Selection of the most efficient wavelength bands for discriminating weeds from crop

peer reviewedThe aim of this study was to select the best combination of filters for detecting various weed species located within carrot rows. In-field images were taken under artificial lighting with a multispectral device consisting of a black and white camera coupled with a rotating wheel holding 22 interference filters in the VIS-NIR domain. Measurements were performed over a period of 19 days, starting 1 week after crop emergence (early weeding can increase yields) and seven different weeds species were considered. The selection of the best filter combination was based on a quadratic discriminant analysis. The best combination of filters included three interference filters, respectively centred on 450, 550 and 700 nm. With this combination, the overall classification accuracy (CA) was 72%. When using only two filters, a slight degradation of the CA was noticed. When the classification results were reported on field images, a systematic misclassification of carrot cotyledons appears. Better results were obtained with a more advanced growth stage. (c) 2007 Elsevier B.V. All rights reserved

DIRAC framework evaluation for the Fermi\boldsymbol{Fermi}-LAT and CTA experiments

DIRAC (Distributed Infrastructure with Remote Agent Control) is a general framework for the management of tasks over distributed heterogeneous computing environments. It has been originally developed to support the production activities of the LHCb (Large Hadron Collider Beauty) experiment and today is extensively used by several particle physics and biology communities. Current ($Fermi$ Large Area Telescope -- LAT) and planned (Cherenkov Telescope Array -- CTA) new generation astrophysical/cosmological experiments, with very large processing and storage needs, are currently investigating the usability of DIRAC in this context. Each of these use cases has some peculiarities: $Fermi$-LAT will interface DIRAC to its own workflow system to allow the access to the grid resources, while CTA is using DIRAC as workflow management system for Monte Carlo production and analysis on the grid. We describe the prototype effort that we lead toward deploying a DIRAC solution for some aspects of $Fermi$-LAT and CTA needs.Comment: proceedings to CHEP 2013 conference : http://www.chep2013.org

Resources Annotation, Retrieval and Presentation: a semantic annotation management system

International audienceThis paper addresses the problem of the management of resources metadata. A variety of responses are discussed, and we describe one possible way forward, which uses a semantic annotation management tool. The term 'semantic' describes the ability to create, retrieve, query and navigate knowledgeably about things identified by a Web URI. The support for this semantic tool is RDF, through the integration of Jena, an open-source RDF API provided by HP laboratory. Thanks to RDF capabilities, this tool offers new search features such as hierarchical browsing based on the structure of RDF vocabularies and faceted-browsing using properties lists defined by the end-user. The navigation inside annotations uses intuitive modes such as left/right and backward/forward movements. Presentation is controlled by the user using a subset of the Fresnel language to specify how RDF graphs are presented. This work is ongoing; certain open issues are raised

Interpretation of the evolution parameter of the Feynman parametrization of the Dirac equation

The Feynman parametrization of the Dirac equation is considered in order to obtain an indefinite mass formulation of relativistic quantum mechanics. It is shown that the parameter that labels the evolution is related to the proper time. The Stueckelberg interpretation of antiparticles naturally arises from the formalism.Comment: 6 pages, RevTex, no figures, submitted to Phys. Lett.

Les signes en société

Stéphane Breton, maître de conférences Anthropologie de la Mélanésie : la visibilité des relations Les sociétés de Mélanésie ont une manière particulière de poser la question de l’origine et de l’issue des biens et des êtres. Elles redoublent l’idée d’une fécondité pulsative par la circulation des choses. C’est ce qu’on appelle l’« échange », qui règle l’énergie sociale par des mouvements de concentration, d’exposition et de dispersion. En somme, ces sociétés pensent que toute fécondité est f..

Les signes en société

Stéphane Breton, maître de conférences Anthropologie de la Mélanésie : la visibilité des relations Les sociétés de Mélanésie ont une manière particulière de poser la question de l’origine et de l’issue des biens et des êtres. Elles redoublent l’idée d’une fécondité pulsative par la circulation des choses. C’est ce qu’on appelle l’« échange », qui règle l’énergie sociale par des mouvements de concentration, d’exposition et de dispersion. En somme, ces sociétés pensent que toute fécondité est f..

Les signes en société

Stéphane Breton, maître de conférencesJacques Aumont, directeur d’études Le regard et le réel : le point de vue dans le cinéma documentaire Le réalisateur de films documentaires enregistre l’image de faits dont il est le contemporaln. Ce que je vous montre, peut-il dire (tout comme l’ethno graphe), n’existe que parce que j’étais là. La conséquence, contre toute prétention positiviste, c’est que le réel n’est pas libre du point de vue porté sur lui et que le regard ne manque pas d’apparaître d..

Les signes en société

Stéphane Breton, maître de conférencesJacques Aumont, directeur d’études Le regard et le réel : le point de vue dans le cinéma documentaire Le réalisateur de films documentaires enregistre l’image de faits dont il est le contemporaln. Ce que je vous montre, peut-il dire (tout comme l’ethno graphe), n’existe que parce que j’étais là. La conséquence, contre toute prétention positiviste, c’est que le réel n’est pas libre du point de vue porté sur lui et que le regard ne manque pas d’apparaître d..

Single spacecraft nulling interferometer for exoplanets: preliminary concept

editorial reviewedOne of the most ambitious goals of modern astronomy is to uncover signs of extraterrestrial biological activity, primarily achieved through spectroscopic analysis of light emitted by exoplanets to identify specific atmospheric molecules. Most exoplanets are indirectly identified through techniques like transit or Doppler shift of the host star's flux. Long-term surveys have yielded statistical insights into the occurrence rates of different planet types based on factors such as radius/mass, orbital period, and the spectral type of the host star. Initial estimates of terrestrial planets within the habitable zone have also emerged. However, the difficulty of detecting light from these exoplanets leaves much unknown about their nature, formation, and evolution. As the number of rocky exoplanets around nearby stars rises, questions about their atmospheric composition, evolutionary trajectory, and habitability increase. Direct measurement of an exoplanet's atmospheric composition through its spectral signature in the infrared can provide answers. Measuring the infrared spectrum of these planets poses significant challenges due to the star/planet contrast and very small angular separation from their host stars. Previous research showed that space-based telescopes are mandatory, and unless large primary mirrors (>30m in diameter) can be sent into space, interferometric techniques become essential. Combining light from distant telescopes with interferometric techniques allows access to information at minimal angular separation, operating within the diffraction limit of individual telescopes. Successful demonstrations of on-ground nulling interferometry open a new era for such space-based missions. They are vital to sidestep and tackle these scientific questions. We recently initiated a new study with the European Space Agency to explore the design parameters and the performances related to an interferometric concept based on a single spacecraft and sparse multiple sub-apertures. Launch constraints are linked to the use of an Ariane 6 launch vehicle. Our parametric study covers a range of 1-4 m for the diameter of the telescope and a 10-60 m baseline. The most promising concept working in the infrared range (3-20μm) will be highlighted. This study is conducted by TUDelft in cooperation with KULeuven, CSL/ULiège, and Amos with the support of the European Space Agency