1,721,063 research outputs found
SCREAM: A novel method for multi-way regression problems with shifts and shape changes in one mode
No full textSome fields where calibration of multi-way data is required, such as hyphenated chromatography, can suffer of high inaccuracy when traditional N-PLS is used, due to the presence of shifts or peak shape changes in one of the modes. To overcome this problem, a new regression method for multi-way data called SCREAM (Shifted Covariates REgression Analysis for Multi-way data), which is based on a combination of PARAFAC2 and principal covariates regression (PCovR), is proposed. In particular, the algorithm combines a PARAFAC2 decomposition of the X array and a PCovR-like way of computing the regression coefficients, analogously to what has been described by Smilde and Kiers (A.K. Smilde and H.A.L. Kiers, 1999) in the case of other multi-way PCovR models. The method is tested on real and simulated datasets providing good results and performing as well or better than other available regression approaches for multi-way data. (C) 2013 Elsevier B.V. All rights reserved
A classification tool for N-way array based on SIMCA methodology
No full textIn the literature there are only fewpapers concerned with classification methods for multi-way arrays. The mostcommon procedure, by far, is to unfold the multi-way data array into an ordinary matrix and then to apply thetraditional multivariate tools for classification. As opposed to unfolding the data several possibilities exist forbuilding classification models more directly based on the multi-way structure of the data. As an example, multiwaypartial least squares discriminant analysis has been used as a supervised classification method, anotheralternative that has been investigated is to perform classification using Fisher's LDA or SIMCA on the score matrixfrom e.g. a PARAFAC or a Tucker model. Despite a few attempts of applying such multi-way classificationapproaches, no-one has looked into how such models are best built and implemented.In this work, the SIMCA method is extended to three-way arrays. Included in this work is also actual code thatwill work on general multi-way arrays rather than just three-way arrays. In analogy with two-way SIMCA, adecomposition model is separately built for the multi-way data for each class, using multi-way decompositionmethod such as PARAFAC or Tucker3. In the choice of the best class dimensionality, i.e. number of latent factors,both the results of cross-validation but mainly the sensitivity/specificity values are evaluated. In order toestimate the class limits for each class model, orthogonal and score distances are considered, and differentstatistics are implemented and tested to set confidence limits for these two parameters. Classificationperformance using different definitions of class boundaries and classification rules, including the use of crossvalidatedresiduals and scores is compared.The proposed N-SIMCA methodology and code, besides simulated data sets of varying dimensionality, has beentested on two case studies, concerning food authentication tasks for typical food products
Classification Methods of Multiway Arrays as a Basic Tool for Food PDO Authentication
No full text[No abstract available
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
Wheat flour formulation by mixture design and multivariate study of its technological properties
No full textWheat flour plays a pivotal role in determining the overall quality of bread (loaf dimensions, crumb texture and consistency). A precise knowledge of flour chemical and technological properties is of paramount importance for the baking industry, to tune the modifications of the recipe and production parameters. However, it is still common to have to deal with an empirical, trial and error-based approach, and generally, time consuming techniques are employed to determine the quality indexes for flour.In the context of an industrial bread-making process, this study addresses the evaluation of the effect of a systematic variation in the mixture composition of wheat flours on their properties. The main objective is to offer this field a more rigorous method to evaluate and improve flour properties, by employing experimental design methodologies and interpreting the results in a multivariate way, instead of the common one variable at a time approach. The results show that a careful planning of flour mixtures when testing new varieties and formulation helps to obtain meaningful and easy-to-understand results as far as their properties are concerned
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