1,721,443 research outputs found
Solving cubic matrix equations arising in conservative dynamics
Full text linkIn this paper we consider the spatial semi-discretization of conservative PDEs. Such finite dimensional approximations of infinite dimensional dynamical systems can be described as flows in suitable matrix spaces, which in turn leads to the need to solve polynomial matrix equations, a classical and important topic both in theoretical and in applied mathematics. Solving numerically these equations is challenging due to the presence of several conservation laws which our finite models incorporate and which must be retained while integrating the equations of motion. In the last thirty years, the theory of geometric integration has provided a variety of techniques to tackle this problem. These numerical methods require solving both direct and inverse problems in matrix spaces. We present three algorithms to solve a cubic matrix equation arising in the geometric integration of isospectral flows. This type of ODEs includes finite models of ideal hydrodynamics, plasma dynamics, and spin particles, which we use as test problems for our algorithms.In this paper we consider the spatial semi-discretization of conservative PDEs. Such finite dimensional approximations of infinite dimensional dynamical systems can be described as flows in suitable matrix spaces, which in turn leads to the need to solve polynomial matrix equations, a classical and important topic both in theoretical and in applied mathematics. Solving numerically these equations is challenging due to the presence of several conservation laws which our finite models incorporate and which must be retained while integrating the equations of motion. In the last thirty years, the theory of geometric integration has provided a variety of techniques to tackle this problem. These numerical methods require solving both direct and inverse problems in matrix spaces. We present three algorithms to solve a cubic matrix equation arising in the geometric integration of isospectral flows. This type of ODEs includes finite models of ideal hydrodynamics, plasma dynamics, and spin parti..
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Erratum: Subleading contributions to the three-nucleon contact interaction (Phys. Rev. C (2011)84 (014001) DOI: 10.1103/PhysRevC.84.014001)
No full textWe obtain a minimal form of the two-derivative three-nucleon contact Lagrangian, by imposing all constraints deriving from discrete symmetries, Fierz identities, and Poincaré covariance. The resulting interaction, depending on 10 unknown low-energy constants, leads to a three-nucleon potential which we give in a local form in configuration space. We also consider the leading (no-derivative) four-nucleon interaction and show that there exists only one independent operator
Cavitation tunnel in Naval Architecture: from cavitation prediction to radiated noise
No full textCavitation tunnels represent one of the most important typologies of model test ing facilities used in Naval Architecture These facilities are employed to study the hydrodynamics of marine propellers, with special attention on cavitation and its side effects. These effects include: loss of propeller thrust and efficiency, erosion, inboard noise and vibration, underwater ra diated noise. The latter aspect is one of the hot topics in the field of ship h ydrodynamics because of the concerns related to its impact on marine life. This paper presents the general setup and test procedures used to predict the propeller radiated noise based on model tests. In addition, some of the main experimental issues relate d to these activities are described
Theoretical description of three- and four-nucleon scattering states using bound-state-like wave functions
No full textBound-state-like wave functions are used to determine the scattering matrix corresponding to low-energy n-d and p-(3)He collisions. To this end, the coupled-channel form of the integral relations derived from the Kohn variational principle is used. The construction of degenerate bound-state-like wave functions belonging to the continuum spectrum of the Hamiltonian is discussed. Examples are shown using realistic nucleon-nucleon forces
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