On the validity of the method of reduction of dimensionality: area of contact, average interfacial separation and contact stiffness

It has recently been suggested that many contact mechanics problems between solids can be accurately studied by mapping the problem on an effective one dimensional (1D) elastic foundation model. Using this 1D mapping we calculate the contact area and the average interfacial separation between elastic solids with nominally flat but randomly rough surfaces. We show, by comparison to exact numerical results, that the 1D mapping method fails even qualitatively. We also calculate the normal interfacial stiffness $K$ and compare it with the result of an analytical study. We attribute the failure of the elastic foundation model to the neglect of the long-range elastic coupling between the asperity contact regions.Comment: 5 pages, 4 figures, 29 reference

Dynamic model of elastoplastic normal collision of spherical particles under nonlocal plasticity

The problem of normal collision of a spherical particle with a half-space is considered with allowance for nonlocal plastic deformation in the case where the strength limit depends on the contact radius, as well as for the strengthening effect in the deformed material. The dimensionless coefficient of normal velocity restitution has been calculated numerically as a function of the initial velocity of the spherical particle. The obtained data coincide well with experimental results available in the literature

ПОРІВНЯЛЬНА ОЦІНКА ЕКСПОРТНИХ МОЖЛИВОСТЕЙ ПРОДУКЦІЇ ГІРНИЧОДОБУВНОГО КОМПЛЕКСУ УКРАЇНИ (на прикладі залізної руди)

The article analyzes the state of the domestic mining industry and the factors that influence its development. Problems and prospects of development of export opportunities of iron ore products of the mining complex are investigated. Tendencies, problems have been identified, and proposals have been developed to ensure sustainable development of the extractive industry of Ukraine in the current economic conditions. Accordingly, in the course of the study, in order to solve the problems, the indicator of the marketing attractiveness of the countries leading in exports of mining products using the Rush model was calculated, economic analysis of selected countries was carried out, the development of their mining industry was investigated, and exports developed in these countries. The level of attractiveness of Ukraine is determined in comparison with the countries cited. With the help of the Revealed Comparative Advantage (RCA), a comparative assessment of the prospects for the development of export opportunities for the mining industry of selected countries was carried out. Financial and regulatory regimes for stimulating subsoil users and investors in the extractive industry have been developed. The development of the metallurgical industry through the prism of the export of steel to Brazil and Turkey in comparison with our country has been studied. In order to improve the sectoral (sectoral) competitiveness, it was suggested that measures should be taken to increase energy efficiency and reduce the material intensity and improve the quality of marketing activities, in order to create the network of export-import sectoral (branch) associations under the aegis of the above-mentioned Ministry of Industry and Trade of Ukraine, on the principles of public-private partnership — Energoimpex, Mashbudimpex, Rudpromimpex, Metallimpex and others. As a result of the analysis, ways and recommendations for creating conditions for the further development of the Ukrainian mining complex and its export potential have been proposed.Приведена оценка современного состояния отечественной горнодобывающей промышленности, осуществлен анализ факторов, влияющих на ее развитие. Исследованы проблемы и перспективы развития экспортных возможностей железорудной продукции горнодобывающего комплекса. Определены тенденции, проблемы, а также разработаны предложения по обеспечению устойчивого развития добывающей промышленности Украины в современных экономических условиях. Соответственно, в ходе исследования, для решения проблем, был проведен поиск стран с экономическими показателями, приближающимися к показателям нашей страны, рассчитан показатель маркетинговой привлекательности данных стран с помощью модели Раша, проведен экономический анализ выбранных стран, исследовано развитие их горнодобывающей промышленности, как развит экспорт в приведенных странах, определен уровень привлекательности Украины по сравнению с приведенными странами. С помощью индекса сравнительного превосходства (Revealed Comparative Advantage, RCA) проведена сравнительная оценка перспектив развития экспортных возможностей горнодобывающей отрасли выбранных стран. Разработаны финансово-регуляторные режимы стимулирования недропользователей и инвесторов добывающей промышленности. Изучено развитие металлургической промышленности сквозь призму экспорта стали Бразилии и Турции по сравнению с нашей страной. С целью повышения секторальной (отраслевой) конкурентоспособности предложено проведение мероприятий по повышению энергоэффективности и снижению материалоемкости, а также повышения качества маркетинговой деятельности, в подчинении вышеуказанному Минпромзовништоргу Украины создать сеть экспортно-импортных секторальных (отраслевых) объединений возможно на принципах государственно-частного партнерства — Энергоимпекс, Машбудимпекс, Рудпромимпекс, Металимпекс и других.В результате проведенного анализа предложены пути и рекомендации по созданию условий для дальнейшего развития горнодобывающего комплекса Украины и его экспортного потенциала.Наведено оцінку сучасного стану вітчизняної гірничодобувної промисловості, здійснено аналіз чинників, що впливають на її розвиток. Досліджено проблеми та перспективи розвитку експортних можливостей залізорудної продукції гірничодобувного комплексу. Визначено тенденції, проблеми, а також розроблено пропозиції щодо забезпечення сталого розвитку добувної промисловості України в сучасних економічних умовах. Відповідно, в ході дослідження, для вирішення проблем, було проведено пошук країн з економічними показниками, що наближаються к показникам нашої країни, розраховано показник маркетингової привабливості даних країн за допомогою моделі Раша, проведено економічний аналіз обраних країн, досліджено розвиток їх гірничодобувної промисловості, як розвинений експорт в наведених країнах, визначено наскільки Україна приваблива в порівнянні з наведеними країнами. За допомогою індексу порівняльної переваги (Revealed Comparative Advantage, RCA) проведено порівняльну оцінку перспектив розвитку експортних можливостей гірничодобувної галузі обраних країн. Розроблено фінансово-регуляторні режими стимулювання надрокористувачів та інвесторів добувної промисловості. Вивчено розвиток металургійної промисловості крізь призму експорту сталі Бразилії і Туреччини в порівнянні з нашою країною. З метою підвищення секторальної (галузевої) конкурентоздатності запропоновано проведення заходів з підвищення енергоефективності та зниження матеріалоємності, а також підвищення якості маркетингової діяльності, у підпорядкуванні вищезазначеному Мінпромзовнішторгу України створити мережу експортно-імпортних секторальних (галузевих) об’єднань можливо на принципах публічно-приватного партнерства — Енергоімпекс, Машбудімпекс, Рудпромімпекс, Металімпекс та інших. У результаті здійсненого аналізу запропоновано шляхи та рекомендації щодо створення умов для подальшого розвитку гірничодобувного комплексу України та його експортного потенціалу

Substantiation of parameters of mine working drivage with blasting technique and cleaning charges in advance cutting holes

Drilling and blasting operations (D&B) are the most difficult and laborious operations in the process of mineral extraction, requiring permanent development and upgrading of methods and equipment. The aim of the study is to substantiate the parameters of drilling and blasting drivage of horizontal and inclined (up to 12o) mine workings on the basis of high-performance self-propelled equipment and new designs of box cuts with cleaning explosive charges (0.2 kg of 6ZhV ammonite), placed in advance holes of 65 to 105 mm in diameter. The paper presents the results of the analysis of practical experience and scientific achievements in the field of drilling-andblasting rupture of solid media and continuum mechanics. The need for new designs of box cuts, reliability of which in the formation of high-quality (clean) cut cavity reaches 0.95-1.00, was substantiated. New design options of box cuts have been developed, the peculiarity of which consists in provision of sufficient compensation (peripheral) volume with the use of blast hole cut charges for blasting rupture of trapezoidal partitions, with the compensation volume factor of 2.50 to 1.34. Promising areas of research were shown using the example of complicated structure ore deposits and large faults in the Kirovograd ore district and crystalline rocks of the Ukrainian shield at the following mines of Ukraine: PJSC KZhRK, CJSC Sukhaya Balka (Kryvyi Rih), Vostok-Ruda LLC, SE VostGOK (Zheltye Vody), CJSC ZZhRK, etc. Promising areas of research were proposed using the example of complicated structure ore deposits typically formed at the junction of large faults; besides, the use of environmentally friendly emulsion explosives and self-propelled emulsion explosive chargers was recommended

A Comparative Numerical Study on GEM, MHSP and MSGC

In this work, we have tried to develop a detailed understanding of the physical processes occurring in those variants of Micro Pattern Gas Detectors (MPGDs) that share micro hole and micro strip geometry, like GEM, MHSP and MSGC etc. Some of the important and fundamental characteristics of these detectors such as gain, transparency, efficiency and their operational dependence on different device parameters have been estimated following detailed numerical simulation of the detector dynamics. We have used a relatively new simulation framework developed especially for the MPGDs that combines packages such as GARFIELD, neBEM, MAGBOLTZ and HEED. The results compare closely with the available experimental data. This suggests the efficacy of the framework to model the intricacies of these micro-structured detectors in addition to providing insight into their inherent complex dynamical processes

Justification of drill and blast pattern designs for ore treatment before in-situ leaching

The article discusses drill and blast pattern designs for ore treatment before in-situ leaching (ISL) in ore bodies of complex structure with a view to ensuring ecological safety, enhanced ISL efficiency, as well as balanced subsoil protection and management. This is achievable using cut-and-fill method with cemented backfill of different composition and strength, as well as with other geotechnical methods. It is shown that ISL of metals from solid ore requires high-quality preparation of large volume blocks, associated with blasting of tens of tones of explosives at a time. Rock fragmentation by blasting is improved through the higher powder factor to 2.9–3.3 kg/m3, as well as through accumulation of rocks with a degree of fragmentation not less than Kf = 1.2–1.3 in a limited space at the bottom of a stope. A case study of the concurrent application of a conventional mining technology and ISL technology in the Michurin deposit, on level 26–21 m, at the ISL block width of 20 m and shrinkage height of 35 to 50 m has proved the required stability of roof spans, without any falls of oversizes or off-standard sizes to ISL ore blocks. The recommendations for the design approaches to ISL are developed and tested in mined-out stopes in test block 5-86 and in pilot production blocks 5-84-86, 5-88-90 and 1-75-79

Multifractal analysis of stress time series during ultrathin lubricant film melting

Melting of an ultrathin lubricant film confined between two atomically flat surfaces is we studied using the rheological model for viscoelastic matter approximation. Phase diagram with domains, corresponding to sliding, dry, and two types of $stick-slip$ friction regimes has been built taking into account additive noises of stress, strain, and temperature of the lubricant. The stress time series have been obtained for all regimes of friction using the Stratonovich interpretation. It has been shown that self-similar regime of lubricant melting is observed when intensity of temperature noise is much larger than intensities of strain and stress noises. This regime is defined by homogenous distribution, at which characteristic stress scale is absent. We study stress time series obtained for all friction regimes using multifractal detrended fluctuation analysis. It has been shown that multifractality of these series is caused by different correlations that are present in the system and also by a power-law distribution. Since the power-law distribution is related to small stresses, this case corresponds to self-similar solid-like lubricant.Comment: 22 pages, 10 figures, 41 reference

Апроксимація ДФВЗ кубічним поліномом

Розглянуто різні підходи апроксимації дистрибутивної функції відбивної здатності поверхні. Розроблено апроксимацію ДФВЗ, основану на використанні косинус-кубічної функції, що має численні переваги порівняно з поширеними сьогодні

First results of the Kourovka Planet Search: discovery of transiting exoplanet candidates in the first three target fields

We present the first results of our search for transiting exoplanet candidates as part of the Kourovka Planet Search (KPS) project. The primary objective of the project is to search for new hot Jupiters which transit their host stars, mainly in the Galactic plane, in the $R_c$ magnitude range of 11 to 14 mag. Our observations were performed with the telescope of the MASTER robotic network, installed at the Kourovka astronomical observatory of the Ural Federal University (Russia), and the Rowe-Ackermann Schmidt Astrograph, installed at the private Acton Sky Portal Observatory (USA). As test observations, we observed three celestial fields of size $2\times2$ deg$^2$ during the period from 2012 to 2015. As a result, we discovered four transiting exoplanet candidates among the 39000 stars of the input catalogue. In this paper, we provide the description of the project and analyse additional photometric, spectral, and speckle interferometric observations of the discovered transiting exoplanet candidates. Three of the four transiting exoplanet candidates are most likely astrophysical false positives, while the nature of the fourth (most promising) candidate remains to be ascertained. Also, we propose an alternative observing strategy that could increase the project's exoplanet haul.Comment: 11 pages, 16 figures; Accepted for publication in Monthly Notices of the Royal Astronomical Society 201