Resummed Kinetic Field Theory: Using Mesoscopic Particle Hydrodynamics to Describe Baryonic Matter in a Cosmological Framework

Recently, Bartelmann et al. presented a 'Kinetic Field Theory' (KFT) formalism to tackle the difficulties of large scale structure formation. In this approach, the dynamics of a non-equilibrium ensemble of classical particles are examined based on methods of statistical field theory. So far, only contributions coming from dark matter were considered, which is assumed to pose an accurate description of our universe on very large scales. Nevertheless, going to smaller scales, also baryonic contributions have to be taken into account. Building on the ideas of Viermann et al. we present an effective particle model of hydrodynamics to describe baryonic matter in a cosmological framework. Using this model, the baryonic density contrast power spectrum is computed to lowest perturbative order within the resummed KFT framework of Lilow et al. We discuss the qualitative differences to the dark matter case and perform a quantitative comparison to the baryonic spectrum obtained from Eulerian perturbation theory. A subsequent paper will resolve the problem of coupling both theories describing dark and baryonic matter, respectively, to gain a full model of cosmic matter. Even though our focus is on cosmological systems only, we want to emphasize that all methods presented here are of a quite general fashion, making it applicable also to other fields.Comment: 24 pages, 2 figures, current version: added more explanatory material (especially on the underlying RKFT-formalism), added references to literature on non-linear structure formation, make difference to pure dark matter model clearer, further minor changes; content matches published versio

Avaliação da eficiência do tratamento preservante em moirões de Eucalyptus dunnii pelo método de substituição de seiva.

Organizado por Patricia Póvoa de Mattos, Celso Garcia Auer, Rejane Stumpf Sberze, Katia Regina Pichelli e Paulo César Botosso

Experimental investigation of the blade/seal interaction

International audienceThe use of dynamic seals to reduce the rotor/stator dynamic clearance in jet engine compressor stages leads to a higher rubbing occurrence between each blade and the coated inside of the casing. This article describes the development of a test rig capable to investigate forces and wear at the dynamic blade/seal interaction, in conjunction with blade kinetics. Testing conditions are consistent with those of low-pressure compressor stages of jet engines: high-speed rubbing occurs between a TA6V blade substitute and an aluminium-silicon/boron nitride abradable seal. The platform is instrumented to allow a dynamic measurement of forces and displacements as well as high-speed imaging of the blade/seal interaction zone throughout the experiment. The experiments showed that the blade incursion speed and penetration depth in the abradable seal both affect the amplitude and frequency of blade vibration. The amount and severity of blade incursions into the abradable seal have an impact on seal wear type and intensity, which can in turn increase blade excitation

Contribution to the definition of a partial overlapping plastic strain rates domain for moderate loadings - application to tensile testing on metallic materials

Generally, tensile testing on Hopkinson bars requires some particular considerations. Most of the specific devices, designed to hold tensile sheet specimens on the bars, involve the degradation of the pulses in particular case of no-direct tensile loadings. A tensile testing configuration for sheet specimens is proposed on the basis of classical split Hopkinson pressure bars (SHPB). Specimens holding is obtained with an epoxy adhesive and provides good measurements on sheet specimens. A comparison is made for the same two metallic materials results extracted from literature and dynamic tensile tests performed with a high speed hydraulic machine and another split Hopkinson bars (SHPB) facility using hat-specimens. A partial overlapping domain in terms of plastic strain is shown at moderate strain rates from 200 to 400 s−1