Time-periodic feedback stabilization for an ensemble of half-spin systems

Feedback stabilization of an ensemble of non interacting half spins described by Bloch equations is considered. This system may be seen as a prototype for infinite dimensional systems with continuous spectrum. We propose an explicit feedback law that stabilizes asymptotically the system around a uniform state of spin +1/2 or -1/2. The closed-loop stability analysis is done locally around the equilibrium. The local convergence is shown to be a weak asymptotic convergence for the H1 topology. The proof relies on an adaptation of the LaSalle invariance principle to infinite dimensional systems. Numerical simulations illustrate the efficiency of these feedback laws, even for initial conditions far from the equilibrium

First exposure to Arduino through peer-coaching: Impact on students' attitudes towards programming

In this paper we report the work that jeKnowledge (Júnior Empresa da Faculdade de Ciências e Tecnologias da Universidade de Coimbra), a student-led initiative, has done in the ‘jeKnowledge academy’ courses to actively engage Portuguese high-school students in STEM education through hands-on projects based on the low-cost Arduino platform. F2F activities, based on a peer-assisted learning strategy, were complemented with tutorials and more advanced project suggestions in a blog. Pre and post surveys on students'' attitudes towards programming and peer-coaching were administered to pre-university and first year college participants, finding an overall increase in the Likert scale for all the programming-related constructs under study (confidence, interest, gender, usefulness and professional) after the introductory course. As regards the peer-based learning approach, younger students seemed to be more eager to be taught in a less formal way than their older counterparts. The course resulted in high degrees of satisfaction for both the student tutors and their tutees

An erbium(III)-based NIR emitter with a highly conjugated ß-diketonate for blue-region sensitization

The sensitization of lanthanide complexes in the visible region is of particular interest for practical applications such as labeling, biological analysis and optoelectronics. A visible-light sensitized Er3+complex based on the use of a highly conjugated ß-diketonate (1, 3-di(2-naphthyl)-1, 3-propanedione, Hdnm) and 5-nitro-1, 10-phenanthroline (5NO2phen) as an ancillary ligand, [Er(dnm)3(5NO2phen)], has been synthesized, fully characterized and its photophysical properties have been investigated. Suitably expanded p-conjugation in the complex molecule makes the excitation window red-shifted to the visible region (up to 550 nm). Efficient energy transfer by antenna effect results in 1.53 µm emission from the Er3+ion

Efeito da aplicação de biocarvão, cama de frango e formulado npk no estado nutricional de laranjeira em terra mulata

Growing in orange on Terra Mulata has been submitted nutrient limitation requiring correction in agricultural areas. The application of biochar associated with another source of nutrients can be a viable alternative to increase the efficiency of fertilizers and reduce losses in the areas. The objective of this study was to evaluate the effect of biochar, poultry litter and NPK in the nutritional status of orange trees grown in an Oxisol with anthropogenic A horizon (Terra Mulata). The study was conducted in a rural property landfall in Manacapuru (AM) in a randomized block design with eight treatments using biochar, poultry litter and NPK (4-14-8) applied in isolation and associates. To review two samples were taken at different periods of sheets to determine the nutritional status. Fertilizers applied did not increase the efficiency in the availability of contents of N, P, Fe and Zn, being the latter below the range of suitable content. As for the K, compost chicken manure and their combinations increased their availability, and the highest levels of Mg were found in the control treatment. © 2015, Universidade Federal de Uberlandia. All rights reserved