La canalisation et la création de canaux de liaison, destinées à faciliter le développement industriel et les échanges commerciaux ont entraîné une forte pollution historique ainsi qu’une artificialisation de milieux naturels, désormais soumis aux objectifs de bon potentiel. La remise en suspension par le trafic fluvial des sédiments pose la question de son impact sur la qualité des eaux et sur l’atteinte des objectifs d’état. L’étude de la qualité chimique des sédiments et de l’eau de trois canaux du Nord de la France, la Deûle, la Sensée (naviguées) et la Scarpe (non naviguée) montre que ceux-ci présentent des concentrations variables en P et en ETM (globalement Deûle ~ Scarpe > Sensée), ces derniers restant globalement bien piégés par les sulfures dans les sédiments. Même si les concentrations en ETM dissous restent relativement faibles par rapport aux concentrations enregistrées dans les sédiments, elles peuvent parfois excéder les normes de qualité environnementales de la DCE. La labilité de ces ETM estimée par les DGT s’avère faible y compris pour Pb qui est cependant accumulé de façon importante par les gammares encagés déployés sur les trois sites. La navigation ne semble jouer qu’un rôle limité sur l’enrichissement de la colonne d’eau en métaux et en phosphore dissous, ainsi que sur l’oxygénation des eaux de surface. Le phytoplancton apparaît avoir une influence plus importante que la navigation sur l’évolution de ces milieux. Finalement, l’impact de la navigation sur la qualité chimique de l’eau reste limité en raison de la géochimie singulière du bassin Artois-Picardie. / Rivers channelization and creation of linking channels to facilitate industrial development and trade have led to a strong historical pollution and artificialization of aquatic environments that are now subjected to good potential status objectives. Sediment resuspension by navigation, its impact on water quality and the achievement of status are the main concern of this thesis. Sediment and water chemical quality of three channels of Northern France have been studied: the Deûle River, the Sensée River (both navigated) and the Scarpe River (not navigated). The rivers have varying concentrations of P and ETM (overall Deûle ~ Scarpe > Sensée), which are generally well trapped with sulfides in sediments. Although the concentrations of dissolved ETM remain relatively low compared to the levels recorded in the sediment, they can sometimes exceed the environmental quality standards of the WFD. Lability of these ETM estimated by DGT is weak, even for Pb which is however significantly accumulated by caged gammarids deployed on the three sites. The navigation seems to play a limited role in the enrichment of the water column in dissolved metals and phosphorus, as well as the oxygenation of surface waters. Phytoplankton appears to have a greater influence on the evolution of these environments. Finally, the impact of navigation on the chemical quality of the water remains limited due to the peculiar geochemistry of the Artois-Picardie basin.

This thesis is broadly concerned with online-optimizing anti-windup control. These are control structures that implement some online-optimization routines to compensate for the windup effects in constrained control systems. The first part of this thesis examines a general framework for analyzing robust preservation in anti-windup control systems. This framework - the robust Kalman conjecture - is defined for the robust Lur’e problem. This part of the thesis verifies this conjecture for first-order plants perturbed by various norm-bounded unstructured uncertainties. Integral quadratic constraint theory is exploited to classify the appropriate stability multipliers required for verification in these cases. The remaining part of the thesis focusses on accelerated gradient methods. In particular, tight complexity-certificates can be obtained for the Nesterov gradient method, which makes it attractive for implementation of online-optimizing anti-windup control. This part of the thesis presents a proposed algorithm that extends the classical Nesterov gradient method by using available secant information. Numerical results demonstrating the efficiency of the proposed algorithm are analysed with the aid of performance profiles. As the objective function becomes more ill-conditioned, the proposed algorithm becomes significantly more efficient than the classical Nesterov gradient method. The improved performance bodes well for online-optimization anti-windup control since ill-conditioning is common place in constrained control systems. In addition, this thesis explores another subcategory of accelerated gradient methods known as Barzilai-Borwein gradient methods. Here, two algorithms that modify the Barzilai-Borwein gradient method are proposed. Global convergence of the proposed algorithms for all convex functions is established by using discrete Lyapunov theorems.

While geographic distance is a variable often used to explain population genetic differentiation, dynamic processes leading to stochastic population structure are more likely driving factors. The following thesis presents the population structure of a common reef sponge, Stylissa carteri, and yields hypotheses on the influence of environmental heterogeneity as a predictor of the observed population structure. This project represents the largest population genetics study thus conducted in the Red Sea and also includes the first population genetics data gathered for sites off the coast of Sudan and Soccotra. The study herein presented includes both a large scale (36 reef sites covering over 1000km of coastline) and small-scale (16 transects of 50m each) analysis of gene flow in a benthic dwelling organism. The variable effect of geography and environmental conditions on S. carteri population structure is assessed using a seascape genetics approach. Environmental factors from a nine-year dataset accessed from the NASA Giovanni website including chlorophyll a, sea surface temperature, dissolved and particulate organic matter for both the annual and winter temporal scale were considered.

Knowledge regarding carbon dioxide (CO2)-brine interfacial tension (IFT) is important for petroleum industry and Carbon Capture and Storage (CCS) strategies. In petroleum industry, CO2-brine IFT is especially importance for CO2 – based enhanced oil recovery strategy as it affects phase behavior and fluid transport in porous media. CCS which involves storing CO2 in geological storage sites also requires understanding regarding CO2-brine IFT as this parameter affects CO2 quantity that could be securely stored in the storage site. Several methods have been used to compute CO2-brine interfacial tension. One of the methods employed is by using Density Gradient Theory (DGT) approach. In DGT model, IFT is computed based on the component density distribution across the interface. However, current model is only applicable for modelling low to medium ionic strength solution. This limitation is due to the model only considers the increase of IFT due to the changes of bulk phases properties and does not account for ion distribution at interface. In this study, a new modelling strategy to compute CO2-brine IFT based on DGT was proposed. In the proposed model, ion distribution across interface was accounted for by separating the interface to two sections. The saddle point of tangent plane distance where ( ) was defined as the boundary separating the two sections of the interface. Electrolyte is assumed to be present only in the second section which is connected to the bulk liquid phase side. Numerical simulations were performed using the proposed approach for single and mixed salt solutions for three salts (NaCl, KCl, and CaCl2), for temperature (298 K to 443 K), pressure (2 MPa to 70 MPa), and ionic strength (0.085 mol·kg-1 to 15 mol·kg-1). The simulation result shows that the tuned model was able to predict with good accuracy CO2-brine IFT for all studied cases. Comparison with current DGT model showed that the proposed approach yields better match with the experiment data. In this study, the thermodynamic properties were computed using Cubic Plus Association (CPA) equation of state, and the electrolyte contribution was accounted for by adding Debye-Huckel activity coefficient in the thermodynamic properties computation.

京都大学 / 新制・論文博士 / 博士(社会健康医学) / 乙第13422号 / 論社医博第16号 / 新制||社医||11(附属図書館) / 京都大学大学院医学研究科社会健康医学系専攻 / (主査)教授 佐藤 俊哉, 教授 藤渕 航, 教授 黒田 知宏 / 学位規則第4条第2項該当 / Doctor of Public Health / Kyoto University / DFAM

This thesis if focused to assessment of phenological characteristics of European beech (Fagus sylvatica L.) and European larch (Larix decidua Mill.). The observation was performed in two mixed forests of the same age situated at different altitudes 300 and 600 meters, respectively. Main meteorological variables were measured on both sites in order to describe the mezoclimate of the site. Observation of phenological phases was conducted in regular intervals twice a week. The results of the study confirm the strong dependence on both air and soil temperature. Collected data show the importance of temperature at the end of winter and early spring. Starting time of spring phenological phases depends on reaching of species specific temperature limits. The highest variability among individual years shows the time of beginning of budbreak. The temperature increase results in earlier beginning of spring phenological phases as well as shortening of their duration. For similar reason, also autumnal phenological phases are shifted towards the winter time. This fact causes longer vegetation period at the expense of winter dormancy.

The application of silicon nanocrystals as non-toxic bio-labels and downconverters requires their uniform size distribution in order to minimize the inhomogeneous broadening of the photoluminescence peak. In this thesis, we set the basis for their size-separation via the density-gradient centrifugation method. To be more precise, we successfully apply this technique to separate 5 and 10 nm gold nanoparticles from an ensemble by using an engineered medium layer stack. In addition, we explain how atomic force microscopy is used to measure the size of the nanoparticles, with a particular attentionon the removal of unwanted solvent-related effects. As a future plan, we will implement the technique for the size-separation of silicon nanocrystals.

The aim of the present work is to study the formation of the cubic carbide phase (gamma phase) free gradient zone and the gamma cone structure at the edges of gradient sintered cemented carbides. Four types of cemented carbides; WCTi(C,N)-Co, WC-Ti(C,N)-Ni, WC-Ti(C,N)-Fe, WC-(Ti,Ta,NB)(C,N)-Co were gradient sintered and the thicknesses of the gradients were measured. Formation of the gradients is simulated and the simulations results are compared with experimental data. For all of the one-dimensional simulations, the DICTRA [1] software is used. The two-dimensional simulations are carried out by using a new simulation tool which is called “YAPFI”. The YAPFI software is a tool for simulation of diffffusion in multiphase systems along one, two, or three spatial coordinates. Various numerical parameters have been studied by running less computationally demanding one-dimensional simulations. The optimized parameters are used to setup the two-dimensional simulations. Two different kinetic databases were used in the simulations. The effect of different so-called labyrinth factors were studied systematically. The simulation results are in close agreement with the experimental observations, although some anomalies are present in the results. Results of the two-dimensional simulations show the formation of the gamma cone at the edges of the insert.

Wind farm layout optimization can greatly improve wind farm performance. However, past wind farm design has been limited in several ways. Wind farm design usually assumes that all the turbines throughout the farm should be exactly the same. Oftentimes, the location of every turbine is optimized individually, which is computationally expensive. Furthermore, designers fail to consider turbine loads during layout optimization. This dissertation presents four studies which provide partial solutions to these limitations and greatly improve wind farm layout optimization. Two studies explore differing turbine designs in wind farms. In these studies, Wind farm layouts are optimized simultaneously with turbine design. We found that for small rotor diameters and closely spaced wind turbines, wind farms with different heights have a 5–10% reduction in cost of energy compared to farms with all the same turbine height. Coupled optimization of turbine layout and full turbine design results in an 2–5% reduction in cost of energy compared to optimizing sequentially for wind farms with turbine spacings of 8.5–11 rotor diameters. Wind farms with tighter spacing benefit even more from coupled optimization. Furthermore, we found that heterogeneous turbine design can produce up to an additional 10% cost of energy reduction compared to wind farms with identical turbines throughout the farm, especially when the wind turbines are closely spaced. The third study presents the boundary-grid parameterization method to reduce the computational expense of optimizing wind farms. This parameterization uses only five variables to define the layout of a wind farm with any number of turbines. For a 100 turbine wind farm, we show that optimizing the five variables of the boundary-grid method produces wind farms that perform just as well as farms where the location of each turbine is optimized individually, which requires 200 design variables. The presented method facilitates the study for both gradient-free and gradient-based optimization of large wind farms. The final study presents a model to calculate fatigue damage caused by partial waking on a wind turbine which is computationally efficient and can be included in wind farm layout optimization. Compared to high fidelity simulation data, the model accurately predicts the damage trends of various waking conditions. We also perform a wind farm layout optimization with the presented model in which we maximize the annual energy production of a wind farm while constraining the damage of each turbine. The results of the optimization show that the turbine damage can be constrained with only a very small sacrifice of less than 1% to the annual energy production.

Gradient-based optimisers are a natural way to solve optimisation problems, and have long been used for their efficacy in exploiting the search space. Particle swarm optimisers (PSOs), when using reasonable algorithm parameters, are considered to have good exploration characteristics. This thesis proposes a specific way of constructing hybrid gradient PSOs. Heterogeneous, hybrid gradient PSOs are constructed by allowing the gradient algorithm to optimise local best particles, while the PSO algorithm governs the behaviour of the rest of the swarm. This approach allows the distinct algorithms to concentrate on performing the separate tasks of exploration and exploitation. Two new PSOs, the Gradient Descent PSO, which combines the Gradient Descent and PSO algorithms, and the LeapFrog PSO, which combines the LeapFrog and PSO algorithms, are introduced. The GDPSO represents arguably the simplest hybrid gradient PSO possible, while the LeapFrog PSO incorporates the more sophisticated LFOP1(b) algorithm, exhibiting a heuristic algorithm design and dynamic time step adjustment mechanism. The strong tendency of these hybrids to prematurely converge is examined, and it is shown that by modifying algorithm parameters and delaying the introduction of gradient information, it is possible to retain strong exploration capabilities of the original PSO algorithm while also benefiting from the exploitation of the gradient algorithms. / Dissertation (MSc)--University of Pretoria, 2010. / Computer Science / unrestricted