Vol 23, No 2 (2015)

The following paper suggests and studies the algorithms to control the relay automatic oscillation systems with negative variable hysteresis in a static characteristics of controlling device and variable structure which provide the advanced rapidity of the system during transition period and full invariance of static mistakes under constant impact and nonsymmetrical control. The invariability effect of is reached by means of forming the compensating signals without active change of controlling device parameters. The paper shows the results of computer modeling.

The paper shows a new method of measuring the frequency of harmonic signals based on the formation of additional voltage signal and identification of zero transition moments. The block diagram of measurement tool for implementation of the method is provided. Implementation of the method provides exclusion of the error caused by the non-ideal structure of phase-shifting units which form the additional signals by correcting the instantaneous values of the additional signal. The paper gives the results of analysis of the method error caused by the deviation of the actual signal from the harmonic model. The results allow to choose the appropriate hardware and measurement process parameters depending on the requirements of accuracy and measurement time and the specified frequency range.

The authors continue to research the stability of quality of investment portfolio management systems on the financial market, started in previous paper. The following paper deals with the portfolio management systems optimized within a multi-criteria task. The paper proposes the method of retrospective cross-validation which allows us to estimate the decline in quality caused by the non-optimality of settings. This method also allows us to compare the efficiency of various systems during parametric optimization and testing using multiple series. The paper provides a number of variants of domination of reflections efficient frontiers of set of feasible portfolios for comparison between various optimized systems. The paper also describes the hierarchy of such domination variants.

Fast digital algorithms for computing estimates of the Fourier coefficients are presented. They are based on the sign-function analog-stochastic quantization which is used as primary transformation of investigated random processes. We used the method of partitioning the process analyzed into individual segments to enhance the statistical stability of estimates calculating amplitude spectrum. In accordance with this method the final spectral amplitude estimation is performed by averaging of the processing results of individual segments. To test the metrological characteristics of the developed algorithms we carried out experimental research of estimates amplitude spectrum using the model of a random process. This model represents the sum of statistically independent harmonic components in the additive white noise. For exa mple we present the results of the calculation of spectral amplitude estimation for one, three, seven and ten segments. Processing segments was carried out with their half-overlapping.

The paper deals with a number of problems considering the modelling of processes of heat exchange in the “gas stream-pipe-environment” system. The paper analyses the effect of seasonal air temperature changes on the heat flow from the pipe to the ground and pipe temperature. Great inertance of the heat exchange process in the ground is revealed. Numerical and analytical models of heat spread in the ground are developed, parameters of models for the stationary modes are defined. On the basis of the connected thermohydraulic model of a gas stream in the pipe with consideration of heat exchange with the environment the velocity profile is defined, as well as the wall layer thickness; it allows to pass to a thermal problem with the moving two-layer medium equivalent in terms of temperature distribution in the pipeline and magnitude of a thermal stream into the environment.

This paper deal with the problem of building an automatic system to control the temperature of water which is supplied to the consumer via a closed dependent heat supply system equipped with mixing pumps. The paper suggests a model of control object which considers the spatial distribution of heat transfer process as a nonlinear dynamic closed-loop system with variable feedback gain. The feedback gain works as a command variable. The model is identified on the basis of the results of active experiment. Automatic control system is synthesized and studied by means of numerical simulation of dynamic system. The paper lists the results of the control object identification and investigates the transition behavior of the automatic control system in terms of control and disturbance.

The paper deals with the issues of heat distribution in the DSC furnace with consideration of its basic operation modes and geometrical dimensions. The paper lists the results of experiments conducted for numerical determination of the influence of the radiation of the substrate on the process of heat transfer from the heater to the cells with the test substance through the effect of heat conduction. An equation of heat conduction of the substrate in the oven with consideration of change of the ratio of heat conduction of the air layer between the substrate and the oven cover with consideration of the influence of the thermal radiation of the substrate at high temperature operation modes. The resulting equation is fundamental for mathematical description of the object of the automatic substrate temperature control which allows to provide the best indices of heating quality of the test substance.

In article the way of determination of distances to places of double short circuits on the earth on one power line by measurement of emergency components of phase current and phase tension is offered. Results of theoretical calculations coincided with results of modeling in the program MatLab Simulink environment.

The paper considers the interaction of a shock wave front with the powder particles used for the deposition of wear resistant coatings by the method of explosive spraying. Analyzed the algorithms for solving the problem in different settings explosive shock wave. Comparative analysis of various options for the approximation of the velocity of the shock wave in the air is done. By the method of quadratures numerically solved the integral equation describing the " entrainment" of the powder particles of the products of detonation (PD) explosives. Тhe nature of changes in the velocity of the particles in the wave front of the rarefaction PD is examined.

Influence of the modes of heat treatment on obtaining qualitative mechanical properties and microstructure in the details from casting aluminum alloy АК7ч conforming to requirements of the production instruction on heat treatment is investigated. Methods of the metalgraphic analysis studied the microstructure of details and explosive samples and their mechanical properties on two different modes (with natural aging and without natural aging). The choice of the further heat treatment modes of material is described. Due to the research of technological details production the time of their production is reduced without loss of quality of their properties.

The method of rating the forcing of bearing assembly spindle unit preload. A test-bench has been developed to quantify vibroacoustics, featuring the dimension of the identified preload forcing. Amplitude-frequency response characteristics of vibration acceleration of spindle unit during short-term forcing directly on the spindle became available by experiments. The frequency range of a signal of vibration acceleration was selected from 3200 Hz to 4200 Hz. The frequency content of amplitude spectra has been analyzed to determine eigen frequency peaks of spindle unit at various preload values.

The method of calculating of residual stress ring roller bearing formed in a circular plunge grinding outer raceway using the finite element method was developed. It is assumed that the main influence have temperature deformations. Initially solved the corresponding plane problem of unsteady heat conduction, with a movable source of heat in the cutting zone. In the second stage sequentially solved plane nonlinear deformation problems for each step transient thermal analysis, which was discussed above. The dependence of physical properties on temperature is considered. Compiled computer programs, which allows to determine the temperature field and residual stress in rings of different sizes with different modes of grinding. Results of calculation of residual stresses in typical rings are set.

Questions of quality control of polymeric and varnish-and-point covers are considered. Dependences that allow to determine a moment when the medium has penetrated through the cover are offered. Characteristics of polymeric cover with and without induced defect are presented. Experiments in which penetration moment was measured are carried. Recommendations for cover lifetime determining are considered. Method of penetration moment registration are considered. Method of penetration moment registration are presented.

The paper studies the protective effect of the protectors on the dissolution of metals in the environment of the electrolyte. An experimental setup with which to study the distribution of the metal dissolution rate as a function of the distance from the tread. A model process to represent dissolving of the fiberglass with copper film in ferric chloride solution. It was found that as the distance from the tread increases the rate of dissolution of the metal and from a certain distance, it becomes practically constant. Dissolving speed distributions was obtained for different solution concentrations. Results of experiments allow determining the protection radius.

The paper is about the automation of telecommunication cable isolation processes: describes the role of a system approach to the automation of complex systems with distributed parameters, presented the main technological steps of applying an insulating coating on a conductor, formed the main local and global parameters of telecommunication cable as the channels of communication in the isolation process.

The paper deals with the nomograms reflecting the relationship of basic parameters of the technological mode of formation of aluminum alloy ingots for continuous casting in an electromagnetic mold. Design analysis is made on the basis of previously synthesized approximate models such as regression on the results of a numerical study of the temperature field of the ingot. It is shown that by lowering the maximum technologically permissible cooling intensity at the corresponding adjustment of the casting speed can reduce the size of the two-phase region in the central zone of the ingot. The application of this approach, it is advisable to the stage of development of ingots production with regulated quality requirements.