Articles de revista
http://hdl.handle.net/2117/3918
Wed, 25 Nov 2015 14:52:31 GMT2015-11-25T14:52:31ZIonospheric and plasmaspheric electron contents inferred from radio occultations and global ionospheric maps
http://hdl.handle.net/2117/79027
Ionospheric and plasmaspheric electron contents inferred from radio occultations and global ionospheric maps
González Casado, Guillermo; Juan Zornoza, José Miguel; Sanz Subirana, Jaume; Rovira Garcia, Adrià; Aragón Angel, Angela
We introduce a methodology to extract the separate contributions of the ionosphere and the plasmasphere to the vertical total electron content, without relying on a fixed altitude to perform that separation. The method combines two previously developed and tested techniques, namely, the retrieval of electron density profiles from radio occultations using an improved Abel inversion technique and a two-component model for the topside ionosphere plus protonosphere. Taking measurements of the total electron content from global ionospheric maps and radio occultations from the Constellation Observing System for Meteorology, Ionosphere, and Climate/FORMOSAT-3 constellation, the ionospheric and plasmaspheric electron contents are calculated for a sample of observations covering 2007, a period of low solar and geomagnetic activity. The results obtained are shown to be consistent with previous studies for the last solar minimum period and with model calculations, confirming the reversal of the winter anomaly, the hemispheric asymmetry of the semiannual anomaly, and the existence in the plasmasphere of an annual anomaly in the South American sector of longitudes. The analysis of the respective fractional contributions from the ionosphere and the plasmasphere to the total electron content shows quantitatively that during the night the plasmasphere makes the largest contribution, peaking just before sunrise and during winter. On the other hand, the fractional contribution from the ionosphere reaches a maximum value around noon, which is nearly independent of season and geomagnetic latitude.
Wed, 11 Nov 2015 13:07:44 GMThttp://hdl.handle.net/2117/790272015-11-11T13:07:44ZGonzález Casado, GuillermoJuan Zornoza, José MiguelSanz Subirana, JaumeRovira Garcia, AdriàAragón Angel, AngelaWe introduce a methodology to extract the separate contributions of the ionosphere and the plasmasphere to the vertical total electron content, without relying on a fixed altitude to perform that separation. The method combines two previously developed and tested techniques, namely, the retrieval of electron density profiles from radio occultations using an improved Abel inversion technique and a two-component model for the topside ionosphere plus protonosphere. Taking measurements of the total electron content from global ionospheric maps and radio occultations from the Constellation Observing System for Meteorology, Ionosphere, and Climate/FORMOSAT-3 constellation, the ionospheric and plasmaspheric electron contents are calculated for a sample of observations covering 2007, a period of low solar and geomagnetic activity. The results obtained are shown to be consistent with previous studies for the last solar minimum period and with model calculations, confirming the reversal of the winter anomaly, the hemispheric asymmetry of the semiannual anomaly, and the existence in the plasmasphere of an annual anomaly in the South American sector of longitudes. The analysis of the respective fractional contributions from the ionosphere and the plasmasphere to the total electron content shows quantitatively that during the night the plasmasphere makes the largest contribution, peaking just before sunrise and during winter. On the other hand, the fractional contribution from the ionosphere reaches a maximum value around noon, which is nearly independent of season and geomagnetic latitude.Identifying optimal components in a reliability system
http://hdl.handle.net/2117/78945
Identifying optimal components in a reliability system
Freixas Bosch, Josep; Pons Vallès, Montserrat
The first step in a reliability optimization process is to
make a reliability assessment for each component in the system. If
this assessment is made in a qualitative way, by grouping together
components with the same reliability, and establishing a prevalence
order among groups, is there a way to decide which components
have the greatest Birnbaum measure without computing the exact
value of this measure? In this paper, three relations between com-
ponents are introduced and studied, and it is proved that they are
useful for selecting the components that have the biggest effect on
the system reliability in the sense of Birnbaum. An algorithm that
uses the results in the paper to select these important components
is also provided.
Mon, 09 Nov 2015 17:12:18 GMThttp://hdl.handle.net/2117/789452015-11-09T17:12:18ZFreixas Bosch, JosepPons Vallès, MontserratThe first step in a reliability optimization process is to
make a reliability assessment for each component in the system. If
this assessment is made in a qualitative way, by grouping together
components with the same reliability, and establishing a prevalence
order among groups, is there a way to decide which components
have the greatest Birnbaum measure without computing the exact
value of this measure? In this paper, three relations between com-
ponents are introduced and studied, and it is proved that they are
useful for selecting the components that have the biggest effect on
the system reliability in the sense of Birnbaum. An algorithm that
uses the results in the paper to select these important components
is also provided.Dynamics of the parabolic restricted three-body problem
http://hdl.handle.net/2117/78941
Dynamics of the parabolic restricted three-body problem
Barrabés Vera, Esther; Cors Iglesias, Josep Maria; Ollé Torner, Mercè
The main purpose of the paper is the study of the motion of a massless body attracted, under the Newton's law of gravitation, by two equal masses moving in parabolic orbits all over in the same plane, the planar parabolic restricted three body problem. We consider the system relative to a rotating and pulsating frame where the equal masses (primaries) remain at rest. The system is gradient like and has exactly ten hyperbolic equilibrium points lying on the boundary invariant manifolds corresponding to escape of the primaries in past and future time. The global flow of the system is described in terms of the final evolution (forwards and backwards in time) of the solutions. The invariant manifolds of the equilibrium points play a key role in the dynamics. We study the connections, restricted to the invariant boundaries, between the invariant manifolds associated to the equilibrium points. Finally we study numerically the connections in the whole phase space, paying special attention to capture and escape orbits. (C) 2015 Elsevier B.V. All rights reserved.
Mon, 09 Nov 2015 15:11:24 GMThttp://hdl.handle.net/2117/789412015-11-09T15:11:24ZBarrabés Vera, EstherCors Iglesias, Josep MariaOllé Torner, MercèThe main purpose of the paper is the study of the motion of a massless body attracted, under the Newton's law of gravitation, by two equal masses moving in parabolic orbits all over in the same plane, the planar parabolic restricted three body problem. We consider the system relative to a rotating and pulsating frame where the equal masses (primaries) remain at rest. The system is gradient like and has exactly ten hyperbolic equilibrium points lying on the boundary invariant manifolds corresponding to escape of the primaries in past and future time. The global flow of the system is described in terms of the final evolution (forwards and backwards in time) of the solutions. The invariant manifolds of the equilibrium points play a key role in the dynamics. We study the connections, restricted to the invariant boundaries, between the invariant manifolds associated to the equilibrium points. Finally we study numerically the connections in the whole phase space, paying special attention to capture and escape orbits. (C) 2015 Elsevier B.V. All rights reserved.Overconvergent generalised eigenforms of weight one and class fields of real quadratic fields
http://hdl.handle.net/2117/78762
Overconvergent generalised eigenforms of weight one and class fields of real quadratic fields
Darmon, Henri; Lauder, Alan; Rotger Cerdà, Víctor
This article examines the Fourier expansions of certain non-classical p-adic modular forms of weight one: the eponymous generalised eigertforms of the title, so called because they lie in a generalised eigenspace for the Hecke operators. When this generalised eigenspace contains the theta series attached to a character of a real quadratic field K in which the prime p splits, the coefficients of the attendant generalised eigenform are expressed as p-adic logarithms of algebraic numbers belonging to an idoneous ring class field of K. This suggests an approach to
Wed, 04 Nov 2015 11:14:19 GMThttp://hdl.handle.net/2117/787622015-11-04T11:14:19ZDarmon, HenriLauder, AlanRotger Cerdà, VíctorThis article examines the Fourier expansions of certain non-classical p-adic modular forms of weight one: the eponymous generalised eigertforms of the title, so called because they lie in a generalised eigenspace for the Hecke operators. When this generalised eigenspace contains the theta series attached to a character of a real quadratic field K in which the prime p splits, the coefficients of the attendant generalised eigenform are expressed as p-adic logarithms of algebraic numbers belonging to an idoneous ring class field of K. This suggests an approach toVariational principles for multisymplectic second-order classical field theories
http://hdl.handle.net/2117/78759
Variational principles for multisymplectic second-order classical field theories
Román Roy, Narciso; Prieto Martínez, Pedro Daniel
We state a unified geometrical version of the variational principles for second-order classical field theories. The standard Lagrangian and Hamiltonian variational principles and the corresponding field equations are recovered from this unified framework.
Wed, 04 Nov 2015 11:07:30 GMThttp://hdl.handle.net/2117/787592015-11-04T11:07:30ZRomán Roy, NarcisoPrieto Martínez, Pedro DanielWe state a unified geometrical version of the variational principles for second-order classical field theories. The standard Lagrangian and Hamiltonian variational principles and the corresponding field equations are recovered from this unified framework.Algorithms for chow-heegner points via iterated integrals
http://hdl.handle.net/2117/78758
Algorithms for chow-heegner points via iterated integrals
Darmon, Henri; Daub, Michael; Lichtenstein, Sam; Rotger Cerdà, Víctor
Let E/Q be an elliptic curve of conductor N and let f be the weight 2 newform on G0(N) associated to it by modularity. Building on an idea of S. Zhang, an article by Darmon, Rotger, and Sols describes the construction of so-called Chow-Heegner points, PT,f ¿ E(Q), indexed by algebraic correspondences T ¿ X0(N) × X0(N). It also gives an analytic formula, depending only on the image of T in cohomology under the complex cycle class map, for calculating PT,f numerically via Chen's theory of iterated integrals. The present work describes an algorithm based on this formula for computing the Chow-Heegner points to arbitrarily high complex accuracy, carries out the computation for all elliptic curves of rank 1 and conductor N < 100 when the cycles T arise from Hecke correspondences, and discusses several important variants of the basic construction.
Wed, 04 Nov 2015 10:59:38 GMThttp://hdl.handle.net/2117/787582015-11-04T10:59:38ZDarmon, HenriDaub, MichaelLichtenstein, SamRotger Cerdà, VíctorLet E/Q be an elliptic curve of conductor N and let f be the weight 2 newform on G0(N) associated to it by modularity. Building on an idea of S. Zhang, an article by Darmon, Rotger, and Sols describes the construction of so-called Chow-Heegner points, PT,f ¿ E(Q), indexed by algebraic correspondences T ¿ X0(N) × X0(N). It also gives an analytic formula, depending only on the image of T in cohomology under the complex cycle class map, for calculating PT,f numerically via Chen's theory of iterated integrals. The present work describes an algorithm based on this formula for computing the Chow-Heegner points to arbitrarily high complex accuracy, carries out the computation for all elliptic curves of rank 1 and conductor N < 100 when the cycles T arise from Hecke correspondences, and discusses several important variants of the basic construction.Some inequalities for the triangle
http://hdl.handle.net/2117/78747
Some inequalities for the triangle
Gibergans Baguena, José; Díaz Barrero, José Luis
Wed, 04 Nov 2015 09:29:48 GMThttp://hdl.handle.net/2117/787472015-11-04T09:29:48ZGibergans Baguena, JoséDíaz Barrero, José LuisHybridizable discontinuous Galerkin p-adaptivity for wave propagation problems
http://hdl.handle.net/2117/78723
Hybridizable discontinuous Galerkin p-adaptivity for wave propagation problems
Giorgiani, Giorgio; Fernandez Mendez, Sonia; Huerta, Antonio
A p-adaptive hybridizable discontinuous Galerkin method for the solution of wave problems is presented in a challenging engineering problem. Moreover, its performance is compared with a high-order continuous Galerkin. The hybridization technique allows to reduce the coupled degrees of freedom to only those on the mesh element boundaries, whereas the particular choice of the numerical fluxes opens the path to a superconvergent postprocessed solution. This superconvergent postprocessed solution is used to construct a simple and inexpensive error estimator. The error estimator is employed to obtain solutions with the prescribed accuracy in the area (or areas) of interest and also drives a proposed iterative mesh adaptation procedure. The proposed method is applied to a nonhomogeneous scattering problem in an unbounded domain. This is a challenging problem because, on the one hand, for high frequencies, numerical difficulties are an important issue because of the loss of the ellipticity and the oscillatory behavior of the solution. And on the other hand, it is applied to real harbor agitation problems. That is, the mild slope equation in frequency domain (Helmholtz equation with nonconstant coefficients) is solved on real geometries with the corresponding perfectly matched layer to damp the diffracted waves. The performance of the method is studied on two practical examples. The adaptive hybridizable discontinuous Galerkin method exhibits better efficiency compared with a high-order continuous Galerkin method using static condensation of the interior nodes.
Tue, 03 Nov 2015 14:03:44 GMThttp://hdl.handle.net/2117/787232015-11-03T14:03:44ZGiorgiani, GiorgioFernandez Mendez, SoniaHuerta, AntonioA p-adaptive hybridizable discontinuous Galerkin method for the solution of wave problems is presented in a challenging engineering problem. Moreover, its performance is compared with a high-order continuous Galerkin. The hybridization technique allows to reduce the coupled degrees of freedom to only those on the mesh element boundaries, whereas the particular choice of the numerical fluxes opens the path to a superconvergent postprocessed solution. This superconvergent postprocessed solution is used to construct a simple and inexpensive error estimator. The error estimator is employed to obtain solutions with the prescribed accuracy in the area (or areas) of interest and also drives a proposed iterative mesh adaptation procedure. The proposed method is applied to a nonhomogeneous scattering problem in an unbounded domain. This is a challenging problem because, on the one hand, for high frequencies, numerical difficulties are an important issue because of the loss of the ellipticity and the oscillatory behavior of the solution. And on the other hand, it is applied to real harbor agitation problems. That is, the mild slope equation in frequency domain (Helmholtz equation with nonconstant coefficients) is solved on real geometries with the corresponding perfectly matched layer to damp the diffracted waves. The performance of the method is studied on two practical examples. The adaptive hybridizable discontinuous Galerkin method exhibits better efficiency compared with a high-order continuous Galerkin method using static condensation of the interior nodes.Spatial behaviour in thermoelastostatic cylinders of indefinitely increasing cross-section
http://hdl.handle.net/2117/78647
Spatial behaviour in thermoelastostatic cylinders of indefinitely increasing cross-section
Knops, Robin J.; Quintanilla de Latorre, Ramón
Alternative growth and decay estimates, reminiscent of the classical Phragmén-Lindelöf principle, are derived for a linearised thermoelastic body whose plane crosssections increase unboundedly with respect to a given direction. The proof uses a modified Poincaré inequality to construct a differential inequality for a weighted linear combination
of the cross-sectional mechanical and thermal energy fluxes. Decay estimates are deduced also for the cross-sectional mean square measures of the displacement and temperature. An explicit upper bound in terms of base data is established for the amplitude occurring in the decay estimates.
The final publication is available at Springer via http://dx.doi.org/10.1007/s10659-015-9523-8
Mon, 02 Nov 2015 14:30:12 GMThttp://hdl.handle.net/2117/786472015-11-02T14:30:12ZKnops, Robin J.Quintanilla de Latorre, RamónAlternative growth and decay estimates, reminiscent of the classical Phragmén-Lindelöf principle, are derived for a linearised thermoelastic body whose plane crosssections increase unboundedly with respect to a given direction. The proof uses a modified Poincaré inequality to construct a differential inequality for a weighted linear combination
of the cross-sectional mechanical and thermal energy fluxes. Decay estimates are deduced also for the cross-sectional mean square measures of the displacement and temperature. An explicit upper bound in terms of base data is established for the amplitude occurring in the decay estimates.On gardeners, dukes and mathematical instruments
http://hdl.handle.net/2117/78617
On gardeners, dukes and mathematical instruments
Blanco Abellán, Mónica
Mon, 02 Nov 2015 11:13:56 GMThttp://hdl.handle.net/2117/786172015-11-02T11:13:56ZBlanco Abellán, Mónica