898 research outputs found
Warped product approach to universe with non-smooth scale factor
In the framework of Lorentzian warped products, we study the
Friedmann-Robertson-Walker cosmological model to investigate non-smooth
curvatures associated with multiple discontinuities involved in the evolution
of the universe. In particular we analyze non-smooth features of the spatially
flat Friedmann-Robertson-Walker universe by introducing double discontinuities
occurred at the radiation-matter and matter-lambda phase transitions in
astrophysical phenomenology.Comment: 10 page
Relationship between frequencies of pressure oscillations and rotor speed under rotating stall
The correlation between the frequencies of pressure oscillation ωosc and the rotor speed (frequencies of rotor rotation ωRR) under established rotating stall were determined by three methods: directly from the time diagram of the oscillation process, from the behavior diagram of parameters in space and time and from frequency characteristics. In total accordance with the Theory of Nonlinear Oscillation, by all methods of analysis, the links are in the form of integer ratios: ωosc / ωRR = 1:2 (for n/ nd= 0.6, where n - rotor speed in the experiment and nd- rotor speed from data-sheet) and ωosc / ωRR = 3:7 (for n/ nd = 0.8 and 0.95). The phases of parameter oscillations in the transverse cross-section are equal to the sensor angles in compressor stator. This is in agreement with the theoretical concept of single-cell configurations of rotating stall
Two-dimensional steady nonviscous and viscous compressible flow through a system of equidistant blades
Orbital Selective Magnetism in the Spin-Ladder Iron Selenides BaKFeSe
Here we show that the 2.80(8) {\mu}B/Fe block antiferromagnetic order of
BaFe2Se3 transforms into stripe antiferromagnetic order in KFe2Se3 with a
decrease in moment to 2.1(1) {\mu}B/Fe. This reduction is larger than expected
from the change in electron count from Ba to K, and occurs with
the loss of the displacements of Fe atoms from ideal positions in the ladders,
as found by neutron pair distribution function analysis. Intermediate
compositions remain insulating, and magnetic susceptibility measurements show a
suppression of magnetic order and probable formation of a spin-glass. Together,
these results imply an orbital-dependent selection of magnetic versus bonded
behavior, driven by relative bandwidths and fillings.Comment: Final versio
Quantum Corrections to the Reissner-Nordstrom and Kerr-Newman Metrics: Spin 1
A previous evaluation of one-photon loop corrections to the energy-momentum
tensor has been extended to particles with unit spin and speculations are
presented concerning general properties of such forms.Comment: 21 pages, 1 Figur
Involving older people in the design of an innovative technological system promoting active aging: the Saapho project
Active Ageing refers to the optimization process in health, social engagement, and security opportunities as people age. The demand to introduce technology to improve older people’s quality of life is progressively increasing. The objective of the SAAPHO project is to support Active Aging by assisting older people to participate in society, preserving their independence and dignity through the application of innovative Information and Communication Technologies (ICT)-based solutions. SAAPHO creates a usable system that covers health, safety and social needs of end-users taking into account their preferences in the design of the system behaviour and architecture. Questionnaires and focus groups were run during the product design early stages to guarantee this. After completing the first year prototype, controlled sessions using the SAAPHO platform were performed with older people to study its usability. This article presents the general results of older people’s participation in the design of SAAPHO system after completing the first year prototype.Peer Reviewe
Black string and velocity frame dragging
We investigate velocity frame dragging with the boosted Schwarzschild black
string solution and the boosted Kaluza-Klein bubble solution, in which a
translational symmetry along the boosted -coordinate is implemented. The
velocity frame dragging effect can be nullified by the motion of an observer
using the boost symmetry along the coordinate if it is not compact.
However, in spacetime with the compact coordinate, we show that the effect
cannot be removed since the compactification breaks the global Lorentz boost
symmetry. As a result, the comoving velocity is dependent on and the
momentum parameter along the coordinate becomes an observer independent
characteristic quantity of the black string and bubble solutions. The dragging
induces a spherical ergo-region around the black string.Comment: 8 pages, no figure, some correction
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