Mining economist opinions on using multi-agent methodology to simulate metal markets

International audienceIn coming years, mining economists expect the international demand for metals to rise. Market distortions are likely to appear, because producing countries controlling the resources can implement exportation quotas for certain categories of metals. Consequently , consuming countries like France face increasing risks of shortages of some metals. In response, the French government suggests that a set of prospective tools be implemented, including a prospective simulation tool based on a multi-agent system approach. The goal of this paper is to report and discuss critiques by mining economists on the value and abilities of multi-agent systems (MAS) to simulate critical metal markets whenever the approach is appropriate. The critiques are collected by confronting an existing agent-based computational economics (ACE) model of the lithium market with market reality and then by applying the discussions generally to other metals. The motivation is (a) to define the gaps currently existing between MAS and mining (b) to provide indicators on how the ACE model should be enhanced to reduce these gaps and (c) to produce an improved initial metal classification that is suitable for such a modelling exercise

Métaux des batteries Li-ion : état des lieux et risques d’approvisionnements

International audienceLe développement de la mobilité électrique va entraîner un accroissement important de la consommation de certains matériaux, dits critiques ou sensibles, principalement utilisés dans la fabrication des électrodes des batteries au lithium. Certaines études relaient régulièrement des interrogations mettant en cause la viabilité de ce développement : le cobalt, le nickel ou le lithium, et même le cuivre utilisé pour les moteurs, ne seraient pas disponibles en quantités suffisantes pour alimenter la demande. Qu’en est-il en réalité et, si tensions il doit y avoir, comment y faire face

Transition énergétique, « intensité matières » et criticité

L’augmentation régulière des concentrations de gaz à effet de serre dans l’atmosphère sous l’effet des activités anthropiques conduit aujourd’hui à des modifications majeures du climat terrestre comme vient de le rappeler le rapport du GIEC

Les matériaux pour les batteries Li-Ion : faut-il s’inquiéter ?

International audienceLa très forte croissance attendue du marché de la mobilité électrique va entraîner la fabrication à très grande échelle de batteries au lithium. Des interrogations se manifestent quant à la disponibilité de certains matériaux utilisés pour leur fabrication. Certaines études relaient régulièrement des interrogations mettant en cause la viabilité de ce développement : le cobalt, le nickel ou le lithium, et même le cuivre utilisé pour les moteurs, ne seraient pas disponibles en quantités suffisantes pour alimenter la demande. Qu’en est-il en réalité et, si tensions il doit y avoir, comment y faire face

Interactions territoriales, dynamique des usages et de la biodiversité dans les zones humides du delta du Rhône : une approche par la modélisation multi-agents (Territorial interactions, uses and biodiversity dynamics within the wetlands of Rhone river delta : a multi agent modelling approach)

Abstract. - Mediterranean reedbeds are subject to different human uses, each associated with a particular water and reed management that affects the functioning of the ecosystem and the conservation of endangered species. We present here the general structure ofReedSim, a multiagent model that integrates the horizontal (spatial configurations) and vertical (social organization) relationships of the territory. Using the CORMAS software, the model is based on a hydro-ecological submodel (reedbed, water level and bird), and a socio-economic submodel (reed market and management). The model is designed to be used in environmental planning, and to support collective decision-making.Résumé. - Les roselières méditerranéennes sont l'objet de multiples usages, chacun étant associé à une gestion de l'eau et du roseau qui affecte le fonctionnement de l'écosystème et la conservation des espèces associées. Nous présentons ici la structure générale de ReedSim, un modèle multi-agents qui intègre les relations horizontales (configurations spatiales) et les relations verticales (organisations sociales) du territoire. Utilisant la plateforme de simulation CORMAS, le modèle se décompose en un sous-modèle écologique (roselière, niveaux d'eau et oiseaux), et un sous- modèle socio-économique (marché du roseau et gestion). Le modèle est destiné à être utilisé en aménagement du territoire et comme support d'aide à la décision collective.Mathevet Raphaël, Mauchamp André, Lifran Robert, Poulin Brigitte, Lefebvre Gaétan. Interactions territoriales, dynamique des usages et de la biodiversité dans les zones humides du delta du Rhône : une approche par la modélisation multi-agents (Territorial interactions, uses and biodiversity dynamics within the wetlands of Rhone river delta : a multi agent modelling approach). In: Bulletin de l'Association de géographes français, 80e année, 2003-4 ( décembre). Milieux subpolaires et subpolaires. Territoires de l'eau, géomatique, sous la direction de Marie-Françoise André et Denis Mercier. pp. 417-429

High Stocking Density Controls Phillyrea Angustifolia in Mediterranean Grasslands

International audienceExtensive grazing applied in the form of low instantaneous pressure over a long period is a widespread management practice in protected areas. However this kind of stocking method does not always achieve the expected results, in particular because it fails to limit colonization by woody plants.This is the case in the relict xero-halophytic grasslands of the northern Mediterranean coastal region, subjected to widespread colonization by the shrub Phillyrea angustifolia despite the presence of extensive grazing. In this study, we investigated, for an equal annual stocking rate, the respective impact of high stocking density applied over a short period (mob grazing) and low stocking density applied over a long period on both P. angustifolia and herbaceous cover, using an in situ experimental design run for 7 years. Only mob grazing was effective both in controlling the establishment and increasing the mortality of P. angustifolia individuals. We did not find any difference after the 7 years of experimentation between the two stocking methods with regard to the herbaceous community parameters tested: species richness, diversity, evenness, contribution of annual characteristic species. By contrast, the exclusion of domestic grazing led to a strong reduction of these values.The use of mob grazing may be well suited for meeting conservation goals such as maintaining open habitats in these grasslands

Re-localising the extraction of mineral resources: the challenges of lithium in Europe

article de vulgarisation en anglaisInternational audienc

Paracrine control of steroidogenesis by serotonin in adrenocortical neoplasms.

International audienceSerotonin (5-hydroxytryptamine; 5-HT) is able to activate the hypothalamo-pituitary-adrenal axis via multiple actions at different levels. In the human adrenal gland, 5-HT, released by subcapsular mast cells, stimulates corticosteroid production through a paracrine mode of communication which involves 5-HT receptor type 4 (5-HT4) primarily located in zona glomerulosa. As a result, 5-HT is much more efficient to stimulate aldosterone secretion than cortisol release in vitro and administration of 5-HT4 receptor agonists to healthy individuals is followed by an increase in plasma aldosterone levels without any change in plasma cortisol concentrations. Interestingly, adrenocortical hyperplasias and tumors responsible for corticosteroid hypersecretion exhibit various cellular and molecular defects which tend to reinforce the intraadrenal serotonergic tone. These pathophysiological mechanisms, which are summarized in the present review, include an increase in adrenal 5-HT production and overexpression of 5-HT receptors in adrenal neoplastic tissues. Altogether, these data support the concept of adrenal serotonergic paracrinopathy and suggest that 5-HT and its receptors may constitute valuable targets for pharmacological treatments of primary adrenal diseases

Des terres si rares ?

International audienc

Observability measurement and control strategy for induction machine sensorless drive in traction applications

International audienceElectrical traction using induction machine sensorless control requires high observer performance for all speed ranges, even for low speed or regenerative braking conditions which appear frequently during long time. It is well known that the speed of induction motors is unobservable at very low stator frequencies. This paper uses an observability index to continuously analyze speed observability for sensorless control of induction machines. The correlation between observability-index and observer performance is illustrated in a Hardware in the Loop (HIL) experimental test-bench combining the well-known vector control with an extended Kalman filter. Thanks to the observability-index information, an optimal strategy is proposed to design controllers to guide the system away from undesirable behavior and avoid the weak observability-index region by taking into account all working constraints. A simplified case is presented to improve the speed observer performance, which was tested in the same conditions with the same HIL test-bench to experimentally validate the proposed sensorless control for traction applications