1,720,985 research outputs found
Stable numerical evaluation of multi-degree B-splines
Full text linkMulti-degree splines are piecewise polynomial functions having sections of different degrees. They offer significant advantages over the classical uniform-degree framework, as they allow for modeling complex geometries with fewer degrees of freedom and, at the same time, for a more efficient engineering analysis. Moreover they possess a set of basis functions with similar properties to standard B-splines. In this paper we develop an algorithm for efficient evaluation of multi-degree B-splines, which, unlike previous approaches, is numerically stable. The proposed method consists in explicitly constructing a mapping between a known basis and the multi-degree B-spline basis of the space of interest, exploiting the fact that the two bases are related by a sequence of knot insertion and/or degree elevation steps and performing only numerically stable operations. In addition to theoretically justifying the stability of the algorithm, we will illustrate its performance through numerical experiments that will serve us to demonstrate its excellent behavior in comparison with existing methods, which, in some cases, suffer from apparent numerical problems
Beccari (C), S. J., Rerum AEthiopicarum scriptores occidentales inediti a saeculo XVI ad XIX
No full textGrumel Venance. Beccari (C), S. J., Rerum AEthiopicarum scriptores occidentales inediti a saeculo XVI ad XIX. In: Échos d'Orient, tome 28, n°154, 1929. pp. 236-237
A Cox-de Boor-type recurrence relation for C1 multi-degree splines
Full text linkMulti-degree splines are piecewise functions comprised of polynomial segments of different degrees. A subclass of such splines, that we refer to as C1 MD-splines, is featured by arbitrary continuity between pieces of same degree and at most C1 continuity between pieces of different degrees. For these spline spaces a B-spline basis can be defined by means of an integral recurrence relation, as an instance of the more general construction in Beccari et al. (2017). In this paper, we provide efficient formulas for evaluating C1 MD-splines and their derivatives, akin to the classical B-spline recurrence relations. Furthermore we derive algorithms for geometric design, including knot insertion and local degree elevation. Finally we demonstrate the utility of these splines, not only for geometric modeling, but also for graphical applications, discussing in particular the advantages for modeling and storing vector images
Assessing math attitude through the Attitude Toward Mathematics Inventory – Short form in introductory statistics course students
No full textMath attitude refers to emotional responses, beliefs, and behaviors towards mathematics. Several studies measured the relation with math learning and related variables, but very few with statistics learning. To better investigate this relation has become increasingly relevant to have a measure that ensuring multidimensionality and shortness. The aim of the present paper was to confirm the factor structure of the Lin and Huang (2014)'s ATMI - Short Form (ATMI - SF) when administered to Italian college students attending introductory statistics course, and to test its measurement invariance applying a multigroup confirmatory analysis. We also assessed the reliability and the incremental validity of the ATMI - SF by verifying whether it predicted statistics achievement over and above the effect of math knowledge. The overall findings provide that ATMI - SF is a reliable and valid measure to assess math attitude among college students who attend introductory statistics courses in non-mathematical courses
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
A fast interactive reverse-engineering system
No full textA new method of reverse engineering for fast, simple and interactive acquisition and reconstruction of
a virtual three-dimensional (3D) model is presented. We propose an active stereo acquisition system,
whichmakes use of two infrared cameras and awireless active-pen device, supported by a reconstruction
method based on subdivision surfaces. In the 3D interactive hand sketching process the user draws and
refines the 3D style-curves, which characterize the shape to be constructed, by simply dragging the
active-pen device; then the systemautomatically produces a low-resolutionmesh that is naturally refined
through subdivision surfaces. Several examples demonstrate the ability of the proposed advanced design
methodology to produce complex 3D geometric models by the interactive and iterative process that
provides the user with a real-time visual feedback on the ongoing work
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