One-sided approximation in L of the characteristic function of an interval by trigonometric polynomials

The value of the best one-sided integral approximation of the characteristic function of the interval (-h, h) by trigonometric polynomials of given degree is found for any 0 < h ≤ π. © 2013 Pleiades Publishing, Ltd

Design of water-drip cooling facilities for heat treatment of mill rollers

Water-drip cooling devices based on centrifugal jet atomizers are studied experimentally. Their main operating characteristics such as the irrigation density, the uniformity of the distribution of irrigation over the cooled surface, the dependence of the heat transfer factor on the surface temperature, etc. are determined. The effect of the design and production parameters of the quenching facilities on their operating characteristics and mode of cooling of large steel articles is considered for mill rollers as an example. The results of the tests are used to design cooling facilities and heat treatment processes for mill rollers with the use of water-drip quenching. © 2013 Springer Science+Business Media New York

Polystyrene-based nanocomposites with different fillers: fabrication and mechanical properties

The paper presents a comprehensive analysis of elastic properties of polystyrene-based nanocomposites filled with different types of inclusions: small spherical particles (SiO2 and Al2O3), alumosilicates (montmorillonite, halloysite natural tubules and Mica) and carbon nanofillers (carbon black and multi-walled carbon nanotubes). Composites were fabricated by melt technology. The analysis of composite melts showed that the introduction of Montmorillonite, Multi-walled carbon nanotubes, and Al2O3 particles provided an increase in melt viscosity by an average of 2 to 5 orders of magnitude over the pure polystyrene. Block samples of composites with different filler concentrations were prepared, and their linear and nonlinear elastic properties were studied. The introduction of more rigid particles led to a more profound increase in the elastic modulus of the composite, with the highest rise of about 80% obtained with carbon fillers. Carbon black particles provided also an enhanced strength at break of about 20% higher than that of pure polystyrene. The nonlinear elastic moduli of composites were shown to be more sensitive to addition of filler particles to the polymer matrix than the linear ones. The nonlinearity coefficient $\beta$ comprising the combination of linear and nonlinear elastic moduli of a material demonstrated considerable changes correlating with changes of the Young's modulus. The absolute value of $\beta$ showed rise in 1.5-1.6 times in the CB- and HNT-containing composites as compared to that of pure PS. The changes in nonlinear elasticity of fabricated composites were compared with measurements of the parameters of bulk nonlinear strain waves in them. Variations of wave velocity and decay decrement correlated with observed enhancement of materials nonlinearity

Organization of security control of wireless telecommunication network based on fuzzy networks

The problem solution of security control of wireless computer network nodes, which is based on the use of the apparatus of fuzzy sets is presented in this article. The approach used in the paper aims to an automation that will improve the efficiency of control of the nodes and operations of a network administrator. The approach allows forming a system of security control of the wireless computer network based on neuro-fuzzy (hybrid) network, which is characterized by high adaptability, ease use, the ability to identify better the sequence of the analysis of vulnerabilities in the wireless computer network nodes. The feature of the proposed approach takes the dynamic nature of the wireless computer network into account

Research of academic motivation at the stage of forming a threshold level of mastering competences

The relevance of researched problem is caused by the society requirement to form and implement educational and creative potential of a student as a conductor of changes that set a high level of motivational behavior. The aim of this article is to develop a structural model of motivational behavior of students that allow carrying out modeling of specific characteristics and their practical application. The leading approach to the research of this problem is the provision of the theory of self-determination on basic needs that allow considering basics of intrinsic motivation. The results of the research are: the structural model of motivational behavior is considered in the article, the questions are selected and the questionnaire on educational motivation is developed for the poll of student's groups “Economy and Management”. The development and approbation of multi-profile software programs are “Students’ Questionnaire” to implement on-line poll or interviews with students on academic motivation. The results of the research can be useful for specialized structural divisions of the university, teachers, and also for the students in case of further research of the issues of academic motivation and individual educational paths. © 2016 Eremicheva et al

Effect of SLM parameters on the structure and properties of CP-Ti

Selective laser melting (SLM) is an additive manufacturing technique, which allows varying the relative porosity at the micro and macro levels. In this study, the microstructure, including the porous structure, of cp-Ti Grade 1 ELI produced by SLM and the effect of the scanning parameters on mechanical properties are studied. The mechanical properties are analyzed in terms of ISO 5832-2 for metal implants for surgery. The cp-Ti samples processed by SLM are characterized by increased strength due to the low porosity condition and the acicular martensitic structure. The ductility data scattering is explained by the stratified distribution of porosity in the metal after SLM. © 2018 Author(s)

The Features of Bainite Transformation in Alloyed Steels

The main factors affecting the kinetics of isothermal bainite transformation in alloyed steels were determined using the algorithms of the computer modelling of phase transformations in the solid state. The experimental and calculated transformation kinetics was described and compared using well known Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation and Austin-Rickett (AR) equation. The effect of the initial configuration and the nucleation rate of the new phase nuclei on the parameters of the bainite transformation was analysed. The calculated kinetics of phase transformation at different nucleation rates was compared with the experimentally observed for HY-TUF and D6AC steels. The mechanism of the bainite transformation in alloyed steels was explained. © Published under licence by IOP Publishing Ltd.The work was supported by the Act 211 of Government of the Russian Federation, contract № 02.A03.21.0006, the Ministry of Science and Higher Education of the Russian Federation, project №11.1465.2014/K