31 research outputs found
SIMULATION OF WAKE VORTEX AIRCRAFT IN GROUND EFFECT
The problem developed in this paper is encountered in airplane aerodynamics and concernsthe influence of long life longitudinal wake vortices generated by wing tips or by external obstaclessuch as reactors or landing gears. More generally it concerns 3D bodies of finite extension in crossflow. At the edge of such obstacles, longitudinal vortices are created by pressure differences inside theboundary layers and rotate in opposite senses. It can constitute a danger to another aircraft that fliesin this wake, especially during takeoff and landing. In this case the wake vortex trajectories andstrengths are altered by ground interactions. This study presents the results of a Large EddySimulation of wake vortex in ground effect providing the vorticity flux behavior
The nuclei of radio galaxies in the UV: the signature of different emission processes
We have studied the nuclei of 28 radio galaxies from the 3CR sample in the UV
band. Unresolved nuclei (central compact cores, CCC) are observed in 10 of the
13 FR I, and in 5 of the 15 FR II. All sources that do not have a CCC in the
optical, do not have a CCC in the UV. Two FR I (3C 270 and 3C 296) have a CCC
in the optical but do not show the UV counterpart. Both of them show large
dusty disks observed almost edge-on, possibly implying that they play a role in
obscuring the nuclear emission. We have measured optical-UV spectral indices
alpha_o,UV between ~0.6 and ~7.0. BLRG have the flattest spectra and their
values of alpha_o,UV are also confined to a very narrow range. This is
consistent with radiation produced in a geometrically thin, optically thick
accretion disk. On the other hand, FR I nuclei, which are most plausibly
originated by synchrotron emission from the inner relativistic jet, show a wide
range of alpha_o,UV. There is a clear trend with orientation in that sources
observed almost edge-on or with clear signs of dust absorption have the
steepest spectra. These observations imply that in FR I obscuration can be
present, but the obscuring material is not in a ``standard'' geometrically
thick torus. The most striking difference between these absorbing structures
and the classic AGN ``tori'' resides in the lower optical depth of the FR I
obscuring material.Comment: 15 pages, 4 figures, accepted for publication on Ap
Modelling human choices: MADeM and decision‑making
Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)