Stability and control of compressible flows over a surface with concave-conves curvature

The active control of spatially unstable disturbances in a laminar, two-dimensional, compressible boundary layer over a curved surface is numerically simulated. The control is effected by localized time-periodic surface heating. We consider two similar surfaces of different heights with concave-convex curvature. In one, the height is sufficiently large so that the favorable pressure gradient is sufficient to stabilize a particular disturbance. In the other case the pressure gradient induced by the curvature is destabilizing. It is shown that by using active control that the disturbance can be stabilized. The results demonstrate that the curvature induced mean pressure gradient significantly enhances the receptivity of the flow localized time-periodic surface heating and that this is a potentially viable mechanism in air

Gaze cueing elicited by emotional faces is influenced by affective context

When we observe someone shift their gaze to a peripheral event or object, a corresponding shift in our own attention often follows. This social orienting response, joint attention, has been studied in the laboratory using the gaze cueing paradigm. Here, we investigate the combined influence of the emotional content displayed in two critical components of a joint attention episode: The facial expression of the cue face, and the affective nature of the to-be-localized target object. Hence, we presented participants with happy and disgusted faces as cueing stimuli, and neutral (Experiment 1), pleasant and unpleasant (Experiment 2) pictures as target stimuli. The findings demonstrate an effect of ‘emotional context’ confined to participants viewing pleasant pictures. Specifically, gaze cueing was boosted when the emotion of the gazing face (i.e., happy) matched that of the targets (pleasant). Demonstrating modulation by emotional context highlights the vital flexibility that a successful joint attention system requires in order to assist our navigation of the social world

Gaze cueing and affective judgments of objects: I like what you look at

When we see another person look somewhere, we automatically attend to the same location in space. This joint attention emerges early in life and has a great impact on social interactions in development and in everyday adult life. The direction of another's gaze indicates what object is of current interest, which may be the target for a subsequent action. In this study, we found that objects that are looked at by other people are liked more than objects that do not receive the attention of other people (Experiment 1). This suggests that observing averted gaze can have an impact on the affective appraisals of objects in the environment. This liking effect was absent when an arrow was used to cue attention (Experiment 2). This underlines the importance of other people's interactions with objects for generating our own impressions of such stimuli in the world

Numerical simulation of boundary layer excitation by surface heating/cooling

The concept of active control of growing disturbances in an unstable compressible flow by using time periodic, localized surface heating is studied numerically. The simulations are calculated by a fourth-order accurate solution of the compressible, laminar Navier-Stokes equations. Fourth-order accuracy is particularly important for this problem because the solution must be computed over many wavelengths. The numerical results demonstrate the growth of an initially small fluctuation into the nonlinear regime where a local breakdown into smaller scale disturbances can be observed. It is shown that periodic surface heating over a small strip can reduce the level of the fluctuation provided that the phase of the heating current is properly chosen

Active control of compressible flows on a curved surface

The effect of localized, time periodic surface heating and cooling over a curved surface is studied. This is a mechanism for the active control of unstable disturbances by phase cancellation and reinforcement. It is shown that the pressure gradient induced by the curvature significantly enhances the effectiveness of this form of active control. In particular, by appropriate choice of phase, active surface heating can completely stabilize and unstable wave

Dynamo action at low magnetic Prandtl numbers: mean flow vs. fully turbulent motion

We compute numerically the threshold for dynamo action in Taylor-Green swirling flows. Kinematic calculations, for which the flow field is fixed to its time averaged profile, are compared to dynamical runs for which both the Navier-Stokes and the induction equations are jointly solved. The kinematic instability is found to have two branches, for all explored Reynolds numbers. The dynamical dynamo threshold follows these branches: at low Reynolds number it lies within the low branch while at high kinetic Reynolds number it is close to the high branch.Comment: 4 pages, 4 figure

Sex differences in eye gaze and symbolic cueing of attention

Observing a face with averted eyes results in a reflexive shift of attention to the gazed-at location. Here we present results that show that this effect is weaker in males than in females (Experiment 1). This result is predicted by the ‘extreme male brain’ theory of autism (Baron-Cohen, 2003), which suggests that males in the normal population should display more autism-like traits than females (e.g., poor joint attention). Indeed, participants′ scores on the Autism-Spectrum Quotient (Baron-Cohen, Wheelwright, Stott, Bolton, & Goodyear, 2001) negatively correlated with cueing magnitude. Furthermore, exogenous orienting did not differ between the sexes in two peripheral cueing experiments (Experiments 2a and 2b). However, a final experiment showed that using non-predictive arrows instead of eyes as a central cue also revealed a large gender difference. This demonstrates that reduced orienting from central cues in males generalizes beyond gaze cues. These results show that while peripheral cueing is equivalent in the male and female brains, the attention systems of the two sexes treat noninformative symbolic cues very differently

Rings of fire and Grooved Ware settlement at West Kennet, Wiltshire

Alasdair Whittle has had a career-long interest in the Neolithic of the Avebury area (Fig. 17.1). In the late 1980s and early 1990s he undertook a major research project in the region to investigate the Neolithic sequence and its environment (Whittle 1993). This included a series of excavations of early Neolithic sites including the causewayed enclosure at Windmill Hill (Whittle et al. 1999), the chambered tomb at Millbarrow (Whittle 1994), and an earthen long barrow at Easton Down (Whittle et al. 1993). A series of trenches were also cut through two palisade enclosures at West Kennet (Whittle 1997). This campaign of new excavation was accompanied by research into the archives of previous investigations, particularly the publication and subsequent dating of Richard Atkinson’s excavation on and within Silbury Hill in 1968–70 (Bayliss et al. 2007a; Whittle 1997) and a reassessment of the date and development of Avebury itself (Pitts and Whittle 1992). The subsequent decades have seen continued work in the Avebury region, given focus by the Archaeological Research Agenda for the Avebury World Heritage site (AAHRG 2001). Alasdair himself has been instrumental in producing refined chronologies for the West Kennet long barrow (Bayliss et al. 2007b) and the causewayed enclosures at Windmill Hill and Knap Hill (Whittle et al. 2011, chapter 3), and in producing synthetic narratives of early Neolithic sites in the region and beyond (Whittle et al. 2007; 2011, chapters 14 and 15). Further understanding of the late Neolithic landscape has been gained through research excavations at the Beckhampton Avenue and Longstones Cove and ditched enclosure (Gillings et al. 2008), and through rescue excavations undertaken in advance of consolidation works at Silbury Hill (Leary et al. 2013a). The latter in particular has done much to improve our understanding of the development and date of Silbury Hill (Marshall et al. 2013; in prep. a; in prep. b), which has been put into context by a recent synthesis of the available scientific dating evidence for the Avebury area by Frances Healy (2016)

IntCal20 tree rings: an archaeological Swot analysis

We undertook a strengths, weaknesses, opportunities, and threats (SWOT) analysis of Northern Hemisphere tree-ring datasets included in IntCal20 in order to evaluate their strategic fit with the demands of archaeological users. Case studies on wiggle-matching single tree rings from timbers in historic buildings and Bayesian modeling of series of results on archaeological samples from Neolithic long barrows in central-southern England exemplify the archaeological implications that arise when using IntCal20. The SWOT analysis provides an opportunity to think strategically about future radiocarbon (14C) calibration so as to maximize the utility of 14C dating in archaeology and safeguard its reputation in the discipline