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Estudo da eletro-oxidação de moléculas orgânicas pequenas sobre multicamadas metálicas Ptpc/Rh/Pt e Ptpc/Ru/Pt utilizando FTIR in situ
(Universidade Federal de São Carlos, 2018-09-06) Silva, Camila Daiane Ferreira da; Souza, Ernesto Chaves Pereira de; https://lattes.cnpq.br/1505400360366643; https://lattes.cnpq.br/8646821920462899
The modification of platinum-based electrodes for the efficiency optimization of the fuel cells has generated a great scientific interest, due to the problems associated with the poisoning of the catalytic surface. In addition, the use of renewable fuels is an important advantage for these systems by associating the high performance of the electric motors with the low emission of pollutants. In this way, the scientific community has studied numerous materials such as alloys and multilayer metallic structures (MM), and fuels as small organic molecules. In this work, Ptpc/M/Pt metallic multilayers were developed, in which rhodium or ruthenium was used as an intermediate layer, and their catalytic activities were investigated for the methanol and ethanol electro-oxidation in acid medium. For this purpose, cyclic voltammetry (VC) and in situ infrared spectroscopy (in situ FTIR) were used. In addition, the behavior and catalytic activity of MM Ptpc/Rh/Pt for the methanol electro-oxidation in alkaline medium using VC was evaluated. In acid medium, the compositions Ptpc/Rh2,0/Pt1,0 and Ptpc/Ru5,0/Pt2,0 presented increases of 283% and 422%, respectively, in the peak current density compared to Ptpc for the methanol oxidation and 32% and 67%, respectively, for the ethanol electro-oxidation. Using FTIR in situ, the appearance of a band at ~ 2340 cm-1, attributed to CO2, which is the total oxidation product of the alcohols, was observed. In alkaline medium, Ptpc/Rh2,0/Pt1,0 had an increase in the current density of 70% compared to Ptpc. Therefore, the addition of rhodium and ruthenium as intermediate layers promoted an improvement in the catalytic activity compared to Ptpc, probably by altering the electronic configuration of the platinum or improving the bifunctional effect.
Plataforma Khan Academy: uma análise de suas potencialidades na visão de professores do Ensino Fundamental I de um município do interior de São Paulo
(Universidade Federal de São Carlos, 2018-09-06) Duarte, Priscila Vandrea Camargo; Onofre, Márcia Regina; https://lattes.cnpq.br/7176529351192598; https://lattes.cnpq.br/2774473522034136
This research aimed the analysis of the potential use of the Khan Academy platform in the perspective of Elementary School I teachers from the education system in the inner state of São Paulo. The relevance of this research moves towards the unveiling of the universe of studies and researches concerning the challenges and perspectives of blended teaching, as well as to investigate the contribution of integrated experiences and active methodologies as tools and alternative ways to improve teachers’ actions and, consequently, the students learning process. This qualitative research was conducted by online questionnaires containing open and closed questions to (25) twenty-five Elementary school teachers of the municipal education system which has been investigated through sampling, and (1) one professional responsible for the platform deployment in the city, identifying the knowledge concerning the set of themes, its resources and strategies, possibilities of application, the tool limits and ranges as well as the achieved results. The presented data show an identity profile of teachers aged 26 to 45; married in their majority, and with a degree, being a total of (13) thirteen experts and (1) one with a professional Master’s Degree. They are teachers with over 8 years of experience in teaching, with a weekly schedule from 35 to 40 working hours, working during the first years of Elementary School with 3rd and 5tg grades. Regarding the answers related to teachers’ experience with the Khan Academy platform, data revealed that most teachers had from 6 (six) months to 2 (two) years or more using the tool; they were responsible for preparing classes on the platform; they dedicated from 1 to 3 working hours with students; also had an awareness of active methodologies and used different methods in classes because they believed the tool contributed to students learning process; integrated technologies were applied to the syllabus and allowed students to interact with different tools developing learning; cooperation during group activities and the interest in learning by gamification; they highlight that, while using blended teaching, it is necessary to rethink the organization of the classroom and the pedagogical plan elaboration making learning closer to the students’ reality. Although the platform represents an important tool before the current demands of technology and learning in face of a new social model, effective actions to its improvement are necessary and, consequently, the participation of teachers in the process of these activities; construction in the formative processes; and in the mediation with students. This is a collective action which must start from the students' needs, reflect on them to search alternative ways which guarantee a meaningful learning for all.
Descoberta de preços e especulação no mercado de milho brasileiro
(Universidade Federal de São Carlos, 2018-09-06) Raniro, Luisa Rasera; Cruz Júnior, José César; https://lattes.cnpq.br/0086426315229286; https://lattes.cnpq.br/9231847375086915
University of São Carlos, Sorocaba, 2018. Since the 2000s, several changes occurred in the Brazilian and international corn markets. In Brazil, due primarily to the increasing importance of the winter crop, the central-west region became the main corn producer in the country, overcoming the South, the main summer crop producer. On the international market, the increase in demand for the commodity - mainly in the Chinese and U.S. markets - also changed the behavior of prices worldwide. Based on all the aforementioned changes, we analyzed prices relationships in the corn spot and futures markets in the south and central-west regions of Brazil, between 2004 and 2016. We used various price discovery measures to find that Brazilian corn futures market leads the price information in the country. Our analysis for the spot market indicates that the South, represented by the production region of Cascavel, shows the highest share of price information, and therefore can be considered the primary reference in the price discovery process. However, we found that this result was not consistent, as the region of Rio Verde in the Center-West was the benchmark in the price discovery process during the period when summer crop production was higher than winter crop production (prior to 2011). We analyzed short-term price relationships using the Generalized Supremum Augmented Dickey-Fuller (GSADF) test to identify periods of speculative bubbles. Our results indicated the occurrence of several explosive episodes in all markets. In most cases such episodes were short-lived (lasting less than seven days), with differing characteristics, and had periods of both positive and negative bubbles. In addition, we identified periods when bubbles occurred simultaneously in all markets. This result indicates that there may also be a relationship between regional price volatilities. We expect that our results can be useful for those looking for references in price formation, and for improving commodity trading strategies in the cash market. In addition, once a bubble period is identified, traders can possibly use our results to build their expectations regarding the duration of bubbles and the average price variation (increase and decrease) within a bubble period.