1,721,046 research outputs found
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
Measurement of methane emissions from confined sources using the inverse dispersion method
Full text linkGreenhouse gas (GHG) emissions are reported in annual national inventories. Globally, the main anthropogenic sources of methane (CH4) are fossil fuel burning, agriculture, landfills, and waste management. The main source of CH4 from agriculture is enteric fermentation in the digestive tract of ruminants and a minor source are emissions from manure management. In 2019, the Swiss Federal council decided that Switzerland must reduce its GHG emission to net-zero until 2050. To reach this goal, the agricultural sector is obliged to contribute to the emission reduction. However, emissions from the agriculture and waste sector imply large uncertainties as, among other reasons, the availability of data based on real-world studies is limited. Several investigations showed that measurements from laboratory- or pilot-scale experiments do often not comply with real-world conditions. For studies under real-world conditions, different measurement approaches are available. One of the most promising methods is the inverse dispersion method (IDM) that was applied in this thesis to measure CH4 emissions from livestock production and the waste management sector in order to evaluate the method for complex source configurations and to specify emission factors of these sources.
For the IDM, a backward Lagrangian stochastic (bLS) model in combination with concentration measurements up- and downwind of the source using open-path tunable diode laser spectrometers (GasFinders) were employed. GasFinders are simple to use, flexible in their application, and relatively cost-effective measuring devices. However, several challenges were faced and overcome throughout the thesis. The precision of the employed GasFinder model was about 10 times lower than the manufacturer stated, which necessitated adaptation in the measurement setup. Additionally, an intercomparison before or after each measurement campaign was necessary to correct the offset and span between the employed GasFinders.
In the first two studies presented in this thesis, experiments were conducted to evaluate the IDM. In a third study, experiments were conducted to assess the handling of complex source configurations with the IDM. The emissions determined in the third study were used as a basis for emission factors of Swiss biogas plants (BGPs) and wastewater treatment plants (WWTPs).
In the first study, a known and predefined amount of CH4 was released by an artificial source in a barn that mimics a dairy housing. For concentration measurements, GasFinders with a path length of 110 m were placed in downwind direction of the barn at a distance of 50 m, 100 m, 150 m, and 200 m. At the first three distances, an ultrasonic anemometer was placed in the middle of the GasFinder path length for executing turbulence measurements. Upwind of the barn, an additional GasFinder and an ultrasonic anemometer were installed. The main objective was to test the ideal measurement fetch for the IDM. The results of this experiment are included in the method section, where the conditions and the setup of an IDM measurement campaign are outlined. A release rate of 140 norm litres min-1 was chosen to achieve sufficient concentration enhancement at the GasFinder locations. The mean recovery rates of the experiment were between 0.55 – 0.76.
In the second study, CH4 emission measurements from a naturally ventilated dairy housing were conducted in two measurement campaigns. During part of the campaign duration, emissions were also measured inside the housing with the inhouse tracer ratio method (iTRM). This allowed comparing the IDM with the iTRM, which was considered as a reference method for naturally ventilated livestock housings. For simultaneous emission intervals, the average IDM emissions were lower by 1 % and 8 % compared to the iTRM measurements, which was within the uncertainty of either of the two methods. Additionally, an uncertainty analysis for the IDM showed that measurement campaigns of at least 10 consecutive days are necessary to acquire reliable emission data.
The third study addressed the handling of complex source configurations with the IDM. Emissions from four agricultural BGPs and two WWTPs in Switzerland were measured. The average BGP CH4 emission varied between 0.39 kg h-1 and 2.22 kg h-1, which was less than 5 % of the plant’s CH4 production. The average CH4 emissions for the two WWTPs were 166 g population-equivalent-1 y-1 and 381 g population-equivalent-1 y-1, respectively. The BGPs often had livestock housings nearby that needed to be discriminated from the plant emission. It was demonstrated how the plant emission can be corrected for the nearby CH4 sources, which confounded the GasFinder measurements. Further, it was demonstrated how to combine multiple GasFinder measurements to a single line concentration for the bLS modelling. WWTPs are complex sources as they consist of multiple sub-sources with different emission strengths spread over a large area. Three different calculation approaches with different degree of details are presented for the combination of the individual sources in the bLS modelling: (i) A polygon over the entire WWTP area as a single source. (ii) All potential sources within the WWTP have a uniform emission density. (iii) Based on literature data, relative weighting of the individual sources is carried out. The maximum difference in emission between the most complex approach (iii) and the simplest approach (i) was 42 %. It could be shown that for large source areas (> 10,000 m2), approach (iii) is the preferred option, whereas for the measured BGPs the simple polygon approach (i) was sufficient.
The recovery rate of the IDM from the release experiment (study 1) was below 1 and somewhat lower than previous studies with a similar experimental setting have shown. I was not able to conclusively identify the reasons for this result, which contrasts with the outcome of study 2 at the naturally ventilated dairy housing with a high consistency between the IDM and the iTRM used as a reference. Therefore, I suggest repeating the release experiment with an adapted setting and additionally roughly mapping the emission plume by a drone or a high-precision handheld sensor to monitor the dispersion of the plume. The field measurements at the WWTPs and the BGPs based on the chosen approach of source combination yielded data that are in the expected range according to current state of knowledge.
The presented PhD thesis supports the aptitude of the IDM to measure emissions from complex sources like farms, BGPs, or WWTPs. Such measurements contribute to increasing the accuracy of national GHG inventories. Nevertheless, I suggest further investigations to better assess the accuracy of the IDM under complex conditions
Bridging the gap between animal and ecosystem emissions: Performance of CH4 and CO2 eddy covariance measurements over a grazed pasture
No full textVariations 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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