Navegando por Autor "GOMES, Cristiane Ruiz"

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Acesso aberto (Open Access)
Localização de falhas em linhas de transmissão utilizando decomposição harmônica e redes neurais artificiais
(Universidade Federal do Pará, 2006-07-05) GOMES, Cristiane Ruiz; VIEIRA JÚNIOR, Petrônio; http://lattes.cnpq.br/1958791286192330
This work proposes a new methodology for fails location in transmission lines. This methodology consists in using harmonic decomposition of the leakage current and in the application of an Artificial Neural Network (ANN), this is able to recognize patterns of normal and fails conditions of a transmission line. It was developed a Pi model capable to use real data of voltage and current of the three phases. In this model values of capacitance, inductance and resistance can be modified in agreement of weather conditions. Fails were generated in all the towers with different values of capacitance. The input/output data were used to train the neural network. The real voltage and current data acquisition were done by instruments installed in the two terminals of the Guamá-Utinga transmission line belonging to Centrais Elétricas do Norte - ELETRONORTE. The computation of the parameters was made by the well known matricial method and was improved by Finite Element Method. An ANN was developed with Matlab software. For training the ANN it was used the backpropagation resilient algorithm, which presented good performance, been fast and accurate. The ANN was trained by two different sets to analyze differences between outputs. In the two cases results were satisfactory.
Acesso aberto (Open Access)
Modelo de rádio propagação em UHF para ambientes não homogêneos e climas distintos utilizando técnica de aprendizagem de máquina
(Universidade Federal do Pará, 2015-08-20) GOMES, Cristiane Ruiz; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382
The digital TV broadcasts have greatly increased worldwide in recent years, especially in Brazil. The establishment and improvement of these transmission systems rely on models that take into account, among other factors, the geographical characteristics of the region, as these contribute to signal degradation. In Brazil, there is a great diversity of scenery and climates. For years several propagation models have been studied many for several frequency bands and types of paths. This thesis proposes an outdoor empirical radio propagation model for UHF band, which is used in digital TV. The proposed model estimates received power values can be applied to non-homogeneous paths and different climates, this latter presents innovative character for the UHF band. Different artificial intelligence techniques were chosen for theoretical and computational basis for having the ability to introduce, organize and describe quantitative and qualitative data quickly and efficiently, making it possible to determine the received power in a variety of settings and climates. The proposed model was applied to a city in the Amazon region with heterogeneous paths and wooded urban areas, fractions of freshwater among others. Measurement campaigns were conducted to obtain data signals from two digital TV stations in the metropolitan area of the city of Belém-Pará to model, compare and validate the model. The results are consistent. The model depicts a distinct difference between the two seasons of the studied year and small RMS errors for all cases studied. The validation of the model was based on the comparison with empirical and deterministic models.
Acesso aberto (Open Access)
Radio-wave propagation model for UHF band in different climatic conditions with dyadic green’s function
(2015-06) GOMES, Cristiane Ruiz; SILVA, Diego Kasuo Nakata da; ARAÚJO, Jasmine Priscyla Leite de; GOMES, Hermínio Simões; CAVALCANTE, Gervásio Protásio dos Santos
This article proposes a deterministic radio propagation model using dyadic Green's function to predict the value of the electric field. Dyadic is offered as an efficient mathematical tool which has symbolic simplicity and robustness, as well as taking account of the anisotropy of the medium. The proposed model is an important contribution for the UHF band because it considers climatic conditions by changing the constants of the medium. Most models and recommendations that include an approach for climatic conditions, are designed for satellite links, mainly Ku and Ka bands. The results obtained by simulation are compared and validated with data from a Digital Television Station measurement campaigns conducted in the Belém city in Amazon region during two seasons. The proposed model was able to provide satisfactory results by differentiating between the curves for dry and wet soil and these corroborate the measured data, (the RMS errors are between 2-5 dB in the case under study).