Взаимная диффузия в системах на основе тугоплавких металлов с ОЦК-решеткой: титан–тантал и титан – многокомпонентный (высокоэнтропийный) сплав

In this work, the interdiffusion features in multicomponent (high-entropy) alloys of refractory metals were studied. The following pairs were chosen as the diffusion study objects: titanium–equiatomic alloy (Hf–Nb–Ta–Ti–Zr–Mo) and titanium–tantalum for the sake of comparison. The article covers the issues of sample preparation, microstructure study, sample preparation methodology for diffusion research, and experimental results. Diffusion annealing was carried out for 12 h in a vacuum at a residual argon pressure of 6.65·10–3 Pa and a temperature of 1200 °С. Particular attention was paid to the method of combining diffusion pairs (titanium with tantalum, titanium with alloy) by thermal cycling near the polymorphic transformation temperature in titanium (882 °C) within ± 50 °C. The behaviour of the most characteristic elements (Ta, Zr, Ti) in the weld area after the titanium and alloy diffusion pair joining was demonstrated. This is the first time that data on the dependence of the intensity of the corresponding spectral line for titanium and elements of a multicomponent alloy on the penetration depth were obtained. A change in the signal intensity for system elements was observed at a depth of 150–200 μm, whereas a sharp drop in the signal intensity was seen to occur at depths of about 50 μm. The effective value of the coefficient of diffusion of elements into titanium averaged over all elements of the alloying system (except for titanium) at a temperature of 1200 °C was calculated. The obtained value was compared to reference data: the self-diffusion coefficient in β-titanium and diffusion coefficients in titanium pairs with alloy doping elements.Изучены особенности взаимной диффузии в многокомпонентных (высокоэнтропийных) сплавах на основе тугоплавких металлов. В качестве объектов диффузионного исследования были выбраны следующие пары: титан – эквиатомный сплав (Hf–Nb–Ta–Ti–Zr–Mo) и, для сравнения, титан–тантал. Рассмотрены вопросы приготовления образцов, исследования микроструктуры, методика подготовки образцов для изучения диффузии и экспериментальные результаты. Диффузионный отжиг был проведен в течение 12 ч в вакууме с остаточным давлением аргона 6,65·10–3 Па при температуре 1200 °С. Особое внимание уделено методике соединения диффузионных пар (титана с танталом, титана со сплавом) путем термоциклирования вблизи температуры полиморфного превращения в титане (882 °С) в пределах ±50 °С. Показано поведение наиболее характерных элементов (Ta, Zr, Ti) в области сварного шва после соединения диффузионной пары титана и сплава. Впервые получены данные о зависимости интенсивности соответствующей линии спектра для титана и элементов многокомпонентного сплава от глубины проникновения. Изменение интенсивности сигнала для элементов систем наблюдается на глубине 150–200 мкм, а резкое падение интенсивности сигнала происходит на глубинах порядка 50 мкм. Рассчитано усредненное по всем элементам системы легирования сплава (за исключением титана) эффективное значение коэффициента диффузии элементов в титан при температуре 1200 °С. Проведено сравнение полученного значения со справочными данными: коэффициентом самодиффузии в β-титане, коэффициентами диффузии в парах титана с легирующими элементами сплава

Chern-Simons like term generation in an extended model of QED under external conditions

The possibility of a Chern-Simons like term generation in an extended model of QED, in which a Lorentz and CPT non-covariant interaction term for fermions is present, has been investigated at finite temperature and in the presence of a background color magnetic field. To this end, the photon polarization operator in an external constant axial-vector field has been considered. One-loop contributions to its antisymmetric component due to fermions in the linear order of the axial-vector field have been obtained. Moreover, the first nontrivial correction to the induced CS term due to the presence of a weak constant homogeneous color magnetic field has been derived.Comment: RevTex, 10 pages with 3 figure

ПОВРЕЖДЕНИЕ КОНСТРУКЦИИ САМОЛЕТА МОЛНИЕЙ ПРИ НАЛИЧИИ ОСАДКОВ НА ЕГО ПОВЕРХНОСТИ

When an aircraft is struck by lightning damage of external structural elements is primarily caused by mechanical electrical impact of discharge on the aircraft, which results in the formation of dents on the skin, bends of panel elements (there have been cases of bending turbofan blades) and other deformations. Firstly, the mechanism of such lightning effect is caused by the action of ponderomotive forces generated by the interaction of the current in the lightning channel with currents flowing through the metal structures of the aircraft. Secondly, the shockwave of lightning has a physical impact on the elements of construction. The presence of condensation (moisture, ice) on the surface of the aircraft can significantly increase the damage of fuselage skin resulting from the electromechanical impact of lightning, which was confirmed by the results of the experimental research conducted at the Chair of Physics of the Moscow State Technical University of Civil Aviation. The water depth (as far as it is known, thunderstorm in most cases is accompanied by rain precipitation) can be large enough especially on the ground during parking and taxiing, as well as at takeoff operation and landing. Sheet samples of aluminum alloy skin D16AT with electrical discharge parameters (current amplitude 50–60 kA, duration of the first half-wave 30 microseconds) which were relatively equal to average parameters of natural lightning strike were tested. With water depth of not over 8 mm the indentations up to 2 mm deep and 30 mm in diameter were formed on samples up to 1,5 mm thick, with a sample thickness of 0,8 mm – over 10 mm in depth and up to 60–70 mm in diameter. Educated estimates indicated that presence of water increases the electrodynamic pressure on the skin several times. Firstly, having in consideration the elastic component such deformation can bring a danger to control mechanisms and surfaces located proximately under the skin when subjected to lightning strike. Secondly, electromechanical pressure amplification coupled with the striking acoustic wave generated by lightning can result in supercritical pressures in the mounting hardware of the skin. All of this should be taken into account both at the design stage of the aircraft and during aircraft operation including in particular post-flight inspection of the aircraft struck by lightning.При поражении самолета молнией повреждение наружных элементов конструкции вызывается в первую очередь электромеханическим воздействием разряда на воздушное судно (ВС), следствием которого является образование вмятин на обшивке, загибов консольных элементов (известны случаи загиба лопастей винтов ТВД) и  подобных деформаций. Механизм такого воздействия молнии обусловлен, во-первых, действием пондеромоторных сил, рождаемых взаимодействием тока в канале молниевого разряда с токами, растекающимися по металлическим конструкциям ВС. Во-вторых, механическое воздействие на элементы конструкции оказывает ударная волна от молнии. Наличие на поверхности воздушного судна конденсата (влаги, льда) может  существенно усилить повреждение обшивки в результате электромеханического воздействия молнии, что подтвердили результаты экспериментальных исследований, проведенных на кафедре физики МГТУ ГА. Толщина слоя воды (как известно, гроза в подавляющем большинстве случаев сопровождается осадками) может быть достаточно большой, особенно на земле во время стоянки и руления, а также при взлете и во время посадки. При параметрах испытательного электрического разряда (амплитуда тока 50–60 кА, длительность первой полуволны 30 мкс), близких к средним параметрам натуральной молнии, поражающей воздушные суда, испытывались листовые образцы обшивки из алюминиевого сплава Д16АТ. При варьировании толщины слоя воды до 8 мм на образцах толщиной 1,5 мм образовывались вмятины глубиной до 2 мм и диаметром до 30 мм, при толщине образца 0,8 мм – глубиной свыше 10 мм и диаметром до 60–70 мм. Расчетные оценки показали, что наличие воды в несколько раз увеличивает электродинамическое давление на обшивку. С учетом упругой  составляющей такая деформация при ударе молнии может, во-первых, представлять опасность для устройств и коммуникаций, расположенных непосредственно под обшивкой. Также усиление электромеханического давления вкупе с ударной акустической волной, рождаемой молнией, может привести к сверхкритическим нагрузкам в элементах крепления обшивки. Все это должно быть учтено как на стадии проектирования воздушного судна, так и в процессе эксплуатации, в частности при послеполетном осмотре ВС, пораженного молнией

Бурение осадков оз. Каракель (долина р. Теберда) и перспективы реконструкции истории оледенения и климата голоцена на Кавказе

Lacustrine sediments represent an important data source for glacial and palaeoclimatic reconstructions. Having a number of certain advantages, they can be successfully used as a means of specification of glacier situation and age of moraine deposits, as well as a basis for detailed climatic models of the Holocene. The article focuses on the coring of sediments of Lake Kakakel (Western Caucasus) that has its goal to clarify the Holocene climatic history for the region, providing the sampling methods, lithologic description of the sediment core, obtained radiocarbon dating and the element composition of the sediments. The primary outlook over the results of coring of the sediments of the Lake Karakyol helped to reconsider the conventional opinion on the glacial fluctuations in the valley of Teberda and to assume the future possibility for high-definition palaeoclimatic reconstruction for Western Caucasus.Озёрные отложения – важный источник данных для реконструкции колебаний ледников и изменений климата. Рассмотрены первые результаты бурения осадков оз. Каракель (долина р. Теберда, Западный Кавказ), выполненного для реконструкции голоценовой истории оледенения и климата в регионе. Описаны методика отбора образцов и особенности стратиграфии керна донных отложений оз. Каракель, приведены три радиоуглеродные датировки, позволившие оценить скорости осадконакопления в верхней части толщи (поздний голоцен). Датировка нижнего слоя озёрных отложений – 11 700 л.н. (календарный возраст) – одновременно представляет собой оценку минимального возраста морены, подпруживающей оз. Каракель

Sensing, measuring and modelling the mechanical properties of sandstone

We present a hybrid framework for simulating the strength and dilation characteristics of sandstone. Where possible, the grain-scale properties of sandstone are evaluated experimentally in detail. Also, using photo-stress analysis, we sense the deviator stress (/strain) distribution at the microscale and its components along the orthogonal directions on the surface of a V-notch sandstone sample under mechanical loading. Based on this measurement and applying a grain-scale model, the optical anisotropy index K0 is inferred at the grain scale. This correlated well with the grain contact stiffness ratio K evaluated using ultrasound sensors independently. Thereafter, in addition to other experimentally characterised structural and grain-scale properties of sandstone, K is fed as an input into the discrete element modelling of fracture strength and dilation of the sandstone samples. Physical bulk scale experiments are also conducted to evaluate the load-displacement relation, dilation and bulk fracture strength characteristics of sandstone samples under compression and shear. A good level of agreement is obtained between the results of the simulations and experiments. The current generic framework could be applied to understand the internal and bulk mechanical properties of such complex opaque and heterogeneous materials more realistically in future

Еstimation of Therapeutic Effect of Endonasal Electrophorosis with Methylethylpyridinol in Partial Optic Nerve Atrophy

Purpose: to evaluate the therapeutic effect of the drug Emoxypin administered by the method of endonasal electrophoresis to patients with partial atrophy of the optic nerve (PAON).Patients and methods. The treatment was conducted in 43 patients, the average age was 53 ± 2 years, with partial optic nerve  atrophy of different etiology. The main group consisted of 22  patients who received Emoxypin by endonasal electrophoresis and a  comparison group of 21 people who received Emoxypin by  parabulbar injections. Each patient underwent ophthalmological  examination, which included: visometry, perimetry, refractometry,  biomicroscopy, ophthalmoscopy, examination of visual performance,  evaluation of the state of bulbar microcirculation (general  conjunctival index — OCI). In addition, electrophysiological studies  of the vision organ carried out: the critical frequency of flicker fusion  (CSFM) and the electrical sensitivity of the eye (EF).Results. The results of statistical analysis showed the effectiveness of the drug Emoksipin for the treatment of PAON by endonasal  electrophoresis and revealed improvement in visual functions:  widening the field of view to white, red and green colors, reducing  visual fatigue, improving electrophysiological parameters and bulbar microcirculation.Conclusion. Evaluation of the effectiveness of Emoxypin use by  endonasal electrophoresis with partial optic nerve atrophy of various  etiologies showed a statistically significant positive therapeutic effect (79 %) in the form of restoration of visual functions. With parabulbar injection of this medicine, as well as with endonasal electrophoresis  in 81 %, the field of view was widened from 5° to 25° in various  meridians, the number of relative cattle in the field of vision  decreased, and in both groups, there was an improvement in visual  performance. Among patients who underwent endonasal electrophoresis, no side effects were observed

Review of Nugayev's book "Reconstruction of Scientific Theory Change"

Nugayev’s book is one of the first Soviet monographs treating the theory change problem. The gist of epistemological model consists in consequent account of intertheoretical relations. His book is based on the works of Soviet authors, as well as on Western studies (K.R. Popper, T.S. Kuhn, I. Lakatos, P. Feyerabend et al.) Key words: epistemological model, Soviet philosophy, Western studie

RESIDUAL STRENGTH AND ENDURANCE OF ROD CONSTRUCTION ELEMENTS OF AIRCRAFT AFTER THE DAMAGE BY LIGHTNING-LIKE ELECTRICAL DISCHARGES

Caused by lightning damage to the external elements of construction of the aircraft, in the form of deformities, burn-through and erosive craters and also hidden defects in the affected area can cause a reduction in the strength of damaged parts. Fatigue tests of samples of rod construction elements damaged by lightning-like electrical discharges showed that for a symmetric cycle of variable loading at an amplitude of 100 kPa and a frequency of 50 Hz supply of fatigue strength decreased in 1,5-1,7 times, and fatigue life decreased in 25 times at local burns and in 70 times at annular burns. The main reason is education on the details of micro cracks in the area of erosive craters formed by discharge