) show it contains between 3 and 20 weight percent Ni. Prompt gamma-ray activation analysis (PGAA) of a particle extracted from the bison skull indicates ~0.4 mg of iron, in agreement with a micrometeorite ~1 mm in diameter. In addition, scanning electron microscope (SEM) images and XRF analyses of the skull show possible entry channels containing Fe-rich material. The majority of tusks (5/7) have a calibrated weighted mean 14C age of 32.9 1.8 ka BP, which coincides with the onset of significant declines
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Modeling of heat exchange processes under electrocontact cutting of metals
Статья научная
The mathematical model of a thermal condition of blank under electrocontact cutting has been offered. The way of the improvement of electrocontact cutting is recommended in order to improve the technological indicators of a process at the expense of temperature regulation in a cutting zone under observance of the calculated modes of processing.
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Modeling of structure evolution during hot rolling of aluminum alloys in the software package Deform
Статья научная
The study provides modeling of aluminum alloy 5182 БТ (Al-Mg 4,5%) structure evolvement during hot rolling in each stand of 5-stand continuous hot rolling mill. Mathematical modeling was made in DEFORM software product, Johnson-Mehl-Avrami-Kolmogorov equation was used for recrystallization kinetics setup. DEFORM enables to consider recrystallization of three types: dynamic, meta-dynamic and static recrystallization. Proceeding from actual rolling process temperature and speed parameters, the task was converted to static recrystallization calculation. Input coefficients were taken from literature data review. The output is volume of recrystallized grains and their sizes calculated throughout the rolling process. Description of processes related to grain size changes in rolling aluminum alloys is peculiar due to lack of consistent patterns. This is explained by the fact that grain growth during rolling is influenced by many factors associated with both internal metal structure and individual process specifics. That is why modeling results should be compared with industrial experimental data. In this case, texture and structure evolvement data received as a result of Hot Rolling Mill 2800 forced stop with subsequent quenching of metal were used for comparison.
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Modeling thermal conditions of the process combined rolling-extruding
Статья научная
Were obtained the dependences and through them analyzed the thermal interaction of the metal and the tool during combined rolling-extruding. Given graphs temperature change of deformable metal to obtain rods by method CRE at various geometrical and technological parameters of the process.
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Статья научная
The article introduces modernizing the global approximation method of the posterior probability density function in the implementation of phase-locked loop algorithms which improves the accuracy of clock synchronization in telecommunication networks, and reduces the time of entering into synchronism.
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Статья научная
The problem of temperature anomalies is typical for all major cities in the world. Space thermal images are a powerful source of information for analyzing and determining outlines of temperature anomalies within a single territory. Determination of the nature and boundaries of temperature anomalies will help to understand the causes of the unfavorable ecological situation in Krasnoyarsk: where, in addition to high industrial emissions, atmospheric processes also exert their influence, which lead to the fact that impurities linger and concentrate over the city. The development of advanced space technologies allows the collection of a variety of diverse data more efficiently and at a lower cost than the organization of an appropriate ground network of observation posts and points. One of the most interesting and important indicators about the surface of the Earth is the land surface temperature. Land surface temperature is determined by the balance of incoming and outgoing energy. The main and overwhelming source of energy coming to the surface of the Earth is solar radiation. The 10th and 11th bands of Landsat 8 satellite measure thermal infrared radiation (TIR). The thermal infrared range is particularly useful for determining the temperature difference between the city and surrounding rural areas, and for studying the phenomenon of an urban heat island (UHI).
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Monte Carlo numerical method in the problem of temperature stability analysis of electronic devices
Статья научная
The problem of ensuring high temperature stability of parameters by reason of the characteristic features inherent in the integral performance becomes especially urgent for microminiature electronic devices. For the mathematical description of the electronic devices’ temperature error it is proposed to use the method of experiment’s statistical planning in combination with regression analysis. There are classes of electrical circuits in which the output parameter depends mainly on one-parameter electrical radio elements. In the article it is shown that the problem of obtaining the temperature error equation for such electrical circuits can be reduced to the problem of effective finding of the one-parameter electro radio elements’ influence coefficients. A modification of the Monte Carlo statistical method with the computational factor experiment’s scenario to find the temperature error equation is considered. Approbation of the proposed modification is carried out using the example of the electric circuit of the generator with the Wien bridge.
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Статья научная
NMR Imaging results of polymethylmethacrylate colloidal crystals infiltration are presented. For infiltration study the colloidal silica and fluids with different relation of surface tension and viscosity were utilized. Wetting front has a trend to be steady while propagated into bulk sample as revealed by means of NMR Imaging. As regards of powder sample, the wetting front instability was observed. Both the wetting front dynamic and structural properties of samples namely porous media permeability, fractal dimension of porous space and tortuosity were successfully measured. NMR Imaging techniques was demonstrated to be suitable for noninvasive study of infiltration processes occurred in the course of inverse opals preparation.
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Статья научная
This paper is concerned with developing and introducing into industry new technologies of producing multi-component media (emulsions, suspensions, aqueous solutions and systems) with the use of cavitation, which allows to obtain considerable positive results in heat-and-power engineering, building industry, agriculture, and other industries, sciences and engineering. Power efficiency and environmental safety of the processes based on cavitation effects have been show, promising further research is expected.
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Nature prerequisites for zoning of suburban area of Krasnoyarsk city
Статья научная
The suburban area is a multifunctional area that has a few problems. This area should protect the ecological city area, should solve the recreation problems of the city, should supply citizens with perishable goods, and should also have an economy and science functions for the city development. In connection with the development process of suburbanization, this territory is very important for city development. Russia’s economy is going through major transitions. These transitions are rapidly changing the relationship between cities (urban areas), countryside (rural areas) and the development, growth, and popularity of suburbia. The process of suburbanization takes place in biggest cities of Russia, including Krasnoyarsk City. The modern Krasnoyarsk with a population of about 1mln people occupies the territory of 34115 ha. This article examines the analysis of functions of suburban area and connects these functions with zoning of the suburban territory. The author analyze the nature conditions of suburban area and it connection with functional zoning of territory.
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Network services for active learning computer systems design
Статья научная
CDIO Initiative involves active learning in the project team. To carry out projects in the limited time needed program-methodical complexes. An example of a multi-level complex developed by COD - Conceptual Object Design, for multiple designing computer systems and automatic evaluation of resources for local installation and a network services.
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Статья научная
Today, it is relevant to develop a methodology for assessing the degree of deterioration of a building based on the loss of heat-shielding properties of its external enclosing structures, and hence the establishment of the physical parameters of the fences responsible for the formation of comfortable conditions in the internal environment of the premises. Based on the research carried out, the dependence of the air flow through the cell of free volume per unit time was obtained as a function of the cell diameter and the modulus of the pressure gradient. This article presents the results of the obtained mathematical model of the interaction of the building envelope with external climatic factors, taking into account the regularities of changes in the characteristics of the outdoor climate.
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New methodology for designing external fencing structures energy efficient civil buildings
Статья научная
Based on the performed theoretical studies and calculations, the developed methodological foundations of designing the external enclosing structures of energy-efficient buildings based on cellular concrete with a given set of properties are presented, which are of great economic importance for construction oriented in the modern period towards the creation of energy-efficient civil facilities.
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New type of detachable contact joints for aluminium cell busbar arrangement
Статья научная
The new type of detachable contact joints (DJC) for the aluminium industry is offered. It is shown, that DJC with cylindrical split contact inserts allow to provide stability of electrotechnical characteristics of connection from -50 to + 40ºC.
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Northern technology and engineering: information support of the problem
Статья научная
The article represents databases for research information support on the problems related to providing northern regions with reliable equipment and technologies. It gives characteristics of information resources on cold regions engineering topic from foreign and Russian databases: IEEE Xplore, ScienceDirect, ASCE Library, VINITI RAS, “Scientific Sibirica”. It analyses a documentary flow “Northern engineering and technology” selected from information array “Problems of the North”, which is a constituent part of DB with current replenishment “Scientific Sibirica” generated by the Department of Scientific Bibliography of the State Public Scientific-Technological Library of the Siberian Branch of the Russian Academy of Sciences. The documentometric analysis (a kind of bibliometric one) shows the chronological, quantitative, type-species, thematic structures of Russian documents.
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Статья научная
The paper proposes a numeric-analytical method for determining the communication equations of Laplace’s transformants of dynamic functions of the universal unit of radial externally-pressurized gas bearings which movable element makes small radial oscillations in the locality in its central position. Method and obtained dependences provide links between integro-differential Laplace’s transformants of the unit such as load capacity and local input and output mass flow rates with transformants of eccentricity and gas lubricant pressure at inlet and outlet of the unit. It is shown that the local transfer functions of the unit model are rational functions of the Laplace’s transform variable and all such functions have a common denominator in the form of a polynomial of this variable. The method allows to calculate the required dynamic criterion of gas bearings containing this unit with prescribed accuracy. Founded dependences give ready formulas for calculation dynamic criteria of radial single-row or multi-row ordinary passive or active externally-pressurized gas bearings in which this unit can be used for description of radial movement of its movable element.
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Статья научная
Emissions of nitrogen oxides from coal combustion are a major environmental problem because they have been shown to contribute to the formation of acid rain and photochemical smog. Coal thermalpreparation before furnace delivery is effective method to reduce NOx emissions, shown by experiments in small-scale facilities [1]. This paper presents the mathematical model of burning thermal preparation coal. Validation of the model was carried out on laboratory-scale plant of All-Russia thermal engineering institute. Modeling of low-emissive burner with preliminary heating coal dust is made for the purpose of search of burner optimal constructions which provides low concentration of nitric oxides in the boiler. For modeling are used in-house CFD code «SigmaFlow» [2].
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Numerical modeling of tribological characteristics of fibrous polymer composite materials
Статья научная
The paper presents a numerical simulation of the contact interaction of fibrous polymer composite materials in a finite element ANSYS package and studies the friction coefficients for cells with wear of 0%, 25%, 50% and 75%. To predict the coefficient of friction of composites it was proposed to use the method of mechanics of composite materials - the method of local approximation. With the help of numerical simulation, the fields of distribution of normal stresses and contact stresses in the contact zone were obtained and the corresponding conclusions were drawn.
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