University of Marne-la-Vallée

About: University of Marne-la-Vallée is a based out in . It is known for research contribution in the topics: Estimator & Context (language use). The organization has 831 authors who have published 1855 publications receiving 55316 citations.

Speciation of Fe in silicate glasses and melts by in-situ XANES spectroscopy

Abstract: In-situ X-ray absorption spectroscopy at the Fe K -edge was used to characterize the local structural environment of Fe 2+ and Fe 3+ in silicate melts at high temperature (up to 1050 °C) in comparison to their quenched glassy analog at room temperature. Measurements were performed on binary alkali-silicate compositions and on haplogranitic compositions, which were doped with about 5 wt% Fe 2 O 3 . Changes in the structural environment of Fe were evaluated by analyzing both the pre-edge feature and the first maximum of the EXAFS of the spectra. In most cases, the spectra collected at high temperature differed from those of the quenched samples. At reducing conditions, the melts showed slightly higher amounts of low-coordinated Fe 2+ than their glassy counterparts. This finding is consistent with results of earlier studies (e.g., Jackson et al. 1993), but the observed change in speciation is smaller than reported by these authors. At oxidizing conditions, glasses and melts displayed a more heterogeneous behavior. The spectra of alkali-silicate compositions indicate higher amounts of low-coordinated Fe 3+ in the melt, whereas no significant difference between melt and glass was observed for Fe 3+ in haplogranitic compositions, even if the latter are peralkaline. The amount of non-bridging O atoms in the glass/melt system appears to play an important role particularly for Fe 3+ . However, more complex relationships between Fe and other structural components, especially Al, are possible.

Building robust wavelet estimators for multicomponent images using Stein's principle

Abstract: Multichannel imaging systems provide several observations of the same scene which are often corrupted by noise. In this paper, we are interested in multispectral image denoising in the wavelet domain. We adopt a multivariate statistical approach in order to exploit the correlations existing between the different spectral components. Our main contribution is the application of Stein's principle to build a new estimator for arbitrary multichannel images embedded in additive Gaussian noise. Simulation tests carried out on optical satellite images show that the proposed method outperforms conventional wavelet shrinkage techniques.

Direct Construction of Compact Directed Acyclic Word Graphs

Abstract: The Directed Acyclic Word Graph (DAWG) is an efficient data structure to treat and analyze repetitions in a text, especially in DNA genomic sequences. Here, we consider the Compact Directed Acyclic Word Graph of a word. We give the first direct algorithm to construct it. It runs in time linear in the length of the string on a fixed alphabet. Our implementation requires half the memory space used by DAWGs.

Minor identities for quasi determinants and quantum determinants

Abstract: We present several identities involving quasi-minors of noncommutative generic matrices. These identities are specialized to quantum matrices, yieldingq-analogues of various classical determinantal formulas.