The Block Distributed Memory Model

We introduce a computation model for developing and analyzing parallel algorithms on distributed memory machines. The model allows the design of algorithms using a single address space and does not assume any particular interconnection topology. We capture performance by incorporating a cost measure for interprocessor communication induced by remote memory accesses. The cost measure includes parameters reflecting memory latency, communication bandwidth, and spatial locality. Our model allows the initial placement of the input data and pipelined prefetching. We use our model to develop parallel algorithms for various data rearrangement problems, load balancing, sorting, FFT, and matrix multiplication. We show that most of these algorithms achieve optimal or near optimal communication complexity while simultaneously guaranteeing an optimal speed-up in computational complexity. (Also cross-referenced as UMIACS-TR-94-5.

A high-fidelity approach to conceptual design

We created a new methodology to perform conceptual design analysis on aircraft, using off-the-shelf, high-fidelity software tools to explore the project design space, including important preliminary design factors and thereby producing a more robust result which is less subject to compromise at later design stages. We claim that this analysis can be performed in one hour with commonly available computation resources, and therefore is applicable to conceptual design. We used the case study of a supersonic transport jet to develop these methods. For this application, we used Solidworks to create a parameterized three-dimensional CAD solid to define the exterior geometry of the aircraft, and create populations of design candidates. We used STAR-CCM+ to perform an automated fluid flow analysis of these candidates, using three-dimensional, viscous, turbulent finite volume analysis and incorporating internal engine performance characteristics. We then used MATLAB to collect the data produced by these analyses, compute additional results of interest, and quantify the design space represented by a population of candidates. We heavily automated the steps of this process, to allow large studies or optimization frameworks to be implemented. Our results show that the method produces a data set which is much more rich than conventional conceptual design techniques. The method captures many interactions between aircraft systems which are normally not quantified until later phases of design: aerodynamic interactions between external lifting surfaces and between the external body and internal engine performance, and how structural constraints affect wing performance. We also produce detailed information about the aircraft static stability. Further, the method is able to produce these results with commonly available computer hardware within the one-hour timeframe we allow for a conceptual design analysis

What’s specific about the nature of mental health difficulties in students and how can this inform treatment?

This thesis explores how mental health service provision in university settings could be adapted to better meet the needs of students with mental health disorders. A systematic review and meta-analysis was conducted to assess the effectiveness of psychological interventions in student populations with, or at risk of, mental health disorders. The impact of adapting interventions for the particular needs of university students was also explored. Next, a cross-sectional survey of university students was conducted to explore differences in preferences for sources of support, and consider whether these may differ between international and UK resident students. Qualitative interviews and a confirmatory focus group further explored students’ experience of mental health support while at university, and provided preliminary ideas for the types of changes in services that students would hope to see. Finally, analyses were conducted using a large dataset of people who use National Health Service (NHS) psychological therapies: outcomes were compared between students and adults of the same age who were employed using multivariate logistic regression analyses. For the student population only, the association between changes on measures of social functioning and treatment outcomes was also explored using Growth Mixture Model analysis. Together, the research suggests that the adaptation of current service provision to consider a number of additional student-specific factors contributing to mental health difficulties could usefully be applied in both university mental health services and NHS psychological services. Improved integration of support across these two settings could also significantly contribute to improved university student well-being and mental health

Flow charts: visualization of vector fields on arbitrary surfaces

Journal ArticleWe introduce a novel flow visualization method called Flow Charts, which uses a texture atlas approach for the visualization of flows defined over curved surfaces. In this scheme, the surface and its associated flow are segmented into overlapping patches, which are then parameterized and packed in the texture domain. This scheme allows accurate particle advection across multiple charts in the texture domain, providing a flexible framework that supports various flow visualization techniques. The use of surface parameterization enables flow visualization techniques requiring the global view of the surface over long time spans, such as Unsteady Flow LIC (UFLIC), particle-based Unsteady Flow Advection Convolution (UFAC), or dye advection. It also prevents visual artifacts normally associated with view-dependent methods. Represented as textures, Flow Charts can be naturally integrated into hardware accelerated flow visualization techniques for interactive performance

Aspects of Unstructured Grids and Finite-Volume Solvers for the Euler and Navier-Stokes Equations

One of the major achievements in engineering science has been the development of computer algorithms for solving nonlinear differential equations such as the Navier-Stokes equations. In the past, limited computer resources have motivated the development of efficient numerical schemes in computational fluid dynamics (CFD) utilizing structured meshes. The use of structured meshes greatly simplifies the implementation of CFD algorithms on conventional computers. Unstructured grids on the other hand offer an alternative to modeling complex geometries. Unstructured meshes have irregular connectivity and usually contain combinations of triangles, quadrilaterals, tetrahedra, and hexahedra. The generation and use of unstructured grids poses new challenges in CFD. The purpose of this note is to present recent developments in the unstructured grid generation and flow solution technology