Simulation of the loss-cone instability in spherical systems. I. Dominating harmonic potential

A new so-called `gravitational loss-cone instability' in stellar systems has recently been investigated theoretically in the framework of linear perturbation theory and proved to be potentially important in understanding the physical processes in centres of galaxies, star clusters, and the Oort comet cloud. Using N-body simulations of a toy model, we confirm previous findings for the harmonic dominating potential and go beyond the linear theory. Unlike the well-known instabilities, the new one shows no notable change in the spherical geometry of the cluster, but it significantly accelerates the speed of diffusion of particles in phase space leading to an early instability saturation.Comment: 6 pages, 9 figures, MNRAS accepte

Simulation of the loss-cone instability in spherical systems - II. Dominating Keplerian potential

According to our previous theoretical findings, physical processes in centres of galaxies, star clusters, and the Oort comet cloud can be significantly altered by a new so-called `gravitational loss-cone instability'. Using N-body simulations of a spherical stellar model in the dominating Keplerian potential, we confirm the possibility of the instability and go beyond the linear theory. Unlike most other instabilities, the new one shows no notable change in spherical geometry of the cluster, but it significantly accelerates the speed of diffusion of particles in phase space leading to a repopulation of the loss cone and early instability saturation

Simulation of the loss-cone instability in spherical systems - I. Dominating harmonic potential

A new so-called `gravitational loss-cone instability' in stellar systems has recently been investigated theoretically in the framework of linear perturbation theory and proved to be potentially important in understanding the physical processes in centres of galaxies, star clusters, and the Oort Cloud. Using N-body simulations of a toy model, we confirm previous findings for the dominating harmonic potential and go beyond the linear theory. Unlike the well-known instabilities, the new one shows no notable change in the spherical geometry of the cluster, but it significantly accelerates the speed of diffusion of particles in phase space leading to an early instability saturation

Effect of angular momentum distribution on gravitational loss-cone instability in stellar clusters around massive BH

Small perturbations in spherical and thin disk stellar clusters surrounding massive a black hole are studied. Due to the black hole, stars with sufficiently low angular momentum escape from the system through the loss cone. We show that stability properties of spherical clusters crucially depend on whether the distribution of stars is monotonic or non-monotonic in angular momentum. It turns out that only non-monotonic distributions can be unstable. At the same time the instability in disk clusters is possible for both types of distributions.Comment: 14 pages, 7 figures, submitted to MNRA

On the use of cloud community access center to the software and methodical materials in schools of Orenburg region

In the article functional possibilities of cloud educational portal are described. Cloud educational portal includes two subsystems: virtual resource center and electronic educational methodical center. Virtual resource center provides a virtual desktop with needed software for users. Access to the resources is performed remotely via Internet. The students can use desktop computers, notebooks and smartphones. A set of methodical materials was implemented by lead teachers of Orenburg region. Materials for each school subject are structured by years of studying, sections and themesВ статье описаны функциональные возможности облачного образовательного портала, созданного на базе Оренбургского государственного университета. Разработанный портал включает в себя две подсистемы: ресурсный центр и методический электронный образовательный центр. Ресурсный центр портала предоставляет пользователю виртуальный рабочий стол с установленным программным обеспечением. Доступ осуществляется учащимися удаленно, через Интернет, с использованием компьютеров образовательных организаций (которые могут иметь устаревшую конфигурацию) или мобильных устройств (ноутбуков, планшетных компьютеров, смартфонов). Набор методических материалов разработан ведущими учителями Оренбургской области. Для каждого школьного предмета материалы структурированы по годам обучения, разделам и тема

What Competences Does the Regional Market of IT Specialists Want? Development and Approbation of Technology for Analysis of Current Vacancies in the Labor Market

One of the most dynamically developing industries in Russia is IT industry. The main problem of IT development is the lack of highly qualified specialists. Determining the relevant and in-demand knowledge and skills of specialists is possible on the basis of an analysis of vacancies posted on Internet job search portals. The study is aimed at development and approbation of the technology for analysis of current vacancies for IT specialists for further designing the content of additional vocational educational programs. Modern machine learning techniques such as Natural Language Processing can be used for automatic position selection based on skills in vacancies. K-means method was used in this paper for cluster analysis of hard and soft skills lists from vacancies posted on the HeadHunter website. The most popular skills have been determined such as teamwork skills, knowledge of working with databases and version control systems, as well as proficiency in English. It has been established that in 2021 the most popular programming language is JavaScript. As a result, two variants of programmer specialization were formed, hard and soft skills for each specialization were determined

Analysis and Forecasting Students’ Academic Performance Using a Digital Educational Environment

Analysis and Forecasting Students’ Academic Performance Using a Digital Educational Environment The article discusses technical solutions used at Orenburg State University to organize a digital educational environment. Also, the authors have studied the academic performance of technical and humanities students during the period of face-to-face education and during the lockdown period. The analysis of academic performance shows the absence of significant deviations in one direction or another. The key internal and external factors that influence the students’ academic performance are highlighted. It can be concluded that the use of both internal and external factors gives a high accuracy in predicting the final progress of students

ATTACK DETECTION IN ENTERPRISE NETWORKS BY MACHINE LEARNING METHODS

Detection of network attacks is currently one of the most important problems of secure use of enterprise networks. Network signature-based intrusion detection systems cannot detect new types of attacks. Thus, the urgent task is to quickly classify network traffic to detect network attacks. The article describes algorithms for detecting attacks in enterprise networks based on data analysis that can be collected in them. The UNSW-NB15 data set was used to compare machine learning methods for classifying attack or-normal traffic, as well as to identify nine more popular classes of typical attacks, such as Fuzzers, Analysis, Backdoors, DoS, Exploits, Generic, Reconnaissance, Shellcode and Worms. Balanced accuracy is used as the main metric for assessing the accuracy of the classification. The main advantage of this metric is an adequate assessment of the accuracy of classification algorithms given the strong imbalance in the number of marked records for each class of data set. As a result of the experiment, it was found that the best algorithm for identifying the presence of an attack is RandomForest, to clarify its type - AdaBoost

Approaches to Educational Programs Modeling, Design and Implementation for Continuous Training of Various Experts

This article describes an approach to model, construct and implement multilevel system of continuous educational programs. The training content is determined by the system of generalized professional competencies. The educational levels correspond to the competency levels. The multilevel system includes five educational levels: primary professional training programs (perhaps at high school), secondary vocational programs (which are transformed into applied bachelor programs), bachelor programs, master programs, and postgraduate programs. This multi-level educational system may be implemented effectively using the fractal model of regional educational structures. The fractal model is based on self-similarity, self-organization and self-development. This implemented educational system makes possible to use individual learning tracks both in one educational program and during the transition between educational levels. DOI: 10.5901/mjss.2015.v6n2s3p14

A Dipole Vortex Model of Obscuring Tori in Active Galaxy Nuclei

The torus concept as an essential structural component of active galactic nuclei (AGN) is generally accepted. Here, the situation is discussed when the torus "twisting" by the radiation or wind transforms it into a dipole toroidal vortex which in turn can be a source of matter replenishing the accretion disk. Thus emerging instability which can be responsible for quasar radiation flares accompanied by matter outbursts is also discussed. The "Matreshka" scheme for an obscuring vortex torus structure capable of explaining the AGN variability and evolution is proposed. The model parameters estimated numerically for the luminosity close to the Eddington limit agree well with the observations.Comment: 17 pages, 11 figures, version of this paper is published in Astronomy Report