French Politicians on Facebook and Twitter. Revitalizing political representation?

In contrast to the previous contribution, this paper tackles the issue of transparency and social media with a more national perspective. By looking at French deputies posts on Facebook and Twitter, but also by directly inquiring how French citizens assess the issue of political transparency on social media, this analysis aims at providing new insights into the issue as to whether the presence of politicians on social media can affect power relations between citizens and politicians. The underlying rationale is to find out whether this form of transparency ultimately enhances representative democracy.Over the last decades transparency has often been depicted as the ultimate remedy for various political, economic and societal problems. Stiglitz (1999; 2000; 2002) outlines the significance of transparency for averting market failures and enhancing public financing. Similarly, Lindstedt and Naurin (2010) investigate the capacity of transparency to reduce corruption and achieve fairer and more efficient governance, while Schultz and Kenneth (1998) analyse how better means of communication and transparency can diminish risks of war and international conflicts. Recent cases and scandals have added fuel to debates about transparency. The Luxleaks affair revealed the need for more transparency with regard to existing tax schemes for multinational companies (Gotev, 2015). The opacity of the TTIP negotiations has made experts and citizens suspicious regarding the content of this trading agreement and signal the risk of lowering safety standards and endangering customers’ safety. If we turn to the realm of politics, we quickly notice that the relationship between transparency and democracy has provoked intense and convoluted debates. Is transparency of governments a necessary feature of democratic regimes? Or, is transparency a political key for better governance? In his succinct definition of democracy, Schumpeter (1942) did not yet consider transparency as an inherent and essential characteristic of democratic regimes. Democracy, he argues, is only determined by the electoral competition and free elections. By contrast, Dahl (1971) - with his famous concept of Poliarchy – places transparency at the core of the democratic framework. As he claims, a democratic regime is not only a regime in which electors have the right to freely vote for their future representatives and governments, it is also a system that allows its citizens to be fully informed - by different and independent sources of information - before they cast their ballot. This implies a free and transparent flow of information

Stress Concentration and Material Failure During Coiling of Ultra-Thin TRAC Booms

Ultra-thin TRAC booms are a promising technology for large deployable structures for space applications. A manufacturing process producing composites TRAC booms with flange thickness as low as 53 μm is proposed. Coiling behavior around hub with radii ranging from 19.1 mm to 31.8 mm is studied both experimentally and through finite element simulations. Due to the thinness of the TRAC boom, a buckle appears in the inner flange, in the transition region from the fully deployed to the coiled configurations. Material failure is observed at this location, and this correlates well with stresses computed in simulation, coupled with the fiber microbuckling failure criterion. Reducing the thickness, either by changing the laminate or by improving the manufacturing process, is shown to reduce stresses, allowing coiling around smaller hubs without material failure

Stress Concentration and Material Failure During Coiling of Ultra-Thin TRAC Booms

Ultra-thin TRAC booms are a promising technology for large deployable structures for space applications. A manufacturing process producing composites TRAC booms with flange thickness as low as 53 μm is proposed. Coiling behavior around hub with radii ranging from 19.1 mm to 31.8 mm is studied both experimentally and through finite element simulations. Due to the thinness of the TRAC boom, a buckle appears in the inner flange, in the transition region from the fully deployed to the coiled configurations. Material failure is observed at this location, and this correlates well with stresses computed in simulation, coupled with the fiber microbuckling failure criterion. Reducing the thickness, either by changing the laminate or by improving the manufacturing process, is shown to reduce stresses, allowing coiling around smaller hubs without material failure

Mechanics of Ultra-Thin Composite Coilable Structures

Coilable structures are thin-shell structures that can be coiled around a hub by flattening their cross-section. They are attractive for multiple space applications as they allow efficient packaging and deployment of large planar structures. Reducing the shell thickness enables smaller coiling radius and more efficient packaging. This thesis investigates TRAC structures, a type of coilable structure, made of ultra-thin composite materials. A design using a laminate made of glass fiber plainweave fabric and carbon fiber unidirectional tape is proposed, leading to a shell thickness of 0.08 mm. An in-autoclave, two-cure manufacturing process is presented, and a shape measurement method is used to mitigate post-cure shape changes due to residual stresses. A study of the structure behavior in its deployed configuration is performed. First, the behavior when subjected to pure bending is investigated experimentally for structures with a length of 575 mm. Two regimes are observed, with a pre-buckling phase transitioning to a stable post-buckling phase after an initial buckling event. The ultimate buckling moment following the stable post-buckling regime can be as high as four times the initial buckling moment. A finite element model is developed and is able to reproduce all the features observed experimentally, except the ultimate buckling. This simulation model is used to study the effect of varying the structure length from 300 mm to 5000 mm on the initial buckling moment. Results show that nonlinearities in the pre-buckling deformations of the flanges under compression lead to a constant wavelength lateral-torsional buckling mode for which the critical moment is mostly constant across the range of length. The torsional behavior of the TRAC structure is also investigated. Good agreement is obtained between experiments and numerical simulations, and initial twist in the structure is shown to have little effect on the overall behavior due to the small torsional stiffness in the underformed configuration. An analytical method to predict the buckling load of a TRAC structure under pure bending is presented. It is achieved by considering only one flange of the structure and solving the problem of a cylindrical shell panel with a longitudinal free edge under non-uniform axial compression. Partially uncoupled stability equations for a balanced laminate are derived and are used in conjunction with the Rayleigh-Ritz method to approximate the buckling load. This method overestimates the buckling load by 44% in the case of a 500 mm TRAC structure made with ultra-thin composite materials. A study of the coiling behavior is also presented. High localized curvature in the transition region between the coiled and deployed regions is observed in experiments, leading to material failure for a structure made only of carbon fiber unidirectional tape. A numerical framework is developed and reproduces the localized curvature observed in experiments, predicting stress concentration at this location. The study shows that changing the laminate to a a single ply of carbon fiber unidirectional tape sandwiched between plies of glass fiber plainweave fabrics reduces significantly the maximum stress in the transition region, to the extent that the highest stress is now in the fully coiled region and can be accurately predicted using simple equations based on the change of curvatures due to the coiling process.</p

Simulation numérique de l'écoulement tridimensionnel turbulent dans un parc éolien

Principe de fonctionnement d'une éolienne -- Couche limite terrestre et stabilité -- Caractéristiques du sillage d'une éolienne -- Modèle mathématique -- Équations de transport -- Propriétés de la couche de surface terrestre en conditions thermiques neutres -- Modèles de fermeture -- Résumé du modèle mathématique -- Spécialisation du modèle mathématique : développement d'une formulation axisymétrique -- Modélisation numérique -- Description de la méthode -- Modèle axisymétrique -- Modèle tridimensionnel -- Validation du modèle : sillage axisymétrique -- Formulation axisymétrique -- Formulation tridimensionnelle

Characterization of Ultra-Thin Composite Triangular Rollable and Collapsible Booms

The paper studies the behavior of Triangular Rollable and Collapsible (TRAC) booms made from ultra-thin carbon fiber, with a total flange thickness of 71 µm. Both bending and torsional behavior of the deployed booms are studied using numerical analysis and experimental testing. The coiling of the booms around hubs of large radius is also studied

Characterization of Ultra-Thin Composite Triangular Rollable and Collapsible Booms

The paper studies the behavior of Triangular Rollable and Collapsible (TRAC) booms made from ultra-thin carbon fiber, with a total flange thickness of 71 µm. Both bending and torsional behavior of the deployed booms are studied using numerical analysis and experimental testing. The coiling of the booms around hubs of large radius is also studied

Comparing the Analysis and Results of a Modified Social Accounting Matrix Framework with Conventional Methods of Reporting Indirect Non-Medical Costs

Background Assessing the societal perspective in economic evaluations of new interventions requires estimates of indirect non-medical costs caused by the disease. Different methods exist for measuring the labor input function as a surrogate for these costs. They rarely specify the effect of health on labor and who gains and who loses money. Social accounting matrix (SAM) is an established framework that evaluates public policies with multiple perspectives that could help. Objectives We evaluated the use of a modified SAM to assess money flows between different economic agents resulting in economic transactions following policy changes of medical interventions. Methods We compared conventional methods of measuring indirect non-medical costs related to rotavirus vaccination in the Netherlands with a modified SAM framework. To compare the outcome of each method, we calculated returns on investment (ROI) as the net amount of money per euro invested in the vaccine. One-way and probabilistic sensitivity analyses were carried out for each method, focusing on critical variables with the largest impact on indirect cost estimates. Results The ROI was higher for the modified SAM (1.33) than for the conventional methods assessing income calculations (range - 0.178 to 1.22). Probabilistic sensitivity analyses showed wide distributions in the ROI estimates, with variation in the variable impact on the indirect cost results per method selected. Conclusions In contrast to conventional methods, the SAM approach provides detailed and comprehensive assessments of the impact of new interventions on the indirect non-medical costs and the financial interactions between agents, disclosing useful information for different stakeholders.</p

Optical whole-cell biosensor using Chlorella vulgaris designed for monitoring herbicides

International audienceAn optical biosensor was designed for determination of herbicides as aquatic contaminants. Detection was obtained with immobilised Chlorella vulgaris microalgae entrapped on a quartz microfibre filter and placed in a five-membrane-home-made-flow cell. The algal chlorophyll fluorescence modified by the presence of herbicides was collected at the tip of an optical fibre bundle and sent to a fluorimeter. A continuous culture was set up to produce algal cells in reproducible conditions for measurement optimisation. Effects of flow rate, algal density, temperature, and pH on the biosensor response to atrazine were studied. Reversibility and detection limits were determined for DNOC and atrazine, simazine, isoproturon, diuron. Detection of photosystem II (PSII) herbicides was achieved at sub-ppb concentration level