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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Přístavy ve starém Egyptě / Přístavy ve starém Egyptě

Šichan, Daniel January 2011 (has links)
The work deals with landing facilities in ancient Egypt, both in the Nile Valley and in coastal areas. The aim has been to collect and interpret written, iconographic and archaeological evidence from the Early Dynastic to the Late Periods. The material is presented chronologically and individual groups of sources are arranged by type (written, archaeological and iconographic). The knowledge thus obtained has then been used to form a comprehensive overview of the development, function, importance and organization of harbour/port facilities in ancient Egypt. The main problem of the study of landing facilities in ancient Egypt lies in the extreme fragmentation of sources which makes it impossible to provide a continuous picture of the development of the subject and which raises as many questions as answers. The best preserved group of sources is written evidence, followed by information obtained by archaeology. The least informative is iconographic evidence. Although the majority of these sources are relatively straightforward to interpret, there are cases where interpretation is speculative. A fundamental question has arisen during this study. It is the relationship of the ancient Egyptians themselves to the facilities which undoubtedly played a significant role in the life of the inhabitants of the...
2

Nonlinear transient dynamics of on-board rotors supported by Active Magnetic Bearings / Prévision du comportement dynamique d'une turbomachine supportée par des Paliers Magnétiques Actifs durant un évènement critique

Jarroux, Clément 19 July 2017 (has links)
De manière générale, les turbomachines sont des machines tournantes permettant la conversion des différents types d’énergie. Ces dernières sont composées d’une partie mécanique en rotation, appelée rotor, interagissant avec un fluide. La rotation a donc un rôle clé pour ces machines et la liaison entre les parties fixes et les parties tournantes, appelée palier, est primordiale pour un fonctionnement fiable et optimal. Les turbomachines supportées par des paliers magnétiques actifs (PMAs) sont de plus en plus utilisées par les industriels notamment grâce à l’absence de contact direct entre parties fixes et parties tournantes, permettant un gain d’énergie et une réduction des émissions de CO2. La plupart du temps, ces machines sont « embarquées » et reposent sur des supports mobiles. Les mouvements générés par ces supports doivent être considérés dans la prévision du comportement dynamique des turbomachines afin d’améliorer les designs en conséquence. Cette thèse est une contribution à l’étude des turbomachines supportées par des PMAs sujettes à de fortes sollicitations extérieures. L’approche est numérique et expérimentale. L’utilisation d’un banc d’essais académique composé d’un système rotor-PMA, aux propriétés d’une turbomachine industrielle, a permis de tester les modèles développés pour des cas de sollicitations extérieures de type séisme et choc, générées grâce à l'excitateur 6-axes de l'equipex PHARE. Il est montré que le modèle permet la bonne prévision du comportement réel de la machine. Cet outil pourra donc être utilisé pour des designs de type industriel. / Turbomachines are rotating machines enabling the conversion of the different types of energy. The latter are composed of a rotating mechanical part, called rotor, interacting with a fluid. Therefore, rotation play a key role in these machines and the mechanical link between the fixed and the rotating parts, called bearing, is essential for reliable and optimal operations. Turbomachines supported by active magnetic bearings (AMBs) are increasingly used by industrial companies, especially thanks to the absence of direct contact between fixed and rotating parts, enabling energy savings and reduction of CO2 emissions. Most of the time, these machines are "on-board" and are fixed on mobile supports. The motions generated by these supports must be considered in the prediction of the dynamic behaviour of turbomachinery in order to improve the designs accordingly. This PhD is a contribution to the study of turbomachines supported by AMBs subjected to strong external base motions. The approach is numerical and experimental. The use of an academic scale test rig comprising a rotor-AMB system, with the properties of an industrial turbomachine, allowed to test the developed models for cases of external solicitations such as earthquake and shock, thanks to the 6-axis shaker of the equipex PHARE. It is shown that the model provides good predictions of the behaviour of the machine for the tested cases. This tool can therefore be used for industrial designs.

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