Nanoplasmonics has opened up the gates for numerous innovations. Recent studies showed that metal nanoparticles, when introduced into the solar cells and organic light emitting diodes, would greatly enhance their efficiencies. Though these advances are promising, they require a tool for investigating the interactions occuring at the microscopic level to further optimize their performance. In that context, we are interested in understanding the energy transfer mechanism between molecules in the vicinity of metal nanoparticle. Time-resolved fluorescence intensity and anisotropy experiments on single and clusters of Silver-Silica core-shell nanoparticles coated with Rhodamine B(RB) dye molecules, (Ag-SiO2-RB) were performed. We witnessed the signature of the interaction between RB molecules and metal nanoclusters in the form of the enhanced fluorescence intensity decay rates. The fluorescence lifetime of RB in the vicinity of the nanoparticles was (600 +/- 100) ps, as compared to (2.4+/-0.3)ns in the absence of nanoparticle. While the anisotropy of RB molecules in the absence of nanoparticle has remained almost constant(0.075+/-0.029) over long times; anisotropy in the presence of particles showed wide range of values immediately after excitation. Surprisingly high anisotropy values, at about 10 ns after excitation, were observed with a mean of about (0.145+/-0.025). We interpret the high and low initial anisotropies of the clusters, relative to the case of RB alone, to be due to the interaction of dye molecules with collective plasmon modes of the clusters. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2011-06-30 23:29:38.658

No description available.

Recent research demonstrated that polymer based nanocomposites (PNCs) have been engineered in order to improve the arc interruption capability of the circuit breakers. PNCs are the combination of nano-sized inorganic nanoparticles (NPs) and polymers, opened up new developments in materials science and engineering applications. Inorganic NPs are selected based on their physical and chemical properties which could make multifunctional PNCs in order to interrupt the electrical arcs effectively. In particular, we presented the PNCs fabricated by using CuO, Fe3O4, ZnO and Au NPs in a poly (methyl methacrylate) (PMMA) matrix via in-situ polymerization method, recently developed method to avoid NPs agglomeration, leading to good spatial distribution in the polymer matrix. Thus, several samples with various wt% of NPs in PMMA matrix have been fabricated. These PNCs have been characterized in detail for the morphology of NPs, interaction between NPs and polymer matrix, and radiative/thermal energy absorption properties. In the next stage, PNCs are tested to determine their arc interruption performance and impact on the electrical arcs of current 1.6 kA generated using a specially designed test set-up. When PNCs interact with the electrical arcs, they generate ablation of chemical species towards core of the electrical arc, resulting in cooling-down the arc due to strong temperature and pressure gradient in the arc quenching domain. This thesis demonstrates for the first time that these engineered PNCs are easily processed, reproducible, and can be used to improve the arc interruption process in electrical switching applications. / Ny forskning har visat att polymerbaserade nanokompositer (PNCs) har utformats för att förbättra strömbrytares förmåga att undvika ljusbågar vid överslag. PNCs är en kombination av nanostora oorganiska nanopartiklar (NP) och polymerer, som har öppnat upp för ny utveckling inom materialvetenskap och tekniska tillämpningar. Oorganiska NP väljs baserat på deras fysikaliska och kemiska egenskaper som kan hjälpa PNCs att motverka elektriska ljusbågar effektivt. I synnerhet, presenterade vi PNCs tillverkade genom användning av CuO, Fe3O4, ZnO och Au NP i en poly (metylmetakrylat) (PMMA)-matris via in situ-polymerisationsmetod, nyligen utvecklad för att undvika NP-agglomerering, vilket leder till god rumslig fördelning i polymermatrisen. Därför har flera prover med olika vikt% av NP i PMMA-matris tillverkats. Dessa PNCs har utvärderats i detalj för NP-morfologi, interaktion mellan NP och polymermatris, och strålnings- och värmeenergiabsorption. I nästa skede testas PNCs för att bestämma deras förmåga att undvika ljusbågar och påverkan på de elektriska ljusbågarna av 1,6 kA strömstyrka, genererade med hjälp av en specialdesignad test-set-up. När PNCs interagerar med de elektriska ljusbågarna, genererar de ablation av kemiska ämnen mot kärnan i den elektriska ljusbågen, vilket resulterar i nedkylning av ljusbågen på grund av starka temperatur- och tryckgradienter i området. Denna avhandling visar för första gången att dessa konstruerade PNCs är lätta att framställa, reproducerbara, och kan användas för att förbättra avbrottsprocessen för ljusbågen i elektriska kopplingstillämpningar. / <p>QC 20170303</p>

La modélisation de la propagation des feux de forêt est une matière complexe pouvant être abordée de différentes manières (approche physique, semi-physique, empirique). Nombre de simulateurs existent avec chacun leurs particularités, leurs avantages et leurs points faibles. Les travaux qui ont conduits à la rédaction de cette thèse visent à l’amélioration du modèle physique simplifié de propagation de Balbi et al, 2007 ainsi qu’à la pose des premières pierres visant à le faire évoluer vers un modèle de comportement du feu. Ils se sont articulés autour de 3 grands axes :• La modélisation de la propagation d’un feu de surface avec pour principal moteur le transfert de chaleur radiatif. Cette modélisation à conduit à réaliser des améliorations concernant la formulation de la vitesse à plat sans vent. Elle a enfin conduit à caractériser de deux critères d’extinction portant sur des valeurs critique de deux paramètres du combustible (l’indice de surface foliaire et de la teneur en eau du combustible).• La quantification de l’énergie rayonnée par le front de flamme. Cette quantification, a été réalisée en prenant pour hypothèse le modèle de flamme solide. Cette approche a conduit à l’obtention d’une relation analytique permettant l’évaluation des Distances de Sécurité Admissibles (DSA) dans un temps très restreint.• L’étude de sensibilité des différents résultats obtenus afin de valider l’ensemble de ceux-ci et identifier l’influence relative des différents paramètres / Modeling the spread of forest fires is a complex affair which can be examined in different ways (physical, semi-physical, empirical). Numerous simulators exist, each one bearing its own particularities, benefits and weak points. The work which has led to the writing of this thesis aims at improving the simplified physical model of fire propagation (Balbi et al, 2007), as well as at laying down the first foundation stones of what will favor an evolution towards a fire behavioral pattern. This study is based upon three main themes :• Modeling the spread of a surface fire with the main engine the radiative heat transfer. This modeling leads to achieve improvements in the formulation of its speed on flat ground, without wind. It finally led to the characterization of two criteria of extinction with characterization of critical values of two parameters (leaf area index and the water content of the fuel).• Quantification of the energy radiating from the flame front. This quantification was performed assuming the solid flame model. This approach has led to obtaining an analytical relationship for the evaluation of Admissible Safety Distance (ASD) in a very short time. • Sensitivity analysis of the different results attained in order to confirm them as a whole and identify the relative influence of various parameters.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The SNABP [40SiO2.30Na2CO3.1Al2O3.25B2O3.PbO2 (mol%)] glass system, nanostructured with PbS Quantum Dots (QDs) and/or doped with Er3+ ions, was successfully synthesized by the Fusion Method, when it was subjected to appropriate thermal annealing. The glass transition temperatures (Tg) were obtained by Differential Thermal Analyze (DTA), in which it was possible to define a suitable temperature to be used in the thermal annealing of the synthesized samples. As results of these thermal annealing, the formation and growth of PbS QDs have occurred in the glass environment. The optical properties of samples were investigated by Optical Absorption (OA), Photoluminescence (PL), and Photoluminescence with Temporal Resolution (PLTR). Moreover, the Atomic Force Microscopy (AFM) and X-Ray Diffractometry were employed in study of morphological and structural properties of samples, respectively. The size dispersions of PbS QDs were determined from OA spectra. Once using both the Method and OA data, it was also possible to estimate the average diameters of these nanoparticles, which grow with the increase in annealing time. The characteristic transitions of Er3+ ions were clearly identified in OA spectra. In addition, it was observed that the increase in annealing time of samples had provoked amplification in the overlapping between PL bands of both the PbS QDs and Er3+ ions, as well as with the absorption 4I15/2 -> 4I13/2 of these ions. Thus, the PLTR measurements have confirmed the decrease in lifetime of the 4I13/2 level (of Er3+ ions), with the amplification in the overlapping of PL emissions. Finally, as a main result of this work, it was proved that the SNABP glass system, nanostructured with PbS QDs and doped with Er3+ ions, displays to be quite favorable to the radiative energy transfer process (from PbS QDs to Er3+ ions), as well as the occurrence of stimulated emission of 4I13/2 level. / O sistema vítreo SNABP [40SiO2.30Na2CO3.1Al2O3.25B2O3.PbO2 (mol%)] nanoestruturado com pontos quânticos (PQs) de PbS e/ou dopados com íons Er3+ foi sintetizado com sucesso pelo Método de Fusão, quando submetido a tratamentos térmicos apropriados. As temperaturas de transição vítrea (Tg) foram obtidas por Análise Térmica Diferencial (DTA), em que foi possível definir uma temperatura adequada para ser utilizada nos tratamentos térmicos das amostras sintetizadas. Como resultados desses tratamentos térmicos, a formação e crescimento dos PQs de PbS ocorreram no ambiente vítreo. As propriedades ópticas das amostras foram investigadas por Absorção Óptica (AO), Fotoluminescência (PL) e Fotoluminescência com Resolução Temporal (PLRT). Além disso, a Microscopia de Força Atômica (AFM) e Difratometria de Raios-X (DRX) foram empregadas no estudo das propriedades morfológicas e estruturais das amostras, respectivamente. As dispersões de tamanho dos PQs de PbS foram determinadas a partir dos espectros de AO. Com a utilização do Método e os dados de AO, foi também possível estimar os diâmetros médios dessas nanopartículas, que aumentaram com o aumento no tempo de tratamento térmico. As transições características dos íons Er3+ foram claramente identificadas nos espectros de AO. Em adição, foi observado que o aumento no tempo de tratamento das amostras provocou um aumento na sobreposição entre as bandas de PL dos PQs de PbS e dos íons Er3+, bem como com a absorção 4I15/2 -> 4I13/2 desses íons. Assim, as medidas de PLRT confirmaram o decréscimo no tempo de vida do nível 4I13/2 (dos íons Er3+) com o aumento dessa sobreposição das emissões de PL. Finalmente, como principal resultado deste trabalho, foi comprovado que o sistema vítreo SNABP nanoestruturado com PQs de PbS dopados com íons Er3+ mostrou-se bastante favorável ao processo de transferência de energia radiativa (dos PQs de PbS para os íons Er3+), bem como a ocorrência da emissão estimulada do nível 4I13/2. / Mestre em Física