CT - DCO - Departamento de Engenharia de Comunicações
URI Permanente desta comunidadehttps://repositorio.ufrn.br/handle/123456789/29842
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Artigo 2.4–5.8 GHz dual-band patch antenna with FSS reflector for radiation parameters enhancement(Elsevier, 2019-08) Fernandes, Elidiane Mirella Farias; Silva, Maurício Weber Benjó; Briggs, Lucianada Silva; Campos, Antônio Luiz Pereirade Siqueira; Araújo, Humberto Xavier; Casellas, Ivan Roberto Santana; Capovilla, Carlos Eduardo; Souza, Vanessa Przybylski Ribeiro Magri; Matos, Leni JoaquimIn this paper, a dual-band patch antenna is developed for the Industrial, Scientific and Medical (ISM) bands of 2.4 GHz and 5.8 GHz with improved performance in terms of radiation pattern characteristics (antenna gain, front-to-back ratio and directivity) for both bands. For this purpose, a bandstop reflector based on Frequency Selective Surface (FSS) was designed and optimized. Simulation results show improved gain for the proposed structure for both frequency bands, with a gain of 7.54 dBi and 6.8 dBi at 2.4 GHz and 5.8 GHz, respectively. Measurement results showed a gain value of 7.46 dBi at 2.4 GHz. A bandwidth of 7% was obtained at the central frequency of 2.4 GHz (ranging from 2.37 to 2.56 GHz), while a bandwidth of 1.07 GHz (18.8% fractional bandwidth) was achieved at the frequency of 5.8 GHz. The measured experimental results were in agreement with those obtained by computational simulations and the satisfactory performance validate the proposed structureArtigo Análise comparativa de desempenho de redes residenciais IEEE 802.11N e homeplug AV(Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Norte (IFRN), 2013-12) Trindade, E. L.; Campos, Antonio Luiz Pereira de Siqueira; Moreira, Ricardo César de OliveiraEste artigo apresenta uma análise comparativa dos padrões 802.11n e Homeplug AV, abordando melhorias desses padrões com relação aos seus anteriores. São realizados testes do desempenho de cada padrão em ambiente residencial, considerando como parâmetro analisado a taxa de transmissão. O interesse foi determinar o desempenho relativo destas tecnologias, considerando a taxa de transmissão em função da distância de transmissão, do tamanho dos pacotes e do número de nós ativos na redeArtigo Análise de desempenho da tecnologia homeplug 1.0 em ambientes domésticos e não domésticos(Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Norte, 2007) Campos, Antonio Luiz Pereira de Siqueira; Moreira, Ricardo César de Oliveira; Araújo, Lincoln MachadoNa literatura, podem ser encontrados vários artigos que analisam as características das redes elétricas para transmissão de dados bem como as técnicas de comunicação empregadas para essa finalidade. Quase todos os artigos que estudam o padrão HomePlug fazem testes de desempenho protocolo. Alguns desses artigos fazem testes comparativos entre a sub-camada MAC do HomePlug e do IEEE 802.11. Este trabalho complementa as avaliações encontradas na literatura e tem por objetivo o estudo do padrão HomePlug 1.0, em relação ao seu desempenho em ambientes domésticos e não-domésticos. A vazão da rede Homeplug foi analisada, considerando-se vários fatores, como o tamanho dos arquivos enviados, efeito de cargas elétricas e número de nós ativosArtigo Análise de desempenho de transformadas wavelet para remoção de ruído de sinais presentes em DOAS(Instituto Federal de Educacao, Ciencia e Tecnologia do Rio Grande do Norte (IFRN)., 2015-09) Araújo, Boanerges Victor Soares de; Campos, Antonio Luiz Pereira de SiqueiraEste trabalho apresenta um estudo comparativo entre o desempenho de diversas wavelets distintas aplicadas à remoção de ruído de sinais típicos encontrados na Espectroscopia de Absorção Óptica Diferencial (DOAS). Os testes realizados utilizaram a transformada wavelet discreta (DWT) e níveis de ruído distintos para contaminar os sinais base, em busca das wavelets mais apropriadas para tratá-los. Como critério de desempenho, utilizou-se a energia da diferença entre o sinal de origem e o sinal filtradoArtigo Blockchain in health information systems: a systematic review(International Journal of Environmental Research and Public Health, 2024-11-14) Fonsêca, Aleika Lwiza Alves; Barbalho, Ingridy Marina Pierre; Fernandes, Felipe Ricardo dos Santos; Arrais Júnior, Ernano; Nagem, Danilo Alves Pinto; Cardoso, Pablo Holanda; Veras, Nícolas Vinícius Rodrigues; Farias, Fernando Lucas de Oliveira; Lindquist, Ana Raquel; Santos, João Paulo Queiroz dos; Morais, Antonio Higor Freire de; Henriques, Jorge; Lucena, Marcia Jacyntha Nunes Rodrigues; Valentim, Ricardo Alexsandro de MedeirosAbstract: (1) Background: With the increasing digitalization of healthcare systems, data security and privacy have become crucial issues. In parallel, blockchain technology has gradually proven to be an innovative solution to address this challenge, as its ability to provide an immutable and secure record of transactions offers significant promise for healthcare information management. This systematic review aims to explore the applications of blockchain in health information systems, highlighting its advantages and challenges. (2) Methods: The publications chosen to compose this review were collected from six databases, resulting in the initial identification of 4864 studies. Of these, 73 were selected for in-depth analysis. (3) Results: The main results show that blockchain has been used mainly in electronic health records (63%). Furthermore, it was used in the Internet of Medical Things (8.2%) and for data sharing during the COVID-19 pandemic (6.8%). As advantages, greater security, privacy, and data integrity were identified, while the challenges point to the need for standardization and regulatory issues. (4) Conclusions: Despite the difficulties encountered, blockchain has significant potential to improve healthcare data management. However, more research and continued collaboration between those involved are needed to maximize its benefitsArtigo Compact and high-performance band stop filter on textile substrate(Institution of Engineering and Technology (IET), 2015-03) D´Assunção, Adaildo Gomes; Cavalcante, Gustavo Araújo; Minervino, Diego Ramalho; D’Assunção Junior, Adaildo GomesA band stop filter developed on a denim textile substrate is presented. The filter geometry is composed of interconnected half-wave-length parallel coupled resonators, in a novel microstrip filter configuration. Simulated results were obtained through the wave concept iterative method and Ansoft Designer software, for comparison purposes. In addition, prototypes were fabricated and measured for validating the simulation results. Good agreement is reported between simulated and measured resultsArtigo CSRR-Based microwave sensor for dielectric materials characterization applied to soil water content determination(MDPI, 2020-01-01) D´Assunção, Adaildo Gomes; Oliveira, João Guilherme Domingos de; Pinto, Erica Natasche de Medeiros Gurgel; Silva Neto, Valdemir Praxedes daA new and compact sensor based on the complementary split-ring resonator (CSRR) structure is proposed to characterize the relative permittivity of various dielectric materials, enabling the determination of soil water content (SWC). The proposed sensor consists of a circular microstrip patch antenna supporting a 3D-printed small cylindrical container made out of Acrylonitrile-Butadiene-Styrene (ABS) filament. The principle of operation is based on the shifting of two of the antenna resonant frequencies caused by changing the relative permittivity of the material under test (MUT). Simulations are performed enabling the development of an empirical model of analysis. The sensitivity of the sensor is investigated and its effectiveness is analyzed by characterizing typical dielectric materials. The proposed sensor, which can be applied to characterize different types of dielectric materials, is used to determine the percentage of water contained in different soil types. Prototypes are fabricated and measured and the obtained results are compared with results from other research works, to validate the proposed sensor effectiveness. Moreover, the sensor was used to determine the percentage of water concentration in quartz sand and red clay samplesLivro Design instrucional para cursos a distância: um guia para a construção de material didático do AVASUS(EDUFRN, 2016) Burlamaqui, Akynara Aglaé; Dias, Aline de Pinho; Oliveira, Carlos Alberto Pereira de; Gusmão, Cristine Martins Gomes de; Nagem, Danilo Alves Pinto; Lins, Hertz Wilton de Castro; Silva Júnior, José Adailton da; Machiavelli, Josiane Lemos; Araújo, Kaline Sampaio de; Coutinho, Karilany Dantas; Cortez, Lyane Ramalho; Oliveira Junior, Mauricio da Silva; Valentim, Ricardo Alexsandro de MedeirosÉ com grande satisfação que apresentamos este manual. Ele tem a finalidade de fornecer orientações básicas sobre a construção de material didático para a educação a distância. A educação a distância tem eculiaridades que exigem maiores cuidados no que se refere à comunicação e utilização de Tecnologias da Informação e Comunicação (TIC) no processo de ensino-aprendizagem, considerando ainda as estratégias pedagógicas necessárias para a construção do conhecimento. Nesse sentido, uma construção criteriosa do material didático é essencial, uma vez que é por meio dele que o itinerário formativo, as estratégias pedagógicas, a comunicação, interação e interatividade com o aluno poderão acontecer. Apresentamos, neste material, orientações e estratégias de como o conteudista poderá de senvolver seu material de forma a atender as especificidades da modalidade a distância e do Ambiente Virtual de Aprendizagem do Sistema Único de Saúde (AVASUS). Assim, trataremos de aspectos relacionados à estrutura didática dos módulos, ao tipo de linguagem que deve ser empregada, aos recursos utilizados para apresentar informações adicionais ao módulo, à estrutura e dimensão do módulo, ao referenciamento, à sugestão de uso de recursos tecnológicos, ao guia para elaboração de questões, ao modelo de caso clínico, aos critérios de validação dos módulos e à visão geral do processo de produção do material. Todas essas orientações objetivam possibilitar que o aluno seja protagonista de seu processo de aprendizagem, realizando transformações positivas nos serviços de saúde ao quais está vinculado. É indispensável que você leia com pletamente este manual para assim compreender a filosofia, metodologia e organização que queremos construir juntos no AVASUS. Desejamos a todos a construção de um material didático vivo, que permita aos alunos um itinerário exitoso, que garanta uma Educação Permanente em Saúde, supra as necessidades de aperfeiçoamento e, assim, fortaleça a aten ção no âmbito da saúde em nosso paísArtigo Design of miniaturized frequency selective surfaces using minkowski island fractal(SBMO/SBMag, 2010-08-01) Campos, Antonio Luiz Pereira de Siqueira; Oliveira, Elder Eldervitch Carneiro de; Silva, Paulo Henrique da FonsecaThis paper presents a simulation and experimental investigation of a frequency selective surface (FSS). The design is achieved by using the Minkowski island fractal. Two structures were designed with Minkowski island fractal level 1 and 2, which act as stop-band filters with resonant frequencies of 9 GHz and 10 GHz, respectively. Both simulation and experimental investigations were conducted. Simulation investigation was carried out using Ansoft DesignerTM software, while experimental investigation used an Agilent Technologies vector network analyzer model N5230AArtigo A design proposal for ultrawide band frequency selective surface(FapUNIFESP (SciELO), 2013-08) Segundo, Francisco Carlos Gurgel Silva; Campos, Antonio Luiz Pereira de Siqueira; Gomes Neto, AlfredoIn this paper a three layer FSS is described which provides a ultrawide band (UWB) response. The layers use plain rectangular patches, and rectangular patches with one or two notches which provide multi-band responses; by cascading them an UWB response is obtained covering the band 4.05 - 14.12 GHz, for vertical polarization and the band 5.05 - 15.00 GHz, for horizontal polarization. Transmission properties of the proposed structure were simulated and measuredArtigo Dielectric resonator antenna based in ZrTiO with high dielectric constant(SBMO/SBMag, 2015-09) D´Assunção, Adaildo Gomes; Oliveira, Elder Eldervitch Carneiro de; Vieira, Marcelo da Silva; Silva, Paulo Henrique da F.; Oliveira, Maciel Alves deA novel cylindrical DRA antenna based on chemical compound Zr0.25Ti0.75O2 (zirconia titanate) with a high dielectric constant is proposed for the first time for wireless communication systems in high frequency. Numerical and experimental results are presented, as well as a discussion for the proposed antenna and its frequency response. Results of return loss, radiation pattern and input impedance are illustrated and discussed. Numerical results are obtained using Ansoft HFSS based on the element finite method and compared with experimental results, producing a broadband response. A good agreement among results were verified and discussedArtigo Double layer frequency selective surface for ultra wide band applications with angular stability and polarization independence(Sociedade Brasileira de Microondas e Optoeletrônica, 2019-09) Segundo, Francisco Carlos Gurgel da Silva; Campos, Antonio Luiz Pereira de Siqueira; Gomes Neto, Alfredo; Alencar, Marina de OliveiraIn this paper, a double layer stopband Frequency Selective Surface (FSS) for Ultra-Wide Band (UWB) applications is presented. The proposed FSS consists of two cascaded conventional FSS, one with double square loops and other with square loops. The − 10dB frequency band from 3.00 GHz to 11.64 GHz is achieved, with a fractional bandwidth of 149 %. Effects of angular stability and polarization independence over the frequency response are investigated and conclusions are presented. In order to show transmission performance, the FSS was simulated by ANSYS HFSS. The FSS shows angular stability and polarization independence in entire UWB band (3.10 – 10.60 GHz). A prototype was built and measurements were performed. A good agreement between simulated and measured results was observedArtigo Effects of an FSS reflector on a microstrip line fed bow-tie slot antenna(Scielo, 2020-09-16) D´Assunção, Adaildo Gomes; Peixeiro, Custódio; Brito, Augusto César Rebouças de; Abreu, Antonio Salvio deThis paper describes the analysis of the effects of a frequency selective surface (FSS) on the characteristics of a microstripline fed antenna with a bow-tie slot in the ground plane for operation in the frequency range 1 to 10 GHz. The use of the FSS is proposed to miniaturize the antenna structure and increase the number of resonance frequencies and the gain. Air gaps can be inserted between the antenna and the FSS to allow for the adjustment of the resonance frequencies and increase the bandwidth. To prove the concept, antenna prototypes printed on a 30×30 mm2 FR4 low-cost substrate are designed, fabricated and tested. Good agreement is obtained between numerical simulations and experimental results, thus validating the proposed design procedure. The obtained miniaturization and multiband effects can be most convenient for multiservice wireless system applications such as WLAN, WiMAX, 4G, and 5G mobile communication systemsArtigo Efficiency estimative and characterization of nickel ferrite nanoparticles produced by sol-gel modified by ICR cross-linked technique(Elsevier, 2019-11-01) D´Assunção, Adaildo Gomes; Silva, Isaac Barros Tavares da; Oliveira, João Bosco Lucena de; Holanda, Samanta Mesquita deThis paper describes nickel ferrite (NiFe2O4) synthesis by sol-gel modified by Ionic Coordination Reaction (ICR) cross-linked technique according to nitrate concentration on organic based solution, aiming a reduction in losses associated to production process. Chitosan is used to increase the coordination between the ions along with chelate agent glutaraldehyde, used to form the gel in sol-gel technique. Calcination process was also applied, with temperature of 1100 C, 10 C/min step for 10 h, to eliminate organic composes and obtain NiFe2O4 with particles over 300 nm diameter. The obtained efficiency results show that A03 (120 g/L) sample has better final efficiency between the proposed concentrations, reaching a 57.39% value with 95.86% purity, estimated by XRD and EDS. SEM was also performed, and confirmed size distribution based on XRD results, presenting homogeneous morphology along with narrow particle size distributionArtigo Full-Wave analysis of stable cross fractal frequency selective surfaces using an iterative procedure based on wave concept(Hindawi, 2015-08) D´Assunção, Adaildo Gomes; Silva Neto, V. P.; Duarte, M. J.This work presents a full-wave analysis of stable frequency selective surfaces (FSSs) composed of periodic arrays of cross fractal patch elements.The shapes of these patch elements are defined conforming to a fractal concept, where the generator fractal geometry is successively subdivided into parts which are smaller copies of the previous ones (defined as fractal levels). The main objective of this work is to investigate the performance of FSSs with cross fractal patch element geometries including their frequency response and stability in relation to both the angle of incidence and polarization of the plane wave. The frequency response of FSS structures is obtained using the wave concept iterative procedure (WCIP). This method is based on a wave concept formulation and the boundary conditions for the FSS structure. Prototypes were manufactured and measured to verify the WCIP model accuracy. A good agreement between WCIP and measured results was observed for the proposed cross fractal FSSs. In addition, these FSSs exhibited good angular stabilityArtigo Grating lobes suppression in frequency selective surfaces using electromagnetic band gap with square holes(SBMO/SBMag, 2020-10-19) Bezerra, Tiago dos Santos; Campos, Antonio Luiz Pereira de Siqueira; Lira, Ruann Victor de Andrade; Gomes Neto, AlfredoIn this paper, the authors present a proposal for an application of electromagnetic bandgap (EBG), for suppression of grating lobes, in frequency selective surfaces (FSS), not yet studied in the literature. An alternative type of EBG with square holes was proposed to reduce the computational effort in simulations. The study consists of an application of a rectangular periodic array of cylindrical and square holes in FSS dielectric substrate to create rejection bands and suppress specific resonant frequency modes. We built four prototypes and compared measured results with simulated results obtained with ANSYS HFSS. Simulations and measurements show suppression levels up to 6 dB. A good agreement between the results is observed. The FSS with EBG with square holes allows a simulation time 70 % lower than FSS with EBG with cylindrical holesArtigo Higher order mode attenuation in microstrip patch antenna with DGS H filter specification from 5 to 10 GHz Range(Scielo, 2020-06-02) Souza, Francisco Ary Alves; Campos, Antonio Luiz Pereira de Siqueira; Gomes Neto, Alfredo; Serres, Alexandre Jean René; Albuquerque, Camila Caroline RodriguesThis work proposes the application of a slot in the ground plane, Defected Ground Structure (DGS), of a microstrip patch antenna. The application of this technique aims to attenuate higher-order excited modes without deteriorating the antenna parameters in the fundamental mode. The methodology for the design of the slot in H-format is presented, based on the physical dimensions of the microstrip patch antenna. The positioning of the DGS concerning the feed line was determined from a detailed parametric analysis. The antenna was designed for the fundamental mode at 2.45 GHz frequency. Two antenna prototypes were built, with and without DGS, and measurements of reflection coefficient, gain, and radiation pattern were performed. The measured results show that the application of DGS considerably attenuated higher order excited modes. A good agreement between simulated and measured results is achievedArtigo A Hybrid path loss prediction model based on artificial neural networks using empirical models for LTE and LTE-A at 800 MHz and 2600 MHz(Scielo, 2017-09) D´Assunção, Adaildo Gomes; Cavalcanti, Bruno J.; Cavalcante, Gustavo A.; Mendonça, Laércio M. de; Cantanhede, Gabriel Moura; Oliveira, Marcelo M.M.deThis article presents the analysis of a hybrid, error correction-based, neural network model to predict the path loss for suburban areas at 800 MHz and 2600 MHz, obtained by combining empirical propagation models, ECC-33, Ericsson 9999, Okumura Hata, and 3GPP’s TR 36.942, with a feedforward Artificial Neural Network (ANN). The performance of the hybrid model was compared against regular versions of the empirical models and a simple neural network fed with input parameters commonly used in related works. Results were compared with data obtained by measurements performed in the vicinity of the Federal University of Rio Grande do Norte (UFRN), in the city of Natal, Brazil. In the end, the hybrid neural network obtained the lowest RMSE indexes, besides almost equalizing the distribution of simulated and experimental data, indicating greater similarity with measurementsArtigo Improvement of the equivalent circuit method for analysis of frequency selective surfaces using genetic algorithms and rational algebraic models(EMW Publishing, 2015-08-21) Araújo, Gilmara Linhares Ramos de; Campos, Antonio Luiz Pereira de Siqueira; Martins, Allan de MedeirosIn this paper, we propose an enhancement of the Equivalent Circuit Method (ECM) foranalysis of frequency selective surfaces (FSS) with square loop geometry of the unit cell. For this,genetic algorithms and rational algebraic models are used to obtain a more accurate value of the effectiveelectrical permittivity (εeff). We use simulated data obtained with a commercial software to adjust someparameters. So, genetic algorithm is used to obtain a better value of an exponent that calculatesεeffminimizing the rational algebraic models. In this paper, this is done for the square loop geometry, butthe methodology can be extended to any geometry. Finally, prototypes are built and the technique isvalidatedArtigo Investigação experimental da geração de energia elétrica solar fotovoltáica(Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Norte, 2010) Farias, Leandro Alves; Pereira Júnior, Valter Nogueira; Costa, Bruno Palhano; Macedo, Idelcácio Paulino; Farias, Aécio Vinícius Amorim; Campos, Antonio Luiz Pereira de SiqueiraOs painéis solares fotovoltaicos são dispositivos desenvolvidos para a geração de energia elétrica. Este trabalho aborda conceitos envolvidos na fabricação e funcionamento desses dispositivos tais como: histórico da energia solar fotovoltaica, tipos de painéis solares e aplicação de painéis solares em sistemas isolados. Foi feito um estudo de eficiência de geração elétrica de um painel solar existente no Campus Natal – Zona Norte do IFRN. Nesse estudo, foram levadas em consideração a incidência solar e a hora do dia. Por fim, são apresentadas conclusões sobre o estudo desenvolvido
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