Navegando por Assunto "Electric field"

Agora exibindo 1 - 7 de 7

Acesso aberto (Open Access)
Análise de desempenho de pará-raios de ZnO sob diversos cenários de poluição utilizando método de elementos finitos
(Universidade Federal do Pará, 2022-08-16) LISBOA, Mellina Modesto; NUNES, Marcus Vinícius Alves; http://lattes.cnpq.br/9533143193581447
Metal-Oxide Surge Arrester is one of the protection devices of vital importance for Electric Power Systems and the equipment that composes them, since it ensures the reliability and continuity of operation of these systems based on their ability to attenuate transient overvoltage resulting from lightning strikes or switching surges. This equipment is formed by blocks of variable ZnO resistors, associated in series or in parallel, whose voltage-current curve presents high non-linearity. In view of the relevance of using the lightning rod, it is necessary to investigate its operating conditions. In the literature, several procedures and techniques are found for this purpose, among which monitoring through measurement and analysis of the leakage current stands out, since this represents one of the main factors that contribute to the degradation of this equipment. Given this context, the present master's dissertation implements a two-dimensional model of a 30 kV Zinc Oxide lightning arrester, using the Finite Element Method, to obtain the leakage current curves, electrical potential distributions, current density and that of electric field lines, when this device is subject to voltage variations and pollution conditions. The results show a significant increase in these measured quantities as the level of pollution intensifies, as well as with the increase in voltage levels.
Acesso aberto (Open Access)
Dinâmica molecular de armazenamento de H2 em nanotubos de carbono sob ação de campo elétrico externo
(Universidade Federal do Pará, 2016-01-27) AIRES, Júlio Cesar Nunes; CHAVES NETO, Antônio Maia de Jesus; http://lattes.cnpq.br/3507474637884699; https://orcid.org/0000-0002-9730-3512
Several thermodynamic properties were analyzed through computer simulations systems, in which we used a carbon nanotube a gas molecule (H2), the very low initial temperature of 10-3K order. This H2 molecule was chosen because of its properties are of great application in different branches of study, the physical sciences, chemical and biological. The H2 molecule is individually relaxed inside and outside the nanotube during simulations. Each system was under the influence of a uniform electric field parallel to the carbon nanotube and the thermal effect on the initial temperature in the simulations generating the evanescent effect. Due to the electric field, the molecule rotates at a low temperature in orbit about the carbon nanotube while increasing the value of the electric field permitted the variation of the radius of the orbit atoms. The calculated amounts were the following: kinetic energy, potential energy, the total energy, temperature variation in situ, the molar entropy and the mean radius of the orbit atoms. The data suggest the action of the electric field is sufficient only to generate the evanescent attractive potential and this system can be used as a sensor selector atoms.
Acesso aberto (Open Access)
Uma metodologia para predição do campo elétrico de radiodifusão sonora em ondas médias utilizando inferências bayesianas
(Universidade Federal do Pará, 2013-06-11) COSTA, Juliana Santiago Monteiro; ARAÚJO, Jasmine Priscyla Leite de; http://lattes.cnpq.br/4001747699670004; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
The adoption of digital sound broadcasting systems, which are under testing in the country, allows new studies aimed a better planning for the implementation of new stations, which means to reassess the major existing radio propagation models or propose new alternatives to meet demands inherent in digital systems. The current models, as Recommendations ITU-R P. 1546 and ITU-R P. 1812, do not match closely with the reality of some regions of Brazil, especially in the tropical regions, such as the Amazon Region, due to the high rainfall and the vast existing flora. Using models suited to the propagation channel, it becomes feasible to develop planning tools covering most accurate and efficient. The use of these tools is applicable both to ANATEL, for the elaboration of the basic plans, as distribution channels for broadcasters. This paper presents a methodology using a computational intelligence based in Bayesian Networks for prediction of electric field intensity, which can be applied to planning or expanding coverage areas in broadcasting systems for frequencies in the range of medium wave (300 kHz to 3 MHz). This methodology generates electric field values estimated from the values of terrain altitude (through analysis of conditional probability tables) and provides a comparison of these values with the measured electric field. The data used in this study were collected in Brazil’s central region, nearby the city of Brasilia. The transmitted signal was an AM radio signal transmitted at a frequency of 980 kHz. With the data collected during the measurement campaigns, simulations were performed using conditional probability tables generated by Bayesian Networks. Thus, it’s proposed a method for predicting values of electric field based on the correlation between the measured electric field and the altitude through the use of artificial intelligence. Compared to numerous studies in the literature that have the same goal, the results found in this study validate the use of the methodology to determine the electric field in medium wave radio broadcasting using Bayesian Networks.
Acesso aberto (Open Access)
Modelo de propagação de campo elétrico para TV digital em percursos mistos do tipo cidade-rio na região Amazônica
(Universidade Federal do Pará, 2016-02-24) ERAS, Leslye Estefania Castro; PELAES, Evaldo Gonçalves; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
In this work the study of the electric field propagation is presented for two typical mixed paths in the Amazon region. A first scenario discussed is Belém-Bay Guajará located in the state of Pará. This path has 24% of land and 76% of water. A measurement campaign was carried out over land and over water; using the digital channel 22 of a TV station in the frequency of 521 MHz. Were measured a total of 239 points, including 19 over ground and 220 over water distributed in 3 Radials. Data were compared with various empirical and deterministic propagation models, found in the literature. The metric to test the performance of the models was the RMS error. Furthermore, it is proposed in this paper, the combination of two models: ITU-R P.1546 and Millington. This model had the lowest RMS error compared to the other models used in this work and follows the signal behavior in the transition area land-water, where the signal experiences an increment of the electric field strength, a phenomenon known as "Recovery Effect." Other models used were: Okumura-Hata, Free space, Dyadic Green's function, ITU-R P.1546-5 and Ray Tracing. Such models did not adapt to the signal behavior. In order to evaluate the proposed model a second scenario was used Belém-Mosqueiro, this has 25% of water and 75% of land. In this case, the data was measured only over land, the water data were obtained by simulation. In this situation, the data calculated with the proposed model has agreement with measured data. The simulated water data showed the characteristic of "Recovery Effect," phenomenon that is not described by the other models. It is concluded that the combination of the ITU-R P 1546-5 and Millington models has a better agreement with the data measured on mixed paths land-water than the other models.
Acesso aberto (Open Access)
Predição de campo elétrico para TV digital usando Funções de Green diádicas
(Universidade Federal do Pará, 2014-07-01) SILVA, Diego Kasuo Nakata da; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
This work provides a method for the prediction of electric field intensity to Digital TV using the Dyadic Green's function. The Dyadic is a powerful mathematical tool which has symbolic simplicity and robustness, thus enabling some characteristics of the medium (such as permittivity, conductivity and permeability, for example) are considered in developing the electric field model, as well as take into account the anisotropy of the medium. In most related works using the dyadic Green's functions are related in the VHF band. This work will present from basic concepts of dyadic, developing it for the calculation of a model which can predict the electric field to the UHF band, in which systems are Digital TV. A theoretical explanation and mathematical development will be made such that a clear understanding and objective are achieved in the study of dyadic Green's functions, in a part of the theory of electromagnetism Tests were performed to confirm the applicability of the suggested formulation, making simulations that perform a comparison between measured data, from two TV stations located in the city of Belém, and the Okumura-Hata model modified, showing satisfactory results for both frequencies in VHF and UHF.
Acesso aberto (Open Access)
Projeto, montagem e testes de fonte Cockcroft - Walton para Electrospinning
(Universidade Federal do Pará, 2022-06-06) ARAÚJO FILHO, Paulo Sérgio Alves de; VIEIRA JÚNIOR, Petrônio; http://lattes.cnpq.br/1958791286192330; DIAS, Carmen Gilda Barroso Tavares; http://lattes.cnpq.br/2113791118142177
Electrospinning is a way of spinning using an electric field, the wire formed has a nanometric diameter and is used in biomaterials, pharmaceuticals, electronics, in the area of semiconductors and energy generation. During electrospinning, the solution leaves a starter vessel and reaches a screen through the force of the electric field. The method fits according to the purpose of the experiment. For each objective there are a variety of polymers, solvents, the latter defining the operating ranges for: field strength, voltage and operating distance. A source was designed and assembled using the Cockcroft multiplier. For the design of the circuit, design and simulations were carried out. For validation, electrospinning was performed using the source.
Acesso aberto (Open Access)
Sensores de narcóticos, gás natural e syngás utilizando nanotubos de carbono sob ação de campo elétrico externo
(Universidade Federal do Pará, 2021-02-15) AIRES, Júlio Cesar Nunes; CHAVES NETO, Antonio Maia de Jesus; http://lattes.cnpq.br/3507474637884699; https://orcid.org/0000-0002-9730-3512
This work presents an analysis of the molecular dynamics between several illicit drugs: benzoylmethylecgonine, diacetylmorphine, 3,4 methylenedioxymethamphetamine, D-Deoxefedrine, lysergic acid diethylamide and, interacting with a section of carbon nanotubes at low initial temperature, corresponding to 10-3 K, and under a uniform electric field, like a drug detection system. In addition to the analysis of the behavior of natural gas molecules and SYNGAS interacting with a carbon nanotube at an initial simulation temperature of 300K, with all systems being relaxed by 50 ps outside the carbon nanotube, describing each possible arrangement for capture; a constant external electric field was then applied to the systems, longitudinally, along the length of the carbon nanotube, promoting an evanescent effect, capable of trapping them orbiting the carbon nanotube. Simulations for electric field intensities within a range of 10-5 to 10-1 a.u. were performed, to verify the behavior of drugs, while for the molecules that comprise Natural Gas and SYNGAS, a range of 10-8 to 10-1 a.u. was adopted. Average orbital radii were estimated, in addition to a number of thermodynamic properties. Our results indicate that the combination of a uniform external electric field and van der Waals interactions in a carbon-derived nanotube is enough to create an evanescent field of attractive potential, modeling it as a system for the detection of temperature and drug rays .