1,474 research outputs found
Some forgotten equilibria of the Bertrand duopoly!?
No full textThis note analyzes the Bertrand duopoly with constant but asymmetric marginal costs on a market with homogenous products. It is shown that there exist some equilibria that are ignored in the literature on IO. In addition, in this setting (perfectly or nearly perfectly) competitive equilibria exist.
A computational approach to design new tests for viscoplasticity characterization at high strain-rates
No full textRate-dependent behaviour characterization of metals at high strain rate remains challenging mainly because of the strong hypotheses when tests are processed with statically determinate approaches. As a non-standard methodology, Image-Based Inertial Impact (IBII) test has been proposed to take advantage of the dynamic Virtual Fields Method (VFM) which enables the identification of constitutive parameters with strain and acceleration fields. However, most of the test parameters (e.g. projectile velocity, specimen geometry) are not constrained. Therefore, an FE-based approach is addressed to optimize the identification over a wide range of strain and strain-rate, according to two design criteria: (1) the characterized viscoplastic spectra, (2) the identifiability of the parameters. Whereas the first criterion is assessed by processing the FEA simulations, the second is rated extracting material parameters using synthetic images to input the VFM. Finally, uncertainties regarding the identification of material constants are quantified for each IBII test configuration and different camera performances.</p
Optimization of an image-based experimental setup for the dynamic behaviour characterization of materials
No full text
The present work aims at identifying an elastic-viscoplastic material constitutive model over a wide strain and strain-rate range (up to 0.1 and 1000 s
−1
respectively), using the so-called Virtual Fields Method. To define the experimental campaign, a design process has been set. It relies on the numerical optimization of the setup – notably the specimen shape, the impact conditions and the measurement resolution (time and space) – with respects to user-defined criteria. Finally, the selected configuration ensures an accurate and robust identification.
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Heterogeneous Behavioral Rules in the Oligopolistic Case
No full textIn a static symmetric duopoly the set of behavioral rules is extended to different types of markup pricing. Using an equilibrium concept suggested in Pasche (2001), it is shown that dependend on the markup neither pure Cournot nor pure Bertrand behavior is a behavioral equilibrium profile. Instead, there is a rationale for the usage of simple heuristics. The presence of markup rules leads to Stackelberg outcomes. Furthermore, pure markup behavior is more competitive than in Cournot case but less competitive than in Bertrand case. It is shown, that multiple behavioral equilibria and heterogeneous behavior may arise, where at least one player uses price setting strategies.oligopoly, markup rules, heterogeneity, behavioral equilibrium.
A Bertrand-Edgeworth-oligopóliumok (Bertrand-Edgeworth oligopolies – a survey of the literature)
No full textAz irodalomban az olyan oligopolmodellek, amelyekben mind az ár, mind a mennyiség döntési változó, Bertrand-Edgeworth-oligopóliumok néven ismertek. E tanulmányban a Bertrand-Edgeworth-oligopóliumokkal kapcsolatos érdekesebb eredményeket tekintjük át. Tárgyaljuk a Bertrand-Edgeworth-típusú oligopolmodellek specifikációját, a Nash-egyensúly létezését, a Nash-egyensúly meghatározását és a Bertrand-Edgeworth-oligopóliumok alkalmazásait. / === / Oligopoly models in which both price and quantity are decisive variables are known in the literature as Bertrand-Edgeworth oligopolies, the most interesting results with which are surveyed in this paper. The author assumes the existence of the Nash equilibrium, as the specification of Bertrand-Edgeworth-type oligopoly models, the determination of the Nash equilibrium, and the application of Bertrand-Edgeworth oligopolies
Data used for the spatio-temporal analysis of the climatic debt observed in understory plant communities
No full textDetails about the variables' computation and definition are provided in Bertrand 2018 and Bertrand et al. 2016. References: Bertrand, R.et al. (2016) Ecological constraints increase the climatic debt in forests. Nature communications 7: 12643. Bertrand, R. (2018) Unequal contributions of species’ persistence and migration on plant communities’ response to climate warming throughout forests. Ecography. Accepted Author Manuscript
Le origini del liberalsocialismo di Bertrand Russell
No full textIl saggio prende in esame le origini del liberalsocialismo di Bertrand Russell. Afferma che tutte le tesi maggiori dell'autore inglese sono presenti nelle prime opere politiche che pubblica.The essay deals with the origins of the liberal socialism of Bertrand Russell. The thesis is that all major ideas of the english author are present in first political books he publish
Super-element for riveted plates in structural computations
No full textLa thèse s’inscrit dans un axe de recherche visant à améliorer l’analyse par éléments finis (EF) des structures aéronautiques soumises au crash et à l’impact. L’étude s’intéresse, en particulier, à la modélisation des assemblages rivetés dans les calculs de structures, qui sont des zones de concentrations de contraintes propices à l’initiation de ruptures. Si la rupture de la fixation est maîtrisée, les modes de rupture dus aux perforations sont, quant à eux, difficiles à simuler dans un calcul sur structure complète. Afin de prendre en compte avec précision l’influence des perforations sur la réponse mécanique de telles structures, un super-élément perforé à 8 nœuds a été formulé lors d’une précédente thèse. Cependant, sa frontière interne est analytique et libre de chargement, ce qui rend difficile la connexion avec un élément rivet, et donc la modélisation de l’assemblage. L’étude proposée ici consiste donc à développer un super-élément perforé qui soit capable de tenir compte de l’influence de la perforation sur les champs mécaniques, d’une part, et qui soit formulé de façon à rendre possible l’interaction avec un macro-élément rivet, d’autre part.The thesis is made in a context which consists in improving the finite element (FE) analysis of full-scale aircraft structures subjected to crash and impact loadings. The study is focused, in particular, on the rivetedassemblies modeling in structural computations, which are stress concentrations areas where ruptures initiation can occur. If the fastener rupture is mastered, the rupture modes due to perforations are, however, difficult to simulate in a complete structure computation. In order to accurately take into account the perforations influence on the mechanical response of such structures, a perforated super-element featuring 8 nodes have been formulated in a previous thesis. Nevertheless, its internal boundary is analytic and free of loads, which makes difficult the connection with a rivet element, and consequently the assembly modeling. The study proposed here consists in the developement of a perforated super-element which is, on the one hand, able to take into account the perforation influence on the mechanical fields, and which is, on the other hand, formulated such as the interaction with a rivet macro-element is possible
Bertrand Russell y el pragmatismo
No full textThis paper analyzes the two stages of the relationship of the British philosopher Bertrand Russell withpragmatism. The first section reviews the criticisms that the author made to American pragmatists.The second exposes Russell’s pragmatic turn, exposing the causes of this turn and its consequences. This paper argues that both stages should be understood in the context of the discussions about truth that were observed in philosophy in the first decades of the 20th century
Fatigue modeling of metallic assemblies using a local approach
No full textDe nos jours, deux défis importants à relever en matière de prédiction de la tenue fatigue concernent la multiaxialité et les sollicitations aléatoires, en particulier lorsque ces deux effets sont combinés. Ceci est particulièrement vrai dans les structures aéronautiques assemblées où de nombreux phénomènes non-linéaires interagissent (non-linéarité du comportement du matériau, contact avec frottement, comportement de la fixation...). L'objectif de cette thèse est de proposer une démarche de prédiction de tenue en fatigue robuste, afin d'estimer la durée de vie en fatigue d'assemblages métalliques boulonnés soumis à des conditions de sollicitations multiaxiales variées. Il s'agit d'estimer la durée de vie de pièces assemblées par une approche locale reposant sur une modélisation explicite de la fixation et des efforts induits. À cette fin, une campagne expérimentale majeure a été entreprise avec des essais de complexité croissante allant d'éprouvettes de caractérisation uniaxiale, à des assemblages complexes chargés multiaxialement au moyen d'un dispositif expérimental biaxial. Parallèlement, une analyse numérique par éléments finis a été réalisée pour modéliser aussi fidèlement que possible des assemblages industriels représentatifs, en tenant compte de toutes les non-linéarités observées (géométriques, induites par le problème de contact, la flexion secondaire, l'entaille, le matériau ...). Le dialogue entre les résultats expérimentaux et les simulations numériques a permis de tester et de valider le modèle d'endommagement de fatigue développé, ainsi que de mieux comprendre les mécanismes d'amorçages de fissures dans les assemblages métalliques boulonnés soumis à des chargements multiaxiaux.Nowadays, two important challenges to be addressed in fatigue prediction deal with multiaxiality and random loads, especially when both effects are combined. This is particularly true in assembled aircraft structures where many nonlinear phenomena interact (non-linearity of the behavior of material, contact with friction, behavior of the screw ...). The aim of this thesis is to develop a robust fatigue life prediction approach for estimating the fatigue life of bolted metallic assemblies subjected to a variety of multiaxial loading conditions. It consists in predicting the fatigue life of assembled parts using a local approach based on explicit modeling of the fastener and induced forces. For this purpose, a major experimental campaign has been undertaken with experiments of increasing complexity ranging from uniaxial characterization specimens, to complex multiaxially loaded assemblies by means of a biaxial (tension/compression) experimental device. At the same time, a numerical finite element analysis was carried out to model representative industrial assemblies as faithfully as possible, taking into account all observed non-linearities (geometric, induced by the contact problem, secondary bending, notching, material...). The dialog between experimental results and numerical simulations has allowed us to test and validate the fatigue damage model developed, as well as to improve our understanding of crack initiation mechanisms in bolted metal assemblies subjected to multiaxial loading
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