Optimal control of non-linear systems through hybrid cell-mapping/artificial-neural-networks techniques

In this paper, a real-time optimal control technique for non-linear plants is proposed. The control system makes use of the cell-mapping (CM) techniques, widely used for the global analysis of highly non-linear systems. The CM framework is employed for designing approximate optimal controllers via a control variable discretization. Furthermore, CM-based designs can be improved by the use of supervised feedforward artificial neural networks (ANNs), which have proved to be universal and efficient tools for function approximation, providing also very fast responses. The quantitative nature of the approximate CM solutions fits very well with ANNs characteristics. Here, we propose several control architectures which combine, in a different manner, supervised neural networks and CM control algorithms. On the one hand, different CM control laws computed for various target objectives can be employed for training a neural network, explicitly including the target information in the input vectors. This way, tracking problems, in addition to regulation ones, can be addressed in a fast and unified manner, obtaining smooth, averaged and global feedback control laws. On the other hand, adjoining CM and ANNs are also combined into a hybrid architecture to address problems where accuracy and real-time response are critical. Finally, some optimal control problems are solved with the proposed CM, neural and hybrid techniques, illustrating their good performance.

Análisis de las noticias sobre lectura digital en Portugal: Jornal de Noticias y Correio da Manhã (2005-2009)

Este trabajo recoge el estudio de los discursos públicos sobre lectura basado en un total de 60 noticias de los periódicos portugueses de especial relevancia: Jornal de Noticias y Correio da Manhã. El análisis se basa en el estudio del índice de frecuencia y valor semántico de una selección de términos relevantes —presentes en el corpus de noticias— para el tema objeto de estudio. Los cuales permiten observar la evolución de los discursos públicos a lo largo del periodo estudiado como consecuencia del desarrollo de las nuevas tecnologías. Asimismo, se revisa la evolución del concepto de lectura a lo largo del período y se aporta información acerca de las cuestiones directamente relacionadas con el estudio de la lectura como es la sociología de la lectura, su relación con la educación, así como los nuevos soportes de lectura.