Guillaume Bouchez

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (5)17.06 Total impact

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    ABSTRACT: The orientation of the high-spin (HS)-low-spin (LS) macroscopic interface at the thermal transition of thin [{Fe(NCSe)(py)2 }2 (m-bpypz)] crystals is explained by considering the possible vanishing of the structural mismatch between the coexisting phases. The structural property which allows mismatch-free interfaces is characterized. The observed orientations of the interface and the tilt angle between the HS and LS domains are accurately reproduced by a two-dimensional continuous medium model, based on the structural data. Simulations using an atomistic electro-elastic model meet the predictions of the macroscopic analysis and provide information on the distribution of the elastic energy density in the biphasic state. The presence of mismatch-free domain structures can explain the exceptional resilience of these crystals upon repeated switching.
    Angewandte Chemie International Edition in English 06/2014; · 13.45 Impact Factor
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    ABSTRACT: The study of the distorting action of the atmospheric turbulence is important to understand the reason of the astronomical seeing variability, and to propose reliable methods to estimate the seeing quality. The influence of the atmospheric surface layer thermal turbulence on distortion of astronomical images is investigated. During a campaign carried out at Concordia station at Dome C, East Antarctica in winter 2012, an experiment was carried out to determine the behaviour and the contribution of the optically-active atmospheric turbulence in the lowest tens meters. The surface layer in the interior of Antarctica during winter is extremely stably stratified with the difference of temperature between the surface and the top of the inversion reaching 30-40 °C. Direct optical measurements of the seeing made by differential image motion monitors (DIMM) at two levels, 8 and 20 m, were made simultaneously with turbulence observations in the near-surface atmospheric layer. The intensity of the thermal turbulence was detected and evaluated using both a specially designed high-resolution sodar, and sonic anemometer measurements. The statistics of some meteorological variables, including long-wave downwelling radiation, characterising the presence of cloudiness are obtained. Typical patterns of the turbulence shown by sodargrams are analysed and classified. The statistics of the heights of the surface-based turbulent layer and of the seeing quality values are presented. A correlation exists between the seeing quality and the intensity of turbulence measured by sodar. Statistics of turbulent optical factor (TOF) for different layers within the surface layer are analysed for the total period and for clear sky conditions to give recommendations on how to choose an optimal height for the installation of the astronomical instrumentation.
    04/2013;
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    ABSTRACT: We present long term site testing statistics based on DIMM and GSM data obtained at Dome C, Antarctica. These data have been collected on the bright star Canopus since the end of 2003. We give values of the integrated turbulence parameters in the visible (wavelength 500 nm). The median value we obtained for the seeing are 1.2 arcsec, 2.0 arcsec and 0.8 arcsec at respective elevations of 8m, 3m and 20m above the ground. The isoplanatic angle median value is 4.0 arcsec and the median outer scale is 7.5m. We found that both the seeing and the isoplanatic angle exhibit a strong dependence with the season (the seeing is larger in winter while the isoplanatic angle is smaller).
    IAU 288 Astrophysics from Antarctica; 08/2012
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    ABSTRACT: The colorimetric analysis of images recorded with an optical microscope during the onset of the spin crossover transformation allows monitoring separately the involved electronic and structural aspects, through the separation of resonant absorption and scattering effects. Complementary information can also be obtained by using the polarized modes of the microscope. These potentialities are illustrated by the observation of [Fe(ptz)(6)](BF(4))(2) single crystals during the onset of the thermal transitions in the 110-140 K range. We characterized the interplay between the electronic (HS <--> LS) and structural (order <--> disorder) transformations. Elastic stresses and mechanical effects (hopping, self-cleavage) generated by the volume change upon electronic transition are also illustrated, with their impact on the photoswitching properties of the crystals.
    The Journal of Physical Chemistry B 02/2010; 114(5):1975-84. · 3.61 Impact Factor
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    Damien Chapon, Guillaume Bouchez
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    ABSTRACT: When designing complex systems such as Aircraft, harmonizing the way we describe and analyze sys-tems physical architectures is important in order to reduce costs, lead-time, and to increase systems ma-turity at entry into service. As Modelica has interest-ing multi-domain modeling capabilities, we define a harmonization approach that is based on the use of Modelica in an Integrated Development Environ-ment.
    01/2009;