469 research outputs found
Time evolution of galactic warps in prolate haloes
A recent observation with the Hipparcos satellite and some numerical
simulations imply that the interaction between an oblate halo and a disc is
inappropriate for the persistence of galactic warps. Then, we have compared the
time evolution of galactic warps in a prolate halo with that in an oblate halo.
The haloes were approximated as fixed potentials, while the discs were
represented by N-body particles. We have found that the warping in the oblate
halo continues to wind up, and finally disappears. On the other hand, for the
prolate halo model, the precession rate of the outer disc increases when the
precession of the outer disc recedes from that of the inner disc, and vice
versa. Consequently, the warping in the prolate halo persisted to the end of
the simulation by retaining the alignment of the line of nodes of the warped
disc. Therefore, our results suggest that prolate haloes could sustain galactic
warps. The physical mechanism of the persistence of warp is discussed on the
basis of the torque between a halo and a disc and that between the inner and
outer regions of the disc.Comment: 8 pages, 8 figures. Accepted for publication in MNRA
Development of Non-intrusive Fluid Thermometry in Air with Temperature-sensitive Particles by Two-gated Method
A non-intrusive fluid thermometry technique using in-house temperature-sensitive particles by means of two-gated method was demonstrated. In the present research, phosphorescence signals were integrated over exposure time that was much longer than the phosphorescence, thus lower frame rate could be used to avoid faster frame rate which would have compromised spatial resolution. Ruthenium-based temperature-sensitive particles were scattered in a heated turbulent jet emanating from a pipe and its phosphorescence was captured by a sCMOS camera in double-frame mode. Calibration function for temperature vs. intensity ratio between 1st and 2nd frame of the double-frame images was generated by two means: static calibration using a sample on a temperature-controlled surface and dynamic calibration using the potential core of the heated jet. Calibration function of the dynamic case was used to convert the raw images to instantaneous thermal captions, and the thermal captions exhibited typical flow characteristics of a heated turbulent pipe jet such as hot potential core, and low-temperature shear layer with fine-scale structures. The average temperature field of the present demonstration agreed well with temperature distribution measured by conventional T-type thermocouple, confirming the accuracy of the technique. Using 95%-confidence level, the uncertainty in temperature was evaluated to be ±4.9°C at the jet temperature of 96.3°C. Future work is to investigate the factors that contribute to the uncertainty to improve accuracy and precision of the technique
Self-Energy Effects on the Low- to High-Energy Electronic Structure of SrVO3
The correlated electronic structure of SrVO3 has been investigated by
angle-resolved photoemission spectroscopy using in-situ prepared thin films.
Pronounced features of band renormalization have been observed: a sharp kink
~60 meV below the Fermi level (EF) and a broad so-called "high-energy kink"
~0.3 eV below EF as in the high-Tc cuprates although SrVO3 does not show
magnetic fluctuations. We have deduced the self-energy in a wide energy range
by applying the Kramers-Kronig relation to the observed spectra. The obtained
self-energy clearly shows a large energy scale of ~0.7 eV which is attributed
to electron-electron interaction and gives rise to the ~0.3 eV "kink" in the
band dispersion as well as the incoherent peak ~1.5eV below EF. The present
analysis enables us to obtain consistent picture both for the incoherent
spectra and the band renormalization.Comment: 5 pages, 3 figure
An energy scale directly related to superconductivity in the high- cuprate superconductors: Universality from the Fermi arc picture
We have performed a temperature dependent angle-resolved photoemission
spectroscopy (ARPES) study of the tri-layer high- cuprate superconductor
(HTSC) BiSrCaCuO (Bi2223), and have shown that
the \textquotedblleft effective\textquotedblright superconducting (SC) gap
defined at the end point of the Fermi arc and the (=
110 K) approximately satisfies the weak-coupling BCS-relationship
2 = 4.3. Combining this result with previous
ARPES results on single- and double-layer cuprates, we show that the
relationship between 2 = 4.3 holds for various
HTSCs. Furthermore, at , the quasi-patricle width at the end
point of the Fermi arc is found to coincide with , consistent
with the context of Planckian dissipation.Comment: 5 pages, 4 figure
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