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Advanced Engineering Research (Rostov-on-Don)

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Vol 14, No 4 (2014)

PHYSICAL AND MATHEMATICAL SCIENCES

5-16 611
Abstract

A hidden semi-Markov QP-model is considered; and the way it could be embedded in a general hidden semi-Markov model is shown. The estimation problem (the first of three classical theory problems of the hidden Markov models and hidden semi-Markov models) is solved for the hidden semi-Markov QP-model. The solution is based on Shun-Zheng Yu forward algorithm for a general hidden semi-Markov model. This approach differs from the traditional one and employs posterior probabilities. The estimation problem solution of the hidden semi-Markov QP-model is an important step in solving the following more specific problem. That is the selection problem based on the recorded in the data channel model error sequence from the base of hidden semi-Markov QP-models that generates the closest to the channel sequence error streams. The fitting problem solution will make it possible to evaluate the correcting capability of the noise-free codec towards errors of various types, and to select the optimal codec for a particular communication channel on the basis of the computer simulation experiments.

17-29 598
Abstract

A one-dimensional thermoelastic contact problem on the vertical insertion of a rigid half-plane moving horizontally at a constant speed over the elastic coating (strip) while the bottom side of the latter rigidly resting on the non-deforming foundation is considered. On the foundation surface, the temperature is kept constant. A heat flow generated by the frictional contact is directed to the coating. The problem solution is obtained using the Laplace integral transform and is represented in the form of contour integrals. The location of the solution integrand poles is studied at various task options. Temperature, displacement, and stress distributions over the coating depth are derived in the form of the infinite series over eigenfunctions. It is shown that the thermoelastodynamic instability of the obtained solutions is present across the whole time interval and at any velocity of the half-plane sliding over the coating surface.

30-38 635
Abstract

A plane deformation of a circular cylinder under different systems of statically equivalent loads is considered. The loading is done by the symmetrical constant-rate loads with respect to the centerline; the loads are applied to the cylinder side. Three load cases are analyzed: diametric forces along two generators (Hertz basic feasible solution), uniform normal loads, and uniform parallel forces. The comparison of equivalent stresses based on Mohr theory of strength with the tension intensity of the basic feasible solution in the failure plane is presented. Based on this comparison, the appropriateness of identifying the normal stress in the diametric plane under the specimen fracture, and of its tension stress limit is discussed. It is proved that the normal stress in the diametric plane of crushing the specimen in the Brazilian test technique is not a material tension limit; and it may be several times less than the specified stress limit for some brittle solids.

TECHNICAL SCIENCES

39-49 566
Abstract

The subharmonic response of one third order of Duffing oscillator under harmonic and random excitations is investigated for the first time by a technique combining the stochastic averaging method, the equivalent linearization method, and the technique of auxiliary function for Fokker-Planck equation. The averaged equations are linear zed so that the stationary density function of the approximate response can be found exactly by the technique of auxiliary function. The one third order subharmonic response obtained by the present technique is validated by numerical simulation. The significant contribution of this work is that it may lead to a new trend in investigating subharmonic oscillators in random nonlinear systems.

50-59 442
Abstract

The concept of connecting large-diameter pipes by the electrofusion welding using couplings with tapered cuffs is considered. Practical aspects of the coupling of such pipes are described. In particular, the reasons for the increase in requirements to the quality of welded joints with the enlargement of the pipe diameter are stated. The design of the coupling with tapered cuffs, as well as the assembly technique of this type of coupling is considered. Two technologies – the electrofusion welding of large-diameter pipes using cylindrical couplings, and the electrofusion welding of pipes by means of couplings with tapered cuffs – are compared. In conclusion, a list of the European regulations on which the welds made by means of couplings with tapered cuffs are tested, is given.

60-71 617
Abstract

The applicability of the artificial neural networks to the synthesis of the intellectual systems with the synergetic control law is considered. The key points of the synergetic approach to the system synthesis problem are stated. An example of the synergetic synthesis of the robot electrodrive control law under the conditions of its uncontrolled parametric variation and external disturbances is considered. An algorithm for synthesis of the neural network controller based on a predetermined synergetic control law is presented. The algorithm is based on the synergetic controller behavior simulated by an artificial neural network as a result of its training through harmonic signals of different frequencies. The key element of the proposed integrated approach to the synthesis of the intelligent control system is that it involves a combination of the self-organization unity principle and the training of the neural network at the preliminary stage. This ensures a subsequent stable system operation.

72-85 532
Abstract

The processes of surface nanostructuring of titanium carbide by Nd radiation: YAG-laser with the wavelength of 1.06 microns is investigated. The laser pulse length is 40 ns, the travel rate is 10 mm / s. The radiation energy density on the surface of titanium carbide at the oscillation frequency of 2000 Hz is 2.06 ÷ 6.36 J / cm2. The results of ab initio study of the atomic, electronic structure, and the elastic characteristics of TiC and TiC1-хOх (x = 0,25; 0,5; 0,75) are presented. The band structure of TiC calculated with the use of the density functional theory corresponds to a metal type. It is shown that the calculated elastic properties of titanium carbide are in good agreement with the known theoretical and experimental estimates. The study of the microstructures topography on the of titanium carbide surface using the atomic force microscopy (AFM) shows that in the area of the direct laser action, the roughness is 0.254 µm. Mechanical properties in the direct laser impingement spots, and in the temperature exposure regions are investigated by the nanoindentation. The effect of nanostructuring is determined: the titanium carbide surface hardness goes up to 47.2 hPa after the laser action.

86-92 502
Abstract

Vibration and noise levels of the split-type spindle heads are theoretically investigated. It is noted that in this case, the head oscillating system changes and this leads to the need of modeling the vibroacoustic dynamics of these structures. The calculation of the noise and vibration spectra is based on the power balance method of the construction consisting of a system of rectangular plates where the vibration power flows from spindle bearings are transmitted. The appropriate calculations for spindle cases made of steel and cast iron are carried out. The following data are obtained. The propagation velocity of flexural waves of an iron spindle case is factor of 0.62 lower, its own oscillation frequency is factor of  0.78 lower, the vibration power absorption coefficient is 11.4 times larger, which leads to a significant reduction in noise levels. The investigation timeliness is proved by an extended application of split-type spindle heads in the production, particularly in lathe tools.  

93-102 570
Abstract

Some aspects of representing the fuzzy expert knowledge in the decision-making problems on the process machine adjustment are considered. The technique based on the use of different criteria of consistency in the representation of fuzzy knowledge which includes considering various expertise hierarchy is offered. This technique allows determining a rational term set of the linguistic variable for the construction of the generic membership functions under the input and output system parameters specification. The improved background for choosing terms of the linguistic variables allows optimizing the KB parameters based on the fuzzy production rules. The technique is applied in the subject domain of “Grains combining”; several input linguistic variables are considered; fuzzy knowledgebase creation phases are exemplified by them; models consistency indices are calculated; optimum term sets of each of the variables are selected; generic membership function parameters are obtained.

103-116 510
Abstract

The analysis of the cutting area circuit diagram has shown that coatings on the edges of the hole and on the flank surface of the tool change the thermoelectric power measured by the dynamic thermocouple to the value of not more than 0.3-0.7%. So, only the composition and properties of the coatings will have an effect on the cutting temperature. Model theoretical temperature calculations according to the dependence proposed by the authors have shown that the temperatures are minimal when using single coatings ZrO2, TiN, AlN (for couples Т15К6 — St45), and ZrN, AlN, ZrO2, Al2O3 (for couples Т15К6 – 12H18N10Т). Experiments on turning St45 by carbide plates made of T15K6 have proved the efficiency of TiN+AlN coatings when the cutting temperature, chip shrinkage, and contact length on the front face (lc) are less than for the base alloy T15K6.

117-124 556
Abstract

The design and training scheme for the artificial neural network is considered. An expert system of evaluating a craftsman’s motor skills stability while working on the welder simulator is based on this technique. It is assumed that the weld joint quality depends directly on the welding behavior stability. While the stability of the manual arc and mechanized welding depends on the welder’s motor skills. It is proposed to use an expert system to determine the stability criterion of the welding process. A step by step design of the artificial neural network architecture considering the specific weld formation is described. It is shown that the application of artificial neural networks based on the expert system allows evaluating the welder’s job stability. A training technique which shortens the time and reduces the number of experiments without loss of the data adequacy and the expert system training quality is described. When creating a database, the experimental results presented as "Quality domain" that connects the welder’s motor actions and the fillet joints defects are used.

125-132 477
Abstract

It is stated analytically and proved experimentally that in the heavy-loaded conjugations such as a break system of the rolling stock the maximum temperature in the wheel is reached not on the surface but in the subsurface layer. The study of the non-stationary contact coupled thermoelasticity problem on the brake disk rotation, and on the experimental research of the hydrogen diffusion has shown that the design dependence type of the thermal field describes adequately the process of the hydrogen diffusion in its functional dependence on the temperature. Under these conditions, maximum of the hydrogen concentration coincides with maximum temperature. The study results on the segregation processes of the alloying and doping elements in the wheel - brake shoe tribosystem are presented. The elemental composition on the boundaries of the steel grains of the railway wheel is determined using Auger spectroscopy. The upper metal layers in the defected wheel contain iron, sulfur, phosphorus, and zinc. In the tread working layer, the sulfur and phosphorus content is much less, and it conforms to their volumetric content.

133-141 538
Abstract

The effect of the elbow motion kinematic parameters (angular displacement, velocity, and acceleration) on the surface electromyographic (EMG) signal of the biceps of the arm under the elbow motion execution with different load is analyzed. The dependences of the frequency and amplitude parameters of EMG signals on the elbow motion parameters under load lifting and lowering are established. The test bench structure is shown. The technique of recording EMG signals from the biceps, as well as of the signal processing methods are presented. Methods of statistical and spectral analysis are used for the quantification of the EMG signal values. In the time domain, the statistical analysis includes the determination of the following parameters: EMG amplitude values dispersion, average and RMS values, zero crossing value, waveform length. These parameters are determined on the measured values array basis of the signal generated within 0.3 sec. of the current time (‘sliding’ interval). The developed muscle force value is estimated; the cepstral coefficients are found. EMG biopotential distribution histograms are constructed. In the frequency domain, the EMG signals spectral analysis is carried out by Fast Fourier Transform. The spectrum total power, the average frequency, the median, and a spectral component with the dominant frequency are determined. The EMG biopotential registration and analysis are performed by means of Matlab. Information features which can be used for the intelligent control system synthesis based on neural networks are identified.

142-149 490
Abstract

The method of frequency estimation of the simultaneously and independently operating generators under unpredictable changes in the measurement interval size is studied. Errors arising under the method application due to the transiency of the oscillator frequencies on the frequency estimation interval are considered. The first error component is related to the deviation of the measurable generator phase due to the inherent generator frequency instability; and the second one is determined by the unpredictable changes in the oscillator frequency on the measurement interval. It is noted that the decrease of each of the components imposes incompatible requirements on the duration of the time length. On the basis of the known relations identifying the potentially reachable value of the root-mean-square frequency deviation from the nominal value, the expressions determining the optimum time length are obtained. As a criterion when choosing the time length, the minimum of two errors sum is considered. The analytical relations determining potentially reachable accuracy of the frequency estimates are presented. The unbiasedness, efficiency, and consistency of the estimates obtained are proved.

150-157 480
Abstract

The applicability of the jatropha culture as a biofuel material is considered. The description of the culture and its main characteristics are presented. The seed technological properties characterizing the subsequent oil quality are studied. The fundamental agronomical properties under growing the jatropha culture, the area of its growing are described. A chemical analysis of the produced jatropha oil and the subsequent processed biofuel is carried out. A comparative analysis with the diesel indices is conducted. The technology of the biofuel production based on jatropha is proposed. The basic technological processes and their implementers in the engineering solutions are determined. Diesel fuel oil and jatropha oil were mixed in various percentage ratings. A comparative analysis of various types of the mixed fuel on the main characteristics is carried out; and the best mixture ratio of the jatropha oil to the diesel is specified. A comparative economic analysis of the production costs for various kinds of raw materials is conducted. A scheme of the biofuel generation and application is developed.

158-165 543
Abstract

A model of the indirect control flow divider for the steady state operation which maintains a twin-engined hydromechanical system in the synchronous common mode is considered. The divider is presented as an astatic regulator consisting of the sensor, amplifier, and regulating elements. However, its main static characteristics are the dependences of the timing failure on the regulating element spool speed, and those of the regulating element spool speed on the input control. The investigation of the static characteristics conducted according to a special program developed in the Mathcad package allows determining the presence of the hysteresis nonlinearity. The presence of the ambiguity zone is a troublesome factor indicating the self-oscillations onset probability in the closed loop system having a controller with such a property. In this case, the system would require the design constraints to ensure the characteristic of proportionality with saturation. Various design and operating parameters for the flow divider of the indirect control and the hydromechanical system are analyzed. This allows evaluating its effect, range of variation, and obtaining the basic approaches to designing synchronous in-phase systems. Two astatic regulator models with and without leakage at the amplifier element, as well as various types of the amplifier orifice overlapping are considered. This analysis has demonstrated the sufficient accuracy of the models, and the agreement of the results under the boundary conditions.

166-175 452
Abstract

On the basis of the Navier-Stokes equations for the case of a ‘thin layer’, the continuity equation, Lame equations, and Darcy equation, considering the boundary conditions on the pin and bearing face at the layer interface, a method of generating an exact self-similar solution to the problem of calculating the hydrodynamic elastically deformed radial bearing working on a two-layer lubrication and having damping properties is provided. The problem solution is resulted in identifying the velocity and pressure field in the lubricating layer, and in obtaining the analytical expressions for the basic performance of the elastically deformed radial bearing. A numerical analysis of the obtained analytical expressions for the non-dimensional load-carrying capacity of the elastically deformed radial bearing with a porous layer on the pin surface is performed. The effect of the parameter values providing the bearing with an increased load-carrying capacity is assessed.

176-185 520
Abstract

An element of the working body (brush) of the aerodrome sweeper – a synchronous hydromechanical drive – is considered. It is based on the throttle flow divider of the non-spool type plunger setters, and it is driven by two hydraulic motors. Its mathematical model is offered. Special attention is given to describing the stress state of the brush shaft when twisting under the variable load, and to identifying the effect of the shaft elastic properties on the dynamic properties of the synchronous hydromechanical system. In this paper, modeling of the synchronous hydromechanical brush drive system, unlike the conventional method, is based on the use of the reduced volume stiffness of the hydraulic system. This simplifies the modeling and allows performing a rapid analysis of the test drive operation which significantly reduces the design time of the drive system with the given performance properties.

186-193 607
Abstract

The causes of the destruction of the crane Gottwald НМК 170 EG (63 t) which happened in 2011 on the territory of “Novorossiysk Commercial Sea Port” are analyzed. The structural and engineering recommendations on the platform bearing capacity restoration are developed. These proposals are based on the failure analysis of the weld joints of the prow rotating platform, and on the 3D numerical simulation of its stress state. It is shown that an abrupt change in the welded assembly compliance in the area of the stiffening ribs supporting the platform bedplate causes a local increase in stress and predetermines the fatigue-crack nucleation. The results of the crack nucleation regions simulation are in good agreement with the crane diagnostic results. It is shown that the stress localization in the welded node joints with non-uniform compliance of the connected components is a common pattern. It must be taken into account in both the designing and the development of the repair technique. A specific case suggests extra pads to provide a smooth change in the welded assembly compliance in the area of the platform stiffening rib under the weld assembly repair.

194-202 542
Abstract
For the first time, the acoustic emission (AE) method applicability to study the processes ongoing in the microporous medium under capillary pore filling with liquid is investigated. In particular, the temperature contribution to the dynamics of the porous materials impregnation is studied. The experimental results have shown that the most informative AE parameters reflecting the capillary liquid rise dynamics are the signal sum and the oscillation sum. The curve shape of the signal sum dependence on the AE amount follows the curve shape of the dynamic pattern of changing in the liquid elevation through the capillaries of the ceramic sample constructed from the experimental data. At the beginning of the capillary rise, the AE activity is significantly higher at higher temperatures. With increase of the liquid capillary rise, the process intensity decreases. The experimental data indicate that the AE parameters reflect the impregnation dynamics and kinetics under any change in the impregnation conditions, and they can be used for the remote process control.

SOCIAL SCINCES

203-209 568
Abstract

Some ways to improve the efficiency of the enterprise management system are considered. The solution to this problem from the perspective of the synergistic approach, will allow increasing the utilization of the industrial enterprises’ potential, accelerating their economic development rate, and ensuring their product competitiveness. The aim of the article is to study the synergistic effects of the enterprise. The causes of positive and negative synergistic effects are considered. A generalized model of various in-plant synergistic effects formation is presented. The significance of the external and internal environmental impact on the synergies formation is shown. Types of synergetic effects reliant on the sources and their areas of origin are described. Knowledge of the cause-and-effect relations forming one or another type of the synergistic effect allows elaborating an effective strategy for the enterprise development.  

210-218 481
Abstract

The structure of communication and its role in the management when building the University production and business integration are studied. The organization of the educational process on the basis of the communication component and its integration into the innovative educational activities of the University are considered. The key aim of building the communications process – to develop the approach to achieve the strategic objectives of the University – is presented. It is shown that various types of communication process (personalized and non-personalized, endogenous and exogenous) are used to provide individual attention to each student, to prove that the choice of the University is optimum. It is found that the communication processes of the University are always aimed to improve the quality and competitiveness of the educational services. It is noted that the industrial management theory and the complimentary sciences have created integration tools of the communication processes and have determined the opportunities for their codifiability. Some of these tools are of the methodological nature. Others are regarded as certain patterns, effects, principles, rules, and algorithms based on these models. Using the potential of this device determines the educational services quality.

219-226 602
Abstract

The research results of determining the professional development of contemporary teachers are presented. A theoretical analysis of the essence and motivation of the professional development of the teaching subject is performed. ‘Factors-blockers’ and ‘factors-facilitators' of the professional and personal growth are identified and described. The significance of the teacher’s subjected involvement in the process of self-development is shown. Contradictions of the present-day teaching practice are described and structured. Levels of accepting innovations by teachers, and their approach to self-development are considered. The obtained data are typed. The reference vectors of the development of the teaching subject are determined. The self-development mechanisms: self-acceptance, reflection, life events planning and forecasting, social modeling are discovered. The study data have shown that the career development system requires designing programs of the sense-generative nature aimed at the development of the personal sense of the self-transformation. A modular program of the psychological support for the teacher’s professional development at different professionalization stages is described.

227-232 677
Abstract

Work devoted to the study of risks arising at different stages of implementation of system of electronic document. The implementation of electronic document management system is a complex process whose success depends on several factors, therefore it is necessary in the planning phase of the project to take control of all of its the stages. This article examines the impact of the organizational, administrative, subjective and technological risks at each stage of implementation of the system, and the mechanisms that hinder achievement of goal set by in the automation. The article provides theoretical analysis of the possible consequences of risk events at all stages of implementation and maintenance of electronic document management system. This article describes a theoretical analysis of the possible consequences of risk events at all stages of implementation and maintenance of electronic document management system and the basic principles of risk management to prevent and reduce the possibility of their occurrence.



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ISSN 2687-1653 (Online)