A Dynamics and Stability Framework for Avian Jumping Take-off

Jumping take-off in birds is an explosive behaviour with the goal of providing a rapid transition from ground to airborne locomotion. An effective jump is predicated on the need to maintain dynamic stability through the acceleration phase. The present study concerns understanding how birds retain control of body attitude and trajectory during take-off. Cursory observation suggests that stability is achieved with relatively little cost. However, analysis of the problem shows that the stability margins during jumping are actually very small and that stability considerations play a significant role in selection of appropriate jumping kinematics. We use theoretical models to understand stability in prehensile take-off (from a perch) and also in non-prehensile take-off (from the ground). The primary instability is tipping, defined as rotation of the centre of gravity about the ground contact point. Tipping occurs when the centre of pressure falls outside the functional foot. A contribution of the paper is the development of graphical tipping stability margins for both centre of gravity location and acceleration angle. We show that the nose-up angular acceleration extends stability bounds forward and is hence helpful in achieving shallow take-offs. The stability margins are used to interrogate simulated take-offs of real birds using published experimental kinematic data from a guinea fowl (ground take-off) and a diamond dove (perch take-off). For the guinea fowl the initial part of the jump is stable, however simulations exhibit a stuttering instability not observed experimentally that is probably due to absence of compliance in the idealised joints. The diamond dove model confirms that the foot provides an active torque reaction during take-off, extending the range of stable jump angles by around 45{\deg}.Comment: 21 pages, 11 figures; supplementary material: https://figshare.com/s/86b12868d64828db0d5d; DOI: 10.6084/m9.figshare.721056

Voyage of the "Mary and Sally" to Macquarie Island for the purpose of obtaining sea elephant oil and seal skins.

This vessel of 130 tons, Captain James Kelly, master, is noted in the " Sydney Gazette " of 18.9.32 as having left Sydney Cove for the Derwent, en route for Macquarie Island. After a stay of nearly two months at Hobart Town her voyage proper commenced on 16th November, 1813. The brig was no stranger to the Southern Antarctic Islands, and, since her arrival from Bengal, had made voyages in the two previous years to Campbell and Macquarie Islands, under the command of Captain Feen. At this time, two and a half years after its discovery, although the fur-bearing seal had been so depleted in numbers, Macquarie Island was still the home of large numbers of sea elephants. The object of the voyage was primarily to obtain oil from the latter and the skins of the fur-bearing seal

On two Tasmanian Crania (Immature)

In describing these two crania I am infiuenced by the comparative rarity of such specimens, and the opportunity, now offered, of comparison with the adult Crania in the large collection of the Tasmanian Museum. There remain for description of this extinct race the Crania of only eight children (of which one is of doubtful authcnticity), (1899, p. 191). The Crania under consideration are as follows: A). Cranium of a child of about 6 years or a little more, with the Mandible in situ. This was found by Dr. Inglis Clark and myself about Christmas, 1908, at Oyster Cove. B). The Cranium of a child of 6-7 years discovered by Mrs. R. W. Legge, on the West Coast of Tasmania, in the summer of 1927. It will be of interest to see to what extent the features, that are regarded as typical of the Adult Tasmanian Cranium, are present in these immature types. In Conclusion, generally, it may be said that in their Physical Characters both these immature Crania conform to the Adult types of their race, and could be distinguished by their Tasmanian characteristics. Neither, however, shows the very typical carination of the Vault of the Cranium. The Facial Features are worthy of detailed attention, in a larger series of skullls; as it seems that in early life a marked width of the face at the expense of its Height is not pronounced

An investigation of control strategies on gearbox damage

The impact of control on structural elements such as tower and blades have been thoroughly researched and the validity of analysis methods based on aeroelastic simulations is widely accepted. The implications on gearbox wear for various control strategies is less studied. Using RomaxDesigner for gearbox analysis, MLS and Romax have carried out an investigation where the impact of different control strategies on wear is assessed. The best measures accounting for gearbox damage are described and the different control strategies and their impact on the gearbox are detailed

Bridging Gaps through Light: An Archaeological Exploration of Light and Dark in the Atlantic Scottish Iron Age

Representing a broad attempt to open up debate on an issue that has been largely overlooked, this thesis aims to explore the relationship between Atlantic Scotland’s Iron Age communities (and in particular, the broch cultures of Northern Scotland) and light – a complex, multifaceted, and universally significant facet of human existence. Thus far, the role of light has received little interest in prehistoric studies, and when such an interest does occur, it has often been restricted to entrance orientation research. Indeed, little attempt has actually been made to understand how light was orchestrated to shape social experience in the past, or how differing dimensions of light work to reveal or conceal aspects of social life; how was light experienced? What did light mean? Proposing an alternative approach to the study of light, these are questions which this thesis aims to explore; seeking to understand how Scottish Iron Age society orchestrated and manipulated light to create social experience. Due to light’s complexity, the thesis sections its study into a number of separate themes: structural orientation, the cosmological model and space, light and functionality, the psychological impact of light and dark, and light in the landscape and the influence of the weather and the environment. To explore each of these, the thesis pursues a plural methodology, combining typical data-based approaches (map-based studies, broad ranging landscape and GIS research; architectural-typological studies) with more qualitative analysis (e.g. phenomenology, ethnographic analogy, folklore analysis), attempting to explore both the physical and cognitive effects of light and darkness in the past

Stimulation of bone growth with thrombin peptide derivatives

Disclosed is a method of stimulating bone growth at a site in a subject in need of osteoinduction. The method comprises the step of administering a therapeutically effective amount of an agonist of the non-proteolytically activated thrombin receptor to the site.Board of Regents, University of Texas Syste

Aerodynamic performance of flying discs

The purpose of this paper is to examine geometrical design influence of various types of flying discs on their flight performance from the aerodynamics perspective. The lift, drag and moment coefficients of the discs were measured experimentally using a wind tunnel. Three types of golf discs and four sets of simpler parametric discs were studied to analyze and isolate the effect of design factors on these aerodynamic characteristics. Full six degree-of-freedom simulations of the discs were performed to visualize their flight trajectories and attitudes. These simulations, combined with the experimental data, provide details on the well-known “S-shaped” ground-path traced by a flying disc. This study reveals two key parameters to evaluate the flight performance of a disc: its coefficient of lift-to-drag ratio (CL/CD) and, more importantly, its coefficient of pitching moment (CM). The latter influences the tendency of the disc to roll from its intended path, and the former influences its throwing distance. The work suggests that to optimize the flight performance of a disc, the magnitudes and gradient of its CM should be minimized and its trim-point shifted from origin, while its CL/CD should be maximized with a flatter peak. In this study, the design parameters and the aerodynamic characteristics of various types of flying discs are analysed, compared and discussed in depth. Recommendations of design improvements to enhance the performance of any flying disc are offered as well