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

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

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

Quantum tops as examples of commuting differential operators

We study the quantum analogs of tops on Lie algebras $so(4)$ and $e(3)$ represented by differential operators.Comment: 24 p

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

Trophic preferences of Pterostichus oblongopunctatus (Coleoptera, Carabidae) in conditions of south forest-steppe

Досліджено переваги Pterostichus oblongopunctatus (Fabricius, 1787) у виборі об’єктів живлення в умовах лісових біогеоценозів південного Лісостепу Полтавської області. Проаналізовано таксономічну, розмірно-вагову та трофічну структуру запропонованих P. oblongopunctatus безхребетних. Установлено критерії вибору P. oblongopunctatus потенційних трофічних об’єктів: міцність покривів і розміри здобичі, а також її здатність до швидкого пересування.Исследованы предпочтения Pterostichus oblongopunctatus (Fabricius, 1787) в выборе потенци­альных объектов питания в условиях лесных биогеоценозов южной Лесостепи Полтавской области. Проанализирована таксономическая, размерно-весовая и трофическая структура предложенных P. oblongopunctatus беспозвоночных. Установлены критерии выбора P. oblongopunctatus потенциальных трофических объектов: твердость покровов и размеры добычи, а также ее способность быстро передвигаться.The specific trophic preferences of Pterostichus oblongopunctatus (Fabricius, 1787) as one of the common litter zoophages in forests biogeocenoses of the south forest-steppe in the Poltava region are investigated. Taxonomic, size-weight and trophic structure of potential food objects offered to the P. oblongopunctatus was analysed. P. oblongopunctatus choice criteria of potential food objects were established: hardness of exoskeleton and size of prey and also victim’s ability for to fast moving

Budgeting simulation of expenses trade enterprises in structure management accounting

Стаття присвячена дослідженню моделі бюджетування затрат торговельних підприємств. Уточнена відмінність між поняттями «Витрати», «Валові витрати» та «Затрати». Досліджено відмінність між плануванням, прогнозуванням і бюджетуванням. Визначено роль бюджетування у бізнесовій діяльності підприємств торгівлі та етапи створення бюджетів окремих видів затрат.The Article denoted study to models of process of budgeting trade enterprise’s expenses. The Article elaborated difference between «Expenses», «Gross expenses» and «Expenses». The Article is exploring difference between planning, forecasting and budgeting. The Article is exploring certain role of budgeting in business activity trade enterprise and stages of the creation budget separate type of the expenses

Identification of corner separation modelling in axial compressor stage

The paper presents a study of corner separations in hub to blade region at various operation conditions towards compressor stall. It is known that for compressor flows with low or none separations computation fluid dynamics with RANS methods work quite well, however, for highly separated flows they are no longer entirely valid. Therefore, several criteria were applied for prediction and quantification of possible corner separation, and the main interest of this work is in predicting the separation just before it will actually happen by certain flow metrics, so these metrics can be further used as a 'pre-stall' criteria whilst the RANS CFD operating point still behave within its appropriate limits. Also the effect of shear lean is discussed in the presented context. © The Authors, published by EDP Sciences, 2020

FEATURES MODIFYING VARIOUS TYPES OF IRON-CARBON ALLOYS

The article describes the features of the modification of cast iron, high chrome cast iron and steel. It is shown that the modification of cast iron complex modifier should be based on the thickness of the walls of castings, and for steel and high chrome cast iron, it is beneficial to the macro and microstructure. The data confirming the removal of transcrystallization and size reduction microand macrostructure of castings in various types of iron-carbon alloys. Experimentally proved that in the transition from columnar to equiaxed structure observed increase in the number of eutectic cells, which confirms the position that transcrystallization terminated as a result of nucleation and growth of equiaxed crystalsin the area of concentration supercoolin