Estudamos o fenômeno de correlação entre dois bosons idênticos (efeito Hanbury Brown-Twiss) no caso de fontes em rápida expansão. Partimos da hipótese que, em colisões hadrônicas a altas energias, forma-se um plasma de quarks e gluons, o qual se expande de acordo com as equações do Modelo Hidrodinâmico de Landau. Ao atingir a temperatura crítica, o fluido sofre uma transição de fase de plasma para hadrons usuais, os quais são então emitidos. Estudamos a dependência da função de correlação de duas partículas em algumas grandezas, como por exemplo, no momento transversal médio das partículas finais e na massa do estado de plasma inicialmente formado. Analisamos também a compatibilidade dos cálculos efetuados com alguns dados experimentais disponíveis. Mostramos que a consideração de expansão da fonte emissora introduz efeitos cinemáticos importantes no comportamento da função de correlação. Assim sendo, os resultados usualmente obtidos com a hipótese de fontes estáticas devem ser completamente modificados no caso de fontes que se expandem rapidamente, como aquelas formadas em colisões hadrônicas a altas energias. / The phenomenon of correlation among two identical bosons (Hanbury Brown-Twiss effect) is studied for rapidly expanding sources. We consider the hypothesis of a quark-gluon plasma formation in high energy hadronic collisions, which expands according to Landau\'s Hydrodynamical Model. When the fluid reaches the critical temperature it undergoes a phase transition from plasma to ordinary hadrons t which are then emitted. We study the dependence of the two-particle correlation function on some quantities, such as the average transverse momentum of final particles and the mass of the initially formed plasma. Vile also analyse the compatibility of our resulte with some available experimental data. We show that the source expansion causes important kinematical effects Oh the behavior of the correlation function. Being so, the results usually obtained by means of static sources, should be completely changed in case of rapidly expanding ones, such as the sources formed in high energy hadronic collisions.

The discovery of carbon nanotubes by Iijima in 1991 has created a torrent of new research activities. Research on carbon nanotubes ranges from studying their fundamental properties, such as their electron band structure and plasma frequencies, to developing new applications, such as self-assembled nano-circuits and field emission displays. Robust models are now needed to enable a better understanding of the electronic response of carbon nanotubes. We use time-dependent density functional theory to derive a two-fluid two-dimensional (2D) hydrodynamic model describing the collective response of a multiwalled carbon nanotube with dielectric media embedded inside or surrounding the nanotube. We study plasmon hybridization of the nanotube system in the UV range, the stopping force for ion channelling, the dynamical image potential for fast ions, channelled diclusters and point dipoles, and the energy loss for ions with oblique trajectories. Comparisons are made of results obtained from the 2D hydrodynamic model with those obtained from an extension of the 3D Kitagawa model to cylindrical geometries.

The demand of electric power has rapidly increased in China along with the financial development. High pollution rates have pushed the development towards more renewable energy generating alternatives. In recent years larger investments of hydropower- generated electricity have been to satisfy the increased demand. Hydropower can cause non-energy related problems when implemented in a large scale. In this project the Nanjing Reach of Yangtze River was investigated through a hydrodynamic and sediment transport perspective. Nanjing Reach consists of two river branches and the upstream construction of the Three Gorges Dam has caused an imbalance of sediment composition that leads to an increasing difference of the diversion ratio between the branches. This is causing a problematic navigational situation for larger vessels along the north branch. In this project non-submerged water diverting dykes were modelled using two-dimensional depth averaged finite element method to estimate the impact on the hydrodynamic and sediment transport conditions. The examination showed that engineering measures at the downstream part of the reach were more effective than structures at the front, when taking both hydrodynamic and the more long-term impacts from sediment transport into account. Although the results of the sediment transportation are uncertain, the long- term consequences with investigated engineering measures can be concluded to have negative impact on the sustainability of the reach, however short-term improvements can be achieved. Other factors such as stability, material use, economics and marine conditions were not treated in this project but are vital for a reliable solution.

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Estudamos o fenômeno de correlação entre dois bosons idênticos (efeito Hanbury Brown-Twiss) no caso de fontes em rápida expansão. Partimos da hipótese que, em colisões hadrônicas a altas energias, forma-se um plasma de quarks e gluons, o qual se expande de acordo com as equações do Modelo Hidrodinâmico de Landau. Ao atingir a temperatura crítica, o fluido sofre uma transição de fase de plasma para hadrons usuais, os quais são então emitidos. Estudamos a dependência da função de correlação de duas partículas em algumas grandezas, como por exemplo, no momento transversal médio das partículas finais e na massa do estado de plasma inicialmente formado. Analisamos também a compatibilidade dos cálculos efetuados com alguns dados experimentais disponíveis. Mostramos que a consideração de expansão da fonte emissora introduz efeitos cinemáticos importantes no comportamento da função de correlação. Assim sendo, os resultados usualmente obtidos com a hipótese de fontes estáticas devem ser completamente modificados no caso de fontes que se expandem rapidamente, como aquelas formadas em colisões hadrônicas a altas energias. / The phenomenon of correlation among two identical bosons (Hanbury Brown-Twiss effect) is studied for rapidly expanding sources. We consider the hypothesis of a quark-gluon plasma formation in high energy hadronic collisions, which expands according to Landau\'s Hydrodynamical Model. When the fluid reaches the critical temperature it undergoes a phase transition from plasma to ordinary hadrons t which are then emitted. We study the dependence of the two-particle correlation function on some quantities, such as the average transverse momentum of final particles and the mass of the initially formed plasma. Vile also analyse the compatibility of our resulte with some available experimental data. We show that the source expansion causes important kinematical effects Oh the behavior of the correlation function. Being so, the results usually obtained by means of static sources, should be completely changed in case of rapidly expanding ones, such as the sources formed in high energy hadronic collisions.

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L'objectif de cette thèse est d'étudier l'oscillation collective dans un matériau semi-conducteur (InGaAs) dans le but d'élargir les connaissances théoriques et de proposer de nouvelles configurations et des structures pour la conception de détecteurs ou émetteurs THz innovants et efficaces. Pour ce faire, nous développons un modèle théorique permettant l'étude de l'oscillation collective soumis ou non à une excitation externe (battement optique ou rayonnements THz). Une attention particulière est faite pour prendre en compte des phénomènes physiques importants tels que la mobilité différentielle dynamique négative et les oscillations de Gunn.Cette étude est faite à travers le développement d'un outil de simulation numérique basé sur l'approche HD couplé à un solveur de Poisson unidimensionnel. Le modèle HD décrit le temps de vol et le mécanisme de diffusion par l'énergie et la vitesse de relaxation. En outre, on prend en compte les frottements et leur évolution, la variation de l'énergie, la vitesse, et la masse effective. Par conséquent, le modèle HD permet l'observation des régimes transitoires ainsi que d'effectuer des études de fréquence. L'influence des différents paramètres physiques et technologiques sur les oscillations et résonances collectives des électrons sont évalués. Ensuite, le régime de petits signaux est étudié et la réponse de la diode aux perturbations optiques et électriques harmoniques et non harmoniques est évaluée. L'influence du fort biais appliqué à la diode sur les processus d'émission et de détection est ensuite décrit. / The purpose of this thesis is to obtain theoretical results in order to propose new configurations and structures for the conception of innovant and efficient THz detectors or emitters. For this sake, we develop a theoretical model allowing the study of collective oscillation in a semiconductor materials (we choose InGaAs), submitted or not to an external excitation (that is to optical beating or THz radiations). A particular attention is payed also to important physical phenomena such as negative dynamic differential mobility and Gunn oscillations.This study is made through the development of numerical simulation tool, which is based on the HD approach coupled to a one-dimensional Poisson solver. The HD model describes the free-flight and scattering mechanism through energy and velocity relaxation rates. Also it takes into account frictions and their evolution, the variation of energy, velocity and effective mass. Hence, the HD model allows us observing the transient regimes and performing frequency studies. The influence of the different physical and technological parameters on the electron collective oscillations and resonances are evaluated. Then, small-signal regime is studied and the diode response to harmonic and non-harmonic optical and electrical perturbations is evaluated. The influence of the high bias applied to the diode on emission and detection processes is then described.

The tidal current energy resource is challenging to assess with accuracy and precision. An accepted standard methodology is lacking, which in turn perpetuates uncertainty and hinders the industry’s development. Technical Committee 114 of the International Electro-technical Commission (IEC-TC-114) is working to develop a standard for emerging tidal energy conversion systems. The draft standard prescribes methods for determining, objectively and reliably, the scale and character of tidal current energy resources at a site. The IEC-TC-114 draft standard for tidal energy resource assessment and characterisation has not yet been tested in a real world case study. Hence, it is not yet known whether the proposed methods will yield the desired outcome. This research has adopted the Fundy Ocean Research Center for Energy (FORCE) project in Minas Passage, Nova Scotia, for pilot application of the draft standard on tidal current resource assessment. The Bay of Fundy, located on the Atlantic coast of North America between the Canadian provinces of New Brunswick and Nova Scotia, is known for having the highest tidal range in the world and has long been recognised as an ideal stage for tidal energy development. The thesis is presented in three main parts. Firstly, the latest peer-reviewed scientific literature is summarised and the standard is reviewed in view of lessons learned. The aim of this exercise is to establish a scientific basis for and to develop suggestions towards improving and extending future revisions of the standard. Secondly, a comprehensive assessment of the tidal current energy resource at the FORCE project site is conducted in a manner that is consistent with IEC-TC-114 protocol based on available measurements from static current profiler surveys and a two-dimensional hydrodynamic model of the upper Bay of Fundy developed for this study. Thirdly, a sensitivity analysis is performed to determine the main sources of error and uncertainty affecting resource assessment, a topic which has yet to be addressed in the literature.

In the development of the watershed, hydrodynamic, and water quality models for St. Louis Bay in Mississippi, the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS 2.0) - Nonpoint Source Model (NPSM) was selected as the watershed model and the Environmental Fluid Dynamics Code (EFDC) which includes hydrodynamic and water quality models was selected as the Bay model. Watershed model calibration was initially accomplished utilizing historical data collected by the U.S. Geological Survey (USGS), U.S. Environmental Protection Agency (USEPA), Mississippi Department of Environmental Quality (MDEQ), and Gulf Coast Research Laboratory (GCRL). The watershed model simulated nonpoint source flow and pollutant loadings for all sub-watersheds, routed flow and water quality, and accounted for all major point source discharges in the St Louis Bay watershed. The model was executed for the period of time spanning from 1965 through 1999 in order to quantify flow and pollutant loadings under a variety of hydrologic conditions. Time varying output from the watershed model was applied directly to the St. Louis Bay model. The Bay model, in turn, simulated hydrodynamics and water quality, including water depth, velocities, salinity, temperature, and fecal coliforms. Final Bay model calibration was performed utilizing a set of site specific data acquired on St. Louis Bay during the period July 14-18, 1998. Model verification was conducted against another set of field data taken in the Bay, during April 18-27, 1999. Fecal coliform was modeled in each of the 750 segments of a three-dimensional system. Comparisons of the predicted and observed data are made qualitatively by using spatial and temporal comparisons. The response of model prediction calculations is consistent with trends of the observed data ranges. The applicability of the mathematical models is also demonstrated for the development of Total Maximum Daily Load (TMDL) for fecal coliform in the St. Louis Bay. The calibrated/verified model will be used as a planning tool to assess the water quality in the Watershed and the Bay as well as for calculating TMDL and Waste Load Allocation (WLA).

No description available.