13,949 research outputs found
Hawking radiation for non asymptotically flat dilatonic black holes using gravitational anomaly
The -dimensional scalar field action may be reduced, in the background
geometry of a black hole, to a 2-dimensional effective action. In the near
horizon region, it appears a gravitational anomaly: the energy-momentum tensor
of the scalar field is not conserved anymore. This anomaly is removed by
introducing a term related to the Hawking temperature of the black hole. Even
if the temperature term introduced is not covariant, a gauge transformation may
restore the covariance. We apply this method to compute the temperature of the
black hole of the dilatonic non asymptotically flat black holes. We compare the
results with those obtained through other methods.Comment: Latex file, 22 pages. Some discussions enlarged. New references.
Accepted for publication in the European Physical Journal
Local entropic effects of polymers grafted to soft interfaces
In this paper, we study the equilibrium properties of polymer chains
end-tethered to a fluid membrane. The loss of conformational entropy of the
polymer results in an inhomogeneous pressure field that we calculate for
gaussian chains. We estimate the effects of excluded volume through a relation
between pressure and concentration. Under the polymer pressure, a soft surface
will deform. We calculate the deformation profile for a fluid membrane and show
that close to the grafting point, this profile assumes a cone-like shape,
independently of the boundary conditions. Interactions between different
polymers are also mediated by the membrane deformation. This pair-additive
potential is attractive for chains grafted on the same side of the membrane and
repulsive otherwise.Comment: 10 pages, 9 figure
Scattering from Solutions of Star Polymers
We calculate the scattering intensity of dilute and semi-dilute solutions of
star polymers. The star conformation is described by a model introduced by
Daoud and Cotton. In this model, a single star is regarded as a spherical
region of a semi-dilute polymer solution with a local, position dependent
screening length. For high enough concentrations, the outer sections of the
arms overlap and build a semi-dilute solution (a sea of blobs) where the inner
parts of the actual stars are embedded. The scattering function is evaluated
following a method introduced by Auvray and de Gennes. In the dilute regime
there are three regions in the scattering function: the Guinier region (low
wave vectors, q R << 1) from where the radius of the star can be extracted; the
intermediate region (1 << q R << f^(2/5)) that carries the signature of the
form factor of a star with f arms: I(q) ~ q^(-10/3); and a high wavevector zone
(q R >> f^(2/5)) where the local swollen structure of the polymers gives rise
to the usual q^(-5/3) decay. In the semi-dilute regime the different stars
interact strongly, and the scattered intensity acquires two new features: a
liquid peak that develops at a reciprocal position corresponding to the
star-star distances; and a new large wavevector contribution of the form
q^(-5/3) originating from the sea of blobs.Comment: REVTeX, 12 pages, 4 eps figure
Portugal gestual : a importância do utilizador na criação da interface
Para o estudo da criação gráfica de uma interface de tradução
entre a Língua Gestual Portuguesa e a Língua Portuguesa, é primordial
considerar o utilizador. Centrar o design no Surdo [1] e identificar as
lacunas existentes nos espaços públicos comunicacionais são os objetivos
deste artigo. Embora, nas últimas décadas, se tenha vindo a registar o
reconhecimento dos direitos dos Surdos, oficialmente com a promulgação
de leis, os resultados deste estudo apontam para a persistência de um
fosso entre os princípios e as práticas. Em síntese, falta reconhecer que a
“deficiência” pode estar na sociedade por esta não querer, não poder ou
não saber organizar-se no sentido de se incrementar como inclusiva.ABSTRACT: In order to study the graphic creation of a interface for
translation between the Portuguese sign language and the Portuguese
language, it is essential to consider the user. The main purpose of this
article is to centre the design around the deaf and identify the existing
gaps in the public communication spaces. Although in the past decades
there has been a growing acknowledgement of the rights of the Deaf
through the promulgation of Laws, the results from this study point to the
persistence of a gap between the principles and what is, in facts,
practiced. In conclusion, it is necessary to acknowledge that the
"handicap" may lay in society because it either does no want, can not or
does not know how to organize itself in the sense of increasing the
inclusion.info:eu-repo/semantics/publishedVersio
Robotic deployment of stabilized shearography unit for wind turbine blade inspection
A wind turbine blade inspection system called Winspector has been developed by a European consortium to automate the in-situ non-destructive testing of wind blades. A robot platform is winched up a wind turbine tower to reach a blade locked into a 90-degree pitch angle. The blade region to be inspected is reached by a combination of an extension ladder and a 5-axis robot arm to place an end-effector onto the blade surface. The end-effector is critical to the success of the shearography technique used to detect subsurface defects when the blade is experiencing inevitable out-of-plane, in-plane, and root-to-tip vi-brations. The paper describes the development of the end-effector which carries the shearography unit and ensures (with passive compliance and design based on analysis of aerodynamic blade shapes) that the unit remains at a constant distance from blade surface in the presence of blade vibrations. The system has been tested with three separate field trials in a wind farm near Athens in Greece. Sub-surface defect detection with shearography has been successfully demon-strated
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