Numerical study on the structural response of a masonry arch bridge subject to flood flow and debris impact

Extreme flood flows in rivers and the floating debris they carry have the potential to generate significant impact forces on bridges spanning the watercourse. Recent flood events have highlighted the vulnerability of masonry arch bridges in flood events. This paper explores the structural response of a typical masonry arch bridge subject to flood flow and impact from flood-borne debris using a validated numerical modelling approach. The meshless method smoothed particle hydrodynamics (SPH) is used to model the fluid behaviour giving the pressure distributions on a single-span arch bridge arising from both the fluid and debris impact. Taking the pressure-time histories derived from the SPH model, the response of the bridge structure is then simulated using a nonlinear finite element (FE) model via Abaqus/Explicit. The effects of submergence ratio of bridge components: abutment, arch barrel, spandrel wall, debris orientation and flow velocity are explored. Results indicate that the debris impact resulted in greatest increase in the stresses in the bridge with a fully submerged abutment and side-on (0-degree) debris orientation. The influence of the debris impact with end-on (90-degree) orientation on the structural response was relatively low despite its higher peak pressure values. Moreover, for the type of realistic flow scenarios considered, significant local tensile stresses can be generated in the spandrel wall and arch barrel leading to structural damage

Square to stripe transition and superlattice patterns in vertically oscillated granular layers

We investigated the physical mechanism for the pattern transition from square lattice to stripes, which appears in vertically oscillating granular layers. We present a continuum model to show that the transition depends on the competition between inertial force and local saturation of transport. By introducing multiple free-flight times, this model further enables us to analyze the formation of superlattices as well as hexagonal lattice

Theoretical study of incoherent phi photoproduction on a deuteron target

We study the photoproduction of phi mesons in deuteron, paying attention to the modification of the cross section from bound protons to the free ones with the aim of comparing with recent results at LEPS. For this purpose we take into account Fermi motion in single scattering and rescattering of the phi to account for phi absorption on a second nucleon as well as the rescattering of the proton. We find that the contribution of the double scattering is much smaller than the typical cross section of gamma p to phi p in free space, which implies a very small screening of the phi production in deuteron. The contribution from the proton rescattering, on the other hand, is found to be not negligible compared to the cross section of gamma p to phi p in free space, and leads to a moderate reduction of the phi photoproduction cross section on a deuteron at forward angles if LEPS set up is taken into account. The Fermi motion allows contribution of the single scattering in regions forbidden by phase space in the free case. In particular, we find that for momentum transferred squared close to the maximum value, the Fermi motion changes drastically the shape of d sigma / dt, to the point that the ratio of this cross section to the free one becomes very sensitive to the precise value of t chosen, or the size of the bin used in an experimental analysis. Hence, this particular region of t does not seem the most indicated to find effects of a possible phi absorption in the deuteron. This reaction is studied theoretically as a function of t and the effect of the experimental angular cuts at LEPS is also discussed, providing guidelines for future experimental analyses of the reaction.Comment: 17 pages, 16 figure

Specific Heat of Liquid Helium in Zero Gravity very near the Lambda Point

We report the details and revised analysis of an experiment to measure the specific heat of helium with subnanokelvin temperature resolution near the lambda point. The measurements were made at the vapor pressure spanning the region from 22 mK below the superfluid transition to 4 uK above. The experiment was performed in earth orbit to reduce the rounding of the transition caused by gravitationally induced pressure gradients on earth. Specific heat measurements were made deep in the asymptotic region to within 2 nK of the transition. No evidence of rounding was found to this resolution. The optimum value of the critical exponent describing the specific heat singularity was found to be a = -0.0127+ - 0.0003. This is bracketed by two recent estimates based on renormalization group techniques, but is slightly outside the range of the error of the most recent result. The ratio of the coefficients of the leading order singularity on the two sides of the transition is A+/A- =1.053+ - 0.002, which agrees well with a recent estimate. By combining the specific heat and superfluid density exponents a test of the Josephson scaling relation can be made. Excellent agreement is found based on high precision measurements of the superfluid density made elsewhere. These results represent the most precise tests of theoretical predictions for critical phenomena to date.Comment: 27 Pages, 20 Figure

Magnetic Reconnection in Extreme Astrophysical Environments

Magnetic reconnection is a basic plasma process of dramatic rearrangement of magnetic topology, often leading to a violent release of magnetic energy. It is important in magnetic fusion and in space and solar physics --- areas that have so far provided the context for most of reconnection research. Importantly, these environments consist just of electrons and ions and the dissipated energy always stays with the plasma. In contrast, in this paper I introduce a new direction of research, motivated by several important problems in high-energy astrophysics --- reconnection in high energy density (HED) radiative plasmas, where radiation pressure and radiative cooling become dominant factors in the pressure and energy balance. I identify the key processes distinguishing HED reconnection: special-relativistic effects; radiative effects (radiative cooling, radiation pressure, and Compton resistivity); and, at the most extreme end, QED effects, including pair creation. I then discuss the main astrophysical applications --- situations with magnetar-strength fields (exceeding the quantum critical field of about 4 x 10^13 G): giant SGR flares and magnetically-powered central engines and jets of GRBs. Here, magnetic energy density is so high that its dissipation heats the plasma to MeV temperatures. Electron-positron pairs are then copiously produced, making the reconnection layer highly collisional and dressing it in a thick pair coat that traps radiation. The pressure is dominated by radiation and pairs. Yet, radiation diffusion across the layer may be faster than the global Alfv\'en transit time; then, radiative cooling governs the thermodynamics and reconnection becomes a radiative transfer problem, greatly affected by the ultra-strong magnetic field. This overall picture is very different from our traditional picture of reconnection and thus represents a new frontier in reconnection research.Comment: Accepted to Space Science Reviews (special issue on magnetic reconnection). Article is based on an invited review talk at the Yosemite-2010 Workshop on Magnetic Reconnection (Yosemite NP, CA, USA; February 8-12, 2010). 30 pages, no figure

The impact of curriculum hierarchies on the development of professional self in teaching: student-teachers of drama negotiating issues of subject status at the interface between drama and English

At the level of policy the relative ‘value’ of subjects is determined by their official curriculum designation, creating a hierarchy of learning within which particular subjects are categorised as optional to the educational experience of young people. This situation is well-illustrated by the marginalised position of drama in the National Curriculum for England and Wales in which drama appears as an adjunct to the ‘core’ subject English. Yet at school level drama has survived as a discrete and reasonably embedded subject. Drawing on questionnaire and interview data, I investigate the effects of this mismatch on the emergence of pedagogical content knowledge, linked to notions of professional self, in drama student-teachers at one university in the UK. Findings indicate that the student-teachers, whilst not entirely eschewing a less-regulated relationship between the two subjects, view the curriculum for English and its accompanying assessment regime as an inadequate host for drama. In addition, they regard teacher autonomy over curriculum content and pedagogy as indicative of a high degree of professional expertise. This suggests that a case can be made for re-evaluating the nature of the relationship between drama and English and its representation in policy-constructed curricula

Developing the digital self-determined learner through heutagogical design

This empirical qualitative study investigates whether the introduction of heutagogy in contemporary nursing education can foster the development of the digital self-determined learner, who is prepared to work and live in the fourth industrial age and beyond. The impact of heutagogical design on learner process and outcomes is explored through qualitative framework analysis of learner data and reflective educator observations. Findings suggest that with careful scaffolding and courage in remaining true to the educational philosophy, this approach has the potential to develop learners who demonstrate key principles of heutagogy including non-linear learning, learner agency, capability, self-reflection and metacognition and double-loop learning. This innovative study provides insight into the process of developing the self-determined learner and encourages further research into flexible and learner-centred approaches across Higher Education

Exploring the stability of super heavy elements: First measurement of the fission barrier of 254No

The gamma-ray multiplicity and total energy emitted by the heavy nucleus 254No have been measured at 2 different beam energies. From these measurements, the initial distributions of spin I and excitation energy E * of 254No were constructed. The distributions display a saturation in excitation energy, which allows a direct determination of the fission barrier. 254No is the heaviest shell-stabilized nucleus with a measured fission barrier. © Owned by the authors, published by EDP Sciences, 2014

An Alternative Ethics? Justice and Care as Guiding Principles for Qualitative Research

The dominant conception of social research ethics is centred on deontological and consequentialist principles. In place of this, some qualitative researchers have proposed a very different approach. This appeals to a range of commitments that transform the goal of research as well as framing how it is pursued. This new ethics demands a participatory form of inquiry, one in which the relationship between researchers and researched is equalized. In this paper we examine this alternative approach, focusing in particular on two of the principles that are central to it: justice and care. We argue that there are some significant defects and dangers associated with this new conception of research ethics

Self-help groups challenge health care systems in the US and UK

Purpose: This research considers how self-help groups (SHGs) and self- help organizations (SHOs) contribute to consumerist trends in two different societies: United States and United Kingdom. How do the health care systems and the voluntary sectors affect the kinds of social changes that SHGs/SHOs make? Methodology/approach: A review of research on the role of SHGs/SHOs in contributing to national health social movements in the UK and US was made. Case studies of the UK and the US compare the characteristics of their health care systems and their voluntary sector. Research reviews of two community level self-help groups in each country describe the kinds of social changes they made. Findings: The research review verified that SHGs/SHOs contribute to national level health social movements for patient consumerism. The case studies showed that community level SHGs/SHOs successfully made the same social changes but on a smaller scale as the national movements, and the health care system affects the kinds of community changes made. Research limitations: A limited number of SHGs/SHOs within only two societies were studied. Additional SHGs/SHOs within a variety of societies need to be studied. Originality/value of chapter Community SHGs/SHOs are often trivialized by social scientists as just inward-oriented support groups, but this chapter shows that local groups contribute to patient consumerism and social changes but in ways that depend on the kind of health care system and societal context