Molecular-dynamics investigation of nanoburnishing process

It is well known that the burnishing process affects the surface characteristic, namely: surface roughness, surface hardness, wear resistance, fatigue resistance and increased maximum residual stress in compression. Unfortunately we still far from full understanding what parameters and mechanisms are responsible for the certain surface modification. That is why methods of computer modeling can be considered as useful tool to investigate surface changing during contact interaction as well as burnishing process. It is more essential if we consider processes are taking place at atomic scale level. In the paper we try to reproduce the details of burnishing process at nano-scale level. To investigate features of surface treatment we use the molecular dynamics simulation. Various pure crystalline materials were considered. Results of our modeling are very close to the experimental observatio

Numerical study of conditions for subsurface shear instability under contact interaction

Numerical modeling of nanostructuring burnishing has been carried out to reveal the limiting values of process parameters, which serve both to provide the appropriate surface quality and positive deformation-induced structural modification of the subsurface layers as well as to avoid shear instability in the subsurface layers of burnished metal. The effects of load, burnishing speed, tool pass number and tribological transfer on the burnished surface roughness have been elucidated by the example of quenched and tempered steels 20X (EN 20Cr4). It was shown that overloading results in quasi-viscous flow of the subsurface material, deterioration of the surface and ruining the positive effect of nanostructuring burnishing

Effect of adhesion transfer on the surface pattern regularity in nanostructuring burnishing

In the paper the influence of friction-induced adhesion of metal to the tool on the formation of surface topography under nanostructuring burnishing was studied. A comprehensive approach, including both experimental (optical microscopy and profilometry) and theoretical (computer-aided simulation) methods was used. The results showed a direct connection between values of adhesion strength of materials in contact with the workpiece surface pattern quality caused by the tool movement. Results of the experimental and theoretical study are in good agreement and allow us to identify the reason of regular profile forming during surface burnishing

Cost Optimization of Donetsk Railway in the Procurement of Electricity for Traction

Бітюков С. Д. Оптимізація витрат Донецької залізниці при закупівлі електроенергії на тягу поїздів / С. Д. Бітюков, В. Г. Кузнецов, В. Г. Сиченко, Т. І. Кирилюк // Збірник наукових праць Української державної академії залізничного транспорту. — 2011. — № 122. — С. 93—100.UK: У статті обґрунтовано принципи модернізації тягових підстанцій Донецької залізниці з урахуванням вимог з енерго- та ресурсозбереження. На основі обробки експериментальних даних з витрат електроенергії на тягу поїздів Донецької залізниці показано переваги переводу тяги поїздів на вищий рівень напруги. Розраховано економічний ефект.RU: В статье обоснованы принципы модернизации тяговых подстанций Донецкой железной дороги с учетом требований по энерго- и ресурсосбережению. На основании обработки экспериментальных данных по затратам электроэнергии на тягу поездов Донецкой железной дороги показаны преимущества перевода тяги поездов на высший уровень напряжения. Рассчитан экономический эффект.EN: In this article, grounded principles of modernization of traction substations Donetsk railway to meet the requirements for energy- and resource conservation. On the basis of experimental data on the cost of electricity for traction Donetsk railway shows the benefits of translation traction trains at the highest level of voltage. Calculated economic effect

Site- and spin-dependent coupling at the highly ordered h-BN/Co(0001) interface

Using photoelectron diffraction and spectroscopy, we explore the structural and electronic properties of the hexagonal boron nitride (h-BN) monolayer epitaxially grown on the Co(0001) surface. Perfect matching of the lattice parameters allows formation of a well-defined interface where the B atoms occupy the hollow sites while the N atoms are located above the Co atoms. The corrugation of the h-BN monolayer and its distance from the substrate were determined by means of R-factor analysis. The obtained results are in perfect agreement with the density functional theory (DFT) predictions. The electronic structure of the interface is characterized by a significant mixing of the h-BN and Co states. Such hybridized states appear in the h-BN band gap. This allows to obtain atomically resolved scanning tunneling microscopy (STM) images from the formally insulating 2D material being in contact with ferromagnetic metal. The STM images reveal mainly the nitrogen sublattice due to a dominating contribution of nitrogen orbitals to the electronic states at the Fermi level. We believe that the high quality, well-defined structure and interesting electronic properties make the h-BN/Co(0001) interface suitable for spintronic applications.L.V.Ya. acknowledges the RSF (Grant No. 16-42-01093). A.V.T., V.O.S., K.A.B., O.Yu.V., and D.Yu.U. acknowledge St. Petersburg State University for research Grant No. 11.65.42.2017. M.V.K. and I.I.O. acknowledge the RFBR (Grant No. 16-29-06410). C.L. acknowledges the DFG (Grant Nos. LA655-17/1 and LA655-19/1).Peer reviewe

EUNIS Habitat Classification: Expert system, characteristic species combinations and distribution maps of European habitats

Aim: The EUNIS Habitat Classification is a widely used reference framework for European habitat types (habitats), but it lacks formal definitions of individual habitats that would enable their unequivocal identification. Our goal was to develop a tool for assigning vegetation‐plot records to the habitats of the EUNIS system, use it to classify a European vegetation‐plot database, and compile statistically‐derived characteristic species combinations and distribution maps for these habitats. Location: Europe. Methods: We developed the classification expert system EUNIS‐ESy, which contains definitions of individual EUNIS habitats based on their species composition and geographic location. Each habitat was formally defined as a formula in a computer language combining algebraic and set‐theoretic concepts with formal logical operators. We applied this expert system to classify 1,261,373 vegetation plots from the European Vegetation Archive (EVA) and other databases. Then we determined diagnostic, constant and dominant species for each habitat by calculating species‐to‐habitat fidelity and constancy (occurrence frequency) in the classified data set. Finally, we mapped the plot locations for each habitat. Results: Formal definitions were developed for 199 habitats at Level 3 of the EUNIS hierarchy, including 25 coastal, 18 wetland, 55 grassland, 43 shrubland, 46 forest and 12 man‐made habitats. The expert system classified 1,125,121 vegetation plots to these habitat groups and 73,188 to other habitats, while 63,064 plots remained unclassified or were classified to more than one habitat. Data on each habitat were summarized in factsheets containing habitat description, distribution map, corresponding syntaxa and characteristic species combination. Conclusions: EUNIS habitats were characterized for the first time in terms of their species composition and distribution, based on a classification of a European database of vegetation plots using the newly developed electronic expert system EUNIS‐ESy. The data provided and the expert system have considerable potential for future use in European nature conservation planning, monitoring and assessment

The origins and spread of domestic horses from the Western Eurasian steppes

This is the final version. Available on open access from Nature Research via the DOI in this recordData availability: All collapsed and paired-end sequence data for samples sequenced in this study are available in compressed fastq format through the European Nucleotide Archive under accession number PRJEB44430, together with rescaled and trimmed bam sequence alignments against both the nuclear and mitochondrial horse reference genomes. Previously published ancient data used in this study are available under accession numbers PRJEB7537, PRJEB10098, PRJEB10854, PRJEB22390 and PRJEB31613, and detailed in Supplementary Table 1. The genomes of ten modern horses, publicly available, were also accessed as indicated in their corresponding original publications57,61,85-87.NOTE: see the published version available via the DOI in this record for the full list of authorsDomestication of horses fundamentally transformed long-range mobility and warfare. However, modern domesticated breeds do not descend from the earliest domestic horse lineage associated with archaeological evidence of bridling, milking and corralling at Botai, Central Asia around 3500 BC. Other longstanding candidate regions for horse domestication, such as Iberia and Anatolia, have also recently been challenged. Thus, the genetic, geographic and temporal origins of modern domestic horses have remained unknown. Here we pinpoint the Western Eurasian steppes, especially the lower Volga-Don region, as the homeland of modern domestic horses. Furthermore, we map the population changes accompanying domestication from 273 ancient horse genomes. This reveals that modern domestic horses ultimately replaced almost all other local populations as they expanded rapidly across Eurasia from about 2000 BC, synchronously with equestrian material culture, including Sintashta spoke-wheeled chariots. We find that equestrianism involved strong selection for critical locomotor and behavioural adaptations at the GSDMC and ZFPM1 genes. Our results reject the commonly held association between horseback riding and the massive expansion of Yamnaya steppe pastoralists into Europe around 3000 BC driving the spread of Indo-European languages. This contrasts with the scenario in Asia where Indo-Iranian languages, chariots and horses spread together, following the early second millennium BC Sintashta culture