1,721,023 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
Satellite-enabled early warning system for geotechnical structures
Get PDFThere is a critical need to protect communities, natural habitats and the ecosystems from toxic mine waste pollution that can result from the collapse of tailings storage facilities (TSFs). With increasing role of mining in the transition away from fossil fuels, the need to do mining safely and sustainably is of critical importance. Satellite Synthetic Aperture Radar Interferometry (InSAR) shows much promise towards this monitoring ambition on the global scale. In this work, the opportunities and challenges for developing a satellite based early warning system for TSFs are explored. This necessarily brings together three separate fields - geotechnical engineering, satellite remote sensing and deep learning. Firstly, ground deformation measurements from InSAR and ground-based prism monitoring are compared to Finite Element (FE) simulation results for a recent tailings dam collapse. The study highlights the efficacy and complementarity of geotechnical and remote sensing techniques for the monitoring of TSFs. Moreover, extracting meaningful information and interpreting the deformation patterns from InSAR data can be a challenging task. One approach to address this challenge is through the use of data science techniques. The representation of InSAR metadata as Embedded Entities within a Deep Learning framework (EE-DL) is proposed for modelling the spatiotemporal deformation response. This study demonstrated that EE-DL can detect and predict the fine spatial movement patterns that eventually resulted in the TSF collapse. Overall, EE-DL is proposed as a promising approach for building early-warning systems for critical infrastructures that use InSAR to predict ground deformations. This research is designed to push the limits of what is possible from the globally available open source data from the Sentinel-1 satellite. Moreover, the value and improvement in the early warning framework offered by commercial, high resolution data from the satellite Radarsat-2 are also investigated
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
Measurement and modelling of soil-structure interaction for open caisson shafts
Get PDFMonolithic open caissons are a common method of constructing underground shafts, for applications including storage tanks, pumping stations, deep foundations and tunnelling. The caisson construction process uses concurrent casting of massive reinforced concrete walls and excavation of soil within the structure, causing the caisson to ‘sink’ into the ground under its self-weight. Achieving controlled sinking relies on accurate estimation of the resistance generated by the interaction between the caisson and the surrounding soil. The lack of dedicated research and design methods means there is significant uncertainty in determining the frictional and bearing resistances during design, particularly in cohesionless soils.
This thesis aims to explore the soil-structure interaction during caisson sinking in sands, through numerical modelling and experimental testing. The outputs of recent caisson field monitoring were limited by critical failures of electrical sensors. To facilitate measurement of the caisson-soil contact stresses, the development of more robust sensor technology is necessarily pursued. A new framework for multi-axis force sensing is demonstrated, to enable optical strain measurement in the form of FBGs to be utilised. This is applied to create a sensor for detailed measurements of combined normal and frictional interface stresses in underground construction applications. Numerical simulation and physical testing build confidence in the new design, as well as exploring a novel approach for measuring effective normal stress.
Friction at the caisson external surface is explored through laboratory-scale testing in dense sand, using a bespoke large-displacement interface shear apparatus. The new optical sensors are employed to obtain localised contact stress measurements and particle image velocimetry provides observations of the soil displacements. The results give insight into the mechanisms associated with different interface conditions, including over-cut creation and lubrication.
The bearing capacity at the base of the caisson wall is explored through numerical modelling. An extensive parametric study using finite element limit analysis considers the influence of salient caisson parameters, including the taper angle and cutting shoe. A complimentary targeted study with finite element analysis is used to assess the influence of soil non-associativity and the development of horizontal reaction. Detailed observations of the soil failure mechanisms provide new insight into the bearing behaviour in sands. The numerical results are compared against recent laboratory-scale experimental tests and used to develop simplified closed-form expressions for bearing capacity estimation in routine design
Investigation of soil-structure interaction for large diameter caissons
Get PDFLarge diameter open caissons are widely adopted in civil engineering infrastructure projects for deep foundations, underground storage and attenuation tanks, pumping stations, and launch and reception shafts for tunnel boring machines. These structures are commonly formed using cast in place reinforced concrete, with the structural self-weight in combination with soil excavation within the caisson, forcing the caisson continuously into the ground. This sinking process presents several engineering challenges for engineers, including maintenance of caisson verticality, control of the rate of caisson sinking, and minimisation of soil-structure frictional stresses through the use of lubricating fluids. Controlled sinking of caissons requires a thorough understanding of the interaction between the caisson shaft and the surrounding soil, as well as the bearing capacity at the base of the caisson. New understanding has been developed by instrumenting a number of caisson shafts, on live construction sites, for the measurement of soil-structure interaction stresses, structural performance and caisson movements. All data was processed in real-time and displayed to the site construction team via wireless technology, giving the team control over the construction process and allowing them to respond rapidly to adverse responses. This unique set of field data provides new insight into soil-structure interaction stresses, lubrication and structural performance, as well as caisson movements in varying ground conditions. Bearing capacity beneath the tapered face at the base of the wall was explored through experimental testing and numerical modelling. A simplified closed-form design method for the prediction of the bearing capacity of a sloped footing in clay is established, with insight into the bearing failure mechanisms in both sand and clay also established. The design methods are validated against the monitored data from the field projects as well as small-scale laboratory testing
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
Soil-lubricant-structure interface mechanics for microtunnelling
Get PDFPipe-jacking is a trenchless underground construction technique commonly used to create conduits for conveying services such as electrical cables, gas, sewerage, or water pipes whilst keeping surface disruption to a minimum. The installation process consists of a tunnel boring machine (TBM) undertaking controlled excavation at the front of a string of pipes, whilst thrust is applied from a jacking frame located at the rear of the string. As the jacking frame advances the machine and pipe string, lubricant (typically comprising Bentonite clay) is simultaneously injected into an overcut between the pipes and soil formed by the TBM . This process is periodically paused whilst pipes are added and for planned or unplanned stoppages. Currently, there is no commonly accepted model for the behaviour of the soil-lubricant-structure (SLS) interface around these tunnel pipes during advances and stoppages, which results in excessive conservatism in the design stage.
This thesis explores the behaviour of the SLS interface using a combination of field and laboratory study. Two custom instrumented jacking pipes have been developed and deployed during two instrumented tunnel drives. Strain gauges, pore pressure sensors and contact stress sensors were used to identify the location and magnitude of stresses at the interface. These field studies are supplemented by analysis of 12 industry case histories, which provide insight into the SLS interface response in different ground conditions.
The field study program is complemented by a suite of laboratory scale testing of tunnelling lubricants and SLS interface behaviour. To facilitate this, a novel scale interface test apparatus has been developed. The plane strain apparatus has been designed to faithfully recreate the conditions at the SLS interface during tunnelling by incorporating such key features as: discrete lubricant injection, large uni-directional shear strains, variable normal stress, and the creation of an overcut at the interface. The apparatus has been used to complete a test program examining the influence of these factors on the SLS interface conditions during tunnelling in sand. To guide this experimentation, an elemental study has been completed to examine the salient properties of common tunnelling lubricants and explore their interaction with sand in isolation.
The findings from the laboratory experimentation and SLS interface behaviours observed during field monitoring are then applied in the development of a new conceptual model of the SLS interface during tunnelling, from which an empirical model of friction prediction is derived that predicts interface friction in different ground conditions during tunnelling. Using this new understanding of the mechanics of the SLS interface, methods to minimise interface friction are also proposed
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