bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic nanoparticles Fe3O4 modified with sodium dodecyl sulphate for removing methylene blue from water
Authors: Magomedov K. E. , Omelyanchik A. S. , Vorontsov S. A. , Čižmár E. , Rodionova V. V. , Levada E. V.
Published: April 2024

We show that surface-modified magnetic iron oxide nanoparticles with an average size of about 10 nm have a high adsorption capacity for sorption of pollutants from wastewater. A significant advantage of using magnetic materials is the ability to extract the sorbent using an external magnetic field, which makes the purification process more efficient. We found that the anionic substance sodium dodecyl sulfate increases the electrostatic attraction to the cationic compound methylene blue, and also prevents the aggregation of nanoparticles, thus increasing the active surface. The sorption capacity of magnetic nanoparticles after surface functionalization increased by a factor of 250 compared to unmodified iron oxide nanoparticles. The mechanism and kinetic parameters of the sorption process were determined, as well as the optimal conditions for increasing the efficiency of the sorption process.
Interface electronic states contribution into terahertz photoconductivity in structures based on Hg1 – xCdxTe with inverted energy spectrum
Authors: Kazakov A. S. , Galeeva A. V. , Artamkin A. I. , Ikonnikov A. V. , Chmyr S. N. , Dvoretskiy S. A. , Mikhailov N. N. , Bannikov M. I. , Danilov S. N. , Ryabova L. I. , Khokhlov D. R.
Published: April 2024

We show the differences in the necessarily formed electronic states at the boundaries of the topological phase with a vacuum and with a trivial buffer in the regions of heterojunction in topological materials based on epitaxial films Hg1 – xCdxTe. It was demonstrated that the PT-symmetric terahertz photoconductivity observed in these structures is due precisely to the states in the region of the topological film/trivial buffer (or cap-layer) interfaces.
On a shape of band-to-acceptor luminescence line in semiconductors
Authors: Kokurin I. A. , Averkiev N. S.
Published: April 2024

A theoretical explanation is proposed for the shape of the long-wavelength edge of the luminescence line, which is caused by the recombination of a free electron and a hole of a neutral acceptor. The formation of complexes, in which a single hole is localized by the field of two attracting ions (\(A_{2}^{ - }\) complexes) and the subsequent recombination of holes in such complexes with electrons of the conduction band are considered. The Coulomb repulsion in the final state after recombination and the dispersion of the complexes in terms of the interionic distance provide an extended long-wavelength tail of the luminescence line, comparable in magnitude to the ionization energy of a single acceptor.
Investigation of the biexciton radiative cascade in a single InAs/GaAs quantum dot embedded in a high-Q microcavity
Authors: Serov Yu. M. , Galimov A. I. , Toropov A. A.
Published: April 2024

A biexciton radiative cascade was recorded in the photoluminescence spectra of an InAs/GaAs QD embedded in a λ-cavity with a relatively high-quality factor of 4600, formed in a micropillar with GaAs/AlGaAs distributed Bragg reflectors. The spectrum and kinetics of the radiation, measured under conditions of two-photon excitation, demonstrated a significant effect of the microcavity on the emission process. A possible improvement based on this effect in the generation of entangled photon pairs is discussed.
Lithium and beryllium isotopes in the PAMELA experiment
Authors: Bogomolov E. A. , Vasilyev G. I. , Menn W. , Adriani O. , Bazilevskaya G. A. , Barbarino G. C. , Bellotti R. , Boezio M. , Bonvicini V. , Bongi M. , Bottai S. , Bruno A. , Vacchi A. , Vannuccini E. , Voronov S. A. , Galper A. M. , De Santis C. , Di Felice V. , Zampa G. , Zampa N. , Casolino M. , Campana D. , Carlson P. , Castellini G. , Cafagna F. , Kvashnin A. A. , Kvashnin A. N. , Koldobskiy S. A. , Lagoida I. A. , Leonov A. A. , Mayorov A. G. , Malakhov V. V. , Martucci M. , Marcelli L. , Merge M. , Mikhailov V. V. , Mocchiutti E. , Monaco A. , Mori N. , Munini R. , Osteria G. , Panico B. , Papini P. , Picozza P. , Ricci M. , Ricciarini S. B. , Simon M. , Sparvoli R. , Spillantini P. , Stozhkov Y. I. , Yurkin Y. T.
Published: April 2024

Using PAMELA flight data for 2006–2014 on the rigidity of detected nuclei and their velocity (time-of-flight analysis and ionization losses in the multilayer calorimeter of the device), a new analysis of the isotopic composition of Li and Be nuclei in the rigidity range 1–5 GV (nuclear energies 0.1–1.5 GeV/nucleon) was carried out. The new PAMELA data expand the energy range of previous measurements, are consistent with the few existing measurements, and indicate correlated deviations of Li and Be isotope ratios from the GALPROP data for GCRs, which can be interpreted as evidence of the observation of contributions from several nearby local sources against the GCR background. The analysis of precision AMS-02 data on the spectra of positrons, antiprotons, secondary nuclei Li, Be, and B, also carried out in this work, indicates correlated increases in intensity at rigidities of ~50–1000 GV, which could be associated with local sources as well. We estimate the contribution of local sources against the GCR background at the level of tens of percent for rigidities of 1–5 GV and at the level of a few percent for rigidities of 50–1000 GV.
Fluxes and spectral indices of rare and abundant nuclei of cosmic rays according to the data of the NUCLEON satellite experiment
Authors: Kudryashov I. A. , Turundaevskiy A. N. , Karmanov D. E. , Kovalev I. M. , Kurganov A. A. , Panov A. D. , Podorozhny D. M.
Published: April 2024

During the processing of the data obtained in the space experiment NUCLEON, results were obtained that were of significant astrophysical importance. Using the GALPROP package, the inverse problem of the propagation of cosmic rays from the source (close Supernovae) to the observer was solved, a component spectrum was calculated at the source. It was shown that a systematic change in the power index (slope of the spectrum) was observed at the source, which can be interpreted as incomplete ionization of cosmic rays now of acceleration at the front of the supernova shock wave. Magnetic rigidity spectra analysis was applied for nitrogen nuclei fluxes and the total spectrum of rare nuclei with odd charges from 9 to 19 (F, Na, Al, P, Cl, K). Ratios of odd and even nuclei fluxes are calculated. It turned out that the spectrum of rare, odd nuclei is more rigid than the spectrum of abundant even nuclei (Z = 10–20) at the magnetic rigidity area 300–10 000 GV.
Solar flare phenomena forecast: solar proton events
Authors: Ishkov V. N.
Published: April 2024

The problems of predicting solar flare events, the only source of high-energy protons, both from the process of energy release itself and from the accompanying dynamic phenomena: shock waves and coronal mass ejections propagating from the place of energy release, are considered from modern positions. The possibility of predicting the flare events themselves ensures the interaction of new emerging magnetic fluxes with the magnetic fields of active regions and outside them, but always on the dividing line of polarities. The possibility of the release of solar protons during of a flare event is determined by the characteristics and localization of the flare event, its CME parameters, and the ratio of its energy in different radiation ranges.
What potassium abundance in the Earth does the Borexino experiment admit?
Authors: Bezrukov L. B. , Karpikov I. S. , Mezhokh A. K. , Silaeva S. V. , Sinev V. V.
Published: April 2024

The results of analysis for the single events energy spectrum obtained in phase III of Borexino detector operation are considered. The experimental spectrum was fitted by a set of standard single events sources with the addition of events from potassium geo-antineutrinos (40K-geo-v) scattering on electrons. The addition of 40K-geo-v events makes it possible to improve the agreement of the experimental and fitted spectra. Experimental results indicate the presence of a significant amount of potassium in the Earth.
Magnetospheric current system parameters during the geomagnetic disturbances in May 1998
Authors: Lukovnikova A. A. , Sdobnov V. E.
Published: April 2024

Based on the data from the global network of neutron monitors, by using the spectrographic global survey, we obtained the parameters of magnetospheric current systems in the 1998 May events. Within the axisymmetric model for the bounded Earth magnetosphere, we determined the DR (ring current) and DCF (magnetopause currents) parameters for the current systems, as well as their contribution to variations in the rigidity of the geomagnetic cutoff and to the Dst-index over the addressed period.
6Li(d, α)4He reaction cross sections
Authors: Generalov L. N. , Zherebtsov V. A. , Selyankina S. M.
Published: April 2024

New evaluation of 6Li(d, α)4He reaction integral cross sections obtained in our electronic SaBa (Sarov Base) library by mathematic tools (spline-approximation) of this library is presented. The motivation of the research is the results of our measurements of this reaction differential cross sections at energy range 3.75–8 MeV.
New local magic nucleus 146Gd
Authors: Boboshin I. N.
Published: April 2024

Recently, the existence of a special class of atomic nuclei, local magic nuclei, has been discovered. In the present paper, evidence for the existence of a new local magic nucleus, 146Gd, is presented on the base of experimental data. This nucleus has a magic pair of nucleons (N, Z) = (82, 64). The shell evolution scheme leading to this phenomenon was obtained. It is shown that the tensor proton-neutron force plays a crucial role in this evolution.
Modern technologies to produce radionuclides for nuclear medicine
Authors: Zherebchevsky V. I. , Alekseev I. E. , Maltsev N. A. , Petrov V. V. , Prokofiev N. A. , Zemlin E. O. , Torilov S. Yu.
Published: April 2024

We discussed nuclear technologies to produce radioactive isotopes, with a focus on radionuclides used as radiopharmaceuticals in novel methods of cancer diagnosis and radionuclide therapy—theranostics. New target materials and nuclear reactions to produce these radionuclides were considered. The experimental and theoretical results of excitation functions of reactions (p, xn) studies in energy range 6–80 MeV for medium mass nuclear systems to produce radionuclides: scandium, technetium, antimony, terbium are presented. These radionuclides are promising for their use in nuclear medicine methods for diagnostics, therapy and theranostics.
Superсоnduсting spin vаlve СоОx/Fe1/Аl/Fe2/Аl/Pb оn lead magnesium niobate–lead titanate ferrоeleсtriс substrаte
Authors: Kаmаshev А. А. , Bolshakov S. А. , Mamin R. F. , Gаrifullin I. А.
Published: April 2024

We study the struсturаl prоperties оf а superсоnduсting spin vаlve СоОx/Fe1/Аl/Fe2/Аl/Pb оn а PMN-PT ferrоeleсtriс substrаte under the асtiоn оf аn eleсtriс field. Аn externаl eleсtriс field сreаtes elаstiс stresses аnd defоrmаtiоns in the ferrоeleсtriс substrаte, whiсh саn leаd tо а сhаnge in the mutuаl direсtiоn оf the mаgnetizаtiоns оf the ferrоmаgnetiс lаyers in the struсture оf the spin vаlve. According to the results of our research, when applying an electric field of 1 kV/cm, it is possible to register a shift in the transition temperature to the superconducting state of the СоОx/Fe1/Al/Fe2/Al/Pb system by 25 mK.
Ferroelectric ceramics based on Bi4Ti3O12 designed for extreme conditions
Authors: Marakhovskiy М. А. , Talanov М. V. , Panich А. А.
Published: April 2024

A comparative study of ceramics based on high-temperature ferroelectric Bi4Ti3O12, made by using three different sintering methodswas carried out. The dependences of the microstructure, dielectric and piezoelectric properties of ceramics on the sintering method are established. It is shown that ceramics sintered by hot pressing have an optimal combination of functional characteristics.
Crystal structure and dielectric properties of BiFeO3 multiferroics heteroepitaxial films grown on Pt(001)/MgO(001) substrates
Authors: Nazarenko A. V. , Matyash Ya. Yu. , Popov P. V. , Pavlenko A. V. , Stryukov D. V.
Published: April 2024

The crystal structure, dielectric and polarization properties of BiFeO3 films grown on a Pt(001)/MgO(001) substrate have been studied. It is established that the obtained films are single-phase, pure, single-crystal and have a high structural perfection. The obtained experimental results are discussed.
Study of the sensitivity of moisture-sensitive structures with UV reduction on the basis of ZnO produced by the sol-gel method
Authors: Permyakov D. S. , Belykh M. A. , Strogonov A. V.
Published: April 2024

A structure based on a thin-film nanocrystalline zinc oxide obtained by the sol-gel method on a flexible Kapton substrate has been developed. It has been established that its electrical resistance increases significantly under the influence of moisture contained in the air. When irradiated with ultraviolet radiation, the resistance of the structure decreases by almost two orders of magnitude. After the UV exposure finish, a long-term process of restoration of electrical conductivity is observed, which is described by the fractional-exponential Kohlrausch function.
Effect of prolonged annealing on the morphology and optical properties of ZnO films produced by magnetron sputtering
Authors: Tomaev V. V. , Polishchuk V. A. , Leonov N. B. , Vartanyan T. A.
Published: April 2024

The effect of annealing time on the structural and optical properties of ZnO films, which are formed from Zn films obtained by magnetron sputtering followed by oxidation in air, is described. Thermal oxidation in air was carried out for 7 and 24 hours, respectively, in a programmable muffle furnace at T = 750°C. A change in the structure of the film surface depending on the annealing time of the Zn film and the substrate material was found, which manifests itself in the optical properties of the films.
Analysis of intermittency near the boundary of the phase synchronization in systems with complex topology of attractor
Authors: Tarasova A. A. , Moskalenko O. I.
Published: April 2024

Intermittent behavior near the boundary of phase synchronization in systems with a complex topology of attractor is studied. Using the calculation of statistical characteristics of the laminar phase lengths it is shown that in the case of a relatively small detuning of the control parameters of interacting systems near the phase synchronization boundary the eyelet intermittency takes place.
Features of the composition and magnetic properties of composites based on ultrafine particles NiFe2O4 produced under low-temperature underwater plasma
Authors: Khlyustova A. V. , Shipko M. N. , Stepovich M. A. , Agafonov A. V. , Sirotkin N. A. , Savchenko E. S.
Published: April 2024

The results of studies of NiFe2O4 and ε-Fe2O3 nanoparticles synthesized in a low-temperature underwater plasma are presented. The results obtained indicate the possibility of synthesizing nanocomposites with a given ratio of nickel ferrite, which provides low ferromagnetic resonance linewidths, and ε-Fe2O3, which exhibits high-frequency resonance in the millimeter range of electromagnetic radiation.
Three-Airy beams propagated in free space
Authors: Prokopova D. V. , Abramochkin E. G.
Published: April 2024

We investigated propagation of three-Airy beams with or without an optical vortex in free space by theoretical, numerical and experimental means. These light fields are an object of interest for applications of modern photonics due to strong localization of the transverse intensity of the field upon propagation, self-healing and autofocusing properties.
The effects of e-beam irradiation with doses up to 1 GGy on the propertie of titanium foil
Authors: Sergeev P. B. , Kovalets N. P. , Kozhina E. P. , Bedin S. A.
Published: April 2024

The properties of titanium foils that have been used for a long time in electron guns of e-beam-pumped excimer lasers have been studied. The tensile strength of these foils did not change when irradiated with e-beam pulses (300 keV) with doses up to 1 GGy. On the surface of Ti foils in contact with a fluorine-containing gas mixture during irradiation by e-beam, peaks corresponding to TiO2, TiN, and TiF were detected by Raman scattering.
Transformations of Pd/(N-Heterocyclic Carbene) Molecular Complexes into a Nanosized Catalytic Systems in the Mizoroki–Heck Reaction
Authors: Kostyukovich A. Yu. , Patil E. D. , Burykina J. V. , Ananikov V. P.
Published: April 2024

The mechanism of the formation of catalytic species in the practically important Mizoroki–Heck reaction, which is in demand in modern fine organic synthesis, has been studied. It has been shown that catalysts based on palladium complexes with N-heterocyclic carbene ligands are transformed into a “ligand-free” form under the conditions of the Mizoroki–Heck reaction. Molecular modeling performed using quantum chemical methods showed that these processes compete with the target reaction at three of the six stages of the catalytic cycle. The presence of catalyst transformation products in the reaction system was confirmed by methods of nuclear magnetic resonance and mass spectrometry. Important mechanistic data have been obtained for the rational design of catalytic systems for cross-coupling reactions.
Room Temperature Oxidation of Graphite by Nitrogen Dioxide with the Participation of Nanoparticles of Platinum Group Metals
Authors: Smirnov M. Yu. , Kalinkin A. V. , Sorokin A. M. , Salanov A. N. , Bukhtiyarov V. I.
Published: April 2024

This paper presents a review of the results obtained in studying the room temperature interaction of NO2 with model systems prepared by vacuum deposition of platinum group metals on the surface of highly oriented pyrolytic graphite (M/HOPG, M = Pt, Pd, Rh) at pressure of 10–6–10–4 mbar. Particular attention was focused on establishing the chemical state of the supported metal particles and carbon support using X-ray photoelectron spectroscopy (XPS). Before treatment in NO2, M/HOPG samples were characterized by scanning tunneling and/or scanning electron microscopy (STM and SEM). Upon interaction with NO2, supported palladium and rhodium remained in the metallic state and, at the same time, exhibited catalytic activity in the oxidation of graphite. The process was accompanied by the destruction of ≥10–15 graphene layers with the penetration of metal particles deep into the carbon support. Rhodium was less active in the oxidation of graphite compared to palladium due to the filling of its surface with NO molecules arising from the dissociation of NO2. When the samples with deposited platinum were treated in NO2, the carbon support underwent minimal changes without disturbing its original structure. Platinum retained its metallic state when deposited on the surface of graphite annealed in vacuum and was oxidized to PtO and PtO2 oxides on the surface activated by etching with argon ions. Based on the results obtained, a mechanism was proposed for the room temperature interaction of M/HOPG systems with NO2.
Quantum-Chemical Study of C–H Bond Activation in Methane on Ni–Cu Oxide and Sulphide Clusters
Authors: Bandurist P. S. , Pichugina D. A.
Published: April 2024

Density functional theory (DFT) (PBE) was used for modeling of C–H bond breaking in methane on Ni–Cu clusters enriched in copper as the first stage of catalytic dry reforming of methane. Nanosized clusters NiCu11S6(PH3)8, NiCu11S6, NiCu11O6(PH3)8, NiCu11O6 are considered as catalyst models. The binding energy for methane with clusters was calculated and the activation energy of the \({\text{CH}}_{4}^{*}\) → \({\text{CH}}_{3}^{*}\) + H* step was determined. Based on the data obtained, it was found that the NiCu11O6 catalytic system is the most promising for CH4 activation both in kinetic (activation energy is 99 kJ/mol) and thermodynamic (step energy change is –29 kJ/mol) aspects. To assess the stability of the NiCu11O6 cluster towards coke formation, CH adsorption followed by dissociation (CH* → C* + H*) was modeled. The calculated value of the activation energy of this step is rather high, 159 kJ/mol.
Synergistic Effect of Catalytic Action of Copper and Cerium in the Oxidation of CO on Modified Zeolites Cu/Ce/ZSM-5
Authors: Ivanin I. A. , Kruchinin T. V. , Udalova O. V. , Tedeeva M. A. , Shilina M. I.
Published: April 2024

A series of mono- and bimetallic copper-cerium catalysts based on ZSM-5 zeolite with different aluminium content (SiO2/Al2O3 = 30 and 55) was synthesised by incipient wetness impregnation. The copper content was 0–4.3 wt %, and cerium loading varied in the range from 0 to 6 wt %. The obtained composites have been investigated by low temperature N2 sorption, XPS, EPR spectroscopy, UV-vis diffuse reflectance spectroscopy, DRIFT spectroscopy of adsorbed CO and tested in the reaction of catalytic oxidation of CO with oxygen. In the systems under study а pronounced synergistic effect of catalytic action of copper and cerium is observed, associated with the redox interaction between the metals. With an increase in the proportion of cerium in bimetallic systems from Сu : Ce = 6 to Сu : Ce = 1, the catalytic activity of the composites grows monotonically. The most active catalysts show 50% CO conversion at temperatures of 90–100°C. Decrease in the aluminium content in the zeolite contributes to higher catalytic activity. It has been shown that Cu+ ions bound to the surface of CeO2 particles play a key role in catalysis.
Activation of Molecules H2 on Platinum and Platinovanadium Clusters: Quantum-Chemical DFT Modeling
Authors: Panina N. S. , Buslaeva T. M. , Fischer A. I.
Published: April 2024

The NEB DFT/PBE0/def2tzvp quantum-chemical method with the construction of minimum energy paths (MEP) was used to study the activation of H2 molecules by Pt4 and Pt3V clusters. It is shown that, in the case of Pt4 and Pt3V clusters, barrier-free dissociative adsorption of H2 molecules occurs on platinum centers, while molecular adsorption of hydrogen occurs on the vanadium atom in Pt3V with a slight weakening of the H–H bond, but without its breaking. The noted features of the coordination of H2 molecules are explained at the level of the MO method. It has been established that the migration of the H atom from one cluster metal center to another in the considered model clusters, as, possibly, in the phenomenon of hydrogen spillover, occurs at small activation barriers in the direction of the displacement vector corresponding to the normal vibration of the system in the transition state. In the process of hydrogen migration, a significant role of Pt–H–Pt and V–H–Pt bridging groups, which facilitate the transition of H atoms from one metal center of the cluster to another, has been revealed.
Structural, Morphological, Optical, Magnetic and Photocatalytic Properties of ZnO/CoFe2O4 Nanocomposites
Authors: Yadav Dheeraj , Shukla Rajni
Published: April 2024

ZnO and CoFe2O4 nanoparticles were synthesized via co-precipitation route and the composites ZnO/CoFe2O4 (ZC1 (3 : 2), ZC2 (2 : 3), ZC3 (1 : 4)) were obtained by the sonochemical process. X-ray diffraction (XRD) study reveals the existence of two phases in the material: a hexagonal wurtzite structure of ZnO and a cubic lattice structure of CoFe2O4. The flower-shaped rod-like structure of ZnO nanoparticles and agglomeration of CoFe2O4 nanoparticles are observed using field emission scanning electron microscopy (FESEM). The elemental composition of the synthesized material is confirmed through energy dispersive spectroscopy (EDS). Light absorbance performance of the material is determined by using UV-visible spectroscopy. Further, the band gap of pure and composite materials is calculated by employing a Tauc plot. Fourier transform infrared spectroscopy (FTIR) reveals the creation of cationic and anionic bonding at different interstitial sites. The magnetic properties of the material were studied using vibrating sample magnetometer (VSM). Various magnetic parameters, for instance Ms, Mr, Hc, nB, and Mr/Ms ratio were traced from M–H loops. The photocatalytic performance of the materials under UV irradiation is examined through degradation of methylene blue (MB) dye. The efficiency of composite ZC1 is found to be better than that of pure ZnO, CoFe2O4 and composites ZC2 and ZC3.
Variations of Cobalt Catalytic Activity and Selectivity in Ethylene Oxidation against Stepwise Oxidation of Cobalt Surface
Authors: Bychkov V. Yu. , Tulenin Yu. P. , Gulin А. A. , Korchak V. N.
Published: April 2024

Catalytic activity of Co foil in ethylene oxidation was studied against oxidation degree of Co surface at stepwise foil oxidation. Experiments were conducted at temperatures of 500–800°C by a pulse method using alternative pulses of 0.2% C2H4–0.25% O2–1% Ar–He testing mixture and 1% O2–1% Ar–He oxidative mixture. Oxidation degree of Co foil varied from a totally reduced surface to an oxidation depth about a hundred of cobalt oxide “monolayers”. Using XRD, SEM and EDS, it was shown that CoO phase formed during a first stage of the stepwise oxidation (from 0 to ~60 oxide “monolayers”) at the all tested temperatures and modifications of surface morphology could be observed. At this stage the samples had a relatively high activity in both partial and total oxidation of ethylene at 500–600°C. On the contrary, at 700–800°C total oxidation was practically absent and the rate of partial oxidation was much lower than that at 500–600°C. During a second stage of Co surface oxidation (from ~60 to ~120 oxide “monolayers”) at 500–600°C also Co3O4 phase was found as well as a gradual ordering of the oxide crystals. In that state, the samples demonstrated a stationary (at 500°C) or an extremal (at 600°C) activity in total oxidation of ethylene. On the contrary, a temperature increase up to 800°C led to a sharp decrease of catalytic activity of the Co foil in this interval of oxidation degree.
Dimethyl Ether Carbonylation on H-MOR Zeolite, Modified Cu, Co, Mg
Authors: Kipnis M. A. , Galkin R. S. , Volnina E. A. , Belostotskii I. A. , Bondarenko G. N. , Arapova O. V.
Published: April 2024

Mordenite and ferrierite (Zeolyst International, H-form, SiO2/Al2O3 ≈ 20) were used to study the adsorption, thermally programmed desorption, and carbonylation of dimethyl ether (DME). The behavior of mordenite with Cu, Co, and Mg cations introduced by ion exchange has also been studied. DME carbonylation was carried out at 200°C, pressure 3 MPa, space velocity 8000 ml g–1 h–1 in a mixture, vol. %: ⁓2.2 DME, 92.8–95.5 CO, rest. N2. After the induction period, the methyl acetate content is about 4–5 times higher for mordenite compared to ferrierite. The formation of water, methanol and hydrocarbons was observed in small quantities. The introduction of Cu, Co, Mg cations into mordenite by ion exchange (single ion exchange, cation/Al ratio no more than 35%) not only increased the stability, but also increased the activity in the DME carbonylation reaction. It was found that an increase in the content of copper (from 1.19 to 2.23 wt %) and Mg (from 0.62 to 1.8 wt %) differently affects the activity. In the case of copper, an increase in activity was observed, while in the case of magnesium, the activity decreased. Preliminary reduction of copper-exchange mordenite leads to a decrease in activity and the appearance of metallic copper particles on the surface of mordenite crystallites. According to in situ diffuse reflectance infrared spectroscopy, the introduction of magnesium cations by triple ion exchange leads to a noticeable decrease in the number of Brønsted acid sites (BACs) in both the 12-MR and 8-MR channels of mordenite. The catalytic characteristics of ferrierite practically do not change when copper and magnesium are introduced by ion exchange.
Ammonia Synthesis and Decomposition with Ru Supported Catalysts
Authors: Shlyapin D. A. , Borisov V. A. , Temerev V. L. , Iost K. N. , Fedorova Z. A. , Snytnikov P. V.
Published: April 2024

An analytical equation for the rate of formation/consumption of nitrogen in the reversible reaction N2 + + 3H2 ↔ 2NH3 was obtained on the base of the analysis of the catalytic properties of 4%Ru–13.6%Cs/Sibunit and 4%Ru–5.4%Ba–7.9%Cs/Sibunit in the processes of ammonia decomposition (105 Pa; 350–470°C) and synthesis ammonia (6×105–5×106 Pa; 400–430°C). This equation allows one to describe correctly the dependence of the chemical reaction rate on the partial pressures of the components of the reaction mixtures for both forward and reverse reactions. The approach used to obtain the kinetic equation is based on the assumption that the adsorption sites on the ruthenium surface are initially filled with hydrogen and then replaced by nitrogen during competitive interaction. The values of the equilibrium constants and apparent activation energies for the synthesis and decomposition of ammonia on the 4%Ru–13.6%Cs/Sibunit and 4%Ru–5.4%Ba–7.9%Cs/Sibunit was found by using the proposed kinetic equation. The data are in good agreement with the ones presented in the literature.
Investigation of Flow and Spectral Characteristics in a Flow-Flow
Hydrodynamic Generator of the Flat Type with Changes in the Degree of Flow Blockage
Authors: Ganiev S. R. , Kryukov A. I. , Rudakov V. P. , Shmyrkov O. V.
Published: April 2024

The paper presents the results of studying the flow past cylindrical bodies located in a flattype flow-through hydrodynamic generator. The result were obtained on the hydrodynamic test bench of the experimental base of the Scientific Center of the Mechanical Engineering Research Institute of the Russian Academy of Sciences with the degree of flow blockage by the bluff bodies St /S0 = 10– 82%, the Re numbers (0.5–5) × 105 , and the inlet pressure Рin= 0.1–0.9 MPa. It was found that at certain values of the inlet/outlet pressure ratio, which are constant for each of the degrees of flow blockage, powerful resonant-type pressure peaks arise at frequencies of 0.5–5 kHz with the amplitude more than 4–5 times higher than the maximum inlet pressure.
Formation of Shock-Wave Flow during Nanosecond Discharge Localization in Unsteady Flow in a Channel with Obstacles
Authors: Dolbnya D. I. , Znamenskaya I. A. , Lutsky A. E. , Sysoev N. N.
Published: April 2024

The results of studies of the effect of volume and surface pulse discharges on high-speed gas flow in a rectangular shock-tube channel with a change in the profile (obstacle on the lower wall) are given. A single nanosecond surface discharge or a discharge with preionization induced by the plasma electrodes (combined discharge) was initiated in flow downstream of the shock wave with the Mach numbers Ms = 3.2–3.4. The obstacle determines the distribution of the parameters of flow past the obstacle and the pulse discharge plasma redistribution. The density fields of gas dynamic flow under the experimental conditions are obtained and compared with the discharge plasma distribution. It is shown that the shock-wave effect of the discharge on flow behind the obstacle continued from 25 to 70 μs.
Gas Injection and Suction Effect on the Instability of a Supersonic Boundary Layer
Authors: Novikov A. V. , Obraz A. O. , Timokhin D. A.
Published: April 2024

We present the results of an investigation of the boundary layer stability on a flat plate having a region of gas injection/suction normal to the wall at a large supersonic freestream Mach number. The laminar flow past a flat plate having a region of distributed injection/suction of fixed intensity is modeled numerically using the integration of Navier—Stokes equations. The unstable disturbances in the boundary layer distorted by injection/suction are analyzed within the framework of the linear stability theory and the eN{{e}^{N}} method for compressible flows. High-frequency disturbances belonging to the plane second mode of the boundary layer, which are the most unstable at high velocities, are considered. It is shown that gas injection/suction leads to a nonmonotonic variation of disturbance growth rates with the appearance of stabilization/destabilization regions, as compared with the case in which injection/suction is absent.
Evolution of Viscous Electrically Conducting Fluid Flow on a Rotating Wall in the Presence of a Magnetic Field with Account for the Induction and Diffusion Effects
Authors: Gurchenkov A. A.
Published: April 2024

The evolution of a viscous conducting fluid flow on a rotating plate in the presence of a magnetic field is studied. The analytical solution of the three-dimensional time-dependent magnetohydrodynamics equations is found. In this case, the full magnetic induction equation is used, i.e., both the dissipation effect and the energy dissipation as a result of the electric current flow are taken into account. The fluid, together with the bounding plane, rotates as a whole at a constant angular velocity about a direction not perpendicular to the plane. The velocity field and the induced magnetic field in the flow of viscous electrically conducting fluid that occupies a half-space bounded by a flat wall are determined. The motion of wall is considered in a series of particular cases. Based on the results obtained, the individual structures of the near-wall boundary layers are investigated
Interaction of the supersonic stellar wind with the incoming flow of the interstellar medium: the influence of the azimuthal magnetic field of the star
Authors: KOROLKOV S. D. , IZMODENOV V. V.
Published: April 2024

The problem of the interaction of a hypersonic stellar wind with the surrounding interstellar medium is considered. The media are regarded as fully ionized and are accounted for within the framework of ideal magnetohydrodynamics. The scientific novelty consists in taking into account the magnetic field of a star. The magnetic field qualitatively changes the shape of the astropause under certain parameters. Astropause is a tangential gap that separates the stellar wind from the interstellar medium. Instead of the classical paraboloidal shape, astropause acquires a tube (or cylindrical) shape. It was demonstrated that the tube shape takes place for slowly moving stars or, in the star's coordinate system, for incoming streams with the Mach number ($M_\infty$) less than the critical one. When a critical Mach number ($M_\infty^*$) is reached, the flow regime bifurcates, and the astropause shape changes from tube to classical. For stars with a strong magnetic field, bifurcation occurs at higher Mach numbers than for stars with a weak magnetic field. It is also shown that one more qualitative restructuring of the flow occurs at $M_\infty = 1$. In this case, the shape of the astropause does not change, but a bow shock and a Mach disk are formed.
Correction of a Strapdown Inertial Navigation System During Descent in the Atmosphere
Authors: Korolev O. E.
Published: April 2024

The article deals with the problem on determining the angular position during descent on an apparatus with low lift-drag ratio. A solution is presented using the least squares method, which reduces to determining the orientation quaternion using a system of linear algebraic equations. The proposed method is based on the algebraic properties of quaternions. A vibrating string accelerometer and a fiber optic gyroscope are used to obtain acceleration and angular velocity measurements. Data on the speed and coordinates of the device are available according to the readings of the satellite navigation equipment.
Investigation of the Errors of Fast Trigonometric Interpolation in Solving the Problem of Stresses in a Bar
Authors: Chernyshov A. D. , Goryainov V. V. , Popov M. I.
Published: April 2024

Using the fast trigonometric interpolation, the problem on stresses in a rectangular bar is solved. The obtained approximate analytical solution is compared with the exact one. During this analysis the relative error of the displacement components, the stress tensor components, the discrepancy between the Lame equilibrium equations, and the discrepancy of the boundary conditions are investigated. It has been established that when using the second-order boundary function in fast expansions and a small number of terms in the Fourier series (from two to six), the maximum relative error δmath max of the displacement components and the stress tensor components is less than one percent. With an increase in the order of the boundary function and/or the number of terms N in the Fourier series, δmath decreases rapidly. Increasing the order of the boundary function is a more effective way to reduce the calculation error of δmath max than increasing the number of terms in the Fourier series. When studying the intensity of stresses σ in a bar with different overall dimensions of a rectangular cross-section, but with the same area of all sections, it has turned out that the smallest value of σmath all cross-sections is observed for a bar with a square section.
Quaternion Methods and Regular Models of Celestial and Space Flight Mechanic: Using Euler (Rodrigues-Hamilton) Parameters to Describe Orbital (Trajectory) Motion. II: Perturbed Spatial Restricted Three-Body Problem
Authors: Chelnokov Yu. N.
Published: April 2024

The article considers the problem of regularizing the features of the classical equations of celestial mechanics and space flight mechanics (astrodynamics), which use variables that characterize the shape and size of the instantaneous orbit (trajectory) of the moving body under study, and Euler angles that describe the orientation of the used rotating (intermediate) coordinate system or the orientation of the instantaneous orbit, or the plane of the orbit of a moving body in an inertial coordinate system. Singularity-type features (division by zero) of these classical equations are generated by Euler angles and complicate the analytical and numerical study of orbital motion problems. These singularities are effectively eliminated by using the four-dimensional Euler (Rodrigues-Hamilton) parameters and Hamiltonian rotation quaternions. In this (second) part of the work, new regular quaternion models of celestial mechanics and astrodynamics are obtained that do not have the above features and are built within the framework of a perturbed spatial limited three-body problem (for example, the Earth, the Moon (or the Sun) and a spacecraft (or an asteroid)): equations of trajectory motion written in non-holonomic or orbital or ideal coordinate systems, for the description of the rotational motion of which the Euler (Rodrigues-Hamilton) parameters and quaternions of Hamilton rotations are used. New regular quaternion equations of the perturbed spatial restricted three-body problem are also obtained, constructed using two-dimensional ideal rectangular Hansen coordinates, Euler parameters and quaternion variables, as well as using complex compositions of Hansen coordinates and Euler parameters (Cayley-Klein parameters). The advantage of the proposed orbital motion equations constructed using the Euler parameters over the equations constructed using the Euler angles is due to the well-known advantages of the quaternion kinematic equations in the Euler parameters included in the proposed equations over the kinematic equations in the Euler angles included in the classical equations.
On a Class of Semi-Regular Gyrostat Precessions with Variable Gyrostatic Moment
Authors: Gorr G. W.
Published: April 2024

The article considers the problem of the motion of a gyrostat under the action of potential and gyroscopic forces in the case of a variable gyrostatic moment. The conditions for the existence of semi-regular precessions characterized by the constancy of their own rotation rate are studied. A new solution of the equations of the Kirchhoff–Poisson class is constructed, based on a special type of three invariant relations with respect to the main variables of these equations.
Subsea Gas Pipeline Floatation
Authors: Ilgamov M. A.
Published: April 2024

The linear and non-linear bending of the span of a subsea pipeline between two supports has been studied. The weight of the pipeline with the transported medium, the buoyancy force of water, the transverse distributed forces due to pressures on the inner and outer surfaces, the change in the curvature of the axial line during bending, as well as the decrease in the average pressure on the pipe walls during its rise are taken into account. The supports allow movement in the axial direction in proportion to the resulting force. The static bend of the pipeline is considered up to a position coinciding with the surface of the water. A parametric analysis of the bend is given, in particular, depending on the gas pressure and the depth of the reservoir. The conditions for the surfacing of the pipeline are determined.
On the Problem of Anisotropic Rods Torsion under External Pressur
Authors: Mironov B. G. , Mironov Yu. B.
Published: April 2024

The paper is devoted to the study of the general relations of the theory of torsion of rods from an ideal rigid-plastic anisotropic material. In this case, it is assumed that the rod is under the action of an external pressure that varies linearly along its generatrix. The stress-strain state of an anisotropic rod is determined under an arbitrary condition of plasticity. Equations for the characteristics of general relations and the stress and strain components along these characteristics are found.
Mechanics of Defects in Dislocation-Free Silicon Single Crystals
Authors: Verezub N. A. , Prostomolotov A. I.
Published: April 2024

The problems of defect mechanics in dislocation-free silicon single crystals are relevant and technically significant due to the intensive development of microelectronics, which imposes increasingly high demands on minimizing the level of micro- and nanodefects in silicon wafers used to manufacture microelectronic chips. The solution of these problems is associated with the study of the regularities of thermomechanical processes both at the stage of growing silicon single crystals and at subsequent thermal annealing of wafers cut from them. The article provides an overview of theoretical and experimental work aimed at developing ways to control these processes. This includes the development of physical concepts of defect formation in dislocation-free single-crystal silicon and the development of mathematical models corresponding to different temperature ranges, implemented both during the growth of a single crystal and during thermal annealing of wafers cut from it. Thus, near the crystallization temperature, the processes of fast recombination and diffusion transfer of intrinsic point defects (vacancies and interstitial silicon atoms) are simulated, while at lower temperatures, the processes of their agglomeration into microdefects (pores and clusters of interstitial silicon atoms) are simulated. The verification of such models is illustrated for two experimental processes of growing silicon single crystals with a diameter of 150 mm by the Czochralski method, as well as for the process of rapid high-temperature thermal annealing of silicon wafers cut on their basis.
Model of a Micromechanical Modal-Localized Accelerometer with a Sensitive Element in the Form of a Beam with an Initial Deflection
Authors: Indeytsev D. A. , Mozhgova N. V. , Lukin A. V. , Popov I. A.
Published: April 2024

The present study is devoted to mathematical modeling of the proposed new architecture of a microelectromechanical modally localized acceleration sensor (MEMS accelerometer/gravimeter) with a sensitive element in the form of a microbeam pinched at both ends with an initial deflection, made in the form of the first asymmetric mode of free vibrations. The article demonstrates that with an asymmetric form of the initial deflection in the region of positive axial forces, there are zones of proximity of the frequency branches corresponding to the second symmetric and the first asymmetric vibration modes. When the required value of the axial tensile force in the microbeam is provided structurally, this effect can be used, in particular, to measure the axial component of the transfer acceleration according to the principle of amplitude modal localization. The possibility of heating the sensitive element with the help of an electric current flowing through the microbeam, provided in the sensor layout, makes it possible to control the operating point of the oscillation mode and, thus, to vary the range of measured accelerations and the degree of sensor sensitivity within a very wide range. The configuration of the oscillation excitation and output signal pickup electrodes proposed in the article makes it possible, with the help of a feedback loop, to stabilize the oscillation amplitude at the required level in the working (third) symmetrical form and, at the same time, to measure the oscillation amplitude associated with the change in the value of the measured component of the portable acceleration according to the asymmetric form. Thus, a mathematical model of an original modal-localized accelerometer (gravimeter) containing a single sensitive microbeam element and involving the effect of energy exchange between its various modes of vibration is proposed and investigated in the article.
Auxetics among Two-Layered Composites Made of Cubic Crystals. Analytical and Numerical Analysis
Authors: Demin A. I. , Volkov M. A. , Gorodtsov V. A. , Lisovenko D. S.
Published: April 2024

The results of calculations of the effective Young's modulus of longitudinally stretched twolayered plates made of identically oriented cubic crystals are presented on the basis of analytical analysis and the numerical finite element method. Analytical dependences of effective Young's modulus on Young's moduli and Poisson's ratios of crystals in layers are presented. Combinations of pairs of crystals with a significant deviation of the effective characteristics from ones found by the rule of mixtures are determined. The dependences of the effective Young's moduli on extreme values of the Young's moduli and Poisson's ratios of crystals in layers are established. They are presented graphically, and in some cases are reflected in the form of a table.
Regularities of Changing the Limiting Values of Stress and Strain Invariants in Microinhomogeneous Media
Authors: Marina V. Yu.
Published: April 2024

By using nonlinear equations of constraints between macro- and micro-states, the regularities of changes in the limiting values of stress and strain invariants in microinhomogeneous media are studied. It is shown that the extreme relative moduli of stress tensor deviators in polycrystals with a cubic lattice are invariant with respect to external conditions of reversible force and depend only on the crystal anisotropy factor. In the irreversible region of deformation, analytical relations are obtained for bulk and tensile normal stresses. The effect of cyclic change in bulk and tensile stresses in some subelements under external monotonic loading has been established. It is shown that, on the basis of nonlinear equations of constraints, a complex pattern of material failure can be described using the theory of maximum normal stresses at the local level.
Periodic Contact Problems for a Wedge with Friction Forces
Authors: Pozharskaya E. D. , Pozharskii D. A. , Sobol B. V.
Published: April 2024

Periodic contact problems for a three-dimensional elastic wedge (a dihedral angle, a half-space and a quarter of space are particular cases), taking into account the Coulomb friction forces in unknown contact areas are considered. One face of the wedge is rigidly fixed, and the other face interacts with an infinite rectilinear chain of identical rigid dies, the axis of the chain is parallel to the edge of the wedge. Friction forces perpendicular or parallel to the edge of the wedge are taken into account. Integral equations are derived in which the series generated by the Cerruti components of the contribution of friction forces are summed exactly. Problems are solved using the method of nonlinear integral equations, which makes it possible to simultaneously determine the contact area and contact pressures. The mechanical characteristics are calculated, the transition from a discrete to a continuous contact area of infinite length is studied.