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Optimizing Resource Allocation and Scheduling towards FRMCS and GSM-R networks coexistence in Railway Systems
No full textInternational audienceThe actual railway communication system used in Europe for high-speed trains (HST) is called the GSM-R system, which is a communication system based on 2G infrastructure. This system is meant to be replaced by a new system based on 5G NR infrastructure called the Future Railway Mobile Communication System (FRMCS) by 2030. For the next years, both systems will probably coexist in the same frequency band since the migration from GSM-R to FRMCS is planned to be done progressively until the GSM-R system is completely shut down, mainly due to safety and budget constraints. In this paper, we study the resource allocation for the FRMCS system sharing the same frequency band as the already deployed GSM-R system. We formulate the resource allocation problem as an integer linear problem (ILP), known to be NP-hard.To solve it in a reasonable time, we propose a scheduling algorithm, called Intelligent Traffic Scheduling Preemptor (ITSP), that allocates resources for the different FRMCS traffic types considered (critical traffic and performance traffic) in the same frequency band with the GSM-R system. Our algorithm is channel quality Indicator (CQI) aware and uses the preemption mechanism in 5G NR standards to optimize the resource allocation for the FRMCS system without impacting the actual GSM-R resource allocation in the context of the white space concept
Présentation à l'occasion de la table ronde « Éditer après la publication » aux 6ᵉ Rencontres de l’édition en sciences humaines et sociales
No full textNational audienceLes erreurs dans la littérature scientifique et leurs modalités de correction. Comment les informations de correction sont-elles reportées sur les sites web des revues et dans les différentes bases de données, notamment les archives ouvertes et les bases bibliographiques
Entre parenthèse enchantée et héritage : la crise sanitaire de COVID-19 et la gouvernance des politiques d'aménagements cyclables en Île-de-France
No full textInternational audienceThe COVID-19 pandemic opened a window of oppor- tunity for the development of cycling. In May 2020, several French local authorities started implementing pop-up cycling lanes to anticipate the end of the lockdown. The implementa- tion of these temporary infrastructures disrupted governance practices in a short timeframe to provide solutions to the crisis urgency. This article aims at analyzing the effects of the health crisis on the governance of cycling infrastructure poli- cies in the suburban areas of Paris Region. It investigates the transformations of stakeholders’ cooperation that happened during this short period between spring and autumn 2020, and their legacies in the following two years. It explores two case studies of first and third ring intercommunal entities in Paris Region. This research shows that the health crisis en- hanced both the acceleration and amplification of the cycling infrastructure development identified in pre-existing plans. The role of the national State was crucial to this dynamic, as it was strongly involved in the stakeholders’ coordination, even though it took a step back after the crisis peak as the regional mobility authority rose as the main coordinator. The health crisis also was an opportunity to implement a mul- tilevel governance of cycling infrastructure policies that the stakeholders built on afterwards to develop a flagship project of the regional cycling policy: the cycling express network.Avec la pandémie de la COVID-19 s’est ouverte une fenêtre d’opportunité pour le développement du vélo ; dès mai 2020, la perspective du déconfinement a amené de nombreuses collectivités locales françaises à se lancer dans le déploiement rapide d’aménagements cyclables temporaires. Durant un court laps de temps, entre le print- emps et l’automne 2020, les interactions entre acteurs et les modes d’action ont été transformés pour répondre à l’urgence de la situation. Cet article interroge les effets de cet épisode de crise sur la gouvernance des politiques d’aménagements cyclables dans les zones périphériques franciliennes, en s’intéressant aux reconfigurations du jeu d’acteurs observables à l’occasion de la mise en place des aménagements temporaires et à leur héritage dans les deux années suivantes. Une enquête auprès de deux intercommu- nalités de petite et grande couronne montre que la crise sani- taire a permis l’accélération et l’amplification de la mise en place d’aménagements cyclables intégrés à des schémas de réseaux déjà identifiés. Cette accélération a été facilitée par le rôle de chef d’orchestre pris par l’État, engagé activement dans la coordination des acteurs, et qui s’efface après la crise au profit de la région, autorité organisatrice de la mobilité. La crise a permis de développer la gouvernance multini- veaux des politiques d’aménagement cyclable, dans laquelle l’échelon communal reste à consolider, et sur laquelle les acteurs capitalisent après la crise pour développer un projet phare de la politique vélo francilienne : le réseau express vélo
The Vicious Circle of Xenophobia: Immigration and Right-Wing Populism
No full textWe investigate the bidirectional relationship between immigration and right-wing populism, which we characterize as a self-reinforcing dynamic process where anti-immigrant rhetoric and populist policies lead to a deterioration in the average education and skill level of immigrants. The deterioration in the ratio of high-skill to low-skill immigrants in turn fuels populist support and anti-immigration attitudes, creating what we call “the vicious circle of xenophobia”. We review some historical and contemporary studies that are suggestive of such vicious circle. In particular, recent cross-country evidence shows that low-skill immigration tends to exacerbate populism, while high-skill immigration tends to mitigate it. Conversely, populist policies and xenophobic attitudes have a strong repulsive effect on highly-skilled immigrants and result in adverse immigrant selection. We use the empirical results from those studies to inform a theoretical model of joint determination of immigrants’ skill-ratio and right-wing populism levels. The model displays multiple equilibria, with the inferior equilibrium – corresponding to our vicious circle -- characterized by high levels of right-wing populism and a high proportion of low-skill workers among immigrants. In this framework, structural trends such as internet penetration, economic erosion of themiddle class, demographic pressure from poor countries as well as adverse cyclical shocks make the good, efficient equilibrium less likely and the inferior equilibrium of explosive populism and deteriorated immigrants’ skill-ratio more likely
A mesh based improved plane wave expansion method for complex 2-D phononic crystals
No full textInternational audienceThis paper introduces a spectral method based on free triangular meshes, termed the mesh based improved plane wave expansion method (MIPWEM), aimed at simplifying the design and analysis of phononic crystals (PnCs) in complex scenarios. This method, built upon the improved plane wave expansion method (IPWEM) theoretical framework, incorporates free triangular meshes to approximate various complex geometries, significantly reducing the derivation costs associated with handling complex inclusions. By varying factors such as the number of plane waves and mesh generation, this paper investigates the computational efficiency of the proposed MIPWEM from different perspectives. Additionally, the method is successfully applied to compute cases with complex geometries. These results further validate the advantages of the new method in handling complex geometries, computational speed, and other aspects. The MIPWEM with superior efficiency, shows great potential for PnCs research in multiphysics and high-frequency applications
A Production Routing Problem with Mobile Inventories
No full textHydrogen is an energy vector, and one possible way to reduce CO 2 emissions. This paper focuses on a hydrogen transport problem where mobile storage units are moved by trucks between sources to be refilled and destinations to meet demands, involving swap operations upon arrival. This contrasts with existing literature where inventories remain stationary. The objective is to optimize daily routing and refilling schedules of the mobile storages. We model the problem as a flow problem on a time-expanded graph, where each node of the graph is indexed by a time-interval and a location and then, we give an equivalent Mixed Integer Linear Programming (MILP) formulation of the problem. For small to medium-sized instances, this formulation can be efficiently solved using standard MILP solvers. However, for larger instances, the computational complexity increases significantly due to the highly combinatorial nature of the refilling process at the sources. To address this challenge, we propose a two-step heuristic that enhances</div
Identifying Critical Commuters: A Machine Learning Approach to Flexible Work Hours and Urban Congestion
No full textInternational audienceCongestion remains one of the most prevalent transport problems in major cities. Recent approaches to managing demand aim to make working hours flexible to reduce congestion during peak periods. However, these approaches must also address synchronization needs at the employer, household, and individual levels. This study presents a framework to identify critical commuters who can adjust their arrival times, benefiting individual motivations, and managing arrival time demands. We explore multiple machine learning approaches to model and predict an individual's ability to shift their workplace arrival times. Ultimately, we choose gradient boosting due to its superior performance. Utilizing this ensemble approach on an employee survey data from Rennes Metropole in France, we analyze the factors that influence individual's flexibility in their arrival times. Key determinants identified include regular school drop-offs, theoretical arrival time contract with employer, and, to a lesser extent, age and income. Our findings demonstrate the need for a bi-level framework that incorporates both arrival time demand management and social justice analyses to ensure effective and equitable outcomes
A comparison of eight weakly dispersive Boussinesq-type models for non-breaking long-wave propagation in variable water depth
No full textInternational audienceWeakly dispersive Boussinesq-type models are extensively used to model long-wave propagation in coastal areas and their interaction with coastal infrastructures. Many equations falling in this category have been formulated during the last decades, but few detailed comparisons between them can be found in the literature. In this work, we investigate theoretically and with computational experiments eight variants of the most popular models used by the coastal engineering community. Both weakly nonlinear and fully nonlinear models are considered, hoping to understand better when the additional complexity of the latter class of models is necessary or justified. We provide an overview and discuss the properties of these models, including the linear dispersion relation in uniform water depth, the second-order nonlinear coupling coefficient, the shoaling gradient, and the sensitivity to wave trough instabilities. The models are then numerically discretised using the same general strategy in a single numerical code, using fourth-order methods for time and space discretisation. Their capacity to simulate coastal wave propagation and their transformation when approaching the shore is assessed on three challenging one-dimensional benchmarks. It appears that fully nonlinear models are more consistent than their weakly nonlinear counterparts, which can occasionally perform better but show different behaviours depending on the case.</div