Er3+ as marker for order-disorder determination in the PbTiO3 system

Er3+ ions were added to the PbTiO3 network using the polymeric precursor method to characterize the order-disorder transformation found in this material by means of experimental and theoretical approach. The disordered and ordered material structures were studied by photoluminescence measurements, X-ray diffraction (XRD) and U-V-visible spectroscopy. The Er3+ ions served as a marker to identify the structural short-range order beginning in the PbTiO3 matrix. From photoluminescence results it was concluded that disordered PbTiO3 powders have a certain short range order in the network that are undetected by XRD measurements. The electronic structures were calculated by the ab initio periodic method in DFT level with the non-local B3LYP hybrid approximation for the Ti atom site interpretation using density of states (DOS) results. This analysis enabled understanding that Ti atom sphere coordination can create possible states for radioactive return and trap of electron-holes pair. (c) 2007 Elsevier B.V. All rights reserved.

Single molecule electron transfer dynamics in complex environments

We propose a new theoretical approach to study the kinetics of the electron transfer (ET) under the dynamical influence of the complex environments with the first passage times (FPT) of the reaction events. By measuring the mean and high order moments of FPT and their ratios, the full kinetics of ET, especially the dynamical transitions across different temperature zones, is revealed. The potential applications of the current results to single molecule electron transfer are discussed.

Energy efficiency for standard penetration tests

The need for standardization of the measured blow count number N-spt into a normalized reference energy value is now fully recognized. The present paper extends the existing theoretical approach using the wave propagation theory as framework and introduces an analysis for large displacements enabling the influence of rod length in the measured N-spt values to be quantified. The study is based on both calibration chamber and field tests. Energy measurements are monitored in two different positions: below the anvil and above the sampler. Both experimental and numerical results demonstrate that whereas the energy delivered into the rod stem is expressed as a ratio of the theoretical free-fall energy of the hammer, the effective sampler energy is a function of the hammer height of fall, sampler permanent penetration, and weight of both hammer and rods. Influence of rod length is twofold and produces opposite effects: wave energy losses increase with increasing rod length and in a long rod composition the gain in potential energy from rod weight is significant and may partially compensate measured energy losses. Based on this revised approach, an analytical solution is proposed to calculate the energy delivered to the sampler and efficiency coefficients are suggested to account for energy losses during the energy transference process.

Novas Fronteiras Acadêmicas: Cooperação entre grupos de pesquisa em ciência da informação no Brasil

Displays the context of the Project Network cooperation and learning in information science: PPGCI / UFPB and PPGCI / UNESP / Marilia, under the National Program of Academic Cooperation - Action New Frontiers (NF-Procad) Coordination for the Improvement of Higher (CAPES). Describes the procedures for financing, consisting of Missions Studies, Missions Teaching and Research and Post-Doctoral Internship in the country highlights the Groups and Research areas involved in the project and discusses the theoretical approach adopted and the conceptual network that guides actions teaching and research. We report the activities in the first two years of the project and discusses ongoing and planned activities.

A DC-DC converter based on the three-state switching cell for high current and voltage step-down applications

This paper presents a pulsewidth modulation dc-dc nonisolated buck converter using the three-state switching cell, constituted by two active switches, two diodes, and two coupled inductors. Only part of the load power is processed by the active switches, reducing the peak current through the switches to half of the load current, as higher power levels can then be achieved by the proposed topology. The volume of reactive elements, i.e., inductors and capacitors, is also decreased since the ripple frequency of the output voltage is twice the switching frequency. Due to the intrinsic characteristics of the topology, total losses are distributed among all semiconductors. Another advantage of this converter is the reduced region for discontinuous conduction mode when compared to the conventional buck converter or, in other words, the operation range in continuous conduction mode is increased, as demonstrated by the static gain plot. The theoretical approach is detailed through qualitative and quantitative analyses by the application of the three-state switching cell to the buck converter operating in nonoverlapping mode $(D < 0.5)$. Besides, the mathematical analysis and development of an experimental prototype rated at 1 kW are carried out. The main experimental results are presented and adequately discussed to clearly identify its claimed advantages. © 1986-2012 IEEE.

Marcadores discursivos no processo de retextualizaçao de entrevistas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Conversor buck utilizando célula de comutação de três estados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Processos inferenciais: contribuições das ciências cognitivas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A campanha presidencial e o Vota Brasil em 2006: marketing e contexto político

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

O discurso da cor na construção do imaginário político: análise das informações visuais da mídia na cobertura da campanha presidencial de 2010

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Taxa de câmbio: uma abordagem integrada - teoria e história econômica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Teorias de conta corrente: uma aplicação ao caso do Brasil nos anos noventa

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Imprensa, educação e sociedade no interior paulista: Ribeirão Preto (1948-1959)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Os desafios e limites na construção do projeto profissional dos jovens que frequentam o ensino médio público e privado

Pós-graduação em Educação - IBRC

Etnomatemática e economia solidária: o caso de um grupo de fabricação de sabão caseiro

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)