994 resultados para 0-6 años


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Experimental studies on phase equilibria in the multi-component system PbO-ZnO-CaO-SiO2-FeO-Fe2O3 in air have been conducted to characterize the phase relations of a complex slag system used in the oxidation smelting of lead and in typical lead blast furnace sinters. The liquidus in two pseudoternary sections ZnO-Fe2O3-(PbO + CaO + SiO2) with the CaO/SiO2 weight ratio of 0.1 and the PbO/(CaO + SiO2) weight ratio of 6.2, and with CaO/SiO2 weight ratio of 0.6 and the PbO/(CaO + SiO2) weight ratio of 4.3, have been constructed.

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We present new measurements of the luminosity function (LF) of luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS) and the 2dF SDSS LRG and Quasar (2SLAQ) survey. We have carefully quantified, and corrected for, uncertainties in the K and evolutionary corrections, differences in the colour selection methods, and the effects of photometric errors, thus ensuring we are studying the same galaxy population in both surveys. Using a limited subset of 6326 SDSS LRGs (with 0.17 < z < 0.24) and 1725 2SLAQ LRGs (with 0.5 < z < 0.6), for which the matching colour selection is most reliable, we find no evidence for any additional evolution in the LRG LF, over this redshift range, beyond that expected from a simple passive evolution model. This lack of additional evolution is quantified using the comoving luminosity density of SDSS and 2SLAQ LRGs, brighter than M-0.2r - 5 log h(0.7) = - 22.5, which are 2.51 +/- 0.03 x 10(-7) L circle dot Mpc(-3) and 2.44 +/- 0.15 x 10(-7) L circle dot Mpc(-3), respectively (< 10 per cent uncertainty). We compare our LFs to the COMBO-17 data and find excellent agreement over the same redshift range. Together, these surveys show no evidence for additional evolution (beyond passive) in the LF of LRGs brighter than M-0.2r - 5 log h(0.7) = - 21 ( or brighter than similar to L-*).. We test our SDSS and 2SLAQ LFs against a simple 'dry merger' model for the evolution of massive red galaxies and find that at least half of the LRGs at z similar or equal to 0.2 must already have been well assembled (with more than half their stellar mass) by z similar or equal to 0.6. This limit is barely consistent with recent results from semi-analytical models of galaxy evolution.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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In this work, Pr0.6Sr0.4FeO3-δ -Ce0.9Pr0.1O2-δ (PSFO-CPO) nanofibers were synthesized by a one-step electrospin technique for use in intermediate-temperature solid oxide fuel cell (IT-SOFC) applications. PSFO-CPO nanofibers were produced with a diameter of about 100nm and lengths exceeding tens of microns. The thermal expansion coefficient (TEC) matches with standard GDC electrolytes and the resulting conductivity also satisfies the needs of IT-SOFCs cathodes. EIS analysis of the nanofiber structured electrode gives a polarization resistance of 0.072Ωcm2 at 800°C, smaller than that from the powdered cathode with the same composition. The excellent electrochemical performance can be attributed to the well-constructed microstructure of the nanofiber structured cathode, which promotes surface oxygen diffusion and charge transfer processes. All the results imply that the one-step electrospin method is a facile and practical way of improving the cathode properties and that PSFO-CPO is a promising cathode material for IT-SOFCs.

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Cobalt-free composite cathodes consisting of Pr0.6Sr0.4FeO 3-δ -xCe0.9Pr0.1O 2-δ (PSFO-xCPO, x = 0-50 wt%) have been synthesized using a one-pot method. X-ray diffraction, scanning electron microscopy, thermal expansion coefficient, conductivity, and polarization resistance (R P ) have been used to characterize the PSFO-xCPO cathodes. Furthermore the discharge performance of the Ni-SSZ/SSZ/GDC/PSFO-xCPO cells has been measured. The experimental results indicate that the PSFO-xCPO composite materials fully consist of PSFO and CPO phases and posses a porous microstructure. The conductivity of PSFO-xCPO decreases with the increase of CPO content, but R P of PSFO-40CPO shows the smallest value amongst all the samples. The power density of single cells with a PSFO-40CPO composite cathode is significantly improved compared with that of the PSFO cathode, exhibiting 0.43, 0.75, 1.08 and 1.30 W cm-2 at 650, 700, 750 and 800 °C, respectively. In addition, single cells with the PSFO-40CPO composite cathode show a stable performance with no obvious degradation over 100 h when operating at 750 °C.

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El propósito de este artículo es, a través de un profundo análisis de recopilación, recoger la información relevante en relación con la habilidad básica del giro, enmarcando dicha información dentro de la etapa infantil y centrándose especialmente en la evolución que sigue la misma con el desarrollo del niño. Este trabajo se puede concluir con la necesidad de realizar más estudios sobre esta habilidad básica, especialmente en la etapa infantil, donde su tratamiento es muy escaso.

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En este proyecto está prevista la realización de una "investigación-intervención", que se llevará a cabo siguiendo el modelo del Project Cycle Management. En la fase de análisis se ha llegado a identificar los ámbitos de intervención y de investigación que, en nuestro caso, a partir del árbol de objetivos ha sido identificado como una acción prioritaria en la formación de educadores / enseñantes, que también influye en el ámbito del uso de los espacios escolares

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En este proyecto está prevista la realización de una "investigación-intervención", que se llevará a cabo siguiendo el modelo del Project Cycle Management. En la fase de análisis se ha llegado a identificar los ámbitos de intervención y de investigación que, en nuestro caso, a partir del árbol de objetivos ha sido identificado como una acción prioritaria en la formación de educadores / enseñantes, que también influye en el ámbito del uso de los espacios escolares

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En este proyecto está prevista la realización de una "investigación-intervención", que se llevará a cabo siguiendo el modelo del Project Cycle Management. En la fase de análisis se ha llegado a identificar los ámbitos de intervención y de investigación que, en nuestro caso, a partir del árbol de objetivos ha sido identificado como una acción prioritaria en la formación de educadores / enseñantes, que también influye en el ámbito del uso de los espacios escolares