Search results for "Jet"

The project for the “Galleria Oretea” by Giuseppe Damiani Almeyda and other unbuilt “passages” in Palermo

2022

The contribution aims to conjecturally reconstruct and analyze the unrealized project by Giuseppe Damiani Almeyda regarding the “Galleria Oretea” for Palermo. It is an urban project of considerable size and impact, which should have provided the city of Palermo, in the old town, with a gallery in the style of the Parisian “passages”, inspired by the contemporary creations of Milan and Naples. Thanks to the recent cataloging and publication of the entire corpus of drawings in the Damiani Archive, a reinterpretation of the project was carried out through a three-dimensional recomposition of the immersed in the places where it was originally conceived. Two other projects were developed for the…

Sub-Optimal Control Law for Active Magnetic Bearings Suspension

2012

This paper deals with the comparison of three types of sub-optimal control law for the stable levitation of a turbojet shaft, sustained by two radial active magnetic bearings (AMBs). Shaft is considered rigid for the procedure simplification. The utilized approach leads to development of different sub-optimal control laws to use in speed-varying simulations in the angular speed of the shaft. The first control matrix is obtained by explicit relationships of the parameters of the control law vs. speed, obtained using a curve-fitting procedure neglecting the speed-varying elements out of the main diagonal of each single block constituting the entire control matrix. The second control law is ob…

Modelling and bench scale investigation of inclined dense jets

2002

Socialisation scolaire et projets d'avenir chez les lycéens et les lycéennes : la "causalité du probable" et son interprétation sociologique

1995

International audience; Ce texte présente une analyse des projets de vie de jeunes gens et jeunes filles de première. La section fréquentée, mais aussi l'avenir perçu comme le plus probable, confinent les choix dans les limites de ce qui est possible vu les contraintes structurelles, notamment la division du travail entre les deux sexes. Les différents modèles théoriques mis en oeuvre par les sociologues pour rendre compte de ce jeu entre "choix" individuels et contraintes structurelles sont ensuite présentées. L'hypothèse est faite d'une certaine convergence entre modèles, au sein de la sociologie mais aussi entre sociologues et psychologues.

Spectral evolution of flaring blazars from numerical simulations

2016

High resolution Very Long Baseline Interferometry (VLBI) observations of Active Galactic Nuclei (AGN) revealed traveling and stationary or quasi-stationary radio-components in several blazar jets. The traveling ones are in general interpreted as shock waves generated by pressure perturbations injected at the jet nozzle. The stationary features can be interpreted as recollimation shocks in non-pressure matched jets if they show a quasi-symmetric bump in the spectral index distribution. In some jets there may be interactions between the two kinds of shocks. These shock--shock interactions are observable with VLBI techniques, and their signature should also be imprinted on the single--dish lig…

Impact of red giant/AGB winds on active galactic nucleus jet propagation

2017

Astronomy and astrophysics 606, A40 (2017). doi:10.1051/0004-6361/201630117

Testing jet geometries and disc-jet coupling in the neutron star LMXB 4U 0614 + 091 with the internal shocks model

2020

Multi-wavelength spectral energy distributions of Low Mass X-ray Binaries in the hard state are determined by the emission from a jet, for frequencies up to mid-infrared, and emission from the accretion flow in the optical to X-ray range. In the last years, the flat radio-to-mid-IR spectra of Black Hole (BH) X-ray binaries was described using the internal shocks model, which assumes that the fluctuations in the velocity of the ejecta along the jet are driven by the fluctuations in the accretion flow, described by the X-ray Power Density Spectrum (PDS). In this work we attempt to apply this model for the first time to a Neutron Star (NS) LMXB, i.e. 4U 0614+091. We used the multi-wavelength d…

X-ray Emission from Protostellar Jets

2008

Long-term FRII jet evolution: Clues from three-dimensional simulations

2018

We present a long-term numerical three-dimensional simulation of a relativistic outflow designed to be compared with previous results from axisymmetric, two-dimensional simulations, with existing analytical models and state-of-art observations. We follow the jet evolution from 1~kpc to 200~kpc, using a relativistic gas equation of state and a galactic profile for the ambient medium. We also show results from smaller scale simulations aimed to test convergence and different three-dimensional effects. We conclude that jet propagation can be faster than expected from axisymmetric simulations, covering tens of kiloparsecs in a few million years, until the dentist drill effect produced by the gr…

3D simulations of microquasar jets in clumpy stellar winds

2011

High-mass microquasars consist of a massive star and a compact object, the latter producing jets that will interact with the stellar wind. The evolution of the jets, and ultimately their radiative outcome, could depend strongly on the inhomogeneity of the wind, which calls for a detailed study. The hydrodynamics of the interaction between a jet and a clumpy wind is studied, focusing on the global wind and single clump-jet interplay. We have performed, using the code \textit{Ratpenat}, three-dimensional numerical simulations of a clumpy wind interacting with a mildly relativistic jet, and of individual clumps penetrating into a jet. For typical wind and jet velocities, filling factors of abo…