1,720,952 research outputs found
Ceramic material under ballistic loading: A numerical approach to sphere impact on ceramic armour material
No full textArmour systems for ballistic protection can be made from many materials. One type of material used in armour systems is ceramic. Ceramic materials, such as alumina and silicon carbide, can be beneficial in an armour system because of their high hardness and relatively low weight. The high hardness of the ceramic potentially causes a projectile to deform heavily and fracture upon impact with the armour, thereby reducing or even eliminating the threat. The ceramic itself may also damage during the interaction. Although ceramics can damage under impact, they contribute to the protective capability of the armour system as long as they exert a force on the projectile to deformand deceleration it. In order to improve an armour system one does not only need to know when the ceramic component fails, but also how it fails. Once the failure mechanisms of the ceramic are known the armour design may be modified to delay or in an ideal scenario even prevent catastrophic failure of the ceramic. This will eventually result in stronger and lighter armour systems.Applied Mechanic
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
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
Numerical modeling of cone cracking in ceramics via indentation
No full textCeramic is a hard and brittle material with little ductility. It has wide applications in diverse industries viz. metallurgy, atomic energy, electronics, communication, space, military, insulation, biomechanical appliances etc. It is preferred material for armour protection due to its high strength-weight ratio. Its plastic deformation and failure behavior have, therefore, become a subject of extensive research in the recent past. Consequently, several material models were formulated in the second half of the nineteenth century by researchers such asJohnson- Holumquist, Rajendran-Grove, Deshpande-Evans etc. to study ceramic response under high-velocity impact. But these models are complex and require extensive calibration, while the Drucker-Prager (DP) Model is easy to implement. It was developed for study in soil and rock and is chosen to analyze ceramic quasi-plastic and tensile behaviour as part of research through the current thesis.Tensile ring and cone cracks, first observed by Hertz, are one of the modes of failure in brittle materials like ceramic. The prime objective of the thesis is the study of ceramic failure as well as cone crack initiation and its propagation through the ceramic body under the influence of varying material parameters such as cohesion, friction angle, dilatancy and softening of ceramics besides confinement by indentation. The Drucker Prager model is employed to studyindentation by simulation through numerical methods in JEM JIVE FEM library. Verification of the model was done through simulation of unit cubes subjected to unidirectional stresses at prescribed displacements. Suitable modification for pressure dependent softening behaviour of the ceramic is also made into the model and simulations undertaken in order to get insight into the nonlinear strength degradation of the ceramic post-elastic limit. Since the DP criteriontends to overestimate material strength, a suitable mechanism to limit the material strength is integrated with DP yield function and also to facilitate the comparison of results arrived through DP and modified yield functions. The results obtained by a simulated indentation in accordance with the DP formulation suggest that ceramic having high dilatancy, low friction angle and small softening modulus under confined conditions is more suited for use as armor protection. The pressure dependent softening behavior of ceramic is favorable for it being a good armor protection material. The DP Yield function modified to limit the material strength to a finite value, did not have any significant impact on crack initiation though the zone of compressive plastic strain grew in size during indentation. The DP based numerical model suffered from mesh sensitivity. The introduction of viscoplasticity to the numerical model was observed to have a positive influence in mitigating mesh sensitivity.Civil Engineering | Structural Engineerin
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
A fully implicit plasticity model for the characterization of ceramics in ballistic protection
No full textThe Johnson-Holmquist-2 ceramic model is used for quasi-static indentation simulation. A modification is proposed to an associated plasticity formulation. This allows for a fully implicit solution scheme, where dilatation is used instead of the traditional explicit bulking formulation. Dilatation is shown to have an important influence on ring-crack formation during indentation. A mesh refinement study is performed to show the current tensile failure behaviour leads to mesh-dependent results
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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