Vol 63, No 6 (2018)

A method for simulation of images in a scanning probe microscope (SPM) using simultaneous wavelet transform and median filtering is proposed. The wavelet transform with the fourth-order Daubechies kernel is used. Such a transform makes it possible to select details of different scales in the SPM image and, hence, study fractal properties of surfaces. Simulation is used to show that ultrahigh (atomic) resolution is possible in SPM provided that the size of the contact region in the probe–sample system is significantly greater than atomic size and the lattice atoms are randomly distributed. Contrast inversion in the SPM images in the multiscan mode is interpreted.

An experimental and theoretical complex was created to study the physical processes accompanying the interaction of the air flow carrying ice crystals with the heated surface of the streamlined body. An effective coefficient of phase transformations (evaporation and transition—through melting and solidifying in a liquid film—into barrier ice) of the mass of crystals bombarding a dry or moistened heated surface taking into account their partial entrainment with flowing air has been found. The physical and mathematical model of hydrothermodynamics of a liquid film is developed, the numerical data for the thickness, velocity, and temperature, complementing the results of the experiment, are obtained.

A short (without a positive column) Knudsen thermionic discharge initiated in barium and strontium vapor has been investigated. It has been shown that the behavior of these discharges and their formation mechanism, effective heating of the plasma electrons by a cathode electron beam, are, in general, similar to the discharge in cesium.

A microchannel structure of a spark discharge initiated in atmospheric-pressure air in a point–plane gap has been discovered by shadow photography. The structure has been observed since the onset of the discharge glow. The evolution of the microstructure over times from several nanoseconds to several tens of nanoseconds has been traced. Specifically, the development of microchannels from the point into the discharge gap, expansion of the microchannels, and their interaction have been observed. A correlation has been found between the microstructure of the spark channel in the discharge gap and its autograph on the surface of the plane electrode.

The functional properties of rod-shaped Cu–Al–Ni single-crystal alloy with the shape memory effect (SME) have been studied experimentally. Tensile tests of the samples have been carried out in the conditions imitating the operation of load-bearing elements in linear and rotary SME engines in the cyclic regime. Basic principles of constructing and the operating conditions of engines with load-bearing elements based on these single crystals have been formulated from the results of investigation. Basic relations between the functional properties of the single-crystal alloy and the main parameters of the engines have been established. Such characteristics as the maximal rod stroke in the linear engine and the angle of rotation of the shaft in the rotary engine, the maximal generated force and moment, as well as the effective work done by the engines, have been analyzed.

We consider the autowave mechanism of evolution of a localized plastic deformation of crystalline solids of different origins. It is found that localization of the plastic flow is determined by the relation between elastic and plastic phenomena in deforming materials. It is shown that the main parameter of deformation processes is the elastic–plastic deformation invariant, viz., a dimensionless quantity connecting quantitatively the parameters of elastic waves and self-sustained waves (autowaves) of localized plastic deformation. The correctness of this statement is verified for metals, alkali-halide crystals, and rocks. The physical origin of the invariant is explained on the basis of thermodynamic considerations.

We have obtained restructured zinc (high-purity zinc prepared by mechanothermal action of various intensity levels) and have analyzed its structure by the positron spectroscopy methods. Bulk vacancytype defects (vacancies and vacancy clusters), as well as the regions with an extended crystal lattice, have been discovered in the restructured samples and analyzed quantitatively. These effects are responsible for the emergence of internal microstresses in the material, which modify its properties.

We present the research results of the fabrication technology of magnetoresistive (MR) elements based on the multilayer spin-valve magnetoresistive (SVMR) Ta–FeNiCo–CoFe–Cu–CoFe–FeNiCo–FeMn–Та nanostructures and CoNi micromagnets for the construction of digital galvanic interchanges and the magnetic field sensors. The results of experimental studies of test elements based on multilayer SVMR nanostructures with an MR effect from 7 to 8% and films of magnetically hard materials with a coercive force of up to 95 Oe formed on a single silicon die are presented.

The thermal evolution of the conductivity of a VO₂ film and database-obtained band gap E_g of film nanocrystallites is traced in the temperature range of –196°C < T < 100°C (77 K < T < 273 K); the level position of donor impurity centers is determined to be E_d = 0.04 eV. It is shown that energy E_g decreases from 0.8 to ∼0 eV with an increase in temperature in the range of 273 K < T < 300 K, which is caused by the narrowing of the energy gap due to correlation effects and considered as the temperature-extended Mott “insulator–metal” electron phase transition with the monoclinic lattice symmetry retained. The subsequent jump in the symmetry from monoclinic to tetragonal with a further increase in temperature is considered as the Peierls structural phase transition, the temperature of which is in the vicinity of 340 K and determined by the size effects, nonstoichiometry of VO₂ film nanocrystallites, and degree of their adhesion to the substrate.

A method for fabrication of mechanical elements (microturbines) that receive torque from vortex optical beams is proposed. Experimental results on fabrication of multiple microturbines are presented. Shapes of the microturbines are measured using an optical microscope, ZYGO white-light interferometer, and electron microscope.

Peculiarities of anisotropic acousto-optic Bragg diffraction in paratellurite by a slow acoustic wave have been considered. The ranges of frequency-angular dependences have been found, in which effective diffraction occurs, and their practical relevance has been formulated. The numerical values for light radiation with a wavelength of 1.06 μm have been obtained. We have proposed the method of enhancement of a diffraction efficiency of divergent optical radiation, which in turn leads to the increase of the response time of an acousto-optical modulator. The method is based on a multifrequency electric control of the acousto-optical modulator. We have shown experimentally that, as distinct from the single-frequency control, a considerable intensity suppression of the zero diffraction order from 30 to 8% is achieved.

Excitation of electromagnetic fields at extremely low and lower frequencies in the near-field zone of the Earth–ionosphere waveguide is considered. Variations in the field amplitude in the lower part of the extremely low frequency (ELF) range and lower frequencies are experimentally determined under different geophysical conditions in the absence of variations in the ultralow frequency (ULF) range. The effects related to such variations are analyzed with the aid of theoretical calculations that show significant effect of ionosphere in the near-field zone at relatively low terrestrial conduction.

It is shown that low-energy beams with a high efficiency in a wide range of beam currents can be obtained in electron sources with a hollow cathode in the forevacuum pressure range. By varying the geometrical parameters of the electrode system and electromagnetic optics of the electron source, we succeeded in reaching the efficiency at a level of 0.9 for an accelerating potential of 1 kV and beam currents from 100 to 300 mA. The parameters affecting most strongly the efficiency and stability of operation of the electron source with a hollow cathode have been determined.

It has been found experimentally that the field emission current passing through a single multiwall carbon nanotube heats it up and generates a thermionic component. The nanotube is heated by the Joule heat that releases on its series resistance, through which the current passes. From the solution to the heat conduction equation, the overheating temperature of the emitting end has been estimated. Conditions for field emission stability and for the onset of thermal field emission have been found.

Dielectric and optical methods were used to reveal the complex nature of globule–coil–coil associate phase transitions in solutions of human serum albumin. The impedancemetric and nephelometric curves of temperature dependences of the parameters of the phase transitions in albumin that was introduced into the standard saline were obtained. Impedancemetry revealed a two-stage mechanism of the globule–coil phase transition, and nephelometry established a two-stage mechanism of the coil–coil associate phase transition. The concentration dependences of the critical indices and temperatures were determined for both phase transitions.

The method of video goniography and the device for its implementation has been described. The results of the study of the morphology of the lateral surface of profiled monocrystalline sapphire rods, which were grown by Stepanov’s method, of three main crystallographic orientations c{0001}, a{112̅0}, and m{101̅0} have been presented.

The object of this work is the apokamp—a new type of plasma jet, which is formed from a bright offshoot emerging at the bending point of a channel of a high-voltage pulse-periodic discharge under conditions where the electrodes have a capacitive decoupling with the ground. The aim of this work is the identification of distinctive properties of the offshoot in comparison with the apokamp. The differences in the spectra of the offshoot and plasma jet (apokamp) were detected experimentally in air under normal conditions. The results of the previous studies, according to which the apokamp is a wave of ionization, were confirmed. The launch of a helium plasma jet from the offshoot of the pulse-periodic discharge in a mode of the apokamp forming was demonstrated experimentally. It was shown that the offshoot of high-voltage pulsed discharge in the mode with the apokamp is a medium that is strongly heated and conducting electric current.