873 research outputs found
Dark spot, Spiral waves and the SW Sex behaviour: it is all about UX Ursae Majoris
We present an analysis of time-resolved, medium resolution optical
spectroscopic observations of UX UMa in the blue (3920-5250 A) and red
(6100-7200 A) wavelength ranges, that were obtained in April 1999 and March
2008 respectively. The observed characteristics of our spectra indicate that UX
UMa has been in different states during those observations. The blue spectra
are very complex. They are dominated by strong and broad single-peaked emission
lines of hydrogen. The high-excitation lines of HeII 4686 and the Bowen blend
are quite strong as well. All the lines consist of a mixture of absorption and
emission components. Using Doppler tomography we have identified four distinct
components of the system: the accretion disc, the secondary star, the bright
spot from the gas stream/disc impact region, and the unique compact area of
absorption in the accretion disc seen as a dark spot in the lower-left quadrant
of the tomograms. In the red wavelength range, both the hydrogen (H_alpha) and
neutral helium (HeI 6678 and HeI 7065) lines were observed in emission and both
exhibited double-peaked profiles. Doppler tomography of these lines reveals
spiral structure in the accretion disc, but in contrast to the blue wavelength
range, there is no evidence for either the dark spot or the gas stream/disc
impact region emission, while the emission from the secondary star is weak.
During the observations in 1999, UX UMa showed many of the defining properties
of the SW Sex stars. However, all these features almost completely disappeared
in 2008. We have also estimated the radial velocity semi-amplitudes K_1 and K_2
and evaluated the system parameters of UX UMa. These estimates are inconsistent
with previous values derived by means of analysis of WD eclipse features in the
light curve in the different wavelength ranges.Comment: 16 pages, 9 figures, Accepted for publication by MNRA
Temperature and coupling dependence of the universal contact intensity for an ultracold Fermi gas
Physical properties of an ultracold Fermi gas in the temperature-coupling
phase diagram can be characterized by the contact intensity C, which enters the
pair-correlation function at short distances and describes how the two-body
problem merges into its surrounding. We show that the local order established
by pairing fluctuations about the critical temperature Tc of the superfluid
transition considerably enhances the contact C in a temperature range where
pseudogap phenomena are maximal. Our ab initio results for C in a trap compare
well with recently available experimental data over a wide coupling range. An
analysis is also provided for the effects of trap averaging on C.Comment: 5 pages, 5 figure
Improving mechanical properties of 18%Mn TWIP steels by cold rolling and annealing
The microstructures and mechanical properties of Fe-0.4C-18Mn and Fe-0.6C-18Mn steels subjected to large strain cold rolling followed by annealing werestudied. Cold rolling with a total reduction of 86% resulted in substantial strengthening at expense of plasticity. The yield strength and the ultimate tensile strength of above 1400MPa and 1600MPa,respectively,were achieved in both steels, whereas total elongation decreased below 30
Deformation mechanisms operating in TWIP/TRIP steels processed by warm to hot working
The mechanical properties of medium to high-Mn austenitic TWIP/TRIP steels subjected to warm to hot working were studied. The steel samples were processed by plate rolling at various temperatures ranging from 500 ◦C to 1150 ◦C. The deformation microstructures depend significantly on the rolling temperature. The discontinuous dynamic recrystallization readily developed during hot rolling at temperatures of T ≥ 800 ◦C, whereas the work hardened microstructures with high dislocation densities evolved by warm rolling at temperatures below 800 ◦
Исследование работы стеклопластиковых крепежных элементов в стеновых конструкциях
The article is devoted to the study of pull-out tests of fiberglass plastic dowels installed in the walls made of lightweight concrete. The authors have undertaken experimental tests of anchors in use on the construction site and conducted analysis of test results.Работа посвящена исследованию характеристик сцепления композитных стеклопластиковых дюбелей с легким бетоном. Авторами проведены экспериментальные испытания анкеров в натурных условияx на строительной площадке и выполнен анализ результатов испытаний
Superscaling in dilute Fermi gas and its relation to general properties of the nucleon momentum distribution in nuclei
The superscaling observed in inclusive electron scattering is described
within the dilute Fermi gas model with interaction between the particles. The
comparison with the relativistic Fermi gas (RFG) model without interaction
shows an improvement in the explanation of the scaling function in
the region , where the RFG result is . It is found
that the behavior of for depends on the particular
form of the general power-law asymptotics of the momentum distribution
at large . The best agreement with the empirical
scaling function is found for in agreement with the asymptotics
of in the coherent density fluctuation model where . Thus,
superscaling gives information about the asymptotics of and the NN
forces.Comment: 6 pages, 5 figures, accepted for publication in Physical Review
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