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A partir des connaissances acquises depuis plusieurs années sur les différents concepts de propulsion électrique distribuée, l'ONERA a étudié la viabilité d'une configuration d'avion hybride électrique d'un avion de transport transsonique monocouloirs type A320 ou B737 : le concept DRAGON (Distributed fans Research Aircraft with electric Generators by ONera). La conception de cette nouvelle architecture de puissance a nécessité l'intégration « multi-physique » de différents domaines tels que les performances de vol, la sécurité et les exigences énergétiques et environnementales (gestion thermique, systèmes électriques, compatibilité électromagnétique). Cet article décrit l’analyse effectuée sur l'architecture hybride électrique afin d’évaluer les caractéristiques de la chaîne d'alimentation électrique tout en considérant des scénarios de défaillance. En complément, l’analyse du système d'interconnexion du câblage électrique (EWIS) a aussi été réalisée pour évaluer l'influence des caractéristiques technologiques des composants électriques sur les performances de l'avion.

The dependence of ionic transport on crystal orientations in NaSICON-type solid electroytes is studied on flux-grown M3Sc2(PO4)3 (M = Na, Ag) single crystals with well-defined facets. Herein, we provide the first impedance spectroscopy study to characterize ion conduction along different crystallographic orientations in this important class of materials for electrochemical energy storage systems. Moreover, we used single crystal X-ray diffraction, differential scanning calorimetry, 23Na NMR spin-lattice relaxation measurements, and ab initio molecular dynamics simulations to study the interplay of structure and ion transport taking place at different length scales. We conclude that the phase behavior in NaSICON-type materials is strongly linked to ion diffusion. At room temperature, ionic conductivity is slightly anisotropic along the crystallographic orientations [001] and [100]. The slightly different activation energies are related to diffusion bottlenecks solely changing along [001]. This change is caused by anisotropic thermal lattice expansion. With increasing temperature, ion transport increasingly becomes isotropic finally resulting in an order-disorder phase transition from C2/c to R−3c. This phase transition is associated with a clear change in activation energy solely along [001]; it can be traced back to the increasing jump distance along this crystal orientation with temperature. Astonishingly, changing the ionic charge carrier, i.e., when going from Na+ to Ag+, shifts the phase transition temperature by 140 K toward lower temperature. The Arrhenius behaviour remains, however, similar. This finding is related to the higher mobility of Ag+ in the NaSICON framework leading to isotropic ion diffusion at much lower temperatures. Overall, flux-grown M3Sc2(PO4)3 allowed us to show that ionic transport parameters and phase stability sensitively depend on crystal chemistry.

We have investigated PLLA crystallization in lamellae-forming PS-b-PLLA confined to straight cylindrical nanopores under weak confinement (nanopore diameter D / equilibrium PS-b-PLLA period L0 larger than 4.8). Molten PS-b-PLLA predominantly forms concentric lamellae along the nanopores, but intertwined helices occur even for D/L0 = 7.3. Quenching PS-b-PLLA melts below TG(PS) results in PLLA cold crystallization strictly confined by the vitrified PS domains. Above TG(PS), PLLA crystallization is templated by the PS-b-PLLA melt domain structure in the nanopore centers, while adsorption on the nanopore walls stabilizes the outermost cylindrical PS-b-PLLA shell. In between, the nanoscopic PS-b-PLLA melt domain structure apparently ripens to reduce frustrations transmitted from the outermost immobilized PS-b-PLLA layer. The onset of PLLA crystallization catalyzes the ripening while transient ripening states are arrested by advancing PLLA crystallization. Certain helical structure motifs persist PLLA crystallization even if PS is soft. The direction of fastest PLLA crystal growth is preferentially aligned with the nanopore axes to the same degree as for PLLA homopolymer, independent of whether PS is vitreous or soft.

This thesis includes three chapters across the areas of cliometrics, growth theory, and economic development. The cliometric study surveys the Great Divergence in the last millennium. The growth model provides the explanation for the demographic transition in the East between the 15th and the 19th centuries. The development study documents how income influences inequality in India since the late 1950s. This chapter briefly introduces the three studies. Apart from confirming the effect of culture and institutions on the Great Divergence, the first study suggests a new timing for Great Divergence which is the 10th century instead of between the 15th and the 18th centuries. The relative standstill of per capita income and technology in the East over the last millennium, in terms of the theory of Malthus, however, contradicts the tremendous population expansion in China and India after the 15th century. The second study examines the paradoxical demographic transition in China and India during the 15th and the 19th centuries. In simple words, at the same wage level, the increase of output resulting from more use of unskilled workers relative to skilled workers brings about neither higher average production costs nor higher marginal production costs. Because of the resultant scale economies, China and India overcame the checks of diminishing returns through population expansion. Finally, the third study turns its attention to income distribution of modern India. It argues that higher income resulting from the expansion of productivity frontier is the cause of higher income disparity. Since productive workers in urban areas are paid at a higher wage rate, workers migrate from less productive rural areas to more productive urban areas. Such migration not only enlarges economic duality between urban and rural areas but also make the poor’s life in cities more grievous under the work of the impersonal labor market. The economic duality hides the complexities of political economy. How to make resource allocation fairer is crucial to the economy of India. In a nutshell, the investigation from old civilizations to modern India seems to imply no ending of the divergence among world economies. Since, as is shown in this study, there has been world divergence between the West and the East since 750 years ago, the relevance between geography and economic development can hardly be regarded as a coincidence. More specifically, in long human history, that the West experienced modification of institutions and expansion of the set of values could be attributed to its geographical limits that prevented it from pursuing scale economies to overcome the threat of diminishing returns. By contrast, that the East lacked good institutions or a larger set of values that favoured innovation and technological development could be accounted for by its geography that imposed limits on its production. Because of such limits, the East’s production pattern must be agricultural; and, its labor inputs must be unskilled. Can the East catch up to the West in the future? This question indeed triggers more questions that await resolution.

Solid-state batteries represent an exciting future direction for energy storage. While tremendous progress has been made in developing novel solids with very high Li-ion conductivity, electrochemical decomposition and reactivity of conductors with the anode or cathode material remains a major concern for the long-term stability of solid-state batteries. Using ab-initio computations we have evaluated the chemical and electrochemical stability of a large number of coating materials and conductors. I will discuss the clear set of chemical rules that appears from these results. Interestingly, the optimal coating materials depend very much on the specific electrode/conductor interface that needs to be protected.

The formation of polymer nanowires containing metal nanoparticle chains by low-temperature thermolyses of metal precursors has remained challenging. We report the block copolymer-assisted generation of locally regular chains of quasi-spherical gold nanoparticles with narrow particle diameter distribution by mild thermolysis of the non-polar gold precursor gold mesitylene inside the cylindrical nanopores of self-ordered anodic aluminium oxide (AAO). The block copolymer separates the gold mesitylene as well as the developing gold nanoparticles from the AAO pore walls so that surface nucleation and pinning of gold clusters are prevented. Growing quasi-spherical gold nanoparticles locally deform the polymer chains irreversibly adsorbed on the AAO pore walls, and the polymer chains are pushed into the space between the gold nanoparticles. The gold nanoparticles have, therefore, larger diameters and smaller specific surface than hypothetical pluglike gold entities with the same volume, the formation of which is suppressed.

We have investigated PLLA crystallization in lamellae-forming PS-b-PLLA confined to straight cylindrical nanopores under weak confinement (nanopore diameter D/equilibrium PS-b-PLLA period L0 ≥ 4.8). Molten PS-b-PLLA predominantly forms concentric lamellae along the nanopores, but intertwined helices occur even for D/L0 ≈ 7.3. Quenching PS-b-PLLA melts below TG(PS) results in PLLA cold crystallization strictly confined by the vitrified PS domains. Above TG(PS), PLLA crystallization is templated by the PS-b-PLLA melt domain structure in the nanopore centers, while adsorption on the nanopore walls stabilizes the outermost cylindrical PS-b-PLLA shell. In between, the nanoscopic PS-b-PLLA melt domain structure apparently ripens to reduce frustrations transmitted from the outermost immobilized PS-b-PLLA layer. The onset of PLLA crystallization catalyzes the ripening while transient ripening states are arrested by advancing PLLA crystallization. Certain helical structure motifs persist PLLA crystallization even if PS is soft. The direction of fastest PLLA crystal growth is preferentially aligned with the nanopore axes to the same degree as for PLLA homopolymer, independent of whether PS is vitreous or soft.