Ara es mostren els items 1-20 de 46

    • A one-phase Stefan problem with size-dependent thermal conductivity 

      Font Martínez, Francesc (2018-07-02)
      Article
      Accés obert
      In this paper a one-phase Stefan problem with size-dependent thermal conductivity is analysed. Approximate solutions to the problem are found via perturbation and numerical methods, and compared to the Neumann solution for ...
    • A refined statistical cloud closure using double-Gaussian probability density functions 

      Naumann, Ann Kristin; Seifert, Alex; Mellado González, Juan Pedro (2013-10-08)
      Article
      Accés obert
      We introduce a probability density function (PDF)-based scheme to parameterize cloud fraction, average liquid water and liquid water flux in large-scale models, that is developed from and tested against large-eddy simulations ...
    • Assessing the physics of models for transition in pipe flow 

      Cela París, José María (Universitat Politècnica de Catalunya, 2022-07-06)
      Treball Final de Grau
      Accés obert
      Realitzat a/amb:   Universität Bremen / Zentrum für angewandte Raumfahrt­technologie und Mikro­gravitation
      Transition to turbulence in pipe flow is a long standing problem in the field of turbulence research. In the route to fully turbulent pipe flow, turbulence presents itself in a wide variety of forms. In recent years, a ...
    • Computational methodologies for quasi-periodic orbits and invariant manifold connections in non-autonomous problems 

      Li, Ruilong; Masdemont Soler, Josep; Zhu, Zhanxia (International Astronautical Federation (IAF), 2023)
      Text en actes de congrés
      Accés restringit per política de l'editorial
      Semi-analytical and numerical techniques to systematically analyze and compute natural connections between quasi-periodic orbits associated to non-autonomous systems are considered. Focusing in the non-autonomous Sun-Earth+Moon ...
    • Controlling chaotic transport in two-dimensional periodic potentials 

      Chacon, R.; Lacasta Palacio, Ana María (2010-10-07)
      Article
      Accés obert
      We uncover and characterize different chaotic transport scenarios in perfect two-dimensional periodic potentials by controlling the chaotic dynamics of particles subjected to periodic external forces in the absence of a ...
    • Dilute quantum Bose gases beyond its limit of universality 

      Planasdemunt Hospital, Martí (Universitat Politècnica de Catalunya, 2023-07-10)
      Treball Final de Grau
      Accés obert
      The Bose equation of state has not progressed significantly since the universality regime discovery in terms of the s-wave scattering length, a. Nowadays no expansion exists to calculate the energy at higher densities, ...
    • Direct Numerical Simulation of evaporative cooling at the lateral boundary of shallow cumulus clouds 

      Abma, Dick; Heus, Thijs; Mellado González, Juan Pedro (2013-07-23)
      Article
      Accés obert
      This study investigates the dynamics of the subsiding shell at the lateral boundary of cumulus clouds, focusing on the role of evaporative cooling. Since the size of this shell is well below what large-eddy simulations can ...
    • Dynamical sectors for a spinning particle in AdS(3) 

      Batlle Arnau, Carles; Gomis, Jaoquim; Kamimura, kiyoshi; Zanelli, Jorge (American Physical Society, 2014-09-12)
      Article
      Accés obert
      We consider the dynamics of a particle of mass M and spin J in AdS(3). The study reveals the presence of different dynamical sectors depending on the relative values of M, J and the AdS(3) radius R. For the subcritical ...
    • Dynamics of Many-Body Quantum Systems 

      Giménez Grau, Aleix (Universitat Politècnica de Catalunya, 2015-07-03)
      Treball Final de Grau
      Accés obert
      We study the ground state and the excitations of quantum bose systems. The hypernetted chain equations (HNC) are introduced and we show that the methods based on them produce acceptable approximations of the static structure ...
    • Eigenvalue curves for generalized MIT bag models 

      Arrizabalaga, Naiara; Mas Blesa, Albert; Sanz Perela, Tomás; Vega González, Luis (Springer Nature, 2022-11-22)
      Article
      Accés obert
      We study spectral properties of Dirac operators on bounded domains O¿R3 with boundary conditions of electrostatic and Lorentz scalar type and which depend on a parameter t¿R; the case t=0 corresponds to the MIT bag model. ...
    • Exploration of the internal flux rope current density using a spacecraft constellation 

      Ayora Mexia, Marcel (Universitat Politècnica de Catalunya, 2022-05)
      Treball Final de Grau
      Accés obert
      Realitzat a/amb:   Goddard Space Flight Center
      Durant molts anys la comunitat científica ha estat treballant per entendre millor la topologia i les propietats físiques dels tubs de flux (flux ropes en anglès), car són una de les principals formes en les quals l’activitat ...
    • Factorization of the Fourier transform of the pressure-Poisson equation using finite differences in colocated grids 

      Mellado González, Juan Pedro; Ansorge, Cedrick (Wiley-VCH, 2012-02-29)
      Article
      Accés obert
      The zero-divergence constraint on the velocity field in the numerical simulation of incompressible flows can be reduced, in certain cases, to a set of one-dimensional linear difference equations for the pressure. These ...
    • Geometric Hamilton-Jacobi theory for higher-order autonomous systems 

      Colombo, Leonardo; de León, Manuel; Prieto Martínez, Pedro Daniel; Román Roy, Narciso (2013-09-09)
      Report de recerca
      Accés obert
      The geometric framework for the Hamilton-Jacobi theory is used to study this theory in the ambient of higher-order mechanical systems, both in the Lagrangian and Hamiltonian formalisms. Thus, we state the corresponding ...
    • Geometric Quantization of real polarizations via sheaves 

      Miranda Galcerán, Eva; Presas, Francisco (2013-01)
      Report de recerca
      Accés obert
      In this article we develop tools to compute the Geometric Quantization of a symplectic manifold with respect to a regular Lagrangian foliation via sheaf cohomology. The starting point is the definition of representation ...
    • Global analysis of direct transfers from lunar orbits to sun-earth libration point regimes 

      Masdemont Soler, Josep; Gómez Muntané, Gerard; Peng, Hao (Springer Nature, 2021-04-01)
      Article
      Accés obert
      In this paper we look forward to obtain a global picture of simple transfer opportunities from Lunar to Sun-Earth libration orbits, useful for a preliminary design of these mission scenarios. Considering the trajectory of ...
    • Gravitational Particle Production in Massive Chaotic Inflation and the Moduli Problem 

      Haro Cases, Jaume; Elizalde, Emilio (2012-02)
      Article
      Accés restringit per política de l'editorial
      Particle production from vacuum fluctuations during inflation is briefly revisited. The moduli problem occurring with light particles produced at the end of inflation is addressed, namely the fact that some results are in ...
    • Groupoids and Faà di Bruno formulae for Green functions in bialgebras of trees 

      Gálvez Carrillo, Maria Immaculada; Kock, Joachim; Tonks, Andrew (2014)
      Article
      Accés restringit per política de l'editorial
      We prove a Faà di Bruno formula for the Green function in the bialgebra of P-trees, for any polynomial endofunctor P. The formula appears as relative homotopy cardinality of an equivalence of groupoids.
    • Groupoids and Faà di Bruno Formulae for green functions in bialgebras of trees 

      Gálvez Carrillo, Maria Immaculada; Tonks, Andrew; Kock, Joachim (2012-07)
      Report de recerca
      Accés obert
      We prove a Faa di Bruno formula for the Green function in the bialgebra of P-trees, for any polynomial endofunctor P. The formula appears as relative homotopy cardinality of an equivalence of groupoids. For suitable choices ...
    • Heterogenous mean-field analysis of a generalized voter-like model on networks 

      Moretti, Paolo; Liu, S.Y.; Baronchelli, Andrea; Pastor Satorras, Romualdo (Springer, 2012-03)
      Article
      Accés obert
      We propose a generalized framework for the study of voter models in complex networks at the heterogeneous mean-field (HMF) level that (i) yields a unified picture for existing copy/invasion processes and (ii) allows for ...
    • High order dynamical systems approaches for low-thrust station-keeping of libration point orbits 

      Gao, Chen; Masdemont Soler, Josep; Gómez, Gerard; Chen, Jianlin; Yuan, Jianping (2022-01-01)
      Article
      Accés obert
      We derive two families of low-thrust station-keeping control procedures based on the dynamical properties of the phase space near libration point orbits. The first family is obtained as the limit of impulsive maneuvers, ...