1,722,466 research outputs found
Replication Data for #DictatorErdogan: How Social Media Bans Trigger Backlash
No full textThis repository includes the data and code for "#DictatorErdogan: How Social Media Bans Trigger Backlash" forthcoming in Political Communication. See READ ME file for more information
Mathematical modelling of fractures, silica deposition and thermoelasticity in hydrothermal upflow zones
No full textThe permeability of the fractured geothermal systems in the Taupo Volcanic Zone (TVZ) of New Zealand is continually evolving due to mineral deposition and stress transients. It is generally accepted that a cyclic process, involving mineral deposition and crack dilation, is responsible for the formation of mineral veins of up to a metre in thickness. Studies of vein formation have focussed on the mechanics of dilation. Seismic activity and hydrofracturing are commonly accepted as mechanisms that generate the stress transients required to cause refracturing. By contrast, thermal stress transients generated during the mineral deposition process have received very little attention. In this thesis we construct and analyse mathematical models to investigate aspects of possible thermo-fracturing quartz vein formation processes.A first model is presented for thermally driven flow in a homogeneous porous medium. Approximate steady state analytical solutions are obtained for the flow resulting from point and line heat sources using similarity methods and asymptotic analysis for different permeability structures representing the extreme cases of very small and very large crack spacing. These solutions are used as the basis to perform a detailed study, in a simple geometry, of the transient process of a single fracture, within the porous medium, healing by silica deposition. Solutions are obtained using analytical and numerical techniques. It is shown that the resulting temperature variations in the plume are always small and depend on the thickness and profile of the initial fracture aperture.Using the ideas and insight obtained, a simplified model is constructed for a radially fractured upflow zone which incorporates the thermally driven flow, silica deposition and thermal stress effects.It is shown that a temperature change of as little as 10°C in the upflow zone is sufficient to generate lithostatic size stresses in the upper kilometre of the hydrothermal system. A numerical solution is obtained using asymptotic analysis for the case of a large number of small individual fractures. The solution indicates that thermal stresses can act to enhance fracture permeability in upflow zones.The results of the modelling indicate that the permeability structure in a geothermal system has considerable affect on the distribution of temperature variations in the plume. For a large crack spacing the temperature variations in the upflow zones of geothermal systems are confined to a region with sharp outer boundary. The results also show that the effect of silica deposition in fractured geothermal systems depends highly on the permeability structure. Silica deposition resulting in large fractures within a smaller scale fracture system produces only small changes in plume temperature,whilst silica deposition in large fractures in a less permeable rock mass can cause 'choking' of the flow and hence large changes in flow paths and temperatures in the plume
Fog formation in rapidly cooled gas - vapour mixtures
No full textFollowing a review of the literature concerning droplet formation and the supersaturation of gas-vapour mixtures, an experimental test rig was designed and manufactured with which to study fog formation during rapid cooling and partial condensation. On completion a large number of experiments were performed using water vapour-air mixtures with a wide range of temperatures, partial vapour pressures and velocities. During each test, measurements of the droplet sizes and number concentrations were performed and recorded using a Laser Doppler Anemometer. The measurements were carried out at a number of points between the condenser walls, as the fog exited the experimental condenser.To complement the experimental program a theoretical study of fog formation within a partial condenser was completed. The resulting predictions of temperature drop along the condenser and bulk fog formation rates were used in conjunction with the experimental results and visual observations to present a clear description of the phenomena of fog formation within a partial condenser.Fog formation was shown to occur inside a condenser for a wide range of temperatures and relative humidities of the initial gas vapour mixture, though in many cases the vast majority of droplets were confined to a narrow region close to the condenser walls. In all the experiments conducted that led to a reasonable level of fog formation the total mass of liquid existing in the form of submicron droplets was insignificant (<< 1% of the total mass of fog). In general the extent of fog formation and the size of the droplets formed increased with increasing vapour pressure, coolant flow rate and condenser length, and with decreasing temperature and velocity. The presence of submicron droplets in the fog exiting the condenser was avoided completely by supersaturating the mixture by 15% or more prior to it entering the condenser.</p
Alien Registration- Miller, Andrew J. (Wells, York County)
Get PDFhttps://digitalmaine.com/alien_docs/6315/thumbnail.jp
Using machine learning and the Hough transform to search for gravitational waves due to r-mode emission by isolated neutron stars
Get PDFWe present two new methods to search for gravitational waves (GWs) from isolated neutron stars lasting O(hours-days), and the results of three searches of real LIGO/Virgo data. One method is a generalization of a method to detect continuous waves (CWs) that looks for signals that follow a specific model; the other uses machine learning to detect signals that deviate from this model. In two of our searches, we tried to find a remnant of the first-ever binary neutron star (BNS) merger, GW170817; in the third search, we looked everywhere in the sky for any kind of long duration transient signal in LIGO's third observing run. For the first method developed, the Generalized Frequency Hough, we present empirical and theoretical estimates of its sensitivity, an extensive follow-up procedure of GW candidates, the parameter space to which it is sensitive, and computational constraints when using it. For the second method, an application of convolutional neural networks, we demonstrate that its sensitivity is comparable to that of first method but is much faster to apply and can find signals that the first method cannot. Estimates of rates and sensitivities in future detectors, as well as implications of a GW detection from a neutron star, are also discussed. Additionally we explore the prospects of using a two-dimensional Fast Fourier Transform to improve the quality of time/frequency images to be used by either method
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
Septonema lohmanii G. Delgado & O. Koukol, sp. nov., a new species in Mytilinidiales (Dothideomycetes) and the phylogenetic position of S. fasciculare (Corda) S. Hughes
No full textDelgado, Gregorio, Koukol, Ondřej, Miller, Andrew N., Piepenbring, Meike (2019): Septonema lohmanii G. Delgado & O. Koukol, sp. nov., a new species in Mytilinidiales (Dothideomycetes) and the phylogenetic position of S. fasciculare (Corda) S. Hughes. Cryptogamie, Mycologie 20 (2): 3-21, DOI: 10.5252/cryptogamie-mycologie2019v40a
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