586 research outputs found
Masters Students' Experiences of Learning to Program: An Empirical Model
The investigation reported here examined how Masters students experience learning to program. The phenomenographic research approach adopted permitted the analysis of 1) how students go about learning to program, that is the âActâ of learning to program, and 2) what students understand by âprogrammingâ, that is the âObjectâ of learning to program. Analysis of data from twenty-three participants identified five different experiences of the Act of learning to program and five different experiences of the Object of learning to program. Together the findings comprise an empirical model of the learning to program experience amongst the participating students. We suggest how our findings are significant for programming teachers and offer tools to explore studentsâ views
Thermal & Non-Thermal Signatures From Galactic Nuclei
The bifurcation of Galactic Nuclei into active galactic nuclei (AGN) and low-luminosity accreting systems is ultimately related to the gas dynamics and therefore the observed emission. Relativistic jets in AGN produce bright and variable emission emanating across the electromagnetic spectrum. The ultra-fast variability, occurring on timescales of several minutes, observed from blazars, a subclass of AGN, pose tight constraints on theoretical models as they require compact objects characterized by fast motions and high Doppler boosting within the jet. Here, I report on the relativistic magnetic reconnection model as a source of blazar emission. By using the results of first principle numerical simulations of relativistic reconnection, I compute the emission produced by hundreds of radiating blobs containing magnetic fields and relativistic particles, the so-called plasmoids. The observed emission from low-luminosity AGNs, such as our own Galactic Center, is produced by an radiatively inefficient accretion flow. Theoretical models of radiatively inefficient accretion flows have been show to accurately account for the observed spectrum and luminosity from our Galactic Center. However, the physical properties of the accretion flow as well as the origin of the gas remain elusive. Here, I explore several models for indirectly probing the properties of the gas and provide a natural origin for the population of relativistic particles while providing several key observational signatures
Ascent trajectory optimisation for a single-stage-to-orbit vehicle with hybrid propulsion
This paper addresses the design of ascent trajectories for a hybrid-engine, high performance, unmanned, single-stage-to-orbit vehicle for payload deployment into low Earth orbit. A hybrid optimisation technique that couples a population-based, stochastic algorithm with a deterministic, gradient-based technique is used to maximize the nal vehicle mass in low Earth orbit after accounting for operational constraints on the dynamic pressure, Mach number and maximum axial and normal accelerations. The control search space is first explored by the population-based algorithm, which uses a single shooting method to evaluate the performance of candidate solutions. The resultant optimal control law and corresponding trajectory are then further refined by a direct collocation method based on finite elements in time. Two distinct operational phases, one using an air-breathing propulsion mode and the second using rocket propulsion, are considered. The presence of uncertainties in the atmospheric and vehicle aerodynamic models are considered in order to quantify their effect on the performance of the vehicle. Firstly, the deterministic optimal control law is re-integrated after introducing uncertainties into the models. The proximity of the final solutions to the target states are analysed statistically. A second analysis is then performed, aimed at determining the best performance of the vehicle when these uncertainties are included directly in the optimisation. The statistical analysis of the results obtained are summarized by an expectancy curve which represents the probable vehicle performance as a function of the uncertain system parameters. This analysis can be used during the preliminary phase of design to yield valuable insights into the robustness of the performance of the vehicle to uncertainties in the specification of its parameters
A forward solution for RF impedance tomography in wood
Both integral equation and differential equation methods enable modelling current and
hence impedance of wood, to provide the forward solution for impedance tomography that in turn
provides a measure of its internal moisture distribution. Previously, we have used a series impedance
model and successfully demonstrated measurement of internal moisture distribution. Here we describe
the adaptation of our integral equation method for this application. This has required an alternative
calculation to model the impressed field from the segmented electrodes used in the measurements to
date, and we demonstrate distortion of the anomalous field due to the presence of a wood dielectric,
and the field magnitude. Further work will be required to translate the resulting field distribution from
our model, to complex current and hence impedance readings, to allow completion of tomographic
reconstruction using this approach
Exploring inner worlds: where cognitive psychology may take us
Tim Smith researches visual cognition through a variety of techniques that capture what subjects do when they watch naturalistic visual scenes. Although much research into scene perception uses static visual scenes, he is interested in how we process dynamic visual scenes, including feature films. Using techniques such as tracking the eye movements of viewers watching film sequences in combination with behavioural probes during and after viewing, he investigates the cognitive processes occurring during film viewing. His research has contributed to a computational model of fixation durations in scene viewing (Nuthmann, Smith, Engbert, & Henderson, 2010), and he has proposed an Attentional Theory of Cinematic Continuity (Smith, 2012), which has attracted the interest of âcognitivistâ film scholars, leading to his involvement in a number of presentations and projects that use empirical testing and modelling to explain what happens when we watch film sequences.
I too am interested in the long history of attempts to understand the perceptual and cognitive processes involved in film viewing, which stretch from pioneering work by Munsterberg and Rank in the 1910s, through the renewed interest of Russian psychologists in the 1920s, following Pavlovâs classic studies in conditioning, and later of the Gestalt school, up to present-day work such as that of James Cutting (starting from the âpsychophysicsâ tradition) and Uri Hasson (âneurocinematicsâ). In this exchange, written as a dialogue over several months, I invite Tim Smith to summarise some of his own work and to speculate on what value it may have for non-scientists interested in understanding how and why we perceive film as we do â and how this may be changin
Opening Our Eyes : How film contributes to the culture of the UK
Opening our eyes looks at how films are consumed and the factors which affect peopleâs viewing choices. It also covers the relationships audiences report between film and other activities. It goes on to explore the sorts of effects which film has upon people, their sense of identity and relationship with the world. Finally it looks at the various effects which individual films have had on those surveyed and reaches a number of conclusions.Final Published versio
Developing a Carbon Baseline to Support Multi-Stakeholder, Multi-Level Climate Governance at County Level - Chapter 6
Orchestration requires political commitment and engagement on the basis of evidence, knowledge and progress-checking. Local actors face challenges in compiling carbon baselines that offer useful production and consumption emissions
Borehole seismic studies of a volcanic succession from the Lopra-1/1A borehole in the Faroe Islands, northern North Atlantic
Extruded basalt flows overlying sedimentary sequences present a challenge to hydrocarbon exploration using reflection seismic techniques. The Lopra-1/1A re-entry well on the Faroese island of SuĂ°uroy allowed us to study the seismic characteristics of a thick sequence of basalt flows from well logs and borehole seismic recordings. Data acquired during the deepening operation in 1996 are presented here. The re-entry well found that the seismic event at 2340 m, prognosed from the pre-drill Vertical Seismic Profile (VSP) as a decrease in impedance, was not base basalt and the deepened well remained within the lower series basalts. Nonetheless, compressional and shear sonic logs and a density log were recorded over the full open hole interval. These allowed a firm tie to be made with the reflected wavefield from a new VSP. The sonic logs show a compressional to shear wavespeed ratio of 1.84 which is almost constant with depth. Sonic compressional wavespeeds are 3% higher than seismic velocities, suggesting dispersion in the basalt flows. Azimuthal anisotropy was weakly indicated by the shear sonic log but its orientation is consistent with the directions of mapped master joints in the vicinity of the well. The VSP downgoing compressional wavelet shows good persistence, retaining a dominant period of 28 ms at 3510 m depth. Average vertical velocity is 5248 m/s, higher than previously reported. Attenuation can largely be modelled by geometrical spreading and scattering loss, consistent with other studies. Within the piled flows, the effective Q from scattering is about 35. Elastic layered medium modelling shows some hope that a mode-converted shear wave may be observed at moderate offsets. Like its predecessor, the 1996 VSP indicates a decrease in impedance below the final depth of the well. However, it is unlikely to be basement or sediment and is probably an event within the volcanic sequence
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