Journal of Physics and Electronics

3-8

Authors: O.A. Borisenko, V.V. Skalozub

In SU(2) gluodynamics, the Debye gluon contribution WD(A0) to the effective action of the temporal gauge field component (we consider A0 = const) in the background Rξext is calculated at high temperaturegauge. It is shown that at A0 ≠ 0 the standard definition k0 = 0 , |k| → 0 corresponds to long distance correlations for the longitudinal in internal space gluons. The transversal gluons become screened by the A0 background field. Therefore, they give zero contributions and have to be excluded from the correlation corrections. The total effective action accounting for the one-loop, two-loop, and correct WD(A0) satisfies Nielsen’s identity that proves gauge invariance of the A0 condensation phenomenon.

17-28

Authors: S.F. Lyagushyn, A.I. Sokolovsky, S.A. Sokolovsky

Kinetics of electromagnetic field in noneqilibrim medium of atoms is studied on the basis of the Dicke model. The field is described by average electric and magnetic fields and their binary correlations. The atoms are considered in two-level approximation and assumed to be fixed in the space. States of the medium are described by the energy density. Nonresonant atom-field interaction is accounted phenomenologically. The theory is built on the Bogolyubov idea of the functional hypothesis that is the basis of his method of the reduced description of nonequilibrium processes. The investigation of the system is carried out in the framework of the Peletminsky–Yatsenko model. Atom-field interaction is assumed to be small and is taken into account up to the second contributions in the interaction included. Average electric and magnetic fields satisfy the Maxwell equations. Material equations for them express average current and charge densities through the average field. Evolution equations for the binary correlation of the field are constructed. Material equations for these equations express correlations field-current trough correlations field-field. The time equation for energy density of the medium is obtained. Density evolution is governed by the average field and field correlations. All material coefficients of the system are found.

37-42

Authors: A.N. Galdina

The supercritical transitions are widely occurring. They include the supercritical transitions in the liquid-vapor system, ferromagnetic transitions, transitions in polymers, many transitions in liquid crystals, and some structural transitions. In the paper it is emphasized that the nature of the critical and supercritical transitions is the same – these are continuous fluctuation transitions. Above the critical temperature the system passes through a region of lowered stability, which leads to increase of fluctuations of energy and external parameters of the system. From the point of view of thermodynamic stability this indicates the existence of a continuous supercritical transition between supercritical mesophases. Knowing the basic stability characteristics of a system, we derive the equation of these mesophase transitions. Depending on a thermal equation type, we can get one or several such equations, which may not coincide. This approves the fact that a supercritical transition occurs in a certain interval of thermodynamic forces. In the paper the relations between the critical exponents of thermodynamic parameters of the system are obtained and the conditions of continuous conjugation of the lowered stability line to subcritical coexistence line are investigated. The results are applied to the Curie–Weiss and van der Waals models: we obtain the quasi-spinodal equation for these systems and analyze the critical and supercritical behavior of the stability characteristics.

47-50

Authors: V.F. Bashev, N.A. Kutseva, O.I. Kushnerov, S.I. Ryabtsev, O.V. Yelina, O.O. Veres

Using the modernized three-electrode ion-plasma sputtering method, homogeneous thin films of FePt and Fe (Pt/Bi) were obtained. Films were deposited on NaCl and glass-ceramic substrates. The film thickness was 120-530 nm. In this case, the calculated cooling rate reached ~ 1012–1014 K/s. The structure of the FePt and Fe (Pt/Bi) films was investigated using X-ray diffraction and electron microscopy methods. It was established that metastable phases were formed in freshly sputtered films, including a supersaturated solid solution, a nanocrystalline and amorphous phases. It was determined that the obtained metastable structures are stable when heated to 540-880 K, depending on the composition. It was established that Bi additives significantly reduce the coercive force of films in the as-sputtered state. It was shown that a heat treatment increased the coercive force up to 36 kA/m in FePt films and up to 10 kA/m in Fe (Pt/Bi) films. The composition of Fe (Pt/Bi) films with a small value of the temperature coefficient of resistance (TCR ~3·10-5 K-1) was determined.

55-60

Authors: L.I. Fedorenkova, G.P. Fedina

The work is devoted to the research of influence of the electrolysis on the saturating ability of the electrolyte, which is a borax melt. To establish regularity when the saturating medium activity changes, which influences the intensification of saturation process, the structure and properties of borax during electrolysis were investigated. The change in the saturating medium activity was estimated by a relative value equal to the ratio of the boride layer depth obtained by non-electrolysis borating to the layer depth obtained by electrolysis borating. When comparing the real and theoretical saturating abilities, their convergence was observed. It was found that the saturation ability of the borax melt increases with increasing electrolyte runtime, which is due to a change in the structural components of the borax melt. A quantum-chemical calculation of the borax molecule structure was carried out using the non-empirical method of molecular orbitals in the theory of the density functional (DFT) with the three-parameter exchange-correlation functional B3LYP. Calculations show that two main structures are characteristic of a borax molecule: non-coplanar, with two mutually perpendicular 4-membered boron-oxygen cycles and flat linear. An increase in the saturation ability of the borax melt during electrolysis allows the development of new low-energy borating processes.

65-68

Authors: N.A. Kutseva, V.F. Bashev, S.I. Ryabtsev, O.S. Krapivina-Soloviova

Effect of geometrical parameters (metallic core diameter, glass cover thickness) on the structure and magnetic properties of glass-coated Fe-Si-B-Nb-Cu microwires is investigated. The structure of as-prepared Fe73.8Cu1Nb3.1Si13B9.1 microwire is nanocrystalline, consisting of α-Fe(Si) crystallites in a residual amorphous matrix. It is shown that great residual stresses arising at the manufacturing processes greatly influence the microstresses and crystallite sizes of α-Fe(Si) crystals. An increasing of stress magnitude results to structure refinement. The size of α-Fe(Si) crystals and crystallized volume fraction decrease from approximately 105 nm and 71 % to 9 nm and 34 %, respectively, with glass cover thickness increasing. Grain size refinement of α-Fe(Si) leads to the considerable decrease of coercivity of microwires from 1800 A/m to 160 A/m.

77-80

Authors: Y. Syetov

Lattice vibrations are studied theoretically by density-functional based tight-binding methods for the model structure of 2-(2'-hydroxyphenyl)benzoxazole crystal with defects. 2-(2'-hydroxyphenyl)benzoxazole is a photoreactive compound that exhibits excited state intramolecular proton transfer in the structure with an OH...N hydrogen bond. The unit cell of the model structure consists of two crystal unit cells where the molecules have the structure with intramolecular hydrogen bonds OH...N and one molecule is supposed to have a different orientation of the whole molecule or its fragment. The different orientation of the fragment forms the structure with an intramolecular hydrogen bond OH...O. It is calculated that defect caused by the different orientation of the molecule have a lower energy than the defect caused by the different orientation of the fragment. In the frequency region where the contribution of external vibrations of the molecules is significant, the vibrations mainly involve several molecules in the cell. In the region of internal vibrations there are modes, which are local vibrations of the defects. These local vibrations involve mainly motion of the atoms constituting the defect molecule. The number of local vibrations is larger for the defect that corresponds to the formation of the structure with the OH...O hydrogen bond than for the defect that corresponds to the different orientation of the whole molecule with the OH...N hydrogen bond. The internal vibrations of the defect molecule formed by the different orientation of phenol fragment in the lattice undergoes frequency shift in relation to the frequency of the modes of isolated molecule.

85-88

Authors: T.V. Panchenko, L.M. Karpova

The temperature-frequency dependences of the complex dielectric permittivity ε and the voltage-farad characteristics of undoped and aluminum doped Bi12SiO20 crystals are studied before and after their polarization. It is shown that Al ions in the Bi12SiO20 dielectric matrix provide a significant increase as well as nonlinearity of ε in the temperature range 300 – 800 K and electric field strengths Е = 103 – 104 V/cm. It is shown that polarization causes the appearance of dielectric hysteresis loops. Al impurity significantly affects the appearance and parameters of these loops. The role of Al ions in increasing the contribution of the quasi-dipole mechanism in the polarization processes is revealed.

93-98

Authors: A.I. Ivon, R.I. Lavrov

The current-voltage characteristics of various compositions of nonlinear varistor ceramics based on ZnO (ZOC) and SnO2 (TOC) are studied in a wide range of electric current. On the basis of obtained data were determined the parameters that allow finding the coefficients kprs and kprl, which define the protection levels against the switching surge and the lightning surge for surge suppressors on the basis of ZOC and TOC varistors. The lower the value of these coefficients are, the significantly higher the efficiency of surge protection is. A relationship between kprs, kprl, and the effective linear resistivity ρlin limiting the current of intergranular barriers in varistor ceramics are established. It is shown that the values of kprs and kprl increase with increasing ρlin, which value is determined by the bulk resistance of the ceramic grains. The studied TOC compositions have 2-3 times larger values of ρlin and more high values of kprs and kprl than ZOC. ZOC-based varistors with lower kprs and kprl values provide more effective surge protection than TOC-based varistors.

105-110

Authors: A.B. Gnilenko, S.V. Plaksin

Millimeter waves are now considered as an important part of 5G spectrum. Higher frequencies provide larger bandwidth giving the ability to support very high data rate, ultra high capacity and very low latency. The utilization of millimeter wave frequency bands for 5G mobile applications requires effective solutions in the design of antennas and antenna arrays which are the key parts of modern communication systems. In this paper a 4x4 microstrip patch antenna array sub-module is presented to be a part of 5G wireless communication system. The antenna array is designed and optimized to operate at a frequency of 85 GHz which corresponds to the middle of the second atmospheric transparency window. The antenna array is simulated using the time domain solver of the CST Microwave Studio software package. Simulation results are demonstrated and discussed for an optimized array. The designed patch antenna array provides good directivity characteristics with a main lobe magnitude of 16 dBi, angular width of 28 degree and can be applied as a part of a wireless communication system operating at a high frequency band of 5G frequency range.

3-8

Authors: V. D. Gladush

Analytical aspects of the classical geometrodynamics for the spherically-symmetric configuration of the electromagnetic and gravitational fields in GR are considered. The feature of such configurations is that they admit two motion integrals – the total mass and charge. The Einstein-Hilbert action for the configuration, after dimensional reduction, by means of the Legendre transformation is reduced to the Hamiltonian action. Using the conservation laws for the mass and charge, as well as the Hamiltonian constraint, the momenta are found as functions of configuration variables. The set of equations, which associate momenta and functional derivatives of the action in the configuration space (CS) is integrable. This allows us to obtain the action functional as a solution of the Einstein-Hamilton-Jacobi equation in functional derivatives. Variations of the action functional with respect to mass M and charge Q of the configuration lead to the motion trajectories in the CS. We note that the minisuperspace metric, which is induced by the kinetic part of the Lagrangian, does not coincide with the CS metric that arises when the function of lapse N is excluded from the action. The space-time metric for which the indicated metrics coincide in the T-region up to a coefficient are considered. The metric of CS is constructed and its geometry is studied. Under the trivial embedding of hypersurfaces of the foliation into a dynamical T-region, the CS is flat. It allows introducing pseudo-Cartesian coordinates in which the CS metric takes the Lorentz form.

19-26

Authors: A.N. Galdina

It is known that basic stability characteristics of a system are inversely proportional to fluctuations of external parameters. Above the critical point there is a region remaining homogeneous macroscopically, but becoming microheterogeneous within an interval of thermodynamic forces. Within this interval thermodynamic coefficients of stability pass finite non-zero minima. This corresponds to the considerable growth of fluctuations and indicates the occurrence of supercritical transition of continuous kind. The limit case of such continuous phase transitions is the critical state, which is also the limit point of some first-kind transitions (the limit point of phase equilibrium curve). In this paper we consider the relation between thermodynamic stability conditions and fluctuations of external parameters of the system. We study the behavior of a simple one-component thermodynamic system (liquid, magnet, and ferroelectric) in the supercritical region and derive the equation of the line of supercritical transition for this system.

31-36

Authors: N.Yu. Filonenko, A.N. Galdina

It is known that solubility of elements affects the phase composition of alloys that are formed in the solidification process. To predict the phase composition of alloys, it is necessary to determine the solubility limit in the phases. In the paper the structural properties of austenite of alloys in the system of Fe-B-C are studied and the solubility limit of boron and carbon is determined. The investigation is carried out for the specimens with carbon content of 0.0001–2.3 wt.% and boron content of 0.0001–1.0 wt.%, the rest is iron. To determine the physical properties of alloys, we use the microstructure analysis, X-ray microanalysis, X-ray structure analysis and differential thermal analysis. It is shown experimentally that the maximum shift of the eutectoid point is observed when boron content is up to 0.004 wt.%. When boron content of the alloy increases to 0.01 wt.%, the eutectoid point shifts to the left to 0.21 wt.%-carbon and the austenite area decreases. Further increase in the numerical value of boron content in the alloy is hardly caused the eutectoid point to shift. In this paper, the vertical section of the Fe-B-C system state diagram is obtained from experimental data. For the first time we obtain temperature dependence of the free energy of γ-iron solid solution, using the quasi-chemical method, and determine the solubility limit of carbon and boron. The maximum weight fraction of boron in the austenite can be up to 0.0136 wt.%, and that for carbon – up to 1.12 wt.%.

41-46

Authors: O.I. Kushnerov

The processes of melting and solidification of AlCoCuFeNi nanoparticle of about 10 nm is studied by molecular dynamics simulation at three different cooling rates (1∙1011 K/s, 1∙1012 K/s, and 1∙1013 K/s) using the embedded atom model (EAM) potential. The melting and crystallization of the nanoparticle are characterized by studying the temperature dependence of the potential energy. The adaptive common neighbor analysis (CNA) is performed and the radial distribution function (RDF) is calculated to determine the structure and lattice parameters of phases of the AlCoCuFeNi nanoparticle. It is shown that the final structure of the investigated nanoparticle changes from amorphous to crystalline with decreasing of the rate of cooling, and the temperature hysteresis takes place during the melting and crystallization of AlCoCuFeNi HEA nanoparticle.

51-56

Authors: O.V. Ohiienko, V.N. Moiseienko, M.D. Volnyanskij

The work is devoted to the study of photoluminescence spectra of weakly polar ferroelectric crystals Li2Ge7O15 and Li2O – 7GeO2 glasses. For all initial samples was observed the wide intensive luminescence band with maximum in the region of 525–550 nm. The spectral distribution of intensity and the position of the maximum of the band for a Li2Ge7O15 crystal depended on the excitation wavelength (λex=405 nm or 365nm were used). The spectral profile of the luminescence band was broadened in glass containing of 0.67% copper. The intensity of the luminescence band was decreased 6 times for glass doped with Cr3+ ions (0.01%) as compared with glass containing Cu2+ ions. The intense luminescence band of Cr3+ ions with λmax=659nm was appeared starting from 600. The assumption about the nature of the broad luminescence band observed in both nominally pure and doped glasses and crystals was made: the source of luminescence can be germanium - oxygen complexes [GeO4] and [GeO6] of the tetrahedral and octahedral configuration in the material structure.

63-70

Authors: V.S. Khandetskyi

A theoretical analysis of the interaction of the eddy current sensor field with powder particles makes it possible to calculate the particle conductivity using the measured value of the sensor added active resistance. Relative to its own reactance, the value of this resistance is proportional to powder density, frequency of the probing field, electrical conductivity of particles and square of their diameter. Particles of spherical shape and cylindrical shape, the height of which is equal to the diameter of the base, are considered. The analysis allows to explain the experimentally observed different character of the resistance frequency dependences for powder and corresponding solid material when measuring by the same sensor.

79-88

Authors: A.V. Ivanchenko, A.S. Tonkoshkur, S.V. Mazurik

The problems of reducing the cost of ensuring the safe operation of solar cells by using low-cost elements of solid-state electronics to protect against overvoltage photovoltaic cells of solar arrays are considered. The results of experimental studies of the use of a varistor-posistor structure based on a metal oxide varistor and PPTC fuses of the PolySwitch type being in thermal contact to prevent overvoltages in series connections of photovoltaic cells are presented. General schemes for using the considered solid-state structure to limit the indicated constant overvoltages are given and justified. The requirements to the parameters of this structure are determined and experimentally verified. It is shown that such a device makes it possible to limit the long-term constant overvoltages that occur in photovoltaic arrays at the level of photovoltaic cells in the case of their malfunction or shadowing, which can lead to fire hazard and other “abnormal” situations during the operation of solar electric energy sources.

95-100

Authors: V.V. Ovsyanikov, D.M. Svynarenko, O.R. Beznosova, L.Z. Tsypko

The article presents the results of theoretical and experimental studies of the current distribution, the values and coordinates of the load connection points, as well as the radiation patterns for two-band linear microwave antennas with quarter-wave two-wire shunts of the upper range and concentrated reactive loads. Such antennas are promising for use in two-band duplex mobile satellite systems for receiving and transmitting data, for example, GLOBALSTAR, IRIDIUM, ELLIPSO, GPS and others. Theoretical studies are carried out by the method of integral equation. It is found that with a constant length of a quarter-wave shunt and different sizes of the antenna, the antenna can acquire or lose the property of two frequencies. A method for eliminating this negative phenomenon is proposed.