63 research outputs found
Period Measurement of AGB Stars in the Outer Galactic Disk
Light variation of the 47 AGB star candidates in the outer Galactic disk has
been monitored at I-band for 5 years. Periods were determined well for 18 of
them and less reliably for the other 25. The average period of the objects is
then 500 days. According to the period-luminosity relation, the mean luminosity
of the sample stars is 10000 \LO. Based on the absolute luminosity derived
from the period-luminosity relation and the apparent luminosity from the
observation, the distances to the objects are determined. The distances
calculated are slightly greater than those obtained previously on the
assumption of constant luminosity of 8000 \LO. In addition, SiO maser
emission was detected for most of the observed objects so that their radial
velocities were known accurately. With the assumption of circular rotation in
the Galactic disk, the rotation curve and Oort's constants were derived.Comment: 13 pages including 4 tables, and 13 postscript figures. Accepted for
PASJ (Publication of the Astronomical Society of Japan
Expanding selfsimilar solutions of a crystalline flow with applications to contour figure analysis
A numerical method for obtaining a crystalline flow starting from a general polygon is presented. A crystalline flow is a polygonal flow and can be regarded as a discrete version of a classical curvature flow. In some cases, new facets may be created instantaneously and their facet lengths are governed by a system of singular ordinary differential equations(ODEs). The proposed method solves the system of the ODEs numerically by using expanding selfsimilar solutions for newly created facets. The computation method is applied to a multi-scale analysis of a contour figure
Molecular simulations on the chirality preference of single-walled carbon nanotubes upon ductile behavior under tensile stress at high temperature
Molecular dynamics simulations were carried out on the ductile behavior of single-walled carbon nanotubes (SWNTs) under tensile stress by moving both ends at constant velocity at high temperature. The (10,10) armchair-SWNT resulted in plastic elongation through the sequential Stone-Wales (S-W) transformation, and the chirality changed keeping the two indices equal by alternately taking two dislocation directions with Burgers vectors bâ=(1,0) and (0,1) instead of choosing only one of them toward zigzag-chirality with one index equal to zero. The comparison in the activation and formation energies for the two directions revealed that the torsional strain induced by the preceding S-W sequence was the main cause of this alternating choice.Hirotoshi Deguchi, Yasutaka Yamaguchi, Kaori Hirahara, Yoshikazu Nakayama. Molecular simulations on the chirality preference of single-walled carbon nanotubes upon ductile behavior under tensile stress at high temperature. Chemical Physics Letters, Volume 503, Issues 4â6, 2011, Pages 272-276, https://doi.org/10.1016/j.cplett.2011.01.023
Expanding selfsimilar solutions of a crystalline flow with applications to contour figure analysis
AbstractA numerical method for obtaining a crystalline flow starting from a general polygon is presented. A crystalline flow is a polygonal flow and can be regarded as a discrete version of a classical curvature flow. In some cases, new facets may be created instantaneously and their facet lengths are governed by a system of singular ordinary differential equations (ODEs). The proposed method solves the system of the ODEs numerically by using expanding selfsimilar solutions for newly created facets. The computation method is applied to a multi-scale analysis of a contour figure
Pressure Study of BiS2-Based Superconductors Bi4O4S3 and La(O,F)BiS2
We report the electrical resistivity measurements under pressure for the
recently discovered BiS2-based layered superconductors Bi4O4S3 and La(O,F)BiS2.
In Bi4O4S3, the transition temperature Tc decreases monotonically without a
distinct change in the metallic behavior in the normal state. In La(O,F)BiS2,
on the other hand, Tc initially increases with increasing pressure and then
decreases above ? 1 GPa. The semiconducting behavior in the normal state is
suppressed markedly and monotonically, whereas the evolution of Tc is
nonlinear. The strong suppression of the semiconducting behavior without doping
in La(O,F)BiS2 suggests that the Fermi surface is located in the vicinity of
some instability. In the present study, we elucidate that the superconductivity
in the BiS2 layer favors the Fermi surface at the boundary between the
semiconducting and metallic behaviors.Comment: 4 pages, 6 figures, Accepted for publication in J. Phys. Soc. Jp
SiO Maser Survey of the Inner Bar of the Galactic Bulge
We surveyed 291 MSX/2MASS infrared objects in the 7 x 2 deg area of the
galactic center in the 43 GHz SiO J=1--0 v=1 and 2 maser lines, obtaining
accurate radial velocities of 163 detected objects. The surveyed area is the
region where the IRAS catalog is incomplete due to contamination by high source
density. The objects in the present MSX/2MASS sample were chosen to have
similar infrared characteristics to those of the previous SiO-maser-survey
samples based on the color selected IRAS sources. The sampling based on the
2MASS catalog causes a bias to the foreside objects of the bulge due to heavy
obscuration by interstellar dust; the detections are considerably leaned on the
V_{lsr}<0 side. The l--v diagram reveals two conspicuous features, which were
not present or tenuous in the previous studies: one feature indicating a linear
velocity increase with longitude with |l|<1.5 deg, which is likely associated
with the inner bar, and the other feature having considerably eccentric
velocities more than those of the normal x_1-orbit family feature. The
extinction-corrected K magnitudes (if used as a distance modulus) tend to show
a sequential deposition of these objects along the line of sight toward the
Galactic center depending on their radial velocities. The tendency that
appeared in the distance measures is consistent with the bulge-bar dynamical
model utilizing the periodic orbit families in the bar potential.Comment: Full high resolution figures available as NRO report No.638 at
http://www.nro.nao.ac.jp/library/report/list.html. PASJ 58, No. 3 (June 25
issue in press
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