1,720,955 research outputs found
Applicability of low-cost cameras for monitoring suspended sediment in rivers through close-range remote sensing
Get PDFSuspended sediment in rivers is a major problem globally. Monitoring of water turbidity and suspended sediment concentration (SSC) using satellites and in-situ sampling has been used widely to assess fine sediment pollution. However, due to low image resolution, application of satellite remote sensing is limited to only large water bodies, while in-situ sampling does not provide the continuous spatial data that are needed to address certain scientific questions or management problems. This research aimed to understand the potential of using low-cost cameras to estimate SSC in smaller rivers and streams and produce reach scale ‘maps’ of SSC. The study consists of development and testing of statistical models to predict SSC from pixel information contained in digital images, and validation of these models through field tests. An overarching goal was to assess the transferability of models between rivers and the effects of different camera sensors on SSC predictions. Laboratory experiments developed predictive models for two cameras (Vivo V9 smartphone and DJI Mavic Pro drone). Experiments involved manipulation of SSC in a water filled tank, with images taken with each camera and over a different coloured bed at each controlled sediment concentration. Digital Number (DN) values for each bed colour, camera and colour channel combination was extracted, with Generalised Additive Models fitted to Red, Blue and Green (R, G, B) colour bands.
In general, there were significant relations between SSC and the mean DN values, with G and B most frequently providing the best fits. Relations differed appreciably depending on bed characteristics, as a function of the relative colour of the bed and the material in suspension; some relations were direct (positive) and some indirect (negative). Thus, laboratory tests indicated that predictive relations need to be developed on a river-by-river basis due to differences in bed characteristics. There were some subtle differences between the two cameras, but in general both yielded images from which SSC could be predicted reliably in laboratory conditions. However, almost all relations broke down at very high SSCs depending on the bed colour, camera and colour channel combination; once the amount of fine material in suspension exceeded a certain threshold, SSC could not be predicted reliably from DN values. The field tests demonstrated that it is possible to produce accurate maps of SSC using an orthomosaic developed directly using DN values. These involved developing a calibration relationship for SSC v DN from images collected from drone flights at 30 m height above a reach of the Semenyih River, Malaysia. This relationship successfully predicted SSC, with the B colour band providing the best fit (R2 >0.86 for the observed v predicted). The SSC map was able to shed light on the influence of a tributary on main stem SSCs and patterns of mixing of the fine sediment delivered by the tributary. Such fine scale spatial patterns (1cm2/pixel) are evident neither from satellite data nor in-situ monitoring. The methods presented here are applicable to a variety of questions and contexts, from understanding downstream changes in SSC in glacial rivers to assessing effects of forest loss on SSC in tropical systems
Applicability of low-cost cameras for monitoring suspended sediment in rivers through close-range remote sensing
Get PDFSuspended sediment in rivers is a major problem globally. Monitoring of water turbidity and suspended sediment concentration (SSC) using satellites and in-situ sampling has been used widely to assess fine sediment pollution. However, due to low image resolution, application of satellite remote sensing is limited to only large water bodies, while in-situ sampling does not provide the continuous spatial data that are needed to address certain scientific questions or management problems. This research aimed to understand the potential of using low-cost cameras to estimate SSC in smaller rivers and streams and produce reach scale ‘maps’ of SSC. The study consists of development and testing of statistical models to predict SSC from pixel information contained in digital images, and validation of these models through field tests. An overarching goal was to assess the transferability of models between rivers and the effects of different camera sensors on SSC predictions. Laboratory experiments developed predictive models for two cameras (Vivo V9 smartphone and DJI Mavic Pro drone). Experiments involved manipulation of SSC in a water filled tank, with images taken with each camera and over a different coloured bed at each controlled sediment concentration. Digital Number (DN) values for each bed colour, camera and colour channel combination was extracted, with Generalised Additive Models fitted to Red, Blue and Green (R, G, B) colour bands.
In general, there were significant relations between SSC and the mean DN values, with G and B most frequently providing the best fits. Relations differed appreciably depending on bed characteristics, as a function of the relative colour of the bed and the material in suspension; some relations were direct (positive) and some indirect (negative). Thus, laboratory tests indicated that predictive relations need to be developed on a river-by-river basis due to differences in bed characteristics. There were some subtle differences between the two cameras, but in general both yielded images from which SSC could be predicted reliably in laboratory conditions. However, almost all relations broke down at very high SSCs depending on the bed colour, camera and colour channel combination; once the amount of fine material in suspension exceeded a certain threshold, SSC could not be predicted reliably from DN values. The field tests demonstrated that it is possible to produce accurate maps of SSC using an orthomosaic developed directly using DN values. These involved developing a calibration relationship for SSC v DN from images collected from drone flights at 30 m height above a reach of the Semenyih River, Malaysia. This relationship successfully predicted SSC, with the B colour band providing the best fit (R2 >0.86 for the observed v predicted). The SSC map was able to shed light on the influence of a tributary on main stem SSCs and patterns of mixing of the fine sediment delivered by the tributary. Such fine scale spatial patterns (1cm2/pixel) are evident neither from satellite data nor in-situ monitoring. The methods presented here are applicable to a variety of questions and contexts, from understanding downstream changes in SSC in glacial rivers to assessing effects of forest loss on SSC in tropical systems
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
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
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
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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