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Ligas multicomponentes produzidas a partir de cavacos de Ti e/ou materiais com pureza comercial para armazenagem de hidrogênio
(Universidade Federal de São Carlos, 0026-02-20)
Ferraz, Mariana de Brito
;
Zepon, Guilherme
;
https://lattes.cnpq.br/7924187202036614
;
https://lattes.cnpq.br/5414167939699652
;
Mazzer, Eric Marchezini
This work aims to investigate multicomponent alloys for hydrogen storage through the formation of metal hydrides, using titanium alloy scrap (Ti Grade 2 – ASTM F67 and Ti6Al4V-ELI – ASTM F136) and commercially pure metallic elements, with the goal of obtaining more sustainable materials in terms of the environmental impact of raw materials. Initially, the Ti-V-Nb-Cr system was studied by replacing high-purity Ti with Ti6Al4V-ELI scrap, resulting in the Ti18Nb23V24Cr33Al2 alloy, whose major phase exhibits a body-centered cubic (BCC) structure. The presence of Al and the lower Ti content increased the equilibrium pressure and reduced hydride stability compared to the reference alloy (TiVNb)65Cr35, produced from high-purity elements. Nevertheless, the recycled alloy showed a hydrogen storage capacity of 2.7 wt.% H at room temperature and improved cyclic stability. To further reduce the carbon footprint, vanadium was eliminated from the composition, as primary V presents the highest CO2-equivalent emissions in the Ti-V-Nb-Cr system. Alloys from the T-Nb-Cr system were then developed using Ti Grade 2 and Ti6Al4V-ELI scrap. The Ti33Nb33Cr33 and Ti32Al2V1Nb37Cr28 alloys exhibited predominantly BCC microstructures, with a fraction of C15Laves phase, and hydrogen storage capacities between 2.25 and 2.5 wt.% H. CO2 emissions associated with raw materials were reduced by approximately 30% after removing V from the composition. Finally, the Ti15Zr17Fe22Mn21Cr22Al2V1 alloy, produced from Ti6Al4V-ELI scrap and commercial elements, was investigated. This alloy formed a C14 Laves phase and exhibited a hydrogen storage capacity of 1.2 wt.% H, with excellent reversibility at room temperature. Despite the lower capacity, the emissions associated with its raw materials were only 1.3 kg CO2-eq, corresponding to reductions of 89% and 80% compared to the Ti-V-Nb-Cr and Ti-Nb-Cr systems, respectively.
A antipedagogia de Tolstói na educação infantil
(Universidade Federal de São Carlos, 0028-11-25)
Camargo, Isabela Ferreira da Silva
;
Martins, Marcos Francisco
;
https://lattes.cnpq.br/4515924584428591
;
https://orcid.org/0000-0002-8220-2030
;
https://lattes.cnpq.br/2554863459380617
This final project focuses on the reflective exploration and research of the pedagogical experiences of Yasnaya Polyana, seeking to identify the aggregative and applicable possibilities that the pedagogical framework constructed by Tolstoy can offer to contemporary Brazilian early childhood education, with a view to enabling more humane and emancipatory teaching practices. The project employed a methodological bibliographic collection process of various textual genres, expanding the boundaries of traditional academic and scientific sources. The primary sources used were literary, didactic, religious, and other critical works by Tolstoy, in national and foreign languages, as well as those of commentators, who comprise a limited universe. The work concluded that Tolstoy and Russian education possess a rich historical and cultural heritage, whose analysis and reflection, especially on the experience developed in Yasnaya Polyana, can favor the development of new educational approaches and practices in our current reality.
O aprendizado em saúde mental durante as diferentes etapas da graduação de medicina: uma narrativa crítico-reflexiva
(Universidade Federal de São Carlos, 0029-10-25)
Ilhesca, Milena Sandri
;
Martini, Larissa Campagna
;
https://lattes.cnpq.br/8969823407559809
;
https://lattes.cnpq.br/6322541815489822
This paper presents a critical-reflective analysis of the author's medical degree from 2020 to 2025, from the perspective of her experiences with the topic of mental health. The methodology for this work is based on a qualitative analysis of documentary records developed by the author throughout her undergraduate studies. The results, presented in narrative form, highlight the importance of the subject in question and its application across the different undergraduate cycles. They also address the impact of the COVID-19 pandemic - which the author experienced throughout her undergraduate studies - on her desire to delve deeper into the subject. Finally, it explains how these lessons were incorporated into the author's professional practice and personal life, highlighting the impact of the topic beyond the medical field.
Trajetória na medicina UFSCar: uma narrativa reflexiva
(Universidade Federal de São Carlos, 0029-10-25)
Bueno, Lucas Ferreira de Godoy
;
Martini, Larissa Campagna
;
https://lattes.cnpq.br/8969823407559809
The Medical School at UFSCar is based on active learning methodologies applied to medical graduate programs, combining theory with field practice, prioritizing an early approach in healthcare services, a horizontal relationship between professors and students, and continuous reflection in the teaching-learning process. From this perspective, this course completion project aims to reflect on this author's trajectory in the Medical School at the Federal University of São Carlos (UFSCar) through the years 2020 and 2025, based on the principles of the 2007 Pedagogical Project - in effect during this author's undergraduate studies -, and complementing with the new 2025 Pedagogical Project.
Vivências em um curso de medicina durante a pandemia de COVID-19
(Universidade Federal de São Carlos, 0029-10-25)
Rodrigues, Amanda Ponce
;
Martini, Larissa Campagna
;
https://lattes.cnpq.br/8969823407559809
This final paper aims to report the experiences faced during the Medical graduation course at the Federal University of São Carlos (UFSCar) by a student of the XV class, between 2020 and 2025, focusing on the obstacles caused by the Covid-19 pandemic. The social isolation, whether academical or interpersonal, the fear of contamination and the experience of death and grief were the pillars of this dark times, impacting not only the lives, but also the mental and physical health of many students. Furthermore, the delay in returning to the practical activities, as recommended by the political-pedagogical project of the Medicine Department, and the risks involved in said return, caused great psychic impairment. However, the shared coping of said obstacles, the resilience and the empathy, tools used to build a repertoire of skills to solve problems and manage frustration, were positive and welcomed results of such a terrible historical event. Equipped with these experiences and emotional instruments, I now finish the Medical graduation with the expectation of not having to face such a barrier evermore, and if it so comes to be necessary, then let it be with better strategy and easiness, with greater knowledge, skills and attitudes.
A dimensão pedagógica na atuação do diretor de escola pública de primeiro e segundo graus
(Universidade Federal de São Carlos, 1988)
Cury, Diana
;
Mizukami, Maria da Graça Nicoletti
This work is characterized as an analytical descriptive study that investigates, in the context of public elementary and high schools in the city of São Carlos, São Paulo, Brazil, the possible conditions for the lack of commitment of school principals to the pedagogical dimension of their role. The research was motivated by the author's observation of an antagonistic situation in the performance of these professionals: on the one hand, the need for a pedagogical posture from the school principal that enables the execution of the teaching-learning process; on the other hand, the resistance, manifested by these professionals in their daily lives, in assuming the pedagogical dimension of their role. The subjects of this investigation were 32 school principals of the public elementary and high schools network of the state of São Paulo, from the cities linked to the São Carlos education department. A questionnaire consisting predominantly of open-ended questions related to the problem investigated was used as the instrument for data collection. Data analysis was performed by considering groups of statements with similar meanings configured in response classes quantified as percentages. This analysis includes both the academic and post-academic training of school principals and their conceptions, opinions, explanations and/or justifications in relation to the problem investigated; the intra- and extra-school requests made to them and the predictions and alternative proposals expressed by these professionals. The results obtained confirm the antagonistic situation identified. School principals acknowledge the importance and need for their pedagogical work in order to make the teaching-learning process viable in their schools, but they do not assume, in their daily school life, the pedagogical dimension of their work. The possible conditions for the lack of commitment to the pedagogical dimension of their role were revealed, according to the reports of school principals, to be of diverse natures and levels: excess of tasks performed, division and fragmentation of daily activities, constant and diverse requests both within and outside the school, failure to fill modules with the consequent reduction of professionals needed by schools, minimal and sometimes non-existent decision-making power and lack of direct participation in proposals for curricular change and/or pedagogical innovations.
Preparação e caracterização do catalisador óxido misto de cobre-zinco-alumínio, obtido via complexação (processo citrato), para a transformação do etanol a acetato de etila
(Universidade Federal de São Carlos, 1991-07-02)
Reis, Rubem da Cunha
;
Bueno, José Maria Corrêa
;
https://lattes.cnpq.br/0157452280626031
;
https://lattes.cnpq.br/7399042394479529
Cu-Zn-Al mixture oxides catalysts with atomic ratios r-Cu/Zn=3,0 and R=Cu+Zn/Al=1,2 were obtained by means of citric complexing method. The influence of citric acid content was studied varying P=(eq.citric acid/Eq.metal) between 0,7-1,5 and the calcination temperature from 400 to 700°C in the precursors. Precursors and oxides were characterized by IR, TDA, TGA, XRD, SBET, TPR, SCU and SEM. The thermal decomposition of the precursors was studied in N2 and air atmosphere. The X-rays diphratograms of the calcinated oxides presented two cristallite phases: CuO and ZnAl2 04. The TPR curves showed an increment of CuO phase segregation as the calcination temperature was increased. The catalytic activity of this system was checked through the direct transformation of ethanol varying contact tim e and reaction temperature. It was verified that the catalysts presented decreasing activity for ethyl acetate when Cuo segregation increased.
Resistividade elétrica de cerâmicas de alumina a temperatura ambiente e a 600oC
(Universidade Federal de São Carlos, 1992-03-10)
Kawasaki, Jorge Massato
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Paulin Filho, Pedro Iris
;
https://lattes.cnpq.br/9542027656569433
;
https://lattes.cnpq.br/2259221412556239
Alumina (Al2O3) ceramic specimens have been prepared via traditional ceramic process, namely, powder analyses, classification and conditioning, uniaxial cold pressong and sintering. DC electrical resistivity measurements has been carried out at RT and 600oC. A tubular resistive furnace with an alumina sample chamber with platinum leads and electrodes was used. The main results show that the electrical resistivity of polycrystalline alumina increases with the decrease of the porosity, having as a limit the single crystal resistivity. Moreover, the electrical resistivity depends on the average grain size in the 4Wm 10 Wm range. For grain sizes smaller than 4 Wm the porosity is found to be higher than 0,1%.
Uma abordagem para trabalho cooperativo com suporte computadorizado
(Universidade Federal de São Carlos, 1993-11-01)
Albino, João Pedro
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Santos, Antônio Carlos dos
;
https://lattes.cnpq.br/5173313475335608
;
https://lattes.cnpq.br/9638407992652406
;
https://orcid.org/0000-0001-5965-1869
Nowadays, the modern society is going through radical technological changes that are generating debate and proposals concerning new ways of working. Information, computer and communication technologies represent an important role as modifiers of the way the work is done. When people in any kind of organization join themselves in workgroups to solve a problem or make a decision it is necessary to develop or use new dynamic group techniques for these people to work together. So, this work is concerned with matters of this kind where the computer is used to support the tasks of workgroups, what is quite new and revolucionary, being necessary some facilities to aid in the development and coordination of the work. In this dissertation it is introduced and defined this new technology. It is also presented a prototype of a groupware tool which helps people organize workshops, conferences, seminars, etc. The developed prototype brings some contributions to the CSCW área an is the begining of a more complex system to help the organization of Academic Events (conferences, workshops, etc.). From the user point of view the cooperation is seen as the possibility to the program committee, to share the decision to choose the papers that will make the technical program. In this case the decision should be centralized on-line. The tool allows that the referres can make, in assincronous mode, the assessment of the papers they are judging. Among many others tasks the tool allows the recording of the structure of the event, incluiding comittes,their chairs and participants, role definition and script of each stake holder, etc.
Designing intersections-designing subjectivity: feminist theory and praxis in a sex discrimination legislation system
(Universidade Federal de São Carlos, 1995)
Adam, Alison
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Furnival, Ariadne Chloe Mary
;
https://lattes.cnpq.br/1291482506649810
This paper looks at the intersections between feminist epistemology, feminist jurisprudence and research on artificial intelligence and the law. It is suggested that feminist theory highlights the role of subjectivity which is ignored in the traditional epistemology of AI systems. This allows AI systems to appear to be "perspectiveless" when they may be tacitly used in a normative role which ignores alternative knowledges. The paper looks at the Cyc system as an example. In developing an expert system to advise on Sex Discrimination law a number of lessons are learned both from the Forms Helper system and more particularly from feminist jurisprudence and from the critique of AI from feminist epistemology.
A participação dos usuários no desenvolvimento de sistemas de informação
(Universidade Federal de São Carlos, 1995)
Furnival, Ariadne Chloe Mary
;
https://lattes.cnpq.br/1291482506649810
As abordagens tradicionais de design de sistemas de informação (SIs) computadorizados fundamentam-se em certos pressupostos técnicos que geralmente não englobam fatores sociais e psicológicos da organização na qual o novo sistema será implantado. Os custos de se ignorar tais fatores são as vezes altos, pois usuários insatisfeitos podem resistir ao uso do sistema, ou usá-lo de uma maneira diferente daquela para a qual foi originalmente projetado. As limitações das metodologias de design tradicionais têm sido mitigadas pela adoção de metodologias soft, que baseiam-se na ideia de que somente a participação contínua dos usuários no desenvolvimento do novo sistema pode evitar problemas futuros, pois são os usuários - e não o analista - que detêm o conhecimento especializado do seu trabalho, o que é necessário para a construção de um sistema de alta qualidade e, portanto, produtivo.
Delineando as limitações: sistemas especialistas e conhecimento tácito
(Universidade Federal de São Carlos, 1995)
Furnival, Ariadne Chloe Mary
;
https://lattes.cnpq.br/1291482506649810
As aplicações de inteligência artificial (IA) e de sistemas especialistas (SEs), em particular, já fazem parte do espectro dos softwares existentes em muitas bibliotecas e centros de informação. Os profissionais da informação precisam, portanto, dominar os conceitos básicos da área de SEs. Entretanto, a mera compreensão dos componentes de um SE é vista como menos necessária que uma apreciação de alguns dos aspectos mais fundamentais que sustentam e influenciam o próprio processo do desenvolvimento dos SEs. Uma consideração das limitações dos paradigmas dominantes de aquisição de conhecimento, que não conseguem lidar adequadamente com a questão do corpo de conhecimento tácito que constitui uma parte substancial do conhecimento de um especialista, permitirá aos profissionais da informação relegar estas tecnologias à tarefa para qual são apropriadas: a saber, como colaboradores “inteligentes” nas tarefas de rotina e de tomada de decisão, e não como tomadores de decisão independentes, cedendo aconselhamento para usuários leigos, sem um intermediário humano.
Ensino de comportamentos básicos de basquetebol para crianças portadoras de síndrome de Down
(Universidade Federal de São Carlos, 1996)
Stefane, Claudia Aparecida
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Kubo, Olga Mitsue
;
https://lattes.cnpq.br/4047528382287783
;
https://lattes.cnpq.br/7808406751232968
The goals of Physical Education have changed in the past few years based on the different interests of the educational institutions and their political orientation, From the beginning of the 70's on. an increasing preoccupation not only with the essays related to Physical Education, but with the graduation of teachers in this area, till then were characterized by the repetition of the motion behavior to be taught. To be able to present a strategy of action different from the perspective discussed above, implies having knowledge of good quality about the leaming process the abilities required for the execution of these contests and more efficient procedures of teaching, for both normal and physical or mental disabled ones. The main aim of this work is to demonstrate that the required behavior background organized as a teaching programme, allow children with Down's Syndrome to leam basic basketball movements in a easy way without the need of motion leaming through repetition. This programme was divided into teaching units, each of them formed by a set of hierarchical abilities in a sequence according to its complexity and functionality. For each motion ability or a set of it, teaching facilities have been elaborated in order to ease the leaming process. An evaluation programme and the performance of each child was done individually, based on the quality of the motion behavior performed, on the frequency of correct abilities presented and on the levei of help offered to the pupils. We have studied four children with Down's Syndrome with age in the six-13 years range, registered in a special educational school in São Carlos city. It was observed that ali individuais, on the whole, showed a performance considered correct in the last sessions, whose objective was the leaming of behaviors considered more complex, faster when compared to the leaming in the beginning of the programme, indicating that the individuais learned how to leam. It also enabled the teacher to quickly and easily identify the abilities involved in the behaviors and the degree of difficulty presented by the students in their acquisition, and thus choose and/or modify the strategies for the teaching of each and every objective. These results may contribute both to the practice of physical education teachers, in the perspective of a transforming action, and to increasing the knowledge on how individuais with Down's Syndrome leam motion behavior and which benefits may be derived from them.
Produção de exopolissacarídeos em diferentes fases do crescimento de Staurastrum tohopekaligiensis Wolle (Chlorophyceae)
(Universidade Federal de São Carlos, 1996-03-12)
Dulcini, Silvana Elizabeth de Méo
;
Vieira, Armando Augusto Henriques
;
https://lattes.cnpq.br/4428377384377272
Laboratory experiments were carried out with the aim of studying the production of dissolved and capsular exopolysaccharides in diíFerent growth ages by Staurastrum tohopekaligiensis Wolle. This microalga was isolated from a marginal lagoon of the Mogi- Guaçu River, SP-Brazil. The cells were grown axenically in artificial culture médium under controlled conditions of light intensity, temperature, aeration and light/dark cycle. After 25 and 48 days of growth, the cells were harvested by centrifligation, washed with distilled water by centrifiigation, resuspended in distilled water, and submitted to 40 0C under mixing with a magnetic stirrer to extract the capsules. The capsular material and the dissolved one were both filtered, concentrated, dialyzed and ffeeze-dried. The production of exopolysaccharides was greater in the stationary growth phase than in the exponential one. Gel filtration chromatography analysis revealed that both the capsular and the extracellular polysaccharides obtained at different growth ages can be ífactioned in two fractions, "A" and "B". Fraction "A" presented a molecular weight close to or larger than 2 x 106 daltons, while fraction "B" of 2 x IO6 daltons, approximately. lon exchange chromatography data showed great similarities between capsular polysaccharide and extracellular polysaccharide, both having acid nature. When different growth ages are considered, a significant variation was observed in relation to the percentual participation of fractions "A" and "B" of the capsular polysaccharide. It was observed that fraction "B" from "old" cultures represents 92% of the total. Biochemical analysis revealed that the extracellular material does not have a sulphate group but has a proteic fraction. Gas chromatography analysis of extracellular and capsular polysaccharides revealed the presence of neutral sugars and acid sugars. The neutral sugars are; flicose, galactose, glucose, mannose, rhamnose, arabinose and 3-O-methyl galactose and the acid ones are: galacturonic acid and glycuronic acid.
Planejamento ambiental na cidade de São Carlos (SP) com ênfase nas áreas públicas e áreas verdes diagnóstico e propostas
(Universidade Federal de São Carlos, 1996-09-19)
Oliveira, Carlos Henke de
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Santos, José Eduardo dos
;
https://lattes.cnpq.br/8533387365058570
This study has aimed to environmental planning on São Carlos City through the purpose of a classification system for public areas and public green areas, based on its structural, functional, utilitarian and legal attributes of public areas, to allow the social and environmental diagnosis based on population density, percentage of green areas and green area/population ratio to whole urban nucleus. The GIS (Geographical Information System) IDRISI provided a necessary support to development and application of operational models. The diagnosis of arborization allows determine 8 strategies that will operate over public and particular areas, aiming enhance the quality of environment and life. The proposition of implantation of new green areas was evaluated through prognosis. The results have shown 2.07 percentage of green areas. The green area/population ratio was 2.59 m2/person. The proposal of new areas for arborization would result at 6.98 m2/person, representing a real ameliorate from the present situation, however the prognosticated value was considerate low when comparing to other Brazilian cities. It was conclude that the Classification Model for Public Areas is adequate for the defined purposes and there is a need to review the specific legislation, therefore, planning and organizing the Local Government which would act effectively to accomplish the environmental policy.
Estudo da origem do cromossomo 21 extra em portadores de Síndrome de Down
(Universidade Federal de São Carlos, 1996-09-27)
Silva, Wellington dos Santos
;
Barbosa, Calógeras Antonio de Albergaria
;
https://lattes.cnpq.br/0434592982925844
Down syndrome is usually due to meiotic nondisjunction leading to trisomy 21.The origin of nondisjunction in trisomy 21 has so far been studied using cytogenetic heteromorphisms and DNA polymorphisms. Short sequence repeats have recently been described as an abundant class of DNA polymorphisms in the human genome, which can be typed using the Polymerase Chain Reaction (PCR) amplification. Analysis of these polymorphisms may provide a more accurate understanding of the meiotic stage of nondisjunction in trisomy 21 than that previously provided by chromosomal heteromorphisms. The following DNA polymorphisms located in pericentromeric region of human chromosome 21. Were typed D21S13E, D21S16 and D21S120. The other polymorphism studied was HMG14-GT2 which map to the terminal band 21q22.3. In the present stud such markers were used in order to the determine the parental origin and the meiotic stage of the additional chromosome 21 in 32 cases of Down syndromy. Seven families were informative showing that nondisjunction ocurred in meiosis I and three were from maternal origin using HMG14-GT2 polymorphism. In the other molecular systems the families are not informatives.
Estudo do reprocessamento de terpolímeros ABS
(Universidade Federal de São Carlos, 1997)
Pagliarussi, Marcelo Sanches
;
Agnelli, José Augusto Marcondes
;
https://lattes.cnpq.br/7592090152400440
;
https://lattes.cnpq.br/6172932804874946
This study studied the effects of reprocessing on the terpolymer acrylonitrile-butadiene-styrene (ABS). ABS presents an intrinsic instability to oxidative, thermal or photochemically initiated degradation. Therefore, we sought to adopt a methodology for thermal restabilization of ABS, through the use of different commercial thermal stabilizers (always in the form of a blend of phenolic antioxidants and phosphites in a ratio of 1:2, respectively), and to study the effects of restabilization on the overall performance of the material. The study was divided into two stages: pre-selection of formulations and accelerated thermal aging. In the pre-selection, processing tests were performed to evaluate the processing stability of the four formulations used in relation to the reprocessed regrind without restabilization. Multiple-pass tests were performed with monitoring of the flow index and processing simulation tests on the Haake torque rheometer. The four samples with restabilization (formulations 1-4) and the non-restabilized regrind showed essentially the same stability characteristics, with no significant differences between the samples. In any case, formulation 2 was chosen to proceed, together with the regrind, to the accelerated aging test, due to its flow stability according to the evaluations of fluidity index and torque stability in the Haake Torque Rheometer. Test specimens for tensile and impact tests were injected from formulation 2 and the regrind, and these were subjected to the accelerated thermal aging test, in an oven with air circulation, at 100°C, for 1000 hours. After this period, the unaged (to) and aged (ti) specimens were characterized by monitoring their mechanical properties, and the samples from the granulated reprocessed material (pellets) to the aged c.p. (ti) were characterized by differential scanning calorimetry (DSC) and infrared spectroscopy with attenuated total reflectance (FTIR-ATR). It was observed that the ABS terpolymer presents good reprocessing conditions, despite its low thermooxidative stability. The material presented a small variation in the fluidity index, demonstrating that the thermooxidative degradation did not cause significant changes in molecular weight. On the other hand, degradation manifested itself quickly in the polybutadiene (PB) phase, indicating that, in the long term, it can cause a significant decrease in impact resistance. The behaviors were very similar, both in the restabilized sample (formulation 2) and in the ground sample without restabilization.
Caracterização e análise ambiental do Campus da Universidade Federal de São Carlos (UFSCar), São Carlos, SP
(Universidade Federal de São Carlos, 1997-10-03)
Paese, Adriana
;
Santos, José Eduardo dos
;
https://lattes.cnpq.br/8533387365058570
It was made an environmental characterization as a preliminar basis for the environmental planning and land ocupation strategies, at the Federal University of São Carlos’s campus (São Carlos, SP), through its structural variables conversion (hidrology, altimetry, land use patterns, vegetation cover) to digital format, using GIS-IDRISI. The resulting thematic maps, besides gathering important information which can subside the development of other studies, allowed the landscape units (biotopes) identification. The biotopes spatial patterns suggest different proposals for the urbanized and not urbanized areas
Crescimento de monocristais supercondutores de YBa2Cu3O7-ȣ pelo método de fluxo em cadinhos de SnO2
(Universidade Federal de São Carlos, 1998-02-27)
Ramírez, Roberto Antonio Rojas
;
Leite, Edson Roberto
;
https://lattes.cnpq.br/1025598529469393
Nowadays, the flux method is one of the most widely used techniques promote growth of YBa2Cu3O7-ȣ single crystal superconductor. By using the material in a melted state, the reactions due to temperature are possible. To prepare single crystal superconductors of the family Y-Ba-Cu-O, a long period of time is necessary to melt the material in adequate conditions. In order to do this a satisfactory performance of the crucible is required; it must be resistant to any kind of chemical attack. In this work some materials used were investigated in crucibles. Platinum, gold (noble metals), oxides like Al2O3, ZrO2 showed problems when used in processing Y123 superconductors. To avoid this problem the zirconiaytria system is largely applied. Some authors have investigated the SnO2 crucible, but they found problems related to the densification of the SnO2. Recently, it was discovered that SnO2 can be densified without liquid phase, showing 99,7% of the theoretical density when sinterized up to 1300°C. Then, this condition was used to produce crucibles by slip casting to form the YBa2Cu3O7-ȣ single crystal superconductors without contamination. It was observed, in a first instance, that SnO2 crucibles are resistant to chemical attack of the flux that is rich in barium and copper. During the process it was observed an interface wall between the vial and the flux formed by BaSnO3. This protection is formed after heat treatment at 1025°C during 4, 17 and 24 hours. By increasing the treatment time (up to 24 hours), it was observed that the wall thickness increased too and it was possible stablish a relation between treatment time/thickness wall (that defines the resistance of chemical attack). This enabled the determination of the SnO2 crucible resistance to corrosion, under the flux condition. The second part of this work involved the Y123 single crystal growth. After produced, they were analysed by x-ray diffraction and SEM with microanalysis in cross sections of the crucibles to observe the BaSnO3 interface. It was observed that single crystals were not contaminated by tin, and they were analyzed through measuring magnetization vs. Temperature. The single crystal showed a critical temperature (Tc) around 90,5K with a transition width (Tc) around 19,5K before treatment with an oxygen flux at 450°C. After seven days of a second treatment under the same conditions, the Tc was increased to 92K with a decreasing to 4,5K in Tc. The results showed that SnO2 vials are resistant to BaO-CuO flux and appropriate to single crystal growth in YBa2Cu3O7-ȣ superconductors without external.
Redes para cooperação internacional: uma janela de oportunidade para os países recém industrializados?
(Universidade Federal de São Carlos, 1998-07)
Furnival, Ariadne Chloe Mary
;
https://lattes.cnpq.br/1291482506649810
Aborda o papel das redes eletrônicas de informação e das redes inter-firmas, como fator determinante para maior integração e cooperação entre os países recém industrializados, à luz de pesquisas já desenvolvidas por autores que consideram as redes como mecanismos que meramente reforçam as desigualdades globais existentes.