25,239 research outputs found

    Switching circuit Patent

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    Solid state circuit for switching alternating current input signal as function of direct current gating transisto

    Arts curriculum implementation: Adopt and adapt as policy translation

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    This paper examines macro, meso and micro understandings of policy enactment within Western Australian primary school arts education where a new national arts curriculum is being revised and implemented through a process colloquially known as ‘adopt and adapt’. This paper focuses on how a government led implementation policy has influenced arts teaching and learning in unintended ways. It Includes a theoretical reflection and a consideration of the effects of such policies. Using policy enactment theory as the enquiry lens, four contextual variables are highlighted for their impact on teachers and schools. The variables include situated contexts, material contexts, professional cultures and external factors. Effects are discussed through the perspectives of eleven arts curriculum leaders drawn from in-depth semi-structured interviews. Marginalisation of the arts, the disconnection of schools and teachers to the arts and professional learning impacts are discussed as results of this policy translation

    Report of the Terrestrial Bodies Science Working Group. Volume 8: The comets

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    The determination of the nuclear and atmospheric properties of comets, and the interaction of the solar wind with the comet tail are scientific objectives for a mission to one or more comets in the next decade. Recommended priorities for direct cometary exploration are listed

    Controlled splitting of an atomic wave packet

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    We propose a simple scheme capable of adiabatically splitting an atomic wave packet using two independent translating traps. Implemented with optical dipole traps, our scheme allows a high degree of flexibility for atom interferometry arrangements and highlights its potential as an efficient and high fidelity atom optical beam splitter.Comment: 4 pages, 4 figures. Accepted by Phys. Rev. Let

    Structure and thermodynamics of a mixture of patchy and spherical colloids: a multi-body association theory with complete reference fluid information

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    A mixture of solvent particles with short-range, directional interactions and solute particles with short-range, isotropic interactions that can bond multiple times is of fundamental interest in understanding liquids and colloidal mixtures. Because of multi-body correlations predicting the structure and thermodynamics of such systems remains a challenge. Earlier Marshall and Chapman developed a theory wherein association effects due to interactions multiply the partition function for clustering of particles in a reference hard-sphere system. The multi-body effects are incorporated in the clustering process, which in their work was obtained in the absence of the bulk medium. The bulk solvent effects were then modeled approximately within a second order perturbation approach. However, their approach is inadequate at high densities and for large association strengths. Based on the idea that the clustering of solvent in a defined coordination volume around the solute is related to occupancy statistics in that defined coordination volume, we develop an approach to incorporate the complete information about hard-sphere clustering in a bulk solvent at the density of interest. The occupancy probabilities are obtained from enhanced sampling simulations but we also develop a concise parametric form to model these probabilities using the quasichemical theory of solutions. We show that incorporating the complete reference information results in an approach that can predict the bonding state and thermodynamics of the colloidal solute for a wide range of system conditions.Comment: arXiv admin note: text overlap with arXiv:1601.0438

    Transitions to improved confinement regimes induced by changes in heating in zero-dimensional models for tokamak plasmas

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    It is shown that rapid substantial changes in heating rate can induce transitions to improved energy confinement regimes in zero-dimensional models for tokamak plasma phenomenology. We examine for the first time the effect of step changes in heating rate in the models of E-J.Kim and P.H.Diamond, Phys.Rev.Lett. 90, 185006 (2003) and M.A.Malkov and P.H.Diamond, Phys.Plasmas 16, 012504 (2009) which nonlinearly couple the evolving temperature gradient, micro-turbulence and a mesoscale flow; and in the extension of H.Zhu, S.C.Chapman and R.O.Dendy, Phys.Plasmas 20, 042302 (2013), which couples to a second mesoscale flow component. The temperature gradient rises, as does the confinement time defined by analogy with the fusion context, while micro-turbulence is suppressed. This outcome is robust against variation of heating rise time and against introduction of an additional variable into the model. It is also demonstrated that oscillating changes in heating rate can drive the level of micro-turbulence through a period-doubling path to chaos, where the amplitude of the oscillatory component of the heating rate is the control parameter.Comment: 8 pages, 14 figure

    New Green-Kubo formulas for transport coefficients in hard sphere-, Langevin fluids and the likes

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    We present generalized Green-Kubo expressions for thermal transport coefficients ÎŒ\mu in non-conservative fluid-type systems, of the generic form, ÎŒ\mu =Ό∞= \mu_\infty +\int^\infty_0 dt V^{-1} \av{I_\epsilon \exp(t {\cal L}) I}_0 where exp⁥(tL)\exp(t{\cal L}) is a pseudo-streaming operator. It consists of a sum of an instantaneous transport coefficient Ό∞\mu_\infty, and a time integral over a time correlation function in a state of thermal equilibrium between a current II and its conjugate current IÏ”I_\epsilon. This formula with Ό∞≠0\mu_\infty \neq 0 and Iϔ≠II_\epsilon \neq I covers vastly different systems, such as strongly repulsive elastic interactions in hard sphere fluids, weakly interacting Langevin fluids with dissipative and stochastic interactions satisfying detailed balance conditions, and "the likes", defined in the text. For conservative systems the results reduce to the standard formulas.Comment: 7 pages, no figures. Version 2: changes in the text and references adde

    Plate-impact loading of cellular structures formed by selective laser melting

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    Porous materials are of great interest because of improved energy absorption over their solid counterparts. Their properties, however, have been difficult to optimize. Additive manufacturing has emerged as a potential technique to closely define the structure and properties of porous components, i.e. density, strut width and pore size; however, the behaviour of these materials at very high impact energies remains largely unexplored. We describe an initial study of the dynamic compression response of lattice materials fabricated through additive manufacturing. Lattices consisting of an array of intersecting stainless steel rods were fabricated into discs using selective laser melting. The resulting discs were impacted against solid stainless steel targets at velocities ranging from 300 to 700 m s-1 using a gas gun. Continuum CTH simulations were performed to identify key features in the measured wave profiles, while 3D simulations, in which the individual cells were modelled, revealed details of microscale deformation during collapse of the lattice structure. The validated computer models have been used to provide an understanding of the deformation processes in the cellular samples. The study supports the optimization of cellular structures for application as energy absorbers. © 2014 IOP Publishing Ltd
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