8 resultados para R3
em Universidade Federal do Rio Grande do Norte(UFRN)
Resumo:
Metal powder sintering appears to be promising option to achieve new physical and mechanical properties combining raw material with new processing improvements. It interest over many years and continue to gain wide industrial application. Stainless steel is a widely accepted material because high corrosion resistance. However stainless steels have poor sinterability and poor wear resistance due to their low hardness. Metal matrix composite (MMC) combining soft metallic matrix reinforced with carbides or oxides has attracted considerable attention for researchers to improve density and hardness in the bulk material. This thesis focuses on processing 316L stainless steel by addition of 3% wt niobium carbide to control grain growth and improve densification and hardness. The starting powder were water atomized stainless steel manufactured for Höganäs (D 50 = 95.0 μm) and NbC produced in the UFRN and supplied by Aesar Alpha Johnson Matthey Company with medium crystallite size 16.39 nm and 80.35 nm respectively. Samples with addition up to 3% of each NbC were mixed and mechanically milled by 3 routes. The route1 (R1) milled in planetary by 2 hours. The routes 2 (R2) and 3 (R3) milled in a conventional mill by 24 and 48 hours. Each milled samples and pure sample were cold compacted uniaxially in a cylindrical steel die (Ø 5 .0 mm) at 700 MPa, carried out in a vacuum furnace, heated at 1290°C, heating rate 20°C stand by 30 and 60 minutes. The samples containing NbC present higher densities and hardness than those without reinforcement. The results show that nanosized NbC particles precipitate on grain boundary. Thus, promote densification eliminating pores, control grain growth and increase the hardness values
Resumo:
The cerium oxide has a high potential for use in removing pollutants after combustion, removal of organic matter in waste water and the fuel-cell technology. The nickel oxide is an attractive material due to its excellent chemical stability and their optical properties, electrical and magnetic. In this work, CeO2-NiO- systems on molars reasons 1:1(I), 1:2(II) e 1:3(III) metal-citric acid were synthesized using the Pechini method. We used techniques of TG / DTG and ATD to monitor the degradation process of organic matter to the formation of the oxide. By thermogravimetric analysis and applying the dynamic method proposed by Coats-Redfern, it was possible to study the reactions of thermal decomposition in order to propose the possible mechanism by which the reaction takes place, as well as the determination of kinetic parameters as activation energy, Ea, pre-exponential factor and parameters of activation. It was observed that both variables exert a significant influence on the formation of complex polymeric precursor. The model that best fitted the experimental data in the dynamic mode was R3, which consists of nuclear growth, which formed the nuclei grow to a continuous reaction interface, it proposes a spherical symmetry (order 2 / 3). The values of enthalpy of activation of the system showed that the reaction in the state of transition is exothermic. The variables of composition, together with the variable temperature of calcination were studied by different techniques such as XRD, IV and SEM. Also a study was conducted microstructure by the Rietveld method, the calculation routine was developed to run the package program FullProf Suite, and analyzed by pseudo-Voigt function. It was found that the molar ratio of variable metal-citric acid in the system CeO2-NiO (I), (II), (III) has strong influence on the microstructural properties, size of crystallites and microstrain network, and can be used to control these properties
Resumo:
To enhance the maintenance practices, Oil and Gas Pipelines are inspected from the inside by automated systems called PIG (Pipeline Inspection Gauge). The inspection and mapping of defects, as dents and holes, in the internal wall of these pipelines are increasingly put into service toward an overall Structural Integrity Policy. The residual life of these structures must be determined such that minimize its probability of failure. For this reason, the investigation on the detection limits of some basic topological features constituted by peaks or valleys disposed along a smooth surface is of great value for determining the sensitivity of the measurements of defects from some combinations of circumferential, axial and radial extent. In this investigation, it was analyzed an inductive profilometric sensor to scan three races, radius r1, r2, r3, in a circular surface of low carbon steel, equipped with eight consecutive defects simulated by bulges and holes by orbit, equally spaced at p/4 rad. A test rig and a methodology for testing in laboratory were developed to evaluate the sensor response and identify their dead zones and jumps due to fluctuations as a function of topological features and scanning velocity, four speeds different. The results are presented, analyzed and suggestions are made toward a new conception of sensor topologies, more sensible to detect these type of damage morphologies
Resumo:
A 3D binary image is considered well-composed if, and only if, the union of the faces shared by the foreground and background voxels of the image is a surface in R3. Wellcomposed images have some desirable topological properties, which allow us to simplify and optimize algorithms that are widely used in computer graphics, computer vision and image processing. These advantages have fostered the development of algorithms to repair bi-dimensional (2D) and three-dimensional (3D) images that are not well-composed. These algorithms are known as repairing algorithms. In this dissertation, we propose two repairing algorithms, one randomized and one deterministic. Both algorithms are capable of making topological repairs in 3D binary images, producing well-composed images similar to the original images. The key idea behind both algorithms is to iteratively change the assigned color of some points in the input image from 0 (background)to 1 (foreground) until the image becomes well-composed. The points whose colors are changed by the algorithms are chosen according to their values in the fuzzy connectivity map resulting from the image segmentation process. The use of the fuzzy connectivity map ensures that a subset of points chosen by the algorithm at any given iteration is the one with the least affinity with the background among all possible choices
Resumo:
INTRODUCTION: Chronic kidney disease (CKD) is a global health problem, with increasing prevalence in its terminal stage and one of the factors that can contribute is the failure to recognize the disease and its risk factors. OBJECTIVE: To evaluate the knowledge of medical residents (MR) and medical preceptors (MP) in hospitals in the Federal University of Rio Grande do Norte in Natal-RN - Brazil, on the DRC, based on the policy of the Kidney Disease Improving Global Outcomes (KDIGO ). METHODS: Cross-sectional study where 64 MR (R1 = 32; R2 = 15; R3 = 17) and 63 MP answered a questionnaire divided into seven sessions that addressed aspects of the DRC since the setting up referral to a nephrologist. RESULTS: Only 20 participants (15.7%) reported using any guidelines for the management of CKD. The scores obtained by session were: Definition and classification (46.1 ± 47.8); Risk factors (70.5 ± 27.9); Laboratory evaluation (58.2 ± 8.8); Clinical action plan (57.6 ± 19.9); Reduction in proteinuria (68.3 ± 15.0); Complications (64.8 ± 19.9); Referral to a nephrologist (73.0 ± 44.6). There was a statistically significant difference between the knowledge of MR and MP in the sessions: Laboratory evaluation (MR 61.5 ± 8.4 vs 54.8 ± 7.9 MP; p <0.001); Reduction in proteinuria (73.1 ± 11.4 vs MR MP 63.5 ± 16.7; p <0.001) and Referral to a nephrologist (MR 81.2 ± 39.3 vs 64.5 ± 48.2 MP; p = 0.035). Among the MR, the R2 obtained the best score (63.9 ± 22.6 vs R1 R2 R3 71.9 ± 17.2 vs 63.5 ± 22.5, p = 0.445). It identified a low percentage of success of the doctors on the definition of CKD (MP = 46%; R1 = 40.6%; R2 = 60%; R3 = 52.9%; p = 0.623) and classification (MP = 34.9%; R1 = 53.1%, R2 = 60%; R3 = 52.9%; p = 0.158). CONCLUSION: The study showed that most doctors do not use any guidelines for clinical management of CKD and that there are gaps in knowledge on the subject, even among physicians who work in the university environment. In this sense, we propose the realization of mini-workshops for participants and students from boarding UFRN, using Case-Based Learning Strategy (CBL), with small group discussion, to strengthen the incorporation of CKD guidelines in undergraduate teaching and in clinical medical practice in general.
Resumo:
INTRODUCTION: Chronic kidney disease (CKD) is a global health problem, with increasing prevalence in its terminal stage and one of the factors that can contribute is the failure to recognize the disease and its risk factors. OBJECTIVE: To evaluate the knowledge of medical residents (MR) and medical preceptors (MP) in hospitals in the Federal University of Rio Grande do Norte in Natal-RN - Brazil, on the DRC, based on the policy of the Kidney Disease Improving Global Outcomes (KDIGO ). METHODS: Cross-sectional study where 64 MR (R1 = 32; R2 = 15; R3 = 17) and 63 MP answered a questionnaire divided into seven sessions that addressed aspects of the DRC since the setting up referral to a nephrologist. RESULTS: Only 20 participants (15.7%) reported using any guidelines for the management of CKD. The scores obtained by session were: Definition and classification (46.1 ± 47.8); Risk factors (70.5 ± 27.9); Laboratory evaluation (58.2 ± 8.8); Clinical action plan (57.6 ± 19.9); Reduction in proteinuria (68.3 ± 15.0); Complications (64.8 ± 19.9); Referral to a nephrologist (73.0 ± 44.6). There was a statistically significant difference between the knowledge of MR and MP in the sessions: Laboratory evaluation (MR 61.5 ± 8.4 vs 54.8 ± 7.9 MP; p <0.001); Reduction in proteinuria (73.1 ± 11.4 vs MR MP 63.5 ± 16.7; p <0.001) and Referral to a nephrologist (MR 81.2 ± 39.3 vs 64.5 ± 48.2 MP; p = 0.035). Among the MR, the R2 obtained the best score (63.9 ± 22.6 vs R1 R2 R3 71.9 ± 17.2 vs 63.5 ± 22.5, p = 0.445). It identified a low percentage of success of the doctors on the definition of CKD (MP = 46%; R1 = 40.6%; R2 = 60%; R3 = 52.9%; p = 0.623) and classification (MP = 34.9%; R1 = 53.1%, R2 = 60%; R3 = 52.9%; p = 0.158). CONCLUSION: The study showed that most doctors do not use any guidelines for clinical management of CKD and that there are gaps in knowledge on the subject, even among physicians who work in the university environment. In this sense, we propose the realization of mini-workshops for participants and students from boarding UFRN, using Case-Based Learning Strategy (CBL), with small group discussion, to strengthen the incorporation of CKD guidelines in undergraduate teaching and in clinical medical practice in general.
Resumo:
Metal powder sintering appears to be promising option to achieve new physical and mechanical properties combining raw material with new processing improvements. It interest over many years and continue to gain wide industrial application. Stainless steel is a widely accepted material because high corrosion resistance. However stainless steels have poor sinterability and poor wear resistance due to their low hardness. Metal matrix composite (MMC) combining soft metallic matrix reinforced with carbides or oxides has attracted considerable attention for researchers to improve density and hardness in the bulk material. This thesis focuses on processing 316L stainless steel by addition of 3% wt niobium carbide to control grain growth and improve densification and hardness. The starting powder were water atomized stainless steel manufactured for Höganäs (D 50 = 95.0 μm) and NbC produced in the UFRN and supplied by Aesar Alpha Johnson Matthey Company with medium crystallite size 16.39 nm and 80.35 nm respectively. Samples with addition up to 3% of each NbC were mixed and mechanically milled by 3 routes. The route1 (R1) milled in planetary by 2 hours. The routes 2 (R2) and 3 (R3) milled in a conventional mill by 24 and 48 hours. Each milled samples and pure sample were cold compacted uniaxially in a cylindrical steel die (Ø 5 .0 mm) at 700 MPa, carried out in a vacuum furnace, heated at 1290°C, heating rate 20°C stand by 30 and 60 minutes. The samples containing NbC present higher densities and hardness than those without reinforcement. The results show that nanosized NbC particles precipitate on grain boundary. Thus, promote densification eliminating pores, control grain growth and increase the hardness values
Resumo:
The cerium oxide has a high potential for use in removing pollutants after combustion, removal of organic matter in waste water and the fuel-cell technology. The nickel oxide is an attractive material due to its excellent chemical stability and their optical properties, electrical and magnetic. In this work, CeO2-NiO- systems on molars reasons 1:1(I), 1:2(II) e 1:3(III) metal-citric acid were synthesized using the Pechini method. We used techniques of TG / DTG and ATD to monitor the degradation process of organic matter to the formation of the oxide. By thermogravimetric analysis and applying the dynamic method proposed by Coats-Redfern, it was possible to study the reactions of thermal decomposition in order to propose the possible mechanism by which the reaction takes place, as well as the determination of kinetic parameters as activation energy, Ea, pre-exponential factor and parameters of activation. It was observed that both variables exert a significant influence on the formation of complex polymeric precursor. The model that best fitted the experimental data in the dynamic mode was R3, which consists of nuclear growth, which formed the nuclei grow to a continuous reaction interface, it proposes a spherical symmetry (order 2 / 3). The values of enthalpy of activation of the system showed that the reaction in the state of transition is exothermic. The variables of composition, together with the variable temperature of calcination were studied by different techniques such as XRD, IV and SEM. Also a study was conducted microstructure by the Rietveld method, the calculation routine was developed to run the package program FullProf Suite, and analyzed by pseudo-Voigt function. It was found that the molar ratio of variable metal-citric acid in the system CeO2-NiO (I), (II), (III) has strong influence on the microstructural properties, size of crystallites and microstrain network, and can be used to control these properties
