The rotational shear layer inside the early red-giant star KIC 4448777

We present the asteroseismic study of the early red-giant star KIC 4448777, complementing and integrating a previous work (Di Mauro et al. 2016), aimed at characterizing the dynamics of its interior by analyzing the overall set of data collected by the {\it Kepler} satellite during the four years of its first nominal mission. We adopted the Bayesian inference code DIAMOND (Corsaro \& De Ridder 2014) for the peak bagging analysis and asteroseismic splitting inversion methods to derive the internal rotational profile of the star. The detection of new splittings of mixed modes, more concentrated in the very inner part of the helium core, allowed us to reconstruct the angular velocity profile deeper into the interior of the star and to disentangle the details better than in Paper I: the helium core rotates almost rigidly about 6 times faster than the convective envelope, while part of the hydrogen shell seems to rotate at a constant velocity about 1.15 times lower than the He core. In particular, we studied the internal shear layer between the fast-rotating radiative interior and the slow convective zone and we found that it lies partially inside the hydrogen shell above $r \simeq 0.05R$ and extends across the core-envelope boundary. Finally, we theoretically explored the possibility for the future to sound the convective envelope in the red-giant stars and we concluded that the inversion of a set of splittings with only low-harmonic degree $l\leq 3$, even supposing a very large number of modes, will not allow to resolve the rotational profile of this region in detail.Comment: accepted for publication on Ap

The feasibility issue in trajectory tracking by means of regions-of-attraction-based gain scheduling

Linear control theory has been long established and a myriad of techniques are available for designing controllers for linear systems in view of conflicting performance requirements. On the other hand, nonlinear control techniques are often tailored to specific applications and versatile nonlinear control frameworks are still on their infancy. A common approach is to resort to local linearized descriptions at desired set-points over a given desired trajectory and employ linear tools. Furthermore, to enforce stability when switching controllers, the regions-of-attraction approach has gained recent attention. This paper questions whether such method - when applied to a well-posed smooth nonlinear controllable system - always yields a sequence of controllers that successfully tracks a given reference equilibrium trajectory, and an analytic counter-example is provided and thoroughly discussed. Finally, our case study additionally shed light on how gain scheduling fails to track particular trajectories for certain globally controllable systems

Longitudinal study of a tilt-body vehicle: modeling, control and stability analysis

This work studies a longitudinal high incidence flight envelope dynamic model for use in a convertible tilt-body vehicle designed for indoor/outdoor environments. The model assumptions are chosen so that a singularity-free nonlinear differential equation system is obtained. The model is complex enough to predict wind tunnel experiments yet simple enough to be described by analytical expressions (instead of physically difficult to interpret lookup tables). Wind tunnel measurements took place to identify flying model parameters, validate model and support autopilot design by means of scheduled linear quadratic regulator controller. Finally, controller design is validated by means of stability analysis based on regions of attraction computation via Lyapunov theorems and invariant sets during the entire transition between airplane mode and hover mode

Development of the flight model of a tilt-body MAV

This article presents the results of a wind tunnel campaign for a tilt-body UAV, the MAVion. The objective of this campaign is to develop a simplified flight model for use in control systems design and implementation. In order to achieve precise flight control during transition, stationary and cruise modes, the aerodynamic coefficients are identified for a wide flight envelope of angle of attack and sideslip. Additionally, the equilibrium transition is studied and the results validate the MAVion design. Moreover, an analysis of performance on aerodynamics due to addition of winglets in this platform is carried out

Evaluation of Water Quality for Water Bathing Conditions on Querer Beach in the Municipality of Santa Rosa, Tocantins

The water is an indispensable natural resource for life, economic development, and the conservation and maintenance of ecosystem services. It is known that the quantity and quality of water available for consumption is decreasing considerably and the increasing scarcity of this resource may be associated with factors such as the irregular distribution of water, waste and irrational use of it, socioeconomic and environmental problems, pollution of resources inadequate disposal of sewage, lack of basic sanitation and treatment of sewage, among others. In this way, the environmental problems have gained relevant space in the current discussions due to their importance, making the debates of these questions in the society necessary. Because of the anthropic activities that have been developed in a disorderly way and without planning, it reflects drastically in the environmental degradation, especially in this case, in the quality of the waters, which compromises this natural resource, whatever the purpose of its use. Thus, the objective of this work is to evaluate the water quality of Querer Beach in Santa Rosa-TO, promoting a water bathing condition study. Therefore, to investigate the effects of anthropogenic interferences on water quality, the water quality was evaluated by means of monitoring. The analyzes of the bathing conditions, show the percentages obtained for the situations in which the beach is classified as suitable for bathing, the investigations followed the criteria established by the CONAMA resolution nº 274/00. The water quality at a specific point of the beach was evaluated and monitored for a determined period of six weeks, and the microbiological indicator of water quality according to the Collilert technique according to the methodology described by Standard Methods was used as a parameter. In this way, it was possible to verify the tolerances of the Brazilian parameters for the water bathing conditions indicators of Querer Beach

Definition of a landing strategy for a model-scale reusable rocket

Model-scale rockets differ from their real-size counterparts in important ways. For one, the lack of significant thrust throttling limits retro propulsion landing capabilities. This paper studies its feasibility by employing model-scale non-throttleable solid-propellant engines. Our landing strategy comprises an aerodynamic passive descent followed by a thrust vector control touchdown, and thus thrust is modulated not by magnitude but by direction. This strategy imposes additional levels of under-actuation and nonlinearities that cannot be easily tackled with linear approaches. We propose a Nonlinear Model Predictive Controller as a solution and test its performance and robustness in simulation in different scenarios

Global Singularity-Free Aerodynamic Model for Algorithmic Flight Control of Tail Sitters

This paper addresses fundamental issues in tail-sitting and transition flight aerodynamics modeling in view of sumof- squares (SOS) algorithmic guidance and control design. A novel approach, called ϕ theory, for modeling aerodynamic forces and moments is introduced herein. It yields polynomial-like differential equations of motion that are well suited to SOS solvers for real-time algorithmic guidance and control law synthesis. The proposed ϕ theory allows for first principles model parameter identification and captures dominant dynamical features over the entire flight envelope. Furthermore, ϕ theory yields numerically stable and consistent models for 360 deg angles of attack and sideslip. Additionally, an algorithm is provided for analytically computing all feasible longitudinal flight operating points. Finally, to establish ϕ-theory validity, predicted trim points and wind-tunnel experiments are compared