Watch U - La webTV de l'UDA ! https://webtv.u-clermont1.fr Toutes les dernières vidéos de l'Université d'Auvergne. Toutes les dernières vidéos de l'Université d'Auvergne. Wed, 02 Dec 2020 00:00:00 +0100 2020 <![CDATA[Séminaire LIMOS - 2 avril 2020 - Optimization of routing and resource allocation in communication networks]]> https://webtv.u-clermont1.fr/media-MEDIA200710134351207

Presenter : ZHOU Fen - ISEP

Abstract : This talk will first show my research activities related to routing and resource allocation in different communication networks (optical networks, wireless ad-hoc networks, and content delivery networks).

In wireless sensor networks (WSNs), we studied the problem of maximizing the network lifetime for data gathering tree. To this end, we considered several data aggregation modes, and proposed an integer linear program to obtain the optimal data gathering tree in each mode respectively.

Then, I will present our work on the service provisioning against disaster failures in optical datacenter networks, where we considered the survivability of both the service content and the provisioning path. To solve this problem efficiently, we proposed a column generation based method.


Bio. Since September 2018, Fen Zhou is working as an Associate Professor at the Institut Supérieur d'Electronique de Paris (ISEP, on leave from Univ. Avignon). Before that, he has been an Associate Professor at the LIA lab of Avignon University, from 2012 to 2018. He obtained the HDR degree from Avignon University in 2018 and his PhD from INSA of Rennes in 2010.

Dr. Zhou is a Senior Member of IEEE. He has served as the TPC co-chair of IEEE BMSB 2020, symposium co-chair for IEEE ICNC’18 and WCSP’14, publicity co-chair for IEEE Wimob’15/19 and NetgCOOP’16, etc. He has also served on
the program committees for several international conferences such as IEEE INFOCOM, IEEE GLOBECOM, IEEE ICC, and IEEE IWCMC.

For 2016-2020, he is
awarded the French Research Bonus (PEDR).

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Fri, 10 Jul 2020 01:43:00 +0200
<![CDATA[Séminaire LIMOS - 16 avril 2020 - Self-stabilization and Highly Dynamic Networks]]> https://webtv.u-clermont1.fr/media-MEDIA200710134226421

Presenter : Anais DURAND - MC LIMOS, Université Clermont Auvergne

Abstract : Mobile networks, robot fleets, swarms of drones are example of highly dynamic networks, i.e., networks whose topology changes overtime. In these networks, topological changes cannot simply be considered as a perturbation but are truly inherent to the system. However, fault-tolerant distributed computing researches mainly focused on networks whose topology is static or systems where topological changes are rare and sparse.

Self-stabilizing systems are able to recover a correct behavior in finite time and without any external intervention, after some perturbations (e.g., memory corruption, message losses) put the system in an arbitrary state. Self-stabilization is a very promising solution to withstand faults in highly dynamic networks.

I will present some ongoing work aiming to explore the power of self-stabilization in highly dynamic networks (what problems can we solve? what hypotheses on the dynamic of the system are necessary?, etc.). We consider Time-Varying Graphs to model the dynamic of the network topology.

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Fri, 10 Jul 2020 01:42:00 +0200
<![CDATA[Séminaire LIMOS - 28 mai 2020 - Optimal deterministic and robust selection of electricity contracts - joint work with Michel Minoux et David Wu]]> https://webtv.u-clermont1.fr/media-MEDIA200710133903313

Presenter : Viet Hung NGUYEN - Professeur LIMOS, Université Clermont Auvergne

Abstract : In this talk, we address the problem of finding the best parameters of an electricity contract for a client based on her past records of electricity consumption over a fixed time period, typically one year.
The electricity bill is composed by some fixed cost, the cost of the subscription of the electricity contract and penalties due to overpowering of consumption. The problem can be formulated as a problem of minimizing a convex separable function with constraints featuring node-arc inciden matrix structure which can be solved in polynomial time by flow-based algorithms (Ahuja et al 2003, Karzanov et al 1997, Minoux 1984, Minoux 1986).
We propose a simple special purpose iterative algorithm  for the deterministic version of the problem which has a better time complexity than the above cited algorithms.
We also consider a robust version of the problem using the concept of budget of uncertainty introduced by (Bertsimas and Sim 2004).
We prove that the resulting worst case cost minimisation problem can be solved by using the same algorithm as for the deterministic case.

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Fri, 10 Jul 2020 01:39:00 +0200
<![CDATA[Des couleurs structurelles à l'optimisation de structures photoniques]]> https://webtv.u-clermont1.fr/media-MEDIA180927151418605

Beaucoup d’animaux présentent des couleurs éclatantes et changeantes – du paon aux mouches vertes que nous connaissons bien, en passant par les plus beaux des papillons ou les oiseaux les plus communs comme les pigeons ou les canards.

Ce sont des couleurs structurelles : elles ne font appel à aucun colorant. Il s’agit de structures photoniques - des géométries complexes, incroyablement élégantes qui agissent directement sur la lumière.

En s’inspirant de la façon dont ces structures sont apparues dans la nature, on peut amener un ordinateur à les retrouver – et à conclure que ce sont les meilleures. Et on peut alors essayer de répondre à une question bizarre : qu’aurait fait la nature, si elle avait eu à faire des panneaux photovoltaïques ?

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Wed, 26 Sep 2018 03:14:00 +0200
<![CDATA[La muographie ou comment ausculter les volcans et les pyramides avec des particules]]> https://webtv.u-clermont1.fr/media-MEDIA180615091810897

Depuis la radiographie de la main de Mme Roentgen à la fin du 19ème siècle, l’imagerie a envahi nos vies. Les radiations utilisées sont de plus en plus nombreuses et les techniques plus précises.
Une des radiations naturellement présentes dans l’atmosphère, les muons atmosphériques, est particulièrement adaptée pour l’étude des grandes structures. La muographie (c’est-à-dire l’imagerie à l’aide des muons atmosphériques) fut déjà utilisée avec succès pour sonder les pyramides. Peut-elle être utile également en volcanologie ? Que peut elle nous apporter de plus par rapport aux autres méthodes traditionnellement utilisées en volcanologie pour l’étude de structure des volcans ?
Nous allons aussi voir comment, en plus d’être très utiles à la société, les muons ont su garder tout leur charme et mystère pour les physiciens des particules …

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Wed, 13 Jun 2018 09:18:00 +0200