Efeitos do envelhecimento ambiental acelerado em compósitos poliméricos

The advantages of the use of vegetable fibers on the synthetic fibers, such as glass fibers, in the reinforcements in composites are: low cost, low density, good tenacity, good thermal properties and reduced use of instruments for their treatment or processing. However, problems related to poor performance of some mechanical natural fibers, have hindered its direct use in structural elements. In this sense, the emergence of alternative materials such as hybrids composites, involving natural and synthetic fibers, has been encouraged by seeking to improve the performance of structural composites based only on natural fibers. The differences between the physical, chemical and mechanical properties of these fibers, especially facing the adverse environmental conditions such as the presence of moisture and ultraviolet radiation, is also becoming a concern in the final response of these composites. This piece of research presents a comparative study of the strength and stiffness between two composite, both of ortoftalic polyester matrix, one reinforced with fibers of glass-E (CV) and other hybrid reinforced with natural fibers of curauá and fiberglass-E (CH). All the comparative study is based on the influence of exposure to UV rays and steam heated water in composites, simulating the aging environment. The conditions for the tests are accelerated through the use of the aging chamber. The composites will be evaluated through tests of uniaxial static mechanical traction and bending on three points. The composite of glass fiber and hybrid manufacturing industry are using the rolling manual (hand lay-up) and have been developed in the form of composites. All were designed to meet possible structural applications such as tanks and pipes. The reinforcements used in composites were in the forms of short fiber glass-E quilts (450g/m2 - 5cm) of continuous wires and fuses (whose title was of 0.9 dtex) for the curauá fibers. The results clearly show the influence of aging on the environmental mechanical performance of the composite CV and CH. The issues concerning the final characteristics of the fracture for all types of cargoes studied were also analyzed

Maturidade em gerenciamento de projetos no contexto da gestão estratégica no setor público: análise na Secretaria de Estado da Tributação do Rio Grande do Norte

This paperwork attempts to measure the project management maturity in the State Department of Taxation in Rio Grande do Norte. Project management has shown to be a critical component to any organization success, as the projects are directly related to a set of activities resulting into organizational innovations such as products, services and processes; and its improvement is directly aligned with the strategic management. Methodologically, this paperwork uses both a quantitative and qualitative approach that will be applied to the coordinators, sub-coordinators, and directors of the Regional Offices of the State Department of Taxation. In the theoretical reference it is about the public management and analyzes the strategic management in contemporary public administration. Presents the maturity in project management is by discussing the main models: CMM, Capability Maturity Model; PMMM, Project Management Maturity Model; OPM3, Organization Project Maturity Model and the Prado-MMGP, Modelo de Maturidade em Gerenciamento de Projetos. From this analysis, considering attributes as an aid in taking strategic positioning, access to the model, possibility of benchmarking and continuous improvement, the Prado-MMGP model was the most appropriate for this research process. It has been proved that the State Department of Taxation shows a very low project management maturity level. Regarding the acceptance of the maturity dimensions by the State Department, it is still in an early developmental stage, as one of the dimensions showed a poor performance while the rest showed a regular one. In contrast with similar organizations, the maturity results have shown to be below the national average. The maturity assessment enables in the institution the implementation of a plan for institutional growth with the creation of sector strategic and project management

Modelos de condutividade térmica em rochas silicáticas, com ênfase em rochas da província Borborema, NE do Brasil

A practical approach to estimate rock thermal conductivities is to use rock models based just on the observed or expected rock mineral content. In this study, we evaluate the performances of the Krischer and Esdorn (KE), Hashin and Shtrikman (HS), classic Maxwell (CM), Maxwell-Wiener (MW), and geometric mean (GM) models in reproducing the measures of thermal conductivity of crystalline rocks.We used 1,105 samples of igneous and metamorphic rocks collected in outcroppings of the Borborema Province, Northeastern Brazil. Both thermal conductivity and petrographic modal analysis (percent volumes of quartz, K-feldspar, plagioclase, and sum of mafic minerals) were done. We divided the rocks into two groups: (a) igneous and ortho-derived (or meta-igneous) rocks and (b) metasedimentary rocks. The group of igneous and ortho-derived rocks (939 samples) covers most the lithologies de_ned in the Streckeisen diagram, with higher concentrations in the fields of granite, granodiorite, and tonalite. In the group of metasedimentary rocks (166 samples), it were sampled representative lithologies, usually of low to medium metamorphic grade. We treat the problem of reproducing the measured values of rock conductivity as an inverse problem where, besides the conductivity measurements, the volume fractions of the constituent minerals are known and the effective conductivities of the constituent minerals and model parameters are unknown. The key idea was to identify the model (and its associated estimates of effective mineral conductivities and parameters) that better reproduces the measures of rock conductivity. We evaluate the model performances by the quantity  that is equal to the percentage of number of rock samples which estimated conductivities honor the measured conductivities within the tolerance of 15%. In general, for all models, the performances were quite inferior for the metasedimentary rocks (34% <  < 65%) as compared with the igneous and ortho-derived rocks (51% <  < 70%). For igneous and ortho-derived rocks, all model performances were very similar ( = 70%), except the GM-model that presented a poor performance (51% <  < 65%); the KE and HS-models ( = 70%) were slightly superior than the CM and MW-models ( = 67%). The quartz content is the dominant factor in explaining the rock conductivity for igneous and ortho-derived rocks; in particular, using the MW-model the solution is in practice vi UFRN/CCET– Dissertação de mestrado the series association of the quartz content. On the other hand, for metasedimentary rocks, model performances were different and the performance of the KEmodel ( = 65%) was quite superior than the HS ( = 53%), CM (34% <  < 42%), MW ( = 40%), and GM (35% <  < 42%). The estimated effective mineral conductivities are stable for perturbations both in the rock conductivity measures and in the quartz volume fraction. The fact that the metasedimentary rocks are richer in platy-minerals explains partially the poor model performances, because both the high thermal anisotropy of biotite (one of the most common platy-mineral) and the difficulty in obtaining polished surfaces for measurement coupling when platyminerals are present. Independently of the rock type, both very low and very high values of rock conductivities are hardly explained by rock models based just on rock mineral content.

Uma técnica de linearização por realimentação para compensação de agarramento em válvulas de controle pneumáticas

In control loops valve stiction is a very common problem. Generally, it is one of main causes of poor performance of industrial systems. Its most commonly observed effect is oscillation in the process variables. To circumvent the undesirable effects, friction compensators have been proposed in order to reduce the variability in the output. This work analyzes the friction compensation in pneumatic control valves by using feedback linearization technique. The valve model includes both dead zone and jump. Simulations show that the use of this more complete model results in controllers with superior performance. The method is also compared through simulations with the method known as Constant Reinforcement (CR), widely used in this problem.

Uso didático do Facebook como estratégia de leitura para o gênero textual poesia

The poor performance of students in reading and writing activities, prompted the search for actions that would minimize this problem, noticeable mainly in public education. The lack of interest in reading of poetic texts seen in students from the 7th year in a public school in RN, has led us to question the reasons for the rejection of poetry. Thus, the idea to organize and develop new reading possibilities mediated by digital technologies, considering the preference of teenagers by virtual environments. Therefore, it was essential to observe how students used web resources in order to plan actions that aimed to improve their reading performance. We present to justify the need for reflection on the educational problems starting from our reality, in order to establish appropriate procedures to minimize them. To this end, we draw is to investigate how students appropriated the Facebook social network in order to elaborate reading strategies using this platform. The study is anchored in the reflections of the following theorists and researchers: language concepts and language: Bakhtin (2011 [1979] 2006 [1999]), Bronckart (2012 [1999]), Marcuschi (2008); reading strategies: Leffa (1996) Solé (1998), Antunes (2009), Kleiman (2013); genre: Bakhtin (2011 [1979] 2006 [1999]), Marcuschi (2008); didactic sequence: Dolz, Noverraz and Schneuwly (2013 [2004]); technologies: Moran (2008 [2000]), Kenski (2007), Bento (2012), Behrens (2013); literary literacy: Cosson (2007); other theoretical orientations: PCN (1998), PDE (2008), Perrenoud (1999), among others. The methodology followed action research guidelines, a qualitative approach perspective. The research instruments included questionnaires, interviews, observations and field notes. The results pointed to the interest of students in this social network, which favored the development of a didactic sequence whose activities converged on the didactic use of Facebook as a support for the presentation of textual poetry genre, drawing the attention of students for reading. Thus, we reiterate the need to include the pedagogical use of Information and Communication Digital Technologies educational activities to better meet the expectations of the generation of "digital natives", offering them a significant Portuguese-speaking school that fits your interests.

Uso didático do Facebook como estratégia de leitura para o gênero textual poesia

The poor performance of students in reading and writing activities, prompted the search for actions that would minimize this problem, noticeable mainly in public education. The lack of interest in reading of poetic texts seen in students from the 7th year in a public school in RN, has led us to question the reasons for the rejection of poetry. Thus, the idea to organize and develop new reading possibilities mediated by digital technologies, considering the preference of teenagers by virtual environments. Therefore, it was essential to observe how students used web resources in order to plan actions that aimed to improve their reading performance. We present to justify the need for reflection on the educational problems starting from our reality, in order to establish appropriate procedures to minimize them. To this end, we draw is to investigate how students appropriated the Facebook social network in order to elaborate reading strategies using this platform. The study is anchored in the reflections of the following theorists and researchers: language concepts and language: Bakhtin (2011 [1979] 2006 [1999]), Bronckart (2012 [1999]), Marcuschi (2008); reading strategies: Leffa (1996) Solé (1998), Antunes (2009), Kleiman (2013); genre: Bakhtin (2011 [1979] 2006 [1999]), Marcuschi (2008); didactic sequence: Dolz, Noverraz and Schneuwly (2013 [2004]); technologies: Moran (2008 [2000]), Kenski (2007), Bento (2012), Behrens (2013); literary literacy: Cosson (2007); other theoretical orientations: PCN (1998), PDE (2008), Perrenoud (1999), among others. The methodology followed action research guidelines, a qualitative approach perspective. The research instruments included questionnaires, interviews, observations and field notes. The results pointed to the interest of students in this social network, which favored the development of a didactic sequence whose activities converged on the didactic use of Facebook as a support for the presentation of textual poetry genre, drawing the attention of students for reading. Thus, we reiterate the need to include the pedagogical use of Information and Communication Digital Technologies educational activities to better meet the expectations of the generation of "digital natives", offering them a significant Portuguese-speaking school that fits your interests.