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Photopolymerization of methacrylated dental resins at room temperature leads to the appearance of long-life free radicals because of system vitrification. These free radicals were observed by electronic paramagnetic resonance (EPR), and their characterization was undertaken by reference to the reactional mechanism, from the comparison with the model EPR signal and from theoretical simulation. Overlapping of two EPR signals assigned to two different kinds of radicals because of methacrylate end groups accounted for all the experimental and theoretical results. (C) 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1691-1699, 2003.

Owing to their low polydispersity and their well controlled molecular architecture, 3-arms stars polystyrenes made by anionic synthesis are suitable models to study the solution proper-ties of long chain branched polymers. A fine characterization of such polymers by size exclusion chromatography-viscometry has shown that they often contain unwanted linear chains, leading to chromatograms presenting overlapping peaks. A mathematical procedure has been developed in order to deconvolute these chromatograms and has been validated, thanks to blends of polystyrene standards. It allows one to calculate the purity of the sample as well as the intrinsic viscosity and molar mass distribution of each component. For stars with three arms of the same length, branching parameters have also been calculated and a viscosity law has been established. (C) 2002 Elsevier Science Ltd. All rights reserved.

International audience; This paper deals with the high-order discontinuous Galerkin (DG) method for solving wave propagation problems. First, we develop a one-dimensional DG scheme and numerically compute dissipation and dispersion errors for various polynomial orders. An optimal combination of time stepping scheme together with the high-order DG spatial scheme is presented. It is shown that using a time stepping scheme with the same formal accuracy as the DG scheme is too expensive for the range of wave numbers that is relevant for practical applications. An efficient implementation of a high-order DG method in three dimensions is presented. Using 1D convergence results, we further show how to adequately choose elementary polynomial orders in order to equi-distribute a priori the discretization error. We also show a straightforward manner to allow variable polynomial orders in a DG scheme. We finally propose some numerical examples in the field of aero-acoustics.

I Introduction 2II Mathematical model 2A Finite and infinite elements, frequency-domain approach . . . . . . . . . . . . . . . . . . . . . 21 Governing equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Free field boundary condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Coupling with acoustic ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Spatial discretization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Solver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4B RK-DGM approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Governing equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Spatial discretization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Implementation of the space Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Optimization of the computation of surface fluxes . . . . . . . . . . . . . . . . . . . . 75 Convergence properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Time discretization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Boundary conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10IIIValidation 12A Test case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12IVLarge-scale applications 15A Parallel implementation of the DG method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15B Test case 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15C Test case 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17V Conclusions 18VIAcknowledgments 18

In this paper, we investigate the use of the variational formulation of Lighthill’s analogy, implemented in a Finite/Infinite Element framework. We present an innovative way to handle porous boundaries (or equivalently, control surfaces upon which aerodynamic sources are defined). We show how Lighthill’s analogy can be used to predict broadband blower noise. Infinite elements are used to enforce the Sommerfeld radiation boundary condition. A derivation of the analogy is presented and is compared with the derivation of Curle’s analogy (extended to handle porous boundaries). The implementation is described and is validated on a test case. Preliminary results on a real automotive HVAC blower case are presented.

The quintessential aeroacoustic test case of an Helmholtz resonator was studied, deploying the recently released coupling between the Engineering design tools STAR-CD (a CFD code) and Actran/LA (a CA code). The objective, to accurately model both the frequency and magnitude of the aeroacoustic resonance phenomenon in the geometry as compared with both experimental and analytical data, was achieved. This paper presents the methodology used, demonstrates the importance of accurate representation of compressible effects in CFD, and presents methods to optimise the data transfer between the codes by focusing on the dominant source regions.

The flow through an HVAC blower fan, typical to the automotive industry, was solved using STAR-CD. Time varying pressure data was then exported to ACTRAN/TM where the CFD results were decomposed into acoustic duct modes, using a multiple plane matching method. These duct modes were then propagated to far field locations and compared with experimental data at the blade passing frequency, obtained in the semi-anechoic chamber at Denso Thermal Systems. Good agreement was attained for microphones located downstream of the inlet and outlet ducts. At the other microphone locations there is doubt that the dominant noise generation mechanism is purely aeroacoustic: vibroacoustic noise sources are present. Since aeroacoustic noise sources alone were modeled, there was a deterioration in the simulation/experimental comparison.