223 research outputs found
Effects of Sliding Velocity and Thermal Conduction of the Tool on X20Cr4 Steel Friction Coefficient and Structure in Nanostructuring Burnishing
The developmental study has succeeded in finding how the sliding velocity of an indenter affects the friction coefficient and changes the structure and phase state in the surface layer of a X20Cr13 stainless steel when nanostructuring burnishing is done with a tool with no heat removal and, alternatively, when the tool is equipped with a cooling system. It has been shown that structural dispersion of the treated material results in obtaining 20⋯80 nm nanocrystallites if the friction coefficient of the spherical synthetic diamond indenter is within 0.15⋯0.18 nm. Application of a compact cooling system, based on Peltier's thermoelectric module, made it possible to stabilize the friction coefficient at 0.17 and to increase the sliding velocity from 13 m/min, this being the case of no heat removal, to 45 m/min in the case when the cooling system having a cooling performance of 120 W was used. TEM and SEM analyses of the surface layer structure confirmed that there is a correlation between the friction coefficient and the size of nanocrystallites and the thickness of the dispersed layer. EBSD analysis of the structure showed that a maximum permissible sliding velocity can be established as referenced to the nucleation and growth of γ-phase grains in the nanostructured layer caused by heating of the material under deformation and reaching the temperature beyond the point α→γ phase transition as well as by behavior of dynamic recrystallization. It was established that the heat removal ensures suppression of dynamic recrystallization when the sliding velocity is increased up to 50 m/min. © 2018 Published under licence by IOP Publishing Ltd
Noncommutative geometry and stochastic processes
The recent analysis on noncommutative geometry, showing quantization of the
volume for the Riemannian manifold entering the geometry, can support a view of
quantum mechanics as arising by a stochastic process on it. A class of
stochastic processes can be devised, arising as fractional powers of an
ordinary Wiener process, that reproduce in a proper way a stochastic process on
a noncommutative geometry. These processes are characterized by producing
complex values and so, the corresponding Fokker-Planck equation resembles the
Schroedinger equation. Indeed, by a direct numerical check, one can recover the
kernel of the Schroedinger equation starting by an ordinary Brownian motion.
This class of stochastic processes needs a Clifford algebra to exist. In four
dimensions, the full set of Dirac matrices is needed and the corresponding
stochastic process in a noncommutative geometry is easily recovered as is the
Dirac equation in the Klein-Gordon form being it the Fokker--Planck equation of
the process.Comment: 16 pages, 2 figures. Updated a reference. A version of this paper
will appear in the proceedings of GSI2017, Geometric Science of Information,
November 7th to 9th, Paris (France
Random Forest identification of the thin disk, thick disk and halo Gaia-DR2 white dwarf population
Gaia-DR2 has provided an unprecedented number of white dwarf candidates of
our Galaxy. In particular, it is estimated that Gaia-DR2 has observed nearly
400,000 of these objects and close to 18,000 up to 100 pc from the Sun. This
large quantity of data requires a thorough analysis in order to uncover their
main Galactic population properties, in particular the thin and thick disk and
halo components. Taking advantage of recent developments in artificial
intelligence techniques, we make use of a detailed Random Forest algorithm to
analyse an 8-dimensional space (equatorial coordinates, parallax, proper motion
components and photometric magnitudes) of accurate data provided by Gaia-DR2
within 100 pc from the Sun. With the aid of a thorough and robust population
synthesis code we simulated the different components of the Galactic white
dwarf population to optimize the information extracted from the algorithm for
disentangling the different population components. The algorithm is first
tested in a known simulated sample achieving an accuracy of 85.3%. Our
methodology is thoroughly compared to standard methods based on kinematic
criteria demonstrating that our algorithm substantially improves previous
approaches. Once trained, the algorithm is then applied to the Gaia-DR2 100 pc
white dwarf sample, identifying 12,227 thin disk, 1,410 thick disk and 95 halo
white dwarf candidates, which represent a proportion of 74:25:1, respectively.
Hence, the numerical spatial densities are , and
for the thin disk, thick disk and
halo components, respectively. The populations thus obtained represent the most
complete and volume-limited samples to date of the different components of the
Galactic white dwarf population.Comment: 18 pages, 11 figures and 3 tables. Accepted for publication in MNRA
On Albanese torsors and the elementary obstruction
We show that the elementary obstruction to the existence of 0-cycles of
degree 1 on an arbitrary variety X (over an arbitrary field) can be expressed
in terms of the Albanese 1-motives associated with dense open subsets of X.
Arithmetic applications are given
Crystal Undulator As A Novel Compact Source Of Radiation
A crystalline undulator (CU) with periodically deformed crystallographic
planes is capable of deflecting charged particles with the same strength as an
equivalent magnetic field of 1000 T and could provide quite a short period L in
the sub-millimeter range. We present an idea for creation of a CU and report
its first realization. One face of a silicon crystal was given periodic
micro-scratches (grooves), with a period of 1 mm, by means of a diamond blade.
The X-ray tests of the crystal deformation have shown that a sinusoidal-like
shape of crystalline planes goes through the bulk of the crystal. This opens up
the possibility for experiments with high-energy particles channeled in CU, a
novel compact source of radiation. The first experiment on photon emission in
CU has been started at LNF with 800 MeV positrons aiming to produce 50 keV
undulator photons.Comment: Presented at PAC 2003 (Portland, May 12-16
NANOSTRUCTURING OF SURFACE LAYER OF 1.3505 STEEL BY WEDGE CYLINDRICAL TOOL
This paper discusses the issues of normal load during burnishing by a wedge cylindrical tool that influences the hardening of the 1.3505 steel surface according to the criteria of microhardness and thickness of nanostructuring layer. It has been established that burnishing with a normal force of 200 and 250 N provides formation of a nanostructured layer with a 4,3–5,5 µm thickness and a maximum micro-hardness of 1120–1170 HV0,05.В работе рассмотрены вопросы влияния нормальной нагрузки при выглаживании клиновым цилиндрическим инструментом на упрочнение поверхности стали ШХ15 по критериям микротвердости и толщины наноструктурированного слоя. Установлено, что выглаживание с нормальной силой 200 и 250 Н обеспечивает формирование наноструктурированного слоя толщиной 4,3–5,5 мкм с максимальной микротвердостью 1120–1170 HV0,05
Effects of interatomic interaction on cooperative relaxation of two-level atoms
We study effects of direct interatomic interaction on cooperative processes
in atom-photon dynamics. Using a model of two-level atoms with Ising-type
interaction as an example, it is demonstrated that interparticle interaction
combined with atom-field coupling can introduce additional interatomic
correlations acting as a phase synchronizing factor. For the case of weakly
interacting atoms with , where is the interparticle
coupling constant and is the atomic frequency, dynamical regimes of
cooperative relaxation of atoms are analyzed in Born-Markov approximation both
numerically and using the mean field approximation. We show that interparticle
correlations induced by the direct interaction result in inhibition of
incoherent spontaneous decay leading to the regime of collective pulse
relaxation which differs from superradiance in nature. For superradiant
transition, the synchronizing effect of interatomic interaction is found to
manifest itself in enhancement of superradiance. When the interaction is strong
and , one-partice one-photon transitions are excluded and
transition to the regime of multiphoton relaxation occurs. Using a simple model
of two atoms in a high-Q single mode cavity we show that such transition is
accompanied by Rabi oscillations involving many-atom multiphoton states.
Dephasing effect of dipole-dipole interaction and solitonic mechanism of
relaxation are discussed.Comment: 34 pages, 8 figure
ИСПОЛЬЗОВАНИЕ ФЛУОРИМЕТРИИ В БЛИЖНЕЙ ИК-ОБЛАСТИ С ФОТОГРАФИЧЕСКОЙ РЕГИСТРАЦИЕЙ СИГНАЛА В МЕТОДЕ «ОТПЕЧАТКОВ ПАЛЬЦЕВ» С ДОБАВКОЙ ФЛУОРОФОРА К ОБЪЕКТУ: ДИСКРИМИНАЦИЯ ЯБЛОЧНЫХ СОКОВ
The application of dyes, that fluoresce in the near infrared (NIR, 700-800 nm) region, for the recognition of samples using a fingerprinting method with the addition of fluorophores to the samples (“fluorescent eye”) is proposed. The technique has been successfully applied to the classification of samples of various nature. In the current work, this strategy has been tested on the example of discrimination of 17 samples of apple juice from different manufacturers, purchased at different times. An indolenine series heptamethine carbocyanine dye in the presence of surfactants was used as the added fluorophore, red LEDs were used as an excitation source, and the signal was recorded using a digital camera with an additional IR filter installed; a spectrofluorimeter with a 96-well plate accessory was used to record the spectra. Photographic images were processed using Unscrambler X and Excel software. The results were presented using the following coordinates: intensity of NIR fluorescence - intensity of visible light reflection (using the photographic images). It was found that such presentation allowed the samples to be divided into groups associated with the manufacturer. We have also obtained intrinsic fluorescence spectra, including those with the addition of NIR dye, and these results were processed by the principal component analysis. It was possible to distinguish 5–6 groups of samples by their intrinsic emission, not counting the blank, while the spectra with the addition of the dye allowed to isolate the largest number of groups of samples (9). At the same time, the classification using spectra did not allow juices to be grouped by the producer. Also, obtaining photographs using a visualizer was easier and faster than recording the fluorescence spectra. The joint processing of emission spectra and photographs did not improve the quality of discrimination.Keywords: fingerprinting method, NIR fluorimetry, apple juice, principal component analysisDOI: http://dx.doi.org/10.15826/analitika.2022.26.1.005E.V. Skorobogatov, I.A. Stepanova, V.S. Orekhov, M.K. Beklemishev Department of Chemistry, Lomonosov Moscow State University, Russin Federation, 119991, GSP-1, Moscow, Leninskie gory, 1, building 3Предложено использовать красители, флуоресцирующие в ближней ИК (БИК) области спектра (700–800 нм), для распознавания объектов методом «отпечатков пальцев», основанным на добавке флуорофоров к объекту («флуоресцентный глаз»). Метод успешно применяется в классификации объектов различной природы. В данной работе метод опробован на примере дискриминации 17 образцов яблочного сока разных производителей, выпущенных в разное время. В качестве добавляемого флуорофора использовали гептаметиновый карбоцианиновый краситель индоленинового ряда в присутствии ПАВ, в качестве источника излучения – красные светодиоды, а сигнал регистрировали с помощью цифрового фотоаппарата с дополнительным ИК-светофильтром; для записи спектров применяли спектрофлуориметр с приставкой для 96-луночного флуориметрического планшета. Фотографические изображения обрабатывали с помощью стандартного программного обеспечения Unscrambler X и Excel. Результаты представили в координатах: интенсивность БИК-флуоресценции – интенсивность отражения видимого света (с использованием соответствующих фотографий). Обнаружили, что такое представление позволяет разделить образцы на группы, связанные с производителем. Получали также спектры собственной флуоресценции, в том числе с добавкой БИК-красителя, обрабатывая эти результаты методом главных компонент. По собственной эмиссии можно выделить 5–6 групп образцов, не считая контрольного, тогда как по спектрам с добавкой красителя удается добиться выделения наибольшего числа групп образцов (девять). При этом классификация с использованием спектров не позволяет группировать соки по производителям. Кроме того, получение фотографий с помощью визуализатора проще и экспресснее, чем регистрация спектров флуоресценции. Совместная обработка эмиссионных спектров и фотографий не позволяет повысить качество дискриминации образцов.Ключевые слова: метод «отпечатков пальцев», флуориметрия в ближней ИК-области, яблочный сок, метод главных компонентDOI: http://dx.doi.org/10.15826/analitika.2022.26.1.00
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