Efficiency-based design of bending-active tied arches

[EN] Active bending is recently attracting considerable attention as a new paradigm to build lightweight structures both in research and practice. While there are many references dealing with form-finding methods for bending-active structures, the literature on their performance in relation to their shape and member proportioning is still scarce. This paper addresses the relationship between configuration finding and structural performance in bending-active tied arches: planar arches composed of a bent (active) rod, lower spanning cables and secondary struts that are joined to the rod and act as cable deviators. This simple bending-active arrangement allows to state key relationships between shape, proportion and performance. Starting from the fact that rod segments between struts behave as elastica segments, and selecting the mechanical slenderness of the rod as key parameter, scale-independent relationships between rise-to-span ratio, rod slenderness and stresses after activation have been established for a three-strut tied arch. The limitations posed by keeping stresses in cables after the activation within an acceptable range have been also addressed. Span-deflection ratios corresponding to Eurocode loads for the serviceability limit state have been obtained for a set of three-strut configurations using a non-linear structural model. Results have been represented in terms of rod slenderness, cable slenderness and rise-to-span ratio. The same procedure has been used to determine and represent proper utilization ratios for rod cross-sections in ultimate limit state. All the results have been combined to show the design space corresponding to the given constraints and to exemplify how to extract from it a suitable structural configuration. Finally, we explain how to extend the proposed method to design bending-active tied arches with an arbitrary number and proportion of deviators.The authors gratefully acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness through grant BIA2015-69330-P (MINECO) and the support from CALTER Ingenieria and SOFiSTiK AG for providing a software license.Bessini, J.; Lazaro, C.; Casanova Colón, J.; Monleón Cremades, S. (2019). Efficiency-based design of bending-active tied arches. Engineering Structures. 200:1-11. https://doi.org/10.1016/j.engstruct.2019.109681S11120

Set up of a methodology for participatory plant breeding in bread wheat in France

In Organic Agriculture, cultivation environments and agronomic practices are very diverse. This diversity can be handled with decentralized selection based on the knowledge of farmers and scientists. A collaborative work between associations from Réseau Semences Paysannes and the DEAP team from INRA du Moulon set up an innovative breeding approach on farm based on decentralization and participation of farmers. This approach makes it possible to (i) create new population varieties of bread wheat locally adapted (genetic innovation) (ii) set up an organizational scheme based on decentralization and co construction between actors (societal innovation) and (iii) develop experimental designs, create statistical and data management tools which stimulate these genetic and societal innovations

Evaluation of spatial indices implemented with the DBMS O 2

this paper, we restrict our attention to geographic information systems (GIS). Such systems use as a kernel a geographic database management system (DBMS). Data handled by geographic DBMS has structured attributes as well as spatial attributes that describe the geometry and the topology of geographic objects. A fast access to such data, the volume of which is usually extremely large, requires the use of indices. Indices as provided by regular DBMS, e.g., B-tree like structures [BM72] are inefficient when the query is related to the location (geometry) of the objects. One major issue related to the choice of such indices, central to the design of geographic DBMS is the variety of geometric queries: one might argue that there is no index which performs best whatever the operation is. However we believe that all commercial systems will eventually provide a single simple-to-be-implemented data structure, although it might lead to uneven results depending on the query. This is the case with relational database technology: most of the commercial relational DBMS provide a unique B-tree-like index data structure. The objective of this paper is to contribute to the choice of such a single index. The problem is quite challenging for two reasons: 1. there is no standard yet concerning the query language and therefore there is no agreement on which are the most important spatial operations which require the use of a spatial index for performance reasons. Geometric selection, clipping and map overlay are among the most common operations. Examples of geometric selection are point queries (find the objects that contain a given point) and window queries (objects overlapping, i.e., intersecting or containing a given rectangle). In this paper, we restrict our attention to point queries. ..

Transformer une caméra conventionnelle en caméra 3D à l'aide d'un composant optique additionnel

International audienceWe propose to add an optical component in front of a conventional camera to improve depth estimation performance of Depth from Defocus (DFD), an approach based on the relation between defocus blur and depth. The add-on overcomes ambiguity and dead zone, which are the fundamental limitations of DFD with a conventional camera, by adding an optical aberration to the whole system which makes the blur unambiguous and measurable for each depth. We look into two optical components: the first one adds astigmatism and the other one chromatic aberration. In both cases we present the principle of the add-on and experimental validations on real prototypes.Nous proposons d'ajouter une composent optique devant une caméra conventionnelle pour améliorer les performances d'estimation de profondeur par estimation du flou de défocalisation (DFD), approche basée sur la relation entre le flou de défocalisation et la profondeur. Le composant additionnel permet d'éviter les problèmes d'ambiguité et de zone aveugle qui sont les principales limitations du DFD avec une caméra conventionnelle, grâce à l'ajout d'une aberration optique au système globale qui rend le flou non ambigue et mesurable pour chaque profondeur. Nous nous intéressons à deux types de composents : le premier ajoute de l'aberration astigmatique et l'autre de l'aberration chromatique. Dans chaque cas, nous présentons le principe du composent et des validations expérimentales sur des prototypes réels