Imperfect Homoclinic Bifurcations

Experimental observations of an almost symmetric electronic circuit show complicated sequences of bifurcations. These results are discussed in the light of a theory of imperfect global bifurcations. It is shown that much of the dynamics observed in the circuit can be understood by reference to imperfect homoclinic bifurcations without constructing an explicit mathematical model of the system.Comment: 8 pages, 11 figures, submitted to PR

Evaluation of the personal health budget pilot programme

1. The personal health budget initiative is a key aspect of personalisation across health care services in England. Its aim is to improve patient outcomes, by placing patients at the centre of decisions about their care. Giving people greater choice and control, with patients working alongside health service professionals to develop and execute a care plan, given a known budget, is intended to encourage more responsiveness of the health and care system. 2. The personal health budget programme was launched by the Department of Health in 2009 after the publication of the 2008 Next Stage Review. An independent evaluation was commissioned alongside the pilot programme with the aim of identifying whether personal health budgets ensured better health and care outcomes when compared to conventional service delivery and, if so, the best way for personal health budgets to be implemented

A simple method to determine soil–water retention curves of compacted active clays

Determining the Soil Water Retention Curve (SWRC) of an active clay constitutes a challenge due to the significant, and sometimes irreversible, volume changes that occur during wetting and drying cycles. A novel yet simple method of experimentally determining the evolution of the SWRCs with moisture cycles is presented based on the results of a rigorous experimental study. Its purpose is to support the modelling of water flux in earthworks exposed to weather cycles that cause deterioration. Firstly, three SWRC branches (the primary drying, a scanning drying, and a scanning wetting branch) are measured and used to fit the proposed generic SWRC semi-empirical model in terms of water ratio, that, in the adsorptive region, is independent of the compaction conditions (void ratio and water content at compaction). Soil Shrink-Swell Curves (SSSCs) in terms of water ratio versus void ratio, that are easy to measure, can be determined for different compaction conditions over several drying and wetting cycles. Finally, the SSSCs are combined with the generic SWRC model to determine the evolution of the SWRCs with moisture cycles for the compaction conditions of interest. This method is demonstrated for two London clays of high and very high plasticity. Samples were compacted in five different conditions, varying in gravimetric water content and dry density, and were cycled six times between 1 and 80 MPa of total suction. The generic SWRC model was fitted to the experimental data. The model was able to estimate the SWRC in terms of degree of saturation over the six drying-wetting cycles without propagation of error. The significance of the research is that SWRC can now be determined over a range of wetting and drying cycles quickly and simply and enable modelling of deterioration of clays fills due to the action of weather to be accurate

Hidden dynamics for piecewise smooth maps

From IOP Publishing via Jisc Publications RouterHistory: received 2020-05-28, rev-recd 2021-02-07, oa-requested 2021-02-08, accepted 2021-02-17, ppub 2021-05, open-access 2021-05-07, epub 2021-05-07Publication status: PublishedAbstract: We develop a hidden dynamics formulation of regularisation for piecewise smooth maps. This involves blowing up the discontinuity into an interval, but in contrast to piecewise smooth flows every preimage of the discontinuity needs to be blown up as well. This results in a construction similar to classic approaches to the Denjoy counterexample

Construction, management and maintenance of embankments used for road and rail infrastructure: implications of weather induced pore water pressures

Understanding the age and construction quality of embankments used for road and rail infrastructure is critical in the effective management and maintenance of our transport networks, worth £billions to the UK economy. This paper presents for the first time results from full-scale, carefully controlled experiments on a unique model embankment conducted over the 4-year period between 2008 and 2011. It combines point location and spatially distributed measurements of pore water pressures and water content with outputs from hydrological modelling to draw conclusions of significance to both ongoing research in this field and to the asset management practices of infrastructure owners. For researchers, the paper highlights the crucial importance of transient permeability and soil water retention behaviour of fill materials in controlling the magnitude and distribution of pore water pressure in response to climate and weather events. For practitioners, the work demonstrates that there are significant differences in pore water pressure behaviour across the embankment, which is influenced by construction-related issues such as compaction level, aspect and presence of a granular capping material. Permeability was also observed to vary across the embankment both spatially and with depth, being dependent on degree of saturation and macroscale effects, particularly within a ‘near surface zone’. It is proposed that this ‘near surface zone’ has a critical effect on embankment stability and should be the focus of both ongoing scientific research and inspection and monitoring as encompassed by asset management regimes