Multiphase modelling of desiccation cracking in compacted soil

PhD ThesisThe development of cracking as a result of desiccation is increasingly under investigation. This work is set within the context of climate change effects on surface processes influencing infrastructure slope stability. The inherent changes to the mechanical and hydrological behaviour of clayey soils subjected to desiccation are significant. The preferential transmission of water due to cracking is widely cited as a source of strength reduction that leads to infrastructure slope failure. In order to gain a better understanding of the cracking mechanism in typical compacted fill conditions, finite difference continuum modelling has been undertaken using FLAC 2D. The two-phase flow add-on has enabled the unsaturated behaviour of the desiccating soil to be included within the mesh. Physical behaviour observed in laboratory experiments has informed the development of the numerical model by allowing better constraint of boundary conditions. Model development has featured the inclusion of several non-linear processes that are fundamental to the changing soil response during drying. The influence of significant parameters has been identified and by means of a varied experimental program, the design, manufacture and testing of a laboratory test apparatus and procedure to define the tensile strength of compacted fills under varying saturation conditions was undertaken and subsequently validated. The factors affecting crack initiation and propagation have been investigated via parametric study. This demonstrated the significant influence of basal restraint on the generation of tensile stresses conducive to cracking and the fundamental importance of the tensile strength function within the proposed modelling methodology. Experimentation with the shape of the SWRC has shown the model to be very sensitive to the hydraulic properties of the material with not only the occurrence of primary cracking being affected but also the development of the desiccated crust. The findings of this work are relatable to the incorporation of desiccation effects in the development of coupled hydrological-mechanical continuum models where atmosphere-soil interactions are increasingly significant.Newcastle University with contribution from the EPSRC project, iSMART

Observations of Cannibalism by Polar Bears (Ursus maritimus) on Summer and Autumn Sea Ice at Svalbard, Norway

We report three instances of intraspecific killing and cannibalism of young polar bears by adult males on the sea ice in Svalbard in summer and autumn. During breakup and melting in summer, the area of sea ice around the Svalbard Archipelago declines to a fraction of the winter total, and in many areas it disappears completely. As the area of sea ice that polar bears can use for hunting declines, progressively fewer seals are accessible to the bears, and therefore the bears’ hunting success likely declines as well. Thus, at this time of year, young polar bears may represent a possible food source for adult males. As the climate continues to warm in the Arctic and the sea ice melts earlier in the summer, the frequency of such intraspecific predation may increase.Nous signalons trois cas d’ours polaires adultes qui ont tué de jeunes ours polaires et fait du cannibalisme intra-spécifique sur la glace de mer de Svalbard à l’été et à l’automne. Pendant la débâcle et les fontes de l’été, la zone de glace de mer aux environs de l’archipel de Svalbard n’occupe qu’une fraction de la superficie totale atteinte en hiver et dans bien des endroits, elle disparaît complètement. Puisque la zone de glace de mer dont les ours polaires se servent pour leur activité de chasse devient plus petite, il y a de moins en moins de phoques à la disposition des ours, ce qui fait que la récolte de chasse des ours est susceptible de chuter par le fait même. Par conséquent, à ce moment-là de l’année, les jeunes ours polaires peuvent représenter une source de nourriture possible pour les adultes mâles. Au fur et à mesure que le climat de l’Arctique continuera de se réchauffer et que la glace fondra plus tôt en été, la fréquence de cette prédation intraspécifique sera susceptible d’augmenter

NLL BFKL and NNLO

The BFKL resummation at LL and NLL accuracy is briefly reviewed, with particular emphasis on the connection between the NLL corrections to the BFKL equation and exact NNLO calculations.Comment: LaTeX, 4 pages, with npb.sty. To appear in the Proceedings of DIS99, Zeuthen, Germany, in Nucl. Phys. B (Proc. Suppl.

Community resilience to climate change: an evidence review

The concept of community resilience to climate change in the UK has a diverse range of meanings and associated activities. This review of evidence and practice explores this varied and contested field to build the evidence base and help support the development of community resilience to climate change. The report shows: •the variety of actions being carried out across the UK that can be classed as improving resilience of communities to climate change; •the barriers and facilitators to improving resilience to climate change for communities; •the value of a framework to understand resilience of communities to climate change that emphasises existing capacities of communities, engagement and empowerment of citizens, and multi-level governance; and •examples of innovative actions to improve resilience of communities to climate change with a focus on four case studies, which are further explored in a separate report

Black hole accretion disks in the canonical low-hard state

Stellar-mass black holes in the low-hard state may hold clues to jet formation and basic accretion disk physics, but the nature of the accretion flow remains uncertain. A standard thin disk can extend close to the innermost stable circular orbit, but the inner disk may evaporate when the mass accretion rate is reduced. Blackbody-like continuum emission and dynamically-broadened iron emission lines provide independent means of probing the radial extent of the inner disk. Here, we present an X-ray study of eight black holes in the low-hard state. A thermal disk continuum with a colour temperature consistent with $L \propto T^{4}$ is clearly detected in all eight sources, down to $\approx5\times10^{-4}L_{Edd}$. In six sources, disk models exclude a truncation radius larger than 10rg. Iron-ka fluorescence line emission is observed in half of the sample, down to luminosities of $\approx1.5\times10^{-3}L_{Edd}$. Detailed fits to the line profiles exclude a truncated disk in each case. If strong evidence of truncation is defined as (1) a non-detection of a broad iron line, {\it and} (2) an inner disk temperature much cooler than expected from the ${\rm L} \propto {\rm T}^{4}$ relation, none of the spectra in this sample offer strong evidence of disk truncation. This suggests that the inner disk may evaporate at or below $\approx1.5\times10^{-3}L_{Edd}$.Comment: Accepted for publication in MNRAS, 20 pages, 18 figure

Report of the Working Group on `W Mass and QCD' (Phenomenology Workshop on LEP2 Physics, Oxford, April 1997)

The W Mass and QCD Working Group discussed a wide variety of topics relating to present and future measurements of M(W) at LEP2, including QCD backgrounds to W+W- production. Particular attention was focused on experimental issues concerning the direct reconstruction and threshold mass measurements, and on theoretical and experimental issues concerning the four jet final state. This report summarises the main conclusions.Comment: 43 pages LaTeX and 15 encapsulated postscript figures. Uses epsfig and ioplppt macros. Full Proceedings to be published in Journal of Physics

Challenges in monitoring and managing engineered slopes in a changing climate

© 2016 The Authors. Geotechnical asset owners need to know which parts of their asset network are vulnerable to climate change induced failure in order to optimise future investment. Protecting these vulnerable slopes requires monitoring systems capable of identifying and alerting to asset operators changes in the internal conditions that precede failure. Current monitoring systems are heavily reliant on point sensors which can be difficult to interpret across slope scale. This paper presents challenges to producing such a system and research being carried out to address some of these using electrical resistance tomography (ERT). Experimental results show that whilst it is possible to measure soil water content indirectly via resistivity the relationship between resistivity and water content will change over time for a given slope. If geotechnical parameters such as pore water pressure are to be estimated using this method then ERT systems will require integrating with more conventional geotechnical instrumentation to ensure correct representative information is provided. The paper also presents examples of how such data can be processed and communicated to asset owners for the purposes of asset management

Improving response rates using a monetary incentive for patient completion of questionnaires: an observational study

Background: Poor response rates to postal questionnaires can introduce bias and reduce the statistical power of a study. To improve response rates in our trial in primary care we tested the effect of introducing an unconditional direct payment of 5 pound for the completion of postal questionnaires. Methods: We recruited patients in general practice with knee problems from sites across the United Kingdom. An evidence-based strategy was used to follow-up patients at twelve months with postal questionnaires. This included an unconditional direct payment of 5 pound to patients for the completion and return of questionnaires. The first 105 patients did not receive the 5 pound incentive, but the subsequent 442 patients did. We used logistic regression to analyse the effect of introducing a monetary incentive to increase the response to postal questionnaires. Results: The response rate following reminders for the historical controls was 78.1% ( 82 of 105) compared with 88.0% ( 389 of 442) for those patients who received the 5 pound payment (diff = 9.9%, 95% CI 2.3% to 19.1%). Direct payments significantly increased the odds of response ( adjusted odds ratio = 2.2, 95% CI 1.2 to 4.0, P = 0.009) with only 12 of 442 patients declining the payment. The incentive did not save costs to the trial - the extra cost per additional respondent was almost 50 pound. Conclusion: The direct payment of 5 pound significantly increased the completion of postal questionnaires at negligible increase in cost for an adequately powered study

Financing renewable energy: Who is financing what and why it matters

Successful financing of innovation in renewable energy (RE) requires a better understanding of the relationship between different types of finance and their willingness to invest in RE. We study the ‘direction’ of innovation that financial actors create. Focusing on the deployment phase of innovation, we use Bloomberg New Energy Finance (BNEF) data to construct a global dataset of RE asset finance flows from 2004 to 2014. We analyze the asset portfolios of different RE technologies financed by different financial actors according to their size, skew and level of risk. We use entropy-based indices to measure skew, and construct a heuristic index of risk that varies with the technology, time, and country of investment to measure risk. We start by comparing the behavior of private and public types of finance and then disaggregate further along 11 different financial actors (e.g. private banks, public banks, and utilities) and 11 types of RE technologies that are invested in (e.g. different kinds of power generation from solar radiation, wind or biomass). Financial actors vary considerably in the composition of their investment portfolio, creating directions towards particular technologies. Public financial actors invest in portfolios with higher risk technologies, also creating a direction; they also increased their share in total investment dramatically over time. We use these preliminary results to formulate new research questions about how finance affects the directionality of innovation, and the implications for RE policies