210 research outputs found

    An investigation into the prevalence of non-tripod pengrip and its implications for secondary school writers

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    This research addresses the twin issues of whether non-tripod grips are becoming more common and whether young people who adopt any of these grips experience greater problems than their peers. Existing research into writing grip focuses on young children, leaving the long-term consequences of an unorthodox grip poorly reported. The initial demographic survey investigated changes in penhold. The survey was conducted in a single secondary school, its satellite primary schools and adults in West Wales. This established a high frequency of non-tripod grips occurred among children and young adults that were not replicated in older adults. Statistical analysis of the data indicates that this change in grip happened quite abruptly to young people who began school in the early 1980s. The research also identified ninety-three secondary school pupils, using a range of non-tripod grips and matched each to a pupil using an orthodox grip. Thirteen non-tripod grips were identified, three for the first time, while the severity of others appears greater than in the existing literature. The effects of each grip were considered statistically, using the null hypothesis that groups of matched pupils sharing a grip, will have similar characteristics. Several consequences of the different grips were established, some of which can adversely affect performance and attitudes. These consequences include high levels of pain after even very short writing periods, a high number of adjustments needed to maintain writing, as well as different writing speeds, some of which fall below generally accepted norms. There is thus support for the initial hypothesis that those using non-tripod grips are affected by their choice of grip, which may negatively affect their education. This research ascertained, for the first time, the suitability of a range of unorthodox grips for the demanding writing tasks required by secondary schooling. It also identifies some grips that should be avoided if unnecessary difficulties with writing are to be prevented

    Inertial effects in three dimensional spinodal decomposition of a symmetric binary fluid mixture: A lattice Boltzmann study

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    The late-stage demixing following spinodal decomposition of a three-dimensional symmetric binary fluid mixture is studied numerically, using a thermodynamicaly consistent lattice Boltzmann method. We combine results from simulations with different numerical parameters to obtain an unprecendented range of length and time scales when expressed in reduced physical units. Using eight large (256^3) runs, the resulting composite graph of reduced domain size l against reduced time t covers 1 < l < 10^5, 10 < t < 10^8. Our data is consistent with the dynamical scaling hypothesis, that l(t) is a universal scaling curve. We give the first detailed statistical analysis of fluid motion, rather than just domain evolution, in simulations of this kind, and introduce scaling plots for several quantities derived from the fluid velocity and velocity gradient fields.Comment: 49 pages, latex, J. Fluid Mech. style, 48 embedded eps figs plus 6 colour jpegs for Fig 10 on p.2

    Analysis of a spatial Lotka-Volterra model with a finite range predator-prey interaction

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    We perform an analysis of a recent spatial version of the classical Lotka-Volterra model, where a finite scale controls individuals' interaction. We study the behavior of the predator-prey dynamics in physical spaces higher than one, showing how spatial patterns can emerge for some values of the interaction range and of the diffusion parameter.Comment: 7 pages, 7 figure

    Tests of Dynamical Scaling in 3-D Spinodal Decomposition

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    We simulate late-stage coarsening of a 3-D symmetric binary fluid. With reduced units l,t (with scales set by viscosity, density and surface tension) our data extends two decades in t beyond earlier work. Across at least four decades, our own and others' individual datasets (< 1 decade each) show viscous hydrodynamic scaling (l ~ a + b t), but b is not constant between runs as this scaling demands. This betrays either the unexpected intrusion of a discretization (or molecular) lengthscale, or an exceptionally slow crossover between viscous and inertial regimes.Comment: Submitted to Phys. Rev.

    3D Spinodal Decomposition in the Inertial Regime

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    We simulate late-stage coarsening of a 3D symmetric binary fluid using a lattice Boltzmann method. With reduced lengths and times l and t respectively (scales set by viscosity, density and surface tension) our data sets cover 1 < l 100 we find clear evidence of Furukawa's inertial scaling (l ~ t^{2/3}), although the crossover from the viscous regime (l ~ t) is very broad. Though it cannot be ruled out, we find no indication that Re is self-limiting (l ~ t^{1/2}) as proposed by M. Grant and K. R. Elder [Phys. Rev. Lett. 82, 14 (1999)].Comment: 4 pages, 3 eps figures, RevTex, minor changes to bring in line with published version. Mobility values added to Table

    Entropy-induced smectic phases in rod-coil copolymers

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    We present a self-consistent field theory (SCFT) of semiflexible (wormlike) diblock copolymers, each consisting of a rigid and a flexible part. The segments of the polymers are otherwise identical, in particular with regard to their interactions, which are taken to be of an Onsager excluded-volume type. The theory is developed in a general three-dimensional form, as well as in a simpler one-dimensional version. Using the latter, we demonstrate that the theory predicts the formation of a partial-bilayer smectic-A phase in this system, as shown by profiles of the local density and orientational distribution functions. The phase diagram of the system, which includes the isotropic and nematic phases, is obtained in terms of the mean density and rigid-rod fraction of each molecule. The nematic-smectic transition is found to be second order. Since the smectic phase is induced solely by the difference in the rigidities, the onset of smectic ordering is shown to be an entropic effect and therefore does not have to rely on additional Flory-Huggins-type repulsive interactions between unlike chain segments. These findings are compared with other recent SCFT studies of similar copolymer models and with computer simulations of several molecular models.Comment: 13 pages, 8 figure
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