1,720,970 research outputs found
Vibration analysis of functionally graded epoxy/graphene composite plates using the Boundary Element Method and new micromechanical model
No full textThis paper studies the free vibration and harmonic response of Functionally Graded graphene/Epoxy composite plates, considering the First Order Shear Deformation Plate Theory. The weight fraction of graphene variation along the thickness direction with graphene homogeneous dispersed in a polymer matrix. The effective Young Modulus of the plate is predicted by a new micro-mechanical model. The model includes the aspect ratio and weight fraction of nanoplatelets embedded into the matrix. The modal and harmonic of Graphene/Epoxy plates are obtained by the Boundary Element Method formulation for composite plates. The Young modulus calculatedfrom the proposed micro-mechanical model highly agrees with those obtained from experimental results reported in the literature. Results demonstrate a high correlation of the micromechanical model with experimental results and other analytical models. Graphene weight fraction and ratio aspect increase the effective Young modulus of the composite. Boundary Element resultsshow high agreement with Finite Element solutions. Numerical results for modal and harmonic analysis show concentrating graphene near the top and bottom surfaces of the plate is the most effective way to reinforce the plate for increased natural frequencies. The results demonstrate the BEM formulation and micromechanical model can be used as reliable engineering toolsfor the vibrational analysis of functionally grade graphene composite plates.Fil: Useche, Jairo. Universidad Tecnologica de Bolivar; ColombiaFil: Pagnola, Marcelo Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentin
Fabricación de sensores de Grafeno para mediciones de esfuerzo/fuerza en unidades mecatrónicas/roboticas
Full text linkEl presente trabajo muestra las diferentes técnicas de producción empleadas para
la obtención de nanoplacas de grafeno con pocas capas, así como la síntesis de
polisilicona reticulada, ambas necesarias para la fabricación del sensor
nanocompuesto de matriz blanda a base de polisilicona y grafeno. Se determinó
que con la técnica de exfoliación en fase líquida en N-metil-pirrolidona podemos
obtener grafeno con las características deseadas como lo indican las pruebas
XDR, SEM y TEM; sólo se debe ajustar el tiempo de sonicación para lograr las
dimensiones deseadas. Y posteriormente, fabricar el sensor.The present work shows the different production techniques used to obtain graphene nanoplates with few layers, as well as the synthesis of cross-linked polysilicone, both necessary for the manufacture of the soft matrix nanocomposite sensor based on polysilicon and graphene. It was determined thatwith the liquid phase exfoliation technique in N-methyl-pyrrolidone we can obtain graphene with the desired characteristics since the XDR, SEM, and TEM tests indicate it; only the sonicated time should be adjusted to achieve the desired dimensions. And after that step, to manufacture the sensor.Fil: Peña Consuegra, Jorge Mario. Universidad Simón Bolívar; VenezuelaFil: Useche, Jairo. Universidad Tecnologica de Bolivar; ColombiaFil: Pagnola, Marcelo Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Alcoberro, Rodrigo. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; ArgentinaFil: Bauer, Jorge Martin. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentin
A model for the simulation of the chill block melt spinning (CBMS) process using OpenFOAM®
No full textThis work shows the results of a numerical model developed to simulate the CBMS technique for the production of the Fe78Si9B13 metallic magnetic ribbons for application in electronics. The model proposes a numerical approximation to a Vogel-Fulcher-Tammann (VFT) expression as a method in the solidification process. This approximation is introduced into the “compressibleInterFoam” routine, included in the OpenFOAM® suite, originally developed for the simulation of two immiscible, non-isothermal and compressible fluids. This routine solves, the phase fraction transport using the Volume of Fluids (VOF) approach. The boundary conditions imposed in the model were experimentally validated by digital image analysis with a high-speed camera at 5602 fps for the determination of the temperature profiles. The phase change is represented as a growth of several orders of magnitude of the alloy viscosity (μ) as the temperature (T) decreases, reaching solidification around the crystallization temperature (Tg). Also, we establish the condition of initial stability of CBMS process (R > 1.5) for Peclet numbers close to 400, and the validity up to limits of rotation in the wheel close to 40 m s−1. The proposed methodology is validated with previous work. Encouraging results show that the solution of the CBMS process can be adequately simulated with the proposed approach.Fil: Barone, Marcelo Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Barceló, Francisco. Universidad Argentina de la Empresa; ArgentinaFil: Pagnola, Marcelo Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Larreteguy, Axel Eduardo. Universidad Argentina de la Empresa; ArgentinaFil: Marrugo, Andrés G.. Universidad Tecnológica de Bolivar; ColombiaFil: Useche, Jairo. Universidad Tecnológica de Bolivar; Colombi
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
Mechanical Characterisation of Polycarbonate for Helicopter Windshields
No full textTransparent thermoplastics like polycarbonate are widely used as windshields for its optical properties and
for their higher specific mechanical properties compared to glass. Under use in airframe front windshields,
plastics transparencies can be exposed to impact scenarios such as bird-strikes. The resulting load can
lead to a complex loading of the material dominated by tension and bending.
In order to generate input for realistic simulation results, experiments have been performed to characterise
the materials under these loading modes at coupon level in the elastic and plastic domain. On the simulation side, numerical models comprising a discretisation with elements applying Reissner’s plate bending theory have been used in the explicit finite-element method within the LS-DYNA framework with latest solver version R10.1.
Experiments were performed at different strain-rates ranging from quasi-static to approx. 75 1/s. The
numerical modelling has been done with thin and thick shell elements. The thin shell element approach
used the Reissner-Mindlin kinematic assumption in fully-integrated shells. Additionally, some thick shell
formulations with various approaches were applied. To cover the strain-rate sensitive behaviour, a material model based on the Johnson-Cook theory was applied. The influence of the modelling was investigated and compared to the experimental characterisation
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
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