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Francoise Combes 《Astrophysics and Space Science》2001,277(1):29-38
Knowledge of the molecular component of the ISM is fundamental to understand star formation. The H2 component appears to dominate the gas mass in the inner parts of galaxies, while the HI component dominates in the outer parts. Observation of the CO and other lines in normal and starburst galaxies have questioned the CO-to-H2 conversion factor, and detection of CO in dwarfs have shown how sensitive the conversion factor is to metallicity. Our knowledge has made great progress in recent years, because of sensitivity and spatial resolution improvements. Large-scale CO maps of nearby galaxies are now available, which extend our knowledge on global properties, radial gradients, and spiral structure of the molecular ISM. Millimetric interferometers reveal high velocity gradients in galaxy nuclei, and formation of embedded structures, like bars within bars. Galaxy interactions are very effective to enhance gas concentrations and trigger starbursts. Nuclear disks or rings are frequently observed, that concentrate the star formation activity. Since the density of starbursting galaxies is strongly increasing with redshift, the CO lines and the mm dust emission are a privileged tool to follow evolution of galaxies and observe the ISM dynamics at high redshift: they could give an answer about the debated question of the star-formation history, since many massive remote starbursts could be dust-enshrouded. 相似文献
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Richard Giot Albert Giraud Francoise Homand 《Geotechnical and Geological Engineering》2006,24(4):919-947
This paper deals with a new strategy for initial stress identification by stress relaxation methods, coupled with finite element
calculation, and applied to the overcoring test. The back-analysis of such a test uses an inversion method which consists
in the minimisation, with a gradient-based algorithm, of a cost functional of least-squares type, which quantizes the difference
between measured and computed strains. The computed strains are assessed by three-dimensional finite element modellings of
the overcoring test. The inversion methodology is applied to a recent in situ overcoring test performed at Mont Terri laboratory, Switzerland. The inversion gave good results and allows us to validate
the inversion methodology. The constitutive law considered for this application is transverse isotropic elasticity but the
inversion method developed is applicable to most constitutive laws and every kind of in situ test. 相似文献