Donets'k, Ukraine
Donets'k, Ukraine

Donetsk National University is the leading higher educational institution in Donetsk Oblast, Ukraine. The University's history starts in 1937 from the moment of creation of a pedagogical institute in Donetsk . In 1965, the Institute was transformed into Donetsk State University. It was accorded the National status in 2000. Wikipedia.

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Goltsov V.A.,Donetsk National University
Metal Science and Heat Treatment | Year: 2017

Data on the phase transformations induced in metals by hydrogen are generalized and analyzed. It is suggested to classify hydrogen-induced phase transformations on the basis of allowance for the temperature dependence of the parameters of diffusion of substitutional and interstitial (hydrogen) atoms like in the classical science of metals. A pioneer classification of hydrogen-induced phase transformations by this method is developed. © 2017 Springer Science+Business Media New York

Storozhev V.I.,Donetsk National University
International Applied Mechanics | Year: 2013

A method for the theoretical analysis of the spectra and properties of electroelastic waves in multilayer piezoelectric cylinders with a longitudinal sector notch with arbitrary angle is developed. The real and imaginary branches of the dispersion curves and ratios of period-averaged power flows in the inside and outside layers of the cylinder (waveguide) are studied. It is shown that the dispersion characteristics of cylinders vary widely with the material characteristics of the layers and the geometry of the cross-section © 2013 Springer Science+Business Media New York.

Puzyrev V.,Donetsk National University
International Journal of Solids and Structures | Year: 2010

The propagation of elastic waves in piezoceramic cylindrical waveguides of circular cross-sections with sector cut is investigated on the basis of the linear theory of electroelasticity. Dispersion functions are obtained from boundary conditions in an analytical form of functional determinants for each value of the generalized wave number. A selected set of numerical results including real, imaginary and complex branches of full dispersion spectrums with various symmetry of wave movements is presented to describe the essential characteristics of the waves. Leading effects of spectrums transformation by change of waveguide's angular measure are enlightened, and wave asymptotic behavior is analyzed. The variation of the cross-section is considered as a mechanism to control the dispersion characteristics of waveguides. © 2010 Elsevier Ltd. All rights reserved.

Tkachenko V.S.,Donetsk National University | Kuchko A.N.,Donetsk National University | Dvornik M.,University of Exeter | Kruglyak V.V.,University of Exeter
Applied Physics Letters | Year: 2012

We report a continuous medium theory of dispersion and scattering of spin waves propagating in thin nanowire magnonic waveguides with curved regions. Assuming that the static magnetization is aligned along the waveguide, the curvature leads to a geometrical effective magnetic field term that is proportional to the square of the ratio of the exchange length to the radius of curvature of the waveguide. The term is small enough to favor the use of bended nanowire waveguides in planar magnonic data architectures. However, a stronger (multiple) winding (e.g., within helical structures) could enable design of magnonic waveguides with desired properties. © 2012 American Institute of Physics.

Kaloerov S.A.,Donetsk National University
International Applied Mechanics | Year: 2012

A method to solve a thermoviscoelastic problem for multiply connected anisotropic plates is proposed. The perturbation method is used to reduce the problem to a recurrent sequence of thermoelastic problems that are solved using generalized complex potentials. By expanding the unknown functions into Faber-Laurent series and satisfying the boundary conditions using the generalized least-squares method, the problem for a plate with elliptic rigid inclusions is reduced to a system of algebraic equations. The thermostressed state of a plate with one or two inclusions is numerically analyzed depending on time and geometry © 2012 Springer Science+Business Media, Inc.

Tkachenko V.S.,Donetsk National University | Kruglyak V.V.,University of Exeter | Kuchko A.N.,Donetsk National University | Kuchko A.N.,University of Exeter
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

Using the transfer-matrix method, we have developed a theory of exchange spin waves in a thin cylindrical magnonic crystal (periodically layered all-ferromagnetic nanowire) with diffuse interfaces. The magnonic spectrum and the frequency dependence of the reflection coefficient of spin waves from a junction between a homogeneous magnetic nanowire and a magnonic crystal have been calculated and compared. Diffuse interfaces with linear and sinusoidal profiles of variation in the uniaxial anisotropy value have been considered, also allowing for asymmetry in the relative thicknesses of either main layers, or interfaces, or both. We have found that, although the thickness and profile of interfaces have a significant effect on the size and position of the magnonic band gaps, the smoothing of interfaces does not lead to disappearance of the band gaps. At the same time, the profiles and relative thicknesses of interfaces might provide additional means by which to design magnonic crystals with a desired magnonic spectrum. © 2010 The American Physical Society.

Metlov L.S.,Ukrainian Academy of Sciences | Metlov L.S.,Donetsk National University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

In the framework of a two-defect model, based on a variation of the Landau technique, the kinetics of structural defect generation in solids under severe external load is investigated. The approach is based on a special form of kinetic equation in terms of internal energy, which is applied here to the description of an important practical problem of fine-grained structure formation in metals under severe plastic deformation. It unifies strengthening curves over the entire range of deformation, including the Hall-Petch and linear strengthening sections. © 2014 American Physical Society.

Kazak O.,Donetsk National University | Semko O.,Donetsk National University
Ironmaking and Steelmaking | Year: 2013

The article is devoted to the investigation of interaction between electrovortex and heat flows of liquid metal in dc arc furnaces with a bottom electrode. A mathematical model of liquid steel flows in a dc arc furnace with a bottom electrode was developed, and an algorithm of a three-stage solution was produced based on standard software packages. The results of electromagnetic, heat transfer and hydrodynamic analysis in industrial dc arc furnaces are given. It is shown that the Lorentz force makes up, 30% of the volumetric gravity force and makes the main contribution to vortex flow of liquid metal in a dc arc furnace. The convection flows with the maximum heat power of furnace make a significant contribution to the vortex flow of liquid metal, and the maximum value of the vortex flow velocity is ∼ 1.5 times more than the movement without convection. The verification of results has been carried out by comparing them with general electrovortex flows theory, experimental data and results of similar software packages. © 2013 Institute of Materials, Minerals and Mining.

Ignatenko P.I.,Donetsk National University
Technical Physics | Year: 2011

The influence of the relative supersaturation, elastic strain energy of the growing phase, and adhesion energy on the morphology and orientation of boride, nitride, and silicide coatings is estimated using X-ray diffraction, electron microscopy, and secondary-ion mass spectrometry data. A diagram is constructed from which growth conditions for phases with given morphology and structural perfection can be found. © 2011 Pleiades Publishing, Ltd.

Kuslyva A.,Donetsk National University
Proceedings of Meetings on Acoustics | Year: 2013

The research of anharmonic effects is essential for the design of nonlinear acousto-electronic devices. Such effects involve the generation of nonlinear second harmonics in propagation of normal electroelastic waves in crystal plates. Thereby the analytical and numerical technique of the analysis of small nonlinear anharmonic effects in distribution of normal electroelastic waves in the layer of a trigonal piezocrystal of lithium niobate with thin short-circuited electro-onductive coverings of sides has been developed. The research is based on the model of physically and geometrically nonlinear electroelastic deformation with finite deformations and Gibbs's function that includes quadratic and cubic components on deformations and characteristics of intensity of quasistatic electric field. The analysis of nonlinear wave effects is build on the representation of characteristics of a normal electroelastic wave in the form of the sum of summands which are proportional to the powers of the small parameter. The analytical form has been received for the representations of functions of the elastic displacements, intensity, induction of quasistatic electric field in nonlinear second harmonics for the studied waves from the different modes of the dispersive spectrum. Quantitative estimates have been researched for the amplitude levels of second harmonics for normal electroelastic waves with variable frequencies. © 2013 Acoustical Society of America.

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