1,721,137 research outputs found
Setting-up kriging-based adaptive sampling in metrology
No full textStatistical sampling is a fundamental tool in science, and metrology is no exception. The merit of a sample is its efficiency, i.e. a good trade-off between the information collected and the sample size. Although the sample sites are ordinarily decided prior to the measurements, a different option would be to select them one at a time. This strategy is potentially more informative as the next site can be decided based also on the measurements taken up to that time. The core of the method is to drive the next-site selection by a non-parametric model known as kriging, namely a stationary Gaussian stochastic process with a given autocorrelation structure [1,2]. The main feature of this model is the ability to promptly reconfigure itself, changing the pattern of the predictions and their uncertainty each time a new measurement comes in. Since the model is re-estimated after each added point the sampling procedure is an adaptive one. The next sampling site can be selected via a number of model-based criteria, inspired by the principles of reducing prediction uncertainty or optimizing an objective function, or a combination of the two. The methodology has been applied by the authors [3,4] to design inspection plans for measuring geometric errors using touch-probe Coordinate Measuring Machines (CMM). Results showed that both the non adaptive statistical plans (Random, Latin Hypercube sampling, uniform sampling) and two adaptive deterministic plans from the literature were largely outperformed by the proposed plans both in terms of accuracy and cost. Here we further investigate on a number of important questions related to adaptive kriging: which is the best trade-off between the number of adaptive and non-adaptive points (the latter chosen according to uniform coverage), which next-site selection criteria are more suitable to capturing extreme values of the signal in order to provide a good estimate of the geometric errors
Kriging quick adaptive sampling for multivariate optimization
No full textThe paper describes a general adaptive sampling methodology useful in multivariate optimization involving finite element analysis that typically requires a long time. The proposed adaptive sampling method was obtained by starting from a model-based statistical methodology developed to design an adaptive inspection plan for the geometric control of mechanical parts. The novelty of the new kriging adaptive sampling procedure consists in overcoming some critical issues, such as the reduction of the estimation time to have an efficient tool for quick application. The others are related to how to set up a kriging-based adaptive sampling, how to choose the stopping rule, and how to remove the dependence on the statistical variability. These issues are the subject of this work to develop a useful tool for multivariate optimization. By improving the methodology in these aspects, it was possible to obtain a feasible and useful instrument for the application in a quick sampling procedure within the inspection process. After this enhancement process, the method is sufficiently general to be extended in the multivariate optimization field that requires a multi-factorial finite element analysis. To demonstrate this, an illustrative real case study from an industrial application is presented and it was found that the proposed method reduces significantly the time required to reach the optimal solutio
E-Learning and Affective Student’s Profile in Mathematics
No full textThis paper is concerned with the personalisation of teaching/learning paths in mathematics education. Such personalisation would exploit the research results on the connection between the affective experience of the student learning mathematics and his/her success or failure in mathematics, which produces the learner’s attitude towards mathematics. We present a model for the learner’s affective profile in mathematics, which would extend the current user profile in an e-learning platform taking into account the learner’s attitude, to be used in order to offer and manage a Unit of Learning in mathematics better tailored on the global student’ needs. Tools for the implementation of the model in an e-learning platform have been devised. Activities templates suitable to various attitudes towards mathematics have been designed and their experimentation is in progress
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
ONE-STAGE CORONARY AND ABDOMINAL AORTIC OPERATION WITH OR WITHOUT CARDIOPULMONARY BYPASS:EARLY AND MIDTERMS FOLLOW-UP.
No full textAppropriate 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
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