Obtenção e caracterização de um compósito de matriz polimérica com carga de bucha vegetal luffa cylindrica

Composite materials arise from the need for lighter materials and with bigger mechanical and thermal resistance. The difficulties of discard, recycling or reuse are currently environmental concerns and, therefore, they are study object of much researches. In this perspective the feasibility of using loofahs (Luffa Cylindrica) for obtainment of a polymeric matrix composite was studied. Six formulations, with 4, 5 and 6 treated layers and untreated, were tested. The loofahs were treated in boiling water to remove lignins, waxes and impurities present in the fibers. After that, they were dried in a direct exposure solar dryer. For the characterization of the composite, thermal (thermal conductivity, thermal capacity, thermal diffusivity and thermal resistivity), mechanical (tensile and bending resistance) and physicochemical (SEM, XRD, density, absorption and degradation) properties were determined. The proposed composite has as advantage the low fiber density, which is around 0.66 g/cm³ (almost half of the polyester resin matrix), resulting in an average composite density of around 1.17g/cm³, 6.0 % lower in relation to the matrix. The treatment carried out in the loofahs increased the mechanical strength of the composite and decreased the humidity absorption. The composite showed lower mechanical behavior than the matrix for all the formulations. The composite also demonstrated itself to be feasible for thermal applications, with a value of thermal conductivity of less than 0.159 W/m.K, ranking it as a good thermal insulator. For all formulations/settings a low adherence between fibers and matrix occurred, with the presence of cracks, showing the fragility due to low impregnation of the fiber by the matrix. This composite can be used to manufacture structures that do not require significant mechanical strength, such as solar prototypes, as ovens and stoves.

Obtenção e caracterização de um compósito de matriz polimérica com carga de bucha vegetal luffa cylindrica

Composite materials arise from the need for lighter materials and with bigger mechanical and thermal resistance. The difficulties of discard, recycling or reuse are currently environmental concerns and, therefore, they are study object of much researches. In this perspective the feasibility of using loofahs (Luffa Cylindrica) for obtainment of a polymeric matrix composite was studied. Six formulations, with 4, 5 and 6 treated layers and untreated, were tested. The loofahs were treated in boiling water to remove lignins, waxes and impurities present in the fibers. After that, they were dried in a direct exposure solar dryer. For the characterization of the composite, thermal (thermal conductivity, thermal capacity, thermal diffusivity and thermal resistivity), mechanical (tensile and bending resistance) and physicochemical (SEM, XRD, density, absorption and degradation) properties were determined. The proposed composite has as advantage the low fiber density, which is around 0.66 g/cm³ (almost half of the polyester resin matrix), resulting in an average composite density of around 1.17g/cm³, 6.0 % lower in relation to the matrix. The treatment carried out in the loofahs increased the mechanical strength of the composite and decreased the humidity absorption. The composite showed lower mechanical behavior than the matrix for all the formulations. The composite also demonstrated itself to be feasible for thermal applications, with a value of thermal conductivity of less than 0.159 W/m.K, ranking it as a good thermal insulator. For all formulations/settings a low adherence between fibers and matrix occurred, with the presence of cracks, showing the fragility due to low impregnation of the fiber by the matrix. This composite can be used to manufacture structures that do not require significant mechanical strength, such as solar prototypes, as ovens and stoves.

Estudo da evolução das tensões residuais através da difratometria de raios x em aço rolamento submetido a esforços cíclicos

The micro-deformations caused by cyclic loading origins the variation of the distances between atoms of the crystal lattice producing the irreversible component. In order to study and understand the microstructural behavior of the material this paper investigated the influence suffered by residual stresses in thrust rolling bearing races fabricated in AISI 52100 steel, after tests by cyclic rolling contact in a tribometer at 1m/s under two contact pressures (500 MPa and 1400 MPa) in dry and boundary lubrication conditions. Procedures of tests thermo-acustically isolated were developed for monitoring the contact temperature and sound pressure level signals to establish a comparison between the residual stress measurements, micro-hardness Vickers and micrographic registers searching an indication of wear evolution. The sin²ψ method by X-ray diffraction technique was used to quantify the residual stresses. Three raceway zones were selected for the evaluation of wear and surface morphology after predetermined cycling, comparing with their new condition ("as received"). Micro-hardness and residual stress measurements showed significant changes after the tests and it was possible to observe the relationship between the increase of sound pressure level and the residual stress for dry and lubricated conditions.

Estudo da evolução das tensões residuais através da difratometria de raios x em aço rolamento submetido a esforços cíclicos

The micro-deformations caused by cyclic loading origins the variation of the distances between atoms of the crystal lattice producing the irreversible component. In order to study and understand the microstructural behavior of the material this paper investigated the influence suffered by residual stresses in thrust rolling bearing races fabricated in AISI 52100 steel, after tests by cyclic rolling contact in a tribometer at 1m/s under two contact pressures (500 MPa and 1400 MPa) in dry and boundary lubrication conditions. Procedures of tests thermo-acustically isolated were developed for monitoring the contact temperature and sound pressure level signals to establish a comparison between the residual stress measurements, micro-hardness Vickers and micrographic registers searching an indication of wear evolution. The sin²ψ method by X-ray diffraction technique was used to quantify the residual stresses. Three raceway zones were selected for the evaluation of wear and surface morphology after predetermined cycling, comparing with their new condition ("as received"). Micro-hardness and residual stress measurements showed significant changes after the tests and it was possible to observe the relationship between the increase of sound pressure level and the residual stress for dry and lubricated conditions.

Caracterização de um compósito utilizando cimento com agregado de resíduo plástico e resíduo de gesso

The demand for environmental comfort in construction systems within the insulation and thermal comfort, plus the advent of new laws regulating the minimum requirements of comfort, disposal of solid industrial waste, construction waste, the requirements of consumers by adopting construction methods "cleaner", encouraged the development of this work. Aims technologically characterize the composite proposed in three types of samples (10%, 30% and 50% of thermoset plastic industrial waste) and raw materials: gypsum waste, cement and plastic thermosetting industrial waste in order to produce the composite with properties of thermal insulation: conductivity, thermal diffusivity, specific heat and resistivity. The physical, structural and morphological properties of the raw materials were investigated by thermogravimetry analysis (TG / DSC), X-ray diffraction (DRX), X-ray fluorescence (FXR) and scanning electron microscopy (MEV). Obtaining mechanical properties through the compression strength test. The analysis results indicate characteristics suitable for cement matrix composite production with the addition of thermosetting plastic industrial waste and gypsum waste, with potential application of these materials in composites with properties of thermal insulation. Finally, assessing what proportion showed up with better performance. Considering the analysis and testing carried out.

Caracterização de um compósito utilizando cimento com agregado de resíduo plástico e resíduo de gesso

The demand for environmental comfort in construction systems within the insulation and thermal comfort, plus the advent of new laws regulating the minimum requirements of comfort, disposal of solid industrial waste, construction waste, the requirements of consumers by adopting construction methods "cleaner", encouraged the development of this work. Aims technologically characterize the composite proposed in three types of samples (10%, 30% and 50% of thermoset plastic industrial waste) and raw materials: gypsum waste, cement and plastic thermosetting industrial waste in order to produce the composite with properties of thermal insulation: conductivity, thermal diffusivity, specific heat and resistivity. The physical, structural and morphological properties of the raw materials were investigated by thermogravimetry analysis (TG / DSC), X-ray diffraction (DRX), X-ray fluorescence (FXR) and scanning electron microscopy (MEV). Obtaining mechanical properties through the compression strength test. The analysis results indicate characteristics suitable for cement matrix composite production with the addition of thermosetting plastic industrial waste and gypsum waste, with potential application of these materials in composites with properties of thermal insulation. Finally, assessing what proportion showed up with better performance. Considering the analysis and testing carried out.

Análise de falhas em rolamentos por análise de vibração aplicado a aerogeradores

With the heavy use of bearings in various segments of the industry, there are a large number of necessary interruptions in industrial processes to perform maintenance on these devices, with the case study wind turbines. The growth of the wind energy sector, encouraged to conduct research that helps to solve this problem. To contribute to predictive maintenance has been carried out a signal analysis using techniques which allow detection and location of the problem in order to prevent accidents caused and losses due to unexpected equipment failures, whereas low system rotation complicates the detection of the failure. To work around this problem, there was the indication of standard signals for defects in the bearings, making diagnosis of possible failures. With this diagnosis can be performed predictive maintenance, identifying the failure of the system that were tested, such as the introduction of grains of sand in the bearing, wear on the outer race of the bearing and bearing rust. By processing signals it is possible to construct graphs developing a mapping of defects by different peaks in the frequency band.

Uma interface para o controle de robôs móveis por intermédio de gestos

The main objective of this work was to enable the recognition of human gestures through the development of a computer program. The program created captures the gestures executed by the user through a camera attached to the computer and sends it to the robot command referring to the gesture. They were interpreted in total ve gestures made by human hand. The software (developed in C ++) widely used the computer vision concepts and open source library OpenCV that directly impact the overall e ciency of the control of mobile robots. The computer vision concepts take into account the use of lters to smooth/blur the image noise reduction, color space to better suit the developer's desktop as well as useful information for manipulating digital images. The OpenCV library was essential in creating the project because it was possible to use various functions/procedures for complete control lters, image borders, image area, the geometric center of borders, exchange of color spaces, convex hull and convexity defect, plus all the necessary means for the characterization of imaged features. During the development of the software was the appearance of several problems, as false positives (noise), underperforming the insertion of various lters with sizes oversized masks, as well as problems arising from the choice of color space for processing human skin tones. However, after the development of seven versions of the control software, it was possible to minimize the occurrence of false positives due to a better use of lters combined with a well-dimensioned mask size (tested at run time) all associated with a programming logic that has been perfected over the construction of the seven versions. After all the development is managed software that met the established requirements. After the completion of the control software, it was observed that the overall e ectiveness of the various programs, highlighting in particular the V programs: 84.75 %, with VI: 93.00 % and VII with: 94.67 % showed that the nal program performed well in interpreting gestures, proving that it was possible the mobile robot control through human gestures without the need for external accessories to give it a better mobility and cost savings for maintain such a system. The great merit of the program was to assist capacity in demystifying the man set/machine therefore uses an easy and intuitive interface for control of mobile robots. Another important feature observed is that to control the mobile robot is not necessary to be close to the same, as to control the equipment is necessary to receive only the address that the Robotino passes to the program via network or Wi-Fi.

Formulação de pasta de cimento flexível utilizando planejamento experimental

Steam injection is an oil recovery method accomplished by introducing steam directly into the oil well to the reservoir. The steam causes dilation of the casing, which, after reduction in temperature, tends to return to the initial dimensions: causing the formation of cracks in the cement and loss of hydraulic isolation.. In this context, the type of the SBR latex is used to improve the flexibility of the cement matrix by reducing the amount of fatigue failure. To prevent these failures, the mechanical resistance parameters should be carefully adjusted to well conditions. This work aims to study the mechanical behavior of cement slurry systems additivated with SBR latex for cementing oil wells subject to steam injection. Through the central composite factorial design was studied the behavior of the compressive strength by varying the density of the paste between 1.75 g /cm³ (14.6 lb/ Gal) and 1.89 g/cm³ (15,8lb / Gal), curing time between 4 days and 28 days and concentration of SBR Latex between 0 L / m³ and 534.722 L / m³ (0 gpc and 4 gpc). The results showed that increasing the concentration of SBR latex, within the given ranges, there was a decreased compression resistance and elastic modulus by increasing the elastic deformability of the slurry. From the results it can determine best slurries formulation conditions in oil well cementing operations subject to steam injection.

Formulação de pasta de cimento flexível utilizando planejamento experimental

Steam injection is an oil recovery method accomplished by introducing steam directly into the oil well to the reservoir. The steam causes dilation of the casing, which, after reduction in temperature, tends to return to the initial dimensions: causing the formation of cracks in the cement and loss of hydraulic isolation.. In this context, the type of the SBR latex is used to improve the flexibility of the cement matrix by reducing the amount of fatigue failure. To prevent these failures, the mechanical resistance parameters should be carefully adjusted to well conditions. This work aims to study the mechanical behavior of cement slurry systems additivated with SBR latex for cementing oil wells subject to steam injection. Through the central composite factorial design was studied the behavior of the compressive strength by varying the density of the paste between 1.75 g /cm³ (14.6 lb/ Gal) and 1.89 g/cm³ (15,8lb / Gal), curing time between 4 days and 28 days and concentration of SBR Latex between 0 L / m³ and 534.722 L / m³ (0 gpc and 4 gpc). The results showed that increasing the concentration of SBR latex, within the given ranges, there was a decreased compression resistance and elastic modulus by increasing the elastic deformability of the slurry. From the results it can determine best slurries formulation conditions in oil well cementing operations subject to steam injection.

O Litoral e a metrópole dinâmica imobiliária, turismo e expansão urbana na região metropolitana de Natal-RN

The metropolitan regions of Northeast Brazil are being gradually included in a scenario of international investments, which are motivated by the restructuring of both touristic and real-estate sectors. The new capital, real-estate developers and space configurations that result from this process indicate the need for the creation and implementation of public tools which should, at least, allow the mitigation of the urban impacts and environmental losses resulting from this situation. The effects on landscape and on the socio-spatial configuration result from the intensification caused by the dynamism of the "real estate-tourism" sector. There is a regional integration as an expression of the urban expansion of the metropolitan area of Natal. This study investigates the uniqueness of the restructuring and territorial integration of coastal areas and the strategies of the circuit of capital accumulation formed by linking the real estate to tourism. It is intended to increase the understanding about the strategies of tourism, real estate and public policy agents involved in this territorial reconfiguration and in the fund-raising needed for the investments, to understand the existing social and environmental effects and their future trends and also to understand the forms of spatial production as results from the practices of approaching the land transformation and the tourism valorization of the landscape, in a synchronous manner, first in the Northeast region and, as a focal study, in the Metropolitan Area of Natal. Likewise, it is intended to apprehend the current processes of metropolization of the eastern coast of Rio Grande do Norte, in addition to indicate its physical-territorial transformation and the types of projects/developments promoted by the market in the recent period. Based upon analysis undertaken for the Metropolitan Region of Natal RN, this piece of work presents some considerations on possible legal instruments that can be adjusted to the municipalities which are experiencing the impact of this peculiar and recent phenomenon in the region, caused by the arrival of the real estate-touristic capital. It is also intended to point out basic proposals to the forms of public intervention, in a speculative way, starting from a Metropolitan Planning project within a medium and long term

O computador no ensino de lígnua inglesa no CEFET/RN

The present study has as goal to analyze the aplicability of the computational technology as mediator in the english-speaking teaching in the Centro Federal de Educação Tecnológica do Rio Grande do Norte-CEFET/RN. The object of study was centered in the use of the computer incorporated in the teaching of English by four institution groups. The research was ruled metodologically in the study of case, adopting a qualitative and quantitative boarding of interpretative-reflexive mark. We support ourselves on a bibliographical literature revision that cares of the use of the computational technology matter into the class-room, aiming an education new practice, regarding the current reality conceptions in what we live in the technological education. We also use a referencial for a pedagogical action, trying to offer subsidies for a practice that provides the knowledges generation through the interaction, aiming a subject reflexive and critical education. For materialization of this study, we used esrutuctured action, as interviews for the teachers and students, besides the observations of the dayly in class-room, in order to get the necessary datas for analysis. During this study, we oserved that the use of the computer, while pedagogical support instrument in the english-speaking teaching, has acted like mediator of the teaching-learning process. The results demonstrate use of the computer use has been each more a practice adopted by other institution languages teachers. The conclusions confirm the hypothesis showed at the beginning of the work and evidence that the teachers are warden of forming thinking, reflexive and critical subjects. For that, they need to be prepared to face situations in which they can take the pedagogical practice to tune with the technological advances, consequently providing an effective technological education

Práticas pedagógicas das escolas de ensino médio que contribuem para a escolha do aluno pelo curso de Engenharia de Produção da UFRN

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Tratamento termoquímico do titânio auxiliado por plasma de ar - N2 - O2

Discs were grade II cp Ti oxynitride by plasma of Ar - N2 - O2 using different proportions of individual gases. These ratios were established from analysis of optical emission spectroscopy (OES) of plasma species. The proportions that resulted in species whose spectra showed an abrupt change of light intensity were chosen for this study. Nanohardness tests revealed that there was a correlation between the intensity of N2 + species with the hardness, because the treatments where they had a higher intensity, obtained a higher value nanohardness, although the crystalline phases have remained unchanged. With respect to topography, it was observed that in general, the surface roughness is related to the intensities of plasma species, because they may have different values depending on the behavior of the species. Images obtained by optical microscopy revealed a surface with grains of different colors to optical reflectance showed a peak of reflection in the red area. Measures the contact angle and surface tension showed hydrophilic properties and hydrophilic with little variation of polar and dispersive components of surface tension

Formação de professores, saberes, reflexividade e apropriação da cultura digital no Projeto Um Computador por Aluno (UCA)

This study investigates teacher training and cognitive practice of teachers in a Basic Education school that adopted the Project One Computer per Student (OCS) in their school routine. Its relevance consists in provide directions for the continuation of training activities on the Project and guide the teachers with their pedagogical practices using the laptop model one to one. The thesis defended is that the educator formation for social using of digital media (specially the laptops from the Project UCA) gives space to establish new sociotechnical relationships, of new social and professionals practices, new identitary components and a process of reflexivity and knowledge reconstruction to teach. We reaffirm the importance of reflexivity and appropriation of digital culture for the better development of teaching practice using the Information and Communication Technologies (ICTs), giving focus to the aspects of social and professional use of the technology. The study is part of the qualitative aspect and is a procedural tracking based on principles of ethnographic research. As procedures and methodological tools, were used: intensive observation of school environments, documental analysis, focal group, semi-structured questionnaires and semi-structured individual interviews. The research was held in a public school in the city of Parnamirim - RN. The subject sample relates to 17 teachers, coming from the elementary school I and II, Youth and Adult Education and High School, who went through the process of training UCA and having entered the laptops in their teaching. The research corpus is structured based on the messages built into the process of data collection and is analyzed based on principles of Content Analysis, specified by Laurence Bardin (2011). Was taken as theoretical reference studies by Tardif (2000; 2011), Pimenta (2009), Gorz (2004, 2005), Giddens (1991), Dewey, J. (1916), Boudieu (1994; 1999), Freire (1996; 2005), among others. The analysis indicates a process of reconstruction / revision of knowledge to teach and work in digital culture, being these knowledges guided by the experience of the subjects investigated. The reconstructed knowledges will be revealed from a categorization process. The following groups of knowledges: "technical knowledges", "didactic-methodological knowledges and knowledges of professionalization" were built on the assumption of ownership of digital culture in the educational context. The analysis confirms the appearance of new ways of sociability when acquiring other forms of acting and thinking ICTs, despite the environment adverse to the reflexivity shared among the teachers. Also reveals, based on the ownership concept present on the data analysis, the construction of meanings of belonging and transformation of individuals into social routes from the interweaving of the teaching practice with the digital culture. Emphasizes, finally, the importance of a training for use of ICTs that exceeds the instrumentation, in other words, what we call "technical knowledges", but taking on its structural basis the shared reflection, the opening for the ressignificance (new meaning) and reconstruction of new knowledges and practices and that really allows, to the teacher, the living of an experience capable of providing socio-technical transformations of their relationships