3,739 research outputs found
The Bosonic Ancestor of Closed and Open Fermionic Strings
We review the emergence of the ten-dimensional fermionic closed string
theories from subspaces of the Hilbert space of the 26-dimensional bosonic
closed string theory compactified on an lattice. They arise
from a consistent truncation procedure which generates space-time fermions out
of bosons. This procedure is extended to open string sectors. We prove, from
bosonic considerations alone, that truncation of the unique tadpole-free
bosonic string theory compactified on the above lattice determines
the anomaly free Chan-Paton group of the Type I theory. It also yields the
Chan-Paton groups making Type O theories tadpole-free. These results establish
a link between all M-theory strings and the bosonic string within the framework
of conformal field theory. Its significance is discussed.Comment: LaTeX files, 16 pages. Contribution to the Francqui meeting, Brussels
2001 and Corfu Summer Institute 2001. Based on hep-th/010623
Potential of Artificial Wetlands for Removing Pesticides from Water in a Cost-effectiveness Framework
Resource /Energy Economics and Policy,
Potential of Artificial Wetlands for Removing Pesticides from Water in a Cost-Effective Framework
The purpose of this paper is to analyze the implication of wetland construction for the cost-effective design of a pesticide charge. A model is developed in order to show that, for a given target, the introduction of wetland construction can reduce overall abatement costs and can lower the input charge asked to the farmers. This result remains true as long as the cost of constructing a wetland is not too high. A numerical illustration is carried out in order to simulate pesticide regulations in a wine catchment in North-East of Francewater policy, constructed wetlands, agricultural pollution regulation, Agribusiness, Land Economics/Use, Q25, Q58, K32,
Identification of the Isotherm Function in Chromatography Using CMA-ES
This paper deals with the identification of the flux for a system of
conservation laws in the specific example of analytic chromatography. The
fundamental equations of chromatographic process are highly non linear. The
state-of-the-art Evolution Strategy, CMA-ES (the Covariance Matrix Adaptation
Evolution Strategy), is used to identify the parameters of the so-called
isotherm function. The approach was validated on different configurations of
simulated data using either one, two or three components mixtures. CMA-ES is
then applied to real data cases and its results are compared to those of a
gradient-based strategy
Higher-twist contributions to large pT hadron production in hadronic collisions
The scaling behavior of large-pT hadron production in hadronic collisions is
investigated. A significant deviation from the NLO QCD predictions is reported,
especially at high values of xT=2pT/sqrt(s). In contrast, the prompt photon and
jet production data prove in agreement with leading-twist expectations. These
results are interpreted as coming from a non-negligible contribution of
higher-twist processes, where the hadron is produced directly in the hard
subprocess. Predictions for scaling exponents at RHIC are successfully compared
to PHENIX preliminary measurements. We suggest to trigger on isolated large-pT
hadron production to enhance higher-twist processes, and point that the use of
isolated hadrons as a signal for new physics at colliders can be affected by
the presence of direct hadron production processes.Comment: 4 pages, 2 figures. Talk given at the 45th Rencontres de Moriond QCD
and High Energy Interactions, La Thuile, Italy, 13-20 March 201
Thermo-mechanical FE model with memory effect for 304L austenitic stainless steel presenting microstructure gradient
The main purpose of this study is to determine, via a three dimensions Finite
Element analysis (FE), the stress and strain fields at the inner surface of a
tubular specimen submitted to thermo-mechanical fatigue. To investigate the
surface finish effect on fatigue behaviour at this inner surface, mechanical
tests were carried out on real size tubular specimens under various thermal
loadings. X ray measurements, Transmission Electron Microscopy observations and
micro-hardness tests performed at and under the inner surface of the specimen
before testing, revealed residual internal stresses and a large dislocation
microstructure gradient in correlation with hardening gradients due to
machining. A memory effect, bound to the pre-hardening gradient, was introduced
into an elasto-visco-plastic model in order to determine the stress and strain
fields at the inner surface. The temperature evolution on the inner surface of
the tubular specimen was first computed via a thermo-elastic model and then
used for our thermo-mechanical simulations. Identification of the
thermo-mechanical model parameters was based on the experimental stabilized
cyclic tension-compression tests performed at 20^{\circ}C and 300^{\circ}C. A
good agreement was obtained between numerical stabilized traction-compression
cycle curves (with and without pre-straining) and experimental ones. This 3
dimensional simulation gave access to the evolution of the axial and tangential
internal stresses and local strains during the tests. Numerical results showed:
a decreasing of the tangential stress and stabilization after 40 cycles,
whereas the axial stress showed weaker decreasing with the number of cycles.
The results also pointed out a ratcheting and a slightly non proportional
loading at the inner surface. The computed mean stress and strain values of the
stabilized cycle being far from the initial ones, they could be used to get the
safety margins of standard design related to fatigue, as well as to get
accurate loading conditions needed for the use of more advanced fatigue
analysis and criteria
Investigating differences in vigilance tactic use within and between the sexes in eastern grey kangaroos
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