État | EPFL Graph Search

thumb|Nicolas Machiavel fut un des premiers à faire usage du mot stato dans le sens d'. L’État possède une triple signification : sociologique ; organisationnelle ; juridique. Sur le plan sociologique, c'est alors une population vivant sur un territoire déterminé et soumise à un gouvernement. Cette définition rejoint celle de la première édition du dictionnaire de l’Académie française de 1696, qui définit l'État comme le , ou bien le pays lui-même, c'est-à-dire l'État entendu . Du point de vue organisationnel, c'est une forme d'organisation que la société utilise pour s'orienter et se gérer. L'État désigne également un ensemble de personnes qui acceptent de s'imposer un ordre sous certaines conditions. Sur le plan juridique, . Sur le plan juridique et selon le droit international, un État souverain est vu comme délimité par des frontières territoriales établies, à l'intérieur desquelles ses lois s'appliquent à une population permanente, et comme constitué

Numerical and experimental investigations on non-contacting seals for small-scale applications

Suresh Katuwal Chhetri

Dynamic non-contacting seals have been identified as the most appropriate sealing technology for reduced-scale and high-speed turbomachinery applications since they provide a clearance gap preventing rotor-to-seal contact during operation. Yet, any clearance, however small, between rotor and seal permits the passage to fluid flow across regions of unequal pressure as a leakage which penalize the overall system efficiency. A thorough theoretical and experimental investigation of these types of gas seal at a reduced scale, however, is missing today. Furthermore, in thermodynamic cycles, fluids often operate within the vicinity of the saturation line where the well-known ideal gas law is not valid. For reduced scale turbomachinery seals operating close to the fluid saturation line, validated models to capture the real gas effects are not available yet. The aim of this thesis is to address these shortcomings. Initially, a qualitative research approach has been used for the selection of the ideal seals for reduced-scale applications. Using the qualitative data available from the literature of large-scale seals, a weighted decision matrix has been implemented. For assessing the robustness of the selection process, the sensitivity analysis has been carried out by using different weight distributions. The top two ranked seals, namely, Hole Pattern Seal (HPS) and Pocket Damper Seal (PDS), have been identified as the most promising seals for reduced-scale turbomachinery applications due to their low leakage rates and their low influence on the rotordynamic system. In order to predict the seal performance, the commonly used bulk-flow approach has been used for the numerical modeling approach. Furthermore, for the comparison purpose, three different state-of-the-art models have been implemented. As a benchmark, the predicted results from the different models are compared with the experimental data of well-established literature. A good agreement between the different seal models and the experimental data has been observed. A dedicated hermetic test-rig for the experimental investigations on the reduced-scale seal has been designed and built. A modular test section design has been adopted to test different types and sizes of seals. Six different reduced-scale seals, both on cylindrical and conical cross-section, have been investigated experimentally at different inlet boundary conditions with R134a and air. The experimental data for different seals were compared between the predicted results from the developed models as a validation process. Compared to the-state-of the-art models, the authorâs model demonstrates a superior prediction quality in terms of leakage, cavity pressure, and temperature distribution in all test cases. The Hole Pattern Seal (HPS) has been identified as the most effective seal for reduced-scale applications. The experimental data suggests a strong impact of the real gas effects on leakage. Compared to a high degree of superheat the leakage increases by up to 10% for an operation close to the saturation line. The authorâs model shows better prediction quality at different degrees of superheat compared to state-of-the-art models and demonstrates its ability to capture the real gas effect.

EPFL2020

Multi-level governance and transport policy: the case of local roads in Italy

Amanda Blomberg Stathopoulos

Italy is a multi-level polity where policymaking and implementation involves both public and private actors. Both territorial and functional decentralisation have an impact on the final results of policy making. In fact, territorial decentralisation implies the delegation of functions to wide multi-purpose tiers of sub-national governance, which has been a central dynamic of Italian governance. Furthermore, functional decentralization stresses the assignment of functions, vertically and horizontally, to single-purpose quasiautonomous agencies. Multi level governance (MLG) aims at understanding the nature and explaining the structure of governance networks, their inter- relationship with control, capacity, accountability and efficiency of political systems (Bache and Flinders, 2004 ; Piattoni, 2010 ). To date, only a limited use has been made of this important instrument of analysis, at least in Italy, in transport policy, in general, and in the road sector, in particular. Research in various domains such as political geography (Shaw et al., 2009), regional and urban studies (Kern and Bulkeley, 2009) and institutional economics (Marsden et al., 2009) have all stressed the crucial role governance plays in the transport sector notwithstanding the lack of a common framework of analysis. The paper synthetically reports the definitions of MLG proposed, describing their characteristics and clarifying their implications for the transport sector, as well as discussing the implications of a specific MLG for the transport sector regulatory system and for the role of local public authorities. Management and programs of the local road sector in Italy are discussed with a particular focus on the different types of solutions adopted and on the level of integration among different governance levels. Finally, a critical discussion of the situation of the local road sector in Italy, its governability and some suggestions for the future are reported.

2012

Nature of the Bad Metallic Behavior of Fe1.06Te Inferred from Its Evolution in the Magnetic State

Marco Grioni, Ping-Hui Lin

We investigate with angle-resolved photoelectron spectroscopy the changes of the Fermi surface and the main bands from the paramagnetic state to the antiferromagnetic (AFM) state occurring below 72 K in Fe1.06Te. The evolution is completely different from that observed in Fe pnictides, as nesting is absent. The AFM state is a rather good metal, in agreement with our magnetic band structure calculation. On the other hand, the paramagnetic state is very anomalous with a large pseudogap of similar to 65 meV on the electron pocket that closes in the AFM state. We discuss this behavior in connection with spin fluctuations existing above the magnetic transition and the correlations predicted in the spin-freezing regime of the incoherent metallic state.