Effect of grain refinement on deformation behavior of technical grade titanium under tension

The paper deals with the study on the impact of grain refinement by severe plastic deformation upon the microstructure, as well as deformation and fracture behavior under tensile loading of technical grade titanium. The microstructure of coarse- and ultra-fine grain technical grade titanium was investigated by optical, transmission electron microscopy and X-ray diffraction. In situ monitoring of deformation behavior was conducted by means of acoustic emission and digital image correlation. Scanning electron microscopy was employed for fracture surface observation. The results of the tensile tests have revealed significant growth in ultimate strength and decrease of ductility due to grain-boundary strengthening. The experimental data obtained allow one to get the appropriate understanding of the mechanisms responsible for variation of mechanical properties and fracture patterns as well as to attain quantitative estimation of strain localization induced by the grain refinement

Correlation effects during liquid infiltration into hydrophobic nanoporous mediums

Correlation effects arising during liquid infiltration into hydrophobic porous medium are considered. On the basis of these effects a mechanism of energy absorption at filling porous medium by nonwetting liquid is suggested. In accordance with this mechanism, the absorption of mechanical energy is a result expenditure of energy for the formation of menisci in the pores on the shell of the infinite cluster and expenditure of energy for the formation of liquid-porous medium interface in the pores belonging to the infinite cluster of filled pores. It was found that in dependences on the porosity and, consequently, in dependences on the number of filled pores neighbors, the thermal effect of filling can be either positive or negative and the cycle of infiltration-defiltration can be closed with full outflow of liquid. It can occur under certain relation between percolation properties of porous medium and the energy characteristics of the liquid-porous medium interface and the liquid-gas interface. It is shown that a consecutive account of these correlation effects and percolation properties of the pores space during infiltration allow to describe all experimental data under discussion

The Phantom Bounce: A New Oscillating Cosmology

An oscillating universe cycles through a series of expansions and contractions. We propose a model in which ``phantom'' energy with $p < -\rho$ grows rapidly and dominates the late-time expanding phase. The universe's energy density is so large that the effects of quantum gravity are important at both the beginning and the end of each expansion (or contraction). The bounce can be caused by high energy modifications to the Friedmann equation, which make the cosmology nonsingular. The classic black hole overproduction of oscillating universes is resolved due to their destruction by the phantom energy.Comment: Four pages, one figure. V3: version to appear in JCA

Gravitational Wave Bursts from Collisions of Primordial Black Holes in Clusters

The rate of gravitational wave bursts from the mergers of massive primordial black holes in clusters is calculated. Such clusters of black holes can be formed through phase transitions in the early Universe. The central black holes in clusters can serve as the seeds of supermassive black holes in galactic nuclei. The expected burst detection rate by the LISA gravitational wave detector is estimated.Comment: 10 pages, 2 figure

Gamma Ray Bursts from the Evolved Galactic Nuclei

A new cosmological scenario for the origin of gamma ray bursts (GRBs) is proposed. In our scenario, a highly evolved central core in the dense galactic nucleus is formed containing a subsystem of compact stellar remnants (CSRs), such as neutron stars and black holes. Those subsystems result from the dynamical evolution of dense central stellar clusters in the galactic nuclei through merging of stars, thereby forming (as has been realized by many authors) the short-living massive stars and then CSRs. We estimate the rate of random CSR collisions in the evolved galactic nuclei by taking into account, similar to Quinlan & Shapiro (1987), the dissipative encounters of CSRs, mainly due to radiative losses of gravitational waves, which results in the formation of intermediate short-living binaries, with further coalescence of the companions to produce GRBs. We also consider how the possible presence of a central supermassive black hole, formed in a highly evolved galactic nucleus, influences the CSR binary formation. This scenario does not postulate ad hoc a required number of tight binary neutron stars in the galaxies. Instead, it gives, for the most realistic parameters of the evolved nuclei, the expected rate of GRBs consistent with the observed one, thereby explaining the GRB appearance in a natural way of the dynamical evolution of galactic nuclei. In addition, this scenario provides an opportunity for a cosmological GRB recurrence, previously considered to be a distinctive feature of GRBs of a local origin only. We also discuss some other observational tests of the proposed scenario.Comment: 25 pages, LATEX, uses aasms4.sty, accepted by Ap

The Development of Youth Entrepreneurship at a University Taking into the Factor of Cooperation with Partners

The article presents the author’s view on the development of youth entrepreneurship at a university based on the factor of cooperation with partners. The main objective of the study is to establish the methodological framework for the use of the potential of the partners of a university for the development of youth entrepreneurship. The relevance of the study is determined by the need to develop approaches to stimulate the development of youth entrepreneurship in Russia, including at universities. The article considers theoretical and methodological foundations of youth entrepreneurship. The authors defines the stimulatory and constraining factors, as well as endogenous (transformational and transactional) and exogenous conditions for the development of youth entrepreneurship. A comprehensive mechanism is proposed in the context of four main structural units and principles of entrepreneurship taking into account the interaction of the university with its partners - businesses, territorial, educational and scientific communities. The authors systematizes the specific experience of Russian universities in the framework of the functioning elements of an integrated mechanism for the development of youth entrepreneurship, considering interaction with their partners. Common features and differences in the intensity of the support and development of youth entrepreneurship have been identified. The significant role of partners at this stage of the functioning of universities is obvious. Interaction with partners of a university in the development of youth entrepreneurship has a significant potential, based on the relevance of entrepreneurship support as a whole, the need to intensify the development of business activities of individual companies and institutions through the implementation of entrepreneurial initiatives and the social importance of discovering entrepreneurial skills in young people. The universities that have been studied use opportunities to attract external projects that further the development of youth entrepreneurship. The results can be used for analysis of current activity and formation of strategic documents in the field of youth entrepreneurship development for universities, private companies, scientific organizations and public associations.В статье представлен авторский взгляд на развитие молодежного предпринимательства в университете на основе фактора взаимодействия с партнерами. Основная цель исследования состоит в формировании методологической базы для использования потенциала партнеров университета для развития молодежного предпринимательства. Актуальность исследования определяется необходимостью выработки подходов к стимулированию развития молодежного предпринимательства в России, в том числе на базе университетов. В статье рассмотрены теоретико-методологические основы молодежного предпринимательства. Авторами определены стимулирующие и сдерживающие факторы, а также эндогенные (трансформационные и трансакционные) и экзогенные условия развития молодежного предпринимательства. Предложен комплексный механизм в разрезе четырех основных структурных блоков и принципы развития предпринимательства с учетом взаимодействия университета со своими партнерами – деловым, территориальным, образовательным и научным сообществами. Авторами статьи систематизирован частный опыт российских университетов в рамках функционирования элементов комплексного механизма развития молодежного предпринимательства с учетом взаимодействия с партнерами университета. Выявлены общие черты и различие в интенсивности поддержки и развития молодежного предпринимательства. При этом действенная роль партнеров на текущем этапе функционирования университетов очевидна. Взаимодействие с партнерами университета в области развития молодежного предпринимательства имеет значительный потенциал, опирающийся на актуальность поддержки предпринимательства в целом, необходимости интенсификации развития хозяйствующей деятельности отдельных компаний и учреждений за счет реализации предпринимательских инициатив и общественной значимости раскрытия предпринимательских способностей молодежи. Все проанализированные авторами работы университеты используют возможности, способствующие развитию молодежного предпринимательства. Результаты работы могут быть использованы для анализа текущей деятельности, а также формирования стратегических документов в сфере развития молодежного предпринимательства для университетов, частных компаний, научных организации и общественных объединений.Статья выполнена в соответствии с планом НИР Института экономики УрО РАН № темы 0404-2015-0021 в ИСГЗ ФАН

Improving accuracy and generalization performance of small-size recurrent neural networks applied to short-term load forecasting

The load forecasting of a coal mining enterprise is a complicated problem due to the irregular technological process of mining. It is necessary to apply models that can distinguish both cyclic components and complex rules in the energy consumption data that reflect the highly volatile technological process. For such tasks, Artificial Neural Networks demonstrate advanced performance. In recent years, the effectiveness of Artificial Neural Networks has been significantly improved thanks to new state-of-the-art architectures, training methods and approaches to reduce overfitting. In this paper, the Recurrent Neural Network architecture with a small-size model was applied to the short-term load forecasting of a coal mining enterprise. A single recurrent model was developed and trained for the entire four-year operational period of the enterprise, with significant changes in the energy consumption pattern during the period. This task was challenging since it required high-level generalization performance from the model. It was shown that the accuracy and generalization properties of small-size recurrent models can be significantly improved by the proper selection of the hyper-parameters and training method. The effectiveness of the proposed approach was validated using a real-case dataset. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Phantom scalar emission in the Kerr black hole spacetime

We study the absorption probability and Hawking radiation spectra of a phantom scalar field in the Kerr black hole spacetime. We find that the presence of the negative kinetic energy terms modifies the standard results in the greybody factor, super-radiance and Hawking radiation. Comparing with the usual scalar particle, the phantom scalar emission is enhanced in the black hole spacetime.Comment: 11 pages, 6 figures, a revised version accepted for publication in CQ

Data Mining Applied to Decision Support Systems for Power Transformers’ Health Diagnostics

This manuscript addresses the problem of technical state assessment of power transformers based on data preprocessing and machine learning. The initial dataset contains diagnostics results of the power transformers, which were collected from a variety of different data sources. It leads to dramatic degradation of the quality of the initial dataset, due to a substantial number of missing values. The problems of such real-life datasets are considered together with the performed efforts to find a balance between data quality and quantity. A data preprocessing method is proposed as a two-iteration data mining technology with simultaneous visualization of objects’ observability in a form of an image of the dataset represented by a data area diagram. The visualization improves the decision-making quality in the course of the data preprocessing procedure. On the dataset collected by the authors, the two-iteration data preprocessing technology increased the dataset filling degree from 75% to 94%, thus the number of gaps that had to be filled in with the synthetic values was reduced by 2.5 times. The processed dataset was used to build machine-learning models for power transformers’ technical state classification. A comparative analysis of different machine learning models was carried out. The outperforming efficiency of ensembles of decision trees was validated for the fleet of high-voltage power equipment taken under consideration. The resulting classification-quality metric, namely, F1-score, was estimated to be 83%. © 2022 by the authors.Ministry of Education and Science of the Russian Federation, MinobrnaukaThe research funding from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program) is gratefully acknowledged

Supernovae - Optical Precursors of Short Gamma-Ray Bursts

The probability of observing "supernova - gamma-ray burst" (GRB) pair events and recurrent GRBs from one galaxy in a time interval of several years has been estimated. Supernova explosions in binary systems accompanied by the formation of a short-lived pair of compact objects can be the sources of such events. If a short GRB is generated during the collision of a pair, then approximately each of ~300 short GRBs with redshift z must have an optical precursor - a supernova in the observer's time interval <2(1+z)yr. If the supernova explosion has the pattern of a hypernova, then a successive observation of long and short GRBs is possible. The scenario for the generation of multiple GRBs in collapsing galactic nuclei is also discussed.Comment: 12 pages, 1 figure; this paper has the e-precursor arXiv:1101.3298 [astro-ph.HE