Th. doct.-ing.--Nancy, I.N.P.L., 1982.

Th. doct.-ing.--Nancy, I.N.P.L., 1978.

Th. doct.-ing.--Nancy, I.N.P.L., 1978.

[No abstract available] / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The acid mine-drainage contaminated Blesbokspruit catchment west of Witbank in Mpumalanga province, South Africa has been investigated, by analysis of its waters, sediments, precipitates and algae, to obtain an understanding of the processes which control the mobility of metals in these waters. The Blesbokspruit drains acid mine drainage originating in surrounding, abandoned coal mine workings. The upper Blesbokspruit (approximately 8 km) including the stream origin, AMD outwelling points, downstream AMD retention ponds and a small wetland were selected for this study. Water, sediment, precipitate, and algae samples were collected from the Blesbokspruit. The water quality of the catchment was determined and compared to mineralogical and major and trace element analyses of sediments, precipitates, and algae. The pH and total dissolved solids of the catchment waters ranged from pH 2.6 to 7.4 and 147 to 3071 mg/ t, respectively. Associated precipitates consisted primarily of jarosite with minor amounts of goethite, lepidocrocite, ferrihydrite and gypsum, with ferrihydrite being the major component of only one precipitate sample. The presence of algae at one of the sampling sites appeared to act as a template for the precipitation of ferrihydrite in a low pH and high acidity environment. Speciation modelling of the Blesbokspruit waters indicated waters saturated with respect to jarosite, goethite, and quartz, in equilibrium with jurbanite, alunite and gypsum, and undersaturated with respect to ferrihydrite and kaolinite. The mobility of iron in the sulphate rich Blesbokspruit waters appeared to be controlled by pyrite oxidation and the solubility of the basic iron sulphate mineral jarosite. In contrast Al mobility appeared to be influenced by different mechanisms. Acidity of the Blesbokspruit waters correlated well (r = 0.942) with Al concentrations in the waters. Dissolved Al correlated with dissolved silica (r = 0.757) in the Blesbokspruit waters and exchangeable acidity correlated with exchangeable Al (r = 0.761) in the associated sediments. The data suggested that Al behaved conservatively in the pH < 4 Blesbokspruit waters and that Al solubility is controlled by dissolution of clay minerals and adsorption to organic matter in the sediments. Although precipitates contain trace elements, precipitation does not have a major effect on the concentration of trace elements in the associated low pH waters. Trace elements were, however, accumulated in the sediments of the Blesbokspruit streambed and the wetland. The wetland acts as a sink for dissolved Na, Ca, Mg, Fe, Mn, Zn, Ni, Pb U, Cu and Co. The mobility of these elements appeared to be controlled by the dissolution of minerals containing these elements and adsorption to organic matter in the wetland and streambed sediments. Not all metals were, however, completely immobilised, and toxic concentrations of Pb (1.3 mg/ t) and elevated concentrations of Al (40 mg/ t ), Fe (1.6 mg/t) and Mn (6.5 mg/t) remained in the water downstream of the wetland.

With the end of the Cold War, NATO countries have embarked on transformation initiatives within their militaries to address the new security realities of the 21st century. One of the realities that has not changed is the threat posed to modern navies by sea mines. Global proliferation of sea mines, both older variants and advanced designs, has continued to grow and presents a unique challenge to maritime security for NATO. As NATO forces engage in more expeditionary operations, they must be prepared to counter the danger posed by mines from state and non-state actors. This includes ensuring that vital sea lines of communication (SLOCS), strategic chokepoints throughout the world, commercial ports and naval bases remain open and uncontested. In order to meet the challenge of the 21st century mine threat, NATO must continue to develop balanced MCM capabilities that satisfy expeditionary requirements (such as OMCM for in-stride operations) while maintaining effective dedicated forces to conduct sustained MCM operations against more traditional mining operations.

Reproduction de : Thèse : Droit : Lyon : 1926. / Titre provenant de l'écran-titre. Bibliogr. p. 5-6.

La modification de surface par plasma est une technique largement utilisée pour améliorer les propriétés de surface de polymères par le greffage de différents groupes fonctionnels. Dans ce projet de recherche, différentes méthodes pour améliorer les techniques de caractérisation de décharge micro-ondes de N2 et N2-H2 ont été étudiées dans le but d’optimiser le procédé de traitement de surface par plasma. Tout d'abord, un certain nombre de paramètres du plasma ont été mesurés à différentes conditions de traitement. Pour déterminer les paramètres du plasma, la spectroscopie d'émission optique a été utilisée dans la région l’ultraviolet, du visible et l’infrarouge (rarement utilisée dans la littérature scientifique). L’utilisation de la spectroscopie d'émission dans cette dernière région spectrale est avantageuse car elle permet d'éliminer les forts chevauchements entre les transitions atomiques et moléculaires et de pallier la faible intensité du signal observée dans la région de l’ultraviolet et du visible. Par la suite, la composition chimique de surface du PTFE a été analysée par XPS pour déterminer les concentrations en carbone, fluor, azote et des groupements amine suite à un traitement par plasma. Les résultats mentionnés ci-dessus ont été utilisés pour corréler les conditions de traitement et les paramètres de décharge micro-ondes à la composition chimique du PTFE modifié, dans l’objectif de mettre en évidence les paramètres expérimentaux du plasma et les espèces présentes dans le plasma qui jouent un rôle clé pour maximiser la fonctionnalisation de surface du polymère avec des groupements amine. En outre, un modèle mathématique a été développé en utilisant la technique de régression PLS. Pour construire ce modèle, un ensemble de données de variables d'entrée contenant les conditions de traitement et les paramètres spectroscopiques du plasma et une matrice de réponse contenant les propriétés de surface du polymère ont été générées. La base de données obtenue a été utilisée pour établir la relation entre les paramètres du plasma, les conditions de traitement et la chimie de surface du film. Cela a finalement permis de prédire la composition chimique de la surface à partir d’informations relatives au plasma, sans avoir à effectuer des analyses de surface après le traitement. / Plasma surface modification is a widely used technique for improving the surface properties ‎of ‎polymers through the introduction of different functional groups. In ‎the current research project, ‎different methods to improve the characterization techniques of ‎N2 and N2-H2 microwave discharge ‎were investigated with the aim of optimizing the ‎plasma surface process. First of all, a number of plasma parameters were measured at ‎different process conditions. To determine the plasma ‎parameters, optical emission spectroscopy was used ‎not only within the well-documented ‎UV-Visible region but also within the rarely ‎studied infrared zone. Using infrared optical emission ‎spectroscopy is advantageous as it ‎eliminates the strong overlap between atomic and molecular ‎transitions as well as the low ‎intensity UV-Visible emission spectroscopy limitations. In the next step, the PTFE surface chemical composition was analyzed via XPS to quantify the ‎concentrations of carbon, fluorine, and nitrogen after a plasma treatment in a N2-H2 gaseous ‎environment. The XPS analyses were also performed after chemical derivatization to quantify the ‎surface concentration of amino groups (%NH2) at different process conditions. The above-mentioned results were used to correlate process conditions and microwave N2-‎H2 ‎discharge‏ ‏parameters‏ ‏to the chemical composition of the modified ‎PTFE. The purpose was ‎to ‎determine the external plasma parameters and species present within the plasma ‎which ‎‎play a key ‎role in the introduction of amino groups to the polymer surface. ‎Furthermore, a mathematical model was developed using ‎the Partial Least Squares ‎Regression, ‎‎(PLSR) ‎using custom scripts written in MATLAB. A data set of ‎input variables including the process conditions ‎and plasma ‎parameters for each experiment ‎were generated along with the corresponding response ‎matrix which in turn contained the ‎surface ‎properties of the film.‎ ‎The resulting database was used to ‎build the relationship ‎between the plasma parameters, ‎process condition and the resulting film ‎surface chemistry. ‎This ultimately enabled to predict the PTFE surface chemistry from data originating ‎from the plasma, without having to proceed to post-plasma surface characterization.

No description available.

No description available.