Multi-objective design of robust flight control systems

A multi–objective evolutionary algorithm is used in the framework of H1 control theory to find the controller gains that minimize a weighted combination of the infinite–norm of the sensitivity function (for disturbance attenuation requirements) and complementary sensitivity function (for robust stability requirements). After considering a single operating point for a level flight trim condition of a F-16 fighter aircraft model, two different approaches will then be considered to extend the domain of validity of the control law: 1) the controller is designed for different operating points and gain scheduling is adopted; 2) a single control law is designed for all the considered operating points by multiobjective minimisation. The two approaches are analyzed and compared in terms of effectiveness of the design method and resulting closed loop performance of the system

Multi-objective design of robust flight control systems

The aim of this work is to demonstrate the capabilities of evolutionary methods in the design of robust controllers for unstable fighter aircraft in the framework of H1 control theory. A multi–objective evolutionary algorithm is used to find the controller gains that minimize a weighted combination of the infinite–norm of the sensitivity function (for disturbance attenuation requirements) and complementary sensitivity function (for robust stability requirements). After considering a single operating point for a level flight trim condition of a F-16 fighter aircraft model, two different approaches will then be considered to extend the domain of validity of the control law: 1) the controller is designed for different operating points and gain scheduling is adopted; 2) a single control law is designed for all the considered operating points by multiobjective minimisation. The two approaches will be analysed and compared in terms of efficacy and required human and computational resources

On the sensitivity of extrasolar mass-loss rate ranges: HD 209458b a case study

We present a 3D hydrodynamic study of the effects that different stellar wind conditions and planetary wind structures have on the calculated Ly-$\alpha$ absorptions produced during the transit of HD 209458b. Considering a range of stellar wind speeds $\sim$[350-800] km s$^{-1}$, coronal temperature $\sim$[3-7] $\times10^{6}$ K and two values of the polytropic index $\Gamma$ $\sim$[1.01-1.13], while keeping fixed the stellar mass loss rate, we found a that a $\dot M_p$ range between $\sim$[3-5] $\times 10^{10}$g s$^{-1}$ give account for the observational absorption in Ly-$\alpha$ measured for the planetary system. Also, several models with anisotropic evaporation profiles for the planetary escaping atmosphere were carried out, showing that both, the escape through polar regions and through the night side yields larger absorptions than an isotropic planetary wind

Dystonia: sparse synapses for D2 receptors in striatum of a DYT1 knock-out mouse model

Dystonia pathophysiology has been partly linked to downregulation and dysfunction of dopamine D2 receptors in striatum. We aimed to investigate the possible morpho-structural correlates of D2 receptor downregulation in the striatum of a DYT1 Tor1a mouse model. Adult control Tor1a+/+ and mutant Tor1a+/− mice were used. The brains were perfused and free-floating sections of basal ganglia were incubated with polyclonal anti-D2 antibody, followed by secondary immune-fluorescent antibody. Confocal microscopy was used to detect immune-fluorescent signals. The same primary antibody was used to evaluate D2 receptor expression by western blot. The D2 receptor immune-fluorescence appeared circumscribed in small disks (~0.3–0.5 μm diameter), likely representing D2 synapse aggregates, densely distributed in the striatum of Tor1a+/+ mice. In the Tor1a+/− mice the D2 aggregates were significantly smaller (μm2 2.4 ± SE 0.16, compared to μm2 6.73 ± SE 3.41 in Tor1a+/+) and sparse, with ~30% less number per microscopic field, value correspondent to the amount of reduced D2 expression in western blotting analysis. In DYT1 mutant mice the sparse and small D2 synapses in the striatum may be insufficient to “gate” the amount of presynaptic dopamine release diffusing in peri-synaptic space, and this consequently may result in a timing and spatially larger nonselective sphere of influence of dopamine action

Astrophysics in S.Co.P.E

S.Co.P.E. is one of the four projects funded by the Italian Government in order to provide Southern Italy with a distributed computing infrastructure for fundamental science. Beside being aimed at building the infrastructure, S.Co.P.E. is also actively pursuing research in several areas among which astrophysics and observational cosmology. We shortly summarize the most significant results obtained in the first two years of the project and related to the development of middleware and Data Mining tools for the Virtual Observatory

Photo-ionization of planetary winds: case study HD209458b

Close-in hot Jupiters are exposed to a tremendous photon flux that ionizes the neutral escaping material from the planet leaving an observable imprint that makes them an interesting laboratory for testing theoretical models. In this work we present 3D hydrodynamic simulations with radiation transfer calculations of a close-in exoplanet in a blow-off state. We calculate the Ly-$\alpha$ absorption and compare it with observations of HD 209458b an previous simplified model results.Our results show that the hydrodynamic interaction together with a proper calculation of the photoionization proccess are able to reproduce the main features of the observed Ly-$\alpha$ absorption, in particular at the blue-shifted wings of the line. We found that the ionizing stellar flux produce an almost linear effect on the amount of absorption in the wake. Varying the planetary mass loss rate and the radiation flux, we were able to reproduce the $10\%$ absorption observed at $-100~\mathrm{km~s^{-1}}$.Comment: 9 pages, 6 figure

On the width and shape of the corotation region for low-mass planets

We study the coorbital flow for embedded, low mass planets. We provide a simple semi-analytic model for the corotation region, which is subsequently compared to high resolution numerical simulations. The model is used to derive an expression for the half-width of the horseshoe region, x_s, which in the limit of zero softening is given by x_s/r_p = 1.68(q/h)^(1/2), where q is the planet to central star mass ratio, h is the disc aspect ratio and r_p the orbital radius. This is in very good agreement with the same quantity measured from simulations. This result is used to show that horseshoe drag is about an order of magnitude larger than the linear corotation torque in the zero softening limit. Thus the horseshoe drag, the sign of which depends on the gradient of specific vorticity, is important for estimates of the total torque acting on the planet. We further show that phenomena, such as the Lindblad wakes, with a radial separation from corotation of ~ a pressure scale height H can affect x_s, even though for low-mass planets x_s << H. The effect is to distort streamlines and to reduce x_s through the action of a back pressure. This effect is reduced for smaller gravitational softening parameters and planets of higher mass, for which x_s becomes comparable to H.Comment: 15 pages, 11 figures, accepted for publication in MNRA

Type I Planet Migration in Nearly Laminar Disks

We describe 2D hydrodynamic simulations of the migration of low-mass planets ($\leq 30 M_{\oplus}$) in nearly laminar disks (viscosity parameter $\alpha < 10^{-3}$) over timescales of several thousand orbit periods. We consider disk masses of 1, 2, and 5 times the minimum mass solar nebula, disk thickness parameters of $H/r = 0.035$ and 0.05, and a variety of $\alpha$ values and planet masses. Disk self-gravity is fully included. Previous analytic work has suggested that Type I planet migration can be halted in disks of sufficiently low turbulent viscosity, for $\alpha \sim 10^{-4}$. The halting is due to a feedback effect of breaking density waves that results in a slight mass redistribution and consequently an increased outward torque contribution. The simulations confirm the existence of a critical mass ($M_{cr} \sim 10 M_{\oplus}$) beyond which migration halts in nearly laminar disks. For \alpha \ga 10^{-3}, density feedback effects are washed out and Type I migration persists. The critical masses are in good agreement with the analytic model of Rafikov (2002). In addition, for \alpha \la 10^{-4} steep density gradients produce a vortex instability, resulting in a small time-varying eccentricity in the planet's orbit and a slight outward migration. Migration in nearly laminar disks may be sufficiently slow to reconcile the timescales of migration theory with those of giant planet formation in the core accretion model.Comment: 3 figures, accepted to ApJ

No role for neutrons, muons and solar neutrinos in the DAMA annual modulation results

This paper summarizes in a simple and intuitive way why the neutrons, the muons and the solar neutrinos cannot give any significant contribution to the DAMA annual modulation results. A number of these elements have already been presented in individual papers; they are recalled here. Afterwards, few simple considerations are summarized which already demonstrate the incorrectness of the claim reported in PRL 113 (2014) 081302.Comment: 11 pages, 1 tabl

Model independent result on possible diurnal effect in DAMA/LIBRA-phase1

The results obtained in the search for possible diurnal effect in the single-hit low energy data collected by DAMA/LIBRA-phase1 (total exposure: 1.04 ton x yr) deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. are presented. At the present level of sensitivity the presence of any significant diurnal variation and of diurnal time structures in the data can be excluded for both the cases of solar and sidereal time. In particular, the diurnal modulation amplitude expected, because of the Earth diurnal motion, on the basis of the DAMA Dark Matter annual modulation results is below the present sensitivity.Comment: 14 pages, 5 figures, 2 tables; in publication on Eur. Phys. J.