Use of Articulated Transport Systems in the Mining Industry

The work is devoted to the possibility and prospects of the use of all-wheels drive articulated transport systems in the mining complex. A comparative analysis of the traditional methods of exporting minerals in open pit mining and the method of using active trailed elements are given. The trailer has a load factor several times higher than the same rate for mining dump trucks. The use of an active trailer makes it possible to reduce the mass of the tractor and trailer by almost 40 tons and increase the specific power of the road train. © Published under licence by IOP Publishing Ltd

Quantized Rotation of Atoms From Photons with Orbital Angular Momentum

We demonstrate the coherent transfer of the orbital angular momentum of a photon to an atom in quantized units of hbar, using a 2-photon stimulated Raman process with Laguerre-Gaussian beams to generate an atomic vortex state in a Bose-Einstein condensate of sodium atoms. We show that the process is coherent by creating superpositions of different vortex states, where the relative phase between the states is determined by the relative phases of the optical fields. Furthermore, we create vortices of charge 2 by transferring to each atom the orbital angular momentum of two photons.Comment: New version, 4 pages and 3 figures, accepted for publication in Physical Review Letter

О ДИАГРАММЕ СОСТОЯНИЯ СИСТЕМЫ Cu–Ni–Mn

By means of the theoretical analysis and based on the experimental data, the part of the Cu–Ni–Mn structural diagram from 0 to 20 % Ni and from 30 to 50 % Mn has been specified. The supposition, which is contained in a number of works, of the existence in the ternary Cu–Ni–Mn state diagram of the line, along which the zero crystallization range alloys are arranged, is shown to be incorrect. The alloys in the double Cu–Mn and Ni–Mn systems have the zero crystallization range only. The primary supposition of impossibility to present nonequilibrium crystallization according to Petrov–Scheil with lacking of the minimum line in the Cu–Ni–Mn system has not been confirmed because formerly the investigations were carried out with a model system in which there observed a convex line of the liquidus curve on the polythermal cross-section joining the minima in the double systems. The present work shows this line that is concave towards the temperature decrease.С помощью теоретического анализа и на основании экспериментальных данных уточнена часть диаграммы состояния Cu–Ni–Mn от 0 до 20 % Ni и от 30 до 50 % Mn. Показано, что содержащееся в ряде работ предположение о существовании в тройной системе Cu–Ni–Mn линии, по которой располагаются сплавы с нулевым интервалом кристаллизации, неверно. Нулевой интервал кристаллизации имеют лишь сплавы в двойных системах Cu–Mn и Ni–Mn. Высказанное первоначально предположение о невозможности представить неравновесную кристаллизацию по Петрову–Шейлю при отсутствии линии минимума в системе Cu–Ni–Mn не подтвердилось, так как прежде исследования выполнялись на модельной системе, в которой на политермическом сечении, соединяющем минимумы в двойных системах, имелась выпуклая линия ликвидуса. В настоящей работе показано, что эта линия вогнута в сторону понижения температуры

Efficiency of the Left Atrial Appendage Thrombus Dissolution in Patients with Persistent Nonvalvular Atrial Fibrillation with Warfarin or Direct Oral Anticoagulants Therapy

Aim. Compare the incidence of the left atrial appendage (LAA) thrombus dissolution in patients with persistent nonvalvular atrial fibrillation receiving warfarin and direct oral anticoagulants (DOAC).Materials and methods. 68 patients with persistent nonvalvular atrial fibrillation were included in a retrospective study (age was 59.7±9.8 years, 60.3% men), in whom at least one repeated transesophageal echocardiographic examination was performed after detecting a thrombus. After detecting a thrombus in the LAA, 37 (54.4%) patients started or continued taking warfarin in doses that ensure the INR maintenance at the level of 2-3, 14 (20.6%) started or continued taking dabigatran at a dose of 150 mg 2 times/day, 14 (20.6%) started or continued taking rivaroxaban 20 mg 1 time/day and 3 (4.4%) started or continued taking apixaban 5 mg 2 times/day. Repeated transesophageal echocardiographic examination was performed on average 33.3±14.2 days after the first one.Results. Dissolution of a previously identified thrombus was found in 26 (83.9%) of 31 patients receiving DOAC and in 19 (51.4%) of 37 patients receiving warfarin (p=0.011). The logistic regression analysis showed that the chances of a thrombus dissolution in LAA while taking DOAC are 14.8 times (95% confidence interval [CI] was 2.469-88.72) higher than while taking warfarin. The size and the rate at which blood is expelled from the LAA also have an independent influence on the chances of thrombus dissolution. An increase in the size of a thrombus by 1 mm reduces the chances of a thrombus dissolution by 1.136 (95% CI was 1.040-1.244) times, and an increase in the rate of blood expulsion from the LAA by 1 cm/sec increases these chances by 1.105 (95% CI was 1.003-1.219) times.Conclusion. In the present study, the incidence of the LAA thrombus dissolution in patients with persistent nonvalvular atrial fibrillation while receiving DOAC was higher than while receiving warfarin

ВЛИЯНИЕ ХИМИЧЕСКОГО СОСТАВА И РЕЖИМОВ ТЕРМИЧЕСКОЙ ОБРАБОТКИ НА ФАЗОВЫЙ СОСТАВ И МЕХАНИЧЕСКИЕ СВОЙСТВА МАГНИЕВОГО СПЛАВА ZK51A (МЛ12)

This paper examines the ZK51A (ML12) alloy samples with the content of Zn from 3.5 to 5.5 wt.% and Zr from 0.5 to 0.8 wt.%. The influence of the Zn and Zr content on phase transition temperatures and phase composition in equilibrium conditions and with the Scheil-Gulliver solidification model was determined using the phase diagram calculation in Thermo-Calc software. It is shown that the Zr content of 0.8–0.9 wt.% leads to a significant increase in the alloy liquidus temperature and requires raising the melting temperature over 800 °С. This is undesirable when using steel crucibles. The equilibrium content of alloying elements in the magnesium solid solution was calculated at different temperatures. Scanning electron microscopy was used to study the microstructures of ascast and heat-treated alloys with different alloying elements content. The distribution of Zn and Zr in a dendritic cell of the alloy in as-cast and heat-treated conditions was investigated. Zinc in an as-cast condition is accumulated on the dendritic cell boundary, but after the heat treatment its concentration in the center of the dendritic cell became higher than concentration on the cell boundary.Zirconium is accumulated in the center of the dendritic cell. We determined the effect of the solution heat treatment conditions on the alloy hardness. The maximum hardness gain was achieved using a two-step treatment at 330 °С for 5 h and then at 400 °С for 5 h. We studied the effect of aging heat treatment (150 and 200 °C) on the alloy hardness. The better hardness was achieved after aging at 200 °С. The maximum value was reached after 8–10 h of aging. The tensile strength 285 ± 13.5 MPa and elongation 11.4 ± 1 % were achieved after the two-step heat treatment consisting of isothermal holding at 330 °С for 5 h and then at 400 °С for 5 h with quenching and aging at 200 °С for 8 h.Объектом исследования были образцы сплава ZK51A (МЛ12), содержащие от 3,5 до 5,5 мас.% Zn и 0,5–0,8 мас.% Zr. С помощью расчета диаграмм состояния в программе «Thermo-Calc» установлено влияние концентраций Zn и Zr на температуры фазовых превращений и фазовый состав в равновесных условиях и при использовании модели полностью неравновесной кристаллизации Шейла–Гулливера. Показано, что при доле циркония в сплаве более 0,8–0,9 мас.% происходит значительное повышение температуры ликвидуса сплава и требуется увеличение температуры плавки выше 800 °С, что нежелательно при использовании стальных плавильных тиглей. Рассчитано равновесное содержание легирующих компонентов в твердом растворе на основе магния при различных температурах. С помощью электронной микроскопии изучены микроструктуры сплавов с различными концентрациями легирующих компонентов в литом и термообработанном состояниях. Исследовано распределение Zn и Zr в дендритной ячейке сплава в литом и термо-обработанном состояниях. В литом состоянии цинк концентрируется по границам дендритных ячеек, однако после термообработки его концентрация в их центре становится выше, чем по границам. Цирконий концентрируется в центре дендритных ячеек. Установлено влияние режимов закалки сплавов на их твердость. Показано, что наибольший прирост этого показателя дает двухступенчатый режим закалки: 330 °С, 5 ч + 400 °С, 5 ч. Изучено влияние температуры старения (150 и 200 °C) на твердость образцов – выявлено, что она выше в случае старения при 200 °С, причем ее максимум наблюдался при выдержке 8–10 ч. Термообработка сплава, включающая изотермическую выдержку (330 °С, 5 ч + 400 °С, 5 ч) с последующей закалкой и старение (200 °С, 8 ч), позволила достичь предела прочности сплава 285 ± ± 13,5 МПа и относительного удлинения 11,4 ± 1 %

Direct generation of optical vortices

A detailed scheme is established for the direct generation of optical vortices, signifying light endowed with orbital angular momentum. In contrast to common techniques based on the tailored conversion of the wave front in a conventional beam, this method provides for the direct spontaneous emission of photons with the requisite field structure. This form of optical emission results directly from the electronic relaxation of a delocalized exciton state that is supported by a ringlike array of three or more nanoscale chromophores. An analysis of the conditions leads to a general formulation revealing a requirement for the array structure to adhere to one of a restricted set of permissible symmetry groups. It is shown that the coupling between chromophores within each array leads to an energy level splitting of the exciton structure, thus providing for a specific linking of exciton phase and emission wavelength. For emission, arrays conforming to one of the given point-group families’ doubly degenerate excitons exhibit the specific phase characteristics necessary to support vortex emission. The highest order of exciton symmetry, corresponding to the maximum magnitude of electronic orbital angular momentum supported by the ring, provides for the most favored emission. The phase properties of the emission produced by the relaxation of such excitons are exhibited on plots which reveal the azimuthal phase progression around the ring, consistent with vortex emission. It is proven that emission of this kind produces electromagnetic fields that map with complete fidelity onto the phase structure of a Laguerre-Gaussian optical mode with the corresponding topological charge. The prospect of direct generation paves the way for practicable devices that need no longer rely on the modification of a conventional laser beam by a secondary optical element. Moreover, these principles hold promise for the development of a vortex laser, also based on nanoscale exciton decay, enabling the production of coherent radiation with a tailor-made helical wave front

О ВНУТРИКРИСТАЛЛИТНОЙ ЛИКВАЦИИ В ТРОЙНЫХ СПЛАВАХ – ТВЕРДЫХ РАСТВОРАХ

Calculations of nonequilibrium crystallization after Petrov-Sheil model in ternary alloys – solid solutions of the A–B–C model system and the real Cu–Ni–Mn system have been carried out. A discrepancy of the temperature, at which the medium-melting component distribution factor is equal to 1 and the temperature at which the component content in precipitated solid phase is maximum, is shown to be characteristic for intracrystalline segregation in both cases. The conditions under which the parameters of intracrystalline segregation should be compared with the indicators of dendritic segregation are formulated.Проведены расчеты неравновесной кристаллизации по модели Петрова–Шейля в тройных сплавах – твердых растворах модельной системы A–B–C и реальной Cu–Ni–Mn. Показано, что для внутрикристаллитной ликвации в обоих случаях характерно несовпадение температуры, при которой коэффициент распределения среднеплавкого компонента равен 1, и температуры, при которой содержание этого компонента в выпадающей твердой фазе максимально. Сформулированы условия, при которых параметры внутрикристаллитной ликвации следует сопоставлять с показателями дендритной ликвации

Left atrial strain in assessing heart failure with preserved ejection fraction in hypertensive patients

Aim. To compare the results of diagnosing heart failure with preserved ejection fraction (HFpEF) in patients with hypertension (HTN) according left atrial (LA) strain values with the results obtained using the H2FPEF score and diastolic stress testing (DST).Material and methods. The study included 293 patients with previously established HTN who were examined due to complaints of shortness of breath and/or palpitations (men, 97 (33,5%), mean age, 62,0 (55,0; 67,0) years). All patients underwent transthoracic echocardiography with the assessment of LA strain parameters and probability of HFpEF using the H2FPEF score. Eighty five patients with an intermediate probability of HFpEF underwent DST.Results. A low probability of HFpEF according to the H2FPEF score was registered in 35 (11,9%) patients, uncertain — in 206 (70,3%), high — in 52 (17,7%). DST was negative in 43 (50,6%) and positive in 42 (49,4%) patients with an intermediate probability of HFpEF. LA strain in the reservoir phase in patients with a low probability of HFpEF averaged (median and interquartile interval) 28,0 (23,6; 31,5)%, while in patients with an intermediate probability and negative DST — 24,0 (22,0; 26,8)%, with an intermediate probability and positive DST — 20,0 (18,0; 21,0)%, and with a high probability of HFpEF — 19,6 (16,9; 21,8)%. HFpEF was diagnosed in 94 patients, including 52 with a high probability on the H2FPEF score and 42 with an intermediate probability and positive DST. The diagnosis of HFpEF was ruled out in 78 patients, including 35 with a low probability on the H2FPEF score and 43 with an intermediate probability and negative DST. Further, 172 patients with confirmed or excluded HFpEF were randomly divided into two equal cohorts. In the training cohort, HFpEF was diagnosed in 44 (51,2%) patients, in the validation cohort — in 50 (58,1%). ROC analysis performed on the training cohort for the LA strain in reservoir phase showed AUC of 0,920 (95% confidence interval (CI), 0,842-0,968) and cut-off point of 21,5%. In the training cohort, the results of HFpEF diagnosis using the indicated criterion coincided with those using H2FPEF score and DST in 86,1% (95% CI, 77,2-91,8) of cases. The Cohen’s kappa was 0,721 (95% C,I 0,575-0,868). In the validation cohort, agreement was observed in 84,9% (95% CI 75,8-91,0) of cases with Cohen’s kappa of 0,702 (95% CI 0,553-0,851).Conclusion. In hypertensive patients, the diagnosis of HFpEF made on the basis of a decrease in the LA strain in reservoir phase to ≤21,5%, is in good agreement with the diagnosis made using the H2FPEF score and DST

Эффективность многопоточных вычислений в системах компьютерного моделирования литейных процессов

The utilization of computer simulation software for casting process simulation is becoming essential in the advancement of casting technology in aviation and other high-tech engineering fields. With the increase in the number of computational cores in modern CPUs, the use of multi-threaded computations is becoming increasingly relevant. In this study, the efficiency of multi-threaded computations in modeling casting processes was evaluated using finite element method casting simulation software ProCast and PoligonSoft, which utilize parallel computing architectures with distributed (DMP) and shared (SMP) memory, respectively. Computations were performed on Intel and AMD-based computers, varying the number of computational threads from 4 to 32. The calculation efficiency was evaluated by measuring the calculation speed increase in the filling and solidification of GP25 castings made of ML10 alloy, as well as the complex task of filling and solidification modeling nickel superalloy casing castings with radiation heat transfer simulation. The results indicate that the minimum computation time in ProCast software is observed when using 16 computational threads. This pattern holds true for both computing systems (Intel and AMD processors), and increasing the number of threads beyond this point does not make a practical difference. The performance decrease in this scenario can be attributed to the low-performance energy-efficient cores in systems based on Intel processors or the decrease in core frequency and full loading of physical cores in systems based on AMD processors. Multi-threading the modeling task in PoligonSoft software is less efficient than in ProCast, which is a result of the shared-memory architecture used in PoligonSoft. Despite the significant difference in parallel efficiency, the task of GP25 casting solidification in both PoligonSoft and ProCast is solved in a time close enough to be considered sufficient.Применение систем компьютерного моделирования литейных процессов (СКМ ЛП) становится обязательным при разработке литейной технологии в авиации и других наукоемких областях техники. В связи с увеличением числа расчетных ядер в современных процессорах актуальным становится осуществление многопоточных вычислений. В работе оценивалась эффективность многопоточных вычислений при моделировании литейных процессов с помощью конечно-элементных СКМ ЛП «ProCast» и «ПолигонСофт», использующих архитектуры параллельных расчетов с распределенной (DMP) и общей (SMP) памятью соответственно. Для вычислений применяли компьютеры на базе платформ от компаний «Intel» и «AMD». Число расчетных потоков варьировали от 4 до 32. Эффективность оценивали по приросту скорости расчета заполнения и затвердевания отливки «ГП25» из сплава МЛ10, а также решения сложной задачи моделирования заполнения и затвердевания корпусных отливок из никелевого жаропрочного сплава с учетом радиационного теплообмена. Показано, что минимальное время расчета в СКМ ЛП «ProCast» наблюдается при использовании 16 вычислительных потоков. Причем это характерно для обеих вычислительных систем (на процессорах «Intel» и «AMD»), и увеличение числа потоков выше этого предела не имеет практического смысла. Снижение производительности в данном случае может быть связано с наличием малопроизводительных энергоэффективных ядер в случае применения системы на процессоре «Intel», а также полной загрузки физических ядер и уменьшением частоты ядер для системы на процессоре от «AMD». Распараллеливание задачи моделирования в СКМ ЛП «ПолигонСофт» менее эффективно, чем в СКМ ЛП «ProCast», вследствие реализации архитектуры с общей памятью. В то же время, несмотря на значительную разницу в эффективности распараллеливания, задача затвердевания отливки «ГП25» в СКМ ЛП «ПолигонСофт» и «ProCast» решается за достаточно близкое время