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Papers by jose alfredo hoyos
2013 Latin American Robotics Symposium and Competition, 2013
ABSTRACT We propose the use of the extreme learning machine in programming by demonstration. Some... more ABSTRACT We propose the use of the extreme learning machine in programming by demonstration. Some advantages of this technique are a fast training phase and avoiding falling in local minima. We present two ways of using it: (i) for encoding one or several trajectories of a demonstration and (ii) for learning the direct kinematic model of a robot, which once known, allows changing the final position of the demonstrated trajectory. Through comparison with other commonly used techniques, it is experimentally shown that this technique has the lowest learning time and the second lowest error. Also, using a real robot, the learning of the kinematic model was tested, reaching the final position even when this is different to the final of the emonstrated trajectory.
The Astrophysical Journal, 2005
We study the influence of nonlinear circularly polarized waves, propagating backward relative to ... more We study the influence of nonlinear circularly polarized waves, propagating backward relative to the external magnetic field, on the behavior of linear instabilities in a system composed of electrons, background protons, and a proton beam. We find that the presence of both nonlinear left-and right-handed polarized backward-propagating waves induces the stabilization of linear right-hand polarized forward-propagating instabilities when the amplitude wave is above a threshold value. It is shown that the threshold amplitude is lower for backward-propagating waves than for forward-propagating waves in the parameter space we surveyed. We also find that the presence of nonlinear backward-propagating waves can destabilize linear ion-acoustic modes. These ion-acoustic modes are supported either by the proton core or by the proton beam. The instabilities occur when the phase velocities of the forward-and backward-propagating ion-acoustic waves relative to the proton core or to the proton beam become equal. We study the dependence of the amplitude threshold on the large-amplitude wave frequency, the plasma-of the various species, and the proton-beam velocity. These results have already been invoked in order to explain some features of the solar wind. We believe that they can also be important in the study of other stars and quite generally in any astrophysical system involving beam-plasma interactions.
EPL (Europhysics Letters), 2009
We present a large-N variational approach to describe the magnetism of insulating doped semicondu... more We present a large-N variational approach to describe the magnetism of insulating doped semiconductors based on a disorder-generalization of the resonating-valence-bond theory for quantum antiferromagnets. This method captures all the qualitative and even quantitative predictions of the strong-disorder renormalization group approach over the entire experimentally relevant temperature range. Finally, by mapping the problem on a hard-sphere fluid, we could provide an essentially exact analytic solution without any adjustable parameters.
2013 Latin American Robotics Symposium and Competition, 2013
ABSTRACT We propose the use of the extreme learning machine in programming by demonstration. Some... more ABSTRACT We propose the use of the extreme learning machine in programming by demonstration. Some advantages of this technique are a fast training phase and avoiding falling in local minima. We present two ways of using it: (i) for encoding one or several trajectories of a demonstration and (ii) for learning the direct kinematic model of a robot, which once known, allows changing the final position of the demonstrated trajectory. Through comparison with other commonly used techniques, it is experimentally shown that this technique has the lowest learning time and the second lowest error. Also, using a real robot, the learning of the kinematic model was tested, reaching the final position even when this is different to the final of the emonstrated trajectory.
The Astrophysical Journal, 2005
We study the influence of nonlinear circularly polarized waves, propagating backward relative to ... more We study the influence of nonlinear circularly polarized waves, propagating backward relative to the external magnetic field, on the behavior of linear instabilities in a system composed of electrons, background protons, and a proton beam. We find that the presence of both nonlinear left-and right-handed polarized backward-propagating waves induces the stabilization of linear right-hand polarized forward-propagating instabilities when the amplitude wave is above a threshold value. It is shown that the threshold amplitude is lower for backward-propagating waves than for forward-propagating waves in the parameter space we surveyed. We also find that the presence of nonlinear backward-propagating waves can destabilize linear ion-acoustic modes. These ion-acoustic modes are supported either by the proton core or by the proton beam. The instabilities occur when the phase velocities of the forward-and backward-propagating ion-acoustic waves relative to the proton core or to the proton beam become equal. We study the dependence of the amplitude threshold on the large-amplitude wave frequency, the plasma-of the various species, and the proton-beam velocity. These results have already been invoked in order to explain some features of the solar wind. We believe that they can also be important in the study of other stars and quite generally in any astrophysical system involving beam-plasma interactions.
EPL (Europhysics Letters), 2009
We present a large-N variational approach to describe the magnetism of insulating doped semicondu... more We present a large-N variational approach to describe the magnetism of insulating doped semiconductors based on a disorder-generalization of the resonating-valence-bond theory for quantum antiferromagnets. This method captures all the qualitative and even quantitative predictions of the strong-disorder renormalization group approach over the entire experimentally relevant temperature range. Finally, by mapping the problem on a hard-sphere fluid, we could provide an essentially exact analytic solution without any adjustable parameters.