Time filter

Source Type

Ribeiro S.,Brazilian Center for Research and Development in Telecommunications | Suiama D.,Elektro Electricity and Services
Communications in Computer and Information Science | Year: 2011

This paper presents a method able to identify and analyze authentication mechanisms for a given type of application. Currently, there are several applications that use and require a mechanism to provide the user with physical or logical access. This article proposes a solution developed by Fundação CPqD that identifies which mechanism is more suitable and recommended for a given type of application, considering the restrictions and challenges for every type of mechanism. Finally, a case study will be exposed providing an example of authentication mechanism analysis and identification system. © 2011 Springer-Verlag.

Madeiro S.,University of Campinas | Galvao E.,Elektro Electricity and Services | Cavellucci C.,University of Campinas | Lyra C.,University of Campinas | Von Zuben F.,University of Campinas
2011 IEEE Congress of Evolutionary Computation, CEC 2011 | Year: 2011

There are two common strategies for technical loss reduction in electric power distribution networks: (a) the installation of capacitor banks to compensate the losses produced by reactive currents; and (b) the redefinition of the topology of electric distribution networks by changing the state of some sectionalizing switches to balance the load. Both strategies can be formulated as combinatorial optimization problems. The optimization problems for the first and the second strategies are usually known as Capacitor Placement Problem (CPP) and Network Reconfiguration Problem (NRP), respectively. In this paper, we propose a new approach based on Genetic Algorithm (GA) to solve both CPP and NRP simultaneously. The new approach makes use of two previously proposed and independent techniques for the CPP and the NRP. The performance of the new approach is compared with the performance of the two previously proposed techniques applied in a separate manner. The experiments show that the new method is more efficient regarding the metrics of power loss reduction and voltage profile enhancement. © 2011 IEEE.

Wilhelm H.,Diagno Materiais | Feitosa L.,Diagno Materiais | Silva L.,Diagno Materiais | Cabrino A.,Elektro Electricity and Services | Ramos L.,Federal University of Parana
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2015

The Rancimat method was used to evaluate the consumption of antioxidant additive in a natural ester insulating fluid (NEI). NEI samples were aged in the laboratory with and without oxygen bubbling. NEI samples were also collected from a transformer in operation. Samples of NEI (unused, aged in the laboratory and collected from transformer in operation) were analyzed by Fourier-transform infrared spectroscopy (FTIR) and by the Rancimat method for induction time (IT) measurement. The results showed that it is possible to evaluate the consumption of antioxidant additive in NEI in service by the Rancimat method. Laboratory tests were also performed to extend the lifetime of NEI in service by adding new loads of antioxidant additive. The results showed that the addition of new antioxidant additive loads when the IT of in-service NEI (determined by Rancimat method) reaches about 3 h extends the lifetime of this oil. © 1994-2012 IEEE.

Gutnik Y.,University of Sao Paulo | Altafim R.A.P.,University of Sao Paulo | Veronese P.R.,University of Sao Paulo | Resende J.F.,Elektro Electricity and Services | And 3 more authors.
Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP | Year: 2012

Piezoelectrets from thin electrically charged cellular polypropylene-foam films have been suggested for numerous transducer applications, such as force sensors for keyboards, flat microphones for conference environments, or devices for ultrasound generation and detection. In addition to polypropylene piezoelectrets, other materials systems - such as thermo-fused polymer-film stacks - were developed in order to generate piezoelectrets that are thermally more stable and contain geometrically well-controlled air cavities. Here, we demonstrate the viability of the recently developed piezoelectret systems that had been prepared by thermo-lamination with templates for the acoustical detection of electric discharges in air. Furthermore, we show that the resonance behavior of the air cavity in which the electric discharge occurs can also be assessed from the acoustic signal. For the experiments, a transducer prototype with a preamplifier directly connected to the laminated piezoelectret sensor inside an electrically shielded package was developed. Reproducible sound measurements according to the ASTM E976-10 standard were performed with the transducer prototype. The prototype was later employed in acoustical measurements of electric discharges in an air gap inside an acoustical chamber - in order to reduce external noise - and in a metallic chamber for reducing electrical interference. The recorded signals were compared by means of Fast-Fourier-Transform (FFT) analysis. © 2012 IEEE.

Assagra Y.A.O.,University of Sao Paulo | Altafim R.A.P.,Federal University of Paraiba | Silva J.F.R.D.,Elektro Electricity and Services | Basso H.C.,University of Sao Paulo | And 2 more authors.
Materials Research | Year: 2013

New environmental laws have restricted the use of hardwood trees in overhead power lines structures, such as, poles and cross-Arms, leading companies to seek alternative materials. Reforested wood coated with polymeric resin has been proposed as an environmental friendly solution, with improved electrical properties and protection against external agents, e.g. moisture, ultraviolet radiation and fungi. However, the single thin layer of resin, normally applied on such structures reveal to be inefficient, due to be easily damage during handling. In this paper, we present a composite coating, based on geotextile fibers and polyurethane resin that is suitable for wooden structures. Results obtained from two different tree species (from managed and reforested areas) coated with the composite reveal that the additional layer not only provided a stronger adhesion between wood and ccoating layer but also a further improvement in the electrical properties and better protection against abrasion and moisture. © 2013.

Discover hidden collaborations