Living and Learning With New Media: Summary of Findings From the Digital Youth Project

Summarizes findings from a three-year study of how new media have been integrated into youth behaviors and have changed the dynamics of media literacy, learning, and authoritative knowledge. Outlines implications for educators, parents, and policy makers

A cellular automaton model of laser-plasma interactions

This paper deals with the realization of a CA model of the physical interactions occurring when high-power laser pulses are focused on plasma targets. The low-level and microscopic physical laws of interactions among the plasma and the photons in the pulse are described. In particular, electron–electron interaction via the Coulomb force and photon–electron interaction due to ponderomotive forces are considered. Moreover, the dependence on time and space of the index of refraction is taken into account, as a consequence of electron motion in the plasma. Ions are considered as a fixed background. Simulations of these interactions are provided in different conditions and the macroscopic dynamics of the system, in agreement with the experimental behavior, are evidenced

Living and Learning with New Media

This report summarizes the results of an ambitious three-year ethnographic study, funded by the John D. and Catherine T. MacArthur Foundation, into how young people are living and learning with new media in varied settings—at home, in after school programs, and in online spaces. It offers a condensed version of a longer treatment provided in the book Hanging Out, Messing Around, and Geeking Out (MIT Press, 2009). The authors present empirical data on new media in the lives of American youth in order to reflect upon the relationship between new media and learning. In one of the largest qualitative and ethnographic studies of American youth culture, the authors view the relationship of youth and new media not simply in terms of technology trends but situated within the broader structural conditions of childhood and the negotiations with adults that frame the experience of youth in the United States. The book that this report summarizes was written as a collaborative effort by members of the Digital Youth Project, a three-year research effort funded by the John D. and Catherine T. MacArthur Foundation and conducted at the University of California, Berkeley, and the University of Southern California. John D. and Catherine T. MacArthur Reports on Digital Media and Learnin

Model-Based Design of a Control System for the Upgrade of Biogas with Zeolite Sorbent Reactors

To remove carbon dioxide from biogas so as to produce biomethane, a fixed-bed tubular reactor filled with a zeolite pelleted solid sorbent is considered. To generate biomethane continuously, three batch reactors are operated in coordinated cycles. The control system operates in a two-level structure: a high-level coordination algorithm determines the shift from a process stage to another for each single reactor and computes the setpoints for the low-level controllers of each reactor; the low-level controllers regulate the process variables, such as the inlet gas flow rate, the inlet or outlet gas pressure and the sorbent temperature, according to the setpoints. In this paper, we first investigate the modelling of the batch process by means of mass, energy and momentum conservation equations. The concurrent adsorption of methane is also taken into account. The model parameters are identified by means of a two-stage procedure using experimental measurements from two plants, a laboratory-scale one located in Piacenza (Italy) and a pilot-scale one located in Camposampiero (Italy). With the identified model we design a control system for the coordination of three batch reactors

A parallel prefiltering approach for the identification of a biased sinusoidal signal: theory and experiments

The problem of estimating the amplitude, frequency, and phase of an unknown sinusoidal signal from a noisy-biased measurement is addressed in this paper by a family of parallel prefiltering schemes. The proposed methodology consists in using a pair of linear filters of specified order to generate a suitable number of auxiliary signals that are used to estimate\u2014in an adaptive way\u2014the frequency, the amplitude, and the phase of the sinusoid. Increasing the order of the prefilters improves the noise immunity of the estimator, at the cost of an increase of the computational complexity. Among the whole family of estimators realizable by varying the order of the filters, the simple parallel prefilters of orders 2 C 2 and 3 C 3 are discussed in detail, being the most attractive from the implementability point of view. The behavior of the two algorithms with respect to bounded external disturbances is characterized by input-to-state stability arguments. Finally, the effectiveness of the proposed technique is shown both by comparative numerical simulations and by a real experiment addressing the estimation of the frequency of the electrical mains from a noisy voltage measurement