Práticas pedagógicas para a construção do conceito de número: o que dizem os documentos do arquivo Lucília Bechara Sanchez?

Disponível em: https://www.fe.unicamp.br/revistas/ged/zetetike/article/view/4358Este texto apresenta os resultados de pesquisa que investigou as práticas pedagógicas para o ensino do conceito de número. O trabalho situa-se no que é possível denominar “era cognitivista no ensino de matemática” (1960-1980). Levou-se em conta o Arquivo Lucília Bechara Sanchez – APLBS – como fonte de pesquisa, para dar resposta à seguinte questão: De que modo o Movimento da Matemática Moderna – MMM – concretizou propostas para o ensino do conceito de número nas séries iniciais

Electrochemical characterization of YSZ thick films deposited by dip-coating process

Yttria stabilized zirconia (YSZ, 8% Y2O3) thick films were coated on dense alumina substrates by a dip-coating process. The suspension was obtained by addition of a polymeric matrix in a stable suspension of commercial YSZ (Tosoh) powders dispersed in an azeotropic mixture MEK–EtOH. The suspension composition was improved by the addition of YSZ Tosoh particles encapsulated by zirconium alkoxide sol containing yttrium nitrate which are the precursors of the 8-YSZ oxide. This optimal formulation allowed preparing, via a dip-coating process, thick films which were, after thermal treatment, homogeneous, dense and crack-free. A specific method was performed to measure the electrical conductivity, i.e. to determine the ionic conductivity of the film: it uses the four-point probe technique combined with ac impedance spectroscopy. The good agreement between the classical two-electrode measurements performed on YSZ pellets and the four-electrode ones performed on YSZ films allows concluding that this method is relevant for characterizing the transport properties of thick films

Cléopâtre dans les tragédies françaises de 1553 à 1682 (Une dramaturgie de l'éloge)

Dernière reine d Égypte, Cléopâtre est, en France, la première héroïne de tragédie. Présentée comme un monstre de débauche et d ambition par les auteurs latins, elle devient une figure majestueuse et digne sur la scène : la dramaturgie humaniste naît sous le signe de l éloge.L entrelacement des thèmes et des motifs, la composition des pièces ainsi que le travail stylistique et rhétorique des dramaturges mettent en place un tribunal où est instruit le procès de Cléopâtre, l étrangère, la femme fatale qui a déjà séduit César et qui, responsable d Actium, précipite la mort de Marc Antoine. Mais le suicide de la reine est mis en valeur par le recours au dénouement étendu, instrument dramaturgique au service d une logique d héroïsation. Ainsi réhabilitée dans le théâtre humaniste et classique , la figure de Cléopâtre illustre à merveille la définition du héros tragique.Cleopatra, the last queen of Egypt, is the first heroine of tragedy in France. Depicted by Latinauthors as a debauched and ambitious monster, she became a lofty and dignified figure onstage: thus was born humanist dramaturgy under the sign of eulogy. The interlacing ofthemes and topics, the composition of the plays together with the stylistic and rhetorical workof the playwrights set up a court where is conducted the trial of Cleopatra, the foreigner, thefemme fatale who had seduced Caesar and who, responsible for the defeat of Actium,hastened Mark Antony s death. But the suicide of the queen is enhanced by the use of theextended outcome, a dramatic instrument serving a logic of heroizing. Thus cleared of hermisdeeds in the humanist and "classic" theatre, the figure of Cleopatra marvelouslyillustrates the definition of the tragic heroAVIGNON-Bib. numérique (840079901) / SudocSudocFranceF

Do not forget the electrochemical characteristics of the membrane electrode assembly when designing a Proton Exchange Membrane Fuel Cell stack

International audienceThe membrane electrode assembly (MEA) is the key component of a PEMFC stack. Conventional MEAs are composed of catalyzed electrodes loaded with 0.1-0.4 mgPt cm−2 pressed against a Nafion® membrane, leading to cell performance close to 0.8 W cm−2 at 0.6 V. Due to their limited stability at high temperatures, the cost of platinum catalysts and that of proton exchange membranes, the recycling problems and material availability, the MEA components do not match the requirements for large scale development of PEMCFs at a low cost, particularly for automotive applications. Novel approaches to medium and high temperature membranes are described in this work, and a composite polybenzimidazole-poly(vinylphosphonic) acid membrane, stable up to 190 ◦C, led to a power density of 0.5 W cm−2 at 160 ◦C under 3 bar abs with hydrogen and air. Concerning the preparation of efficient electrocatalysts supported on a Vulcan XC72 carbon powder, the Bönnemann colloidal method and above all plasma sputtering allowed preparing bimetallic platinum-based electrocatalysts with a low Pt loading. In the case of plasma deposition of Pt nanoclusters, Pt loadings as low as 10 g cm−2 were achieved, leading to a very high mass power density of ca. 20 kW g−1 Pt . Finally characterization of the MEA electrical properties by Electrochemical Impedance Spectroscopy (EIS) based on a theoretical model of mass and charge transport inside the active and gas diffusion layers, together with the optimization of the operating parameters (cell temperature, humidity, flow rate and pressure) allowed obtaining electrical performance greater than 1.2 W cm−2 using an homemade MEA with a rather low Pt loading

Electromodulated infrared spectroscopy of methanol electrooxidation on electrodispersed platinum electrodes: Enhancement of reactive intermediates

EMIRS spectra of the surface species resulting from methanol electrosorption on electrodispersed Pt were obtained by working under a wide range of experimental conditions, i.e. electrode roughness factor, methanol concentration and mean modulation potential. The intensity of the absorption band related to linearly adsorbed CO-species, COL, at ca. 2030–2080 cm−1 decreases on increasing the electrode roughness factor, a fact which is interpreted as a decrease in the CO adsorbate poisoning effect on electrodispersed Pt surfaces. As a consequence, under well-defined conditions, several bands are observed which might be assigned to adsorbed intermediates and reactive species. EMIRS also reveals a competition between COB and COL at high surface coverages. Spectral data for methanol electrooxidation on electrodispersed electrodes correlate well with the expected structure of this type of electrode.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Egyenlőtlen Európa

A „Szociális Unió” témáján dolgozó magas szintű szakértő csoport zárójelentése 2015. tavasz, Brüsszel

Electromodulated infrared spectroscopy of methanol electrooxidation on electrodispersed platinum electrodes: Enhancement of reactive intermediates

EMIRS spectra of the surface species resulting from methanol electrosorption on electrodispersed Pt were obtained by working under a wide range of experimental conditions, i.e. electrode roughness factor, methanol concentration and mean modulation potential. The intensity of the absorption band related to linearly adsorbed CO-species, COL, at ca. 2030–2080 cm−1 decreases on increasing the electrode roughness factor, a fact which is interpreted as a decrease in the CO adsorbate poisoning effect on electrodispersed Pt surfaces. As a consequence, under well-defined conditions, several bands are observed which might be assigned to adsorbed intermediates and reactive species. EMIRS also reveals a competition between COB and COL at high surface coverages. Spectral data for methanol electrooxidation on electrodispersed electrodes correlate well with the expected structure of this type of electrode.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta