Papers by Keyword: Fluctuations

Abstract: Thin-walled cylindrical shell made of reinforced concrete, is widely used in the construction of buildings and structures as coatings and forms of architecture of buildings. Thin-walled shell its shape can give entertainment to the architectural design of buildings, and their rigidity helps to block large spans, creating more closure of the room without additional supports. Another advantage of using cloud forms of structures is the efficiency of this design, since for the manufacture of shell forms of structures less construction material is spent than any other design for coating. The purpose of theoretical calculations and the studied excrement over reinforced concrete shells with different elastic modules, is to ensure reliability in the operation of buildings and structures, and to exclude accidents arising resonance phenomena of free vibrations of the shells from the effects of external forces (loads). On the basis of the laboratories of Komsomolsk-on-Amur state University in the laboratory of building materials and structures, experimental studies were conducted to determine the spectra of forced and free vibrations of the reinforced concrete shell with different elastic modules. The purpose of research on reinforced concrete shells is to determine the oscillation frequencies at different locations of the combined masses. The article deals with the theoretical calculation based on the equation of the theory of flat thin-walled shells, using the Bubnov-Galerkin method, by which we determine how the parameters of the shell affect the process of free oscillation.

Abstract: The aim of this investigation is to provide theoretical justification of the crystallizing nucleus formation in liquid iron. To solve this problem, the authors put forward the fluctuation hypothesis: short range order region formation in liquid metal takes place due to temperature fluctuations, and the temperature of the short range order is the temperature fluctuation around Kelvin scale zero in the course of crystallization time. The investigations were carried out for liquid state of the substance, in particular, for iron in paramagnetic state at the melting temperature. Analytical derivation of the temperature fluctuation value was given. Analytical expressions were obtained to define the average number of atoms in the short range order region for crystallizing iron. The investigation results show that short range order contains enough atoms to provide interaction with pulsed magnetic field resulting in the increase in the number of crystallization nuclei and in the decrease of their size. The obtained results can be used in the decision-making process concerning some manufacturing operations aimed at providing homogeneous structure of metals, particularly, in ferrous and non-ferrous metallurgy.

Abstract: We study the structure of nonstoichiometric HfO_x films with variable composition using methods of XPS, spectroscopic ellipsometry, and ab initio calculations. According to XPS and optical absorption experiment data HfO_x consists of metal Hf and ~10-15% of nonstoichiometric hafnium sub-oxide HfO_y (y<2). HfO_y can be placed between HfO₂ and Hf, inside HfO₂, inside Hf. According to this model space fluctuations of chemical composition cause space fluctuations of bandgap in HfO_x. We found that transport in such electronic systems is described by percolation theory. This approach can be applied to explain LRS transport of HfO_x-based RRAM.

Abstract: In the given paper the influence of friction forces in the bearing on the accuracy of automatic balancing unbalanced rotors by pendular automatic balance devices is considered. Magnitude of residual offset of a rotor–pendulums system depending on the friction forces is received, that allows defining residual vibration of the mechanism.

Abstract: In this article the time change automatically balanced unbalanced rotor automatic ball balancing devices is considered. The calculation of original differential equations is made with numeral calculation using the Runge-Kutt method. The time dependence of the transition process of the balancing process from the parameters of the automatic balancing device is obtained.

Abstract: This article is devoted to creation of mathematical models of overhead transmission lines (OHTL), taking into account the glaze. In the studying and designing of transmission lines is often necessary to construct mathematical model taking into account the influence of natural factors and all the basic physical parameters affecting or hindering them. The main difficulties arise when describing the equation of oscillations, as they nonlinear. Numerical experiments and comparative analysis with previously reported models was presented. The main setting is the critical velocity of the wind flow and its dependence on the angle of attack to OHTL.

Abstract: The fluctuations observed in tokamaks, stellarators and linear machines were similar with turbulent plasma in fusion devices, which were stochastic system, and the application of statistics method on them is studied in depth. First, the relating theories were summarized; Second, the mathematical model of the multifractal process is analyzed; Finally, the simulation on multifractal analysis of plasma turbulence and financial time series is carried out, results show that this method can be applied in time series effectively.