DSpace Community:
http://hdl.handle.net/2117/127
2014-12-18T16:30:33ZNonlinear equations for fractional Laplacians, I: Regularity, maximum principles, and Hamiltonian estimates
http://hdl.handle.net/2117/22391
Title: Nonlinear equations for fractional Laplacians, I: Regularity, maximum principles, and Hamiltonian estimates
Authors: Cabré Vilagut, Xavier; Sire, Yannick
Abstract: This is the first of two articles dealing with the equation (-)sv = f (v) in Rn, with s ¿ (0,1), where (-)s stands for the fractional Laplacian — the in¿nitesimal generator of a Lévy process. This equation can be realized as a local linear degenerate elliptic equation in Rn+1+ together with a nonlinear Neumann boundary condition on ¿Rn+1 + =Rn.
In this ¿rst article, we establish necessary conditions on the nonlinearity f to admit certain type of solutions, with special interest in bounded increasing solutions in all of R. These necessary conditions (which will be proven in a follow-up paper to be also suficient for the existence of a bounded increasing solution) are derived from an equality and an estimate involving a Hamiltonian — in the spirit of a result of Modica for the Laplacian. Our proofs are uniform ass ¿1, establishing in the limit the corresponding known results for the Laplacian.
In addition, we study regularity issues, as well as maximum and Harnack principles associated to the equation.Estructuras A-infinito en la opérada de cactus
http://hdl.handle.net/2117/22097
Title: Estructuras A-infinito en la opérada de cactus
Authors: Gálvez Carrillo, Maria Immaculada; Lombardi, Leandro; Tonks, Andrew
Abstract: Diversas versiones de la opérada de cactus inicialmente definida por Voronov han sido estudiadas. Es conocida su equivalencia débil con la opérada de pequeños discos. Se conoce pues que la opérada de cactus admite una acción de la opérada de Gerstenhaber salvo homotopía. En este proyecto, nuestro objetivo es obtener una realización explícita de dicha acción. Por el momento, hemos construido una acción explícita de la opérada A8 en la opérada de cactus, que presentamos en este pósterJ2 effect and elliptic inclined periodic orbits in the collision three-body problem
http://hdl.handle.net/2117/21117
Title: J2 effect and elliptic inclined periodic orbits in the collision three-body problem
Authors: Barrabes, Esther; Cors Iglesias, Josep Maria; Pinyol, Conxita; Soler Villanueva, Jaume
Abstract: The existence of a new class of inclined periodic orbits of the collision restricted
three{body problem is shown. The symmetric periodic solutions found are perturbations of elliptic
kepler orbits and they exist only for special values of the inclination and are related to the motion
of a satellite around an oblate planet.AAR-based decomposition algorithm for non-linear convex optimisation
http://hdl.handle.net/2117/25084
Title: AAR-based decomposition algorithm for non-linear convex optimisation
Authors: Rabiei, Syednima; Muñoz Romero, José2014-12-18T14:03:50ZAAR-based decomposition method for limit analysis
http://hdl.handle.net/2117/25083
Title: AAR-based decomposition method for limit analysis
Authors: Rabiei, Nima; Muñoz Romero, José2014-12-18T13:50:48ZSimulation analysis of a dynamic ridesharing model
http://hdl.handle.net/2117/25015
Title: Simulation analysis of a dynamic ridesharing model
Authors: Guasch Petit, Antonio; Figueras Jové, Jaume; Fonseca Casas, Pau; Montañola Sales, Cristina; Casanovas Garcia, Josep
Abstract: A dynamic ridesharing service is a system that enables drivers and riders to arrange one-time shared rides, with sufficient convenience and flexibility to be used on a daily basis. The quality of a dynamic ridesharing service is critical for commuters who need to reach their end destination on time every day.
To ensure satisfactory quality, the waiting times in a ridesharing service must be low. This paper describes a dynamic ridesharing model proposal for commuters living in a small community in the Barcelona metropolitan area. The proposal solves transport problems between the community and a communication hub served by trains and buses. A survey was sent to community residents to find out whether they would be interested in the idea and willing to participate in a pilot test. A simulation model
was built to determine to most suitable type of dynamic ridesharing model given the limited numbers of responses received and the heterogeneous mobility patterns of drivers and riders in the community. Reasonable good results are obtained for the morning commute but improvements are needed for the return commute in the afternoon. Further work will be required to increase the number of drivers interested in the ridesharing service.2014-12-12T13:37:46ZSufficient conditions for controllability and observability of serial and parallel concatenated linear systems
http://hdl.handle.net/2117/25002
Title: Sufficient conditions for controllability and observability of serial and parallel concatenated linear systems
Authors: García Planas, María Isabel; Domínguez García, José Luis; Um, Laurence Emilie
Abstract: This paper deals with the sufficient conditions
for controllability and observability characters of finitedimensional
linear continuous-time-invariant systems of serial
and parallel concatenated systems. The obtained conditions
depend on the controllability and observability of the systems
and in some cases, the functional output-controllability of the
first one.2014-12-11T12:39:29ZXiao's conjuecture for general fibred surfaces
http://hdl.handle.net/2117/24999
Title: Xiao's conjuecture for general fibred surfaces
Authors: Barja Yáñez, Miguel Ángel; González Alonso, Víctor; Naranjo del Val, Joan Carles
Abstract: We prove that the genus g, the relative irregularity q_f and the Clifford index c_f of a non-isotrivial fibration
f satisfy the inequality q_f=g-c_f. This gives in particular a proof of Xiao’s conjecture for
fibrations whose general fibres have maximal Clifford index.
Description: Prerpint2014-12-11T12:05:29ZStability and singularities of relative hypersurfaces
http://hdl.handle.net/2117/24998
Title: Stability and singularities of relative hypersurfaces
Authors: Barja Yáñez, Miguel Ángel; Stoppino, Lidia
Abstract: We study relative hypersurfaces, and prove an instability condition for the fibres. This
is the starting point for an investigation of the geometry of effective divisors on relative
projective bundles.2014-12-11T12:01:17ZAddendum to “Frobenius and Cartier algebras of Stanley–Reisner rings” [J. Algebra 358 (2012) 162–177]
http://hdl.handle.net/2117/24996
Title: Addendum to “Frobenius and Cartier algebras of Stanley–Reisner rings” [J. Algebra 358 (2012) 162–177]
Authors: Álvarez Montaner, Josep; Yanagawa, Kohji
Abstract: We give a purely combinatorial characterization of complete Stanley–Reisner rings having a principally generated (equivalently, finitely generated) Cartier algebra.2014-12-11T09:15:25ZAlgebraic description of Jacobians isogeneous to certain Prym varieties with polarization (1,2)
http://hdl.handle.net/2117/24994
Title: Algebraic description of Jacobians isogeneous to certain Prym varieties with polarization (1,2)
Authors: Fedorov, Yuri; Enolski, Viktor Z.
Abstract: For a class of non-hyperelliptic genus 3 curves C which are 2-fold coverings of elliptic curves E, we give an explicit algebraic description of all birationally non-equivalent genus 2 curves whose Jacobians are degree 2 isogeneous to the Prym varieties associated to such coverings. Our description is based on previous studies of Prym varieties with polarization (1,2) in connection with separation of variables in a series of classical and new algebraic integrable systems linearized on such varieties.
We also consider some special cases of the covering C -> E, in particular, when the corresponding Prym varieties contain pairs of elliptic curves and the Jacobian of C is isogeneous (but not isomorphic) to the product of 3 different elliptic curves.
Our description is accompanied with explicit numerical examples2014-12-11T08:09:29ZA new approach to the vakonomic mechanics
http://hdl.handle.net/2117/24993
Title: A new approach to the vakonomic mechanics
Authors: Llibre Saló, Jaume; Ramírez Ros, Rafael; Sadovskaia Nurimanova, Natalia Guennadievna
Abstract: The aim of this paper was to show that the Lagrange-d'Alembert and its equivalent the Gauss and Appel principle are not the only way to deduce the equations of motion of the nonholonomic systems. Instead of them we consider the generalization of the Hamiltonian principle for nonholonomic systems with non-zero transpositional relations. We apply this variational principle, which takes into the account transpositional relations different from the classical ones, and we deduce the equations of motion for the nonholonomic systems with constraints that in general are nonlinear in the velocity. These equations of motion coincide, except perhaps in a zero Lebesgue measure set, with the classical differential equations deduced with the d'Alembert-Lagrange principle. We provide a new point of view on the transpositional relations for the constrained mechanical systems: the virtual variations can produce zero or non-zero transpositional relations. In particular, the independent virtual variations can produce non-zero transpositional relations. For the unconstrained mechanical systems, the virtual variations always produce zero transpositional relations. We conjecture that the existence of the nonlinear constraints in the velocity must be sought outside of the Newtonian mechanics. We illustrate our results with examples.2014-12-11T08:01:15ZZero, minimum and maximum relative radial acceleration for planar formation flight dynamics near triangular libration points in the Earth-Moon system
http://hdl.handle.net/2117/24992
Title: Zero, minimum and maximum relative radial acceleration for planar formation flight dynamics near triangular libration points in the Earth-Moon system
Authors: Salazar, F.J.T; Masdemont Soler, Josep; Gómez Muntané, Gerard; Macau, E.E.N.; Winter, O. C.
Abstract: Assume a constellation of satellites is flying near a given nominal trajectory around L-4 or L-5 in the Earth-Moon system in such a way that there is some freedom in the selection of the geometry of the constellation. We are interested in avoiding large variations of the mutual distances between spacecraft. In this case, the existence of regions of zero and minimum relative radial acceleration with respect to the nominal trajectory will prevent from the expansion or contraction of the constellation. In the other case, the existence of regions of maximum relative radial acceleration with respect to the nominal trajectory will produce a larger expansion and contraction of the constellation. The goal of this paper is to study these regions in the scenario of the Circular Restricted Three Body Problem by means of a linearization of the equations of motion relative to the periodic orbits around L-4 or L-5. This study corresponds to a preliminar planar formation flight dynamics about triangular libration points in the Earth-Moon system. Additionally, the cost estimate to maintain the constellation in the regions of zero and minimum relative radial acceleration or keeping a rigid configuration is computed with the use of the residual acceleration concept. At the end, the results are compared with the dynamical behavior of the deviation of the constellation from a periodic orbit. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.2014-12-11T07:49:26ZCombined low-thrust propulsion and invariant manifold trajectories to capture NEOs in the Sun-Earth circular restricted three-body problem
http://hdl.handle.net/2117/24981
Title: Combined low-thrust propulsion and invariant manifold trajectories to capture NEOs in the Sun-Earth circular restricted three-body problem
Authors: Mingotti, Giorgio; Sánchez Cuartielles, Joan Pau; McInnes, Colin
Abstract: In this paper, a method to capture near-Earth objects (NEOs) incorporating low-thrust propulsion into the invariant manifolds technique is investigated. Assuming that a tugboat-spacecraft is in a rendez-vous condition with the candidate asteroid, the aim is to take the joint spacecraft-asteroid system to a selected periodic orbit of the Sun-Earth restricted three-body system: the orbit can be either a libration point periodic orbit (LPO) or a distant prograde periodic orbit (DPO) around the Earth. In detail, low-thrust propulsion is used to bring the joint spacecraft-asteroid system from the initial condition to a point belonging to the stable manifold associated to the final periodic orbit: from here onward, thanks to the intrinsic dynamics of the physical model adopted, the flight is purely ballistic. Dedicated guided and capture sets are introduced to exploit the combined use of low-thrust propulsion with stable manifolds trajectories, aiming at defining feasible first guess solutions. Then, an optimal control problem is formulated to refine and improve them. This approach enables a new class of missions, whose solutions are not obtainable neither through the patched-conics method nor through the classic invariant manifolds technique.2014-12-10T12:43:20ZAutomatic subsystem identification in statistical energy analysis
http://hdl.handle.net/2117/24965
Title: Automatic subsystem identification in statistical energy analysis
Authors: Díaz Cereceda, Cristina; Poblet-Puig, Jordi; Rodríguez Ferran, Antonio
Abstract: An automatic methodology for identifying SEA (statistical energy analysis) subsystems within a vibroacoustic system is presented. It consists in dividing the system into cells and grouping them into subsystems via a hierarchical cluster analysis based on the problem eigenmodes. The subsystem distribution corresponds to the optimal grouping of the cells, which is defined in terms of the correlation distance between them. The main advantages of this methodology are its automatic performance and its applicability both to vibratory and vibroacoustic systems. Moreover, the method allows the definition of more than one subsystem in the same geometrical region when required. This is the case of eigenmodes with a very different mechanical response (e.g. out-of-plane or in-plane vibration in shells).2014-12-09T18:47:12Z