1,720,977 research outputs found
I Congreso Argentino de Desarrollo Territorial. III Jornadas de Desarrollo Local Regional : las redes locales y el desafío de la innovación en una nueva etapa de la globalización
Get PDFFil: Souto, Gabriel. Universidad Nacional Villa María; Argentina.Fil: Sánchez, Mónica Elisa. Universidad Nacional Villa María; Argentina.Fil: Yañez, Javier Ignacio. Universidad Nacional Villa María; Argentina.Fil: Suárez, Gabriel, . Universidad Nacional de Villa María; Argentina.Fil: Suárez, Gabriel, . Universidad Nacional de Villa María; Argentina
Estudo paramétrico sobre superfícies seletivas em frequência reconfiguráveis
No full textThe demand for solutions in communication technologies grows as new services and applications emerge. Like any circuit involving electromagnetic signals, telecommunication systems can use active and passive filters to better serve this expanding service. This work presents parametric and operation analyzes of frequency filters as a means of selecting electromagnetic signals, presenting a complete analysis of the design, execution and validation of a Frequency Selective Surfaces (FSS) project used as a filter in communication systems. Through these filtering elements, it is possible to achieve increased directivity of antennas, electromagnetic shielding, beam stirring and beam switching in the active selection of signals and applications in the detection and characterization of materials in any state. When placed under an incident wavefront, thin conducting planar elements that act as an obstacle to an incident wavefront and interact with certain frequencies determined by the designer, in order to reject them or not, so that a service is served. FSS are selective in propagation frequency, incidence angles or even propagation modes. Through the Equivalent Circuit Method, from its primordial elements to its active arrangements, three active band-reject solutions are designed using the short-circuit method; taking the double square loop and double ring model, both with two resonance frequencies, and Jerusalem Cross / Ring, with three resonance frequencies or Tri-band, with FR4 substrate aiming to apply them in Stealth and Beam Switching solutions . Parametric analysis was performed by varying the thickness for all elements of each geometry for the three designs, resulting in variations in the transmission coefficient that form a behavior pattern. The commercial Finite Element Method using the HFSS® (High Frequency Structural Simulator) was used to observe the project's operability in the S band, and later prototypes were built, in switched and non-switched mode, for the three projects, totaling six different prototypes that were measured to search for the transmission coefficient using the Free Space Method through the VNA (Vector Network Analyzer) R & S® 100 kHz / 8.5 GHz. The comparison of the measured and simulated results showed that the project is operational in the design ranges with classic parameters with a transmission coefficient of -17.53 dB, -30.03 dB, -19.06 dB at 1.8 GHz, 3.1 GHz and 5.8 GHz, for the Jerusalem Cross / External Ring project , respectively; -25.03 dB and -27.45 dB for the frequencies of 2.3 GHz and 5.8 GHz, for the double square loop design, respectively and -24.35 dB and -50.01 dB for 2.45 and 5.8 GHz for the 2.45 GHz and 5.8 GHz frequencies for the double circular loop design, respectivelyA demanda por soluções em tecnologias de comunicação cresce conforme surgem novos serviços e aplicações. Como qualquer circuito que envolve sinais eletromagnéticos, os sistemas de telecomunicação podem utilizar filtros ativos e passivos para melhor atender a este serviço em expansão; este trabalho apresenta análises paramétricas e de viabilidade de filtros em frequência como meio de seleção de sinais eletromagnéticos apresentando uma análise completa da parametrização, execução e validação de um projeto de Superfícies Seletivas em Frequência (SSF) utilizadas como filtro em sistemas de comunicação. Através destes elementos filtradores, é possível alcançar o aumento da diretividade de antenas, blindagem eletromagnética, beam stirring e beam switching na seleção ativa de sinais e aplicações em detecção e caracterização de materiais em qualquer estado. Quando colocados sob uma frente de onda incidente, elementos planares condutores finos que atuam como obstáculo para uma frente de onda incidente e interage com certas frequências determinadas pelo projetista, a fim de rejeitá-las ou não, para que um serviço seja atendido. As SSF são seletivas em frequência de propagação, ângulos de incidência ou até modos de propagação. Através do Método do Circuito Equivalente, desde seus elementos primordiais até seus arranjos ativos, são projetadas três soluções rejeita-faixa ativas utilizando o método do curto-circuito; tomando o modelo espira quadrada dupla e anel duplo, ambos com duas frequências de ressonância, e Cruz de Jerusalém/Anel, com três frequências de ressonância ou Tri-band, com substrato de FR4 tendo objetivo de aplica-los em soluções Stealth e Beam Switching. A análise paramétrica foi feita pela variação de espessura para todos os elementos de cada geometria para os três projetos, resultando em variações no coeficiente de transmissão que formam um padrão de comportamento. O Método dos Elementos Finitos comercial através do HFSS® (High Frequency Structural Simulator) foi utilizado para observar a operacionalidade do projeto na banda S e, posteriormente protótipos foram construídos, em modo chaveado e modo não chaveado , para os três projetos, totalizando seis diferentes protótipos que foram medidos para busca do coeficiente de transmissão utilizando o Método do Espaço Livre através do VNA (Vector Network Analyzer) R&S® 100 kHz/ 8,5 GHz. A comparação dos resultados medidos e simulados mostrou que o projeto é operacional nas faixas de projeto com parâmetros clássicos com coeficiente de transmissão em -17,53 dB, -30,03 dB, -19,06 dB em 1,8 GHz, 3,1 GHz e 5,8 GHz, para o projeto em Cruz de Jerusalém/Anel Externo, respectivamente; -25,03 dB e -27,45 dB para as frequências de 2,3 GHz e 5,8 GHz, para o projeto em espira quadrada dupla, respectivamente e -24,35 dB e -50,01 dB para 2,45 e 5,8 GHz para as frequências de 2,45 GHz e 5,8 GHz, para o projeto em espira circular dupla, respectivamenteCoordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPE
Análise, estudo e simulação de linhas de transmissão de microfita
Get PDFArtigo AcadêmicoThis study brings a analitical approach of applied eletromagnetism on microstrip
lines. Through the basic principles of eletromagnetism, using the Maxwell equations and the
Helmholtz equation, taken its solucions applied on the patch line with only one dieletric and
analyse it’s transversal and propagating fields. In conclusion, the impedance matrix is used to
calculate the parameters and patterns that can be found on the propagating field for a given
operation frequency.Este estudo traz uma abordagem analítica dos campos eletromagnéticos que se propagam
em uma linha de microfita. Através dos princípios básicos do eletromagnetismo parte-se
das soluções da equação de Helmholtz e das equações de Maxwell aplicada em uma linha com
apenas um dielétrico e analisa-se o comportamento dos campos transversais e propagantes.
Calcula-se, por fim, a matriz impedância da linha onde é possível, com o uso de softwares de
processamento analítico, encontrar as constantes de propagação para a frequência de operaçãoTrabalho não financiado por agência de fomento, ou autofinanciad
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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