Ces dernières années, nombreux travaux dont l’objectif est de conduire à l’interopérabilité ferroviaire ont permis l’émergence d’un système paneuropéen de contrôle-commande ferroviaire. Ce système exploite des radiocommunications sol-trains fonctionnant selon le protocole GSM-R (Global System for Mobile communications – Railways. La bonne marche de l’exploitation ferroviaire dépend, pour une part, du bon acheminement des données entre sol et trains. Il s’avère donc nécessaire d’assurer un fonctionnement efficace de cette radio sol-trains en dépit de perturbations électromagnétiques intentionnelles ou non intentionnelles qui pourraient la perturber. Ce travail de thèse s’intéresse à cette seconde catégorie de perturbations. Nous développons des méthodes de détection de brouilleurs électromagnétiques afin de mettre en oeuvre rapidement des contre-mesures efficaces contre ces brouillages, à différents niveaux de l’architecture radio. Nous mettons en oeuvre un système de détection supervisé permettant de détecter la présence de signaux de brouillage intentionnels, voire de les reconnaître. Fondé sur l’analyse des signaux échangés, nous développons et évaluons deux méthodes distinctes. L’une exploite les signaux en quadrature mis en évidence par le récepteur dans le canal de communication employé. L’autre méthode considère la densité spectrale de puissance des signaux recueillis dans une bande de fréquence plus large, centrée dans la gamme allouée aux communications GSM-R, et s’étendant de part et d’autre de celle-ci. Ces méthodes sont successivement évaluées par simulation, sur des données issues d’un banc de mesure puis, sur un site ferroviaire réel. / In recent years, numerous studies whose ultimate goal is to drive the railway interoperability have allowed the emergence of a pan-European train control system. This system uses ground-to-train radio operating on the GSM-R (Global System for Mobile communications - Railways) protocol, currently being deployed on a large scale along railway lines. The smooth running of railway operations depends, in part, of the proper routing of radio communications between trains and ground. Therefore, it is necessary to ensure the effective operation of this ground to train link in presence of intentional or unintentional electromagnetic interference that could disrupt communication. This thesis focuses on this second category of disturbances. We develop methods for detecting electromagnetic interference superimposing their signals to GSM-R signals. Then, this detection will promptly set off effective countermeasures against such interference at different levels of the radio architecture, the physical layer, the higher protocol layers. We implement a supervised detection system to detect the presence of jamming signals and, for potentially to recognize them. Based on the analysis of signals exchanged, we develop and evaluate two methods. One considers the quadrature signals recovered by the receiver in the used communication channel. The second method exploits the power spectral density of the signals collected in a wider frequency band, centered in the range allocated to the GSM-R communications and extending on either side thereof. These methods are successively evaluated by simulation, on data obtained using a test bench, and on a real railway site.

Galveston Bay is the second largest estuary in the Gulf of Mexico. The bay’s watershed and shoreline contains one of the largest concentrations of petroleum and chemical industries in the world, with the greatest concentration within the lower 15 km of the San Jacinto River/Houston Ship Channel (SJR/HSC). Extensive groundwater has been withdrawn to support these industries and an expanding population has resulted elevated land subsidence, with the highest land subsidence in the lower SJR/HSC, of over 3 m (3 cm yr^-1) and has decreased seaward throughout the bay to 0.6 cm yr^-1 near Galveston Island. Mercury (Hg) contamination is well documented throughout the bay’s sediments. Sediment vibra-cores were collected throughout the bay systems. 210Pb and 137Cs geochronologies from these cores was used to determine sedimentation rates and correlated to Hg profiles to estimate input histories. Relative Sea Level Rise (RSLR) is the sum of eustatic sea level rise and land subsidence. The results show sedimentation rates are high in areas with high rates of RSLR and the rates are of the same order of magnitude, however, in general, sedimentation rates are as much as 50% of RSLR, indicating that sedimentation has not kept pace with land subsidence, although they have the same relative order. Hg core profiles were correlated with radioisotope geochronologies and show significant input of Hg beginning around 1940, with a peak around 1971, and a dramatic drop off in concentration afterwards, demonstrating it to be a valuable geochronology tool. Hg concentrations were found to be dramatically higher proximal to the SJR/HSC and progressively decreasing seaward and to distal parts of the bay.

This paper uses a quantitative content analysis informed by a critical realist framework to study the patterns of international political economy discourse prevalence within research articles concerning free trade. Once categorized, there are observable differences in the extent to which articles in the different categories address other discourses. Analyzing these patterns using concepts from discourse theory, we suggest that the liberal discourse constitutes a regime of truth to which the other discourses must relate. It is also found that articles published in higher ranking journals are less likely to address other discourses. We argue that this could be explained as being an effect of the larger readership of those journals.