1,917 research outputs found
Electromagnetic field of a charge asymptotically approaching spherically symmetric black hole
We consider a test charged particle falling onto a Schwarzschild black hole
and evaluate its electromagnetic field. The Regge-Wheeler equation is solved
analytically by approximating the potential barrier with Dirac delta function
and rectangular barrier. We show that for asymptotically large time measured by
a distant observer the electromagnetic field approaches the spherically
symmetric electrostatic field exponentially fast. This implies that in the
region accessible to a distant observer the initial state of separated charge
and Schwarzschild black hole becomes asymptotically indistinguishable from the
Reisnner-Nordstr\"om solution. Implications of this result for models with
plasma accretion on black holes are discussed.7 aComment: 7 pages, 2 figure
Structural Peculiarities of A3B5 Nanocrystals Created in Si by Ion-Beam Synthesis
We reported the structure peculiarities of nanocrystals formed in Si by means of high-fluence implantation
at 25 and 500 °С followed by rapid thermal annealing (RTA). The structure of implanted samples
has been investigated by means of transmission electron microscopy (TEM). The crystalline nature of the
precipitates is proved by the Moiré fringe patterns presence in the TEM images. The Moiré fringe distance
(Moiré period) is equal of 1.8 nm for small precipitates. This experimental value coincides with the calculated
one for crystalline InAs. It is noted a Moiré period increasing in the case of large precipitates. We
suppose that this feature is a result of surplus As or In atoms embedded in precipitates. One can see an interesting
effect – “glowng” of nanocrystal/Si interfaces at the dark-field images of implanted and annealed
samples. We ascribe this effect to a presence of misfit dislocation networks at the InAs/Si interfaces generated
as a result of strain relaxation in highly mismatched InAs/Si system.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3543
Quantum tops as examples of commuting differential operators
We study the quantum analogs of tops on Lie algebras and
represented by differential operators.Comment: 24 p
Ion Beam Synthesis of InAs Nanocrystals in Crystalline Silicon
The formation of nanodimensional InAs crystallites on Si wafers was studied by the method of high fluence implantation of As and In ions with subsequent high temperature treatment. It was found that the size and depth distributions of the crystallites depend on both the implantation temperature and the annealing conditions. A broad band in an energy range of 0.75–1.1 eV was recorded in the photolumines cence spectra of the samples
The application of modern computational fluid dynamics techniques for increasing the efficiency and stability of an axial compressor in an industrial gas turbine
This paper contains on-site test data of an axial compressor as part of an industrial gas turbine, as well as the process of Computational Fluid Dynamics (CFD) modelling, verification, research and modernization. The research method has been verified with actual test data gathered from the real gas turbine unit (GTU) test. The computational studies showed significant potential for improving aerodynamic efficiency and the surge margin of a compressor by better matching of inlet and outer groups of stages. A special design approach was used to improve aerodynamic parameters of the inlet system and certain middle stages. Computations made for the improved compressor model showed a 3% efficiency gain and 5% stall margin gain with possibilities for further modernization. © 2014 WIT Press.International Journal of Safety and Security Engineering;International Journal of Sustainable Development and Planning;WIT Transactions on Ecology and the Environmen
Mechanisms of arsenic clustering in silicon
A model of arsenic clustering in silicon is proposed and analyzed. The main
feature of the proposed model is the assumption that negatively charged arsenic
complexes play a dominant role in the clustering process. To confirm this
assumption, electron density and concentration of impurity atoms incorporated
into the clusters are calculated as functions of the total arsenic
concentration. A number of the negatively charged clusters incorporating a
point defect and one or more arsenic atoms are investigated. It is shown that
for the doubly negatively charged clusters or for clusters incorporating more
than one arsenic atom the electron density reaches a maximum value and then
monotonically and slowly decreases as total arsenic concentration increases. In
the case of doubly negatively charged cluster incorporating two arsenic atoms,
the calculated electron density agrees well with the experimental data.
Agreement with the experiment confirms the conclusion that two arsenic atoms
participate in the cluster formation. Among all present models, the proposed
model of clustering by formation of doubly negatively charged cluster
incorporating two arsenic atoms gives the best fit to the experimental data and
can be used in simulation of high concentration arsenic diffusion.Comment: 13 pages, 4 figures. Revised and shortened version of the paper has
been published in Phys. Rev. B, Vol.74 (3), art. no. 035205 (2006
Electromagnetic radiation and electromagnetic self-force of a point charge in the vicinity of Schwarzschild black hole
Point charge, radially moving in the vicinity of a black hole is considered.
Electromagnetic field in wave zone and in the small neighbourhood of the charge
is calculated. Numerical results of the calculation of the spectrum of
electromagnetic radiation of the point charge are presented. Covariant approach
for the calculation of electromagnetic self-force is used for the case of the
slowly moving charge. Numerical results for the self-force in the case of slow
motion of the particle are obtained and compared to the results in literature.Comment: 5 pages, 3 figure
Multi-criteria optimisation of subsonic axial compressor blading
The novel approach to parametric topology of the 2D compressor airfoil was tested at multi-criteria optimisation problem for high speed subsonic application. Some results regarding the shape of the blade are presented. © 2019 Published under licence by IOP Publishing Ltd.The work was supported by Act 211 Government of the Russian Federation, contract №02.A03.21.0006
Analysis of litter mesofauna of Poltava region forest ecosystems
На основі досліджень підстилкової мезофауни 48 обстежених лісових біогеоценозів охарактеризовано закономірності формування угруповань безхребетних на рівні видів і родин. Проаналізовано ступінь подібності пробних ділянок за таксономічною структурою герпетобію. Виявлено чинники, які впливають на формування підстилкової мезофауни лісових біогеоценозів Полтавської області.На основе исследований подстилочное мезофауни 48 обследованных лесных экосистем охарактеризованы закономерности формирования группировок беспозвоночных на уровне видов и семей. Проанализирована степень сходства пробных участков по таксономической структуре герпетобию. Выявлены факторы, влияющие на формирование подстилочное мезофауни лесных экосистем Полтавской областиOn the basis of research of litter mesofauna of 48 forest biogeocenoses the regularities of invertebrate communities formation on the species and families levels are determined. The degree of similarity of test plots are analysed by taxonomic structure of the communities. The factors of the litter invertebrate communities formation in forest ecosystems of the Poltava region are revealed
Trophic structure of litter mesofauna: biomass differentiation between trophic levels
На основі досліджень підстилкової мезофауни чотирьох лісових біогеоценозів Полтавської області побудовано трофічно-вагові моделі угруповань безхребетних. Проаналізовано розподіл біомаси за трофічними рівнями, розмірну і таксономічну структуру окремих рівнів. Охарактеризовано відмінності та спільні риси трофічно-вагових моделей угруповань безхребетних. На основе исследований подстилочное мезофауни четырех лесных экосистем Полтавской области построено трофические-весовые модели группировок беспозвоночных. Проанализировано распределение био¬масы за трофическими уровнями, соразмерную и таксономическую структуру отдельных уровней. Охарактеризованы различия и общие черты трофические-весовых моделей группировок беспозвоночных.On the basis of research of litter mesofauna in four forest biogeocenoses of the Poltava region the trophic-weight models of invertebrate communities are creating. The biomass differentiation between trophic levels, weight and taxonomic structure of the separate levels are analysed. The differentiation and similarity of the trophic-weight models of litter invertebrate communities are discussed
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