Experimental study of continuous electromagnetic casting of aluminum alloys

This work begins with a summary of the characteristics of electromagnetic casting and the present knowledge of the subject. Also described is the use of new local measurement techniques for velocity, magnetic field, current density, and phase difference, which allow experimental investigation of the flow of molten metal in industrial equipment (up to 700 °C) in the presence or absence of an induction magnetic field. Next, these methods are applied to the study of electromagnetic and hydrodynamic phenomena, inside the sumps of both rectangular and circular cross-section ingots of aluminum alloys cast in electromagnetic molds. The important shield effect as a function of the screen location is studied by means of a mercury pool simulating electromagnetic casting.     

Electrochemical perfluorination of organic acids. Contribution to the knowledge of the mechanism

Electrochemical perfluorination of octane-sulphofluoride (OSF) and octanoic-fluoride (OF) to the perfluoro compounds (POSF and POF) has been studied over a wide range of experimental conditions. Significant improvement of the reported yield of perfluoro-product has been achieved with electrolysis at high potential. The results are explained in terms of a model involving simultaneous adsorption of the reactant and of fluorine on a NiF₂ surface.     

A non-conforming finite element method for solving a least-square formulation of tricomi's problem

The purpose of this work is to solve in the plane Tricomi's equation of mixed type by means of global least-square formulation. The resolution is obtained with Zienkiewicz's finite element which verifies the patch test, and the incomplete Cholesky conjugate gradient algorithm (ICCG) yields very fast convergence. The least-square formulation is still applicable when a non-linear term is introduced, and the solution is searched for by Newton's method.     

Ern?hrung

Ohne Zusammenfassung     

Stability of thermal waves in helium-cooled superconducting cables

An analytical approach is presented for the determination of the propagation of thermal waves in helium cooled superconducting cables caused by a disturbance resulting in the energy deposition over a finite length of the conductor. The problem is reduced to the solution of an integral equation for the propagation of the thermal front. Sample calculation are presented to illustrate the effects of the strength of the initial energy deposition and the resulting Julian heating on the propagation of the thermal wave.     

On the numerical determination of ideal MHD limits of stability of axisymmetric toroidal configurations

The various problems that are encountered in searching with ERATO the limits of stability of axisymmetric toroidal equilibria are described and illustrated with specific examples.     

Grafting RGD containing peptides onto hydroxyapatite to promote osteoblastic cells adhesion

Ceramics possess osteoconductive properties but exhibit no intrinsic osteoinductive capacity. Consequently, they are unable to induce new bone formation in extra osseous sites. In order to develop bone substitutes with osteogenic properties, one promising approach consists of creating hybrid materials by associating in vitro biomaterials with osteoprogenitor cells. With this aim, we have developed a novel strategy of biomimetic modification to enhance osseointegration of hydroxyapatite (HA) implants. RGD-containing peptides displaying different conformations (linear GRGDSPC and cyclo-DfKRG) were grafted onto HA surface by means of a three-step reaction procedure: silanisation with APTES, cross-linking with N-succinimidyl-3-maleimidopropionate and finally immobilisation of peptides thanks to thiol bonding. Whole process was performed in anhydrous conditions to ensure the reproducibility of the chemical functionalisation. The three-step reaction procedure was characterised by high resolution X-ray photoelectron spectroscopy. Efficiency of this biomimetic modification was finally demonstrated by measuring the adhesion of osteoprogenitor cells isolated from HBMSC onto HA surface.     

Six-degrees-of-freedom alignment technique that provides diagnostic misalignment information

We introduce a new six-degrees-of-freedom alignment technique that enables the precise alignment of two optical device planes. The method combines linear diffraction gratings and cylindrical Fresnel lenses that allow the diagnosis of misalignment in each degree of freedom independently. The technique was used to align two 20 mm x 20 mm fused-silica substrates separated by 17 mm. The worst-case alignment precision was found to be better than +/- 5 microm laterally, +/- 20 microm longitudinally, +/- 0.036 degrees rotationally, and +/- 0.007degrees in tilt.