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A method for direct laser thermochemical writing of gray-scale microimages in thin chromium films is developed and studied. The method includes exposing a chromium film with a focused laser beam with variable power intensity and developing it in a selective etchant. The range of variation of the transmission by more than 100 times is obtained. The nonlinearity of the dependence of the chromium film transmission on the power intensity of the exposing beam is eliminated by software correction. The samples of the raster (with a size of 64×64 and a step of 176 μm) of apertures (36 μm) with the gray-scale Gaussian transmission function are manufactured experimentally. This raster is used in the modified Shack - Hartmann sensor.

A confocal experimental scheme with two polycapillary lenses is used to analyze the nearsurface layers of samples by X-ray fluorescent microanalysis with an accuracy of up to 10 μm. To increase the spatial resolution, it is required to account for the influence of the spread function of the confocal X-ray optical node. It is interesting to experiment with a tunable aperture of the confocal volume. In this case, the contribution of tuning inaccuracies in the spread function can increase. A method for describing the spread function of a confocal X-ray microscope that allows for its retuning and accounts for the effect of the angular tuning errors is proposed and experimentally proved. The method is based on the use of an approximating expression of the type of asymmetric approximation of the “Gaussian beam caustic”.

A new method for measuring radial and axial displacements of complex-shaped blade tips with the help of a distributed cluster of two single-coil eddy-current sensors with sensitive elements made as conductor strips is described. The main distinctive features of the method and the results of an experimental analysis of families of calibration characteristics of both sensors are considered. This analysis proves a higher sensitivity to changes in radial displacements and an extended range of axial displacement measurements of the new method as compared to the existent one.

A new class of electrostatic power microgenerators, which transform the energy of mechanical microvibrations to the electric form, is described. The transformation principle is based on transmitting external microvibrations to the microgenerator frame where thin layers of electrets are located, and a moving electrode is suspended on a weak suspension between these layers; this moving electrode performs alternating impacts on the frame. Generator operation is numerically analyzed, and analytical estimates of the generated power are obtained. It is shown that the power produced by such a generator is appreciably greater than the power generated in the classical circuit based on excitation of forced vibrations of a moving plate.

The review deals with the analysis of the factors affecting the boundaries of two-phase regimes in the channels of different cross sections, whose minimal size is less than the capillary constant. The channels are classified by size. Data for two-phase flow regimes are systematized and summarized in tables for the round and rectangular tubes. It is indicated that the most studies identify the following two-phase flow regimes: bubble, slug and annular. The regimes found in some papers are described. The terminology used to describe the regimes is kept. Here we analyze the main factors affecting the structure of the two-phase flow, such as gas and liquid flow rates, parameters of the channel and input section, wettability of the inner surface of channels, liquid properties, and gravitational forces. It is shown that development of instability of the two-phase flow has a significant impact on formation, evolution, and change of the flow regimes.

The Landau problem on the evaporation front stability is generalized to the case of finite thickness of the evaporating liquid layer. The analysis of the influence of additional factors, the impermeability condition of solid wall and resulting pulsations of mass velocity, is carried out. Parametric calculations of the stability boundary are performed when changing the liquid film thickness and the relationship between phase densities in the framework of asymptotic Landau approach for the Reynolds number Re > 1. Approximate evaluation of the influence of liquid viscosity on the stability boundary has been done.

The algorithms of solution to the Young–Laplace equation, describing the shape of an axisymmetric droplet on a flat horizontal surface, with various ways of setting the initial data and geometric parameters of a droplet, were derived and tested. Analysis of the Young–Laplace equation showed that a family of curves that form the droplet surface is the single-parametric one with the accuracy of up to the scale factor, whose role is played by the capillary length, and the contact angle determines the curve turn at a contact point, but it does not affect the shape of the curve. The main natural parameter defining the family of the forming curve is the curvature at the droplet top. The droplet shape is uniquely determined by three independent geometric parameters. This fact allows us to calculate the physical properties, such as the capillary length and contact angle, measuring three independent values: height, droplet diameter, and diameter of the droplet base or the area of the axial cross section of the droplet or its volume.

Numerical simulation of the flow of an aerosol of polydisperse composition in a plane duct, where the resonance acoustic oscillations are generated, which are directed across the flow, has been carried out. The peculiarities of the flow, which is followed by coagulation and alteration of the distribution of particles over their sizes, have been described. The carrying medium has been modeled with the aid of the system of NavierStokes equations for compres-sible heat-conducting gas. The polydisperse phase dynamics is described by the systems of equations involving the equations of continuity, conservation of the momentum and internal energy. Equations of the motion of carrying medium and disperse fractions are written with allowance for interphase exchange by the momentum and energy. A Lagrangian model has been used to describe the coagulation process. The dispersion alteration in the gas-particle flow under the action of acoustic oscillations, which are resonant for the duct cross section, is analyzed.

The thermoacoustic effect concerns conversion of energy between a gas and a solid in the presence of acoustic waves. Although the working principle is well understood, the optimal design of thermoacoustic devices remains a challenge. The present work aims to perform a numerical simulation of a simple standing-wave thermoacoustic device. The analysis of the flow and the prediction of the heat transfer are performed by solving the non-linear unsteady Navier–Stokes equations using the finite volume method implemented in the commercial code ANSYS-CFX. The goal of this work is to study the effect of the stack temperature gradient, on the acoustic pressure and the produced acoustic power. This stack temperature gradient generates the thermoacoustic instability in standing-wave thermoacoustic resonator. The obtained results show an increase of the acoustic pressure and the acoustic power while increasing in the stack temperature gradient. The thermodynamic cycles of the thermoacoustic device are illustrated and observed for the different stack temperature gradients.

An experimental study of the structure of a pulsating air flow through a smooth channel was carried out. The flow pulsations were artificially imposed onto the main flow through periodic blockage of channel outlet cross section. A method for determining the additional shear stresses due to the imposed flow pulsations is proposed. The essence of the method consists in the determination of the shear stresses based on the revealed dynamics of the flow velocity field, whose measurements were carried out by the optical method from the results of digital video recording of the flow pattern. Profiles of velocities, accelerations, and additional shear stresses during a period of imposed flow pulsations were obtained.