Vol 62, No 5 (2019)

Results of measurements of the conductivity and electric field strength in the laser radiation propagation channel and near it are presented. An experimental setup and measurement scheme are described. The data have been obtained in the prebreakdown regime. The dependences of the laser-induced field strength on the laser radiation power and the optical characteristics of the propagation channel are investigated. The feasibility of ionization channel diagnostics using the electro-optical effects in the atmosphere is shown.

Statistical analysis of results of long-term continuous 8-day measurements of three components of wind velocity vector with a minisodar in the atmospheric boundary layer is presented for altitudes of 5–200 m and their interdaily variations are studied. The temporal dynamics of vertical profiles of the wind velocity components demonstrates that there are linear segments on the vertical velocity profiles for which the altitude behavior of the velocity components is well approximated by a linear dependence. The analysis of interdaily variations of three wind velocity components has allowed us to establish that all wind velocity components increase with sounding altitude. Attention is drawn to the synchronous character of occurrence of the maxima and minima of x- and y-components. For all components, the semidiurnal behavior (with the velocity decrease since midnight till noon and its subsequent increase since noon till midnight) is clearly traced that can be explained by morning warming and evening cooling of the underlying surface accompanied by the most intensive changes of wind velocity components.

Using the EPR method, an identification of paramagnetic centers formed in TlNO₃ under γ-irradiation at 77 and 300 K is performed. Their spectral characteristics, corresponding to the NO₃ and NO₂ radicals, are determined. The paramagnetic center NO₃ is attributed to the NO₃ (В) radical, which is thermally stable at 77 K. The NO₃ (В) radicals exist in two forms – I and II, which differ by their spatial orientations. The accumulation of paramagnetic centers NO₃ and NO₂ is investigated and so are the optical reflection spectra of polycrystalline TlNO₃ specimens. The final products of radiolysis of thallium nitrate are identified to be the thallium nitrite and peroxonitrite ions.

It is shown that the vector Navier–Stokes equation has a variety of quantum solutions, so the scope of this equation is not limited to the field of classical Newtonian physics, but also includes quantum physics. On this basis, it is shown that the homogeneous quantum velocity is globally defined at all moments in time, is a globally smooth and bounded function, which falls exponentially, and that the kinetic energy is also globally bounded. Its quantum solutions do not depend on the Planck constant, which is instead automatically replaced in the Navier–Stokes equation by its hydrodynamic analog \( \tilde{h}=2 mD>>\mathrm{\hslash}. \) The Navier–Stokes equation gives a deterministic description of the dynamics of a fluid both with respect to the wave function and with respect to velocities. It is shown that taking relativistic effects into account, the Navier–Stokes equation can have a physically meaningful, classical, globally smooth solution of Hubble type, which modifies the isotropic energy-dominance condition, eliminates the cosmological singularity, and accords with the observational data indicating that the Hubble parameter increases with time. The fine structure of the mathematical constants can contain information about interactions of matter. This fact can be used to solve problems on information loss in black holes.

The article presents the results of research on electrical conductivity and diffusion of potassium ions in the borate-barium S78-5 glass when transmitting the electric current through the sample. The authors calculated the time dependences of electric diffusion coefficients in the course of annealing at constant temperatures when transmitting the electric current.

For the first time, the admittance of nBn structures based on HgCdTe grown by molecular beam epitaxy was experimentally investigated in a wide range of frequencies and temperatures. The CdTe content in the barrier layer of studied samples varied from 0.74 to 0.83, and the thickness of this layer was from 210 to 300 nm. The experimental frequency dependences of the admittance of nBn structures are in good agreement with the results of calculation by the equivalent circuit method. The proposed equivalent circuit consists of two seriesconnected chains, each of which contains a capacitance and a resistance connected in parallel. The change in the values of the equivalent circuit elements during heating from 9 to 300 K and under application of the bias voltage was studied. It is shown for the first time that illumination of nBn structures based on HgCdTe by radiation with a wavelength of 0.91 μm causes relaxation of values of the equivalent circuit parameters for hundreds of minutes after the illumination is turned off. Mechanisms of the equivalent circuit element formation, as well as peculiarities of the admittance dependences at various parameters of the barrier layers, are discussed.

Using the methods of X-ray structural analysis and electron and positron spectroscopy, it is found out that an irradiation of the surface of a Zr – 1 wt.% Nb specimen with an electron beam in the melting mode results in the formation of lamellar α+α′-structure, an increase in the dislocation density, a dissolution of the β-Nb phase, and the formation of defects of the vacancy-impurity type. The presence of hydrogen in the alloy irradiated with an electron beam favors the formation of complex hydrogen-vacancy complexes in the surface layer along with dislocations.

The paper studies the changes in the crystal structure and dielectric properties of tungsten(VI) oxide (WO₃) in the temperature range from 83 to 673 K. Investigations are performed using X-ray phase analysis and scanning electron microscopy of the material under study. It is found that the phase transition from triclinic to monoclinic structure occurs at 83 K for the tungsten(VI) oxide powder. When the powder is heated up to 673 K, its crystal structure again becomes triclinic. The peak intensity of the initial WO₃ powder heated up to 673 K is observed at a Bragg angle of 24.34 degrees, while that of the cooled WO₃ powder occurs at 23.08 degrees. The powder calcination changes the crystal lattice parameter at a Bragg angle of 24.34 degrees, such that а = 6.333 Å and а = 6.339 Å for the initial and calcined WO₃ powder, respectively. The main electrophysical properties are obtained for the WO₃ powder specimens, namely: surface resistance, specific surface resistance and conductivity, electric conductivity, permittivity, dissipation factor.

The paper presents research results of the phase composition, crystal structure and hardness of AlMgB₁₄-based ceramic materials obtained by the hot pressing method using powder mixtures of various grain-size composition. It is found that the largest amount of AlMgB₁₄ phase of ~97 wt.% is achieved for the Al–Mg–B powder mixture after 4-hour activation in a planetary mill. The highest value of the hardness is detected as 31.9 GPa.

The influence of an external synchronous axial magnetic field on the characteristics of a vacuum-arc discharge is investigated within the range of discharge currents from 6 to 14 kA. The magnetic field amplitude is regulated in a wide range (from 0 to 190 mT) irrespective of the discharge current, while the specific magnetic field induction (in mT/kA) remains constant during the arc burning time. A critical specific magnetic field induction is determined, which prevents the discharge channel from constriction in the gap. It is shown that an application of an external magnetic field does not give rise to the formation of an anode spot, while the cathode is covered with a large number of microspots evenly distributed across its surface. An analysis of the probe currents demonstrates that the density of the post-arc plasma under these conditions decreases, and its decay is accelerated.

On the basis of fundamental probabilistic arguments, a theory of spatial transitions of atoms in configurations with number of spatial dimensions D = 1, 2, and 3 is proposed. Relations linking the 1 ↔ 3 and 2 ↔ 3 transition probabilities and the mean numbers of atoms in the 1, 2, and 3 configurations are obtained, assuming the existence of only these pairs of spatial configurations, as has been observed in earlier experiments. A similar program was realized in a situation with possible simultaneous existence of all three spatial configurations with these same transitions plus the transitions 1 ↔ 2, and the mean numbers of atoms was also found although the corresponding experiments have still not been performed. All of the conclusions of this work and the adequacy of the implemented approach can be verified in experiments with systems of atoms. In this regard, the possibility of extending the given theory to other (including not-necessarily physical) systems consisting of an invariant number of identical objects that can be found in two or three states is discussed.

Properties of single-walled carbon nanotubes (SWCNTs) obtained by the floating catalyst CVD method using ethyl alcohol and coal (anthracite and semi-anthracite) particles are investigated. Structural and vibrationalcharacteristics of synthesis products are determined. It is revealed that enrichment of the reaction mixture by anthracite particles increases the concentrations of CO and CH₄ in the reaction zone, which contributes to the growth of the SWCNTs. A comparison of the Raman spectra of the samples shows an increase in the content of small-diameter semiconductor SWCNTs, whereas a set of chirality indices of the resulting nanotubes remains unchanged.

Increasing frequency of functioning and decreasing transistor sizes in high performance logical circuits may result in illegal capacities, inductivities, resistances, and so on that generate decreasing estimated circuit frequency. These defects cannot be detected by physical methods. The main way of solving the problem is based on delay testing of logical circuits within the path delay fault (PDF) model. In this paper, facilities of enhancing PDF test sequence quality based on application of Reduced Ordered Binary Decision Diagrams (ROBDDs) that compactly represent all test pairs of neighbor test patterns for the circuit path are studied. Test patterns (Boolean vectors) are neighbor if they differ by only one component. It is established that using of these ROBDDs cut the lengths of test sequences by more than 1/3 in comparison with traditional scan test sequences simultaneously enhancing test sequence quality. In particular, we derive test sequences for robust testable PDFs of sequential circuits decreasing their power consumption and peak power values.

We consider an approach to constructing approximate analytical solutions for the one-dimensional twocomponent reaction-diffusion model describing the dynamics of population interacting with the active substance surrounding the population. The system of model equations includes the nonlocal generalized Fisher–Kolmogorov–Petrovsky–Piskunov equation for the population density and the diffusion equation for the density of the active substance. Both equations contain additional terms describing the mutual influence of the population and the active substance. To find approximate solutions of the system of model equations, we first use the perturbation method with respect to the small parameter of interaction between the population and the active substance. Then we apply the well-known iterative method developed by G. Adomian to solve equations for terms of perturbation series. In the method proposed, the solution is presented as a series whose terms are determined by the corresponding iterative procedure. In this work, the diffusion operator is taken as the operator for which the inverse operator is expressed in terms of the diffusion propagator. This allows one to find the approximate solutions in the class of functions decreasing at infinity. As an illustration, we consider an example of solving the Cauchy problem for the initial functions of a Gaussian form.

A corona discharge is experimentally studied in atmospheric air on a needle electrode with the curvature radius 40 μm. For both electrode voltage polarities, but different discharge burning modes, repetitive current pulses with the FWHM ~200 ns are registered. It is shown that in a wide range of negative-polarity voltages the area of the glow registered in the vicinity of the needle has a spherical shape, and in the case of a positive polarity of the needle tip, starting from a certain voltage value, cylindrical streamers are formed from the spherical glow area, whose length increases with the voltage. It is found out that the size of the glowing spherical formations near the needle tip, given the same voltage value, is larger in the case of negative polarity than in the positive one. It is validated that the radiation of the second positive system of nitrogen in the UVspectral region dominates in the corona discharge emission spectrum before its transition into a spark discharge.

Scientific-methodical approaches to a study of nonlinear physicochemical processes are considered and an experimental setup intended for investigation of nonlinear physical and chemical processes accompanying irradiation of solids of various classes (including energetic materials) by UV, visible, and IR laser radiation is described. The possibility of synchronous multi-parameter measurements of the amplitude, spectral, kinetic, and spatial characteristics of the near-surface and bulk luminous laser plasma, solid-phase luminescence, acoustic pulses formed in the bulk of the samples, and morphology of residual damages has been demonstrated with a nanosecond time resolution. The energy density on the irradiated target surfaces varied from fractions of mJ/cm² to 10⁴ J/cm² depending on the problem to be solved. The spectral range recorded for one irradiation pulse was 200–1100 nm, the spectral resolution was ~1.5 nm, and the spatial resolution was ~10 μm. A pressure pulse formed in the sample volume was recorded by an acoustic sensor with sensitivity of 0.15 V/bar and temporal resolution of ~5 ns.