Processo de attachment, densidade de raios e a ocorrência de flashover em linhas de transmissão de eletricidade

Esta tese refere-se ao uso de modelos de attachment de lideres (Leader Progression Model – LPM) para estimativa da distancia de salto, que, junto com dados de densidade de raios como coletado pelo sistema de detecção de raios do SIPAM, são usados para estimar a taxa de flashover em linhas de transmissão de eletricidade na Amazônia. O modelo de progressão de líder desenvolvido nesta tese é denominado ModSalto, que, para estimar a distancia de salto: 1- integra a densidade linear de cargas elétricas devida ao líder, proporcional a prospectiva corrente de primeira descarga (1º stroke) Ip, para determinar o campo elétrico produzido pelo líder descendente na estrutura sob estudo (para-raios, arestas, condutores, etc.); 2 – integra a distribuição imagem do líder descendente, fazendo uso da característica de poder das pontas como fator de estimulo e intensificação do campo elétrico devido a streamers nas partes aguçadas das estruturas sob estudo, para temporizar o momento do processo de attachment. O gatilho para o líder descendente, por hipótese, se deve a ejeção aleatória de pacotes de cargas elétricas em domínios turbulentos no interior das nuvens que recebem energia por processos de cascata da turbulência geral, e o comportamento do líder descendente, deve obedecer à equação da força de Lorentz, no espaço de campos cruzados elétrico devido às nuvens a cima e o campo magnético da Terra, que obriga as cargas do líder a desenvolverem movimentos cicloidais que podem explicar a natureza tortuosa do trajeto do líder descendente. Com o objetivo de formalizar dados consistentes de densidade de raios é feita uma reanalise do conjunto de dados coletado pelo LLS SIPAM de outubro de 2006 a julho de 2008 na região amazônica, com cerca de 3 milhões de eventos, comparando-os com dados de torres instrumentadas para evidenciar-se sua qualidade e usabilidade. Dados de elevação de terreno do SRTM da NASA são usados para gerar formula do raio de atração (Ra) das estruturas passiveis de serem atingidas por raios e para gerar formulas de área de atração, usadas para quantificar o numero de raios que provavelmente atingirão determinada estrutura, baseado no valor de densidade de raios (raios/km2/ano) na área em estudo.

X1X1X2X2/X1X2Y sex chromosome systems in the Neotropical Gymnotiformes electric fish of the genus Brachyhypopomus

Several types of sex chromosome systems have been recorded among Gymnotiformes, including male and female heterogamety, simple and multiple sex chromosomes, and different mechanisms of origin and evolution. The ₁X₁X₂X₂/X₁X₂Y systems identified in three species of this order are considered homoplasic for the group. In the genus Brachyhypopomus, only B. gauderio presented this type of system. Herein we describe the karyotypes of Brachyhypopomus pinnicaudatus and B. n. sp. FLAV, which have an X₁X₁X₂X₂/X₁X₂Y sex chromosome system that evolved via fusion between an autosome and the Y chromosome. The morphology of the chromosomes and the meiotic pairing suggest that the sex chromosomes of B. gauderio and B. pinnicaudatus have a common origin, whereas in B. n. sp. FLAV the sex chromosome system evolved independently. However, we cannot discard the possibility of common origin followed by distinct processes of differentiation. The identification of two new karyotypes with an X₁X₁X₂X₂/X₁X₂Y sex chromosome system in Gymnotiformes makes it the most common among the karyotyped species of the group. Comparisons of these karyotypes and the evolutionary history of the taxa indicate independent origins for their sex chromosomes systems. The recurrent emergence of the X₁X₁X₂X₂/X₁X₂Y system may represent sex chromosomes turnover events in Gymnotiformes.

Chromosomal diversity in three species of electric fish (Apteronotidae, Gymnotiformes) from the Amazon Basin

Cytogenetic studies were carried out on samples of Parapteronotus hasemani, Sternarchogiton preto and Sternarchorhamphus muelleri (Apteronotidae, Gymnotiformes) from the Amazon basin. The first two species exhibited both a 2n = 52 karyotype, but differed in their karyotypic formulae, distribution of constitutive heterochromatin, and chromosomal location of the NOR. The third species, Sternarchorhamphus muelleri, was found to have a 2n = 32 karyotype. In all three species the DAPI and chromomycin A3 staining results were consistent with the C-banding results and nucleolar organizer region (NOR) localization. The 18S rDNA probe confirmed that there was only one pair of ribosomal DNA cistron bearers per species. The telomeric probe did not reveal interstitial telomeric sequences (ITS). The karyotypic differences among these species can be used for taxonomic identification. These data will be useful in future studies of these fishes and help understanding the phylogenetic relationships and chromosomal evolution of the Apteronotidae.

Profile of micronucleus frequencies and nuclear abnormalities in different species of electric fishes (Gymnotiformes) from the Eastern Amazon

The frequency of spontaneous micronucleus (MN) formation in fish species needs to be determined to evaluate their usefulness for genotoxic biomonitoring. The definition of a good bioindicator takes into account the current knowledge of its metabolic traits as well as other factors including its feeding behavior and relationship to the environment. In this study, we compared the basal frequencies of micronucleated erythrocytes and nuclear abnormalities (NA) among different species of the fish Order Gymnotiformes (Rhamphichthys marmoratus, Steatogenys elegans, Sternopygus macrurus, Parapteronotus hasemani, Gymnotus mamiraua, Gymnotus arapaima, Brachyhypopomus beebei, Brachyhypopomus n. sp. BENN) sampled in several localities of the Eastern Amazon. A baseline of MN and NA frequency in these fish was determined, enabling the identification of potentially useful species as models for genotoxicity studies. Only one impacted sample collected at a site in the River Caripetuba showed a significant number of NAs, which may be due to the release of wastewater by neighbouring mining industries and by the burnt fuel released by the small boats used by a local community. Our results may provide support for further studies in areas of the Eastern Amazon affected by mining, deforestation and other anthropogenic activities.

Otimização combinatória para alocação de fontes renováveis em microrredes de corrente contínua

Pós-graduação em Engenharia Elétrica - FEIS

Correspondence between the one-loop three-point vertex and the Y and Delta electric resistor networks

Different mathematical methods have been applied to obtain the analytic result for the massless triangle Feynman diagram yielding a sum of four linearly independent (LI) hypergeometric functions of two variables F-4. This result is not physically acceptable when it is embedded in higher loops, because all four hypergeometric functions in the triangle result have the same region of convergence and further integration means going outside those regions of convergence. We could go outside those regions by using the well-known analytic continuation formulas obeyed by the F-4, but there are at least two ways we can do this. Which is the correct one? Whichever continuation one uses, it reduces a number of F-4 from four to three. This reduction in the number of hypergeometric functions can be understood by taking into account the fundamental physical constraint imposed by the conservation of momenta flowing along the three legs of the diagram. With this, the number of overall LI functions that enter the most general solution must reduce accordingly. It remains to determine which set of three LI solutions needs to be taken. To determine the exact structure and content of the analytic solution for the three-point function that can be embedded in higher loops, we use the analogy that exists between Feynman diagrams and electric circuit networks, in which the electric current flowing in the network plays the role of the momentum flowing in the lines of a Feynman diagram. This analogy is employed to define exactly which three out of the four hypergeometric functions are relevant to the analytic solution for the Feynman diagram. The analogy is built based on the equivalence between electric resistance circuit networks of types Y and Delta in which flows a conserved current. The equivalence is established via the theorem of minimum energy dissipation within circuits having these structures.

Electrical and Superconducting Properties in Lap Joints for YBCO Tapes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

FINITE ELEMENT SIMULATIONS FOR THE COMPREHENSION OF PHYSICAL PHENOMENA INVOLVED IN ELECTRIC IMPEDANCE TOMOGRAPHY OF MASONRY STRUCTURES

The paper describes the preliminary studies of University of Minho on the use of Electric Impedance/Resistance Tomography to assess masonry structures. The study is focused on the analysis of values of current and voltage resulting from the use of an electrical source with voltage and frequency values from a distribution network. The analysis is made from results obtained through computer simulations, using a three-dimensional model of the idealized masonry structures. A finite element program was used for the simulations. Three types of electrodes were used in simulations, and the analysis of the results led to significant conclusions. Later masonry specimens were built and a series of preliminary tests were carried out in the laboratory. The comparative analysis of simulated and experimental results allowed identifying the factors that have influence on the physical results.

Estudo das propriedades elétricas do cobre e alumínio; sobre a força magnética em um imã caindo dentro de um tubo

Magnetic fields can be produced by natural magnets, artificial magnets, and by circulating electric currents in wires and solenoids. An interesting experiment to observe the interaction between the magnetic field and free charges in a conductor, a magnet falling inside a tube made of conductive materials. The slowing down of the magnet by the appearance of a field in the opposite direction to the original one (Lenz's Law) is function the number of free electrons in the conductor and the electrical properties of this. Based on this, the objective of this study is to analyze the relationship between the electrical properties of conductors, copper and aluminum, with magnetic force on a neodymium magnet-iron-boron magnet falling inside a copper tube and aluminum, positioned vertically. In performing this experiment, we observed that it is a demonstration of Lenz-Faraday’s Law

Geometrical hypercomplex coupling between electric and gravitational fields

The present work shows a coupling of electrical and gravitational fields through Cauchy-Riemann conditions for quaternions present in a previous paper [1]. It is also obtained an extended version of the Laplace-like equations for quaternions, now written in terms of both electric and gravitational fields.

Electron and neutron electric dipole moment in the 3-3-1 model with heavy leptons

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Hopping-tunneling model to describe electric charge injection at metal/organic semiconductor heterojunctions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reconfiguration of radial electric power distribution system via a scatter search algorithm

In this paper, to solve the reconfiguration problem of radial distribution systems a scatter search, which is a metaheuristic-based algorithm, is proposed. In the codification process of this algorithm a structure called node-depth representation is used. It then, via the operators and from the electrical power system point of view, results finding only radial topologies. In order to show the effectiveness, usefulness, and the efficiency of the proposed method, a commonly used test system, 135-bus, and a practical system, a part of Sao Paulo state's distribution network, 7052 bus, are conducted. Results confirm the efficiency of the proposed algorithm that can find high quality solutions satisfying all the physical and operational constraints of the problem.

An MILP model for the plug-in electric vehicle charging coordination problem in electrical distribution systems

A new mixed-integer linear programming (MILP) model is proposed to represent the plug-in electric vehicles (PEVs) charging coordination problem in electrical distribution systems. The proposed model defines the optimal charging schedule for each division of the considered period of time that minimizes the total energy costs. Moreover, priority charging criteria is taken into account. The steady-state operation of the electrical distribution system, as well as the PEV batteries charging is mathematically represented; furthermore, constraints related to limits of voltage, current and power generation are included. The proposed mathematical model was applied in an electrical distribution system used in the specialized literature and the results show that the model can be used in the solution of the PEVs charging problem.