11,334 research outputs found
Estimations for the Single Diffractive production of the Higgs boson at the Tevatron and the LHC
The single diffractive production of the standard model Higgs boson is
computed using the diffractive factorization formalism, taking into account a
parametrization for the Pomeron structure function provided by the H1
Collaboration. We compute the cross sections at next-to-leading order accuracy
for the gluon fusion process, which includes QCD and electroweak corrections.
The gap survival probability () is also introduced to account for
the rescattering corrections due to spectator particles present in the
interaction, and to this end we compare two different models for the survival
factor. The diffractive ratios are predicted for proton-proton collisions at
the Tevatron and the LHC for the Higgs boson mass of = 120 GeV.
Therefore, our results provide updated estimations for the diffractive ratios
of the single diffractive production of the Higgs boson in the Tevatron and LHC
kinematical regimes.Comment: 20 pages, 6 figures, 3 table
Darth Fader: Using wavelets to obtain accurate redshifts of spectra at very low signal-to-noise
We present the DARTH FADER algorithm, a new wavelet-based method for
estimating redshifts of galaxy spectra in spectral surveys that is particularly
adept in the very low SNR regime. We use a standard cross-correlation method to
estimate the redshifts of galaxies, using a template set built using a PCA
analysis on a set of simulated, noise-free spectra. Darth Fader employs wavelet
filtering to both estimate the continuum & to extract prominent line features
in each galaxy spectrum. A simple selection criterion based on the number of
features present in the spectrum is then used to clean the catalogue: galaxies
with fewer than six total features are removed as we are unlikely to obtain a
reliable redshift estimate. Applying our wavelet-based cleaning algorithm to a
simulated testing set, we successfully build a clean catalogue including
extremely low signal-to-noise data (SNR=2.0), for which we are able to obtain a
5.1% catastrophic failure rate in the redshift estimates (compared with 34.5%
prior to cleaning). We also show that for a catalogue with uniformly mixed SNRs
between 1.0 & 20.0, with realistic pixel-dependent noise, it is possible to
obtain redshifts with a catastrophic failure rate of 3.3% after cleaning (as
compared to 22.7% before cleaning). Whilst we do not test this algorithm
exhaustively on real data, we present a proof of concept of the applicability
of this method to real data, showing that the wavelet filtering techniques
perform well when applied to some typical spectra from the SDSS archive. The
Darth Fader algorithm provides a robust method for extracting spectral features
from very noisy spectra. The resulting clean catalogue gives an extremely low
rate of catastrophic failures, even when the spectra have a very low SNR. For
very large sky surveys, this technique may offer a significant boost in the
number of faint galaxies with accurately determined redshifts.Comment: 22 pages, 15 figures. Accepted for publication in Astronomy &
Astrophysic
A construção de saberes sobre a Área de Reserva Legal em assentamento rural.
Este artigo apresenta uma ?Pesquisa-Ação? realizada em uma pesquisa de doutoramento, que utilizou os momentos metodológicos propostos por João Bosco Pinto, sob um referencial do materialismo histórico. Para tanto, o pesquisador-coordenador lançou mão da Teoria das Representações Sociais de Serge Moscovici e outros autores, visando a construção, juntamente com as dez famílias assentadas no Projeto Olga Benário, em Santa Tereza do Oeste, Estado do Paraná, de um determinado conhecimento sobre a área de Reserva Legal (ARL) daquele assentamento, com a finalidade de um possível manejo daquela área em bases sustentáveis.Disponível online
Avaliação das propriedades mecânicas da madeira in situ por ensaios em mesoprovetes
Uma das principais dificuldades da avaliação do estado de segurança de estruturas de
madeira existentes é a determinação das propriedades mecânicas a utilizar para efeitos de
cálculo. Os procedimentos habituais de estabelecimento das propriedades mecânicas com
base no estabelecimento de classes de resistência por avaliação visual validada com ensaios
não-destrutivos conduzem a resultados muito conservativos. No presente trabalho será
apresentado um método semi-destrutivo que avalia a resistência à tracção da madeira
através de amostras recolhidas do elemento estrutural, sendo estabelecidas relações entre
resultados análogos de mesoprovetes e provetes normalizados para peças de pinho bravo
(Pinus pinaster Ait.) e castanho nacional (Castanea sativa Mill.)
Selected research and case studies in ancient portuguese structures
The present paper presents some of the recent activity of University of Minho, regarding case
studies for Portuguese timber structures in four ancient buildings, including the Cathedral of Porto,
a Church in Coimbra and a Church in Braga. NDT is combined with analysis methods aiming at
non-invasive strengthening solutions or replacement of the timber structure (only as a last resort).
Research studies carried out in UM and currently running on LNEC and UM are also presented,
being showed the relevance of this research studies for the assessment and analysis of historical
timber structures
Survival of branching random walks in random environment
We study survival of nearest-neighbour branching random walks in random
environment (BRWRE) on . A priori there are three different
regimes of survival: global survival, local survival, and strong local
survival. We show that local and strong local survival regimes coincide for
BRWRE and that they can be characterized with the spectral radius of the first
moment matrix of the process. These results are generalizations of the
classification of BRWRE in recurrent and transient regimes. Our main result is
a characterization of global survival that is given in terms of Lyapunov
exponents of an infinite product of i.i.d. random matrices.Comment: 17 pages; to appear in Journal of Theoretical Probabilit
A semi-destructive tension method for evaluating the strength and stiffness of clear wood zones of structural timber elements in-service
The paper presents a new semi destructive method for obtaining a prediction of the tension
parallel to the grain properties of clear wood of structural timber members. This method is less intrusive than other existing methods and consists in extracting four small specimens along the
length of the timber members. The tension strength and stiffness obtained is intended to be used
as input data for the assessment of timber members in situ. Since the method only provides
information regarding clear wood, it will have to be used together with other non or semidestructive
methods that could accommodate the effect of defects on the loss of clear wood
properties. The validation of the method was carried out by a comparison with results obtained
from a standard method used for determination of clear wood properties. The results show a
good agreement between stiffness values but a medium agreement in the case of tension strength.The authors acknowledge the support given by the Fundacao para a Ciencia e a Tecnologia (FCT) for the PhD Grant SFRH/BD/27353/2006, as well as for the research Project "Safety evaluation of timber structures by means of non-destructive tests and stochastic analysis" (FCT PTDC/ECM/66527/2006)
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