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Bailat C.J.,IRA | Keightley J.,NPL | Nedjadi Y.,IRA | Mo L.,Australian Nuclear Science and Technology Organization | And 21 more authors.
Metrologia | Year: 2014

Detailed uncertainty reporting is imperative for proficiency tests and comparison exercises since uncertainties need to be comparable and trusted by all the participants. Even though participants do their best to follow the Guide to the Expression of Uncertainty in Measurement1, ambiguities and divergences about uncertainty evaluation remain. Consequently, to analyze the situation, the CCRI (II) Uncertainties Working Group proposed a comparison exercise (CCRI(II)-S7) about the uncertainty evaluation of a relatively simple primary activity measurement: The standardization of a 60Co source by coincidence counting. To be able to understand how various NMIs calculate coincidence counting uncertainties, our study focused on two of the dominant uncertainty components commonly quoted for 4 αβ-γ coincidence counting in the International Reference System (SIR) submissions and Key Comparison exercises: Efficiency-extrapolation and weighing. Participants from twelve different laboratories were sent the same set of measurement data from the analysis of a 60Co solution standardized at the National Physical Laboratory (NPL). Our study demonstrated the extent of the different interpretations of the uncertainty components. Some factors causing large discrepancies were isolated and are discussed. Further studies of other techniques using a similar approach would be beneficial for the metrology community. Source

Since 2009, 3 national metrology institutes (NMI) have submitted 3 samples of known activity of 133Ba to the International Reference System (SIR) for activity comparison at the Bureau International des Poids et Mesures (BIPM), with comparison identifier BIPM.RI(II)-K1.Ba-133, to update their earlier result dating more than 15 years ago. The values of the activity submitted were between about 2 MBq and 3 MBq. There are now nine results in the BIPM.RI(II)-K1.Ba-133 comparison. The degrees of equivalence between each equivalent activity measured in the SIR and the key comparison reference value (KCRV) have been calculated and the results are given in the form of a table. A graphical presentation is also given. Source

Loireau M.,IRD Montpellier | Sghaier M.,IRA | Guerrero B.,IRD Montpellier | Chouikhi F.,IRA | And 5 more authors.
Ingenierie des Systemes d'Information | Year: 2015

Combating desertification in the Southern hemisphere representing 75% of the world population with 75% of them working in the agriculture sector is a priority. Within a GIS platform the paper presents a complete approach to characterizing quantifying and modelling spatially agricultural practices along with available natural resources, both in interaction in a given landscape area. The description of a geocomputational workflow modelling of rural landscapes into units where the causes and intensity of desertification risk can be associated is detailed. The SIEL software allows to set up the parameters of a modelling simulation according to the scientific workflow and to perform its execution. Results over several observatories in the circum-Saharan area are presented. They open the discussion on future and the potential developments of the SIEL in the context of observatories dedicated to support decision making to combat desertification. © 2015 Lavoisier. Source

Fetoui M.,IRA | Loireau M.,IRD Montpellier | Sghaier M.,IRA | Chouikhi F.,IRA | And 8 more authors.
Science et Changements Planetaires - Secheresse | Year: 2012

Developing models that can supply indicators which integrate socioeconomic and environmental dimensions with their spatial and temporal diversity, which deal with phenomena on a local scale, and which can be integrated into decision-making support systems remains a great challenge. It is, however, necessary in order to understand, spatialize, monitor, assess, and anticipate the complex dynamics of desertification. This article presents the imagined approach and the software platform prototype entitled SIELO (information system for operational desertification monitoring at the local scale) to address this scientific issue. This system attempts to create the link between i) spatialized indicators of desertification risks, built in connection with the systematic complexity of desertification and ii) observed Land Cover Change. The first type of data arises from systematic models already implemented in a pre-existing tool, the LEIS model. The second type of data is extracted from satellite images acquired according to regular time steps. The proposed approach is based on the spatializing of knowledge, via the "landscape" tool in particular. In this article we describe the proposed approach and its specificities that can lead to feeding operational assessment and monitoring of desertification within the framework of local scale observatories. We illustrate the feasibility and the operational effectiveness of its implementation with an initial application in a Tunisian dry zone via a developed software prototype (SIELO v1.0). Source

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