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  • Comparative analysis of porous piezoceramics modelling by effective moduli and finite element methods with experimental data

    The results of computational experiments to determine the characteristics of the porous piezoelectric ceramics based on the methodology, including the effective modules method, simulations of representative volumes on a simple random method and the method of Witten-Sander, finite element method to solve static piezoelectric problems for heterogeneous composite media and the accounting of inhomogeneous polarization near the pores are presented. A comparison of the results of computer simulation with the known experimental data for the porous material PZT-4 and its analogs is realized. It is concluded that the accounting of inhomogeneous polarization in the vicinity of porous provide the better agreement between numerical results and large number of known experimental data. Thus, for most effective constants the smallest errors are obtained for a representative volume of the porous piezoelectric material, constructed by Witten-Sander method.

    Keywords: piezocomposite, porous piezoelectric ceramics, inhomogeneous polarization, mathematical modelling, models of representative volumes, finite element method, effective moduli

  • Methods for the synthesis of LaMnO3 (Review)

    "This review covers various methods of synthesis LaMnO3 ferroics. The general analysis of the solid-phase synthesis reactions methods and wet methods (sol-gel, sorption, co-precipitation) are carred out. The original results of LaMnO3 syntheses from various precursors by means of the in situ method are showned. The advantages and disadvantages of different methods of synthesis are determined. The analysis of synthesis LaMnO3 ferroics published data is shown:
    - the structure formation of LaMnO3 in perovskite-type phases occurs at different temperatures, depending on precursors states;
    - LaMnO3 perovskite phases differ in symmetry and unit cells parameters at room temperature, depending on the preparation conditions;
    - the highest synthesis temperature of LaMnO3 are typical for solid phase reactions method (950-1050 ° C), the lowest - for wet synthesis methods (500-700 ° C);
     - the synthesis conditions effect the stoichiometry of LaMnO3 for oxygen content.
    Our studies of structure formation processes of LaMnO3 by in situ method are allowed to define the role of precursors states at synthesis of solid phase reactions methods, adsorption, co-precipitation and sol-gel mixtures.
    It is determined that in samples prepared by wet chemical methods, the formation processes of  LaMnO3 perovskite phases occur at lower temperatures than by solid phase reaction (sol-gel precursor - 500 <T <600 ° C; precursors obtained by coprecipitation and sorption methods - at 600 <T <700 ° C and 700 <T <800 ° C, respectively).  

    Keywords: ferroics, LaMnO3, X-ray diffraction, solid-phase synthesis, sol-gel synthesis, sorption, co-precipitation

  • Methods of measurement of small inductors for radio systems on a chip

    Technique for measurement of inductances (L) about 1 nanohenry or less one, is discussed. Two measurements of inductance L are executed. First one is executed for stub length l0, another - for stub length, shortened into N times. Formula for calculation of unknown inductance’ error has been obtained, where determination of unknown L with error closed to meter error has been succeeded by choice of parameters. It is shown that required measurement’s error of initial stub length for N=2 and N=5 is in tens micrometers’ range. Techniques for error’s diminishing have been considered. Estimation for basic stub length of 6,6 mm and 8,3 mm for N=2 and N=5 respectively has been executed. 

    Keywords: inductance, least-squares procedure, meter error, stub base

  • Induced brain activity during the perception of Kanizs figures

    The problems of visual perception whole object are considered in the paper. As an objective method to explore these issues, are used as incentives figure in subjective contours - Kanizs figures. The survey was attended by eight healthy men (SFU students and staff), right-handed, aged 22 to 35 years. The results of analysis of variance characteristics visual EP, recorded in the perception of different figures, showed that significant differences were found when comparing the real and illusory form with a figure control.

    Keywords: Visual perception, Kanizs figures, evoked potentials (EP), dispersion

  • A new approach to provide web accessibility for the blind users based on the enhance of navigational characteristics of web pages

    Most of web pages of the Web are inaccessible for the blind users. And the main reason is a lack of the semantics at the source code (technical) level of web pages and absence of the navigational components. In this work we propose a new web page representation---multiaxial navigation model---representing web documents in the form convinient for the blind users. Moreover, we present methodology for the navigation on the model proposed, that ensure an efficiency of user mobility. Automatic transformation of a web page into the multiaxial navigation model and navigation means are realized in the Blindzilla prototype. An efficiency of the proposed concepts is proven experimentally regarding contemporary screen readers, such as JAWS, Window-Eyes, and Fire Vox.

    Keywords: web accessibility, navigation, web page, web technologies

  • Latest Nanotechnology (review)

    This article is an overview of the latest nanotechnology. Advancing the development of nanotechnology in the world due to the use of such areas as microelectronics, special materials, energy and military equipment. Given in the article data show widespread use of new nanotechnologies in various branches of engineering. 

    Keywords: nanotechnology, nanotubes, graphene transistors, microelectronics

  • Selective growth of ZnO nanorods arrays by hydrothermal method on silicon

    In the present work we have carried out studies of the processes of growth of zinc oxide nanorods by hydrothermal method on silicon substrates. As sublayer catalyst used growth caused by laser deposition of zinc oxide, various thicknesses. Studied selective growth of nanorods on the microstructure of thin-film sub-layers of zinc oxide obtained by laser deposition. The optimal conditions for the synthesis of: the concentration of Zn (NO3) 2 - 0.4 mol / l, hexamethylenetetramine - 0.4 mol / l, the concentration of NH3 · H2O - 0,01 mol / L -0.01, process time 4:00, the process temperature is 80 ° C. Sublayer thickness of zinc oxide, as shown by experiment, the growth of the rods has no noticeable effect. Oriented arrays of nanorods were obtained up to 500 nm and a diameter of 60-150 nm.
    Keywords: zinc oxide nanorods and micro-oriented arrays of nanorods, hydrothermal synthesis method, selective growth, thin film underlayer.

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    Keywords: nanoparticles, nanotubes, nanotechnology, security, technology, environment, energy, microelectronics.

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