1,720,995 research outputs found
Proposal and simulation of a structure of routing for Switching ATM
No full textEste trabalho aborda o problema decorrente da necessidade de realizar tráfego multicast em redes ATM. Para isto, foi proposta uma arquitetura para a estrutura de célula da chave, mais especificamente a estrutura de roteamento de células no interior da chave ATM. Como o ATM se propõe a atender a todas as exigências do B-ISDN, a necessidade essencial da chave ATM, é que o transporte de células entre suas portas de entrada e saída se faça o mais rápido possível. Para se conseguir isso, a arquitetura proposta não utiliza buffer nos seus elementos de roteamento. O trabalho não implementa no todo a chave ATM, deixando em aberto o problema da perda de seqüência de células no interior da estrutura de roteamento, que seria uma responsabilidade do módulo de saída da chave. A arquitetura proposta foi modelada e um simulador foi construído para a realização dos testes. Para as simulações foram levados em conta os tráfegos de células unicast e multicast. Como as células unicast e as cópias das células multicast disputavam por um mesmo link de saída, foi proposta uma estratégia para separar estas células. Isto resultou no projeto de posicionar a rede de cópia de células no segundo estágio da estrutura de roteamento, deixando o primeiro estágio para o roteamento das células unicast. O resultado disso foi um segundo estágio agora destinado para as cópias de células multicast absolutamente descongestionado, reduzindo \'drasticamente a possibilidade de disputa por um link de saída. Além disso, a estrutura incorpora os conceitos de TBSF (Tandem Banyan Switch Fabric), e duplicidade de rota, que tornam a estrutura extremamente modular e flexível. Para atender a preocupação em separar o tráfego, foi introduzido entre um estágio e outro da rede Banyan, uma saída de fuga, permitindo que células que tenham atingido a porta de saída desejada possam deixar a estrutura. São apresentados os resultados da simulação, objetivando a validação do trabalho proposto.This thesis addresses the problem of accomplishing multicast traffic in ATM networks. An architecture is proposed for the cell structure of the switch, more specifically the routing of cells inside an ATM switch. Because ATM tries to satisfy all the demands of the B-ISDN model, an ATM switch must transport cells between its input and output ports as fast as possible. To achieve that, the proposed architecture does not use buffers in its commutation elements. This work does not implement a complete ATM switch, leaving the problem of the loss of sequence of cells inside the routing structure open. This problem must be solved by the output module of the switch. The proposed architecture was modeled and a simulator was built for testing purposes. For the simulations, both the unicast and the multicast traffic were taken into account. As the unicast cells and the copies of the multicast cells disputed for the same output link, a strategy was proposed to separate these cells. This resulted in the positioning of the cell copy network in the second stage of the routing structure, leaving the first stage for the routing of unicast cells. The result was a very free second stage used for copying multicast cells. This new stage reduced the contention for an exit link. The structure incorporates the concepts of TBSF, and route duplicity, which make it extremely modular and flexible. To separate the traffic, it was introduced between the two stages of the Banyan Network an escape exit, allowing cells that have reached the correct output port to leave the structure
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Get PDFEste trabalho aborda fundamentalmente os estudos do comportamento de sistemas de aterramentos quando submetidos à altas correntes impulsivas oriundas das descargas atmosféricas. Nestas situações, nas regiões próximas aos eletrodos, poderá ocorrer um processo de ionização do solo, que torna a resistência dos aterramentos não lineares. Para levar em consideração esses efeitos em estudos de sobretensões e de cálculos de proteção de sistemas, foi desenvolvido uma nova metodologia de cálculo de resistência de terra, na freqüência industrial, denominada série-paralelo, e um circuito elétrico equivalente não linear, que simula o processo de ionização. Uma caracteristica relevante desta nova metodologia é a fácil inclusão do comportamento não linear do solo, nos estudos. Neste contexto, as resistências de diferentes regiões do solo são associadas de forma serial ejou paralela, compondo os diferentes circuitos elétricos equivalentes que podem, assim, ser solucionados por programas simuladores comerciais, a exemplo do programa MICROCAP II e PSPICE. Esta metodologia pode ser aplicada não somente a pequenos aterramentos, como as hastes, mas também a grandes sistemas, a exemplo das malhas e cabos contra-peso. Neste trabalho, também serão apresentados os résultados laboratoriais decorrentes de ensaios efetuados em modelos físicos, e resultados dos ensaios de campo que foram efetuados objetivando criar parâmetros para a validação desta nova metodologia.This work fundamentally contains the studies of the grounding systems submitted to lightning impulse currents. In these situations, next to electrodes, a ionization process will be able to occur, resulting that grounding systems have non linear resistances. To take in count these effects in overvoltage and protection studies, a new methodology of grounding resistance calculus for industrial frequency, named serial-parallel, anda non linear equivalent circuit, which simulates the ionization process, were developed. A relevant characteristic of the serial-parallel methodology is which allows easily to include the non linear behavior of the soil in the grounding studies. In this context, different regions of the soil can have its resistances associated in serial andjor parallel way, forming the equivalent circuit which can be solved by simulating commercial program, for instance, SPICE and MICROCAP PROGRAM. This methodology can be used to solving small and big grounding systems, such as parallel rods and substation grids. In thi s work, the comparison between the field results and the simul ating wi ll be also presented, showing which there is very good agreement between the
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
Spatiotemporal prediction of the number of electric power outages
No full textPower outages are a significant issue that cause financial losses and negatively impact the quality of life for consumers. To better manage these occurrences, energy utilities require effective tools and indicators for decision-making and efficient resource allocation. This work proposes the application of Machine Learning techniques to forecast the monthly volume of power outages based on regional climatic, structural, and electrical factors. The study utilizes publicly available and cost-free data from Brazilian governmental regulatory agencies, such as the National Electric Energy Agency (ANEEL), the National Institute of Meteorology (INMET), and the Brazilian Institute of Geography and Statistics (IBGE). A framework was developed using open-source technologies such as Python and MySQL, inspired by the Data Lakehouse Medallion architecture, to facilitate data extraction, storage, and transformation, resulting in a robust database prepared for analysis and machine learning model training. Multiple Regression and Random Forest models were trained and evaluated using the Mean Absolute Percentage Error (MAPE) metric, and their results were compared with a heuristic strategy for outage prediction. Considering the heterogeneity of the Brazilian national territory and its potential influence on outage occurrences, consumer units were clustered into five distinct groups based on regional characteristics using the K-Means algorithm, enabling tailored model training within each cluster. The results demonstrated consistent model performance, underscoring the framework's effectiveness across diverse Brazilian regions106 f
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
Interoperabilidade com base na Norma IEC 61850: revisão sistemática e estudo de caso
No full textA Norma International Electrotechnical Commission (IEC) 61850 trouxe vantagens operativas aos sistemas elétricos ao estabelecer requisitos de rede, protocolos de comunicação e modelagem de informação padronizados, além de diretrizes que trazem mais confiabilidade as redes de sistemas elétricos e a promessa de interoperabilidade entre equipamentos de diferentes fabricantes. No entanto, a sua aplicação não trivial e tem se mostrado desafiadora, devido as diferentes interpretações e metodologias adotadas pelos fornecedores. Da mesma forma, a própria definição da Norma da argem para implementações variadas com informações opcionais ou informações a serem preenchidas conforme critério do usuário na modelagem de dados. Além disso, a falta de capacitação em redes
de comunicação e estruturas de dados pelo corpo técnico tradicionalmente presente em sistemas elétricos, torna a tarefa ainda mais desafiadora. Com isso, no presente trabalho é realizada uma Revisão Sistemática da Literatura (RSL) da literatura, através de buscas bem definidas em cinco bases bibliográficas distintas. Foi realizado um levantamento dos requisitos para a realização da interoperabilidade, além dos desafios encontrados na implementação de projetos de interoperabilidade, também foi buscado os estudos de caso em laboratórios ou projetos e, além disso, as diretrizes para a certificação e averiguação em torno da interoperabilidade por diferentes fabricantes pela Norma IEC 61850. Por fim, é proposto um fluxo esquemático inicial para averiguação da interoperabilidade para
testes com diferentes fabricantes. Para validar o método, é realizado um estudo de caso
de interoperabilidade entre relés de proteção SEL 421-7 (Assinante) e Siemens 7SA87, a ser certificado a partir da metodologia proposta. Nos resultados foi possível capturar, através do software WireShark, as mensagens Generic Object Oriented Substation Event (GOOSE) enviadas pelo relé de proteção Siemens 7SA87 ao relé SEL 421-7 e sinalização do recebimento da mensagem pelo 421-7 a partir de seu sequencial de eventos e sua interface homem-máquina.The IEC 61850 Standard brought operational advantages to electrical systems while
establishes network requirements, communication protocols, and standardized information models. It also adressed guidelines that bring more reliability to electrical systems
networks and the promise of interoperability between equipment from different manufacturers. However, the implementation is not trivial, and it has been challenging due
to different interpretations and methodologies adopted by vendors. Besides that, the
Standard definitions themselves provide margin to various implementations with optional
information or information that can be filled on user criteria. Besides that, the lack of training in communication networks and data structure by the traditional staff in electrical
systems makes the task even more challenging. With that in mind, a Systematic Review
of literature is made on a well-defined search in five different bibliographic bases. A requirement gathering on performing interoperability is carried out. Also, it was explored the
challenges on interoperability projects by case studies on laboratories or implementation
projects, and also it was searched the guidelines for certification and verification on the
subject of interoperability by different manufacturers according to IEC 61850. Lastly, it
is proposed an initial schematic flow on verifying the interoperability between different
vendors based on IEC 61850 Standard. To validate the method, a case study of interoperability between Siemens 7SA87 and SEL 421-7 protection relays is carried out to be certified with the proposed method. In the results, it was possible to capture, through the WireShark software, the GOOSE messages send by Siemens 7SA87 relay to SEL 421-7 relay, and the message was certified by his human-machine interface and sequence of events report
Aplicação do ciclo PDCA na análise de estrutura de uma empresa de distribuição de energia elétrica
No full textA regulação aplicada às concessionárias de distribuição tem como objetivo incentivar a produtividade no setor. Nessa regulação, é aplicado o modelo de preço-teto, onde é definido o valor da tarifa de energia elétrica que vai remunerar as companhias através da análise de todos os custos necessários para a prestação do serviço com qualidade e eficiência. Para garantir que esses custos serão colocados em prática, as empresas precisam monitorar constantemente seus indicadores financeiros e operacionais, além de adotar modelos de gestão que a auxiliem nesse processo, sendo um desses modelos, o ciclo PDCA. Esse trabalho mostra a aplicação do ciclo PDCA na análise de estrutura de uma empresa distribuidora de energia elétrica que atua no Brasil, detalhando os tipos de análises realizadas em cada setor da companhia, os problemas levantados, suas formas de resolução e o resultado financeiro gerado ao final do projeto, onde mostrou-se a oportunidade de redução de 7% do valor gasto atualmente.The regulation applied to distribution concessionaires aims to encourage productivity in the sector. In this regulation, the price-cap model is applied, which defines the value of the electricity tariff that will remunerate companies through the analysis of all the costs necessary to provide the service with quality and efficiency. To ensure that these costs are put into
practice, companies need to constantly monitor their financial and operational indicators, in addition to adopting management models that help in this process, one of these models being the PDCA cycle. This document shows the application of the PDCA cycle in the analysis of the structure of an electricity distribution company operating in Brazil, detailing the types of analyzes carried out in each sector of the company, the problems raised, their forms of resolution and the financial result generated by the end of the project, which showed the opportunity to reduce the amount currently spent by 7%.60 p
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