Mathematical investigation of pressure pulsations characteristics and natural acoustic frequencies in the gas-dynamic channel

Paper presents a numerical simulation of the occurrence of flow instability and pressure self-oscillations for a complex configuration of the gas-dynamic tract in combustion chamber. Unsteady axisymmetric two-dimensional Navier-Stokes equations are used for mathematical modelling of compressible one-phase medium. To simulate turbulence, the k-ε and LES models were used. Fast Fourier Transform (FFT) determined the frequency spectrum of pressure pulsations in the combustion chamber. It is shown that in the case of a simple geometry of the free gas cavity in combustion chamber, both models of turbulence make it possible to determine the spectrum of the natural acoustic frequencies. Using the LES model in the case of complex geometry makes it possible to predict the hydrodynamic structure of a flow accurately. The flow, in this case, has an intensive vortex generation. Formation of small-scale vortex occurs in the near-wall regions and large eddies in the core of a flow. Frequency of large eddies formation can be combined with the natural acoustic frequencies of combustion chamber and can affect the amplitude of pressure pulsation

To the definition of the concept economic competence of the teacher

Essential signs of the concept of the teacher’s economic competence are determined, and a description of the structure of this competence is offered. The revealed theoretical construct is used as a methodological basis for designing the content of the academic discipline “Economics of Education”Определены существенные признаки понятия «экономическая компетентность педагога», предложено описание структуры этой компетентности. Выявленный теоретический конструкт применяется в качестве методологического основания проектирования содержания учебной дисциплины «Экономика образования

Overcoming cognitive-sensitive barriers in research activities as the condition of development of the methodological culture of a teacher

The phenomen of cognitive-semantic barriers arising in students' research activity is considered. Some ways of overcoming the barriers for the development of the methodological culture of the teacher are suggestedРассмотрен феномен познавательно-смысловых барьеров, возникающих в исследовательской деятельности студентов. Предложены некоторые способы преодоления барьеров для развития методологической культуры педагог

The universal algorithm for solving the gas dynamics equations on the mesh with arbitrary number of cell faces

The paper presents methodology and algorithm for calculating the equations of gas dynamics on arbitrary computational meshes with a mixed type of cells. The calculation method is based on the method of linear reconstruction proposed by Barth and Jesperson. The algorithm for determining the geometric parameters of arbitrary computational cell is presented. To implement the calculation algorithm, a data storage system has been proposed and tested. The algorithm of the solver and the algorithm of docking the computational meshes in the case of using block-structured meshes are proposed. The efficiency of methodology and developed program of calculation are demonstrated by the calculation example of the air flow in flat air intakes. The structure of flow and position of the bow shock wave are determined. These results with the theoretical values were compared. The application of the proposed methodology and calculation algorithm to arbitrary computational meshes with a mixed cell type makes it possible to optimize the process of constructing computational mesh and conduct numerical studies of gas dynamics in regions of complex geometry

Calculation and experimental study on high-speed impact of heat-resistant coating materials with a meteoric particle

The given article presents the conducted calculation and experimental study on destruction of heat-resistant coating material of an aircraft in the process of high-speed interaction of the steel spherical projectile. The projectile is imitating a meteoric particle. The study was conducted in the wide range of velocities. The mathematical behavioral model of heat-resistant coating under high-speed impact was developed. The interaction of ameteoric particle with an element of the protective structure has especially individual character and depends on impact velocity and angle, materials of the interacting solids

The accumulation of femtosecond laser radiation energy in crystals of lithium fluoride

We present the results of studies of energy accumulation during the non-destructive interaction of extremely intense near infrared laser radiation with model wide band gap dielectric crystals of lithium fluoride, when the intensity of pulses is sufficient for effective highly nonlinear absorption of light and for the excitation of the electron subsystem of matter and the energy of pulses is still not sufficient for significant heating, evaporation, laser breakdown or other destruction to occur. We studied the emission of energy in the form of light sum of thermally stimulated luminescence accumulated under conditions of self-focusing and multiple filamentation of femtosecond laser radiation. It was established that it's the F2 and F[3]{+} color centers and supplementary to them centers of interstitial type which accumulate energy under the action of a single femtosecond laser pulses. When irradiated by series of pulses the F3, F[3]{-} and F[4] centers additionally appear. F2 centers are the main centers of emission in the process of thermally stimulated luminescence of accumulated energy. The interstitial fluoride ions (I-centers) are the kinetic particles. They split off from the X[3]{-} centers in the result of thermal decomposition of latter on the I-centers and molecules X[2]{0}. I-centers recombine with F[3]{+} centers and form F[2] centers in excited state. The latter produce the characteristic emission spectrum emitted in the form of thermally stimulated luminescence

Новые виды и наиболее интересные находки для флоры Урала и прилегающих территорий

The article provides information about rare and newly described species for the flora of the Urals and adjacent territories, namely: Astragalus saphronovae Kulikov, Atraphaxis decipiens Jaub. et Spach., Carex amgunensis F. Schmidt, Galium densiflorum Ledeb., Jovibarba globifera (L.) J. Parn., Najas minor All., Potamogeton nodosus Poir., Pseudorchis albida (L.) Á. Löve et D. Löve, Salix myrsinites L., Veronica agrestis L. Essays include the information on the species ecology and short taxonomic notes. © 2021 Altai State University. All rights reserved.The work was supported by the state assignments: АААА-А19-119031290052-1 “Sosudistye rasteniia Evrazii: sistematika, flora, rastitelʹnye resursy” [“Vascular plants of Eurasia: systematics, flora, plant resources”], АААА-А18-118011990151-7 “Izucheniye, sokhraneniye i rasshireniye bioraznoobraziya rasteniy v prirode i pri introduktsii na Yuzh nom Urale i Priuralye” [“Study, conservation and expansion of plant biodiversity in nature and during introduction in the Southern Urals and the Cis- and Trans-Urals region”], AAAA-A17-117050400146-5 “Otsenka prostranstvennovremennoy izmenchivosti bioraznoobraziya i usloviy yego formirovaniya na Severe Zapadnoy Sibiri v svyazi s izmeneniyem klimata i osvoyeniyem neftegazovykh resursov” [“Assessment of the spatio-temporal variability of biodiversity and the conditions for its formation in the north of Western Siberia in connection with climate change and the development of oil and gas resources”], and by “Programmoy povysheniya konkurentosposobnosti Uralskogo federalnogo universiteta” [“The program for improving the competitiveness of the Ural Federal University”] (the decree no. 211 of the Government of the Russian Federation, contract no. 02.A03.21.0006)

Structure and nonlinear optical properties of novel transparent glass-ceramics based on Co2+:ZnO nanocrystals

Transparent glass-ceramics (GCs) based on Co2+:ZnO nanocrystals (mean diameter, 11 nm) are synthesized on the basis of cobalt-doped glasses of the K2O–ZnO–Al2O3–SiO2 system. For these GCs, the absorption band related to the 4A2(4F) → 4T1(4F) transition of Co2+ ions in tetrahedral sites spans until ~1.73 μm. Saturation of the absorption is demonstrated at 1.54 μm, with a saturation fluence Fs = 0.8 ± 0.1 Jcm−2 (σGSA = 1.7 ± 0.2 × 10−19 cm2) and a recovery time of 890 ± 10 ns. Passive Q-switching of an Er,Yb:glass laser is realized with the synthesized GCs. This laser generated 0.37 mJ/100 ns pulses at 1.54 μm. The developed GCs are promising as saturable absorbers for 1.6–1.7 μm crystalline erbium lasers

ПРИБОР ДЛЯ ИЗМЕРЕНИЯ ВРЕМЕНИ РЕЛАКСАЦИИ ПРОСВЕТЛЕННОГО СОСТОЯНИЯ ОПТИЧЕСКИХ МАТЕРИАЛОВ МЕТОДОМ «ВОЗБУЖДЕНИЕ-ЗОНДИРОВАНИЕ» В СУБМИКРОСЕКУНДНОМ ДИАПАЗОНЕ

The use of passive shutters to control the duration of the light pulses is an important aspect in the miniature and microchip lasers. One of the key spectroscopic characteristics which determine the properties of the material, which can be used as a passive shutter is relaxation time of its bleached state.We describe a device for determination of relaxation time of the bleached state in optical materials by the «pump-probe» method in the sub-μs time domain. This device allows one to determine relaxation times for materials which absorb at the light wavelength of 1.5 μm, e.g., materials doped with cobalt ions Co2+. The results of test examinations of the device are described, and the relaxation time of the bleached state of Co2+ ions is measured for a novel material – transparent glass-ceramics with Co2+:Ga2 O3 nanophase – amounting to 190 ± 6 ns. Применение пассивных затворов для управления длительностью импульсов оптического излучения является актуальной задачей в миниатюрных и микрочип лазерах. Одной из ключевых спектроскопических характеристик, определяющих свойства материала, который может быть использован в качестве пассивного затвора, является время релаксации его просветленного состояния. В статье описан прибор для измерения времени релаксации просветленного состояния оптических материалов методом «возбуждение-зондирование» в субмикросекундном временном диапазоне. Представлены его структура и характеристики. Прибор позволяет измерять времена релаксации просветления у материалов, поглощающих на длине волны 1,5 мкм, т.е., в частности, у сред, легированных ионами кобальта Co2+. Приведены результаты тестовых испытаний прибора, а также измерено время релаксации просветленного состояния нового материала – ситалла с кристаллической фазой Co2+:Ga2 O3 – оно составило 190 ± 6 нс.

Pteridophyte Distribution of the Urals and Adjacent Areas: a Dataset

Background Data on the species diversity and distribution of pteridophytes (lycophytes and ferns) in the Urals and adjacent areas are presented. The dataset includes 13,742 observations of two classes Lycopodiopsida and Polypodiopsida. In total, the dataset contains information on 16 families, 28 generas, 65 species, four subspecies and nine interspecies hybrids. All records are for lycophytes and ferns collected over 170 years between 1853 and 2021. The dataset presented is based on herbarium specimens, published data and field research conducted by the authors. This dataset is the first and important step towards generalising information on the current diversity and geographical distribution of pteridophytes in the Urals and adjacent areas. © Melnikov D et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Funding: This work was supported in part by the Program for Improving the Competitiveness of the Ural Federal University (the decree no. 211 of the Government of the Russian Federation, contract No. 02.A03.21.0006), the state assignments АААА-А19-119031290052-1 (Komarov Botanical Institute RAS), no. 0111-2019-0001 (Tsitsin Main Botanical Garden of the RAS), no. AAAA-A17-117072810011-1 (Institute Botanical Garden UB RAS) and no. АААА-А19-119031890084-6 (Institute of Plant and Animal Ecology UB RAS). This research was carried out within the project No. 121041600045-8 "Western Siberia in the context of Eurasian ties: man, nature, society". We thank the Ministry of Higher Education and Science of Russian Federation for the supportgiven to the Center of Collective Use “Herbarium MBG RAS” (Agreement No. 075-15-2021-678). The work was carried out as part of the Russia 2021 project