Approximate Selection Rule for Orbital Angular Momentum in Atomic Radiative Transitions

We demonstrate that radiative transitions with \Delta l = - 1 are strongly dominating for all values of n and l, except small region where l << n.Comment: 5 pages, 1 figur

Evolution of the First Supernovae in Protogalaxies: Dynamics of Mixing of Heavy Elements

The paper considers the evolution of the supernova envelopes produced by Population III stars with masses of $M_*\sim 25-200 M_\odot$ located in non-rotating protogalaxies with masses of $M\sim 10^7 M_\odot$ at redshifts $z=12$, with dark-matter density profiles in the form of modified isothermal spheres. The supernova explosion occurs in the ionization zone formed by a single parent star. The properties of the distribution of heavy elements (metals) produced by the parent star are investigated, as well as the efficiency with which they are mixed with the primordial gas in the supernova envelope. In supernovae with high energies (E\simgt 5\times 10^{52} erg), an appreciable fraction of the gas can be ejected from the protogalaxy, but nearly all the heavy elements remain in the protogalaxy. In explosions with lower energies (E\simlt 3\times 10^{52} erg), essentially no gas and heavy elements are lost from the protogalaxy: during the first one to threemillion years, the gas and heavy elements are actively carried from the central region of the protogalaxy ($r\sim 0.1 r_{vir}$, where $r_{vir}$ is the virial radius of the protogalaxy), but an appreciable fraction of the mass of metals subsequently returns when the hot cavity cools and the envelope collapses. Supernovae with high energies (E\simgt 5\times 10^{52} erg) are characterized by a very low efficiency of mixing of metals; their heavy elements are located in the small volume occupied by the disrupted envelope (in a volume comparable with that of the entire envelope), with most of the metals remaining inside the hot, rarified cavity of the envelope. (abridged)Comment: 25 pages, 9 figures, 1 tabl

The failure criterion based on hydrogen distribution ahead of the fatigue crack tip

The hydrogen effect on the fracture toughness and fatigue crack growth behaviour in themartensitic high strength steel is investigated. The secondary ion mass spectrometry method has beenemployed to analyse the distribution of hydrogen concentration in the zone of the crack tip and at its edges.Changes in hydrogen concentration are observed in the vicinity of the propagating crack tip and at a remotesite. The hydrogen peak H C is reduced and moves away from the fatigue crack tip with the increase of themaximum stress intensity factor max K . The concept of damage evolution is used to explain fatigue crackpropagation in connection with the hydrogen redistribution ahead of the crack tip. The physical failure criterionbased on the hydrogen peak in the vicinity of the fatigue crack tip and the maximum stress intensity factor hasbeen proposed. The criterion reflects changes in the hydrogen peak which resulted from the hydrogenredistribution due to the increase of the maximum stress intensity factor as the crack length increases underfatigue loading

Уровни развития самоконтроля студентов в процессе учебной деятельности

У статті розглянуто проблеми розвитку самоконтролю, як одного з важливих компонентів розвитку особистості, а також вплив рівнів розвитку самоконтролю на успішність навчальної діяльності студентів. Прагнення до саморозвитку, самореалізації є показником зрілої, високорозвиненої особи. Процес вдосконалення самого себе, реалізації своїх можливостей, творчого потенціалу передбачає розвиненість суб’єктивних властивостей, серед яких важливе місце посідає самоконтроль людини.In the article are considered problems of development of self-control, as one of important components of development of personality, and also influence of levels of development of self-control on progress of educational activity of students.В статье рассмотрены проблемы развития самоконтроля, как одного из важных компонентов развития личности, а также влияние уровней развития самоконтроля на успеваемость учебной деятельности студентов

Determination of fracture mechanics parameters on a base of local displacement measurements

New experimental technique for a determination of the stress intensity factor (SIF) and T-stressvalues is developed and verified. The approach assumes combining the crack compliance method and opticalinterferometric measurements of local deformation response on small crack length increment. Initialexperimental information has a form of in-plane displacement component values, which are measured byelectronic speckle-pattern interferometry at some specific points located near a crack tip. Required values offracture mechanics parameters follow from the first four coefficients of Williams’ series. A determination ofinitial experimental data at the nearest vicinity of notch tip is the main feature of the developed approach. Thatis why it is not necessary to involve complex numerical models, which include global geometrical parameters,loading and boundary conditions of the object under study, in a stage of experimental data interpretation. Anavailability of high-quality interference fringe patterns, which are free from rigid-body motions, serves as areliable indicator of real stress state around a crack tip. A verification of the technique is performed bycomparing experimental results with analogous data of FEM modelling. Experimentally determined mode I SIFfor DCB specimen with end crack is in 5 per cent agreement with the numerically simulated case. Proposedapproach is capable of estimating an influence of the notch radius on fracture mechanics parameters.Comparing SIF and T-stress obtained for U-notches of different radius both in actual and residual stress fieldconfirms this statement

Земства України на тлі суспільно-політичних процесів доби Центральної Ради (березень 1917 р. – квітень 1918 р.)

Matvienko T. Zemstvos of Ukraineon the Background of Social and Political Processes in Ukraine of the Central Council Period (March 1917 - April 1918) – Qualification research work on the rights of a manuscript. The thesis for the degree of Candidate of Historical Sciences specialty 07.00.01 "HistoryofUkraine",V.N. Karazin Kharkiv National University, Kharkiv, 2019. The influence of socio-political processes in Ukraine of the Central Council period (March 1917 ‒ April 1918) on zemstvos and their reverse impact on social and political transformations and Ukrainian statemaking process of that time are comprehensively analysed in this research work. The Interim Government and the Ukrainian Central Council zemstvo policy, the attitude evolution of the latter state body towards social and political processes of the Ukrainian revolution are analysed. The reasons of support for the Interim Government, created after the Russian autocracy overthrow, by the most part of Ukrainian zemstvos are substantiated. Its attempts to base on district and provincial zemstvos in developing local administrative authorities are analysed. Based on the analysis of social and political attitudes of the democratic population circles, the falsity of the Interim Government appropriate expectations are proved.У дисертаційному дослідженні комплексно проаналізовано політику Тимчасового уряду та Української Центральної Ради щодо земств, еволюцію ставлення останніх до суспільно-політичних процесів Української революції та національного державотворення. Досліджено особливості демократизації земств на весні 1917 року та під час виборів до волосних, повітових і губернських органів самоврядування сільського населення влітку ‒ восени 1917 року. Визначено вплив більшовицького Жовтневого перевороту 1917 року в Петрограді на земства України, наслідки агресії більшовицької Росії в Україну для земських органів Української Народної Республіки. З’ясовано особливості функціонування органів земського самоврядування УНР за присутності на її території австронімецьких військ. В диссертационном исследовании комплексно анализируется политика Временного правительства и Украинской Центральной Рады относительно земств, эволюция отношения последних к общественно-политическим процессам Украинской революции и национального строительства государства. Исследованы особенности демократизации земств весной 1917 года и вовремя выборов в волостные, уездные и губернские органы самоуправления сельского населения летом ‒ осенью 1917 года. Определено влияние большевистского Октябрьского переворота 1917 года в Петрограде на земства Украины, последствия агрессии большевистской России в Украину для земских органов Украинской Народной Республики. Выяснены особенности функционирования органов земского самоуправления УНР в присутствии на ее территории австрогерманских войск