227 research outputs found

    Ab initio oscillator strengths for transitions between J=1 odd and J=1,2 even excited states of Ne I

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    Ab initio theory is developed for radiative transitions between excited states of neon. Calculations of energies for even excited states J=1, J=2 supplement our previous calculations for J=1 odd excited states. Line strengths for transitions between J=1 odd and J=1,2 even states of Ne I are evaluated. A comparison with experiments and semiempirical calculations is given.Comment: 5 page

    A robust semantics hides fewer errors

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    In this paper we explore how formal models are interpreted and to what degree meaning is captured in the formal semantics and to what degree it remains in the informal interpretation of the semantics. By applying a robust approach to the definition of refinement and semantics, favoured by the event-based community, to state-based theory we are able to move some aspects from the informal interpretation into the formal semantics

    Antiferromagnetic ordering in a 90 K copper oxide superconductor

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    Using elastic neutron scattering, we evidence a commensurate antiferromagnetic Cu(2) order (AF) in the superconducting (SC) high-Tc\rm T_c cuprate YBa2(Cu1yCoy)3O7+δ\rm YBa_2(Cu_{1-y}Co_y)_3O_{7+\delta} (y=0.013, Tc\rm T_c=93 K). As in the Co-free system, the spin excitation spectrum is dominated by a magnetic resonance peak at 41 meV but with a reduced spectral weight. The substitution of Co thus leads to a state where AF and SC cohabit showing that the CuO2_2 plane is a highly antiferromagnetically polarizable medium even for a sample where Tc_c remains optimum.Comment: 3 figure

    Periodic Travelling Waves in Dimer Granular Chains

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    We study bifurcations of periodic travelling waves in granular dimer chains from the anti-continuum limit, when the mass ratio between the light and heavy beads is zero. We show that every limiting periodic wave is uniquely continued with respect to the mass ratio parameter and the periodic waves with the wavelength larger than a certain critical value are spectrally stable. Numerical computations are developed to study how this solution family is continued to the limit of equal mass ratio between the beads, where periodic travelling waves of granular monomer chains exist

    Existence and stability of viscoelastic shock profiles

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    We investigate existence and stability of viscoelastic shock profiles for a class of planar models including the incompressible shear case studied by Antman and Malek-Madani. We establish that the resulting equations fall into the class of symmetrizable hyperbolic--parabolic systems, hence spectral stability implies linearized and nonlinear stability with sharp rates of decay. The new contributions are treatment of the compressible case, formulation of a rigorous nonlinear stability theory, including verification of stability of small-amplitude Lax shocks, and the systematic incorporation in our investigations of numerical Evans function computations determining stability of large-amplitude and or nonclassical type shock profiles.Comment: 43 pages, 12 figure

    Posibilidades de reproducción del atún rojo, Thunnus thynnus, en cautividad

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    This paper describes results achieved in a 3-year-long research project supported by the European Commission (EU) aimed at studying the feasibility to achieve reproduction of Bluefin tuna (BFT), Thunnus thynnus, in captivity. The project involves nine partners from seven Mediterranean countries. The overall objective of this project is to improve our understanding of the reproductive physiology of BFT as the basis to develop a suitable methodology for the control of its reproduction in captivity. Results have indicated that BFT reared in captivity are able to achieve maturation and spawn, naturally or hormonally induced, and consequently get larvae by in vitro fertilization. Thus, opening the possibility to an eco-friendly and economically sustainable production of BFT in the Mediterranean

    PAB3D: Its History in the Use of Turbulence Models in the Simulation of Jet and Nozzle Flows

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    This is a review paper for PAB3D s history in the implementation of turbulence models for simulating jet and nozzle flows. We describe different turbulence models used in the simulation of subsonic and supersonic jet and nozzle flows. The time-averaged simulations use modified linear or nonlinear two-equation models to account for supersonic flow as well as high temperature mixing. Two multiscale-type turbulence models are used for unsteady flow simulations. These models require modifications to the Reynolds Averaged Navier-Stokes (RANS) equations. The first scheme is a hybrid RANS/LES model utilizing the two-equation (k-epsilon) model with a RANS/LES transition function, dependent on grid spacing and the computed turbulence length scale. The second scheme is a modified version of the partially averaged Navier-Stokes (PANS) formulation. All of these models are implemented in the three-dimensional Navier-Stokes code PAB3D. This paper discusses computational methods, code implementation, computed results for a wide range of nozzle configurations at various operating conditions, and comparisons with available experimental data. Very good agreement is shown between the numerical solutions and available experimental data over a wide range of operating conditions
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