Журнал Сибирского федерального университета. Серия: Техника и технологии @technologies-sfu
Статьи журнала - Журнал Сибирского федерального университета. Серия: Техника и технологии
Все статьи: 1471
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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Formation of nanomaterials based on non-ferrous and noble metals in autoclaves
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.
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Full analysis of Sierra Leone bauxite and possibilities of bauxite residue filtration
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.
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Further developments and advantages utilizing slotted anodes
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.
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Harmonics and neutral line current compensation in three-phase four-wire power systems
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.
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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.
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High gain Ku-band substrate integrated waveguide slot antenna array
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.
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High-level design flows for VLSI circuit
Статья научная
Design flows for very-large-scale integration circuit are considered. The problems arising from the realization of the project using top-down and system design methods are highlighted. The technology of an architecture-independent design for computer systems on a chip is suggested. The technology is based on a functional data-flow presentation of the initial algorithms and their subsequent step-bystep transformation at the register transfer level into description of the system being designed. Using methods of formal description and verification allows developers to transfer initial high-level parallel algorithms on topologies of the confi gurable integrated circuits being developed.
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Hydraulic calculations of earthen channels for reconstruction
Статья научная
The problems in the design, operation, and reconstruction of earthen channels analyzed on the example of Mirishkor canal. The need for a new approach to the reconstruction have been defined using the results of field study and HEC-RAS modelling software. Recommendations are given for improving the hydraulic calculation of irrigation canals.
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Hydrodynamic dispersion of calcium aluminosilicate from technogenic and nonmetallic materials
Статья научная
Physicochemical properties of two calcium aluminosilicate materials after reducing in the hydrodynamic rotary generator in supercavitation mode were studied. The samples are the crystal ceramic foam based on Kansko-Achinsk lignite-ash and the porous glass material obtained from low-manganese nonmetallic feed. X-ray phase analysis, EPR-method, NPR-method (the Mossbauer Effect) and optical microscopy were used. It was found that the material is changing its stucrure in a hydrodynamic dispersion process caused by high-cavitation. The nature of the changes depends on its initial state.
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Hypergene units of the Proterozoic Tatar carbonatite formation of the Yenisey Ridge
Статья научная
The Yenisey Ridge Proterozoic carbonatite and metasomatite unit developed in the belt of near-meridian strike, 20×2-5 km in size, is described. Dolomite carbonatites host en echelon beds of pyrochlore-apatite ores with the average Nb 2 O 5 grades 0.23 % and the average P 2 O 5 grades 4.71 %. Apatite beds are locally developed. As for metasomatites, muscovite-biotite mica is of specific interest. Cretaceous-Paleocene kaolinite-hydromica weathering crusts of aluminum silicate rocks and polygenetic unconsolidated compositions on carbonatites, representing vermiculite-clayey ochers in combination, are developed in the northern part of the productive zone. Crandallite-bearing ochers with higher Nb 2 O 5 grades are developed in the southern part in the aleurite ferriferous material. In the northern part of the zone the pit mines granular ores consisting of pyrochlore and columbite crystals in the francolite-vermiculite-clayey material. Vermiculite and francolite are stored in special dumps. The author recommends using phosphates of bedrock deposits, special dumps and slimes as a resource for fertilizer production.
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IMS quality of service estimation with tensor concept
Статья научная
In this work, we propose methods of tensor analysis for the IMS network QoS characteristic estimation. Modern communication networks are representing a set of devices, systems and networks with the given interaction structure for a heterogeneous information streams processing. QoS support is a necessary mechanism for rendering of services in a modern communication networks but it increase cost and complexity equipment of service providers. In present, the main mathematical apparatus of QoS estimation is a queuing theory but it has some drawbacks. It should be noted that the base of next generation networks is an IP Multimedia Subsystem (IMS). IMS network have a many systems and complicated topology. Consequently, the task of supply QoS and QoS characteristic estimation in IMS is a very important for communications development. However, the efficient allocation of network resource management is complicated because it needs management many systems and processing the considerable amount information streams with a specified QoS for every type of the streams. Tensor analysis of networks provide opportunities to take into account the process-structure interaction and the application flexibility that result in the compute cost decreasing, the delay reducing due to dynamic management infocommunication systems and the good network scalability.
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Статья научная
The alumina concentration in the bath plays a fundamental role on cell operation. Local depletion may lead to an anode effect when using carbon anodes. A mathematical model describing the alumina convection-diffusion process in the bath coupled to the cell magneto-hydrodynamic (MHD) in the presence of small bubbles is presented. Small bubbles may be assumed when slotted anodes are used. The relative importance of the velocity felds generated by the magnetic effects and/or the small bubbles on the alumina concentration in the bath is discussed.
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