De Souza A.D.,French National Center for Scientific Research |
Fernandes M.B.,Observatorio Nacional MCTI |
Carciofi A.C.,IAG |
Chesneau O.,French National Center for Scientific Research
Proceedings of the International Astronomical Union | Year: 2014
The research of stars with the B[e] phenomenon is still in its infancy, with several unanswered questions. Physically realistic models that treat the formation and evolution of their complex circumstellar environments are rare. The code HDUST (developed by A. C. Carciofi and J. Bjorkman) is one of the few existing codes that provides a self-consistent treatment of the radiative transfer in a gaseous and dusty circumstellar environment seen around B[e] supergiant stars. In this work we used the HDUST code to study the circumstellar medium of the binary system GG Car, where the primary component is probably an evolved B[e] supergiant. This system also presents a disk (probably circumbinary), which is responsible for the molecular and dusty signatures seen in GG Car spectra. We obtained VLTI/MIDI data on GG∼Car at eight baselines, which allowed to spatially resolve the gaseous and dusty circumstellar environment. From the interferometric visibilities and SED modeling with HDUST, we confirm the presence of a compact ring, where the hot dust lies. We also show that large grains can reproduce the lack of structure in the SED and visibilities across the silicate band. We conclude the dust condensation site is much closer to the star than previously thought. This result provides stringent constraints on future theories of grain formation and growth around hot stars. Copyright © International Astronomical Union 2015.
Nguyen T.,U.S. National Institute of Standards and Technology |
Gu X.,U.S. National Institute of Standards and Technology |
Vanlandingham M.,U.S. National Institute of Standards and Technology |
Vanlandingham M.,U.S. Army |
And 3 more authors.
Journal of Coatings Technology Research | Year: 2013
The objective of this study is to assess the degradation modes of crosslinked coatings exposed to photolytic environments. Three model crosslinked coatings were exposed in various ultraviolet environments. Atomic force microscopy and Fourier transform infrared spectroscopy were used in following nanoscale physical and chemical degradation during exposures. Results indicated that photodegradation of crosslinked coatings is a spatially localized (inhomogeneous) process in which nanometer-sized pits are initially formed; these pits deepen and enlarge with exposure. A conceptual model is proposed to explain the inhomogeneous degradation mode. The model proposes that nanosize "hydrophilic" domains are dispersed randomly with the highly crosslinked units. These hydrophilic domains, which are energetically preferred, comprise polar, unreacted and partially polymerized molecules, chromophores, and other additives. Photodegradation initiates at degradation-susceptible hydrophilic domains spreading to surrounding areas contiguous with the initiation site. © 2012 American Coatings Association & Oil and Colour Chemists' Association (outside the USA).
Raithel M.,Kempfert Geotechnik GmbH |
Kuster V.,IAG |
Alexiew D.,Huesker Synthetic GmbH
Geotechnik | Year: 2013
Foundation systems using geotextile encased columns for earth structures (e.g. embankments) on soft subsoil with a low bearing capacity were established in geotechnical engineering about 20 years ago and today are state-of-the-art in Germany. The system offers a geotechnical solution for foundations even in highly deformable soils of extremely low shear strength, in which traditional soil improvement techniques reach their limit of practicability. This paper gives a description of the system of geotextile encased columns, of design and construction procedures and in particular of the results of long-term measurements. Further information is given on ongoing developments of the system corresponding to technical and economical requirements of major geotechnical projects as well as further application options. Copyright © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
Do Nascimento J.D.,Federal University of Rio Grande do Norte |
Petit P.,IRAP |
Castro M.,Federal University of Rio Grande do Norte |
Porto De Mello G.F.,Federal University of Rio de Janeiro |
And 4 more authors.
Proceedings of the International Astronomical Union | Year: 2014
κ1 Cet (HD 20630, HIP 15457, d = 9.16 pc, V = 4.84) is a dwarf star approximately 30 light-years away in the equatorial constellation of Cetus. Among the solar proxies studied in the Sun in Time, κ1 Cet stands out as potentially having a mass very close to solar and a young age. On this study, we monitored the magnetic field and the chromospheric activity from the Ca II H & K lines of κ1 Cet. We used the technique of Least-Square-Deconvolution (LSD, Donati et al. 1997) by simultaneously extracting the information contained in all 8,000 photospheric lines of the echelogram (for a linelist matching an atmospheric model of spectral type K1). To reconstruct a reliable magnetic map and characterize the surface differential rotation of κ1 Cet we used 14 exposures spread over 2 months, in order to cover at least two rotational cycles (Prot ∼9.2 days). The Least Square deconvolution (LSD) technique was applied to detect the Zeeman signature of the magnetic field in each of our 14 observations and to measure its longitudinal component. In order to reconstruct the magnetic field geometry of κ1 Cet, we applied the Zeeman Doppler Imaging (ZDI) inversion method. ZDI revealed a structure in the radial magnetic field consisting of a polar magnetic spot. On this study, we present the fisrt look results of a high-resolution spectropolarimetric campaign to characterize the activity and the magnetic fields of this young solar proxy. © International Astronomical Union 2014.
Guinouard I.,University Paris Diderot |
De Oliviera L.S.,LNA |
De Oliviera A.C.,LNA |
Hammer F.,University Paris Diderot |
And 7 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012
The OPTIMOS-EVE concept provides optical to near-infrared (370-1700 nm) spectroscopy, with three spectral resolution (5000, 15000 and 30000), with high simultaneous multiplex (at least 200). The optical fibre links are distributed in four kinds of bundles: several hundreds of mono-object systems with three types of bundles, fibre size being used to adapt spectral resolution and 30 deployable medium IFUs (about 2"x3"). We are optimising the design of deployable IFUs to warrant sky subtraction for the faintest extragalactic sources. This paper gives the design and results of the prototype for the high resolution mode and the preliminary design of a medium IFU developed in collaboration between the GEPI and the LNA. © 2012 SPIE.