Recent changes in melliferous resources in the french agricultural landscape: the case of field crops and fodder production

The present article describes how melliferous resources have changed in France over the past fifty to sixty years, both in large-scale crops (cereals, oleaginous et proteaginous) and in fodder production (annual and pluriannual). Over this period, new crops, very useful for bees, were introduced (rapeseed, sunflower), whereas others declined sharply or even disappeared. The simplification of crop rotations and landscape standardisation lead to a scarcity of supply in pollen and nectar, sometimes in quantity, but also in quality, or even in availability over time. These changes alone cannot explain the excessive bee mortality, but by destabilising the colonies, they probably contribute to their current general weakening, particularly in crop production areas. Hence once again, agricultural practices, which have undergone major changes over the past decades to meet the needs of a growing population and provide abundant and cheap food, must adapt. Such adaptation will require the design then adoption of new, low-input crop production systems, more friendly towards bees in particular, and towards animal and plant diversity in generalLe présent article s’attache à décrire comment ont évolué les ressources mellifères en France au cours des cinquante à soixante dernières années, tant dans le domaine des grandes cultures (céréales, oléagineux et protéagineux) que des cultures fourragères (annuelles et pluriannuelles). Pendant la période considérée, des espèces végétales cultivées, très utiles aux abeilles, ont fait leur apparition (colza, tournesol), alors que d’autres ont fortement régressé, voire disparu. La simplification des assolements et l’uniformisation des paysages ont pu générer une raréfaction de l’offre en pollen et nectar, en quantité parfois, mais aussi en qualité, voire en disponibilité dans le temps. Ces modifications n’expliquent pas, à elles seules, les surmortalités d’abeilles. Toutefois, en déstabilisant les colonies, elles contribuent vraisemblablement au phénomène général d’affaiblissement qui est constaté, notamment en zones de grandes cultures. Pour cette raison, les pratiques agricoles qui ont profondément évolué depuis les dernières décennies, afin de satisfaire les besoins d’une population croissante et de permettre l’accès à une alimentation abondante et bon marché, doivent encore une fois s’adapter. Cette adaptation passe par la conception, puis l’adoption de nouveaux systèmes de cultures, économes en intrants, plus respectueux des abeilles en particulier, et de la biodiversité animale et végétale en général

Buckling of stiffened curved panels under uniform axial compression

In bridge construction, the use of stiffened plates for box-girder or steel beams is common day to day practice. The advantages of the stiffening from the economical and mechanical points of view are unanimously recognized. For curved steel panels, however, applications are more recent and the literature on their mechanical behaviour including the influence of stiffeners is therefore limited. Their design with commercial finite element software is significantly time-consuming, which reduces the number of parameters which can be investigated in an optimization procedure. The present paper is thus dedicated to the study of the behaviour of stiffened curved panels under uniform longitudinal compression. It addresses the linear buckling and the ultimate strength which are both influenced by the coupled effects of curvature and stiffening. It finally proposes a design methodology based on that for stiffened flat plates adopted by European Standards and a column-like behaviour

A preliminary design formula for the strength of stiffened curved panels by design of experiment method

International audienceIn bridge construction, the use of stiffened plates for box-girder or steel beams is common day to day practice. The advantages of the stiffening from the economical and mechanical points of view are unanimously recognized. For curved steel panels, however, applications are more recent and the literature on their mechanical behaviour including the influence of stiffeners is therefore limited. Their design with actual finite element software is possible but significantly time-consuming and this reduces the number of parameters which can be investigated to optimise each panel. The present paper is thus dedicated to the development of a preliminary design formula for the determination of the ultimate strength of stiffened cylindrical steel panels. This approximate formula is developed with the help of a design of experiment method which has been adapted from the current statistical knowledge. This method is first presented, and its feasibility as well as its efficiency are illustrated through an application to the reference case of unstiffened curved panels. Then, the case of stiffened curved panels is investigated and a preliminary design formula is developed. The ease of use of this formula for preliminary design is finally illustrated in a cost optimisation problem

Bridge Design to Eurocodes – Worked examples

This document is a Technical Report with worked examples for a bridge structure designed following the Eurocodes. It summarizes important points of the Eurocodes for the design of concrete, steel and composite road bridges, including foundations and seismic design, utilizing a common bridge project as a basis. The geometry and materials of the example bridge as well as the main assumptions and the detailed structural calculations are presented in the first chapter of the report. Each of the subsequent chapters presents the main principles and rules of a specific Eurocode and their application on the example bridge, namely: • The key concepts of basis of design, i.e. design situations, limit states, the single source principle and the combinations of actions (EN 19990); • Permanent, wind, thermal, traffic and fatigue actions on the bridge deck and piers and their combinations (EN 1991); • Bridge deck modeling and structural analysis; • The design of the bridge deck and the piers for the ULS and the SLS, including the second-order effects (EN 1992-2); • The classification of the composite cross-sections, the ULS, SLS and fatigue verifications and the detailed design for creep and shrinkage (EN 1994-2); • The settlement and resistance calculations for the pier, three design approaches for the abutment and the verification of the foundation for the seismic design situation (EN 1997); • The conceptual design for earthquake resistance considering the alternative solutions of slender or squat piers; the latter case involves seismic isolation and design for ductile behavior (EN 1998-1, EN 1998-2). The bridge worked example analyzed in this report was prepared and presented at the workshop “Bridge Design to the Eurocodes” that was held on 4-6 October 2010 in Vienna, Austria. The workshop was organized by JRC with the support of DG ENTR and in collaboration with CEN/TC250/Horizontal Group Bridges, the Austrian Federal Ministry for Transport, Innovation and Technology and the Austrian Standards Institute. The document is part of the Report Series “Support to the implementation, harmonization and further development of the Eurocodes”, prepared by JRC in collaboration with DG ENTR and CEN/TC250 “Structural Eurocodes”.JRC.G.5-European laboratory for structural assessmen

Web-Based Virtual Microscopy for Parasitology: A Novel Tool for Education and Quality Assurance

Here, we describe a novel tool to observe parasites by virtual microscopy on the Internet. Microscopy-based identification of parasites is the basis for both diagnostics and epidemiological assessment of parasite burden globally. Yet, quality assessment of diagnostic parasitology laboratories is difficult, as delivering identical educational specimens has been impossible. In this study, a series of parasite specimens on ordinary glass slides were digitized using a recently developed microscope scanner technique. Up to 50,000 images captured at high magnification are digitally stitched together to form a representation of the entire glass slide. These “virtual slides” digitized at a thousand-fold magnification can hold more than 60 gigabytes of data. Handling such large amounts of data was made possible because of efficient compression techniques and a viewing system adopted from the geospatial imaging industry. Viewing the samples on the Internet very much resembles, for example, the use of Google Maps, and puts only modest requirements on the viewer's computer. In addition, we captured image stacks at different focal planes, and developed a web-based viewing system for three-dimensional navigation in the specimens. This novel technique is especially valuable for detailed visualization of large objects such as helminth eggs in stool specimens

Effective width equations accounting for element interaction for cold-formed stainless steel square and rectangular hollow sections

Rectangular hollow sections featuring high height-to-width (aspect) ratios have shown to offer improved ultimate capacity due to the effects of the interaction between the elements within the cross-section which are particularly significant for slender cross-sections (class 4) undergoing local buckling. The European design rules dealing with stainless steel, EN 1993- 1-4 [1], utilises the concept of cross-section classification and the effective width method for the design of slender cross-sections susceptible to local buckling neglecting such interaction effects, hence resulting in conservative predictions. This paper examines the benefits of element interaction effects on cold-formed ferritic stainless steel compressed sections on the basis of carefully validated finite element models. Following parametric studies, the applicability of various alternative design approaches accounting for element interaction to ferritic stainless steel is assessed and effective width curves, as well as a Class 3 limiting slenderness equation, are derived herein as an explicit function of the aspect ratio. Comparisons with the loads achieved in the FE models have shown that the proposed effective width equations allowing for the benefits of element interaction improve capacity predictions making design more cost-effective.Ministerio de Ciencia e Innovació