Learning to Bid - an Experimental Study of Adaptation in Auctions and Fair Division Games

We examine learning behavior in auctions and fair division games with independent private values under two di¤erent price rules, …rst and second price. Participants face these four games repeatedly and submit complete bid functions rather than single bids. This allows us to examine whether learning is in‡uenced by the structural di¤erences between games. We …nd that within the time horizon which we investigate, learning does not drive toward risk neutral equilibrium bidding and characterize some features of observed learning: Bid functions are adjusted globally rather than locally, decision time matches the sequencing structure of game types, game rules do matter, and directional learning theory o¤ers a partial explanation for bid adjustments. The evidence supports a cognitive approach to learning. JEL classi…cation: D44, C9

Bis(2,3,5,6-tetra-2-pyridyl­pyrazine-κ3 N 2,N 1,N 6)nickel(II) dithio­cyanate dihydrate

In the title compound, [Ni(C24H16N6)2](NCS)2·2H2O, the central NiII ion is octahedrally coordinated by six N atoms of two tridentate 2,3,5,6-tetra-2-pyridyl­pyrazine ligands (tppz). Two thio­cyanate anions act as counter-ions and two water mol­ecules act as solvation agents. O—H⋯N hydrogen bonds are observed in the crystral structure

Laser-plasma-based space radiation reproduction in the laboratory

Space radiation is a great danger to electronics and astronauts onboard space vessels. The spectral flux of space electrons, protons and ions for example in the radiation belts is inherently broadband, but this is a feature hard to mimic with conventional radiation sources. Using laser-plasma-accelerators, we reproduced relativistic, broadband radiation belt flux in the laboratory, and used this man-made space radiation to test the radiation hardness of space electronics. Such close mimicking of space radiation in the lab builds on the inherent ability of laser-plasma-accelerators to directly produce broadband Maxwellian-type particle flux, akin to conditions in space. In combination with the established sources, utilisation of the growing number of ever more potent laser-plasma-accelerator facilities worldwide as complementary space radiation sources can help alleviate the shortage of available beamtime and may allow for development of advanced test procedures, paving the way towards higher reliability of space missions

From harmful Microcystis blooms to multi-functional core-double-shell microsphere bio-hydrochar materials

Harmful algal blooms (HABs) induced by eutrophication is becoming a serious global environmental problem affecting public health and aquatic ecological sustainability. A novel strategy for the utilization of biomass from HABs was developed by converting the algae cells into hollow mesoporous biohydrochar microspheres via hydrothermal carbonization method. The hollow microspheres were used as microreactors and carriers for constructing CaO2 core-mesoporous shell-CaO2 shell microspheres (OCRMs). The CaO2 shells could quickly increase dissolved oxygen to extremely anaerobic water in the initial 40 min until the CaO2 shells were consumed. The mesoporous shells continued to act as regulators restricting the release of oxygen from CaO2 cores. The oxygen-release time using OCRMs was 7 times longer than when directly using CaO2. More interestingly, OCRMs presented a high phosphate removal efficiency (95.6%) and prevented the pH of the solution from rising to high levels in comparison with directly adding CaO2 due to the OH− controlled-release effect of OCRMs. The distinct core-doubleshell micro/nanostructure endowed the OCRMs with triple functions for oxygen controlled-release, phosphorus removal and less impact on water pH. The study is to explore the possibility to prepare smarter bio-hydrochar materials by utilizing algal blooms

Contribution à l'optimisation de la conception des engrenages coniques à denture droite (analyse et synthèse de la géométrie et des tolérances)

La maîtrise accrue des matériaux et des procédés de forgeage permet aujourd'hui d'obtenir des engrenages coniques d'une qualité suffisante pour pouvoir les utiliser sans autre procédé de finition. Ce sont les pièces dites net shape . Grâce à cette évolution technologique, il est nécessaire de d'optimiser la définition géométrique de ces engrenages en tenant compte des possibilités des procédés de forgeage, en particulier. Tout d'abord, la définition de la géométrie nominale des engrenages coniques à denture droite basée sur les propriétés géométriques et cinématiques du profil en développante de cercle sphérique est réétudiée et a abouti à une modélisation paramétrique des surfaces actives en intégrant un bombé longitudinal. Afin de garantir un certain niveau de qualité de l'engrènement, il est nécessaire de limiter les variations inhérentes au procédé de forgeage et aux ressources de fabrication, il s'agit de l'analyse et de la synthèse des tolérances. Cette analyse a nécessité une modélisation géométrique des engrenages incluant les écarts intrinsèques et les écarts de situation. L'analyse de l'impact de ces écarts sur l'erreur cinématique (Tooth Contact Analysis) repose sur la résolution d'un système d'équations non linéaires pour chaque position du pignon et d'un traitement de ces résultats; la difficulté de cette analyse est la grande sensibilité des résultats aux écarts. Cet outil TCA est le module principal de l'analyse des tolérances qui est réalisée de façon statistique par simulation de Monte Carlo. L'analyse des tolérances permet de valider une solution d'allocation de celles-ci mais ne permet pas son allocation automatique. Ainsi une approche de synthèse des tolérances a été validée, il s'agit de l'optimisation par algorithme génétique où la fonction objectif est de minimiser le ratio coût des tolérances sur la probabilité de respect des exigences. Cette analyse et cette synthèse ont été menées dans un premier temps sans charge, en considérant l'engrenage comme indéformable. Puis, la prise en compte des déformations est réalisée par la méthode des coefficients d'influences. Le problème de contact et de déformation globale de la denture sont découplés. Les coefficients d'influences de contact sont estimés par la méthode de Boussinesq et Cerruti. Les coefficients d'influence de flexion sont estimés par interpolation et méthode des éléments finis. Ce modèle permet l'analyse de l'engrènement sous charge mais les temps de calculs restent un handicap pour l'analyse des tolérances. Ces modèles de comportement pourront être affinés dans de futurs travaux et être le support de nouveaux modèles de spécification des engrenages, de suivi du processus de fabrication, d'une meilleure connaissance des interactions géométrie-mécanique-matériau, etc.As technology increases and performance requirements continually tighten, the cost and required precision of assemblies increase as well. The forging evolution enables us to realize bevel gear net shape. Therefore, this work focuses on the parametric and tolerance design optimization of bevel gear. The synthesis of bevel gear nominal model is based on geometrical properties and kinematic properties of spherical involute. To ensure a quality level of meshing, it is necessary to limit the geometrical variations which are due to the manufacturing process (tolerance analysis and tolerance synthesis). To achieve this, we establish a geometrical model which includes the deviations (form, orientation and position). This model enables the evaluation of the impact of these deviations on the kinematic behaviour. This evaluation is T.C.A. (Tooth Contact Analysis) is based on the simulation of tangency of tooth surfaces being in mesh. The tolerance analysis is based on TCA and Monte Carlo simulation which computes the probability that the product respects the requirements of the kinematic error, under given individual tolerances. Moreover, to optimize the ratio of tolerance cost (tolerance synthesis) on probability that the product respects the requirements, genetic algorithm is improved. These tolerance analysis and synthesis do not take into account the teeth distortions. To do so, we propose to integrate the distortions which are evaluated by the influence coefficient method. Contact problem and bending problem of teeth are delinked. The contact influence coefficients are estimated by Boussinesq and Cerruti method. The bending influence coefficients are evaluated by interpolation and finite elements method. This model allows gearing analysis under load but the calculation time is a handicap for tolerance analysis. This behaviour models may be refined in future works and support the new geometrical specification models, process control and better knowledge of geometry-mechanic-material interaction.CACHAN-ENS (940162301) / SudocPARIS-Arts et Métiers (751132303) / SudocMETZ-Arts et Métiers (574632301) / SudocSudocFranceF