1,720,955 research outputs found
Controlling clay pore pressures for cut-and-cover tunneling
No full textTo facilitate construction of the Channel Tunnel Rail Link through Ashford in cut-and-cover tunnels and retained cut, it was necessary to control pore water pressures in the relatively low-permeability, laminated Weald Clay. This was achieved by means of an ejector well dewatering system. This paper describes and discusses the investigations carried out to characterise the in situ permeability of the Weald Clay, the design and performance of the ejector well system installed, and the associated soil surface settlements. The correlation between the changes in pore pressure and settlements at the site is compared with that given by Preene et al. This comparison is used to evaluate the method, and to provide some insights into the selection of appropriate parameter values of soil permeability and stiffnes
Mechanical and hydrological impacts of tree removal on a clay fill railway embankment
Full text linkSeasonal shrinkage and swelling of clay fill railway embankments can disturb the track geometry, resulting in train speed restrictions that disrupt normal operations. Such movements are exacerbated by vegetation, but reliable analytical descriptions of the effects of trees on embankment behaviour are not yet established. This paper presents and analyses the results of a field experiment, carried out on a heavily vegetated clay railway embankment to investigate quantitatively the influence of trees. After the first year of monitoring, the mature trees initially present on the upper two-thirds of the embankment slopes were removed. The field monitoring data are used to assess and understand the mechanisms of soil water content and pore water pressure changes before and after tree removal, and their influence on the vertical and lateral displacements of the embankment slopes. Removal of the vegetation stopped seasonal volume changes in the clay fill at the crest of the earthwork, but also resulted in the loss of the deep-seated suctions generally beneficial to embankment stability. The wider implications for the management of vegetation on embankment slopes are discusse
Managing the extent of tree removal from railway earthwork slopes
Full text linkTrees cover the slopes of many earthworks (embankments and cuttings) supporting the UK’s rail network. Trees provide ecological and slope stability benefits to earthwork slopes but they can also cause seasonal shrinking and swelling of the soil. Seasonal shrink-swell movement in earthworks can affect the level and alignment of the track, causing delays for rail passengers and a substantial cost for infrastructure owners. Guidance is required to identify and manage the removal of problematic trees, while avoiding full tree clearance on earthworks slopes.A study was undertaken on behalf of London Underground Ltd (LUL) to assess whether the National House Building Council (NHBC) guidance, considering tree species and the ratio of the distance of the tree from the track, D, to the mature tree height H, might be applicable to trees located on railway earthwork slopes. Excessive seasonal track movement was shown to correlate with the presence of high water demand (HWD) tree species located within a certain D/H ratio of the track, but not other tree species.Soil heave was measured on the slope of an instrumented railway embankment following removal of trees from the embankment slope. The rate and magnitude of soil heave was estimated from five years of pore water pressure data, using a one dimensional settlement/heave calculation based on a linear swelling index. It was found that while the removal of HWD trees reduced seasonal shrink-swell movement, soil heave and upward track movement continued for at least 4 years after tree felling
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
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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