1,720,974 research outputs found
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
Utilizing legacy seismics and non-seismic geophysical methods for deep mineral targeting and near-surface characterization: implications for mine development planning
No full textA thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy In the Faculty of Science, School of Geosciences University of the Witwatersrand, Johannesburg 2023This thesis demonstrates through several case studies how the reprocessing of legacy reflection seismic data using advanced algorithms can be of value to mineral exploration and mine development, especially in hard-rock environments. The thesis also showcases how the integration of seismic and non-seismic geophysical datasets can assist in delineating near- surface geological structures (e.g., boulders and fractures) for mine planning and designs. Papers I and II demonstrate how the reprocessed legacy reflection seismic data have been used to delineate and image the world-class gold deposits such as the Black Reef (BLR) and Ventersdorp Contact Reef (VCR) of the Witwatersrand goldfields in South Africa. The two legacy reflection seismic profiles (Paper I) were acquired in 1988 for deep mineral exploration and mine planning over an area that is dominated by dolomitic outcrops that cause scattering of seismic energy at the near-surface, preventing energy propagation into the subsurface. Various migration approaches, namely, pre-stack time, pre-stack depth, and post-stack time migration were applied to test their capabilities in improving structural imaging. Reprocessing results from the pre-stack depth migration using the Kirchhoff algorithm provided the most improved subsurface images, especially the deeper targets due to its ability to honour complex lateral variations in the velocity field. In addition, Kirchhoff's pre-stack and post-stack time migration techniques improved the continuity of the near-surface reflections below the dolomitic rocks.
Paper II presents the results from the recovered and processed 25.3 km long legacy seismic survey that was acquired in 1983 by the Gold Division of Anglo-American as part of the Witwatersrand goldfields exploration program. The reprocessing of the data improved the imaging of the gold-bearing horizon termed Ventersdorp Contact Reef (VCR), which is situated at depths between ~2400 and ~4100 m below the ground surface near the South Deep mine in Fochville, South Africa. The pre-stack time and phase-shift migration approaches were tested during processing, and both revealed a dipping reflection associated with the gold-bearing horizon and major steeply dipping faults that crosscut and displace the deposit. The interpretation of the results was constrained using borehole logs and surface geology. This is encouraging and motivates the use of legacy seismic data in the exploration of deep-seated targets.
Papers III, IV and V present the results from the use of multi-geophysical methods (resistivity, magnetics, seismic, ground penetrating radar and multichannel analysis of surface waves) at Tharisa platinum mine to provide a comprehensive understanding of the subsurface geology by accurately delineating and locating boulders, mapping fractures and groundwater aquifers to improve Platinum Group Elements (PGEs) mining efficiency and reduce risks. The results from these integrated geophysical methods were successful in complementing each other in terms of providing a clear picture of the near-surface geological structures to help the mine plan better for future operations.Research Office Carnegie BursaryKirsh FoundationMM202
Physical property studies, tunnel numerical simulations and in-mine seismic experiments to image the gold orebody at South Deep Gold Mine
No full textA dissertation submitted in fulfilment of the requirements for the degree of Master of Science, to the Faculty of Science, School of Geosciences, University of the Witwatersrand, Johannesburg, 2024.The investigation endeavors to assess the physical characteristics of deep borehole cores within the Upper Elsburg Reefs (UER) of the South Deep gold mine of the West Rand goldfield. Specifically, these cores are sourced from three boreholes situated approximately 2.6 km beneath the surface within the confines of the South Deep gold mine. The focal point of this study lies in non-destructive testing methods aimed at elucidating the intrinsic attributes of these rocks, with particular attention directed towards seismic velocities and densities. These measurements hold paramount importance in conducting numerical simulations to designing the in-mine (or tunnel) seismic reflection surveys acquired at South Deep gold mine, as part of the ERA-Min3 FUTURE (Fiber-optic sensing and UAV-platform techniques for innovative mineral exploration) project. Cultivating a profound comprehension of the seismic velocities and densities across diverse rock formations can significantly augment the interpretation of seismic reflections, thereby facilitating more refined assessments of subsurface geology and structural configurations. In pursuit of this goal, our study endeavors to delve into the fundamental acoustic properties of the gold-rich UER, with the overarching aim of deepening our understanding of its seismic reflectivity. To realize this objective, a comprehensive array of physical measurements, encompassing ultrasonic velocities and bulk densities, were conducted on drill-core specimens. To accurately portray the physical attributes of the lithological units under scrutiny, a total of twenty-four samples were subjected to exhaustive analysis for density and seismic velocity utilizing a spectrum of methodologies. Density determinations were procured through a diverse set of techniques, including dimensional assessments, employment of the KT20 MagSus tool, and utilization of the SNOWREX AHW-3 Professional Weighing Scale boasting a heightened sensitivity of 0.01 g. Ultrasonic measurements were undertaken employing the Proceq Pundit PL 2000 ultrasonic pulser velocity tester, equipped with two pairs of transducers boasting a center frequency of 54 kHz. The in-mine seismic survey was acquired to delineate geological structures that crosscut and displace the orebody. The study locale encompasses three distinct rock formations: the UER, gold-bearing conglomerate units (termed reefs), basaltic lava, and dyke specimens. The UER primarily comprises quartzites, exhibiting a P-wave velocity range of 5202-5802 m/s, an S-wave range of 3037-4768 m/s, and bulk densities spanning from 2.66 - 2.71 g/cm³. Conglomerate reefs exhibit a P-wave velocity range of 4467-5970 m/s, an S-wave range of 4040-4854 m/s, and bulk densities ranging from 2.67-2.94 g/cm³. Lava samples extracted from the boreholes showcase a P-wave velocity range of 5916 - 6711 m/s, an S-wave range of 3275-5659 m/s, and bulk densities spanning from 2.75-2.90 g/cm³. Singular dyke samples were encountered, exhibiting a P-wave velocity of 5921.5 m/s, an S-wave velocity of 5385 m/s, and a density of 2.85 g/cm³. The study employed the synth-seis code to simulate 1D seismic responses based on borehole data collected from the mine, aiming to validate findings from velocity and density measurements. Analysis of the seismograms indicated notable contrasts between conglomerates and quartzites, particularly evident in density and S-wave measurements, suggesting potential for improved rock discrimination with alternative seismic sources. Additionally, 2D numerical simulations were conducted to model wave propagation in the Upper Elsburg Reef (UER), revealing discrepancies between simulated and synthetic seismogram results, indicating potential limitations in seismic imaging. Furthermore, ray tracing was used to design a seismic survey inside the mine along the tunnel floor to image VCR (Ventersdorp Contact Reef) orebody and other geological structures. The real seismic survey was finally conducted inside the tunnel (SDT1), demonstrated the value of in-mine reflection seismic surveys for mapping geological structures at significant depths, which would otherwise be costly and logistically challenging. Despite noise interference from mine operations, processing algorithms enabled extraction of reflections and structural mapping from the dataset, underscoring the importance of such surveys in mining exploration and planning.DST - National Research Foundation (NRF)Department of Science and Innovation (DSI)Advanced Orebody Knowledge ProgrammeMMM202
Intergrated Geophysical Methods to Delineate R21 Sinkholes Near Olifantsfontein, Gauteng, South Africa
No full textA thesis submitted in fulfilment of the requirements for the degree of Master of Science, to the Faculty of Science, School of Geosciences, University of the Witwatersrand, Johannesburg, 2024The Gauteng province in South Africa is known for having a significant portion, at least 25%, of its land is underlain by dolomite rocks. An integrated approach of non-invasive geophysical methods was utilised to map the geometry (shape, size and extent) of the R21 highway sinkhole that formed near Olifantsfontein. These methods include seismic (reflection and refraction), multi-channel analyses of surface waves (MASW), electrical resistivity tomography (ERT), and ground penetrating radar (GPR). The objectives of the investigation were three-fold: (1) to understand the geology and formation of sinkholes in Gauteng; (2) to use geophysical techniques to map and characterize sinkholes in the study area, including determining their geometry, lateral and vertical extents; and (3) to determine the effectiveness of each method in mapping sinkholes. Despite the high level of noise along the highway, the geophysical surveys were conducted successfully and provided a good basis for the integrated interpretations. This study showcases the importance of utilising multiple geophysical methods to obtain a comprehensive understanding of sinkholes and their subsurface characteristics. It also demonstrates the practical application of these methods in real-world scenarios for improved hazard assessment and risk mitigation. The GPR results suggest that a sinkhole extends by ~2.5 m further into the R21 highway surface with a depth of ~8-10 m (top to bottom). The refraction seismic method suggests that the sinkhole is ~20 m wide, while the ERT results suggest that the sinkhole starts at 10 m and extends to 15 m depth. The results from reflection seismics indicate that the R21 sinkhole is structurally controlled and it is characterised by fracturing and faulting that manifest as diffractions on the seismic sections. Understanding the extent and characteristics of sinkholes is crucial for infrastructure planning and hazard mitigation, especially in areas prone to subsidence and sinkhole formation like in Gauteng. These findings can inform decision-making processes related to road maintenance, construction, and land use planning in sinkhole-prone regions. The success of the integrated geophysical approach in this study highlights its potential for similar investigations in other areas with karst geology and sinkhole risks.MMM202
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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