Navegando por Data de Publicação, começando com "2020-02-03"

Filtrar resultados por ano ou mês

Agora exibindo 1 - 5 de 5

Propriedades residuais de compósitos cimentícios de alto desempenho com pó de vidro submetidos a altas temperaturas
(Universidade Federal de São Carlos, 2020-02-03) Oliveira Júnior, Adalberto de; Castro, Alessandra Lorenzetti de; https://lattes.cnpq.br/8618479812591256; Ferreira, Fernanda Giannotti da Silva; https://lattes.cnpq.br/0329487394818763; https://lattes.cnpq.br/1428341266349960
High performance cementitious composites are a technological trend in Brazil and in the world due to their better rheological, mechanical, durability properties, and rational use of raw materials in relation to conventional cementitious composites. The use of supplementary materials, especially pozzolanic, allows obtaining composites with improved properties. Glass, which contains large amounts of amorphous silica in its composition, requiring relatively simple processing processes to obtain its powder, has potential for use as a pozzolanic material. Construction elements are subject to performance situations, including high temperatures. The high performance cementitious composite, which has inherent characteristics of high strength, tend to show greater fragility at high temperatures. This work seeks to investigate the mineralogical, microstructural, physical and mechanical properties of high performance cementitious composites with glass powder in partial replacement of cement, when subjected to high temperatures. To evaluate their properties, cementitious composites were made and characterized without and with the incorporation of glass powder in partial volumetric substitution to cement in the proportions of 10, 20 and 50%. The samples without and with glass powder were subjected to temperatures of 200ºC, 400ºC, 600ºC and 800ºC and their residual properties after cooling were evaluated. Samples heated to 800ºC were rehydrated by immersion in water for 56 days and characterized. The results of the rheological, physical and mechanical characterizations show that the incorporation of 10, 20 and 50% of glass powder results in composites with properties of workability, resistance and water absorption similar to the reference mixture, that is, without glass powder. , demonstrating the viability of glass powder as a pozzolanic material. At high temperatures, the physical and mechanical properties of the reference cementitious composite and with glass powder show similar results up to 400ºC. At temperatures of 600ºC and 800ºC, the differences are evident, with the glass powder mixture presenting a lower performance in compressive strength and higher in rigidity and porosity. Upon rehydration, the reference mixture recovered approximately 98% of its compressive strength and 75% of its stiffness, while the glass powder trace recovered approximately 32% in both properties due to the presence of non-rehydratable or low strength products such as wollastonite, melilite and aluminosilicate.
Retornos à educação no Brasil: uma abordagem de pseudo painel e viés de seleção amostral
(Universidade Federal de São Carlos, 2020-02-03) Hartze, Wilhelm Matheus; Ferro, Andrea Rodrigues; https://lattes.cnpq.br/3432809140419477; https://lattes.cnpq.br/9596171718211332
The goal of this work is to analyze the returns to education in the hourly wages in Brazil for the period of 2011 to 2015, last five years of PNAD data. Even thought the relationship between years of education and wages has been long studied, the accuracy of the results from traditional models like the Ordinary Least Squares are to be questioned due to the necessity to check the presence of group heterogeneity and sample bias. The hypothesis tested in this work is that there is significant effect from non observable factors that leads to biased estimators if not taken into account. By estimating a pseudo panel, through the creation of cohorts, it is seen that the group heterogeneity leads to underestimation of the returns to education from the WLS model. The sample bias also affects the magnitude of the coefficients, however, the two different models used to capture and correct the estimators present different results. The two step model reports smaller returns in comparison to the WLS benchmark, while the Maximum Likelihood model had mixed results.
Synthesis and graphitization of phenolic resins for carbon-containing refractory applications
(Universidade Federal de São Carlos, 2020-02-03) Talabi, Segun Isaac; Luz, Ana Paula da; https://lattes.cnpq.br/3470395641242374; Lucas, Alessandra de Almeida; https://lattes.cnpq.br/9754332336954137; https://lattes.cnpq.br/8467407863782789
Carbon-containing refractories’ (CCRs) present special chemical and thermomechanical properties, which depend on the presence of carbonaceous phase with a structure similar to those of graphite. However, phenolic resins that are commonly used as binder for such refractories produce amorphous carbon, which can limit their performance. Consequently, this research focused on the synthesis and graphitization of these resins under temperatures and conditions suitable for refractory production. In the study, some series of experiments were conducted to investigate the role of boron oxide, boric acid and ferrocene as graphitizing agent for phenolic resins under various processing conditions such as mixing technique and heating procedure. Both conventional (commercial and laboratory synthesized products) and lignin modified phenolic resins were considered. The resulting carbon samples were characterized using X-ray Diffractometer (XRD) to determine the amount of generated graphitic carbon after carbonization. Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) were also used to corroborate the information obtained from the XRD analysis. The results showed that these additives can induce crystalline carbons generation during pyrolysis depending on the resin chemistry and processing parameters. The mechanism leading to carbon crystallization was attributed to the formation of B‒O‒C bonds for the boron compounds modified resins. The B‒O‒C bonds has a lower binding energy (compared to C‒C), which permits the rotation/reorganization that is necessary for graphitic carbons production. Similarly, Fe3C acted as active sites for crystalline carbon generation during pyrolysis of the resins-ferrocene formulations. Thermogravimetric analysis (TGA) of the carbon samples show that several factors such as bond strength, composition and atoms arrangement control their oxidation resistance. Moreover, the prepared CCR castables show improved oxidation resistance based on in-situ graphitization of the binder component.
Microplásticos: impacto ambiental de polímeros fotodegradados
(Universidade Federal de São Carlos, 2020-02-03) Moreira, Ana Carolina Cugler; Mancini, Sandro Donnini; https://lattes.cnpq.br/5091149098462301; Waldman, Walter Ruggeri; https://lattes.cnpq.br/0616238673458322; https://lattes.cnpq.br/3186005447606808
Plastics have been studied for their environmental impact, since when discarded in the environment they do not disappear. Over time they degrade and fragment into smaller pieces, reaching the microscale. When exposed to sunlight these materials can photodegrade, generating fragments that can be consumed by animals, either directly when confused with food or indirectly when they ingest contaminated food/animals. One way to verify and quantify the microplastics (MP) present in marine animals and invertebrate is through advanced oxidative processes (AOP). AOPs are mainly used in oxidation of persistent contaminants, but they have been used to separate organic matter and plastic fragments because of their oxidative power. In order to verify if the AOPs aggravate in some way the fragmentation of degraded polymer, it was proposed to analyze the interaction between AOPs, such as Fenton reaction and alkaline solution, and polymer samples with different photodegradation levels. Superficial changes were observed in some samples with advanced degradation levels, with higher carbonyl concentrations. Comparing the level of degradation, samples with higher carbonyl concentration showed variations post-tested, while samples without or withlow concentration of carbonyl showed no variations. With these results it was possible to confirm the interaction of some AOPs with photodegraded materials and, therefore, that this type of analysis can interfere with the amount of fragments obtained after chemical digestion of marine animals and/or invertebrate. This result helps to put into perspective the research done with invertebrates that had degraded polymers as part of their diet, since there may be an incorrect extrapolation in the amount of MP present in these animals.
Composição de formação: narrativas (auto)biográficas como acordes do formador-professor
(Universidade Federal de São Carlos, 2020-02-03) Schiavon, Tatiana de Camargo; Sant'Ana, Izabella Mendes; lattes.cnpq.br/7860235863062183; https://lattes.cnpq.br/9626264926154468
The field of formation of the trainer is a recent theme and still little investigated in the educational literature, which justifies the importance of this study. This work is configured as a research-training, because when performing the research one can live in itself the transformations mediated by the reflexive movement lived, as well as the awareness of the performance as teacher trainers, from the dialogy between the act of self-forming and ecoforming, recognizing the conviviality with the group and with the context. We sought, therefore, to answer the question: How do the teacher trainer training processes take place from the perspective of continued training from the dialogy between the act of training teachers and graduating? How does he act? How do you become a trainer? In view of the problem, the objectives aimed to know the profile of the trainers and the reasons that led them to constitute trainers; identify convergences and divergences in the relationship with the constitution of themselves in the lived experience, as well as to know the marks that integrate the process of forming and/or (self-forming), enabled a comprehensive and interpretative analysis of this process. With this, biographical (auto)biographical narratives were used, from the biographical studio device of the project, which underwent some alterations in order to potentiate the reflections. As theoretical and methodological input, Delory-Momberger (2006, 2011, 2012, 2014), Passeggi (2006, 2008, 2011, 2016), Josso (2002, 2007, 2008), among others, was used. The information obtained indicates that the group's formation movement covered cultural, social and political aspects, which mobilized the processes of learning to learn, which points to a need for training through the experiences lived, as well as the finding of a permanent formation in the face of the conjuncture of relationships that are established in intersubjectivity. The use of the biographical studio device of project made it possible to raise awareness of the group, leading participants to think about the constant learning to learn about themselves, which opportunistic one look not only at the path of learning itself, but of the other, in acting as teacher trainers. It results in a recognition that the trainer needs to be attentive to the needs of teachers and the context in which they act, in order to enable moments and spaces of reflection on the trajectories, finding strategies to problematize the various experiences so that they consolidate themselves in meanings, providing the other to experience in themselves processes of resignification that he himself lived. Keywords: formation of trainers; research-training; methodology (auto)biographical