53 research outputs found
Dynamic Local Strain Measurement From the Digital Image Processing of the Grating Interrogation
Prediction of marbofloxacin dosage for the pig pneumonia pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida by pharmacokinetic/pharmacodynamic modelling
PK/PD integration data. (DOCX 7 kb
Micro-combs: a novel generation of optical sources
The quest towards the integration of ultra-fast, high-precision optical clocks is reflected in the large number of high-impact papers on the topic published in the last few years. This interest has been catalysed by the impact that high-precision optical frequency combs (OFCs) have had on metrology and spectroscopy in the last decade [1â5]. OFCs are often referred to as optical rulers: their spectra consist of a precise sequence of discrete and equally-spaced spectral lines that represent precise marks in frequency. Their importance was recognised worldwide with the 2005 Nobel Prize being awarded to T.W. HĂ€nsch and J. Hall for their breakthrough in OFC science [5]. They demonstrated that a coherent OFC source with a large spectrum â covering at least one octave â can be stabilised with a self-referenced approach, where the frequency and the phase do not vary and are completely determined by the source physical parameters. These fully stabilised OFCs solved the challenge of directly measuring optical frequencies and are now exploited as the most accurate time references available, ready to replace the current standard for time. Very recent advancements in the fabrication technology of optical micro-cavities [6] are contributing to the development of OFC sources. These efforts may open up the way to realise ultra-fast and stable optical clocks and pulsed sources with extremely high repetition-rates, in the form of compact and integrated devices. Indeed, the fabrication of high-quality factor (high-Q) micro-resonators, capable of dramatically amplifying the optical field, can be considered a photonics breakthrough that has boosted not only the scientific investigation of OFC sources [7â13] but also of optical sensors and compact light modulators [6,14]
Vegetation succession and climate change across the Plio-Pleistocene transition in eastern Azerbaijan, central Eurasia (2.77â2.45 Ma)
The Plio-Pleistocene transition marked a key moment in global climate history, characterised by the onset of major glaciations in the Northern Hemisphere. The palaeoenvironmental history of the Plio-Pleistocene transition is not well known for the Caspian Sea region, despite its importance for global climate dynamics. Here we present an independently 40Ar/39Ar dated, high-resolution terrestrial palynological record spanning the Plio-Pleistocene boundary based on a lacustrine-marine sedimentary sequence from eastern Azerbaijan. Despite complex pollen transport pathways and the proximity of closely stacked mountain vegetation belts in the Greater and Lesser Caucasus, the record shows that regional vegetation responded to Milankovitch forced glacial-interglacial cycles, tentatively correlated with global climatic records spanning MIS G8 to 98 (âŒ2.77â2.45 Ma). The persistence of mesophilous forests during glacial times indicates that some settings in the South Caspian Basin acted as glacial refugia, and that vegetation response to glaciations was muted by increased moisture availability, linked to Caspian transgression. The palynological record shows a relationship with global [delta]18O stacks and specifically to the obliquity record. We anticipate that precise correlation with the global climatostratigraphic timescale will allow better understanding of the nature and timing of important transgressive events in the Caspian Sea and their relevance on a global scale
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 dĂ©formations en dynamique met Ă
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 Ă©tats de dĂ©formation Ă
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
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