Підвищення якості контуру «літак–система автоматичного керування»

This article deals with model based approach to mathematical modeling process of an aircraftflight control system. Analysis of emergency situations depend on phases of flight is done. Application ofmodern model based technologies for automatic flight control systems development is considered. Theprogram for aircraft-automatic flight control system control loop simulation and visualization is developed.Improvement of the automatic flight control system characteristics is showed. Availability of practicalapplication of developed program in aerospace scope is considered. Use of the mentioned approachallows to facilitate automatic flight control system development, analyze and certification processПредставлен модельно-ориентированный подход к процессу математического моделирования законов системы автоматического управления. Выполнен анализ аварийных ситуаций в зависимости от этапа полета. Рассмотрено применение современной модельно ориентированной технологии разработки законов системы автоматического управления. Разработана программа моделирования и визуализации контура самолет-система автоматического управления. Показано улучшение точности выдерживания параметров системы автоматическогоуправления. Рассмотрена возможность практического применения разработанной программы в авиационнойотрасли. Использование указанного подхода позволит сократить время на разработку, анализ и сертификациюсистемы автоматического управленияПредставлено модельно-орієнтований підхід до процесу математичного моделювання законів системи автоматичного керування. Виконано аналіз аварійних ситуацій в залежності від етапу польоту. Розглянуто використання сучасної модельно-орієнтованої технології розробки законів системи автоматичного керування. Розроблено програму моделювання і візуалізації контуру літак-система автоматичного управління. Показано поліпшення точності витримування параметрів системи автоматичного керування. Розглянуто можливість практичного застосування розробленої програми в авіаційній галузі. Використання вказаного підходу дозволить скоротити час на розробку, аналіз і сертифікацію системи автоматичного керуванн

Oxygen transport in Pr nickelates: Elucidation of atomic-scale features

Pr2NiO4+δ oxide with a layered Ruddlesden–Popper structure is a promising material for SOFC cathodes and oxygen separation membranes due to a high oxygen mobility provided by the cooperative mechanism of oxygen migration involving both interstitial oxygen species and apical oxygen of the NiO6 octahedra. Doping by Ca improves thermodynamic stability and increases electronic conductivity of Pr2 − xCaxNiO4+δ, but decreases oxygen mobility due to decreasing the oxygen excess and appearing of 1–2 additional slow diffusion channels at x ≥ 0.4, probably, due to hampering of cooperative mechanism of migration. However, atomic-scale features of these materials determining oxygen migration require further studies. In this work characteristics of oxygen diffusion in Pr2 − xCaxNiO4+δ (x = 0–0.6) are compared with results of the surface analysis by X-ray photoelectron spectroscopy and modeling of the interstitial oxygen migration by the plane-wave density functional theory calculations. According to the X-ray photoelectron spectroscopy data, the surface is enriched by Pr for undoped sample and by Ca for doped ones. The O1s peak at ~531 eV corresponding to a weakly bound form of surface oxygen located at Pr cations disappears at ~500 °C. Migration of interstitial oxygen was modeled for a I4/mmm phase of Pr2NiO4+δ. The interstitial oxygen anion repulses the apical one in the NiO6 octahedra pushing it into the tetrahedral site between Pr cations. The calculated activation barrier of this migration is equal to 0.585 eV, which reasonably agrees with the experimental value of 0.83 eV obtained by the oxygen isotope exchange method. At the same time, for the model compound Ca2NiO4+δ, obtained by isomorphic substitution of Pr by Ca in Pr2NiO4+δ, calculations implied formation of the peroxide ion comprised of interstitial and lattice oxygen species not revealed in the case of incomplete substitution (up to PrCaNiO4+δ composition). Hence, calculations in the framework of the plane-wave density functional theory provide a realistic estimation of specificity of oxygen migration features in Pr2NiO4+δ doped by alkaline-earth metals. © 2019 Elsevier B.V.Russian Science Foundation, RSF: 16-13-00112Support by Russian Science Foundation (Project 16-13-00112 ) is gratefully acknowledged

Near Ambient Pressure XPS and MS Study of CO Oxidation over Model Pd Au HOPG Catalysts The Effect of the Metal Ratio

In this study, the dependence of the catalytic activity of highly oriented pyrolytic graphite HOPG supported bimetallic Pd Au catalysts towards the CO oxidation based on the Pd Au atomic ratio was investigated. The activities of two model catalysts differing from each other in the initial Pd Au atomic ratios appeared as distinctly different in terms of their ignition temperatures. More specifically, the PdAu 2 sample with a lower Pd Au surface ratio 0.75 was already active at temperatures less than 150 C, while the PdAu 1 sample with a higher Pd Au surface ratio 1.0 became active only at temperatures above 200 C. NAP XPS revealed that the exposure of the catalysts to a reaction mixture at RT induces the palladium surface segregation accompanied by an enrichment of the near surface regions of the two component Pd Au alloy nanoparticles with Pd due to adsorption of CO on palladium atoms. The segregation extent depends on the initial Pd Au surface ratio. The difference in activity between these two catalysts is determined by the presence or higher concentration of specific active Pd sites on the surface of bimetallic particles, i.e., by the ensemble effect. Upon cooling the sample down to room temperature, the reverse redistribution of the atomic composition within near surface regions occurs, which switches the catalyst back into inactive state. This observation strongly suggests that the optimum active sites emerge under reaction conditions exclusively, involving both high temperature and a reactive atmospher

Ferromagnetic HfO2/Si/GaAs interface for spin-polarimetry applications

In this letter, we present electrical and magnetic characteristics of HfO2-based metal-oxide-semiconductor capacitors (MOSCAPs), along with the effect of pseudomorphic Si as a passivating interlayer on GaAs(001) grown by molecular beam epitaxy. Ultrathin HfO2 high-k gate dielectric films (3–15 nm) have been grown on Si/GaAs(001) structures through evaporation of a Hf/HfO2 target in NO2 gas. The lowest interface states density Dit at Au/HfO2/Si/GaAs(001) MOS-structures were obtained in the range of (6−13)×101

The crystal growth and properties of novel magnetic double molybdate RbFe5_{5}(MoO4_{4})7_{7} with mixed Fe3+^{3+}/Fe2+^{2+}states and 1D negative thermal expansion

Single crystals of new compound RbFe$_5$(MoO$_4$)$_7$ were successfully grown by the flux method, and their crystal structure was determined using the X-ray single-crystal diffraction technique. The XRD analysis showed that the compound crystallizes in the monoclinic space group P21/m, with unit cell parameters a = 6.8987(4), b = 21.2912(12) and c = 8.6833(5) Å, β = 102.1896(18)°, V = 1246.66(12) Å$^3$, Z (molecule number in the unit cell) = 2, R-factor (reliability factor) = 0.0166, and T = 293(2) K. Raman spectra were collected on the single crystal to show the local symmetry of MoO$_4$ tetrahedra, after the confirmation of crystal composition using energy dispersive X-ray spectroscopy (EDS). The polycrystalline samples were synthesized by a solid-state reaction in the Ar atmosphere; the particle size and thermal stability were investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) analyses. The compound decomposes above 1073 K in an Ar atmosphere with the formation of Fe(III) molybdate. The thermal expansion coefficient along the c direction has the value α = −1.3 ppm K$^{−1}$ over the temperature range of 298–473 K. Magnetic measurements revealed two maxima in the magnetization below 20 K, and paramagnetic behavior above 50 K with the calculated paramagnetic moment of 12.7 μB per formula unit is in good agreement with the presence of $_3$Fe$^{3+}$ and $_2$Fe$^{3+}$ in the high-spin (HS) state. The electronic structure of RbFe5(MoO4)7 is comparatively evaluated using X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations

Constructing g-C3N4/Cd1−xZnxS-Based Heterostructures for Efficient Hydrogen Production under Visible Light

Two types of photocatalysts, 1%Pt/Cd1−x Znx S/g-C3 N4 (x = 0.2–0.3) and Cd1−x Znx S/1% Pt/g-C3 N4 (x = 0.2–0.3), were synthesized by varying the deposition order of platinum, and a solid solution of cadmium and zinc sulfides onto the surface of g-C3 N4. The characterization of photo-catalysts showed that, for 1%Pt/Cd1−x Znx S/g-C3 N4, small platinum particles were deposited onto a solid solution of cadmium and zinc sulfides; in the case of Cd1−x Znx S/1%Pt/g-C3 N4, enlarged platinum clusters were located on the surface of graphitic carbon nitride. Based on the structure of the photocatalysts, we assumed that, in the first case, type II heterojunctions and, in the latter case, S-scheme heterojunctions were realized. The activity of the synthesized samples was tested in hydrogen evolution from triethanolamine (TEOA) basic solution under visible light (λ = 450 nm). A remarkable increase in hydrogen evolution rate compared to single-phase platinized 1%Pt/Cd1−x Znx S photocat-alysts was observed only in the case of ternary photocatalysts with platinum located on the g-C3 N4 surface, Cd1−x Znx S/1%Pt/g-C3 N4. Thus, we proved using kinetic experiments and characterization techniques that, for composite photocatalysts based on Cd1−x Znx S and g-C3 N4, the formation of the S-scheme mechanism is more favorable than that for type II heterojunction. The highest activity, 2.5 mmol H2 g−1 h−1, with an apparent quantum efficiency equal to 6.0% at a wavelength of 450 nm was achieved by sample 20% Cd0.8 Zn0.2 S/1% Pt/g-C3 N4. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This work was supported by the Ministry of Science and Higher Education of the Russian Federation within the governmental order for Boreskov Institute of Catalysis (project AAAA-A21-121011390009-1) and was also funded by the Russian Foundation for Basic Research (project No. 20-33-70086). A.S.V. and I.A.W. thank Minobrnauki research project FEUZ-2020-0059 for financial support

Rare-earth-containing magnetic liquid crystals

Rare-earth-containing metallomesogens with 4-alkoxy-N-alkyl-2- hydroxybenzaldimine ligands are reported. The stoichiometry of the complexes is [Ln(LH)3(NO3)3], where Ln is the trivalent rare-earth ion (Y, La, and Pr to Lu, except Pm) and LH is the Schiff base. The Schiff base ligands are in the zwitterionic form and coordinate through the phenolic oxygen only. The three nitrate groups coordinate in a bidentate fashion. The X-ray single- crystal structures of the nonmesogenic homologous complexes [Ln(LH)3(NO3)3], where Ln = Nd(III), Tb(III), and Dy(III) and LH = CH3OC6H3(2-OH)CH=NC4H9, are described. Although the Schiff base ligands do not exhibit a mesophase, the metal complexes do (SmA phase). The mesogenic rare-earth complexes were studied by NMR, IR, EPR, magnetic susceptibility measurements, X-ray diffraction, and molecular modeling. The metal complexes in the mesophase have a very large magnetic anisotropy, so that these magnetic liquid crystals can easily be aligned by an external magnetic field

SRPES and STM data for the model bimetallic Pd In HOPG catalysts Effects of mild post synthesis oxidative treatments

Post synthesis treatment of bimetallic catalysts in different gas phases resulting in the adsorption induced segregation is among promising approaches to enhance their activity not compromising selectivity towards a number of low temperature reactions. Our recently published paper M.A. Panafidin, A.V. Bukhtiyarov, I.P. Prosvirin, I.A. Chetyrin, A.Yu. Klyushin, A. Knop Gericke, N.S. Smirnova, P.V. Markov, I.S. Mashkovsky, Y.V. Zubavichus, A.Yu. Stakheev, V.I. Bukhtiyarov, A mild post synthesis oxidative treatment of Pd In HOPG bimetallic catalysts as a tool of their surface structure fine tuning. Appl. Surf. Sci. reports on Pd In intermetallic formation regularities and their evolution after storage in air as well as during treatment in oxygen at submillibar pressures. The current paper gives an extended representation of experimental ex situ in situ synchrotron based photoelectron spectroscopy SRPES and scanning tunnelling microscopy STM data used to derive scientific conclusions in the paper quoted abov