6,807 research outputs found
Modeling of "groove" rolling defect on internal surface of pipes at lengthwise rolling
The research has been conducted in pipe forming at rolling off by lengthwise rolling mill with stub mandrel; the patterns of change in dimensionless parameters were determined, which characterize deformation in side angle depending on http://www.multitran.ru/c/m.exe?t=424995_2_1elongation ratio. The model of formation of lengthwise groove on internal surface of pipes has been proposed
Space-Time Description of Scalar Particle Creation by a Homogeneous Isotropic Gravitational Field
We give the generalization of the method of the space-time description of
particle creation by a gravitational field for a scalar field with nonconformal
coupling to the curvature. The space-time correlation function is obtained for
a created pair of the quasi-particles, corresponding to a diagonal form of the
instantaneous Hamiltonian. The case of an adiabatic change of the metric of
homogeneous isotropic space is analyzed. We show that the created pairs of
quasi-particles in de Sitter space should be interpreted as pairs of virtual
particles.Comment: 7 pages, 3 figure
Electronic structure of FeSe monolayer superconductors
We review a variety of theoretical and experimental results concerning
electronic band structure of superconducting materials based on FeSe
monolayers. Three type of systems are analyzed: intercalated FeSe systems
A_xFe_2Se_{2-x}S_x and [Li_{1-x}Fe_xOH]FeSe as well as the single FeSe layer
films on SrTiO_3 substrate. We present the results of detailed first principle
electronic band structure calculations for these systems together with
comparison with some experimental ARPES data. The electronic structure of these
systems is rather different from that of typical FeAs superconductors, which is
quite significant for possible microscopic mechanism of superconductivity. This
is reflected in the absence of hole pockets of the Fermi surface at
\Gamma-point in Brillouin zone, so that there are no "nesting" properties of
different Fermi surface pockets. LDA+DMFT calculations show that correlation
effects on Fe-3d states in the single FeSe layer are not that strong as in most
of FeAs systems. As a result, at present there is no theoretical understanding
of the formation of rather "shallow" electronic bands at M points. LDA
calculations show that the main difference in electronic structure of FeSe
monolayer on SrTiO_3 substrate from isolated FeSe layer is the presence of the
band of O-2p surface states of TiO_2 layer on the Fermi level together with
Fe-3d states, which may be important for understanding the enhanced T_c values
in this system. We briefly discuss the implications of our results for
microscopic models of superconductivity.Comment: 21 pages, 13 figures, minor typos correcte
Polarization of Thermal X-rays from Isolated Neutron Stars
Since the opacity of a magnetized plasma depends on polarization of
radiation, the radiation emergent from atmospheres of neutron stars with strong
magnetic fields is expected to be strongly polarized. The degree of linear
polarization, typically ~10-30%, depends on photon energy, effective
temperature and magnetic field. The spectrum of polarization is more sensitive
to the magnetic field than the spectrum of intensity. Both the degree of
polarization and the position angle vary with the neutron star rotation period
so that the shape of polarization pulse profiles depends on the orientation of
the rotational and magnetic axes. Moreover, as the polarization is
substantially modified by the general relativistic effects, observations of
polarization of X-ray radiation from isolated neutron stars provide a new
method for evaluating the mass-to-radius ratio of these objects, which is
particularly important for elucidating the properties of the superdense matter
in the neutron star interiors.Comment: 7 figures, to be published in Ap
Адаптивний алгоритм реалізації постійного зниження літака
In this article we describe the main aspects of continuous descent operations (CDO). Advantages of CDO application are discussing. CDO can enable several specific strategic objectives to be met and should therefore be considered for inclusion within any airspace concept or redesign. Considered also is the general adaptive algorithm of the forecast of continuous descent path and described influence of wind on the flight pathOписываются основные аспекты применения процедуры непрерывного снижения (CDO). Обсуждаются преимущества применения CDO. Данная процедура может способствовать достижению ряда конкретных стратегических целей и поэтому должна предусматриваться в любой концепции или изменяемой структуре воздушного пространства. Кроме того, в работе рассмотрен общий адаптивный алгоритм прогноза траектории непрерывного снижения и описано влияние ветра на данную траекториюOписано основні аспекти застосування процедури неперервного зниження (CDO). Обговорюються переваги застосування CDO. Дана процедура може сприяти досягненню цілого ряду конкретних стратегічних цілей і має передбачуватись у будь-якій концепції чи змінній структурі повітряного простору. Також розглянуто загальний адаптивний алгоритм урахування впливу вітру на траєкторію польоту літака й описано вплив вітру на дану траєкторі
An anomalous subauroral red arc on 4 August, 1972: comparison of ISIS-2 satellite data with numerical calculations
International audienceThis study compares the Isis II satellite measurements of the electron density and temperature, the integral airglow intensity and volume emission rate at 630 nm in the SAR arc region, observed at dusk on 4 August, 1972, in the Southern Hemisphere, during the main phase of the geomagnetic storm. The model results were obtained using the time dependent one-dimensional mathematical model of the Earth's ionosphere and plasmasphere (the IZMIRAN model). The major enhancement to the IZMIRAN model developed in this study to explain the two component 630 nm emission observed is the analytical yield spectrum approach to calculate the fluxes of precipitating electrons and the additional production rates of N+2, O+2, O+(4S), O+(2D), O?(2P), and O+(2P) ions, and O(1D) in the SAR arc regions in the Northern and Southern Hemispheres. In order to bring the measured and modelled electron temperatures into agreement, the additional heating electron rate of 1.05 eV cm?3 s?1 was added in the energy balance equation of electrons at altitudes above 5000 km during the main phase of the geomagnetic storm. This additional heating electron rate determines the thermally excited 630 nm emission observed. The IZMIRAN model calculates a 630 nm integral intensity above 350 km of 4.1 kR and a total 630 nm integral intensity of 8.1 kR, values which are slightly lower compared to the observed 4.7 kR and 10.6 kR. We conclude that the 630 nm emission observed can be explained considering both the soft energy electron excited component and the thermally excited component. It is found that the inclusion of N2(v > 0) and O2(v > 0) in the calculations of the O+(4S) loss rate improves the agreement between the calculated Ne and the data on 4 August, 1972. The N2(v > 0) and O2(v > 0) effects are enough to explain the electron density depression in the SAR arc F-region and above F2 peak altitude. Our calculations show that the increase in the O++N2 rate factor due to the vibrationally excited nitrogen produces the 5?19% reductions in the calculated quiet daytime peak density and the 16?24% decrease in NmF2 in the SAR arc region. The increase in the O++N2 loss rate due to vibrationally excited O2 produces the 7?26% decrease in the calculated quiet daytime peak density and the 12?26% decrease in NmF2 in the SAR arc region. We evaluated the role of the electron cooling rates by low-lying electronic excitation of O2(a1?g) and O2(b1?g+), and rotational excitation of O2, and found that the effect of these cooling rates on Te can be considered negligible during the quiet and geomagnetic storm period 3-4 August, 1972. The energy exchange between electron and ion gases, the cooling rate in collisions of O(3P) with thermal electrons with excitation of O(1D), and the electron cooling rates by vibrational excitation of O2 and N2 are the largest cooling rates above 200 km in the SAR arc region on 4 August, 1972. The enhanced IZMIRAN model calculates also number densities of N2(B3∏g+),N2(C3∏u), and N2(A3?u+) at several vibrational levels, O(1S), and the volume emission rate and integral intensity at 557.7 nm in the region between 120 and 1000 km. We found from the model that the integral intensity at 557.7 nm is much less than the integral intensity at 630 nm
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