1,720,963 research outputs found
Effects of sampler design on tube sampling disturbance - numerical and analytical investigation
No full textThe detailed features of the design of a sampling tube, such as area ratio, inside clearance, cutting edge taper angle, etc., have an important influence on the disturbance caused when a tube sampler is pushed into cohesive soil. Currently, most tube sampler designs have evolved on the basis of empirical design rules, and local good practices, developed for particular soil conditions. The strain path method provides a basis upon which the influence and importance of different features of tube sampler design can be evaluated, and the design of future samplers optimized. This paper examines the use of Baligh's strain path method for the assessment of tube sampling disturbance, and implements the method via a finite-element approach to assess the influence of area ratio, cutting-edge angles and inside clearance, on sample disturbance evaluated on the basis of the strains imposed on the centre-line of a soil sample.The detailed features of the design of a sampling tube, such as area ratio, inside clearance, cutting edge taper angle, etc., have an important influence on the disturbance caused when a tube sampler is pushed into cohesive soil. Currently, most tube sampler designs have evolved on the basis of empirical design rules, and local good practices, developed for particular soil conditions. The strain path method provides a basis upon which the influence and importance of different features of tube sampler design can be evaluated, and the design of future samplers optimized. This paper examines the use of Baligh's strain path method for the assessment of tube sampling disturbance, and implements the method via a finite-element approach to assess the influence of area ratio, cutting-edge angles and inside clearance, on sample disturbance evaluated on the basis of the strains imposed on the centre-line of a soil sample
Progresive destruction of the Bothkennar city: implications for sampling and reconsolidation procedures
No full textTriaxial stress and strain path tests have been carried out on high-quality Laval and Sherbrooke samples of lightly overconsolidated Bothkennar clay. The specimens were instrumented with local axial and radial strain and mid-plane pore pressure measurement, with precautions being taken to retain the existing pore water chemistry. The test programme imposed shear and volumetric strains of various magnitudes to assess the reduction in strength and stiffness caused by sampling and laboratory reconsolidation procedures. It is concluded that for this clay even very high quality tube samples will suffer a significant loss in mean effective stress, and some loss of structure during sampling, as a result of the imposed undrained shear strain cycle. Re-establishment of the initial effective stress level, by an appropriate stress path, will recover a proportion of the undisturbed undrained compressive strength that depends on the amount of destructuring: stiffness cannot be fully recovered. Reconsolidation procedures risk taking the specimen through the current yield surface, in which case large volumetric strains will occur and be accompanied by significant destructuring and, hence, irrecoverable loss of strength and stiffness. For natural clays, such as Bothkennar clay, the variability of structure within the deposit means that normalization solely with respect to effective stress cannot be used to allow for the disturbance caused by tube sampling, or to recover in situ soil properties
The effects of varying centerline tube sampling disturbance on the behavior of reconstituted clay
No full textIn order to simulate varying degrees of disturbance of soil at the centerline of a tube sampler, triaxial stress and strain path tests have been carried out on normally consolidated and overconsolidated reconstituted London clay specimens. The tests were carried out using an automated system capable of controlling both stresses and deformations imposed on specimens. The specimens were instrumented with local axial and radial strain and mid-plane pore pressure measuring devices.Test results indicate that the most pronounced effects due to imposed tube sampling strains in reconstituted normally consolidated London clay are significant reductions of mean effective stress and undrained small-strain stiffness, which are accompanied by reductions in the excess pore pressure generated during shearing. The higher the magnitudes of tube sampling strains, the greater the change in behavior. In over-consolidated reconstituted London clay, however, laboratory simulation of tube sampling strains together with deviatoric stress relief (i.e., “ideal” sampling) causes little change in effective stress, stiffness, and strength.<br/
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
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