L'utilisation d'un matériau granulaire au sein de structures industrielles afin de diminuer les niveaux vibratoires est une solution alternative aux revêtements viscoélastiques, qui ont une dépendance forte aux conditions de température. Pour l'industrie navale et aéronautique l'enjeu est ainsi d'améliorer la fiabilité et le confort. Les niveaux d'interaction entre les grains dépendent des paramètres de contrôle (niveaud'accélération), mais aussi des caractéristiques des matériaux constitutifs des grains, du taux d'humidité dufluide environnant, de la géométrie et des dimensions des grains, ainsi que des conditions de confinement.Pour une accélération donnée, indépendante du point de la structure, la pertinence du choix d'unmatériau granulaire par rapport à une même masse indéformable est mise en évidence par l'étude de lavibration d'une cavité rigide montée sur un oscillateur partiellement remplie. La variation paramétrique destypes de confinements dans la cavité ainsi que le matériau constitutif des grains permet d'extraire lesparamètres influents dans la dissipation d'énergie. Le développement d'un modèle analytique à constanteslocalisées permet de simuler l'énergie dissipée par le système via un nombre réduit de coefficients représentantla dynamique vibratoire de la matière en grains. La confrontation de ce modèle avec différentesexpérimentations permet de valider son efficacité et son caractère prédictif dans la dissipation de l'énergievibratoire d'un système dynamique.Pour une structure modale en vibration, où le niveau d'accélération est dépendant du point de lastructure, l'optimisation du positionnement des amas de grain est montrée. / The use of granular material in industrial structures to reduce vibration levels is an alternative toviscoelastic surfacing, which is highly dependent on temperature conditions. For the naval and aeronauticalindustry, the challenge is to improve reliability and comfort. The levels of interaction between the grainsdepend on the control parameters (acceleration level), but also on the characteristics of the constituentmaterials of the grains, the moisture content of the surrounding fluid, the geometry and dimensions of thegrains, as well as their containment conditions.For a given acceleration, independent of the point of structure, the relevance of the choice of a granularmaterial with respect to the same non-deformable mass is demonstrated by the study of the vibration of a rigidcavity mounted on an oscillator partially filled. The parametric variations of the types of confinement in thecavity as well as the constituent material of the grains make it possible to extract the influent parameters inthe energy dissipation. The development of an analytical model with localized constants allows to simulate theenergy dissipated by the system via a reduced number of coefficients representing the vibratory dynamics ofthe granular matter. The comparison of this model with experiments makes it possible to validate itseffectiveness and its predictive character in the dissipation of the vibratory energy of a dynamic system.For a modal structure, where the acceleration level is dependent on the point of the structure, theoptimization of the grain cluster positioning is shown.

The measurement of submicrometre (< 1.0 m) and ultrafine particles (diameter < 0.1 m) number concentration have attracted attention since the last decade because the potential health impacts associated with exposure to these particles can be more significant than those due to exposure to larger particles. At present, ultrafine particles are not regularly monitored and they are yet to be incorporated into air quality monitoring programs. As a result, very few studies have analysed their long-term and spatial variations in ultrafine particle concentration, and none have been in Australia. To address this gap in scientific knowledge, the aim of this research was to investigate the long-term trends and seasonal variations in particle number concentrations in Brisbane, Australia. Data collected over a five-year period were analysed using weighted regression models. Monthly mean concentrations in the morning (6:00-10:00) and the afternoon (16:00-19:00) were plotted against time in months, using the monthly variance as the weights. During the five-year period, submicrometre and ultrafine particle concentrations increased in the morning by 105.7% and 81.5% respectively whereas in the afternoon there was no significant trend. The morning concentrations were associated with fresh traffic emissions and the afternoon concentrations with the background. The statistical tests applied to the seasonal models, on the other hand, indicated that there was no seasonal component. The spatial variation in size distribution in a large urban area was investigated using particle number size distribution data collected at nine different locations during different campaigns. The size distributions were represented by the modal structures and cumulative size distributions. Particle number peaked at around 30 nm, except at an isolated site dominated by diesel trucks, where the particle number peaked at around 60 nm. It was found that ultrafine particles contributed to 82%-90% of the total particle number. At the sites dominated by petrol vehicles, nanoparticles (< 50 nm) contributed 60%-70% of the total particle number, and at the site dominated by diesel trucks they contributed 50%. Although the sampling campaigns took place during different seasons and were of varying duration these variations did not have an effect on the particle size distributions. The results suggested that the distributions were rather affected by differences in traffic composition and distance to the road. To investigate the occurrence of nucleation events, that is, secondary particle formation from gaseous precursors, particle size distribution data collected over a 13 month period during 5 different campaigns were analysed. The study area was a complex urban environment influenced by anthropogenic and natural sources. The study introduced a new application of time series differencing for the identification of nucleation events. To evaluate the conditions favourable to nucleation, the meteorological conditions and gaseous concentrations prior to and during nucleation events were recorded. Gaseous concentrations did not exhibit a clear pattern of change in concentration. It was also found that nucleation was associated with sea breeze and long-range transport. The implications of this finding are that whilst vehicles are the most important source of ultrafine particles, sea breeze and aged gaseous emissions play a more important role in secondary particle formation in the study area.