Numerical simulation of the airflow–rivulet interaction associated with the rain-wind induced vibration phenomenon

Rain-wind induced vibration is an aeroelastic phenomenon that occurs on the inclined cables of cable-stayed bridges. The vibrations are believed to be caused by a complicated nonlinear interaction between rivulets of rain water that run down the cables and the wind loading on the cables due to the unsteady aerodynamic flow field. Recent research at the University of Strathclyde has been to develop a numerical method to simulate the influence of the external air flow on the rivulet dynamics and vice versa, the results of which can be used to assess the importance of the water rivulets on the instability. The numerical approach for the first time couples a Discrete Vortex Method solver to determine the external flow field and unsteady aerodynamic loading, and a pseudo-spectral solver based on lubrication theory to model the evolution and growth of the water rivulets on the cable surface under external loading. The results of the coupled model are used to assess the effects of various loading combinations, and importantly are consistent with previous full scale and experimental observations of rain-wind induced vibration, providing new information about the underlying physical mechanisms of the instability

The Social Context as a Determinant of Teacher Motivational Strategies in Physical Education

The purpose of the study was to provide an in-depth analysis of how Physical Education (PE) teachers perceive the social context to influence the motivational strategies that they use towards students. Semi-structured interviews of 22 PE teachers were examined using categorical content analysis. The teachers perceived that an emphasis on student assessment and the time constraints associated with PE lessons influenced their motivational strategies towards students; however, these strategies often conflicted with the teachers’ beliefs about the most appropriate motivational strategies. The teachers’ own performance evaluations and pressure to conform to other teachers’ methods also influenced the teachers’ motivational strategies, but these influences were often congruent with their teaching beliefs. Additionally, the teachers discussed how perceived cultural norms associated with the teacher-student relationship impacted upon their chosen motivational strategies. These cultural norms were reported by different teachers as either in line, or in conflict with their teaching beliefs. Finally, the influence of the teachers’ perceptions of their students helped produce strategies that were congruent with their beliefs, but often different to empirically suggested strategies. Consequently, it is important that teacher beliefs are targeted in education programs and that the teaching context aid in facilitating adaptive motivational strategies

Tadpoles and Closed String Backgrounds in Open String Field Theory

We investigate the quantum structure of Witten's cubic open bosonic string field theory by computing the one-loop contribution to the open string tadpole using both oscillator and conformal field theory methods. We find divergences and a breakdown of BRST invariance in the tadpole diagram arising from tachyonic and massless closed string states, and we discuss ways of treating these problems. For a Dp-brane with sufficiently many transverse dimensions, the tadpole can be rendered finite by analytically continuing the closed string tachyon by hand; this diagram then naturally incorporates the (linearized) shift of the closed string background due to the presence of the brane. We observe that divergences at higher loops will doom any straightforward attempt at analyzing general quantum effects in bosonic open string field theory on a Dp-brane of any dimension, but our analysis does not uncover any potential obstacles to the existence of a sensible quantum open string field theory in the supersymmetric case.Comment: 51 pages, 11 eps figures, Latex; v2: References adde

The Fish Funnel: A Trawl Modification to Reduce Fish Escapement

In the Gulf of Mexico there is a need to assess the potential of underutilized fish resource stocks before a commercial fishery develops. Standard sampling trawls used in the Gulf are ineffective for sampling the resource, so larger, high opening, bottom trawls have been introduced. The larger trawls are more effective, but most of the faster swimming fish species are able to escape these nets, especially during haul back. To reduce fish escapement, webbing panels, attached inside the trawls ahead of the cod ends, were tested. Initial tests were conducted with two single panel designs--a fish flap and a "floppa." Neither design reduced fish escapement. The floppa distorted the trawl webbing and actually increased fish escapement. A multi-panel conical funnel design (the fish funnel) was tested and found to increase fish retention by trapping the fish after they passed through it. When used in combination with a technique known as pulsing the trawl, the fish funnel substantially increased trawl catch rates with no indication of fish escapement

Entanglement of a 3D generalization of the Kitaev model on the diamond lattice

We study the entanglement properties of a three dimensional generalization of the Kitaev honeycomb model proposed by Ryu [Phys. Rev. B 79, 075124, (2009)]. The entanglement entropy in this model separates into a contribution from a $Z_2$ gauge field and that of a system of hopping Majorana fermions, similar to what occurs in the Kitaev model. This separation enables the systematic study of the entanglement of this 3D interacting bosonic model by using the tools of non-interacting fermions. In this way, we find that the topological entanglement entropy comes exclusively from the $Z_2$ gauge field, and that it is the same for all of the phases of the system. There are differences, however, in the entanglement spectrum of the Majorana fermions that distinguish between the topologically distinct phases of the model. We further point out that the effect of introducing vortex lines in the $Z_2$ gauge field will only change the entanglement contribution of the Majorana fermions. We evaluate this contribution to the entanglement which arises due to gapless Majorana modes that are trapped by the vortex lines.Comment: 25 pages, 5 figures. Invited article to JSTAT Special Issue: Quantum Entanglement in Condensed Matter Physic

Australian Growth: A California Perspective

Examination of special cases assists understanding of the mechanics of long-run economic growth more generally. Australia and California are two economies having the rare distinction of achieving 150 years of sustained high and rising living standards for rapidly expanding populations. They are suitable comparators since in some respects they are quite similar, especially in their initial conditions in the mid-nineteenth century, their legal and cultural inheritances, and with respect to some long-term performance indicators. However, their growth trajectories have differed markedly in some sub-periods, and over the longer term with respect to the growth in the size of their economies. Most important, the comparison of an economy that remained a region in a much larger national economy with one that evolved into an independent political unit helps identify the role of several key policies. California had no independent monetary policy, or exchange rate, or controls over immigration or capital movements, or trade policy. Australia did, and after 1900 pursued an increasingly interventionist and inward-oriented development strategy until the 1970s. What difference did this make to long-run growth? And what other factors, exogenous and endogenous, account for the differences that have emerged between two economies that shared such similar initial conditions?

The nature of X-ray spectral variability in Seyfert Galaxies

We use a model-independent technique to investigate the nature of the 2-15 keV X-ray spectral variability in four Seyfert galaxies and distinguish between spectral pivoting and the two-component model for spectral variability. Our analysis reveals conclusively that the softening of the X-ray continuum with increasing flux in MCG -6-30-15 and NGC 3516 is a result of summing two spectral components: a soft varying component (SVC) with spectral shape independent of flux and a constant hard component (HCC). In contrast, the spectral variability in NGC 4051 can be well described by simple pivoting of one component, together with an additional hard constant component. The spectral variability model for NGC 5506 is ambiguous, due to the smaller range of fluxes sampled by the data. We investigate the shape of the hard spectral component in MCG -6-30-15 and find that it appears similar to a pure reflection spectrum, but requires a large reflected fraction (R>3). We briefly discuss physical interpretations of the different modes of spectral variability.Comment: Accepted for publication in MNRAS letter