1,721,763 research outputs found

    Finite-Time Observer-Based Formation Tracking With Application to Omnidirectional Robots

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    The challenging problem of robust formation control pertaining to omnidirectional robots with model uncertainty and actuator saturation is comprehensively investigated in this article. First, an observer-based formation controller is designed to ensure the semiglobal uniform ultimate boundedness of the system’s formation tracking error. Then, both global stability and practical finite-time stability are achieved to ascertain the practicality of the observer design. Apart from restricting the control input amplitude, we also investigate the reverse effect caused by saturated and coupled control input. As such, an adaptive compensator is formulated to attenuate the state oscillation caused by the reverse effect. Both numerical simulations and hardware-in-the-loop experiments are carried out to illustrate and evaluate the effectiveness and potentials of the proposed new techniques for real-world applications.Yang Fei, Peng Shi, Chee Peng Lim, and Xin Yua

    Discriminative Clustering of High-Dimensional Data Using Generative Modeling

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    We approach unsupervised clustering from a generative perspective. We hybridize Variational Autoencoder (VAE) and Generative Adversarial Network (GAN) in a novel way to obtain a vigorous clustering model that can effectively be applied to challenging high-dimensional datasets. The powerful inference of the VAE is used along with a categorical discriminator that aims to obtain a cluster assignment of the data, by maximizing the mutual information between the observations and their predicted class distribution. The discriminator is regularized with examples produced by an adversarial generator, whose task is to trick the discriminator into accepting them as real data. We demonstrate that using a shared latent representation greatly helps with discriminative power of our model and leads to a powerful unsupervised clustering model. The method can be applied to raw data in a high-dimensional space. Training can be performed end-to-end from randomly-initialized weights by alternating stochastic gradient descent on the parameters of the model. Experiments on two datasets including the challenging MNIST dataset show that the proposed method performs better than the existing models. Additionally, our method yields an efficient generative model.Masoud Abdi, Chee Peng Lim, Shady Mohamed, Saeid Nahavandi, Ehsan Abbasnejad, Anton Van Den Henge

    Going Beyond Counting First Authors in Author Co-citation Analysis

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    The 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

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    “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

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    We 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

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    We 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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