Les perceptions de la violence politique en Égypte. Présentation

L’assassinat de Farag Fawda l'a relancée ; les récurrentes émeutes de Haute-Égypte puis du Caire lui ont donné un nouveau souffle ; le recours, à partir du mois de juillet, aux attentats aveugles (notamment contre les touristes) et le surcroît de répression qu'ils ont engendré en ont – si cela était encore possible – fait une nouvelle fois monter le ton : l'Égypte politique et intellectuelle vit à bien des égards depuis plus d'une année – mais en fait bien davantage – à l'heure du débat sur l..

Continuous odour measurement from fattening pig units

peer reviewedA study in experimental slatted-system fattening pig units was conducted with the aim of estimating the odour emission factor (in ou/s.pig), which can subsequently be used in dispersion models to assess the odour annoyance zone. Dynamic olfactometry measurements carried out at different development stages of pigs showed a logical trend of the mean predicted odour emission factor with the pig weight. However, the variation within the same weight class was much larger than variation between classes. Possible causes of such variation were identified as the evolution of ventilation rate during the day and the circadian rhythm of pig. To be able to monitor continuously the daily variation of the odour, an electronic nose was used with suitable regression model calibrated against olfactometric measurements. After appropriate validation check, the electronic nose proved to be convenient, as a complementary tool to dynamic olfactometry, to record the daily variation of the odour emission factor in the pig barn. It was demonstrated that, in the controlled conditions of the experimental pens, the daily variation of the odour emission rate could be mainly attributed to the sole influence of the circadian rhythm of pig. As a consequence, determining a representative odour emission factor in a real case cannot be based on a snapshot odour sampling

A FE Billet Model and a Spring-Mass-Damper Model for the Simulation of Dynamic Forging Process: Application to a Screw Press

In forging processes, the determination of blow efficiency is very important, as it quantifies the part of the stroke energy actually transmitted to the billet. Thus, forging processes should be deeply analyzed in order to better understand the stroke energy conversion, accurately estimate blows efficiency and thus better predict process parameters. In this paper, a spring-mass-damper vibration model is proposed to describe forming operations of a screw press. Parameters specially adapted to the machine-tools system are identified thanks to a stroke without billet. Thereafter, the experimental upsetting of a copper cylinder is realized, and two independent numerical simulations are performed. First, the billet upsetting is simulated by FE simulation with no consideration of the elastic and damping effect due to the machine-tools behavior in order to determine a relation between the load and the billet height. Then, forging load from the FE simulation is used to perform another simulation of the forging process with the spring-mass-damping model. Results show that the model is relevant to simulate load and ram displacement. Moreover, simulation can predict the distribution of the energy during the simulation and the blow efficiency can be calculated. This new way to obtain blow efficiency might improve productivity in process development and provide a better understanding of energy driven machine

A new tailored solution to predict blow efficiency and energy consumption of hammer-forging machines

Energy saving has become a real issue in process management and has led to the analysis of the energy consumption of forging machines, for the purpose of optimization. This study focuses on the amount of energy lost due to machine behaviour during the forming process. A spring-mass-damping model of the machine and tools system is associated with a billet model to describe hammer-forming operations only during the forging phase. Themodel parameters are identifiedwith experimental measurements of process variables during a stroke, providing parameters specifically adapted to the machine-tools system. Then, model predictions are validated by the experimental upsetting of steel and aluminium billets. The model accurately predicts forging process variables for consecutive blows with different materials. The decrease in process efficiency and the evolution from inelastic to elastic blows after several strokes on the same billet are also predicted by the model. This methodology provides a new, tailored solution that enables forging manufacturers to predict the forging energy consumption of their own machines. The approach developed in this work concerns gravity drop hammers but is also transferable to other energy-driven machines

State and evolution of the African rainforests between 1990 and 2010

This paper presents a 2005 map of Africa’s rainforests with new levels of spatial and thematic detail, being derived from 250m resolution MODIS data, and having an overall accuracy of 84%. A systematic sample of Landsat images (with supplemental data from equivalent platforms to fill sample gaps) is used to produce a consistent assessment of deforestation between 1990, 2000 and 2010 for West Africa, Central Africa and Madagascar. Net deforestation is estimated at 0.28% yr-1 for the period 1990-2000 and 0.14% yr-1 for the period 2000-2010. West Africa and Madagascar exhibit a much higher deforestation rate than the Congo Basin. Based on a simple analysis of the variance over the Congo Basin, we show that expanding agriculture and increasing fuelwood demands are key drivers of deforestation while well-controlled timber exploitation programmes have little or no direct influence on forest-cover reduction at present. Rural and urban population concentrations and fluxes are identified as strong underlying causes of deforestation in this study.JRC.H.5-Land Resources Managemen

Rapport fait a la classe des sciences mathématiques et physiques dans sa séance du 6 messidor an 8

Los miembros de la comisión según consta en la obra fueron Cels, Chaptal, Darcet, Fourcroy, Guyton, Parmentier, Tessier, Vauquelin y DeyeuxFecha deducida del tít.Sign.: A-D4, E

Validation of a purely elastic model and a finite element model for a screw press

The increasing use of superalloys in the industry brings new issues to forging manufacturers concerning Finite Element analysis of the forming process. Once we consider high performing materials, significant differences can occur between numerical and experimental results. The lack of knowledge about materials and thermal exchanges explains a part of these differences but it has been shown that the machine behavior has a significant impact on the forging process. Press modelling is a way to quantify the energy dissipated in the machine structure and improve simulations. This study is a first step in the screw press modelling. Starting from an approximation of the press geometries, a purely static elastic (PSE) model is developed and a numerical simulation considering only uprights is performed. Uprights stiffness predictions from the PSE model and the FE simulation are compared and the PSE model is validated. Then, the press is approximated by a portal frame and FE simulation is realized to determined uprights stiffness by considering links effects and bending behaviors in the structure. Comparison with experimental results validates the approximation.région Grand Est Manoir Industrie Bouzonvill

Précis des opérations qui ont servi à déterminer les bases du nouveau systême métrique : li á la séance publique de l'Institut des sciences et des arts le 15 messidor an 7

En verso de port. consta: Extrait des procès-verbaux des séances de l'Institut national des sciences et artsSubtít. y mención de responsabilidad tomados de p. 1Impresor tomado del colofónSign.: [ ]2, A-B4, C

Rapport sur le Virgile de Didot l'aine : [fait a l'Institut National le 5 ventose an VI

Sub. y mención de responsabilidad tomado del principio del textoSign.: A