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Novo enfoque no estudo da transição de fase composicional da solução sólida ferroelétrica (Pb,Ca)TiO3
(Universidade Federal de São Carlos, 2006-11-13) Lucena, Poty Rodrigues de; Varela, José Arana; https://lattes.cnpq.br/1807399214239200; https://lattes.cnpq.br/8318844758415721
Ferroelectric materials have a vast application in modern industry as data storage devices. Some of this materials, as the ferroelectric oxides class ABO3, have phase transitions with the alteration of of the lattice modifiers concentration ("A"). The aim of this work was to study the tetragonal to cubic phase transition in (Pb,Ca)TiO3 ferroelectric solid solution with a experimental and theoretical view point. The powders and thin films were achieved by the polymeric precursor method and characterized by X ray diffraction, Raman spectroscopy, capacitance vs voltage and capacitance vs frequency electrical measurements on thin films. The theoretical results were obtained by periodic quantum-mechanical calculations of (Pb,Ca)TiO3 structure in discrete compositions, applying the density functional theory (DFT) for the calculations in CRYSTAL98r code. The comparison of theoretical and experimental results pointed that the solid solution starts from a ferroelectric tetragonal structure to a paraelectric cubic structure with the increase of calcium relative content and, albeit cubic in calcium concentrations above 40%, the perovskite structure conserve a local disorder of titanium atom in the perpendicular direction relative to the unit cell z axis. This local disorder was confirmed by the appearing of characteristics vibrational modes in Raman spectrum of the oxide powders of the higher symmetry. The theoretical results suggest that Ti-O bonds in the oxides posses a great influence in the unit cell electronic densities distribution. The X-ray diffraction profiles of (Pb,Ca)TiO3 reveal that the relative intensities of (hkl) plans of tetragonal structure obeys a first order exponential decay function with the increase of calcium concentration on the PbTiO3 structure. The ferroelectric experiments in thin films show a decrease of relative dielectric permittivity with calcium incorporation due the structural modifications imposed by alkaline cation increase. The thin films displayed formation of space charges, perceived in the degradation of capacitance vs voltage profile in low application frequencies of the reversal electric field.
Programa de habilidades sociais em situação natural de trabalho de pessoas com deficiência : análise dos efeitos
(Universidade Federal de São Carlos, 2006-11-13) Campos, Juliane Aparecida de Paula Perez; Almeida, Maria Amélia; https://lattes.cnpq.br/3169299095370522
Some social skills are crucial to contribute to friendship formation, social support and work satisfaction; moreover, the social skilled behaviors have been identified as a pre requisite for workers with disabilities to have a good performance and to maintain their jobs in the competitive world. The main objective of the present research was to elaborate, to apply and to analyze the effects of a Social Skills Program for Work (PHST) with workers with physical and mental deficiency in natural work situations. The selection of the participants took place after a initial study about the instrument construction on social abilities. The selected workers to participate in this study were one female and two males, with ages ranging from 21 to 36 years old. In order to characterize the selected participants it was used a questionnaire about professional performance and a structured interview. In order to achieve the study objective, a multiple probe design was employed baseline, intervention and probes), being the PHST the independent variable and the quality of performance on social skills was the dependent variable evaluated by the instrument: PRQDHS: Protocol to register the level of performance quality on social skills throughout the experimental design. The results indicated a gradual increase in the performance of social skills, such as: to question if there were things to do; to offer and ask for help; to talk about personal needs. Those aspects were worked with participants and their job colleagues. Since this area is nationally still under investigation, other studies are suggested as well as a training of the job colleagues in the promotion of social repertoires of workers with deficiency