卷 61, 编号 10 (2019)

An approach to inkjet printing of low-viscosity liquids is suggested consisting in suppression of undesirable weakly damped acoustic oscillations under the action of a double pulse. The duration and amplitude of the second pulse are adjusted so that the arising acoustic oscillations are in antiphase to those of the first pulse.

The hybrid multilevel approach based on molecular dynamics, quantum mechanics, and statistical theory has been applied to profiles of electronic absorption bands of a number of thiazine dyes (phenothiazine, methylene blue, and methylene green), whose photochemical and biological properties depend on the external medium. The effect of single fragments of the methylene green (MG) molecule on its spectral-luminescent properties is studied. The most preferred geometry for the MG molecule is identified, and its relations with the spectral properties and the solvent nature are established. The energies of the electron states are calculated, and their nature is revealed. The electrostatic potential is analyzed, and the places of the most probable interaction of the molecule with the medium are found. Conclusions on the mechanism of forming the MG absorption spectrum are made based on the observations and calculations performed within the framework of the present work. It is established that the formation of the N–H bonds leads to the formation of an inactive lower excited singlet state and delocalization of the electron charge upon excitation. The position of the maximum of the long-wavelength absorption band of the MG correlates with the donor number of solvents in the series acetonitrile < water < ethanol < isopropanol < dimethyl sulfoxide. The position of the MG electron transition in the region of 630 nm is determined by the interaction of nitrogen and sulfur atoms of the central ring rather than by the increased number of substituents in the structure of the molecule.

Temporal fluctuations of the intensity of radiation of the π component and of the sum of the σ⁺ and σ components of capillary low-pressure lamps filled with mercury of natural isotopic composition are experimentally investigated in the presence of the transverse Zeeman effect. Results of investigations allow the operating regimes of such lamps used in a new experimental model of analyzer of mercury vapor concentration in atmospheric air to be optimized.

Based on the micromagnetic model which takes into account the random distribution of the uniaxial magnetic anisotropy directions in crystallites of a nanocrystalline film, an effective method has been implemented for calculation of the magnetization dynamics in microwave fields. For a certain range of crystallite sizes, when the energy of the random magnetic anisotropy is comparable to the exchange energy, a significant change of the ferromagnetic resonance field, broadening of the resonance line, and the appearance of an asymmetry in the shape of the resonance curve were found. With an increase of the crystallite sizes, the resonance field first grows, then, it quickly decreases to its minimum, and then, it grows again to reach saturation. In this case, the steepness of the left slope of the broadening resonance curve first decreases faster than that of the right slope, leading to the symmetry breaking of the resonance curve shape, then, the curve becomes symmetrical again, and then, the steepness of the left slope becomes greater than that of the right slope.

Mathematical models describing the cosmological evolution of classical and phantom scalar fields with self-action are formulated and analyzed. Systems of dynamical equations in the plane, describing homogeneous cosmological models, have been obtained. It is shown that depending on the parameters of the field model, it is possible to violate the single connection of the phase space of the corresponding dynamical model.

A calculation of the electron interaction energy for the CH molecule with an open electron shell is performed using a basis of Slater atomic orbitals. The molecular orbitals are represented in the form of a linear combination of the 1s, 2s, 2p_x, 2p_y, and 2p_z atomic orbitals of the C atom and the 1s orbital of the H atom. As a result of solving the Hartree–Fock–Roothaan equation, numerical values of the coefficients in this linear combination have been found.

The results of a theoretical analysis of the stress fields and elastic energy distributions of the disclinational grain-boundary structure in nanocrystalline metallic materials as a function of grain size are presented. Considering the superposition of these stresses during screening of the piled-up disclinations it is found out that the maximal values of the principal components of the stress tensors are achieved in the planes of disclination occurrence P = Tr(σ_ij)/3 >  > E/25, while the stress gradients are characterized by the maximum values in the nodal points ∂P/∂x ≈ 0.08 E nm^–1 (Е – Young’s modulus). It is determined that a considerable part of the shear stress components is localized inside the grain. It is shown that the characteristic features of the specific elastic energy distribution in these configurations are the local energy maxima, which could be a reason for the physical broadening of the nanograin boundaries.

A possibility of simulating the structure of real nanomaterials in the elliptical Riemannian space is discussed. It is shown that the experimentally determined parameters of nanomaterials are quite consistent with the simulation patterns. The results of computer simulations and experimental modeling of non-linear processes in solids using the geometrical method and interpretation of the model design patterns are presented. Basically new options of using non-Euclidian models of crystal structures for solving the materials science problems are demonstrated.

The results of investigation of the influence of the structural element size and phase state of the Ti – 45 wt.% Nb and Zr – 1 wt.% Nb binary alloys on their mechanical properties are presented. The structural states of the alloys with the structural elements of different dimensions were formed from the ultrafine-grained state via annealing. The curves of dependence of the yield strength and microhardness on the average size of the structural elements, d –^1/2, are obtained using the Hall–Petch relation. It is shown that for the Zr – 1 wt.% Nb alloy, the Hall–Petch relation is fulfilled in the entire range of sizes under study, from ultrafine-grained to finegrained states 0.2–1.9 μm. For the Ti – 45 wt.% Nb alloy, in the analysis of the Hall–Petch relationship within the structural element size range 0.43–45 μm, its phase composition is taken into consideration, specifically, the presence of dispersion-strengthened β-phase grains, α-phase subgrains, nonequilibrium nanosized ω- phase, and the bimodal grain-subgrain structure.

Conditions of stability of charged air nanobubbles in water are considered. Ranges of values of the charge and radius in which coalescence and division predominate are theoretically determined. The stability region is revealed in which the given processes are thermodynamically improbable. A comparison of the theory with the available experiment is performed. Based on the results of our analysis, it is concluded that the main stabilizing factor for nanosized particles is their surface charge.

The paper presents the sol-gel synthesis of porous silica monolith in the presence of cetyltrimethylammonium bromide and polyethylene glycol. Parameters of the porous structure and mechanical properties of silica monolith are varied by the reaction mixture composition and reprecipitation and thermal treatment conditions. Mechanical properties and permeability of obtained material are investigated and optimal parameters are identified for the synthesis of porous silica monolith for flow reactors.

The problem of resonant transfer of atomic excitations in low-temperature plasma is solved by the Monte Carlo method. The boundary effect on the spatial distribution of excitations is investigated in cylindrical and spherical geometries. The concept of the boundary effect is discussed within the framework of the nonlocal Biberman–Holstein theory.

Infrared heating was used to synthesize FeCoNi/С nanocomposites, where nanoparticles of FeCoNi ternary alloy are stabilized and uniformly distributed in the carbon matrix volume. The authors studied the impact of synthesis temperature and percentage ratio of metals upon the structure, composition and electromagnetic properties. X-ray phase analysis and Mössbauer spectroscopy showed that ternary alloy nanoparticles with different compositions and crystalline lattice types can be formed with the rise in synthesis temperature and iron concentration. Resonator method was used to examine frequency dependencies of relative complex dielectric and magnetic permeabilities of nanocomposites in the range of 3–12 GHz. Calculation of reflection coefficient based on experimental permeability data showed that by varying synthesis temperature and percentage ratio of metals one can control the frequency range of effective absorption of electromagnetic waves. It was established that increase in relative iron content from 33 to 50 rel.% leads to the shift of minimal electromagnetic wave reflection coefficient band from f ~ 12+ GHz to frequency f ~ 6 GHz at identical absorber thickness.

A connection between the scheme of unitary quantization (uniquantization) and para-Fermi statistics of order 2 is considered. An appropriate generalization of the Green’s ansatz is suggested based on incorporation of the additional operator Ω which allows one to transform into the identity the bilinear and trilinear commutation relations of unitary quantization for the creation and annihilation operators of two different para-Fermi fields φ_а and φ_b. The way of incorporating para-Grassmann variables ξ_k into the general scheme of unitary quantization necessary for the definition of coherent states is suggested. For parastatistics of order 2, the new fact of existence of two alternative definitions of the coherent state for the para-Fermi oscillators is established.

Gains of lasers with regular polygon cross sections of tubes having curvilinear sections are considered. Calculations are performed for parabolic polygons, a triangle, and a circle with extra curvature. Results obtained show the consistency of the model.

On the basis of the density functional theory using the CRYSTAL code, electronic and vibrational properties of lithium metaborate in the monoclinic and tetragonal phases are studied. The band spectra, elastic moduli, long-wave vibrational frequencies at the point Г, dynamic charges, and acoustic velocities are calculated for both phases. The influence of structural features and short-range order in trigonal BO₃- and tetragonal BO₄- groups on the significant difference in physical properties in the low-temperature and high-temperature phases of LiBO₂ crystal is established.