Group and individual risk preferences : a lottery-choice experiment

This paper focuses on decision making under risk, comparing group and individual risk preferences in a lottery-choice experiment inspired by Holt and Laury (2002). The experiment presents subjects with a menu of unordered lottery choices which allows us to measure risk aversion. In the individual treatment, subjects make lottery choices individually ; in the group treatment, each subject was placed in an anonymous group of three, where unanimous lottery choice decisions were made via voting. Finally, in a third treatment, called the choice treatment, subjects could choose whether to be on their own or in a group. Our main findings are that groups are more likely than individuals to choose safe lotteries for decisions with low winning percentages. Moreover, groups converge toward less risky decisions because subjects who were relatively less risk averse were more likely to change their vote in order to conform to the group average decision ; more risk-averse individuals were less likely to change their preferences. Finally our results reveal a positive relationship between preference for risk and willingness to decide alone.Experiment, decision rule, individual decision, group decision.

Direct numerical simulations of mass transfer in square microchannels for liquid-liquid slug flow

Microreactors for the development of liquid-liquid processes are promising technologies since they are supposed to offer an enhancement of mass transfer compared to conventional devices due to the increase of the surface/volume ratio. But impact of the laminar flow should be negative and the effect is still to be evaluated. The present work focuses on the study of mass transfer in microchannels by means of 2D direct numerical simulations. We investigated liquid-liquid slug flow systems in square channel of 50 to 960 μm depth. The droplets velocity ranges from 0.0015 to 0.25 m/s and the ratio between the channel depth and the droplets length varies between 0.4 and 11.2. Droplet side volumetric mass transfer coefficients were identified from concentration field computations and the evolution of these coefficients as a function of the flow parameters and the channel size is discussed. This study reveals that mass transfer is strongly influenced by the flow structure inside the droplet. Moreover, it shows that the confinement of the droplets due to the channel size leads to an enhancement of mass transfer compared to cases where the droplets are not constrained by the walls

Analyse de données pour des graphes étiquetés

International audienceNous proposons une méthode de fouille de données pour un graphe dont les sommets sont étiquetés. Deux approches sont décrites et illustrées sur un jeu de données réelles : elles permettent une représentation du graphe qui combine les informations sur sa structure et sur la valeur de ses étiquettes. Cette visualisation peut être utilisée à des fins d'interprétation pour apporter des informations plus nuancées sur la caractérisation des sommets du graphe

Analysis of the influence of a network on the values of its nodes : the use of spatial indexes.

National audienceA growing number of data are modeled by a graph that can sometimes be weighted: social network, biological network... In many situations, additional informations are provided with these relational data, related to each node of the graph: this can be a membership to a given social group (for social networks) or to a given proteins family (for protein interactions network). In this case, a important question is to understand if the value of this additional variable is influenced by the network. This paper presents exploratory tools to address this question that are based on tests coming from the field of spatial statistic. The use of these tests is illustrated on several examples, all coming from the social network framework

Optimisation of operating conditions in batch for more sustainable continuous process transposition

Implementation of exothermic and fast reactions requires a perfect temperature control to avoid thermal runaway and in most cases to limit by-products production. In order to fit with the heat removal capacity of common devices, expensive strategies are currently used to slow down this kind of reactions in order to avoid a strong temperature increase such as reactants dilution. Within the concept of process intensification, industries could move towards more sustainable process by reducing technology constraints to the benefit of chemistry. For that purpose, a two-step methodology is implemented. The first step consists in the optimisation of the operating conditions only based on stoichio-chemical scheme and kinetic laws. This is carried out by adjusting temperature profile and feeding rate strategy in a batch operation. Then a design for a continuous process is proposed, trying to approach the optimal batch operating conditions. This methodology is applied to the linear alkylbenzene sulfonation

Boosting de bonzaïs pour la combinaison efficace de descripteurs : application à l'identification du rôle du locuteur

International audienceDans ce travail, nous nous intéressons au problème de la détection du rôle du locuteur dans les émissions d'actualités radiotélévisées. Dans la littérature, les solutions proposées sont de combiner des indicateurs variés provenant de l'acoustique, de la transcription et/ou de son analyse par des méthodes d'apprentissage automatique. De nombreuses études font ressortir l'algorithme de boosting sur des règles de décision simples comme l'un des plus efficaces à combiner ces différents descripteurs. Nous proposons ici une modification de cet algorithme état-de-l'art en remplaçant ces règles de décision simples par des mini arbres de décision que nous appelons bonzaïs. Les expériences comparatives menées sur le corpus EPAC montrent que cette modification améliore largement les performances du système tout en réduisant le temps d'apprentissage de manière conséquente

Brain, language, and handedness: a family affair

The left planum temporale is a marker of left hemisphere language specialization. We investigated the effect of individual handedness and familial sinistrality on left planum temporale surface area and found the size is reduced in proportion with the number of left-handed immediate family members and is lowest when one's mother is left-handed. This reduction is independent of an individual's handedness or sex and has no counterpart in the right hemisphere

Mixing characterization inside microdroplets engineered on a microcoalescer

We use a microdevice where microdroplets of reagents are generated and coalesce in a carrier continuous phase. The work focuses on the characterization of the mixing step inside the droplets, in the perspective to use them for chemical kinetic data acquisition. A dye and water are used, and an acid–base instantaneous chemical reaction is monitored thanks to a colored indicator. Acquisitions are done with a high-speed camera coupled to a microscope and a mixing parameter is calculated by image analysis. Different angles of bended channels and different ways of coalescence are compared. It is shown that the homogenization of the droplets can be reached in less than 10 ms after coalescence. This is achieved by forcing the droplets to coalesce in a “shifted” way, and later by adding 45◦ angle bends along the channel

Nitrogen isotopic fractionation during abiotic synthesis of organic solid particles

The formation of organic compounds is generally assumed to result from abiotic processes in the Solar System, with the exception of biogenic organics on Earth. Nitrogen-bearing organics are of particular interest, notably for prebiotic perspectives but also for overall comprehension of organic formation in the young solar system and in planetary atmospheres. We have investigated abiotic synthesis of organics upon plasma discharge, with special attention to N isotope fractionation. Organic aerosols were synthesized from N2-CH4 and N2-CO gaseous mixtures using low-pressure plasma discharge experiments, aimed at simulating chemistry occurring in Titan s atmosphere and in the protosolar nebula, respectively. Nitrogen is efficiently incorporated into the synthesized solids, independently of the oxidation degree, of the N2 content of the starting gas mixture, and of the nitrogen speciation in the aerosols. The aerosols are depleted in 15N by 15-25 permil relative to the initial N2 gas, whatever the experimental setup is. Such an isotopic fractionation is attributed to mass-dependent kinetic effect(s). Nitrogen isotope fractionation upon electric discharge cannot account for the large N isotope variations observed among solar system objects and reservoirs. Extreme N isotope signatures in the solar system are more likely the result of self-shielding during N2 photodissociation, exotic effect during photodissociation of N2 and/or low temperature ion-molecule isotope exchange. Kinetic N isotope fractionation may play a significant role in the Titan s atmosphere. We also suggest that the low delta15N values of Archaean organic matter are partly the result of abiotic synthesis of organics that occurred at that time