This thesis presents a study of the centre bifurcation and chaotic behaviour of three dimensional Lotka-Volterra systems. In two dimensional systems, Christopher (2005) considered a simple computational approach to estimate the cyclicity bifurcating from the centre. We generalized the technique to estimate the cyclicity of the centre in three dimensional systems. A lower bounds is given for the cyclicity of a hopf point in the three dimensional Lotka-Volterra systems via centre bifurcations. Sufficient conditions for the existence of a centre are obtained via the Darboux method using inverse Jacobi multiplier functions. For a given centre, the cyclicity is bounded from below by considering the linear parts of the corresponding Liapunov quantities of the perturbed system. Although the number obtained is not new, the technique is fast and can easily be adapted to other systems. The same technique is applied to estimate the cyclicity of a three dimensional system with a plane of singularities. As a result, eight limit cycles are shown to bifurcate from the centre by considering the quadratic parts of the corresponding Liapunov quantities of the perturbed system. This thesis also examines the chaotic behaviour of three dimensional Lotka-Volterra systems. For studying the chaotic behaviour, a geometric method is used. We construct an example of a three dimensional Lotka-Volterra system with a saddle-focus critical point of Shilnikov type as well as a loop. A construction of the heteroclinic cycle that joins the critical point with two other critical points of type planar saddle and axial saddle is undertaken. Furthermore, the local behaviour of trajectories in a small neighbourhood of the critical points is investigated. The dynamics of the Poincare map around the heteroclinic cycle can exhibit chaos by demonstrating the existence of a horseshoe map. The proof uses a Shilnikov-type structure adapted to the geometry of these systems. For a good understanding of the global dynamics of the system, the behaviour at infinity is also examined. This helps us to draw the global phase portrait of the system. The last part of this thesis is devoted to a study of the zero-Hopf bifurcation of the three dimensional Lotka-Volterra systems. Explicit conditions for the existence of two first integrals for the system and a line of singularity with zero eigenvalue are given. We characteristic the parameters for which a zero-Hopf equilibrium point takes place at any points on the line. We prove that there are three 3-parameter families exhibiting such equilibria. First order of averaging theory is also applied but we show that it gives no information about the possible periodic orbits bifurcating from the zero-Hopf equilibria.

Les thérapeutiques individualisées et ciblées se développent actuellement, les formes galéniques évoluent donc en parallèle pour contrôler la libération des principes actifs (PA) et les conduire au plus proche des sites d’intérêts. Les formes orales solides représentent les formulations galéniques les plus utilisées, faciles d’emploi, indolores et réduisant le risque d’infection. Lors de leur conception, il est aussi possible de moduler la libération du PA.Deux approches sont étudiées dans ce manuscrit, l’une correspond au ciblage de la libération d’un PA vers son site d’action thérapeutique qui est le colon, la seconde consiste à contrôler la libération du PA pour maintenir une concentration constante, minimiser les effets indésirables et les périodes de présence de concentrations sub-thérapeutiques au niveau du site d’action.Première approche :Les traitements des Maladies Inflammatoires Chroniques de l’Intestin (MICI) peuvent être significativement améliorées par une libération localisée du PA. Une des approches est l’utilisation d’enrobages composés de polysaccharides dégradés par les enzymes sécrétées par la microflore colique. Mais l’absence d’une méthode in vitro reproductible simulant les conditions physiologiques du colon et l’impact potentiel des traitements antibiotiques associées qui pourraient affecter la quantité et la qualité des bactéries présentes et des enzymes sécrétées est un obstacle à sa mise au point. L’objectif de l’étude était d’effectuer un screening de polysaccharides ayant un intérêt dans le développement de nouvelles formulations à libération colique. Après cette sélection, la libération des formulations retenues ont été évaluées par une méthode utilisant des selles de patients atteints de MICI traités ou non par antibiothérapie. Enfin, l’utilisation de mélanges bactériens pour un éventuel remplacement de l’utilisation de selles fraiches a été évaluée.Seconde approche : Les formes orales enrobées présentent un grand potentiel pour la libération contrôlée de PA. Néanmoins, il est difficile d’obtenir une libération à vitesse constante avec ce type de formulation. Ceci est généralement dû au rôle prédominant du transport de masse par diffusion, ce qui entraine, avec le temps, une diminution de la concentration en PA au cœur du système, donc une réduction du gradient de concentration qui est la force motrice de la libération du PA. Ce type de cinétique de libération peut être inapproprié pour un traitement médicamenteux sûr et efficace. Malgré l’importance pratique de ce défi crucial de formulation, étonnamment, peu de stratégies efficaces sont connues. Dans cette étude, une nouvelle approche, basée sur une succession de couches de PA et de polymères (initialement dépourvu de PA) présentant une distribution initiale de PA non homogène, associé à un effet de temps de latence et à une diffusion partielle initiale à travers le noyau de la minigranule. Des variations de type, de quantité, d’épaisseur et de séquence des couches de PA et de polymères ont été testées. Un système assez simple composé de quatre couches (deux couches de PA et deux couches de polymère) permettait d’aboutir à une libération relativement constante durant 8h. / Individualized and targeted therapies are currently developed, therefore the dosage forms move in parallel to control the drug release and drive it nearest to interest sites. Solid oral dosage forms are the pharmaceutical formulations the most common, easy to use, painless and reducing the infectious risk. In these formulation designs, it is also possible to adjust the drug release.Two approaches are discussed in this manuscript, the first one targets the drug release to the therapeutic site of action which is the colon, and the second one consists on controlling the drug release to maintain a constant concentration, minimize side effects and periods of presence of sub-therapeutic concentrations at the site of action.The first approach:The treatment of colonic disease like Inflammatory Bowel Diseases (IBD), can be significantly improved via local drug delivery. One approach is to use polysaccharide coatings, which are degraded by enzymes secreted by the colonic microflora. However, the lack of a reliable in vitro test simulating conditions in a living colon and the potential impact of associated antibiotic treatments that could affect the quality and quantity of bacteria and enzymes secreted is an obstacle to its development. The aim of the study was to perform a screening of polysaccharides suitable for the development of new colonic release formulations. After this selection, the drug release of selected formulations were evaluated by a method using the stools of IBD patients treated or not with antibiotics. Finally, the use of bacterial mixtures substituting fresh fecal samples has been evaluated.The second approach: Coated pellets offer a great potential for controlling drug delivery systems. However, constant drug release rates are difficult to achieve with this type of dosage forms if the drug is freely water-soluble. This is because diffusional mass transport generally plays a major role and with time the drug concentration within the system decreases, resulting in decreased concentration gradients, which are the driving forces for drug release. This type of release kinetics might be inappropriate for an efficient and safe drug treatment. Despite the great practical importance of this potentially crucial formulation challenge, surprisingly little is yet known about efficient formulations. In this study, a novel approach is presented based on sequential layers of drug and polymer (initially free of drug) to provide a non-homogeneous initial drug distribution, combined with lag-time effects and partial initial drug diffusion towards the pellet’s core. By changing the type, number, thickness and sequence of the drug and polymer layers, a rather simple 4 layers system (2 drug and 2 polymer layers) allowed an about constant drug release during 8 h.

This thesis deals with problems arising in the study of nonlinear partial differential equations arising from many-body problems. It is divided into two parts: The first part concerns the derivation of a nonlinear diffusion equation from a microscopic stochastic process. We give a new method to show that in the hydrodynamic limit, the particle densities of a one-dimensional zero range process on a periodic lattice converge to the solution of a nonlinear diffusion equation. This method allows for the first time an explicit uniform-in-time bound on the rate of convergence in the hydrodynamic limit. We also discuss how to extend this method to the multi-dimensional case. Furthermore we present an argument, which seems to be new in the context of hydrodynamic limits, how to deduce the convergence of the microscopic entropy and Fisher information towards the corresponding macroscopic quantities from the validity of the hydrodynamic limit and the initial convergence of the entropy. The second part deals with problems arising in the analysis of nonlinear Schrödinger equations of Gross-Pitaevskii type. First, we consider the Cauchy problem for (energy-subcritical) nonlinear Schrödinger equations with sub-quadratic external potentials and an additional angular momentum rotation term. This equation is a well-known model for superfluid quantum gases in rotating traps. We prove global existence (in the energy space) for defocusing nonlinearities without any restriction on the rotation frequency, generalizing earlier results given in the literature. Moreover, we find that the rotation term has a considerable influence in proving finite time blow-up in the focusing case. Finally, a mathematical framework for optimal bilinear control of nonlinear Schrödinger equations arising in the description of Bose-Einstein condensates is presented. The obtained results generalize earlier efforts found in the literature in several aspects. In particular, the cost induced by the physical work load over the control process is taken into account rather then often used L^2- or H^1-norms for the cost of the control action. We prove well-posedness of the problem and existence of an optimal control. In addition, the first order optimality system is rigorously derived. Also a numerical solution method is proposed, which is based on a Newton type iteration, and used to solve several coherent quantum control problems.

This thesis explores efficiency of monetary policy under zero lower bound condition. At first, is defined a role of monetary policy and criteria to judge the effectiveness of monetary policy are introduced. Then reactions of central banks of USA, Japan and Euro zone are explored. Thesis found out that monetary policy can be effective under a condition of zero lower bound. As last is introduced idea how to improve current monetary regime.

The UK is committed to cutting greenhouse gas emissions by 80% from 1990 levels by 2050, with intermediate targets set in the form of 5-year carbon budgets. Residential sector emissions accounted for 26% of UK greenhouse gas emissions in 2009. For the UK to meet its carbon budgets, residential sector emission reductions of 35-40% are required by 2022 from 2009 levels, with further reductions beyond. As shown here, the UK has a range of policies and initiatives to reduce carbon emissions from the residential sector; and there is a range of methods and technologies available to reduce carbon emissions from dwellings. The process of selecting the combination of methods and technologies to reduce carbon emissions from dwellings is here termed the specification of a construction strategy. Energy assessment tools (such as SAP, BREDEM and PHPP) are integral to this process. They are used to predict the energy use of dwellings, to demonstrate compliance with targets and regulations, and to compare and choose between alternative construction strategies. However, current energy assessment tools, and the associated methodologies and data, are insufficient for optimal strategy selection. This is because they do not assist in the systematic comparison of all combinations of options; they do not assist in the evaluation of whole life energy, carbon and cost; they do not always allow sufficient flexibility for key inputs and assumptions characterising the dwelling and its use; and they do not allow sufficient flexibility for the key metrics (weather data, carbon emission factors, and energy costs) or lead users to develop values for these metrics appropriate to the study period. Following detailed analysis of the current processes of construction strategy selection for dwellings, a framework is developed for the rapid identification of the optimal construction strategy (within the constraints of the tools and data used), whilst evaluating the whole life energy, carbon, cost and performance of alternative strategies. Methodologies are developed and implemented in a working tool for the systematic comparison of all combinations of options entered by the user; the evaluation of whole life energy, carbon and cost in an energy assessment tool; the use of flexibility for key inputs and assumptions to test the sensitivity of strategy performance to changes in these values; and the development and application of metrics appropriate to the study period under consideration. The use of the framework, methodologies, and tool are demonstrated in worked examples for a new dwelling constructed to the proposed 2016 ‘Zero Carbon Homes’ standard, and for the renovation of an existing dwelling.

Driven by climate change and the impending depletion of fossil fuels, the UK Government has set the great challenge to UK builders to produce zero-carbon homes as of 2016. Due to a lack of experience the merits of integrating onsite micro renewable energy systems were largely unknown. Barratt Development PLC, UK's largest builder, set out in 2006 to investigate how these new building regulations can best be tackled. The key points to be investigated are: how much CO2 can be offset using renewable energy systems in standard homes and at what cost; how reliable are these systems; and how can their performance be improved? At the EcoSmart village several systems were tested under realistic conditions, including PV, Solar Thermal, Micro Wind Turbines, GSHPs and microCHP. The systems were tested over a 12-month period, integrated into standard Barratt homes, and running under near real-life conditions. Data was recorded from the test-site, including heat and electrical energy generation and consumption, temperature data and weather data. This data was used to establish the theoretical performance of the systems at the test site, and by doing so simple methods were found and tested that can be used by builders or architects to gain a better understanding of the expected performance of a particular system. The estimated energy generation was then compared to the measured performance. Detailed modelling and analysis of observations was carried out to provide explanations for any discrepancies, and based on this general recommendations were made on how the performance of the systems could be improved. Given the commercial drivers behind carrying out this research project, a high emphasis was given to financial implications of installing the systems. For this purpose payback periods and life-time savings were estimated, based on measured performance and other influences such as feed-in tariffs. This was also done for embodied energy and embodied carbon, as this will ultimately determine how the systems can help to fulfil the purpose of Government legislation, which is to reduce the carbon footprint of the UK domestic sector.

Future aircraft are likely to employ electrically powered actuators for adjusting flight control surfaces, and other high power transient loads. To meet the peak power demands of aircraft electric loads and to absorb regenerated power, an ultracapacitor-based energy storage system is examined in which a bidirectional dual active bridge DC-DC converter is used. This Thesis deals with the analysis, design, development and performance evaluation of the dual active bridge (DAB) converter, which can act as an interface between the ultracapacitor energy storage bank and the aircraft electrical power network. A steady-state analysis is performed for the DAB converter producing equations for the device RMS and average currents and the peak and RMS currents in the coupling inductor. This analysis focuses on understanding converter current shapes and identifying the zero-voltage switching (ZVS) boundary condition. A converter prototype was designed and built and its operation verified through SABER simulations confirming the accuracy of the analysis. Experimental results are included to support the analysis for 7kW, 20 kHz operating conditions giving a measured efficiency of 90%. To enhance the performance of the converter under light-loads, a quasi-square-wave mode of operation is proposed in which a dead-time is introduced either on the transformer primary voltage, or on the transformer secondary voltage, or simultaneously on both transformer primary and secondary. A similar detailed analysis as that for square-wave operation has been undertaken for all three cases and the converter performance was analysed focusing on ZVS operating range, impact of the RMS/peak inductor currents and converter efficiency. The theoretical work was validated through SABER simulations and proof of concept experimental measurements at 1kW, 20 kHz, which resulted in converter efficiency well above 91%. A 9%-17% improvement in efficiency and a 12%-17% improvement in ZVS operating range over square-wave operation are observed for similar operating conditions. Furthermore, a novel bidirectional current control technique for the DAB converter is presented. A SABER simulation has been performed and the converter operation is validated for square-wave and quasi-square-wave modes under steady-state and transient conditions.

The intent of this study was to design produce a comprehensible but user-friendly method that would provide a step-by-step process and guide in originating sustainable, affordable and energy efficient net-zero residential housing. The right-step procedure of the VERSAE Method was linked to the traditional vernacular architecture of the Hopi, a Native American people who still reside on part of their aboriginal lands in northeastern Arizona. The process combined traditional strategies identified in local vernacular Hopi architecture with modern strategies to successfully design sustainable, affordable and energy efficient (net-zero) housing specifically for contemporary Hopi housing. The process was documented in the capstone project, "Housing for the Hopi Community: Designing Sustainable, Affordable and Energy Efficient Housing in the Hopi Community, Linking to Cultural Patterns of Sustainability". For this thesis, the VERSAE method and process was replicate to create a sustainable, affordable and net-zero housing prototype for the Omaha Nation located in Nebraska with significantly different climate, environment, local materials and cultural patterns. Both case studies validated the VERSAE method as conductive to sustainable, affordable and energy efficient (net-zero) housing design.

Made available in DSpace on 2014-06-12T23:02:12Z (GMT). No. of bitstreams: 2 arquivo8603_1.pdf: 3357618 bytes, checksum: 675a22cf3dd870de5f50ce95aad44c4f (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2007 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / A implementação de políticas públicas na área de alimentação e nutrição ganhou espaço importante na pauta federal a partir do governo Vargas, fomentado em especial pelas idéias e estudos de Josué de Castro. Atualmente, muitas de suas concepções fundamentam as propostas da Segurança Alimentar e Nutricional (SAN), temática chave que visa conduzir as políticas sociais do país, e que tem sido implementada através do Programa Fome Zero, lançado no início de 2003, no primeiro mandato do Presidente Luiz Inácio Lula da Silva. No eixo de ação do programa que visa aumentar o acesso de famílias pobres aos alimentos foi criado o Programa Bolsa Família (PBF), originado da união de antigos programas de transferência de renda e propondo avanços no desenho operacional dos programas de renda mínima do país. O presente estudo tem por finalidade avaliar a implementação do PBF no município de Gameleira, localidade da Zona da Mata de Pernambuco, uma das regiões mais pobres e desassistidas do país. A pesquisa inclui um componente quantitativo, a partir de dados coletados de 502 famílias residentes em setores de maior vulnerabilidade social no município, e um componente qualitativo, obtido pela aplicação de entrevistas semiestruturadas aos gestores do PBF e das Secretarias de Saúde e Educação, e um representante do Conselho Municipal de Assistência Social, responsável pelo controle social do PBF no município. Os resultados foram obtidos a partir da comparação das famílias inscritas com as não inscritas no programa e mostram que, de forma geral, ambas se encontram em situação de baixas condições de vida, sendo que algumas evidências apontam maior vulnerabilidade social entre as inscritas no PBF. O programa foi considerado bom pela maioria dos beneficiários e mostrou um possível incremento na diversidade da dieta destes, embora esteja aquém do recomendado. A operacionalização do Cadastro Único mostrou desempenho satisfatório, entretanto, a oferta de serviços e o acompanhamento das condicionalidades, principalmente as de saúde, colocam-se como desafios importantes ao bom funcionamento do programa. Observou-se também a fragilidade do município quanto à proposta de gestão intersetorial do PBF, no seu controle social, e em relação à implementação de ações complementares ao programa e de SAN. A avaliação de programas como o PBF possibilita identificar suas potencialidades e entraves, permitindo fundamentar as necessárias ações para o aperfeiçoamento das políticas públicas

Recent developments in deep reinforcement learning applied to abstract strategy games such as Go, chess and Hex have sparked an interest within military planning. This Master thesis explores if it is possible to implement an algorithm similar to Expert Iteration and AlphaZero to wargames. The studied wargame is Risk, which is a turn-based multiplayer game played on a simplified political map of the world. The algorithms consist of an expert, in the form of a Monte Carlo tree search algorithm, and an apprentice, implemented through a neural network. The neural network is trained by imitation learning, trained to mimic expert decisions generated from self-play reinforcement learning. The apprentice is then used as heuristics in forthcoming tree searches. The results demonstrated that a Monte Carlo tree search algorithm could, to some degree, be employed on a strategy game as Risk, dominating a random playing agent. The neural network, fed with a state representation in the form of a vector, had difficulty in learning expert decisions and could not beat a random playing agent. This led to a halt in the expert/apprentice learning process. However, possible solutions are provided as future work.