The revision or reorganisation of hierarchical data sets can result in many possible hierarchical classifications composed of the same or overlapping data sets existing in parallel with each other. These data sets are difficult for people to handle and conceptualise, as they try to reconcile the different perspectives and structures that such data represents. One area where this situation occurs is the study of botanical taxonomy, essentially the classification and naming of plants. Revisions, new discoveries and new dimensions for classifying plants lead to a proliferation of classifications over the same set of plant data. Taxonomists would like a method of exploring these multiple overlapping hierarchies for interesting information, correlations, or anomalies. The application and extension of Information Visualisation (IV) techniques, the graphical display of abstract information, is put forward as a solution to this problem. Displaying the multiple classification hierarchies in a visually appealing manner along with powerful interaction mechanisms for examination and exploration of the data allows taxonomists to unearth previously hidden information. This visualisation gives detail that previous visualisations and statistical overviews cannot offer. This thesis work has extended previous IV work in several respects to achieve this goal. Compact, yet full and unambiguous, hierarchy visualisations have been developed. Linking and brushing techniques have been extended to work on a higher class of structure, namely overlapping trees and hierarchies. Focus and context techniques have been pushed to achieve new effects across the visually distinct representations of these multiple hierarchies. Other data types, such as multidimensional data and large cluster hierarchies have also been displayed using the final version of the visualisation.

The movement of pedestrians in the urban environment is vital for sustaining the social and economic relationships essential to the quality of life. To enable and encourage walking, suitable facilities must be available and planning and implementing such facilities requires an understanding of the characteristics of pedestrian movements. This thesis examined the factors which influence walking speeds, related them to current pedestrian modelling techniques and developed a series of new models to improve their estimation. A comprehensive review of current practices and procedures for modelling pedestrian walking speeds was carried out, identifying the factors currently used in existing methodology and highlighted its deficiencies. A significant finding from this study was that the industry-standard Highway Capacity Manual (HCM) methodology as it currently stands is not fully applicable to the types of walking environments that were the subject of this research (on-street walkways in UK shopping and Central Business District areas). It was shown there is a need to provide more holistic relationships which take into account the interactions between the characteristics of pedestrians and their walking environments (both built and natural). A number of additional factors which have a significant affect on walking speeds were identified and a series of new statistical relationships were developed which were also tested and validated against independent data. The predictive performance of the new models was also compared against the leading industry-standard methodology and shown to provide significantly better estimates. Future areas of research were also identified and described. The research thus provided a greater understanding of the dynamics affecting walking speeds, thereby helping to assist transport planners and engineers with the study and design of suitable pedestrian facilities.

This thesis explores the acquisition of spatial knowledge as a means to support wayfinding in virtual environments. Specifically, the thesis presents an investigation into the potential benefits one might gain through the application of a variety of tools, each of which has been designed to support one of the three stages of cognitive map development - landmark-based representation, route-based representation, and survey-based representation (Siegel & White, 1975). Each tool has been evaluated with respect to improvements in wayfinding, and also in their support for environmental learning. Measures were taken of each tool used in isolation, and also when used together as a complete toolset. The between-subjects evaluation process involved 101 participants, randomly assigned to one of five conditions. Each participant was asked to navigate a virtual environment to locate three specific items. To evaluate wayfinding, participants were asked to perform the same task on six occasions within the same session. After discovering all items, a measure indicating route efficiency was recorded. On completing all six trials participants were asked to produce a map of the virtual environment. It was hypothesised that the presence of tools would improve the acquisition of spatial knowledge, and thus route efficiency and map production. Comparing the 'no-tool' and the 'all tool' conditions, a 2x6 repeated measures ANOVA found that when providing the tools concurrently there was a statistically significant improvement in the efficiency of route taken (F(1,38)=4.63, p<0.05). However, when evaluating the tools in isolation, no significant improvement in route efficiency was found. Also, no significant difference between conditions was identified when comparing the quality of maps produced by participants across conditions. The thesis concludes by arguing that the application of the complete toolset benefits wayfinding, although it is noted that the evidence does not support the hypothesis that this is caused by improved spatial learning.

This thesis investigates whether information technology [IT] ameliorates or exacerbates the information asymmetry between management and external users of financial information, and ascertains whether and under what circumstances IT has an impact on external reporting. These two issues are investigated under the proposed contingency perspective. The main aims of this thesis are to provide a policy-making basis for regulators of corporate financial reporting [CFR], and to formulate a theoretical framework which can be used for research in this area. A survey design has been adopted. Mail questionnaires have been used to collect data from a sample of UK public companies, supplemented by personal interviews. Statistical procedures have been applied to analyse the data. The results demonstrate that, while contributing to some improvements in CFR, the use of IT has played a role in the aggravation of the information asymmetry between management and external users, and in this sense it has counteracted the social benefits of financial reporting. A major implication of this is that the use of IT in accounting requires monitoring and control at a societal level. However, UK regulators have done little in this respect and thus this thesis proposes several courses of action for them. Moreover, although IT plays a role in improving external reporting, the impact of IT varies depending on factors such as company size and leverage. These results are useful for regulators since they enhance the understanding of and, the ability to predict, the impact of IT. This thesis is the first study which has empirically evaluated the influence of IT on external reporting and has put the impact of IT into the context of information asymmetry. Moreover, although it should be subject to further empirical test, the proposed contingency framework proves general, flexible, analytical and operational, and appears to be widely applicable.

The boundary element method was applied to polymer analysis. The comparison of two existing BEM approaches was carried out solving a benchmark viscoelastic problem numerically and comparing with the analytical solutions. The fundamental solutions due to both Heaviside and Dirac impulse were obtained for a generalised Maxwell SLS material model. A new time-domain BEM formulation for viscoelasticity was derived, and the computer program was implemented and validated. A mixed method for quasi-static viscoelasticity was proposed. Several viscoelastic problems were solved for the purpose of validating this formulation. Numerical results were compared with analytical solutions, and good agreement was achieved. The BEM was applied to viscoelastic fracture problems. The effectiveness of the adopted BEM modelling was tested on an elastic fracture problem. The time-dependent strain energy release rate and J-integral in viscoelasticity were evaluated under different loading conditions. The crack propagation velocity under constant strain loading was also obtained. Adopting BE methodology, an integral equation for nonlinear viscoelastic problems was derived. The method to remove the high singularity in the irreducible domain integral was proposed. A computer program for this nonlinear viscoelastic formulation was developed. A central-crack problem was solved and the expected effect of non-linearity on stress field was obtained.

Systems have been designed and synthesized using CMOS technology for many years, with improvements in the fabrication process allowing designs to be scaled onto smaller areas with relative ease. The introduction of nano scale CMOS technologies has ended this time of simple scaling, as variations within the silicon now dramatically affect circuit performance and manufacturing yield. These random physical variations cannot be removed from the manufacturing process, requiring that their affects are modelled, predicted and accommodated within the design process. This thesis presents an investigation into the challenges of including these affects within the design process, with a review of the recent research conducted in incorporating variability within timing analysis tools. The conclusion from the literature review is that an accurate, efficient and transparent method of predicting the impact of statistical process variations on the performance of a circuit has not yet been created and adopted by the IC design industry. The investigation begins with the modelling of transistor based statistical process variations at the standard cell level, where it is determined that simple statistical models do not accurately reflect the extremes in performance, and can provide overly pessimistic predictions. The techniques of Monte Carlo Cell Characterisation (MCCC) and Monte Carlo Static Timing Analysis (MCSTA) are introduced as more suitable approaches, which accurately reflect the performance of circuits as modelled by Monte Carlo SPICE simulations, with far less pessimism than the traditional method of Corner Analysis or even modern Statistical Static Timing Analysis. The final section of this thesis focuses on practical implementations of MCSTA, where the sample sizes required to accurately predict circuit behaviour (to within 1% of SPICE)can be reduced to as few as ten, using simple statistical sampling techniques.

Genetic Programming is a form of Evolutionary Computation in which computer programs are evolved by methods based on simulating the natural evolution of biological species. A new generation of a species acquires the characteristics of previous generations through the inheritance of genes by sexual reproduction and through random changes in alleles by random mutation. The new generation may enhance its ability to survive by the acquisition of cultural knowledge through learning processes. This thesis combines the transfer of knowledge by genetic means with the transfer of knowledge by cultural means. In particular, it introduces a new evolutionary operator, memory operator. In conventional genetic programming systems, a new generation is formed from a mating pool whose members are selected from the fittest members of previous generation. The new generation is produced by the exchange of genes between members of the mating pool and the random replacement of genes in the offspring. The new generation may or may not be able to survive better than its predecessor in a given environment. The memory operator augments the evolutionary process by inserting into new chromosomes genetic material known to often result in fitness improvements. This material is acquired through a learning process in which the system is required to evolve generations that survive in a less demanding environment. The cultural knowledge acquired in this learning process is applied as an intelligent form of mutation to aid survival in a more demanding environment.

Electrical stimulation applied to the common peroneal nerve during the swing phase of gait is an established clinical technique for the correction of dropped foot following upper motor neuron injury. The catch-like effect of skeletal muscle refers to force augmentation resulting from the inclusion of an initial high frequency burst of two or more stimuli prior to conventional low frequency electrical stimulation. There is interest in clinical utilisation of catch-like stimulation during functional applications; however the mechanism of the effect is not fully understood. The purpose of this research was to determine if the catch-like effect is a property of the muscle alone or related to spinal reflex mediated activation. In order to investigate this, direct and reflex motor effects of conventional and catch-like stimulation during dropped foot correction and other controlled conditions were assessed in unimpaired (n=12) and stroke (n=13) populations through use of electromyography. A system was developed to enable analysis of electromyography activity shortly after the application of configurable stimulation patterns. Innovative design minimised effects of stimulation artefact such that electromyography of the tibialis anterior and soleus muscles during dropped foot correction could be assessed. This system was utilised and further refined during exploratory investigations prior to structured use with study participants. Both direct and reflex motor effects of conventional stimulation were found to vary with muscle length. At typical stimulation intensities and frequencies used during dropped foot correction, direct (orthodromic) motor activation dominates voluntary or reflex mediated activation of the tibialis anterior. Enhanced contractile force when utilising catch-like stimulation with human participants, appears an effect solely inherent to muscle with no excitatory or inhibitory spinal reflex contribution. Facilitation of reflected antidromic motor activation (F-waves) with voluntary effort, observed only within the unimpaired participant group, may be an indicator of normal neuroplasticity at the spinal cord. Findings highlight the need to consider antidromic motor effects of electrical stimulation when combining its use with voluntary function during future clinical development.

Hydrological extremes within the UK have increased in intensity, frequency and persistence over recent years and are predicted to increase in variability throughout the 21st century. Past and future changes in hydrological extremes relative to climate change were investigated within Severn Uplands, a climate sensitive catchment. Using the Mann- Kendall trend detection test, time-series analysis over a 30-year period revealed a significant increase in winter and autumn precipitation and a decrease in summer precipitation. The analysis of flow time-series indicated an increase in winter and July flows and a decrease in spring flows. Changes in climate variability over the same period showed increases in air temperature and SST, and a reduction in snow cover. Climate variables were found to largely correlate with hydrological extremes which were characteristic of certain weather types and largely influenced by the NAO. To model future flows within the Severn Uplands a hydrological model (HEC-HMS) was used to simulate hydrological processes. The extreme hydrological event of November- December 2006 was used to calibrate the model. The difference between using radar and gauge precipitation data to drive the model was quantified. Radar data resulted in the smallest prediction accuracy followed by gauge-corrected radar data (corrected using the mean-field bias where gauge rainfall was interpolated using cokriging) and then gauge precipitation which had the largest prediction accuracy. Model accuracy was sufficient using the gauge corrected radar and gauge precipitation data as inputs, so both were altered for future predictions to investigate the propagation of uncertainty. Predicted changes in temperature and precipitation by the UKCIP02 scenarios were used to alter the baseline extreme event to predict changes in peak flow and outflow volume. Both radar- and gaugedriven hydrological modelling predicted large flow increases for the 21st century with increases up to 8% by the 2020s, 18% by the 2050s and 30% by the 2080s. Discrepancies between predictions were observed when using the different data inputs.

This thesis explores the gap between theory and practice within the context of humancomputer interaction (HCI), specifically relating to effective implementation of HCI methods and frameworks within practice. The thesis is structured as follows: three connected but stand-alone papers are presented preceded by an introduction, and followed by a conclusion. The introduction defines HCI, discusses its history and evolution, and how it has been influenced by different disciplines. The first paper covers the usability of personalisation of Web sites and consists of three quantitative studies. The main measurements are effciency, effectiveness, and satisfaction as indicators of usability. Two of the studies show a significant relationship between the amount of content on a page and time taken to find information. The third study shows that when users are only allowed 3-5 seconds to glance through the page (skim), the significance, found in the other two studies, disappeared. There is, however, no indication that subjective satisfaction is affected, regardless of the amount of time users take to find information in any of the studies. The second paper is a case study: a practical evaluation of how usability is implemented in commercial website design projects. It compares the difference between targeting usability issues early in the design and later in the development. The third paper conceptualises involving users early on in design projects, how this affects design projects in the context of Garrett's (2002) framework and how it compares with current and optimal approaches. It shows that involving users early in the design process does not negatively affect time or effort and concludes by defining areas where research should concentrate to provide further evidence towards involving stakeholders in Web design through researchable propositions. Finally, the conclusion chapter summarises each of the paper's limitations and conclusions. It links the three papers through a discussion on how they are related in addition to how this research could benefit the practitioner