1,720,976 research outputs found
CHARACTERIZATION AND MODELLING OF MECHANICAL PROPERTIES OF POLYMER/CLAY NANOCOMPOSITES BY FILM BLOWING
No full textThe present work focuses on the modelling of mechanical behaviour of polyamide based nanocomposite films whose tensile properties were correlated to the structural changes promoted by the biaxial deformation imposed during the film blowing process.
It is well known that the nanocomposite properties are strictly related to the microstructure developed during the processing. The ideal situation of full exfoliation, dispersion and orientation of silicate layers in the polymer matrix is not easily achieved in melt compounding process. Actually, a more common situation is represented by partially exfoliated and intercalated morphology. Therefore, a 3D-FEM numerical model which takes into account a mixed exfoliated and intercalated nanostructure has been used to fit the experimental mechanical results. In particular, the algorithm imposes periodic boundary conditions, so that the mean value of the elastic constants, for even RVEs containing very few particles, is close to the exact value for large composite volume.
Comparison of simulation results with experimental data has confirmed the reliability of the numerical simulation method used in the present study
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
A user-friendly system for identifying the optimal insertion direction and to choose the best pedicle screws for patient-specific spine surgery
No full textBackground and objective: Many diseases of the spine require surgical treatments that are currently performed based on the experience of the surgeon. The basis of this study is to deliver an automatic and patient-specific algorithm able to come to the aid of the surgeons in pedicle arthrodesis operations, by finding the optimal direction of the screw insertion, the maximum screw diameter and the maximum screw length. Results: The paper introduce an algorithm based on the reconstructed geometry of a vertebra by 3D-scan that is able to identify the best introduction direction for screw and to select, from commercial and/or personalised databases, the best screws in order to maximize the occupation of the bone while not intersecting each other and not going through the walls of the pedicle and the bounds of the vertebral body. In fact, for pedicle arthrodesis surgery, the incorrect positioning of the screws may cause operating failures, an increase in the overall duration of surgery and, therefore, more harmful, real-time X-ray checks. In case of not availability on market, the algorithm also suggests parameters for designing and manufacturing an ‘ad hoc’ solution. The algorithm has been tested on 6 vertebras extracted by a medical database. Furthermore, the algorithm is based on a procedure through which the surgeon can freely choose the entering point of the screw (based on his/her own experience and will). A real patient vertebra has been processed with almost 400 different entering point, always giving a feedback on the possibility to use the entering point (in case of unavailability of a good trajectory) and on the individuation of the right trajectory and the choose of the better screws. Conclusions: In very recent bibliography, several papers deal with procedure to screw’ trajectory planning in arthrodesis surgery by using Computer Aided surgery systems, and some of them used also modern methodologies (KBE, AI, Deep learning, etc.) methods for planning the surgery as better as possible. Nevertheless, no methodologies or algorithm have been still realized to plan the trajectory and choose the perfect fitting screws on the basis of the patient-specific vertebra. This paper represents a wind of novelty in this field and allow surgeons to use the proposed algorithm for planning their surgeries. Finally, it allows also the easy creation of a customized surgical template, characterized by two cylindrical guides that follow a correct trajectory previously calculated by means of that automatic algorithm generated on the basis of a vertebra CAD model for a specific patient. The surgeon will be able to set the template (drilling guides) on the patient's vertebra and safely apply the screws
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
La polemica Riccioli-Borelli-Angeli e la deviazione dei gravi in caduta
No full textThe controversy between the Jesuit Giovanni Battista Riccioli and the Galileans Giovanni Alfonso Borelli and Stefano degli Angeli is part of the broader question of the opposition to the Copernican system on the part of Catholic orthodoxy. However, it had a
fundamental role in highlighting an unresolved crucial question of Galilean dynamics: the “true” or “absolute” motion of falling bodies distinct from the apparent motion with respect to the rotating Earth. The starting point of the controversy was the proof of the immobility of the Earth, sustained by Riccioli in his Almagestum novum (1651) and reaffirmed in the Astronomia Reformata (1665), which criticized Galileo’s hypothesis of a semicircular trajectory, travelled with uniform motion. Riccioli’s argument was based on the impact of a falling body on the ground, which varied with height. Borelli in De vi percussionis liber (1667) affirmed that the trajectory could be neither circular nor spiral, but he opposed Riccioli’s objection since this was based on the uniformity of the absolute motion while the variation of the impetus concerned the relative motion. A few months later, Angeli intervened against both Riccioli’s demonstration and Borelli’s arguments and the controversy developed into a long series of cross replicas (1666-1669). All the participants in the controversy were convinced that the trajectory should tend towards the center of the Earth, but, at a certain point within the debate, the consideration of a deviation emerged. It was Angeli, who, believing that the angular velocity was conserved during the fall, highlighted the consequence of Borelli’s hypothesis, namely, that by maintaining the transverse velocity constant, the body would fall east of the vertical. The deviation of a falling body later became the experimental proof in favor of the rotation of the Earth, and the trajectory of a body in absolute space the theme of the famous correspondence exchanged between Newton and Hooke (1679-1680)
Enhancing students’ understanding of “science in the making” within a historical perspective
No full textThe role of history in enhancing the understanding of scientific rationality is acknowledged by scholars from various fields. However, the problem of how to use history to design effective teaching-learning activities is still open. In this regard, we outline the project of a workshop on History and Science Education (HSE) at the University of Urbino, to be carried out in collaboration with the Physics Laboratory: Urbino Museum of Science and Technology. Taking the HSE workshop as a case study, the purpose of the ongoing research is to try to operationalize a historical-epistemological approach to Physics education that can enhance students’ understanding of science in the making, while meeting some suggestions
from current trends in education
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
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