114 research outputs found
Optimization clustering techniques on register unemployment data
An important strategy for data classification consists in organising data
points in clusters. The k-means is a traditional optimisation method applied to
cluster data points. Using a labour market database, aiming the segmentation of this
market taking into account the heterogeneity resulting from different unemployment
characteristics observed along the Portuguese geographical space, we suggest the
application of an alternative method based on the computation of the dominant
eigenvalue of a matrix related with the distance among data points. This approach
presents results consistent with the results obtained by the k-means.info:eu-repo/semantics/publishedVersio
Scaling and universality in the phase diagram of the 2D Blume-Capel model
We review the pertinent features of the phase diagram of the zero-field
Blume-Capel model, focusing on the aspects of transition order, finite-size
scaling and universality. In particular, we employ a range of Monte Carlo
simulation methods to study the 2D spin-1 Blume-Capel model on the square
lattice to investigate the behavior in the vicinity of the first-order and
second-order regimes of the ferromagnet-paramagnet phase boundary,
respectively. To achieve high-precision results, we utilize a combination of
(i) a parallel version of the multicanonical algorithm and (ii) a hybrid
updating scheme combining Metropolis and generalized Wolff cluster moves. These
techniques are combined to study for the first time the correlation length of
the model, using its scaling in the regime of second-order transitions to
illustrate universality through the observed identity of the limiting value of
with the exactly known result for the Ising universality class.Comment: 16 pages, 7 figures, 1 table, submitted to Eur. Phys. J. Special
Topic
Complete breeding failures in ivory gull following unusual rainy storms in North Greenland
Natural catastrophic events such as heavy rainfall and windstorms may induce drastic decreases in breeding success of animal populations. We report the impacts of summer rainfalls on the reproductive success of ivory gull (Pagophila eburnea) in north-east Greenland. On two occasions, at Amdrup Land in July 2009 and at Station Nord in July 2011, we observed massive ivory gull breeding failures following violent rainfall and windstorms that hit the colonies. In each colony, all of the breeding birds abandoned their eggs or chicks during the storm. Juvenile mortality was close to 100% at Amdrup Land in 2009 and 100% at Station Nord in 2011. Our results show that strong winds associated with heavy rain directly affected the reproductive success of some Arctic bird species. Such extreme weather events may become more common with climate change and represent a new potential factor affecting ivory gull breeding success in the High Arctic
Bony sclerosis and the battered child
A case of child battering in a four monthold infant is presented. In additional to typical physical and radiographic findings isolated sclerosis of the left tibia is described. Diffuse bony sclerosis in battered children has been proposed as evidence for an underlying metaphyseal fragility. Similar sclerosis in an isolated bone in our case suggests that the diffuse bony sclerosis seen in some of these battered children may reflect a more widespread posttraumatic change and not a basic metabolic defect. A radionuclide bone scan was also normal in this patient.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46800/1/256_2004_Article_BF00364627.pd
Critical aspects of the random-field Ising model
We investigate the critical behavior of the three-dimensional random-field Ising model
(RFIM) with a Gaussian field distribution at zero temperature. By implementing a
computational approach that maps the ground-state of the RFIM to the maximum-flow
optimization problem of a network, we simulate large ensembles of disorder realizations of
the model for a broad range of values of the disorder strength h and
system sizes  = L3, with L â€Â 156. Our averaging procedure
outcomes previous studies of the model, increasing the sampling of ground states by a
factor of 103. Using well-established finite-size scaling schemes, the
fourth-orderâs Binder cumulant, and the sample-to-sample fluctuations of various
thermodynamic quantities, we provide high-accuracy estimates for the critical field
hc, as well as the critical exponents Μ,
ÎČ/Îœ, and ÎłÌ
/Μ of the correlation length, order parameter, and
disconnected susceptibility, respectively. Moreover, using properly defined noise to
signal ratios, we depict the variation of the self-averaging property of the model, by
crossing the phase boundary into the ordered phase. Finally, we discuss the controversial
issue of the specific heat based on a scaling analysis of the bond energy, providing
evidence that its critical exponent α â 0â
Thermodynamic Treatment of Undercooled Cu-Mg Liquid and the Limits for Partitionless Crystallization
Multiple metal sources in the glaciomarine facies of the Neoproterozoic Jacadigo iron formation in the âSanta Cruz depositâ, CorumbĂĄ, Brazil
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