[pt] Este trabalho amplia a estrutura clássica de decomposição de sinais em sub-bandas de freqüência. É desenvolvida uma estrutura capaz de decompor simultaneamente sinais quaisquer e sistemas lineares, discretos e invariantes no tempo. As funções codificadas podem ser implementadas nas sub-bandas de forma paralela, a uma taxa de operação mais baixa do que a do sistema original. É proposta uma arquitetura para implementação, em cujas simulações o sinal decomposto e processado é recuperado com baixa distorção, caracterizando a reconstrução perfeita da estrutura. Os filtros utilizados para o processo de decomposição caracterizam-se por sua simplicidade (passa-tudo de 2a. ordem) com boa rejeição em freqüência. Os filtros de reconstrução, normalmente instáveis, são estabilizados por técnicas que realizam reversão do sinal no tempo. Uma das soluções utiliza a passagem de condições iniciais do bloco de decomposição para o de reconstrução. É apresentada também, outra solução, mais gera, que dispensa esta passagem e faz uso da característica de convergência assintótica dos filtros de reconstrução. A estrutura de decomposição proposta pode ser aplicada recursiva, gerando uma estrutura em árvore binária. / [en] This work extends the classical signal subband decomposition scheme to incorporate the decomposition of linear systems. A network decomposition structure is developed to simultaneously decompose signals and systems into subband of frequencies. The procedure allows simply rate reduction, as well as the network partition repetitive subnetworks. The method uses second order allpass as decomposition/synthesis filters and a specific structure is proposed to implement the unstable synthesis filters. In the system simulation the signal is processed with very small distortion supporting the theory.

[pt] Neste trabalho são examinadas técnicas de compressão de imagens por sub-bandas. O algoritmo de análise/síntese utilizado emprega filtros recursivos passa-tudo de 1º ordem, o que reduz a complexidade computacional sem introduzir aliasing ou distorção de fase. Técnicas de processamento específicas para o caso destes filtros foram discutidas. As limitações da codificação direta das sub-bandas mostraram a conveniência de, inicialmente, separar componentes de baixa e alta freqüências. A imagem de baixa freqüência representa o brilho e a textura e é codificada por blocos no domínio da Transformada Cossenoidal Discreta. A imagem de erro, com aspecto essencialmente passa-alta, destacando as transições, é dividida em sub-bandas que são quantizadas vetorialmente. A exploração das características e correlação das sub-bandas permite aperfeiçoar esta técnica. A qualidade objetiva de cada técnica é medida pela razão sinal/ruído de pico e a subjetiva resulta da análise visual das imagens. Ambas são comparáveis ou superiores às de codificadores existentes com complexidade semelhante, para taxas entre 0.6 e 0.7 bits/pixel. / [en] Image compression techniques based on subband coding are studied in this work. The analysis/synthesis algorithm is implemented using first-order all-pass recursive filters, which significantly reduces the computational complexity and reconstructs the input with neither aliasing nor phase distortion. Specific processing techniques for these filters were discussed. Limitations in direct subband coding show the convenience of initially splitting the image to be compressed into its low-pass and high-pass components, representing sharp edges, is divided into subbands which are vector quantized. Further improvement of this technique results from the study of subband characteristics and correlacion. Objective quality of each technique is measured by the peak signal-to-noise ratio and subjective quality results from visual inspection of reconstructed images. Both are superior or comparable to existing coders of similar complexity, for rates between 0.6 and 0.7 bits/pixel.

Cette thèse s’intéresse à l’endommagement laser d’optiques réflectives en régime sub-picoseconde. Ces composants optiques, réalisés à partir d’empilements sub-micrométriques de matériaux diélectriques, sont couramment utilisés dans les installations laser de puissance telles que le laser PETAL. Ce dernier, construit sur le centre du CEA-CESTA en France, a été conçu pour délivrer des impulsions de 500 fs et de quelques kJ à une longueur d’onde de 1053 nm, dans le but d’atteindre des puissances supérieures à 6PW. Dans ce type d’installations de puissance, afin de limiter l’accumulation d’effets non-linéaires liés à la propagation d’impulsions intenses, des optiques réflectives en fin de chaîne se substituent aux optiques en transmission. Les composants optiques illuminés par les plus fortes densités de puissance sont des réseaux de compression, des miroirs et une parabole qui servent respectivement à la compression temporelle des impulsions, au transport du faisceau ainsi qu’à sa focalisation. Le phénomène d'endommagement laser est le paramètre principal qui limite la puissance accessible par ces lasers. Il est nécessaire de comprendre et de maîtriser ce phénomène afin de fiabiliser une installation laser et également d’améliorer ses performances. Trois axes d’études ont donc été explorés. Le premier concerne la conception d’optiques réflectives. Des définitions de structures sont recherchées afin d’obtenir de hautes efficacités de diffraction dans le cas des réseaux et des forts coefficients de réflexion dans le cas des miroirs, tout en diminuant le renforcement du champ électrique dans les structures, l’une des causes de l’endommagement laser. Le second axe d’étude porte sur la mise en place d’une métrologie fine de l’endommagement laser avec le développement de nouvelles procédures de test. Elles amènent de nouveaux points de vue pour la qualification de la résistance au flux laser des optiques. En dernier lieu, nous étudions le phénomène de croissance des dommages lorsqu’ils sont soumis à plusieurs irradiations laser. L’évolution de la surface des dommages lors de séquences de croissance est observée, quantifiée et comparée à un modèle numérique. Cela nous permet de mieux comprendre la phénoménologie de la croissance des dommages en régime sub-picoseconde. A terme, elles permettront de développer des modèles de prédiction de l’endommagement et des outils pour l’amélioration des optiques utilisées sur chaîne laser. / In this thesis, laser-induced damage phenomenon of reflective components is investigated in the sub-picosecond regime. These components, made of stacks of dielectric materials, are widely used in powerful laser facilities such as PETAL laser. PETAL laser has been built at the CEA-CESTA in France to deliver multi-kJ/500fs pulses at 1053nm and reach a power higher than 6PW. For this kind of laser systems, reflective components are commonly used instead of optics operating in transmission to limit the accumulation of non-linear phase along the beam propagation due to the high intensities. Optical components irradiated by the highest power densities are the pulse compression gratings, transport mirrors and the focusing parabola, located at the end of the laser chain. Nowadays, laser-induced damage is the main factor that limits the overall performances of powerful laser systems. This manuscript presents three study axes to better understand and control damage phenomenon. The first one concerns the conception of reflective optics for the petawatt applications. The design of new structures has been investigated to reach high diffraction efficiencies in the case of pulse compression gratings and a high reflectivity in the case of mirrors, while reducing the Electric-field enhancement which is one of the causes of the laser-induced damage. The second axis deals with the development of a precise damage metrology with new testing tools which brings new perspectives and a new viewpoint for the assessment of the laser resistance of optical components. Finally, the third axis concerns the study the damage growth after several irradiations in the sub-picosecond regime. The evolution of the damage area during growth sequences is observed and compared to numerical simulations. It enables to improve the understanding in the growth phenomenon. In the end, these studies will allow to develop predictive models of the laser-induced damage and new tools for the conception of reflective optics for petawatt applications.

Abstract In this work the LCVD of copper and nickel from the precursor gases Cu(hfac)tmvs and Ni(CO)4 has been investigated. The in-house constructed LCVD system and processes and the practical utilisation of these in prototype integrated circuit edit work are described. The investigated process parameters include laser power, laser scan speed, precursor partial pressure and the effect of H2 and He carrier gases. The deposited metal conductor lines have been examined by LIMA, AFM, FIB secondary electron/ion micrography, and by electrical measurements. Furthermore, the study of experimental FIB circuit edit processes is carried out and discussed with particular emphasis on ion beam induced ESD damages. It is shown how the LCVD and FIB methods can be combined to create a novel method to carry out successfully circuit edit cases where both methods alone will fail. The combined FIB/LCVD- method is shown to be highly complementary and effective in practical circuit edit work in terms of reduced process time and improved yield. Circuit edit cases where both technologies are successfully used in a complementary way are presented. Selected examples of some special circuit edit cases include RF- circuit editing, a high resolution method for FIB-deposited tungsten conductor line resistance reduction and large area EMI shielding of IC surfaces. Based on the research it was possible for a formal workflow for the combined process to be developed and this approach was applied to 132 circuit edit cases with 85% yield. The combined method was applied to 30% of the total number of edit cases. Finally, the developed process and constructed system was commercialized.

Nous proposons un nouveau schéma d’échantillonnage non uniforme périodique appelé Système d’Échantillonnage Non Uniforme en Radio Intelligente (SENURI). Notre schéma détecte la localisation spectrale des bandes actives dans la bande totale échantillonnée afin de réduire la fréquence moyenne d’échantillonnage, le nombre d’échantillons prélevé et par conséquent la consommation d’énergie au niveau du traitement numérique. La fréquence moyenne d’échantillonnage du SENURI dépend uniquement du nombre de bandes contenues dans le signal d’entrée x(t). Il est nettement plus performant, en termes d’erreur quadratique, qu’une architecture classique d’échantillonnage non uniforme périodique constituée de p branches, lorsque le spectre de x(t) change dynamiquement. / In this work we consider the problem of designing an effective sampling scheme for sparse multi-band signals. Based on previous results on periodic non-uniform sampling (Multi-Coset) and using the well known Non-Uniform Fourier Transform through Bartlett’s method for Power Spectral Density estimation, we propose a new sampling scheme named the Dynamic Single Branch Non-uniform Sampler (DSB-NUS). The idea of the proposed scheme is to reduce the average sampling frequency, the number of samples collected, and consequently the power consumption of the Analog to Digital Converter (ADC). In addition to that our proposed method detects the location of the bands in order to adapt the sampling rate. In this thesis, we show through simulation results that compared to existing multi-coset based samplers, our proposed sampler provides superior performance, both in terms of sampling rate and energy consumption. It is notconstrained by the inflexibility of hardware circuitry and is easily reconfigurable. We also show the effect of the false detection of active bands on the average sampling rate of our new adaptive non-uniform sub-Nyquist sampler scheme.

Utilising the Grounded Theory Research Method, this study identified a range of open, axial and selective codes, through a literature review, which resulted in the formulation of a proposed theory of how war economies are formed and maintained. Based on the theoretical proposition of the proposed theory, a policy framework for dismantling such war economies was also developed and presented. The proposed theory of war economies essentially argues that war economies are formed in post-colonial sub-Saharan Africa because of the existence of an artificial state. The existence of an artificial state is ascribed to the emerging legacies of colonial state formation processes, which created failed state entities which are unable to produce public goods for all its citizens because of its inability to maintain a monopoly of violence whilst maintain full administrative control over its territory. This inability results in an increase in the vulnerability of state and non-state actors. In response to these vulnerabilities, both state and non-state actors established a range of parallel political, economic and military structures. These structures in turn made use of both network and resource capacities to create an environment where politics are economised and conflict is commercialised, in order to mitigate the impacts of state failure and the inability to produce public goods. The result of the creation of an environment where politics are economised and conflict is commercialised, is the creation of incentives, structures and processes to ensure that conflict and associated conditions of instability are sustained in order to ensure primitive accumulation of wealth and resources. Based on the core theoretical proposition of the proposed theory, the study also presents a broad policy framework for dismantling war economies. In broad terms the framework proposes an integrated state-building process, based on a range of policy mechanisms aimed at maintaining a monopoly over violence, increasing administrative control, dismantling conflict networks and ensuring effective and efficient resource management.

This research deals with achieving and maintaining price stability in Sub-Saharan Africa (SSA) through the practice of monetary-policy transparency (MPT). On the one hand, MPT refers to a monetary strategy whereby the central bank is insulated from political influence and made accountable to society through disclosure of its policies, procedures, economic models, data and forecasts, operations and political practices (such as objectives, personnel independence, and the like). On the other hand, price stability refers to achieving and maintaining low and stable levels of inflation conducive for long-term planning and poverty alleviation. The primary objective of this research was to investigate MPT in SSA as it represents a powerful means whereby economic agents’ expectations may be coordinated and managed by the central bank to achieve its societal, objective function of low inflation. The empirical evidence shows that, first, a dependent central bank is more likely to slip into hyperinflation. Second, a SADC (2008) model central bank law is not independent enough to be used as a benchmark for any central bank or as a charter for a regional central bank. Third, the degree of central bank independence in SSA is relatively lower than that in industrialised economies. Fourth, the determinants of MPT in SSA are trade openness, and financial depth that are important factors influencing policy-makers to adopt monetary-policy transparency. Fifth, MPT is associated with a decline in the inflation rate. Sixth, MPT had no significant effect on economic output, whilst trade openness was positively associated with real GDP.

Continued debates on economic development, poverty eradication and the growing skeptism concerning the paradigms proposed through many decades, has led to a continued search for a paradigm that would, finally, resolve the issue of pervasive poverty in the Sub-Saharan Africa. Having implemented decentralization within government entities without any significant contribution to poverty eradication, the focus has now turned to the development agencies themselves. What are the inefficiencies in these agencies which if addressed might enable them deliver development aid more efficiently thus, providing more resources for development from being lost in the attrition of overheads? It is, therefore, argued that decentralization of development agencies will improve the efficiency and effectiveness of IFIs in delivering development aid. At the same time, decentralization reforms have been proposed as a response to the failures of highly centralized states (or organizations in this case). Empirical evidence, strongly, suggests that physical proximity and more "face-time", promotes better results-on-the-ground, delivered by staff who are better attuned to local conditions and have a better understanding of the client and their development agenda. But, will decentralization alone solve the issue of pervasive poverty? This research recognises that the factors affecting poverty are diverse and intricate and isolating just one part of the puzzle is not enough. Nevertheless, it is argues that decentralization, has a positive impact on poverty reduction thus, this study presents both practical and theoretical considerations from which policy measures can be derived. This thesis focused on establishing how the World Bank, changed its strategies through the implementation of decentralization of its operations as proposed in the ‗Strategic Compact‘, renewed the way it worked in order to maintain its relevance in the development world. The World Bank President, James Wolfensohn, proposed the Compact as a solution to the organization‘s self diagnosis that it was in distress, in a state of possible decline and was not fulfilling its mission of poverty eradication. This research, using Uganda Country Office as a case study, undertook, mainly, a qualitative review of the overall strategy of decentralization and its implementation organization wide and specifically, in Uganda. The research examined how the implementation of the strategy impacted on poverty trends in Uganda. This research found that the decentralization strategy was, fundamentally, the right one to deliver better results of the Bank‘s mission of ‗fighting poverty for lasting results‘ and its vision of ‗A World Free of Poverty‘. Contrary to the popular notion that the World Bank has been, largely ineffective in the delivery of its mission and its decentralization strategy just another one of its 'shams‘, this research established that the implementation of the strategy, although not having a direct or causal relationship, did have positive impact on poverty alleviation in Uganda. This study, therefore, makes a case for decentralization of donor organizations as a means of better delivery of the poverty eradication agenda in the developing world. The benefits though hard to measure in monetary terms are, nevertheless, real in terms of faster and better quality engagement with the clients which in turn, result into better delivery of services and programmes.

The main goal of master thesis is to proof that investment into renewable energy may have a positive impact on standard of living for local community and the region of Sub-Saharan Africa. The thesis is divided into three main chapters, while the first one is dedicated to detailed analysis of renewable energies, demographic and geographical indicators, the second one is focused on investment and financing of energy projects. The last chapter leads readers through case study of small hydropower plant into findings that are essential in proving the main idea of whole thesis.

This thesis examines Chinese foreign direct investments in Sub-Saharan Africa and their influence on Chinese foreign policy on the continent between the years 2004 and 2010. It is often believed that oil and raw materials are the principal determinants of Chinese investments in Africa. However, this research suggests that even though there exists strong correlation between the existence of reserves of raw materials and FDI distribution, such motivation is not the only one. Pragmatism, manifested by the Chinese government in FDI allocation, can lead the People's Republic to invest in controversial countries with bad governance like Sudan. China is then forced to keep closer relations with such countries and thus promote their stability to protect its investments. Tools of such efforts include foreign policy, closer cooperation on multilateral level, which includes establishment of Forum on China-Africa Cooperation, and foreign aid.