1,721,220 research outputs found
Applicability of Reinforced Ribs om Sprayed Concrete in Sections of Poor Quality and Swelling Rock Mass
No full textWhen excavating tunnels, reinforcement and support is required depending on the quality of the rock mass. In good quality rock mass, simple reinforcement such as sprayed concrete and rock bolts is usually adequate as support. In areas with very weak rock mass and unfavourable stresses, more comprehensive support methods need to be applied to avoid large deformations in the rock mass. In Norwegian hard rock tunnelling, the geology is characterised mostly by hard rock intersected by weakness zones that often contain swelling minerals. The common rock support in such weakness zones is rebar reinforced ribs of sprayed concrete (RRS) combined with rock bolts and reinforced sprayed concrete between the ribs. This practice is mostly based on experience and the scientific basis to support the practise and its best application is limited.
The main objective of this thesis was to explore deformations in sections of weak rock in hard rock tunnels, with the purpose of developing a better understanding of the use of RRS in tunnelling. A special focus have been placed on how swelling minerals may affect the system. This has been achieved by performing full-scale in-situ monitoring, laboratory testing, numerical modelling and collection and systemization of existing data.
Field monitoring of RRS in Norwegian road tunnels has shown only small deformations in the rock mass and no substantial strain in the rebar of the RRS. When evaluating the field measurements based on numerical modelling, it has been found that the RRS have not been subjected to any load, and hence have had no load-bearing function.
By comparing data from a parameter study based on numerical modelling with data extracted from The Norwegian Public Roads Administration (NPRA) tunnel data base, it was discovered that that RRS has been applied in tunnels where the conditions probably would not require load-bearing support. In the literature, a convergence of 1% is suggested as the limit for the rock to require load-bearing support. This implies that there is an interval where the need for rock support exceeds bolts and sprayed concrete, but where load-bearing support is too extensive.
To explore how swelling minerals may affect the support construction, reconstituted cores of swelling gouge have been tested triaxially. The registered deformation was found to be dominated by creep in the material and no swelling was observed during the saturation of the initially dry specimens. This implies that swelling was insignificant compared to other deformation processes, but as the deformation rate increased during saturation, it may have accelerated the creep process.
Oedometer testing on the swelling gouge with different initial water contents was conducted on the fraction < 20 µm. The behaviour of the material suggests that one could find the water content for where the intracrystalline swelling ends and the osmotic swelling begins. This is important since the rock stress in many cases exceeds the osmotic swelling stress, while it will not exceed the intracrystalline swelling stress. Related to in-situ gouge, one may thus be able to predict whether the material will swell if exposed to water or if the rock stress may force water out, making it shrink. The oedometer testing also showed that the swelling pressure was dependent on the density of the material.
The results described above imply that the current design of the RRS is in most cases over-dimensioned and that a leaner design, which is not load-bearing, is probably sufficient for most cases. Earlier, reinforced but unarched RRS was used, which require less material (steel, concrete) compared to the load-bearing arched RRS used today. By performing surveillance of the deformations based on total stations, the use of unarched RRS could be safely implemented, first at a project level and later, when having more data, on a systematic level. As part of implementing such a leaner RRS, it is important that effort is also devoted to characterizing the weakness zones and identifying the most important parameters of their deformability
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
Toward the Perceptual Quality Evaluation of Compressed Light Field Images
Full text linkEvaluation of perceived quality of light field images,as well as testing new processing tools, or even assessing the effectiveness of objective quality metrics, relies on the availabilityof test dataset and corresponding quality ratings. This article presents SMART light field image quality dataset. The dataset consists of source images (raw data without optical corrections), compressed images, and annotated subjective quality scores. Furthermore, analysis of perceptual effects of compression on SMART dataset is presented. Next, the impact of image content on the perceived quality is studied with the help of image quality attributes. Finally, the performances of 2D image quality metrics when applied to light field images are analyzed.</p
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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