Showing papers by "University of Lorraine published in 1998"
TL;DR: Variability in the faunal assessment of a station assemblage owing to the mesohabitats sampled can have a strong impact on the biological assessment of this station, and recommendations are suggested to alleviate this problem.
Abstract: Benthic macroinvertebrate communities are used widely to assess change in biological quality of streams, with taxa generally pooled across a variable number of different mesohabitats sampled at each station. Computer simulations showed the potential variation in the record of a station community according to the combination of mesohabitats sampled. For each station, all the faunal lists obtained by combining six, eight or ten sampled mesohabitats were compared on the basis of their structure (biocenotic indices) and composition (Jaccard's similarity index). Relative abundances of taxa varied depending on the combination of mesohabitats sampled. Total abundance and the dominance index in a station community were the most variable parameters, whereas taxonomic richness depended to a lesser extent on mesohabitats sampled. Differences in community composition were readiiy explained by taxa which were only present in one, two, or three mesohabitats. These taxa accounted for a minimum of 46 % taxonomic richness in each station and were mainly present with low abundances. Because most mesohabitats contained these kinds of taxa, invertebrate assemblages contrasted in composition although they displayed similar taxonomic richness. Variability in the faunal assessment of a station assemblage owing to the mesohabitats sampled can have a strong impact on the biological assessment of this station. Recommendations are suggested to alleviate this problem.
24 citations
TL;DR: In this paper, the effects of spectral aliasing for the white-phase noise are shown and a procedure for estimating both white phase noise level and high cut-off frequency is given.
Abstract: The noise levels given by spectral analysis are relevant parameters for the characterization of the time-domain stability of oscillators. The estimation of the noise levels of a sampled signal may be achieved with variances even if the sampling frequency is far lower than the high cut-off frequency. The effects of spectral aliasing for the white-phase noise are shown and a procedure for estimating both white-phase noise level and high cut-off frequency is given in this paper.
13 citations
TL;DR: In this paper, the effects of spectral aliasing for different types of noise are reviewed and the responses of the Allan variance and the modified Allan variance for high-frequency noises are calculated taking into account the spectral interference.
Abstract: We showed in Part I of this paper that the estimation of the white-phase noise level of a sampled signal may be achieved with variances even if the sampling frequency is far lower than the high cut-off frequency. In Part II, the effects of spectral aliasing for the different types of noise are reviewed. The responses of the Allan variance and the modified Allan variance for high-frequency noises are calculated taking into account the spectral aliasing. It is demonstrated that the effects of spectral aliasing for low-frequency noises may be neglected.
12 citations
01 Jan 1998
3 citations
15 Dec 1998
TL;DR: Guimezanes et al. as discussed by the authors, 12 mai, 1998, p. 7087 ; C.I. const., dec. n° 24, p p. 1025 and JCP (G) 1998, Act. 98-399 DC du 5 mai 1998.
Abstract: (JO, 12 mai, p. 7087 ; C. const., dec. 98-399 DC du 5 mai 1998, meme JO, p. 7092 ; pour une analyse globale, N. Guimezanes, JCP (G), 1998, Act. n° 24, p. 1025 et JCP (G) 1998.I.180) interesse le droit penal, general et special
1 citations