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NODAL O(h^4)-SUPERCONVERGENCE IN 3D BY AVERAGING PIECEWISE LINEAR,BILINEAR,AND TRILINEAR FE APPROXIMATIONS

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Journal of Computational Mathematics 2010年第1期28卷 1-10页

作者： Antti Hannukainen sergey Korotov Michal Krízek Institute of Mathematics Helsinki University of Technology Department of Mathematics Tampere University of Technology Institute of Mathematics Academy of Sciences

We construct and analyse a nodal O（h^4）-superconvergent FE scheme for approximating the Poisson equation with homogeneous boundary conditions in three-dimensional domains by means of piecewise trilinear functions. The scheme is based on averaging the equations that arise from FE approximations on uniform cubic, tetrahedral, and prismatic partitions. This approach presents a three-dimensional generalization of a two-dimensional averaging of linear and bilinear elements which also exhibits nodal O（h^4）-superconvergence （ultracon- vergence）. The obtained superconvergence result is illustrated by two numerical examples.

关键词： Higher order error estimates Tetrahedral and prismatic elements Supercon-vergence Averaging operators.

Influence of non-equilibrium reactions on the optimization of aerothrust aeroassisted maneuver with orbital change

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Chinese Journal of Aeronautics 2020年第8期33卷 2133-2145页

作者： Nikolay AELISOV sergey AISHKOV Igor ALOMAKA Valentin GSHAKHOV Department of Space Engineering Samara National Research UniversitySamara 443086Russia Inter-University Department of Space Research Samara National Research UniversitySamara 443086Russia Department of Aircraft Construction and Design Samara National Research UniversitySamara 443086Russia

The spaceplane is perspective vehicle due to wide maneuverability in comparison with a space capsule. Its maneuverability is expressed by the larger flight range and also by a possibility to rotate orbital inclination in the atmosphere by the aerodynamic and thrust forces. Orbital plane atmospheric rotation maneuvers can significantly reduce fuel costs compared to rocket-dynamic non-coplanar maneuver. However, this maneuver occurs at Mach numbers about 25, and such velocities lead to non-equilibrium chemical reactions in the shock wave. Such reactions change a physicochemical air property, and it affects aerodynamic coefficients. This paper investigates the influence of non-equilibrium reactions on the aerothrust aeroassisted maneuver with orbital *** approach is to solve an optimization problem using the differential evolution algorithm with a temperature limitation. The spaceplane aerodynamic coefficients are determined by the numerical solution of the Reynolds-averaged Navier-Stokes equations. The aerodynamic calculations are conducted for the cases of perfect and non-equilibrium gases. A comparison of optimal trajectories,control laws, and fuel costs is made between models of perfect and non-equilibrium gases. The effect of a chemically reacting gas on the finite parameters is also evaluated using control laws obtained for a perfect gas.

关键词： Atmospheric entry Boundary value problem Computational fluid dynamics Differential evolution Flight mechanics Non-equilibrium flow Spaceplane

Structure and heterogeneity of habitat determine diet of predators despite prey abundance:Similar response in Long-eared,Short-eared Owls and Common Kestrels

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Avian Research 2023年第1期14卷 54-61页

作者： Tatyana Kovinka Alexander Sharikov Tatyana Massalskaya sergey Volkov Zoology and Ecology Department Moscow State Pedagogical UniversityKibalchicha Str.6-3129164MoscowRussid Severtsov Institute of Ecology and Evolution Russian Academy of SciencesMoscow119071Russia

According to one of the theses of optimal foraging theory,main prey species abundance in the hunting area is the main factor determining the diet and habitat choices of birds of *** other factors can also be *** habitat structure influences the predators’diets as *** this study we examined the influence of habitat structure on diet compositions of three species of birds:Long-eared Owl(Asio otus),Short-eared Owl(***)and Common Kestrel(Falco tinnunculus).The study was carried out from 2007 to 2019 in a 48 km2area of the Crane’s Homeland Reserve,Moscow Region,*** habitat structures of model species’hunting territories(ratio of different types of landscape elements)were classified in module"Semi-Automatic Classification Plugin"based on the QGIS.A boosted regression tree analysis identified that the share of the main prey species in the diet is primarily determined by the landscape structure of hunting *** largest share of Common Vole(Microtus arvalis)in birds’diet was determined by the shrubs area(15%of hunting area),the meadow area(75%),the habitat heterogeneity(70%)and the arable land area(5%).The same predictors determined the largest share of Root Vole(Microtus oeconomus):the shrubs area 25%,the meadow area 70%,and the arable land area 3%.The annual mean abundance of prey species did not determine their importance in the diet of birds of ***,the main prey abundance in the hunting area is not a determining factor for the formation of diet composition of birds of prey.

关键词： Birds of prey diet Boosted regresion tnee Habitat strnocture efiect Prey sbundance

Impact of drilling waste pollution on land cover in a high subarctic forest-tundra zone

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Pedosphere 2022年第3期32卷 414-425页

作者： Anatoly OPEKUNOV Marina OPEKUNOVA Stepan KUKUSHKIN sergey LISENKOV Institute of Earth Sciences St.Petersburg State UniversitySt.Petersburg 199178(Russia)

Global climate changes can lead to the destruction of the permafrost zone and contribute to the active transfer of pollutants to natural *** can be especially pronounced in the areas of oil and gas production in the *** study aimed to define the landscape components(i.e.,groundwater,soil water,soil,and indicator plant species)of chemical pollution with metals,oil hydrocarbons,and polycyclic aromatic hydrocarbons,from the discharge of drill *** at two sites in the forest-tundra zone of Western Siberia(Russia)were carried out within two years of *** migration was found in peaty-gley heavy loamy soils and iron-illuvial clayey podburs,but lateral migration of different pollutants did not exceed 200 ***,radial migration was practically absent owing to the high buffering capacity of the soil organic horizon and the upward flow of matter in the seasonal melt *** main indicators of drilling waste pollution were high concentrations of Sr,Ba,petroleum hydrocarbons,and Cl^(-)*** the waste disposal sites,the concentration of Ba and Sr in the soil water were 1150 and 1410μg L^(-1),respectively;in groundwater,they reached 721 and 2360μg L^(-1),*** the soil,Ba and Sr accumulated in the peaty horizon(798 and 706 mg kg^(-1),respectively).The concentration of Cl^(-)ions in the soil water at the site of waste discharge was 1912 mg L^(-1),and at a distance of 200 m,it decreased to 77.4 mg L^(-1).The Cl^(-)concentration in the groundwater was lower,and at a distance of 200 m,it was 38.9 mg L^(-1).The highest concentration of petroleum hydrocarbons in the surface layer was found in the peaty-gley soils(up to 2400 mg kg^(-1)).In glandular-illuvial podburs,it was 420 mg kg^(-1).In horizons BH and BC,it was close to the background values(27 and 33 mg kg^(-1),respectively).Alkalinization of soils and water under the influence of drill cuttings led to the death of oligotrophic and acidophilic vegetation at a distanc

关键词： metal petroleum hydrocarbons plant indicator species pollutant migration in soil polycyclic aromatic hydrocarbon

Tunable vertical ferroelectricity and domain walls by interlayer sliding inβ-ZrI_(2)

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npj Computational Materials 2021年第1期7卷 1600-1608页

作者： Xiaonan Ma Chang Liu Wei Ren sergey A.Nikolaev Physics Department State Key Laboratory of Advanced Special Steeland International Center of Quantum and Molecular StructuresShanghai UniversityShanghai 200444China Materials Genome Institute and Shanghai Key Laboratory of High Temperature SuperconductorsShanghai UniversityShanghai 200444China Tokyo Tech World Research Hub Initiative(WRHI) Institute of Innovative ResearchTokyo Institute of Technology4259 NagatsutaMidori-kuYokohamaKanagawa 226-8503Japan Laboratory for Materials and Structures Tokyo Institute of Technology4259 NagatsutaMidori-kuYokohamaKanagawa 226-8503Japan National Institute for Materials Science MANA1-1 NamikiTsukubaIbaraki 305-0044Japan

Vertical ferroelectricity where a net dipole moment appears as a result of in-plane ionic displacements has gained enormous attention following its discovery in transition metal *** on first-principles calculations,we report on the evidence of robust vertical ferroelectricity upon interlayer sliding in layered semiconductingβ-ZrI_(2),a sister material of polar semimetals MoTe_(2)and WTe_(2).The microscopic origin of ferroelectricity in ZrI_(2)is attributed to asymmetric shifts of electronic charges within a trilayer,revealing a subtle interplay of rigid sliding displacements and charge redistribution down to ultrathin *** further investigate the variety of ferroelectric domain boundaries and predict a stable charged domain wall with a quasi-twodimensional electron gas and a high built-in electric field that can increase electron mobility and electromechanical response in multifunctional *** behaviour and a small switching barrier of ZrI_(2)hold promise for various ferroelectric applications,and our results provide important insights for further development of slidetronics ferroelectricity.

关键词： ferroelectric interlayer walls

Intelligent metaphotonics empowered by machine learning

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Opto-Electronic Advances 2022年第3期5卷 1-24页

作者： sergey Krasikov Aaron Tranter Andrey Bogdanov Yuri Kivshar Nonlinear Physics Center Research School of PhysicsThe Australian National UniversityCanberra ACT 2601Australia School of Physics and Engineering ITMO UniversitySt.Petersburg 197101Russia Centre for Quantum Computation and Communication Technology Department of Quantum ScienceResearch School of PhysicsThe Australian National UniversityCanberraACT 2601Australia

In the recent years,a dramatic boost of the research is observed at the junction of photonics,machine learning and artifi-cial intelligence.A new methodology can be applied to the description of a variety of photonic systems including optical waveguides,nanoantennas,and *** novel approaches underpin the fundamental principles of light-matter interaction developed for a smart design of intelligent photonic *** intelligence and machine learn-ing penetrate rapidly into the fundamental physics of light,and they provide effective tools for the study of the field of metaphotonics driven by optically induced electric and magnetic *** we overview the evaluation of meta-photonics induced by artificial intelligence and present a summary of the concepts of machine learning with some specif-ic examples developed and demonstrated for metasystems and metasurfaces.

关键词： metaphotonics machine learning artificial intelligence

Inverse shadowing and related measures

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Science China Mathematics 2020年第9期63卷 1825-1836页

作者： sergey G.Kryzhevich Sergei Yu.Pilyugin Department of Mathematical Physics Saint Petersburg State UniversitySaint Petersburg 199034Russia Department of Mathematics and Computer Science Saint Petersburg State UniversitySaint Petersburg 199034Russia

We study various weaker forms of the inverse shadowing property for discrete dynamical systems on a smooth compact ***,we introduce the so-called ergodic inverse shadowing property(Birkhoff averages of continuous functions along an exact trajectory and the approximating one are close).We demonstrate that this property implies the continuity of the set of invariant measures in the Hausdorff *** show that the class of systems with ergodic inverse shadowing is quite broad;it includes all diffeomorphisms with hyperbolic nonwandering ***,we study the so-called individual inverse shadowing(any exact trajectory can be traced by approximate ones,but this shadowing is not uniform with respect to the initial point of the trajectory).We demonstrate that this property is closely related to structural stability andΩ-stability of diffeomorphisms.

关键词： inverse shadowing invariant measure hyperbolicity axiom A stability

Statistical relations between stellar spectral and luminosity classes and stellar effective temperature and surface gravity

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Research in Astronomy and Astrophysics 2020年第9期20卷 183-191页

作者： Oleg Malkov Dana Kovaleva sergey Sichevsky Gang Zhaol Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijjing 100012China Institute of Astronomy Russian Academy of Sciences48 Pyatnitskaya St.Moscow 119017Russia

We have determined new statistical relations to estimate the fundamental atmospheric parameters of effective temperature and surface gravity,using MK spectral classification,and vice *** relations were constructed based on the published calibration tables(for main sequence stars)and observational data from stellar spectral atlases(for giants and supergiants).These new relations were applied to field giants with known atmospheric parameters,and the results of the comparison of our estimations with available spectral classification have been quite satisfactory.

关键词： stars:fundamental parameters

Dynamics of magnetic flux tubes and IR-variability of young stellar objects

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Research in Astronomy and Astrophysics 2018年第8期18卷 13-20页

作者： sergey Khaibrakhmanov Alexander Dudorov Andrey Sobolev Kourovka Astronomical Observatory Ural Federal University Theoretical Physics Department Chelyabinsk State University

We simulate the dynamics of slender magnetic flux tubes （MFTs） in the accretion disks of T Tauri stars. The dynamical equations of our model take into account aerodynamic and turbulent drag forces, and the radiative heat exchange between the MFT and ambient gas. The structure of the disk is calculated with the help of our MHD model of the accretion disks. We consider the MFTs formed at distances of 0.027 - 0.8 au from the star with various initial radii and plasma betas β0. The simulations show that MFTs with a weak magnetic field （β0 = 10） rise slowly with speeds less than the speed of sound. MFTs withβ0 = 1 form an outflowing magnetized corona above the disk. Strongly magnetized MFTs （β0 = 0.1） can cause outflows with velocities 20 - 50 km s-1. The tubes rise periodically over times from several days to several months according to our simulations. We propose that periodically rising MFTs can absorb stellar radiation and contribute to the IR-variability of young stellar objects.

关键词： accretion disks- instabilities- magnetohydrodynamics (MHD) - protoplanetary disks