398 research outputs found
Revisiting the models of vibration screening process
This talk presents two approaches for modeling of the vibration screening process. The first approach is analytical. It models the screening process as a diffusion of undersize fraction taking into account the special term for vibration separation (the Brazil nut effect). The talk provides a solution of the corresponding partial differential equation. The solution in turn allows estimation of the screening performance dependence on both deterministic and stochastic factors as well as evaluation of the factors dominance conditions. The talk presents simple evaluation formulae for the screening process performance. The second approach is based on a simulation model. The model deals with monolayer dynamics. Embodying traditional concepts of vibration transportation, the approach introduces some novel techniques of evaluation of the effect of the granular particles shape. Taking into account the particle shape factor may significantly improve the modeling precision for nonspherical particles
An X-ray photoelectron spectroscopy study of uranyl-chitosan interaction
An X-ray photoelectron spectroscopy study of uranium sorption by spherically-granulated chitosan in sulphate solutions, as well as the study of the nature of the U(VI) - chitosan interaction was carried out in this work. The X-ray photoelectron spectroscopy analysis showed that the uranyl - chitosan interaction results in the formation of complexes with aminogroup nitrogen, and possibly chitin ring oxygens and free hydroxyl groups in the equatorial plane. Under the UHV in the spectrometer chamber, the uranyl-amin and uranyl-hyroxide bonds were shown to break and tetravalent uranium compounds were shown to form on the sample surface. Hydroxyl groups were shown to evaporate. The calculated DG0 = -1,3 kJ/mol can be an evidence of several concurrent processes, some of which require energy, as well as of the formation of a surface chemical compound
An X-ray photoelectron spectroscopy study of the products of the interaction of gaseous IrF6 with fine UO2F2
Nuclear fuel reprocessing by fluorination, a dry method of regeneration of spent nuclear fuel, uses UO2F2 for the separation of plutonium from gaseous mixtures. Since plutonium requires special treatment, IrF6 was used as a thermodynamic model of PuF6. The model reaction of the interaction of gaseous IrF6 with fine UO2F2 in the sorption column revealed a change of color of the sorption column contents from pale-yellow to gray and black, indicating the formation of products of such an interaction. The X-ray photoelectron spectroscopy study showed that the interaction of gaseous IrF6 with fine UO2F2 at 125 °C results in the formation of stable iridium compounds where the iridium oxidation state is close to Ir3+. The dependence of the elemental compositions of the layers in the sorption column on the penetration depth of IrF6 was established
XPS Study of Ion Irradiated and Unirradiated UO2 Thin Films
XPS determination of the oxygen coefficient k O =2+x and ionic (U 4+ , U 5+ and U 6+ )
composition of oxides UO 2+x formed on the surfaces of differently oriented (hkl) planes of thin
UO 2 films on LSAT (Al 10 La 3 O 51 Sr 14 Ta 7 ) and YSZ (yttria-stabilized zirconia) substrates was
performed. The U 4f and O 1s core-electron peak intensities as well as the U 5f relative intensity
before and after the 129 Xe 23+ and 238 U 31+ irradiations were employed. It was found that the
presence of uranium dioxide film in air results in formation of oxide UO 2+x on the surface with
mean oxygen coefficients k O in the range 2.07-2.11 on LSAT and 2.17-2.23 on YSZ substrates.
These oxygen coefficients depend on the substrate and weakly on the crystallographic
orientation.
On the basis of the spectral parameters it was established that uranium dioxide films
AP2,3 on the LSAT substrates have the smallest k O values, and from the XRD and EBSD results
it follows that these samples have a regular monocrystalline structure. The XRD and EBSD
results indicate that samples AP5-7 on the YSZ substrates have monocrystalline structure,
however, they have the highest k O values. The observed difference in the k O values, probably,
caused by the different nature of the substrates: the YSZ substrates provide 6.4% compressive
strain, whereas (001) LSAT substrates result only in 0.03% tensile strain in the UO 2 films.
129 Xe 23+ irradiation (92 MeV, 4.8 × 10 15 ions/cm 2 ) of uranium dioxide films on the LSAT
substrates was shown to destroy both long range ordering and uranium close environment, which
results in increase of uranium oxidation state and regrouping of oxygen ions in uranium close
environment. 238 U 31+ (110 MeV, 5 × 10 10 , 5 × 10 11 , 5 × 10 12 ions/cm 2 ) irradiations of uranium
dioxide films on the YSZ substrates were shown to form the lattice damage only with partial
destruction of the long range ordering
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 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 deg
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
XPS Study of Ion Irradiated and Unirradiated UO2 Thin Films.
XPS determination of the oxygen coefficient kO = 2 + x and ionic (U(4+), U(5+), and U(6+)) composition of oxides UO2+x formed on the surfaces of differently oriented (hkl) planes of thin UO2 films on LSAT (Al10La3O51Sr14Ta7) and YSZ (yttria-stabilized zirconia) substrates was performed. The U 4f and O 1s core-electron peak intensities as well as the U 5f relative intensity before and after the (129)Xe(23+) and (238)U(31+) irradiations were employed. It was found that the presence of uranium dioxide film in air results in formation of oxide UO2+x on the surface with mean oxygen coefficients kO in the range 2.07-2.11 on LSAT and 2.17-2.23 on YSZ substrates. These oxygen coefficients depend on the substrate and weakly on the crystallographic orientation. On the basis of the spectral parameters it was established that uranium dioxide films AP2,3 on the LSAT substrates have the smallest kO values, and from the XRD and EBSD results it follows that these samples have a regular monocrystalline structure. The XRD and EBSD results indicate that samples AP5-7 on the YSZ substrates have monocrystalline structure; however, they have the highest kO values. The observed difference in the kO values was probably caused by the different nature of the substrates: the YSZ substrates provide 6.4% compressive strain, whereas (001) LSAT substrates result only in 0.03% tensile strain in the UO2 films. (129)Xe(23+) irradiation (92 MeV, 4.8 × 10(15) ions/cm(2)) of uranium dioxide films on the LSAT substrates was shown to destroy both long-range ordering and uranium close environment, which results in an increase of uranium oxidation state and regrouping of oxygen ions in uranium close environment. (238)U(31+) (110 MeV, 5 × 10(10), 5 × 10(11), 5 × 10(12) ions/cm(2)) irradiations of uranium dioxide films on the YSZ substrates were shown to form the lattice damage only with partial destruction of the long-range ordering.The irradiation experiment was performed at the Grand Accelé rateur National d ́ ’Ions Lourds (GANIL) Caen, France, and supported by the French Network EMIR. The support in planning and execution of the experiment by the CIMAPCIRIL and the GANIL staff, especially I. Monnet, C. Grygiel, T. Madi, and F. Durantel, is much appreciated. The work was supported by RFBR grant no. 16-03-00914-a and partially supported by M.V. Lomonosov Moscow State University Program of Development. A.J.P. acknowledges funding from the UK EPSRC (grant EP/I036400/1) and Radioactive Waste Management Ltd. (formerly the Radioactive Waste Management Directorate of the UK Nuclear Decommissioning Authority, contract NPO004411A-EPS02), a maintenance
grant from the Russian Foundation for Basic Research (projects 13-03-90916) and CSAR bursary. Thanks are given to A.M. Adamska, G.I. Lampronti, V.A. Lebedev, P.G. Martin, L. Payne, and A.A. Shiryaev for their help in characterization of the samples
Impulsive Fermi magnon-phonon resonance in antiferromagnetic
Understanding spin-lattice interactions in antiferromagnets is one of the
most fundamental issues at the core of the recently emerging and booming fields
of antiferromagnetic spintronics and magnonics. Recently, coherent nonlinear
spin-lattice coupling was discovered in an antiferromagnet which opened the
possibility to control the nonlinear coupling strength and thus showing a novel
pathway to coherently control magnon-phonon dynamics. Here, utilizing intense
narrow band terahertz (THz) pulses and tunable magnetic fields up to 7 T, we
experimentally realize the conditions of the Fermi magnon-phonon resonance in
antiferromagnetic . These conditions imply that both the spin and the
lattice anharmonicities harvest energy transfer between the subsystems, if the
magnon eigenfrequency is twice lower than the frequency of the phonon
. Performing THz pump-infrared probe spectroscopy in conjunction
with simulations, we explore the coupled magnon-phonon dynamics in the vicinity
of the Fermi-resonance and reveal the corresponding fingerprints of an
impulsive THz-induced response. This study focuses on the role of nonlinearity
in spin-lattice interactions, providing insights into the control of coherent
magnon-phonon energy exchange
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