26,704 research outputs found
Energy dependence of a vortex line length near a zigzag of pinning centers
A vortex line, shaped by a zigzag of pinning centers, is described here
through a three-dimensional unit cell containing two pinning centers positioned
symmetrically with respect to its center. The unit cell is a cube of side
, the pinning centers are insulating spheres of radius , taken
within the range to , being the coherence length. We
calculate the free energy density of these systems in the framework of the
Ginzburg-Landau theory.Comment: Submitted to Braz. Jour. Phys. (http://www.sbfisica.org.br/bjp) 11
pages, 6 figures, 1 table, LaTex 2
Letter to the editor: autoimmune pathogenic mechanisms in Huntington’s disease
Letter to the Editor: Autoimmune pathogenic mechanisms in Huntington's disease
A Laplace transform approach to the quantum harmonic oscillator
The one-dimensional quantum harmonic oscillator problem is examined via the
Laplace transform method. The stationary states are determined by requiring
definite parity and good behaviour of the eigenfunction at the origin and at
infinity
A variational formulation of analytical mechanics in an affine space
Variational formulations of statics and dynamics of mechanical systems
controlled by external forces are presented as examples of variational
principles.Comment: 17 pages, corrected typos, accepted for publication in Rep. Math.
Phy
Generalized Galileon cosmology
We study the cosmology of a generalized Galileon field with five
covariant Lagrangians in which is replaced by general scalar functions
(i=1,...,5). For these theories, the equations of motion remain
at second-order in time derivatives. We restrict the functional forms of
from the demand to obtain de Sitter solutions responsible for
dark energy. There are two possible choices for power-law functions
, depending on whether the coupling with the Ricci
scalar is independent of or depends on . The former
corresponds to the covariant Galileon theory that respects the Galilean
symmetry in the Minkowski space-time. For generalized Galileon theories we
derive the conditions for the avoidance of ghosts and Laplacian instabilities
associated with scalar and tensor perturbations as well as the condition for
the stability of de Sitter solutions. We also carry out detailed analytic and
numerical study for the cosmological dynamics in those theories.Comment: 24 pages, 10 figures, version to appear in Physical Review
On Poisson quasi-Nijenhuis Lie algebroids
We propose a definition of Poisson quasi-Nijenhuis Lie algebroids as a
natural generalization of Poisson quasi-Nijenhuis manifolds and show that any
such Lie algebroid has an associated quasi-Lie bialgebroid. Therefore, also an
associated Courant algebroid is obtained. We introduce the notion of a morphism
of quasi-Lie bialgebroids and of the induced Courant algebroids morphism and
provide some examples of Courant algebroid morphisms. Finally, we use paired
operators to deform doubles of Lie and quasi-Lie bialgebroids and find an
application to generalized complex geometry.Comment: 12 page
Neural networks and spectra feature selection for retrival of hot gases temperature profiles
Proceeding of: International Conference on Computational Intelligence for Modelling, Control and Automation, 2005 and International Conference on Intelligent Agents, Web Technologies and Internet Commerce, Vienna, Austria 28-30 Nov. 2005Neural networks appear to be a promising tool to solve the so-called inverse problems focused to obtain a retrieval of certain physical properties related to the radiative transference of energy. In this paper the capability of neural networks to retrieve the temperature profile in a combustion environment is proposed. Temperature profile retrieval will be obtained from the measurement of the spectral distribution of energy radiated by the hot gases (combustion products) at wavelengths corresponding to the infrared region. High spectral resolution is usually needed to gain a certain accuracy in the retrieval process. However, this great amount of information makes mandatory a reduction of the dimensionality of the problem. In this sense a careful selection of wavelengths in the spectrum must be performed. With this purpose principal component analysis technique is used to automatically determine those wavelengths in the spectrum that carry relevant information on temperature distribution. A multilayer perceptron will be trained with the different energies associated to the selected wavelengths. The results presented show that multilayer perceptron combined with principal component analysis is a suitable alternative in this field.Publicad
Participatory approach for integrated basin planning with focus on disaster risk reduction : the case of the Limpopo river
This paper defends the idea that a participatory approach is a suitable method for basin planning integrating both water and land aspects. Assertions made are based on scientific literature review and corroborated by field experience and research carried out in the Limpopo River basin, a transboundary river located in southern Africa which is affected by periodical floods. The paper explains how a basin strategic plan can be drafted and disaster risk reduction strategies derived by combining different types of activities using a bottom-up approach, despite an institutional context which operates through traditional top-down mechanisms. In particular, the "Living with Floods" experience in the lower Limpopo River, in Mozambique, is described as a concrete example of a disaster adaptation measure resulting from a participatory planning exercise. In conclusion, the adopted method and obtained results are discussed and recommendations are formulated for potential replication in similar contexts of the developing world
Modelo de cuantificación del consumo energético en edificación
The research conducted in this paper focuses on the generation
of a model for the quantification of energy consumption
in building. This is to be done through one of
the most relevant environmental impact indicators associated
with weight per m2 of construction, as well as the
energy consumption resulting from the manufacturing
process of materials used in building construction.
The practical application of the proposed model on different
buildings typologies in Seville, will provide information
regarding the building materials, the subsystems
and the most relevant construction elements. Hence, we
will be able to observe the impact the built surface has
on the environment.
The results obtained aim to reference the scientific community,
providing quantitative data comparable to other
types of buildings and geographical areas. Furthermore,
it may also allow the analysis and the characterization of
feasible solutions to reduce the environmental impact
generated by the different materials, subsystems and
construction elements commonly used in the different
building types defined in this study.La investigación realizada en el presente trabajo plantea
la generación de un modelo de cuantificación del consumo
energético en edificación, a través de uno de los indicadores
de impacto ambiental más relevantes asociados
al peso por m2 de construcción, el consumo energético
derivado del proceso de fabricación de los materiales de
construcción empleados en edificación.
La aplicación práctica del modelo propuesto sobre diferentes
tipologías edificatorias en Sevilla aportará información
respecto a los materiales de construcción, subsistemas
y elementos constructivos más impactantes,
permitiendo visualizar la influencia que presenta la superficie
construida en cuanto al impacto ambiental generado.
Los resultados obtenidos pretenden servir de referencia
a la comunidad científica, aportando datos numéricos
que podrán ser comparados en otras tipologías y ámbitos
geográficos, a la vez que permitirán analizar y precisar
mejoras en cuanto al impacto ambiental generado
por los diferentes materiales, subsistemas y elementos
constructivos habitualmente utilizados en las tipologías
edificatorias definidas
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