Seminars

In the context of team Cornet’s seminars, Mandar Datar (LIA) will present her research work on Online algorithms in games and convex optimization, on March 10, 2023, at 11:35 in the meeting room.

In the context of team Cornet’s seminars, Panagiotis Andrianesis (Boston University) will present his research work on Optimal Distributed Energy Resource Coordination: A Hierarchical Decomposition Method Based on Distribution Locational Marginal Costs, on February 23, 2023, at 11:35 in the meeting room. Abstract: In this work, we consider the day-ahead operational planning problem of a radial distribution network hosting Distributed Energy Resources (DERs) including rooftop solar and storage-like loads, such as electric vehicles. We present a novel hierarchical decomposition method that is based on a centralized AC Optimal Power Flow (AC OPF) problem interacting iteratively with self-dispatching DER problems adapting to real and reactive power Distribution Locational Marginal Costs. We illustrate the applicability and tractability of the proposed method on an actual distribution feeder, while modeling the full complexity of spatiotemporal DER capabilities and preferences, and accounting for instances of non-exact AC OPF convex relaxations. We show that the proposed method achieves optimal Grid-DER coordination, by successively improving feasible AC OPF solutions, and discovers spatiotemporally varying marginal costs in distribution networks that are key to optimal DER scheduling by modeling losses, ampacity and voltage congestion, and, most importantly, dynamic asset degradation.

In the context of team Cornet’s seminars, Sébastien De Valeriola (Free University of Brussels) will present his research work on “Fading Footprints in the Sand”: Analysis of Historical Networks and Robustness of Centrality Metrics, on February 10, 2023, at 11:35 in the room S6. Abstract: In this presentation, we consider centrality measures in their use in the analysis of historical networks. Since the sources used by historians to construct such networks are inherently incomplete and imperfect, it is necessary to take into account the robustness of these metrics as much as possible, i.e., their stability in the face of the vagaries that time has subjected historical documents to. To study this, we apply a battery of tests to three networks constructed from medieval history data. The first is a network of political history, representing the connections among the key figures in the conflict for the episcopal seat of Cambrai in the 11th century. The second is a network of socio-economic history, describing credit relationships among merchants in Ypres in the 13th century. The third is a hagiographical network depicting the connections between the lives of saints often compiled together in manuscripts. These tests are designed to simulate the processes of Plus d'infos

In the context of team Cornet’s seminars, Felipe Albuquerque (LIA/Espace) will present his research work on January 13, 2023, at 11:35 in the meeting room. Abstract: Frequently, social network information has been used to solve applications in Operation Research, such as the Team Formation Problem, whose goal is to find a subset of the workers that collectively cover a set of skills and can communicate effectively with each other. We use the Structural Balance Theory to define the compatibility between pairs of workers in the same team. For such, the social networks are represented by signed graphs, and the compatibility metric is calculated from the analysis of possible positive paths between pairs of distinct vertices. To solve this new version of the problem, we introduce an Integer Linear Programming formulation and a decomposition for it. We present an analysis of the performed computational tests that prove the potential efficiency of the decomposition proposed.

In the context of team Cornet’s seminars, Olivier Tsemogne (LIA) will present his research work on Game Theory for Cyber Deception against Network SIR Epidemics, on December 12, 2022, at 11:35 in the meeting room. Abstract: One of the deleterious aspects of the evolution of information and communication technologies is the combination of efficiency and effectiveness in the malware spread, which clearly constitutes a threat to the security of the users of these technologies. The term “user” here covers individuals, companies, governmental or non-governmental organizations, states, in short, any person or group of persons who communicate using the new technologies. Among these threats, we can cite rumors in a social network and the stealthy recruitment of naive users into a cyber terrorist army capable, for example, of causing serious damage to a company whose services are used by these same users. In these two cases, as in many others, users, tricked by skilled experts, participate against their will and against their own interest in a cyber attack of which they are not aware, the bearer of the attack being deception. Moreover, cybercriminals, unlike cyber defenders, violate the rules of privacy and are therefore the best, if not the only, informed Plus d'infos

In the context of team Cornet’s seminars, Olivier Bilenne (ENPC) will present his research work on Solutions of Poisson’s equation for first-policy improvement in parallel queueing systems, on November 18, 2022, at 11:35 in the meeting room. Abstract: This talk addresses the problem of (state-aware) job dispatching at minimum long-run average cost in a parallel queueing system with Poisson arrivals. Policy iteration is a technique for approaching optimality through improvement of an initial dispatching policy. Its implementation rests on the computation of value functions. In this context, we will consider the M/G/1-FCFS queue endowed with an arbitrary cost function for the waiting times of the incoming jobs. The associated relative value function is a solution of Poisson’s equation for Markov chains, which I propose to solve in the Laplace transform domain by considering an ancillary stochastic process extended to (imaginary) negative backlog states. This construction enables us to issue closed-form solutions for simple cost functions (polynomial, exponential, and their piecewise compositions), in turn permitting the derivation of interval bounds for the relative value functions to more general cost functions. Such bounds allow for an exact implementation of the first improvement step of policy iteration in a parallel queueing system.One objective Plus d'infos

In the context of team Cornet’s seminars, Omar Boufous (OrangeLabs) will present his research work on Learning a Correlated Equilibrium with Perturbed Regret Minimization, on October 22, 2021, at 11:35 in the meeting room. Abstract: We consider the problem of learning a correlated equilibrium of a finite non-cooperative game and show a new learning procedure, called Correlated Perturbed Regret Minimization (CPRM), for this purpose. CPRM uses a perturbed variant of a regret minimization to approach the set of correlated equilibrium distributions and a simple correlation device to stabilize the empirical probability distribution over action profiles. Numerical experiments provide evidence of the long run convergence of the realized sample paths to points in the set of approximate correlated equilibrium distributions. Additional simulation results suggest that CPRM is adaptive to changes in the game such as departures or arrivals of players.

In the context of team Cornet’s seminars, Rosa Figueiredo (LIA) will present her research work on Multiplicity in Signed Graph Partitioning, on June 6, 2022, at 11:35 in the meeting room. Abstract: In order to study real-world systems many works model them through signed graphs, i.e. graphs whose edges are labeled as either positive or negative. Such a graph is considered as structurally balanced when it can be partitioned into a number of modules, such that positive (negative) edges are located inside (in-between) the modules. When it is not the case, authors look for the closest partition to such balance, a problem called Correlation Clustering (CC). The standard approach used in the literature is to find a single partition and focus the rest of the analysis on it, as if it was sufficient to fully characterize the studied system. Yet, it may not reflect the structure of the network, and one may need to seek for other partitions to build a better picture. We study the space of optimal solutions of the CC. We propose an efficient enumeration method allowing to retrieve the complete space of optimal solutions of the CC. It combines an exhaustive enumeration strategy with neighborhoods of Plus d'infos

In the context of team Cornet’s seminars, Mandar Datar (LIA) will present his research work on Fisher market model-based resource allocation for 5G network slicing, on June 6, 2022, at 11:35 in the meeting room. Abstract: Network slicing is one of the potential technologies to support a higher degree of heterogeneity and flexibility required by next-generation services in 5G networks. In a 5G network, slicing is a specific form of virtualization that allows multiple logical networks (e.g., Mobile Virtual Network Operators (MVNOs)) to run on top of shared physical infrastructure. In the multi-resource allocation scheme, a set of heterogeneous resources (e.g., radio resource, CPU, memory, bandwidth) is shared among Slice tenants or MVNOs, and a portion of them is allocated to each MVNO to support dedicated service to their customers. We consider a scenario where service providers or slice tenants need heterogeneous resources at geographically distributed locations to support the service for their end-users. We propose a resource sharing scheme based on the Fisher market model and the Trading post mechanism. In the proposed scheme, each slice owns the budget representing its infrastructure share or purchasing power in the market. The slices acquire different resources by spending their budgets to Plus d'infos

In the context of team Cornet’s seminars, Naresh Modina (LIA) will present his research work on Multi Resource Allocation (MRA) for network slices with Multi-Level Fairness, on May 5, 2022, at 11:35 in the meeting room. Abstract: Network slicing is becoming the platform of choice for several applications and services. Nowadays most applications are virtualized to gain flexibility and portability. With network slicing, operators can create multiple network slices or tenants, which can be used for certain applications with specific requirements. Behind the network slicing, a slice expresses the need to access a precise service type, under a fully qualified set of computing and network requirements. Resource allocation decision encompasses a combination of different resource types (e.g., radio resource, CPU, memory, bandwidth). In this paper, we explore a differential pricing scheme that maximizes social welfare among slices as well as among end-users. To do so, we propose a pricing mechanism that makes fairness at multiple levels: fairness among slices and fairness among slice locations supported by each slice. Therefore, the proposed scheme is beneficial for both the slices and the end-users independent of their location. Additionally, we study the case where slices can manipulate their preferences to improve their utility. Plus d'infos