Heterogeneity and Increasing Returns May Drive Socio-Economic Transitions

There are clear benefits associated with a particular consumer choice for many current markets. For example, as we consider here, some products might carry environmental or `green' benefits. Some consumers might value these benefits while others do not. However, as evidenced by myriad failed attempts of environmental products to maintain even a niche market, such benefits do not necessarily outweigh the extra purchasing cost. The question we pose is, how can such an initially economically-disadvantaged green product evolve to hold the greater share of the market? We present a simple mathematical model for the dynamics of product competition in a heterogeneous consumer population. Our model preassigns a hierarchy to the products, which designates the consumer choice when prices are comparable, while prices are dynamically rescaled to reflect increasing returns to scale. Our approach allows us to model many scenarios of technology substitution and provides a method for generalizing market forces. With this model, we begin to forecast irreversible trends associated with consumer dynamics as well as policies that could be made to influence transition

Mobilité étudiante en Europe : une idée qui mérite mieux que des quotas

Face à la mobilité étudiante envahissante une alternative aux quotas existe, plus efficace et équitable à la fois. Elle n’implique ni le recours à l’impôt européen ni l’augmentation du coût privé des études. Plus simplement il s’agit de transformer le rôle des pouvoirs publics de financeur des établissements d’enseignement situés sur leur territoire en financeur des étudiants résidents de ce territoire, en même temps que garant de la qualité des études.

Identification and validation of a continuum damage model applied for the lifetime prediction of H11 tool steel

Extrait de : Proceedings of 7th International tooling conference : tooling materials and their applications from research to market / sous la dir. de M. ROSSO, M. ACTIS GRANDE et D. UGUES. - 7th International tooling conference on tooling materials and their applications from research to market, Torino, ITALIE, 2-5 May 2006International audienceThis paper describes the work performed to identify and validate a non-isothermal continuum damage model for a widely used hot-work tool steel H11 at a hardness of 47 HRc. The investigation is based on an extensive high-temperature low-cycle fatigue database performed under strain rate controlled tests with and without dwell times in the range of 300°C-600°C. The approach gives a good description of the thermomechanical behaviour of H11 tool steel under various test conditions and constitutes a very good prediction tool for a very large amount of fatigue tests. This work is divided into three stages. First, isothermal fatigue tests are performed on flat specimens in order to identify lifetime model parameters. Then, thermo mechanical fatigue tests are considered in order to validate the model in a non-isothermal case. Lastly, low-cycle fatigue tests are carried out on notched specimens in order to investigate the model capabilities in a multiaxial condition

Les Français et la lecture - 2017

Selon le baromètre bisannuel Ipsos/CNL, 91% des personnes interrogées déclarent avoir lu au moins un livre au cours des 12 derniers mois. Si le papier demeure le format le plus courant pour 89% des lecteurs, le numérique progresse (+5% par rapport à 2015). À retenir, le développement du livre d\u27occasion et la progression de la vente en ligne au détriment de la librairie, en raison d\u27une méconnaissance du prix unique du livr

Reduced Complexity Controllers for LPV Systems: Towards Incremental Synthesis

International audienceExisting synthesis methods for LPV systems often result in controllers of high complexity. So far, there is no efficient and systematic remedy to this issue as there exists no convex formulation of the problem of finding a solution of reduced complexity to the general case LPV synthesis problem. In this paper, the specific case is considered when parameter-dependent signals are measured. It is proven that these measures can be exploited so that the problem of reduced-complexity controller synthesis can be written as an LMI optimization problem. A complete procedure for the controller construction is provided. The interest of the result is discussed in relation with nonlinear methods. First, an interpretation of the controller strategy is proposed with regard to the feedback linearization method. Second, it is proven that a nonlinear controller ensuring the closed loop incremental properties can be constructed

Asymmetric copper-catalyzed Diels-Alder reaction revisited: control of the structure of bis(oxazoline) ligands

International audienceSynthesis of 1,4-bis(oxazoline) ligands bearing a bicyclo[2,2,2]backbone derived from 9,10-dihydro-9,10-ethanoanthacene trans-dicarboxylic acid was revisited. Starting from L- or D-amino alcohols and either (S,S) or (R,R)-dihydroethano trans-dicarboxylic acid, a complete series of ligands was evaluated in the copper-catalyzed Diels-Alder reaction. The most efficient ligands with a phenyl substituent on the oxazoline ring afforded enantiomeric excess up to 98%. This is different from previous results indicating that the best enantioselectivity involved a diastereomeric ligand with the meso-backbone

Annular interdigital transducer focuses piezoelectric surface waves to a single point

We propose and demonstrate experimentally the concept of the annular interdigital transducer that focuses acoustic waves on the surface of a piezoelectric material to a single, diffraction-limited, spot. The shape of the transducing fingers follows the wave surface. Experiments conducted on lithium niobate substrates evidence that the generated surface waves converge to the center of the transducer, producing a spot that shows a large concentration of acoustic energy. This concept is of practical significance to design new intense microacoustic sources, for instance for enhanced acouto-optical interactions

Modelling of multiple impacts for the prediction of distortions and residual stresses induced by ultrasonic shot peening (USP)

During a manufacturing process, the ultrasonic shot peening (USP) technique can be used as the final surface treatment. The aim of this operation is to introduce surface compressive residual stresses in order to prevent crack propagation advancement. Although the numerical simulation method is able to predict the level of residual stresses in a peened part, the 3D modelling of the real USP process, in which many successive and shifted impacts take place, is very delicate to perform and costly in terms of computing time and memory space required. In this paper, a two step method based at first on the calculation of the averaged plastic strain tensor in a half-space by using a semi-analytical method and in a second time on the transfer of this plastic strain field to a finite element model is proposed in order to simulate the effects of the USP process in thin structures. The accuracy and advantages of the semi-analytical method are validated by a benchmark with several finite element codes. Experiments, similar to the Almen test, are performed on thin plates of Inconel 600. Numerical results in terms of distortions and residual stresses are compared with the experimental data

La mathématique fait-elle exception à la loi historique des trois états ?

L’article examine le problème des restrictions qu’il faut apporter à la loi des trois états : la loi du développement de l’esprit est-elle valable à tous les degrés de l’échelle hiérarchique ? Ou bien la mathématique fait-elle exception à la loi historique ? La réponse apportée par Brentano est assez surprenante et semble même contradictoire. Dans certains textes, il soutient que la mathématique est soumise au même régime que les autres branches du savoir ; et que si restriction il y a, ces restrictions doivent être pensées avec Comte, et non pas contre lui. Dans d’autres textes, Brentano semble se ranger à la position critique de J. S. Mill. Comment concilier ces affirmations apparemment contradictoires ? On se propose de répondre à cette question en montrant que la position de Brentano a évolué au tournant des années 1870, et en indiquant le rôle de la nouvelle classification des sciences dans cette évolution

Cyclic behaviour simulation of X38CRMOV5-47HRC (AISI H11)-tempered martensitic hot-work tool steel

Issu de : 7th International tooling conference on tooling materials and their applications from research to market, Torino, ITALY, 2-5 May 2006International audienceThe cyclic behaviour of X38CrMoV5 (AISI H11) tool steel with a nominal hardness of 47HRC has been predicted. Basically, thermo-elastoplastic and thermo-elastoviscoplastic constitutive laws are investigated. First, various uniaxial isothermal conditions (LCF) with different strain rate, strain amplitude and temperature level are investigated. Then the constitutive laws are examined under various TMF loading conditions. The simulated results by both the approaches are compared with experimental results in terms of stress?strain behaviour and cyclic softening. Some applications of the model for simulation of thermal fatigue sample are shown. Taking into consideration the results of this work, the goal is to further characterise the limitations of these constitutive laws under complex and severe loading conditions, i.e., under variable temperature, variable strain amplitude and thermal fatigue structural specimen