Dynamic Duopoly with Congestion Effects

We analyze duopolistic competition between horizontally differentiated firms selling durable goods or services subject to congestion. At each point of time, new customers buy one unit of the commodity from one of the firms, by comparing present prices and future congestion rates. We study the linear Markov equilibrium of this game which exists and is unique when firms are not too different. The existence of negative consumption externalities is shown to soften the price competition. Moreover, we show that the firm with the larger capacity has, at the steady state, a larger market share, a higher price, and a lower congestion rate. The price of an entrant decreases gradually after entry, while the price of the incumbent rises. The speed of convergence to the steady state is faster, the stronger is the congestion effect. On étudie la concurrence entre deux firmes qui vendent des biens ou des services durables sous la condition d'encombrement. À chaque instant, des clients nouveaux achètent une unité du bien, en comparant les prix et les taux d'encombrement futur. On caractérise l'équilibre markovien de ce jeu. L'existence des externalités négatives rend la concurrence moins féroce. On montre que la firme qui a la plus grande capacité a, dans l'état stationnaire, une plus grande part de marché, un prix plus élevé, et un taux d'encombrement plus faible. Le prix du bien d'une nouvelle firme diminue continuellement, tandis que celui de son rival en exercise monte. La vitesse de convergence est une fonction croissante de l'effet d'encombrement.duopoly, differential games, Markov perfect equilibrium, duopole, jeux différentiels, équilibre markovien parfait

Strategic Separation from Suppliers of Vital Complementary Inputs: A Dynamic Markovian Approach

In a model where a monopolistic downstream firm (assembler) negotiates simultaneously with each of its intermediate-input suppliers the prices of the complementary components which enter its product, we analyze the process by which the assembler separates from its suppliers as a Markov Perfect equilibrium. Due to a negative strategic effect (the prices and profits of independent suppliers decrease when their number increases), the assembler's marginal return from keeping an upstream subsidiary is lower than its market value as an independent supplier. Separation is immediate when the downstream firm's initial number of upstream subsidiaries is below a critical level. It is progressive in the reverse case and eventually leads to a mixed strategy whereby it keeps all the remaining subsidiaries with some probability, and sells all them off in one go with the complementary probability. Nous étudions le processus de séparation entre une firme à l’aval et des firmes à l’amont qui lui fournissent des inputs complémentaires. À cause d’un effet stratégique négatif, le profit marginal de la firme à l’aval de garder une firme à l’amont comme filiale est moins élevé que la valeur de cette dernière au marché des bourses. La séparation est immédiate si le nombre de filiales à l’amont est inférieur à un certain niveau critique. La séparation est graduelle dans le cas inverse et demande une stratégie mixte éventuelle.Vertical disintegration, vertical structure, Markov perfect equilibrium, dynamic games. , Séparation verticale, structure verticale, équilibre Markov-parfait, jeux dynamiques

FORENSIC EVALUATION AND LESSONS LEARNED OF PRESTRESSED CONCRETE POLE FAILURES IN PUERTO RICO DURING HURRICANE MARIA

This article summarizes the lessons learned from the evaluation of failed concrete utility poles in Puerto Rico as a consequence of Hurricane Maria. Teams were deployed between October 3rd to 11th 2017, to cover the west, northwest, south, and east of the island. The evaluation presents sample cases of the failed poles around the island but does not attempt to conduct an inventory. The Puerto Rico building code was being updated based on changes in the International Building Code and the effects of Hurricane Georges. However, many poles made from previous designs are still in service, and many of them failed as a consequence of design deficiencies and improper construction practices. Poles manufactured under the updated codes failed mostly due to foundation issues or structural overload from nearby vegetation impact and the failure of in-line poles, especially wood poles and pre-Georges concrete poles

Dynamique moléculaire et plasticité d'un polymère amorphe sous traction

L'amélioration des performances des matériaux polymères passent notamment par une meilleure compression du lien entre dynamiques moléculaires à l'échelle microscopique et propriétés mécaniques macroscopiques. Dans ce but, la mobilité des chaînes polymères a été sondée par une mesure de spectroscopie diélectrique lors de la déformation plastique d'un polymère vitreux

Singular Cucker-Smale Dynamics

The existing state of the art for singular models of flocking is overviewed, starting from microscopic model of Cucker and Smale with singular communication weight, through its mesoscopic mean-filed limit, up to the corresponding macroscopic regime. For the microscopic Cucker-Smale (CS) model, the collision-avoidance phenomenon is discussed, also in the presence of bonding forces and the decentralized control. For the kinetic mean-field model, the existence of global-in-time measure-valued solutions, with a special emphasis on a weak atomic uniqueness of solutions is sketched. Ultimately, for the macroscopic singular model, the summary of the existence results for the Euler-type alignment system is provided, including existence of strong solutions on one-dimensional torus, and the extension of this result to higher dimensions upon restriction on the smallness of initial data. Additionally, the pressureless Navier-Stokes-type system corresponding to particular choice of alignment kernel is presented, and compared - analytically and numerically - to the porous medium equation

Urban Climate, Human behavior & Energy consumption: from LCZ mapping to simulation and urban planning (the MapUCE project)

International audienceThe MApUCE project aims to integrate in urban policies and most relevant legal documents quantitative data from urban microclimate, climate and energy.The primary objective of this project is to obtain climate and energy quantitative data from numerical simulations, focusing on urban microclimate and building energy consumption in the residential and service sectors, which represents in France 41% of the final energy consumption. Both aspects are coupled as building energy consumption is highly meteorologically dependent (e.g. domestic heating, air-conditioning) and heat waste impact the Urban Heat Island. We propose to develop, using national databases, a generic and automated method for generating Local Climate Zones (LCZ) for all cities in France, including the urban architectural, geographical and sociological parameters necessary for energy and microclimate simulations.As will be presented, previous projects on adaptation of cities to climate change have shown that human behavior is a very potent level to address energy consumption reduction, as much as urban forms or architectural technologies. Therefore, in order to further refine the coupled urban climate and energy consumption calculations, we will develop within TEB (and its Building Energy Module) a model of energy consumer behavior.The second objective of the project is to propose a methodology to integrate quantitative data in urban policies. Lawyers analyze the potential levers in legal and planning documents. A few “best cases” are also studied, in order to evaluate their performances. Finally, based on urban planning agencies requirements, we will define vectors to include quantified energy-climate data to legal urban planning documents. These vectors have to be understandable by urban planners and contain the relevant information.To meet these challenges, the project is organized around strongly interdisciplinary partners in the following fields: law, urban climate, building energetics, architecture, sociology, geography and meteorology, as well as the national federation of urban planning agencies.In terms of results, the cross-analysis of input urban parameters and urban micro-climate-energy simulated data will be available on-line as standardized maps for each of the studied cities. The urban parameter production tool as well as the models will be available as open-source. LCZ and associated urban (and social!) indicators may be integrated within the WUDAPT database

The effect of an intracerebroventricular injection of metformin or AICAR on the plasma concentrations of melatonin in the ewe: potential involvement of AMPK?

<p>Abstract</p> <p>Background</p> <p>It is now widely accepted that AMP-activated protein kinase (AMPK) is a critical regulator of energy homeostasis. Recently, it has been shown to regulate circadian clocks. In seasonal breeding species such as sheep, the circadian clock controls the secretion of an endogenous rhythm of melatonin and, as a consequence, is probably involved in the generation of seasonal rhythms of reproduction. Considering this, we identified the presence of the subunits of AMPK in different hypothalamic nuclei involved in the pre- and post-pineal pathways that control seasonality of reproduction in the ewe and we investigated if the intracerebroventricular (i.c.v.) injection of two activators of AMPK, metformin and AICAR, affected the circadian rhythm of melatonin in ewes that were housed in constant darkness. In parallel the secretion of insulin was monitored as a peripheral metabolic marker. We also investigated the effects of i.c.v. AICAR on the phosphorylation of AMPK and acetyl-CoA carboxylase (ACC), a downstream target of AMPK, in brain structures along the photoneuroendocrine pathway to the pineal gland.</p> <p>Results</p> <p>All the subunits of AMPK that we studied were identified in all brain areas that were dissected but with some differences in their level of expression among structures. Metformin and AICAR both reduced (p < 0.001 and p < 0.01 respectively) the amplitude of the circadian rhythm of melatonin secretion independently of insulin secretion. The i.c.v. injection of AICAR only tended (p = 0.1) to increase the levels of phosphorylated AMPK in the paraventricular nucleus but significantly increased the levels of phosphorylated ACC in the paraventricular nucleus (p < 0.001) and in the pineal gland (p < 0.05).</p> <p>Conclusions</p> <p>Taken together, these results suggest a potential role for AMPK on the secretion of melatonin probably acting trough the paraventricular nucleus and/or directly in the pineal gland. We conclude that AMPK may act as a metabolic cue to modulate the rhythm of melatonin secretion.</p

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes