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Various failure modes of the electrodes and insulators of pulsed X-ray tubes with explosive electron emission operating in a single-pulse flash mode are investigated. The operating parameters are as follows: capacitor bank discharge energy into the tube 30-50 J, pulse duration 40-100 ns, and electron energy incident on the anode 200-300 keV. The following experimentally observed damage types are identified: sublimation, spallation, surface melting, formation of Taylor cones drawn from the surface, droplet ejection, surface etching in the form of deep longitudinal grooves, periodic chevron-like surface patterns, deep surface cracks, micrometer-scale droplets atop Taylor cones that have traveled from the cathode to the anode, cathode bombardment by material ejected from the anode, dust-like deposition in the form of island films on the cathode and insulator, and surface flashover along the insulator accompanied by film evaporation. The mechanisms underlying the effects of high-current pulsed electron beams on the components and the influence of these damage types on the service life of the tubes are discussed.

A comprehensive experimental study aimed at generating a training dataset for the development of a neural network model to optimize the control of environmental and energy performance parameters of hydrocarbon fuel flame combustion is presented. Flame characteristics are investigated for liquid fuel combustion using a flare burner with a thermal capacity of 300-1500 kW and mechanical atomization. The experiments examine operating modes at various power levels (400, 700, and 1000 kW) and equivalence ratios (1.06, 1.17, 1.28, and 1.40). Simultaneous measurements of flame temperature, combustion product gas composition analysis, and visual flame monitoring are performed. The dependence of combustion parameters on operating conditions is established: an increase in power and a decrease in the equivalence ratio elevate the flame temperature. Alternatively, dropping airflow reduces CO concentration to <10 mg/m³ but increases NO_x emissions to >125 mg/m³. Correlations between the visual flame characteristics (size and luminous intensity) and the equipment operating parameters are identified, which opens prospects for the development of automated machine-vision-based control systems.

An asymptotic model of large-amplitude stationary inertial waves in an axisymmetric swirling flow of an ideal fluid in a circular pipe of varying diameter is developed. Calculations are performed for a flow with solid-body rotation far upstream; in this case, vortex breakdown is caused by the pipe geometry and the emergence of a separation zone. The separation zone is shown to be axially asymmetric. For a separation region to form at a fixed position relative to the onset of pipe expansion, the flow swirl should be stronger for larger pipe expansion angles.

Results of an experimental study on the effectiveness of controlling incompressible turbulent flow over an asymmetric Clark Z airfoil using a perforated surface are presented. The perforated surface consists of an array of cylindrical cavities or through-holes with variable geometric parameters. The cavities are located on the lower surface of the wing, most of which is exposed to zero-pressure-gradient flow. The study is conducted over a chord Reynolds number range of Re_c = (0.601-1.324) × 10⁶ at an angle of attack of 3.6°, corresponding to a momentum thickness Reynolds number range at the perforated surface inlet Re_θ = 527-992. Particular attention is given to a previously unexplored analysis of the potential for reducing the aerodynamic drag of the airfoil under these conditions. It is shown that none of the perforated surface configurations under study provides a drag reduction within the experimental uncertainty.

The flow structure and pressure fluctuation characteristics generated when a supersonic underexpanded jet impinges on a flat semi-infinite obstacle with a coaxial hole are investigated. Different interaction regimes are found to arise depending on the hole diameter and the distance from the nozzle exit to the obstacle. The presence of a hole in the obstacle is found to significantly intensify wall pressure fluctuations for nozzle-to-obstacle distances in the following range: h/D_a = 1-4. In the case where h/D_a = 4-15, the interaction regimes are similar to those observed for a jet impinging on a solid (impermeable) obstacle.

This paper presents the results of a study of the parachute -type fragmentation process. This process serves as a source of the dispersed phase in various natural and industrial multiphase flows in which a planar liquid surface is exposed to a gas stream. Experiments are performed using shadowgraph visualization and high-speed imaging, with artificial initiation of the process under controlled conditions. Computer-based image processing is used to determine the dome dimensions and film thickness, as well as to detect the resulting droplets and quantify their number. Based on the analysis of the results, it is concluded that rupture of the dome film occurs due to Rayleigh-Taylor instability. The dependence of the average number of droplets produced by rupture of the parachute dome film on the governing parameter-the Weber number-is obtained.

The effect of free rotation of the cylindrical housing of a centrifugal reactor on the structure of vortex fluid flow is investigated experimentally. The working fluid is driven by rotation of the upper disk, while the reactor housing is free to rotate about its axis under the action of viscous friction from the fluid. The flow energy expended in overcoming friction in the stationary housing is converted into kinetic energy of rotation of the reactor housing. Even slight free rotation of the reactor housing is found to lead to a significant intensification of the vortex motion. The proposed reactor design enables efficient control of vortex flows without the additional energy expenditure required for forced rotation of the sidewalls at a fixed speed. The results obtained can be used in the development of compact centrifugal reactors for biological, chemical, and energy technologies.

Forced nonlinear oscillations of a gas bubble in a viscoelastic fluid are considered for the case where the oscillation frequency of the external fluid pressure coincides with the undamped linear resonant frequency of the bubble. The averaging method is applied to derive a formula for the dependence of the bubble oscillation amplitude on the external pressure amplitude, the adiabatic exponent, and the viscoelastic properties of the fluid. Computational results obtained using this formula are shown to be in good agreement with numerical simulation results.

The data on the concentrations of phenolic compounds, photosynthetic pigments, pectin substances and triterpenoid saponins in the leaves of Chlorophytum сomosum Thunb. Jacques are presented, the antioxidant and antiviral activity of the extracts of this plant species is assessed. High concentrations of chlorophyll a and b (434.67 and 245.11 mg/100 g, respectively), tannins (82.34 mg/g), catechins (0.73 mg/g), hydroxycinnamic acids (36.67 mg/g), saponins (64.53 mg/g), carotenoids (75.70 mg/100 g) and pectin substances are detected in the leaves of this plant species. The total content of phenolic compounds and flavonols was termed as insignificant. The water-ethanol extracts of the leaves exhibited antiradical activity in the reaction with the stable free radical 2,2-diphenyl-1-picrylhydrazyl. The antiviral activity of the aqueous extract was detected with respect to the avian virus A/chicken/ Kurgan/05/2005 (H5N1).

A new synthetic approach has been developed on the structure modification of bioactive furanolabdanoid phlomisoic acid methyl ester by introducing 1,3,4-oxadiazolylcarbonyl fragment at position 16 of the carbon framework. The key steps of the synthesis are the preparation of (2-(2-(aryloyl/hetaryloyl)hydrazinyl)-2-oxoacetyl)furans and their subsequent heterocyclisation proceeding under the action of dehydrating agents. The cytotoxic properties of the obtained compounds were evaluated with MTT test against three human cancer cell lines. It has been shown that introduction of (5-(pyridin-4-yl)-1,3,4-oxadiazol-1-yl)methanone motif on the furan ring of the starting labdanoid significantly increases the cytotoxic action.