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International audienceThe Cell-ID positioning technique is usually implemented on cellular networks to locate mobile phones according to the cell identification code forwarded by the Base Transceiver Station (BTS). The user is then assumed to be located at the same coordinate position as the BTS. However, this simple positioning method, also used in indoor location systems with WiFi or RFID technologies, suffers from a lack of accuracy due to the size and the density of cells. In this paper we propose an indoor positioning system in underground mine tunnels based on the cell-ID method and the innovative Visible Light Communications (VLC) technology. Unlike previous technologies, it is possible to increase the position accuracy in controlling the number of light sources, i.e. the distribution of overlapping cells. As a result, self-adaptive positioning systems could be developed, where the switch on (or off) of the individual LEDs is determined according to the precision required by the application. We present an analytical model for such systems, based on Euclidean geometry equations. It is shown that the maximum position error in each cell may be fixed to obtain a positioning system with a constant accuracy. Finally, an application of this system is given to locate people or machinery in underground mine tunnels

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International audienceTypically in a scheduling problem we are given jobs of different processing times $p_j$ and different priority weights $w_j$, and need to schedule them on a single machine in order to minimize a specific cost function. In this paper we consider the non-linear objective function $\sum w_j C_j^\beta$, where $C_j$ is the completion time of job $j$ and $\beta>0$ is some arbitrary real constant. Except for $\beta=1$ the complexity status of this problem is open. Past research mainly focused on the quadratic case ($\beta=2$) and proposed different techniques to speed up exact algorithms. This paper proposes new pruning rules and generalizations of existing rules to non-integral $\beta$. An experimental study evaluates the impact of the proposed rules on the exact algorithm A*

International audienceSince a few years there is an increasing interest in minimizing the energy consumption of computing systems. However in a shared computing system, users want to optimize their experienced quality of service, at the price of a high energy consumption. In this work, we address the problem of optimizing and designing mechanisms for a linear combination of weighted completion time and energy consumption on a single machine with dynamic speed-scaling. We show that minimizing linear combination reduces to a unit speed scheduling problem under a polynomial penalty function. In the mechanism design setting, we define a cost share mechanism and study its properties, showing that it is truthful and the overcharging of total cost share is bounded by a constant

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We are given n airplanes, which can refuel one another during the flight. Each airplane has a specific tank volume and gas consumption rate. The goal of the airplane refueling problem is to find a drop out permutation for the planes that maximizes the distance traveled by the last plane to drop out. This paper studies some structural properties of the problem and proposes pruning rules for an exact resolution.

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