1,720,985 research outputs found
Key features impacting soil-conductor lateral behaviour as illustrated by centrifuge tests
No full textConductors are a type of pile used during subsea drilling operations to prevent hole collapse and to provide axial support to the well. The response of the conductor to lateral movement, as induced by environmental conditions, contributes to the assessment of fatigue damage of the entire wellhead system. Such assessment requires soil-structure interaction analysis, typically performed by modelling the soil-conductor lateral behaviour as non-linear springs called p-y curves. While bespoke approaches do exist, current industry practice often involves the use of p-y curves given in API RP2GEO, which were originally developed for foundation piles. Recent studies have shown that these curves do not adequately capture the soil-conductor response, especially at small lateral displacements. In addition, no account is given to load-history effects. This paper presents results from centrifuge testing of a rigid length of conductor installed in reconstituted samples of carbonate silt and subject to cycles of lateral displacement, with focus on identifying key features that influence soil-conductor behaviour. The results show that the degraded secant stiffness is impacted by load history – for example, after applying cycles of large amplitude displacement, the secant stiffness at smaller amplitude cycling will be significantly lower than if it had not previously experienced the more onerous loading. Furthermore, pore pressure dissipation between or during cyclic events can result in secant stiffness increasing. The results presented in this paper are part of an ongoing research project, aimed at improving fatigue design of subsea wells
Life cycle changes in p-y stiffness for a conductor pile installed in carbonate silt
No full textLateral soil stiffness has a strong influence on the overall strength and fatigue life of well conductors and piles. This paper reviews data from centrifuge testing of a short model pile embedded in carbonate silt, which was subjected to packets of cyclic lateral displacement. Key conclusions are that (i) cyclic lateral stiffness is significantly affected by prior loading history due to the generation and dissipation of pore pressure, (ii) the generation process leads to the well recognized softening of p-y curves, (iii) the dissipation process leads to a less recognised stiffening of the response, and (iv) carbonate silts show a different shape of cyclic lateral response compared to non-carbonate clays, meaning that existing ‘fully degraded’ steady state p-y models are not appropriate. Future ideas to capture these improvements in lateral response modelling are set out, with the aim of allowing more accurate and reliable design of conductors and piles
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
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
On the behaviour of pipe-clamping mattresses to arrest pipeline walking
No full textA novel solution to mitigate pipeline walking, namely the use of pipe-clamping mattresses (PCMs), was first developed for the Malampaya project (Frankenmolen et al. 2017). Comprising a hinged concrete structure designed to clamp onto a section of pipeline, and supporting (post-installed) ballast weight that is transferred directly to the pipeline, PCMs are considered a highly efficient alternative to more traditional solutions such as rock dump or concrete mattress. The original PCM geotechnical design was based primarily on analyses extrapolated from pipeline-seabed interaction, supported by a standard suite of classification and interface tests. Physical model testing was not performed. While observations (taken since installation) show that the PCMs have effectively mitigated pipeline walking in the seabed conditions at Malampaya, their performance in other soil types has not been investigated. To provide further evidence on the effectiveness of PCMs, and investigate their performance over time, a series of centrifuge tests were performed in a soil sample representative of deep-water Gulf of Mexico conditions. In each test, a model representing the PCM was installed on the pipeline section, which was then subjected to cyclic axial displacement. Settlement of the pipeline-PCM system, as well as changes in axial resistance, were directly measured and are reported in this paper.<br/
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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