Comunidades virtuales y producción de inteligencia económica y competitiva

CARVALHO, Andréa Vasconcelos . Comunidades virtuales y producción de inteligencia económica y competitiva. Inteligencia y Seguridad: revista de análisis y prospectiva, v. 3, p. 13-45, 2007

Capacidade de absorção de energia de tubos de compósitos submetidos à compressão

Structures capable of absorbing large amounts of energy are of great interest, particularly for the automotive and aviation industries, to reduce tbe impact on passengers in the case of a collision. The energy absorption properties of composite materials structures can be tailored, thus making these structures an appealing option a substitute of more traditional structures in applications where energy absorption is crucial. ln this research, the influence of some parameters, which affect the energy absorption capacity of composite material tubes, was investigated. The tubes were fabricated by hand lay-up, using orthophthalic polyester resin and a plain weave E-glass fabric Test specimens were prepared and tested under compression load. The ínfluence of the following parameters on the specific energy absorption capacity of the tubes was studied: fiber configuration (0/90º or ± 45°), tube cross-section (circular or square), and processing conditions (with or without vacuum). The results indicated that circular cross-section tubes with fibers oriented at 0/90º presented the highest level of specific energy absorbed. Further, specimens from tubes fabricated under vacuum displayed higher energy absorption capacity, when compared with specimens from tubes fabricated without vacuum. Thus, it can be concluded that the fabrication process with vacuum produce composite structures with better energy absorption capacity

Efeito de adições poliméricas na aderência de pastas de cimento a tubos metálicos após ciclagem térmica

Thermal recovery methods, especially steam injection, have been used to produce heavy oils. However, these methods imply that the metallic casing-cement sheath interface is submitted to thermal cycling. As a consequence, cracking may develop due to the thermal expansion mismatch of such materials, which allows the flow of oil and gas through the cement sheath, with environmental and economical consequences. It is therefore important to anticipate interfacial discontinuities that may arise upon Thermal recovery. The present study reports a simple alternative method to measure the shear strength of casing-sheath interfaces using pushthrough geometry, applied to polymer-containing hardened cement slurries. Polyurethane and recycled tire rubber were added to Portland-bases slurries to improve the fracture energy of intrinsically brittle cement. Samples consisting of metallic casing sections surrounded by hardened polymer-cement composites were prepared and mechanically tested. The effect of thermal cycles was investigated to simulate temperature conditions encountered in steam injection recovery. The results showed that the addition of polyurethane significantly improved the shear strength of the casing-sheath interface. The strength values obtained adding 10% BWOC of polyurethane to a Portland-base slurry more than doubled with respect to that of polyurethane-free slurries. Therefore, the use of polyurethane significantly contributes to reduce the damage caused by thermal cycling to cement sheath, improving the safety conditions of oil wells and the recovery of heavy oils

Estudo de um isolante térmico para tubos fabricado em material compósito

It presents a new type of insulation for ductwork hot water, which can be used in solar systems for heating water, which consists of a composite of different compositions based on plaster, cement and EPS ground, palm and water. This composite has as its main features easy assembly and manufacturing processes and low cost. Comparative results will be presented on the tests of materials and thermal tubes proposed. Four formulations were used to manufacture tubes with three diameters 70, 65 and 42mm. It was also tested conventionally used for elastomeric foam insulation to 110 ° C, for a comparative analysis with the composite pipe insulator proposed. It will demonstrate that the cost of manufacturing of such tubes is competitive with alternative elastomeric foam tested, but results of the composite tube to the temperature range studied, are lower. Another drawback of the composite insulator tube is its large mass. It would be important to test such a composite for greater levels of temperature to a diagnostic technique competitive with conventionally used insulators. A positive factor of using the proposed composite-tube would be the recycling of EPS so damaging to the environment, representing an environmentally friendly application of science

Modelagem e simulação da solubilização da parafina em tubos circulares e em regime laminar

O óleo produzido nos novos campos de petróleo está cada vez mais parafínico e viscoso, com isso, à medida que o óleo é escoado, parafinas são depositadas sobre as paredes internas do tubo, e ao longo do tempo, tendem a reduzir drasticamente a área transversal ao escoamento. Visando estudar o processo de solubilização da parafina em dutos, esse trabalho objetiva desenvolver modelos matemáticos que represente o processo, com base nos fenômenos envolvidos no mesmo tais como transferência de massa, transferência de energia e equilíbrio sólido-líquido, implementando-os em um ambiente de desenvolvimento VBA (Visual Basic) for Excel ®. O presente trabalho foi realizado em quatro etapas: i) modelagem dos fenômenos de transferência de calor e massa, ii) modelagem da rotina dos coeficientes de atividade através do modelo UNIFAC e modelagem do sistema de equilíbrio sólido-líquido; iii) modelagem matemática do processo de solubilização e cálculo da espessura da parafina ao longo do tempo; iv) implementação dos modelos em um ambiente de desenvolvimento VBA for Excel® e criação de um simulador com uma interface gráfica, para simular o processo de solubilização da parafina depositada em dutos e sua otimização. O simulador conseguiu produzir soluções bastante adequadas, mantendo continuidade das equações diferenciáveis do balanço de energia e de massa, com uma interpretação física viável, sem a presença de dissipação de oscilações nos perfis de temperatura e massa. Além disso, esse simulador visa permitir a simulação nas diversas condições de escoamento, bem como compreender a importância das variáveis (vazão, temperatura de entrada, temperatura externa, cadeia carbônica do solvente). Através dos resultados foram possíveis verificar os perfis de temperatura, fração molar e o de solubilização