Vol 44, No 8 (2018)

The excitability (increase in the number of charges at the poles of nonpoint dipoles) in chains of nanoscale dipoles with varying moments in weak external alternating electric fields (at the level E = 10^–13–10^–4 V/m) at low frequencies Ω < 10⁵ Hz has been investigated numerically. It has been found that the level of charge excitations in such systems has a nonlinear dependence with a maximum on the radius (in the range r = 20–200 nm) of nanoscale dipoles. It is concluded that, in these ranges, the probability of self-assembling of single dipoles into the chains is increased.

ZrO₂(Y) ceramic with embedded particles of a pore-forming agent—ultrahigh molecular weight polyethylene—has been studied. It has been shown that the porosity of samples after sintering changed from 2 to 42 vol % and the grain size changed from 0.5 to 1.55 μm depending on sintering regime. The strength of materials with minimum porosity was 3000 ± 200 MPa, while the strength of materials with maximum porosity was 100 ± 20 MPa, regardless of grain size. It has been shown that the tetragonal to monoclinic martensitic phase transformation related to mechanical stresses takes place in the material without any effect on the macrostrength of the material. Internal microscopic stresses decreasing with an increase in porosity and ceramic grain size are the main factor causing this transformation in a porous material.

Living sensory neurons were studied by atomic force microscopy in the PeakForce QNM mode under near-physiological conditions. The dependence of the measured apparent Young modulus of cells on the ratio of the probe height to the beam length on a used cantilever was revealed. A qualitative explanation based on the analysis of beam strains in two limit cases, in which the probe slides over a studied object and the probe sticks to the latter, was given to the obtained result. It was proposed to classify native cells by the character of their interaction with the probe (sliding or sticking).

Deformation of an amorphous cobalt alloy of strip configuration in creep tests in a variable temperature field is studied. An analytical form of the creep curve is found, and a prediction calculation of the resistivity by means of the proposed creep function is carried out. The physical meaning of the parameters of the creep equation is established, and their dimensionality is found. It is shown that, under the action of a variable temperature field, the creep of the alloy is not Newtonian and the material under strain exhibits pseudoplastic properties. It was found that, in the absence of heating, the viscosity of amorphous strip alloys can be considered within the Bingham plastic model.

The problem of increasing the accuracy of calculating the characteristics of complex dynamics in threshold systems is solved using the example of Lyapunov’s exponents. Despite the existence of theoretical and numerical studies that earlier have allowed one to substantiate the possibility of recovery of dynamic systems from the signals at the output of threshold systems, the problem of diagnostics of dynamics in the case of a small amount of data in the presence of noise requires a separate study. It has been shown how preliminary data processing that provides the transition to uniform sampling can significantly reduce the computation errors.

It is proposed to characterize levels of deformation by a size of its jumps, which can be observed when the strain rate is accurately measured in experiments with load that is constant or defined according a certain law. At the micro- and nanometer scales, the strain rate was measured and the deformation jumps were computed for copper, lead, and tin using a precision interferometric method. A correlation of the size of jumps with the Burgers vector of dislocations in metals was shown, and hypotheses about ensembles of dislocations participating in the formation of a deformation jump are made.

Diamond single-crystal Schottky barrier mip-structures (metal–intrinsic diamond–p-doped diamond) with dimensions of 3 × 3 and 4.1 × 4.28 mm are fabricated on the basis of HTHP p-diamond and CVD i-diamond. The betavoltaic characteristics of the diamond structures are studied using a wide-aperture electron beam with an initial energy of 110 keV, partially scattered on the way to a converter by a 14-μm-thick aluminum layer and a 17-mm-thick air layer. The maximum generated power reached 2.18 mW (41 mW/cm²) with a conversion efficiency of 2–3%.

We have studied the filtration of surface spin waves in yttrium iron garnet (YIG) films of variable width excited by focusing transducers integrated with the film.

We have studied transient processes of the thermal ionization of sodium on the surface of NaAu_y semiconductor film under the action of a variable external electric field. It is established that the kinetics of Na⁺ ion current during variation of the external field is determined by the establishment of charge distribution in the NaAu_y film, while the efficiency of thermal ionization of Na atoms is related to the concentration of holes near the NaAu_y/vacuum interface.

We have identified the asymptotic behavior of the kernels with large indices of integral operators representing the coefficients of expansion in Legendre polynomials of the collision integral of the linear Boltzmann equation for hard-sphere potential. In the case of interacting particles with nonequal absolute values of velocities, the kernels exhibit exponential decay, where the base of the exponent contains the ratio of the lower to higher velocity. In the case of interacting particles with equal absolute values of velocities, the kernels decay according to the power law.

An experimental investigation of the multipath propagation of ultrawideband (UWB) microwave chaotic radio pulses in a wireless channel has been carried out. Based on the results of measurements, conditions of receiving chaotic radio pulses upon passage via a multipath channel are established for various signal delay times.

A laser structure comprising metamorphic InGaAsP layer and InGaAs quantum wells on a non-inclined Si(001) substrate with relaxed Ge buffer layer has been grown for the first time by metal-organic vapor phase epitaxy (MOVPE). The optically pumped lasers exhibit stimulated emission at a wavelength of 1.3 μm. At liquid-nitrogen temperature, the threshold power density of pumping at 0.8 μm amounted to 250 kW/cm².

Thermodynamic spin fluctuations in strongly correlated plutonium (Pu) phases with exchange and spin–orbit interactions are considered. In α- and δ-Pu phases, the spin fluctuations lead to a negative magnetovolume effect that is determined by the parameter of intermode coupling and depends on features of the electron structure. It is shown that the negative volumetric thermal expansion coefficient of δ-Pu is related to an anomalously strong interaction of spin fluctuation modes.

We have studied the influence of silver addition in various concentrations on the structure and shape memory effect of biocompatible TiNiMoFe alloys. All these alloys at room temperature occur in a mixed state (B2 + R or B2 + R + B19′) with B2 austenite phase as the main component. It is established that small concentrations of silver (within 0.5 at % Ag) suppress the shape memory effect, while greater additions (1 at % Ag) stimulate the nucleation and growth of martensite crystals. This is accompanied by increasing content of the main B2 austenite phase and Ag particles in the alloy.