1,720,958 research outputs found
Edição especial - IV Jornada de Matemática e Matemática Aplicada - PPGMat/UFSM
No full textA IV Jornada de Matemática e Matemática Aplicada (IV JMMA) foi um evento ocorrido na Universidade Federal de Santa Maria (UFSM), durante os dias 15, 16 e 17 de Novembro de 2023, e organizado pelo Programa de Pós-Graduação em Matemática (PPGMat) dessa instituição. Além de palestras e minicursos, o evento contou com as sessões técnicas, nas quais os alunos e alunas de graduação e pós-graduação apresentaram seus trabalhos de pesquisa, de forma oral ou em banners. A edição especial da IV Jornada de Matemática e Matemática Aplicada (IV JMMA) na revista Ciência e Natura contém os trabalhos que foram apresentados de forma oral durante o evento. Esses foram expandidos e passaram por uma nova revisão indicada pelo Comitê Cientı́fico do evento
Reduction techniques applied to the oxidation of ethanol
Full text linkNumerical simulation of reactive flows, such as combustion, has a highly non-linear character due to the presence of several chemical reactions that occur among the chemical species that describe the process of fuel’s oxidation. Besides, such processes occur at a molecular level, making the system of governing equations stiff, which implies in the need of high order numerical schemes as well as fine meshes and small time step, enhancing considerably the computational cost. In this sense, the use of detailed oxidation mechanisms in the numerical simulation is prohibitive, and chemical reduction techniques are needed in order to develop reduced models with less variables and moderate stiffness, while maintaining the accuracy and comprehensiveness of the detailed model. The objective of the present works if to obtain a comparison between two chemical reduction techniques, the Directed Relation Graph - DRG, based on the skeletal mechanisms generation, and the Reaction Diffusion Manifolds - REDIM, based on the separation of time scales. As validation of the proposed models, one-dimensional numerical simulations of premixed and non-premixed flames, as well as homogeneous reactors, are carry out. Besides, a coupled methodology between DRG and REDIM is presented, that will provide a useful tool for simulation of fuels with very large detailed kinetic mechanisms.A simulação numérica de escoamentos reativos, como a combustão, tem um caráter altamente não-linear devido a presença de diversas reações químicas que acontecem entre as espécies que descrevem o processo de oxidação do combustível. Além disso, tais processos ocorrem a nível molecular, tornando o sistema de equações governantes rígido, o que implica na necessidade de esquemas numéricos de alta ordem bem como malhas finas e passo de tempo pequeno, aumentando consideravelmente o custo computacional. Neste sentido, o uso de mecanismos de oxidação detalhados na simulação numérica é proibitivo, e técnicas de redução química são necessárias de modo a desenvolver modelos reduzidos com menos variáveis e rigidez moderado, mantendo a precisão e abrangência do modelo detalhado. O objetivo do presente trabalho é obter uma comparação dos resultados obtidos para duas técnicas de redução química diferentes, Directed Relation Graph - DRG, baseada no desenvolvimento de mecanismos esqueletos, e a Reaction Diffusion Manifolds - REDIM, baseada na separação das escalas de tempo. Como validação dos modelos propostos, simulações numéricas 1D de chamas pré-misturadas e não pré-misturadas, bem como de reatores homogêneos, são desenvolvidas. Além disso, uma estratégia que une as duas técnicas de redução é apresentada, com o objetivo de ser aplicada em mecanismos cinéticos grandes
Solução para as Equações de Navier-Stokes em Domínios Tridimensionais Finos
Full text linkThe classical form of the Navier-Stokes equations system, which is derived from the principle of conservation of mass and momentum, describes the motion of a homogeneous fluid subject to a field of external forces. In this work, we develop a study to find the maximal interval of existence of solutions in time to the Navier-Stokes equations in a three dimensional thin domain, i.e., Ω = ω × (0, ∈), where ω ⊂ R² e ∈ ∈ (0, 1), considering different combinations of boundary conditions.A forma clássica do sistema de equações de Navier-Stokes, o qual deriva do princípio de conservação de massa e momento linear, descreve o movimento de um fluido homogêneo sujeito a um campo de forças externas. Neste trabalho, desenvolve-se um estudo para encontrar o intervalo maximal de existência de soluções no tempo para as equações de Navier-Stokes em um domínio tridimensional fino, isto é, Ω = ω × (0, ∈), where ω ⊂ R² e ∈ ∈ (0, 1), considerando combinações de diferentes condições de fronteira
Development of a reduced kinetic mechanism for ethanol based on DRG and sensitivity analysis
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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