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Filho G.L.T.,IRN UNIFEI | Santos I.F.S.D.,UNIFEI | Barros R.M.,IRN UNIFEI
Renewable and Sustainable Energy Reviews | Year: 2017

Hydroelectric power plants help to reduce greenhouse gas emissions, expand renewable energy generation, and distribute national energy generation. This is particularly true for small hydroelectric plants (SHPs). However, the development of SHPs is dependent on the economic and financial feasibility, which must be evaluated by cost estimates before starting construction. The parameterization of these costs with satisfactory precision can be difficult or even impossible due to the particularities a project or region. Thus, this study presents the aspect factor (AF), which is as a parameter based on the least squares method that represents the physical characteristics of a plant scheme. This factor was applied to determine the unit cost of SHP projects in Brazil and India. The results were evaluated using statistical tests. The cost estimate equations found in the literature were also revised and compared with the AF to characterize its applicability to other regions of the world. © 2017 Elsevier Ltd

Carvalho T.C.O.,Federal University of Minas Gerais | Duque C.A.,Federal University of Juiz de fora | Silveira P.M.,UNIFEI | Mendes M.A.S.,Federal University of Minas Gerais
Proceedings of International Conference on Harmonics and Quality of Power, ICHQP | Year: 2014

Traditional analysis of waveform distortion assumes balanced and steady-state conditions. However, due to the widespread use of power electronics, non-linear loads and a multiplicity of harmonic-producing loads, power signals are becoming increasingly distorted and time varying. This complex scenario demands appropriate analysis. This paper illustrates the visualization of power quantities under time-varying conditions based on the defitions of IEEE Standard 1459. The Sliding Window Recursive Fourier Transform is used to decompose real signals in time-varying harmonics and subsequently it calculates the main parameters as function of time. These include symmetrical components, total harmonic distortions and apparent power. This visulization can lead to a better understanding of the nature of power signals under time-varying conditions. © 2014 IEEE.

Antunes F.A.S.,CEMIG | Ribeiro P.F.,Federal University of Itajubá | Silveira P.M.,UNIFEI
IEEE Power and Energy Society General Meeting | Year: 2015

One of the most challenging proposals about the smart grid concept is the deployment of features that enable a power grid to reconfigure itself, isolating defects and recovering through alternative available routes after disturbances. This ability is known as Self-Healing, a concept most widespread in distribution power systems. In transmission power systems, however, there is a substantially lower amount of research. Some authors says the actual transmission is inherently self-healing since its topology is meshed designed, which ensures redundancy for equipment trips, preventing a load outage. Nevertheless, automatic transmission systems reconfiguration presents high improvement potential in the restoring process, in terms of security and agility. Under this scenario, this paper sets the framework for a self-healing system to perform in the transmission system. In this framework, are considered the main technical requirements, concerns, points of attention and inherent issues of transmission operation process. The Assisted-Healing concept will also be considered for such circumstances in which the Self-Healing is not convenient or not possible to be fully performed. The main aim is support operators to deal better with stressful decisions related to the restoration process after power systems disturbances, reducing assets and load outages periods. © 2015 IEEE.

Melloni R.,Federal University of Itajubá | Belleze G.,UNIFEI | Pinto A.M.S.,UNIFEI | Dias L.B.P.,UNIFEI | And 4 more authors.
Revista Brasileira de Ciencia do Solo | Year: 2013

Minas Gerais stands out as the largest coffee-producing state of Brazil. This crop is extremely susceptible to weeds, which can be handled by manual, mechanized and/or chemical methods, which strongly affect production costs and soil quality. In this sense, the objective of this study was to evaluate the effect of different weed control methods in and between coffee rows on the soil microbiota and its processes. For this purpose, soil samples were taken in April 2010 from an Oxisol on the experimental farm of the Agricultural Research Company of Minas Gerais (EPAMIG), in São Sebastião do Paraíso, MG, at a depth of 0-10 cm in the middle of the track (interrow) of coffee and 20 cm away from the stem of the coffee trees (row), to determine the following properties: total density of bacteria and fungi, phosphate solubilizers, cellulolytic and ammonifying microorganisms, non-symbiotic diazotrophic bacteria, carbon biomass and microbial activity, metabolic quotient (qCO2) and enzymatic activity by the hydrolysis of fluorescein diacetate. The coffee plants were subjected to seven methods of weed control: mowing, coffee tandem disk harrow (grid), rotary tiller, post-emergence herbicide, preemergence herbicide, manual weeding, and no weed control. The results showed the complexity of the effects of these different methods on soil and its processes, with lowest impacts of manual weeding and rotary hoe. Mowing, coffee tandem disk harrow, no weed control and pre-emergence herbicide caused intermediate impacts, while the application of post-emergence herbicides inbetween coffee rows caused the most negative impacts on the evaluated properties. It is suggested that these impacts must be considered when evaluating and selecting the method for weed control in coffee plants.

Pereira R.L.,UNIFEI | Kienitz K.H.,Brazilian Technological Institute of Aeronautics | de Moraes A.T.,Brazilian Technological Institute of Aeronautics
Journal of Control, Automation and Electrical Systems | Year: 2016

A new control design procedure is presented to obtain an H∞ loop shaping controller with guaranteed robustness properties in the presence of both nonparametric and parametric uncertainties. The method allows to describe imprecise parameters in terms of norm-bounded parametric uncertainties that are considered in addition to perturbations to normalized coprime factors of the shaped plant. In order to obtain an H∞ controller that ensures stability and performance of the closed-loop system considering both uncertainties, a set of sufficient conditions based on LMIs is provided. Finally, the effectiveness of the design method was evaluated considering an industrial pilot plant where the proposed design procedure yields a reduction in the impact of imprecise resistance values caused, for example, by the encrusting of pipes. © 2016, Brazilian Society for Automatics--SBA.

Schettino B.M.,Federal University of Juiz de fora | Duque C.A.,Federal University of Juiz de fora | Silveira P.M.,UNIFEI
IEEE Transactions on Power Delivery | Year: 2016

A new application of the Savitzky-Golay (SG) filters in current-transformer saturation detection is proposed. The ability of the SG filters to handle noisy signals improves the robustness of the detection process in the presence of noise while requiring only low computational effort. © 2016 IEEE.

Santos I.N.,Federal University of Uberlandia | Bollen M.H.J.,LTU | Ribeiro P.F.,UNIFEI
IEEE Power and Energy Society General Meeting | Year: 2015

The increasing penetration of renewable/distributed sources with non-linear characteristics demands a clear methodology for determining the amount of generation which can be connected to the system without deteriorating the performance (the 'hosting capacity'). This paper proposes a methodology for determining the hosting capacity regarding harmonic distortions. To exemplify an application of the proposed procedure, a simple case study is performed and analyzed. © 2015 IEEE.

Action research is a qualitative method that is increasingly achieving a place of prominence as a technical procedure used in production engineering research. However, this method is discriminated in its scientific merit and lacks conduction validation. In an attempt to fill in these gaps in the literature, this paper proposes a process for conducting research in production engineering by means of action research. The scientific contributions of this work are the discussion about the forms of initiation and the implementation of validation phases employing the action research method. It was concluded that, within the scientific paradigm of realism, the most appropriate criteria for the validation of action research method are the ontological appropriateness, contingent validity, multiple perception of participants, methodological trustworthiness, analytic generalization, and construction validity.

The Product Development Process (PDP) is a critical success factor in launching a new product to meet customer requirements. The adoption of a reference model serves as a comprehensive guide to assist organizations in managing and systematization of the PDP, through standardized sequence of steps that are adapted to the type of product that the company develops. The aim of this paper is to select a reference model of the product development process for the auto part sector by establishing an aid to multi-criteria decision known as Analytic Hierarchy Process (AHP). The research method used was modeling, which before six alternatives, three criteria and trial of five experts resulted in the selection of Rozenfeld et al. (2006) reference model as the most suitable model to analyze the company's PDP selected as object of study in future research.

Motta R.S.N.,Engineering University of Itajuba | De Souza L.E.,UNIFEI
Stahl und Eisen | Year: 2010

A new process is described of handling the pulverized coal injection (PCI) into blast furnaces in an energy efficient way, aiming at decreasing the specific consumption of electricity and nitrogen. The process improvement included two new phases in the main coal vessels sequence. The return on investment (ROI) was high as the specific electricity and nitrogen consumption were reduced and the lifetimes of operational valves were increased as well. The process is now operationally more stable when compared to the original design.

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