Contribution à l'étude d'un radiomètre portatif pour la mesure in situ des propriétés biochimiques des feuilles

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Sample volume of a capacitance moisture sensor in function of its geometry

International audienceWe have developed a permittivity-based sensor using a new and more accurate measurement technique. We now investigate the optimum geometry of sensor electrodes to apply models of conversion of medium permittivity into its water content (and salinity), while accounting for field constraints of compactness and simplicity. Models assume medium volume sampled by sensor to be large enough to consider a quasiuniform permittivity. Using this hypothesis, and verifying ex-post its consistency, we carried out an exhaustive study of sample volume dependence on electrode geometry. In particular, we examine the role of electrode diameter, oversight by previous works. Besides, our approach permits a direct experimental validation with profiles of sensor sensitivity. For a two-rod design with electrode spacing D and diameter Φ, sample-volume size and localization is determined by the ratio α = Φ/D. For α lower than 0.25 or thin electrodes-a geometry extensively studied and commonly encountered-theory and measurements show that the volume is concentrated around electrode surface. As α is increased it becomes localized between electrodes with a more uniform sensitivity, like for a parallel-plate capacitor. Volume size at fixed D is also assessed, with its highest value between α = 0.30 and 0.50. We adopted this range for our sensors

APPROCHE SYSTEMIQUE DE LA QUALITE DES EAUX DE LA MAULDRE ET DE SES AFFLUENTS

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Dynamique de la couche limite de surface semi-aride (approche des caractéristiques turbulentes par anemometrie a coupelles et effets des traitements de surface du sol)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Comparison of the energy efficiency to produce agroethanol between various industries and processes: The transport stage

International audienc

Développement et application du modèle SiSPAT-RS à l'échelle de la parcelle dans le cadre de l'expérience Alpilles ReSeDA

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Contribution à l'étude des échanges à l'interface bulle liquide, issue d'un éjecteur venturi horizontal, en vue du traitement des poussières

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

De la détermination du rendement des filières énergétiques

International audienceThe authors propose a specific methodology and definitions to determine the energetic efficiency of any energy production system and process therein, in agreement with the laws of physics and taking into account technical constraints. The method rests on the calculation of a modular indicator, the expenditure rate, ratio of the energetic costs to the gains of the system. An expenditure rate above I questions the system efficiency. We underline the importance of the data sources and of their uncertainties to calculate the expenditure rate starting from the deconvolution of a system in various stages, from the extraction of the natural resource to its final form of use, including the materials, the losses, and the energy contributions. As the efficiency indicator does not inform us about the extractible amount of the studied resource and of others, it should be completed with a specific study about their reserve and future production (where the expenditure rate acts as a criterion)

Smart Networks of Autonomous In-situ Soil Sensors

International audienceThe article describes a modern system of control and communication integrated in an in-situ soil sensor to make it autonomous in operation, energy and data transfer at low cost. Network of such sensors can monitor continuously soil moisture over a catchment with low maintenance. A recent industrial standard of radio communication, Long Range Wide Area Network (LoRaWAN) is presented. It permits rapid deployment of a sensor in a remote observatory, and the transfer in real time of sensor data to a central web-accessed database, via a LoRaWAN receiver, or gateway, 12 km away. In this situation transmission loss can reach a rate of 30%. Good quality antenna can lower it below 5% without extensive cost. Double messaging and other transmission algorithms are a possibility, taking into account consumption. Currently, sensors measuring one point every ten minutes can last seven months with four cheap AA alkaline batteries. Further gains would increase lifetime in same conditions by 30%