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This thesis explored, in two parts, the macroeconomic impacts of exchange rate regimes (ERR), as well as the recent developments in fiscal policy and fiscal decentralization. Part I has reconsidered the role of ERR and its interplay with fiscal, monetary and tax policy. The first result that emerges (Chapter 1) is that fixed ERR can serve as a credible policy tool for stabilizing fiscal policy. However, this stabilizing effect is conditional upon the inter-temporal distribution of the costs of loose fiscal policy. In assessing the linkage between ERR and crises (banking/financial, currency and debt), Chapter 2 evidenced that the bipolar view is no longer valid, and that, crisis proneness rather depends on the macroeconomic fundamentals (the volatility of private sector credit, the deficit-financing mechanism, and the debt-to-GDP ratio). In Chapter 3, we unveiled a strong relationship between ERR and tax policy. Countries with pegged regimes have greater reliance on domestic taxation -such as the VAT- to make up for the loss of seigniorage revenue (substitution effect). Moreover, peggers tend to collect more VAT revenue to offset the shortfall in cross border taxes following the trade liberalization reform (competitiveness effect). Part II discussed the cyclical response of fiscal policy in high debt periods, and focused on fiscal decentralization issues. In Chapter 4, we showed that the reaction of fiscal policy to the business cycle is non-linear and conditional to the level of public debt. When the debt-to-GDP ratio goes beyond a certain threshold (87%), fiscal policy loses its counter-cyclical properties. Further, we highlighted that carefully-designed fiscal rules help maintaining counter-cyclicality through an ex ante disciplinary effect. Chapters 5 and 6 analyzed the impact of fiscal decentralization on the efficiency of public service delivery and fiscal policy performance, respectively. Chapter 5 revealed that a sufficient level of expenditure decentralization, coupled with revenue decentralization, improves the efficiency of public service delivery. However, the political and institutional environment is critical for reaping decentralization-led benefits. Lastly, Chapter 6 concluded that fiscal decentralization has destabilizing effect by reducing the counter-cyclicality of fiscal policy. In addition, we found that decentralization strengthens the structural fiscal balance; however, vertical fiscal imbalances reduce the benefits of decentralization. It is therefore critical to limit asymmetries between expenditure and revenue decentralization, so as to reduce the transfer-dependency of local governments to the central level, and thus prevent decentralization from weakening the fiscal stance at the general government level., Cette thèse s’intéresse d’une part aux effets macroéconomiques des régimes de change, et d’autre part, aux récentes évolutions sur la politique budgétaire et la décentralisation. La partie I met essentiellement l’accent sur l’interaction entre les régimes de change (RC) et la politique budgétaire, monétaire et fiscale. Tout d’abord, nous mettons en évidence que les RC peuvent avoir un effet stabilisateur sur la politique budgétaire (chapitre 1). Cependant, cet effet stabilisateur des RC n’est pas automatique mais dépendrait plutôt des conséquences d’une politique budgétaire laxiste. Le chapitre 2 s’intéresse quant à lui à la causalité entre RC et crises (bancaire/financière, de change et de dette) et remet en cause la vision bipolaire qui prétendait que les RC intermédiaires sont plus vulnérables aux crises que les solutions en coin (RC fixes/flexibles). Il ressort de notre analyse que les fondamentaux macroéconomiques (la volatilité du crédit au secteur privé, le financement du déficit, et le ratio dette sur PIB) jouent un rôle considérable. Le chapitre 3 met en évidence un lien entre les RC et la politique fiscale. Les pays à RC fixes montrent une plus grande dépendance aux recettes domestiques –telles que la TVA-, comparativement aux pays en change intermédiaires/flexibles pour compenser les pertes de recettes de seigneuriage (effet de substitution). De plus, ces pays avec RC fixes collectent plus de recettes domestiques en compensation de la perte de recettes douanières, suite à la libéralisation commerciale (effet de compétitivité). Dans les trois derniers chapitres (partie II), nous mettons le focus sur la politique budgétaire et les effets de la décentralisation. Le chapitre 4 révèle une relation non-linéaire entre la politique budgétaire et le cycle économique, qui dépend du niveau de la dette publique. Lorsque celle-ci dépasse un certain seuil (87%), la politique budgétaire perd toute propriété contra-cyclique. Nous montrons par ailleurs que l’effet disciplinaire ex-ante des règles budgétaires aide à restaurer la contra-cyclicité de la politique budgétaire. A travers le chapitre 5, nous montrons que la décentralisation budgétaire, dans un cadre politico-institutionnel sein et dépourvu de corruption, améliore l’offre de biens et services publics. Le chapitre 6 conclut que la décentralisation impacte positivement le solde structurel. Cependant une asymétrie entre la décentralisation des dépenses et celle des recettes accroit la dépendance des gouvernements locaux vis-à-vis du gouvernement central en termes de transferts, et amoindrirait considérablement à l’effet positif de la décentralisation.

We propose, for the first time to our knowledge, the theoretical investigation of optical soliton excitation inside very short silicon nanocrystal based sandwiched slot waveguides, only 1.6 mm long. Several parametric simulations have been carried out by means of finite element method in order to select the best waveguide cross section for anomalous-dispersion regime around 1550 nm.

Modulation and detection methods have been studied to improve the performance of optical long distance communication systems. Polarization division multiplexed modulation and multilevel phase modulation format have been evaluated. Coherent detection associated with digital signal processing has been selected at the receiver side to optimize system performance. This receiver design allows especially to compensate linear distortions induced by fiber optics propagation very efficiently. After long distance propagation, optical signal to noise ratio is a major limitation. The other main limitation comes from non linear interactions of light and fiber optics which put a limit on the maximum power to be injected within fiber optics.The first wavelength division multiplexed transmission over long distances (>1000km) using coherent detection has been demonstrated.Various strategies have been proposed to minimize the impact of non linear effect. The impact of polarisation multiplexing has been quantified in configuration where chromatic dispersion is either regularly optically compensated within the line or digitally compensated at the receiver end.The proposition to use a polarization multiplexed format using only 2 phase levels as well as the algorithms capable to detect them has been done. The performance gain obtained compared to the convention solution using 4 phase levels has been demonstrated.At 100Gb/s bit rate, the demonstration of the first transmission over trans-oceanic distance has also been done.These research work have been used to define and then develop Alcatel-Lucent products which are now commercialized, at 40Gb/s by using a polarization multiplexed and 2 phase levels modulation format, and at 100Gb/s by using a polarization multiplexed 4 phase levels format.; Des méthodes de modulation et de détection de la lumière originales ont été étudiées afin d’améliorer la performance des systèmes de transmission optique longue distance. Des formats de modulation multiplexés en polarisation, utilisant plusieurs niveaux de phase ont été étudiés en particulier. La détection cohérente associée à un traitement numérique du signal a également été choisie au niveau de la réception afin d’optimiser la performance du système. Cela permet notamment de compenser de façon très efficace les distorsions linéaires introduites par la propagation dans le fibre optique, telles que la dispersion chromatique et la dispersion modales de polarisation. Après propagation sur grande distance, le rapport signal à bruit devient une limitation importante. L’autre limitation provient des interactions non linéaire entre la lumière et la fibre optique qui limitent la puissance maximale que l’on peut injecter dans la fibre optique.La première transmission multiplexée en longueur d’onde sur grandes distances (>1000km) utilisant la détection cohérente a notamment été démontrée.Afin de minimiser l’impact de ces effets non linéaires, différentes stratégies ont été proposées et investiguées. L’impact du multiplexage de polarisation a notamment été quantifié dans des configuration où la dispersion chromatique de la fibre est compensée régulièrement dans la liaison et dans le cas où elle n’est compensée qu’en fin de liaison de façon numérique.La proposition d’utiliser un format de modulation à 2 niveaux de phase ainsi que les algorithmes permettant de le détecter ont été fait. Le gain de performance obtenu par rapport à la solution conventionnelle à 4 niveaux de phase a été montré.Au débit de 100Gb/s, la démonstration de la première transmission sur des distances transocéanique a également été faite.Ces travaux de recherche ont été notamment utilisés pour définir puis développer des produits Alcatel-Lucent qui sont maintenant commercialisés, à 40Gb/s en utilisant un format de modulation multiplexé en polarisation à deux niveaux de phase, et à 100Gb/s en utilisant un format multiplexé en polarisation à quatre niveaux de phase.

The spectral broadening of the pump pulse through self phase modulation in a time domain distributed Brillouin sensor is demonstrated to have a non-negligible detrimental effect, leading to a doubling of the effective gain linewidth after some 20 km in standard conditions. The theoretical modeling is fully confirmed by experimental results.

Ground motion has been computed for the 6 April 2009 earthquake (Mw = 6.3) by using a hybrid method (modal summation and finite difference techniques) along a geological section crossing L'Aqilla.

Neste artigo, analisa-se o desempenho do modelo não-linear tridimensional de Navier-Stokes, FLUINCO, na simulação da propagação de ondas sobre fundos de profundidade variável. O modelo numérico é baseado na integração direta das equações de Navier-Stokes (Teixeira), as quais são discretizadas no tempo e no espaço através de um esquema de Taylor-Galerkin semi-implícito de dois passos usando um elemento tetraédrico linear. Adapta uma formulação arbitrária Lagrangeana-Euleriana que é compatível com o movimento da superfície livre. Primeiramente, o código é testado para o caso da propagação de uma onda monocromática em um canal, sendo comparados os resultados numéricos (campos de pressão o de velocidades) com as soluções teóricas. Seguidamente, o modelo é sucessivamente aplicado a problemas que envolvem os quebra-mares trapezoidais. São considerados três casos de teste com a mesma inclinação da rampa a montante, 1:20, mas com rampas a jusante de inclinações 1:10 (estudado experimentalmente por Dingemans), 45º e 90º. Além dos resultados de elevação da superfície em vários pontos do domínio, são apresentados também os campos de pressão e de velocidades. Enquanto que no primeiro caso, com rampa a jusante 1:10, o escoamento não apresenta se a presença de vórtices nas proximidades da junção do patamar com a rampa a jusante. Os resultados mostraram a capacidade do modelo em tratar problemas em que a circulação vertical é significativa, incluindo fenômenos como a separação do escoamento e formação de vórtices.

Extraordinary high powers are nowadays available out of fiber lasers and amplifiers (» 10 kW in continuous wave regime and » 1 MW peak power in pulsed regime). Such an increase can initiate the apparition of some undesirable effects.During this thesis, we have developed and studied some high power Ytterbium doped fiber systems both in continuous wave and pulsed regimes. For this purpose, we have chosen to use the technology of double-clad fibers in association with adapted pumping techniques.Especially, we have developed an original approach that allows to efficiently amplify wavelengths of small emission cross sections. High output powers, in continuous wave regime, have been achieved experimentally and these results are in good agreement with the theoretical ones.The spatial and spectral properties of high output power lasers or amplifiers can be significantly degraded compared to those at low power. We have studied and developed an original approach allowing, for a system in pulsed regime, to maintain, up to extreme high output peak powers, the spectral purity of the source.Moreover, we have computed and theoretically analysed the evolution of the pulse shape in amplification by a high power fiber amplifier. The study of the influence of various parameters of the seed pulse on the output pulse shape allows to significantly decrease the penalties induced by the apparition of non linear effects and to increase their thresholds while output power and energy become important. Comparison between computed results and theoretical ones are of good agreement.These results, associated with the development of new components, indicate the possibility to achieve even higher output powers while preserving good spectral and spatial properties and retaining the same techniques as those used or demonstrated during this thesis., Des puissances extraordinaires sont, de nos jours, extraites de systèmes à fibres dopées (» 10 kW de puissance continue et » 1 MW de puissance crête en régime d'impulsions). L'augmentation de la puissance dans les systèmes s'accompagne de l'apparition d'effets qui peuvent limiter leurs performances. Parmi ceux-ci citons, notamment, les effets non linéaires, thermiques, de dégradation des propriétés spatiales et spectrales de faisceau, . . . ). Au cours de cette thèse, nous avons développé et étudié des systèmes à fibre dopée Ytterbium délivrant de très fortes puissances en régime de fonctionnement continu et en régime d'impulsions. Pour ce faire, nous avons retenu une technologie à fibre double-gaine couplée à des techniques de pompage adaptées. La puissance s'élevant, nous avons été confrontés à l'apparition d'effets non linéaires. Une étude théorique de ces effets nous permet de proposer des méthodes originales pour s'en affranchir ou en augmenter le seuil. Nos expériences confrontées à notre étude théorique et, le cas échéant, à un modèle d'analyse numérique, nous permettent d'accroître la puissance obtenue. Un amplificateur optimisé pour l'amplification d'un signal à gain faible en régime continu est étudié. Les mêmes méthodes, en régime d'impulsions, permettent de préserver les propriétés spectrales d'une source laser très cohérente à très forte puissance crête. Dans ce régime, une technique de modelage de l'impulsion source est mise en oeuvre, en amplification à l'aide d'une structure à oscillateur amplifié, pour réduire l'impact sur les performances à très forte puissance des effets non linéaires. Celle-ci est étudée, pour l'extraction de très fortes énergies, de manière théorique et nos résultats de simulations confrontés à l'expérience. Avec les technologies utilisées nous proposons, enfin, une ouverture vers l'obtention de davantage de puissance.

conference 5709 « Fiber Lasers II: Technology, Systems, and Applications », session: « Nanosecond fiber sources » [5709-51]; International audience; Fiber lasers and amplifiers are used in a variety of applications either for scientific (spectroscopy, medicine...) or industrial applications (free space communications, laser marking and drilling ...). The combination of doped double clad fibers (DCF) and high power multimode semiconductors laser diodes technologies allows to achieve very high output power in very compact, robust and maintenance free systems. Yb3+ doped DCF are well suited for 1µm wavelength amplification. In pulsed regime, achievable peak power can be strongly limited by nonlinear effects such as Kerr effect, Stimulated Raman Scattering (SRS) or Stimulated Brillouin Scattering (SBS). Consequently, the optimisation of optical amplifier architecture is required. In this paper, we demonstrate performances obtained for the generation of 2ns optical pulses up to >1.7kW peak power in a Master Oscillator Power Fiber Amplifier (MOPFA) configuration. The laser seed signal at 1060nm is emitted out of a single longitudinal mode source with spectral linewidth 10W average output power with a good beam quality M21.7kW. These high performances are obtained in a fully-integrated device.

Aldol condensation of synthetic equivalents of acetacetic esters allows the formation of a polyfunctional C5 fragment and the corresponding aldols have proven to be versatile key-intermediates in the synthesis of complex, biologically active natural products. O-silyldienolates 1 and 2 can be considered among the most popular masked acetacetic esters and in these last years the silyl dienolate 1a (R1 = R2 = Me), deriving from commercially available 2,2,6-trimethyl-4H-1,3-dioxin-4-one, has been used in a variety of aldol reactions (based on the employment of Ti(IV), or Cu(II), chiral complexes) taking place with high efficiency and enantioselectivity; on the contrary, the highly oxygenated diene 2 (Chan's diene) has been essentially used in the synthesis of racemic aldols by TiCl4 catalysis. The aldol condensation of the synthetic equivalents of acetoacetic ester 1-2 can be conveniently performed in the presence of a chiral Ti(O-i-Pr)4/BINOL complex under catalytic conditions. The reported procedure is of particular synthetic value since the addition of masked acetoacetic esters proceeds efficiently with aromatic, heteroaromatic, alpha,beta-unsaturated and aliphatic aldehydes too. In the course of the investigation on the mechanistic aspects of the reaction, positive non-linear effects have been observed; rather interestingly, the mode of preparation and the concentration of the catalyst has been found to exert a marked influence on the non linear effects. Furhermore, the occurence of a concomitant auto-inductive process with amplification of the enantiomeric excess in the aldol reaction of 2 has been pointed out.