1,721,182 research outputs found
A New SJ* Value Based on Sievers' J-Miniature Drill Tests to Determine the Drillability of Limestones
Get PDF[EN] This research presents a new drillability value (SJ*) that corrects the most-used Sievers¿ J-value (SJ) by removing the accommodation effect of the drill bit in the first tenths of a millimetre to better represent the real drillability of limestones. Moreover, this research demonstrates how such an effect is more notable when porosity and micro-cracking increase, which in this study has been achieved by inducing thermal damage in the samples. To do so, limestone samples from the Prada formation were subjected to temperatures of 105, 300 and 600 °C and then cooled at fast and slow rates to induce porosity and micro-cracking. Two characteristic zones were identified in the penetration¿time plots: (a) a shallow region (Zone 1) with a variable drilling rate including an initial peak and (b) a deeper region (Zone 2) where the drilling rate stabilises. These drilling rates increase with thermally induced porosity and mi-cro-cracking, and the authors propose a new method to delimit Zones 1 and 2. Zone 1 is attributed to the time it takes for the drill bit to adjust and settle in the rock surface, while Zone 2 more realistically represents the drillability of the material. The above influ-ences the SJ value derived from Sievers¿ J-miniature drill tests, so a new drillability value SJ* is proposed that corrects SJ by ex-cluding Zone 1 and giving more weight to Zone 2. The novel SJ* presented in this research constitutes a more accurate tool to assess and predict the drilling performance in limestones.This research received no external funding. The author, Roberto Tomas, is supported by the Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital within the framework of the CIAICO/2021/335 project.Martínez Ibáñez, V.; Garrido De La Torre, ME.; Hidalgo Signes, C.; Tomás, R.; Álvarez-Fernández, M. (2023). A New SJ* Value Based on Sievers' J-Miniature Drill Tests to Determine the Drillability of Limestones. Sustainability. 16(1):1-17. https://doi.org/10.3390/su16010008S11716
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
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
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
Numerical Modelling of Frictional Sliding Induced Damage and Heating Effects on Rock With an Application to Sievers’ J-Miniature Drilling on Granite
No full textThe present study develops a finite element-based numerical method for simulation of frictional rotational sliding induced damage and heating effects on rock. The method is applied to the Sievers’ J- miniature drill test, which is widely used for estimating the rock drillability and predicting the cutter life. A continuum approach based on a damage-viscoplastic model for rock failure is adopted. The viscoplasticity part, based on the Drucker–Prager yield surface with a rounded Rankine criterion as the tensile cut-off, defines the stress states leading to rock failure. This failure is captured by the damage model, which uses separate damage variables for tension and compression (shear). A special workflow for generating granite mineral mesostructures based on Neper, DREAM3D, and Matlab software is developed. Moreover, nanoindentation tests are performed for determination of the elastic material constants for the Kuru granite constituent minerals. The global coupled thermo-mechanical problem with frictional contact is solved with a staggered globally iterative approach. The FE discretized balance of linear momentum is time discretized with the Newmark scheme, and the FE discretized heat equation is time discretized with the Backward Euler scheme. The tangent stiffness operator required by the Newton–Raphson iteration is derived for the isothermal case using the penalty method for contact modelling. Preliminary numerical simulations of the Sievers’ J-miniature drill test on granite demonstrate that the approach holds some promise and thereby provides a platform to be extended to simulate frictional rotational sliding induced damage and heating effects on rocks in other applications as well.Peer reviewe
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
