References of "Delchambre, Ludovic"
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See detailWeighted principal component analysis: a weighted covariance eigendecomposition approach
Delchambre, Ludovic ULg

in Monthly Notices of the Royal Astronomical Society (2014), 446(2), 3545-3555

We present a new straightforward principal component analysis (PCA) method based on the diagonalization of the weighted variance-covariance matrix through two spectral decomposition methods: power ... [more ▼]

We present a new straightforward principal component analysis (PCA) method based on the diagonalization of the weighted variance-covariance matrix through two spectral decomposition methods: power iteration and Rayleigh quotient iteration. This method allows one to retrieve a given number of orthogonal principal components amongst the most meaningful ones for the case of problems with weighted and/or missing data. Principal coefficients are then retrieved by fitting principal components to the data while providing the final decomposition. Tests performed on real and simulated cases show that our method is optimal in the identification of the most significant patterns within data sets. We illustrate the usefulness of this method by assessing its quality on the extrapolation of Sloan Digital Sky Survey quasar spectra from measured wavelengths to shorter and longer wavelengths. Our new algorithm also benefits from a fast and flexible implementation. [less ▲]

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See detailSpectroscopic binaries as observed by the future Gaia space mission
Damerdji, Yassine ULg; Delchambre, Ludovic ULg; Morel, Thierry ULg et al

in Bulletin de la Societe Royale des Sciences de Liege (2011), 80

The future Gaia satellite will observe a large number of stars through its three main channels: astrometric, photometric and, for the brightest stars, spectroscopic. The satellite is equipped with the RVS ... [more ▼]

The future Gaia satellite will observe a large number of stars through its three main channels: astrometric, photometric and, for the brightest stars, spectroscopic. The satellite is equipped with the RVS spectrograph, which will provide medium-resolution spectra over a small wavelength range. These spectra should allow us to identify stars exhibiting a composite spectrum, either because of a chance alignment or a true binarity. We discuss the various aspects related to the data treatment of the binary candidates and describe the algorithms that are intended to be included in the processing pipeline. [less ▲]

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See detailThe International Liquid Mirror Telescope (ILMT) as a Variability Time Machine
Poels, Joël ULg; Borra, Ermanno; Hickson, Paul et al

in Griffin, Elisabeth (Ed.) New Horizons In Time-Domain Astronomy, IAU Symposium No. 285, 2011 (2011)

During the year 2012 the International Liquid Mirror Telescope (a collaboration between astronomical institutions in Belgium, Canada, India and Poland) will see first light. The instrument will provide ... [more ▼]

During the year 2012 the International Liquid Mirror Telescope (a collaboration between astronomical institutions in Belgium, Canada, India and Poland) will see first light. The instrument will provide substantial, in-depth sky coverage and make an unprecedented number of nightly observations. [less ▲]

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