EE - Artigos Publicados em Periódicos
URI permanente para esta coleçãohttps://rihomolog.furg.br/handle/1/513
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- ItemO regime de metas de inflação foi a melhor escolha para o Brasil?(2011) Leal, Ricardo Aguirre; Feijó, Flávio TosiO objetivo deste artigo é apresentar as opções de regimes monetários que defrontavam a autoridade monetária brasileira com o fim do câmbio fixo em janeiro de 1999 e verificar se a escolha pelo regime de metas de inflação foi a mais adequada. Através da análise dos aspectos teóricos, das vantagens e desvantagens de cada regime e, dado o histórico de instabilidade da inflação e falta de credibilidade da autoridade monetária brasileira concluiu-se que o regime de metas de inflação foi a melhor escolha para aquele momento.
- ItemMigração interestadual de retorno e autosseleção: evidências para o Brasil(2011) Ramalho, Hilton Martins de Brito; Queiroz, Vívian dos SantosEste trabalho analisa os impactos da experiência de migração interestadual no Brasil sobre salários dos trabalhadores remigrados a seus estados de nascimento. Para tanto, a partir dos dados recentes da Pesquisa Nacional por Amostra de Domicílios (PNAD) de 2007 foi empregado um modelo empírico de determinação conjunta de migração e rendimentos. Os principais resultados apontam que os migrantes de retorno são negativamente selecionados em relação aos migrantes não retornados. Contudo, a remigração produz ganhos salariais para os trabalhadores mais instruídos, possivelmente pela melhor absorção de capital humano específico à região de destino inicial.
- ItemCiclos econômicos e emissão de CO2 no Brasil: uma análise dinâmica para políticas ambientais ótimas(2015) Leal, Ricardo Aguirre; Ely, Regis Augusto; Uhr, Júlia Gallego Ziero; Uhr, Daniel de Abreu PereiraEste artigo estuda como as políticas ambientais devem responder de forma ótima aos ciclos econômicos no Brasil. Para isso utilizamos um modelo de ciclos reais de negócios (RBC) com externalidades de poluição. Os resultados indicam que o custo de mitigação de emissões de carbono é mais baixo que o da poluição no Brasil, justificando a adoção de políticas restritivas. Além disso, diante de choques de produtividade, o comportamento ótimo é uma política de mitigação pró-cíclica, onde o imposto e o teto de emissões devem aumentar em períodos de expansão da economia e diminuir em períodos de crise. Também definimos uma regra de decisão para a dinâmica da política de mitigação.
- ItemAn experimental investigation by towing tank on VIV of a long flexible cylinder for deepwater riser application(Springer, 2013) Jijun, Gu; Vitola, Marcelo Araujo; Coelho, Jairo Fernando de Lima; Pinto, Waldir Terra; Duan, Menglan; Levi, CarlosIn this study, the dynamic response of a vertical flexible cylinder vibrating at low mode numbers with combined x-y motion was investigated in a towing tank. The uniform flow was simulated by towing the flexible cylinder along the tank in still water; therefore, the turbulence intensity of the free flow was negligible in obtaining more reliable results. A lower branch of dominant frequencies with micro vibration amplitude was found in both cross-flow and in-line directions. This justifiable discrepancy was likely caused by an initial lock-in. The maximum attainable amplitude, modal analysis and x-y trajectory in cross-flow and in-line directions are reported here and compared with previous literature, along with some good agreements and different observations that were obtained from the study. Drag and lift coefficients are also evaluated by making use of a generalized integral transform technique approach, yielding an alternative method to study fluid force acting upon a flexible cylinder.
- ItemÍndices de Eficácia e Eficiência para a Política Monetária: Uma análise do desempenho brasileiro nas Metas de Inflação(2013) Leal, Ricardo Aguirre; Feijó, Flávio TosiO presente estudo teve o objetivo de avaliar e quantificar o desempenho da política monetária brasileira no regime de Metas de Inflação, utilizando Indicadores de Eficácia e Eficiência, o que pode ser considerado uma nova metodologia para avaliação de política monetária. Ao final concluiu-se que a política monetária, ao longo dos doze anos completos de Metas de Inflação, foi ineficaz em quatro anos do período e ineficiente em cinco anos, ao passo que a meta da inflação não foi atingida apenas em três anos do período.
- ItemResin transfer molding process: a numerical analysis(2014) Oliveira, Iran Rodrigues de; Amico, Sandro Campos; Souza, Jeferson Avila; Lima, Antonio Gilson Barbosa deThis work aims to investigate the infiltration of a CaCO3 filled resin using experiments and the PAM-RTM software. A preform of glass fiber mat, with dimensions 320 x 150 x 3.6 mm, has been used for experiments conducted at room temperature, with injection pressure of 0.25bar. The resin contained 10 and 40% CaCO3 content with particle size 38μm. The numerical results were evaluated by direct comparison with experimental data. The flat flow-front profile of the rectilinear flow was reached approximately halfway the length of the mold. It was observed, that the speed of the filling decreases with increasing CaCO3 content and,the higher the amount of CaCO3 in the resin, the lower the permeability of the reinforcement that is found. The reduction in permeability is due to the presence of calcium carbonate particles between the fibers, hindering the resin flow in the fibrous media. The computational fluid flow analysis with the PAM-RTM proved to be an accurate tool study for the processing of composite materials.
- ItemNumerical analysis of the resin transfer molding process via PAM - RTM Software(2015) Oliveira, Iran Rodrigues de; Amico, Sandro Campos; Souza, Jeferson Avila; Lima, Antonio Gilson Barbosa deThis work aims to investigate the infiltration of a CaCO3 filled resin in fibrous porous media (resin transfer molding process) using the PAM-RTM software. A preform of glass fiber mat (fraction 30%), with dimensions 320 x 150 x 3.6 mm, has been used in rectilinear injection experiments conducted at room temperature and injection pressure 0.25, 0.50 and 0.75 bar. The polyester resin contain 0% and 40% CaCO3. The numerical results were evaluated by direct comparison with experimental data. The flat flow-front profile of the rectilinear flow was reached approximately half length of the mold. It was observed, that the both velocity infiltration and permeability have decreased with increasing the CaCO3 content, thus, increasing the time to processing of the composite material.
- ItemTypical scenarios of wave regimes off Rio Grande do Sul, Southern Brazil(2015) Romeu, Marco Antônio Rigola; Fontoura, Jose Antonio Scotti; Melo Filho, EloiIn this study, 30 years of sea state data, reconstructed by the wave generation model WWIII for the oceanic area, were used to investigate wave regimes in southern Brazil. By applying a splitting routine to the spectra generated by WaveWatch III (WWIII), each sea state was decomposed into its primary and secondary wave systems. Histograms of the wave height and period against the direction of incidence, constructed for the 30-year period, showed that the region possesses two major wave systems: seas from the E quadrant, and swells from the S quadrant. In a more detailed characterization, histograms constructed with 30 years of data were compared with annual histograms. and the results were used to identify the year that best represented the totality of the data. For the representative year identified, clusters analysis was applied, and six typical scenarios were found for the wave system off Rio Grande do Sul, southern Brazil: (1) E swells, (2) E seas, (3) W seas, (4) S seas, (5) S swells, and (6) SE ground swells. A seasonal analysis revealed that S swells are dominant in the autumn and winter, whereas E quadrant waves (ENE swells and ENE seas) predominate in summer and spring, with more swells in spring and more seas in summer.
- ItemTemperature and pressure drop model for gaseous helium cooled superconducting DC cables(2013) Ordonez, Juan Carlos; Souza, Jeferson Avila; Shah, Darshit Rajiv; Vargas, Jose Viriato Coelho; Hovsapian, RobThe need to transfer large amounts of power in applications where cabling weight and space are a major issue has increased the interest in superconducting cables. Gaseous helium and neon are being considered as possible coolants due to their suitability for the expected operating temperature ranges. Gaseous helium is preferred due to its higher thermal conductivity and relatively lower cost than neon. This paper enhances a previously presented mathematical model of a superconducting cable contained in a flexible cryostat by including flow pressure drops. In this way, the model is capable of properly sizing and minimizing fan power, and allows the prediction of system response to localized heating events (e.g., quenching). A volume element model approach was used to develop a physics model, based on fundamental correlations, and principles of classical thermodynamics, mass and heat transfer, which resulted in a system of ordinary differential equations with time as the independent variable. The spatial dependence of the model is accounted for through the three-dimensional distribution of the volume elements in the computational domain. The model numerically obtains the temperature distribution under different environmental conditions. Pressure drop calculations are based on realistic correlations that account for the wavy nature of the coolant channels. Converged solutions were obtained within the imposed numerical accuracy even with coarse meshes.
- ItemA volume element model (VEM) for energy systems engineering(2015) Dilay, Emerson; Vargas, Jose Viriato Coelho; Souza, Jeferson Avila; Ordonez, Juan Carlos; Yang, Sam; Mariano, André BellinThis work presents a simplified modeling and simulation approach for energy systems engineering that is capable of providing quick and accurate responses during system design. For that, the laws of conservation are combined with available empirical and theoretical correlations to quantify the diverse types of flows that cross the system and produce a simplified tridimensional mathematical model, namely a volume element model (VEM). The physical domain of interest is discretized in space, thus producing a system of algebraic and ODEs with respect to time, whose solution delivers the project variables spatial distribution and dynamic response. In order to illustrate the application of the VEM in energy systems engineering, three example problems are considered: (i) a regenerative heat exchanger; (ii) a power electronic building block (PEBB); and (iii) a notional all-electric ship. The same mathematical model was used to analyze problems (ii) and (iii), that is, the thermal management of heat-generating equipment packaging. In the examples, the converged mesh had a total of 20, 2000, and 7725 volume elements. The third problem led to the largest simulation, which for steady-state cases took between 5 and 10 min of computational time to reach convergence and for the ship dynamic response 50 min (i.e., 80,000 s of real time). The regenerative heat exchanger model demonstrated how VEM allowed for the coexistence of different phases (subsystems) within the same volume element. The thermal management model was adjusted and experimentally validated for the PEBB system, and it was possible to perform a parametric and dynamic analysis of the PEBB and of the notional all-electric ship. Therefore, because of the observed combination of accuracy and low computational time, it is expected that the model could be used as an efficient tool for design, control, and optimization in energy systems engineering.