Uma fonte chaveada de 50kW com correção de fator de potência para alimentação de uma tocha de plasma Indutiva utilizando técnicas de controle digital

This work deals with the development of an experimental study on a power supply of high frequency that provides the toch plasmica to be implemented in PLASPETRO project, which consists of two static converters developed by using Insulated Gate Bipolar Transistor (IGBT). The drivers used to control these keys are triggered by Digital Signal Processor (DSP) through optical fibers to reduce problems with electromagnetic interference (EMI). The first stage consists of a pre-regulator in the form of an AC to DC converter with three-phase boost power factor correction which is the main theme of this work, while the second is the source of high frequency itself. A series-resonant inverter consists of four (4) cell inverters operating in a frequency around 115 kHz each one in soft switching mode, alternating itself to supply the load (plasma torch) an alternating current with a frequency of 450 kHz. The first stage has the function of providing the series-resonant inverter a DC voltage, with the value controlled from the power supply provided by the electrical system of the utility, and correct the power factor of the system as a whole. This level of DC bus voltage at the output of the first stage will be used to control the power transferred by the inverter to the load, and it may vary from 550 VDC to a maximum of 800 VDC. To control the voltage level of DC bus driver used a proportional integral (PI) controller and to achieve the unity power factor it was used two other proportional integral currents controllers. Computational simulations were performed to assist in sizing and forecasting performance. All the control and communications needed to stage supervisory were implemented on a DSP

Estratégia de controle robusto para interconexão de sistemas PV trifásicos à rede elétrica

Atualmente há uma grande preocupação em relação a substituição das fontes não renováveis pelas fontes renováveis na geração de energia elétrica. Isto ocorre devido a limitação do modelo tradicional e da crescente demanda. Com o desenvolvimento dos conversores de potência e a eficácia dos esquemas de controle, as fontes renováveis têm sido interligadas na rede elétrica, em um modelo de geração distribuída. Neste sentido, este trabalho apresenta uma estratégia de controle não convencional, com a utilização de um controlador robusto, para a interconexão de sistemas fotovoltaicos com à rede elétrica trifásica. A compensação da qualidade de energia no ponto de acoplamento comum (PAC) é realizada pela estratégia proposta. As técnicas tradicionais utilizam detecção de harmônicos, já neste trabalho o controle das correntes é feita de uma forma indireta sem a necessidade desta detecção. Na estratégia indireta é de grande importância que o controle da tensão do barramento CC seja efetuado de uma forma que não haja grandes flutuações, e que a banda passante do controlador em regime permanente seja baixa para que as correntes da rede não tenham um alto THD. Por este motivo é utilizado um controlador em modo dual DSM-PI, que durante o transitório se comporta como um controlador em modo deslizante SM-PI, e em regime se comporta como um PI convencional. A corrente é alinhada ao ângulo de fase do vetor tensão da rede elétrica, obtido a partir do uso de um PLL. Esta aproximação permite regular o fluxo de potência ativa, juntamente com a compensação dos harmônicos e também promover a correção do fator de potência no ponto de acoplamento comum. Para o controle das correntes é usado um controlador dupla sequencia, que utiliza o princípio do modelo interno. Resultados de simulação são apresentados para demonstrar a eficácia do sistema de controle proposto

Projeto em FPGA de um controlador unificado para correção de fator de potência em retificadores boost bidirecionais monofásicos

The use of Field Programmable Gate Array (FPGA) for development of digital control strategies for power electronics applications has aroused a growing interest of many researchers. This interest is due to the great advantages offered by FPGA, which include: lower design effort, high performance and highly flexible prototyping. This work proposes the development and implementation of an unified one-cycle controller for boost CFP rectifier based on FPGA. This controller can be applied to a total of twelve converters, six inverters and six rectifiers defined by four single phase VSI topologies and three voltage modulation types. The topologies considered in this work are: full-bridge, interleaved full-bridge, half-bridge and interleaved half-bridge. While modulations are classified in bipolar voltage modulation (BVM), unipolar voltage modulation (UVM) and clamped voltage modulation (CVM). The proposed project is developed and prototyped using tools Matlab/Simulink® together with the DSP Builder library provided by Altera®. The proposed controller was validated with simulation and experimental results

Questões objetivas sobre funções das provas de matemática do vestibular da UFRN dos anos de (2001 a 2008): um diagnóstico sobre os erros que os candidatos cometem

La dificultad que los alumnos encuentran en el aprendizaje de matemática viene siendo objeto de investigación por estudiosos en educación matemática, tanto en Brasil como en el exterior. El objetivo de este estudio consiste em investigar las dificuldades en el aprendizado sobre funciones matemáticas y la influencia de las concepciones alternativas a partir de los errores que los candidatos acerca de las cuestiones sobre funciones en la prueba objetiva de matemática del acceso a la universidad de los años de 2001 a 2008. Teniendo como cuestiones de estudio para alcanzar el objetivo propuesto: identificar la relevancia del tema funciones que son contemplados en las pruebas de acceso a la Universidad; asi como cuáles han sido los tipos de funciones más privilegiados y menos privilegiados; analizar si la contextualización de la pregunta y la presencia de elementos no textuales han influenciado en el aumento de tal dificultad; analizar si la representación semiótica agrega mayor exigencia a la pregunta; analizar respecto a la exigencia matemática de la pregunta; analizar lo que se refiere al desempeño de los candidatos para verificar cuál pregunta tuvo mejor desempeño y cuál el peor e identificar los errores más frecuentemente cometidos por los candidatos en esas pruebas. Las reflexiones de los estudiosos como: Radatz (1980), Cury (1994), Socas (1997), Borasi (1997), Franchi e Rincón (2004), Pochulu (2004) presentan las dificultades en el aprendizaje matemático, que aparecen a partir de los errores cometidos por los alumnos, quando estos errores reciben la influencia de las concepciones alternativas. El estudio que se presenta en esta disertación configura un análisis de los errores que los candidatos han cometido en las preguntas objetivas sobre el tema funciones de las pruebas de acceso a la Universidad de los años de 2001 a 2008, a partir de los relatorios de la Comissão Permanente do Vestibular COMPERVE/UFRN. Con la intención de alcanzar los objetivos propuestos para este estudio, fueran sido construidas categorías de análisis. Los resultados encontrados han sido: El tema funciones es el más frecuente entre los demás con (28,1%); el tipo de función priorizada durante esos años ha sido la función logarítmica con (24%); la contextualización de las preguntas exige una mayor comprensión por parte del candidato de lo que las situaciones directas; la caracterización semiótica posee elementos que estructuran esas preguntas que el educando debe saber asociar al texto; la exigencia matemática posibilitó analizar que el procedimiento medio ha sido el más requisitado; el desempeño de los candidatos ha sido en la mayoría bajo (50%); y los principales errores que ellos han cometido han sido de realizar traducciones incorrectas de las expresiones que aparecen en las situaciones-problema; utilizar todos los datos que aparezcan en el problema sin tomar en cuenta si el cálculo realizado responde a la pregunta solicitada; no interpretar coherentemente las informaciones del gráfico; decodificar incorrectamente los valores representados por literales en una recta numérica. Los resultados señalizan la necesidad de una revisión didáctico-metodológicas de la enseñanza de funciones a raíz de las cuales las dificultades en el aprendizaje se han presentado

A fotossíntese vegetal no 3º ano do Ensino médio: concepções alternativas, erros conceituais e uma proposta de unidade didática baseada no Desenvolvimento Sustentável.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

A prática de correção textual por professoras de língua portuguesa do ensino médio

Cette recherche analyse les pratiques de correction de textes de l'enseignement du 1, 2 et 3 ème niveau. Nous avons parti de discutions avec les professeurs de Langue Portugaise des troisièmes annèes d‟une école appartenant au enseignement publique, située à la ville d‟Assu RN. L'étude a les postulats théoriques de Cruz (2007), Dellagnelo (1998), Oliveira (2005), Pécora (1999), Ruiz (2001), Serafini (1989), et d‟autres. La méthodologie est de nature qualitative et d‟interpretation, dont le matériel a été constitué à partir des rapports des enseignants professionnels, ainsi que les 92 textes recueillies entre juillet et août 2008. Les dés montrent que la correction se configure comme un travail pratique, qui vise à aider les étudiants à améliorer leur écriture. Les professeurs font la correction d‟une forme mélangée, c'est-à-dire dans le texte apparaissent les corrections orthographiques, lexicales, etc., mais la prédominance de la correction est par rapport aux idées, pour le contenu du texte. Dans ce sens, les professeurs se rendent compte du valeur et de la hiérarchisation des idées discutées par les élèves, les reconnaître comme l'organisation de la sémantique et la séquence du texte. Tous les autres aspects (structurelles, grammaticaux) sont importants, cependant, en général, dans la pratique de correction des études, l‟exposition les idées occupent une place importante. Les marques de correction apparaissent sous la forme de petits billets, qui apprécie également toutes les étapes de l'écriture de texte

Determinação do teor de diclofenaco sódico em comprimidos por espectroscopia no infravermelho próximo NIR com calibração multivariada PLS

This work is combined with the potential of the technique of near infrared spectroscopy - NIR and chemometrics order to determine the content of diclofenac tablets, without destruction of the sample, to which was used as the reference method, ultraviolet spectroscopy, which is one of the official methods. In the construction of multivariate calibration models has been studied several types of pre-processing of NIR spectral data, such as scatter correction, first derivative. The regression method used in the construction of calibration models is the PLS (partial least squares) using NIR spectroscopic data of a set of 90 tablets were divided into two sets (calibration and prediction). 54 were used in the calibration samples and the prediction was used 36, since the calibration method used was crossvalidation method (full cross-validation) that eliminates the need for a validation set. The evaluation of the models was done by observing the values of correlation coefficient R 2 and RMSEC mean square error (calibration error) and RMSEP (forecast error). As the forecast values estimated for the remaining 36 samples, which the results were consistent with the values obtained by UV spectroscopy

O uso de analogias para o ensino de equilíbrio químico no ensino médio: facilitação da aprendizagem ou transmissão de erros conceituais?

The use of analogies in high school is often useful for chemistry teaching, either on textbooks or by teachers in the classroom.This use is justified by the large number of abstract concepts that rules this course. Analogies are conceptualized by several authors, which converge on the idea that these are tools that seek a way to elucidate an unknown concept by comparing it to a familiar one, relating their similar and dissimilar features. An analysis on a survey of analogies found in high school chemistry textbooks and chemical equilibrium studies is performed in order to verify whether they are leading to misconceptions for their use by students and/or for their use by teachers in the classroom, or whether they promote a learning facilitation

Utilização da espectroscopia no infravermelho próximo para o controle de qualidade do camarão (Litopenaeus vannamei)

This work was developed with the objective of proposing a simple, fast and versatile methodological routine using near-infrared spectroscopy (NIR) combined with multivariate analysis for the determination of ash content, moisture, protein and total lipids present in the gray shrimp (Litopenaeus vannamei ) which is conventionally performed gravimetrically after ashing at 550 ° C gravimetrically after drying at 105 ° C for the determination of moisture gravimetrically after a Soxhlet extraction using volumetric and after digestion and distillation Kjedhal respectively. Was first collected the spectra of 63 samples processed boiled shrimp Litopenaeus vannamei species. Then, the determinations by conventional standard methods were carried out. The spectra centered average underwent multiplicative scattering correction of light, smoothing Saviztky-Golay 15 points and first derivative, eliminated the noisy region, the working range was from 1100,36 to 2502,37 nm. Thus, the PLS models for predicting ash showed R 0,9471; 0,1017 and RMSEP RMSEC 0,1548; Moisture R was 0,9241; 2,5483 and RMSEP RMSEC 4,1979; R protein to 0,9201; 1,9391 and RMSEP RMSEC 2,7066; for lipids R 0,8801; 0,2827 and RMSEP RMSEC 0,2329 So that the results showed that the relative errors found between the reference method and the NIR were small and satisfactory. These results are an excellent indication that you can use the NIR to these analyzes, which is quite advantageous, since conventional techniques are time consuming, they spend a lot of reagents and involve a number of professionals, which requires a reasonable runtime while after the validation of the methodology execution using NIR reduces all this time to a few minutes, saving reagents, time and without waste generation, and that this is a non-destructive technique.

Avaliação da efetividade do Programa de Alimentação do Trabalhador

This study analyzed the Worker’s Healthy Eating Program in Rio Grande do Norte state (RN) to assess its possible impact on the nutritional status of the workers benefitted. To that end, we conducted a cross-sectional observational prospective study based on a multistage stratified random sample comparing 26 small and medium-sized companies from the Manufacturing Sector (textiles, food and beverages, and nonmetallic minerals) of RN, divided into two equal groups (WFP and Non WFP). Interviews were conducted at each company by trained interviewers from Tuesday to Saturday between September and December 2014. Data were collected on the company (characterization and information regarding the program’s desired results) and workers (personal and professional information, anthropometrics, health, lifestyle and food consumed the previous day). Population estimates were calculated for RN on the characteristics of workers and the study variables. The main variable was BMI. The secondary variables were waist circumference (WC), nutritional diagnosis, calorie intake, blood pressure, metabolic variables and lifestyle indicators. The statistical method used was hierarchical mixed effects linear regression for interval variables and hierarchical mixed effects logistic regression for binary variables. The variables measured in ordinal scales were analyzed by ordinal logistic regression adjusted for correlated variables, adopting robust standard errors. The results for interval variables are presented as point estimates and their 95% confidence intervals; and as odds-ratios and their 95% confidence intervals for binary variables. The Fisher’s exact and Student’s t-tests were used for simple comparisons between proportions and means, respectively. Differences were considered statistically significant at p<0.05. A total of 1069 workers were interviewed, of which 541 were from the WFP group and 528 from the Non WFP group. Subjects were predominantly males and average age was 34.5 years. Significant intergroup differences were observed for schooling level, income above 1 MW (minimum wage) and specific training for their position at the company. The results indicated a significant difference between the BMI of workers benefitted, which was on average 0.989 kg/m2 higher than the BMI of workers from the Non WFP group (p=0.002); and between the WC, with the waist circumference of WFP group workers an average of 1.528 cm larger (p<0.05). Higher prevalence of overweight and obesity (p<0.001) and cardiovascular risk (p=0.038) were recorded in the WFP group. Tests on the possible effect of the WFP on health (blood pressure and metabolic indicators) and lifestyle indicators (smoking, alcohol consumption and exercise) were not significant. With respect to worker’s diets, differences were significant for consumption of saturated fat (lunch and daily intake), salt (lunch, other meals and daily intake) and proteins (other meals and daily intake), with higher consumption of these nutrients in the WFP group. The study showed a possible positive impact of the WFP on nutritional status (BMI and WC) among the workers benefitted. No possible effects of the program were observed for the lifestyle indicators studied. Workers benefitted consumed less salt, saturated fat and protein. The relevance of the WFP is recognized for this portion of society and it is understood that, if the program can reach and impact those involved, the development of educational initiatives aimed at nutritional and food safety may also exert a positive influence.

O turismo de base comunitária como vetor de etnodesenvolvimento: a comunidade Mebêngôkre-Kayapó na Terra Indígena Las Casas - PA

This study aims to analyze the contribution that the future implementation of community-based tourism can provide to Mebengokre-Kayapo, people of the village Tekrejarôti, they re-inhabiting the indigenous land Las Casas, located in southern of Pará, taking into consideration that tourism is as vector of ethnodevelopment, and it can also contribute to the conservation of Sociobiodiversity and local culture through experiences that will enable the realization of acquaintanceship, where there will be sharing of the daily activities of the customs of the local people, and cultural changes, which is the aim between visitors and the community, where these ones can promote the knowledge of non-indigenous people, and to consolidate the ethnic and cultural identity thereof too. Thus, this study guided by the participatory action research, it was used data obtained in 2012, that were results from the application of interviews with the community to make the diagnosis of tourism potential. It is an exploratory and descriptive research about the topic. The field research combined with participant observation, workshops and interviews contributed to it was possible to conduct a depth analysis about the environment studied. This research has the intention to obtain concrete results in the implementation and/or promotion of a cultural practice and environmentally sustainable ruled in organizational processes that permeates the guidelines of community-based tourism, however this depends on the conditions of human and forest resources, and infrastructure conditions in the community, providing in the short and medium terms, social activities and culturally positive for the culture of this people, and providing to long term, environmental and economic landmarks. As result, it was possible to identify that the community with its cultural events, parties and ceremonies being allied to their way of life and taken from their criteria, it is able to work with the tourism within their land and it can makes the tourism, a cultural affirmation opportunity and income generation. But, it concludes that for tourism to become ,in fact, there are required to be carried out some measures, that meets the new Regulatory Instruction IN 3/2015, this IN states that for the community to work with tourism in their land, it is necessary to be prepared a visitation plan that fits the established requirements. This research is constituted as an important tool in building this visitation plan, given that it was done from the community demand and it was conducted in a participatory manner, valuing the horizontal dialogue and the autonomy of this people.

O turismo de base comunitária como vetor de etnodesenvolvimento: a comunidade Mebêngôkre-Kayapó na Terra Indígena Las Casas - PA

This study aims to analyze the contribution that the future implementation of community-based tourism can provide to Mebengokre-Kayapo, people of the village Tekrejarôti, they re-inhabiting the indigenous land Las Casas, located in southern of Pará, taking into consideration that tourism is as vector of ethnodevelopment, and it can also contribute to the conservation of Sociobiodiversity and local culture through experiences that will enable the realization of acquaintanceship, where there will be sharing of the daily activities of the customs of the local people, and cultural changes, which is the aim between visitors and the community, where these ones can promote the knowledge of non-indigenous people, and to consolidate the ethnic and cultural identity thereof too. Thus, this study guided by the participatory action research, it was used data obtained in 2012, that were results from the application of interviews with the community to make the diagnosis of tourism potential. It is an exploratory and descriptive research about the topic. The field research combined with participant observation, workshops and interviews contributed to it was possible to conduct a depth analysis about the environment studied. This research has the intention to obtain concrete results in the implementation and/or promotion of a cultural practice and environmentally sustainable ruled in organizational processes that permeates the guidelines of community-based tourism, however this depends on the conditions of human and forest resources, and infrastructure conditions in the community, providing in the short and medium terms, social activities and culturally positive for the culture of this people, and providing to long term, environmental and economic landmarks. As result, it was possible to identify that the community with its cultural events, parties and ceremonies being allied to their way of life and taken from their criteria, it is able to work with the tourism within their land and it can makes the tourism, a cultural affirmation opportunity and income generation. But, it concludes that for tourism to become ,in fact, there are required to be carried out some measures, that meets the new Regulatory Instruction IN 3/2015, this IN states that for the community to work with tourism in their land, it is necessary to be prepared a visitation plan that fits the established requirements. This research is constituted as an important tool in building this visitation plan, given that it was done from the community demand and it was conducted in a participatory manner, valuing the horizontal dialogue and the autonomy of this people.

A compreensão de reação química como um sistema complexo a partir da discussão dos erros e dificuldades de aprendizagem de estudantes do ensino médio

The study of chemical reactions is among the most important contents to the understanding of Chemistry discipline in basic education. However, there are still few studies about chemical reactions as a complex system because, generally, this content is presented in textbooks, taught and even researched in a fragmented form. The thesis here presented aims to investigate, identify and characterize the mistakes and learning difficulties of the students about chemical reactions as a complex system, using for that purpose the analysis of the answers of 126 exams of candidates for the bachelor’s degree in Chemistry Teaching on the entrance exam for the Federal University of Rio Grande do Norte (UFRN). The mistakes and learning difficulties about the parameters ΔG°, Kp, Ea and of the calculation of the amount of substance in a chemical reaction have been identified, as well as the levels of development of the ability to interpret the chemical reaction as a system. The main theoretical source of this study is structured based on the mistakes and learning difficulties (NÚÑEZ, RAMALHO, 2012), of the chemical reactions as complex systems (NÚÑEZ, 1994; RESHETOVA, 1988; SANDERSON, 1968). As methodology, it was prioritized the analysis of the answers to the exams and the interview with the teachers. The results showed typical mistakes in the study of this subject, especially low levels and skill development. No student was able to integrate the different aspects in the systemic understanding of the chemical reaction. From the interviews with Chemistry teachers from High School, it was determined the reasons the teachers assign to those mistakes and learning difficulties. The interviews revealed that the teachers do not work in the perspective of integration of the contents which leads the students to present difficulties and make mistakes related to the content previously mentioned. The study presents a proposal for the organization of the contents of Chemistry discipline for High School as a possibility of a dialectic systemic integration of contents, understanding that this systematic vision, leads to important contributions to the development of the theoretical thinking of the students. We can mention as one of the conclusions of this study, the fact that the non-systemic organization of contents do not favor this kind of thinking in students.

Desenvolvimento de um sistema misto de pasta à base de geopolímero e cimento portland para correção de perda de circulação

The materials engineering includes processes and products involving several areas of engineering, allowing them to prepare materials that fulfill the needs of various new products. In this case, this work aims to study a system composed of cement paste and geopolymers, which can contribute to solving an engineering problem that directly involves the exploitation of oil wells subject to loss of circulation. To correct it, has been already proposed the use of granular materials, fibers, reducing the drilling fluid or cement paste density and even surface and downhole mixed systems. In this work, we proposed the development of a slurry mixed system, the first was a cement-based slurry and the second a geopolymer-based slurry. The cement-based slurry was formulated with low density and extenders, 12.0 ppg (1.438 g/cm ³), showing great thixotropic characteristics. It was added nano silica at concentrations of 0.5, 1.0 and 1.5 gps (66.88, 133.76 and 200.64 L/m3) and CaCl2 at concentrations of 0.5, 1, 0 and 1.5%. The second system is a geopolymer-based paste formulated from molar ratios of 3.5 (nSiO2/nAl2O3), 0.27 (nK2O/nSiO2), 1.07 (nK2O/nAl2O3) and 13.99 (nH2O/nK2O). Finally, we performed a mixture of these two systems, for their application for correction of circulation lost. To characterize the raw materials, XRD, XRF, FTIR analysis and titration were performed. The both systems were characterized in tests based on API RP10B. Compressive strength tests were conducted after curing for 24 hours, 7 and 28 days at 58 °C on the cement-based system and the geopolymer-based system. From the mixtures have been performed mixability tests and micro structural characterizations (XRD, SEM and TG). The results showed that the nano silica, when combined with CaCl2 modified the rheological properties of the cement slurry and from the concentration of 1.5 gpc (200.64 L / m³) it was possible to obtain stable systems. The system mixture caused a change in the microstructure of the material by favoring the rate of geopolymer formation to hinder the C3S phase hydration, thus, the production of CSH phases and Portlandite were harmed. Through the mixability tests it can be concluded that the system, due to reduced setting time of the mixture, can be applied to plug lost circulation zones when mixed downhole

Adição de poliuretana em pastas de cimento para poços de petróleo como agente de correção do filtrado

Chemical admixtures, when properly selected and quantified, play an important role in obtaining adequate slurry systems for quality primary cementing operations. They assure the proper operation of a well and reduce costs attributed to corrective cementing jobs. Controlling the amount lost by filtering through the slurry to permeable areas is one of the most important requirements in an operation, commonly controlled by chemical admixtures, such as carboxymethylcellulose (CMC). However, problems related to temperature, salttolerance and the secundary retarding effect are commonly reported in the literature. According to the scenario described above, the use of an aqueous dispersion of non-ionic poliurethane was proposed to control the filter loss, given its low ionic interaction with the free ions present in the slurries in humid state. Therefore, this study aims at assessing the efficiency of poliurethane to reduce filter loss in different temperature and pressure conditions as well as the synergistic effect with other admixtures. The temperatures and pressures used in laboratory tests simulate the same conditions of oil wells with depths of 500 to 1200 m. The poliurethane showed resistance to thermal degradation and stability in the presence of salts. With the increase in the concentration of the polymer there was a considerable decrease in the volume lost by filtration, and this has been effective even with the increase in temperature