dos Santos Fonseca A.L.,Federal University of Rio de Janeiro |
dos Santos Fonseca A.L.,Federal University of São Carlos |
Bianchini Jr. I.,Federal University of São Carlos |
Pimenta C.M.M.,Federal University of Rio de Janeiro |
And 2 more authors.
Hydrobiologia | Year: 2013
The water velocity and associated physical forces affect the distribution of organisms in rivers and streams; changes in the flows can also affect the organic matter decomposition and transport of detritus in lotic systems. The main objective of this study was to evaluate (120 days) the effects from the water flow velocity on the mass loss of leaves and stems in artificial channels (at 24 ± 1.0°C; current velocities: 0,5, and 10 cm s-1). The kinetic model used suggested that in addition to abrasion, the velocity of flow stressed the detritus fibers altering the decomposition pathways. Overall, the changes in the kinetic parameters varied linearly with the increase in flow velocity. Weight losses of the leaves were more affected by the flow velocity than those of the twigs. However, abrasion was more effective in the twigs than that in the leaves detritus. In the lotic systems, the leaves have greater importance in the detritus chains in the short term and in the conditions of backwater. The boost of flow velocity tends to change the refractory fractions (RPOM) into more labile/soluble compounds and increase the values of RPOM rate constant, owing to abrasion. © 2012 Springer Science+Business Media Dordrecht.
Da Costa Bortoni E.,Federal University of Itajubá |
Siniscalchi R.T.,Furnas Centrais Eletricas |
Jardini J.A.,University of Sao Paulo
IEEE Transactions on Energy Conversion | Year: 2011
The calorimetric method has for a long time been applied for energy conversion efficiency measurement in electrical machines. The number of temperature sensors necessary for its successful application in the field constitutes in one of the major drawbacks of the method. This paper shows how the usage of IR thermal imaging techniques can reduce costs and the necessary time for the calorimetric method application. In addition, contribution to the heat transfer coefficient determination and a new approach to consider conduction losses in the generator shaft are also presented. © 2011 IEEE.
Jusan F.C.,Furnas Centrais Eletricas |
Gomes Jr. S.,CEPEL - Center of Pesquisas de Enérgia Eletrica |
Taranto G.N.,Federal University of Rio de Janeiro
International Journal of Electrical Power and Energy Systems | Year: 2010
This paper presents the application of an improved dynamic phasor model of Static Var Compensator (SVC) in small-signal subsynchronous resonance (SSR) studies. The model is suitable for high frequency analysis (above 5 Hz) and takes into account the influence of Phase Locked Loop (PLL) circuit dynamics. A supplementary controller is designed for damping torsional modes due to SSR. The controller is designed using modal control theory to damp out critical modes in a wide range of series compensation and loading conditions. The study is conducted on the system-2 of the IEEE Second Benchmark Model. Excitation systems and power system stabilizers (PSS) are properly represented and incorporated into the system. Thus, the dynamic interactions among the several power system controllers and the network are considered in the supplementary controller design. The program PSCAD/EMTDC is used for the validation of the results obtained in the time domain simulations. © 2009 Elsevier Ltd. All rights reserved.
Dester M.,Furnas Centrais Eletricas
IEEE Latin America Transactions | Year: 2016
Integration of renewable sources into Brazils power mix is desirable and necessary. The main benefit from these energy sources is maintaining greenhouse gas emissions at low levels. Nevertheless, high penetration of these energy sources into the power mix can lead to many problems, for instance, intermittency in power generation. There are some mechanisms which can be implemented to mitigate intermittency and allow a higher level of participation of these energy sources in the generation mix. One such mechanism is utilizing Energy Storage Systems (ESS). The goal of this paper is to perform a study to find the best ESS options using Multi-criteria Decision Analysis. Moreover, an examination regarding Hydro Power Plants' reservoirs as an ESS is accomplished through a case study using three of Brazils significant Hydro Power Plants. © 2003-2012 IEEE.
De Oliveira J.A.,Furnas Centrais Eletricas |
Fonseca A.,Furnas Centrais Eletricas
Proceedings of the 3rd International Conference on Applied Robotics for the Power Industry, CARPI 2014 | Year: 2015
The major contribution of this paper is to draw attention to that new designs of robots also seek the joint use of accessories that help its displacement along the transmission lines. © 2014 IEEE.
Araujo F.G.,Federal Rural University of Rio de Janeiro |
Costa De Azevedo M.C.,Federal Rural University of Rio de Janeiro |
Lima Ferreira M.D.N.,Furnas Centrais Eletricas
Lake and Reservoir Management | Year: 2011
The water quality of a eutrophic tropical reservoir was studied over a 5-year period (2000-2004), with quarterly sampling (Jan, Apr, Jul, and Oct) carried out at 3 sampling stations with one station in each of 3 zones (fluvial, transitional, and lacustrine). During the wet season, large amounts of phosphorus were introduced into the reservoir by the increased inflow of the river. Dissolved oxygen, pH, and chlorophyll a levels peaked in the wet season; pH, chlorophyll a, and total phosphorus in several cases were recorded above the recommended Brazilian guidelines. Dissolved oxygen was lower than acceptable levels in the euphotic layer and reached very low levels in the hypolimnion, indicating thermal stratification. Efficient reservoir management is necessary to restore environmental quality, and our results indicate that selective withdrawal may be an effective means of improving the quality of water in Funil Reservoir. © Copyright by the North American Lake Management Society 2011.
Da Costa M.A.,Furnas Centrais Eletricas
Periodico Tche Quimica | Year: 2015
It is very important that the chemical contents are related to the daily life of the student in order to favor the understanding of the social context in which they are inserted. For this to occur the teacher can appropriate the elaboration of didactic sequences to assist you in choosing the best teaching-learning resources to be worked in the classroom, such as games, experiments and activities that favor the contextualization of the contents. In seeking work in this way the contents, from the elaboration of didactic sequences, these will contribute to arouse curiosity, motivation and participation of students in class and encouraging the teaching and learning process. From this perspective the present article focused on the development of a didactic sequence for the chemical content acid, where from that the teacher can work in the classroom various teaching resources for the content herein. However they were developed different methods to teach the chemical content acid and base, using so experimentation, making a game and a contextualized approach. The choice of the methodology presented here it was with the intention that, from this use can encourage a better use of the content by the students and that they can better understand the content and the relationship of chemistry with your social context. © 2015. Porto Alegre, RS. Brasil.
de Carvalho M.R.P.,Federal University of Rio de Janeiro |
Fairbairn E.d.M.R.,Federal University of Rio de Janeiro |
Filho R.D.T.,Federal University of Rio de Janeiro |
Cordeiro G.C.,State University of Norte Fluminense |
Hasparyk N.P.,Furnas Centrais Eletricas
Cement and Concrete Research | Year: 2010
This work presents the results of an experimental research concerning the use of fibers in mortar specimens subjected to alkali-aggregate reaction (AAR). Two types of steel fibers (0.16 mm diameter and 6.0 mm length, and 0.20 mm diameter and 13.0 mm length) were used with fiber volume contents of 1% and 2%. Besides the expansion accelerated tests, compressive tests and flexural tests have also been carried out to display the main mechanical characteristics of the fiber-reinforced mortars after being subjected to AAR. Moreover, the microstructure of the specimens was analyzed by scanning electron microscopy and energy dispersive X-ray. The results shown that the addition of steel fibers reduced the expansion due to AAR for the experimental conditions studied in this paper. The most expressive benefit corresponded to the addition of 13.0 mm fibers in the mixture containing 2% fiber content. This fiber volume content also corresponded to the maximum increment in the mechanical properties compared to the reference mortar, mainly for the post-cracking strength and for the toughness in bending. It was observed that the fibers have a beneficial effect on the material, without compromising its main mechanical properties. © 2009 Elsevier Ltd. All rights reserved.
Rego J.H.S.,University of Brasilia |
Nepomuceno A.A.,University of Brasilia |
Figueiredo E.P.,Federal University of Goais |
Hasparyk N.P.,Furnas Centrais Eletricas
Construction and Building Materials | Year: 2015
Residual rice husk ash (RHA) has been frequently suggested as possible mineral addition in cements. However, the characteristics of residual RHAs produced by different manufacturers and the effect of residual RHA with low amorphous silica content in addition in cement pastes are poorly understood. This paper aims at characterizing the different varieties of residual RHA produced in Brazil and at investigating the microstructure of cement pastes with 20% replacement of ordinary cement by RHAs which presents high and low amorphous silica content. A broad array of techniques was employed in the characterization, such as X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), X-ray microanalysis, and porosimetry by mercury intrusion (PMI). The results demonstrate that RHA with low amorphous silica content, finely divided, reduces the calcium hydroxide content and the Ca/Si ratio of calcium silicate hydrate (C-S-H), and also refines the porous structure of the pastes. Residual RHAs with low amorphous silica content thus proved to be suitable mineral addition for cements. © 2015 Elsevier Ltd.All rights reserved.
News Article | November 29, 2016
SAO PAULO--(BUSINESS WIRE)--Fitch Ratings has affirmed the Foreign and Local Currency Long-Term Issuer Default Ratings (IDRs) of Centrais Eletricas Brasileiras S.A. (Eletrobras) and its wholly owned subsidiary, Furnas Centrais Eletricas S.A. (Furnas) at 'BB-'. The Rating Outlook for both IDRs has been revised to Stable from Negative. Fitch has also affirmed the companies' Long-Term National Scale Ratings at 'AA-(bra)' with a Stable Outlook. A complete list of rating actions follows at the end o