1,828 research outputs found
Relativistic Hartree approach with exact treatment of vacuum polarization for finite nuclei
We study the relativistic Hartree approach with the exact treatment of the
vacuum polarization in the Walecka sigma-omega model. The contribution from the
vacuum polarization of nucleon-antinucleon field to the source term of the
meson fields is evaluated by performing the energy integrals of the Dirac Green
function along the imaginary axis. With the present method of the vacuum
polarization in finite system, the total binding energies and charge radii of
16O and 40Ca can be reproduced. On the other hand, the level-splittings in the
single-particle level, in particular the spin-orbit splittings, are not
described nicely because the inclusion of vacuum effect provides a large
effective mass with small meson fields. We also show that the derivative
expansion of the effective action which has been used to calculate the vacuum
contribution for finite nuclei gives a fairly good approximation.Comment: 15 pages, 8 figure
Investigation of environmental change pattern in Japan
The author has identified the following significant results. A detailed land use classification for a large urban area of Tokyo was made using MSS digital data. It was found that residential, commercial, industrial, and wooded areas and grasslands can be successfully classified. A mesoscale vortex associated with large ocean current, Kuroshio, which is a rare phenomenon, was recognized visually through the analysis of MSS data. It was found that this vortex affects the effluent patterns of rivers. Lava flowing from Sakurajima Volcano was clearly classified for three major erruptions (1779, 1914, and 1946) using MSS data
Earthquake detection capacity of Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET)
We adopted the Probability-based Magnitude of Completeness (PMC) method and
performed a case analysis of the Nankai Trough, a target region monitored for
future megathrust earthquakes. JAMSTEC (Japan Agency for Marine-Earth Science
and Technology) has created a seismicity catalog that includes events in this
region observed by DONET. Using seismicity data for 2015-2019, we found
spatiotemporal variability of completeness magnitude Mp. Mp was lower than 1 in
one of the areas where stations are densely deployed, whereas Mp was larger
than 2 at the periphery and outside of the DONET area. We then evaluated the
temporal evolution of Mp, highlighting how the failure of sets of observing
stations influenced Mp if not repaired. Stations are aggregated around the 12
science nodes (hubs that connect the stations) and connected through the two
oceanfloor backbone cables to JAMSTEC. We explored the possible use of PMC as a
tool with simulation computation of node malfunction. A simulation showed that
completeness estimates in the area near failure nodes were about 1 magnitude
larger. If such failure occurred for nodes near the region which straddles the
rupture zones of the previous Tonankai and Nankai earthquakes in 1940's, it
would most pronouncedly affect earthquake monitoring among nodes' failures. It
is desirable to repair these nodes or replace with new ones when their
malfunction occurs. We then demonstrated an example of how to use Mp
information as prior knowledge to seismicity-related studies. We used the b
value of the Gutenberg-Richter distribution, and computed it taking Mp into
consideration. We found that the spatial and temporal changes in b were
strongly correlated to the magnitude-6 class slow slip that grew over two years
on the Nankai Trough plate boundary, indicating the b value as a proxy that can
help to image stress heterogeneity when there is a slow slip event.Comment: 6 figure
Fluctuation of the Top Location and Avalanches in the Formation Process of a Sandpile
We investigate the formation processes of a sandpile using numerical
simulation. We find a new relation between the fluctuation of the motion of the
top and the surface state of a sandpile. The top moves frequently as particles
are fed one by one every time interval T. The time series of the top location
has the power spectrum which obeys a power law, S(f)~f^{\alpha}, and its
exponent \alpha depends on T and the system size w. The surface state is
characterized by two time scales; the lifetime of an avalanche, T_{a}, and the
time required to cause an avalanche, T_{s}. The surface state is fluid-like
when T_{a}~T_{s}, and it is solid-like when T_{a}<<T_{s}. Our numerical results
show that \alpha is a function of T_{s}/T_{a}.Comment: 15 pages, 13 figure
Polarised target for Drell-Yan experiment in COMPASS at CERN, part I
In the polarised Drell-Yan experiment at the COMPASS facility in CERN pion
beam with momentum of 190 GeV/c and intensity about pions/s interacted
with transversely polarised NH target. Muon pairs produced in Drel-Yan
process were detected. The measurement was done in 2015 as the 1st ever
polarised Drell-Yan fixed target experiment. The hydrogen nuclei in the
solid-state NH were polarised by dynamic nuclear polarisation in 2.5 T
field of large-acceptance superconducting magnet. Large helium dilution
cryostat was used to cool the target down below 100 mK. Polarisation of
hydrogen nuclei reached during the data taking was about 80 %. Two oppositely
polarised target cells, each 55 cm long and 4 cm in diameter were used.
Overview of COMPASS facility and the polarised target with emphasis on the
dilution cryostat and magnet is given. Results of the polarisation measurement
in the Drell-Yan run and overviews of the target material, cell and dynamic
nuclear polarisation system are given in the part II.Comment: 4 pages, 2 figures, Proceedings of the 22nd International Spin
Symposium, Urbana-Champaign, Illinois, USA, 25-30 September 201
4/3-Law of Granular Particles Flowing through a Vertical Pipe
Density waves of granular material (sand) flowing through a vertical pipe
have been investigated. Clear density waves emerge when the cock attached to
bottom end of the pipe is closed. The FFT power spectra were found to show a
stable power-law form The value of the exponent was
evaluated as . We also introduce a simple one-dimensional
model which reproduces from both simulation and theoretical
analysis. (to be published in Phys.Rev.Lett.)Comment: 4 pages, 4 figures, a style fil
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