Effect of blade geometry on the aerodynamic loads produced by vertical-axis wind turbines

Accurate aerodynamic modelling of vertical-axis wind turbines poses a significant challenge. The rotation of the turbine induces large variations in the angle of attack of its blades that can manifest as dynamic stall. In addition, interactions between the blades of the turbine and the wake that they produce can result in impulsive changes to the aerodynamic loading. The Vorticity Transport Model has been used to simulate the aerodynamic performance and wake dynamics of three different vertical-axis wind turbine configurations. It is known that vertical-axis turbines with either straight or curved blades deliver torque to their shaft that fluctuates at the blade passage frequency of the rotor. In contrast, a turbine with helically twisted blades delivers a relatively steady torque to the shaft. In this article, the interactions between helically twisted blades and the vortices within their wake are shown to result in localized perturbations to the aerodynamic loading on the rotor that can disrupt the otherwise relatively smooth power output that is predicted by simplistic aerodynamic tools that do not model the wake to sufficient fidelity. Furthermore, vertical-axis wind turbines with curved blades are shown to be somewhat more susceptible to local dynamic stall than turbines with straight blades

Integral points on varieties with infinite \'etale fundamental group

We study integral points on varieties with infinite \'etale fundamental groups. More precisely, for a number field $F$ and $X/F$ a smooth projective variety, we prove that for any geometrically Galois cover $\varphi\colon Y \to X$ of degree at least $2\dim(X)^2$, there exists an ample line bundle $\mathscr{L}$ on $Y$ such that for a general member $D$ of the complete linear system $|\mathscr{L}|$, $D$ is geometrically irreducible and any set of $\varphi(D)$-integral points on $X$ is finite. We apply this result to varieties with infinite \'etale fundamental group to give new examples of irreducible divisors on varieties for which finiteness of integral points is provable.Comment: 9 pages; comments welcome

Exploring the relationship between effective and reflective practice in applied sport psychology

This study offers an investigation into the concept of effective practice in applied sport psychology (ASP) with emphasis being placed upon the role that reflective practice may have in helping practitioners to develop the effectiveness of their service delivery. Focus groups (n = 2), consisting of accredited and trainee sport psychologists, were conducted to generate a working definition of effective practice, and discuss the concept of effectiveness development through engagement in reflective practices. The resulting definition encapsulated a multidimensional process involving reflection-on-practice. Initial support for the definition was gained through consensus validation involving accredited sport psychologists (n = 34) who agreed with the notion that although effectiveness is context specific it is related to activities designed to meet client needs. Reflective practice emerged as a vital component in the development of effectiveness, with participants highlighting that reflection is intrinsically linked to service delivery, and a key tool for experiential learning.</jats:p

Precise ecology: a foundation for an integrated and quantifiable theory of animal, plant, population and community ecology

Thesis (D.Sc.)--University of Adelaide, 199

Absence of singular superconducting fluctuation corrections to thermal conductivity

We evaluate the superconducting fluctuation corrections to thermal conductivity in the normal state which diverge as T approaches T_c. We find zero total contribution for one, two and three-dimensional superconductors for arbitrary impurity concentration. The method used is diagrammatic many-body theory, and all contributions -- Aslamazov-Larkin (AL), Maki-Thompson (MT), and density-of-states (DOS) -- are considered. The AL contribution is convergent, whilst the divergences of the DOS and MT diagrams exactly cancel.Comment: 4 pages text; 2 figure

Fermented Liquid Feed (FLF) can reduce the transfer and incidence of Salmonella in pigs.

Surveillance studies have shown that feeding pigs liquid diets, and particularly fermented liquid diets reduces the incidence of Salmonella positive herds. Studies have shown that a concentration of 70 mmol kg-1 lactic acid is bacteriostatic to Salmonella and that concentrations \u3e100 mmol kg-1 are bactericidal. Uncontrolled natural fermentation results in lactic acid concentrations varying between 0 and 140 mmol kg-1 so cannot be relied upon to produce bactericidal levels of lactic acid. However, if selected lactic acid bacteria are used as inoculants and the temperature of the fermentation is controlled (circa 30∞C), acid onditions can be produced within 24 h that rapidly and effectively exclude enteropathogens from the diet

Consequences of converting graded to action potentials upon neural information coding and energy efficiency

Information is encoded in neural circuits using both graded and action potentials, converting between them within single neurons and successive processing layers. This conversion is accompanied by information loss and a drop in energy efficiency. We investigate the biophysical causes of this loss of information and efficiency by comparing spiking neuron models, containing stochastic voltage-gated Na+ and K+ channels, with generator potential and graded potential models lacking voltage-gated Na+ channels. We identify three causes of information loss in the generator potential that are the by-product of action potential generation: (1) the voltage-gated Na+ channels necessary for action potential generation increase intrinsic noise and (2) introduce non-linearities, and (3) the finite duration of the action potential creates a ‘footprint’ in the generator potential that obscures incoming signals. These three processes reduce information rates by ~50% in generator potentials, to ~3 times that of spike trains. Both generator potentials and graded potentials consume almost an order of magnitude less energy per second than spike trains. Because of the lower information rates of generator potentials they are substantially less energy efficient than graded potentials. However, both are an order of magnitude more efficient than spike trains due to the higher energy costs and low information content of spikes, emphasizing that there is a two-fold cost of converting analogue to digital; information loss and cost inflation