255,959 research outputs found

    Stresses in the vicinity of an un-reinforced mitre intersection: an experimental and finite element comparison

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    The experimental investigation reported provides elastic stresses in the vicinity of the unreinforced intersection of a single 90° mitred bend, subjected to an in-plane bending moment. The specimen was extensively strain gauged on the outer surface. A small number of rosettes were also laid on the inside surface close to the welded intersection. The procedures used for the successful installation of the inside surface gauges are discussed. In the experiment, consideration was also given to deflections and rotations. Satisfactory comparisons with adaptive-p thin-shell finite element results were obtained in general and differences are explained in terms of the known experimental variables and finite element approximations. The nature of the stresses at such intersections is discussed and various methods of obtaining fatigue 'hot-spot' stresses are considered

    Spatiotemporal properties of multiscale two-dimensional ows

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    The extraordinary complexity of turbulence has motivated the study of some of its key features in flows with similar structure but simpler or even trivial dynamics. Recently, a novel class of such flows has been developed in the laboratory by applying multiscale electromagnetic forcing to a thin layer of conducting fluid. In spite of being stationary, planar, and laminar these flows have been shown to resemble turbulent ones in terms of energy spectra and particle dispersion. In this thesis, some extensions of these flows are investigated through simulations of a layer-averaged model carried out using a bespoke semi-Lagrangian spline code. The selected forcings generalise the experimental ones by allowing for various kinds of self-similarity and planetary motion of the multiple scales. The spatiotemporal structure of the forcings is largely reflected on the flows, since they mainly arise from a linear balance between forcing and bottom friction. The exponents of the approximate power laws found in the wavenumber spectra can thus be related to the scaling and geometrical forcing parameters. The Eulerian frequency spectra of the unsteady flows exhibit similar power laws originating from the sweeping of the multiple flow scales by the forcing motions. The disparity between fluid and sweeping velocities makes it possible to justify likewise the observed Lagrangian power laws, but precludes a proper analogy with turbulence. In the steady case, the absolute dispersion of tracer particles presents ballistic and diffusive stages, while relative dispersion shows a superquadratic intermediate stage dominated by separation bursts due to the various scales. In the unsteady case, the absence of trapping by fixed streamlines leads to appreciable enhancement of relative dispersion at low and moderate rotation frequency. However, the periodic reversals of the large scale give rise to subdiffusive absolute dispersion and severely impede relative dispersion at high frequency

    Evidence for mass ejection associated with long secondary periods in red giants

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    Approximately 30% of luminous red giants exhibit a Long Secondary Period (LSP) of variation in their light curves, in addition to a shorter primary period of oscillation. The cause of the LSP has so far defied explanation: leading possibilities are binarity and a nonradial mode of oscillation. Here, large samples of red giants in the Large Magellanic Cloud both with and without LSPs are examined for evidence of an 8 or 24 μ\mum mid-IR excess caused by circumstellar dust. It is found that stars with LSPs show a significant mid-IR excess compared to stars without LSPs. Furthermore, the near-IR JJ-KK color seems unaffected by the presence of the 24 μ\mum excess. These findings indicate that LSPs cause mass ejection from red giants and that the lost mass and circumstellar dust is most likely in either a clumpy or a disk-like configuration. The underlying cause of the LSP and the mass ejection remains unknown.Comment: 6 pages, accepted for publication in Ap

    Belyi-extending maps and the Galois action on dessins d'enfants

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    We study the absolute Galois group by looking for invariants and orbits of its faithful action on Grothendieck's dessins d'enfants. We define a class of functions called Belyi-extending maps, which we use to construct new Galois invariants of dessins from previously known invariants. Belyi-extending maps are the source of the ``new-type'' relations on the injection of the absolute Galois group into the Grothendieck-Teichmuller group. We make explicit how to get from a general Belyi-extending map to formula for its associated invariant which can be implemented in a computer algebra package. We give an example of a new invariant differing on two dessins which have the same values for the other readily computable invariants.Comment: 13 pages, 7 figures; submitted for publication; revisions are that the paper now deals only with Galois invariants of dessins, and that material is slightly expande

    Silent witness, using video to record and transmit tacit knowledge in creative practices.

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    Over the last ten years, the duration of my ongoing practice-led design research work, video recording has developed from an expensive luxury to being ubiquitous. Whilst this opens up many opportunities for documenting and disseminating research projects, there are also potential drawbacks. I am a multimedia designer who makes extensive use of video both as an observational tool and as a means of helping covey tacit / experiential knowledge in creative practices. In this paper I discuss the use of video for such purposes, drawing on my own experiences and the research of others who use video in research. It builds on methods developed undertaking my own practice-led research described in output 1: Wood N, Rust C & Horne G (2009). A tacit understanding: the designer's role in capturing and passing on the skilled knowledge of master craftsmen. International Journal of Design, 3(3). It also builds on two earlier articles: Wood N (2010). A good record? The use of video in practice-led design research. Reflections 13, Sint Lucas School of Architecture, Brussels. ISSN 1784-7052. Wood N (2008). Unlocking the knowledge of others: knowledge elicitation in practice-led design research. Reflections 7, Sint Lucas School of Architecture, Brussels. ISSN 1784-7052. In my continuing research I have been working with a craftsmen, Ulrik Hjort Lassen a doctoral student at the Department of Conservation, Gothenburg University, who has been undertaking research into traditional methods for scribing the timbers for traditional wooden buildings. The methods described in these papers have formed the theoretical basis for Lassen’s research, developed and testing a multimedia learning resources to provide ‘bridges’ for new learners to this knowledge, the successful outcome of which validates the principles developed in my own research and demonstrates transferability of this technique.</p

    The Shepheard\u27s Calendar

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    In the first eclogue and the last, Colin Clout addresses Pan, complaining about his life. These are the only two eclogues in monologue; they are different in scope but with many comparable passages; and they are the only two in the particularly sustained musical rhyme scheme of iambic pentameter sixains ryhmed ababcc. But in January, Colin is immature, in December he has grown old. In the two complaints, Spenser subtly communicates the vast difference in Colin\u27s experience-he is comprehensive, as in February he only plays. Through images of his relationship with nature, first so superficial and comradely and demonstrative, deepening into reality and resignation with a passion that, having ceased to battle, will spend itself in wonder; turning his life to fit a year, the four ages with the four seasons, Spenser tells a serious story of experience. There is room for a lot of comparison in the two eclogues, but we shall have time only for a glance
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