Versatile surrogate models for IC buffers

In previous papers [1,2] the authors have investigated the use of Volterra series in the identification of IC buffer macro-models. While the approach benefited from some of the inherent qualities of Volterra series it preserved the two-state paradigm of earlier methods (see [3] and its references) and was thus limited in its versatility. In the current paper the authors tackle the challenge of going beyond an application or device-oriented approach and build versatile surrogate models that mimic the behavior of IC buffers over a wide frequency band and for a variety of loads thus achieving an unprecedented degree of generality. This requires the use of a more general system identification paradig

Analyse de la chaîne de valeur du matériel génétique bovin laitier au Sénégal

Ministry of Foreign Affairs, Finlan

Challenges and opportunities on the use of bio fertilizers: examples from Senegal and Kenya

Not only phosphorus (P) bio available in soil is very low but phosphate fertilizing efficiency is also low. Consequently, annual world P demand increases predicting phosphorus stock end in the coming 125 years. In addition to that, the high cost of chemical fertilizers obliges most Sub Sahara African smallholder farmers to do not use fertilizers which ultimately results in poor yields. In this paper, we present opportunities and challenges of using bio fertilizers as sustainable way of alleviating soil P deficiency effects in Kenya and Senegal. In Kenya where soil P deficiency has been identified as the biggest challenge of crop productivity increases, we share results on the use of commercialized arbuscular mycorrhizal inoculants to replenish soil P. While in Senegal known having huge quantities of P rock deposit and important quantities of feed stock material that can be charred (biochar), we present results on the capacities of biochar to improve P availability for plant cultivated in sandy soil. Results from both countries show that current expectations on the use of bio fertilizers are numerous and justified. However challenges on sustainable agriculture through the use of the called bio fertilizers especially mycorrhizal inoculants and biochar are still ahead. (Texte intégral

Traitement contre les nématodes dans le bassin arachidier Nord du Sénégal

Le traitement au dibromochloropropane (DBCP) autorise des augmentations de rendements spectaculaires chez l'arachide en première année de rotation, puis sur les cultures suivantes. Ces résultats mis en évidence par les nématologistes de l'ORSTOM et la Direction de la protection des végétaux sénégalaise ont été jugés suffisamment prometteurs pour mettre en route une opération de recherche développement dont le but est de définir une technique permettant l'utilisation de la fumigation en milieu paysan. Au bout de trois années c'est chose faite et l'on peut penser à une nouvelle extension. Le changement de conditions amené par le traitement tant au point de vue production que système agraire pose comme préalable la connaissance des techniques culturales et de l'environnement qu'il a fallu étudier de ce point de vue phytosanitair

Bayesian networks for the analyses of tree functions trade-offs in tropical agro-silvopastoral systems

Natural system produces several resources and processes, known as ecosystem services (ES), which contribute to human wellbeing. Frequently, different ES are interlinked together, which translates into positive or negative covariation between ES. However, despite its capital importance, very little is known about which are the functions that regulate the different ES, about the effect that different management practices can have on the capacity of natural systems to produce ES or about the trade?offs between different ES. Groups of species with similar attributes can be linked to specific effects on other organisms, which consequently affect ecosystem functioning and the provision of ES. In this study, we explored the use of Bayesian Networks (BN) to represent the probabilistic relationships between effect traits of trees in a seasonally dry agro?silvopastoral system and three service provision functions (grassland productivity and soil properties under the trees and fodder quality of trees). Based on physiological and phenological traits (for grassland and soil) and chemical components (for fodder quality), we classified trees in functional groups (PFG), estimated the linkages between these groups and the studied functions and evaluated the influence of environmental characteristics on these linkages. The BN approach allowed us to assess the trade?offs between different ecosystem functions. We found that different PFG can have very different effects on different functions, and that these effects can be strongly modulated by environmental features. For example, there were marked differences in the productivity of the understorey vegetation between different PFG both within and across environments, which indicates that the attributes of trees play an important role determining the effect of trees on understorey vegetation. These results contrasted with those observed for the effect of trees on soil properties, which was generally positive and independent of the effect on understorey productivity, suggesting the absence of trade?offs between these functions. (Texte intégral