1,720,955 research outputs found
Modelling vapour transport in indoor environments for improved detection of explosives using dogs
No full textAir movement in indoor spaces can be complex due to large regions with no dominant flow direction and low mean velocities. Therefore, vapour released from an explosive indoors would be expected to result in a high degree of temporal and spatial variability in concentration. To improve canine detection capability, specifically training equipment, training methods and concepts of use, the science of vapour signatures in enclosed spaces needs to be improved. Large-eddy simulation has been used to study the vapour field in a benchmark test room. The work provides insight into vapour behaviour within indoor spaces and results have been interpreted in relation to vapour detection using dogs. For the test room, it was shown that vapour concentrations reduce rapidly within a short distance from the source. However, the concentration fluctuations, which occur at frequencies that a dog should be able to detect, can be significantly greater than the mean concentration. Due to the low volatility of many explosives, the vapour they produce will readily partition onto surfaces altering the concentrations in the room. A multi-layer vapour sorption model based on computational fluid dynamics (CFD) was validated. The CFD sorption model and a well-mixed sorption model were applied to the benchmark test room. It was shown, for a moderately high volatility explosive, that absorption had little effect on the well-mixed concentration but could have a significant effect on concentrations in the vicinity of the absorbing surface. When it is not possible/practical to build a CFD model, eddy diffusion models can be used to rapidly predict the spatially resolved concentration field indoors. However, there is uncertainty over the parameter that governs mixing, the eddy diffusion coefficient, De. Work has been carried out to develop a method to predict De for mechanically ventilated, isothermal rooms. It was found that De is a function of the air flow rate, room volume and number of air supply vents only. This will enable eddy diffusion modelling to be used with more confidence in the future to plan canine training experiments or to interpret detection results
A relationship for the diffusion coefficient in eddy diffusion based indoor dispersion modelling
No full textTurbulent or eddy diffusion models are used to predict spatially resolved exposures to toxic airborne materials in indoor environments. The single parameter that governs mixing in these models is the eddy diffusion coefficient. Some relationships that enable this coefficient to be predicted have been proposed in the literature, but wider applicability of these has not previously been tested. In this paper an automated computational fluid dynamics tool was used to calculate the eddy diffusion coefficient in a range of isothermal, mechanically ventilated rooms. Available models for the diffusion coefficient were then tested and the most applicable was found to be one based on a turbulent kinetic energy balance. This relationship was only appropriate when the characteristic length was set to a dimension of the air supply inlet, instead of the length usually applied, i.e. the room height. The validity of this relationship was further demonstrated using experimental test cases and by applying standard error metrics. The eddy diffusion approach can now be used with improved confidence in a wider range of scenarios than was possible before
Predicting vapour transport from semi-volatile organic compounds concealed within permeable packaging
No full textThe vapour concentration present in enclosed spaces containing concealed semi-volatile organic compounds (SVOCs), such as explosives, is difficult to measure experimentally. Therefore, mathematical models play a key role in understanding the transport of these materials. Vapour transport has previously been modelled in a range of environments, from small emission cells to whole rooms, using both analytical and numerical approaches. These models typically include either a well-mixed air volume or a simple sorption model. This work has been extended by including a multi-layer vapour sorption/permeation model within a computational fluid dynamics (CFD) framework. This allows for vapour source terms from items concealed within permeable packaging to be considered. The CFD based permeation model includes sorption/desorption, using a linear isotherm at inner and outer surfaces and a blended wall function to account for the effects of near-wall turbulence. The model has been validated for the explosive SVOC, ethylene glycol dinitrate (EGDN). The model has been used to show how vapour concentrations around a cardboard box containing a SVOC vary when some of the key input parameters are changed. Changing the vapour source from EGDN to the much lower vapour pressure trinitrotoluene (TNT), had a significant effect, as expected, and this was most pronounced early on due to the difference in permeation lag times for the two materials. Conversely, changing the type of cardboard had only a small effect on the concentrations. This type of modelling approach can now be used to study a wide range of SVOC transport problems which would not previously have been possible
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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