1,721,034 research outputs found
Dr Timothy Graham
No full text<p>Dr Timothy Graham is Senior Lecturer in Digital Media at the Queensland University of Queensland (QUT). His research combines computational methods with social theory to study online networks and platforms, with a particular interest in online bots and trolls, disinformation, and online ratings and rankings devices. He develops open source software tools for social media data analysis, and has published in journals such as Information, Communication & Society, Information Polity, Big Data & Society, and Social Media + Society.</p>
<p>In 2021, Tim was announced as an ARC Discovery Early Career Researcher Award recipient and was awarded funding for his project Combating Coordinated Inauthentic Behaviour on Social Media.</p>
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
sj-docx-1-psx-10.1177_00323217241232934 – Supplemental material for What Explains Interest Group Prominence in Parliamentary Speech? Policy Agenda, Partisanship, or Conflict Expansion
No full textSupplemental material, sj-docx-1-psx-10.1177_00323217241232934 for What Explains Interest Group Prominence in Parliamentary Speech? Policy Agenda, Partisanship, or Conflict Expansion by Darren R. Halpin, Timothy Graham, Bert Fraussen, Max Grömping and Zhiheng Zhou in Political Studies</p
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
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
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