The influence of wing–wake interactions on the production of aerodynamic forces in flapping flight

We used two-dimensional digital particle image velocimetry (DPIV) to visualize flow patterns around the flapping wing of a dynamically scaled robot for a series of reciprocating strokes starting from rest. The base of the wing was equipped with strain gauges so that the pattern of fluid motion could be directly compared with the time history of force production. The results show that the development and shedding of vortices throughout each stroke are highly stereotyped and influence force generation in subsequent strokes. When a wing starts from rest, it generates a transient force as the leading edge vortex (LEV) grows. This early peak, previously attributed to added-mass acceleration, is not amenable to quasi-steady models but corresponds well to calculations based on the time derivative of the first moment of vorticity within a sectional slice of fluid. Forces decay to a stable level as the LEV reaches a constant size and remains attached throughout most of the stroke. The LEV grows as the wing supinates prior to stroke reversal, accompanied by an increase in total force. At stroke reversal, both the LEV and a rotational starting vortex (RSV) are shed into the wake, forming a counter-rotating pair that directs a jet of fluid towards the underside of the wing at the start of the next stroke. We isolated the aerodynamic influence of the wake by subtracting forces and flow fields generated in the first stroke, when the wake is just developing, from those produced during the fourth stroke, when the pattern of both the forces and wake dynamics has reached a limit cycle. This technique identified two effects of the wake on force production by the wing: an early augmentation followed by a small attenuation. The later decrease in force is consistent with the influence of a decreased aerodynamic angle of attack on translational forces caused by downwash within the wake and is well explained by a quasi-steady model. The early effect of the wake is not well approximated by a quasi-steady model, even when the magnitude and orientation of the instantaneous velocity field are taken into account. Thus, the wake capture force represents a truly unsteady phenomenon dependent on temporal changes in the distribution and magnitude of vorticity during stroke reversal

Challenges facing green space: is statute the answer?

Against a backdrop of austerity, characterised by public-sector funding cuts and a devolutionary agenda, this paper explores how legislation might address two, inter-related challenges which face public urban green space ('greenspace') in England and Wales; namely, responsibility for provision, and identification of supporting funds. It focuses on two proposals; first, the introduction of legislative powers to enable local authorities to create user-charging schemes, and secondly, the imposition of a local authority statutory duty to provide greenspace

Sense of agency, associative learning, and schizotypy

Despite the fact that the role of learning is recognised in empirical and theoretical work on sense of agency (SoA), the nature of this learning has, rather surprisingly, received little attention. In the present study we consider the contribution of associative mechanisms to SoA. SoA can be measured quantitatively as a temporal linkage between voluntary actions and their external effects. Using an outcome blocking procedure, it was shown that training action-outcome associations under conditions of increased surprise augmented this temporal linkage. Moreover, these effects of surprise were correlated with schizotypy scores, suggesting that individual differences in higher level experiences are related to associative learning and to its impact on SoA. These results are discussed in terms of models of SoA, and our understanding of disrupted SoA in certain disorders

Melt densities in the Na2O-FeO-Fe2O3-SiO2 system and the partial molar volume of tetrahedrally-coordinated ferric iron in silicate melts

The densities of 12 melts in the Na2O-FeO-Fe2O3-SiO2 system have been determined in equilibrium with air, in the temperature range of 1000–1500°C, using the double bob, Archimedean technique. Ferrous iron determinations of 100–200 mg samples, “dip” quenched from high temperature, indicate that all the melts investigated were highly oxidized under these experimental conditions. 57Fe Mössbauer spectra of glasses obtained by drop quenching 80 mg melt samples from loop equilibration runs yield Fe3+/Fe2+ data equivalent to that for the densitometry (dip) samples for all but the most viscous melt, and confirm that all but one melt equilibrated with air during the densitometry measurements. Melt densities range from 2.17 to 2.88 g/cm3 with a mean standard deviation (from replicate experiments) of 0.36%. Least squares regression of the density data at 1300, 1400 and 1500°C, was calculated, both excluding and including excess volume terms (herein named linear and nonlinear fits, respectively) and the root mean squared deviation (RMSD) of each regression was compared with the total experimental error. The partial molar volumes computed for linear fits for Na2O and SiO2 are similar to those previously reported for melts in the Na2O-Al2O3-SiO2 system (Steinet al., 1986). The partial molar volumes of Fe2O3 obtained in these linear fits are equal to those obtained by Shiraishi et al. (1978) in the FeO-Fe2O3-SiO2 system but 5 to 10% lower than reported by Mo et al. (1982) in multicomponent melts. The partial molar volume exhibited by Fe3+ in this system is representative of the partial molar volume of tetrahedrally coordinated Fe3+ in silicate melts

A ground based gamma ray telescope of high sensitivity and low energy threshold

The subject of this thesis is ground based gamma ray astronomy using the atmospheric Cerenkov technique. Chapter 1 defines the gamma ray region of the electromagnetic spectrum, introduces celestial gamma rays as a component of the flux of energetic particles known as cosmic rays and considers the physical mechanisms by which celestial gamma rays may be produced and absorbed. The phenomenon of Cerenkov radiation, and Its production within the extensive air showers which result from the Interaction of energetic cosmic rays with the atmosphere. Is the subject of Chapter 2. Chapter 3 introduces the early Durham telescopes, and considers the possible improvement to instrument sensitivity afforded by invokatlon of more sophisticated background rejection strategies. The Mk.5 telescope, which is the subject of Chapter 4, Is the vehicle by which the Durham group has sought to assess the relative merits of various signal enhancement strategies, and prove the viability of a design for a high resolution Imaging detector with the additional capacity to make observations at very low energies; the Mk.6 telescope. Chapter 5 introduces a novel concept of background rejection based upon the stereoscopic Imaging of extensive air showers, and describes modifications to the Mk.3 necessary to provide a complement to the Mk.5 in this capacity. Chapter 6 presents the analysis of a burst of periodic gamma ray emission from AE Aquarii, which demonstrates the efficacy of the medium resolution 'mono' Imaging and stereoscopic imaging signal enhancement techniques employed by the Mk.5 and modified Mk.3 telescopes. The culmination of the evolution of the Durham telescopes is the Mk.6, described in Chapter 7. Its sensitivity is enhanced by high resolution imaging and the capacity to make observations at energies deficient in background events. Chapter 8 summarises the contemporary status of atmospheric Cerenkov astronomy

Senior Recital, Michael Dickinson, trombone

The presentation of this senior recital will fulfill in part the requirements for the Bachelor of Music degree in Performance. Michael Dickinson studies trombone with Dr. Ross Walter

Junior Recital, Michael Dickinson, bass trombone

The presentation of this junior recital will fulfill in part the requirements for the Bachelor of Music degree in Performance. Michael Dickinson studies bass trombone with Dr. Ross Walter

Greenspace governance: statutory solutions from Scotland?

The environmental, social and economic benefits provided by greenspace are well-documented, and the closure of other types of Third Place has popularised them further. Yet, public sector funding cuts have necessitated local authorities prioritising other facilities that they are statutorily obliged to provide, resulting in a facilities-hierarchy which leaves financially-neglected greenspaces facing a vicious circle of decline. The Big Society agenda has seen local authorities increasingly rely on the voluntary sector to help plug the funding gap, yet there are concerns that such groups are not immune from the effects of austerity themselves which limit their panacean abilities. In exploring whether statute could provide any answers to these greenspace governance challenges, this article considers the lessons to be learned from the approach adopted in Scotland, underpinned by the Land Reform (Scotland) Act 2003 ('the 2003 Act'). In particular, the 2003 Act establishes public rights of access over most greenspace, a local authority duty to uphold these rights and local authority powers to take remedial action. Whilst there have been some issues in implementation, this article explores the potential for adopting a similar model in England & Wales to help secure the future of its greenspace infrastructure