Structural and entropic insights into the nature of the random-close-packing limit

Disordered packings of equal sized spheres cannot be generated above the limiting density (fraction of volume occupied by the spheres) of ??0.64 without introducing some partial crystallization. The nature of this “random-close-packing” limit (RCP) is investigated by using both geometrical and statistical mechanics tools applied to a large set of experiments and numerical simulations of equal-sized sphere packings. The study of the Delaunay simplexes decomposition reveals that the fraction of “quasiperfect tetrahedra” grows with the density up to a saturation fraction of ?30% reached at the RCP limit. At this limit the fraction of aggregate “polytetrahedral” structures (made of quasiperfect tetrahedra which share a common triangular face) reaches it maximal extension involving all the spheres. Above the RCP limit the polytetrahedral structure gets rapidly disassembled. The entropy of the disordered packings, calculated from the study of the local volume fluctuations, decreases uniformly and vanishes at the (extrapolated) limit ?K?0.66. Before such limit, and precisely in the range of densities between 0.646 and 0.66, a phase separated mixture of disordered and crystalline phases is observed

Electronic and atomic kinetics in solids irradiated with free-electron lasers or swift-heavy ions

In this brief review we discuss the transient processes in solids under irradiation with femtosecond X-ray free-electron-laser (FEL) pulses and swift-heavy ions (SHI). Both kinds of irradiation produce highly excited electrons in a target on extremely short timescales. Transfer of the excess electronic energy into the lattice may lead to observable target modifications such as phase transitions and damage formation. Transient kinetics of material excitation and relaxation under FEL or SHI irradiation are comparatively discussed. The same origin for the electronic and atomic relaxation in both cases is demonstrated. Differences in these kinetics introduced by the geometrical effects ({\mu}m-size of a laser spot vs nm-size of an ion track) and initial irradiation (photoabsorption vs an ion impact) are analyzed. The basic mechanisms of electron transport and electron-lattice coupling are addressed. Appropriate models and their limitations are presented. Possibilities of thermal and nonthermal melting of materials under FEL and SHI irradiation are discussed

On the use of cluster analysis for interpretation of soil pollution monitoring data obtained near mining enterprise

Assessment of soil contamination in areas affected by mining facilities is a necessary part of the research during the local environmental monitoring. Different methods of statistical analysis can be used to process and analyze monitoring data. This paper presents the cluster analysis outcomes of the chemical composition of soil samples collected in the area of a copper mine during the annual monitoring. As a result of cluster analysis, all soil sampling points were divided into three clusters, which seem to be characterized by different mechanisms of pollution (background points without pollution, points in the sanitary protection zone of the quarry with aerogenic dust pollution, intermediate points with mixed pollution type). Based on the study outcomes, one can conclude that the application of cluster analysis in the soil monitoring data processing makes it possible to assess the boundaries of the influence zone of the dust pollution source with a little number of soil sampling points. © 2018 Author(s)

On the application of cluster analysis for vegetation pollution assessment in the area of mining enterprise

The assessment of vegetation contamination in the influence area of mining enterprises is an important part of the research during the environment monitoring. There are different statistical methods that can be used for the analysis of data obtained in environmental monitoring. The article presents the results of cluster analysis of the chemical composition of agricultural vegetation samples collected in the area of copper-pyrite ore deposit location. During the analysis, all samples were divided into three clusters. One can suggest that this separation may be due to different mechanisms of pollutants entry into the particular sampling sites, as well as to the location of these sampling sites relatively to the enterprise industrial area. According to the results of the study, it can be concluded that cluster analysis is an effective tool for distinguishing the zones being characterized by different pollution mechanisms of grassy vegetation, when there are a small number of measurements and relatively low levels of the samples pollution. © 2019 Author(s)

Classification of online toxic comments using the logistic regression and neural networks models

The paper addresses the questions of abusive content identification in the Internet. It is presented the solving of the task of toxic online comments classification, which was issued on the site of machine learning Kaggle (www.Kaggle.com) in March of 2018. Based on the analysis of initial data, four models for solving the task are proposed: logistic regression model and three neural networks models - convolutional neural network (Conv), long shortterm memory (LSTM), and Conv + LSTM. All models are realized as a program in Python 3, which has simple structure and can be adapted to solve other tasks. The results of the classification problem solving with help of proposed models are presented. It is concluded that all models provide successful solving of the task, but the combined model Conv + LSTM is the most effective, so as it provides the best accuracy. © 2018 Author(s)

Portfolio analysis of economic decisions in the enterprise

Selection of effective solutions in the enterprise is largely provided by the rational organization of interaction of the enterprise with contractors: raw material suppliers, customers (buyers) of finished goods, government agencies, financial institutions and other organizations. The paper discusses the ways of organizing of such an interaction based on the methods of vector optimization and the theory of portfolio investment which goes back to the works of G. Markowitz. © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved

Fermi-liquid and Fermi surface geometry effects in propagation of low frequency electromagnetic waves through thin metal films

In the present work we theoretically analyze the contribution from a transverse Fermi-liquid collective mode to the transmission of electromagnetic waves through a thin film of a clean metal in the presence of a strong external magnetic field. We show that at the appropriate Fermi surface geometry the transverse Fermi-liquid wave may appear in conduction electrons liquid at frequencies $\omega$ significantly smaller than the cyclotron frequency of charge carriers $\Omega$ provided that the mean collision frequency $\tau^{-1}$ is smaller than $\omega.$ Also, we show that in realistic metals size oscillations in the transmission coefficient associated with the Firmi-liquid mode may be observable in experiments. Under certain conditions these oscillations may predominate over the remaining size effects in the transmission coefficient.Comment: 9 pages, 5 figures, text adde

The assessment of corruption impact on the inflow of foreign direct investment

The aim of this paper is to investigate the impact of corruption on the inflow of foreign direct investment (FDI). The data, taken from official sources, Transparency International and the Heritage Foundation, have been treated in a special program "Deductor Studio Academic" by the method of Machine Learning (cluster analysis using Kohonen Self-Organizing Maps). There was composed a Kohonen map, in which the countries were divided into 4 clusters: countries with low levels of corruption and high level of FDI inflow, countries with low level of corruption and FDI above average, countries with average level of corruption and the average level of FDI, and countries with high level of corruption and low level of FDI. The research has shown that corruption influences the investment attractiveness of the host country. This means that in countries where the level of corruption is low and economic environment is attractive, the level of foreign direct investment is high, and in those countries where the level of corruption is high and and economic attractiveness is low-the level of investment is low. However, the study identified countries which have high level of corruption and high FDI inflow-China, India, Brazil and Russia (BRIC countries). These countries are the exception from the rule due to the wide domestic market, cheap labour, the wealth of natural resources-all these factors increase the investment attractiveness of these countries. It was found that corruption in BRIC countries has similarity being a controlled and predictable phenomenon. This allows calculating the cost of corruption for accounting it in business projects. © 2017 Author(s)