3,301 research outputs found
CIXL2: A Crossover Operator for Evolutionary Algorithms Based on Population Features
In this paper we propose a crossover operator for evolutionary algorithms
with real values that is based on the statistical theory of population
distributions. The operator is based on the theoretical distribution of the
values of the genes of the best individuals in the population. The proposed
operator takes into account the localization and dispersion features of the
best individuals of the population with the objective that these features would
be inherited by the offspring. Our aim is the optimization of the balance
between exploration and exploitation in the search process. In order to test
the efficiency and robustness of this crossover, we have used a set of
functions to be optimized with regard to different criteria, such as,
multimodality, separability, regularity and epistasis. With this set of
functions we can extract conclusions in function of the problem at hand. We
analyze the results using ANOVA and multiple comparison statistical tests. As
an example of how our crossover can be used to solve artificial intelligence
problems, we have applied the proposed model to the problem of obtaining the
weight of each network in a ensemble of neural networks. The results obtained
are above the performance of standard methods
Sustentabilidad de dos sistemas de produccion de semilla pre basica de papa bajo invernadero.
Beyond conventional factorization: Non-Hermitian Hamiltonians with radial oscillator spectrum
The eigenvalue problem of the spherically symmetric oscillator Hamiltonian is
revisited in the context of canonical raising and lowering operators. The
Hamiltonian is then factorized in terms of two not mutually adjoint factorizing
operators which, in turn, give rise to a non-Hermitian radial Hamiltonian. The
set of eigenvalues of this new Hamiltonian is exactly the same as the energy
spectrum of the radial oscillator and the new square-integrable eigenfunctions
are complex Darboux-deformations of the associated Laguerre polynomials.Comment: 13 pages, 7 figure
On the quality of climate proxies derived from newspaper reports ? a case study
International audienceOne of the main problems in climate reconstruction from documentary sources is the evaluation of the quality of non instrumental meteorological records in absence of instrumental observations to perform a calibration. In these cases it is mandatory to envision different approaches to assess the climatic signal in a reconstruction. This work is aimed to test the consistency of a snow frequency reconstruction in the central Argentinean Andes by studying the synoptic patterns related to the occurrence of precipitation in this area. While the original reconstruction covers the period between 1885 and 1996, the insufficiency of overlapping instrumental data limited the calibration to a short 15-year interval. In this paper we evaluate the performance of the reconstructed series for the entire 45-year period between 1958 and 1996 by analyzing the displacement in the jet stream and the patterns of geopotential height related to anomalies in the reconstructed snow frequency series. Previous works have linked the precipitation in the central Andes to the ENSO through the Pacific South American mode. We also have found this connection between ENSO and the reconstructed precipitation. Finally, it is shown that the ENSO relationship is the cause of a significant link between the precipitation anomalies in the central Argentinean Andes and the ice extent around the Antarctic Peninsula
Extended WKB method, resonances and supersymmetric radial barriers
Semiclassical approximations are implemented in the calculation of position
and width of low energy resonances for radial barriers. The numerical
integrations are delimited by t/T<<8, with t the period of a classical particle
in the barrier trap and T the resonance lifetime. These energies are used in
the construction of `haired' short range potentials as the supersymmetric
partners of a given radial barrier. The new potentials could be useful in the
study of the transient phenomena which give rise to the Moshinsky's diffraction
in time.Comment: 12 pages, 4 figures, 3 table
Background analysis and status of the ANAIS dark matter project
ANAIS (Annual modulation with NaI Scintillators) is a project aiming to set
up at the new facilities of the Canfranc Underground Laboratory (LSC), a large
scale NaI(Tl) experiment in order to explore the DAMA/LIBRA annual modulation
positive result using the same target and technique. Two 12.5 kg each NaI(Tl)
crystals provided by Alpha Spectra took data at the LSC in the ANAIS-25 set-up.
The comparison of the background model for the ANAIS-25 prototypes with the
experimental results is presented. ANAIS crystal radiopurity goals have been
achieved for Th-232 and U-238 chains, but a Pb-210 contamination
out-of-equilibrium was identified, whose origin has been studied. The high
light collection efficiency obtained with these prototypes allows to anticipate
an energy threshold of the order of 1 keVee. A new detector, with improved
performances, was received in March 2015 and very preliminary results are
shown.Comment: 6 pages, 7 figure
Preliminary results of ANAIS-25
The ANAIS (Annual Modulation with NaI(Tl) Scintillators) experiment aims at
the confirmation of the DAMA/LIBRA signal using the same target and technique
at the Canfranc Underground Laboratory. 250 kg of ultrapure NaI(Tl) crystals
will be used as a target, divided into 20 modules, each coupled to two
photomultipliers. Two NaI(Tl) crystals of 12.5 kg each, grown by Alpha Spectra
from a powder having a potassium level under the limit of our analytical
techniques, form the ANAIS-25 set-up. The background contributions are being
carefully studied and preliminary results are presented: their natural
potassium content in the bulk has been quantified, as well as the uranium and
thorium radioactive chains presence in the bulk through the discrimination of
the corresponding alpha events by PSA, and due to the fast commissioning, the
contribution from cosmogenic activated isotopes is clearly identified and their
decay observed along the first months of data taking. Following the procedures
established with ANAIS-0 and previous prototypes, bulk NaI(Tl) scintillation
events selection and light collection efficiency have been also studied in
ANAIS-25.Comment: 4 pages, 6 Figure
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