161,701 research outputs found
OBTENCIÓN DE CURVAS Ɛ-T DE ALUMINIO PLEGADO MEDIANTE UN SISTEMA BARRA DE HOPKINSON (OBTAINING CURVES Ɛ-T OF FOLDED ALUMINUM BY MEANS OF A HOPKINSON BAR SYSTEM)
No full textUn Sistema Barra de Hopkinson fue utilizado para medir altas tazas de deformación a compresión de aluminio plegado. Para ello se seleccionó un material adecuado para las barras del Sistema de Hopkinson que fuera cercano a la impedancia del material a estudiar. Se realizó la instrumentación de la barra mediante galgas extensométricas con un arreglo de puente completo de Wheatstone y un adquisidor de datos. Las gráficas obtenidas de deformación (Ɛ) en función del tiempo (t) muestran un comportamiento típico de materiales de baja impedancia, tal como es reportado en la literatura. La configuración lograda para el Sistema Barra de Hopkinson permitirá obtener la respuesta dinámica de deformación de materiales suaves o de baja impedancia, así como caracterizar las propiedades mecánicas de los mismos.Palabra(s) Clave: Aluminio plegado, Barra de Hopkinson, Materiales suaves. AbstractA Hopkinson Bar System was used to measure high rates of compression deformation of folded aluminum. For this, a suitable material was selected for the bars of the Hopkinson System that was close to the impedance of the material to be studied. The instrumentation of the bar was performed by strain gauges with a complete Wheatstone bridge arrangement and a data acquisition. The graphs obtained from deformation (Ɛ) as a function of time (t) show a typical behavior of low impedance materials, as reported in the literature. The configuration achieved for the Hopkinson Bar System will allow to obtain the dynamic deformation response of soft or low impedance materials, as well as to characterize the mechanical properties of them.Keywords: Folded aluminum, Hopkinson Bar, Soft materials
Variations on the Author
No full text“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
CONSTRUCCIÓN DE UNA BARRA DE HOPKINSON PARA PRUEBAS DINÁMICAS EN MATERIALES PLEXOPLEGADOS
No full textRecientemente los materiales ligeros capaces de absorber energía se han estudiado como una alternativa innovadora para diferentes aplicaciones en el transporte o en el diseño de sistemas de absorción de impactos; las espumas de aluminio y las hojas de aluminio plegado ofrecen un campo de estudio muy amplio para las aplicaciones ya mencionadas, por lo que es importante el diseño y construcción de un dispositivo capaz de determinar el comportamiento de estos materiales ante una carga de compresión aplicada a altas velocidades. El ensayo de compresión utilizando un dispositivo de barra de Hopkinson es una opción que puede aportar la información deseada.En este artículo se muestra el proceso de construcción de este dispositivo, en el cual se consideran propiedades del material de ensayo como la impedancia acústica, cuya importancia es significativa para la selección de las barras que realizan la compresión durante el ensayo. Palabra(s) Clave(s): Aluminio plexoplegado, barra de Hopkinson, impedancia acústica, tasa de deformación
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Larry O. Spencer, Conference Author Presentation
No full textGen. Larry O. Spencer, USAF (Ret.), author of Dark Horse: A Journey from the Horseshoe to the Pentago
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Investigating the use of rubber to attenuate the effect of blast load applied to a surrogate lower leg
No full textIncludes abstract.Includes bibliographical references (leaves 191-197).Landmines are the epitome of the perfect soldier: always ready, never tiring. Landmines also do not choose their victims - it may very well be an armed and protected soldier or an innocent civilian who activates the detonator. As such, land mines have reached epidemic proportions in the Third World, affecting both combatants and civilians, whether they are on foot or in a vehicle. When stepping on an anti-personnel land mine, traumatic amputation of the foot, lower leg or upper leg is generally expected. However, an anti-vehicle landmine detonating underneath a vehicle can have equally as detrimental results, as the occupants of the vehicle are bound to sustain serious injuries to the lower extremities. These injuries can vary from being less life threatening to being fatal in some extreme cases. Anthropomorphic test devices have been developed and refined over the years to represent the occupant exposed to simulated land mine detonation and then to retrieve valuable technical information from the test data. In the present investigation a simplified aluminium surrogate lower leg was designed, manufactured and subjected to axial blast testing. In addition, a rubber layer representing the sole of a standard army combat boot was placed below the foot model in a separate series of blast tests. The main factors investigated in this study were the effect of varying the amount and positioning of the explosives and the attenuation produced by including the rubber sole layer. The blast tests were conducted using a horizontal ballistic pendulum, with the foot model placed axially in the pendulum. The disc shaped explosives of different mass was placed in the centre of the detonation plate and axially in line with the heel respectively to draw a comparison between the respective stresses induced in the lower leg. As expected, the stress recorded by the strain gauges placed on the lower leg was significantly higher when the explosives were positioned in line with the heel than when placed in the centre of the detonation plate. The same series of blast tests were performed with the rubber sole being included in the test setup. Alternating the positioning of the explosives did not yield a significant difference in induced stress. Investigation of the blast attenuation provided by the rubber layer showed that the peak stress is mitigated by approximately 70%, which was much greater than expected. An elementary analytical solution was performed as a preliminary validation of the experimental test results. Furthermore, a finite element model of the aluminium surrogate foot and the rubber layer was created and a numerical simulation of each blast test was executed. Material data for the aluminium and rubber obtained via Split-Hopkinson Pressure Bar testing were employed to construct the material models used in the finite element model. The results from the numerical simulations compare well to the experimental test results for the blast loading conditions where the rubber layer was excluded from the test setup. In the case where the rubber layer was included in the testing, the trend and shape of the stress graphs obtained from the numerical simulation results agrees with the stress curves recorded during the actual blast tests. However, the peak stresses recorded during the experimental blast tests are found to be significantly higher than the peak stresses yielded by the numerical simulations
A perspectiva negra na Ficção Científica: o caso de "Clap Back", de Nalo Hopkinson
No full textThe article offers an analysis of “Clap Back” (2021), by writer Nalo Hopkinson, part of the collection Black Stars (Amazon Original Stories). To this end, Science Fiction (SF) is delimited in the contexts of the English language and black authorship, approaching some of its specificities. The results demonstrate how the writer articulates scientific-fictional elements with themes of the black cause, in a dystopian, futuristic environment. This fusion, it is concluded, problematizes racism and at the same time highlights black protagonism and ancestry.
O artigo oferece uma análise sobre “Clap Back” (2021), da escritora Nalo Hopkinson, parte da coletânea Black Stars (Amazon Original Stories). Para isso, delimita-se a Ficção Científica (FC) nos contextos da língua inglesa e da autoria negra, abordando algumas de suas especificidades. Os resultados demonstram como a escritora articula elementos científico-ficcionais com temáticas da causa negra, em ambientação futurista distópica. Esta fusão, conclui-se, problematiza o racismo e ao mesmo tempo realça o protagonismo negro e a ancestralidade.
 
O MARAVILHOSO NA LITERATURA CONTEMPORÂNEA: UMA LEITURA DE SALMAN RUSHDIE, MARGARET ATWOOD, ROBERT COOVER E NALO HOPKINSON
No full textEste artigo discute as relações entre a história e a literatura, por meio do resgate de formas literárias do passado, especialmente o maravilhoso. Analisa, também, o papel do maravilhoso enquanto gênero na pós-modernidade, questionando se ele estaria, ainda, próximo do conceito estabelecido por Todorov ou se a forma como se configura atualmente nas narrativas contemporâneas subverteria o gênero. Para tanto, analisaremos algumas obras de escritores contemporâneos de língua inglesa, que revisitam o maravilhoso,como Robert Coover, Margaret Atwood, Nalo Hopkinson e Salman Rushdie
MODERNIDADE CONTRACULTURAL E PÓS- 'COLONIAL' EM MIDNIGHT ROBBER, DE NALO HOPKINSON
No full textA ficção especulativa pós-colonial de Nalo Hopkinson convoca elementos ‘canônicos’ da ficção científica, tais como o desenvolvimento tecnocientífico, a distopia futurológica, a viagem espacial e o trânsito entre diferentes dimensões, fundindo-os com uma multiplicidade de marcadores do legado colonial caribenho, resultando em uma narrativa de modernidade contracultural, ou o que Ashcroft (2009) denomina modernidade alternativa. Partindo dessas considerações, proponho uma leitura de Midnight Robber (2000), de Hopkinson, argumentando que a obra aponta, metaforicamente, para as tensões entre o arquivo oficial da modernidade e os pontos cegos dessa mesma narrativa.Palavras-chave: Ficção especulativa. Tecnociência. Pós-colonialResumen La ficción especulativa post colonial de Nalo Hopkinson convoca elementos de ficción científica como el desenvolvimento tecnocientífico, la distopía futurológica, el viaje espacial y el trânsito entre diferentes dimensões, fundidos en una multiplicidad de marcadores del legado colonial caribeño, resultando en una narrativa de modernidade contracultural, o lo que Ashcroft (2009) denomina modernidad alternativa. Partiendo de esas consideraciones, propongo una lectura de Midnight Robber (2000), de Hopkinson, argumentando que la obra apunta, metafóricamente, para las tensiones entre el archivo oficial de la modernidad y los puntos ciegos de esa misma narrativa.Palavras claves: Ficçión especulativa. Tecnociencia. Post-colonialAbstract Nalo Hopkinson’s postcolonial speculative fiction deploys ‘canonical’ elements from the science fiction genre, such as technoscientific development, futurological dystopia, space travel, and the transit between different dimensions, fusing them with a multiplicity of markers of the Caribbean colonial legacy. This fusion results in a narrative of countercultural modernity, or alternative modernity (Ashcroft, 2009). In my discussion of Hopkinson’s Midnight Robber (2000), I argue that her work points metaphorically to the tensions between the official archive of modernity and the blind spots in this narrative.Keywords: Speculative fiction. Technoscience. Post-colonia
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