261 research outputs found
Reply to the comment by A. P. Murani and P. J. Brown on "X-ray magnetic circular dichroism study on CeFe2”
No full textAtomic surrounding of Co implanted in AlN at high energy
No full textAlN bulk ceramic has been implanted with energetic Co ions. In order to accurately characterise the atomic surrounding of the implanted ions, X-ray absorption measurements were carried out at 80 K in the fluorescence mode at the Co K edge in the as-implanted and annealed states. Simulation of the EXAFS oscillations allowed us to identify a first stage where Co is inserted in the AlN matrix followed by a second stage where Co precipitates form.Fil: Traverse, Agnès. Lure, Universidad Paris-sud; FranciaFil: Delobbe, Anne. Lure, Universidad Paris-sud; FranciaFil: Zanghi, Didier. Lure, Universidad Paris-sud; FranciaFil: Rentería, Mario. Lure, Universidad Paris-sud; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Gailhanou, Marc. Lure, Universidad Paris-sud; Franci
Is the variogram a good tool for assessing the spatial variability of vertical profiles of reflectivity ?
No full textVarious methods have been proposed in the literature to correct for the errors arising from nonuniform vertical profiles of reflectivity (VPR). All these methods consist in estimating the shape of the VPR and to use it for extrapolating the radar reflectivities measured at high altitude towards ground level. These methods require an assumption on the spatial homogeneity of the VPR over appropriate subdomains during a considered time step. This assumption of spatial homogeneity must therefore ideally be verified in order to apply any correction. In this paper we will explore the ability of a geostatistical tool called variogram to assess the spatial variability of the VPR in volume reflectivity files. The data are measured by the Wideumont radar in Belgium. It is a C-band Doppler radar that performs a 5-elevation scan from 0.3° to 6.0° every 5 minutes and a 10-elevation scan from 0.5° to 17.5° every 15 minutes. Some relevant parameters of the 10-elevation scan are given in Delobbe and Holleman (2006). The final objective of this study is to characterize the spatial and temporal variability of VPRs for different types of meteorological situations and to determine consistent spatial and temporal scales for VPR identification and correction. In this paper we will concentrate on the spatial variability aspect onldy. This paper is organized as follows. We first develop the theory related to variograms applied on VPRs. Then an analysis of one theoretical example is given. This analysis will illustrate some difficulties in the calculation of the variograms. Finally, an analysis of the variograms obtained for several selected observed situations is done and the results are discussed
Analysis of the mean and the variability of the vertical profile of reflectivity over Belgium
No full textVarious methods have been proposed in the literature to correct the errors arising from nonuniform vertical profiles of reflectivity (VPR). All these methods consist in estimating the shape of the VPR and to use it for extrapolating the radar reflectivities measured at high altitude towards ground level. These methods require an assumption on the spatial homogeneity of the VPR over appropriate subdomains during a considered time step. This assumption of spatial homogeneity must therefore ideally be verified in order to apply any correction. In this paper we will analyze the mean and the spatial and temporal variability of the VPR over Belgium for the years 2005 and 2006. The data are measured by the Wideumont radar in Belgium. It is a C-band Doppler radar that performs a 5- elevation scan from 0.3° to 6.0° every 5 minutes and a 10-elevation scan from 0.5° to 17.5° every 15 minutes. Some relevant parameters of the 10-elevation scan are given in Delobbe and Holleman (2006). The final objective of this study is to characterize the spatial and temporal variability of VPRs for different types of meteorological situations and to determine consistent spatial and temporal scales for VPR identification and correction. We will first describe an adaptation for Belgium of the Steiner algorithm aimed at separating convective from stratiform precipitation. Some results will be presented. We will also present the yearly mean VPR obtained from one Belgian radar. Two types of climatological VPR can be calculated: one for the stratiform and one for the convective zones. Then we will develop the theory related to variograms applied on VPRs. We will restrict our analysis to VPRs measured inside stratiform zones. Finally results concerning the spatial and temporal decorrelation distances between VPRs will be presented
Perpendicular magnetic anisotropy and the reorientation transition of the magnetization in CeH2/Fe multilayers probed by x-ray magnetic circular dichroism
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