Residual-based localization and quantification of peaks in x-ray diffractograms

We consider data consisting of photon counts of diffracted x-ray radiation as a function of the angle of diffraction. The problem is to determine the positions, powers and shapes of the relevant peaks. An additional difficulty is that the power of the peaks is to be measured from a baseline which itself must be identified. Most methods of de-noising data of this kind do not explicitly take into account the modality of the final estimate. The residual-based procedure we propose uses the so-called taut string method, which minimizes the number of peaks subject to a tube constraint on the integrated data. The baseline is identified by combining the result of the taut string with an estimate of the first derivative of the baseline obtained using a weighted smoothing spline. Finally, each individual peak is expressed as the finite sum of kernels chosen from a parametric family.Comment: Published in at http://dx.doi.org/10.1214/08-AOAS181 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Mídias Sociais e Administração Pública: Análise do sentimento social perante a atuação do governo federal brasileiro

Este estudo procurou identificar como a análise de sentimento, baseada em textos extraídos de mídias sociais, pode ser um instrumento de mensuração da opinião pública sobre a atuação do governo de forma a contribuir para a avaliação da administração pública. Trata-se de um estudo aplicado, interdisciplinar, exploratório, qualitativo e quantitativo. Foram revisadas as principais formulações teóricas e conceituais acerca do tema e realizadas demonstrações práticas, utilizando-se uma ferramenta de mineração de opinião que proporcionou precisão satisfatória no processamento de dados. Para fins de demonstração, foram selecionados temas que motivaram a realização da onda de protestos que envolveu milhões de pessoas no Brasil em junho de 2013. Foram coletadas, processadas e analisadas, aproximadamente, 130.000 mensagens postadas no Facebook e no Twitter sobre esses temas em dois períodos distintos. Por meio desta investigação, observou-se que a análise de sentimento pode revelar a opinião polarizada dos cidadãos quanto à atuação do governo

DMFC: galvanic or electrolytic cell?

We report measurements of local current distribution in a direct methanol fuel cell with single straight channels and segmented electrodes. The experiments directly confirm the existence of a bifunctional regime of DMFC operation: at low air flow rate the segments located close to the inlet of the oxygen channel generate current (galvanic domain), while the other segments consume current to produce hydrogen (electrolytic domain). The cell voltage in this regime in not a single-valued function of current in the external load. The electrolytic domain disappears at a critical air flow rate, which does not depend on current in the cell. We show that a model (A.A. Kulikovsky, Electrochem. Commun. 6 (2004) 1259) explains this critical behavior. Finally, we extend the method of measurement of methanol crossover rate suggested by Ye and Zhao (J. Electrochem. Soc. 152 (2005) A2238) to the case of arbitrary current in the load. (c) 2006 Elsevier B.V. All rights reserved

Measurement of the current distribution in a direct methanol fuel cell - Confirmation of parallel galvanic and electrolytic operation within one cell

Current production in fuel cells is typically unequally distributed along the cell surface due to inhomogeneous concentration of reactants and temperature. The inhomogeneities in fuel cells can result in reduced output power and accelerated ageing. To quantify the inhomogeneities a measurement system has been developed which allows measuring the local distribution of current and temperature in hydrogen and direct methanol fuel cells. With this system we are able to directly observe the coexistence of galvanic and electrolytic domains in a single channel direct methanol fuel cell (the electrolytic domain is the domain where electrolysis occurs in contrast to the galvanic domain where the fuel cell process takes place). The measurement device also allows for the measurement locally resolved impedance spectra. (c) 2007 Elsevier B.V. All rights reserved