Ce mémoire d'habilitation à diriger des recherches résume les différents travaux menés entre 2000 et 2013 au sein du laboratoire SIC, à l'Université de Poitiers. Le coeur de ces activités est la caractérisation, le calcul, la représentation et l'utilisation de la visibilité entre des ensembles convexes de points de l'espace géométrique en dimension $n\ge2$. Nous avons notamment utilisé l'algèbre de Grassmann pour construire un espace de droites, dans lequel le problème de la visibilité peut être discuté. Nous avons proposé deux méthodes de calculs, l'un explicite et complet, et l'autre reposant sur une évaluation paresseuse. Différentes applications en synthèse d'images reposent sur ces travaux. D'autres travaux autour de la visibilité, en synthèse d'images mais aussi dans le domaine de la propagation des ondes, sont présentés dans ce mémoire. L'ensemble a été réalisé à travers l'encadrement de 5 doctorants.

Limited asset visibility is a key problem in the management of returnable transport items (RTIs) like reusable containers, pallets and kegs. One tool to increase asset visibility is radio frequency identification (RFID) technology. However, RFID requires high investment cost and intensive efforts for implementation. In this study, we investigate the added value of using RFID technology for the management of the RTI pool in a closed-loop supply chain setting considering both costs and benefits. We have conducted a case study in a company which has recently started an RFID application in its closed-loop supply chain of RTIs. The aim of this case study is to identify and understand how an existing RTI pool is managed and the impact of using RFID technology on the management of such an RTI pool. In order to quantify the added value of RFID technology in RTI pool management, we search for the minimum cost solutions both without and with the use of RFID technology in a problem environment similar to that of our case study using the simulation optimization method. We also analyze the impact of using RFID technology on RTI pool management in terms of several performance measures, including RTI pool size, RTI lifetime, RTI trippage and the cycle time for RTIs to complete one trip in the closed-loop supply chain. In our study, we develop a number of discrete event simulation models of the identified closed-loop supply chain of RTIs operating with our predetermined decision rules for the RTI pool management using the simulation software Arena. We then develop our simulation optimization model in OptQuest for Arena in which the discrete event simulation models are embedded. The results from the simulation optimization method show that the added value of using RFID technology is mostly positive and it depends on the severity of the problematic issues in the closed-loop supply chain, as well as on the extent of improvements that RFID brings about.

The electrodeless plasma discharge is typically driven by radio frequency (RF) power supply within the range (0.2 &iexcl / 40 MHz). The applied power is coupled into the plasma inductively called inductively coupled plasma (ICP). RF ICP technique has achieved significance importance in a diversity of research and industrial applications for over the last threes decades. It is still required to undertake both theoretical and experimental research. In this work, RF ICP technique is applied on the torch modeling in 2D. Based on extended electromagnetic vector potential representation, an axisymmetric model in 2D is proposed for the calculations of the electromagnetic fields in an RF ICP torch. The influence of axial vector potential is included to the vector potential formulations. This is achieved by imposing a helical current carrying wire configuration. The corresponding governing equations are solved numerically by applying finite element method (FEM) using commercial partial differential equation solver (Flex PDE3). Based on this model, the plasma behavior and properties are examined in terms of plasma parameters. Besides, a comparative iii analysis is made between proposed model called helical configuration and the one currently available in the literature called circular configuration. This study shows relatively little difference between temperature fields predicted by two models. However, significant difference is observed between corresponding flows and electromagnetic fields. Especially, tangential flow which is observed in helical configuration vanishes in circular configuration. The proposed model offers an effective means of accounting for the variations of the helical coil geometry on the flow and temperature fields and achieving a better representation of the electromagnetic fields in the discharge. Finally, it is concluded that minimum number of turns (n = 2) yields significant difference between two models whereas, maximum allowable number of turns yield no distinctions on the results of two models in terms of azimuthally applied current. However, axial effect of current still exists but very small with respect to the result obtained with minimum number of turns.