1,721,051 research outputs found
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
Modelleren van korrelsplitsing en texturen voor titanium tijdens plastische vervorming
No full textTitanium and its alloys have been widely used in many fields nowadays because of their excellent mechanical, physical and biological performance, among which, the biomedical applications are using more and more commercially pure grade titanium materials as artificial joints, bone plates and dental screws etc. However, these materials suffer from their relatively low strength in comparison with other biomedical materials such as steel-based materials or Ti6Al4V. Therefore, preprocessing which involves grain refinement to the material is generally required in order to enhance the strength for a better service of the biomedical implants.
In the past decades, severe plastic deformation techniques such as equal channel angular pressing have attracted growing interest in producing bulk ultrafine grained materials in the community. For the optimization of processing parameters and material selection, it is a fundamental issue to understand the development of substructure, texture and mechanical properties of the deformed materials as a function of process and material parameters. Although this issue has been well investigated in experiments, there are only a very limited number of micro-mechanical models that are able to predict the plastic response, the substructure and texture evolution of the material. Micro-mechanical models based on the elementary dislocation processes in grains are considered to have a larger range of usability and validity. This is because the effects of the important parameters that are related to the development of substructure, texture and mechanical properties, e.g. interstitial element concentration, stacking fault energy and temperature, can all be investigated in the models.
The current work presents such a micro-mechanical, grain orientation fragmentation model based on the evolution of dislocation densities. The basic assumption of the model is that reorientation banding is triggered as a relaxation mechanism of the excess shears induced by slip bands from neighbouring grains. The model has been applied to a commercially pure grade 1 titanium deformed by one pass of equal channel angular pressing. The predicted results on the evolutions of various dislocation densities, the average cell size, fragment size and work hardening are all in good agreement with experimental findings.
In order to simulate the deformation texture in titanium, we also proposed a combined approach of linking the grain orientation fragmentation model with a polycrystal plasticity model, which is the visco-plastic self-consistent model for the present case. The coupling is implemented with a shear fluctuation formulation and a texture update scheme. Texture simulations using the combined approach are not only performed for equal channel angular pressing, but also for the rolling process for a better validation of the approach. It has been found that the simulated textures using the combined approach show better agreement with the experimental textures, as compared to the results obtained using the standard modelling approach.status: Publishe
Development of Residual Stresses During Laser Cladding
Get PDFLaser cladding rail steel with a hard-wearing martensitic stainless-steel coating is a possible technique for improving the track durability of rail networks. However, the cladding process induces significant residual stresses in the clad material, due to the thermal mismatch between the two materials and the shape changes during the martensitic phase transformation. Predictions of the residual stress remain poorly verified as the process is complex and measurements made on final clad parts can be influenced by multiple parameters. A cladded and heat-treated rail section was subject to sequential laser-pulses representative of the actual cladding process. The thermal cycle of these pulses is much simpler than real clads, easing the task of validating the component parts of simulations. Synchrotron X-ray diffraction was used to determine the phase selective residual stresses around the heated region before and after each pulse. In this manner it was possible to determine the change in stress due to a pulse and the degree of relaxation that is possible due to a neighbouring thermal cycle
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
An analytical method for predicting residual stress distribution in selective laser melted/sintered alloys
Get PDFResidual stresses that build up during selective laser melting or sintering (SLM/SLS) process can influence the dimensional accuracy, mechanical properties and overall in-service performance of SLM/SLS parts. Therefore, it is crucial to understand, predict and effectively control the residual stress distribution in a part. The present study aims at developing an analytical model to predict the distribution of residual stresses in the part-substrate system. The proposed model demonstrates how residual stresses build up in the substrate and previously deposited layers are related to the stress induced by a newly deposited layer, considering the stress and moment equilibrium requirements. The model has been validated by published experimental measurements and verified with existing analytical/numerical models. The outcomes of the study suggest that the proposed analytical model is applicable for quick estimation of residual stress distribution and the order of magnitude. Also, it provides an evaluation tool for SLM/SLS process parameter design
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
Ontwikkeling van restspanningen en interne spanningen in meerfasige legeringen als gevolg van plastische vervorming: Het geval van perliet
No full textA metallic alloy consists of different grains and phases. These different grains and phases will have different mechanical properties. When the material is deformed, this will result in residual stresses in the material. These are stresses that remain after unloading. The main difference between the grains is their orientation with respect to the sample (i.e. crystallography). For the different phases the morphology of the hard second phase particles will play an important role.
Little attention has been paid so far to studying the impact of the alignment of the second phase particles on strength and anisotropy as a function of the crystallographic orientations of the embedding matrix and strengthening phase and to the interplay of the morphological and the crystallographic orientations and textures during plastic deformation and work-hardening. The structure and alignment of the boundary between the two phases controls the fit of plastic deformation from one phase to the other.
This Ph.D. aims to study the above mentioned aspects in detail to get a better insight in the mechanisms that create the residual stresses and how theyevolve throughout deformation. This knowledge can eventually lead to a further improvement of high strength alloys.status: Publishe
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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