Applying ACO To Large Scale TSP Instances

Ant Colony Optimisation (ACO) is a well known metaheuristic that has proven successful at solving Travelling Salesman Problems (TSP). However, ACO suffers from two issues; the first is that the technique has significant memory requirements for storing pheromone levels on edges between cities and second, the iterative probabilistic nature of choosing which city to visit next at every step is computationally expensive. This restricts ACO from solving larger TSP instances. This paper will present a methodology for deploying ACO on larger TSP instances by removing the high memory requirements, exploiting parallel CPU hardware and introducing a significant efficiency saving measure. The approach results in greater accuracy and speed. This enables the proposed ACO approach to tackle TSP instances of up to 200K cities within reasonable timescales using a single CPU. Speedups of as much as 1200 fold are achieved by the technique

JIGSAW-GEO (1.0): locally orthogonal staggered unstructured grid generation for general circulation modelling on the sphere

An algorithm for the generation of non-uniform, locally-orthogonal staggered unstructured spheroidal grids is described. This technique is designed to generate very high-quality staggered Voronoi/Delaunay meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather prediction. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of high-quality unstructured spheroidal Delaunay triangulations is introduced. A locally-orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. It is shown that use of the Frontal-Delaunay refinement technique allows for the generation of very high-quality unstructured triangulations, satisfying a-priori bounds on element size and shape. Grid-quality is further improved through the application of hill-climbing type optimisation techniques. Overall, the algorithm is shown to produce grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. A selection of uniform and non-uniform spheroidal grids appropriate for high-resolution, multi-scale general circulation modelling are presented. These grids are shown to satisfy the geometric constraints associated with contemporary unstructured C-grid type finite-volume models, including the Model for Prediction Across Scales (MPAS-O). The use of user-defined mesh-spacing functions to generate smoothly graded, non-uniform grids for multi-resolution type studies is discussed in detail.Comment: Final revisions, as per: Engwirda, D.: JIGSAW-GEO (1.0): locally orthogonal staggered unstructured grid generation for general circulation modelling on the sphere, Geosci. Model Dev., 10, 2117-2140, https://doi.org/10.5194/gmd-10-2117-2017, 201

Klein Four Actions on Graphs and Sets

We consider how a standard theorem in algebraic geometry relating properties of a curve with a (ℤ/2ℤ)2-action to the properties of its quotients generalizes to results about sets and graphs that admit (ℤ/2ℤ)2-actions

Students as producers: Designing games to teach social science research methods and ethics

In this paper we explore our experiences of a staff-student collaborative project that sought to design games and learning resources that could be used to 'liven-up' research methods and ethics teaching in the social sciences. Final and second year undergraduate social science students were encouraged to reflect on their own experiences of both research methods teaching and the process of doing primary research, in order to design games resources that would be useful for future cohorts of students. The concept of games was applied twofold in the project: the development of the teaching resources was itself set up in a games format: we based our initial workshops on the style of the BBC's "Apprentice" programme in order to come up with ideas for the games resources and to introduce a competitive element into the design process. Two groups of students were given a brief to design a games resource that would 'liven up' social science research methods and ethics teaching. Groups then spent an intensive day working on the brief alongside an academic facilitator before pitching their final game concept in a presentation at the end of the day when a winner was announced. In subsequent workshops students worked collaboratively to further develop both games before piloting them on further groups of students prior to production. The second application of the games concept lay in the development of an actual learning resource to be used in future research methods and ethics teaching. The premise of developing an undergraduate dissertation, its (realistic) design and the potential ethical and methodological problems encountered when doing research underpinned the learning objectives for the games developed. The developed games resources have been introduced into the curriculum to supplement the existing (more traditional) learning and teaching strategies and to add a 'fun' element into research methods teaching. Developing a game-based learning approach themselves has thereby increased students' influence on the design of teaching and learning strategies and helped produce a useful learning resource for future cohorts. The paper highlights the benefits of staff-student collaboration in the design and production of game resources, and in particular, the potential for harnessing students' experiences of teaching and learning through feeding it into curriculum development. The paper also demonstrates the benefits of gamification - through a discussion of the positive student feedback and evaluation received by the developed games

The Aesthetic Uncanny: Staging Dorian Gray

This article discusses my theatrical adaptation of Oscar Wilde's The Picture of Dorian Gray (1891) for the Edinburgh Festival Fringe (2008). Freud's concept of the uncanny (1919) was treated as a purely aesthetic phenomenon and related to late nineteenth century social and literary preoccupations such as Christianity, the supernatural and glamorous, criminal homosexuality. These considerations led to a conceptual ground plan that allowed for experiments during rehearsal in a form of theatrical shorthand

X-ray scattering from surfaces: discrete and continuous components of roughness

Incoherent surface scattering yields a statistical description of the surface, due to the ensemble averaging over many independently sampled volumes. Depending on the state of the surface and direction of the scattering vector relative to the surface normal, the height distribution is discrete, continuous, or a combination of the two. We present a treatment for the influence of multimodal surface height distributions on Crystal Truncation Rod scattering. The effects of a multimodal height distribution are especially evident during in situ monitoring of layer-by-layer thin-film growth via Pulsed Laser Deposition. We model the total height distribution as a convolution of discrete and continuous components, resulting in a broadly applicable parameterization of surface roughness which can be applied to other scattering probes, such as electrons and neutrons. Convolution of such distributions could potentially be applied to interface or chemical scattering. Here we find that this analysis describes accurately our experimental studies of SrTiO3 annealing and homoepitaxial growth.Comment: 15 pages, 7 figure

The origin of fault scarps & fissures on moorland plateaux & in the vicinity of landslides, in the South Wales Coalfield, UK

Fault scarps and fissures occur on moorland plateaux and in the vicinity of deep-seated landslides in the South Wales Coalfield, UK. These scarps may reach about 4 m in height and 3-4 km in length. The ages of the fault scarps and fissures are difficult to determine. Their relatively fresh and unweathered appearance would seem to suggest they were generated during subsidence as a result of coal mining which has taken place for some 150 years. However, their large magnitude, which make them dramatic features of the landscape, sets them apart from the much lesser features generated during coal mining subsidence in other UK coalfields. Some fault scarps seem to pre-date Ordnance Survey and British Geological Survey maps from the late 1800s-early 1900s. As total extraction (longwall) methods associated with fault reactivation had yet to develop widely at that time it is probable that mining subsidence alone could not have generated such distinct topographic features. The paper reviews the evidence of analogous non-mining fault steps and fissuring, mine abandonment plans and recent fissure treatment works to cast new light on the origin and development of these features. A conceptual model to demonstrate the causative mechanisms and evolution of fissures is also presented. The paper concludes that some fault steps and fissures developed in response to stress relief caused by deglaciation and periglacial activity and have subsequently undergone a later phase of development as a consequence of differential mining subsidence