Z calibration of the LNE ultra precision coordinate measuring machine

The Laboratoire National de Métrologie et d’Essais (LNE) has developed an innovative ultra precision coordinate measuring machine [1,2] traceable to the national length standard. This machine can be equipped with different kinds of sensors and is dedicated to the measurement with nanometer uncertainties of features, standards and in more general way three-dimensional objects. The measuring range is 300 mm x 300 mm x 50 μm. The objective in term of uncertainty is to reach 30 nm in X and Y directions for a 300 mm displacement and about few nanometers for the 50 μm vertical displacement. For the geometric calibration of this machine, dedicated procedures have been developed. The present paper will focus more specifically on the one used for the Z calibration

A Herbage Growth Model for Different Types of Natural Grassland

The aim of this work was to extend existing growth models established for pure stands to a wide range of grassland communities. For this purpose we built a simple growth model, including sub-models for radiation interception and use. Parameters for the effect of nutrient rates (N, P) and defoliation regimes were based on a plant trait database. Senescence and reproductive processes were particularly considered because of their importance in late spring growth. The model makes it possible to simulate the daily biomass production as a function of both environmental factors and the functional type of the dominant species in the community

IntroductionEnjeux et cadre d’analyse

Les études et publications sur les risques associés au changement climatique pour l’agriculture sont extrêmement nombreuses. Une rapide revue de cette abondante littérature permet d’identifier les aléas et les risques naturels liés au changement climatique qui affectent le plus — en fréquence et en intensité — les pratiques et les productions des agriculteurs dans le monde : la sécheresse, aléa ponctuel, et l’aridification, péjoration par ..

Conclusion générale

À partir de l’étude détaillée d’un petit nombre de situations très contrastées, nos travaux ont permis de mettre en évidence les processus et les trajectoires expliquant la forte exposition aux aléas de certains groupes d’agriculteurs, ainsi que le maintien ou l’accroissement de cette exposition. Ces travaux permettent d’expliquer, à l’échelle du système agraire et à celle des systèmes de production, les ressorts de cette vulnérabili..

LNE Activies in Nanometrology: flatness reference calibration algorithm

The Laboratoire National de Métrologie et d’Essais (LNE) has developed an innovative ultra precision coordinate measuring machine [LAH07] traceable to the national length standard to measure three-dimensional objects with nanometric uncertainties (figure 1). The measuring range is 300 mm x 300 mm x 50 μm. The objective in term of uncertainty is to reach 30 nm in X and Y directions for a displacement of 300 mm and about few nanometers for a vertical displacement of 50 μm. On this machine, we use four capacitive sensors to measure the position along z direction. These sensors target the flat surface of cylinders (300 mm diameter) used as flatness references. To measure the shape of these aluminum references with nanometric uncertainties, we propose a measurement method based on a propagation process in which we introduce an angular measurement to compensate the curvature error inherent in this method. The measurement process uses the same sensor technology (capacitive sensor) we use on the machine. This paper presents the measurement method, its validation and the first results

Comparison of EFTEM and STEM EELS plasmon imaging of gold nanoparticles in a monochromated TEM

We present and compare two different imaging techniques for plasmonic excitations in metallic nanoparticles based on high energy-resolution electron energy-loss spectroscopy in a monochromated transmission electron microscope. We demonstrate that a recently developed monochromated energy-filtering (EFTEM) approach can be used in addition to the well established scanning technique to directly obtain plasmon images in the energy range below 1 eV. The EFTEM technique is described in detail, and a double experiment performed on the same, triangular gold nanoparticle compares equivalent data acquired by both techniques, respectively

Anomalous dissipation mechanism and Hall quantization limit in polycrystalline graphene grown by chemical vapor deposition

Ajuts: it has been performed within the EMRP (European Metrology Research Program), project SIB51, Graphohm. The EMRP is jointly funded by the EMRP participating countries within EURAMET (European association of national metrology institutes) and the European Union.We report on the observation of strong backscattering of charge carriers in the quantum Hall regime of polycrystalline graphene, grown by chemical vapor deposition, which alters the accuracy of the Hall resistance quantization. The temperature and magnetic field dependence of the longitudinal conductance exhibits unexpectedly smooth power-law behaviors, which are incompatible with a description in terms of variable range hopping or thermal activation but rather suggest the existence of extended or poorly localized states at energies between Landau levels. Such states could be caused by the high density of line defects (grain boundaries and wrinkles) that cross the Hall bars, as revealed by structural characterizations. Numerical calculations confirm that quasi-one-dimensional extended nonchiral states can form along such line defects and short circuit the Hall bar chiral edge states

Application d'une nouvelle conception d'architecture à une machine de mesure de résolution nanométrique Application of a new architecture design to a measuring machine with a nanometric resolution

The purpose of this paper is to present original concepts offering an uncertainty control advancement for measuring machines. Those concepts were developed from the analysis of phenomena that reduce the machine accuracy constructed around principles of standard architecture. A machine being developed is a concrete materialization of those concepts

A combination of methods needed to assess the actual use of provisioning ecosystem services

Failure to recognize that potential provisioning ecosystem services are not necessarily collected and used by people may have important consequences for management of land and resources. Accounting for people's actual use of ecosystem services in decision making processes requires a robust methodological approach that goes beyond mapping the presence of ecosystem services. But no such universally accepted method exists, and there are several shortcomings of existing methods such as the application of land use/cover as a proxy for provisioning ecosystem service availability and surveys based on respondents' recall to assess people's collection of e.g. wild food. By combining four complementary methods and applying these to the shifting cultivation systems of Laos, we show how people’s actual use of ecosystem services from agricultural fields differs from ecosystem service availability. Our study is the first in Southeast Asia to combine plot monitoring, collection diaries, repeat interviews, and participant observation. By applying these multiple methods borrowed from anthropology and botany among other research domains, the study illustrates that no single method is sufficient on its own. It is of key importance for scientists to adopt methods that can account for both availability of various services and actual use of those services