1,721,170 research outputs found
Mixed optimization technique for large scale water-resource systems
No full textDealing with significantly large design problems for water-resource systems a mixed optimization procedure based on network linear programming and the subgradient method will be described. Using a linear problem formulation, the procedure uses network linear programming as a subproblem that assumes the knowledge of design variables. Since inside its domain, the global objective functions is a convex piecewise linear function, a subgradient method is used to obtain the direction of the improvement of design variables at each iteration using the solutions of the network subproblem. The mixed technique permits an efficient evaluation of the design variables in order to reach a good approximation of the global objective function optimum. The solution technique performs well in the purely linear case and, moreover, allows some kinds of nonlinearities in the cost functions of design variables
Guidance and Control Strategies for the Collision-Avoidance Mode of a Satellite Pair Flying in Formation
No full textAbstract. In this paper we present a study on the
Collision-Avoidance mode of a formation flying
satellite pair in which a free-flying chief
spacecraft follows temporary off-nominal
conditions and a controlled deputy spacecraft
performs collision avoidance maneuvers.
The Collision-Avoidance strategy consists in a
Separation Guidance and a Nominal Guidance.
The Separation Guidance is in charge of the
avoidance of a predicted collision soon to
occur, and it is based on a computationally
simple, deterministic and closed-form
algorithm, so that a valid solution is always
available without delay. The Nominal Guidance
uses Genetic Algorithms and it takes charge of
placing the deputy spacecraft in a bounded safe
or “parking” trajectory, while minimizing the
propellant consumption and avoiding the
evaporation of the formation.
The performances of a Linear Quadratic
Regulator and a Model Predictive Control are
also compared in tracking the reference
trajectories provided by the Collision-
Avoidance strategy
Alterazioni visive ed esposizione a solventi organici a basse concentrazioni: studio attraverso l’utilizzo del Functional acuity contrast test (FACT).
No full text
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