1,720,954 research outputs found
Modelagem da pressão e da temperatura do molde em um processo de moldagem por injeção
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Campus Joinville, Programa de Pós-Graduação em Engenharia e Ciências Mecânicas, Joinville, 2021.Processos de moldagem por injeção são o método mais utilizado para produzir peças de plástico. Entretanto a moldagem por injeção é bastante suscetível a perturbações causadas por mudanças nas propriedades do material e nas condições do processo. Abordagens de controle do maquinário hidráulico são capazes de mitigar a variância do processo, mas a qualidade das peças também depende de fenômenos que ocorrem dentro da cavidade do molde. Neste trabalho, perfis de temperatura do molde e de pressão na cavidade (variáveis de processo) foram medidos com o objetivo de ajustar modelos capazes de descrever o processo ? para aplicações futuras em abordagens de controle. A distribuição das etapas da moldagem por injeção e as dinâmicas das variáveis de processo foram consideradas. O estudo do primeiro tópico resultou em um modelo capaz de classificar, por meio do método k-means, a situação atual do processo em regimes de incompressibilidade e compressibilidade. O primeiro regime compreende as etapas de preenchimento e resfriamento, enquanto o segundo compreende as etapas de compressão e recalque. Já a modelagem das dinâmicas das variáveis de processo, através de modelos SARIMA, se mostrou capaz de descrever os comportamentos sazonais do processo. Esta abordagem forneceu modelos cujos resíduos apresentaram valores inferiores aos erros experimentais, inerentes à medição das variáveis de processo.Abstract: Injection moulding processes are the most used method to manufacture plastic parts. However injection moulding is very susceptible to disturbances caused by changes in the material properties or in the processing conditions. Hydraulic machinery control approaches are able to mitigate the process variance, but the quality of the parts also depends on phenomena that occur within the mould cavity. In this work, mould temperature and cavity pressure (process variables) profiles were measured with the aim of fitting models capable of describing the process ? for future applications in control approaches. The stages distribution of injection moulding and the process variables dynamics were addressed. The study of the first topic yielded a model capable of classifying, through the k-means method, the current status of the process in incompressible and compressible regimes. The first regime comprises the stages of filling and cooling, while the second one comprises the stages of packing and holding. The modelling of the process variables dynamics, by means of SARIMA models, was proved capable of describing the seasonal behaviours in the process. This approach furnished models whose residues presented values below the experimental errors, inherent to the measurement of the process variables
Controle digital em cascata de uma planta didática de levitação magnética com linearização por realimentação
Get PDFTCC (graduação) - Universidade Federal de Santa Catarina. Campus Joinville. Engenharia Mecatrônica.A suspensão de uma esfera de material ferromagnético em um campo magnético induzido por um eletroímã é um exemplo didático de suspensão magnética. Este sistema é instável em malha aberta e requer o controle em malha fechada para ter características aceitáveis de suspensão. Neste trabalho foi projetado um sistema de controle digital, empregando a técnica de controle em cascata para a planta descrita. Além disso, o sistema de controle incluiu um processo de linearização baseado nos valores instantâneos das variáveis de estado. O sistema de controle foi projetado com base em um modelo da planta no espaço de estados e seu desempenho foi avaliado através de simulações. A suspensão estável da esfera foi alcançada para perfis de referência com aceleração contínua. Além disso, perturbações determinísticas foram rejeitadas. Concluiu-se que a técnica de controle adotada é eficiente para estabilizar a posição da esfera e realizar o seguimento de referência para um certo tipo de perfil.The suspension of a sphere of ferromagnetic material in a induced magnetic field by an electromagnet is a didactic example of magnetic suspension. This system is unstable in open loop and it requires closed loop control to have acceptable suspension characteristics. In this work, a digital control system for the described plant has been designed using the cascade control technique. In addition, the control system included a linearization process based on the instantaneous values of the state variables. The control system is based on a plant's model in state space and its performance was evaluated through simulations. The stable sphere suspension was achieved for reference profiles with continuous acceleration. Furthermore, deterministic perturbations were rejected. It was concluded that the adopted control technique is efficient to stabilize the ball position and to perform the reference tracking for a certain type of profile
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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