1,720,980 research outputs found
NUMERICAL ANALYSIS OF THE EFFECT OF MEMBRANE PRELOADS ON THE LOW-SPEED IMPACT RESPONSE OF COMPOSITE LAMINATES
No full textThis article presents a comprehensive study on the mechanical behaviour of composite laminated plates undergoing a low-speed impact of an external body while they are subjected to in-plane preloads. The effect of such preloading was investigated by means of finite-element analysis of several impact events on laminates with three different span-to-thickness ratios. Tensile and compressive preloads, both uniaxial and biaxial, were considered; in the case of compression, the impact on buckled specimens was also studied. The results obtained show that the span-to-thickness ratio is a fundamental parameter in determining the effect of initial strains. Under a tensile preload, the impact-caused peak stresses were higher than in the case of no preload, and their increment was higher in thicker laminates. Under compression, the most dangerous influence of initial
stresses was found at medium span-to-thickness ratios for preloads comparable with the buckling load, whereas, in other cases, negligible or even beneficial effects were observed. These results can justify some experimental findings from the existing literature, even if they were obtained without modelling the material degradation due to damage. Also, they allow us to conclude that the explanation of other phenomena strictly related to damage, as well as an accurate prediction of the extent of damage, requires a failure model
Falling weight impact and indentation damage characterisation of sandwich panels for marine applications
No full textOn three configurations of laminates for nautical use, impact and indentation properties have been compared, in the understanding that these represent two different and significant cases in the laminate service, namely contact with fal- ling body and ramming. All the laminate configurations were fabricated using the same stacking sequence of E-glass mats (of weight 225 and 600 g/m2) as skins, while the core was obtained with different types of rigid PVC foams in the case of A laminate (HEREX C-75) and in that of B and C laminates (COLTH C-55). The latter laminates are also protected with Gelcoat on the outer side. The resin used for A and B laminates was a conventional vynilester (DISTITRON VE 100 SC), while for C laminate a polyester-based including some non-oil derived components was used (ENVIREZ 1807). Laminates of each of the three configurations have been impacted from 1, 1.5 and 2 meters with a 1.25 kg mass using a 12.7 mm hemispherical nose, therefore yielding impact energies of 12.25, 18.37 and 24.5 Joules respectively. Subsequently, other laminates have been quasi-statically indented at with 0.05 mm/s cross-head speed, using the same indentor, until the maximum average displacement obtained during low velocity impact for each configuration and each energy was obtained. The results obtained show that strain rate has an effect on the performance of these laminates. In particular, the improved resistance to penetration appears to occur at the expense of damage dissipation due to vibrations. Quasi-static indentation does not appear to fully reproduce the effect of low velocity impact loading for these sandwich structures, showing significant differences in the hysteresis cycles, both during loading and during the damping phase, which need to be combined with the variable effect of damage on the laminates
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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