Home – Home – Jornals – Thermophysics and Aeromechanics 2026 number 1

This study analyzes the amplitude-frequency characteristics (AFC) of deep GPR data gathered using variable offsets within the permafrost of the Nadym District, Yamalo-Nenets Autonomous Okrug. The initial frequency response of the raw data, which underwent only basic pre-processing, is presented, evaluating the effects of transmitter-receiver separation (100–750 m) as well as the spatial and depth-based placement of the analysis zone. This approach reveals the spectral evolution of electromagnetic signals within the geological environment during the late stages of the process. Results indicate that as the distance from the source increases, the signal undergoes standard attenuation, alongside three primary spectral effects: a downward frequency shift of the peak amplitude, a narrowing of the spectral bandwidth, and a significant rise in low-frequency components—the latter being primarily attributed to zero-line drift. Adopting spectral analysis techniques from seismic exploration for deep GPR data is a promising way to refine data processing and improve subsurface interpretation.

Sobolevite with low Mn content from the Karnasurt deposit (Lovozero, Kola peninsula) has been characterized by electron microprobe analysis, single-crystal structure refinement, high-temperature X-ray diffraction and density functional theory (DFT) calculations. The chemical formula can be written as Na_7.04(Ca_0.87Mg_0.16)_S=1.03(Ti_1.48Zr_0.20Mn²⁺_0.18 Nb_0.10Fe²⁺_0.06)_S=2.02Si_2.05P_2.02O_17.12F_0.88. The crystal structure refined to R₁ = 0.037 (P2₁/c, a = 7.0908(3), b = 5.4108(2), c = 40.6179(19) Å, b = 93.095(4)^o, V = 1556.11(11) ų) is based upon the [Ti₂O₂[Si₂O₇](PO₄)]^5- titanosilicate-phosphate HOH layers (TS blocks). The interlayer space is occupied by the AC complex formed by Na⁺, Ca²⁺ and Mg²⁺ cations along with (P1O₄)^3- groups and F^- anions. The F- anions are coordinated octahedrally by Na and Ca to form antiperovskite [FA₃] chains (A = Ca, Na) running parallel to the b axis. The crystal chemical formula of sobolevite is (Na_6.92Ca_0.92Mg_0.16)_S=2.00(Ti_1.46Zr_0.18Mn²⁺_0.15Nb_0.15Fe²⁺_0.06)_S=2.00(Si₂O₇)(PO₄)(F_0.81O_0.19)_S=1.00, which corresponds to the idealized formula Na₇CaTi₂O₂[Si₂O₇](PO₄)₂F and allows to consider it as a polymorph of quadruphite. The relations between sobolevite and quadruphite are pseudo-polytypic. The thermal behavior of sobolevite is typical for layered structures corrected by shear deformations. According to DFT calculations, sobolevite exhibits p-type semiconductor behavior with a band gap of approximately 2.75 eV. Altering the Ti/Nb ratio influences the band structure, inducing magnetism in the crystal and transforming it from a semiconductor to a semimetal or even a metal. The material exhibits strong absorption in the ultraviolet region, with an absorption coefficient reaching up to 2×10⁵ cm^-1. The overall structural architecture of sobolevite combines features of both titanosilicates and antiperovskite-type structures, which makes it an interesting example of hybrid structures with potentially interesting functional properties.

The article presents a methodology for quantitative verification of three-dimensional geoelectric models constructed from electrical tomography (ET) data in complex geological conditions. As an example of real data, a set of measurements is considered in the fault zone of the southeastern boundary of the Gorlovka depression (Novosibirsk region), where an increase in seismic activity has been observed in recent years. It is probably caused by the development of large coal mines. The relevance of the work is due to the interpretative ambiguity of ET data in heterogeneous geological environments and the appearance of artifacts in inversion models, which can subsequently lead to false interpretation of the results. It is proposed to move from the traditional visual comparison of the results of inversion of field and synthetic data to quantitative analysis. For this purpose, the ERT_Comp software tool has been developed, which calculates the relative difference between the model and field values ​​of apparent resistivity at specific spacings. The use of the technique for field data from three parallel profiles made it possible to quantitatively substantiate the choice of the optimal 3D geoelectric model reflecting the presence of a subvertical fault zone. The proposed approach does not completely remove ambiguity, but significantly increases the reliability of interpretation. Prospects for the work involve the use of gradient models and the establishment of standardized threshold values ​​of relative deviations to select the best interpretive model.

The Romanche Fracture Zone plays a crucial role in the distribution of Antarctic Bottom Water between the western and eastern Atlantic. However, the influence of bottom currents and other processes on the sediment infilling of the Romanche valley remains understudied. A large set of high-resolution sub-bottom profiling data was used in this work to solve this issue. The interpretation of the results was supported by numerical modeling of bottom current velocities using an ocean circulation model. The first comprehensive map of echo character distribution along the entire transform valley was built, revealing detailed sediment distribution patterns. The study assessed the modern and past influence of bottom currents on sedimentation and identified areas of intense gravity flow activity. The results highlight the Romanche valley as a promising area for studying the history of water exchange between the western and eastern Atlantic.

Profitability, efficiency, and safety in the
coal mining industry depend on the mining and geological conditions. Quite
often, the geological forecast is not confirmed, especially in the presence of
small-amplitude tectonic disturbances and local geological inhomogeneities,
which is why the development and application of geophysical methods, including
various types of seismic exploration, is of great importance. The article
presents the results of ground-based seismic surveys at the Chulmakan coal
deposit in the Sakha Republic (Yakutia) to clarify the general geological
structure of the study area, identify thin coal layers, study their structure,
and detect tectonic faults. It has been shown that, due to fundamental physical
and technological limitations, the reflected wave method cannot be the only
source of reliable information when studying fine-structured objects. Based on
the joint interpretation of reflected and refracted waves, as well as the
analysis of well data, the authors have successfully traced and refined the
parameters of the thin coal layers, and identified several tectonic faults that
were not detected by drilling. It is also shown that the purposeful development
of methodology, technical means, and technologies for interpreting refracted
waves is not just an academic interest, but an urgent production necessity.

We obtained the experimental and theoretical data on the temperature and pressure dependencies of the viscosity of model ultramafic and basalt melts at mantle thermodynamic parameters. Based on systematic experimental and theoretical studies, we established generalized patterns of the temperature and pressure dependencies of the viscosity of depolymerized magmatic melts (basaltic, model ultramafic and kimberlite) under conditions of the upper mantle. We have established an anomalous and extreme dependence of the viscosity of basaltic melts on pressure: as the pressure increases, the viscosity of such melts decreases, passes through a minimum, and then increases again. In contrast, for depolymerized ultramafic melts, the dependence of their viscosity on pressure corresponds to the theoretical dependence, i.e., as the pressure increases, the viscosity of such melts increases exponentially. A structural - chemical model has been developed for reliable predictions and calculations of the viscosity of magmatic melts in the full range of their basicity, from acidic to ultramafic, at T, P - parameters of the Earth's crust and upper mantle, with an error comparable to the experimental error. Using a computer version of this model, the characteristic features of the change in viscosity of ultramafic and basalt melts as they rise from the mantle to the Earth's crust have been established.

An approach is proposed for assessing the distribution of industrial minerals in the upper part of the geological section based on reprocessing and interpretation of archived 3D seismic data. The approach includes reconstruction of P- and S-wave velocity models using modified refraction and surface wave methods, automated extraction of dispersion curves using a neural network algorithm, as well as calculation and integration of a set of seismic and morphometric attributes. Based on the combined feature space, clustering is performed to delineate facies associated with deposits of different genesis. The approach was tested on the Kharampur license area located in the Arctic zone of West Siberia, characterized by the presence of permafrost. For this site (area ~60 km²), it is shown that the proposed workflow enables the construction of detailed predictive maps consistent with drilling data and active quarries. Clustering based on combined seismic and terrain-related features allowed identification of facies and the construction of physico-geological models of sand and peat bodies with economically significant thicknesses. This approach enables the generation of high-resolution predictive maps without additional field surveys, with a resolution comparable to engineering-scale drilling data.

This paper presents the results of studies of zircon grains from kimberlite and carbonatite bodies, as well as from ancient and modern diamond placers of the Lena–Anabar subprovince of the Siberian Diamond Province. The research includes U–Pb zircon dating and the determination of trace and rare earth element concentrations using the SHRIMP-IIe secondary ion mass spectrometer. The study covered kimberlite primary bodies of different ages, Late Jurassic carbonatite breccias, all diamond placers of the Anabar, Kuonamka, and Prilensky regions, as well as placer occurrences in the Primorsky, Lower Olenek, Middle Olenek, Muno-Tyung, and Daldyn-Alakit diamondiferous regions. In association with diamonds, zircon grains yielded Jurassic, Triassic, Permian, Late Devonian-Early Carboniferous, and Silurian-Early Devonian ages, which are consistent with the ages of known primary sources. New data indicate a broader age range of Triassic productive volcanism. Analysis of all diamond placers showed that approximately 79% of them were formed from Triassic primary sources.

The article presents the results obtained during the crystallization of a melt with the compositionin (in at. %): 14.0 Cu, 30.0 Fe, 4.0 Ni, 51.1 S, 0.1 each of Pt, Pd, Ag, Au, As, Bi, Pb, Se and Sn, in wt. %: 19.5 Cu, 36.7 Fe, 5.1 Ni, 35.8 S, 0.4 Pt, 0.2 Pd, 0.2 Ag, 0.4 Au, 0.2 As,0.5 Bi, 0.5 Pb, 0.2 Se and 0.3 Sn under isothermal conditions and with directional crystallization. Under gradient-free conditions, a homogeneous crystalline massif consisting of a mixture of monosulfide and intermediate solid solutions crystallizes from the melt. When cooled to room temperature, the monosulfide solid solution forms the pyrrhotite structure 1C, 3C, and the intermediate solid solution decomposes into a fine-grained mixture of isocubanite and chalcopyrite. Using the Bridgman-Stockbarger method, a three-zone ingot was obtained with the following sequence of phase crystallization from the melt: Mss / Iss₁ / Iss₂ and secondary zoning: chalcopyrite + pyrrhotite 1C, 3C + isocubanite (zone I) / chalcopyrite + low-temperature intermediate solid solution + Fe-pentlandite, sugakiite (zone II) / chalcopyrite + Ni-pentlandite + millerite + bornite (zone III). The specific influence of As, Bi, Pb, Se and Sn impurities on the behavior of Pt, Pd, Ag and Au under different crystallization conditions was revealed. In both experiments, solid solutions play a minor role in their concentration. The main amount of these impurities is released in the form of independent phases. The main role in their formation is played of immiscibility of the parent sulfide melt, resulting in the formation of a sulfide-metalloid melt, L_s-m, which concentrates impurities of Pt, Pd, Ag, Au, and chalcophile elements. The data on the directionally crystallized sample indicate a more complex process of immiscibility of the initial melt compared to its immiscibility during volumetric crystallization, namely 1) the simultaneous release of two types of liquids during cooling of the initial sulfide melt in zone II: one of these liquids is formed in the (Pd, Au)-(As, Bi) subsystem, and the second in the (Pt, Pd)-Pb-(S, Bi, As) subsystem; 2) in zone III, secondary immiscibility and phase formation processes may occur within the L_s-m droplets during cooling; 3) сoncentration of microphases at the end of the ingot in zone III.

As a result of data processing for more than 3000 clinopyroxene xenocrysts from kimberlites of different ages in the Siberian Platform, a generalized model of the lithospheric mantle thickness evolution within the Yakutian diamond province has been obtained. New data on surface heat flow (SHF) and thermal lithospheric thickness (TLT) have been obtained for seven localities on the Siberian Platform, including Paleozoic and Mesozoic kimberlites from different regions with different diamond potential, as well as Late Triassic sedimentary rocks from the northeastern margin of the platform. The composition of clinopyroxenes from the Late Triassic sedimentary rocks corresponds to the Devonian–Carboniferous type of lithospheric mantle of the Siberian Platform. New data on kimberlites from the northeastern part of the platform (Ivushka and Zaoblachnaya pipes) yield results that contradict previous interpretations. The Ivushka pipe (Toluopka field) exhibits a TLT thickness closer to that of Jurassic kimberlites, but the sampling depth of clinopyroxene-bearing rocks is typical of Devonian–Carboniferous kimberlites. The geotherm of the Zaoblachnaya pipe (Khorbusuon field) corresponds to Devonian–Carboniferous and Triassic kimberlites, which contradicts the absence of diamonds in the pipe and its tectonic setting. The SHF and TLT values separating the Jurassic lithosphere of the northeastern part of the platform from the older lithosphere are 36.9 mW/m² and 230 km, respectively. Based on the TLT and the depth of lithospheric section sampled by kimberlite magmas of different ages, it is shown that the lower diamond potential of Triassic kimberlites may be related not to lithospheric thinning, but to a shallower depth of onset of mantle material entrainment, caused by increased permeability of the lithospheric mantle resulting from the preceding influence of the Permo–Triassic plume.

This paper presents an analysis of compositional data on Proterozoic dolerites from dikes and sills on the southern flank of the Siberian Craton, formed in an intracontinental setting between 1.91 and 0.72 Ga. Indicator geochemical parameters have been established for four age groups of dolerites, reflecting differences in their of mantle sources and the conditions of generation of the initial melts. Neoproterozoic dolerites of the Nersa complex are characterized by lowest (Sm/Yb)_n and (Nb/Y)_pm ratios and were formed with the contribution from enriched subduction-modified lithospheric mantle (SZLM) and a depleted (asthenospheric) source. Dolerites aged 1.35 Ga are distinguished by the maximum concentrations of incompatible rare elements and high (Sm/Yb)_n and (Nb/Y)_pm values, their formation occurred from an enriched plume mantle source. Mesoproterozoic (~1.6 Ga) dolerites of the Prisayan Trough are characterized by elevated contents of TiO₂ and high-field strength (Nb, Ta) elements compared to dolerites of the Nersa Complex. They are dominated by an enriched plume source with high (Nb/Y)_pm and TiO₂/Yb ratios, with limited contribution from SZLM. Paleoproterozoic (1.91 Ga) dolerites, while similar in (Sm/Yb)_n values to Neoproterozoic ones, have lower (Nb/Y)_pm and (Nb/La)_pm ratios, indicating a more depleted mantle source. The proposed diagrams (Sm/Yb)_n – (Nb/Y)_pm and (Nb/La)_pm – (Nb/Y)_pm allow us to systematize dolerites from the dike swarms of the southern flank of the Siberian craton based on the similarity in composition with dolerites of four stages of Proterozoic basic magmatism.

Several thermocirques have been detected in the Oymyakon Upland, in the basin of the upper reaches of the Indigirka River, based on space imagery. Two of these thermocirques were studied in the Suntar River valley. The thermocirqures formed in 2014-2016 after an increase in precipitation, and they continued to grow at a rate of 5-35 m/year until 2023-2024. Currently, they are 130-220 m long. The thermocirques were formed on the slope of a terminal moraine hill at an absolute height of approximately 900 m. The moraine deposits exposed in the back wall of the larger thermocirques consist of clastic material ranging from gravel to large boulders and blocks with a sandy-loamy fill. Two cryofacies were identified in the upper 5 m of the section based on their cryogenic structure: the lower cryofacies is an initially frozen moraine with a primary cryogenic structure, while the upper cryofacies is a taberated deposit of the lower cryofacies that has been re-frozen. Epigenetic ice wedges up to 2.5-3 m wide penetrate from the contact between the cryofacies, forming polygons with a size of approximately 30 m. It is assumed that the terminal moraine was formed during the first cryochron of the Late Pleistocene and is stratigraphically associated with the Yugler horizon, while partial thawing occurred in the first half of the Holocene.

Samples of Jurassic coal-bearing rocks from the Ulug-Khem Coal Basin (Republic of Tyva, Russia) and from the Angren coal mine (Uzbekistan) were investigated. These rocks contain numerous leaf remains of leptostrobaleans. The material from Angren is represented by a mass of numerous leaf fragments of Phoenicopsis taschkessiensis and Czekanowskia eugeniae (Leptostrobales) forming the leaf litter. The hydrocarbon composition of the rock extracts was studied. All the samples showed high concentrations of C₃₃ and C₃₅ n‑alkanes. The rock extract contains high concentrations of abietic acid derivatives such as dehydroabietanes, simonellite, retene, and norisopimarane indicating a relationship between leptostrobaleans and conifers by their biochemistry. Retene was found in a more mature sample from Tyva, containing abundant leaf remains of Czekanowskia tuvensis. The extract of a rock sample from Tyva contains aromatic secobicadinans, which are the major components of the aromatic fraction. Their connection with leptostrobaleans was excluded based on comparison with samples from Angren; however, their botanical affiliation is not obvious. The discovery of polycadinene resin derivatives in the Middle Jurassic material from Tyva indicates that they were probably produced by some groups of Jurassic plants.

Thermodynamic calculations were carried out to model the process of interaction between fluid with different concentrations of fluorine and the mineral association calcite + monazite (in the presence of barite and celestine), in order to establish how fluorine concentrations in the fluid change the initial mineral association and the forms of REE concentration during the formation of carbonatite complexes. Thermodynamic calculations were carried out at temperatures of 500, 400, 300, 200 and 100°C and pressures of 2000, 1000, 500, 250 and 125 bar in the range of fluorine concentrations of 10^-4 – 1 mol/kg H₂O. It has been established that when monazite and calcite are exposed to an acidic (pH 3) fluoride-carbonate-chloride solution, increasing fluorine concentrations result in the formation of REE-containing fluorapatite, fluorite, and the fluorocarbonates – bastnasite and parisite. Fluorocarbonates begin to form in equilibrium with decreasing temperature, beginning with decreasing fluorine concentrations in the initial solution. Formation of parisite, according to the generalized formula CaLn₂(CO₃)₃F₂, requires twice as much fluorine as that for bastnaesite LnCO₃F, and under acidic conditions, it appears only at 200 and 100°C in the range of 0.01–0.1 m HF. At the highest concentration considered (1 m HF), REE-fluorapatite, along with parisite, also disappears from the equilibrium assemblage due to the maximum possible amount of the third calcium consumer, REE-containing fluorite. Lowering the temperature increases the stability of REE-fluorite by reducing the fluorine concentration required for its formation in the fluid. With increasing pH of the ore-forming environment, the formation of parisite at 200°C is observed even at low HF concentrations (0.0001 m), replacing bastnaesite under these conditions. Increasing pH is also accompanied by increased stability of REE fluorite and the appearance of strontium-bearing calcite and hydroxyapatite in fluorine-poor fluids. In an acidic fluoride-carbonate-chloride solution, after its interaction with the monazite+calcite assemblage, the total concentration of lanthanides (Ln _tot) decreases with decreasing temperature. Starting at 400°C, the Ln _tot curve exhibits a complex dependence on the initial HF concentration and reaches its minimum at maximum m HF. The main contribution to Ln _tot comes from the chloro- (at low m HF) and fluoro- (starting at 0.01 m HF with decreasing temperature) complexes of light REEs. The contribution of heavy REEs is approximately three orders of magnitude lower than that of light REEs.

In natural and artificial water bodies, photolysis is the primary process that determines the transformation and fate of many pharmaceuticals. However, there is a lack of information on the degradation products of sulfonamide antibiotics and their toxicity. Phenols are potential transformation products of pharmaceutical contaminants and pose a threat to human health. This paper presents the results of an experimental study of the phototransformation of sulfamethoxazole in water. The irradiation experiments were carried out in a stationary photoreactor using KrCl (222 nm), XeBr (282 nm), and XeCl (308 nm) lamps and a bactericidal irradiator UVb-04 (180-275 nm) as sources of UV radiation. To determine the total phenol content in the photoproducts of sulfamethoxazole, a colorimetric method with Folin-Ciocalteu reagent was used. The changes observed in the absorption and fluorescence spectra after irradiation of aqueous sulfanilamide solutions are described in detail. The formation of three fluorescent photoproducts is shown, one of which is stable and accumulates in the solution regardless of the selected UV radiation source. The total phenol content increased after UV irradiation. It has been established that after 128 min of exposure to a KrCl excimer lamp, the total phenol content is 4 times higher than the initial value and amounts to 331.89 mg GAE/g. The results can be of interest for studying the degradation mechanism of sulfonamides, identifying toxic degradation products, and evaluating their antioxidant activity.

Phenol enters the environment during the combustion of plants and biomass, as well as through anthropogenic emissions. Phenolic compounds can act as precursors to organic aerosols, adversely affects human health, and reduces atmospheric visibility. The static absorption spectra of phenol and its volatile substituted compounds ( p-cresol and vanillin) presented in this work were obtained and analyzed using computer simulations based on quantum-mechanical molecular dynamics. The optical spectra were averaged over excited instantaneous molecular conformers fluctuating along system's evolution trajectories. The photodynamic dissipation of electronically excited states of the molecules was studied by generating trajectories in nonadiabatic molecular dynamics. Changes in the electronic structure of phenol, p-cresol, and vanillin, along with the crossing points and dissociation of potential energy surfaces, were obtained using the mixed-reference spin-flip approach within the time-dependent density functional theory. The O-H bond breaking in the hydroxyl group followed by deprotonation causes minor structural deformations for the molecules under study. It is shown that, upon excitation, the dissociation of the hydroxyl group occurs via an electronic transition to the σ-MO localized on the elongated O-H bond.

The paper presents the results of using carbon dots as luminescent nanosensors of heavy metal ions in aqueous media. The application of machine learning methods to the photoluminescence spectra of nanoparticles in multicomponent aqueous salt solutions made it possible to simultaneously determine the concentrations of desired substances. The comparative analysis of the quality of solving the inverse problem by different neural networks was carried out. Comparison of the results of using neural networks and X-ray fluorescence analysis for determining the ionic composition of industrial process media showed that the accuracy of the developed nanosensor fully meets the requirements for monitoring and controlling the composition of waste and process water.

Properties of high-altitude discharges in the atmosphere of the Earth and other planets and their satellites are actively studied in past three decades due to the acquisition of new data, primarily because of improvement of optical observation methods. This work experimentally and theoretically studies the ratios W₁₊/W₂₊ of radiation energy spectral density of four bands of the 1st positive nitrogen system (1+) to a band of the 2nd positive nitrogen system (2+) with a wavelength of 337 nm. The ratios are compared for atmospheric air and nitrogen with low impurity content at pressures of 0.04-0.4 torr. It is shown that the quenching rate of C³Π_u triplet states of molecular nitrogen increases in a nitrogen-oxygen mixture, which decreases the ratios W₁₊/W₂₊. It is confirmed that quenching of B³Π_g state by nitrogen and oxygen molecules increases with the air density in the Earth's atmosphere. The results can be useful for studying physical processes occurring against the background of the interaction of high-energy electrons with gases in the atmospheres of a number of planets and their satellites, which predominantly contain nitrogen.

Sources of short-wavelength radiation generated by the interaction of high-intensity radiation with matter are in demand for experimental research in physics, chemistry, and biology. Reproducible parameters of the generated short-wavelength pulses require the use of femtosecond pulses with stabilized carrier-envelope phase (CEP). The work is devoted to the study of the effect of pulse envelope noise on the error in determining the CEP. For the CEP stabilization system based on f-2f interferometer with spectral interference pattern resolution, it is shown that an increase in noise of an original pulse increases the error in determining CEP from supercontinuum radiation, which attains about 100 mrad at an envelope noise of 1%. An increase in the radiation peak power increases the influence of noise on the error in determining CEP due to supercontinuum generation. The results can be used to develop and optimize systems for measuring the femtosecond pulses carrier-envelope phase with pulse repetition rates in kilohertz range.

Improving the frequency-energy characteristics of lasers is an important task associated with both fundamental problems and the implementation of new engineering solutions. Increasing the pulse repetition rate of active media based on metal vapor, in particular a manganese atom, is necessary for the creation of high-speed laser monitors. This paper analyzes radiation spectral characteristics of an active element based on manganese atom transitions excited by a high-frequency semiconductor source based on the LTD generator concept. Radiation with an average power of 250 mW, including visible and IR components, was recorded at a pulse repetition rate of 75 kHz. It was experimentally established that the visible component disappears at frequencies above 75 kHz, which had not been previously observed. At a pulse repetition rate of 125 kHz, the average radiation power was 200 mW. In the IR region, the largest contribution (> 50%) comes from radiation at a wavelength of 1291.37 nm. The results of the work can be used in visual-optical diagnostics of various processes in laser monitor.

The development of laser radiation sources in the yellow-red spectral region with an extended range of adjustable generation parameters is a relevant and sought-after task in biomedical applications. This work experimentally studies spectral, temporal, spatial, and energy characteristics of neon atom radiation excited by a pulsed inductive cylindrical discharge. Lasing was obtained at 3 p → 3 s transitions of neutral neon atoms with wavelengths of 594.4 nm and 614.3 nm. The intensity ratio of these spectral components I ₅₉₄ : I ₆₁₄ depended on the pumping conditions and varied from 1 : 1 at pressures of 0.2-0.3 torr to 1 : (2...4) at an optimal pressure of about 0.13 torr. A maximal lasing energy of 17 μJ was achieved at a charging voltage of 29 kV (limited by the excitation system characteristics). A decrease in charging voltage below 20 kV resulted in the breakdown of lasing. The study of the temporal lasing characteristics revealed that lasing at the both wavelengths began simultaneously. The pulse duration was identical and attained an average of 12.5 ± 0.5 ns (FWHM), which corresponded to a pulse power of over 1.4 kW. These results can be used to develop gas-discharge lasers with tunable radiation parameters for ophthalmic applications.

A gas discharge is an effective converter of electrical energy into optical radiation. The mechanisms of current development and the quantitative contribution of electron multiplication and emission processes remain undetermined, even in the simplest discharge types, such as the abnormal glow discharge. In this work, the current-voltage characteristics and the voltage distribution in the cathode sheath region of a DC discharge in helium were investigated in the pressure range 3.5-9 torr and the voltage range 200-1700 V. The non-monotonic behavior of the current-voltage characteristics was demonstrated under conditions minimizing controlled and uncontrolled impurities. It was shown that at powers deposited into the discharge exceeding 3.5 W, a deviation from the asymptotic approximation of the cathode fall length to a value of 0.37 of the normal length is observed, which is associated with a change in particle concentration in the near-cathode region. The derived empirical law made it possible to refine known approximations for the dependence of temperature and particle concentration on the power deposited into the discharge, which is relevant for description of the kinetics of processes in high-voltage gas discharges used as sources of optical radiation.

One of the fundamental directions in the development of lasers based on self-terminating transitions (RM transitions) in metal atoms and ions is their application in brightness amplification systems. Improving such systems requires expanding the operational spectral range and increasing the pulse repetition frequency. A promising approach to addressing these challenges is the use of a new class of high-speed high-frequency switches based on a slit discharge (eptrons) for pumping RM lasers, particularly those operating in the UV range. Within the framework of this approach, this paper studies the frequency-energy characteristics of a mercury ion RM laser (λ = 398.4 nm). The use of a high-speed slit-discharge switch made it possible to generate voltage pulses with a rise time of 2-3 ns across the electrodes of a gas-discharge tube and achieve lasing in a double-pulse mode at repetition frequencies up to 300 kHz.It was determined that the laser pulse energy strongly depends on temperature and repetition frequency, with the optimal frequency decreasing as the temperature increases. Lasing in the form of bursts consisting of four pulses has been demonstrated. The achieved high pulse repetition frequencies of the laser radiation along with its short wavelength can contribute to the creation of unique brightness amplification systems based on the Hg⁺ RM laser.

The dynamics and spatial distribution of atmospheric pressure glow discharge plasma radiation in an argon flow in the plasma generation mode with metal particles is studied. The discharge system consisted of two symmetrical tantalum crucible-electrodes with inserts of a low-melting metal (magnesium) and operated at a current of 100-600 mA, a relatively high discharge voltage of 150 to 200 V, and an argon flow rate of 1-3 L/min, without changing to spark or arc discharge modes. Such parameters ensured the stable generation of magnesium atom fluxes in the discharge plasma, resulting from discharge initiation in the presence of afterglow from the decaying plasma in the interelectrode gap. It is shown that the most intense emission from metal atoms is observed near the electrode which acts as a cathode of the glow discharge during a given pulse half-period. The results of this work are of interest to researchers engaged in aerosol flux generation, synthesis of nanostructured materials, and the application of gas discharge for optical emission generation.

The effect of a compliant coating (film) over a porous surface on the stability of a supersonic (M = 2) boundary layer on a flat plate to disturbances of the first mode of instability under the conditions of experiments in the T-325 wind tunnel was calculated using linear stability theory. The calculations showed that a porous coating with a thin-film membrane on the surface can stabilize the boundary layer at Mach number M = 2 at the frequency most increasing on a solid plate. The dependences of the rates of the spatial growth of disturbances on a number of factors were found. Nonmonotonic (with minima) dependences of these growth rates on film tension, pore radius, porous coating depth, and porosity were obtained. The spatial growth rates of disturbances decrease with decreasing film thickness and the ratio of the gas pressure inside the pores to the static pressure in the boundary layer. It was found that stabilization of a supersonic (M = 2) boundary layer relative to the case of a smooth impermeable plate can occur only with a film thickness of less than 18 nm.

The paper presents experimental results from a study on supersonic flow across a cylinder. Selected measurements of pressure on the cylinder surface were taken. Different variants of jet blowing were tested with a focus on variation in the pressure distribution on a surface. The difference between variants was in positioning the blowing hole on the cylinder circumference in the mean cross-section. The paper describes the influence of the hole position on the pressure distribution for a case of interaction between a supersonic free stream and a jet. New experimental data on a pressure distribution on a circular cylinder surface with at different positions of the blow hole are now available.

Experimental data on the nature, thermophysical parameters, and boiling modes of closed two-phase evacuated water-filled thermosyphons are presented, and their application prospects are discussed. The high efficiency of thermosyphons in slug and hyperslug modes is experimentally confirmed.

Bubble motion in an inclined circular pipe with a cocurrent liquid flow was experimentally studied. The effects of low concentrations of surfactants, the channel inclination angle, and the flow velocity on the size of gas bubbles and their ascent velocities were determined. It was found that the combination of liquid flow and surfactant significantly suppresses bubble coalescence. For the given conditions, the drag coefficient of a bubble rising near the wall was calculated. It was shown that the drag coefficient is inversely proportional to the Weber number both in pure water and with the addition of surfactant.

The article studies the intensification of heat transfer during cooling of a surface modified by laser treatment with a dispersed coolant flow. A laser ablation technique using a pulsed laser is described, leading to the formation of craters up to 600 μm in diameter on a copper surface with the following roughness parameters: Ra = 1.48 μm, Rz = 9.8 μm. The results show an increase in the removed heat flux by 35-40%, the heat transfer coefficient by 38-55% in the intense boiling mode (115-125 °C) compared to the unmodified surface. The proportion of heat removed due to the phase transition reaches 90% at a removed heat flux density of 8.4 MW/m², on the modified surface.

The development of non-stationary thermal gravity-capillary convection in a layer of ethyl alcohol with a free surface after sudden electric heating of one of the vertical walls of a rectangular cavity was experimentally studied. The effect of a heated liquid flow along the free surface onto the opposite thin metal wall of the cavity was studied. The influence of the liquid layer heights and heat flux densities on the heated wall of the cavity was investigated. Temperature fields on the thin wall and on the free surface of the liquid layer were measured using a FLIR x6530sc thermal imager. Computer processing of thermal imaging films allowed the construction of distributions of temperature and temperature gradients along the wall height depending on time. The amplitude-frequency characteristics of temperature pulsations associated with the occurrence of secondary flows in the heated liquid flow on the wall were determined, and their effect on instantaneous temperature fields on the wall was studied against the background of a monotonic change.

Multi-rotor aerial vehicles have the rather short history of active usage, so many aspects of vehicle aerodynamics remain poorly investigated. One of these aspects is a problem how the rotor-generated flow affects the elements of framework ad body of a multi-rotor copter. The paper studies the influence of rotor rotation on the aerodynamic drag coefficient and the sideforce acting on the body of a meteorology drone (body with a spherical shape). Calculations were performed in the RANS statement with a direct account for the rotor rotation. Numerical results are verified on the base of PIV-measurements. The aerodynamic characteristics of the quadcopter body depend significantly on the unsteady flow generated by the rotors.

Some properties of vortex filaments in a weakly nonideal countercurrent Bose-Einstein condensate (BEC) are described. This paper focuses on the study of reconnection processes and the equations of motion. One of the motivations for this study is that the dynamics of quantum vortices in superfluid helium has been obtained at the phenomenological level, and a number of questions requiring clarification can be addressed by studying the corresponding problem in BEC. Considering a vortex filament as the intersection line of surfaces where the real and imaginary parts of the macroscopic wave function ψ(r, t) vanish allowed us to write an equation of motion for the vortex filament. Remarkably, the structure of this equation completely coincides with the structure of the equation for the dynamics of a vortex filament in superfluid helium, which was derived from entirely different, phenomenological considerations.

The dynamics of surface temperature changes for a water droplet resting on a structured black silicon substrate heated to 90°C were studied. The wetting properties of black silicon were analyzed during substrate heating in the temperature range of 30-90°C. Thermal imaging studies revealed that vapor nucleation sites form at temperatures close to the boiling point at the liquid-black silicon interface. The dynamics of temperature changes on the surface of a thin liquid droplet during the final stages of evaporation were studied, including the formation and subsequent development of bubble nuclei within the droplet. Convection and bubble formation were shown to result in non-uniform temperature fields.

This study is aimed at improving environmental efficiency by establishing the dependence of the parameters of optimal combustion of liquid hydrocarbon fuels (diesel fuel, crude oil, fuel oil, kerosene, waste oil) on their physical properties using steam atomization with superheated steam. The methodology includes the construction of regime maps of CO concentration with approximation by radial basis functions and smoothing by a median filter. During the study, a statistically significant linear relationship between the angular coefficients of the optimal regime equations and the Laplace number (r = 0.834, R2 = 0.7) was established. Based on the obtained dependences, an equation is proposed to calculate the optimal flow rate of superheated steam depending on the Laplace number for the optimal combustion mode of liquid hydrocarbon fuels in an atmospheric burner with steam atomization and a gasification chamber to reduce emissions of harmful substances.

An installation was designed, fabricated and studied for methane pyrolysis and hydrogen production. Methane heating and pyrolysis occurs by burning a fraction of methane-hydrogen mixture (60 % hydrogen and 40 % methane) produces by pyrolysis (a return for the plant demand). The installation thermal design was performed with the account for the heat consumed fro pyrolysis, insulation heat loss and flue gases loss. The study determined the plant heat power and the efficiency coefficient. Usage of methane-hydrogen mixture as fuel allows reducing the CO₂ emission as compared to known methods of hydrogen production.

Using the integral heat balance method, analytical solutions were obtained for the formation of dynamic and thermal boundary layers in a methane pyrolysis (thermal decomposition) reactor with variable viscosity and thermal diffusivity within these layers. It is shown that, on the inner surface of a metal reactor wall heated to 1000°C, a layer of stagnant gas forms due to high viscosity and thermal diffusivity, having the same temperature as the wall. Isotachs and isotherms in this layer are located perpendicular to the wall surface. In this case, boundary layers form at a certain distance from the wall, within which the velocity is practically zero and the temperature is equal to the wall temperature, significantly exceeding the gas temperature outside the boundary layers. In the near-wall layer of stagnant gas at high temperatures, intensive carbon formation (pyrolysis graphite) occurs, depositing on the reactor walls until the reactor flow cross-section is completely carbonized and the pyrolysis process stops.

To create an efficient microchannel reactor for hydrogen production, steam reforming of carbon monoxide in a slotted annular channel was experimentally studied. The microchannel reactor is formed by a submillimeter gap between two cylinders, with a catalyst applied to the outer side of the inner cylinder. Platinum applied on cerium oxide was used as a catalyst. The thermal characteristics of the shift reaction with the formation of carbon dioxide and hydrogen were experimentally studied. Experiments were carried out at a steam-to-carbon monoxide ratio of 3:1 at different mixture flow rates. It was shown that a fourfold increase in the mixture flow rate leads to a significant increase in the temperature difference between the reactor inlet and outlet, caused by the heat release of the reaction (from ΔT ≈ 20°C at a contact time of 189 ms to 80°C at a contact time of 46 ms). According to analysis of the composition of the outgoing gas, with an increase in the mixture flow rate, the degree of carbon monoxide conversion decreases significantly.

The paper presents the direct numerical simulation for a laminar flame of a premixed methane-air mixture using a detailed kinetic mechanism. During this study, the numerical module laminarSMOKE is supplemented by a problem of conjugated heat transfer between the flame and nozzle walls. A change in the isothermal boundary condition on the nozzle wall influencing the conjugated heat transfer condition results in a higher temperature of the temperature of the nozzle front edge, reduction in the flow density gradient near the nozzle boundary and a reduction in the low-frequency oscillation of flame caused by the buoyancy effect.

A study on transition processes for experimental time dependencies of the pitch angle for the case of free rotation of a body discovered the final intervals with a steady amplitude of oscillations - known as quasi self-oscillations. Statistical analysis demonstrated that the maximum possible difference between the amplitudes of self-excited oscillations (including the case of quasi self-excited oscillations) at the normalized oscillation frequency of 0.02 was about 1 degree.

A multiblock numerical model was used to study the phenomenon of vacancy formation in a chain of dust particles. Self-consistent spatial distributions of the space charge and electric potential around the dust particles for two cases were obtained by means of numerical calculations: a linear chain of five particles and a chain of four particles with a vacancy. The equilibrium charges of particles and the magnitudes of the main forces acting on them (the ion drag force, the Coulomb force of particle repulsion, and the force exerted by an external electric field on charged particles) were calculated. It was shown that vacancy formation, without changing the structural parameters of the chain, occurs under conditions of strong ion trails, with the fourth and fifth particles in the strong ion trail of the second particle.