Dynamic Local Strain Measurement From the Digital Image Processing of the Grating Interrogation

The direct measurement of local strains during a dynamic loading is proposed from the spectral analysis of a crossed grating using optical diffraction under oblique incidence This procedure is experimentally achieved with acousto-optic modulators which allow to record 24 strain states at a maximum frequency near to 1MHz. The diffraction figures can be recorded on a photographic film or directly on a C.C.D. camera. The automatic localisation of the diffracted spots with the help of data image processing gives the components of the strain tensor. The strain measurement method is performed for compression impact tests using an Hopkinson bar loading.La mesure directe des déformations en dynamique met à profit l'analyse spectrale de réseaux croisés par diffraction sous incidence oblique. La mise en oeuvre expérimentale utilise des modulateurs acousto-optiques qui permettent l'enregistrement de 24 états de déformation à une fréquence maximum proche du MHz. Les figures de diffraction sont enregistrées sur plan film ou directement sur camera C.C.D.. La localisation automatique des taches diffractées au moyen d'une procédure de traitement et d'analyse d'images fournit les composantes du tenseur des déformations. La métrologie développée est appliquée sur des essais d'impact en compression par barres d'Hopkinson

Phase Change Memories challenges: A material and process perspective

peer reviewedAmong all the new memories concepts, Phase Change Memories (PCM) is one of the most promising. However, various challenges remain. This paper reviews the materials and processes required to face these challenges. As an example, attention will be made on the effect of Phase change material composition on stability of the amorphous phase i.e. on the retention of the information. Additionally, it is showed how specific processes such as CVD or ALD can be developed in order to minimize the current required to amorphize the phase change material i.e. to reset the device. Finally, with the perspectives of the advanced integration nodes, experimental results on the effect of scaling on phase transformation are presented and discussed. © 2012 IEEE.PERCEVALL project; MaxCaps project (2T210 - European Medea+ framework); Refined project (CT205 - European Medea+ framework

Highly photostable luminescent poly(caprolactone)siloxane biohybrids doped with europium complexes

In this paper, we propose for the first time that the combination of a sol-gel derived diurethane cross-linked siloxane-based biohybrid host including short poly(ε-caprolactone) segments (PCL(530)) and lanthanide aquocomplexes incorporating β-diketonate ligands yields an effective protecting cage that efficiently encapsulates the emitting centers and reduces luminescence quenching. The results obtained using the Eu(tta) 3 (H 2 O) 2 (where tta - is 2-thenoyltrifluoracetonate) complex demonstrate that 1 (2) carbonyl oxygen atoms of the host matrix enter the Eu 3+ coordination shell, thus replacing the labile water molecule-(s). The significant increase in the quantum efficiency q of the doped hybrid with respect to that of Eu(tta) 3 (H 2 O) 2 (44.2 versus 29.0%, respectively) reveals that complex anchoring to the PCL(530)-based host structure contributes to enhancement of the 5 D 0 quantum efficiency. However, when a complex that contains only strong chelating ligands, such as Eu(tta) 3 phen (where phen is 1,10-phenantroline), is incorporated into the same host medium, the effect is lost and the 5 D 0 nonradiative paths in the doped hybrid are higher than those existing in the complex itself. Under UVA exposure, the emission intensity of PCL(530)/siloxane/Eu(tta) 3 (H 2 O) 2 decreased 10% in 11 h, whereas that of PCL(530)/siloxane/Eu-(tta) 3 phen decreased 25% in the same period of time.Fundação para a Ciência e para a Tecnologia -POCI/CTM/46780/03; POCI/CTM/40063/01.CQ-VR