244 research outputs found
Inferring Unusual Crowd Events From Mobile Phone Call Detail Records
The pervasiveness and availability of mobile phone data offer the opportunity
of discovering usable knowledge about crowd behaviors in urban environments.
Cities can leverage such knowledge in order to provide better services (e.g.,
public transport planning, optimized resource allocation) and safer cities.
Call Detail Record (CDR) data represents a practical data source to detect and
monitor unusual events considering the high level of mobile phone penetration,
compared with GPS equipped and open devices. In this paper, we provide a
methodology that is able to detect unusual events from CDR data that typically
has low accuracy in terms of space and time resolution. Moreover, we introduce
a concept of unusual event that involves a large amount of people who expose an
unusual mobility behavior. Our careful consideration of the issues that come
from coarse-grained CDR data ultimately leads to a completely general framework
that can detect unusual crowd events from CDR data effectively and efficiently.
Through extensive experiments on real-world CDR data for a large city in
Africa, we demonstrate that our method can detect unusual events with 16%
higher recall and over 10 times higher precision, compared to state-of-the-art
methods. We implement a visual analytics prototype system to help end users
analyze detected unusual crowd events to best suit different application
scenarios. To the best of our knowledge, this is the first work on the
detection of unusual events from CDR data with considerations of its temporal
and spatial sparseness and distinction between user unusual activities and
daily routines.Comment: 18 pages, 6 figure
Reduced quasifission competition in fusion reactions forming neutron-rich heavy elements
Measurements of mass-angle distributions (MADs) for Cr + W reactions,
providing a wide range in the neutron-to-proton ratio of the compound system,
(N/Z)CN, have allowed for the dependence of quasifission on the (N/Z)CN to be
determined in a model-independent way. Previous experimental and theoretical
studies had produced conflicting conclusions. The experimental MADs reveal an
increase in contact time and mass evolution of the quasifission fragments with
increasing (N/Z)CN, which is indicative of an increase in the fusion
probability. The experimental results are in agreement with microscopic
time-dependent Hartree-Fock calculations of the quasifission process. The
experimental and theoretical results favor the use of the most neutron-rich
projectiles and targets for the production of heavy and superheavy nuclei.Comment: Accepted to PRC as a Rapid Communicatio
Sub-barrier quasifission in heavy element formation reactions with deformed actinide target nuclei
Background: The formation of superheavy elements (SHEs) by fusion of two massive nuclei is severely
inhibited by the competing quasifission process. Low excitation energies favor SHE survival against fusion-fission
competition. In âcoldâ fusion with spherical target nuclei near 208Pb, SHE yields are largest at beam energies
significantly below the average capture barrier. In âhotâ fusion with statically deformed actinide nuclei, this is not
the case. Here the elongated deformation-aligned configurations in sub-barrier capture reactions inhibits fusion
(formation of a compact compound nucleus), instead favoring rapid reseparation through quasifission.
Purpose: To determine the probabilities of fast and slow quasifission in reactions with prolate statically deformed
actinide nuclei, through measurement and quantitative analysis of the dependence of quasifission characteristics
at beam energies spanning the average capture barrier energy.
Methods: The Australian National University Heavy Ion Accelerator Facility and CUBE fission spectrometer
have been used to measure fission and quasifission mass and angle distributions for reactions with projectiles
from C to S, bombarding Th and U target nuclei.
Results: Mass-asymmetric quasifission occurring on a fast time scale, associated with collisions with the tips of
the prolate actinide nuclei, shows a rapid increase in probability with increasing projectile charge, the transition
being centered around projectile atomic number ZP = 14. For mass-symmetric fission events, deviations of
angular anisotropies from expectations for fusion fission, indicating a component of slower quasifission, suggest
a similar transition, but centered around ZP ⌠8.
Conclusions: Collisions with the tips of statically deformed prolate actinide nuclei show evidence for two distinct
quasifission processes of different time scales. Their probabilities both increase rapidly with the projectile charge.
The probability of fusion can be severely suppressed by these two quasifission processes, since the sub-barrier
heavy element yield is likely to be determined by the product of the probabilities of surviving each quasifission
process.The authors acknowledge support from ARC Grants
No. FL110100098, No. DP130101569, No. FT120100760, No.
DE140100784, No. DP140101337, No. DP160101254, and
No. DP170102318, and support by the Federal Government
NCRIS program for operations of the ANU Heavy Ion Accelerator
Facility
Limit on suppression of ionization in metastable neon traps due to long-range anisotropy
This paper investigates the possibility of suppressing the ionization rate in
a magnetostatic trap of metastable neon atoms by spin-polarizing the atoms.
Suppression of the ionization is critical for the possibility of reaching
Bose-Einstein condensation with such atoms. We estimate the relevant long-range
interactions for the system, consisting of electric quadrupole-quadrupole and
dipole-induced dipole terms, and develop short-range potentials based on the
Na_2 singlet and triplet potentials. The auto-ionization widths of the system
are also calculated. With these ingredients we calculate the ionization rate
for spin-polarized and for spin-isotropic samples, caused by anisotropy of the
long-range interactions. We find that spin-polarization may allow for four
orders of magnitude suppression of the ionization rate for Ne. The results
depend sensitively on a precise knowledge of the interaction potentials,
however, pointing out the need for experimental input. The same model gives a
suppression ratio close to unity for metastable xenon in accordance with
experimental results, due to a much increased anisotropy in this case.Comment: 15 pages including figures, LaTex/RevTex, uses epsfig.st
Theoretical study of the absorption spectra of the sodium dimer
Absorption of radiation from the sodium dimer molecular states correlating to
Na(3s)-Na(3s) is investigated theoretically. Vibrational bound and continuum
transitions from the singlet X Sigma-g+ state to the first excited singlet A
Sigma-u+ and singlet B Pi-u states and from the triplet a Sigma-u+ state to the
first excited triplet b Sigma-g+ and triplet c Pi-g states are studied
quantum-mechanically. Theoretical and experimental data are used to
characterize the molecular properties taking advantage of knowledge recently
obtained from ab initio calculations, spectroscopy, and ultra-cold atom
collision studies. The quantum-mechanical calculations are carried out for
temperatures in the range from 500 to 3000 K and are compared with previous
calculations and measurements where available.Comment: 19 pages, 8 figures, revtex, eps
Recommended from our members
THE METABOLSIM AND TOXICITY OF RADIUM-223 IN RATS
This report covers studies of the excretion and retention of 'tracer' and toxic doses of the 11.2-day Ra{sup 223} isotope, its acute toxicity (organ weight changes, gross and microscopic pathology, and Fe{sup 59} utilization by the bone marrow), and long-term histopathological changes and alterations in the hemogram
Nucleation of a sodium droplet on C60
We investigate theoretically the progressive coating of C60 by several sodium
atoms. Density functional calculations using a nonlocal functional are
performed for NaC60 and Na2C60 in various configurations. These data are used
to construct an empirical atomistic model in order to treat larger sizes in a
statistical and dynamical context. Fluctuating charges are incorporated to
account for charge transfer between sodium and carbon atoms. By performing
systematic global optimization in the size range 1<=n<=30, we find that Na_nC60
is homogeneously coated at small sizes, and that a growing droplet is formed
above n=>8. The separate effects of single ionization and thermalization are
also considered, as well as the changes due to a strong external electric
field. The present results are discussed in the light of various experimental
data.Comment: 17 pages, 10 figure
A randomised multicentre phase II trial of capecitabine vs S-1 as first-line treatment in elderly patients with metastatic or recurrent unresectable gastric cancer
This randomised multicentre phase II study was conducted to investigate the activity and safety of two oral fluoropyrimidines, capecitabine or S-1, in elderly patients with advanced gastric cancer (AGC). Elderly (â©Ÿ65 years) chemo-naive patients with AGC were randomly assigned to receive capecitabine 1250âmgâmâ2 two times daily on days 1â14 every 3 weeks or S-1 40â60âmg two times daily according to body surface area on days 1â28 every 6 weeks. Ninety-six patients were enrolled and 91 patients were randomised to capecitabine (N=46) or S-1 (N=45). Overall response rate, the primary end point, was 27.2% (95% CI, 14.1â40.4, 12 of 44 assessable patients) with capecitabine and 28.9% (95% CI, 15.6â42.1, 13 of 45) with S-1. Median times to progression and overall survival in the capecitabine arm (4.7 and 9.5 months, respectively) were similar to those in the S-1 arm (4.2 and 8.2 months, respectively). The incidence of grade 3â4 granulocytopenia was 6.8% with capecitabine and 4.8% with S-1. Grade 3â4 nonhaematologic toxicities were: asthenia (9.1% with capecitabine vs 7.1% with S-1), anorexia (6.8 vs 9.5%), diarrhoea (2.3 vs 0%), and handâfoot syndrome (6.8 vs 0%). Both capecitabine and S-1 monotherapies were active and tolerable as first-line treatment for elderly patients with AGC
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