The prevailing mathematical model describing the laminar–turbulent transition in a circular pipe is based on a full system of Navier–Stokes equations. Calculations using this model are very expensive; in addition, the computed dynamics is chaotic and too complex to decode the transition scenario. In the present study we consider certain simplifications, including popular cases restricting the dynamics to reflectional and rotational symmetries. We show that in these two cases transitional and turbulent flows cannot be computed properly.

This article presents the results of inelastic scattering studies of neutrons and copper and silver chalcogenides at a temperature of 300 K in the non-superionic phase. We were the first to obtain dynamic structural factors and generalized the phonon densities of the states of these compounds. Inelastic peaks observed at energies of 3–5 meV presumably correspond to the acoustic vibrations of phonons. The phonon spectra of copper and silver chalcogenides have features characteristic of compounds that are structurally disordered.

In the present article it is shown that the presence of defects in a material for a certain duration of heat exposure leads to the necessity of taking into account the dependence of the linear thermal expansion coefficient on the mobility, which determines its operator form. Using the example of the dynamic thermoelastic problem with an inertial inclusion acting as the defect, the change in the thermoacoustic signal caused by its presence is demonstrated. The transfer function of this operator is obtained, the behavior of which corresponds to the experimental result.

We report on developing an ultracompact (∼300 g) fluorescence lidar based on a diode laser (405 nm, 150 mW) and a diffraction spectrometer equipped with a linear photodiode array. Field tests have been performed on remote sensing of vegetation from a quadcopter. The field tests have shown the prospects of autonomous lidar monitoring for early disease detection in crops.

In this paper, we describe a diagnostic method based on “acoustic weighing” of sheet materials. The defect mass or mass deficit determines the frequency shift of the oscillating membrane. The measuring device of Academician N.N. Andreev invented in 1925 and based on the effect of “rattling” due to the “bouncing” of a small weight lying on a telephone membrane is described. The harmonics that appear at sufficiently large oscillation amplitudes are calculated. It is shown that harmonics can also appear during the operation of modern high-precision instruments, for example, tunneling and atomic force microscopes.

This paper presents the results of experimental studies of the influence of the geometry of the flow part of the chamber and the pressure at the inlet and outlet of the vortex-type generator on the intensity and nature of the occurrence of nonlinear wave and hydrodynamic processes.

The results of numerical simulation of experimental data on the thermal and force effects on the experimental hypersonic aircraft HIFiRE-1 at flight speeds of M = 6.58 and 7.16 are presented. The calculations were made using the author’s computer code, which implements the finite-difference technology for integrating the set of Reynolds-averaged Navier–Stokes equations on multiblock structured grids using two algebraic turbulence models. Taking into account the laminar–turbulent transition and the turbulent nature of the flow near the aft skirt of the HIFiRE-1 aircraft makes it possible to obtain good agreement with the experimental data.

In this study, changes in temperature extremes in Russia are considered and the impact of these changes on the balance sheets of Russian power systems is analyzed. On the basis of the current meteorological observations and energy statistics, the change observed in extreme climatic characteristics over the past seventy years is calculated and its impact on power-grid regimes is estimated. It is established that the climate changes in Russia manifesting themselves in increasing air temperature in all regions and all seasons lead to a slowdown in the growth of winter and an increase in the growth of summer peak loads in almost all power grids, thereby contributing to an increase in the reliability of the energy supply. At the same time, disruptions of the electricity supply may arise in the southern energy-deficient regions in the summer as a result of violating the intersystem links and operation modes of generating facilities due to weather and climatic factors.

The eigenfrequencies of bending vibrations are determined for wire with micro- and nanosize cross sections. The surface effects associated with an increase in the specific surface when reducing the cross-section area are taken into account. The first effect is induced by the difference in the elastic characteristics of the material of the surface layer and the bulk. The second effect is associated with the interaction between the excess pressure on the wire surface and the difference in the areas of convex and concave surfaces formed by the bending. The case of the wire hinged fastening at both ends is considered. The eigenfrequencies are determined in the linear and nonlinear formulations. The influence of surface effects and other input data on the eigenfrequencies is analyzed.

For the first time, the results of investigations of ion transport phenomena in high-temperature modifications of single-crystalline copper selenide are presented depending on the temperature and the composition within the homogeneity region as well as the effect of the degree of perfection of single-crystalline samples on the ion transfer. It is found that the activation energy estimated from the temperature dependences of the ionic conductivity for perfect single crystals is significantly higher than in polycrystalline samples and increases with a deviation from stoichiometry. For single crystals, lower values of ionic conductivity are observed. The ionic conductivity in the temperature range of 573–723 K is 1.5–2 times higher for polycrystalline samples than for single crystals.