Investigation on upconversion luminescence in Er3+/Yb3+ codoped tellurite glasses and fibers

The upconversion properties of Er3+/Yb3+ codoped tellurite glasses and glass fibers with D-shape cladding under 980 mu excitation were investigated. Intense emission bands centered at 531, 546 and 658 nm corresponding to the transitions Er3+: H-2(11/2) -> I-4(15/2) , S-4(3/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2), respectively, were observed at room temperature. Compared with that in Er3+/Yb3+ codoped tellurite bulk glass, the upconversion luminescence becomes more efficient in the fiber geometry. The dependence of upconversion intensities on fiber geometry and possible upconversion mechanism are discussed and evaluated. The presented Er3+/Yb3+ codoped tellurite fibers with intense upconversion luminescence can be used as potential host materials for upconversion fiber lasers. (c) 2005 Elsevier B.V. All rights reserved.

A novel polarization modulator for a Moire system with grating imaging

A polarization modulator based on splitting with a Savart plate and rotation of an analyzer for a moire system with grating imaging is presented, and its modulation principle is analyzed. The polarization modulator is simple and achromatic. It is composed of a polarizer, a Savart plate, and an analyzer. The polarizer and the Savart plate are placed in front of the index grating to split the image of the scale grating in the moire system. The analyzer is placed behind the grating and rotated to realize the modulation of the moire signal. The analyzer can be rotated either continually with high speed or step by step with low speed to form different modulation modes. The polarization modulator makes the moire system insensitive to the change of initial intensity. In experiments, we verified the usefulness of the polarization modulator.

Spray combustion synthesis of nanocrystalline Y2O3 and its thermodynamical and morphological study

Nano Y2O3 particles with a spherical shape and narrow size distribution have been prepared by a novel spray combustion method. The experimental procedure is briefly described and the thermodynamical process of the post-heat treatment is investigated in this paper. The precursor fully crystallized when treated at as low as 400 degrees C. Prepared particles showed spherical shape and well dispersibility under different treating conditions. Narrow size distribution of particles was achieved even when the precursor was treated at 1373 K. (C) 2007 Elsevier B.V. All rights reserved.

Estudio de los usos de πλήν ["plén"] y de su empleo en la novela griega antigua

Este trabajo ha sido realizado en el marco del PI UPV 106.130-HA092/99.

A representação dos atores sociais em textos jurídicos sobre o sistema de cotas sob a perspectiva da linguística sistêmico-funcional

O presente trabalho está inserido nas pesquisas sobre linguagem no contexto jurídico, e busca responder às seguintes questões: como os atores sociais beneficiários de cotas para ingresso nas universidades públicas são representados em um conjunto de textos, produzidos pelo Poder Público Brasileiro, acerca do próprio sistema de cotas? E como o Sistema da Transitividade demonstra quem são as forças ativas e as forças passivas da questão das cotas? Para isso, buscou-se um corpus heterogêneo composto pelo voto do Ministro Ricardo Lewandowsky na ADPF168, que decidiu a polêmica das cotas, bem como os textos que apresentam relações de intertextualidade com o julgamento, sejam eles anteriores ao voto, como, a Constituição da República Federativa do Brasil de 1988, em especial o artigo 5, caput e inciso I, e a Lei do Estado do Rio de Janeiro n 4151 de 2003; ou posteriores, como a Lei 12.711 de 29 de agosto de 2012, que veio em resposta ao texto do Supremo Tribunal Federal. A pesquisa tem natureza qualitativa interpretativa, insere-se no ramo da Linguística Sistêmico-Funcional, em especial na Representação dos Atores Sociais de van Leuween (1996) e no Sistema de Transitividade proposto por Halliday (2004)